Research on the Evaluation Method of Electrical Stress Limit Capability Based on Reliability Enhancement Theory

Abstract

This study focuses on the evaluation of electrical stress limit capability for 3D-packaged memory (256 M × 72-bit DDR3 SDRAM) (Shanghai Fudan Microelectronics Group Co., Ltd., Shanghai, China). Guided by Reliability Enhancement Theory, this study presents a meticulously designed comprehensive test profile that incorporates critical stress parameters, including supply voltage, input clock frequency, electrostatic discharge (ESD) sensitivity, and electrical endurance. Explicit criteria for stress selection, upper/lower bounds, step increments, and duration are established. A dedicated test platform is constructed, integrating automated test equipment (ATE) and ESD sensitivity analyzers with detailed specifications on device selection criteria and operational principles. The functional performance testing methodology is systematically investigated, covering test platform configuration, initialization protocols, parametric testing procedures, functional verification, and acceptance criteria. Extreme-condition experiments—including supply voltage margining, input clock frequency tolerance, ESD sensitivity characterization, and accelerated electrical endurance testing—are conducted to quantify operational and destructive limits. The findings provide critical theoretical insights and practical guidelines for the design optimization, quality control, and reliability enhancement of 3D-packaged memory devices.

1. Introduction

With the increasing miniaturization and high-performance demands of electronic devices, 3D-packaged memory has gained widespread adoption in computing, telecommunications, and consumer electronics due to its high integration density, large capacity, and high-speed data transmission capabilities [1,2]. However, the complex and variable operational environments expose 3D-packaged memory to multifaceted electrical stress challenges, including voltage fluctuations, clock frequency variations, electrostatic discharge (ESD), and prolonged electrical loads. These stressors may degrade memory performance, compromise reliability, or induce catastrophic failures, ultimately jeopardizing the overall functionality and stability of electronic systems.

The accurate evaluation of electrical stress limit capability is imperative to ensure the stable and reliable operation of 3D-packaged memory across diverse application scenarios [3]. Such assessments not only facilitate circuit design optimization and enhanced stress resistance during product development but also enable stringent quality control in manufacturing processes to screen high-reliability devices. Although existing research on electrical stress limit evaluation for 3D-packaged memory has made preliminary advancements, critical gaps remain, such as incomplete testing methodologies and the lack of unified parameter selection standards, which impede the industry’s need for high-precision and efficient assessments [4,5].

This study systematically investigates the electrical stress limit capability evaluation of 3D-packaged memory (256 M × 72-bit DDR3 SDRAM) through Reliability Enhancement Theory. A structured methodology is established, encompassing (1) meticulously designed test profiles defining stress parameters (e.g., voltage ranges, frequency steps, ESD pulse levels), (2) a dedicated test platform integrating automated test equipment (ATE) and ESD simulators, and (3) scientific testing protocols for functional performance characterization under multi-stress conditions. By analyzing operational thresholds and failure modes across voltage/frequency margins, ESD susceptibility, and endurance limits, this research addresses existing knowledge gaps in reliability prediction. The findings provide both theoretical frameworks and actionable guidelines for enhancing 3D memory reliability, ultimately advancing the development of robust heterogeneous integration technologies in the semiconductor industry.

2. Test Design Methodology for 3D-Packaged Memory Limit Capability Evaluation

The design of the test profile for electrical stress limit capability assessment is a critical step to achieve the purpose of limit evaluation and accurately assess component capabilities. The test profile must include parameters such as stress selection, upper/lower stress limits, and step increments, as illustrated in Figure 1. The process begins with selecting appropriate test condition stresses, followed by step stress testing, where the chosen stresses are applied in a stepwise ascending manner to observe the product’s responses and capture performance variations across different stress levels. Real-time monitoring during the step stress process helps detect potential failures. In the event of a failure, the “failure localization” phase is initiated, employing specialized techniques such as physical inspection, electrical testing, and material analysis to identify the failure site and root cause. After localization, a determination is made on whether the failure originates from latent defects. If latent defects exist, the process proceeds to limit determination; otherwise, the test conditions or methods may require adjustment. The final step involves recording two critical limits: the operational limit, which defines the maximum stress, allowing the product to maintain basic functionality despite latent defects (crucial for reliability boundaries in real-world applications), and the cyclic limit, which determines the maximum tolerable stress cycles to reflect the product’s long-term reliability and durability under cyclic stress conditions.

The design criteria should encompass the following principles: (1) Stress Selection—Sensitive stresses must be chosen as the test stresses and evaluation parameters for limit capability assessment. (2) Upper/Lower Stress Limits—The upper limit should correspond to functional failure or critical parameter deviations, with the maximum value ensuring consistency in failure mechanisms, while the lower limit should not exceed the maximum stress specified in the product’s detailed specifications (recommended operating conditions) and maintain sufficient defect activation efficiency. (3) Stress Step Increments—Larger steps should be applied within the product’s specification limits to accelerate testing, whereas smaller steps are required beyond these limits to enhance precision in detecting operational and destructive thresholds. (4) Stress Duration—Stresses must persist until stabilization is achieved, ensuring adequate time to activate defects effectively.

2.1. Research on the Test Profile for Electrical Stress Limit Testing

The 3D-packaged memory selected for this study is a high-capacity, high-speed DDR3 SDRAM. The device adopts a stacked encapsulation process using PiP (Package-in-Package) technology, internally integrating five stacked DDR3 SDRAM dies, each with a capacity of 256 M × 16 bits. Among these, four dies are dedicated to data storage, while the fifth serves for Error Checking and Correcting (ECC). The memory architecture is 256 M × 72 bits, with a nominal voltage of 1.5 V ± 0.075 V, a maximum clock frequency of 667 MHz, and an electrostatic sensitivity rating of Class 2 (2000 V).

2.1.1. Research on the Test Profile for Electrical Stress Limit Testing

(1)

Power Voltage Limit Test Profile

Based on the specified nominal operating voltage range of 1.5 V ± 0.075 V, the step-up power voltage limit test starts at 1.5 V (maximum rated value) with increments of 0.05 V. Each step is held for 1 min, followed by parameter and functional testing. The test profile is shown in Figure 2. For the step-down power voltage limit test, the initial voltage is set to 1.5 V with decrements of 0.05 V. Each step is held for 1 min, followed by parameter and functional testing, as illustrated in Figure 3.

(2)

Input Clock Frequency Limit Test Profile

Based on the product’s specified maximum clock frequency of 667 MHz, the input clock frequency limit test starts at an initial frequency of 667 MHz, with increments of 25 MHz. Each step is held for 1 min, followed by parameter and functional testing. The test profile is illustrated in Figure 4.

(3)

Electrostatic Discharge (ESD) Sensitivity Limit Test Profile

Based on the product’s specified ESD failure threshold (2000 V), the ESD sensitivity limit test starts at an initial voltage of 200 V with increments of 100 V. After each increment, parameter and functional testing are conducted. The test profile is illustrated in Figure 5.

(4)

Electrical Endurance Limit Test Profile

The test is initially configured with a temperature of 125 °C, a duration of 1000 h, and an excitation voltage of 1.5 V. The stress is applied in increments of 1000 h. After each increment, parameter and functional testing are performed. The test profile is illustrated in Figure 6.

2.1.2. Construction of Electrical Stress Testing Equipment (Equipment Description)

The electrical stress testing equipment primarily includes an ATE (Automatic Test Equipment) tester [6] and an electrostatic discharge (ESD) sensitivity tester [7].

(1)

ATE Tester

The ATE tester features high testing speed and precision, enabling the rapid processing of large datasets and the completion of tests. It serves as the primary platform for this study to conduct high-precision verification of the functional performance of 3D-packaged memory before and after stress testing, as well as to perform power voltage limit testing and input clock frequency limit testing. A typical ATE tester consists of a computer mainframe, system architecture, test head, workstation, and fixtures, which collectively support connectivity testing, static/dynamic characteristic parameter testing, switching characteristic parameter testing, and functional testing for 3D-packaged memory. The key specifications of the ATE tester are summarized in

Table 1. Typical specifications of the ATE tester.

No.	Test Item	Equipment	Typical Capabilities
1	Functional performance testing before and after stress testing	ATE Tester (Advantest Corporation, Penang, Malaysia)	Maximum channels: 1600; maximum digital transmission rate: 16 Gbps; maximum vector depth: 112 M; maximum scan chain depth: 28.5 G; edge placement accuracy (EPA): 75 ps; 64 independent power supplies; maximum current: 90 A; MTP test suite support; memory chip read/write testing speed: 8 Gbps; time measurement accuracy: 1 ps; high-end programmable logic devices (PLDs) with high-speed SerDes interfaces; testing speed: 25 Gb/s; output port rise/fall time: <20 ps
2	Power voltage limit testing
3	Input clock frequency limit testing

, and its physical appearance is shown in Figure 7.

(2)

Electrostatic Discharge (ESD) Sensitivity Tester

The ESD sensitivity tester evaluates the electrostatic discharge susceptibility of a product by applying static charges or discharging electrostatic energy while monitoring changes in the I-V characteristics of the device pins [8,9]. The tester typically includes a signal generator (to produce electrostatic pulses with specific amplitudes and waveforms), test modules (supporting different models such as the Human Body Model (HBM), Machine Model (MM), and Charged Device Model (CDM)), and a control system (to manage discharge cycles, intervals, and other parameters) [10], enabling it to meet the requirements for verifying the ESD sensitivity limit capabilities of 3D-packaged memory. Since microelectronic devices undergo only HBM testing during qualification, this study also focuses on validating the ESD resistance limits under the HBM [10,11]. For this model, a 100 pF capacitor is discharged through a 1500 Ω resistor to simulate the waveform generated by human body electrostatic discharge. The key specifications of the ESD sensitivity tester are summarized in

Table 2. Typical specifications of the ESD sensitivity tester.

No.	Test Item	Equipment	Typical Capabilities
1	ESD Sensitivity Limit Testing	Multi-Pin ESD Sensitivity Tester (Sakai Denki Kogyo Co., Ltd. Sakai City, Japan)	Pin count: 1152 pin, 1728 pin, 2304 pin; HBM maximum test voltage: 8000 V; MM supported maximum test voltage: 2000 V

, and its physical appearance is shown in Figure 8.

2.1.3. Principles of 3D-Packaged Memory Limit Capability Testing

Integrated circuit testing involves applying test stimuli to the device under test (DUT) and determining whether the DUT meets specifications by comparing its output response to the expected response [12]. The fundamental process flow is illustrated in Figure 9.

Currently, common integrated circuit testing methods primarily include the following three types:

(1)

Scan Path Testing

Scan path testing is a design-for-testability (DFT) approach for sequential circuit chips. Its fundamental principle is that sequential circuits can be modeled as a feedback loop combining a combinational circuit network and a sequential circuit network with flip-flops. In scan design, flip-flops are modified into scan flip-flops and connected into a scan chain. The input to the scan chain can be applied via a small number of chip pins, and the output can also be observed through limited pins, thereby reducing the number of I/O pins occupied and enabling testability for complex chips.

(2)

Built-In Self-Test (BIST) Method [13]

BIST integrates additional self-test circuitry into the chip design. During testing, only external control signals are required to activate the built-in test hardware and software, which then check for defects or faults in the circuit under test. The test patterns for BIST are typically generated internally by a test pattern generator rather than supplied externally. The number of test patterns generated directly determines the test coverage and quality. While BIST simplifies testing, it increases design complexity, chip area, and power consumption.

(3)

Boundary Scan Testing

Boundary scan testing shares the same underlying principle as scan path testing. However, unlike scan path testing and BIST, which target internal chip faults or defects, boundary scan testing focuses on the connections between chip pins and core logic. Since boundary scan testing involves interconnections between chips—which may be designed by different designers or manufacturers—it requires standardized test interfaces to ensure compatibility across vendors.

Classification by Integrated Circuit Type: The 3D-packaged memory selected for this study, the 256 M × 72-bit DDR3 SDRAM, falls under the category of digital integrated circuits. Testing for digital integrated circuits is generally divided into three categories:

Functional Testing: Verifies the correctness and reliability of the integrated circuit under various operational modes. This includes the validation of logic functions, memory functions, interface functions, and reset/initialization processes [14,15,16].

DC Parameter Testing: Evaluates performance and characteristics under DC operating conditions, such as voltage, current, and other DC-related parameters [14,15,16].

AC Parameter Testing: Assesses performance under AC operating conditions, including timing parameters, frequency response, signal integrity, and noise characteristics [14,15,16].

3. Research on Functional Performance Testing Methods for 3D-Packaged Memory

3.1. Construction of Functional Performance Testing Platform and PCB Design for 3D-Packaged Memory

The functional performance testing platform for this experiment utilizes a 3D-packaged memory, whose key characteristics are summarized in

Table 3. Key characteristics of the 256 M × 72-bit DDR3 SDRAM.

No.	Item	Specifications
1	Memory Architecture	256 M × 72 bit
2	Nominal Voltage	1.5 V ± 0.075 V
3	Maximum Clock Frequency	667 MHz
4	Programmable Burst Length	4, 8
5	Package Type	BGA199

, and its electrical schematic is illustrated in Figure 10.

Functional performance testing of the 256 M × 72-bit DDR3 SDRAM before and after stress application is conducted using a dedicated adapter PCB connected to the ATE 93000 test system. The interface configuration of the ATE 93000 test system is shown in Figure 11. The dedicated PCB for functional performance testing is designed according to the interface dimensions and requirements of the test system, with specific dimensional requirements detailed in Figure 12.

The dedicated PCB for functional performance testing of the 3D-packaged memory was designed and fabricated using Altium Designer 25 software. First, the schematic was developed based on the internal electrical principles of the 256 M × 72-bit DDR3 SDRAM (as shown in Figure 13), defining the interconnection relationships between components and verifying circuit connectivity and signal integrity.

Next, based on the interface dimensions of the ATE 93000 test system, the size and shape of the dedicated adapter PCB were designed. To meet the feasibility of circuit testing and high-density routing requirements, a multilayer board was adopted. Compared to single-layer boards, multilayer boards incorporate internal power and ground layers, where power and ground networks are primarily routed, while signal routing focuses on the top and bottom layers, supplemented by intermediate layers. This optimizes internal layer routing, improves circuit board rationality, and enhances electromagnetic compatibility (EMC). Consequently, the PCB was configured as a 10-layer board with a thickness of 3.5 mm. The 256 M × 72-bit DDR3 SDRAM was placed in an optimal location on the PCB, followed by defining rules for trace width, spacing, and routing for signal, power, and ground lines. Finally, the test socket was integrated with the PCB assembly. The dedicated functional performance testing PCB employed a 12-layer stack-up design (with two chips assigned to the same PS1600 unit, their signals distributed across the same PS1600; 9 G signal lines minimized in length and matched for equal length; full-site trace length matching with a tolerance of 50 mil). Partial layout designs are shown in Figure 14 and Figure 15, and the fabricated PCB is displayed in Figure 16.

After fabrication, the functional performance testing dedicated PCB was installed on the ATE 93000 test system, as shown in Figure 17. The device under test (DUT) was then placed for electrical continuity testing to ensure no open or short circuits in traces or solder joints, while simultaneously verifying the integrity of the power supply voltages.

The functional performance testing of the 256 M × 72-bit DDR3 SDRAM is conducted using the configured ADVANTEST 93000 ATE test system and the TA-5000A rapid thermal cycling chamber. Electrical connections to the device under test (DUT) are established via the dedicated testing PCB, as illustrated in Figure 18.

3.2. Three-Dimensional-Packaged Memory Functional Performance Testing Methods

3.2.1. Initialization Setup Methods for Functional Performance Testing

First, initialization is required. The 256 M × 72-bit DDR3 SDRAM must undergo initialization before power-on operation, including configuration of the mode register to define parameters such as Burst Length, Burst Type, and CAS Latency. The initialization steps to be followed are illustrated in Figure 19.

The specific timing and mode register configuration details are illustrated in Figure 20, Figure 21, Figure 22, Figure 23 and Figure 24:

First, the connection relationships between the chip pins and tester channels are configured in the pin file of the testing software to establish signal connectivity between the tester and the 256 M × 72-bit DDR3 SDRAM. In the lev file, the drive voltage levels for input pins and power supply pins, as well as the threshold voltage levels for output pins, are defined. The tim file specifies cycle times and signal waveforms within each cycle. The pmfl file is edited to generate test vectors required for different test items. Finally, through the combination of the lev, tim, and pmfl files, the test stimulus generation and corresponding output signal observation for the 256 M × 72-bit DDR3 SDRAM are achieved. The overall test interface of the testing system is shown in Figure 25.

3.2.2. Performance Parameter Testing Methods

The parameter tests of 256 M × 72-bit DDR3 SDRAM include two categories: DC parameters and AC parameters.

The DC parameter tests mainly include the continuity test, input leakage current, output leakage current, and power supply current. The continuity test refers to determining whether the connectivity of each pin is normal by testing whether the voltage drop of the internal protection diode of each pin is normal. Generally speaking, the continuity test must be carried out first during the test. The input leakage current (ILIH/ILIL) and output leakage current (ILOH/ILOL) refer to the current flowing into or out of the input and output pins of the DDR3 memory under specific voltage conditions. This current reflects the DC impedance between the pins. By applying high- and low-level currents to the input and output pins, it is verified, respectively, whether there is excessive leakage current in the high-impedance state at the input and output ends, so as to avoid generating signal interference or incorrect logic levels. The power supply current refers to the current consumed by the DDR3 memory in different working states (running and sleeping). By testing the power supply current, the power consumption of the DDR3 memory can be evaluated.

The AC parameter tests mainly include the DQS-DQ delay and the average refresh cycle. The DQS (data strobe) delay refers to the relative time difference between the DQS signal and the DQ signal. This delay parameter is particularly important during read and write operations, especially during high-frequency operations, where signal synchronization is even more critical. Testing the DQS-DQ delay is to ensure that the data strobe signal (DQS) and the data signal (DQ) are synchronized at the correct time points, thereby ensuring the accuracy of data transmission. The average refresh cycle refers to the average time interval within which the memory cells need to be refreshed within a specific time. Since the capacitors in the DRAM cells will lose charge over time, they must be refreshed within a specific time. Testing the average refresh cycle can ensure that each memory cell will not lose data before it needs to be refreshed.

Different parameter test items need to be carried out under the corresponding working states. The test code is edited according to the timing diagram in the detailed specification of the 256 M × 72-bit DDR3 SDRAM, and the edited test vectors are called on the ATE test machine to make the 256 M × 72-bit DDR3 SDRAM enter a specific state. Taking the read operation current as an example, the read operation timing is shown in Figure 26. The read operation vector is written according to the timing diagram and the truth table in the product manual. The read operation vector code is shown in Figure 27. High and low levels are applied to the relevant pins in the specified time sequence to make the 256 M × 72-bit DDR3 SDRAM enter the target row activation–read operation–precharge cycle state. At this time, the power supply board of the test machine will read and output the power supply current, which is the chip read current.

3.2.3. Functional Testing Method

The functional algorithms of 256 M × 72-bit DDR3 SDRAM mainly include all-0s, all-1s, a checkerboard pattern, and an inverse checkerboard pattern. Different algorithms check for different faults, and the test durations also vary. Since functional testing generally requires data operations on the entire space of the memory, that is, all memory cells, due to the large capacity of the memory, the number of test vector cycles is extremely large, and the storage depth of the test channels on the testing machine occupied is very great. It is difficult to achieve with the traditional vector generation method.

The MTP function equipped in the V93000 can generate test patterns by writing codes, and the test patterns can be converted into test vectors recognizable by the testing machine through the APG compilation tool. This method does not consume the storage depth of the test channels and is easy to use to edit and modify the patterns. The MTP programming interface is shown in Figure 28.

3.2.4. Criteria Requirements for Functional and Performance Testing

Table 4. Functional and performance testing requirements.

Technical Parameter	Symbol	Basic Testing Conditions	Minimum Value	Maximum Value	Unit
Operating Current (1 Bank Activated–Precharged)	IDD0	(VDD = 1.575 V and 1.283 V, VREF = 0.50 × VDD, VIH = VREF + 0.16 V, VIL = VREF − 0.16 V)	—	375	mA
Operating Current (1 Bank Activated–Read–Precharged)	IDD1		—	650	mA
Precharge Standby Current	IDD2N		—	225	mA
Precharge Power-Down Current (Slow Exit Mode)	IDD2P0		—	90	mA
Precharge Power-Down Current (Fast Exit Mode)	IDD2P1		—	150	mA
Precharge Static Standby Current	IDD2Q		—	225	mA
Activation Standby Current	IDD3N		—	315	mA
Activation Power-Down Current	IDD3P		—	215	mA
Burst Read Operating Current	IDD4R		—	1000	mA
Burst Write Operating Current	IDD4W		—	1100	mA
Burst Auto-Refresh Current	IDD5B		—	1400	mA
Self-Refresh Current	IDD6		—	110	mA
Bank Interleaved Read Operating Current	IDD7		—	2000	mA

shows the criteria requirements for the performance parameters and functional standards of the 256 M × 72-bit DDR3 SDRAM under the specified test conditions. The results of the functional and performance tests before and after each limit test of electrical stress, thermal stress, and wet heat stress need to be within the specified range to be considered qualified.

3.3. Research on the Evaluation Method of the Electrical Stress Limit Capacity of 3D-Packaged Memory

In the research on the evaluation method of the electrical stress limit capacity of 3D-packaged memory, power supply voltage offset limit tests and input clock frequency limit tests were carried out.

For the power supply voltage offset limit test, a 256 M × 72-bit DDR3 SDRAM was installed on an ATE 93000 tester using a dedicated test board, and step-up and step-down voltage limit tests were sequentially performed. During the step-up test, starting from the nominal voltage of 1.5 V with 0.05 V increments, each voltage level was maintained for 1 min for functional testing. The product’s functions and performance parameters remained within the qualified range up to 1.575 V, but read/write functions became abnormal at 2.4 V. During the step-down test, starting from 1.5 V with −0.05 V decrements and similarly maintaining each level for 1 min of functional testing, the product operated normally down to 1.425 V, while read/write functions became abnormal at 1.1 V. From this, the operational limits were determined to be 1.2 V~+2.3 V, and the destruction limits were 1.1 V~+2.4 V.

In the input clock frequency limit test, conducted in the same manner as the power supply voltage offset test using the dedicated test board on the ATE 93000 tester, the frequency was increased from the nominal 667 MHz in 25 MHz increments. When the input clock frequency of Sample #2 reached 692 MHz, the read/write functions of the product became abnormal. Thus, the operational frequency limit was determined to be 667 MHz, and the destruction limit was 695 MHz.

3.3.1. Power Supply Voltage Offset Limit Test for 3D-Packaged Memory

The 256 M × 72-bit DDR3 SDRAM was installed on an ATE 93000 tester via a dedicated test board developed for conducting the power supply voltage offset limit test, as shown in Figure 29.

The power supply voltage offset limit test for the 256 M × 72-bit DDR3 SDRAM was conducted in sequence with a step-up voltage limit test followed by a step-down voltage limit test.

(1) Step-Up Voltage Limit Test: The initial excitation voltage was set to 1.5 V (nominal voltage) with a step increment of 0.05 V. After each step, functional testing was performed for 1 min. The test was terminated when functional abnormalities occurred (since certain performance parameters will change with the voltage and have little practical significance, we are only concerned with whether there are functional abnormalities). The sample was stepped up from the starting voltage of 1.5 V to the upper limit of the design specification, which is 1.575 V. The functions and performance parameters of the product were all within the acceptable range of the qualification criteria. Continuing to increase the voltage in increments of 0.05 V up to 2.4 V, the read and write functions of the product became abnormal.

(2) Step-Down Voltage Limit Test: The initial excitation voltage was set to 1.5 V (nominal voltage) with a step decrement of −0.05 V. After each step, functional testing was performed for 1 min, and the test was terminated when functional abnormalities occurred (since certain performance parameters will change with the voltage and have little practical significance, we are only concerned with whether there are functional abnormalities). The sample was stepped down from the starting voltage of 1.5 V to the lower limit of the design specification, which is 1.425 V. The functions and performance parameters of the product were all within the acceptable range of the qualification criteria. Continuing to step down the voltage in increments of 0.05 V to 1.1 V, the read and write functions of the product became abnormal.

3.3.2. Input Clock Frequency Limit Test for 3D-Packaged Memory

The input frequency limit test for the 256 M × 72-bit DDR3 SDRAM is the same as the power supply voltage offset limit test, both of which are carried out by installing it on an ATE 93000 testing machine via a dedicated test board developed for this purpose.

The initial input clock frequency is set to 667 MHz (with a nominal VDD = 1.5 V), and it is increased in increments of 25 MHz. The test will be terminated once functional abnormalities occur. When the input clock frequency of the sample is stepped up to 692 MHz, the read and write functions of the product become abnormal. The typical test waveform is shown in Figure 30.

3.3.3. Electrostatic Discharge Sensitivity Limit Test for 3D-Packaged Memory

The electrostatic discharge (ESD) sensitivity test of integrated circuits is conducted to evaluate the maximum voltage and circuit that the integrated circuits can withstand during electrostatic discharge loads, so as to ensure their reliability in actual use [17]. There are mainly two types of methods for ESD sensitivity tests: the Human Body Model (HBM) and the Machine Model (MM). For integrated circuits applied in high-reliability fields, the tests are mainly carried out using the Human Body Model in accordance with MIL-STD-883 Method 3015.

Electrostatic Discharge Sensitivity Test Procedure

The product under test shall be tested with three positive and three negative pulses for each combination of terminals, as shown in

Table 5. Combinations of test terminals.

Combination No.	Terminal A Connect Each Terminal to Terminal A in Sequence While Leaving Others Floating	Terminal B All Terminals of the Same Name Are Commonly Connected to Terminal B
1	All terminals except Vps1	All Vps1 terminals
2	All input and output terminals	All other input and output terminals

. There should be an interval of at least 1 s between the pulses. If the product fails, the test shall be repeated at the next lower voltage level. If the product does not fail, record the determined failure threshold and the highest voltage level passed, and classify the product according to

Table 6. ESD failure threshold classification for devices.

Level	Voltage Range
Level 0	<250 V
Level 1A	250 V~499 V
Level 1B	500 V~999 V
Level 1C	1000 V~1999 V
Level 2	2000 V~3999 V
Level 3A	4000 V~7999 V
Level 3B	≥8000 V

.

The combination methods of the test terminals are as follows: Connect the ground terminal of the device to Terminal B, and connect each of the other terminals to Terminal A in sequence. All terminals other than the terminal being tested and the ground terminal should be open-circuited. Connect each group of all terminals named as power supply terminals (such as Vss1 or Vss2 or Vss3 or Vcc1 or Vcc2) to Terminal B in sequence, and connect each of the other terminals to Terminal A in sequence. All terminals other than the terminal being tested and the power supply terminal (group) should be open-circuited. Connect each input or output terminal to Terminal A in sequence, and connect the combination of all the remaining input and output terminals to Terminal B. All other terminals should be open-circuited except for the input or output terminal being tested and the combination of the remaining input and output terminals.

Construction of Electrostatic Discharge Sensitivity Test Platform and PCB Design

The ESD limit test for the 256 M × 72-bit DDR3 SDRAM needs to be carried out after connecting it to the MK4 multi-pin electrostatic discharge sensitivity tester through a dedicated adapter PCB. The interface shape of the MK4 multi-pin electrostatic discharge sensitivity tester is shown in Figure 31. The 3D-packaged memory has 199 pins. Therefore, a dedicated test PCB is designed according to the size requirements of the 256PIN interface of the testing machine. The specific size requirements are shown in Figure 32.

The Altium Designer software is used to design and manufacture the dedicated PCB for the ESD test of the 3D-packaged memory. Firstly, draw the schematic diagram according to the internal electrical principle of the 256 M × 72-bit DDR3 SDRAM, and check the circuit connection and signal integrity. Then, based on the size information of the 256PIN interface of the MK4 multi-pin electrostatic discharge tester, design the size and shape of the dedicated adapter PCB. Considering the complexity of the circuit and the cost, set the PCB as a double-layer board with a thickness of 1.5 mm. Place the 256 M × 72-bit DDR3 SDRAM at an appropriate position on the PCB, configure the rules such as the width and spacing of the traces, and draw the signal lines, power lines, and ground lines. Finally, configure the combined connection between the test socket and the PCB to form the PCB processing layout. The design process is shown in Figure 33 and Figure 34.

After the dedicated adapter PCB is manufactured, it is installed on the MK4 testing machine. The physical object is shown in Figure 35. Place the device under test and conduct an electrical continuity test to ensure that there are no open circuits or short circuits in all the traces and solder joints. At the same time, verify the integrity of the power supply voltage, as shown in Figure 36.

3.4. Electrical Durability Limit Test for 3D-Packaged Memory

3.4.1. Principle of the Electrical Durability Test

The electrical durability test of integrated circuits is to verify the quality and reliability of products during use by simulating the electrical stress conditions in the actual working environment. Electrical durability tests usually include dynamic burn-in tests, static burn-in tests, and steady-state life tests.

Among them, the dynamic burn-in test applies the maximum rated operating conditions and uses a dynamic excitation method to simulate the actual application of the product, so that the tested integrated circuit is under the maximum rated operating conditions to evaluate the long-term reliability of the product under actual working conditions. By activating the dynamic signal of the integrated circuit and applying it to the circuit through the input terminal, the electrical load flows through the internal lines of the circuit. This fully examines the electrical characteristics of various nodes, dielectrics, and conductive paths inside the device, and can more effectively stimulate latent fatal failure defects. The static burn-in test only creates the tested integrated circuit in a static power-on state without applying a working load. The input terminal is connected to the power supply or ground, placing the input transistor in a forward-biased or reverse-biased state, and the output terminal is in a floating state for assessment. This method is likely to trigger failures related to impurity contamination. By maintaining a stable bias voltage at a high temperature, the migration of impurities to the surface of the device is accelerated. Since only the outer edge of the substrate can supply the voltage, and the inside does not experience the electrical load, it can accelerate the exposure of potential defects, such as channel defects, parameter drift, and defects in the dielectric insulation layer. The steady-state life test is to verify the quality or reliability of the device that withstands the specified conditions throughout the operating time. In the life test, usually, no voltage deviation is applied at the power supply terminal, only the rated operating voltage is loaded. A dynamic excitation signal is connected through a resistor at the input terminal, and the life of the maximum load still needs to be verified at the output terminal. The most prominent feature of the life test is its long test cycle, which usually requires a load of 1000 h under the specified temperature conditions. Compared with the dynamic burn-in test, the steady-state life test has the same test principle, a longer test time, and a lower test voltage. Therefore, the life test can be regarded as a dynamic burn-in test with a reduced bias voltage and an extended time.

The burn-in test is mainly based on the classical reaction rate theory. The internal physical and chemical reactions are accelerated with the increase in electrical, thermal, and other stresses. The most commonly used is the Arrhenius model related to thermal stress. In the burn-in test acceleration model, two parameters, the activation energy (Ea) and the acceleration factor (A), are mainly of concern. The activation energy refers to the energy required to stimulate the potential defects of the device into failures; that is, the energy threshold that must be reached when a failure occurs [18,19]. The acceleration factor is defined as the time ratio for the device to reach the same failure rate under the burn-in stress and the normal stress [19]. In the burn-in test of integrated circuits, the temperature stress acceleration factor (A_T) and the electrical stress acceleration factor (A_V) are often used. The greater the stress applied in the test, the larger the acceleration factor, and the faster the product fails.

In the static burn-in test, the voltage is generally the standard voltage of the device. Therefore, the voltage acceleration stress A_V is 1, and only the temperature acceleration factor AT is considered. Thus, we can obtain

$$t\left(T\right)=t_{AT}·e^{E_a/K(T_1^{-1}-T_2^{-1})}$$

(1)

where t(T) is the operating life, in hours; T₁ and T₂ are the chip temperatures under normal operation and burn-in conditions, respectively.

For the dynamic burn-in test, both electrical stress and thermal stress factors need to be considered simultaneously. Thus, we can obtain

$$A=e_K^{E_a\left(T_U^{-1}-T_A^{-1}\right)+V_{EF}(V_A-V_U)}$$

(2)

$$t\left(T\right)=t_A·e^{{\displaystyle \frac{E_a}{K\left(T_1^{-1}-T_2^{-1}\right)}}+V_{EF}(V_A-V_U)}$$

(3)

where V_EF is a constant; V_A and V_U are the normal operating voltages of the bias voltage.

3.4.2. Electrical Durability Test Procedure

The electrical durability test for integrated circuits begins with determining the test temperature and duration, followed by intermediate and final testing to verify the quality and reliability of devices under specified conditions throughout their operational lifespan.

Devices under test shall be subjected to the test duration and temperature specified in MIL-STD-883 Method 1005 or Method 1015 (as shown in

Table 7. Time–temperature corresponding relationship of electrical durability test.

Minimum Temperature TA (°C)	Shortest Time (h)
	S Grade	B Grade	H Grade	K Grade
100	-	-	7500	7500
105	-	-	4500	4500
110	-	-	3000	3000
115	-	-	2000	2000
120	-	-	1500	1500
125	1000	1000	1000	1000
130	900	704	704	-
135	800	496	496	-
140	700	352	352	-
145	600	256	256	-
150	500	184	184	-
175	-	40	-	-
180	-	32	-	-
185	-	31	-	-
≥190	-	30	-	-

Note: Grade S represents aerospace-grade integrated circuits, Grade B represents military-grade integrated circuits, Grade K represents aerospace-grade hybrid integrated circuits, and Grade H represents military-grade hybrid integrated circuits.

). They shall be mounted using leads, bolts, or the enclosure in their normal structural configuration, ensuring that the contact point temperature does not fall below the specified ambient temperature.

Select the corresponding test conditions according to different device types and requirements. The specific details are shown in

Table 8. Test conditions for electrical durability test.

Test Symbol	Test Conditions	Scope of Application
A	Steady-State, Reverse Bias Test	All kinds of linear circuits and digital circuits. Apply the specified reverse bias voltage to as many junctions as possible.
B	Steady-State, Forward Bias Test	All digital circuits and some linear circuits, for as many junctions as possible.
C	Steady-state, Power and Reverse Bias Test	Applicable to various digital circuits and some linear circuits whose input terminals can be reverse-biased and output terminals can be biased at the maximum power consumption state.
D	Parallel Excitation Test	Applicable to all kinds of circuits. During the test, all circuits must be applied with appropriate excitation signals to simulate the actual application as much as possible. Use the maximum external load, and the excitation frequency should not be lower than 50 Hz.
E	Ring Oscillator Test	Connect the output terminal of the last circuit to the input terminal of the first circuit. This series connection will generate free oscillation, and its frequency is determined by the transmission delay of each circuit and the relevant wiring, and the frequency ≥ 50 Hz. In the case where the circuit will cause inversion, an odd number of circuits should be used, and each circuit in the loop should be loaded with the rated maximum load. This condition provides an opportunity for continuous monitoring of fatal failures (i.e., loop blocking), so it cannot replace the intermediate test.
F	Temperature Acceleration Test	The device is biased under an ambient temperature (175 °C to 300 °C) far exceeding its highest rated temperature. At a higher temperature, the device usually cannot work normally. Therefore, special attention must be paid to selecting the bias circuit and conditions to ensure that the important current parts are properly biased and that no destructive overstress is generated on other parts of the circuit.

.

The steady-state bias test circuit, parallel excitation test circuit, and ring oscillator circuit are shown in Figure 37, Figure 38 and Figure 39.

The tests after the electrical durability test are divided into two categories: tests with a test temperature ≤ 150 °C and tests with a test temperature ≥ 175 °C.

(1)

Tests with a test temperature ≤ 150 °C

All specified intermediate and final tests shall be completed within 96 h after the device is removed from the specified test conditions (i.e., the heating condition or the bias is removed). If the tests cannot be completed within 96 h, the device shall be subjected to at least another 24 h of life test before the intermediate or final tests. If the specified test duration exceeds 1000 h, the intermediate test points shall be at 1000 h and 2000 h, and every 1000 h thereafter. The intermediate tests mainly cover the specified parameters and conditions, which shall include the main functional characteristics sufficient to reveal catastrophic failures and degradation failures. The device shall be cooled to a temperature that differs by no more than 10 °C from the temperature at which the device’s power consumption stabilizes at room temperature before the bias is removed.

(2)

Tests with a test temperature ≥ 175 °C

All specified intermediate and final tests shall be completed within 24 h after the device is removed from the specified test conditions (i.e., the heating condition or the bias is removed). If the tests cannot be completed within 24 h, the steady-state life test shall be repeated under the same test conditions, temperature, and duration. Before removing the bias, the device shall be cooled to a temperature that differs by no more than 10 °C from the temperature at which the device’s power consumption stabilizes at room temperature. Interrupting the bias for no more than 1 min to move the device to a cooling position shall not be considered as removing the bias. All specified electrical tests at 25 °C shall be completed before the device is reheated.

3.4.3. Construction of the Electrical Durability Test Platform and PCB Design

The electrical durability test shall be conducted in accordance with MIL-STD-883 Method 1015. The test circuit diagram is shown in Figure 40.

The test conditions in Figure 40 are as follows: The power supply voltage VDD = 1.575 V, the reference voltages (V_REF, V_REFCA, V_REFDQ) and the terminal voltage (V_TT) are V_DD × 0.5, and the frequency of the differential clock (CK, CK#) is 300 MHz. The controller FPGA is interconnected with the 256 M × 72-bit DDR3 SDRAM: The data DQ32~DQ63 are assigned to FPGA BANK32; the data DQ0-31 are assigned to BANK34; the data CB0~7 are assigned to BANK33; the address and control signals are assigned to BANK33. The power supply voltage V_DD of FPGA BANK32, BANK33, and BANK34 is 1.575 V; the reference voltage V_REF of FPGA BANK32, BANK33, and BANK34 is 0.5 × V_DD; the power supply voltage V_DD of the 256 M × 72-bit DDR3 SDRAM is 1.575 V; the reference voltages of the 256 M × 72-bit DDR3 SDRAM are V_REFDQ = 0.5 × V_DD and V_REFCA = 0.5 × V_DD; the V_TT voltage of the 256 M × 72-bit DDR3 SDRAM is V_TT = 0.5 × V_DD.

The FPGA invokes the DDR3 controller to drive the 256 M × 72-bit DDR3 SDRAM, and the operating frequency is 300 MHz. The controller conducts read–write verification for writing data 0 in the entire space of the 256 M × 72-bit DDR3 SDRAM; read–write verification for writing data 1 in the entire space; read–write verification for writing data 0x55 and 0xaa in the entire space; read–write verification for writing data 0xaa and 0x55 in the entire space; read–write verification for writing diagonal data in the entire space; and read–write verification for writing random numbers in the entire space. The diagonal pattern is as follows: when the column address is equal to the row address, write the data 0xFFFF, and write 0x0000 for other addresses; or when the column address is equal to the row address, write the data 0x0000, and write 0xFFFF for other addresses.

According to the electrical durability test conditions, the Altium Designer software is used to design and manufacture the dedicated PCB for the electrical durability limit test of the 3D-packaged memory. Draw the schematic diagram according to the internal electrical principle of the 256 M × 72-bit DDR3 SDRAM and the circuit to be configured (the typical schematic diagrams are shown in Figure 41 and Figure 42), clarify the connection principle among various components, and check the circuit connection and signal integrity. The dedicated PCB for the electrical durability test after manufacturing and processing is shown in Figure 43.

4. Test Results

4.1. Test Results of the Power Supply Voltage Deviation Limit Test

According to the results of the step-up limit test and the step-down limit test, the operating limits and failure limits of the encapsulator of the 3D-packaged memory are shown in

Table 9. Test results of the voltage deviation limit test.

Sample Number	Absolute Maximum Rated Value Specified in the Detailed Specification	Operating Limit	Failure Limit
1#	1.425 V~1.575 V	1.2 V~2.3 V	1.1 V~2.4 V

. The test waveforms when the functions fail at the power supply voltages of 1.1 V and 2.4 V, and the test waveforms when the functions are normal at the power supply voltages of 1.2 V and 2.3 V are shown in Figure 44 and Figure 45.

4.2. Test Results of the Input Clock Frequency Limit Test

The operating limit and failure limit of the input clock frequency of the product are shown in

Table 10. Test results of the input clock frequency limit test.

Sample Number	Maximum Rated Value Specified in the Detailed Specification	Operating Limit	Failure Limit
2#	667 MHz	667 MHz	695 MHz

.

4.3. Analysis of the Test Results of the Electrostatic Discharge Sensitivity Limit Test

Before carrying out the ESD test using the MK4 multi-pin electrostatic discharge tester, the pin combination of the worst waveform is used to verify the current waveform to ensure that the current waveform of each gear meets the requirements of Figure 46, so as to ensure the normal operation of the simulator.

In accordance with MIL-STD-883 Method 3015, an HBM electrostatic discharge sensitivity limit test was performed on each lead combination of the 256 M × 72-bit DDR3 SDRAM (input/output leads to power and ground, between leads, power and ground, etc.) using three positive and three negative pulses with a 1 s interval between pulses. The I-V characteristic curves of the leads were scanned before and after each ESD test, as shown in Figure 47 and Figure 48. Finally, the determined failure threshold and the highest voltage level passed were recorded.

The lead arrangement and lead description of the 256 M × 72-bit DDR3 SDRAM are shown in Figure 49 and

Table 11. Lead description.

Pin Name	Type	Function
A0~A14	Input	15-bit address input
A15/RFU	Input	A15/Reserved for future use pin
BA0~BA2	Input	3-bit Bank address input
A10/AP	Input	A10/Auto Precharge
A12/BC#	Input	A12/Burst Chop
CS#	Input	Chip Select Enable
RESET#	Input	Reset
CAS#	Input	CAS Command Input
RAS#	Input	RAS Command Input
WE#	Input	WE# Command Input
ODT	Input	On-Die Termination
CK,CK#	Input	Differential Clock Input
CKE	Input	Clock Enable Input
DM0~DM9	Input	Data Mask
DQS0~DQS9, DQS0#~DQS9#	Input/Output	Data Strobe Input/Output
DQ0~DQ64	Input/Output	Data Input/Output
CB0~CB7	Input/Output	ECC Data Input/Output
VDD	Supply	Power Supply Voltage
GND	Supply	Ground
VREFDQ	Supply	Data Reference Voltage (0.5 × VDD)
VREFCA	Supply	Control, Command, and Address Reference Voltage (0.5 × VDD)
VTT	Supply	Termination Voltage (0.5 × VDD)
NC		Empty Lead

. Then, each lead combination is compiled on the MK4 testing machine platform, as shown in Figure 50.

Set the test voltage of the HBM to 200 V with a step of 100 V. After each step, scan the I-V characteristic curve of the lead combinations of the 256 M × 72-bit DDR3 SDRAM. When the I-V characteristic curve of the lead combination changes, conduct functional and performance tests on the ATE 93000 test system. If the performance parameters exceed the tolerance and the functions are abnormal, the electrostatic discharge sensitivity limit test is considered completed. When the test voltage of Sample #3 reaches 4000 V, the I-V characteristic curves of Lead #13 and Lead #27 change, as shown in Figure 51 and Figure 52. Conduct functional and performance tests through the ATE 93000 test system. The read–write function of Lead DQ6 of the device is abnormal and there is a leakage current. The operating limit and failure limit of the electrostatic discharge sensitivity of the product under the HBM are shown in

Table 12. Test results of the electrostatic discharge sensitivity limit test.

Sample Number	Rated Value Specified in the Detailed Specification	Operating Limit	Failure Limit
#3	2000 V	3900 V	4000 V

.

4.4. Analysis of the Test Results of the Electrical Durability Limit Test

The 256 M × 72-bit DDR3 SDRAM is installed inside a high-temperature test chamber through the specially developed test board for the electrical durability test, and appropriate excitation signals are applied through the circuit to make the product operate dynamically, as shown in Figure 53. When installing and debugging the burn-in test board, decoupling and high and low RC filtering are required. At the same time, current limiting measures should be taken for the DC power supply and the signal source.

The initial test settings were as follows: test temperature of 125 °C, test duration of 1000 h, excitation voltage of 1.5 V, and frequency of 300 MHz. During the test, if any functional abnormality occurred in the 256 M × 72-bit DDR3 SDRAM, the test would be immediately stopped, and the failure time of the product would be calculated. If the product’s functionality and performance remained normal after 1000 h, the test would continue in 1000 h increments, with functional and performance tests conducted every 1000 h. No significant anomalies were observed in the three tested 256 M × 72-bit DDR3 SDRAM devices during the 1000 h test cycle. The test results of the functional and performance parameters are shown in

Table 13. Test results of functional and performance parameters (1000 h).

Serial Number	Parameter Name	Parameter Symbol	4#	5#	6#	Unit
			Measured Value
1	Operating Current (1 Bank Activated–Precharged)	IDD0	162	165	163	mA
2	Operating Current (1 Bank Activated–Read–Precharged)	IDD1	249	252	250	mA
3	Precharge Standby Current	IDD2N	66	68	65	mA
4	Precharge Power-down Current (Slow Exit Mode)	IDD2P0	16.3	16.5	15.9	mA
5	Precharge Power-down Current (Fast Exit Mode)	IDD2P1	16.2	16.4	16.0	mA
6	Precharge Static Standby Current	IDD2Q	87	88	86	mA
7	Activated Standby Current	IDD3N	50	51.7	49	mA
8	Activated Power-down Current	IDD3P	16.3	16.5	16	mA
9	Burst Read Operating Current	IDD4R	353	354	350	mA
10	Burst Write Operating Current	IDD4W	355	355	345	mA
11	Burst Auto-refresh Current	IDD5B	393	401	397	mA
12	Self-Refresh Current	IDD6	78	88	81	mA
13	Bank Interleaved Read Operating Current	IDD7	545	556	554	mA
14	Input Leakage Current	ILIL	−0.003	−0.002	−0.002	μA
		ILIH	0.009	0.01	0.009	μA
15	Output Leakage Current	ILOL	−0.003	−0.002	−0.002	μA
		ILOH	0.009	0.01	0.009	μA
16	DQS-DQ Delay	tDQSQ	26	35	23	ps
17	Function		Qualified	Qualified	Qualified	/

.

The product continued the test for 2000 h. No significant abnormalities were found during the 2000 h test cycle, and the functional and performance parameters did not change much compared with those in the 1000 h test cycle. The test results are shown in

Table 14. Test results of functional and performance parameters (2000 h).

Serial Number	Parameter Name	Parameter Symbol	4#	5#	6#	Unit
			Measured Value
1	Operating Current (1 Bank Activated–Precharged)	IDD0	165	163	162	mA
2	Operating Current (1 Bank Activated–Read–Precharged)	IDD1	253	251	250	mA
3	Precharge Standby Current	IDD2N	68	68	66	mA
4	Precharge Power-Down Current (Slow Exit Mode)	IDD2P0	16.5	16.8	16.3	mA
5	Precharge Power-down Current (Fast Exit Mode)	IDD2P1	16.4	16.4	16.2	mA
6	Precharge Static Standby Current	IDD2Q	88	88	87	mA
7	Activated Standby Current	IDD3N	51	51.7	50	mA
8	Activated Power-Down Current	IDD3P	16.5	16.9	16.2	mA
9	Burst Read Operating Current	IDD4R	354	349	354	mA
10	Burst Write Operating Current	IDD4W	347	350	353	mA
11	Burst Auto-Refresh Current	IDD5B	402	399	393	mA
12	Self-Refresh Current	IDD6	83	79	78	mA
13	Bank Interleaved Read Operating Current	IDD7	555	551	545	mA
14	Input Leakage Current	ILIL ILIH	−0.002 0.009	−0.004 0.009	−0.003 0.009	μA μA
15	Output Leakage Current	ILOL ILOH	−0.002 0.009	−0.004 0.009	−0.003 0.009	μA μA
16	DQS-DQ Delay	tDQSQ	45	21	37	ps
17	Function		Qualified	Qualified	Qualified	/

.

Taking into account the test cycle and cost comprehensively, the 2000 h test cycle has far exceeded the 1000 h test requirement specified in the product’s detailed specification. Therefore, the test ends when the 2000 h timing is reached. According to the test data of the 256 M × 72-bit DDR3 SDRAM working at a high temperature of 125 °C for 2000 h (only the rated operating voltage is used, and no bias voltage is applied), the average lifespan of the product at the normal operating temperature is estimated based on the Arrhenius model. By substituting relevant parameters such as the actual rated operating temperature of the product at 50 °C, the test temperature at 125 °C, the test time of 2000 h, and the activation energy of 0.7 (the empirical value for silicon-based integrated circuits) into Equations (1) and (2), the acceleration factor A is obtained as 113.86, and the average lifespan at the normal operating temperature is 227,714 h, which is approximately 25 years. The results of the operating limit of the electrical durability test of the product are shown in

Table 15. Test results of the electrical durability limit test.

Sample Number	Electrical Durability Test Time Specified in the Detailed Specification	Operating Limit (Constant Stress with Timed End)
#4~#6	1000 h	2000 h

.

5. Conclusions

This paper conducts research on the evaluation of the electrical stress limit capability of 3D-packaged memory, covering aspects such as test design, test methods, and test results, providing a comprehensive theoretical and practical reference for this field.

1. Test Design: The selection criterion of taking sensitive stress as the test stress is determined. It is clear that the upper and lower limits of the stress need to take into account both the product failure mechanism and the excitation efficiency. The step size is set according to the product specification limits to ensure that the stress loading can stably excite defects. For 3D-packaged memory, test profiles such as power supply voltage, input clock frequency, electrostatic discharge sensitivity, and electrical durability are designed, and the starting values, step values, and holding times of each test are specified in detail.

2. Test Methods: An electrical stress testing device composed of an ATE testing machine and an electrostatic discharge sensitivity tester is constructed. The ATE testing machine is used for functional and performance verification and some limit tests, and the electrostatic discharge sensitivity tester is used to evaluate the electrostatic discharge sensitivity of the product. The common test methods for integrated circuits are described, and the functional, DC, and AC parameter tests for 3D-packaged memory (digital integrated circuits) are explained. A functional and performance test platform is built, including PCB design, initialization settings, parameter and function tests, and clear criterion requirements are formulated.

3. Test Results: Through the power supply voltage deviation limit test, it is concluded that the operating limit of the product is −1.2 V~+2.3 V, and the failure limit is −1.1 V~+2.4 V; the input clock frequency limit test determines that the operating limit is 667 MHz, and the failure limit is 695 MHz; the electrostatic discharge sensitivity limit test shows that under the HBM, the operating limit is 3900 V, and the failure limit is 4000 V; in the electrical durability limit test under the conditions of 125 °C and 2000 h, according to the Arrhenius model, the average lifespan at the normal operating temperature is estimated to be about 25 years.

The theoretical basis for the evaluation of the electrical stress limit capability of 3D-packaged memory is clarified. Multiple limit test platforms are constructed, the test conditions are verified and optimized, the principles of parameter selection are summarized, and the verification of the electrical stress limit capability is completed. This research provides a critical foundation for enhancing reliability in the design and manufacturing of 3D-packaged memory, enabling the optimization of product performance and improving the overall reliability of electronic systems. This paper focuses on the research of evaluating the electrical stress limit capability of 3D-packaged memory, covering aspects such as test design, testing methods, and test results, providing comprehensive theoretical and practical references for this field.