Low-Power IGZO TFTs with Improved Positive Bias Stability via Atomic Layer Deposition-Based H₂O Treatment

Abstract

In this work, a plasma-free atomic layer deposition (ALD)-based H₂O post-treatment method is proposed to precisely modulate hydrogen-related (H-related) traps in indium gallium zinc oxide (IGZO) thin-film transistors (TFTs) by the number of H₂O treatment cycles. Under the optimized condition, the scaled device with a channel length of 70 nm exhibits a near-ideal subthreshold swing of 62.9 mV/dec, a low threshold voltage (V_TH) of 0.18 V, an acceptable static leakage current, and a high drive current of 3.29 μA/μm at an overdrive voltage and drain voltage of 1 V. In addition, the treated device shows only a 13 mV of V_TH shift after 1000 s positive bias stress (PBS), corresponding to a 94% improvement compared with the pristine device. These improvements are attributed to the introduction of two different polarities of hydrogen-related traps after H₂O treatment. Furthermore, the influence of H-related traps on bias stability and the mechanisms responsible for V_TH shift are systematically clarified. These results establish that an optimized hydrogen incorporation window that maximizes the beneficial effects while balancing severe hydrogen-induced degradation caused by excessive hydrogen incorporation. Consequently, scaled IGZO TFTs with fast switching, low-power operation, high performance, and high reliability can be achieved, providing strong potential for back-end-of-line (BEOL)-compatible electronics and monolithic three-dimensional integrated applications.

1. Introduction

In recent years, the rapid development of emerging technologies, such as artificial intelligence, high-performance computing, the Internet of Things, and edge computing, has significantly increased the demand for large-scale data processing and highly efficient energy conversion in modern electronic systems [1,2]. Low power consumption has become one of the most critical requirements for next-generation electronic devices. The total power consumption comprises dynamic and static components. The dynamic power consumption (P_Dynamic) can be expressed as:

P_Dynamic = C_Total·V_DD²·f

(1)

where C_Total is the total load capacitance, V_DD is the supply voltage, and f is the operation frequency. In contrast, the static power consumption (P_Static) can be expressed as:

P_Static = I_OFF·V_DD

(2)

where I_OFF represents the static leakage current. Equations (1) and (2) indicate that P_Dynamic is quadratically proportional to V_DD, while P_Static is linearly proportional to I_OFF, suggesting that reducing V_DD and I_OFF is one of the most effective approaches for achieving low-power operation [3]. In addition to low-power operation capability, device performance and long-term operational stability must also be maintained, particularly under aggressive device scaling and the development of monolithic three-dimensional (M3D) integration [4,5].

Amorphous oxide semiconductors (AOSs) have emerged as promising candidates for next-generation electronic devices under these requirements, gradually replacing conventional silicon-based semiconductors, such as amorphous hydrogenated silicon and low-temperature polycrystalline silicon, as well as organic semiconductors. This is attributed to their advantages, including high electron mobility (10~100 cm²/V·s), low leakage current (<10⁻¹⁴ A/μm), excellent large-area uniformity, and compatibility with low-temperature processing (<400 °C) [6,7]. Among them, indium gallium zinc oxide (IGZO) has become one of the most representative amorphous oxide semiconductor materials and has been widely applied in display panels. Furthermore, its applications have gradually expanded to logic devices, sensors, transparent and flexible electronics, neuromorphic computing, compute-in-memory architectures, and emerging memory devices, attracting significant attention for low-power, high-performance electronic systems [8,9,10,11].

However, as device dimensions continue to scale down, AOS thin-film transistors (TFTs) still face several critical challenges. To reduce overall system power consumption, devices are required to maintain high drive capability and fast switching characteristics under low operating voltages. Therefore, low threshold voltage (V_TH) and steep subthreshold swing (SS) have become essential requirements for low-power devices [12]. Under aggressive scaling, short-channel effects lead to V_TH roll-off, SS degradation, and increased OFF-state leakage current, thereby weakening the electrostatic control capability of the devices [13]. In addition, reliability issues under bias stress become increasingly severe. For enhancement-mode n-type IGZO TFTs, V_TH instability induced by positive bias stress (PBS) is particularly critical. These issues mainly originate from the intrinsic structural disorder of AOSs, which causes tail states and deep states to extend into the bandgap. These defect states, including oxygen vacancies, weakly bonded oxygen, and hydrogen-related (H-related) defects, are considered key factors influencing carrier transport behavior and device reliability [14,15,16]. Among these defects, H-related traps can act as shallow donors to provide free electrons and enhance carrier mobility, or passivate traps to form deep acceptors, thereby improving electrical characteristics and stability [17,18]. However, H-related traps exhibit high sensitivity and facile polarity conversion between H⁺ and H⁻ states [19]. Even a small amount of hydrogen incorporation can significantly alter the electrical properties of the devices [20,21,22]. Hydrogen may originate from oxidant precursors, forming gas annealing, or environmental moisture absorption, making it nearly unavoidable during practical fabrication processes. Consequently, previous studies have primarily focused on suppressing hydrogen incorporation [23,24,25].

Although hydrogen may induce detrimental effects, an appropriate amount of hydrogen incorporation into AOSs can still provide beneficial effects. Recent studies have demonstrated that crystallized structures [26], modulation of oxidant precursor flow during AOS deposition [27], deep ultraviolet irradiation [28], plasma treatment in a hydrogen environment [29], and thermal treatment in a moisture environment [30] can achieve high carrier mobility and long-term stability. However, these methods generally require additional thermal treatment to reform metal–oxygen bonding (M–O), resulting in higher thermal budgets and limited controllability of hydrogen incorporation. Moreover, plasma-based treatments may induce channel surface damage, and most of these approaches have been demonstrated only in large-scale devices, limiting their applicability to aggressively scaled devices. In addition, previous studies have mainly focused on the electrical improvements induced by hydrogen, while the formation of H-related traps with different polarities and their influence on bias stability remain insufficiently understood.

In this work, an atomic layer deposition (ALD)-based, plasma-free H₂O treatment is employed as a gentler, more controllable method for hydrogen incorporation in IGZO TFTs. By precisely modulating the H₂O pulse width at low temperatures, H-related species are gradually introduced into the channel, providing improved control over hydrogen-related defect concentration and enabling more precise tuning of electrical properties. This approach also mitigates plasma-induced channel surface damage and reduces thermal budget requirements. Moreover, the proposed process is designed to establish an optimized hydrogen incorporation window that balances the beneficial effects against the adverse effects associated with excessive hydrogen incorporation. Even under aggressive scaling conditions, the H₂O-treated devices exhibit improved carrier transport, enhanced electrostatic control, and low-power operation. Furthermore, the influence of H-related traps on bias stability is systematically investigated, and the mechanisms responsible for V_TH shift under bias stress are clarified. Two distinct polarities of H-related traps generated after H₂O treatment are further revealed by sub-gap density-of-states analysis, validating improvements in electrical characteristics and positive-bias stability. This work not only provides a more comprehensive understanding of the role of H-related defects in IGZO TFTs, but also evaluates the trade-off between performance enhancement and hydrogen-induced degradation. It demonstrates the potential of ALD-based H₂O treatment for low-power, highly reliable, and scaled AOS devices, providing a viable pathway toward future back-end-of-line (BEOL)-compatible electronics and M3D integrated applications.

2. Results and Discussion

2.1. Electrical Characteristics

Figure 1a shows the transfer characteristics of the short-channel devices as a function of H₂O treatment cycles. The pristine device exhibits typical enhancement-mode switching behavior. As the number of treatment cycles increases to 24 cycles, the device gradually becomes fully conductive and loses its switching capability. The extracted key electrical parameters from the transfer characteristics are summarized in Figure 1b–d to provide a more comprehensive evaluation of the effects of H₂O treatment. As the H₂O treatment cycles increase, the ON-state current (I_ON) gradually increases, while the V_TH shifts continuously toward negative values. This behavior indicates that the H-related species introduced during H₂O post-treatment tend to act as donor-like defects, contributing electrons to the conduction band [17]. Under the optimized 18-cycle condition, the device exhibits an excellent I_ON of 3.29 μA/μm and an optimized V_TH of 0.18 V. Regarding the switching characteristics, the SS remains within the ideal range of approximately 60~70 mV/dec after 6–18 treatment cycles, reaching a near-ideal value of 62.9 mV/dec at 18 cycles. Interestingly, the hysteresis continuously decreases with increasing treatment cycles, reaching 56.8 mV at 18 cycles, corresponding to nearly a 50% reduction compared with the pristine device. It is beneficial for maintaining low-power operation. The improvements in SS and hysteresis are likely attributed to the passivation of interface defects [18]. However, when the treatment condition increases to 24 cycles, the device transitions to depletion-mode operation, and its electrical characteristics rapidly deteriorate. In particular, the static leakage current increases significantly, while the on/off current ratio decreases markedly, indicating that excessive hydrogen incorporation inevitably introduces a trade-off between performance enhancement and hydrogen-induced degradation. This degradation suggests that excessive hydrogen incorporation leads to an excess of donor-like and acceptor-like defects [31].

Through the ALD-based H₂O post-treatment method, the amount of incorporated H-related species can be precisely controlled, allowing an optimized hydrogen incorporation window to be established at the 18-cycle condition. Under the optimized condition, the device achieves high I_ON, near-ideal SS, low hysteresis, acceptable static leakage current, and on/off current ratio, thereby achieving the best balance between enhanced electrical performance and hydrogen-induced degradation. Consequently, the device simultaneously exhibits fast switching, high performance, and low power, demonstrating that positive effects can still be achieved under moisture-related processing conditions.

To evaluate the improvements achieved under the optimized H₂O treatment condition, the electrical characteristics of both long-channel and short-channel devices are compared before and after treatment in Figure 2. The transfer characteristics shown in Figure 2a,b demonstrate that the treated devices exhibit near-ideal SS values of approximately 60 mV/dec, minimum leakage current of approximately 10⁻¹⁴ A/μm, V_TH approaching 0 V, and significantly enhanced I_ON and reduced hysteresis. Figure 2c presents the SS as a function of drain current. The average subthreshold swing (SS_avg) is defined as the average SS over the drain current range from 10⁻¹³ A/μm to 10⁻⁹ A/μm to evaluate switching behavior during the transition from the subthreshold to the ON-state. After H₂O treatment, all devices exhibit improved SS_avg values. Notably, the treated short-channel device achieves an SS_avg of 84.6 mV/dec and an I_ON of 3.29 μA/μm at V_OV = V_D = 1 V. The substantial reduction in SS is attributed to the effective suppression of sub-gap defects, suggesting that the target I_ON can be achieved at lower supply voltages without degrading minimum leakage current, even under aggressively scaled channel lengths. In addition, the approximately tenfold increase in I_ON is attributed to the reduced channel resistance under aggressively scaled channel lengths, which significantly decreases the total device resistance [32]. Figure 2d,e show the output characteristics of the devices. Under V_OV = 2.5 V and V_D = 2 V, the treated devices exhibit significantly enhanced drive current. In particular, the short- channel device demonstrates an approximately fourfold increase in drive current, reaching 22.3 μA/μm. Figure 2f shows μ_FE as a function of overdrive voltage for the long-channel device. According to the carrier transport theory of oxide semiconductors [33], the mobility affected by trap-limited conduction (TLC) can be expressed as:

μ_FE = μ_band·n_free/(n_free + n_trap)

(3)

where μ_band is the band mobility, and n_free and n_trap represent the concentrations of free and trapped carriers, respectively. After H₂O treatment, the introduced H-related species increase both donor-like and acceptor-like defects. Meanwhile, part of the incorporated hydrogen effectively passivates defects, thereby suppressing the influence of TLC and resulting in a steeper mobility transition behavior. However, the increase in donor-like defects is more dominant because hydrogen primarily acts as a donor, leading to an enhanced mobility of 9.5 cm²/V·s. The simultaneous achievement of steep SS, acceptable static leakage current, low-voltage operation, and high performance is not only observed in the long-channel device with L = 10 μm but also maintained in the aggressively scaled short-channel device with L = 70 nm. These results demonstrate the applicability of H₂O post-treatment under extreme channel-length scaling, suggesting its compatibility with the scaling trend of front-end-of-line silicon devices for realizing BEOL-compatible integration and enabling low-power, high-density M3D integration [34,35].

2.2. Analysis of Hydrogen-Related Defects

To investigate the concentration and distribution of H-related traps induced by the incorporation of H-related species into the channel after H₂O treatment, XPS and capacitance–voltage (C–V) measurements were performed. The O 1s spectra before and after treatment were deconvoluted into three peaks, as shown in Figure 3a. Before treatment, the peaks corresponding to hydroxyl bonding (O–H), oxygen vacancies (V_O), and M–O were located at 531.4 eV, 530.3 eV, and 529.7 eV, respectively [29]. After H₂O treatment, the proportion of O–H bonding increased from 29.3% to 37%, which is consistent with hydrogen incorporation into the IGZO film. The incorporated hydrogen may contribute to donor-like behavior by releasing free electrons, consistent with the observed enhancement in mobility and the negative V_TH shift. Interestingly, the concentrations of V_O and M–O bonding decreased after treatment, suggesting that hydrogen incorporation may also be associated with the passivation of oxygen-related defects. This interpretation is further supported by the C–V-derived DoS analysis. Figure 3b shows the voltage-dependent gate capacitance of devices with a channel size of 10 μm × 10 μm, measured at 1 kHz before and after treatment. The negative shift in the flat-band voltage (V_FB) after H₂O treatment is attributed to a hydrogen-induced reduction in the IGZO semiconductor work function and/or the introduction of positively charged hydrogen-related species.

To further clarify the existence and energy distribution of hydrogen-related defects with different polarities in the channel, the sub-gap density-of-states (DoS) distribution of IGZO was extracted from low-frequency (1 kHz) C–V measurements [36], as shown in Figure 3c. The DoS distribution was extracted according to:

$$\mathrm{D}\mathrm{o}\mathrm{S}={\displaystyle \frac{1}{{\mathrm{q}}^2\mathrm{A}{\mathrm{T}}_{\mathrm{C}\mathrm{H}}}}\mathrm{C}{(1-{\displaystyle \frac{\mathrm{C}}{{\mathrm{C}}_{\mathrm{O}\mathrm{X}}}})}^{-1}$$

(4)

where q is the elementary charge, A is the channel area, T_CH is the channel thickness, and C_OX is the maximum gate capacitance in the accumulation region. The energy level was obtained from:

$$\mathrm{E}=\mathrm{q}·{\int }_{{\mathrm{V}}_{\mathrm{F}\mathrm{B}}}^{{\mathrm{V}}_{\mathrm{G}}}(1-{\displaystyle \frac{\mathrm{C}}{{\mathrm{C}}_{\mathrm{O}\mathrm{X}}}})\mathrm{d}{\mathrm{V}}_{\mathrm{G}}$$

(5)

After H₂O treatment, two distinct Gaussian peaks were observed at E_C − 0.25 eV and E_C − 0.48 eV. These peaks are consistent with the energy distributions previously reported for hydrogen-related donor-like and acceptor-like defect states [37]. The corresponding reactions can be expressed as:

H⁰ + O²⁻ → [O²⁻H⁺]⁻ + e⁻

(6)

H⁰ + V_O²⁺ + e⁻ → [M^x+H⁻]^y+

(7)

respectively [18,38]. Reaction (6) is accompanied by the generation of free electrons through H⁺ incorporation. Enhanced carrier transport, increased drive current, and a negative V_TH shift are consequently observed. In reaction (7), effective passivation of oxygen V_O and dangling bonds is achieved through M–H bonding. Suppression of sub-gap defects and carrier trapping behavior is therefore obtained, leading to near-ideal SS and reduced hysteresis. These results confirm that H-related defects generated after H₂O treatment can simultaneously form two different polarities, thereby improving carrier transport and gate controllability. The influence of H-related defects with different polarities on the electrical characteristics after H₂O treatment has therefore been clearly clarified.

2.3. Bias Stability and V_TH Shift Mechanisms

The tolerable margin for electrical variation is significantly reduced, resulting in a much narrower operating window under low-power conditions. Consequently, reliability issues become further amplified, and even a slight V_TH shift may significantly affect normal circuit operation. Since the proposed H₂O-treated IGZO TFTs target BEOL-compatible logic applications, reliability is evaluated using conventional PBS and negative bias stress (NBS), which is directly relevant to logic operation. In contrast, negative-bias illumination-stress is primarily used for display and optoelectronic applications, where light illumination introduces additional photo-induced degradation mechanisms [39,40]. Therefore, the influence of bias instability and the evolution mechanisms of hydrogen-related traps on V_TH shift were further investigated under a fixed bias stress condition of V_OV = ±2 V and V_D = 0.1 V. Figure 4a,b show the dynamic evolution of the transfer characteristics of the long-channel and short-channel devices before and after H₂O treatment under PBS, respectively. In contrast, the corresponding evolution of ΔV_TH is summarized in Figure 4c. During PBS, three major mechanisms contribute to the V_TH shift within the IGZO bulk and at the interface between the channel and gate dielectric: (1) electron trapping and (2) donor-like trap generation, where the former induces a positive V_TH shift, and the latter contributes to a negative V_TH shift [41]. In addition, (3) electric-field-driven H⁺ species can drift from the HfO₂ layer into the channel, further inducing a negative V_TH shift [42]. In the pristine device, the V_TH instability is dominated by electron trapping, resulting in a positive ΔV_TH shift. However, after ALD-based H₂O treatment with an optimized amount of hydrogen incorporation and diffusion into the channel, electron trapping is effectively suppressed. This behavior is attributed to hydrogen preferentially bonding to oxygen to form H⁺ species, which then release electrons, thereby generating donor-like traps. The resulting negative V_TH shift effectively compensates for the positive V_TH shift induced by electron trapping, even though part of the incorporated hydrogen bonds with metal atoms to form H⁻ species and generates acceptor-like traps through electron capture. The detailed PBS mechanism is schematically illustrated in Figure 4d. The ΔV_TH shift was further modeled using the semi-classical power-law model for bias-temperature instability [43], and the experimental results show good agreement with the theoretical fit. Remarkably, the treated short-channel device exhibits a more balanced behavior than the long-channel device. After 1000 s of PBS, the treated short-channel device exhibits only a 13 mV ΔV_TH shift, corresponding to a 94% reduction compared with the pristine device. This improvement may originate from a more uniform distribution of hydrogen-induced donor-like traps, resulting from their diffusion toward the S/D regions in the short-channel device [44].

Although both short- and long-channel devices exhibit excellent PBS stability after H₂O treatment, a slight degradation in stability is observed under NBS. The NBS characteristics before and after treatment are shown in Figure 5a–c. For the treated short-channel device, the ΔV_TH shift slightly degrades from −0.71 V to −0.87 V after stress, while the long-channel device exhibits a similar trend. This behavior is consistent with the prediction of the semi-classical power-law model. Figure 5d illustrates the proposed mechanism of NBS-induced V_TH instability. During NBS, three primary mechanisms contribute to the V_TH shift: (1) electron detrapping and (2) suppression of acceptor-like traps, where the former induces a negative V_TH shift, and the latter contributes to a positive V_TH shift. In addition, (3) electric-field-driven H⁺ species drift from the channel and HfO₂ layer toward the gate electrode, further contributing to a positive V_TH shift [45]. In the pristine device, the V_TH instability is mainly dominated by electron detrapping, resulting in a severe negative ΔV_TH shift. After H₂O treatment, part of the incorporated hydrogen forms O–H bonds, thereby releasing free electrons. Meanwhile, hydrogen-related acceptor-like trap states are distributed near the valence band. Under NBS, the upward band bending reduces the energy between the Fermi level and the valence band, facilitating electron de-trapping from the previously occupied hydrogen-related acceptor-like trap states near the valence band. The released electrons increase the free-electron concentration in the channel, resulting in an additional negative ΔV_TH shift and consequently a slight degradation in NBS stability [20]. However, the optimized H₂O treatment provides the best balance between significantly improved PBS stability and only limited degradation in NBS stability, thereby establishing an optimized hydrogen incorporation window. Since enhancement-mode devices for low-power logic applications are typically operated under PBS conditions, the improvement in PBS stability is considered more critical for practical applications.

2.4. Benchmarking of Low-Power IGZO TFTs in Performance and Reliability

Figure 6a–c compare the key performance metrics of state-of-the-art IGZO-based devices reported in previous studies [8,9,12,14,15,16,23,29,46,47,48]. Under aggressively scaled conditions, the H₂O-treated BG IGZO TFT with L = 70 nm exhibits a near-ideal SS of 62.9 mV/dec, a low V_TH of 0.18 V, a high drive current of 22.3 μA/μm at V_OV = V_D = 1 V, and excellent PBS stability with a ΔV_TH shift of only 13 mV. These results demonstrate that H₂O treatment is an effective and highly competitive post-treatment approach, highlighting its potential for simultaneously achieving fast switching, low-power operation, high performance, and high reliability in scaled IGZO TFTs.

3. Materials and Methods

The fabrication process of the IGZO TFTs began with the deposition of a 100 nm-thick SiO₂ insulating layer on an 8-inch Silicon wafer by plasma-enhanced chemical vapor deposition. After defining the back-gate (BG) region by photolithography, 5 nm Ti and 35 nm Pd were deposited by electron-beam (e-beam) evaporation and subsequently patterned by a lift-off process to form the BG electrode. Subsequently, 10 nm HfO₂ and 5 nm IGZO were sequentially deposited by plasma-enhanced atomic layer deposition (PEALD) as the gate dielectric and channel layer, respectively. For HfO₂ deposition, TMAHf and H₂O were used as the precursor and oxidant, respectively. The IGZO channel with an In:Ga:Zn ratio of 1:1:1 was deposited using oxygen plasma as the oxidant. The deposition temperature was maintained at 250 °C throughout the PEALD process. The active region was then defined by photolithography followed by Ar plasma etching. After source/drain (S/D) pattern definition, 5 nm Ti and 35 nm Ni were deposited by e-beam evaporation and patterned by lift-off to form the S/D contacts. Photolithography, combined with dry and wet etching, was further used to expose the BG electrode. Finally, plasma-free H₂O post-treatment was performed in the PEALD chamber at 250 °C and 0.048 Torr. on BG IGZO TFTs with a channel width (W) of 1 μm, channel lengths (L) of 70 nm and 10 μm, and a gate-to-S/D overlap length of 0.5 μm on both S/D sides. The devices were treated with 6, 12, 18, and 24 H₂O cycles to introduce hydrogen-related species into the IGZO channel and improve the device performance. Each H₂O pulse had a pulse width of 0.06 s, followed by a 5 s N₂ purge. Devices with L = 70 nm and 10 μm were used as representative short-channel and long-channel devices, respectively. The detailed fabrication flow is illustrated in Figure 7. To minimize device-to-device variation, the same device was characterized before and after H₂O treatment. Figure 8a,b show cross-sectional transmission electron microscopy (TEM) images of the BG IGZO TFT, clearly demonstrating the 70 nm channel length and well-defined layer structure. Figure 8c presents the energy-dispersive spectroscopy (EDS) mapping results, confirming the elemental distributions of Ti, Pd, Ni, Hf, Ga, and Zn. The V_TH was extracted using the constant-current method with I_D = (W/L) × 100 pA for short-channel devices and I_D = (W/L) × 1 nA for long-channel devices to obtain an appropriate V_TH extraction criterion under aggressive scaling conditions. The field-effect mobility (μ_FE) was extracted from the maximum transconductance under low drain voltage (V_D) conditions according to:

μ_FE = L·g_m/(W·C_OX·V_D)

(8)

where C_OX and g_m represent the gate oxide capacitance per unit area and transconductance, respectively. The overdrive voltage (V_OV) was defined as V_OV = V_G − V_TH. For the X-ray photoelectron spectroscopy (XPS) samples, HfO₂ was intentionally omitted to avoid the overlap between the Hf 4f and In 3d binding energy peaks, which could interfere with the chemical bonding analysis [49].

4. Conclusions

In this work, an ALD-based plasma-free H₂O treatment method is proposed to effectively modulate H-related defects in IGZO thin-film TFTs through controllable hydrogen incorporation, and its applicability to aggressively scaled short-channel devices is successfully demonstrated. After optimization, the IGZO TFT with a channel length of 70 nm simultaneously exhibits a near-ideal SS, low V_TH, acceptable static leakage current, high drive capability, and excellent PBS stability. Through XPS and DoS analyses, this work further reveals donor-like and acceptor-like defects induced by hydrogen-related traps. It clarifies their influence on carrier transport, gate controllability, bias stability, and the mechanisms responsible for V_TH shift. These improvements are attributed to the formation of H-related traps with two different polarities after H₂O treatment. Hydrogen primarily acts as a shallow donor, providing free electrons and thereby enhancing carrier transport. Meanwhile, another portion of hydrogen passivates oxygen vacancies and dangling bonds through the formation of M–H bonds, thereby suppressing electron trapping. These results demonstrate that controllable hydrogen incorporation achieves the best balance between enhanced electrical performance and hydrogen-induced degradation, enabling scaled IGZO TFTs with low-power operation, high performance, and high reliability, providing a viable pathway toward future high-density BEOL-compatible electronics and M3D integrated applications.