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Open AccessReview

Atomic Layer Deposition (ALD) of Metal Gates for CMOS

by Chao Zhao 1,2,* and Jinjuan Xiang 1,2,*
1
Institute of Microelectronics of Chinese Academy of Sciences, Beijing 100029, China
2
University of Chinese Academy of Sciences, Beijing 101408, China
*
Authors to whom correspondence should be addressed.
Appl. Sci. 2019, 9(11), 2388; https://doi.org/10.3390/app9112388
Received: 29 April 2019 / Revised: 17 May 2019 / Accepted: 22 May 2019 / Published: 11 June 2019
(This article belongs to the Special Issue Atomic Layer Deposition for the Synthesis of Thin Films)
The continuous down-scaling of complementary metal oxide semiconductor (CMOS) field effect transistors (FETs) had been suffering two fateful technical issues, one relative to the thinning of gate dielectric and the other to the aggressive shortening of channel in last 20 years. To solve the first issue, the high-κ dielectric and metal gate technology had been induced to replace the conventional gate stack of silicon dioxide layer and poly-silicon. To suppress the short channel effects, device architecture had changed from planar bulk Si device to fully depleted silicon on insulator (FDSOI) and FinFETs, and will transit to gate all-around FETs (GAA-FETs). Different from the planar devices, the FinFETs and GAA-FETs have a 3D channel. The conventional high-κ/metal gate process using sputtering faces conformality difficulty, and all atomic layer deposition (ALD) of gate stack become necessary. This review covers both scientific and technological parts related to the ALD of metal gates including the concept of effect work function, the material selection, the precursors for the deposition, the threshold voltage (Vt) tuning of the metal gate in contact with HfO2/SiO2/Si. The ALD of n-type metal gate will be detailed systematically, based mainly on the authors’ works in last five years, and the all ALD gate stacks will be proposed for the future generations based on the learning. View Full-Text
Keywords: COMS; metal gate; atomic layer deposition; high-κ dielectric; threshold voltage; flatband voltage; effective work function; effective oxide thickness COMS; metal gate; atomic layer deposition; high-κ dielectric; threshold voltage; flatband voltage; effective work function; effective oxide thickness
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Zhao, C.; Xiang, J. Atomic Layer Deposition (ALD) of Metal Gates for CMOS. Appl. Sci. 2019, 9, 2388.

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