Hydrogen Impacts of PEALD InGaZnO TFTs Using SiO<sub>x</sub> Gate Insulators Deposited by PECVD and PEALD
Seok-Goo Jeong, Hyun‐Jun Jeong, Wan-Ho Choi, KyoungRok Kim, Jin‐Seong Park
Abstract
Amorphous indium gallium zinc oxide (IGZO) deposited by plasma-enhanced atomic layer deposition (PEALD) thin-film transistors (TFTs) was fabricated using SiO <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub> gate insulators synthesized via plasma-enhanced chemical vapor deposition (PECVD, device A) or PEALD (device B). The electrical performance of B devices was higher than that of device A. The mobilities of A and B devices were 19.39 and 21.11 cm <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sup> /Vs, and the subthreshold slopes were 0.25 and 0.22 V/decade, respectively. In addition, the device reliability of A devices shows an abnormal threshold voltage (V <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">th</sub> ) shift of -1.25 V under positive bias temperature stress (PBTS), caused by hydrogen diffusion from the gate insulator to the channel region near the source/drain electrode. However, B devices had a normal V <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">th</sub> shift of +2.87 V. X-ray photoelectron spectroscopy(XPS) and Fourier-transform infrared spectroscopy (FT-IR) results showed that PECVD SiO <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub> has a large amount of hydrogen bonding, such as Si-OH, compared to PEALD SiO <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub> . Rutherford backscattering spectroscopy (RBS) and elastic recoil detection (ERD) measurement results confirmed that the hydrogen content of PECVD SiO <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub> was 2.24%, whereas that of PEALD SiO <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub> was lower at 1.45%.