Location-Controlled Single-Crystal-Like Silicon Thin-Film Transistors by Excimer Laser Crystallization on Recessed-Channel Silicon Strip With Under-Layered Nitride

High-performance Si thin-film transistors (TFTs) on the recessed-channel Si strips with the under-layered nitride film have been fabricated using excimer laser crystallization (ELC). A nitride film was added as a light absorption layer to suppress solidification along the edge of the Si strip. Thus, only one primary grain boundary perpendicular to the Si strip formed in the middle of the recessed region during ELC. The single-crystal-like Si TFTs fabricated on one-half of the recessed region are capable of excellent field-effect mobility of 640 cm²/V-s, with only minor deviation.

I. Introduction

Low-temperature polycrystalline-silicon (LTPS) thin-film transistors (TFTs) fabricated using excimer laser crystallization (ELC) have been extensively investigated for use in active-matrix flat-panel displays (AMFPDs), system on panels (SOPs), and three-dimensional integrated circuits (3-D ICs) [1]–[4]. LTPS TFTs with the electron mobility exceeding 100 cm²/V-s have been realized using ELC in the super-lateral-growth (SLG) regime. However, random grain size distribution, random grain boundary location, and a narrow process window can lead to large variations in device performance, particularly in short-channel TFTs [4]–[6]. This has led to the development of several advanced ELC methods aimed at enlarging the grain size and assuming control over the location of grain boundaries. These methods include sequential lateral solidification (SLS), phase-modulated ELC (PMELC), -Czochralski process, and recessed-channel (RC) structure [3], [7]–[12]. Unfortunately, many of these methods involve complex fabrication process to form the designed film structure or are not readily attached to existing excimer laser annealing systems. Some of these methods have also proven problematic with regard to circuit layout, due to the anisotropic spacing of grain boundaries.