An Advanced 405-nm Laser Diode Crystallization Method of a-Si Film for Fabricating Microcrystalline-Si TFTs

Abstract

This report describes a crystallization method we developed for amorphous (a)-Si film by using 405-nm laser diodes (LDs). The proposed method has been used to fabricate bottom gate (BG) microcrystalline (μc)-Si TFTs for the first time. A μc-Si film with high crystallinity was produced and high-performance BG μc-Si TFTs with a field effect mobility of 3.6 cm 2 /Vs and a current on/off ratio exceeding 10 8 were successfully demonstrated. To determine the advantages of a 405-nm wavelength, a heat flow simulation was performed with full consideration of light interference effects. Among commercially available solid-state lasers and LDs with wavelengths having relatively high optical absorption coefficients for a-Si, three (405, 445, and 532 nm) were used in the simulation for comparison. Results demonstrated that wavelength is a crucial factor for the uniformity, efficiency, and process margin in a-Si crystallization for BG μc-Si TFTs. The 405-nm wavelength had the best simulation results. In addition, the maximum temperature profile on the gate electrode through the simulation well explained the actual crystallinity distributions of the μc-Si films. key words: laser crystallization of a-Si, thin film transistor, microcrystalline silicon, heat flow simulation

9‐1: Fabrication of Lateral Crystal Si on Cu Bottom‐Gate Structure via Blue‐Laser Diode Annealing (BLDA)

“…Continuous wave (CW) laser annealing is capable to fabricate large grain size Si as like lateral and single crystal [2][3][4][5][6]. Such large crystal significantly improve TFT mobility and have high uniformity.…”

P‐12: Self‐Aligned Bottom Gate LTPS Backplanes without Ion‐Implantation Process

“…One of the reasons of this difficulties is the process complexity of LTPS, and the other is that the development of such manufacturing apparatus as excimer laser annealing (ELA) equipment or ionimplantation equipment that also faces difficulties for large glass substrate applications (> Gen. 8). Some groups are trying to overcome these problems by other means [1][2][3][4][5]. Conventional amorphous silicon TFT, on the other hand, has a bottom gate structure that is more easily manufactured for larger glass substrates.…”