Integration Challenges of Flash Lamp Annealed LTPS for High Performance CMOS TFTs

Abstract

This work demonstrates a method of producing polycrystalline silicon TFTs using Flash Lamp Annealing (FLA) as a potential industrial counterpart to excimer laser annealing. Material uniformity and low-temperature dopant activation are explored within an investigation on solid-phase epitaxial regrowth for PMOS TFTs. Silicon self-implantation is used to partially amorphize select regions of FLA LTPS material, allowing epitaxial regrowth to incorporate boron into the resulting lattice. This regime is compared with total amorphization, in which epitaxial regrowth cannot occur. The effects of these different methods of recrystallization are demonstrated through transfer characteristics of fabricated transistors. Devices utilizing a partial pre-amorphization of FLA LTPS demonstrated effective hole channel mobilities of 40 - 50 cm2/(Vs) in low drain bias operation. Additionally, self-aligned TFTs using FLA are presented for the first time, with effective hole channel mobilities of 30 - 60 cm2/(Vs) in low drain bias operation using the same treatment.