Effect of Deposition Temperature of SiOx Passivation Layer on the Electrical Performance of a-IGZO TFTs

We investigated the effect of the deposition temperature on the electrical performance of SiOx passivation layers for amorphous indium-gallium-zinc-oxide thin-film transistors (a-IGZO TFTs). Compared to the time-of-flight secondary ion mass spectroscopy depth profile of the IGZO film with a SiOx passivation layer deposited at low temperature (150^oC ), that with the SiOx film formed at 300^oC exhibited the significant migration of metal ions from the IGZO film into the SiOx passivation layer. These results were attributed to the high-energy ion bombardment on the IGZO channel layer. In order to suppress the interdiffusion of In, Ga, and Zn atoms between the IGZO and passivation layers, we proposed double SiOx passivation using different substrate temperatures. It combines the merits of low-temperature (150^oC) and high-temperature (300^oC) passivations and compensates for their individual weaknesses. We confirmed the enhanced electrical characteristics and improved reliability of the IGZO TFTs compared to those of the conventional device.

I. Introduction

INDIUM-gallium-zinc-oxide thin-film transistors (IGZO TFTs) have attracted considerable interest for use in low-cost and large-size backplanes for advanced displays, such as active matrix liquid crystal and active matrix organic light emitting diode displays, due to their high current driving ability compared to amorphous silicon-based TFTs, the dominant present-day TFT technology [1], [2]. It is well known that the electric characteristics of oxide TFTs are considerably influenced by the deposition conditions of the passivation layers [3]. Until now, various inorganic or organic passivation layers, such as , SiNx, and polymers, have been investigated [4]–[6]. Some researchers have insisted that the inorganic passivations degraded the electrical characteristics of oxide TFTs due to surface damage to the back-channel area of the devices [4].