Tailored Self-Assembled Monolayer using Chemical Coupling for Indium–Gallium–Zinc Oxide Thin-Film Transistors: Multifunctional Copper Diffusion Barrier

Abstract

Controlling the contact properties of a copper (Cu) electrode is an important process for improving the performance of an amorphous indium–gallium–zinc oxide (a-IGZO) thin-film transistor (TFT) for high-speed applications, owing to the low resistance–capacitance product constant of Cu. One of the many challenges in Cu application to a-IGZO is inhibiting high diffusivity, which causes degradation in the performance of a-IGZO TFT by forming electron trap states. A self-assembled monolayer (SAM) can perfectly act as a Cu diffusion barrier (DB) and passivation layer that prevents moisture and oxygen, which can deteriorate the TFT on–off performance. However, traditional SAM materials have high contact resistance and low mechanical-adhesion properties. In this study, we demonstrate that tailoring the SAM using the chemical coupling method can enhance the electrical and mechanical properties of a-IGZO TFTs. The doping effects from the dipole moment of the tailored SAMs enhance the electrical properties of a-IGZO TFTs, resulting in a field-effect mobility of 13.87 cm2/V·s, an on–off ratio above 107, and a low contact resistance of 612 Ω. Because of the high electrical performance of tailored SAMs, they function as a Cu DB and a passivation layer. Moreover, a selectively tailored functional group can improve the adhesion properties between Cu and a-IGZO. These multifunctionally tailored SAMs can be a promising candidate for a very thin Cu DB in future electronic technology.

Benzylphosphonic acid treated ultra-thin ALD-InOx for long term device stability

“…Previously reported contact angles (CAs) with surface modifications using SAMs on a-IGZO film were 92 and 1051 for n-octadecyltrichlorosilane (OTS), 17,[34][35][36][37] 921 for n-octyltriethoxysilan (OTES), and 521 for {(3-aminopropyl)triethoxysilane} (APTMS) and 501 for N- [3-(trimethoxysilyl)propyl] ethylenediamine (TMSPEDA) using customized SAM solutions. 22 For surface modification of In 2 O 3 films, SAM BPA containing solution was used. V th and S.S. are directly linked to the consistent operation and power consumption of the device.…”

“…[17][18][19] Therefore, the use of SAMs in TFTs has shown great potential for improving stability and reducing device degradation over a prolonged time-lapse. [20][21][22][23][24][25] Although In 2 O 3 TFTs with fine thickness control by atomic layer deposition (ALD) have been studied extensively, research on the longterm V th stability of these devices remains limited. 7,9,10,26,27 Given the practical importance of electrical stability, particularly in light of the potential of In 2 O 3 TFTs to achieve high mobility, in this paper, we show that utilizing PA organic layer passivation improves both the electrical stability and V th values of ultra-thin In 2 O 3 TFTs over time.…”