The Effect of Sputtering Gas on the Materials and Electrical Characteristics of p-Si Films Formed by DC Magnetron Sputte

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THE EFFECT OF SPUTTERING GAS ON THE MATERIALS AND ELECTRICAL CHARACTERISTICS OF p-Si FILMS FORMED BY DC MAGNETRON SPUTTERING A.T. VOUTSAS Sharp Labs of America, LCD Process Technology Department, 5700 NW Pacific Rim Blvd., Camas, WA 98607, [email protected]

ABSTRACT In this work we will discuss the feasibility of sputtered-Si as a precursor for low-temperature pSi films. We used DC sputtering to deposit thin Si films (30-100nm) that were subsequently crystallized by excimer-laser annealing using XeCl (308nm) irradiation. The as-deposited films were sputtered with different gases including Ar, He and Ar-He mixtures. As expected, He sputtering led to less dense films that Ar. However, the plasma voltage (during deposition) was also lower in these cases. It was found that mixing of Ar and He gases within an appropriate ratio range produced sputtered films with good optical properties, at much lower plasma voltages that Ar alone. The lower voltage application could be beneficial from the point of view of reducing microarcing and allowing application of higher DC power levels (to improve deposition rate). Polysilicon TFTs fabricated with the optimum Ar-He ratio (>5% Ar in He) demonstrate similar performance between pure-Ar and Ar-He sputtered p-Si TFTs.

INTRODUCTION Physical Vapor Deposition, or sputtering, is a deposition technique that is widely used in the thin film industry. Unlike other deposition methods, sputtering does not involve chemical interaction among the participating species. The main source of energy is the kinetic energy carried by the species that condense on the growing surface. This source of energy can compensate for traditional energy sources, such as heating, that are required to promote film growth and improve film characteristics. Hence, sputtering can be used to deposit good quality films at moderate (