Correlation Between Annealing Temperature and Crystallinity of Si Films Prepared by Thermal Plasma Jet Crystallization T
- PDF / 248,942 Bytes
- 6 Pages / 612 x 792 pts (letter) Page_size
- 22 Downloads / 248 Views
0910-A21-18
Correlation Between Annealing Temperature and Crystallinity of Si Films Prepared by Thermal Plasma Jet Crystallization Technique Hirotaka Kaku, Seiichiro Higashi, Tatsuya Okada, Hideki Murakami, and Seiichi Miyazaki Grad. School of Advanced Sciences of Matter, Hiroshima University, Kagamiyama1-3-1, Higashi-Hiroshima, Hiroshima, 739-8530, Japan
ABSTRACT Transient reflectivity of amorphous Si (a-Si) films during thermal plasma jet (TPJ) irradiation has been measured to characterize the phase transformation in millisecond time domain. The a-Si films first transform to crystalline by solid phase crystallization (SPC) followed by melting of the film, and then solidifies to the final crystalline state. By increasing the SPC temperature from about 1100 K to 1300 K, the duration of phase transformation decreases from about 1 ms to 100 µs. The crystallinity of the SPC films is improved not only by annealing the films at a high temperature but also annealing them with longer duration. INTRODUCTION The crystallization of amorphous Si (a-Si) films at a low temperature is a key for the fabrication of thin film transistors (TFTs) on glass substrates. So far, the crystallization techniques using an excimer laser to the film crystallization have been studied intensively [1]. However, due to the limit to the output power, the application of laser crystallization technique to large area processing leads to difficulties in reduction of the process cost. Recently, we have proposed the application of thermal plasma jet (TPJ) annealing [2] as an alternative crystallization technique and demonstrated its feasibility as obtained from good TFT performance such as the maximum field effect mobility of 70 cm2/Vs and threshold voltage of 3.3 V [3]. The applicability of TPJ annealing to glass substrates has been confirmed [2]. In TPJ annealing of a-Si films, the phase transformation to crystalline occurs in the time domain of millisecond. However, the mechanism of rapid phase transformation in this time domain has not been well understood yet. Moreover, the correlation between the annealing temperature and crystallinity is still a matter of research. In this work, we have demonstrated the direct observation of phase transformation of a-Si films in millisecond time domain using transient reflectivity measurement technique. The relationship between the temperature and the duration of phase transformation has been investigated. We discuss the mechanism of the solid phase crystallization in millisecond and the correlation between the annealing temperature and the Si films’ crystallinity. EXPERIMENT The experimental set up for the crystallization of a-Si films by TPJ is schematically illustrated in Fig. 1. The W cathode and the water-cooled Cu anode separated with a distance of 1 mm each other are connected to a power supply. Arc discharge was performed by supplying DC biases of 13.4 – 14.0 V and 130 - 150 A [power input (p) = 1.81 – 2.12 kW] between the electrodes with an Ar gas flow (f) of 7.0 – 9.4 L/min. The thermal plasma jet was f
Data Loading...
