Structure character of fast growth polycrystalline silicon film from SiCl/sub 4//H/sub 2/

The polycrystalline silicon films with the deposition rate over 4.5 /spl Aring//s prepared at low temperature of 250 /spl deg/ were obtained from the hydrogen dilution of tetrachlorine silicon using PECVD technique. The results show that the growing surface of film contains a large amount of silicon crystalline grains with 30-100 nm in diameter. The crystalline fraction and the crystalline grain size strongly depend on the RF power and the hydrogen dilution ratio. The optimum RF power and the optimum hydrogen dilution ratio for the best crystalline character are related to the deposition rate. On the other hand, the crystalline fraction and the crystalline grain size are almost independent on the substrate temperature. It is considered that the space reaction processes and the Cl element play an important role in the initial stage of the crystalline formation and in the crystalline grain growth for the low-temperature crystallization of the films.

INTRODUCTION

Polycrystalline silicon (poly-Si) films grown on glass substrate have received considerable attention because of their potential such as high mobility and stability for improving the performances of optoelectronic devices. So far, several methods have been performed for fabrication of poly-Si film, including the solid phase crystallization, laser crystallization and metal-induced crystallization [1]–[3]. Apart from these approaches, in our laboratory we directly grow the poly-Si films at low temperature from gaseous mixture of SiCI₄/H₂ using plasma enhanced chemical vapor deposition (PECVD) and have obtained the poly-Si film with the deposition rate and the crystalline fraction over 4.5 Å/s and 80%, respectively [4]. In present work, we found that the dependence of structure character (including the crystalline fraction and the grain size) on PECVD technique parameters using SICI₄/H₂ is different from that using SiH₄/H₂. In this paper, we show the experiment results of all kinds of factors of affecting the structure character and deposition rate. The role of radio frequency power and the CI element in the initial stage of the crystalline formation and in the grain growth for the low-temperature crystallization is discussed also.