Kazuya Murata, Ryoichi Nozawa, Masafumi Ito*, Masaru Hori and Toshio Goto

Department of Quantum Engineering
Nagoya University, Nagoya, 464-8603, Japan
itou@nuee.nagoya-u.ac.jp

ECR plasma CVD using SiH4 with high H2 dilution is a candidate for forming polycrystalline silicon (poly-Si) film at lower substrate temperature (<300 C). Generally, the density of nucleation at an initial growth affects the crystallinity and the grain size. However, the effects of charged species on the initial growth have not been clarified yet. Therefore, we have investigated the initial growth of poly-Si films formed with and without charged species by in-situ Atomic Force Microscopy (AFM) and Raman scattering spectroscopy.

Poly-Si films were prepared by ECR plasma CVD using 10% SiH4 mixed in H2. The plasma was generated at a SiH4/H2 flow rate of 80 sccm, a pressure of 0.5 Pa and a microwave power of 300W. The temperature of quartz substrates was kept to be 300 C. Permanent magnets were employed so that charged species should be pushed away before bombarding the substrate in order to evaluate the effects of the charged species.

The grain sizes and the deposition rates of the films formed without magnets were about 200 nm and 2 A/s, respectively and those of the films with magnets were about 50 nm and 0.2 A/s, respectively. The films formed with magnets were flatter than those without magnets. From Raman spectra, the crystallinity of films formed with magnets was better than that without magnets. However, the deposition rate with magnets is one-tenth of that without magnets. And then, we have investigated the dependence of deposition rate on morphology and crystallinity. From these results, it was found that the morphology and the crystallinity were not affected so much by the deposition rates. It is, therefore, considered that the differences of morphology and crystallinity are mainly due to the ion bombardment on the initial growth.