Growth and Charactenzation of Polycrystalline Silicon Films Deposited by Plasma Enhanced Chemical Vapor Deposition at Low Temperature
December,1995
Ahalapitiya Hewage Jayatissa
The growth of polycrystalline silicon (poly-Si) using plasma enhanced chemical vapor deposition (PECVD) of silane at temperature below 500C has been investigated. The system is a capacitively coupled parallel plate rf glow discharge reactor where the substrates are mounted on the cathode (powered electrode). It was found that the crystallization process in cathode- type rf GD severely depends on power density where low power makes amorphous silicon because of lack of enough H radicals to promote crystallization process and high power makes poor crystallinity due to bombardment of high enery ionic particles.
To reduce the effects from ion bombardment, a mesh was attached to the substrate holding electrode with expecting to reduce the electric field in the film growth zone. When the metal mesh was attached, the crystalline growth was markedly enhanced.
These results strongly support the fact that the atomic H radicals play an important role in the crystalline growth in PECVD of silane. It was also found that the highly oriented and epitaxial like films could be grown on single crystal substrates of silicon and sapphire.
Number of characterization processes have been carried out to realized the properties of silicon films deposited by the above techniques. The properties of f,rlms deposited by this technique were compared with silicon films deposited by conven- tional methods. The films were also used for fabrication of thin film transistors and laser recrystallization process.
-253-
I
