Sequential Lateral Solidification of Ultra-Thin Silicon Films for SOI Applications
Agency / Branch:
DOD / USAF
Compound semiconductors enable numerous important electronics and optoelectronics applications. They are commonly produced via epitaxial deposition methods, but the existing compound semiconductor substrate materials are expensive, highly defective, andnot available in large sizes. The use of silicon substrates is attractive because of their low cost, low defect density, and large sizes. However, lattice mismatch poses a serious problem because it leads to defect generation in the epitaxially grownfilms.So-called compliant substrates, in which the surface atoms can rearrange to accommodate the mismatch, offer a solution; ultra-thin (5 nm) silicon-on-insulator (SOI) films have been identified as an attractive candidate compliant substrate material.Unfortunately, commercially available SOI materials are not sufficiently thin, and cannot be reduced to the desired thickness.Herein we propose to utilize the sequential lateral solidification (SLS) process - an excimer laser crystallization process that can convert as-deposited amorphous or polycrystalline silicon films into large single-crystal regions - to create ultra-thinSOI-quality silicon films on oxidized silicon wafers. SLS was developed to enable the fabrication of high-performance thin-film transistors (TFTs) on low-temperature substrates, but given the high quality of the crystalline silicon films that it canproduce, it has been identified as a potential competitor to traditional SOI methods.The anticipated benefit of the work is the creation of a method and equipment for producing ultra-thin SOI-quality silicon films on insulators, such as SiO2, with theintended purpose of using them as compliant substrates for compound semiconductor heteroepitaxial deposition. Currently, there are no methods capable of providing this material. The commercial benefits encompass all of the electronics and optoelectronicsapplications for which compound semiconductors are used. Furthermore, the technology is relevant to other applications, such as TFTs, that are based on SOI materials.
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