The epitaxial lateral overgrowth (ELO) process of depositing single crystal silicon over a
SiO2
mask is described. A CVD technique has been developed which consists of depositing silicon in openings in a
SiO2
mask and then growing the silicon laterally over the
SiO2
film. By optimizing the
normalHCl
concentration in the gas, growth temperature, and the use of a growth procedure based on a series of growth/etch steps the nucleation of polysilicon over
SiO2
has been eliminated and monocrystalline ELO films have been grown. Low defect density ELO films have been achieved by orientating the oxide islands along the [010] direction on (100) substrates. The growth kinetics, overgrowth morphology, and defect formation in ELO films are described as a function of the growth conditions. One can conclude that optimization of the growth process has allowed us to grow monocrystalline, low defect density ELO films with smooth mirrorlike surfaces.
The growth rate of selective epitaxial silicon is a function of the nucleation site seed area and the ratio of the area of the SiO2 mask to silicon area exposed. Therefore, with commonly employed IC circuit patterns, it is difficult to achieve, using conventional epitaxial growth conditions, silicon deposit thickness uniformity needed for IC processing. This constitutes one of the main obstacles to utilizing CVD selective epitaxy as an SOI process or as a replacement of LOCOS for oxide isolation. Reported in this publication is a method of growing uniformly thick selective epitaxial silicon on a silicon wafer with SiO2 mask openings to the substrate of various dimensions, and with various Si/SiO2 area ratios. The desired control of the deposit thickness is achieved at reduced pressures (below 50 torr) and relatively low deposition temperatures (850 ~ _+ 10~
has been grown on a Si wafer by CVD selective epitaxy with SiO2 mask openings to the substrate of various dimensions and with various Si/SiO2 area ratios.
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