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.

165 160 155 --~ 150 ,~ 145 ~= 140 ~ 135 125 120 115 110 Y. Electrochem. S oc.: SOLID-STATE SCIENCE AND TECHNOLOGY A 1.0 1.2 1.4 1.6 1.8 2.0 2.2 2.4 2.6 2.8 3.0 PROBE RADIOS {p,m] Fig. 12. A series of plots of the results of the calibration investigation for several values of the probe spacing. The values of the probe spacings and the corresponding curves are: S ~-25 ~m (A), S = 50 ~rn (B), S = 75 #m (C), and S = 100 ~m (D). In all cases, the Berkowitz-Lux correction factor scheme was used.sufficient to provide sensitivity and yield the value of a = 2 ~an, which was originally used in the generation of the spreading resistance. In addition, to show that the sensitivity is not degraded by variation of the probe spacing, the results of the analysis for several values of the probe spacing are presented in Fig. 12. It is important to emphasize that the curvature must be sufficient to provide for the evaluation of the value of a. Should the curve be found to be flat, this would preclude the use of this procedure. Conclusions

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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~