Low-temperature silicon cleaning via hydrogen passivation and conditions for epitaxy

Abstract

In low-temperature epitaxial Si deposition methods such as molecular beam epitaxy (MBE), pre-epitaxial substrate preparation usually incorporates a high temperature (≳800 °C) step. Elimination of this step is essential to wider applicability of these epitaxial methods. We show that Si(100) wafers exposed to HF vapors in a laboratory ambience are bulk terminated and that such termination is stable in air for several tens of minutes, and in vacuum for several hours. It is possible to obtain good epitaxy, as determined by surface diffraction and transistor characteristics, provided epitaxy is commenced on these bulk-terminated surfaces. We also give evidence that under certain conditions, bulk-terminated surfaces are maintained in low-temperature epitaxy using the method of ultrahigh vacuum chemical vapor deposition.

Study of oxygen and carbon species on Si substrate during in-situ cleaning prior to high-quality epitaxial deposition

“…Because the adsorption flux of hydrogen is very small compared to the amount of hydrogen introduced into the chamber, adsorption/reaction can be a rate-determining step. It is thought that the carbon removal mechanism at low temperature was related to the removal of the methyl group from the surface by H(g) [11,12]. It is known of the behavior of Si-CH 3 that, at above 577 o C, only the presence of adsorbed carbon on the surface is verified [16] and at below 427 o C, surface carbon will be present as CH 3 (ad) and this can be removed by reactions Si-CH 3 +3H(g)→CH 3 SiH 3 (g).…”

“…Low temperature ( 600 o C) insitu cleaning was performed in our experiments to reduce interfacial carbon and oxygen concentration. There are reports that the low temperature process is more effective in removing hydrocarbons from the surface [11,12]. Recent literature reports that lower temperature in-situ cleaning might be more efficient than higher temperature cleaning in removing oxygen contaminants because at higher temperatures the sticking coefficient of hydrogen to the silicon surface decreases; hydrogen atoms are easily desorbed and hydrogen passivation is lost [6].…”

Effect of in-situ plasma cleaning on the crystalline quality of silicon homoepitaxial films

“…The deposition temperature was adjusted to 600 o C afterwards. Although hydrogen passivation may have begun to be lost at low temperatures of about 400 o C [23], if we accept the report that the hydrogen desorption temperature is between 510 and 520 o C [24], some hydrogen species may stay at 480 o C, so they prevent oxygen species from being adsorbed on the silicon surface. From the micrograph, a defect-free epitaxial layer was grown and the epilayer/substrate interface was thin (less than 20 Å).…”

Epitaxial Mg2SiO4 thin films with a spinel structure grown on Si substrates

“…The optimum sputtering parameters are shown in Table 1. Before deposition, the Si (1 0 0) substrate is dipped in HF:H 2 O (1:8) for 5 min to remove the native oxide layer and then cleaned ultrasonically in acetone and ethanol so that the surface is free of organic contamination, and it is H-terminated [11]. After the Si substrate is transmitted into the chamber and the base pressure is better than 8 Â 10 À4 Pa, heating is turned on to heat the substrate to above 700 1C.…”