Gas Phase Reactions and Transport in Silicon Epitaxy

Abstract

Gas phase transport in Si epitaxial growth has been investigated by means of in situ mass spectrometry measurements. of reaction gas concentration profiles. Five species, SIC14, SiHC13, SiHfC12, SIC12, and HC1 are observed in the reaction gas. Not only SIC14 (source gas) but the other Si chlorides as well contribute to the surface growth reaction. The primary reaction species shifts from SIC14 to the other Si chlorides with decreasing gas velocity and with increasing temperature and position along the susceptor.Gas phase reactions and transport phenomena in Si epitaxial growth have been studied extensively by a number of authors and reaction models deduced from an equilibrium viewpoint (1-5). However, the actual reaction is not in equilibrium, but rather quasiequilibrium (6), and the Si epitaxial reaction is difficult to describe by a theoretical model, It is necessary to observe the reaction gas species by in situ measurements in a reactor. Recently such measurements have been made and reaction models proposed. Ban and Gilbert observed the reaction gas profiles in a reactor by using mass spectrometry and reported that SIC14 and only a small amount of SIC12 were found (7, 8). A reaction mechanism was proposed in which SiCI~ was transported to the substrate surface by diffusion and the source gas decomposed into solid Si and HCI byproduct. The following heterogenous reaction occurred at the surface SiC14(g) + 2H2(g) --> Si(s) -t-4HCI(g) Sedgwick and Smith observed reaction gas concentration profiles using laser Haman spectroscopy in Si epitaxy with SiH2C12 as source material (9). The SiHfCI2 decomposed into SIC12 in the gas phase, and then SIC12 was transported to the surface where the epitaxial layer grew SiHfC12---> SiCI# + H2 (gas phase) SiCI2 + Hf--> Si + 2HC1 (substrate surface) Nishizawa and Nihira observed reaction gas profiles by using infrared absorption spectroscopy and found SIC14, SiHC!~, SiHfC~2, and HC1 species (10). They proposed the following models SiHClz SiCla § H2 ~ SIC1,2 ~__-Si % SiH2C12 + HC1Duchemin also investigated Si epitaxial reactions extensively by observing reaction gas profiles in a vertical type reactor (11).Recently, Pollard and Newman have reported a model in which multicomponent mass transfer was considered (12). However, they used calculated gas concentration profiles for the calculation of growth rates. We have observed the reaction gas concentration profiles by in situ measurements using mass spectrometry while changing the growth parameters. It is apparent that the three models mentioned above are likely to describe only a part of the actual reaction. In this paper, it is proposed that all the Si chlorides, SiCIly, SiHC13, SiH2C12, and SIC12, participate in the surface reaction, and the primary surface reaction species which contributes to the growth rate is suggested to shift with changing gas velocity, substrate temperature, and position along the susceptor.

Co-deposition of Silica, Alumina, and Aluminosilicates from Mixtures of CH3SiCl3, AlCl3, CO2, and H2. Thermodynamic Analysis and Experimental Kinetics Investigation

“…SiCl 2 becomes the main siliconbearing species above 1200 K. The role of SiCl 2 as a major silicon deposition precursor has been established in experimental investigations of silicon deposition using silicon tetrachloride as the source gas. [33,34] SiCl 4 and SiHCl 3 are the two stable silicon chlorides that exist in appreciable quantities in the equilibrium gas phase composition. Because of their stable form, these species must exhibit much lower surface reactivities than SiCl 2 and SiCl 3 , and therefore their contribution to silicon incorporation in the deposit should be important only at low temperatures, where their concentrations become much larger than those of SiCl 2 and SiCl 3 .…”

Homogeneous and Heterogeneous Chemistry Models of the Codeposition of Silica, Alumina, and Aluminosilicates

“…1 and 2. SiCl 2 and SiCl 3 , the silicon chloride radicals that are considered to be the major precursors in the incorporation of Si in the deposit, [13][14][15] are both produced in significant amounts even at the very early stages of the process. SiCl 3 is mainly generated by the decomposition of silicon tetrachloride ͑reactions R18 and R20͒, and its relatively high concentrations at low residence times (10 Ϫ4 to 10 Ϫ3 s) are mainly due to the relatively high rate of R20 ͑Fig.…”

Reaction Mechanism of GaAs Vapor‐Phase Epitaxy

“…On the basis of above considerations, we have investigated the reaction mechanism of GaAs epitaxial growth using the halogen transport method by means of infrared absorption spectroscopy, which has an inherent advantage in its use of low energy light source providing no extra excitation of molecules, compared with Raman spectroscopy (15) and mass spectroscopy (16,17). And so it was already applied to the analysis of Si and GaAs vapor-phase epitaxial growth (18,19) and plasma etching (20).…”