Hiromu Ishii

Selective Ge deposition on Si using thermal decomposition of GeH4

Deposition characteristics of Ge using thermal decomposition of GeH4 are studied. The deposition rate of Ge in a surface reaction region at temperatures below 410u2009°C is formulated as a function of the deposition temperature and GeH4 partial pressure. Selective deposition of Ge occurs reproducibly in the lower temperature range below 410u2009°C. The cause of the suppression of selectivity and epitaxial growth at deposition temperatures above 450u2009°C is confirmed as oxide contamination on the substrate.

Reduction reaction of native oxide at the initial stage of GeH4 chemical vapor deposition on (100) Si

The existence of offset time t0 for the Ge deposition is found at the initial stage of Ge epitaxial growth on the Si(100) surface. The t0 is measured for various GeH4 pressures and Si surface conditions. From this investigation, it was determined that the t0 corresponded to the period for the reduction reaction of surface native Si oxide. It was concluded that the two surface SixO molecules were reduced by one GeH4 molecule.

New platinum silicide formation method using reaction between platinum and silane

The new Pt silicide formation method using the reaction between Pt film and SiH4 has been proposed. It has been found that Pt silicide is formed by the reaction with SiH4 at a low temperature range of 250–400u2009°C. Parabolic relationships of silicide growth using the reaction with SiH4 as well as the growth using the reaction between Pt and substrate Si are confirmed. Pt silicide formation with SiH4 is less influenced by oxygen contamination than the formation by the reaction between Pt and substrate Si.

Effects of hydrogenation of hydrogen termination of p+-silicon (100) surfaces by hydrofluoric acid

We have investigated the hydrogen termination of p+-Si(100) surfaces treated with a dilute hydrofluoric acid solution after hydrogen plasma is used to deactivate the dopant. The carrier concentration of hydrogenated p+-Si is reduced by an order of magnitude by this hydrogen passivation but it can be largely restored simply by thermal annealing at moderate temperatures. Contact angle measurement and thermal desorption spectroscopy revealed that the hydrogenated p+-Si surface is efficiently terminated by hydrogen in HF solutions and that the H-terminated surface is more stable in water than the original p+-Si surface is. The hydrogenated p+-Si surface reacts with HF solutions in ways quite similar to these in which a p−-Si surface does. On the other hand, the hydrogenation does not affect the HF treatment properties of n+-Si. This hydrogen–plasma passivation enables us to obtain a clean H-terminated p+-Si surface by using the conventional dilute HF treatments.

Silicon epitaxial growth on germanium using an Si2H6 low‐pressure chemical vapor deposition technique

Heteroepitaxial growth of silicon on a germanium surface at 580–800u2009°C is investigated using Si2H6/H2 gas low‐pressure chemical vapor deposition processing. Crystalline Si grows on the Ge film surfaces at temperatures of 650–730u2009°C and, by contrast, polycrystalline Si is deposited at low temperatures of 580–630u2009°C. It is clarified that whether crystalline Si grows on the Ge surface depends only on substrate temperature, not on the Si2 H6 partial pressure (4×10−3–1×10−1 Torr) nor the Si growth rate (3–800 nm/min). The growth rate using Si2 H6 is more than one order higher than the SiH4 case. Its activation energy is 1.4 eV.

Growth and Etching of Germanium Films by Chemical Vapor Deposition in a GeCl4 ‐ H 2 Gas System

Croissance et attaque de couches minces de Ge a laide du systeme GeCl 4 −H 2 pour des temperatures comprises entre 490°C et 565°C. A faible pression de GeCl 4 on observe une croissance epitaxique de Ge sur la surface Ge(100). Pour une pression plus elevee, on observe une attaque de la couche de Ge. La reaction de croissance intervient par lintermediaire du mecanisme de Langmuir-Hinshelwood. La vitesse de croissance est determinee en fonction de la temperature et de la pression partielle de GeCl 4 et H 2

Surface Photochemical Reactions of Dimethylgermane, Ge ( CH 3 ) 2 H 2, and Their Application to Stepwise Ge Growth

Surface chemical processes of dimethylgermane are investigated by x-ray photoelectron spectroscopy and thermal desorption spectroscopy. Self-limiting adsorption, in which further adsorption of dimethylgermane is stopped, is found in the exposure range of 3 x 10 5 to 1 x 10 8 Langmuir and in the temperature range of 296 to 673 K. By thermal desorption spectroscopy, it is confirmed that this phenomenon operates by methyl groups terminating in Ge dangling bonds in the adlayer. These methyl groups in the outermost adlayer are found to be further desorbed by ultraviolet light irradiation. Effective wavelengths for photochemical decomposition of Me groups in the dimethylgermane adlayer are confirmed in the wavelength region below 310 nm. On the basis of these results, the feasibility of photochemical stepwise Ge growth is examined by the repetition of a process sequence that consists of dimethylgermane introduction onto the substrate surface, residual dimethylgermane evacuation, and photoirradiation.

Silicon epitaxy on germanium using a SiH4 low-pressure chemical-vapor deposition process

This work describes a process of Si epitaxy on a (100)Ge surface using a SiH4–H2 gas low‐pressure chemical‐vapor deposition (LPCVD) system. Germanium epitaxial film formed on (100)Si wafers using GeH4–H2 gas in a LPCVD reactor was used as the experimental substrates. It was found that Si grew epitaxially through a SiH4 thermal decomposition reaction on the clean Ge surface within a growth temperature range of 650 to 730u2009°C. By contrast, (110)‐oriented polycrystalline Si grew at a higher temperature of 790u2009°C. It was clarified that the reason for this polycrystalline Si growth at 790u2009°C was that the Si epitaxy was disturbed by the Si oxide layer which forms immediately on the Ge surface through susceptor‐induced SiO in the LPCVD reactor.

Elimination of Oxidized Mo by Self‐Cleaning Reaction with WF 6 in the Initial Stages of Selective W Chemical‐Vapor Deposition on Mo Interconnections

Selective W chemical vapor deposition (CVD) on Mo interconnections is studied to elucidate the surface cleaning mechanism in the initial stages of W CVD in a WF 6 -H 2 gas system using ellipsometry, x-ray photoelectron spectroscopy, and Auger electron spectroscopy