Proposal of quasi thermal equilibrium model for etching phenomenon by gases: Example of the etching of 4H-SiC by H₂

Abstract

We propose a new approach to derive the formula for the etching rate of condensed matter with a gaseous etchant, based on the model in which the chemical etching proceeds under nearly thermal equilibrium conditions. The model, called the quasi thermal equilibrium model, is applicable for the case that the reaction time is much shorter than the passage time of carrier gases over substrates. We have derived the formula giving the etching rates as functions of temperature, gas flow rate, and pressure for three cases: (1) a carrier gas acts as an etching gas, (2) a carrier gas is inactive and an etching gas is added, and (3) a carrier gas is active and an etching gas is added. We applied the model to the etching of 4H-SiC by H2 and showed that the quasi thermal equilibrium model proposed can successfully reproduce the experimental results of the temperature, gas flow rate, and pressure dependences of the etching rate.

Investigation of the giant step bunching induced by the etching of 4H-SiC in Ar–H2 mix gases

“…We give the values in Table I, which appeared in our previous paper. 24) ΔG and R in the table are the standard change in reaction at T (K) in Gibbs free energy and the gas constant, respectively. The etching under the Ar-H 2 gas system corresponds to Case (2).…”

“…The value of δ is the same as that of −β from Table I in Ref. 24. The value of γ is easily calculated using the functional relation γ = −ν z =Σν i = 1 − δ.…”

“…From the experiments on SiC etching with 100% H 2 gas and the thermal equilibrium simulation, we obtained the values of α, β, and C as −5.2 × 10 4 K, −0.51, and 4 × 10 12 , respectively. 24) Substituting these values into Eq. (A•4), the etching rate in the chemical reaction limit r c is given as…”

“…Regarding the etching of SiC by H 2 , we have proposed the quasi-thermal equilibrium (QTE) model and clarified the etching mechanism in H 2 atmosphere, 24) although a diffusion process was not involved. On the other hand, in the case of an argon (Ar)-H 2 gas system in which Ar is used as a carrier gas, the etching mechanism cannot be entirely explained by the QTE model, because this system includes the diffusion of H 2 .…”

Proposal of the mechanism for inclination growth on a mesa top during the 4H-SiC trench filling epitaxy

“…We have studied the etching and homoepitaxial growth of SiC and elucidated theoretically their mechanisms. [23][24][25][26][27][28][29] In this communication, we examine the inclination growth phenomena in the trench filling based on the homoepitaxial growth of SiC, i.e., growth on an off-angled substrate surface, and attempt to determine the relationship between the misalignment angle of the trench direction and the inclination growth angle of the epilayer on the mesa top.…”