Mechanism Investigation of Temperature Dependent Growth and Etching Process of GeCl4 on SiGe Surface: ab-initio Study

Herein, we unveil the deposition and etch mechanism of GeCl
4
on the SiGe surface. At the high temperature, GeCl
4
is dissociated to GeCl
2
and then worked as a deposition source. Thus, the rate determinant step of surface growth is GeCl
4
dissociation, and a novel precursor that quickly dissociates to GeCl2 will be a proper precursor target to Ge growth at the low-temperature process. Otherwise, at the low temperature, GeCl
4
works as an etching gas by reacts with surface Ge/Si atoms and forms Ge$_{2} H_{n} {Cl}_{6-n}$ or GeSiH$_{n} Cl_{6-n}$ (n=2,3) molecules. From the etch mechanism analysis, the first activation energy of Ge desorption is lower, 65.8 (kcal/mol), than GeCl
4
dissociation (101 kcal/mol), but the etched surface has higher energy, -6.7 (kcal/mol), than the Ge doped, -19.2 (kcal/mol). This energy profile successfully explains the experimental observation, deposition at high temperature, etch at low temperatures. Additionally, we figured out that the GeCl
3
intermediate shows the most tightly bind to surface atoms.