Method for producing SiC single crystal substrate in which a Cr surface impurity is removed using hydrochloric acid
View Patent ↗A method for producing a SiC single crystal substrate that can remove Cr impurity from the surface of a SiC single crystal that contains Cr as an impurity, is provided. This is achieved by a method for producing a SiC single crystal substrate, wherein the method includes a step of immersing a SiC single crystal substrate containing Cr as an impurity in hydrochloric acid at 50° C. to 80° C.
1. A method for producing a SiC single crystal substrate, wherein the method comprises steps of:
growing a SiC single crystal substrate containing Cr and Si as impurities by using a solution process or sublimation process;
immersing the SiC single crystal substrate containing Cr and Si as impurities in a composition consisting essentially of hydrochloric acid at 50° C. to 80° C.; and
immersing the SiC single crystal substrate in a Si-dissolving solution after the step of immersing in said composition,
wherein the amount of Cr impurity on the SiC single crystal substrate in a surface region thereof is from 1×10 16 to 1×10 19 atoms/cm 2 , and
wherein the Si-dissolving solution is a solution containing hydrofluoric acid and nitric acid.
2. The method according to claim 1 , wherein the method comprises a step of immersing the SiC single crystal substrate in an organic material-dissolving solution before the step of immersing in said composition.
3. The method according to claim 2 , wherein the organic material-dissolving solution is acetone or a solution containing NH 4 OH and H 2 O 2 .
4. The method according to claim 1 , wherein the method comprises a step of RCA cleaning of the SiC single crystal substrate after the step of immersing the SiC single crystal substrate in the Si-dissolving solution.
5. The method according to claim 1 , wherein the step of growing the SiC single crystal substrate containing Cr and Si as impurities is before the step of immersing in said composition, and
wherein the SiC single crystal substrate is not subjected to acid cleaning between the step of growing the SiC single crystal substrate and the step of immersing in said composition, wherein the acid cleaning includes immersing the SiC single crystal substrate into a mixed aqueous solution of hydrochloric acid and hydrogen peroxide water, sulfuric acid, nitric acid, fluoronitric acid, aqua regalis, or hydrochloric acid at less than 50° C.
6. The method according to claim 5 , wherein the method comprises a step of polishing the SiC single crystal substrate after the step of growing the SiC single crystal substrate.
7. The method according to claim 5 , wherein the acid cleaning is immersing the SiC single crystal substrate into a mixed aqueous solution of hydrochloric acid and hydrogen peroxide water.
8. The method according to claim 1 , wherein the step of immersing in said composition is carried out at 55° C. to 75° C.
9. The method according to claim 1 , wherein the step of immersing in said composition is carried out at 60° C. to 70° C.
10. The method according to claim 1 , wherein said composition is an aqueous solution having a hydrochloric acid concentration of from 25 to 37%.
11. The method according to claim 10 , wherein the hydrochloric acid concentration is from 27 to 35%.
12. The method according to claim 10 , wherein the hydrochloric acid concentration is from 29 to 33%.
13. The method according to claim 1 , wherein the amount of Cr impurity in an outermost surface thereof including adhering impurities is from 1×10 16 to 1×10 21 atoms/cm 2 .
14. The method according to claim 5 , wherein the step of growing the SiC single crystal substrate is carried out by a solution process using a Si/Cr solvent.
15. The method according to claim 1 , wherein the composition consisting essentially of hydrochloric acid is a solution consisting of hydrochloric acid.