Method for producing SiC epitaxial wafer including forming epitaxial layer under different conditions
This method of producing a SiC epitaxial wafer having an epitaxial layer on a SiC single crystal substrate, and includes: when performing crystal growth of the epitaxial layer, a step of forming a part of an epitaxial layer under first conditions at an initial stage where the crystal growth is started; and a step of forming a part of a SiC epitaxial layer under second conditions in which a Cl/Si ratio is decreased and a C/Si ratio is increased in comparison to those in the first conditions, wherein the C/Si ratio is equal to or less than 0.6 and the Cl/Si ratio is equal to or more than 5.0 in the first conditions.
1. A method of producing a SiC epitaxial wafer having an epitaxial layer on a SiC single crystal substrate, the method comprising:
when performing crystal growth of said epitaxial layer,
a step of forming a part of an epitaxial layer under first conditions in which a silane-based gas and a carbon-based gas are supplied, at an initial stage where the crystal growth is started; and
a step of forming a part of a SiC epitaxial layer under second conditions in which a Cl/Si ratio is decreased and a C/Si ratio is increased in comparison to those in said first conditions,
wherein the C/Si ratio is equal to or less than 0.6 and the Cl/Si ratio is equal to or more than 5.0 in said first conditions.
2. The method of producing a SiC epitaxial wafer according to claim 1 ,
wherein in said first conditions, chlorosilane (SiH 4−n Cl n : n=0 to 4) and hydrogen chloride (HCl) are used together as supply sources of Cl element.
3. The method of producing a SiC epitaxial wafer according to claim 1 ,
wherein in said second conditions, the C/Si ratio is from 0.8 to 1.5, and the Cl/Si ratio is from 0 to 4.
4. The method of producing a SiC epitaxial wafer according to claim 1 ,
wherein when performing crystal growth of said epitaxial layer, a ramping step is performed wherein the C/Si ratio is increased and the Cl/Si ratio is decreased from said first conditions to said second conditions in a stepwise manner or in a slope-like manner.
5. The method of producing a SiC epitaxial wafer according to claim 4 ,
wherein said epitaxial layer comprises a buffer layer and a drift layer in this order from said SiC single crystal substrate side, and
said ramping step is carried out when growing said buffer layer.
6. The method of producing a SiC epitaxial wafer according to claim 5 ,
wherein a time required for said ramping step is equal to or more than ⅕ of a time required for forming said buffer layer.
7. The method of producing a SiC epitaxial wafer according to claim 4 ,
wherein a layer thickness of an epitaxial layer to be grown as crystals in said ramping step is equal to or more than 0.1 μm.
8. The method of producing a SiC epitaxial wafer according to claim 4 ,
wherein said ramping step is started simultaneously with the start of growth of said epitaxial layer.
9. The method of producing a SiC epitaxial wafer according to claim 1 ,
wherein the C/Si ratio is from 0.4 to 0.6 in the first conditions.
10. The method of producing a SiC epitaxial wafer according to claim 1 ,
wherein the epitaxial layer on the SiC single crystal substrate is a SiC epitaxial layer on the SiC single crystal substrate,
the step of forming a part of an epitaxial layer under first conditions is a step of forming a part of the SiC epitaxial layer under first conditions, and
the step of forming a part of a SiC epitaxial layer under second conditions is a step of forming a part of the SiC epitaxial layer under second conditions.
11. The method of producing a SiC epitaxial wafer according to claim 1 ,
wherein the silane-based gas and the carbon-based gas are supplied together.