Method for manufacturing epitaxial wafer and wafer holder used in the method
A susceptor having a recessed portion and a ring-like step portion is arranged in a reaction chamber, and a plurality of through bores are formed in a bottom wall in the recessed portion excluding the step portion. A lift pin inserted in each of the through bores temporarily holds a wafer, then a lower surface of an outer peripheral portion of the wafer is mounted on the step portion to accommodate the wafer in the recessed portion, and a raw material gas is circulated in the reaction chamber to form an epitaxial layer on a wafer surface in the recessed portion. When forming the epitaxial layer on the wafer surface, the lift pin protrudes upwards from an upper surface of the bottom wall, and a height h of a top portion of the lift pin based on the upper surface of the bottom wall as a reference is set to the range from a position where the height h exceeds 0 mm to a position immediately before the lift pin comes into contact with the wafer.
1. A method for manufacturing an epitaxial wafer, comprising:
arranging in a reaction chamber a susceptor that has a recessed portion and a ring-like step portion formed in the recessed portion and has a plurality of through bores formed in a bottom wall of the recessed portion excluding the step portion;
temporarily holding a wafer by lift pins inserted in the through bores;
mounting a lower surface of an outer peripheral portion of the wafer on the step portion to accommodate the wafer in the recessed portion;
circulating a raw material gas in the reaction chamber to form an epitaxial layer on a surface of the wafer accommodated in the recessed portion,
wherein, each of the lift pins has a lift shaft portion and a lift head portion that is provided on an upper surface of the lift shaft portion, the lift head portion being provided integrally with the lift shaft portion through a lift tapered portion, and the lift head portion having a larger diameter than that of the lift shaft portion, and
wherein a corresponding through bore has a small-diameter bore portion, a tapered bore portion that accommodates the lift tapered portion, and a large-diameter bore portion that accommodates the lift head portion, and an inner surface of the tapered bore portion supports the lift tapered portion such that an upper surface of the lift head portion protrudes outside of the large diameter bore portion, and when forming the epitaxial layer on the wafer surface, each of the lift pins protrudes upwards from an upper surface of the bottom wall, a height h of a top portion of each lift pin based on the upper surface of the bottom wall as a reference is set to fall within the range of 0.05 mm to 0.12 mm and at a position immediately before the lift pin comes into contact with the wafer, and a distance H between an extended surface of an upper surface of the step portion of the susceptor and an extended surface of the upper surface of the bottom wall at a position of the lift pin is 0.1 to 1 mm; and
setting a ratio Wa:Wb to be in a range of 50:50 to 55:45, where Wa is an output of an upper lamp which is provided above the reaction chamber and Wb is an output of a lower lamp which is provided below the reaction chamber.
2. The method for manufacturing an epitaxial wafer according to claim 1 , wherein the susceptor is formed of carbon covered with an SiC film and the lift pin is formed of any one of SiC, glassy carbon, and quartz.