Method for manufacturing SOI substrate
A heating plate having a smooth surface is placed on a hot plate which constitutes a heating section, and the smooth surface of the heating plate is closely adhered on the rear surface of a single-crystal Si substrate bonded to a transparent insulating substrate. The temperature of the heating plate is kept at 200° C. or higher but not higher than 350° C. When the rear surface of the single-crystal Si substrate bonded to the insulating substrate is closely adhered on the heating plate, the single-crystal Si substrate is heated by thermal conduction, and a temperature difference is generated between the single-crystal Si substrate and the transparent insulating substrate. A large stress is generated between the both substrates due to rapid expansion of the single-crystal Si substrate, thus separation takes place at a hydrogen ion-implanted interface.
1. A method for manufacturing an SOI substrate, comprising:
(1) forming a hydrogen ion-implanted layer on the surface side of a first substrate which is a single-crystal silicon substrate;
(2) applying a surface activation treatment to at least one of the surface of a second substrate which is a transparent insulating substrate and the surface of said first substrate;
(3) bonding together the surface of said first substrate and the surface of said second substrate; and
(4) forming an SOI layer on the surface of said second substrate by closely adhering the rear surface of said first substrate of said bonded substrates on a heating plate kept at a temperature of 200° C. or higher but not higher than 350° C. to heat said first substrate and thereby peel off a silicon layer from said first substrate,
wherein (3) includes a sub-step of heat-treating said first substrate and said second substrate at 100 to 350° C. after said bonding, with said first and second substrates bonded together.
2. The method of claim 1 , wherein said second substrate is a quartz substrate, a sapphire (alumina) substrate, a borosilicate glass substrate, or a crystallized glass substrate.
3. The method of claim 1 , wherein the amount of hydrogen ion implantation (dose amount) in (1) is 1×10 16 to 5×10 17 atoms/cm 2 .
4. The method of claim 1 , wherein said surface activation treatment in (2) is carried out by at least one of plasma treatment and ozone treatment.
5. The method of claim 1 , wherein said heating plate used in (4) is one of a semiconductor substrate and a ceramic substrate having a smooth surface.
6. The method of claim 1 , wherein (4) includes a sub-step of applying separation-accelerating external impact from an edge of said hydrogen ion-implanted layer before or after the heating of said first substrate.
7. The method of claim 1 , wherein the hydrogen ion implantation depth is 0.5 μm or less.
8. The method of claim 1 , wherein the hydrogen ion implantation forms a micrrobubble layer locally in a region at a depth corresponding to the average ion implantation depth.
9. The method of claim 8 , wherein the microbubble layer contains Si atoms having unpaired bonds and high density Si—H bonds.