Method of transferring device layer to transfer substrate and highly thermal conductive substrate
A method of transferring a device layer in a SOI wafer obtained by stacking a Si layer, an insulator layer, and the device layer to a transfer substrate, includes a step of temporarily bonding a surface on which the device layer is formed of the SOI wafer to a supporting substrate using an adhesive for temporary bonding, a step of removing the Si layer of the SOI wafer until the insulator layer is exposed and obtaining a thinned device wafer, a step of coating only the transfer substrate with an adhesive for transfer and then bonding the insulator layer in the thinned device wafer to the transfer substrate via the adhesive for transfer, a step of thermally curing the adhesive for transfer under a load at the same time as or after bonding, a step of peeling off the supporting substrate, and a step of removing the adhesive.
1. A method of transferring a device layer in a silicon on insulator (SOI) wafer obtained by stacking a silicon (Si) layer, an insulator layer, and the device layer to a transfer substrate, the method comprising:
temporarily bonding a surface on which the device layer is formed of the SOI wafer to a supporting substrate using an adhesive for temporary bonding;
removing the Si layer of the SOI wafer until the insulator layer is exposed and obtaining a thinned device wafer;
coating only the transfer substrate with an adhesive for transfer and then bonding the insulator layer in the thinned device wafer to the transfer substrate via the adhesive for transfer;
thermally curing the adhesive for transfer under a load at the same time as or after bonding;
peeling off the supporting substrate; and
removing the adhesive for temporary bonding remaining on a surface of the device layer after peeling off;
wherein
the removing the Si layer includes:
grinding and thinning the Si layer,
edge trimming a SOI wafer temporarily bonded to the supporting substrate and an adhesive for temporary bonding, and
removing the remaining Si layer by etching using an acid.
2. The method according to claim 1 , wherein
the adhesive for temporary bonding contains silicone which is resistant to a strong acid as a main component, and
the edge trimming is performed by tape polishing.
3. The method according to claim 1 , wherein a low-stress adhesive having a Young's modulus of 10 MPa to 2 GPa is used as an adhesive for transfer to be applied to the transfer substrate side, and a thickness of the adhesive is 0.1 to 10 μm or less.
4. The method according to claim 1 , wherein the adhesive for transfer is a thermosetting epoxy-modified silicone.
5. The method according to claim 1 , wherein the transfer substrate is selected from sapphire, alumina, an AIN sintered body, a Si 3 N 4 sintered body, a SiC sintered body, poly-SiC, or polycrystalline diamond.
6. The method according to claim 1 , wherein the insulator layer included in the SOI wafer is a buried oxide film.
7. The method according to claim 1 , wherein the supporting substrate is peeled off by a mechanical measure in the peeling off.