Semiconductor device substrate and process for preparing the same

A process for preparing a semiconductor device substrate which comprises a step of making at least one surface of a first substrate composed of Si material porous, a step of oxidizing inside walls of pores in the resulting porous Si surface layer, a step of forming monocrystalline Si layer on the porous Si surface layer, a step of bonding the monocrystalline Si layer to one surface layer of a second substrate composed of Si material through an insulating layer, a step of removing the first substrate to a depth just before the porous Si layer is exposed, or to a depth where the porous Si layer is partially exposed, a first etching step of selectively etching the first substrate by etching except for the porous Si layer, and a second etching step of impregnating the porous Si layer exposed by the removal of the first substrate with hydrofluoric acid or a first liquid mixture of hydrofluoric acid and at least one of an alcohol and a hydrogen peroxide solution, or by buffered hydrofluoric acid, or a second liquid mixture of buffered hydrofluoric acid and at least one of an alcohol and a hydrogen peroxide solution, thereby selectively removing the porous Si layer.

A process for preparing a semiconductor device substrate which comprises a step of making at least one surface of a first substrate composed of Si material porous, a step of oxidizing inside walls of pores in the resulting Si porous surface layer, a step of forming a monocrystalline Si layer on the porous Si surface layer, a step of bonding the surface of the monocrystalline Si layer to one surface of a second substrate composed of a light-transmissive material through an insulating layer, a first etching step of forming an etching resistant mask on the bonded second layer and then removing the first Si substrate by selective etching except for the porous Si layer, a second etching step of impregnating the porous Si layer exposed by the removal of the first Si substrate with hydrofluoric acid or a first liquid mixture of hydrofluoric acid and at least one of an alcohol and a hydrogen peroxide solution or buffered hydrofluoric acid or a second liquid mixture of buffered hydrofluoric acid and at least one of an alcohol and a hydrogen peroxide solution, thereby selectively removing the porous Si layer, and a step of removing the etching-resistant mask and increasing a bonding strength obtained in the bonding step when it fails to reach a desired one.

A process for preparing a semiconductor device substrate which comprises a step of making at least one surface of a first substrate composed of Si material porous, a step of oxidizing inside walls of pores in the resulting porous Si surface layer, a step of forming a monocrystalline Si layer on the porous Si surface layer, a step of bonding the surface of the monocrystalline Si layer to one surface of a second substrate composed of a light-transmissive material through an insulating layer, a step of removing the first substrate to a depth just before the porous Si layer is exposed, or to a depth where the porous Si layer is partially exposed, a first etching step of removing the first substrate by selective etching except for the porous Si layer, a second etching step of impregnating the porous Si layer exposed by the removal of the first substrate with hydrofluoric acid or a first liquid mixture of hydrofluoric acid and at least one of an alcohol and a hydrogen peroxide solution or buffered hydrofluoric acid or a second liquid mixture of buffered hydrofluoric acid and at least one of an alcohol and a hydrogen peroxide solution, thereby selectively removing the porous Si layer, and a step of increasing a bonding strength obtained in the bonding step when it fails to reach a desired one.

A process for preparing a semiconductor device substrate which comprises a step of making at least one surface of a first substrate composed of Si material porous, a step of oxidizing inside walls of pores in the resulting porous Si surface layer, a step of forming a monocrystalline Si layer on the porous Si surface layer, a step of bonding the surface of the monocrystalline Si layer to one surface of a second substrate composed of a light-transmissive material, a first etching step of removing the first substrate by selective etching, a second etching step of impregnating the porous Si layer exposed by the removal of the first substrate with hydrofluoric acid or a first liquid mixture of hydrofluoric acid and at least one of an alcohol and a hydrogen peroxide solution or buffered hydrofluoric acid or a second liquid mixture of buffered hydrofluoric acid and at least one of an alcohol and a hydrogen peroxide solution, thereby selectively removing the porous Si layer, and a step of increasing a bonding strength obtained in the bonding step when it fails to reach a desired one.

A process for preparing a semiconductor device substrate which comprises a step of making at least one surface of a first substrate composed of Si material porous, a step of oxidizing inside walls of pores in the resulting porous Si surface layer, a step of forming a monocrystalline Si layer on the porous Si surface layer, a step of bonding the surface of the monocrystalline Si layer to one surface of a second substrate composed of a light-transmissive material, a step of removing the first substrate to a depth just before the porous Si layer is exposed or to a depth where the porous Si layer is partially exposed, a first etching step of removing the first substrate selective etching except for the porous Si layer, a second etching step of impregnating the porous Si layer exposed by the removal of the first substrate with hydrofluoric acid or a first liquid mixture of hydrofluoric acid and at least one of an alcohol and a hydrogen peroxide solution or buffered hydrofluoric acid or a second liquid mixture of buffered hydrofluoric acid and at least one of an alcohol and a hydrogen peroxide solution, thereby selectively removing the porous Si layer, and a step of increasing a bonding strength obtained in the bonding step when it fails to reach a desired one.