Provided are a composite substrate in which a wafer to be bonded has a sufficiently small surface roughness and which can be prevented from causing film peeling, and a method for producing the composite substrate. The composite substrate 40 of the present invention has a silicon wafer 10, an interlayer 11, and a single-crystal silicon thin film or oxide single-crystal thin film 20a stacked in the order listed and has a damaged layer 12a in a portion of the silicon wafer 10 on the side of the interlayer 11.

A method for assembling a first substrate and a second substrate via metal adhesion layers, the method including: depositing, on a surface of each of the first and second substrates, a metal layer with a thickness controlled to limit surface roughness of each of the deposited metal layers to below a roughness threshold; exposing the metal layers deposited on the surface of the first and second substrates to air; directly adhering the first and second substrates by placing the deposited metal adhesion layers in contact, the surface roughness of the contacted layers being that obtained at an end of the depositing. The adhesion can be carried out in the air, at atmospheric pressure and at room temperature, without applying pressure to the assembly of the first and second substrates resulting from directly contacting the deposited metal adhesion layers.

A flip-chip manufacture is described. Methods of blocking adhesive underfill in flip-chip high speed component manufacture include creating topology discontinuities to prevent adhesive underfill material from interacting with RF sensitive regions on substrates.

A flip-chip manufacture is described. Methods of blocking adhesive underfill in flip-chip high speed component manufacture include creating topology discontinuities to prevent adhesive underfill material from interacting with RF sensitive regions on substrates.

A method for assembling a first substrate and a second substrate via metal adhesion layers, the method including: depositing, on a surface of each of the first and second substrates, a metal layer with a thickness controlled to limit surface roughness of each of the deposited metal layers to below a roughness threshold; exposing the metal layers deposited on the surface of the first and second substrates to air; directly adhering the first and second substrates by placing the deposited metal adhesion layers in contact, the surface roughness of the contacted layers being that obtained at an end of the depositing. The adhesion can be carried out in the air, at atmospheric pressure and at room temperature, without applying pressure to the assembly of the first and second substrates resulting from directly contacting the deposited metal adhesion layers.

Provided are a composite substrate in which a wafer to be bonded has a sufficiently small surface roughness and which can be prevented from causing film peeling, and a method for producing the composite substrate. The composite substrate 40 of the present invention has a silicon wafer 10, an interlayer 11, and a single-crystal silicon thin film or oxide single-crystal thin film 20a stacked in the order listed and has a damaged layer 12a in a portion of the silicon wafer 10 on the side of the interlayer 11.