Composite wafer for fabrication of semiconductor devices
A composite wafer includes a first substrate having a first vertical thickness and a top surface, the top surface being prepared in a state for subsequent semiconductor material epitaxial deposition. A carrier substrate is disposed beneath the first substrate. The carrier substrate has a second vertical thickness greater than the first vertical thickness. An interlayer bonds the first substrate to the carrier substrate.
1. A method comprising:
(a) forming an interlayer that bonds a top surface of a carrier substrate to a bottom surface of a first substrate, the first substrate being of a first semiconductor material type and also having a top surface and a first thickness, the carrier substrate being of a second semiconductor material type and having a second thickness greater than the first thickness, the interlayer comprising silicon dioxide;
(b) forming one or more nitride layers over the top surface of the first substrate;
(c) fabricating nitride-based semiconductor devices in the one or more nitride layers; and
(d) de-bonding the top surface of the carrier substrate from the bottom surface of the first substrate.
2. The method of claim 1 wherein in the first substrate comprises sapphire.
3. The method of claim 1 wherein the second thickness is approximately 400 μm thick or greater.
4. The method of claim 1 wherein the carrier substrate is selected from the group consisting of sapphire, silicon, silicon carbide, diamond, gallium nitride, aluminum nitride, boron nitride, and zinc oxide.
5. The method of claim 1 wherein the de-bonding step comprises performing a wet etch in a chemical solution.
6. The method of claim 1 wherein the nitride-based semiconductor devices are formed on individual dies of a wafer, and further comprising separating the individual dies prior to the de-bonding step.
7. The method of claim 1 wherein the nitride-based semiconductor devices are formed on individual dies of a wafer, and further comprising separating the individual dies after the de-bonding step.
8. The method of claim 1 further comprising polishing the top surface of the first substrate prior to forming the one or more nitride layers.
9. The method of claim 8 wherein the polishing of the top surface results in an atomically-flat top surface.
10. The method of claim 1 wherein the first and second semiconductor material types have respective first and second coefficients of thermal expansion that are substantially matched to one another.
11. The method of claim 1 wherein the first semiconductor material type is selected from a group consisting of sapphire, diamond, gallium nitride, aluminum nitride, boron nitride, silicon carbide, and zinc oxide.
12. The method of claim 1 wherein the second semiconductor material type is selected from a group consisting of silicon and sapphire.
13. The method of claim 1 wherein the nitride-based semiconductor devices are fabricated as a plurality of die, and further comprising:
de-bonding the first substrate from the carrier substrate; and
individuating each of the die.
14. The method of claim 1 wherein the nitride-based semiconductor devices are fabricated as a plurality of die, and wherein the de-bonding comprises:
individuating each of the die; and
for each of the individuated die, de-bonding the first substrate from the carrier substrate.