Virtual substrates by having thick, highly relaxed metamorphic buffer layer structures by hydride vapor phase epitaxy
Virtual substrates made by hydride vapor phase epitaxy are provided comprising a semiconductor growth substrate and a substantially strain-relaxed metamorphic buffer layer (MBL) structure comprising one or more layers of a semiconductor alloy on the growth substrate. The MBL structure is compositionally graded such that its lattice constant transitions from a lattice constant at the interface with the growth substrate that is substantially the same as the lattice constant of the growth substrate to a lattice constant at a surface opposite the interface that is different from the lattice constant of the growth substrate. The virtual substrates comprise relatively thick MBL structures (e.g., >20 μm) and relatively thick growth substrates (e.g., >0.5 mm).
1. A virtual substrate comprising:
a semiconductor growth substrate having a first lattice constant; and
a substantially strain-relaxed metamorphic buffer layer structure comprising one or more layers of a semiconductor alloy on the growth substrate, the metamorphic buffer layer structure being compositionally graded such that the lattice constant of the metamorphic buffer layer structure transitions from a lattice constant at the interface with the growth substrate that is substantially the same as the first lattice constant to a second lattice constant at a surface opposite the interface that is different from the first lattice constant,
wherein the thickness of the metamorphic buffer layer structure is at least about 10 μm,
and further wherein the ratio of the thickness of the metamorphic buffer layer structure to the thickness of the growth substrate is less than a value above which value warping of the metamorphic buffer layer structure would occur.
2. The virtual substrate of claim 1 , wherein the thickness of the metamorphic buffer layer structure is at least about 20 μm.
3. The virtual substrate of claim 1 , wherein the thickness of the metamorphic buffer layer structure is at least about 25 μm.
4. The virtual substrate of claim 1 , wherein the ratio of the thickness of the metamorphic buffer layer structure to the thickness of the growth substrate is less than about 0.08 or the ratio of the thickness of the growth substrate to the diameter of the virtual substrate is at least about 0.20 mm/inch.
5. The virtual substrate of claim 1 , wherein the semiconductor growth substrate is GaAs and the semiconductor alloy is InGaAs, GaAsSb or GaAsP.
6. The virtual substrate of claim 1 , wherein the first lattice constant differs from the second lattice constant by at least about 0.5%.
7. The virtual substrate of claim 1 , wherein the first lattice constant differs from the second lattice constant by at least about 1.5%.
8. The virtual substrate of claim 1 , wherein the semiconductor growth substrate is GaAs and the metamorphic buffer layer structure comprises In x Ga 1-x As wherein x is graded from a value substantially near to 0 to a maximum value, wherein the maximum value is in the range of from about 0.1 to about 0.4.
9. The virtual substrate of claim 8 , wherein the thickness of the metamorphic buffer layer structure is at least about 20 μm.
10. The virtual substrate of claim 8 , wherein the thickness of the metamorphic buffer layer structure is at least about 25 μm.
11. The virtual substrate of claim 8 , wherein the ratio of the thickness of the metamorphic buffer layer structure to the thickness of the growth substrate is less than about 0.08 or the ratio of the thickness of the growth substrate to the diameter of the virtual substrate is at least about 0.20 mm/inch.
12. The virtual substrate of claim 1 , further comprising a selective etch layer on the metamorphic buffer layer structure.
13. The virtual substrate of claim 1 , further comprising a semiconductor device on the metamorphic buffer layer structure.
14. A method of making a virtual substrate, the method comprising
growing a substantially strain-relaxed metamorphic buffer layer structure comprising one or more layers of a semiconductor alloy on a semiconductor growth substrate via hydride vapor phase epitaxy, the metamorphic buffer layer structure being compositionally graded such that the lattice constant of the metamorphic buffer layer structure transitions from a lattice constant at the interface with the growth substrate that is substantially the same as the first lattice constant to a second lattice constant at a surface opposite the interface that is different from the first lattice constant,
wherein the thickness of the metamorphic buffer layer structure is at least about 10 μm,
and further wherein the ratio of the thickness of the metamorphic buffer layer structure to the thickness of the growth substrate is less than a value above which value warping of the metamorphic buffer layer structure would occur.
15. The method of claim 14 , wherein the method further comprises planarizing the top surface of the metamorphic buffer layer structure using chemical-mechanical polishing, wherein the chemical-mechanical polishing is carried out using a polishing pressure of less than about 12 psi.
16. The method of claim 15 , wherein the polishing pressure is in the range of from about 2 psi to about 6 psi.
17. A method of using a virtual substrate, the method comprising
growing a first semiconductor device over a virtual substrate, the virtual substrate comprising
a semiconductor growth substrate having a first lattice constant; and
a substantially strain-relaxed metamorphic buffer layer structure comprising one or more layers of semiconductor alloy on the growth substrate, the metamorphic buffer layer structure being compositionally graded such that the lattice constant of the metamorphic buffer layer structure transitions from a lattice constant at the interface with the growth substrate that is substantially the same as the first lattice constant to a second lattice constant at a surface opposite the interface that is different from the first lattice constant,
wherein the thickness of the metamorphic buffer layer structure is at least about 10 μm,
and further wherein the ratio of the thickness of the metamorphic buffer layer structure to the thickness of the growth substrate is less than a value above which value warping of the metamorphic buffer layer structure would occur;
removing the first semiconductor device from the virtual substrate; and
reusing the virtual substrate to grow a second semiconductor device.
18. The method of claim 17 , further comprising removing the first semiconductor device from the virtual substrate by etching a selective etch layer between the top surface of the metamorphic buffer layer structure and the semiconductor device.
19. The method of claim 17 , further comprising removing a portion of the material at the top surface of the metamorphic buffer layer structure prior to reusing the virtual substrate.
20. The method of claim 19 , further comprising removing at least about 2 μm of the top surface of the metamorphic buffer layer structure.