Method of fabricating diamond-semiconductor composite substrates
A method of fabricating a semiconductor-on-diamond composite substrate, the method comprising: (i) starting with a native semiconductor wafer comprising a native silicon carbide substrate on which a compound semiconductor is disposed; (ii) bonding a silicon carbide carrier substrate to the compound semiconductor; (iii) removing the native silicon carbide substrate; (iv) forming a nucleation layer over the compound semiconductor; (v) growing polycrystalline chemical vapor deposited (CVD) diamond on the nucleation layer to form a composite diamond-compound semiconductor-silicon carbide wafer, and (vi) removing the silicon carbide carrier substrate y laser lift-off to achieve a layered structure comprising the compound semiconductor bonded to the polycrystalline CVD diamond via the nucleation layer, wherein in step (ii) the silicon carbide carrier substrate is bonded to the compound semiconductor via a laser absorption material which absorbs laser light, wherein the laser has a coherence length shorter than a thickness of the silicon carbide carrier substrate.
1. A method of fabricating a semiconductor-on-diamond composite substrate, the method comprising:
(i) starting with a native semiconductor wafer comprising a native silicon carbide growth substrate on which a compound semiconductor is disposed;
(ii) bonding a silicon carbide carrier substrate to the compound semiconductor;
(iii) removing the native silicon carbide growth substrate;
(iv) forming a nucleation layer over the compound semiconductor;
(v) growing polycrystalline CVD diamond on the nucleation layer to form a composite diamond-compound semiconductor-silicon carbide wafer, and
(vi) removing the silicon carbide carrier substrate to achieve a layered structure comprising the compound semiconductor bonded to the polycrystalline CVD diamond via the nucleation layer,
wherein in step (ii) the silicon carbide carrier substrate is bonded to the compound semiconductor via a laser absorption material which absorbs laser light at a coherence length shorter than a thickness of the silicon carbide carrier substrate,
wherein in step (vi) the silicon carbide carrier substrate is removed from the compound semiconductor by:
heating the composite diamond-compound semiconductor-silicon carbide wafer to a temperature of at least 100° C.;
directing laser light having a coherence length shorter than the thickness of the silicon carbide carrier substrate through the silicon carbide carrier substrate, the laser light being absorbed by the laser absorption material; and
cooling the composite diamond-compound semiconductor-silicon carbide wafer after exposure to the laser light causing separation of the silicon carbide carrier substrate from the compound semiconductor.
2. A method according to claim 1 ,
wherein the laser absorption material provided between the silicon carbide carrier substrate and the compound semiconductor is a ceramic material.
3. A method according to claim 2 ,
wherein the laser absorption material provided between the silicon carbide carrier substrate and the compound semiconductor is polycrystalline or amorphous silicon.
4. A method according to claim 1 ,
wherein the laser absorption material is coated on the silicon carbide carrier substrate prior to bonding the silicon carbide carrier substrate to the compound semiconductor.
5. A method according to claim 1 ,
wherein the silicon carbide carrier substrate has a thickness in a range 100 micrometers to 2000 micrometers.
6. A method according to claim 1 ,
wherein in the silicon carbide carrier substrate has a diameter of at least 50 mm, 80 mm, 100 mm, 120 mm, 140 mm, or 150 mm.
7. A method according to claim 1 ,
wherein the native silicon carbide growth substrate is removed using a two-step process comprising:
mechanical lapping or polishing off a majority of the native silicon carbide growth substrate;
dry etching a remainder of the native silicon carbide growth substrate.
8. A method according to claim 1 ,
wherein the nucleation layer comprises one or more of: nanocrystalline diamond; silicon carbide, silicon, silicon nitride, silicon dioxide, aluminium nitride, magnesium oxide, boron nitride, and beryllium oxide.
9. A method according to claim 1 ,
wherein polycrystalline CVD diamond is grown to a thickness of at least 50 micrometers, 100 micrometers, 150 micrometers, 200 micrometers, or 300 micrometers.
10. A method according to claim 1 ,
wherein in step (vi) the composite diamond-compound semiconductor-silicon carbide wafer is heated to a temperature in a range 100 to 550° C.
11. A method according to claim 1 ,
wherein the coherence length of the laser light is in a range 10 micrometers to 400 micrometers.
12. A method according to claim 1 ,
wherein the laser light has a wavelength in a range 400 nm to 1200 nm.
13. A method according to claim 1 ,
wherein the laser light has a pulse width in a range 1 to 1000 nanoseconds.
14. A method according to claim 1 ,
wherein the step of directing laser light through the silicon carbide carrier substrate to be absorbed by the laser absorption material comprises moving the laser beam over the silicon carbide carrier substrate until the entire layer of laser absorption material is exposed to laser light prior to cooling.
15. A method according to claim 1 ,
wherein the compound semiconductor comprises one or more of gallium nitride, aluminium nitride, aluminium gallium nitride, and indium aluminium gallium nitride.