Passivation of wide band-gap based semiconductor devices with hydrogen-free sputtered nitrides
View Patent ↗A passivated semiconductor structure and associated method are disclosed. The structure includes a silicon carbide substrate or layer; an oxidation layer on the silicon carbide substrate for lowering the interface density between the silicon carbide substrate and the thermal oxidation layer; a first sputtered non-stoichiometric silicon nitride layer on the thermal oxidation layer for reducing parasitic capacitance and minimizing device trapping; a second sputtered non-stoichiometric silicon nitride layer on the first layer for positioning subsequent passivation layers further from the substrate without encapsulating the structure; a sputtered stoichiometric silicon nitride layer on the second sputtered layer for encapsulating the structure and for enhancing the hydrogen barrier properties of the passivation layers; and a chemical vapor deposited environmental barrier layer of stoichiometric silicon nitride for step coverage and crack prevention on the encapsulant layer.
1. A method of passivating wide bandgap devices, the method comprising:
sputter-depositing a non-stoichiometric silicon nitride layer on an oxide layer; and
depositing an environmental barrier layer of stoichiometric silicon nitride by chemical vapor deposition.
2. A method according to claim 1 further comprising:
thermally oxidizing a silicon carbide substrate; and
annealing the thermal oxide in a nitrogen-oxide composition;
both prior to the step of sputter-depositing the non-stoichiometric SiC layer.
3. A method according to claim 2 comprising annealing the thermal oxide in N 2 O.
4. A method according to claim 2 comprising annealing the thermal oxide in NO.
5. A method according to claim 1 comprising sputtering a silicon target in a substantially hydrogen-free environment.
6. A method according to claim 5 comprising sputtering the silicon target in an environment of argon and nitrogen.
7. A method according to claim 6 comprising sputtering with a pulsed direct current power source to thereby discharge insulating particles while avoiding arcing.
8. A method according to claim 1 comprising sputtering at room temperature.
9. A method of according to claim 1 comprising sputtering while elevating the substrate temperature, while avoiding exceeding temperatures that would otherwise detrimentally affect the remainder of the device.
10. A method according to claim 9 comprising elevating the substrate temperature to between about 350° C. and 450° C.
11. A method according to claim 1 comprising sputtering in a nitrogen-rich environment to provide a non-stoichiometric silicon nitride.
12. A method according to claim 1 wherein the step of depositing the environmental barrier layer further comprises sputter depositing at least one stoichiometric silicon nitride layer.
13. A method according to claim 1 comprising applying a radio frequency bias to the substrate during the sputtering step to generate an ion bombardment.
14. A method according to claim 1 comprising lowering the ambient pressure during the sputtering step to generate an ion bombardment.
15. A method of passivating wide bandgap devices, the method comprising:
sputter-depositing a non-stoichiometric nitride layer selected from the group consisting of silicon nitride and aluminum nitride on a layer of Group III nitride semiconductor material; and
depositing an environmental barrier layer of stoichiometric silicon nitride by chemical vapor deposition on to the sputter-deposited layer.
16. A method according to claim 15 comprising sputtering a silicon target in a substantially hydrogen-free environment.
17. A method according to claim 16 comprising sputtering the silicon target in an environment of argon and nitrogen.
18. A method according to claim 17 comprising sputtering with a pulsed direct current power source to thereby discharge insulating particles while avoiding arcing.
19. A method according to claim 15 comprising sputtering at room temperature.
20. A method of according to claim 15 comprising sputtering while elevating the substrate temperature, while avoiding exceeding temperatures that would otherwise detrimentally affect the remainder of the device.
21. A method according to claim 20 comprising elevating the substrate temperature to between about 350° C. and 450° C.
22. A method according to claim 15 comprising sputtering in a nitrogen-rich environment to provide a non-stoichiometric silicon nitride.
23. A method according to claim 15 wherein the step of depositing the environmental barrier layer further comprises sputter depositing at least one stoichiometric silicon nitride layer.
24. A method according to claim 15 comprising applying a radio frequency bias to the substrate during the sputtering step to generate an ion bombardment.
25. A method according to claim 15 comprising lowering the ambient pressure during the sputtering step to generate an ion bombardment.