Aluminum-nitride buffer and active layers by physical vapor deposition

1. A method for fabricating a device, comprising:

treating a surface of one or more substrates in a first processing chamber;

transferring the one or more substrates from the first processing chamber to a second processing chamber in a controlled environment; and

depositing a crystalline aluminum-nitride layer on the one or more substrates in the second processing chamber that has one or more walls that define a processing region, wherein depositing the crystalline aluminum-nitride layer comprises:

biasing a target that has a surface that is in contact with the processing region, wherein biasing the target comprises delivering a pulsed DC signal at a power of between 4 kWatts and 6 kWatts, and wherein the target comprises aluminum;

flowing a first gas that comprises nitrogen into the processing region;

flowing a second gas into the processing region, wherein the second gas comprises argon, krypton or neon;

biasing an electrode to form a negative substrate bias potential on the one or more substrates that are disposed over a substrate support, wherein biasing the electrode comprises creating a floating potential on the one or more substrates that varies from between −300 volts and −1 volt, wherein biasing the electrode comprises biasing the electrode for a first period of time that occurs before biasing the target;

transferring the one or more substrates from the second processing chamber to a third processing chamber; and

forming a group III-nitride layer on the crystalline aluminum nitride layer in the third processing chamber, wherein the crystalline aluminum-nitride layer has a surface roughness less than three percent of a thickness of the crystalline aluminum-nitride layer, and wherein forming the group III-nitride layer comprises:

delivering a metal containing precursor and a nitrogen containing gas to a surface of each of the one or more substrates.

2. The method of claim 1 , wherein delivering the pulsed DC signal comprises delivering the pulsed DC signal at a pulse frequency of between 5 kHz and 200 kHz.

3. The method of claim 1 , wherein delivering the pulsed DC signal at the power of between 4 kWatts and 6 kWatts is at a duty cycle between 80% and 95%.

4. A method for fabricating a device, comprising:

treating a surface of one or more substrates in a first processing chamber, wherein treating the surface of the one or more substrates comprises degassing the one or more substrates or sputter etching a surface of the one or more substrates;

transferring the one or more substrates from the first processing chamber to a second processing chamber in a controlled environment;

heating the one or more substrates to a temperature between 200° C. and 1000° C. before biasing the target;

controlling a pressure within the processing region while biasing the target to a pressure between 0.1 mTorr and 200 mTorr; and

depositing the crystalline aluminum nitride layer at a deposition rate between 7 angstroms per second and 20 angstroms per second, wherein the processing chamber has one or more walls that define a processing region, and wherein depositing the crystalline aluminum-nitride layer comprises:

biasing a target that has a surface that is in contact with the processing region, wherein biasing the target comprises delivering a pulsed DC signal and the target comprises aluminum, wherein biasing the target comprises delivering a pulsed DC signal at a power between 4 kWatts and 6 kWatts, flowing a first gas that comprises nitrogen into the processing region;

flowing a second gas into the processing region, wherein the second gas comprises argon, krypton or neon; and

biasing an electrode to form a negative substrate bias potential on the one or more substrates that are disposed over a substrate support, wherein biasing the electrode comprises creating a floating potential on the one or more substrates that varies from between −300 volts and −1 volt.

5. The method of claim 4 , wherein biasing the electrode occurs between 1 and 10 seconds before biasing the target.

6. The method of claim 4 , wherein the pressure within the processing region is less than 10 mTorr.

7. The method of claim 6 , further comprising adjusting the argon to nitrogen gas composition ratio of 60% to 95% N 2 in the processing region.

8. The method of claim 7 , wherein the temperature of the one or more substrates is heated to a temperature between 350° C. and 450° C.

9. The method of claim 4 , wherein delivering the pulsed DC signal is performed using a duty cycle of between 80% and 95%.

10. The method of claim 9 , wherein delivering the pulsed DC signal is performed at a pulse frequency of between 5 kHz and 200 kHz.

11. The method of claim 10 , further comprising adjusting the argon to nitrogen gas composition ratio of 60% to 95% N 2 in the processing region.

12. The method of claim 4 , wherein the first gas is selected from the group consisting of nitrogen dioxide (NO 2 ) and nitric oxide (NO).

13. The method of claim 4 , wherein the pulsed DC signal applied to the target includes a signal that comprises a plurality of alternating first and second intervals, wherein during the first intervals a first negative DC bias voltage is applied to the target, and during the second intervals a DC bias voltage that is less negative than the first negative DC bias voltage is applied to the target.

14. The method of claim 13 , wherein the DC bias voltage applied to the target during the second intervals is a positive voltage.

15. The method of claim 13 , wherein biasing the electrode occurs between 1 and 10 seconds before biasing the target.

16. The method of claim 1 , wherein the crystalline aluminum-nitride layer having Al polarity has a stress between about 10 Gpa and about 10 Gpa.