Methods of forming nitride films

1. A method of depositing a silicon nitride capping layer, said method including;

placing a gallium arsenide (GaAs) substrate which includes a non-activated implant into a chamber;

pre-cleaning the surface of the GaAs substrate using a H 2 plasma; and

introducing into a plasma region of the chamber a silicon containing gas, molecular nitrogen and sufficient hydrogen to dissociate the nitrogen to allow the silicon and nitrogen to react to form a silicon nitride capping layer of at least 400 nanometers in thickness on a surface of the GaAs substrate which includes the non-activated implant adjacent the plasma region,

wherein a flow rate of the nitrogen is in the range 700-900 sccm and a flow rate of the hydrogen is 500-800 sccm, and

wherein a power supplied to the plasma is between 50 and 150 W.

2. The method as claimed in claim 1 wherein the silicon containing gas is silane.

3. The method as claimed in claim 2 wherein a flow rate of the silane is less than 10 sccm.

4. The method as claimed in claim 2 wherein a flow rate of the silane is about 2 sccm.

5. The method as claimed in claim 1 wherein a flow rate of the molecular nitrogen is greater than a flow rate of the hydrogen.

6. The method as claimed in claim 1 wherein the formed film has a refractive index of about 2.

7. The method as claimed in claim 1 wherein a plasma in the plasma region is a high frequency plasma.

8. A method of forming a nitride capping layer, said method including:

placing a gallium arsenide (GaAs) substrate which includes a non-activated implant into a chamber;

pre-cleaning the surface of the GaAs substrate using a H 2 plasma; and

introducing into a plasma region of the chamber a source of an element to be nitrided, molecular nitrogen and sufficient hydrogen to dissociate the nitrogen to allow the element and the nitrogen to react to form a nitride capping layer of at least 400 nanometers in thickness on a surface of the GaAs substrate which includes the non-activated implant adjacent the plasma regions,

wherein a flow rate of the nitrogen is in the range 700-900 sccm and a flow rate of the hydrogen is 500-800 sccm, and

wherein a power supplied to the plasma is between 50 and 150 W.

9. The method as claimed in claim 8 wherein the element is a metal.

10. The method as claimed in claim 9 wherein the element is a transition metal.

11. The method as claimed in claim 8 wherein the formed film has a refractive index of about 2.

12. A method of depositing a stochiometric silicon nitride capping layer, said method including:

placing a gallium arsenide (GaAs) substrate which includes a non-activated implant into a chamber;

pre-cleaning the surface of the GaAs substrate using a H 2 plasma; and

introducing into a plasma region of a the chamber a silicon containing gas, molecular nitrogen and sufficient hydrogen to dissociate the nitrogen to allow the silicon and nitrogen to react to form a stochiometric silicon nitride capping layer of at least 400 nanometers in thickness on a surface of the GaAs substrate which includes the non-activated implant adjacent the plasma region,

wherein a flow rate of the nitrogen is in the range 700-900 sccm and a flow rate of the hydrogen is 500-800 sccm, and

wherein a power supplied to the plasma is between 50 and 150 W.

13. The method as claimed in claim 12 wherein the silicon containing gas is silane.

14. A method as claimed in claim 13 wherein a flow rate of the silane is less than 10 sccm.

15. A method as claimed in claim 13 wherein a flow rate of the silane is about 2 sccm.

16. A method as claimed in claim 12 wherein a flow rate of the molecular nitrogen is greater than a flow rate of the hydrogen.

17. A method as claimed in claim 12 wherein the formed film has a refractive index of about 2.

18. A method of forming a stochiometric nitride capping layer, said method including:

placing a gallium arsenide (GaAs) substrate which includes a non-activated implant into a chamber;

pre-cleaning the surface of the GaAs substrate using a H 2 plasma; and

introducing into a plasma region of the chamber a source of an element to be nitrided, molecular nitrogen and sufficient hydrogen to dissociate the nitrogen to allow the element and the nitrogen to react to form the stochiometric nitride capping layer of at least 400 nanometers in thickness on a surface of the GaAs substrate which includes the non-activated implant adjacent the plasma region,

wherein a flow rate of the nitrogen is in the range 700-900 sccm and a flow rate of the hydrogen is 500-800 sccm, and

wherein a power supplied to the plasma is between 50 and 150 W.

19. A method as claimed in claim 18 wherein the element is a metal.

20. A method as claimed in claim 18 wherein the element is a transition metal.

21. A method of depositing a silicon nitride capping layer, said method including:

placing a gallium arsenide (GaAs) substrate which includes a non-activated implant into a chamber;

pre-cleaning the surface of the GaAs substrate using a H 2 plasma; and

introducing into a plasma region of the chamber a silicon containing gas, molecular nitrogen and sufficient hydrogen to dissociate the nitrogen to allow the silicon and nitrogen to react to form a silicon nitride capping layer of at least 400 nanometers in thickness on a surface of the GaAs substrate which includes the non-activated implant adjacent the plasma region, wherein a flow rate of the nitrogen is in the range 700-900 sccm and a flow rate of the hydrogen is 500-800 sccm, and wherein a power supplied to the plasma is between 50 and 150 W; and then

annealing the GaAs substrate to activate the implant contained therein, wherein the silicon nitride capping layer inhibits diffusion of arsenic from the GaAs substrate during said annealing.

22. The method as claimed in claim 21 wherein the annealing is at about 700° C.

23. The method as claimed in claim 21 wherein the silicon nitride capping layer is formed as a stochiometric film.

24. The method as claimed in claim 21 wherein a temperature of the annealing is at least 650° C.

25. A method of forming a nitride capping layer, said method including:

placing a gallium arsenide (GaAs) substrate which includes a non-activated implant into a chamber;

pre-cleaning the surface of the GaAs substrate using a H 2 plasma; and

introducing into a plasma region of the chamber a source of an element to be nitrided, molecular nitrogen and sufficient hydrogen to dissociate the nitrogen to allow the element and the nitrogen to react to form the nitride film of at least 400 nanometers in thickness on a surface adjacent the plasma region, wherein a flow rate of the nitrogen is in the range 700-900 sccm and a flow rate of the hydrogen is 500-800 sccm, and wherein a power supplied to the plasma is between 50 and 150 W; and then

annealing the GaAs substrate to activate the implant contained therein, wherein the nitride capping layer inhibits diffusion of arsenic from the GaAs substrate during said annealing.

26. The method as claimed in claim 25 wherein the annealing is at about 700° C.

27. The method as claimed in claim 25 wherein the nitride capping layer is formed as a stochiometric film.

28. The method as claimed in claim 25 wherein a temperature of the annealing is at least 650° C.