Method for depositing a low-diffusion TiAlN layer and insulated gate comprising such a layer

1. A method for forming an aluminum titanium nitride layer (TiAlN) on a semiconductor substrate by a plasma-enhanced physical vapor deposition, comprising:

denitriding a titanium-aluminum (TiAl) sputtering target; and

discharging from the TiAl sputtering target an argon and nitrogen plasma onto the semiconductor substrate in a first step at a radio frequency power, and in a second step at a radio frequency power superimposed to a D.C. power.

2. The method of claim 1 , wherein the first step is at a radio frequency power ranging between 100 and 500 W and the second step is at a radio frequency power ranging between 500 and 1,000 W superimposed to the D.C. power ranging between 100 and 1,000 W.

3. The method of claim 1 , wherein the first step lasts for between 1.5 and 2.5 seconds.

4. The method of claim 1 , wherein the the TiAl sputtering target comprises from 65 to 75% of titanium and from 25 to 35% of aluminum, in atomic percentage.

5. The method of claim 1 , wherein the TiAl sputtering target comprises 70% of titanium and 30% of aluminum in atomic percentage.

6. A method for manufacturing an insulated gate on a semiconductor substrate comprising:

denitriding a titanium-aluminum (TiAl) sputtering target;

discharging from the TiAl sputtering target an argon and nitrogen plasma onto the semiconductor substrate to form an aluminum titanium nitride layer (TiAlN) on the semiconductor substrate; and

forming a conductive stack over the TiAlN layer to define the insulated gate.

7. The method of claim 6 , further comprising forming an insulating layer comprising hafnium before forming the TiAlN layer.

8. The method of claim 6 , further comprising forming a titanium nitride layer on the semiconductor substrate.

9. The method of claim 6 , wherein the semiconductor substrate comprises a fully depleted semiconductor substrate of semiconductor-on-insulator type.

10. A method of forming an integrated circuit comprising:

forming a titanium nitride layer over a semiconductor substrate;

denitriding a titanium-aluminum (TiAl) sputtering target;

discharging from the TiAl sputtering target an argon and nitrogen plasma at the semiconductor substrate to form an aluminum titanium nitride layer (TiAlN) over the semiconductor substrate;

forming a conductive stack over the TiAlN layer as the insulated gate; and

forming a hafnium layer before the TiAlN layer.

11. The method of claim 10 , wherein the hafnium layer has a thickness between 1 and 2.5 nm, and the TiAlN layer has a thickness between 3 and 4 nm.

12. The method of claim 10 , comprising forming an insulating interface layer is between the hafnium layer and the semiconductor substrate.