Method for plasma etching a chromium layer suitable for photomask fabrication

1. A method of etching a chromium layer, comprising:

providing a filmstack in an etching chamber, the filmstack having a chromium layer disposed on a quartz layer and the chromium layer being partially exposed through a patterned layer;

providing Cl 2 and O 2 gas to a processing chamber;

forming a plasma from the process gases including ions and etching radicals above an ion-radical shield disposed in the processing chamber;

applying a bias to pass etching radicals through the ion-radical shield to the substrate disposed on a substrate support in the processing chamber with a plurality of power pulses less than 600 Watts; and

etching the chromium layer exposed through a patterned layer below the ion-radical shield.

2. The method of claim 1 , wherein the biasing further comprises:

pulsing power with a duty cycle between about 10 to about 95 percent; and

pulsing power at a frequency between about 2 to about 10 kHz.

3. The method of claim 1 , wherein the providing at least one halogen containing process gas further comprises:

flowing an inert gas into the processing chamber selected from the group consisting of Ar, He, Xe, Ne and Kr.

4. The method of claim 1 , wherein the biasing comprises:

pulsing RF power between about 10 W and about 150 W.

5. The method of claim 1 , wherein the biasing further comprises:

pulsing power with a duty cycle between about 10 to about 95 percent; and

pulsing power at a frequency between about 1 to about 10 kHz.

6. The method of claim 1 , wherein the forming the plasma further comprises:

providing a RF power of between about 250 to about 600 Watts from a plasma power source.

7. The method of claim 1 , wherein the patterned layer is formed by a method comprising:

patterning a layer of resist to form at least one opening in the resist layer; and

depositing a conformal protective layer on the patterned resist.

8. A method of forming a photomask, comprising:

patterning a mask layer on a photomask layer containing at least a chromium layer disposed on a quartz layer;

etching the chromium layer through the mask layer using an etch process comprising:

providing Cl 2 and O 2 gas to a processing chamber;

forming a plasma including ions and etching radicals from a process gas mixture above an ion-radical shield disposed in the processing chamber;

applying a bias to pass etching radicals through the ion-radical shield to the substrate disposed on a substrate support in the processing chamber with a plurality of power pulses less than 600 Watts; and

maintaining a plasma of the process gas with the processing chamber;

removing the mask layer; and

etching the chromium layer below the ion-radical shield.

9. The method of claim 8 , wherein the providing at least one halogen containing process gas further comprises:

flowing an inert gas into the processing chamber selected from the group consisting of Ar, He, Xe, Ne and Kr.

10. The method of claim 8 , wherein the biasing comprises:

pulsing RF power between about 10 W and about 150 W.

11. The method of claim 8 , wherein the biasing further comprises:

pulsing power with a duty cycle between about 10 to about 95 percent; and

pulsing power at a frequency between about 1 to about 10 kHz.

12. The method of claim 8 , wherein the forming the plasma further comprises:

providing a RF power of between about 250 to about 600 Watts from a plasma power source.

13. The method of claim 1 claim 8 , wherein the patterning a mask comprises:

patterning a layer of resist to form at least one opening in the resist layer;

depositing a conformal protective layer on the patterned resist; and

removing portions of the protective layer to expose the chromium layer for etching.

14. The method of claim 8 further comprising:

etching an attenuating layer using the patterned chromium layer.

15. The method of claim 14 further comprising:

removing the patterned chromium layer.

16. The method of claim 8 further comprising:

forming a patterned resist layer on the patterned chromium layer, wherein at least a first opening in the chromium layer is filled with resist and at least a second opening in the chromium layer is open through the patterned resist; and

etching the quartz layer through the second opening.

17. A method of forming a photomask, comprising:

patterning a resist layer on a film stack having a chromium-containing layer disposed on a quartz layer;

plasma etching the chromium-containing layer using the patterned resist layer as an etch mask to expose an underlying layer by supplying a gas mixture including Cl 2 and O 2 gas to a processing chamber;

applying a pulsed bias power of less than 600 Watts during etching of the chromium-containing layer; and

removing the resist layer.

18. The method of claim 17 further comprising:

depositing a conformal protective layer on the patterned resist layer, the protective layer coating side walls of openings formed in the resist layer, wherein plasma etching the chromium-containing layer comprises etching a chromium-containing layer using the patterned resist layer and protective layer as an etch mask.

19. The method of claim 17 , wherein the underlying layer comprises an attenuating layer disposed on a quartz layer, and further comprising:

etching the attenuating layer to expose the quartz layer, wherein the attenuating layer includes molybdenum.

20. The method of claim 17 further comprising:

etching the underlying layer to form an opening, wherein the underlying layer includes quartz; and

removing the chromium-containing layer.

21. A method of forming a photomask, comprising:

providing a film stack having a chromium-containing layer disposed on a quartz layer on a substrate support disposed in a processing chamber having a ion-radial shield spaced above the film stack;

patterning a resist layer disposed on the film stack;

plasma etching the chromium-containing layer using the patterned resist layer as an etch mask to expose an underlying layer by supplying providing Cl 2 and O 2 gas to a processing chamber;

applying a pulsed bias power of less than 600 Watts during etching of the chromium-containing layer to pass etching radicals through the ion-radical shield disposed in the processing chamber; and

removing the resist layer in-situ the processing chamber.