High aspect ratio etch with combination mask

1. A method for etching features in a stack, comprising:

forming a combination hardmask, comprising;

forming a first hardmask layer comprising carbon or silicon oxide over the stack;

forming a second hardmask layer comprising metal over the first hardmask layer;

forming a third hardmask layer comprising carbon or silicon oxide over the second hardmask layer, and

forming a fourth hardmask layer comprising metal over the third hardmask layer;

etching the fourth hardmask layer, comprising:

flowing a fourth hardmask layer etch gas comprising a halogen component; and

forming the fourth hardmask layer etch gas into a plasma; and

stopping the flow of the fourth; and

etching the third hardmask layer, comprising:

flowing a third hardmask layer etch gas comprising oxygen and at least one of COS or SO 2 ;

forming the first hardmask layer etch gas into a plasma; and

stopping the flow of the first hardmask layer etch gas;

patterning the first and second hardmask layers; and

etching the stack through the combination hardmask.

2. The method, as recited in claim 1 , wherein the second hardmask comprises at least one of elemental metal, a metal alloy, a metal oxide, metal carbide, or a metal nitride.

3. The method, as recited in claim 1 , wherein the stack is at least one of a silicon oxide layer, OPOP or ONON.

4. The method, as recited in claim 1 , further comprising ashing the first hardmask layer.

5. The method, as recited in claim 1 , wherein the patterning the first and second hardmask layers comprises:

forming a patterned mask over the hardmask layers;

etching the second hardmask layer; and

etching the first hardmask layer.

6. The method, as recited in claim 5 , wherein the patterning the first and second hardmask layers comprises:

etching the second hardmask layer, comprising:

flowing a second hardmask layer etch gas comprising a halogen component;

forming the second hardmask layer etch gas into a plasma; and

stopping the flow of the second hardmask layer etch gas; and

etching the first hardmask layer, comprising:

flowing a first hardmask layer etch gas comprising oxygen and at least one of COS or SO 2 ;

forming the first hardmask layer etch gas into a plasma; and

stopping the flow of the first hardmask layer etch gas.

7. The method, as recited in claim 6 , wherein the patterning the hardmask layers removes the patterned mask.

8. The method, as recited in claim 5 , wherein the etching the second hardmask layer, comprises:

flowing a second hardmask layer etch gas comprising a halogen component;

forming the second hardmask layer etch gas into a plasma; and

stopping the flow of the second hardmask layer etch gas; and wherein etching the first hardmask layer, comprises:

flowing a first hardmask layer etch gas comprising oxygen and at least one of COS or SO 2 ;

forming the first hardmask layer etch gas into a plasma; and

stopping the flow of the first hardmask layer etch gas.

9. The method, as recited in claim 8 , wherein the second hardmask comprises at least one of elemental metal, a metal alloy, a metal oxide, metal carbide, or a metal nitride.

10. The method, as recited in claim 9 , wherein the stack is at least one of a silicon oxide layer, OPOP or ONON.

11. A method for etching features in a stack, wherein the stack is at least one of a silicon oxide layer, OPOP or ONON, comprising:

forming a combination hardmask, comprising;

forming a first hardmask layer comprising carbon or silicon oxide over the stack;

forming a second hardmask layer comprising metal over the first hardmask layer, wherein the second hardmask layer comprises at least one of elemental metal, a metal alloy, a metal oxide, metal carbide, or a metal nitride;

forming a third hardmask layer comprising carbon or silicon oxide over the second hardmask layer;

forming a fourth hardmask layer comprising metal over the third hardmask layer;

forming a patterned mask over the hardmask layers;

etching the fourth hardmask layer through the patterned mask, comprising:

flowing a fourth hardmask layer etch gas comprising a halogen component; and

forming the fourth hardmask layer etch gas into a plasma, and

stopping the flow of the fourth; and

etching the third hardmask layer, comprising:

flowing a third hardmask layer etch gas comprising oxygen and at least one of COS or SO 2 ;

forming the first hardmask layer etch gas into a plasma; and

stopping the flow of the first hardmask layer etch gas; and

patterning the first and second hardmask layers, wherein the patterning the first and second hardmask layers comprises:

etching the second hardmask layer, comprising

flowing a second hardmask layer etch gas comprising a halogen component;

forming the second hardmask layer etch gas into a plasma; and

stopping the flow of the second hardmask layer etch gas; and

etching the first hardmask layer, comprising;

flowing a first hardmask layer etch gas comprising oxygen and at least one of COS or SO 2 ;

forming the first hardmask layer etch gas into a plasma; and

stopping the flow of the first hardmask layer etch gas;

etching the stack through the combination hardmask.

12. The method, as recited in claim 11 , wherein the patterning the hardmask layers removes the patterned mask.

13. The method, as recited in claim 12 , further comprising ashing the first hardmask layer.

14. A method for etching features in a stack, comprising:

forming a combination hardmask, comprising;

forming a first hardmask layer comprising carbon or silicon oxide over the stack;

forming a second hardmask layer comprising metal over the first hardmask layer; and

forming a patterned mask over the second hardmask layer;

etching the second hardmask layer through the patterned mask, comprising:

flowing a second hardmask layer etch gas comprising a halogen component;

forming the second hardmask layer etch gas into a plasma; and

stopping the flow of the second hardmask layer etch gas;

etching the first hardmask layer, comprising:

flowing a first hardmask layer etch gas comprising oxygen and at least one of COS or SO 2 ;

forming the first hardmask layer etch gas into a plasma; and

stopping the flow of the first hardmask layer etch gas; and

etching the stack through the combination hardmask.

15. The method, as recited in claim 14 , wherein the second hardmask comprises at least one of elemental metal, a metal alloy, a metal oxide, metal carbide, or a metal nitride.

16. The method, as recited in claim 14 , wherein the stack is at least one of a silicon oxide layer, OPOP or ONON.