Silicon oxide silicon nitride stack ion-assisted etch

Patent metadata

Field	Value
Publication number	US-9997366-B2
Application number	US-201715726120-A
Country	US
Kind code	B2
Filing date	Oct 5, 2017
Priority date	Oct 19, 2016
Publication date	Jun 12, 2018
Grant date	Jun 12, 2018

Abstract

A method for ion-assisted etching a stack of alternating silicon oxide and silicon nitride layers in an etch chamber is provided. An etch gas comprising a fluorine component, helium, and a fluorohydrocarbon or hydrocarbon is flowed into the etch chamber. The gas is formed into an in-situ plasma in the etch chamber. A bias of about 10 to about 100 volts is provided to accelerate helium ions to the stack and activate a surface of the stack to form an activated surface for ion-assisted etching, wherein the in-situ plasma etches the activated surface of the stack.

First claim

What is claimed is:

1. A method for ion-assisted etching a stack of alternating silicon oxide and silicon nitride layers in an etch chamber, comprising:
flowing an etch gas comprising a fluorine component, helium, and a fluorohydrocarbon or hydrocarbon into the etch chamber;
forming the etch gas into an in-situ plasma in the etch chamber; and
providing a bias of about 10 to about 100 volts to accelerate helium ions to the stack and activate a surface of the stack to form an activated surface for ion-assisted etching, wherein the in-situ plasma etches the activated surface of the stack.

2. The method, as recited in claim 1 , wherein a flow rate of helium of the etch gas is at least twice a flow rate of remaining components of the etch gas.

3. The method, as recited in claim 1 , wherein the stack comprises at least two pairs of bilayers of silicon oxide and silicon nitride.

4. The method, as recited in claim 1 , wherein the stack comprises at least 100 pairs of bilayers of silicon oxide and silicon nitride.

5. The method, as recited in claim 1 , wherein the forming the etch gas into an in-situ plasma comprises providing RF power to the etch chamber through inductive coupling.

6. The method, as recited in claim 1 , wherein the stack is in a form of a stair-step structure, wherein the stair-step structure has a mask over part of the stack, wherein the mask does not cover some steps and sidewalls of the steps.

7. The method, as recited in claim 1 , wherein the stack is disposed below an organic mask, and the method further comprising trimming the organic mask.

8. The method, as recited in claim 1 , wherein the etch gas further comprises at least one of HBr, COS, Cl 2 , N 2 , Ar, H 2 , or SiCl 4 .

9. The method, as recited in claim 1 , wherein the helium ions do not etch the stack and wherein the in-situ plasma chemically etches only the activated surface of the stack.

10. A method for forming a stair-step structure in a stack in a plasma processing chamber, wherein the stack has an organic mask and wherein the stack comprises a plurality of bilayers of silicon oxide and silicon nitride, comprising a plurality of cycles, wherein each cycle comprises:
a) trimming the organic mask; and
b) ion-assisted etching at least one complete bilayer of the stack, wherein the ion-assisted etching comprises:
flowing an etch gas comprising a fluorine component, helium, and a fluorohydrocarbon or hydrocarbon into an etch chamber;
forming the etch gas into an in-situ plasma in the etch chamber; and
providing a bias of about 10 to about 100 volts to accelerate helium ions to the stack in the etch chamber and activate a surface of the stack to form an activated surface of the stack, wherein the in-situ plasma etches the activated surface of the stack.

11. The method, as recited in claim 10 , wherein the cycle of steps a-b is repeated at least 5 times.

12. The method, as recited in claim 10 , wherein the organic mask is a photoresist mask.

13. The method, as recited in claim 10 , wherein steps a-b are performed in an inductively coupled plasma processing chamber.

14. The method, as recited in claim 10 , wherein a flow rate of helium of the etch gas is at least twice a flow rate of remaining components of the etch gas.

15. The method, as recited in claim 10 , wherein the helium ions do not etch the stack and wherein the in-situ plasma chemically etches only the activated surface of the stack.

16. The method, as recited in claim 10 , wherein the etch gas further comprises at least one of HBr, COS, Cl 2 , N 2 , Ar, H 2 , or SiCl 4 .

Assignees

• Lam Res Corp

Inventors

• Tan Zhongkui
• Xiang Hua
• Hu Wenbing
• Xu Qing
• Fu Qian

Classifications

• H10P90/126

  by chemical etching · CPC title

• H10P50/287

  by chemical means · CPC title

• H10P50/283 Primary

  by chemical means · CPC title

• H10P50/73

  using masks for insulating materials · CPC title

• H10P50/242 Primary

  of Group IV materials · CPC title