Selective SiN lateral recess

• US 10,062,579 B2
• Filed: 10/07/2016
• Issued: 08/28/2018
• Est. Priority Date: 10/07/2016
• Status: Active Grant

• Current Assignee: Applied Materials Incorporated
• Original Assignee: Applied Materials Incorporated
• Inventors: Chen, Zhijun, Huang, Jiayin, Wang, Anchuan, Ingle, Nitin
• Primary Examiner(s): Deo, Duy Vu N
• Application Number:
  US15/288,898
• Publication Number:
  US 20180102255A1
• Time in Patent Office: 690 Days
• CPC Class Codes: H01J 37/32357 Generation remote from the workpiece, e.g. down-stream
• CPC Class Codes: H01L 21/0217 the material being a silicon nitride not containing oxygen, e.g. SixNy or SixByNz H01L21/02126 and H01L21/0214 take precedence
• CPC Class Codes: H01L 21/02323 introduction of oxygen
• CPC Class Codes: H01L 21/31116 by dry-etching

Abstract

Exemplary methods for laterally etching silicon nitride may include flowing a fluorine-containing precursor and an oxygen-containing precursor into a remote plasma region of a semiconductor processing chamber. The methods may include forming a plasma within the remote plasma region to generate plasma effluents of the fluorine-containing precursor and the oxygen-containing precursor. The methods may also include flowing the plasma effluents into a processing region of the semiconductor processing chamber. A substrate may be positioned within the processing region, and the substrate may include a trench formed through stacked layers including alternating layers of silicon nitride and silicon oxide. The methods may also include laterally etching the layers of silicon nitride from sidewalls of the trench while substantially maintaining the layers of silicon oxide. The layers of silicon nitride may be laterally etched less than 10 nm from the sidewalls of the trench.

Claims

1. An etching method comprising:

flowing a fluorine-containing precursor and an oxygen-containing precursor into a remote plasma region of a semiconductor processing chamber;

forming a plasma within the remote plasma region to generate plasma effluents of the fluorine-containing precursor and the oxygen-containing precursor;

flowing the plasma effluents into a processing region of the semiconductor processing chamber, wherein a substrate is positioned within the processing region, and wherein the substrate comprises a trench formed through stacked layers including alternating layers of silicon nitride and silicon oxide; and

laterally etching the layers of silicon nitride from sidewalls of the trench while substantially maintaining the layers of silicon oxide, wherein the semiconductor processing chamber is maintained at a temperature less than −

20°

C., wherein a layer of silicon nitride at an upper region of the trench and a layer of silicon nitride at a lower region of the trench differ in lateral etch amounts by less than about 30%, and wherein the layers of silicon nitride are laterally etched less than 10 nm from the sidewalls of the trench.

2. The etching method of claim 1, wherein a flow-rate ratio of oxygen-containing precursor to fluorine-containing precursor is greater than or about 50:

1.

3. The etching method of claim 1, wherein the stacked layers comprise at least 50 layers of alternating layers of silicon nitride and silicon oxide, and wherein the trench is characterized by an aspect ratio of greater than or about 100:

1.

4. The etching method of claim 1, wherein the temperature is less than or about −

40°

C.

5. The etching method of claim 1, wherein the lateral etching is performed at a chamber operating pressure of less than or about 1 Torr.

6. The etching method of claim 1, wherein the layers of silicon nitride are laterally etched less than or about 6 nm.

7. The etching method of claim 1, wherein the lateral etching comprises oxidizing a portion of the silicon nitride to produce a fluorinated oxide.

8. The etching method of claim 7, wherein fluorine within the fluorinated oxide diffuses through the oxidized portion of the silicon nitride to laterally etch the silicon nitride.

9. The etching method of claim 7, wherein the method further comprises removing the fluorinated oxide from the silicon nitride.

10. The etching method of claim 9, wherein removing the fluorinated oxide comprises etching the fluorinated oxide with plasma effluents produced from a fluorine-containing precursor and a hydrogen-containing precursor.

11. The etching method of claim 1, wherein the layer of silicon nitride at the upper region of the trench and the layer of silicon nitride at the lower region of the trench differ in lateral etch amounts by less than about 20%.

12. An etching method comprising:

flowing a fluorine-containing precursor and an oxygen-containing precursor into a remote plasma region of a semiconductor processing chamber;

forming a plasma within the remote plasma region to generate primary plasma effluents of the fluorine-containing and oxygen-containing precursors;

flowing the primary plasma effluents into a processing region of the semiconductor processing chamber, wherein a substrate is positioned within the processing region, and wherein the substrate comprises a trench formed through stacked layers including alternating layers of silicon nitride and silicon oxide;

maintaining the semiconductor processing chamber at a temperature less than −

20°

C.;

oxidizing a portion of the silicon nitride from sidewalls of the trench to produce a fluorinated oxide region in each layer of silicon nitride;

flowing a fluorine-containing precursor into the remote plasma region of the semiconductor processing chamber while generating a plasma to produce secondary plasma effluents;

flowing the secondary plasma effluents into the processing region of the semiconductor processing chamber; and

laterally etching the fluorinated oxide region from each layer of silicon nitride, wherein a layer of silicon nitride at an upper region of the trench and a layer of silicon nitride at a lower region of the trench differ in lateral etch amounts by less than about 30%.

13. The etching method of claim 12, wherein a flow-rate ratio of oxygen-containing precursor to fluorine-containing precursor used to produce the primary plasma effluents is greater than or about 60:

1.

14. The etching method of claim 12, wherein the silicon nitride is oxidized to a depth of from about 1 nm to about 8 nm.

15. The etching method of claim 12, wherein a bottom of the trench is at least partially oxidized along with the layers of silicon nitride, and wherein the bottom of the trench is etched less than or about 5 nm.

16. The etching method of claim 12, wherein laterally etching the fluorinated oxide region from each layer of silicon nitride further comprises flowing a hydrogen-containing precursor into the semiconductor processing chamber.

17. The etching method of claim 12, wherein the oxidized portion of silicon nitride comprises a lower quality oxide than the layers of silicon oxide.

18. The etching method of claim 12, wherein the layer of silicon nitride at the upper region of the trench and the layer of silicon nitride at the lower region of the trench differ in lateral etch amounts by less than about 20%.