Dual chamber plasma etcher with ion accelerator

• US 10,134,605 B2
• Filed: 08/21/2015
• Issued: 11/20/2018
• Est. Priority Date: 07/11/2013
• Status: Active Grant

• Current Assignee: Lam Research Corporation
• Original Assignee: Lam Research Corporation
• Inventors: Guha, Joydeep
• Primary Examiner(s): Alejandro Mulero, Luz L
• Application Number:
  US14/832,538
• Publication Number:
  US 20150364349A1
• Time in Patent Office: 1,187 Days
• Field of Search: 118723 R, 118723 E, 118723 ER, 118723 I, 118723 IR, 118723 AN, 15634543, 15634548, 15634549, 31511151
• CPC Class Codes: C23F 4/00 Processes for removing metallic material from surfaces, not provided for in group C23F1/00 or C23F3/00
• CPC Class Codes: H01J 2237/334 Etching
• CPC Class Codes: H01J 37/32357 Generation remote from the workpiece, e.g. down-stream
• CPC Class Codes: H01J 37/32422 Arrangement for selecting ions or species in the plasma
• CPC Class Codes: H01J 37/32449 Gas control, e.g. control of the gas flow
• CPC Class Codes: H01L 21/3065 Plasma etching; Reactive-ion etching
• CPC Class Codes: H01L 21/31116 by dry-etching
• CPC Class Codes: H01L 21/31122 of layers not containing Si, e.g. PZT, Al2O3
• CPC Class Codes: H01L 21/31138 by dry-etching
• CPC Class Codes: H01L 21/32136 using plasmas
• CPC Class Codes: H01L 21/32139 using masks
• CPC Class Codes: H01L 21/67069 for drying etching

Abstract

The embodiments herein generally deal with semiconductor processing methods and apparatus. More specifically, the embodiments relate to methods and apparatus for etching a semiconductor substrate. A partially fabricated semiconductor substrate is provided in a reaction chamber. The reaction chamber is divided into an upper sub-chamber and a lower sub-chamber by a grid assembly. Plasma is generated in the upper sub-chamber, and the substrate is positioned in the lower sub-chamber. The grid assembly includes at least two grids, each of which is negatively biased, and each of which includes perforations which allow certain species to pass through. The uppermost grid is negatively biased in order to repel electrons. The lowermost grid is biased further negative (compared to the uppermost grid) in order to accelerate positive ions from the upper to the lower sub-chamber. Etching gas is supplied directly to the lower sub-chamber. The etching gas and ions react with the surface of the substrate to etch the substrate as desired.

Claims

1. An apparatus for etching a substrate, comprising:

(a) a reaction chamber,

(b) a grid assembly positioned in the reaction chamber and thereby dividing the reaction chamber into an upper sub-chamber and a lower sub-chamber, wherein the grid assembly comprises at least an uppermost grid and a lowermost grid,

(c) electrical connections with at least the uppermost and lowermost grids of the grid assembly for independently providing negative bias to the uppermost and lowermost grids,

(d) one or more inlets to the upper sub-chamber,

(e) one or more inlets to the lower sub-chamber,

(f) a plasma generation source configured to produce a plasma in the upper sub-chamber,

(g) one or more gas outlets to the lower sub-chamber configured to remove gas from the lower sub-chamber, and

(h) a controller configured to cause;

(i) supplying a plasma generating gas to the upper sub-chamber and generating the plasma from the plasma generating gas,

(ii) applying a negative bias to at least the uppermost and lowermost grids of the grid assembly, wherein the bias applied to the lowermost grid is more negative than the bias applied to the uppermost grid, and accelerating ions from the plasma in the upper sub-chamber through the grid assembly toward the substrate,

(iii) supplying an etching gas to the lower sub-chamber, and

(iv) etching the substrate, wherein the lower sub-chamber is substantially free of plasma during operations (i)-(iv).

2. The apparatus of claim 1, wherein the grid assembly is configured to serve as one or more of the inlets in (d) and (e).

3. The apparatus of claim 1, wherein a ratio of the height of the upper sub-chamber to the height of the lower sub-chamber is between about 0.1-10.

4. The apparatus of claim 1, wherein the grid assembly is configured to provide different levels of ion flux to different portions of a substrate surface.

5. The apparatus of claim 1, wherein the grid assembly comprises cooling channels embedded in the assembly.

6. The apparatus of claim 1, wherein at least one grid of the grid assembly is movable.

7. The apparatus of claim 6, wherein rotation of the movable grid results in a displacement of some amount of assembly open area from one portion of the grid assembly to another portion of the grid assembly.

8. The apparatus of claim 7, wherein when the grids of the grid assembly are in a first relative position, the grid assembly open area is more concentrated toward the center of the grid assembly compared to when the grids of the grid assembly are in a second relative position.

9. The apparatus of claim 6, wherein the grids of the grid assembly may be positioned in at least a first position and a second position relative to one another, wherein when the grids of the grid assembly are in the first position, the grid assembly has some amount of open area, and when the grids of the grid assembly are in the second position, the grid assembly has no open area.

10. The apparatus of claim 6, wherein the controller is further configured to cause moving the movable grid during (iv) to thereby achieve pulses of ion flux, wherein the ion flux pulses between a low ion flux state and a high ion flux state.

11. The apparatus of claim 10, wherein during the low ion flux state, the grid assembly has no open area, thereby ensuring that substantially no ions pass through the grid assembly.

12. The apparatus of claim 1, wherein the plasma generation source comprises one or more plasma coils positioned above the upper sub-chamber.

13. The apparatus of claim 1, wherein the plasma generation source is a capacitively coupled plasma source.

14. The apparatus of claim 1, wherein the grid assembly comprises more than two grids.

15. The apparatus of claim 1, wherein the grids of the grid assembly are separated by distance of about 5 mm or less.

16. The apparatus of claim of claim 1, wherein at least one of the uppermost and lowermost grids of the grid assembly comprises wires arranged in a grid-shape or a spiderweb-shape.

17. The apparatus of claim 1, wherein at least one grid of the grid assembly is non-planar.

18. The apparatus of claim 1, wherein each grid in the grid assembly comprises perforations extending through the thickness of the grid.

20. The apparatus of claim 18, wherein the grid assembly comprises at least a third grid.

19. An apparatus for etching a substrate, comprising:

(a) a reaction chamber,

(b) a grid assembly positioned in the reaction chamber and thereby dividing the reaction chamber into an upper region and a lower region, wherein the grid assembly comprises at least a first grid and a second grid,

(c) electrical connections with at least the first and second grids of the grid assembly for independently providing negative bias to the first and second grids,

(d) one or more inlets to the upper region of the reaction chamber,

(e) one or more inlets to the lower region of the reaction chamber,

(f) a plasma generation source configured to produce a plasma in the upper region of the reaction chamber,

(g) one or more gas outlets to the lower region of the reaction chamber, the outlet configured to remove gas from the lower region of the reaction chamber, and

(h) a controller configured to cause;

(i) generating the plasma in the upper region of the reaction chamber;

(ii) applying a first negative DC bias to the first grid in the grid assembly and applying a second negative DC bias to the second grid in the grid assembly, and accelerating ions from the plasma onto a surface of the substrate in the lower region of the reaction chamber, wherein the plasma does not contact the substrate;

(iii) delivering an etchant gas to the surface of the substrate, wherein the etchant gas reacts to etch metal or semiconductor from the surface of the substrate and thereby produce a volatile byproduct containing one or more atoms of the metal or semiconductor and one or more ligands from the etchant gas; and

(iv) removing the volatile byproduct from the reaction chamber without having the volatile byproduct substantially contact the plasma and without having the volatile byproduct substantially dissociate to a less volatile material.