Etching of semiconductor structures that include titanium-based layers

Patent metadata

Field	Value
Publication number	US-9330937-B2
Application number	US-201314079473-A
Country	US
Kind code	B2
Filing date	Nov 13, 2013
Priority date	Nov 13, 2013
Publication date	May 3, 2016
Grant date	May 3, 2016

Abstract

Two-step process sequences uniformly etch both tungsten-based and titanium-based structures on a substrate. A sequence of wet etches using peroxide and heated nitric acid uniformly recesses a metal stack that includes W, TiN, and TiAl. W, TiN and TiC are uniformly recessed by a peroxide etch at ˜25 C followed by an acid solution with a very small amount of added peroxide at ˜60 C. TiC is etched without etching trench oxides or other metals in a work-function metal stack by either (1) highly-dilute of ultra-dilute HF at 25-35 C, (2) dilute HCl at 25-60 C, (3) dilute NH 4 OH at 25-60 C, or (4) solution (2) or (3) with small amounts of peroxide. Other metals in the stack may then be plasma-etched without being blocked by TiC residues.

First claim

What is claimed is:

1. A method of uniformly etching a plurality of structures of different materials on a substrate, the method comprising:
exposing the substrate to a first etch process until a first subset of the structures is etched to a first depth;
exposing the substrate to a second etch process until a second subset of the structures is etched to a second depth;
wherein the first subset of the structures comprises W;
wherein the second subset of the structures comprises at least one of titanium nitride (TiN), titanium aluminide (TiAl), or titanium aluminum nitride (TiAlN);
wherein the first etch process comprises a solution of H 2 O 2 and an acid; and
wherein the second etch process comprises a nitric acid (HNO 3 ) solution heated to between 60 C and 95 C,
wherein a weight percentage of HNO 3 in the nitric acid solution is between about 65% and 75%,
wherein, after being exposed to the first etch process and the second etch process, the first subset and the second subset of the structures are etched to within 15% of the same depth;
wherein at least one of the first subset or the second subset of the structures comprises tungsten (W);
wherein at least one of the first subset or the second subset of the structures comprises titanium (Ti); and
wherein the first etch process comprises a solution containing hydrogen peroxide (H 2 O 2 ).

2. The method of claim 1 , wherein the structures are subjected to chemical-mechanical polishing before the substrate is exposed to the first etch process or the second etch process.

3. The method of claim 1 , wherein the first etch process comprises a solution of the H 2 O 2 , the acid, and water.

4. The method of claim 3 , wherein the acid is hydrochloric acid (HCl).

5. The method of claim 3 , wherein a ratio of acid:H 2 O 2 :water in the solution of H 2 O 2 and the acid is about 1:1:4.

6. The method of claim 3 , wherein the first etch process is performed at a temperature between 55 C and 65 C.

7. The method of claim 1 , wherein the first subset of the structures comprises W;
wherein the second subset of the structures comprises at least one of titanium nitride (TiN), titanium aluminide (TiAl), or titanium aluminum carbide (TiAlC);
wherein the first etch process comprises an H 2 O 2 solution; and
wherein the second etch process comprises an acid solution with between 0.0001% and 0.04% H 2 O 2 by weight.

8. The method of claim 7 , wherein a ratio of H 2 O 2 :water in the H 2 O 2 solution is about 1:2.

9. The method of claim 7 , wherein the acid solution comprises HCl.

10. The method of claim 7 , wherein the acid solution comprises water.

11. The method of claim 7 , wherein a ratio of HCl:H 2 O 2 :H 2 O in the acid solution is about 1:0.0125:2.

12. The method of claim 7 , wherein the second etch process is performed at a temperature between 55 C and 65 C.

13. The method of claim 7 , wherein the first etch process comprises an ultra-dilute (<1 picomol/liter) sulfuric peroxide mixed with 50 to 500 ppm HF at 25-35 C.

14. The method of claim 7 , wherein the first etch process comprises a 1:1-100:1 water-HCl mixture or a 1:1-100:1 water-NH 4 OH mixture.

15. The method of claim 14 , wherein the water-HCl mixture or the water-NH 4 OH mixture further comprises at most 1 part for H 2 O 2 for every 10 parts HCl or NH 4 OH.

Assignees

• Intermolecular Inc
• Intermolecular Inc

Inventors

• Nowling Gregory
• Foster John

Classifications

• H10P72/0426

  with the semiconductor substrates being dipped in baths or vessels · CPC title

• H10P50/264 Primary

  by chemical means · CPC title

• H10D64/691

  comprising metallic compounds, e.g. metal oxides or metal silicates  (insulators comprising nitrogen H10D64/693) · CPC title

• H10D64/667

  the conductor comprising a layer of alloy material, compound material or organic material contacting the insulator, e.g. TiN workfunction layers (having lateral variation H10D64/671) · CPC title

• H10D64/017

  using dummy gates in processes wherein at least parts of the final gates are self-aligned to the dummy gates, i.e. replacement gate processes · CPC title