Method for roughening a silicon or polysilicon surface for a semiconductor substrate

• US 5,223,081 A
• Filed: 07/03/1991
• Issued: 06/29/1993
• Est. Priority Date: 07/03/1991
• Status: Expired due to Term

• Current Assignee: Micron Technology, Inc.
• Original Assignee: Micron Technology, Inc.
• Inventors: Doan, Trung T.
• Primary Examiner(s): DANG, THI D
• Application Number:
  US07/725,357
• Time in Patent Office: 727 Days
• Field of Search: 156/628, 156/656, 156/657, 156/662, 427/383.1, 427/383.3, 427/123, 427/96, 427/58, 437/228, 437/245, 437/247
• US Class Current: 438/703
• CPC Class Codes: H01L 21/306 Chemical or electrical treatment, e.g. electrolytic etching to form insulating layers H01L21/31
• CPC Class Codes: H01L 21/32134 by liquid etching only
• CPC Class Codes: H01L 28/84 being a rough surface, e.g. using hemispherical grains
• CPC Class Codes: Y10S 438/964 Roughened surface

Abstract

This invention relates to a method for roughening a silicon or polysilicon substrate of a semiconductor. The method includes the steps of: depositing a metal layer onto the substrate, heating the metal layer and substrate through to form a metal silicide on the substrate by reaction of the metal layer and substrate, and removing the metal silicide and a metal oxide by selective etching to expose the roughened surface. The actual etching process may be a two-step procedure. A first etch uses ammonium hydroxide and hydrogen peroxide to remove the oxide layer formed with the silicide. A second etch uses hydrofluoric acid to remove the silicide.

Claims

1. In semiconductor manufacture a method for roughening a surface of a silicon or polysilicon substrate comprising:

depositing a metal layer on the substrate;

heating the substrate and metal layer in an atmosphere to initiate a chemical reaction between the metal layer and substrate to from a metal silicide layer on the substrate and to form a metal oxide-nitride layer on the metal silicide layer;

removing the metal oxide-nitride layer with an etchant; and

then

removing the metal silicide layer with a selective etchant, thereby exposing a roughened surface area on the substrate t a boundary of the substrate and metal silicide layer.

2. The method as recited in claim 1 wherein:

the metal layer is deposited to a thickness of between about 50 and about 3000 Angstrom (Å

).

3. The method as recited in claim 2 and wherein:

the metal layer thickness is about 500 Å

.

4. The method as recited in claim 1 and wherein:

the metal layer is a refractory metal.

5. The method as recited in claim 4 and wherein:

the metal layer is titanium (Ti).

6. The method as recited in claim 5 and wherein:

the metal silicide layer is titanium silicide (TiSi_x) and is removed by exposure to a hydrofluoric acid solution.

7. The method as recited in claim 6 and wherein:

the metal oxide-nitride layer is titanium oxide-nitride (TiN_x O_y) and is removed with a solution of ammonium hydroxide (NH₄ OH) and hydrogen peroxide (H₂ O₂).

8. In semiconductor manufacture a method for roughening a surface of a silicon or polysilicon substrate comprising:

depositing a titanium layer on the substrate;

heating the substrate and titanium layer in an atmosphere to a temperature for causing a chemical reaction that creates a titanium silicide (TiSi_x) layer on the substrate with a rough and irregular grain boundary and a titanium oxide-nitride (TiN_x O_y) layer on the titanium silicide (TiSi_x) layer; and

then

removing the titanium oxide-nitride (TiN_x O_y) layer with an etchant and removing the titanium silicide (TiSi_x) layer with an etchant selective to titanium silicide (TiSi_x) thereby exposing a roughened surface area on the substrate at the boundary between the silicide, and silicon or polysilicon substrate.

9. The method as recited in claim 8 and wherein:

the titanium oxide-nitride (TiN_x O_y) layer is removed with a solution of ammonium hydroxide (NH₄ OH) and hydrogen peroxide (H₂ O₂).

10. The method as stated in claim 9 and wherein:

the titanium oxide-nitirde (TiN_x O_y) layer is removed by exposing the titanium oxide-nitride (TiN_x O_y) layer to a 1;

1 solution of ammonium hydroxide and hydrogen peroxide.

11. The method as stated in claim 9 and wherein:

the titanium layer thickness is deposited to a thickness between about 50 and about 3000 Angstrom (Å

).

12. The method as stated in claim 11 and wherein:

the titanium layer thickness is about 500 Å

.

13. The method as stated in claim 8 and wherein:

the titanium silicide (TiSi_x) layer is removed by exposing the titanium silicide (TiSi_x) to a hydrofluoric acid solution.