Fabrication of MEMS devices with spin-on glass

• US 6,896,821 B2
• Filed: 08/23/2002
• Issued: 05/24/2005
• Est. Priority Date: 08/23/2002
• Status: Active Grant

• Current Assignee: Teledyne Digital Imaging, Inc. (Teledyne Technologies Incorporated)
• Original Assignee: Dalsa Incorporated (Teledyne Technologies Incorporated)
• Inventors: Louellet, Luc
• Primary Examiner(s): OLSEN, ALLAN W
• Application Number:
  US10/226,189
• Publication Number:
  US 20040035820A1
• Time in Patent Office: 1,005 Days
• Field of Search: 216/2, 216/38, 216/47, 216/49, 216/51, 216/67, 216/72, 216/79, 216/80, 438/48, 438/717, 438/719, 438/723
• US Class Current: 216/2
• CPC Class Codes: B81C 1/00619 Forming high aspect ratio structures having deep steep walls
• CPC Class Codes: G03F 7/094 Multilayer resist systems, e.g. planarising layers
• CPC Class Codes: H01L 21/32137 of silicon-containing layers
• CPC Class Codes: H01L 21/32139 using masks
• CPC Class Codes: Y10T 428/24479 including variation in thickness

Abstract

A method of making an etched structure in the fabrication of a MEMS device involves depositing a bulk layer, typically of polysilicon, prone to surface roughness. At least one layer of photo-insensitive spin-on planarizing material, such as silicate-based spin-on glass, is formed on the bulk layer to reduce surface roughness. This is patterned with a photoresist layer. A deep etch is then performed through the photoresist layer into the bulk layer. This technique results in much more precise etch structures.

Claims

1. A method of marking an etched structure in the fabrication of a MEMS device, comprising the steps of:

depositing a bulk layer forming part of said MEMS device, said bulk layer being prone to surface roughness;

forming at least one layer of spin-on planarizing material on said bulk layer;

depositing a photoresist layer on said planarizing material;

exposing said photoresist layer to define a pattern of exposed regions; and

performing a deep etch into said bulk layer through said photoresist layer and said planarizing material in said exposed regions to farm deep-etched patterns in said bulk layer.

2. A method as claimed in claim 1, wherein said planarizing material is selected from the group consisting of:

silsesquioxane, polyimide, a spin-on antireflective layer;

or an organic or semi-organic material optically resistant to exposure of said photoresist layer.

3. A method as claimed in claim 1, comprising multiple layers of said planarizing material.

4. A method as claimed in claim 1, wherein prior to performing said deep etch into said bulk layer, a preliminary etch is performed to remove said planarizing material in exposed regions.

5. A method as claimed in claim 4, wherein said preliminary etch is a dry oxide etch.

6. A method as claimed in claim 5, wherein the thickness of the photoresist layer lies in the range 1.0 μ

m to 500 μ

m.

7. A method as claimed in claim 1, wherein said bulk layer is polysilicon.

8. A method as claimed in claim 7, wherein said polysilicon is deposited by a technique selected from the group consisting of LPCVD, PECVD and MOCVD.

9. A method as claimed in claim 7, wherein the thickness of said polysilicon layer lies in the range 0.5 μ

m to 100 μ

m.

10. A method as claimed in claim 7, wherein said planarizing material is spin-on glass.

11. A method as claimed in claim 10, wherein said spin-on material is selected from the group consisting of methyl-based, ethyl-based or other semi-organic spin-on glass.

12. A method as claimed in claim 10, wherein said spin-on glass is inorganic spin-on glass.

13. A method as claimed in claim 12, wherein said spin-on glass is a phosphorus-doped silicate-based spin-on glass.

14. A method of making an etched structure in the fabrication of a MEMS device, comprising die steps of:

depositing a thick polysilicon layer forming part of said MEMS device, said thick polysilicon layer being prone to surface roughness;

forming at least one layer of spin-on glass on said polysilicon layer;

depositing a photoresist layer on said spin-on glass;

exposing said photoresist layer to define a pattern of exposed regions;

etching away said planarizing material in said exposed regions; and

performing a deep etch into said polysilicon layer through said photoresist layer and said spin-on glass in said exposed regions to form deep-etched patterns in said polysilicon layer.

15. A method as claimed in claim 14, wherein said spin-on glass is phosphorus-doped silicate-based spin-on glass.