Fabrication of MEMS devices with spin-on glass

• US 7,579,622 B2
• Filed: 02/11/2005
• Issued: 08/25/2009
• 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: Ouellet, Luc
• Primary Examiner(s): LOUIE, WAI SING
• Application Number:
  US11/054,946
• Publication Number:
  US 20050145962A1
• Time in Patent Office: 1,656 Days
• Field of Search: 257/65, 257/644, 438/662, 438/669, 438/672
• US Class Current: 257/65
• 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 microstructure component for a MEMS device, comprising:

a polysilicon bulk layer having a thickness greater than 0.5 μ

m and less than 100 μ

m, said bulk layer being deposited on an underlying sacrificial layer, and said bulk layer having an upper surface with a surface roughness created by a series of randomly shaped pyramids of random height causing local variations in the thickness of the bulk layer;

at least one layer of photo-insensitive spin-on planarizing material deposited directly on said upper surface so as to be in contact therewith and smooth out said surface roughness created by said pyramids;

a photoresist layer deposited directly on said planarizing material so as to be in contact therewith; and

a deep etch trench extending through said photoresist layer to said underlying sacrificial layer.

2. A microstructure as claimed in claim 1, wherein said planarizing material is spin-on glass.

3. A microstructure as claimed in claim 2, wherein said spin-on glass is inorganic spin-on glass.

4. A microstructure as claimed in claim 3, wherein said spin-on glass is a phosphorus-doped silicate-based spin-on glass.

5. A microstructure as claimed in claim 2, wherein said spin-on glass is selected from the group consisting of:

methyl-based, ethyl-based or other semi-organic spin-on glass.

6. A microstructure 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.

7. A microstructure as claimed in claim 1, comprising multiple layers of said planarizing material.

8. A microstructure as claimed in claim 1, wherein the thickness of the photoresist layer lies in the range 1.0 μ

m to 500 μ

m.

9. A microstructure as claimed in claim 7, wherein the thickness of said polysilicon layer is about 11 μ

m.

10. A microstructure as claimed in claim 1, wherein a bottom surface of said bulk layer is flat and straight.