Method for producing a porous silicon film

• US 6,780,786 B2
• Filed: 11/26/2001
• Issued: 08/24/2004
• Est. Priority Date: 11/26/2001
• Status: Expired due to Term

• Current Assignee: Regents of the University of California (University of California)
• Original Assignee: Regents of the University of California (University of California)
• Inventors: Dougherty, George M.
• Primary Examiner(s): Smith, Matthew
• Assistant Examiner(s): Rocchegiani, Renzo
• Application Number:
  US09/994,280
• Publication Number:
  US 20030100136A1
• Time in Patent Office: 1,002 Days
• Field of Search: 438/1-4, 438/22-29, 438/758, 438/753, 438/764, 438/767, 438/694, 438/647, 438/657, 438/684, 438/719, 438/50-53, 210/321.84, 210/500.25, 210/500.26, 156/625.1, 427/2.3, 427/167, 427/255.27, 427/452, 427/563, 427/567, 427/574, 427/578, 427/588
• US Class Current: 438/758
• CPC Class Codes: B01D 2323/10 Specific pressure applied
• CPC Class Codes: B01D 2325/02 Details relating to pores or porosity of the membranes
• CPC Class Codes: B01D 2325/02833 more than 10 and up to 100 nm
• CPC Class Codes: B01D 2325/04 Characteristic thickness
• CPC Class Codes: B01D 67/0072 by deposition from the gaseous phase, e.g. sputtering, CVD, PVD
• CPC Class Codes: B01D 71/02 Inorganic material
• CPC Class Codes: B01D 71/0215 Silicon carbide; Silicon nitride; Silicon oxycarbide
• CPC Class Codes: B81B 2201/10 Microfilters, e.g. for gas or fluids
• CPC Class Codes: B81C 1/00158 Diaphragms, membranes manufacture process for semi-permeable inorganic membranes B01D67/0039
• CPC Class Codes: B81C 2201/0115 Porous silicon
• CPC Class Codes: B81C 2201/017 Methods for controlling internal stress of deposited layers not provided for in B81C2201/0164 - B81C2201/0169
• CPC Class Codes: H01L 21/28525 the conductive layers comprising semiconducting material H01L21/28518, H01L21/28537 take precedence
• CPC Class Codes: H01L 29/16 including, apart from doping materials or other impurities, only elements of Group IV of the Periodic Table

Abstract

A membrane structure comprising a silicon film having a grain structure including grains defining pores therebetween.

Claims

1. A method of fabricating a structure comprising:

forming a sacrificial layer over a first surface of a substrate;

forming a silicon layer over the sacrificial layer;

removing the sacrificial layer; and

controlling a residual stress of the silicon layer to insure that the silicon layer has a residual stress within a range of between about −

50 to 50 mega-Pascals and a grain structure including grains defining pores therebetween wherein the grains have an approximately hemispherical shape.

2. The method of claim 1 further including forming a passageway through the substrate.

3. The method of claim 1 further including forming a conformal layer over the silicon layer to provide a selected chemical or biological function.

4. A method of fabricating a structure comprising:

forming a sacrificial layer over a surface of a substrate;

forming a structural layer over the sacrificial layer;

forming a silicon layer over the structural layer;

removing the sacrificial layer; and

controlling the parameters of the silicon layer forming step to insure that the silicon layer has a residual stress within a range of between about −

100 to 100 mega-Pascals and a grain structure including grains defining pores therebetween wherein the grains have an approximately hemispherical shape.

5. A method of fabricating a structure comprising:

forming a sacrificial layer over a first surface of a substrate; and

growing a silicon film over the sacrificial layer at a temperature near the tensile-to-compressive transition temperature of the silicon film, and controlling a residual stress of the silicon film such that the silicon film has a residual stress within a range of about −

100 to 100 mega-Pascals and a grain structure including a layer of grains having an approximately hemispherical shape wherein pores are defined by gaps between adjacent grains.

6. The method of claim 5 wherein the silicon film is formed under a near zero-stress condition.

7. The method of claim 5 wherein the silicon film has a residual stress within a range of about −

50 to 50 mega-Pascals.

8. The method of claim 5 wherein the silicon film is grown such that a lateral dimension of any pore is less than that of any grain.

9. The method of claim 5 wherein the silicon film is grown such that a lateral dimension of the pores is between about 10 and 50 nanometers.

10. The method of claim 5 wherein the silicon film is grown such that the thickness of the film is between about 50 and 150 nanometers.

11. The method of claim 5 wherein the silicon film is grown such that the roughness of the film is approximately equal to its thickness.

12. The method of claim 5 further including forming a conformal layer on the silicon film to provide a selected chemical or biological function.

13. The method of claim 5 wherein the silicon film is used to form a membrane filter structure.

14. A method of fabricating a structure comprising:

forming a silicon layer over a first surface of a substrate; and

controlling the parameters of the forming step to insure that the silicon layer has a residual stress within a range of between about −

100 to 100 mega-Pascals and

a grain structure including a single layer of grains of approximately hemispherical shape defining pores therebetween.