Process for forming a porous silicon member in a crystalline silicon member

• US 6,004,450 A
• Filed: 09/30/1998
• Issued: 12/21/1999
• Est. Priority Date: 02/27/1997
• Status: Expired due to Fees

• Current Assignee: Regents of the University of California (University of California)
• Original Assignee: Regents of the University of California (University of California)
• Inventors: Northrup, M. Allen, Yu, Conrad M., Raley, Norman F.
• Primary Examiner(s): Valentine, Donald R.
• Application Number:
  US09/165,894
• Time in Patent Office: 447 Days
• Field of Search: 205/665, 205/666, 205/667, 210/502.1, 210/506, 96/11 SP, 96/11, 55/523, 204/601, 204/605
• US Class Current: 205/656
• CPC Class Codes: B01D 2325/04 Characteristic thickness
• CPC Class Codes: B01D 39/2006 the material being particulate
• CPC Class Codes: B01D 57/02 by electrophoresis treatment of water, waste water, sewage or sludge by electrophoresis C02F1/469; electrophoretic production of compounds or non-metals C25B7/00; investigating or analysing materials by using electrophoresis G01N27/26
• CPC Class Codes: B01D 67/0044 by chemical reaction
• CPC Class Codes: B01D 71/0213 Silicon
• CPC Class Codes: B01J 19/0093 Microreactors, e.g. miniaturised or microfabricated reactors laboratory containers with capillary fluid transport in microfabricated channels or chambers B01L3/5027
• CPC Class Codes: B01J 2219/00828 Silicon wafers or plates
• CPC Class Codes: B01J 2219/00873 Heat exchange
• CPC Class Codes: B01J 2219/00905 Separation
• CPC Class Codes: B01J 2219/00912 by electrophoresis
• CPC Class Codes: B01L 2300/0645 Electrodes
• CPC Class Codes: B01L 2300/0681 Filter
• CPC Class Codes: B01L 2300/1827 using resistive heater
• CPC Class Codes: B01L 2400/0421 electrophoretic flow
• CPC Class Codes: B01L 2400/0442 thermal energy, e.g. vaporisation, bubble jet
• CPC Class Codes: B01L 2400/0688 surface tension valves, capillary stop, capillary break
• CPC Class Codes: B01L 3/502707 characterised by the manufacture of the container or its components by shaping or joining plastic parts B29C59/00, B29C65/00; by laminating B32B37/00; manufacture of microstructural devices in general B81C
• CPC Class Codes: B01L 3/50273 characterised by the means or forces applied to move the fluids micropumps F04B19/006, of the membrane type F04B43/043
• CPC Class Codes: B01L 3/502738 characterised by integrated valves microvalves F16K99/0001
• CPC Class Codes: G01N 27/44743 Introducing samples
• CPC Class Codes: G01N 27/44791 : Microapparatus sample containers with integrated microfluidic structures B01L3/5027
• CPC Class Codes: Y10S 977/832 : having specified property, e.g. lattice-constant, thermal expansion coefficient
• CPC Class Codes: Y10S 977/888 : Shaping or removal of materials, e.g. etching

Abstract

Fabrication and use of porous silicon structures to increase surface area of heated reaction chambers, electrophoresis devices, and thermopneumatic sensor-actuators, chemical preconcentrates, and filtering or control flow devices. In particular, such high surface area or specific pore size porous silicon structures will be useful in significantly augmenting the adsorption, vaporization, desorption, condensation and flow of liquids and gasses in applications that use such processes on a miniature scale. Examples that will benefit from a high surface area, porous silicon structure include sample preconcentrators that are designed to adsorb and subsequently desorb specific chemical species from a sample background; chemical reaction chambers with enhanced surface reaction rates; and sensor-actuator chamber devices with increased pressure for thermopneumatic actuation of integrated membranes. Examples that benefit from specific pore sized porous silicon are chemical/biological filters and thermally-activated flow devices with active or adjacent surfaces such as electrodes or heaters.

Claims

1. A process for forming a porous silicon membrane in a crystalline silicon member, comprising:

masking at least a section of the silicon member,

patterning an open area in the masked silicon member to expose the crystalline there under;

electrochemical etching of the exposed crystalline silicon to form pores therein for forming the porous silicon membrane; and

forming a means in the crystalline member selected from the group consisting of heater means and electrode means.

2. The method of claim 1, additionally including forming an opening in the crystalline silicon member adjacent the porous silicon membrane.

3. The method of claim 2, wherein the opening is formed prior to the electrochemical etching of the crystalline silicon.

4. The method of claim 1, additionally including forming a p++ back diffusion layer on a side of the crystalline silicon member opposite the masked section thereof.

5. The method of claim 1, additionally including providing a second substrate, forming a membrane in the second substrate, and bonding the substrates together such that the membrane in the second substrate is in an aligned, spaced relation to the thus formed porous silicon membrane.

6. The method of claim 5, additionally including providing the heating means adjacent the porous silicon membrane.

7. The method of claim 5, additionally including providing the electrode means located in spaced relation to said porous silicon membrane.

8. A process for forming a porous silicon membrane in a crystalline silicon member, comprising:

masking at least a section of the silicon member,

patterning an open area in the masked silicon member to expose the crystalline silicon there under;

the masking and patterning of the crystalline silicon member being carried out to define a plurality of spaced exposed sections of the crystalline silicon member;

electrochemical etching of the exposed crystalline silicon to form pores therein for forming the porous silicon membrane;

the etching being carried out to form a plurality of porous spaced microchannels in the crystalline silicon member; and

providing the plurality of spaced microchannels with a heater means to form a plurality of reaction chambers.

9. The method of claim 8, additionally including providing the plurality of spaced microchannels with positive and negative electrodes at opposite ends thereof to form a plurality of electrophoresis channels.