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US 4,203,128 AGranted
Electrostatically deformable thin silicon membranes
AssigneeWisconsin Alumni Research Foundation
InventorsHenry Guckel, Steven T. Larsen
Life of this patent
Estimating the term…
Abstract
The invention relates to thin silicon membranes formed in layers of silicon such as are normally utilized as substrates in the manufacture of integrated electronic circuits. The thin membranes constructed in accordance with the invention are capable of deformation by electrostatic forces and are applicable to a wide range of uses including the manufacture of solid state pressure sensors, resonant, and antenna structures, as well as electro-optical display elements. A processing technique is disclosed which is particularly adapted to forming membranes in silicon substrates in a manner which is compatible with the construction thereon of other integrated circuit components.
Claims20
An electro-mechanical capacitive device comprising:
- (a) a first substrate of crystalline silicon having opposite sides, a portion of one side having boron diffused therein to a selected depth having a layer between 1 and 10 microns in thickness with boron atom concentrations sufficient to render the layer conductive and resistant to etching by selected silicon etchants, a cavity formed in the opposite side of said substrate bottoming on the boron diffused etchant resistant layer to define a diaphragm in said layer under said cavity having a thickness of between approximately 1 and 10 microns, lateral dimensions between approximately 1 millimeter and 2 centimeters, and internal tension of the order of magnitude of 10.sup.5 dynes per centimeter;
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- (b) a second electrode spaced away and insulated from the boron diffused layer side of said diaphragm at a distance selected such that mechanical deflection of said diaphragm will measurably change the capacitance between said diaphragm and said second electrode, whereby changes in pressure across said diaphragm which deflect said diaphragm can be measured by measuring the change in capacitance between said diaphragm and second electrode, and whereby an oscillating electrical signal applied between said diaphragm and said second electrode will induce mechanical vibration of said diaphragm to provide an effective resonant impedance to the electrical signal.
An electro-mechanical resonant circuit comprising:
- (a) a first substrate of crystalline silicon having opposite sides, a portion of one side having an etchant resistant and electrically conductive layer formed therein to a selected depth, a cavity formed in the opposite side of said substrate bottoming on said etchant resistant layer to define a diaphragm in said layer under said cavity, the thickness of the etchant resistant layer forming said diaphragm and the lateral dimensions of said diaphragm being selected such that said diaphragm exhibits substantial physical deflection and mechanical resonance in response to electrically induced forces on said diaphragm;
- (b) a second electrode spaced away and insulated from the etchant resistant layer side of said diaphragm at a distance selected such that electric charge on said second electrode will cause mechanical deflections of said diaphragm when oppositely charged, whereby said diaphragm and said conducting electrode form two plates of a capacitor having a capacitance varying with the physical deflection of said diaphragm;
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- (c) signal source means for applying an oscillating electrical signal at a selected frequency between said diaphragm and said second electrode so as to cause mechanical vibrations of said diaphragm in response to the varying electric field between said second electrode and said diaphragm.
1 more element
An electro-mechanical capacitive device comprising:
- (a) a first substrate of crystalline silicon having opposite sides, a portion of one side having an etchant resistant layer formed therein to a selected depth, a cavity formed in the opposite side of said substrate bottoming on said etchant resistant layer to define a diaphragm in said layer under said cavity, said diaphragm being of a selected thickness and having selected lateral dimensions whereby it is capable of substantial deflection when exposed to external forces and exhibits mechanical resonance;
- (b) a second conductive silicon electrode spaced away from said etchant resistant layer side of said diaphragm at a selected distance whereby when electric charge is placed on said conducting electrode it will cause mechanical deflection of said diaphragm when oppositely charged, and whereby said diaphragm and said conducting electrode form two plates of a capacitor having a capacitance varying with the physical deflection of said diaphragm;
- (c) insulating material separating and electrically insulating said conductive electrode from said diaphragm, a chamber formed in said insulating material between said diaphragm and said silicon electrode, a channel formed through said silicon electrode leading to an orifice in said chamber;
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- (d) a cap mounted to said diaphragm in position to close said orifice when a selected electrostatic attraction is applied between said diaphragm and said second silicon electrode.
2 more elements
an electro-mechanical device comprising:
- (a) a first substrate of crystalline silicon having opposite sides, a portion of one side having an etchant resistant layer formed therein to a selected depth, a cavity formed in the opposite side to said substrate bottoming on said etchant resistant layer to define a diaphragm in said layer under said cavity, said diaphragm being of a selected thickness and having selected lateral dimensions whereby it is capable of substantial deflection when exposed to external forces and exhibits mechanical resonance;
- (b) a second conductive silicon electrode spaced away from said etchant resistant layer side of said diaphragm at a selected distance whereby when electric charge is placed on said conducting electrode it will cause mechanical deflections of said diaphragm when oppositely charged, and whereby said diaphragm and said conducting electrode form two plates of a capacitor having a capacitance varying with the physical deflection of said diaphragm;
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- (c) a substantially flat optically transparent layer formed on the side of said silicon substrate opposite that facing said conducting electrode and extending over said cavity, whereby displacements of said diaphragm cause visible changes by constructive interference of light coming in through said transparent layer and light reflected from the surface of said diaphragm facing said transparent layer.
1 more element
An electro-mechanical capacitive device comprising:
- (a) a first substrate of crystalline silicon having opposite sides, a portion of one side having an etchant resistant layer formed therein to a selected depth, a cavity formed in the opposite side of said substrate bottoming on said etchant resistant layer to define a diaphragm in said layer under said cavity, said diaphragm being of a selected thickness and having selected lateral dimensions whereby it is capable of substantial deflection when exposed to external forces and exhibits mechanical resonance;
- (b) a second conductive silicon electrode spaced away from said etchant resistant layer side of said diaphragm at a selected distance whereby when electric charge is placed on said conducting electrode it will cause mechanical deflections of said diaphragm when oppositely charged, and whereby said diaphragm and said conducting electrode form two plates of a capacitor having a capacitance varying with the physical deflection of said diaphragm;
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- (c) a plurality of electrically conductive pyramidal prominences formed in association with said conducting electrode in position to be individually contacted by said diaphragm when said diaphragm is deflected a selected distance toward said conducting electrode, each said electrically conductive prominence being capable of being separately provided with electric charge to attract said diaphragm toward contact therewith.
1 more element
Dependencies are inferred from the claim text.