Silicon membrane and method of making same
AssigneesIMS-Ionen Mikrofabrikations Systeme GmbH, Universitat Gesamthochschule Kassel
InventorsHans Loschner, Feng Shi, Ivaylo W. Rangelow
Life of this patent
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Abstract
A silicon membrane for use as a micromechanical sensor or as a mask for projection lithography is fabricated by doping a silicon wafer to different thicknesses at different portions and then electrochemically etching away the undoped portion of the wafer.
Claims21
A method of making a silicon membrane with predetermined stress characteristics, said method comprising the steps of:
- (a) masking at least a selected first portion of a surface of a silicon substrate of a conductivity type of one polarity with a mask and leaving unmasked a second nonmasked portion of said surface;
- (b) doping the second nonmasked portion of said surface with a doping agent of a conductivity type whose polarity is opposite the polarity of the conductivity type of said substrate to form a doped layer at said second portion;
- (c) removing said mask from said first portion of the surface of said substrate;
- (d) doping said surface with a doping agent in a predetermined concentration and of a conductivity type whose polarity is opposite the polarity of the conductivity type of said substrate to form in said first portion a doped layer of a smaller thickness than at said second portion;
- and
- (e) electrochemically etching said substrate to remove said substrate below the doped layers of said first and second portions to form a silicon membrane from said first and second portions whose first portion is thinner than its second portion.
A method of making a silicon membrane with predetermined stress characteristics, said method comprising the steps of:
- (a) forming a barrier layer of a certain thickness on first and second portions of a surface of a silicon substrate;
- (b) reducing the thickness of said barrier layer by a certain amount on said second portion;
- (c) doping said substrate through said barrier layer by implantation or diffusion with a predetermined ion dose, thereby forming a doped layer below said barrier layer and of a thickness greater at said second portion than at said first portion resulting from reduction of the thickness of said barrier layer by said certain amount on said second portion in step (b);
- (d) removing said barrier layer from said surface of said silicon substrate;
- and
- (e) electrochemically etching said substrate to remove said substrate below the doped layer of said first and second portions to form a silicon membrane from said first and second portions whose first portion is thinner than its second portion.
A silicon membrane with predetermined stress characteristics and formed in one piece from a common silicon substrate of at least one first portion and at least one second portion, each of said first portions having a predetermined thickness and a doping agent in a predetermined concentration and of a conductivity type whose polarity is opposite a polarity of a conductivity type of said substrate, each of said second portions having a predetermined thickness greater than the thickness of each of said first portions and a doping agent in a predetermined concentration and of a conductivity type whose polarity is opposite a polarity of the conductivity type of said substrate.
A silicon mask for electromagnetic beam or particle beam lithography comprising a silicon membrane structured with openings, said silicon membrane being formed in one piece from a common silicon substrate of at least one first portion and at least one second portion, each of said first portions having a predetermined thickness, a predetermined density of said openings, and a doping agent in a predetermined concentration and of a conductivity type whose polarity is opposite a polarity of a conductivity type of said substrate, each of said second portions having a predetermined thickness greater that the thickness of each of said first portions, a density of said openings greater than the density of openings of said first portions, and a doping agent in a predetermined concentration and of a conductivity type whose polarity is opposite a polarity of the conductivity type of said substrate.
Dependencies are inferred from the claim text.