Method of etching silicon substrate at different etching rates for different planes of the silicon to form an air bridge

• US 5,683,546 A
• Filed: 10/22/1993
• Issued: 11/04/1997
• Est. Priority Date: 10/23/1992
• Status: Expired due to Term

• Current Assignee: Ricoh Seiki Co. Ltd. (Ricoh Company Limited)
• Original Assignee: Ricoh Seiki Co. Ltd. (Ricoh Company Limited)
• Inventors: Manaka, Junji
• Primary Examiner(s): Tsai, Jey
• Assistant Examiner(s): Pham, Long
• Application Number:
  US08/139,696
• Time in Patent Office: 1,474 Days
• Field of Search: 156/625, 156/616, 156/628, 156/633, 156/643.1, 156/647, 156/654, 437/226
• US Class Current: 216/2
• CPC Class Codes: B81B 2203/0315 Cavities
• CPC Class Codes: B81C 1/00142 Bridges deformable micromirrors G02B26/0841
• CPC Class Codes: B81C 1/00626 Processes for achieving a desired geometry not provided for in groups B81C1/00563 - B81C1/00619
• CPC Class Codes: G01L 9/0042 Constructional details associated with semiconductive diaphragm sensors, e.g. etching, or constructional details of non-semiconductive diaphragms details about the integration or bonding of piezoresistor in or on the diaphragm G01L9/0052 and G01L9/0057 respectively
• CPC Class Codes: H01L 21/30608 Anisotropic liquid etching H01L21/3063 takes precedence
• CPC Class Codes: Y10S 438/924 To facilitate selective etching

Abstract

The present invention is for enlarging a freedom of layout including an air bridge pattern and enhancing the availability for various purposes. A mask layer including an air bridge pattern is formed on a (100) plane of a silicon substrate, isotropic etching is carried out until a point of intersection between tangents of a peripheral curved plane comes to under the air bridge pattern plane, and then an air bridge is formed by means of anisotropic etching.

Claims

1. A method of etching a silicon substrate, for forming an air bridge by making use of differences in etching rates for respective crystal planes of a silicon substrate, comprising the steps of:

forming a mask layer including an air bridge pattern on a (100) plane of the silicon substrate;

generating isotropic defects in said silicon substrate by electrically irradiating the silicon substrate with ions of an inactive element which is heavier than Si; and

forming an air bridge by anisotropic etching of the irradiated silicon substrate.

2. A method of etching a silicon substrate, for forming an air bridge by making use of differences in etching rates for respective crystal planes of a silicon substrate, comprising the steps of:

forming a mask layer including an air bridge pattern on a (100 plane of a silicon substrate;

generating isotropic defects in said silicon substrate by irradiating the silicon substrate with ions of an inactive element which is heavier than Si using a sputter etching process; and

forming an air bridge by anisotropic etching of the irradiated silicon substrate.

3. A method of etching a silicon substrate, for forming an air bridge by making use of a difference in etching rate for each crystal plane of silicon in a silicon substrate, comprising the steps of:

forming a mask layer including an air bridge pattern on a (100) plane of the silicon substrate;

plasma etching isotropically to undercut the masked silicon substrate on opposite sides of the air bridge pattern, until a point of intersection between tangents of a peripheral plane surrounding a cavity undercut under the air bridge pattern, wherein each tangent is inclined at 54.74°

to the silicon substrate, is located just underneath a plane of the air bridge pattern; and

forming an air bridge by anisotropic etching of the silicon substrate beneath the air bridge pattern.