Epi-poly etch stop for out of plane spacer defined electrode

• US 9,469,522 B2
• Filed: 03/07/2014
• Issued: 10/18/2016
• Est. Priority Date: 03/15/2013
• Status: Active Grant

• Current Assignee: Robert Bosch GmbH
• Original Assignee: Robert Bosch GmbH
• Inventors: Graham, Andrew, Yama, Gary, O'Brien, Gary
• Primary Examiner(s): Gupta, Raj R
• Application Number:
  US14/201,453
• Publication Number:
  US 20160137485A1
• Time in Patent Office: 956 Days
• US Class Current: 1/1
• CPC Class Codes: B81B 2201/0271 Resonators; ultrasonic resonators
• CPC Class Codes: B81B 2203/0127 Diaphragms, i.e. structures separating two media that can control the passage from one medium to another; Membranes, i.e. diaphragms with filtering function
• CPC Class Codes: B81B 2203/04 Electrodes
• CPC Class Codes: B81B 2203/053 Translation according to an axis perpendicular to the substrate
• CPC Class Codes: B81B 3/0021 Transducers for transforming electrical into mechanical energy or vice versa dynamo-electric machines H02K99/00; electrostatic machines H02N1/00; piezoelectric devices H10N30/00
• CPC Class Codes: B81C 1/00095 Interconnects
• CPC Class Codes: B81C 1/00158 Diaphragms, membranes manufacture process for semi-permeable inorganic membranes B01D67/0039
• CPC Class Codes: B81C 1/00166 Electrodes
• CPC Class Codes: B81C 2201/0132 Dry etching, i.e. plasma etching, barrel etching, reactive ion etching [RIE], sputter etching or ion milling
• CPC Class Codes: B81C 2201/014 by depositing an etch stop layer, e.g. silicon nitride, silicon oxide, metal
• CPC Class Codes: B81C 2201/0177 Epitaxy, i.e. homo-epitaxy, hetero-epitaxy, GaAs-epitaxy
• CPC Class Codes: B81C 2203/0136 Growing or depositing of a covering layer

Abstract

In one embodiment, a method of forming an out-of-plane electrode includes forming an oxide layer above an upper surface of a device layer, etching an etch stop perimeter defining trench extending through the oxide layer, forming a first cap layer portion on an upper surface of the oxide layer and within the etch stop perimeter defining trench, etching a first electrode perimeter defining trench extending through the first cap layer portion and stopping at the oxide layer, depositing a first material portion within the first electrode perimeter defining trench, depositing a second cap layer portion above the deposited first material portion, and vapor releasing a portion of the oxide layer with the etch stop portion providing a lateral etch stop.

Claims

1. A method of forming an out-of-plane electrode, comprising:

forming an oxide layer above an upper surface of a device layer;

etching an etch stop perimeter defining trench extending through the oxide layer;

forming a first cap layer portion on an upper surface of the oxide layer and within the etch stop perimeter defining trench;

etching a first electrode perimeter defining trench extending through the first cap layer portion and stopping at the oxide layer;

depositing a first material portion within the first electrode perimeter defining trench;

depositing a second cap layer portion above the deposited first material portion; and

vapor releasing a portion of the oxide layer with the etch stop portion providing a lateral etch stop.

2. The method of claim 1, further comprising:

depositing a third cap layer portion above the second cap layer portion after vapor releasing the portion of the oxide layer;

etching a second electrode perimeter defining trench extending through the second cap layer portion and the third cap layer portion; and

depositing a second material portion within the second electrode perimeter defining trench, such that a spacer including the first material portion and the second material portion define a perimeter of an out-of-plane electrode.

3. The method of claim 2, further comprising:

depositing an etch stop layer portion on the deposited first material portion, wherein etching a second electrode perimeter defining trench comprises;

etching a second electrode perimeter defining trench extending through the second cap layer portion and to the etch stop layer.

4. The method of claim 2, wherein the first cap layer portion, the second cap layer portion, and the third cap layer portion are deposited by an epitaxial deposition process.

5. The method of claim 2, wherein the first material portion and the second material portion comprise silicon nitride.

6. The method of claim 2, further comprising:

depositing an etch stop layer portion on the deposited first material portion, wherein etching a second electrode perimeter defining trench comprises;

etching a second electrode perimeter defining trench extending through the second cap layer portion and to the etch stop layer.

7. The method of claim 2, further comprising;

etching vent holes through the first cap layer and the second cap layer, wherein vapor releasing a portion of the oxide layer comprises;

vapor releasing a portion of the oxide layer through the vent holes.