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Title: Redox buffered hydrofluoric acid etchant for the reduction of galvanic attack during release etching of MEMS devices having noble material films

Patent ·
OSTI ID:971540
 [1]
  1. Albuquerque, NM
+ Show Author Affiliations

Etchant solutions comprising a redox buffer can be used during the release etch step to reduce damage to the structural layers of a MEMS device that has noble material films. A preferred redox buffer comprises a soluble thiophosphoric acid, ester, or salt that maintains the electrochemical potential of the etchant solution at a level that prevents oxidation of the structural material. Therefore, the redox buffer preferentially oxidizes in place of the structural material. The sacrificial redox buffer thereby protects the exposed structural layers while permitting the dissolution of sacrificial oxide layers during the release etch.

Research Organization:
Sandia National Lab. (SNL-NM), Albuquerque, NM (United States)
Sponsoring Organization:
USDOE
DOE Contract Number:
AC04-94AL85000
Assignee:
Sandia Corporation (Albuquerque, NM)
Patent Number(s):
7,597,819
Application Number:
11/017,108
OSTI ID:
971540
Country of Publication:
United States
Language:
English

References (10)

Electrochemical Coupling Effects on the Corrosion of Silicon Samples in HF Solutions journal January 1995
Etching and Passivation of Silicon in Alkaline Solution:  A Coupled Chemical/Electrochemical System journal June 2001
Electrochemical aspects of corrosion resistance and etching of metallizations for microelectronics journal July 1995
Galvanic Cell Formation in Silicon/Metal Contacts:  The Effect on Silicon Surface Morphology journal June 2000
Galvanic etching for sensor fabrication journal October 2000
Galvanic cell formation: a review of approaches to silicon etching for sensor fabrication journal January 2001
Silicon dioxide sacrificial layer etching in surface micromachining journal March 1997
IC-Compatible Polysilicon Surface Micromachining journal August 2000
Corrosion Rate of n- and p-Silicon Substrates in HF, HF + HCl, and HF + NH[sub 4]F Aqueous Solutions journal January 1999
Kinetics of electrochemical corrosion of silicon wafers in dilute HF solutions journal February 1997

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