Technical paper

Microsystem Technologies

, Volume 12, Issue 10, pp 935-939

First online:

Defect-free wet etching through pyrex glass using Cr/Au mask

  • Francis E. H. TayAffiliated withDepartment of Mechanical Engineering, National University of SingaporeInstitute of Bioengineering and Nanotechnology
  • , Ciprian IliescuAffiliated withInstitute of Bioengineering and Nanotechnology Email author 
  • , Ji JingAffiliated withDepartment of Mechanical Engineering, National University of Singapore
  • , Jianmin MiaoAffiliated withMicromachines Center, School of Mechanical and Production Engineering, Nanyang Technological University

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This paper reports the highest etch depth of annealed Pyrex glass achieved by wet etching in highly concentrated HF solution, using a low stress chromium–gold with assistance of photoresist as masking layer. The strategies to achieve that are: increasing the etch rate of glass and simultaneously increasing the resistance of Cr/Au mask in the etchant. By annealing the Pyrex glass and using a highly concentrated HF acid, a high etch rate can be obtained. Furthermore, a method to achieve a good resistance of the Cr/Au masking layer in the etching solution is to control the residual stress and to increase the thickness of Au deposition up to 1 μm. In addition, the presence of a hard baked photoresist can improve the etching performance. As a result, a 500-μm thick Pyrex glass wafer was etched through.