etching Al2O3

Baylor Triplett baylor.triplett at
Thu Aug 7 23:35:56 PDT 2008

     While I do not have experience with attempting this particular 
process, it is common for Hf or BHF to penetrate photoresist and result 
in lift off depending on how long the etch solution is applied, and how 
concentrated the etch solution is in HF or fluoride. One first attempt 
is to hard bake the resist which substantially improves the adhesion to 
the substrate. Then the resist is stripped by an aggressive stripper or 
plasma ashed off. Adhesion promoters also can help.
      The ultimate solution can be a second layer or bilayer (sometimes 
called a "hard mask" that can be etched more easily). However, I suggest 
searching first for published papers in this area to see if there isn't 
an easy solution.
shide cheng wrote:
> Hi, Byungha,
> My experience is developer will erode the Al, and Al2O3 during 
> development stage. You may need anther layer to protect them during 
> photo process.
> Shide  
> ------------------------------------------------------------------------
> From: shinbh93 at
> To: labmembers at
> Subject: etching Al2O3
> Date: Thu, 7 Aug 2008 11:40:19 -0700
> Dear Labmembers,
> One of my collaborators try to etch off Al2O3 at the corners of 
> samples (consisting of Al2O3 / InGaAs / InP substrate) for Hall 
> measurements. He found that photo-resist used to define the corners on 
> Al2O3 surface was peeled off during etching by BHF. Has anyone 
> sucessfully done photolithography on Al2O3? If so, what kind of 
> adhesion promotor was used? Also, does anyone know the etch rate of 
> Al2O3 by BHF?
> Thanks,
> Byungha 
> ------------------------------------------------------------------------
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