You can get a very precise alignment by using a special mask to find the
crystal orientation with an anisotropic etchant. One of the processes is
in The thesis of LongSun Huang from our lab. It's on the web at

http://cjmems.seas.ucla.edu/Thesis/longsun.pdf

(Chapter 2)

Jesse Fowler
  UCLA/MAE Dept., 420 Westwood Plaza, Room 37-129, ENGR IV
  Los Angeles, CA 90095-1597 | (310)825-3977
"Observations of nature, no matter how seemingly arcane, are like
peeling off one more layer from the great onion of knowledge"
    -- Don Petit, ISS science officer

On Thu, 27 Feb 2003, Hongjun Zeng wrote:

> Dear colleagues,
>
> A basic question. How did you align the mask along the crystalline
> direction, i.e., <110> on the wafer? Right now we only have the way to align
> a straight in mask with the primary flat. Any more precise way?
>
> Second, anybody knows precisely how long is the primary flat of a n-type or
> p-type 3 inch 100 wafer?
>
> Thanks a lot,
>
> Hongjun Zeng, PhD
> Microfabrication Applications Laboratory (MAL)
> University of Illinois at Chicago
> ERF Building, 842 W. Taylor Street
> Chicago, IL 60607-7022
> Room 3014 ERF
> Tel.: 312-413-5889, Fax: 312-996-6465
>
>
>
>
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