>
>  We make microstructures out of 15 mill single crystal silicon substrates.
> Using 110 oriented silicon and masking along the right 111 plane we can etch
> vertically or almost completely anisotropically.  A recent application
required
> etching 60 mill silicon substrates.   The degree of anisotropy we can achieve
> during etching is inconsistent.  We can rarely get vertical sidewalls while
> etching.  I am told that this is because of "swirl" in the silicon substrates.
> It is my understanding that swirl is a type of "crooked" growth defect during
> LEC crystal growth processing.
>
>
>  Can anyone verify that the poor anisotropic etching is due to "swirl"?  Is
this
> a common problem when performing bulk anisotropic etching of silicon
substrates
> that are > 45 mills thick?  Does anyone know where I can get single crystal
110
> silicon substrates (~ 0.060 ") with minimal swirl?  Is there another way to
get
> excellent wet chemistry anisotropic etching without having to worry about
swirl?
>
> Any information I can get would be helpful.
>
> Thank you,
>
> Andrew J. Nielson
> Graduate Student, Mechanical Engineering
> Brigham Young University
> Mems Group
> email: nielsona@et.byu.edu
> http://www.et.byu.edu:80/~nielsona
>
>
>