Cr etchant: etching rate?

Mary Tang mtang at stanford.edu
Tue Mar 30 10:42:22 PDT 2010


Hi Dany, Kyunghoae, and others --

Thanks for letting us know about the expired Cr-14 etchant -- it should 
not have been in there and has now been replaced with current stock.  
The shelf-life is pretty short (3 months) so we need to keep an eye on it.

As for VLSI etchant etch rates, the Berkeley Microlab lab manual has an 
excellent reference that is linked on the wiki:
http://microlab.berkeley.edu/labmanual/chap1/JMEMSEtchRates2(2003).pdf

Please remember that the etch rates depend on film quality and that can 
vary depending on the machine and conditions of deposition.  So the etch 
rates in this document should not be taken at full face value, but as a 
good starting point -- you should always verify etch rates against the 
actual film you are using in a critical etch.  And so, yes, there is a 
delay in Cr etching because Cr is highly reactive and forms a native 
oxide on the surface which etches more slowly than bulk Cr.


Uli & Mary



Dany-Sebastien Ly-Gagnon wrote:
> For the Cr etchant that we have in lab (Cr-14), the etch rate should 
> be ~93nm/min from literature. Note that our Cr etchant is expired 
> (since April 2009), so literature etch rates may not be reliable.
>
> From experience, the etch seems to start only after ~30sec in 
> solution, and the etch rate is quite fast. In about 1 min, I could 
> etch 10nm Cr. It doesn't seem like the etch rate is linear in time and 
> varies greatly (perhaps because it is expired), so it may undercut 
> resist patterns significantly.
>
> Best,
>
> Dany
>
>
> On Mon, Mar 29, 2010 at 10:27 AM, Kyunghoae Koo <koo1028 at stanford.edu 
> <mailto:koo1028 at stanford.edu>> wrote:
>
>      
>
>     Dear Labmembers,
>
>      
>
>     What is the etching rate of Cr etchant in snf? I need to etch 2nm
>     buffer Cr layer. Lateral etching is not a big issue. How much time
>     will be enough for that?
>
>     Thanks
>
>      
>
>     Kyunghoae
>
>      
>
>      
>
>     ===========================================================
>
>     Kyung-Hoae Koo
>
>     PhD candidate
>
>     Stanford University
>
>     EE department
>
>      
>
>

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