[labnetwork] Ge in a deep Si RIE/ICP

[Noah Clay]

Kurt,

We have a request for deep etching Ge x-ray optics with our SPTS Rapier.  As Yaguang pointed out, we don't have much concern about volatility of the byproducts.  However, we use optical endpoint for chamber cleaning, which is tuned to SiF4 emission; we are not sure of the emission intensity of GeF4 (~400nm) and are therefore not quite certain of how this bodes for chamber cleaning (the endpoint detector gain 
 settings are optimized for SiF4, etc.). Somewhat fortunate for us: we have data for etching similar x-ray structures in silicon and will likely write an over etch recipe for Ge that mirrors Si.

Best,
Noah

Sent from my iPhone

> On Feb 25, 2016, at 17:25, Lian, Yaguang <yglian at illinois.edu> wrote:
> 
> Kurt,
>  
> The MNTL at the University of Illinois has a DRIE (STS ICP). I am the super user of the tool. I don’t have Ge issue right now because no users request using Ge in the system. But if the students want to use it, I will allow Ge into the system. Ge cannot give contamination to the chamber. After chemical reaction between Ge and F, the reactant GeF4 is volatile because the boiling point of GeF4 is -36.5C. After chemical reaction between Si and F, the boiling point of SiF4 is -86C. The fluorine based chemicals can be used to etch Si, and Ge as well, because of the volatile reactants. Some metals are not allowed to the fluorine system, such DRIE, because of non-volatile reactants. Aluminum, for example, the melting point of AlF3 is 1291C. If Al goes to the chamber with fluoride based chemicals, the tiny particles of AlF3 will deposit on the surface of wafer, causing micro-masking problem.
>  
> Best regards,
>  
> Yaguang Lian
> Research Engineer
> 2306 Micro and Nanotechnology Laboratory
> University of Illinois at Urbana-Champaign
> 208 N. Wright St.
> Urbana, IL 61801
> Phone: 217-333-8051
> Email: yglian at illinois.edu
>  
>  
>  
> From: labnetwork-bounces at mtl.mit.edu [mailto:labnetwork-bounces at mtl.mit.edu] On Behalf Of Kurt Kupcho
> Sent: 2016年2月23日 16:18
> To: labnetwork at mtl.mit.edu
> Subject: [labnetwork] Ge in a deep Si RIE/ICP
>  
> Hi All
>  
> Here at UW we have a deep silicon etcher like most academic cleanrooms.  We pretty much restrict the materials allowed in it to Si, SiO2, SiN, and photoresist.  We do not allow any metals in the system.  This is because of worries about mobile conductive ions and micro-masking problems that can occur from using metals in the system.  Recently, we had a student request using Ge in the system.  I know other academic cleanrooms have rather restrictive materials and rules for their Si DRIE systems as well and wanted to get your opinions on allowing Ge in such a system.  Do you?  Is there any problems with contamination or micro-masking?  Any other additional thoughts beyond those two questions are much appreciated as well.
>  
> Thanks!  
>  
> Kurt
>  
>  
> ---------------------------------------------------
> Kurt Kupcho
> Process Engineer
>  
> WCAM
> 1550 Engineering Drive
> ECB Room 3110
> Madison, WI  53706
>  
> E:  kurt.kupcho at wisc.edu
> T:  608-262-2982
>  
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