[mems-talk] Bosche Process explained?

[Jim Beall]

Kathleen,

One description is at:
http://www.stsystems.com/pages/process_content.asp? 
parentID=1017&contID=1020&menuID=37&subID=54&subsub=YES&menuTitle=Techno 
logies&mainMenuTitle=Products%20~%20Applications&parentTitle=Advanced% 
20Silicon%20Etching%20(ASE)&contTitle=How%20it%20works

Basically, you alternate brief, shallow etch steps (perhaps 0.5  
microns) with passivation steps. The passivation step (C4F8 plasma)  
conformally coats everything with an etch resistant polymer. The etch  
step (SF6+O2) uses rf on the wafer platen so it is quite vertically  
active. The passivation on the floor of the previously etched area  
gets removed rapidly and thus the floor of the etched area keeps  
etching while the walls are protected. By balancing the amount of  
passivation, the duration of the etch, the gas flows and power  
levels, the sidewall angle can be precisely 'tuned' to be very  
vertical. In an SEM image you can see the slight scalloping of each  
etch cycle.

  --Jim
On Jun 27, 2007, at 7:42 PM, Holmes, Kathleen wrote:

> I'm a newbie in the mems business. Would someone please explain the
> Bosch process, or direct me to some literature? Thanks
>
> Regards,
> Kathleen Holmes