This phenomena is known in the semiconductor (hillocks) - caused by aluminum
stressing and relieving stress. Slightly better with 1% Si inside but almost
impossible to get rid of it. Replace the aluminum with another metal.

Shay


-----Original Message-----
From: [email protected] [mailto:[email protected]]
On Behalf Of Xin Yan
Sent: Monday, March 05, 2012 4:02 PM
To: General MEMS discussion
Subject: [mems-talk] Al grass on the 7740 glass

Hi everyone,

the process flow as follows,
1 etch cavity on the 7740 glass
2 deposit  200nm Al layer  on the cavity of  7740 glass,
3 anodic bonding process with silicon,  400 degreeC, 800V

the problem:
 we always find the  Al grass on the al layer after the anodic bonding,  the
Al grass dimension: about 2~3um long, and with a diameter of 200nm

the quantity of grass is  not too much , but it cause the device short
circuit.

have somebody met this problem before?  what's the source of this
phenomenon?

Any suggestions would be appreciated!




--
Yan Xin
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