Actually, anodic bonding may still be a viable option.  If you use a Pyrex
wafer that has a flat (this is readily available), then you can mis-align
the flats of the two substrates (i.e., rotate the Pyrex 90 degrees, so that
the flat of the Pyrex corresponds to the rounded edge of the SOI).  Then,
attach some sort of grounding line (even aluminum foil should work) between
the top surface of the SOI and whatever grounding surface you are placing
your wafer on (hot plate, bond tool, etc.).  Then, run the anodic bond.

The electrical conductivity of the silicon should be great enough (depending
on doping, of course) to allow the current to distribute over the entire
wafer surface to complete the bond.  Recommended parameters would be 300 -
350 C (if the bond does not look even, use a lower temperature), and 500 to
1000 V (if a lower temperature is used, then a higher voltage is required).


The reason for a lower temperature is that it decreases the mobility of
sodium ions within the Pyrex, which will decrease the electrical
conductivity.  Then, the relative conductivity of the silicon increases,
causing a more even distribution of potential across the silicon surface.

In terms of cleaning, an oxide removal step is not absolutely necessary when
it comes to performing an anodic bond.  If the surface to be bonded has
little to no oxide (meaning, native oxide only), then all that would really
be necessary is a piranha clean, with maybe an RCA clean thrown in (NO HF
dip) to remove particles.  An anodic bond will proceed just fine through
native oxide.  If there is a significant oxide layer on the bond suface
(greater than aboout 1000 A), then the bond may be hindered somewhat, but
may still proceed.  However, based on your description, I am assuming that
there is no significant oxide layer on top of the SOI, only the 2000A buried
oxide layer.

In terms of adhesive materials, I have experience with a material called
"Staystick", which can handle sustained temeratures up to 200 C, with peak
temperatures up to 400 C.  It comes in both a sheet form, and a paste form
suitable for silk-screening.  It is availbale from Cookson Semiconductor
Packaging Materials.  Another posibility is glass frit, which, depending on
the grade, will bond at temperatures anywhere from 370 C to 500 C.  A good
manufacturer for glass frit is Ferro.

Best Regards,

Chad Brubaker



EV Group-Technology, Tel: (602) 437 9492 x 111, Fax: (602) 437 9435
E-mail: [email protected] , Web:
www.EVGroup.com



-----Original Message-----
From: zhao [mailto:[email protected]]
Sent: Tuesday, December 18, 2001 3:44 PM
To: [email protected]
Subject: [mems-talk] How to adhere si wafer and pyrex glass 7740?


hi#,

!!Could any one tell me how to adhere a Si wafer and pyrex glass 7740?!!
What I want to do is bonding my SOI wafer with pyrex glass. Because
there is a middle layer (2000A) of SiO2 I doubt if the anodic bonding works.

And there is a step of etching SiO2 in our anodic bonding process for
cleaning. However i don't want my SiO2 being etched. So I want to glue
them together instead of anodic bonding. The glue must can sustain
up to 200 centigrade.

Thank you very much in advance.

Yongjun Zhao!!!!!!!!!!!!!!!!

!!!!!!!!!!!!!!!!!!!!!!!!!!!!
!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!2001-12-18

***************************************
  Yongjun Zhao, Ph.D. Student
  Institute for Micromanufacturing
  Louisiana Tech University
  P.O.Box 10137, 911 Hergot Avenue
  Ruston, LA 71272, USA

  Email: [email protected]
                 [email protected]
***************************************
_______________________________________________
[email protected] mailing list: to unsubscribe or change your list
options, visit http://mail.mems-exchange.org/mailman/listinfo/mems-talk
Hosted by the MEMS Exchange, providers of MEMS processing services.
Visit us at http://www.mems-exchange.org/

[demime 0.98e removed an attachment of type application/octet-stream which had a
name of Chad W Brubaker (E-mail).vcf]