At CWRU, we stick pieces of wafers on
4" substrates quite often.  There are
really two ways:

1) coat the 4" substrates with PR and with
a fine brush apply a thin coat of PR to
the back of the smaller piece. Then join
them together and bake them for 30min
at 95oC.

2) using a dropper place PR beads on the
back of the smaller piece and on the
region of contact on the larger substrate.
5 droplet beads should suffice. Then join
the pieces together and bake them for 30
min at 95oC.

#1 give better adhesion, but separation of
the pieces can be challenging...overnite
acetone dip with ultrasonic agitation can
do it.

#2 gives sufficient adhesion and separation
is much easier...use this one if you do
not care for super adhesion.

Good luck!


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| Shuvo Roy                                                     |
| Research Assistant, Microelectromechanical Systems Group      |
|                                                               |
|Office: Rm. 811 Glennan Bldg.                                  |
|        Department of Electrical Engineering & Applied Physics |
|        Case Western Reserve University                        |
|        Cleveland, Ohio 44106                                  |
|        USA                                                    |
|                                                               |
|Telephone: 216-368-3051        Fax: 216-368-2668               |
|                                                               |
|E-mail:  roy@mems4.eeap.edu            sxr37@po.cwru.edu       |
|                                                               |
|WWW: http://mems.cwru.edu/roy                                  |
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