Hello Ashwini,

I have not used an AML bonder but they all apply heat and force, some = just do
it better than others.  80% bonding on a quarter wafer is not = bad.  Keep in
mind the damage to the edge of the wafer when you dice and = the roll off at the
edge of the wafer.  I think you are in the ball park = with your recipe.  Run a
full wafer and see what you get.  There is a = good chance you are seeing the
limitations of the bonder.  Try this:
1.  Place two sheets of graphite foil 1mm thick (one under the sample = and one
on top of the sample)to improve the force uniformity.
2.  Do a two step heating ramp.  Heat to 320C and hold for 10 minutes = with low
force.  This will allow the temperature become stable.  Then = apply the bonding
force and heat to 400C or 420C and hold 15-20 minutes. =  The hold time will be
different depending on your process so this can = be optimized.
3.  Cool quickly with full force to 320C.
4.  Remove force and cool to unload temp.

It works well to cool to just below the eutectic point with force but do = not
cool much lower or you will see cracking.=20

You didn't mention how much bond area you have.  I'm guessing you are = doing
100% Au across the wafer for testing.  Your force will change = depending on the
bond area.

Brad

Brad Johnson
Sales Application Engineer
DJK Global
US Distributor, Semiconductor Inspection Systems
2447 W. 12th St. - Suite 6, Tempe, AZ 85281
480-968-3343 Ext 112 office
602-501-4413 cell
bjohnson@djksemi.com
http://www.djksemi.com



-----Original Message-----
From: ashwini jambhalikar [mailto:ashwini.jambhalikar@gmail.com]
Sent: Monday, December 17, 2007 4:12 AM
To: mems-talk@memsnet.org
Subject: [mems-talk] eutectic bonding conditions

Dear Friends,

I am trying to get eutectic bonding between two Si wafers, with Au/Cr
as an intermediate layer.
I am using AML bonder.

For the ease of visual inspection I am using one glass wafer with Cr/
Au and other Si wafer.

I am giving 400 degree centigrade temperature(as I read one should
give more than eutectic temperature, 363 degree centigrade is eutectic
temp for Si-Au.)

I observed, on quarter wafer, when 1200 N  platen force was given
reasonably good area(like almost 80 %) got bonded.

Can somebody mail me, exact what temperature and platen force I should
apply to get a good bond(99% to 100%)?

Thanks, AShwini