Hi Mario Robles
Thank you for your interest - Let me describe more in detail on the type of
wafer I am working on .
Wafer thickness :15mils , Both top and bottom side has all the saw street
,identical circuit patterns.
Saw street ( both sides) is : 3 mils also has a 0.88um of TAOS passivation
layer on it , no metalisation on it.
Chipping allowed should not be more than 0.6mils.Kerf width plus chipping should
not exceed 2.5mils.
Wafer diameter 6 inch. Die size 53sq.mils.
Cut speed :35mm/sec , Spindle :30krpm
Saw machine : Disco .DAD-341
Wafer are pretty flat at least to our naked eyes.
Blade info : thickness: 20-25um , Exposure : 20-24mils
Micron grit size:4 - 6 um , nickel blade.Hub type
These are about the only info I can provide due to Company confidentiality
policy .
Another challenge is on thin wafer and inconsistance bottom crack issues . (
chips can normally be solved quite easilly)
Do you have any info on sawing 5 mils wafer - RF applications , just silicon -
structrure 1-1-1 . These are extremely difficult to dice as well , even with UV
tape . It normally has all it take for massive bottom crack issues - Au
metallization on alignment patterns, gold metallization at the back, narrow saw
street -3 mils , concave wafers .
Appreciate if you could mail me some articles on the above issues , or atleast
let me know where to source for them.
Thank a million
Have a nice day
YS
>
>
> Subject: RE: Bottom cracks after dicing
> Date: Wed, 3 May 2000 13:16:08 -0700
> From: Mario Robles
> To: "'YS See'" , "MEMS@ISI.EDU"
>
> Hello Eric,
>
> My name is Mario Robles and I work for Tanaka Systems. We sell Asahi Diamond
dicing blades and I will do my best to help improve your process. I have a few
questions regarding your current process and will suggest some of my thoughts.
>
> 1. What saw do you use
>
> 2. What blades do you use, Disco, Semitec....? Specification....S0820 or NBC-
ZH104J 27HDAA?
> 3. What metallization does the wafer have on either side? Is there anything
in the streets? Are there streets on both sides?
> 4. What is the chipping spec you need and are currently achieving?
> 5. How fast are you cutting and current spindle RPM?
> 6. How is the wafer thinned to 6 mils? Diameter?
> 7. Are the wafers warped or bowed?
>
> Depending on chipping spec it will be very difficult to get the same chipping
spec top and bottom using one pass cutting. You can try playing with your saws
software to achieve two pass cutting that might help but still not the greatest.
A blade can help improve your results but will not be the solution. One idea
would be to wax your wafer to another silicon wafer and cut through. This will
reduce the backside chipping quite a bit.
>
> Can you tell me what company or University you work for? Also what sort of
product are these wafers for? DO you cut any other wafers?
>
> Thank you for any information given. It will help me understand what we could
do to improve your process.
>
> Mario Robles
> Technical Sales Manager
>
> 650-966-8001 phone
> 650-966-1881 fax
>
> -----Original Message-----
> From: YS See [SMTP:yatsun@pc.jaring.my]
> Sent: Thursday, April 27, 2000 8:33 PM
> To: MEMS@ISI.EDU
> Subject: Bottom cracks after dicing
>
> Hi,
> I'm Eric - application engr, for wafer saw process. Recently I came
> across a type of wafer known as the 'clipper wafer' whereby both top and
> bottomside of this wafer is identical in order to enable contact to be
> made via miniture clips thus eliminating the need for wire bonding .
> Current process to ensure 99% yield , they have to do a first cut 30%
> thru' with a porous chuck separated by a silk screen , flip the wfr over
> then mounted onto blue tape then sawn thru 1 mil into the tape. This
> process take almost 3hrs to complete. Attempt to do a single pass is
> disasterous almost 99% backside crack die .Street width is 3mil.
> thickness is 6mils . Currently we are using a soft nickel blade, 2 -6 um
> diamond size,low concentration ,thickness 0.8mil blade with exposure of
> 20mils . Tape used Nitto 224 , bake temp . 70deg. for 30min. prior to
> saw .
> Wonder if you can offer any recommendation/info/article to handle thin
> wafer with backside cracks issues . Any form of advise wil be greatly
> appreciated
> Thanks
> Have a nice day.
> Eric See
>
>
>
>