Online Semi-radius Probe Tip Cleaning and Reshaping

Online Semi-radius Probe Tip Cleaning
and Reshaping
Authors:
Sam McKnight and Michael Agbesi
June 3, 2007
IEEE SW Test Workshop 1

Agenda
Acknowledgements
Background info
Setup and measurement technique
Contact resistance results
Cleaning recipe parameters to consider
Silicone vs polymer based materials
Summary
Future work
June 3, 2007
IEEE SW Test Workshop 2

Acknowledgements
Jack Courtney
John Cartier
Steve Duda
Les Griffith
Rob Holwager
Glen Langsman
Josh Pendergast
June 3, 2007
IEEE SW Test Workshop 3

Basic cantilever probe types
June 3, 2007
IEEE SW Test Workshop 4

Why Semi-radius?
Lower pad damage in general for today’s
soft aluminum
Approximately same scrub length as flat tip
while reducing the amount of material
removed from base material
Equivalent contact resistance to flat or full
radius tip
Reflectivity similar to flat tip for prober and
probe metrology alignment (easier to align
to vs. full radius material)
June 3, 2007
IEEE SW Test Workshop 5

Bonding – Semi radius tips
Pad opening shown is 29X29 microns - running out of room!
June 3, 2007
IEEE SW Test Workshop 6

The problem with Semi-
radiused probes
Variable tip geometry using standard
material cleaning solutions
No insitu solution – non silicone based
Either flat tip or radiused tip solution but no
semi-radiused solution
June 3, 2007
IEEE SW Test Workshop 7

Traditional way to maintain semi-radius
probe tips
Use elastomeric abrasive i.e.
polymer based material – continues
to radius tips
Remove periodically to reshape (put
a flat back on it)
June 3, 2007
IEEE SW Test Workshop 8

The solution
Two part cleaning – insitu
‣ Abrasive material for flat tip – SiC
‣ Elastomeric material for radius tip
and removes stringers (contact
pad and cleaning detritus)
June 3, 2007
IEEE SW Test Workshop 9

Two basic cleaning mediums
Two part cleaning – insitu
‣ Solid Abrasive material for flat tip – SiC
(Silicon Carbide)
‣ Elastomeric material for radius tip and
removes stringers (contact pad detritus)
‣ Order is important – see data
June 3, 2007
IEEE SW Test Workshop 10

June 3, 2007
Typical recipes
5 -10 up/down touchdowns on each medium
‣ SiC abrasive removes all detritus down to
base material (flat tip)
‣ Elastomeric abrasive -removes
probing/cleaning detritus (radius tip)
Use same OD as with product for SiC, OD +
30% for elastomeric (typical) - pitch dependant
Move to new location between Up/Down
cycles
IEEE SW Test Workshop 11

Polymer based abrasive clean
Before clean
After clean
June 3, 2007
IEEE SW Test Workshop 12

Contact resistance - Elastomeric
5
4.5
4
Elastomeric cleaner
50um OD 25C clean freq 100 die
Wafer average 0.59 ohms
Cres(ohms)
3.5
3
2.5
2
1.5
Min
Max
Average
1
0.5
Cleaning cycle
0
1
501
1001
1501
2001
2501
3001
3501
4001
4501
Test #
5001
5501
6001
6501
7001
7501
June 3, 2007
Each "test" represents 25 contacts (190K data points total)
opens removed from average data – all CRES charts
IEEE SW Test Workshop 13

Contact resistance – silicon carbid
SIC abrasive
50um OD 25C clean freq 100 die
Cres(ohms)
5
4.5
4
3.5
3
2.5
2
1.5
1
0.5
0
Wafer average 0.10 ohms
Min
Max
Average
Cleaning cycle
1
501
1001
1501
2001
2501
3001
3501
4001
4501
5001
5501
6001
6501
7001
7501
Test #
June 3, 2007
IEEE SW Test Workshop 14

Contact resistance – dual clean
JEM elsatomeric & SIC abrasive
50um OD 25C clean freq 100 die
Each "test" represents 25 contacts (190K data points)
5
4.5
4
Wafer average 0.40 ohms opens
removed from average data
Cres(ohms)
3.5
3
2.5
2
1.5
1
Min
Max
Average
0.5
0
1
501
1001
1501
2001
2501
3001
3501
4001
Test #
4501
5001
5501
6001
6501
7001
7501
S. McKnight
05/02/2007
Cleaning cycle
June 3, 2007
IEEE SW Test Workshop 15

Contact resistance setup and
measurement technique
TEL P12XLN prober @ 25C, Maximum z velocity
Probe – 50 micron pitch 1X25 tungsten rhenium
material, 20 micron nominal tip diameter ~ 1gf/mil spring
rate
50 micron overdrive from first touch (contacts were
within 9 microns from first to last touch)
100 touchdowns between cleans
Relative measurement – not 4 point
All data “nulled” – path or bulk resistance removed
300mm wafer – 1.2 micron as deposited aluminum –
blanket deposition
June 3, 2007
IEEE SW Test Workshop 16

Measurement circuit
• Test stimulus 10 ma forcing current – 5V clamp
• Min - Max - Average data collected plus raw data
• Keithley based matrix switch and source/measurement unit
VI source
Contact under
test
Return path
June 3, 2007
Shorted wafer
Note: actual return path pins = 24
IEEE SW Test Workshop 17

Polymer based abrasive clean
SiC abrasive
Probe tip
Abraded area – largest area expose to cleaning medium
June 3, 2007
IEEE SW Test Workshop 18

SiC clean
Typical flat tip Silicon Carbide abrasive – 3µm
June 3, 2007
IEEE SW Test Workshop 19

“Recipe” Considerations
Probe characteristics
‣ Tip diameter
‣ Tip length
‣ Taper
‣ Spring rate
‣ Material
Cleaning order
‣ Lowest CRES use SIC last
June 3, 2007
‣ Maximum particulate removal use
Elastomeric last
IEEE SW Test Workshop 20

Sequence and motion (use animation)
Elastomeric
material
SIC material
June 3, 2007
IEEE SW Test Workshop 21

Benefits
Low cost solution – use existing materials
Comparable CRES to SiC material
Non Silicone
Uniform tip shape throughout life of probe
Longer probe life
June 3, 2007
IEEE SW Test Workshop 22

Detractor
Die Size limited – effectively cut cleaning
area in half
June 3, 2007
IEEE SW Test Workshop 23

142 mm
155 mm
Cleaning
summary
Flat material
Radius material
Semi-Radius tip
+ =
June 3, 2007
IEEE SW Test Workshop 24

142 mm
155 mm
Future work
Evaluate even lower cost materials
Look for extension to other probe
technologies i.e. Cobra, metrology usage
Maximize cleaning medium lifetime
Larger cleaning plate
Thank you! Questions?
June 3, 2007
IEEE SW Test Workshop 25