with Pyramid Probe Cards - Semiconductor Wafer Test Workshop

Innovating Test
Technologies
for production
probe cards
Production Test of Process
Control Monitors (PCMs) with
Pyramid Probe Cards
Ken Smith, Cascade Microtech
Bill Knauer, Keithley Instruments
Dr. Jerry Broz, Jason Aronoff, Texas Instruments

SWTW 2002: Parametric test
Innovating Test
Technologies
for production
probe cards
Goal of Presentation
• Communicate a joint evaluation effort
between Texas Instruments, Keithley
Instruments and Cascade Microtech
investigating the use of Pyramid Probes for
probing process monitors with copper pads
meeting the shrinking requirements of
smaller scribelines.

SWTW 2002: Parametric test
Innovating Test
Technologies
for production
probe cards
Abstract:
Process monitors are used extensively in semiconductor fabs
to optimize yields, provide process control feedback, and
assure device quality. The scribelines or streets used for
PCMs are under the same unrelenting density pressure as
IC lithography. Reducing the scribeline by 50 microns on
a 5 mm square die, for example, results in a net reduction
in area and cost of 2%. This can provide a huge ROI for
large wafer fabs. Wafer saw and blade manufacturers are
continously reducing saw kerf requirements and PCM pad
size is becoming a limiting factor in realizing this
competitive advantage. This paper presents DC
parametric performance measurements in the femtoamp /
femtofarad range for semiconductor test structures with
Pyramid Probes. Results will include probing both normal
aluminum pads and copper pads. Contact resistance,
probe pad damage, multiple probe cycles and probe life
time results for both pad materials are also discussed.

SWTW 2002: Parametric test
Innovating Test
Technologies
for production
probe cards
Outline:
• DC Parametric requirements
• Design approach
• Electrical performance
• Contact resistance performance
• Probe mark budget
• Conclusion

SWTW 2002: Parametric test
Innovating Test
Technologies
for production
probe cards
DC Parametric Requirements
• General application is for monitoring test
key leakage and capacitance
• Typical production requirements
– 1-2 pA, 1-2 pF measurements
–0.1 pA, 0.1 pF parasitics
• Leading edge engineering requirements
– 10-50 fA measurements
–1-10 fA parasitics
• Probe pads shrinking to meet scribe line
shrinks
– 60-70 um typical today >> 50-40 asap

SWTW 2002: Parametric test
Innovating Test
Technologies
for production
probe cards
Design Approach
• For reference, a typical functional test spec
is 10 nA/volt
– Doesn’t require guards (100 megohm)
• Guards required below 1 nA (1 gigohm)
– milli, micro, nano, pico, femto
– Typical of parametric test equipment
– Guard theory: The guard is driven by a
separate amplifier to the same voltage
as the test pin to reduce current flow to
external conductors

SWTW 2002: Parametric test
Innovating Test
Technologies
for production
probe cards
Pyramid Probe Card with
Keithley S600 Interface
• Coax forcesense
guard
• Twinax routed
cables to lower
board
• Guarded traces
on lower board

SWTW 2002: Parametric test
Pyramid Core for Parametric Test
Innovating Test
Technologies
for production
probe cards
• Guarded circuit board interface
• Guarded traces to probe tips

SWTW 2002: Parametric test
Innovating Test
Technologies
for production
probe cards
Pyramid Card Looking Down
Through Core
• Linear layout typical of scribe line PCMs
• Guarded traces to probe tips (100 um pitch)
• Staggered routing for fine guard pitch

SWTW 2002: Parametric test
Innovating Test
Technologies
for production
probe cards
Link to Keithley Electrical
Performance Report
• Please see Bill Knauer’s presentation
Knauer_SWTW2002.ppt for his original
slides in Keithley format

SWTW 2002: Parametric test
Innovating Test
Technologies
for production
probe cards
Electrical Characterization
Of Pyramid Probe Card
• Leakage / Settling Time Measurements
• Noise and Offset Measurements
• Capacitance Measurements

SWTW 2002: Parametric test
Innovating Test
Technologies
for production
probe cards
Leakage / Settling Comparison
• Initial settling curve is the same as the blade and coax
epoxy cards.
• Longer final settling due to slightly higher leakage and
higher dielectric absorption.
5.00E-13
10V 100pA Range 1plc Probe Card
Current
4.50E-13
4.00E-13
3.50E-13
3.00E-13
2.50E-13
2.00E-13
1.50E-13
1.00E-13
5.00E-14
0.00E+00
Blade Card
Coax Epoxy
Pyramid
0.00
1.36
2.71
4.06
5.46
6.81
8.16
9.52
10.87
12.23
13.58
14.93
16.29
17.64
18.99
20.39
21.74
Time

SWTW 2002: Parametric test
Noise and Offset Comparison
Innovating Test
Technologies
for production
probe cards
• Peak to peak noise and standard deviation of
noise is same as other cards.
• Mean is slightly higher because of leakage.
10V 100pA Range 1plc
5.00E-14
4.50E-14
4.51E-14
4.00E-14
3.50E-14
Current
3.00E-14
2.50E-14
2.00E-14
2.05E-14
2.61E-14
2.34E-14
2.59E-14
2.15E-14
P To P
Stddev
Mean
1.50E-14
1.00E-14
5.00E-15
3.52037E-15
5.21966E-15
3.99263E-15
0.00E+00
Blade Card Coax Epoxy Pyramid

SWTW 2002: Parametric test
Innovating Test
Technologies
for production
probe cards
Capacitance Comparison
• Capacitance is the same as other probe cards
Capacitance Measurement
Capacitance
6.00E-13
5.00E-13
4.00E-13
3.00E-13
2.00E-13
1.00E-13
0.00E+00
-1.00E-13
-2.00E-13
-3.00E-13
Blade Card
Coax Epoxy
PYRAMID
13 - 10
20 - 1
18 - 7
6 - 2
4 - 1
20 - 19
13 - 12
8 - 7
4 - 3
3 - 2
D.U.T. Pins

SWTW 2002: Parametric test
Innovating Test
Technologies
for production
probe cards
Characterization Conclusions
• Pyramid probe card design shows
excellent performance for low current
measurements down to 100fA as
compared to other low current
technologies.
• Increased settling related to dielectric
absorption and not capacitance.
• Probes up offset measurements will allow
card to perform as well as other low current
technologies.

SWTW 2002: Parametric test
Contact Resistance Test Conditions
Innovating Test
Technologies
for production
probe cards
• Loop resistance between each of 20 adjacent channels
• 13000 cycles, measure every 20 cycles, no cleaning cycles
• 17 particle hits: class 10K environment (shown as 50 ohms)
• Room temperature
60
Core A1 on Blanket Copper FT + 140 um
50
CRES (Ohms)
40
30
20
10
0
0 2000 4000 6000 8000 10000 12000 14000
touchdowns

SWTW 2002: Parametric test
Innovating Test
Technologies
for production
probe cards
Cres with Low Overtravel on
Oxidized Copper Wafer
• Relationship between overtravel, Cres, and
copper oxidation time under investigation
Core A3 after IPA FT + 125 um OT (run 5/17)
60
50
CRES (Ohms)
40
30
20
10
0
0 2000 4000 6000 8000 10000 12000 14000 16000 18000 20000
touchdowns

SWTW 2002: Parametric test
Innovating Test
Technologies
for production
probe cards
Contact Resistance Performance
on clean Copper wafers
• Loop resistance: 1.14 to 1.27 ohms
• Cres average: 0.091 ohms
• Cres std dev: 0.032 ohms
2
Core A1 on Blanket Copper FT + 140 um
CRES (Ohms)
1
0
0 2000 4000 6000 8000 10000 12000 14000
touchdowns

SWTW 2002: Parametric test
Innovating Test
Technologies
for production
probe cards
Probe Mark Budget
• Maximum mark size 15 x 20 um
• Positional accuracy +/- 5 um
• Mark budget 25 x 30 um
• Typical marks on 30 x 50 um pads

SWTW 2002: Parametric test
Innovating Test
Technologies
for production
probe cards
Conclusion:
• Pyramid Probe Cards show excellent
performance for low current measurements
on Aluminum or Copper pads

Innovating Test
Technologies
for production
probe cards
Production Test of Process
Control Monitors (PCMs) with
Pyramid Probe Cards
Ken Smith, Cascade Microtech
Bill Knauer, Keithley Instruments
Dr. Jerry Broz, Jason Aronoff, Texas Instruments

SWTW 2002: Parametric test
KGD Workshop Commercial:
Innovating Test
Technologies
for production
probe cards
Flip Chip KGD Workshop
June 24-26 Austin, Texas
IMAPS www.imapsflipchip.com
Pyramid Probe high volume solder ball
probing results for Known-Good-Die