CRES Control Using CDA as a Shielding Gas

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CRES Control Using CDA as a Shielding Gas
Steve Austin, Gary Grayson and Al Wegleitner
Texas Instruments, Dallas, TX
June 11 th 2006
1

Outline
•Background – the journey
•Problem Statement
•Measurement/Methodology
•Key Findings
•Solution's
•Acknowledgments
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Background
•Factory Expansion Phase 4 – just
completed
•Phase 4 automotive factory was
experiencing significant CRes yield loss
issues between testers and devices
•Phase 5 to ramping ~ 150 systems
migrating to automotive 3 insertion test
methodology
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Problem Statement
•Factory was experiencing significant CRes
yield loss issues between testers and
devices during 3 insertion probing
sequence at different temps
•CRes fails were causing significant yield
loss and requiring significant reprobe time
losses
•Traditional CRes solutions were reaching
the limits of effectiveness
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Objective
•Show the effects of CDA on CRes
•Review the potential impact of CDA that
effect die temperature
•Review design/hardware procedures
needed to manage CDA
•Share key learning's – the journey
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CRes Sources
Probe
Bond Pad Surface
Test Program
Diode Structure
PC Planarity
Cleaning Frequency
Debris Field
Test Head Level
Z-Axis Travel
Chuck Speed
Muffin Fans
Air Handlers
Raised Floor
Equipment Density
H 2 0 ?
Conditions
that effect
CRes
500
450
400
M
a
x
C
R
E
S
i
n
O
h
m
s
350
300
250
200
150
100
50
0
Typical CRES performance
curve in SCT and EBT.
VLB105
~ 7 ohms
~ 7 minutes
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Cres Causes by Category
Nearly all are out of the control of
operations
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Cleaning Frequency change most common
approach to control CRES at probe.
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Cleaning Effectiveness
•A Paradigm Shift
◦Improving Contact Resistance without
Increasing on-line Cleaning?
•Injecting Compressed Dry Air (CDA) on the Die
Under Test has improved the stability of CRES and
reduces the need for additional on-line cleaning
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Discovery Experiments
•Blanket Aluminum Wafer
•Cantilever Dual-Site Probe Card
•VLCLT Tester
•CDA
•Nitrogen
•Maximum Contact Resistance
(MAXCRES) used to plot effects
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Single Power Pin Maximum Contact
Resistance (MAXCRES)
10 Ω 20 Ω
Probe
Card
Needles
13 Ω
Die Under Test
12 Ω
11 Ω
12 Ω
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100
Max Contact Resistance wo/w CDA
No CDA CDA
90
80
70
Ohms Contact Resistance
60
50
40
30
20
10
0
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600 Die 600 Die
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Effectiveness of CDA vs. Nitrogen Purge
10.00
9.00
Induced
vibration
8.00
7.00
6.00
Normal
CDA
Nitrogen
5.00
4.00
3.00
1 7 13 19 25 31 37 43 49 55 61 67 73 79 85 91 97 103 109 115 121 127 133 139 145 151
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Oxidation Theory
• Consider the Mechanical Contact to Al Pads
◦ A native oxide layer of Al2O3 exists on the Al pads to be tested at probe
◦ Some of this native oxide is removed by the mechanical probing & good
contact is made by mechanical abrasion
◦ However, once micro-contacts are made, local heating can lead to oxide
growth in the presence of air, leading to the formation of Al2O3 ( GT° ~ -
400kcal, therefore spontaneous)
◦ In the presence of moisture, hydrated aluminum oxides (Al2O3+H2O)
are formed which can be thicker & more porous than the native Al2O3
◦ The hydrated oxides are colorless to white and can lead to resistive or
semiconducting contacts 1
• CDA Purge Effects on Contact Process
◦ Elimination of moisture and therefore, hydration of the oxide
1
Broz & Rincon, “Probe Contact Resistance During Elevated
Temperature Wafer Test,” ITC Proceedings, p. 396, 1999.
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CDA Contamination Within Factory Specs.
• Moisture readings pre and post filter (Spec ~ 100 ppm)
◦ Pre filter was at 9.02 ppm after 14 hours of analysis
◦ Post filter was at 10.8 ppm and dropping after only 2 hours of
analysis
• Hydrocarbon (THC) readings from pre and post filter
(Spec ~ 5 ppm)
◦ Both Samples were analyzed using a GC/FID for total
hydrocarbons (THC) as CH4 per the site specification for CDA
◦ The pre filter sample averaged 3.26 ppm THC as CH4
◦ The post filter sample averaged 3.46 ppm THC as CH4
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CDA vs. Non - CDA Results
MP3 Yield Percentage With and Without CDA
BIN
228
227
224
100.0%
95.0%
Count of DIE_NUM
222
221
220
215
90.0%
85.0%
202
201
178
80.0%
75.0%
76
74
66
70.0%
65.0%
65
56
55
60.0%
55.0%
54
53
49
50.0%
45.0%
47
46
43
40.0%
35.0%
41
39
38
30.0%
D-
D-
D-
D-
D-
D-
D-
D-
D-
D-
D-
D-
D-
D-
D-
D-
D-
D-
D-
D-
D-
D-
D-
D-
D-
D-
D-
D-
D-
D-
D-
D-
D-
D-
D-
D-
D-
D-
D-
D-
D-
D-
D-
D-
D-
D-
D-
37
35
129C
CDA
V3D620B09CDA
125C
CDA Off
V3D620B09
31
21
20
12
0
PROBE_CNT PROG CDA_ON TEMP WAFER
11
1
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CDA vs. Non - CDA Results
Contact Sensitive Fallout (Bins 41, 55, 74, and 201) With and Without CDA
180
Count of DIE_NUM
170
160
150
140
130
120
110
100
90
80
70
BIN
201
74
55
41
60
50
40
30
20
10
0
D-
D-
D-
D-
D-
D-
D-
D-
D-
D-
D-
D-
D-
D-
D-
D-
D-
D-
D-
D-
D-
D-
D-
D-
D-
D-
D-
D-
D-
D-
D-
D-
D-
D-
D-
D-
D-
D-
D-
D-
D-
D-
D-
D-
D-
D-
D-
129C
CDA
V3D620B09CDA
125C
CDA Off
V3D620B09
0
PROBE_CNT PROG CDA_ON TEMP WAFER
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BIN
201
74
55
D-
4334196-
22
D-
4334196-
17
80
70
60
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50
40
30
20
10
0
CDA vs. Non - CDA Results
Contact Sensiive Fallout (Bins 41, 55, 74, and 201) With and Without CDA
Count of DIE_NUM
D-
4334196-
03
D-
4334196-
09
D-
4334196-
23
D-
4334196-
07
D-
4334196-
10
D-
4334196-
24
D-
4334196-
02
D-
4334196-
06
D-
4334196-
14
D-
4334196-
15
D-
4334196-
20
D-
4334196-
21
D-
4334196-
01
D-
4334196-
04
D-
4334196-
05
D-
4334196-
11
D-
4334196-
13
VLB160 VLC45 VLC93
129C 125C
CDA No CDA
V3D944X03CDA V3D944X03
0
41
PROBE_CNT PROG CDA ON TEMP TESTER WAFER

CDA influence on die temperature
• Response of ICCQ to chuck temperature was
characterized with no CDA.
• CDA was injected at room temp (30°C) and hot
chuck(125°C). Changes in ICCQ were recorded
• The equation (CDA Temp – Chuck Temp) / 45°C
closely defines the effect of CDA on die temperature.
◦CDA temperature is 20°C typical
◦Die temp is effected by

Effect of chuck temperature on ICCQ current
uA
ICCQ
Current
Dev A
Dev B
Chuck Temperature
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CDA Hardware Example
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No Measurable ESD Buildup
• Measured ESD on probe needles
◦ACL Model 300B Electrostatic Locator
•Two testers
•CDA on needles
•Measure every 15 minutes
◦No Measurable static build up

0.90%
0.80%
0.70%
0.60%
0.50%
% Opens
0.40%
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0.30%
Wegleitner et al.
Contact Stability - By Week
Opens Before/After Immediate Reprobe - First Probe in EBT/SCT
70%
60%
50%
40%
30%
20%
10%
0.20%
0%
0.10%
0.00%
20-Feb
18-Feb
May-Wk1
May-Wk3
Jun-Wk1
Jun-Wk3
Jun-Wk5
Ju1-Wk2
Ju1-Wk4
Aug-Wk2
Aug-Wk4
Sep-Wk2
Sep-Wk4
Oct-Wk1
Oct-Wk3
Nov-Wk1
Nov-Wk3
Dec-Wk1
Dec-Wk3
Dec-Wk5
Jan-Wk2
Jan-Wk4
Feb-Wk2
Impact on First Pass Opens
CDA
Turned
On
% Opens Before Reprobe
(right axis)
% Opens After Reprobe
(right axis)
Goal for % Changed
% Opens Changed

Conclusion
• An in-situ method of stabilizing contact resistance
using CDA (compressed dry air)
• Reducing oxidation and contaminate build up
• Maximizing yield and reducing reprobe on contact
sensitive BINs
• Reduces the need to increase cleaning intervals. This
results in longer probe card life and improved
throughput.
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Acknowledgements
•Steve Austin
•Kelly Daughtry
•Gary Grayson
•Frank Mesa
•Mark Gillette
•Robert Davis
•PE Techs
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Thanks For Listening –
Enjoy the Conference
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