2000 SouthWest Test
Workshop
“A Method for Probing...
Multiple Four Sided, Fine
Pitch, Small Pad Devices
. . . using Cantilever Probes”
Presented by: Louis Molinari
Director of Engineering
(480) 333-1579
[email protected]
Multi-Site Probing Session
June 14, 2000
“A Method for Probing . . .
1
Overview
• Why the need & why now
• Present day approaches
• Pros/Cons
• A different approach
• Design and characterization results
• Comparisons of “in-line” vs. “diagonal” approaches
•
•
•
•
June 14, 2000
Moving forward . . . design considerations
Manufacturing overview
Review and next step
Questions
“A Method for Probing . . .
2
Why the Need
• As with memory; especially DRAM:
• Need to reduce test times & cost
• Higher throughput
• Increased life expectancy of probing solution(s)
– More “Touched Die” per card
• Why NOW ???
• More advanced testers and probers
• Speed
• Resource availability
• Look-up cameras
June 14, 2000
“A Method for Probing . . .
3
Present Day Approaches
Vertical Solutions
Cantilever Solutions
(AKA: Epoxy Ring)
4 DUT “Parallel”
June 14, 2000
“A Method for Probing . . .
4
Present Day Approaches
Pros / Cons
Cost
Delivery Performance
Vertical Solutions
Med - High 4 - 16 wks
Med - High
Cantilever Solutions
Low - Med
Low - Med
2 - 4 wks
Problem Statement:
• Primary disadvantage of cantilever is
inconsistency of beam lengths
• Resulting in force and scrub variations
• Potential issues on smaller pads; ie: Pad Damage
June 14, 2000
“A Method for Probing . . .
5
A Different Approach
• Goals:
!
Improve cantilever approach, so Force and
Scrub are better controlled,while improving
opportunities for probe placement.
• Requirements:
Tighten accuracy requirements to + 0.3 mil max
!Reduce probing angle to <10°
!Maintain consistency in beam lengths
!
June 14, 2000
“A Method for Probing . . .
6
A Different Approach
Address Accuracy and Probe Angle
Ideal
0.5 mil
error (X,Y)
65µ
65µ
65µ
•
65µ
0.3 mil
error (X,Y)
Example shown is
with:
1.0 mil Tip
! Yielding a 1.5 mil
total scrub
!
Additional improvements
“may” be accomplished
with smaller tip diameters
and tighter specs
65µ
65µ
June 14, 2000
“A Method for Probing . . .
7
A Different Approach
Address Probe Force Consistency
• Typical Force Distribution for Today’s
Cantilever Solutions:
Contact Force, diagonal
Goal: 2 gms/mil
2.50
Variation: 30%
gms/mil
2.00
Std Dev: 0.18
1.50
Series1
1.00
Area with 30 - 45° angles
0.50
65
61
57
53
49
45
41
37
33
29
25
21
17
13
9
5
1
0.00
Pad Numbers
June 14, 2000
“A Method for Probing . . .
8
A Different Approach
• A Better Way:
1X4
2X2
4 DUT Solutions
June 14, 2000
“A Method for Probing . . .
9
Design Criteria
• Test die specifications
0.200 X 0.200
! 120 pads/die peripheral
! Pad size: 65µ
! Pitch: 77µ
!
• Ring design specifications: (1 x 4; 2 x 2)
9 and 11 layers
! 6 mil wire
! 37 and 41 mil maximum tip lengths
• Targeted:
!
!
!
June 14, 2000
1.5 gms/mil
0.6 mil tip diameter
“A Method for Probing . . .
10
Design Approach
• A Better Way:
June 14, 2000
!
Consistent beam lengths, ALL sides of ALL die
!
Results in contact force distribution <10%
!
Results in better control of scrub
“A Method for Probing . . .
11
Characterization Data
10% Variation
Contact Force, in-line
2.50
grms/mil
2.00
1.50
Std Dev = 0.06
1.00
Series1
0.50
477
449
421
393
365
337
309
281
253
225
197
169
141
113
85
57
29
1
0.00
Pad Numbers
Contact Force, diagonal
2.50
gms/mil
2.00
1.50
Series1
Std Dev = 0.18
1.00
0.50
65
61
57
53
49
45
41
37
33
29
25
21
17
13
9
5
1
0.00
30% Variation
Pad Numbers
June 14, 2000
“A Method for Probing . . .
12
Characterization Data
Tip Diameter, in-line
0.90
• Results show consistency . . .
!
Within and between die
From layer to layer (9 layers)
0.70
Diameter (mil)
!
0.80
0.60
0.50
Die 1
0.40
Die 2
0.30
Data from 2 DUTS
0.20
0.10
120
113
106
99
92
85
78
71
64
57
50
43
36
29
22
15
8
1
0.00
Pad Numbers
Scrub Lengths, in-line
1.6
•
1.4
Scrub (mil)
1.2
1
Die 1
0.8
Die 2
0.6
•
Data taken from an Al wafer at:
3mil overdrive
Measured on a:
RAM Optical Measurement System
Data from 2 DUTS
0.4
0.2
99
10
6
11
3
12
0
92
85
78
71
64
57
50
43
36
29
22
8
15
1
0
Pad Numbers
June 14, 2000
“A Method for Probing . . .
13
Moving Forward
Design Considerations
• Design for manufacturability
specifications:
!
Center to center spacing from
columns to row = 200µ minimum
!
!
!
Minimum pad size = 60
Minimum pitch = 70
200µ
200µ
!
June 14, 2000
For ALL four sides of the die
Various exceptions and conditions
always need to be reviewed and
considered
“A Method for Probing . . .
14
Manufacturing Overview
2 X 2 Approach
Ceramic Ring
Die 1
Die 2
Die 3
Die 4
Epoxy
Pt “A”
Pt “B”
Shim (Shelf)
Pt “A”
Pt “B”
• Process is an extension of existing cantilever approaches used in other
applications, such as: Multi-Dut DRAM
• Specialized tooling required for alignment and repair of such
approaches
June 14, 2000
“A Method for Probing . . .
15
Review and Next Step
• Multiple technologies can probe:
“Multiple four sided, fine pitch, small pad devices”
• Cantilever has been capable in the past.
With a low cost and quick turn time solution.
Yet with variations in it’s results.
• Cantilever solutions can now be manufactured to
yield the desired consistency !!!
• Better utilization of prober and reduction in number
of touchdowns (In-Line vs. Diagonal)
• Less potential “touch-offs” or “double touches”
as compared to a diagonal approach
!
June 14, 2000
For the example given: 288 TD vrs 300 TD
of the1100 potential die
“A Method for Probing . . .
16
Review and Next Step
• Appropriate “systems” are required to utilize these
solutions
• Prober Capability: Look-up Cameras
• Repair Capability: Inverted Alignment Systems
• 1x4 and 2x2
June 14, 2000
2x4 and beyond . . .
“A Method for Probing . . .
17
???
June 14, 2000
Questions ? ? ?
“A Method for Probing . . .
18