probe-to-pad positioning process - Semiconductor Wafer Test ...
probe-to-pad positioning process - Semiconductor Wafer Test ...
probe-to-pad positioning process - Semiconductor Wafer Test ...
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PROBE-TO-PAD POSITIONING<br />
PROCESS<br />
Digital Semiconduc<strong>to</strong>r<br />
Hudson MA 01749<br />
R.Hart, A.Miller, C.Tingley<br />
IEEE Southwest <strong>Test</strong> Workshop - ‘97<br />
Digital Semiconduc<strong>to</strong>r 10/12/97 1
TOPIC AREAS<br />
Pad Opening/Scrub Capability<br />
■ Scrub Window Model<br />
■ Scrub Window Measurement<br />
■ Scrub Window Simulation<br />
■ Derived Process Fac<strong>to</strong>rs Signatures<br />
Digital Semiconduc<strong>to</strong>r 10/12/97 2
SCRUB WINDOW MODEL<br />
■ Process Fac<strong>to</strong>rs:<br />
■ Card, System, Set-up, <strong>Wafer</strong><br />
■ Best Fit Probe <strong>to</strong> Pad<br />
■ XY Alignment<br />
■ Z Planarity, , Lateral Scrub Profile<br />
(length, width, angle)<br />
■ Window = Composite of all Scrub Boxes<br />
Digital Semiconduc<strong>to</strong>r 10/12/97 3
Scrub Window Measurement<br />
Parameters<br />
■ Setup and Print<br />
Sample<br />
■ Measure Gap<br />
Passivation Edge <strong>to</strong><br />
Scrub Box<br />
■ Maximize the Gap<br />
Minimize the<br />
Variation<br />
■ Determine the Best<br />
Fit<br />
Digital Semiconduc<strong>to</strong>r 10/12/97 4
Scrub Window Measurement<br />
Yt<br />
w<br />
Xr<br />
Xl<br />
l<br />
Yb<br />
Pad _Opening = Gaps_Dist<br />
+Scrub_Box_Composite<br />
Digital Semiconduc<strong>to</strong>r 10/12/97 5
SCRUB WINDOW MEASUREMENT CASES<br />
■ Pad Bounded (Die, <strong>Wafer</strong>) all fac<strong>to</strong>rs<br />
■ Unbounded (Metal <strong>Wafer</strong>) card, system<br />
fac<strong>to</strong>rs<br />
Note: <strong>probe</strong> tip <strong>to</strong>e overhang will not be<br />
detected, except against passivation<br />
edge<br />
Digital Semiconduc<strong>to</strong>r 10/12/97 6
Pad Bounded Scrub<br />
Scrub<br />
Gaps Measurement Method<br />
Centroids Measurement Method<br />
Best Fit Plane (x,y)<br />
Digital Semiconduc<strong>to</strong>r 10/12/97 7
Unbounded Scrub - Metal <strong>Wafer</strong><br />
x1<br />
x2<br />
y2<br />
y1<br />
card theta<br />
Select a Scrub Centroid Reference o<br />
Best Fit Scrub Locations <strong>to</strong> Pad Ring<br />
Digital Semiconduc<strong>to</strong>r 10/12/97 8
SCRUB WINDOW SIMULATION<br />
■ Relationship of Probe Mechanics <strong>to</strong><br />
Pad Scrub<br />
■ Identification of parameters<br />
which affect the end-result profile<br />
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Digital Semiconduc<strong>to</strong>r 10/13/97 13
DERIVED PROCESS FACTOR VALUES<br />
■ Comparative and Quantitative<br />
■ Analyses per Fac<strong>to</strong>r<br />
■ Capability = Spec/Actual<br />
■ = <strong>pad</strong>_op/scrub_wind_composite<br />
■ =<strong>pad</strong>_op/(<strong>pad</strong>_op-2xgap_mean<br />
■<br />
+3xproc_sigma)<br />
■ proc_sigma = sqrt (sum sqrs fac<strong>to</strong>rsig)<br />
Digital Semiconduc<strong>to</strong>r 10/12/97 14
EXAMPLE:<br />
Proc_sig<br />
= +- sqrt(card_sig2 + prbr_sig2 + opr_sig2)<br />
Proc_sig<br />
= +-sqrt<br />
sqrt(4**2 + 2.1**2 + 3.3**2)<br />
Proc_sig<br />
= 5.6 , 3 proc_sigma = 16.8 microns<br />
Gap_mean = 10 microns<br />
Capability = 67 / (67- (2x10) + 16.8) = 1.05<br />
For 80 micron <strong>pad</strong> pitch - 13 micron pass_space<br />
Digital Semiconduc<strong>to</strong>r 10/12/97 15
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