Adaptive Testing Techniques at Qualcomm, a Fabless Experience

Adaptive Testing Techniques at

Qualcomm, a Fabless Experience

Glenn Plowman

Qualcomm Inc.

[email protected]

Michael Schuldenfrei

OptimalTest

[email protected]

mailto:[email protected]

mailto:[email protected]

Glenn Plowman: Qualcomm Inc.

Michael Schuldenfrei: Optimal Test

Keith Barnes, Mike Campbell of Qualcomm, Pascal Ronde

Abstract

Adaptive testing techniques are becoming more and more popular as a

means to reduce cost of test.

This paper explores adaptive testing challenges and benefits at

Qualcomm.



Executive Summary

Traditional methods of test time reduction are both volume and man

power intensive.

OptimalTest Adaptive TTR (ATTR) can help achieve TTR savings while

reducing manpower for TTR in high volume manufacturing.

Test programming and use of concurrency features must be reviewed

to avoid interference with ATTR.

Data collection, simulation and review processes must be put in place

to define ATTR rules.

Infrastructure is required to deliver, execute and monitor ATTR rules in

production.



Overview

What is OT ATTR?

Benefits

Challenges

ATTR Rule Logistics: simulation, definition, deployment and execution.

Tester Integration




What is Adaptive Test?

•“Adaptive Test is a broad term used to describe methods that change

test conditions, test flow, test content and test limits (potentially at the

die/unit or sub-die level) based on manufacturing test data and statistical

data analysis.” (ITRS Definition)

Feed-forward data from in-line test

Feed-back data from post-test statistical analysis

Real-time & near real-time data analysis

Statistical Process Control (SPC)

Adjust test limits and content on-the-fly.




OptimalTest Adaptive TTR

OptimalTest has 2 Advanced Adaptive TTR (ATTR) methodologies

Parametric Method – performed on parametric tests while analyzing

& evaluating, in real-time, the process stability and making test time

reduction decisions

P/F Method – performed on low fallout tests

Leverage information from actual & historic device test results

Applicable at WS and FT

Selection is based on device & test characteristics and needs

Can be applied simultaneously or individually

No modifications required to existing test programs

Patents pending & issued



linked

reports

OPTIMALTEST

Database



Overview

What is OT ATTR?

Benefits

Challenges


Tester Integration



Lower test costs – Reduce TTR manpower

Better Quality - Test sampling not

test removal

Achieved without changing

test programs

Benefits of Advanced Adaptive Test

9




Qualcomm TTR

• OT TTR Simulation reports help guide engineering to optimal and

automated TTR faster than engineers using manual techniques and

the results have a higher degree of statistical rigor.

Example: Half of the manual TTR savings obtained on a product

was attributed to information found in the simulation reports.

• OT is used to produce rules (recipes) for ATTR on testers with much

lower PTE time commitment.

Impact: EVEN AFTER manual TTR additional saving can be

obtained using ATTR rules with no loss to product quality.



Overview

What is OT ATTR?

Benefits

Challenges


Tester Integration




Challenges for ATTR –Deferred Calculation

Tests like DSP are farmed out to special processors that calculate

results in the background.

When test results are available the test record is generated with the

correct instance and test.

Test instance integrity is preserved but test order is not.

Deferred tests with low failure rates and high test times can be

TTRed.

The current TTR Simulator will be overly pessimistic (see COF).




Challenges for ATTR –Concurrent Test

Concurrent test is coming in IGXL 8.0.

Concurrent execution of instances will require novel solutions.

As of Jan 2011 Teradyne and OptimalTest are actively discussing

the topic of concurrent test.




Challenges for ATTR –Instance/Variable Dependencies

Setup Instances cannot be removed.

Instances that output information cannot be removed.

Instances that create any dependencies for following Instances must

not be removed (e.g. global variables).

TE must decide whether to support ATTR by minimizing inter-

instance dependencies during programming.

TE must identify instances which are not ATTR candidates due to

inter-instance dependencies during simulation.

Instances coded in VBT must also be included in the flow sheet.




Challenges – Continue on Fail

• Test 1 - Pass

• Test 2 - PassInstance A

• Test 3 – Fail => SBIN 1234, HBIN 4

• (TP stops here with Stop On Fail)Instance B

• Test 4 – Pass

• Test 5 – PassInstance C

• Test 6 – Fail

• Test 7 - FailInstance D

• Test 8 – Pass

• Test 9 - PassInstance E

Tests 6 & 7 each

have an

additional failure

if COF is used.

Fails for tests 6

& 7 are over-

reported.

TTR opportunity

for Instance D is

missed.



Overview

What is OT ATTR?

Benefits

Challenges

ATTR Rule Logistics: simulation, definition, deployment and execution

Tester Integration



Process Flow for Test Time Reduction

AnalysisHistorical Data

Test

Candidates

TTR RecipeAdaptive TTR

Rule

TTR Rule in

Real TimeTTR Results

OTPortal

17




ATTR Simulation at Qualcomm

Get TT Profile

Run Simulation

Review Results

Revise Test Candidates

Select TP




ATTR Rule Checkout at Qualcomm


Rule Editing and

Duplication

Correlation

Validation

PTE Review

Simulation Generated

Rule

Publish Correlation ATTR Rule

Publish Validation ATTR Rule



ATTR Rule Deployment

Qualcomm

Subcon 1

Publish Production

ATTR Rule

Rule Statuses

Datalogs w/ TTR

Feedback

Activate /Deactivate

Rule

Publish Validation

ATTR Rule

1 lot

Datalog w/ TTR

Feedback

Publish Production

ATTR Rule

Rule Statuses

Datalogs w/ TTR

Feedback

Subcon 2

ATTR Monitors

Publish Validation

ATTR Rule

2-3 lots

Datalog w/ TTR

Feedback

ATTR Monitors

Activate /Deactivate

Rule

Publish Correlation

ATTR Rule

The same rule may be deployed more quickly at additional subcons (e.g. Subcon 2)



Overview

What is OT ATTR?

Benefits

Challenges


Tester Integration



ATTR Rule Example



OptimalTest – Teradyne Interface for TTR

Before injection of Enable Words

After injection of Enable Words

23



Executive Summary

Traditional methods of test time reduction are both volume and man power intensive.

OptimalTest Adaptive TTR (ATTR) can help achieve TTR savings while reducing manpower for TTR in high volume manufacturing.

Test programming and use of concurrency features must be reviewed to avoid interference with ATTR.

Data collection, simulation and review processes must be put in place to define ATTR rules.

Infrastructure is required to deliver, execute and monitor ATTR rules in production.

Documents

Adaptive Testing Techniques at Qualcomm, a Fabless Experience