xatf - extendible adaptive test format stefan eichenberger 21 st june, 2010

XATF - eXtendible Adaptive Test Format

Stefan Eichenberger

21st June, 2010

Content

The Need: Requirement corner-stones

The Concept: Corner-stones of XATF

Some More Details

Conclusion and Discussion

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Scope: The Adaptive Test Universe


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IEEE 2009 International Test Conference 16

Adaptive Test Flow “RT A/O” stands for “Real-Time Analysis &

Optimization”

Wafer Probe

Final Test

Burn-in

Card/System TestDatabase & Automated

Data Analysis(including post-test statistical analysis, dynamic routings and feedforward data)

Fab data Design data Business data Customer specs

ETESTFab data

FAB

Field Operation

RT A/O

RT A/O

RT A/O

RT A/O

PTAD

PTAD

PTAD

PTAD

“PTAD” is “Post-Test Analysis &

Dispositioning”

PTAD

How do we transport

data here?

ITRS Roadmap, 2009

STDF-v4

STDF-v4/2007

Data Functions

Offline analysis and archiving– parametric data– bin and summary data– fail vector information

adaptive test: real time analysis and optimization

– decision documentation– statistical and model data

adaptive test: automated off-line data analysis

– down-stream processing recipe adaption– data feed-forward– SPC limit calculation / data feedback

Device classification– assembly classification

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ToFrom

WAT Esort Assly Final Board

WAT

Esort E-142

Assly

Final

Board

• Data Feedback• SPC

• Data Feedforward

Which tree was built and used? (PSU)

Which neighborhood was chosen? (TI)

Slope?Intercept?

PCA transformation matrix?

Trends

Some mature concepts– AEC Q001- Part average testing– statistical scan diagnosis

Many concepts in their infancy– the unknown is the only constant factor …– the slow adoption rate of statistical scan diagnosis demonstrates

how a lack of infrastructure capabilities can hinder broad-scale introduction

Increased supply chain complexity– not all data should be sent to everywhere– … but exact flows vary and are very case specific

Hence, we need:– a format with a well defined standard core (which must expand over time)– light-weight, transparent extendibility


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Requirements on a data format

Open, royalty free format

Clear, concise and complete core specification– definition of format (schema)– defined conformance checking– definition of key content elements

Transparent extendibility– supporting forward- and backward compatibility– defined maintenance cycles

Multi-way communication– “dock / un-dock“ chunks to a file as fit a given manufacturing flow

Harvesting existing formats, where they exist (eg. E142)


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But can we define this all today?No, we don’t have to!

Can we fix STDF?

STDF originates from an age where computers were far less powerful

– remember 640kByte memory on 4.66MHz IBM PC?

This dictated some compromises which were great then but a pain today:– file can only be read sequentially– record format is not extendible – leading to bloated files– binary encoding CPU specific

STDF doesn’t have a robust core specification– no reference implementation or compliancy check

Fixing STDF means breaking with history– many STDF applications (readers and writers) will likely not transparently handle extensions– hence, we get the costs of a new format without the benefits


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STDF was a great format!But its place is in history!

If we sweep the floor – what can we gain?

Harvest modern software eco systems– ease of data handling– tap into larger human resource pool– schema language based format definition to allow coherent extendability

Light-weight key infrastructure component– targeted data extraction with few lines of code– supporting low-cost proto-typing of adaptive test concepts

Foundation to grow for years– … it’s not a question whether we drop STDF – it’s a question when we do it


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Content



Some More Details



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What if we could …

… use XML?– large eco-system of software, software components and knowlege– well established, rapidly increasing adaption rate in many areas– narrative

• we can express everything we want: lot descriptions, wafer layouts, adaptive test recipes, …

• perfectly suited to support data routing along a complex supply chain– but it’s huge!

• try this: Michael Hackerott described an XML version of STDF• a 1GByte STDF file grows to 6GByte …

Observation:– XML fits most of our needs – except the actual die specific data!– XML is not good at managing dense data (eg. results tables)


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http://mrhackerott.org/semiconductor-informatics/informatics/

What if we could …

… use SQL right at the tester?– random access to large data sets– performance can be optimized through indices– good at handling dense data, such as results tables– … but what about narrative data

• lot descriptions• recipes• … data models quickly become very complex!

– and do you really want a life data connection from the test cell to a corporate SQL database? (No!) How to handle real time requirements?

Observations– would bring a relational database right to the tester– nice idea – but is it realistic? (Yes, it is!)


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The way to go …

Both XML and SQL schemas can– be formally described– lend themselves to extendibility– are well understood by a large community of software engineers

The only crux is to find how to combine them!


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SQLite is a self-contained, serverless, zero-configuration transactional

SQL database

•portable file format (CPU independent)•public domain license (no restrictions as eg. with GNU licences)•wide industry adaption (eg. Adobe, Mozilla, …)

sqlite.org

http://sqlite.org/


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Concept XATF

The basic data (narrative part) is stored in XML

Dense data can not easily be stored in XML

Such dense data is stored in base64 encoded binary containers at the end of the XML file

– XML elements can refer to specific containers through a BulkID

Typically, the internals of a bulk container are an SQLite database file

Other bulk data can be allowed if needed– even encrypted data

XATF

NativeContainer

@BulkID = 1

@BulkID = 2

@BulkID = 3

<subelement BulkID=2> … some native content</subelement>

So, all we need do is …

Layer 0: Format definition– define a basic XML structure

• must be able to capture most if not all of STDF– define extension mechanisms

• XML schemas are by definition extendible• namespaces allow infinite future growth• how to differentiate between proprietary and public extensions

– define access mechanism to bulk containers

Level 1: Content definition– the essential data elements of the core structure must also be defined in

terms of their exact meaning

Migration path: Map STDF elements to XATF elements– it should be possible to have lossless conversions STDF XATF STDF

(lossless in terms of information, not in exact STDF representation)


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Transition Management: STDF XATF

Large existing investments in STDF– infrastructure, tools (incl. deployment, user training, …)– historical data

Transition requirements– loss-less conversion from STDF

• if converted back to STDF, same information must be present (although potentially in a different STDF representation)

• some (less relevant, t.b.d.) STDF corner cases will be difficult to support

STDF[in] STDF[out]

Other data

XATF

Other dataSame or moreinformation thanin STDF[in]

Content



Some More Details



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Top Level Structure

April 21, 2023Stefan Eichenberger, WT&FO, Operations -

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E142 embedding


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Bulk Storage

Simple data model:– part level data– substrate (wafer) level data– lot level data

The table structure fits standard analysis tools and paradigms

– Example: part specific limits are added as an additional column, just like a test result


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Content



Some More Details



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Summary

Adaptive test is getting out of it’s infancy – time to give it a solid data communication back-bone

the proposed combination of XML with bulk data storage in base64 encoded SQLite database format provides a solid foundation for a new format

extendibility is guaranteed in three ways– extendible XML schemas for narrative data– extendible SQL structures for dense data– other bulk data formats where such is needed

Proposal is to start with a small content coverage and define the extendibility mechanisms

Care must be taken to also specify exact content of general content elements to avoid ambiguities as in STDF


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xatf - extendible adaptive test format stefan eichenberger 21 st june, 2010

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