OCR CHIPPED WAFER DETECTION

(based CIS)

By LV Tailoring Software

OCR CHIPPED WAFER DETECTION

• Significant issues related to the existence of chipped surfaces on

outer periphery of the production wafers as result of improper

wafer handling. Chipped surfaces are exposed to thermal and

mechanical impact subsequently leading to breakage of the silicon

plate.

• Significant impact to tool availability as result of the internal

silicon plate breakage – long clean up and recovery time.

• Expected impact to tool quality – remaining breakage particle

effect.

• No existing monitor for chipped wafers in existence (internal or

external vendors as well.)

12/13/2014

OCR CHIPPED WAFER DETECTION

• Task - Creation prototype of the in line monitor based OCR ( tool

and operation wise) to detect chipped surfaces on outer perimeter

of the wafer plate.

• Basic requirements :

a.Usage OCR as equipment base for inline detector.

b.Show possibility to detect chipped surfaces based on conventional

image acquisition and processing.

c.Development of basic strategy, architecture and algorithms for

such operation

d.Further evaluation of possibilities.

12/13/2014

CAMERA BASED CHIPPED WAFER DETECTOR 12/13/2014

CAMERA BASED OPERATION IMPACT

Impact on OCR operation:

• Extension of OCR operation 40-50 sec to 2 min.

• Layout impact (x 2,5 space).

• Illumination issues

• Ergonomic impact

• Computation impact for front and back (x2 PC x2 Camera etc…)

• Results inconsistency ( cassette previous position dependence –

notch placement)

Placement

of cassette

Regular

OCR rotation

operation

Regular

OCR reading

operation

Camera

snaps- up

to 400 frames

Save snaps

to HD

Image

processing

results

12062 120

Regular

OCR rotation

operation (2)

24

SCANNER CIS BASED CHIPPED WAFER DETECTOR 12/13/2014

SCAN CIS BASED OPERATION IMPACT

Impact on OCR operation:

• Extension of OCR operation 40-50 sec to 70 sec.

• Layout impact (+20%)

Placement

of cassette

Regular

notch

rotation

Regular

Post alignment

rotation

Waiting CCS Scan Image

processing

results

12062 120

Regular

OCR rotation

operation

24

12/13/2014

OCR BASED CHIPPED WAFER DETECTION

• Task - Creation prototype of the in line monitor based OCR ( tool

and operation wise) to detect chipped surfaces on outer perimeter

of the wafer plate.

• Basic requirements :

A.Usage OCR as equipment base for inline detector.

B.Show possibility to detect chipped surfaces based on conventional

image acquisition and processing.

C.Development of basic strategy, architecture and algorithms for

such operation.

12/13/2014

12/13/2014OCR BASED CHIPPED WAFER DETECTION

Comparative results for CIS based detector

Testing SCAN CCSBASED

True detections front and back

Y

Average true detection 92%

Average false detection 10%

Maximum Resolution 150um

Effective Resolution 220um

As result of the scanning operation at 300x300 dpi resulted image ~3000x200 pixels

processed for inconsistencies look up using basic grey morphology algorithms.

Comparative results for Camera and CIS based detectors

Testing CAMERA BASED

SCAN CCS BASED

True detections front 50% N/A

True detections back 83% N/A

Average true detection 66.5% 92%

False alarm front 15% N/A

False alarm back 20% N/A

Average false detection 17.5% 10%

Maximum Resolution 300um 150um

Effective Resolution 500um 200um

Back up

12/13/2014

CIS SCANNNER ON OCR TOOL

Full assembly with OCR

Assembly without OCRSCAN CIS

12/13/2014

WAFERS

SCAN CCS BASED CIS DETECTABILITY

Defect detected by

OCR CIS

Estimated size 400um

Defect detected by OCR CIS

Estimated size 300um

12/13/2014