Warpage of thin wafers using computer aided reflection moire method

Ng, Chi Seng; Chua, Kok Yau; Ong, Meng Tong; Goh, Yoke Chin; Asundi, Anand

doi:10.1117/12.732783

Cited by 5 publications

(2 citation statements)

References 4 publications

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“…The findings from previous paper have been extended and further validated [6]. Studies and experiments were conducted with bare wafers, wafers with different backside metallization and optical flat.…”

Section: Resultsmentioning

confidence: 78%

Whole field residual stress measurement using computer aided reflection grating

Goh²,

Asundi

2008

SPIE Proceedings

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In our previous paper, "Warpage of thin wafers using computer aided reflection moiré method', the surface curvature and residual stresses were evaluated using the versatility of computer aided reflection grating method to manipulate and generate gratings in two orthogonal directions. A very good agreement between the theory and experimental results was established. The bending stresses of wafers due to the deposition of backside metallization were evaluated without the aid of reference grating.In this paper, some aspects of the work is extended. An optical flat with flatness λ/10 is used as a reference plate to extract the residual stress of the wafers with different backside metallization. By utilizing the phase information from the moiré pattern between deformed grating (wafer) and undeformed grating (optical flat), the surface deformation of the wafer and residual stresses are investigated quantitatively and numerically.This technique, with satisfactory sensitivity and accuracy, can be used to characterize the residual stress of wafer due to warpage that may lead to the crack issues in semiconductor manufacturing industry.

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Section: Resultsmentioning

confidence: 78%

Whole field residual stress measurement using computer aided reflection grating

Goh²,

Asundi

2008

SPIE Proceedings

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“…By using this technique, the pitch of horizontal and vertical grating can be varied and controlled without moving parts, thus reducing the possible error and improving the accuracy. The following algorithm is based on literature [4].…”

Section: Methodsmentioning

confidence: 99%

Whole field curvature and residual stress determination of silicon wafers by reflectometry

Asundi

2011

SPIE Proceedings

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Reflectometry, a simple whole-field curvature measurement system using a novel computer aided phase shift reflection grating method has been improved to certain extend. The similar system was developed from our earlier works on Computer Aided Moiré Methods and Novel Techniques in Reflection Moiré, Experimental Mechanics (1994) in which novel structured light approach was shown for surface slope and curvature measurement. This method uses similar technology but coupled with a novel phase shift system to accurately measure surface profile, slope and curvature.In our previous paper, "Stress Measurement of thin wafer using Reflection Grating Method", the surface curvature and residual stresses were evaluated using the versatility of the proposed system.. The curvature of wafers due to the deposition of backside metallization was evaluated and compared with a commercially stress measurement system from KLA-Tencor.In this paper, some aspects of the work are extended. Our proposed system is calibrated using a reference flat mirror and spherical mirror certified by Zygo Corporation. The mirrors together with the camera calibration toolbox allow the system to acquire measurement accuracy that is demanded by semiconductor industry. Finally, the results obtained from Reflectometry are compared and contrast with results from KLA Tencor System.

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