| 摘要 |
A method, apparatus, and computer program product for flattening a warped substrate. The substrate is placed on a planar surface of a clamping apparatus in direct mechanical contact with the planar surface. The substrate comprises surface regions S<SUB>1</SUB>, S<SUB>2</SUB>, . . . , S<SUB>N </SUB>having an average warpage of W<SUB>1</SUB>, W<SUB>2</SUB>, . . . , W<SUB>N</SUB>, respectively, wherein W<SUB>1</SUB><=W<SUB>2</SUB><= . . . <=W<SUB>N </SUB>and W<SUB>1</SUB><=W<SUB>N</SUB>. Zones Z<SUB>1</SUB>, Z<SUB>2</SUB>, . . . , Z<SUB>N </SUB>of the planar surface respectively comprise vacuum port groups G<SUB>1</SUB>, G<SUB>2</SUB>, . . . , G<SUB>N</SUB>. Each group comprises at least one vacuum port. N is at least 2. A vacuum pressure P<SUB>V1</SUB>, P<SUB>V2</SUB>, . . . , P<SUB>VN </SUB>is generated at each vacuum port within group G<SUB>1</SUB>, G<SUB>2</SUB>, . . . , G<SUB>N</SUB>, at a time of T<SUB>1</SUB>, T<SUB>2</SUB>, . . . , T<SUB>N </SUB>to clamp surface region S<SUB>1</SUB>, S<SUB>2</SUB>, . . . , S<SUB>N </SUB>to zone Z<SUB>1</SUB>, Z<SUB>2</SUB>, . . . , Z<SUB>N</SUB>, respectively. The vacuum pressure P<SUB>V1</SUB>, P<SUB>V2</SUB>, . . . , P<SUB>VN </SUB>is maintained at the vacuum ports of group G<SUB>1</SUB>, G<SUB>2</SUB>, . . . , G<SUB>N</SUB>, respectively, until time T<SUB>N+1</SUB>. T<SUB>1</SUB><T<SUB>2</SUB>< . . . <T<SUB>N</SUB><T<SUB>N+1</SUB>.
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