Semiconductor wafer polisher and method

A semiconductor wafer polisher for polishing at least one semiconductor wafer, the wafer having first and second opposite faces, the polisher being adapted to polish the first face of the semiconductor wafer to flatten the first face and reduce the thickness of the wafer from an initial thickness t.sub.1 to a final thickness t.sub.2, the final thickness t.sub.2 being thinner than the initial thickness t.sub.1, the polisher comprising:

• a wafer carrier having a support plate and a generally planar wafer holding surface on the support plate for holding the second face of the wafer;
• a polishing table having a polishing plate and a planar polishing surface on the polishing plate lying in a plane parallel to the planar wafer holding surface;
• at least one of the wafer carrier and polishing table being rotatable about an axis to effectuate relative rotation between the wafer carrier and polishing table;
• the planar polishing surface being adapted to abut the first face of the semiconductor wafer for polishing the first face upon relative rotation between the wafer holding surface and the polishing surface;
• the planar wafer holding surface and the planar polishing surface being urged toward each other to press the first face of the semiconductor wafer and the polishing surface against each other such that the planar polishing surface rubs against the first face of the semiconductor wafer upon rotation of the polishing surface relative to the semiconductor wafer to wear against the first face of the semiconductor wafer, the wafer holding surface and the polishing surface moving axially toward each other as the semiconductor wafer is reduced in thickness;
• a polishing limiter integrally formed with one of the support plate and polishing plate such that the polishing limiter and said one of the support plate and polishing plate constitute a single unitary piece, the polishing limiter extending axially from said one of the support plate and polishing plate toward the other of the support plate and polishing plate for limiting reduction in thickness of the wafer, the polishing limiter having a plate rubbing surface adapted for rubbing against said other of the support plate and polishing plate, the polishing limiter being sized and configured such that the plate rubbing surface is axially spaced from said other of the support plate and polishing plate when the semiconductor wafer has the thickness t.sub.1 and such that the plate rubbing surface rubs against said other of the support plate and polishing plate when the semiconductor wafer has been reduced to the thickness t.sub.2, the plate rubbing surface having a greater resistance to polishing than that of the semiconductor wafer such that the polishing limiter prevents the wafer holding surface and the polishing surface from further moving axially toward each other when the plate rubbing surface rubs against said other of the support plate and polishing plate to prevent the wafer from being reduced in thickness beyond the thickness t.sub.2.

A semiconductor wafer polisher for polishing semiconductor wafers, each semiconductor wafer having first and second opposite faces, the polisher being adapted to polish the first and second faces of the semiconductor wafers to flatten the faces and reduce the thickness of the semiconductor wafers from an initial thickness t.sub.1 to a final thickness t.sub.2, the final thickness t.sub.2 being thinner than the initial thickness t.sub.1, the polisher comprising:

• a first polishing table having a first plate and a first surface on the first plate, the first surface including a first planar polishing surface portion adapted to abut the first faces of the semiconductor wafers;
• a second polishing table having a second plate and a second surface on the second plate, the second surface including a second planar polishing surface portion parallel to the first planar polishing surface portion and adapted to abut the second faces of the semiconductor wafers;
• a generally planar wafer carrier for holding the semiconductor wafers between the first and second polishing surfaces, the carrier having at least three openings therein, two of the openings being adapted for receiving the semiconductor wafers and the other opening being adapted for receiving a dummy wafer, the carrier having a thickness less than the thickness t.sub.2 ;
• the first and second plates each being rotatable about an axis perpendicular to the first and second polishing surface portions to effectuate relative rotation between the first and second polishing surface portions and the first and second faces of the semiconductor wafers for polishing the first and second faces;
• the first and second polishing surface portions being urged toward each other such that upon rotation of the first and second polishing surface portions, the polishing surfaces rub against the first and second faces of the semiconductor wafers to polish the first and second faces of the semiconductor wafers, the polishing surface portions moving axially toward each other as the semiconductor wafers are reduced in thickness;
• at least one dummy wafer receivable within said other opening in the wafer carrier, said dummy wafer having first and second generally planar rubbing surfaces on opposite faces thereof, said surfaces being adapted to rub against the polishing surface portions and being spaced apart a distance equal to the thickness t.sub.2 such that the first and second rubbing surfaces rub against the first and second polishing surface portions respectively when the semiconductor wafers have been polished to the thickness t.sub.2, the dummy wafer having a greater resistance to polishing than that of the semiconductor wafers so that the dummy wafer prevents the polishing surface portions from further moving axially toward each other when the first and second rubbing surfaces respectively rub against the first and second polishing surface portions to prevent the semiconductor wafers from being reduced in thickness beyond the thickness t.sub.2.

A method of polishing a semiconductor wafer wherein the semiconductor wafer has first and second opposite faces and at least the first face of the semiconductor wafer is adapted to be polished to flatten the first face and reduce the thickness of the semiconductor wafer from an initial thickness t.sub.1 to a final thickness t.sub.2, the final thickness t.sub.2 being thinner than the initial thickness t.sub.2, the method comprising:

• supporting the semiconductor wafer between a first table and a second surface by way of a wafer carrier, the first table having a first plate and a first surface on the first plate, the first surface including a planar first surface portion adapted to abut the first face of the semiconductor wafer, the first surface portion of the first table comprising a planar polishing surface, the second surface having a planar second surface portion adapted to abut the second face of the semiconductor wafer, the first and second surface portions lying in respective parallel planes;
• at least one of the first and second surfaces being rotatable about an axis to effectuate relative rotation between the planar first and second surface portions, the axis being perpendicular to the respective parallel planes of the first and second surface portions, the relative rotation between the first and second surfaces effectuating relative rotation between the polishing surface and the first face of the semiconductor wafer for polishing the first face;
• positioning at least one polishing limiter between the first and second surfaces for limiting the reduction in thickness of the wafer, the polishing limiter being integrally formed with the wafer carrier such that the polishing limiter and the wafer carrier constitute a single unitary piece, the polishing limiter having at least one rubbing surface adapted for rubbing against one of the first and second surfaces, the polishing limiter being sized and configured such that the rubbing surface is spaced axially from said one of the first and second surfaces when the semiconductor wafer has the thickness t.sub.1 and such that the rubbing surface rubs against said one of the first and second surfaces and the polishing limiter extends from the second surface to the first surface when the semiconductor wafer has the thickness t.sub.2, the polishing limiter having a greater resistance to polishing than that of the semiconductor wafer such that the polishing limiter prevents the polishing surface and the second surface portion from moving axially toward each other when the polishing limiter extends from the second surface to the first surface to prevent the wafer from being reduced in thickness beyond the thickness t.sub.2 ;
• rotating at least one of the first and second surfaces about the axis;
• urging the planar polishing surface and the second surface portion toward each other to press the first face of the semiconductor wafer and the polishing surface against each other such that the planar polishing surface rubs against the first face of the semiconductor wafer upon rotation of the polishing surface relative to the semiconductor wafer to wear against the first face of the semiconductor wafer, the polishing surface and the second surface portion moving axially toward each other as the semiconductor wafer is reduced in thickness and until the semiconductor wafer has been reduced to the thickness t.sub.2, the rubbing surface rubbing against the one of the first and second surfaces and the polishing limiter extending from the second surface to the first surface when the semiconductor wafer has been reduced to the thickness t.sub.2 to prevent the polishing surface and the second surface portion from further moving axially toward each other thereby to prevent the wafer from being reduced in thickness beyond the thickness t.sub.2.

A method of polishing a semiconductor wafer wherein the semiconductor wafer has first and second opposite faces and at least the first face of the semiconductor wafer is adapted to be polished to flatten the first face and reduce the thickness of the semiconductor wafer from an initial thickness t.sub.1 to a final thickness t.sub.2, the final thickness t.sub.2 being thinner than the initial thickness t.sub.1, the method comprising:

• supporting the semiconductor wafer by way of a wafer carrier having a support plate and a generally planar wafer holding surface on the support plate, the second face of the wafer being held against the wafer holding surface;
• positioning a polishing table against the first face of the semiconductor wafer, the polishing table having a polishing plate and a planar polishing surface on the polishing plate lying in a plane parallel to the planar wafer holding surface, the planar polishing surface abutting the first face of the semiconductor wafer;
• at least one of the wafer carrier and the polishing table being rotatable about an axis to effectuate relative rotation between the wafer carrier and the polishing table, the axis being perpendicular to the planar polishing surface and the planar wafer holding surface;
• limiting reduction in thickness of the semiconductor wafer with a polishing limiter, the polishing limiter being integrally formed with one of the support plate and polishing plate such that the polishing limiter and said one of the support plate and polishing plate constitute a single unitary piece, the polishing limiter extending axially from said one of the support plate and polishing plate toward the other of the support plate and polishing plate and having a plate rubbing surface adapted for rubbing against said other of the support plate and polishing plate, the polishing limiter being sized and configured such that the plate rubbing surface is axially spaced from said other of the support plate and polishing plate when the semiconductor wafer has the thickness t.sub.1 and such that the plate rubbing surface rubs against said other of the support plate and polishing plate when the semiconductor wafer has been reduced to the thickness t.sub.2, the plate rubbing surface having a greater resistance to polishing than that of the semiconductor wafer such that the polishing limiter prevents the wafer holding surface and the polishing surface from moving axially toward each other when the plate rubbing surface rubs against said other of the support plate and polishing plate to prevent the wafer from being reduced in thickness beyond the thickness t.sub.2 ;
• rotating at least one of the wafer carrier and the polishing table about the axis to effectuate relative rotation between the polishing surface and the first face of the semiconductor wafer;
• urging the planar wafer holding surface and the planar polishing surface toward each other during relative rotation between the polishing surface and the first face of the semiconductor wafer to press the first face of the semiconductor wafer and the polishing surface against each other such that the planar polishing surface rubs against the first face of the semiconductor wafer to wear against the first face of the semiconductor wafer, the wafer holding surface and the polishing surface moving axially toward each other as the semiconductor wafer is reduced in thickness and until the semiconductor wafer has been reduced to the thickness t.sub.2, the plate rubbing surface rubbing against the other of the support plate and polishing plate when the semiconductor wafer has been reduced to the thickness t.sub.2 to prevent the wafer holding surface and the polishing surface from further moving axially toward each other thereby to prevent the wafer from being reduced in thickness beyond the thickness t.sub.2.