Independent edge control for CMP carriers
View Patent ↗A wafer carrier for controlling the edge effect during chemical mechanical planarization. A first bladder is disposed within the retaining ring to control the height of the retaining ring relative to the bottom surface of the wafer carrier. A second bladder is disposed within the carrier such that if the pressure in the bladder is regulated, the amount of force on the edge of the wafer changes. If a polishing process would cause material near the edge of the wafer to be removed at a higher rate than from the rest of the wafer, then the pressure is regulated within the bladder to reduce the force against the edge of the wafer. By reducing the force against the edge of the wafer, material is removed from the front side of the wafer at a uniform rate.
1. A wafer carrier comprising a means for securing and holding a wafer, said wafer carrier further comprising:
a mounting plate;
a retaining ring slidably attached to the mounting plate such that the retaining ring may move a distance along the axis of the wafer carrier independent of the mounting plate, said retaining ring having by an inner diameter and having a groove disposed within a top surface of the retaining ring;
an inflatable bladder disposed within the groove, said inflatable bladder sized and dimensioned to substantially conform to the size and dimensions of the groove; and
a membrane extending across the bottom surface of the wafer carrier, said membrane further disposed within the inner diameter of the retaining ring.
2. The wafer carrier of claim 1 further comprising a ridge extending into the groove, wherein the ridge extends from a component of the wafer carrier selected from the group consisting of the mounting plate and the retaining ring.
3. The wafer carrier of claim 1 further comprising a second bladder disposed within the wafer carrier, said second bladder further disposed such that pressure changes in the bladder will change the force applied to the edge of a wafer held by the wafer carrier.
4. The wafer carrier of claim 1 further comprising a shim ring disposed within the inner diameter of the retaining ring, said shim ring further disposed over the edge of the wafer.
5. The wafer carrier of claim 4 further comprising an o-ring disposed within a groove in the shim ring.
6. The wafer carrier of claim 4 further comprising a space disposed within a housing of the wafer carrier, wherein the membrane extends into the space and is sized and dimensioned to move within the space.
7. The wafer carrier of claim 3 further comprising a shim ring disposed between the second bladder and the membrane wherein the force applied to the edge of the wafer is determined by the ratio of areas of contact of the second bladder on the shim ring and the shim ring on the membrane.
8. A wafer carrier comprising a housing and a means for securing and holding a wafer, said wafer carrier further comprising:
a retaining ring;
a mounting plate operatively attached to the housing, said mounting plate adapted to hold the wafer;
a hoop bladder disposed within an inner diameter of the retaining ring, said hoop bladder further disposed over the edge of the wafer during polishing; and
a lip seal operably coupled to the housing such that the lip seal moves independently of the retaining ring and rests against the wafer during polishing.
9. The wafer carrier of claim 8 further comprising a membrane operatively attached to the mounting plate.
10. The wafer carrier of claim 8 , wherein the hoop bladder is disposed between the mounting plate and the lip seal.
11. The wafer carrier of claim 8 further comprising a space disposed within a housing of the wafer carrier, wherein the lip seal extends into the space and is sized and dimensioned to move within the space.
12. The wafer carrier of claim 8 wherein pressure inside the hoop bladder is regulated to control an amount of force the lip seal applies along an edge of wafer.
13. The wafer carrier of claim 8 wherein the hoop bladder and the lip seal are integrally formed.