Removal of charge between a substrate and an electrostatic clamp
An electrostatic clamp, which more effectively removes built up charge from a substrate prior to and during removal, is disclosed. Currently, the lift pins and ground pins are the only mechanisms used to remove charge from the substrate after implantation. The present discloses describes a clamp having one of more additional low resistance paths to ground. These additional conduits allow built up charge to be dissipated prior to and during the removal of the substrate from the clamp. By providing sufficient charge drainage from the backside surface of the substrate 114 , the problem whereby the substrate sticks to the clamp can be reduced. This results in a corresponding reduction in substrate breakage.
1. A clamp for handling a substrate, comprising:
a top layer, made of non-conductive material, adapted to contact said substrate;
an outer annular ring surrounding said top layer that is made of said non-conductive material; and
a connection between said outer annular ring and ground, wherein said connection comprises a carbon film that is semiconducting thereby providing charge drainage for a substrate disposed on said outer annular ring.
2. The clamp of claim 1 , further comprising a lower portion disposed beneath said top layer, wherein said lower portion comprises metal and is grounded, and said connection is between said outer annular ring and said lower portion.
3. The clamp of claim 1 , further comprising electrodes located beneath said top layer, whereby said electrodes are configured to create an electrostatic force to hold said substrate.
4. The clamp of claim 3 , wherein said connection is interrupted during the time in which said electrostatic force is being created.
5. The clamp of claim 1 , further comprising conduits deposited on said top layer, wherein said conduits have a lower resistivity than said top layer.
6. The clamp of claim 5 , wherein said conduits are connected to said outer annular ring.
7. The clamp of claim 1 , further comprising a second connection between said outer annular ring and ground, wherein said second connection comprises said carbon film.
8. The clamp of claim 1 , wherein said connection is disposed around an entire circumference of said outer annular ring.