Cross-contaminant shield in sputtering system
A multi-chamber processing system is described for depositing materials on multiple workpieces (wafers, display panels, or any other workpieces) at a time in a vacuum chamber. The system includes a sputtering chamber and a separate pre-clean chamber, where wafers can be transferred between the two chambers by a robotic arm without breaking a vacuum. The wafers are mounted one-by-one onto a rotating pallet in the pre-cleaning chamber and sputtering chamber. The pallet is firmly fixed to a rotatable table in the sputtering chamber. Copper tubing in the table couples RF energy to the wafers, and a liquid running through the copper tubing controls the temperature of the wafers. Multiple targets, of the same or different materials, may concurrently deposit material on the wafers as the pallet is rotating. Multiple magnets (one for each target) in the magnetron assembly in the sputtering chamber oscillate over their respective targets for uniform target erosion and uniform deposition on the wafers. An electrically insulated target backing plate between each magnet and a target has a liquid channel running through it for controlling temperature. The distance between the magnets and the targets is made very small by a thin aluminum plate fixed to the bottom segment of the target backing plate by a dip brazing process. Various shields are described to prevent cross-contamination from the targets and prevent the sputtered target material from entering gaps in the chamber and shorting out insulators.
1. A sputtering system comprising:
a low pressure chamber;
a pallet in the chamber, the pallet having a plurality of workpiece support areas for concurrently supporting a plurality of workpieces on the pallet;
a generally circular first plate facing the pallet, the first plate supporting a plurality of targets having sputtering surfaces facing the pallet, the first plate being electrically conductive and electrically insulated from the targets, the first plate and targets being at different potentials, the targets being located at different radial positions with respect to a center axis of the first plate such that any single workpiece support area may be positioned under only a single target, there being no target intersecting the center axis of the first plate, the first plate having openings for each of the targets, the first plate extending laterally between the targets, the first plate being insulated from each of the targets by an insulator circumscribing each of the targets;
the first plate forming at least a portion of a wall for the chamber for maintaining a low pressure in the chamber;
a substantially flat and circular shield plate rigidly fixed to the first plate inside the chamber, abutting the first plate, and substantially covering all of the first plate at least between the targets, the shield plate being formed of a metal and being at the same potential as the first plate, the shield plate having separate openings for all the targets to allow sputtered material from all the targets to be deposited on the workpieces below the targets, the shield plate shielding the first plate from sputtered material during a sputtering process, the shield plate being removable from the first plate for cleaning of the shield plate or disposing of the shield plate; and
a plurality of cross-contamination shields fixed to the shield plate, so as to be removed along with the shield plate, and extending toward the pallet, the cross-contamination shields extending radially across the shield plate between adjacent targets, the cross-contamination shields at least partially shielding workpieces not directly beneath a particular target from sputtered material from that particular target, an area between adjacent cross-contamination shields being larger than a workpiece on one of the workpiece support areas.
2. The system of claim 1 wherein there are at least three targets arranged around the generally circular first plate.
3. The system of claim 1 wherein the cross-contamination shields terminate less than 10 mm from workpieces supported by the pallet.
4. The system of claim 1 wherein the cross-contamination shields terminate less than 3 mm from workpieces supported by the pallet.