Physical vapor deposition method using backside gas cooling of workpieces
A circular PVD chamber has a plurality of sputtering targets mounted on a top wall of the chamber. A pallet in the chamber is coupled to a motor for rotating the pallet about its center axis. The pallet has a diameter less than the diameter of the circular chamber. The pallet is also shiftable in an XY direction to move the center of the pallet beneath any of the targets so all areas of a workpiece supported by the pallet can be positioned directly below any one of the targets. A scanning magnet is in back of each target and is moved, via a programmed controller, to only be above portions of the workpiece so that no sputtered material is wasted. For depositing a material onto small workpieces, a cooling backside gas volume is created between the pallet and the underside of sticky tape supporting the workpieces.
1. A method of operation of a physical vapor deposition device, the device having a chamber configured to create a low pressure environment in the chamber while sputtering materials on a workpiece, the method comprising:
providing a workpiece support platform in the chamber, the support platform having openings for a backside gas;
mounting a workpiece on a sticky tape, wherein a ring provides a frame for the sticky tape;
providing one or more magnets on the support platform for attracting the ring to the one or more magnets;
positioning the ring over the one or more magnets such that the ring is attracted to the one or more magnets;
providing a ridge on the support platform that creates a gas seal with respect to the sticky tape as the ring is attracted to the one or more magnets on the support platform, so that an area between the tape and the support platform forms a sealed backside gas volume; and
introducing a backside gas into the backside gas volume for cooling the workpiece supported by the tape.
2. The method of claim 1 wherein the sticky tape has at least one opening that exposes a back surface of the workpiece to the backside gas volume.
3. The method of claim 1 wherein the workpiece is one of a plurality of workpieces supported on a top surface of the sticky tape for batch processing of the workpieces.
4. The method of claim 1 wherein the one or more magnets are permanent magnets.
5. The method of claim 1 wherein the ring is formed of a high magnetic permeability material.
6. The method of claim 1 wherein the ring is formed of steel.
7. The method of claim 1 further comprising depositing a metal shield over the workpiece.
8. The method of claim 1 further comprising depositing a backside metal over the workpiece.