Target backing plate for 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. 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, where the liquid channel has a wider cross-sectional area around the middle portion of the target backing plate to increase cooling of the middle portion of the target. 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.
1. A sputtering system comprising:
a low pressure chamber;
a workpiece support area for supporting a workpiece;
a target backing plate for supporting on a first side of the target backing plate a target having a sputtering surface;
the target backing plate forming at least a portion of a wall of the chamber for maintaining a low pressure in the chamber; and
a magnet opposing a second side of the target backing plate so as to oppose the target through the target backing plate;
the target backing plate comprising a coolant channel formed between opposing walls of the target backing plate, the coolant channel having portions that are between the magnet and the target to cool the target backing plate and the target, the coolant channel having coolant entrance and exit ports in peripheral areas of the target backing plate that are not covered by the magnet, wherein there is only a single entrance port and a single exit port connecting a single coolant channel path for cooling the entire target;
wherein the magnet scans back and forth over the target backing plate, a scanning movement of the magnet being confined within a space over the target backing plate such that a middle portion of the target backing plate requires more cooling than peripheral portions of the target backing plate, the middle portion being within a middle third of the target backing plate, the middle third being bounded on both sides by outer thirds of the target backing plate, the middle third of the target backing plate having the same area as each outer third of the backing plate, and
wherein the coolant channel, forming a single path for a coolant, has a varying cross-sectional area within the target backing plate, with the coolant channel having a cross-sectional area that gradually increases toward a middle of the target backing plate and gradually tapers toward edges of the target backing plate, such that the cross-sectional area of the coolant channel in the middle third of the target backing plate is larger than the cross-sectional area of the coolant channel in the outer thirds of the target backing plate and the total contact area between the coolant and the target backing plate in the middle third is greater than to the outer thirds, to provide greater cooling of the middle portion of the target backing plate.
2. The system of claim 1 wherein the magnet scans back and forth within a depression formed in the target backing plate, wherein a raised wall of the target backing plate substantially surrounds the depression, the coolant entrance and exit ports being located on the raised wall.
3. The system of claim 1 wherein the coolant channel is in a meandering path.
4. The system of claim 1 wherein a thickness of the target backing plate is less than 0.75 inch.