Plasmaterials, Inc. sputtering target bonding process provides all metal bonding to affix sputtering targets to backing plates for systems which do not utilize a bolt-on target assembly. These targets can range from elemental metals to oxides, nitrides, carbides, fluorides, compounds, refractories, ceramics, intermetallic’s, etc., including any combination thereof. Backing plates are typically produced from OFE copper, non-magnetic stainless steel (316 or 304), molybdenum or aluminum. The purpose of the bonding is to provide the following functions during plasma deposition:
- Mechanical Strength
- Electrical Conductivity
- Thermal Conductivity
This proprietary process utilizes a series of thin metallic layers to provide adhesion, diffusion barrier and wetting layers to the target and backing plates. These elemental materials are highly conductive, low vapor pressure materials which are coated on an atomic level. Each layer is specifically design, engineered an applied utilizing state-of-the-art technologies in order to guarantee the quality of each process step, as well as absolute reproducibility from target-to-target.
After the application of this thin film composite, a specially designed solder is used to bond the target to the backing plate. Plasmaterials utilizes different materials for each target/backing plate combination. Depending on the target characterization and backing plate material, a specific solder is chosen to optimize the bond. Attention is paid to the difference between the thermal coefficient of expansion of the target and the backing plate in conjunction with the ductility of the target. The most common solder for metallic bonding of sputtering targets to backing plates is high purity indium.
During sputtering, the target surface is bombarded with high energy icons. The momentum transfer which results from the collision causes the individual atomic bonds on the target surface to be broken. In turn, the exothermic reaction results in a tremendous heat buildup on the target surface which must be dissipated. Typically, this is accomplished through direct water cooling of the backing plate configured within the cathode assembly. By metallically bonding the target directly to the backing plate, a direct link is provided to dissipate the heat from the target surface to the water cooling.