Crack formation commonly occurs in ceramic sputtering targets like oxides, carbides, nitride etc and in brittle material sputtering targets like chromium, antimony, bismuth etc. In this article we will briefly discuss, why sputtering targets cracks and what precautions can be taken to avoid this?
Ceramic or brittle material targets always contain intrinsic stresses. These internal stresses are developed during the manufacturing of the target. Also, these stresses are not completely removed through annealing process as it is an inherent property of these materials. During the sputtering process, bombarding gas ions transfers their momentum to the target atoms providing them enough energy to break from their lattice. This exothermic momentum transfers increases the temperature of the target which could reach 1,000,000 degrees C at the atomic level. These thermal shocks increases the already present internal stresses in target to many folds. Under such circumstances target can break if proper heat dissipation is not taken care of.
In order to prevent target from breaking the important consideration is heat dissipation. Water cooling mechanism is required to remove unwanted thermal energy from the target. Another point that is to be considered is ramping Power. Applying too much power in very short duration of time can also give thermal shock to the target. Also it is always advised these targets should be bonded to the backing plate which not only provide support to the target but also promotes better heat exchange between target and water. If the target is cracked but is bonded to backing plate, it can still be used without problem.
We supply, sputtering targets bonded with backing plate. User must mention in their requirement about backing plate material, thickness and type of bonding required.