The purity of the titanium target has a great influence on the performance of the sputter ...
The purity of the titanium target
has a great influence on the performance of the sputter coating. The higher the purity of the titanium target, the less impurity element particles in the sputtered titanium film, resulting in better PVD coating performance, including better corrosion resistance and electrical and optical properties. However, in practical applications, titanium targets for different purposes have different requirements for purity. The target material is used as the cathode source in sputtering, and the impurity elements and porosity inclusions in the material are the main pollution sources of the deposited film. Stomatal inclusions will be basically removed in the process of non-destructive testing of ingots. Unremoved stomatal inclusions will cause discharge during the sputtering process, thereby affecting the quality of the film; and the content of impurity elements can only be reflected in the test results of full element analysis. , the lower the total impurity content, the higher the purity of the titanium target.
2. Average grain size
Usually the titanium target has a polycrystalline structure, and the grain size can range from micrometers to millimeters. The sputtering rate of the fine-grained target is faster than that of the coarse-grained target. The thickness distribution of the shot-deposited film is also more uniform. The study found that if the grain size of the titanium target is controlled below 100 μm, and the variation of the grain size is kept within 20%, the quality of the sputtered film can be greatly improved.
3. Crystal orientation
Titanium has a close-packed hexagonal structure. Since the atoms of the titanium target are easily sputtered along the hexagonal close-packed direction of the atoms during sputtering, in order to achieve a higher sputtering rate, the crystal structure of the target can be changed by changing the method. to increase the sputtering rate. The crystallographic direction of the titanium target also has a great influence on the thickness uniformity of the sputtered film.
4. Structural uniformity
Structural uniformity is also one of the important indicators to examine the quality of the target. For titanium targets, not only the sputtering plane of the target, but also the normal direction composition, grain orientation and average grain size uniformity of the sputtering plane are required. Only in this way, the titanium target can obtain a titanium film with uniform thickness, reliable quality and consistent grain size at the same time during its service life.
5. Geometry and size
Mainly reflected in machining accuracy and machining quality, such as machining size, surface flatness, roughness, etc. If the angle deviation of the installation hole is too large, it cannot be installed correctly; if the thickness is too small, it will affect the service life of the target; if the sealing surface and the sealing groove are too rough, it will cause problems in the vacuum after the target is installed, which will seriously lead to water leakage; splashing of the target The surface roughening treatment can make the surface of the target covered with abundant raised tips. Under the action of tip effect, the potential of these raised tips will be greatly increased, thereby breaking down the dielectric discharge, but the excessively large The bumps are detrimental to the quality and stability of sputtering.