When im doing reactive DC-sputtering with an aluminum target, the texture after a while tends to be like fine like small 1mm grains on the surface. I guess this is due to the crystal structure in the sintered aluminum target. som times however very lerge structures appear on the alumium target surface. each "grain is about 3-6mm in diameter. They are unevenly distributed.
Could this surface defect aoccure due to to hig temperature on the sputter surface?
See attach picture. A is the normal target surface B is when the problematic structure.
The deposition seems to be affectad also by this texture.
Dear Curt Edström
This was probably a result of excessive stress built up that induced by over estimated volume expansion of target diffusion (implanted) zone.
Best regards
Mohammed Hussein j. H. Al'Atia Thanks for your reply. Do you think it is induced by overheating sputtertarget due to bad cooling? The reflection of the coated substrate is lower from this Al-target. The substate is cool 30deg C. However we dont know the temperature of the target.
Curt Edström
Yes I agree with you, the morphology of the thin coating film is drastically influenced by the substrate temperature, and so it is a key aspect for tailoring the process integrity. Think about the temperature of the metallic aluminum beneath the growing coating film, if the temperature increase to 660oC or higher, a thin pool of aluminum melt forms to destruct the growing coat by inducing enough stress resulted from local volume changes. This case produces such morphology you got.
Best regards
Mohammed Hussein j. H. Al'Atia
thanks. I guess the bonding to the backing plate has some issues. We will mount an isolated PT-100 sensor on the target to monitor the temperature. The strange is that the resulting aluminum coating gets very rough, decreasing the reflectance that is supposed to be over 90%. This usually happens when the coated substrate has a high temperature normally, but now it gets rough even when aluminum is deposited on a cold substrate.
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