Sputtering target assembly having a graded interlayer and methods of making

A method of forming a sputtering target assembly, the method comprising:

• forming a first layer on a surface of a sputtering target or a surface of a backing target from a first mixture containing a first material and a second material;
• forming a second layer on the first layer from a second mixture containing the first material and the second material, wherein the first layer has a higher concentration of the first material than the second layer, and the second layer has a higher concentration of the second material than the first layer;
• arranging the backing plate or the sputtering target on the second layer to form the sputtering target assembly having the first layer and second layer between the sputtering target and backing plate;
• and
• joining the sputtering target, the first layer, the second layer, and the backing plate together in a target assembly bonding step.