Research On Microstructure And Texture Of Ultra High Purity Copper And Cu-Mn Alloy Used In IC Interconnection

With the development of integrated circuit following Moore’s law, the chip size trend to be submicron and nanometer and the metal width is more and more thin. While traditional interconnect material, aluminum and aluminum alloy, can’t meet the development of integrated circuit technology, copper has been the main interconnect material replacing aluminum used in IC manufacturing because of the lower electrical resistivity and higher electromigration resistance, which can reduce the interconnect resistance and wiring layer, improving the speed of integrated circuit logic. In integrated circuit 90-45 nm technology node, the ultra high purity copper is the key interconnect seed layer material, but when the line width narrowed, by using the method of copper alloying can solve the problem of copper diffusion. While added element Mn in copper can effectively prevent the oxidation of the interconnect, Cu-Mn interconnect technology method can form self-diffusion barrier layer, It is important for the surface properties and microstructure of subsequent deposition of thin film growth structure and grain size,orientation and so on. Today’s 45 nm technology node technology mainly using Cu-Mn interconnect technology, Ultra high purity copper and Cu-Mn alloy is key source material of sputtering film seed layer material, its organizational performance directly affect the final performance of a chip manufacturing technology and product.Research conclusion is as follows:(1)The microstructure of ultra-high purity copper and Cu-Mn alloy is very thick,grain size can reach millimeter level. After cold plastic deformation, the obvious rolling deformation zones are formed, containing a lot of fibrous tissue in the layer, and with the increase of the total deformation, layer spacing width getting smaller and smaller.(2)Recrystallization process of ultra-high purity copper start at 150℃ with increasing temperature, recrystallization grain growing. When the annealing temperature to200℃, recrystallization process has been almost completely finished, the size of the grain close to 22μm. When the annealing temperature to 400℃,abnormal grains appear in some position. While Cu-Mn alloy recrystallization temperature starting at higher temperature,under the condition of 390 ℃ annealing recrystallization process begins. When annealing temperature in 450℃ to 540℃, recrystallization process completely finished with isometric grain, the grain size at about 10μm. Continue to anneal until 690℃,the grains are still growing, grain size reached more than 30μm, the abnormal grain growth is not in the case.(3)In the condition of deformation, texture intensity of ultra high purity copper is higher, maximum density can reach above 14, there are(110) [111],(110) [112] and cubic texture(100) [100] etc in the microstructure. Ultra high purity copper under the condition of the complete recrystallization, the strength of the texture declined significantly, a density decreased to about 4, more cold rolled textures and recrystallization textures are formed.When annealing temperature to 400℃, abnormal phenomenon happens, the texture density reaches more than 34, forming many atypical face-centered cubic metal texture.(4)Cu-Mn alloy after plastic deformation formed brass texture, copper texture, S texture and goss texture; After complete recrystallization, rolling texture down to 7%,recrystallization texture to rise to about 20%. Annealing to 600℃, the overall texture slightly rise, random orientation was down.(5) Ultra high purity copper after cold rolling and annealing process optimization,annealing temperature between 200℃ to 250℃, can achieve the ideal of ultra high purity copper. Cu-Mn alloy after cold rolling and annealing process optimization, annealing temperature between 450℃ to 480℃, Cu-Mn alloy can be obtained the ideal organization.(6)Through the same process of ultra high purity copper and Cu-Mn alloy,experimental results shows that, there is no dynamic recrystallization in rolling process of Cu-Mn alloy, microstructure is uniform. Microstructure is easy to control in annealing process, high stability, not easy to an exception occurs mutations. These advantages can better meet the integrated electricity line width narrower demanding performance requirements, is of great significance for the development of the copper interconnect technology.