Golden Parameter Ratio Application in W Via Fill and InterconnectMetal Recipe Development

摘要

In our previous paper, the Golden Parameter Ratio (GPR) application in the blanket Tungsten Etch Back (WEB) process development was discussed. In this paper, we discuss the GPR application in the development of a new W deposition recipe that can be used for high aspect ratio plug fill as well as interconnect metal layers. For this purpose the W film must not only have suitable stress, sheet resistance and reflectivity, but also very good step coverage. It was found that the via fill to interconnect ratio play a key role in the recipe development. If ratio is too high, the film step coverage is good, however, the film stress will high and this will cause the wafer bowing and can't be aligned in the following photo step. If the ratio is too low, the film step coverage and conformality will bad. This will cause via fill voids issue. It was suggest to use 1.0 of the ratio value to give the best result. In this paper, we report that 1.0 ratio value film will sometime give high via resistance variation, the solution to this is to use GPR 0.618. After the implementation of GPR recipe, the variation of the via resistance had been greatly tightened. The mechanism that GPR recipe can tight the via resistance is also discussed.