On-Wafer Tunable Deposition Rates Using Ionized Physical Vapor Deposition

摘要

The selective deposition of vapor-phase metal ions is investigated using differential, on-wafer biasing of microstructures. In this work, metal ions are generated by sputtering titanium atoms into an inductively coupled argon plasma, producing 50-80% ionization of the titanium flux to the wafer. The plasma sheath region surrounding the microstructures is modified by applying a pulsed DC bias to some of the micro-structures such that plasma ions are attracted toward the most negative regions. Enhanced deposition is observed if the negative bias does not cause the impinging ion energy to exceed the sputtering threshold. Reduction of the deposition rate is observed on individual microstructures that are biased above the sputtering threshold due to resputtering of the titanium thin film by argon ions. A simple model is developed to confirm the mechanism of ion focusing, and the model also shows enhanced and then decreased net deposition rates as the ion energy increases.