Metal Flake Defect and Its Formation Mechanism during Replacement Metal Gate CMP Process

摘要

Replacement metal gate (RMG) has been introduced in semiconductor fabrication since 45 nm gate scaling era. RMG process has advantages in prevention of damage by gate etch and thermal process, and it gives work function material stability. Moreover, improvement of device performance is expected as well. Therefore it has been employed as industry standard process for advanced node transistor fabrication. However, the complexity of RMG process flow emphasizes the importance of metal gate chemical mechanical polishing (CMP) which plays a key role in the success of RMG formation. Three complementary CMP steps (gate poly-Si CMP, poly-Si open CMP, metal gate CMP) are involved in RMG formation and comprehensive understanding of interplay among these CMP steps is the key to achieve uniform gate height across the wafer. In addition to extremely tight control of final gate height, post metal gate CMP defects are one of the most critical parameters affecting device performance as well as yield. Among various kinds of defects, metal flakes are most serious defect which fails transistor function by providing gate leakage channel. This paper approaches both integrational and CMP process aspect to reveal the mechanism of metal flake formation. (C) 2016 The Electrochemical Society. All rights reserved.