Ultimate Scaling of CMOS Logic Devices with Ge and III-V Materials

Over the years, many new materials have been introduced in advanced complementary metal oxide semiconductor (CMOS) processes in order to continue the trend of reducing the gate length and increasing the performance of CMOS devices. This is clearly evidenced in the International Technology Roadmap for Semiconductors (ITRS), which indicates the requirements and technological challenges in the microelectronics industry in various technology nodes. Every new technology node, characterized by the minimal device dimensions that are used, has required innovations in new materials and transistor design. The introduction of deposited high-kappa gate dielectrics and metal gates as replacements for the thermally grown SiO2 and poly-Si electrode was a major challenge that has been met in the transition toward the 32 nm technology node since it replaced the heart of the metal oxide semiconductor structure. For the next generation of technology nodes, even bigger hurdles will need to be overcome, since new device structures and high-mobility channel materials such as Ge and III-V compounds might be needed, according to the ITRS roadmap, to meet the power and performance specifications of the 16 nm CMOS node and beyond. The basic properties of these high-mobility channel materials and their impact on the device performance have to be fully understood to allow process integration and full-scale manufacturing. In addition to thermal stability, compatibility with other materials, electronic transport properties, and especially the passivation of electronically active defects at the interface with a high-kappa dielectric, are enormous challenges. Many encouraging results have been obtained, but the stringent demands in terms of electrical performance and oxide thickness scaling needed for highly scaled CMOS devices are not yet fully met. Other areas where breakthroughs will be needed are the formation of low-resistivity contacts, especially on III-V materials, and III-V materials suited for pMOS channels. An overview of the major successes and remaining critical issues in the materials research on high-mobility channel materials for advanced CMOS devices is given in this issue of MRS Bulletin.