Improving Performance and Reliability of MOS Devices Using Deuterium Implantation

Abstract

Our advancing information network society is based on various kinds of digital communication systems in which versatile silicon integrated circuits (ICs) are indispensable key components. For the next-generation networking systems, there is need for higher packing density, higher quality and higher speed of ICs. Much effort is needed to improve the quality of thin silicon dioxide (SiO2) used in submicron metal-oxide-semiconductor (MOS) field-effect transistors (FETs) in ICs. Since MOSFETs with thermal SiO2 were developed in 1960, SiO2 has been widely used as a gate insulator in MOSFETs and has played an important role in rapidly advancing IC development. The quality of the gate insulator or gate oxide is closely related to the control of driving current, which is one of the most important factors for the MOS device. From this point of view, the practical minimum value of gate oxide thickness is below 2 nm at present, and at the same time, defect-free oxide must be prepared for both gate oxide and inter-gate oxide. Many kinds of contaminations from various processes and electrical-stressed-induceddamage on SiO2 and the Si-SiO2 interface must be extensively examined and removed. Progressive silicon complementary MOS (CMOS) IC technologies are also based on reductions in the channel lengths of MOSFETs as well as on reductions in the gate oxide thickness. The reduction in the channel lengths leads to an increase in hot electron generation (for n-channel MOSFETs) owing to an increase in the electric field applied to the channel. The reduction in the gate-oxide film thickness results in an increase in the electric field applied to the thin gate-oxide films. Hot electron generation in short channel MOSFETs is followed by electron trapping in gate oxides on the silicon substrates. The electron trapping in gate oxides is the principal cause of instability for short channel MOSFETs, and electron traps in as-grown oxides need to be studied extensively. At any rate, improvement in the quality and reliability of thin SiO2 is one of the most important concerns for nextgeneration MOS IC development. The central theme of this work is to characterize the electrical reliability of MOS devices related to the nature of thin SiO2 film. This monograph deals with hydrogen or deuterium process employed in fabrication to improve MOS device’s reliability. The process of postmetallization anneal of the wafers at a low temperatures in hydrogen ambient is critical to CMOS fabrication technology to improve MOS device function by passivating the otherwise 2