Arsenic-Only Preamorphization Process Extension For TiSi2 Formation Down to 65-nm Gate Lengths

Abstract

AbstractThe scalabilty of the titanium self-aligned silicide (Salicide) process is one of the main issues for sub-quarter micron technologies. The major difficulty is to achieve a low sheet resistance for very narrow polysilicon lines and highly doped S/D regions, without degrading the transistor performance. A preamorphization implant (PAl) performed before the titanium deposition, can achieve a low Ti silicide sheet resistance (<10 Ohms/sq) down to 0.1 Vim gate lengths [1]. Nevertheless, it has been recently reported that PAI should not be sufficient to achieve low silicide sheet resistance for narrower gate widths (< 0.1 µm) [2]. In this work, an extension of the PAI process down to 0.065µm poly-Si lines width, by only using an arsenic implant is presented, achieving a very low sheet resistance value (∼5 Ohms/sq). This result has been obtained by optimizing both the arsenic implant conditions and the silicon surface cleaning. Moreover, a large statistical analysis of the arsenic PAI process impact on 0.25µm device performances has been done, showing that a defectivity of the NMOS Ioff leakage current can appear if preamorphization implant conditions are not optimized.