Cryo-Implantation Technology for Controlling Defects and impurity out diffusion
- PDF / 2,735,242 Bytes
- 6 Pages / 595 x 842 pts (A4) Page_size
- 56 Downloads / 269 Views
Cryo-Implantation Technology for Controlling Defects and impurity out diffusion. Atsushi Murakoshi, Kyoichi Suguro, Masao Iwase, Mitsuhiro Tomita, and Katsuya Okumura Process & Manufacturing Eng. Center, Semiconductor Company, TOSHIBA Corporation 8, Shinsugita-cho, Isogo-ku, Yokohama 235-8522, Japan Phone: +81-45-770-3663, Fax: +81-45-770-3577 E-mail: [email protected] ABSTRACT We propose a novel process module by using cryo-implantation and rapid thermal annealing (RTA). Boron or arsenic ions were implanted into a 8 inch (100) Si substrate which was cooled by using liquid nitrogen. The substrate temperature was controlled to be below at -160°C during ion implantation. It was found that an amorphous layer was formed by boron or arsenic implantation and the amorphous layer was completely recovered to a single crystal after annealing at 900°C for 30sec. No dislocation was observed in the implanted layer. It was also found that the thermal diffusion of boron was suppressed by cryo-implantation. PN junction depth was found to be about 10-20% shallower than that of room temperature implantation. These results suggest that transient enhanced diffusion of boron can be reduced by suppressing vacancy migration toward the surface during implantation. Cryo-implantation was found to be very effective in reducing defects and PN junction leakage was successfully reduced by one order of magnitude as compared with room temperature implantation. INTRODUCTION Shallow junction technology is becoming increasingly important for high performance transistors with 0.1-0.15 micron gate length. With shrinkage of junction depth, acceleration energy of ion implantation decreases and annealing temperature should be lowered in order to avoid impurity diffusion. On the other hand, it becomes difficult to recover the defects caused by heavy dose ion implantation near shallow trench isolation where the thermal stress is relatively large due to the thermal expansion coefficient difference between Si and SiO2. Therefore, the annihilation of defects by annealing with small thermal budget is a key issue foe 0.1-0.15 micron regime. There are several reports[1-3]. concerned with low temperature ion implantation of B, BF2 and P. However, these papers describe that the residual defect density after furnace annealing for Si substrates implanted at low temperature is lower than that for Si substrates implanted at room temperature. However, complete annihilation of defects was not reported so far. In this paper, we propose a novel process module by using cryo-implantation and rapid thermal annealing. It was found out that the crystal damage due to ion implantation could be completely recovered by using this technology. EXPERIMENTAL Boron or arsenic ions were implanted into (100)Si substrates where the substrate temperature was controlled to be –160°C. Typical acceleration energy of boron and arsenic were 10keV and 20keV, respectively. The implanted dose was in the range from 1e13 to 1e15cm-2. The ion beam current was in the range from 10 to 20 micro
Data Loading...
