Nuclear Instruments and Methods in Physics Research B55 (1991) 821-825 North-Holland 821 zyxwvut Sub-100 nm p +/n junction formation using plasma immersion ion implantation X.Y. Qian, N.W. Cheung and M.A. Lieberman Plasma Assisted Materials Processing Laboratory, Department of Electrical Engineering and Computer Sciences, University of California, Berkeley, CA 94720, USA M.I. Current Applied Materials, Inc., Implant Division: MSO907, 3050 Bowers Avenue, Santa Clara, CA 95054, USA P.K. Chu Charles Evans and Associates, 301 Chesapeake Drive, Redwood City, CA 94063, USA W.L. Harrington, C.W. Magee and E.M. Botnick Evans East, Inc., The Office Center, 666 Plainsboro Road, Suite 1236, Plainsboro, NJ 08536, USA Using plasma immersion ion implantation (PIII), sub-100 nm p +/n junctions were fabricated with SiF, preamorphization followed by BF, doping. With this technique, the dose rate can be as high as 10’6/cm2 per second. The silicon wafer was immersed in SiF, or BF, plasma and biased with a negative voltage. The positively charged ions were accelerated by the electric field in the plasma sheath and implanted into the wafer. The junction depth can be controlled by varying the negative voltage applied to the wafer holder and thermal annealing conditions. zyxwvutsrqponmlkjihgfedcbaZYXWVUTSRQPONMLKJIHGFEDCBA 1. Introduction Extremely shallow zyxwvutsrqponmlkjihgfedcbaZYXWVUTSRQPONMLKJIHGFEDCBA (less than 100 nm) p + / n junc- tion formation is a key issue in the development of submicron CMOS technology. With conventional ion implanters, molecular ion BF$ has been used as the implant species to lower the boron effective kinetic energy [l]. In order to reduce the channeling effect and to activate dopants without excessive diffusion, an im- plantation step to preamorphize the silicon substrate prior to BF*+ implantation is also required [2]. Since relatively large doses are needed for both preamorphiza- tion and doping, the overall implantation process can be time consuming. A large dose rate ion implantation technique, plasma immersion ion implantation (PIII), has been used to implant nitrogen and other ion species into the surface of machine parts to improve wear or corrosion resis- tance [3-41. Recently, a prototype plasma PI11 appara- tus dedicated to integrated circuit processing has been developed, and was successfully applied to implant no- ble gas ions into Si for metallic impurity gettering [5,6]. In this paper, we show that PI11 can be used for sub-100 nm p + / n junction fabrication. Both SiF, preamorphi- zation and BF, doping were carried out in sequential steps by switching the plasma gases. 2. Experiment Shown in fig. 1 is a schematic of the p + / n junction fabrication process using the PI11 technique. The silicon wafer was immersed in a SiF, plasma for preamorphiza- tion, then in a BF, plasma for doping. The wafer was biased with a dc or pulsed negative voltage. A plasma sheath around the wafer was generated by the applied ‘-:y,l - Fig. 1. Schematic of p+/n junction fabrication process using plasma immersion ion implantation. 0168-583X/91/$03.50 0 1991 - Elsevier Science Publishers B.V. (North-Holland) VII. TRENDS & APPLICATIONS