AVS 49th International Symposium
    Applied Surface Science Tuesday Sessions
       Session AS-TuP

Paper AS-TuP1
Observation of Preferably Electrical Activation of Boron Implanted at Low Energy by Scanning Capacitance Microscopy

Tuesday, November 5, 2002, 5:30 pm, Room Exhibit Hall B2

Session: Topics in Applied Surface Science
Presenter: M.-N. Chang, National Nano Device Laboratories, Taiwan R.O.C.
Authors: M.-N. Chang, National Nano Device Laboratories, Taiwan R.O.C.
D.-H. Deng, National Tsing Hua University, Taiwan R.O.C.
C.-Y. Chen, National Nano Device Laboratories, Taiwan R.O.C.
J.-H. Liang, National Tsing Hua University, Taiwan R.O.C.
F.M. Pan, National Nano Device Laboratories, Taiwan R.O.C.
Correspondent: Click to Email
Ultrashallow doping is one of the technical trends on ultra large-scale integrated circuit. Low energy ion implantation combined with rapid thermal annealing (RTA) is necessary to obtain required ultrashallow doping profiles. It is well known that scanning capacitance microscopy (SCM) is a promising technique providing two-dimensional (2D) doping profiles. In this work, we have provided a new method employing plane view SCM images to investigate the lateral carrier distribution in ultrashallow p@super +@ junctions formed by BF@sub 2@@super +@ implantation at low energies. RTA processes were performed at 550, 850 and 1050 °C for different anneal times from 5 to 120 seconds in N@sub 2@ ambient. The width and pitch of the designed grating pattern are 0.8 and 2 @micron@, respectively. The SCM image clearly shows the existence of a transition region at each pattern edge of which the width reveals the carrier concentration gradient of the lateral p-n junction. For the same anneal time, the sample annealed at 850 °C exhibits a wider transition region than the one at 1050 °C, indicating that more electrically active boron atoms can be obtained at higher anneal temperatures. The SCM signal intensity, i.e., dC/dV, is a function of the free carrier concentration of the implanted region. Comparing the dC/dV profiles across the implantation pattern for the samples treated under different RTA conditions, one can find that less implanted boron atoms at the pattern edge are electrically activated than at the center region. According to this study, the edge effect will significantly affect the lateral carrier concentration distribution upon RTA processes when the pattern size decreases.