Depth Profiles of Medium Energy Phosphorus Implants into Silicon
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ENERGY PHOSPHORUS IMPLANTS INTO SILICON
J. P. LAVINE*, L. ZHENG*, P. M. WHALEN*, AND D. F. DOWNEY** *Microelectronics Technology Division, Eastman Kodak Company, Rochester, NY 14650-2008 **Varian Ion Implant Systems, Gloucester, MA 01930-2297
ABSTRACT Secondary ion mass spectrometry (SIMS) is used to produce depth profiles of ion-implanted phosphorus in silicon. The implant energies are 250, 500, and 750 keV, and there is a 0.06-tm thick oxide on the silicon. The experimental profiles are compared with predictions from a variety of simulation programs, most of which give larger projected ranges than the data. The silicon crystal structure needs to be included in the calculations to produce projected ranges and depth profiles that agree with the present experimental data and with data from the literature. INTRODUCTION The implant energies used in silicon device processing are increasing to take advantage of simplified process flows [1] and to introduce gettering sites [2,3]. Useful ion implant parameters are available for 1 MeV and higher [4], but there is only one detailed set of experimental profiles that spans the implant energy range of 100 keV to 1 MeV for phosphorus implants into silicon [5]. Additional depth profiles appear in Refs. [6-8] for energies of 1 MeV and below. The works cited treat implants into bare silicon, although most implants are done through a thin layer of silicon dioxide. Depth profiles are presented here for oxidecoated silicon wafers implanted with phosphorus. Calculations are included to determine how accurately simulation programs fit the measured data. Channeling is found to play an important role and a Monte Carlo program that incorporates crystal structure is used to explore the effects of the oxide thickness and the implant angles. Treatments of channeling are reviewed by Simonton and Tasch [9], and examples for medium and high-energy phosphorus implants appear in Ref. [8]. The next section provides the experimental details, and the third section presents the measured data. The concluding section is a discussion of the calculations and a comparison with the data. 51
Mat. Res. Soc. Symp. Proc. Vol. 396 c"1996 Materials Research Society
EXPERIMENTAL DETAILS The silicon substrates used have -orientation and 0.06 [m of silicon dioxide. The phosphorus implants were performed on a Varian ESO0 or an Eaton 8200P implanter at energies of 250, 500, or 750 keV. The tilt angle was 70 and the rotation or twist angle from the (110) wafer flat was 00, so planar channeling is expected [10]. The dose in every case was 1.5 x 1013 /cm 2 . The oxide was then removed and pieces of the wafer were submitted for secondary ion mass spectrometry (SIMS). At least three profiles were obtained for each implanter at each energy. All the profiles at each energy are equivalent, so one profile at each energy is used here. The SIMS profiles have not been corrected for background effects.
The simulation programs used are PROFILE [11], TRIM (95) [12], and TSUPREM-3 [13]. The latter also has a Monte Carlo option
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