An accurate and computationally-efficient model for boron implants through an overlying oxide layer into single-crystal (100) silicon




Lim, Hsuan-Yu, 1967-

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In many of the current implant applications in integrated circuits, a thin overlying amorphous oxide layer is often used to reduce the depth of dopant profiles by reducing the amount of channeling. The oxide layer is believed to randomly scatter a well-collimated (≤ 0.5° divergence) ion beam into a cone-shape angular distribution prior to its entry into the underlying single-crystal silicon. In this manner, most of the ions are scattered away from major axial and planar channels. A computationally-efficient 1-D model for boron implantation into single-crystal silicon through a screen oxide layer was developed. This model is of great interest and importance to the semiconductor industry for understanding process control issues in manufacturing and for guiding technology development. In developing this model, approximately 400 SIMS experimental profiles were obtained. In addition, the UT-MARLOWE Monte Carlo ion implant code was improved to generate boron profiles for part of the implant parameter space. It has been observed that boron implanted profiles are significantly dependent on the implant dose, energy, oxide layer thickness, tilt angle and rotation angle. A curve-fitting software program that uses the Dual Pearson Distribution function was used to extract the nine parameter values which define each profile. The parameters extracted for each profile are arranged into a lookup table where each set of nine parameter values corresponds to the profile for a particular combination of implant dose, energy, tilt angle, rotation angle and oxide thickness. Linear interpolation functions are employed to generate profiles for which there are no explicit set of parameters. This computationally-efficient model is able to generate as-implanted profiles of boron implantation through thin overlying oxides ranging from bare silicon (with a native oxide of approximately I.6nm) to 40nm, implant energies ranging from 15keV to 80keV, doses up to 1x10¹⁶cm⁻², tilt angles ranging from 0°-10°, and rotation angles ranging from 0°-360°. This model is being implemented into SUPREM III, a widely used process simulation program used in the semiconductor industry in order to demonstrate the model. In this manner, the model will allow users to generate, in a highly computationally-efficient manner, accurate 1-D boron profiles as a function of implant dose, energy, oxide thickness, tilt angle and rotation angle