Implantation/diffusion process matching characterization via secondary ion mass spectrometry (SIMS)

Secondary Ion Mass Spectrometry (SIMS) has been used extensively to characterize dopant distribution in the semiconductor industry. In this work, we will demonstrate the applicability of SIMS for ion implantation dose measurement, implant energy and angle calibration, diffusion dopant profile control using the examples encountered throughout the course of an implant/diffusion process matching between two fabs. Based on the quantitative SIMS results and other electrical measurements, six different implants were adjusted to match the target process from as far as 20% underdose to at least within 5% relative to the target dose, in a reduced cycle time. SIMS was able to provide accurate and reproducible dose measurements for various implants, i.e., arsenic 2e12 atoms/cm², phosphorus 5e15 atoms/cm² and boron 1e13 atoms/cm². The SIMS experimental conditions and procedures for a low dose arsenic implant will be discussed. During the course of this matching exercise, several processing parameters which affected dopant distribution have been identified in order to match the target process. (i) In the comparison of post-annealed dopant profiles, the vertical diffusion furnace tends to drive dopants deeper than the horizontal furnace at similar temperature by the order of 0.1 micron. (ii) SIMS profiles revealed the dose difference of the high dose implants between the two different implanter systems. (iii) In addition, SIMS showed that high energy boron implant has a different channeling effect due to the difference of wafer rotation angle employed between the two fabs