Nuclear Instruments and Methods in Physics Research Section B: Beam Interactions with Materials and Atoms
Section V. New implantation equipment and system techniquesRound-robin “ion-implanter and 4-point probes”
Abstract
A round-robin of the “ German Implant User Group” was carried out in order to compare the performance and absolute setting of ion implanters and 4-point probes. For the round-robin of the 4-point probes 52 test wafers with a very low standard deviation were processed (). The wafers were measured at Siemens before shipment to the participants, and remeasured afterwards. The values derived by the 20 tested probers were all within ± 3% Rs. The 12 Prometrix probers in this comparison showed a good reproducibility of nearly ± 1% Rs. The ion implanter round-robin was arsenic, 80 keV, dose 3 × 1015 and phosphorus, 130 keV, dose 5 × 1013, 70 nm oxide. The tests were carried out on commercially available medium current and high current implanters. Wafer sizes varied from 3 in. to 150 mm. The wafers were annealed at the FHG Eriangen and tested at Siemens. For the arsenic test all implanters were within ± 5% Rs, for the phosphorus test within ±6%.
References (3)
- Michael I. Current
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Ion implant standard
1991, Nuclear Inst. and Methods in Physics Research, BThe Greater Silicon Valley Implant Users Group (GSVIUG) has been working with the American Society for Testing Materials (ASTM) and the National Institute of Standards and Technology (NIST, previously known as NBS) to develop a standard for ion implantation. This standard would address two critical needs of the industry: (1) standard reference material (SRM) for certifying and calibrating equipment, and (2) a recommended standard procedure for fabricating such a standard.
The SRM would be a wafer that had been implanted with a specified species, energy and dose. Its average sheet resistance and uniformity would be certified to be within certain tolerances. It would be used to verify the performance of the four-point probe and sheet resistance mapping equipment and to calibrate analytical characterization techniques such as secondary ion mass spectroscopy (SIMS), Rutherford backscattering spectroscopy (RBS) and spreading resistance profiling (SRP). An unannealed sample could be used to calibrate Thermawave, ellipsometer and other optical tools and to verify annealing systems. The standard procedure would prescribe the recommended steps to produce the same wafer in the fab. This would help determine if an implanter is operating correctly at the specified conditions.
We have reviewed all the previous implant round robins and studies and solicited input from implant vendors and implant service organizations in recommending a set of implant conditions for a proposed standard. Particular attention was paid to the requirement of stability over time and minimum variation with ambient temperature. Fabrication specifications for species, energy and dose are detailed. Plots are also presented for the sensitivity to various parameters that could influence the results, such as substrate resistivity, screen oxide thickness, anneal time and temperature and measurement conditions.
Techniques for dose matching between ion implanters
1991, Nuclear Inst. and Methods in Physics Research, BDose matching between systems installed in a device manufacturer's fab is a critical issue in ion implantation, especially when the process is to be transferred from one system to another. Ion implantation systems, like other types of semiconductor capital equipment, are constantly evolving to keep pace with the ever-increasing demands of device manufacturers. Some hardware changes may be retrofitted to existing equipment, while major changes often result in a new system design. As a result older, retrofitted systems as well as the latest generation equipment may be found operating side by side in the wafer fab. While dose uniformity and repeatability for a given implanter have always been specified, dose matching between implanters, allowing the transfer of process from one system to another, is addressed in this paper. Dose matching characteristics for several Varian implanters will be presented and techniques for matching dose between systems will be discussed. In addition, the key hardware and process issues that may cause mismatching in dose will be addressed.