To take full advantage of the high beam current capability of the Optima XEx on photoresist implants, a new, real-time uniformity correction scheme, IntelliScan, was developed. IntelliScan compensates for the dose asymmetry in beam-scan direction developed by charge exchange reactions due to severe photoresist outgassing. It continuously modifies the 1 KHz beam-scan waveform in real-time, according to instantaneous vacuum level in the angle corrector area. Since IntelliScan does not involve any extra steps in wafer handling, such as alternating 180° twist on every pass, high wafer throughput and implant angle integrity can be maintained throughout the entire implant process. This paper will describe the IntelliScan system and its performance on photoresist implants under extreme beam power conditions.

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Angle control on high energy implanters is important due to shrinking device dimensions, and sensitivity to channeling at high beam energies. On Optima XE, beam-to-wafer angles are controlled in both the horizontal and vertical directions. In the horizontal direction, the beam angle is measured through a series of narrow slits, and any angle adjustment is made by steering the beam with the corrector magnet. In the vertical direction, the beam angle is measured through a high aspect ratio mask, and any angle adjustment is made by slightly tilting the wafer platen during implant.Using a sensitive channeling condition, we were able to quantify the angle repeatability of Optima XE. By quantifying the sheet resistance sensitivity to both horizontal and vertical angle variation, the total angle variation was calculated as 0.04° (1σ). Implants were run over a five week period, with all of the wafers selected from a single boule, in order to control for any crystal cut variation.

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Photoresist outgassing can significantly compromise accurate dosimetry of high energy implants. High energy implant even at a modest beam current produces high beam powers which create significantly worse outgassing than low and medium energy implants and the outgassing continues throughout the implant due to the low dose in typical high energy implant recipes. In the previous generation of high energy implanters, dose correction by monitoring of process chamber pressure during photoresist outgassing has been used. However, as applications diversify and requirements change, the need arises for a more versatile photoresist correction system to match the versatility of a single wafer high energy ion implanter. We have successfully developed a new dosimetry system for the Optima XE single wafer high energy ion implanter which does not require any form of compensation due to the implant conditions. This paper describes the principles and performance of this new dose system.