How to monitor a sub-keV USJ implant

Next generation processes for USJ formation will use sub-keV implant conditions, e.g. ¹¹B⁺ 500 eV 1·10 ¹⁵ cm^-2. To achieve the shallowest junctions after annealing, flash anneals with very fast ramp up and ramp down rates and controlled gaseous ambient have to be applied. To guarantee repeatable process results for sub-keV implants, several parameters of the implanter and the RTP tool have to be controlled, e.g. the dose and energy of the implanter, the gas ambient and thermal budget repeatability of the RTP and the uniformity of both tools. For non-uniformity monitoring of a rapid thermal processing system (RTP) the implant conditions ¹¹B⁺ 25 keV 3·10¹⁵ cm^-2 are ⁷⁵As⁺ 25 keV 1·10¹⁶ cm^-2 are very valuable if the implants are performed with similar beam optics and the same scanning system. Since these conditions show small sheet resistance variations for small dose and energy variation, but are sensitive to RTA parameters such as temperature and ambient. These wafers, thus minimize the implanter variables while calibrating the RTP. Once the RTP system was calibrated, the implanter was calibrated and monitored by annealing ¹¹B⁺ implanted wafers with 3 different energies of 500 eV±100 eV and three doses of 5.4·10¹⁴ cm ^-2 with a maximum dose variation of 30%. Dose versus R_s , dose versus junction depth and R_s versus O₂ concentration were analyzed to determine the implanter effect on the process reproducibility. Additionally, the Boin-Lerch Algorithm was applied to distinguish between the RTP and the implanter-induced uniformity