RTP for shallow junction formation-monitoring with repeatable, reliable sheet resistance measurements

RTP spike anneals are evaluated for various conditions of very low energy B implants. The effects of preamorphisation implant (PAI) and screen oxide on sheet resistance (Rs) are discussed. The implant profiles are analyzed using spreading resistance profiling (SRP), SIMS and 4-point probe measurements. By variation of the junction depth it is shown that the 4-point probes can affect the very shallow p-n junction leading to leakage current that results in erroneously low Rs values. A simple solution for a good process monitor is given. The solution prevents the above measurement artifact, and at the same time is least sensitive to factors other than RTP and implant.