A detailed parametric study was carried out over the course of approximately one year to determine the measurement sensitivity and repeatability of an in-line surface photo-charge metrology system for major implant parameters used in an established, high volume, 0.35 /spl mu/m CMOS process. The critical p-channel transistor implant processes; Threshold Voltage Adjust and Halo were used to characterize the metrology system. Dose variations as small as 1.5% have been measured with statistical accuracy, enabling improvements in process control to be quantified in real time. Long-term system repeatability of less than 1% (1/spl sigma/) for a wide variety of implants has allowed the sensitive visibility of process drift or spike excursions to be highlighted in real-time.
