MOSFET structures yield depth-resolved p-stop doping profiles in p-type silicon sensors

The work fabricates dedicated MOSFET test structures on p-type wafers with varying p-stop geometries and measures threshold voltage shifts as the back-gate voltage sweeps the depletion region past the implant. This isolates the contribution of the p-stop from bulk doping, enabling reconstruction of a one-dimensional doping profile that standard capacitance-voltage profiling cannot resolve at the inter-electrode scale. The method also extracts field-dependent mobility parameters directly relevant to charge-collection modeling in pixel and strip detectors.

Existing p-stop qualification relies on destructive SIMS or spreading-resistance measurements performed on monitor wafers. The MOSFET approach is non-destructive and can be placed in the scribe lines of production sensors, allowing wafer-level statistical monitoring of implant activation and lateral diffusion. Sensitivity analysis in the preprint shows that a factor-of-two change in peak p-stop concentration produces a measurable 150 mV shift in threshold, sufficient for process control.

Because the study remains at the test-structure level, correlation with actual sensor leakage current and breakdown voltage on the same wafers is still required. Full validation on irradiated devices will be needed before the technique can replace existing QA protocols in HL-LHC sensor production.