Buried layer ion implanted resistors

Meg-Ohm silicon monolithic resistors have been fabricated with sheet resistance up to 120k Ω/□ using an implanted p-layer resistor which is buried under an implanted n-guard layer. The n-guard layer protects against slice to slice variations of the fixed surface charge and was made using phosphorus doses and energy of 1.5-5 × 10¹²P/cm²and 30 keV. Resistors have been fabricated up to 20 MΩ(and sheet resistances in the range of 7-120k Ω) using boron doses and energies of 1-3 × 10¹²B/cm²and 30-300 keV. The sheet resistance, voltage dependence of resistance, temperature coefficients, junction leakage and parasitic capacitance have been measured for different cases.