DAILY 2X10(12) MONITORING OF AN ION IMPLANTER

Low-dose monitoring has always been a problem. The monitors drift with time either within minutes of an implant or within days or months. Resistivity excursions in excess of 50% are not uncommon. This paper presents data to understand some of the factors affecting the reliability and repeatability of low-dose, 2 x 10(12) ions cm-2, sheet resistivity measurements. Four-point probe electronic drift, the optimum probe tip size and finish, background silicon substrate doping, surface oxide growth, and silicon surface chemistry are investigated. The correct specifications of the wafers, wafer processing and the four-point probe tips enable reproducible measurement of low-dose boron implants.