Boron,phosphorus,carbon and oxygen are the most common impurities,and in most cases are very critical,of interest in photovoltaic Si feedstock and wafers.Bulk carbon is important because it can form carbon-related defects,such as SiC inclusions.Bulk oxygen is important in boron-doped silicon because a BOx defect can degrade cell efficiency in p-type cells.Boron and phosphorus are common dopants in solar Si wafers that need to be controlled.Secondary Ion Mass Spectrometry (SIMS) can provide direct measurements of total B,P,C and O concentrations in solar wafers and feedstock with excellent detect sensitivities,accuracy and precision [1,2].To achieve the best results,three different analysis conditions are needed for these measurements.However a new SIMS measurement method has been developed under SEMI Standards that measures these four elements under a single measurement condition using only a Cs primary ion beam.This new method offers a quicker and much more economical way to determine bulk B,P,C and O concentrations in solar wafer and feedstock.Detection sensitivities offered in this new test method are sufficient for most solar wafers and feedstock.A preliminary round robin test was completed on three mc-Si solar wafers as shown in Table 1.Results show very good analysis precision.This test method has been approved as a SEMI international standard test method (SEMI PV25 www.semi.org).Thus the SIMS protocol is available to all parties through SEMI.