Determination of nitrogen in silicon carbide by secondary ion mass spectrometry

The importance of silicon carbide (SiC) as a semiconductor material continues to increase. Nitrogen is the most popular donor impurity in this material. The determination of nitrogen by the secondary ion mass spectrometry (SIMS) method is a difficult task because direct monitoring of N± ions suffers from a small ion yield. We investigated the complex nitrogen-matrix ion emission of CnN± and SinN± (n=1,2,3) type to obtain the low detection limit of nitrogen. The oxygen primary beam was used to determine the positive ion yield and cesium primary beam for the negative ions. The maximum ion yield of CN− ions under Cs primary beam was demonstrated. A nitrogen detection limit equal to (1±1)E+16 cm−3 was obtained by high mass resolution (∼7200) to separate 26(12C14N)− from 13C2− analytical signals.