Nitrogen investigation by SIMS in two wide band-gap semiconductors: Diamond and Silicon Carbide

TL;DR

This study demonstrates a method to detect and profile nitrogen impurities in diamond and silicon carbide using SIMS, overcoming previous detection challenges for atmospheric elements.

Contribution

The paper introduces a SIMS-based approach with high mass resolution to effectively measure nitrogen in wide band-gap semiconductors without major process modifications.

Findings

Nitrogen detection limit of 2×10^{17} at/cm³ in diamond

Nitrogen detection limit of 5×10^{15} at/cm³ in SiC

Successful nitrogen depth profiling over several micrometers

Abstract

Diamond and Silicon Carbide (SiC) are promising wide band-gap semiconductors for power electronics, SiC being more mature especially in term of large wafer size (that has reached 200 mm quite recently). Nitrogen impurities are often used in both materials for different purpose: increase the diamond growth rate or induce n-type conductivity in SiC. The determination of the nitrogen content by secondary ion mass spectrometry (SIMS) is a difficult task mainly because nitrogen is an atmospheric element for which direct monitoring of N$^\pm$ ions give no or a weak signal. With our standard diamond SIMS conditions, we investigate 12C14N-secondary ions under cesium primary ions by applying high mass resolution settings. Nitrogen depth-profiling of diamond and SiC (multi-) layers is then possible over several micrometer thick over reasonable time analysis duration. In a simple way and without notably modifying our usual analysis process, we found a nitrogen detection limit of $2\times 10^{17}$ at/cm$^3$ in diamond and $5\times10^{15}$ at/cm$^3$ in SiC.