Isocyanurate, -(O =)C-N, is a unique structure with one-third of its weight percent in its nitrogen and stable C-N ring.From our experience, melamine-type materials have an etch behavior similar to that of isocyanurate, which has twothirds of its weight percent in its nitrogen and stable conjugated C-N ring. Combustion theory explains the function of the C-N ring during polymer degradation in air very well. Since both processes are very aggressive polymer decomposition processes, we applied combustion theory to explain polymer decomposition in O2 plasma. In the combustion process, the structure of the C-N ring could undergo progressive condensation to form a very stable structure, known as melem, which is incorporated into the combustion residue at a higher efficiency than fused aromatic heterocycles [13, 14]. If we apply this mechanism to O2 etching, the C-N ring trends to form a stable structure, just likea benzene ring. The nitrogen in the C-N ring is a slow etch material.