Analysis on the off-state design and characterization of LIGBTs in partial SOI technology

• Discussion on off-state characterization of a superjunction LIGBT on partial SOI.
• Problem related to side-coupling and back-coupling.
• Problem happens especially in thin SOI with partial SOI architecture.
• Solution provided to solve the earlier leakage deal with the problem.
• Analysis at high temperature and comparison to equivalent LDMOS is included.

Classical high voltage devices fabricated on SOI substrates suffer from a backside coupling effect which could result in premature breakdown. This phenomenon becomes more prominent if the structure is an IGBT which features a p-type injector. To suppress the premature breakdown due to crowding of electro-potential lines within a confined SOI/buried oxide structure, the partial SOI (PSOI) technique is being introduced. This paper analyzes the off-state behavior of an n-type Superjunction (SJ) LIGBT fabricated on PSOI substrate. During the initial development stage the SJ LIGBT was found to have very high leakage. This was attributed to the back and side coupling effects. This paper discusses these effects and shows how this problem could be successfully addressed with minimal modifications of device layout. The off-state performance of the SJ LIGBT at different temperatures is assessed and a comparison to an equivalent LDMOSFET is given.