Trap spectroscopy and Ta penetration induced charge trapping in porous SiOCH low-k dielectrics

The method “trap spectroscopy by charge injection and sensing” (TSCIS) is applied to porous SiOCH low-k dielectrics integrated in MIS capacitors with Ta based diffusion barriers. Most of the low-k samples show an unexpected negative flatband voltage shift with charge injection, which we attribute to positive charge built up in the bulk low-k due to Ta penetration. The only porous low-k sample that can be fitted using the standard TSCIS method is a k=2.0 material in combination with a low pore penetration barrier. The fitted trap distribution demonstrates a low trap density and an amorphous structure. It is also shown that UV treatment can change the low-k charge trapping behavior.