Influence of porosity on electrical properties of low-k dielectrics

[Display omitted] ► PE-CVD low-k materials with porosity of 5–33% and k-values of 2.3–3.2. ► TDDB, voltage ramp, and capacitance measurements. ► Higher porosity results in shorter lifetime, higher leakage, lower breakdown field. ► Higher leakage attributed to presence of more porogen residues. TDDB, voltage ramp, and capacitance measurements for a series of low-k materials deposited by PE-CVD, with porosity values between 5% and 33%, are presented. A test structure based on MIS planar capacitors, designed to investigate intrinsic electrical properties, has been used. It is shown that, in general, a higher porosity results not only in a lower k-value, but also a higher leakage current, lower breakdown voltage and shorter lifetime. The higher leakage can be attributed to the presence of more porogen residues. This is confirmed by the decrease of the leakage when a He/H2 plasma, known to remove the porogen residues, is applied.