Bilayer interlayer dielectric having a substantially uniform composite interlayer dielectric constant over pattern features of varying density and method of making the same

摘要

A bilayer interlayer dielectric having a spun-on low k gap filled layer is capped with a higher k dielectric layer. Prior to the capping, the spun-on low k dielectric layer is planarized to reduce or eliminate the systematic variation in the relative thickness of the layers due to pattern density effects on the thickness of the spun-on low k dielectric layer. By removing the variations in the relative thickness of the low k dielectric layer and the capping layer, the effective dielectric constant of the uniformly thick composite interlayer dielectric is independent of location on the circuit, preventing differences in circuit speed and the creation of clock skew in the circuit.