An investigation of ultra low-k dielectrics with high thermal stability for integration in memory devices

For the PMD in a next generation memory device, two kinds of newly developed ultra low-k MSQ materials (k < 2.0) are shown to have good thermal stability, up to 600 °C, while the investigated HSQ (k = 2.9) material degraded at temperatures >500 °C. The thermal stability of the low-k MSQ is correlated with the amount of Si–X (X = H or CH3), the ratio of Si–X to Si–O, and the structure of the Si–O bonds. With PE-SiO2 and PE-SiN capping on HSQ, the k-value of  < 3.0 can be maintained up to 800 °C due to Si–H remaining in the film. Similarly, PE-SiC and PE-SiO2 capping increases the k-value degradation onset temperature of the MSQ materials by 50 °C.