||As IC technology moves into the deep submicrometer regime in high performance ULSI circuits, it is required to decrease the metal pitch and to increase the number of metal layers for interconnect to accommodate the increased packing density and functional complexity. But the signal propagation delay in the interconnect becomes an appreciable fraction of the total time delay. Use of low dielectric constant material (low-k) as the intermetal dielectric (IMD) results in low inter-line capacitance and therefore high performance in speed, low power dissipation, and low cross-talk noise. During various low dielectric materials, porous silica film is one of the possible candidates with an inherent low dielectric constant. In this thesis, the intrinsic properties such as fundamental physical, electrical, thermal stability of the spin on glass (SOG) have been investigated. We also study the properties of the SOG film with various plasma and treatments. An inherent low dielectric constant of 1.9 is achieved for high porosity of the porous silica film and the leakage current density keep at a level of ~10-9 A/cm2 at 1MV/cm electric field strength. After O2 plasma treatment, the Si-C and C-H bonds of the film are almost eliminated, thus the dielectric constant and leakage current are rapid increase than that of those untreated films. We find that H2 plasma can passivate the porous silica surface so that the leakage current can be kept at acceptable range, however, the dielectric constant increase slightly.|
Moreover, the etching issues were also investigated in this study. The mask undercutting on sidewall was observed due to the spontaneous reaction between the porous silca film and fluorocarnbon plasma. Therefore, H2 plasma treatment was provided to suppress this phenomenon.
In this study, the intrinsic properties such as fundamental physical, electrical, and thermal properties of the porous silica have been investigated. The compatibility of the porous silica with integration processes also has been studied comprehensively. We have proposed H2 plasma treatments to improve the dielectric properties of porous silica after photoresist removal. Material and electrical analyses were used to interpret these improvements.