Studies Of Structure And Properties For A-C:F:H Films Deposited By Micro-Wave ECRCVD

The continuous shrink of device feature size in Ultra-Large Scale Integrated circuit gives rise to some problems, such as the interconnection delay, signal cross-talking, power dissipation etc. The solution is to replace the current Al/SiO2 system with new metal line/ low dielectric constant (low-k) insulated materials. a-C:F:H film deposited with chemical vapor deposition (CVD) method is one of the promising candidates of low-k materials. Using microwave electron- cyclotron-resonance plasma chemical vapor deposition method, we have prepared the low k fluorinated carbon films and carried out some related research work.In this thesis, two parts are mainly included: the first part investigates substrate etching and film deposition in the microwave Electron Cyclotron Resonance (ECR) F-containing plasma, and probes the etching selectivity for the substrates under the influence of the RF power; The second part, which is the point of the work, focuses on the a-C:F:H film deposition using ECR CVD method and the film structural property, thermal stability, electrical property, etc.Parti:The influence of pressure, microwave input power, gas flow ratio and substrate RF bias on the substrate (Si and SiOj) surface etching has been studied by using ECR plasma with source gases of CF4, H2, and Ar. The results indicate that etching rate of the substrates increases with decreasing pressure, increasing microwave and RF power, but the etching selectivity of SiO; over Si is very low, maximum of which is 4 at our experiment condition. This poor etching selectivity is partially due to the higher dissociation of gas precursors, which causes higher F radical concentration in the plasma, compared to the conventional reactive ion etching. By using CHFj/C2H2 (or CHF3/C獺6), even not applying RF bias to the substrates, although a thin film can be deposited on substrates, the experimental results imply that a certain etching still occurs on the substrate surface. It is shown that substrate surface etching is formed at the initial ECR discharge.Part II:a-C:F:H films with low dielectric constant are deposited mainly by using ECRCVD technique with the source gases of CHF3/CR,, CHFyCjHj or CHF3/C6H6. The influences of process parameters ( gas flow ratio, deposition pressure, microwave power, substrate position etc.) on the film structure and properties are systematically investigated. It is found that, among the above mentioned three gas systems, evolution of C-F infrared bond structure happens in a-C:F:H films with the increase of CHF3 feed, and final structure ismore like the one of PTFE, which is composed of -CF: structure monomer. For the latter two gas systems, the film contains more C=C bond configurations than the former. C=C configurations affect the film optical band gap together with C-F bonding configurations. It is also found that High C/F atom ratio for source gases, low deposition pressure and high microwave input power contribute to enhancement of cross-linked structure in a-C:F:H films and thus improve the thermal stability of the films. With the help of influence of process parameters on the film deposition, kinetic model of activated film growth is supposed.Thermal stability of a-C:F:H film better than 400, which is designed in damascene process, should be required except for its low dielectric constant (s <3). Therefore, the study of a-C:F:H film thermal annealing is carried out in NI environment. The results from annealing of the a-C:F:H films with different bond configurations deposited by using CHF3/CH4 or CHF3/C6Hs have shown that the presence of H, a few or excessive F content in the film can easily lead to variation of film structure and thickness. The change of a-C:F:H film thickness before/ after annealing is explained by the as-supposed pyrogenic model. The results from annealing of a-C:F:H films deposited with CHF3/C6H6 have shown that we have prepared a a-C:F:H film with its dielectric constant less than 3 and its thermal stability better than 400癈.Owing to the presence of etching on substrat...