The rates of formation of the oxides of nitrogen (NO, N20) and of ozone have been studied in a pulsed electrical discharge in air at atmospheric pressure. The "hybrid" discharge consisted of a brush discharge in which 03 and N20 were produced and of hotter filaments which formed NO. At lower flow rates the effect of N02 poisoning of the ozone production was found to be important. A diffusion model of the flow in the discharge tube was developed to describe the observed results and to predict the onset of N02 poisoning. Using these results an estimate is made of the contribution from natural point discharges at the surface of the earth to the N20 content of the atmosphere. It appears to be very small.

SynopsisThe polymerization of ethylene in an atmospheric pressure-pulsed discharge has been studied.Partial pressures of ethylene up to 4 kN/m2 were used with helium as a diluent. Deposition rates (on glass slides) were the same throughout the discharge volume over a wide range of operating conditions. These rates were in the 1-2 &.ec range. The films were clear, soft, and showed good adhesion to the glass substrates. Oligomers large enough to visibly scatter 637.8-nm light were observed in the gas phase under all conditions in which film deposition occurred. The experimental results suggest that Brownian diffusion of these oligomers was the rate-limiting step in the film deposition process.

Subatmospheric chemical vapor deposited (SACVD) tetraethylorthosilicate (TEOS) oxide provides excellent deposition profiles for submicron device structures. The film properties, such as wet etch rate, shrinkage, and cracking resistance, as well as step-coverage, depend strongly on the Q-to-TEOS ratio. The SACVD oxide film quality correlates to step-coverage and gap-filling ability, and both can be controlled by varying the Q-to-TEOS ratio.In very large scale integrated (VLSI) manufacturing, multilevel metallization schemes require dielectrics with excellent step-coverage, gap-filling, and planarizing capability, and at the same time good film properties. In particular, subatmospheric pressure CVD TEOS/O3 oxide t'2 has demonstrated excellent step-coverage due to the surfacelimited nature of its reaction kinetics. For example, the SACVD oxide is capable of submicron gap-filling (at 0.4 ~m metal line spacing with 2.5:1 aspect ratio), whereas the other widely used oxide, plasma-enhanced TEOS (PECVD) oxide 3 is not. However, the SACVD oxide provides different film quality compared to PECVD oxide. 3 The SACVD films are similar to those obtained with TEOS/O3 atmospheric pressure chemical vapor deposition (APCVD). 4-7 The SACVD films have higher wet etch rates and shrinkage rates than the PECVD films, indicating that the SACVD oxides are porous films. Film quality of the SACVD oxide can be improved by optimizing the process parameters, including deposition temperature and ozone-to-TEOS ratio. High deposition temperature results in better film quality. t,2 However, high temperature is not practical for gapfilling between metal lines in device fabrication. Ozone-to-TEOS ratio therefore becomes the most important factor in determining the film quality of the SACVD oxide. The results presented demonstrate that the step-coverage and film quality of the SACVD oxides correlate to each other, and they also depend on underlying base materials. ~' 9 Both step-coverage and film properties show significant dependence on the Q-to-TEOS ratio. Here, step-coverage, as well as film properties such as wet etch rate, film shrinkage, stress-temperature behavior, and cracking resistance of the SACVD oxide are investigated as a function of the O3-to-TEOS ratio. ExperimentalThe SACVD oxide films were deposited in an Applied Materials Precision 5000 CVD reactor. ~ The process gas was introduced from a showerhead over the wafer, and was exhausted through a throttled valve below the wafer. TEOS vapor was supplied to the reactor by bubbling a carrier gas, helium, through a TEOS bubbler which is temperature controlled at 48~ Ozone is generated to between 8 to 9 weight percent in oxygen by an ozonizer, Onoda, Model OR-4ZA, and added to TEOS/He gas before the showerhead. The SACVD oxide was deposited at a pressure of 600 Torr and a deposition temperature of 400~ using an electrode spacing of 5.6 mm. Two types of substrates were used for this study. One was bare silicon (p-type with boron dopant, <100> orientation); the other was plasma-enhanced TEOS ...

This paper reports characterization and processing of polyimide (PI) thin films for use as intermetal dielectrics. The spin coating and curing processes for PI thin films, the adhesion of PI films on various substrates with and without adhesion promoters, the dielectric properties, and planarization property are presented and discussed. The water sorption isotherm for hard-cured PIQ-13 has been determined. The results obtained from plasma etching of PI contact vias are also reported in this paper.