Carbon doped silicon oxide SiO(C, H) low k thin films (k∼2.9) deposited by the plasma enhanced chemical vapor deposition technique from trimethylsilane (3MS) and oxygen (O2) have been studied. Two types of chemical vapor deposition process recipes, namely CVD1 and CVD2 were applied for film deposition. CVD1 is an initial recipe that resulted in films with a uniform deposition rate irrespective of film thickness and a low dielectric constant of about 2.9. However, it suffers from extraordinarily high post particle counts. CVD2 is a modified recipe adopted to address this issue. The main difference between the two recipes is that a pump down step immediately before the film deposition has been omitted in recipe CVD2, and this has successfully reduced the particle counts to a satisfactory level. However when using recipe CVD2, the deposition rate is nonuniform and the dielectric constant is slightly above 3.0, attributed to the residual oxygen in the process step prior to film deposition. In this study we investigate the effects of oxygen incorporation on the properties of SiO(C, H) films. Surface defects and their element composition, film thickness, refractive index, dielectric constant, and chemical bonding analysis of the films have been carried out. The chemical composition and structure of films deposited by recipes CVD1 and CVD2 show very slight differences, and are also slightly nonuniform along the film depth. Although the nonuniformity does not have much effect on the dielectric constants of the SiO(C, H) films, it may pose a potential challenge for these low k films in terms of advanced integration.

Carbon-doped silicon oxide ͓SiO͑C,H͔͒ dielectric films have been prepared by the plasma-enhanced chemical vapor deposition technique from trimethylsilane in an oxygen ͑O 2 ͒ environment. The process pressure was varied from 1.5 to 8.0 Torr and its effects on the properties of these films have been investigated. The films were also annealed at different temperatures from 400 to 700°C to determine their thermal stability. The thickness, refractive index, dielectric constants, infrared absorption, and surface morphology of the as-deposited and annealed samples were characterized. The dielectric constants of the as-deposited films were found to decrease initially with increasing process pressure and nearly saturate at pressures beyond 4.0 Torr. Dielectric constant as low as 2.86 has been obtained from the as-deposited film at 8.0 Torr process pressure. Lower refractive indexes were also obtained for films deposited at higher pressure. There are no significant changes to the properties of the films upon annealing at temperatures up to 500°C, which is beyond the current highest processing temperature for back end of the line structure of around 450°C. However, beyond that annealing resulted in a sharp increase in the dielectric constants of the films, attributed to the decomposition of CH x and SiCH x bonds.Ultralarge-scale integrated ͑ULSI͒ circuits require the replacement of the SiO 2 interlayer dielectric with low dielectric constants ͑low-k͒ materials to reduce propagation delays, cross-talk noise, and power dissipation arising from resistance-capacitance ͑RC͒ coupling. 1 Low-k materials prepared by the plasma-enhanced chemical vapor deposition ͑PECVD͒ technique are more evolutionary from the current ULSI technology relative to other approaches. Among the PECVD low-k materials, carbon-doped oxide dielectrics ͓SiO͑C,H͔͒ prepared from organosilicon precursor trimethysilane ͑C 3 H 10 Si, also referred to as 3MS͒ is one of the most favorable candidates due to their low-k ͑Ͻ3.0͒ and their key electrical and integration characteristics being similar to those of SiO 2 . 2 The dielectric constant of the PECVD prepared SiO͑C,H͒ films are dependent on the deposition conditions such as temperature, process pressure, radio frequency ͑rf͒ power, and gas flow rate. In our previous work, we have studied SiO͑C,H͒ films deposited with different O 2 /3MS flow ratios at a constant process pressure of 4.0 Torr. 3 The lowest dielectric constant of 2.9 was obtained for the film deposited at a O 2 /3MS flow ratio of 100/600 sccm. In this study, we aim to investigate the effects of process pressure on the characteristics of SiO͑C,H͒ films so as to further optimize the process conditions and lower the dielectric constant. A series of films deposited using the above optimized flow ratio, with the process pressure varied over a wide range from 1.5 to 8.0 Torr, were characterized. Currently, the highest processing temperature for the back end of the line ͑BEOL͒ structure is around 400-450°C, and it is important that any potential low-k dielec...