Effects of Deposition Pressure on Properties of Carbon-Doped Silicon Oxide Low Dielectric Constant Films

Abstract

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...

MEL‐type Pure‐Silica Zeolite Nanocrystals Prepared by an Evaporation‐Assisted Two‐Stage Synthesis Method as Ultra‐Low‐k Materials

“…[3,4] The low-k material currently used in chips is carbon-doped silica, and it can have a k value as low as 3.3, which is lower than that of traditional dense silica (i.e., k % 3.9). [5,6] While the semiconductor industry is already able to produce low-k materials with k values between 2.3 and 2.7, [2,7] the solutions to ultra-low-k materials (i.e., k < 2.1) are still unknown to date. Therefore, ultra-low-k materials have been a bottleneck for the development of next-generation chips in the semiconductor industry.…”