物理学报Issue(10)：1-7,7.DOI:10.7498/aps.64.107701
热退火对等离子体增强化学气相沉积SiCOH薄膜结构与性能的影响∗
Effect of thermal annealing on the structure and prop erties of plasma enhanced chemical vap or dep osited SiCOH film
摘要
Abstract
The development of high-performance integrated circuit chips and the shrinkage of feature sizes according to Moore’s law bring forward continuously the requirements for low dielectric constant (low-k) materials with various excellent properties in the back-end-of-the-line (BEOL) interconnect. Porous SiCOH films prepared by plasma enhanced chemical vapor deposition (PECVD) through a porogen approach are widely applied to industry and extensively studied. Thermal annealing is an important process for fabricating the porous low-k films, which has a great influence on film structure as well as properties. SiCOH films are deposited by PECVD using tetraethoxysilane and limonene as precursors, and annealed at 450 ◦C for 1.5 h under nitrogen atmosphere. The evolutions of film structure and properties during thermal annealing are revealed, and the reaction mechanism for structure change is also proposed. Fourier transform inferred spectroscopy and solid state nuclear magnetic resonance results show that the as-deposited film is an organic-inorganic hybrid film composed of various kinds of Si—O—Si, —CHx, Si—O—CH2CH3, etc. The organic component is removed almost completely during thermal annealing, making a porous film with a Si—O—Si inorganic skeleton. The skeleton is also rearranged at the same time. Deconvolution of the Si—O—Si absorption band of the FTIR spectrum reveals that the cage-like Si—O—Si occupies the major part for both as-deposited and annealed films, while the amount of silicon suboxide Si—O—Si decreases and that of network Si—O—Si increases during thermal annealing, making the film more robust. More C=C and Si—C are formed through chemical reactions between Si—H, —CHx and Si—O—CH2—CH3, and crosslinking is further enhanced. Nitrogen adsorption/desorption isothermal measurement reveals that a large number of micropores with diameter less than 2–3 nm are created during thermal annealing, which is consistent with the removal of organic groups and the existence of cage-like Si—O—Si. As a result, both the refractive index and dielectric constant decrease significantly from 1.476 (λ=630 nm) and 3.45 to 1.365 and 2.60, respectively. Because of the increase of C=C after annealing, extinction coefficient and leakage current density increase. Although there is a shrinkage of 14.7% in film thickness and a reduction of mechanical properties after annealing, the Young’s modulus is still larger than 4 GPa. Considering all kinds of properties, the obtained film appears to be a competitive candidate as inter layer dielectrics in the BEOL interconnect of integrated circuits.关键词
热退火/SiCOH薄膜/等离子体增强化学气相沉积/结构与性能Key words
thermal annealing/SiCOH film/plasma enhanced chemical vapor deposition/structure and properties引用本文复制引用
谭再上,吴小蒙,范仲勇,丁士进..热退火对等离子体增强化学气相沉积SiCOH薄膜结构与性能的影响∗[J].物理学报,2015,(10):1-7,7.基金项目
国家科技重大专项(批准号:2011ZX02703-004)资助的课题.* Project supported by the National Science and Technology Major Project of the Ministry of Science and Technology of China (Grant No.2011ZX02703-004) （批准号:2011ZX02703-004）
