Characterization of Plasma Effects on Low-k Film

• Main Authors: Bo-Wei Tseng, 曾柏瑋
• Other Authors: Ta-Chin Wei
• Format: Others
• Language: zh-TW
• Published: 2016
• Online Access: http://ndltd.ncl.edu.tw/handle/58863520843671348276

碩士 === 中原大學 === 化學工程研究所 === 104 === Plasma technology is extensively used in the etching of low-dielectric constant (low-k) materials in semiconductor industry. However, the low-k films are vulnerable to the damaged by plasma species during dry etching and ashing. This study focuses on gaining fundamental understanding on damage mechanism of low-k films under different plasma treatments. Detailed chemical analysis of the plasma-modified surface with depth profile was characterized by X-ray Photoelectron Spectroscopy (XPS) to investigate the change of molecular structure on the surface of SiOCH low-k films after plasma treatment. First, low-k films were treated by C2H2F4/CF4 and CF4 plasma to simulate the fluorinated surface which formed on low-k film after plasma etching. Then, an optional post-etch treatment (PET) step utilizing N2/H2 plasma was applied to re-condition the low-k film and create a fluorine-free and hydrophilic surface which is required for post-etch residue removal (PERR). After C2H2F4/CF4 plasma treatment, the results revealed that it gained a large amount of carbon and fluorine elements on the low-k film surface. With an increase of C2H2F4 ratio, the content of carbon and fluorine increased. Thus C2H2F4/CF4 plasma deposited a thin layer of fluorocarbon film on the low-k film surface. In contrast, it was found that a small amount of fluorine element was formed with a depth of several nanometers on low-k film surface by CF4 plasma treatment. Judging from the content of fluorine and the depth of fluorinated surface, we suggested that CF4 plasma created a fluorinated low-k film surface by etching/doping mechanism. After PET step, it showed that a large amount of carbon and fluorine elements on the low-k film surface were removed, and moreover, the content of fluorine almost disappeared. Furthermore, the content of carbon decreased with an increase of H2 ratio in N2/H2 plasma.