Arイオン打ち込み処理による高誘電率ポリイミドフイルム表面のSEM観察

摘要

試料作製が比較的容易である走査電子顕微鏡法（SEM）は焦点深度が深いために，試料の表面形態を立体的に観察できることが特長で，現在では汎用的な表面分析に位置づけられている。SEMは加速した電子ビームを試料に走査しながら照射し，試料表面から放出される二次電子を検出して画像に変換する原理で観察する。実際には二次電子の運動エネルギー（＜50eV）を検出しており，SEM像は試料から得られる運動エネルギー情報となる1）。SEMの像分解能は1970年代には40～60nm程度であったが，1980年代後半に電界放射型走査電子顕微鏡（FE－SEM）が開発されると分解能は飛躍的に向上した。%High-resolution scanning electromicroscopy (SEM) is a powerful technique to elucidate surface information. Because Upilex S® film, a polyimide film (PI film), possesses excellent properties such as chemical and heat resistance, it has been used in many flexible printed board fabrications. When surfaces of the PI film with high permittivity are observed using SEM, the thin film coating of a noble metal by evaporation methods is necessary to avoid charging problems. Such a thin film coating creates artifacts on SEM images. Consequently, high-resolution observation often becomes difficult, especially if we attempt to observe the adsorption of nanoparticles such as Pd-Sn catalysts on the PI film. Surface scientists know empirically that Ar ion beam treatment inhibits charging phenomena of the observed samples.rnTo prevent charging problems during SEM observations, we examined Ar ion implantation for the PI film sample with low acceleration voltage (200 - 300 V) applied to Ar ion gun. Regarding acceleration voltage at 300 V, high-resolution SEM images of the PI film surface were obtained without any thin film coating of noble metal. Furthermore, elemental analyses of the PI film were enabled by energy dispersive X-ray spectrometry (EDS) performed with high current.