極薄シリコン酸化膜における原子レベルの膜厚均一性と信頼性

摘要

In this paper, the evaluation methods of the degradation and dielectric breakdown of ultrathin SiO_2 thermally grown on Si, which are one of most superior dielectric films, are introduced along with some examples. SISuR (Stress-Induced oxide Surface Roughness) method with using a reaction between SiO_2 films with trapped charges and etching solution is available to clarify that the degradation in SiO_2 film under high electric field stress is not uniform. Furthermore, it is indicated that thermal oxidation of the atomically-flat Si terrace surface does not progress two-dimensionally uniformly, strictly speaking. The non-uniform oxidation is one of the origins of the wide lifetime distribution of dielectric breakdown of the ultrathin SiO_2 films.%本解説では,代表的な絶縁膜であるシリコンの極薄熱酸化膜の絶縁特性の劣化および破壊について,原子レベルで評価する方法を事例とともに紹介した.シリコン酸化膜中の捕獲電荷とエツチング液の相互作用を利用したSISuR (Stress Induced oxide Surface Roughness)法による不均一な劣化のようすを捉え,つぎに原子的に平坦な原子テラス表面の酸化から明らかにされた不均一な熱酸化の評価と絶縁破壊寿命分布との関連性を示した.