C_8F_(18)プラズマCVDによる非晶質フッ化炭素低誘電率絶縁膜の波状構造積層堆積

摘要

a-C:F堆積膜表面，断面，側面（基板外縁）のSEM 観察rnにより，堆積膜が熱膨張することによって波状膜が形成さrnれることがわかった。一連の実験結果によって確認できたrn波状膜形成の条件は，下層を低電力で堆積する，上層堆積rn中の到達温度が下層の膨張温度以上かつ融解温度以下となrnるように電力と堆積時間を選ぶ，上層は波状化のための柔rn軟性が残る程度の厚さ（約1000nm以下）で堆積する，以上rnの3点を満たした場合のみ波状膜が形成されていた。%We have composed amorphous fluorocarbon (a-C:F) polymer films, which are low-k insulators, by plasma-enhanced chemical vapor rrndeposition using C_8F_(18) as the feedstock. In our previous attempts to form multi-layered a-C:F films under various rrncombinations of plasma power density P and deposition time T, it was found that a-C:F films deposited at a high P (typically rrn2.0 W/cm~3) in a short T (～1 min) became wavy when they are deposited on other a-C:F films deposited at a low P (0.2 rrnW/cm~3). A heating experiment for the films showed that their thermal tolerance was dependent on P; films deposited at 0.2 rrnW/cm~3 started to melt at 250-270℃, while those deposited at 2.0 W/cm~3 did at 350-370℃. It is considered that species of rrnthe precursors for the a-C:F film deposition are determined by P through the degree of C_8F_(18) decomposition. The waving is rinduced by heating the lower layer during the deposition of the upper layer. The following conditions are necessary for ther waving; the lower layer is deposited at a low P, the upper layer is deposited at a temperature at which the lower layer rrnexpands but does not melt, and the upper layer is not thickened excessively to keep its flexibility.