AVS 52nd International Symposium
    Plasma Science and Technology Monday Sessions
       Session PS1-MoA

Paper PS1-MoA2
Difference in Etch Depth between Isolated and Dense Holes in Via-Etching of SiOC Film

Monday, October 31, 2005, 2:20 pm, Room 302

Session: Dielectric Etch I
Presenter: Y. Momonoi, Hitachi, Ltd., Japan
Authors: Y. Momonoi, Hitachi, Ltd., Japan
K. Yonekura, Renesas Technology Corp.
Correspondent: Click to Email
Carbon doped silicon oxide (SiOC) has been widely used in integrated circuits (ICs) in order to reduce the total resistance capacitance (RC) delay in the interconnects. However, we found that there was a significant difference between the etch depths of isolated and dense SiOC via-holes. In addition, we found a mutually opposite dependence of etch depth on pattern density under different etching conditions. Equally, the etching properties, e.g., etch rate and depth of unexpected etch stop that are dependent on pattern density were different in different etching conditions. We expect that the difference in etch depth is a key issue in controlling critical dimensions, mask selectivity, and erosion of etch stop layers. In investigating the difference, it was clarified that the etch depth of isolated patterns was deeper than that of dense patterns when the etch depth was determined by an unexpected etch stop (narrow etch-stop-margin condition), and that the etch rate of isolated patterns was slower than that of dense patterns when the etch depth was based on etch rate (wide etch-stop-margin condition). We also found that the difference increased the longer the wafers were stored, which is in accordance with an increase of a gas degassed from SiOC in thermal desorption spectroscopy. We therefore investigated the influence of the gas on SiOC etching by adding it to plasma. Consequently, the added gas resulted in the same difference in etch depth as the difference that occurred between isolated holes and dense holes in both etch-stop-margin conditions. These results indicate that more of the gas degassed from isolated holes in SiOC determines the difference in etching depth.