Study on low damage engraving of ultra-fine/high aspect ratio hole for ULSI process

点击翻译按钮获取中文摘要

This study was carried out by the purpose that SiO2 contact hole in the ULSI device process was engraved satisfying high aspect ratio, low damage and good reproducibility. The study consists of ultra-high voltage TEM observation of contact holes, interaction between fluorocabon plasmas and an inner wall of a reactor and a sidewall protection etching. At first, bottoms of 0.1μm diameter holes engraved by the magnetron RIE employing were observed by a cross sectional TEM. The spot-like defects were observed, while these defects were annealed out at 500℃. This shows that serious defects are not induced so much. However, it is reported that actual contact resistance for the as-etched bottom surface is increased. This implies requirement of further efforts to improve the defects reduction. Next, to study the wall interaction of fluorocarbon species in C_4F_8 ICP (inductively coupled plasma), an ICP reactor equipped with a small scaled QMS, OES and a temperature controlled metal stage was de … More veloped and dependences of stage temperature, distance from the stage, bias voltage added to the stage and residence time on densities of fluorocarbon species near the stage surface. As a result, total densities of CF_x(x=l-3) radicals increased at any distance with increasing stage temperature. This increase was larger as the gap was closer to the stage surface and especially CF_3 radicals indicated the most increase. In addition, Variations of radical densities with change in temperatures could be suppressed by shorter residence time. Finally, we studied a new method achieving high aspect ratio feature by protection of the mask side wall erosion during etching. For the goal, we preserved the resist mask feature by deposition of species on the resist side wall at a glancing angle. As a result, reduction of the mask thickness and expansion of the opening width could be minimized, thus engraving holes with 0.15μm diameter and 15 of aspect ratio successfully. The method was applied to etching of ultra-high aspect ratio Si trench by improving the Bosch method. To transfer the result to fabricate a bio chip, the Si surface was oxidized and an electroosmosis pump was developed. Furthermore, a new "Flow-FET" was fabricated by forming a Au electrode on the back side of the Si substrate. Consequently, positive and negative Zeta potentials were controlled freely by adding 0 and 5 volts to the electrode. Less