In situ diagnostics of the Si etching structures profile in ICP SF6/C4F8 plasma: Macrostructures

Abstract

Abstract In this work we studied the influence of technological parameters of plasma chemical etching of silicon on photoresist etching rate, silicon etching rate, etching selectivity of silicon in relation to photoresist, and inclination angle of the profile wall of the etched windows. Based on the obtained results, a common regularity between the inclination angle of the profile wall of the etched windows and the optical emission spectra was revealed. The method of in situ diagnostics was proposed, namely, controlling the inclination angle of the profile wall of the etched windows by the ratio of the emission intensities of the carbon line (517.1 nm) to the fluorine line (685.8 nm and 703.9 nm) designated as parameter X. It was found that the inclination angle of the profile wall of the etched windows takes certain values depending on the value of the X parameter. The ranges of X values, at which the inclination angle of the profile wall of the etched windows is acute, right, and obtuse are estimated. So, at values of X from ≈0.15 to ≈0.35 the acute angle (from 81±0.5° to 89±0.5°) is obtained, at X from ≈0.35 to ≈0.42 the right angle is obtained (90±0.5°), and at X from ≈0.42 to ≈0.75 the values of the inclination angle of the profile wall of the etched windows are in the range from 91±0.5° to 94±0.5°, no matter which technological parameters were set. Experiments were conducted for etching windows with linear dimensions from 0.5x20 mm to 2x20 mm.