Effects of deep reactive ion etching parameters on etching rate and surface morphology in extremely deep silicon etch process with high aspect ratio

Abstract

This study empirically investigates the influences of several parameters on surface morphology and etch rate in a high-aspect-ratio silicon etching process. Two function formulas were obtained, revealing the relationship between the controlled parameters and the etching results. All the experiments were conducted on an inductively coupled plasma system, using a Bosch process. The tested trenches' width ranged from 15 to 1500 mm and their depth ranged from 50 to 500 mm, which covers nearly all the typical sizes of micromechanical devices in practical applications. The controlled parameters are etching chamber pressure, bias power, and gas flow rate. The parameters of surface morphology include sidewall angle, surface roughness, and sidewall condition. We tested how the controlled parameters can influence the surface morphology and etch rate and formulated assumptions to explain those relationships. Meanwhile, we utilized linear regression to obtain experiential function formulas of the relationships among etch depth, structure width, etching time, and passivation time, with a correlation coefficient higher than 0.99. Using these formulas, 12-mm-wide and 377-mm-deep (aspect ratio 31.4) trenches with sidewall angles of 89°were achieved. Additionally, this experience was applied as a critical structure in a gas turbine structure system.

The Michelangelo step: removing scalloping and tapering effects in high aspect ratio through silicon vias

“…The authors show how the achievable aspect ratio increases with smaller feature size. Other interesting results were presented by Owen et al 15 achieving an aspect ratio of 97:1 with trenches as large as 3 μm and by Xu et al 13 where the authors achieved an aspect ratio of 31.4:1 with 12 μm trenches. Despite close but not higher than these highly optimized values, which require use of ramping parameters of DRIE process, it has to be noted that the optimization of the etching process is important but not the ultimate goal of this work, which aims at presenting a way of removing scalloping and tapering effects in holes after a Bosch process.…”

“…An alternative and more optimized process has been developed by means of a modified Bosch process. As presented by Xu et al 13 , we added a cleaning step of O 2 plasma between passivation and depassivation steps, in order to clean the excess passivation left over after the plasma etching. The addition of this extra step, the use of a lower chamber pressure, higher plasma bias power and lower chamber temperature of 0 °C, as well as the ramping 14 of process parameters (see Table 1 ) resulted in a much sharper deep reactive ion etching process, with less rough walls and comparable etching rate to the room temperature process, which reached holes with aspect ratios as high as 28:1 and deep trenches with aspect ratios of 75:1 (see Fig.…”

Fabrication of High Aspect Ratio Micro-Structures with Superhydrophobic and Oleophobic Properties by Using Large-Area Roll-to-Plate Nanoimprint Lithography

“…Firstly, the pattern depths on the Si master molds could differ due to the micro-loading and the aspect ratio dependent etching (ARDE) effects, which cause the Si etch rate to be dependent on the density and A.R. of the micro-structures, respectively [ 51 , 52 , 53 ]. Secondly, it could be that the flexible PDMS patterns are stretched during peeling from the Si mold (possibly the case for the PDMS-PIL samples) or have shrunk during curing (possibly the case for the PDMS-C-RESS samples).…”

Anti-Reflectance Optimization of Secondary Nanostructured Black Silicon Grown on Micro-Structured Arrays

“…In order to fabricate hemispherical shape pits and volcanic shape tips, etching gas and high energy density SF 6 /O 2 plasma should not only react with the silicon in the vertical direction but also in the horizontal direction. In previous work, the etching rate ratios in the vertical direction and horizontal direction were measured by considering the different pattern sizes of the masks [ 70 , 71 ]. Therefore, the sizes of the masks were designed according to the results of the etching rate ratio.…”

“…1 to No. 5 tip and pits samples might show different results of depth, which were studied in previous research [ 70 , 71 ]. Therefore, Table 2 indicates the design number of the depths of each sample in Table 1 .…”