A novel non-sequential hydrogen-pulsed deep reactive ion etching of silicon

Abstract

A non-sequential pulsed-mode deep reactive ion etching of silicon is reported that employs continuous etching and passivation based on SF6 and H2 gases. The passivation layer, as an important step for deep vertical etching of silicon, is feasible by hydrogen pulses in proper time-slots. By adjusting the etching parameters such as plasma power, H2 and SF6 flows and hydrogen pulse timing, the process can be controlled for minimum underetch and high etch-rate at the same time. High-aspect-ratio features can be realized with low-density plasma power and by controlling the reaction chemistry. The so-called reactive ion etching lag has been minimized by operating the reactor at higher pressures. X-ray photoelectron spectroscopy and scanning electron microscopy have been used to study the formation of the passivation layer and the passivation mechanism.

Sea of Electrodes Array (SEA): Extremely Dense and High-Count Silicon-Based Electrode Array Technology for High-Resolution High-Bandwidth Interfacing with 3D Neural Structures

“…The conical shape of the shanks and tips shown above is naturally obtained through a special feature of the DRIE etch step called DRIE lag effect. DRIE etch rate is inversely proportional to the aspect ratio of the hole/trench, in other words, holes/trenches with higher ratio of depth to width are etched slower [29][30][31][32][33][34][35]. The variable etch rate at different depths will result in the conical shape of the shank, producing a sharp tip which improves probe insertion into the tissue.…”

Exploitation of semi‐sequential reactive ion etch processes to fabricate in‐plane Si structures

“…We begin our investigations with the oxygen‐free semi‐sequential process reported in [18], which the etching step utilises SF 6 gas, while the passivation step employs H 2 gas. There is no settling time between the etching and passivation sub‐cycles, and as a consequence the remaining trace of SF 6 from the previous etching sub‐cycle helps to from an SiF x H y protecting layer on the surfaces in the passivation step.…”

“…The difference between this process and the one in [18] is that the passivation power is set to zero here; as for high etching depths, more powerful passivation ends to the formation of dense grass‐like features. The overall etch rate of this process is 0.9 μm/min and as is seen in this figure, the amount of under‐etch and surface roughness of sidewalls are considerable.…”

Deep Reactive Etching of Silica with SF6/H2 Plasma

“…Owing to the dominance of the chemical contribution of this method to its physical contribution, the result of this method will be somewhat isotropic, and it does not allow to achieve a high aspect ratio in deep removal [4,5]. Today, many methods such as bosch [6][7][8], cryogenic [7][8][9][10], sequential [11] [12,13] and pulsedmode [14,15] are used for deep silicon removal in which they try to reduce the removal rate of the pattern walls relative to the floor, enhance the removal anitropy and achieve a higher aspect ratio. Creating a protective layer on the pattern walls [6][7][8][9][10][11][12][13][14][15], reducing the temperature of the substrate to temperatures below -100 °C [7][8][9][10] and adding hydrogen to the plasma gases [11][12][13][14][15] are some of the measures that are taken to achieve deep removal with high aspect ratio.…”