Optimization of deep silicon etching process for microstructures fabrication

The paper presents the study of cyclic process of deep anisotropic silicon etching, called Oxi-Etch, in which the steps of etching and oxidation alternate, allowing deep etching of silicon with an anisotropic profile. This process forms typical for cyclic etching process sidewall profile called scalloping. Opportunities for modification and optimization of the process for specific application were investigated. The effects of optimization of the bias voltage and the duration of the etching step on the parameters of the resulting structures, such as the etching depth, wall roughness, and the accuracy of transferring the lithographic size, are considered. Balance between etch rate and scalloping was established.

Research and Development of MEMS Accelerometer's Sensor

Currently, MEMS accelerometers are one of the most promising areas in the inertial sensor industry. The design and study of MEMS accelerometers structures is associated with solving problems of mathematical physics. Also, a very important task is to comply with the technological route, including carrying out such operations as deep etching of silicon. This article describes the modeling of the developed geometric model of the sensitive element MEMS accelerometer. The calculations were carried out, which showed that the developed structure is efficient. As a result of the study of the Bosch process using methods for planning multifactor experiments, the modes of deep etching of silicon were optimized. Prototypes of sensitive element MEMS accelerometers have been produced.

Development of Micron Sized Photonic Devices Based on Deep GaN Etching

In order to design and development efficient III-nitride based optoelectronic devices, technological processes require a major effort. We propose here a detailed review focussing on the etching procedure as a key step for enabling high date rate performances. In our reported research activity, dry etching of an InGaN/GaN heterogeneous structure was investigated by using an inductively coupled plasma reactive ion etching (ICP-RIE). We considered different combinations of etch mask (Ni, SiO2, resist), focussing on the optimization of the deep etching process. A GaN mesa process with an etching depth up to 6 µm was performed in Cl2/Ar-based plasmas using ICP reactors for LEDs dimen sions ranging from 5 to 150 µm². Our strategy was directed toward the mesa formation for vertical-type diode applications, where etch depths are relatively large. Etch characteristics were studied as a function of ICP parameters (RF power, chamber pressure, fixed total flow rate). Surface morphology, etch rates and sidewall profiles observed into InGaN/GaN structures were compared under different types of etching masks. For deep etching up to few microns into the GaN template, we state that a Ni or SiO2 mask is more suitable to obtain a good selectivity and vertical etch profiles. The optimized etch rate was about 200nm/min under moderate ICP conditions. We applied these conditions for the fabrication of micro/nano LEDs dedicated to LiFi applications.

Redeposition-Free Deep Etching in Small KY(WO4)2 Samples

KY(WO4)2 is a promising material for on-chip laser sources. Deep etching of small KY(WO4)2 samples in combination with various thin film deposition techniques is desirable for the manufacturing of such devices. There are, however, several difficulties that need to be overcome before deep etching of KY(WO4)2 can be realized in small samples in a reproducible manner. In this paper, we address the problems of (i) edge bead formation when using thick resist on small samples, (ii) sample damage during lithography mask touchdown, (iii) resist reticulation during prolonged argon-based inductively coupled plasma reactive ion etching (ICP-RIE), and (iv) redeposited material on the feature sidewalls. We demonstrate the etching of 6.5 µm deep features and the removal of redeposited material using a wet etch procedure. This process will enable the realization of waveguides both in ion-irradiated KY(WO4)2 as well as thin KY(WO4)2 membranes transferred onto glass substrate by bonding and subsequent polishing.

Deep Reactive Ion Etching of Z-Cut Alpha Quartz for MEMS Resonant Devices Fabrication

Quartz is widely used in microelectromechanical systems (MEMS). Especially, MEMS quartz resonators are applied to sensors and serve as sensitive elements. The capability of deep etching is a limitation for the application. Presented in this paper is a deep and high accuracy reactive ion etching method applied to a quartz resonator etching process with a Cr mask. In order to enhance the capability of deep etching and machining accuracy, three kinds of etching gas (C4F8/Ar, SF6/Ar and SF6/C4F8/Ar), bias power, inductively coupled plasma (ICP) power and chamber pressure were studied in an industrial reactive ion etching machine (GDE C200). Results indicated that the SF6/C4F8/Ar chemistry gas is the suitable and optimal choice. Experiment results indicate that Cr (chromium) mask can obtain a higher selectivity than aluminum and titanium mask. A “sandwich” structure composed of Al layer-Cr layer-Al layer-Cr layer was proposed. The Al (aluminum) film can play the role of releasing stress and protecting gold electrodes, which can enhance the thickness of metal mask. An optimized process using SF6/C4F8/Ar plasmas showed the quartz etching rate of 450 nm/min. Meanwhile, a microchannel with a depth of 75.4 µm is fabricated, and a nearly vertical sidewall profile, smooth surface is achieved.