Papers by Keyword: Wet Etching

Abstract: This paper describes both aqueous and solvent-based formulations aimed at etching silicon oxide (SiO_x) with etching rates (E/R) of the order of 10-20 A/min with selectivity greater than 5 with respect to silicon nitride (SiN_x) . Diluted hydrofluoric acid (dHF) with very low pH was tried first but the selectivity was found to increase only with higher SiO_x E/R. Solvent-based formulations derived from previous work also behaved in a similar way, however its SiO_x E/R could be reduced by modifying the total fluoride concentration inside formulation. Finally, we found that low SiO_x E/R could also be implemented in the diluted buffer-oxide etch (BOE) solution and the selectivity could be adjusted by addition of a specific surfactant at a very low concentration level.

Abstract: The assembly process of nanostructures from nanoparticles in solution is fundamental for bottom-up fabrication of functional materials and devices. In a similar way, bottom-down fabrication approach requires etching of materials. We take advantages of emerging in-situ liquid cell transmission electron microscopy (TEM) technique and explored several liquid processes such as: (1) nanoparticle-nanoparticle interaction in thin fluid layer, (2) wet etching of nanostructures and (3) pinning and de-pinning of nanodroplets at solid surface. Our approach is to directly visualize nanoscale liquid process, which is important for development of new nanofabrication processes for the design of next generation nanoscale devices. Our finding of nanodroplet pinning has important implications on surface cleaning at the nanoscale.

Abstract: This paper presents the fabrication of a micro-lens array surface with a single-mask process and two etching steps with KOH water solution. Numerical analysis of optics was used to determine the optimal design parameters such as curvature sagitta and radius. The dimension of each lens is 20μm x 20μm. We used anisotropic etching of <100> silicon through a circular and squar mask to produce a pyramidal pit formed by four (111) planes. The oxide mask is stripped and the immersion of the sample in the etchant solution favors the etching of (411) plane transforming the pit into a smooth hemispherical cavity. An intermediate stage exists when a wider 19.47⁰ <411> - face pyramid replaces the initial 54.74⁰ inverted pyramid. The dependence of surface roughness on concentration and temperature of KOH is investigated in the range of 25%-40% and 60°C-80°C, respectively, and compared between them. The surface profiles and roughness was characterized by AFM. The etching depth and radius of micro-lens array was obtained from the SEM images and AFM data. Also, the array of concave depressions was directly used as a mould for replication of KER-2500 transparent polymeric silicon from Shin-Etsu with a refractive index n=1.41. The perfectly matched array of micro-lenses can be detached from substrate and used as a local solar concentrator. Optical properties such as the focal length of the plano-convex micro-lens array, obtained by replication, are measured and analyzed.

Abstract: Transparent ZnO films were deposited by sol-gel spin coating process. HCl acid was used in the wet etching process to modify its surface morphology that can be used as an anti-reflective layer of optoelectric devices. The effect of etching time on its structure, surface morphologies and optical properties were scrutinized. The overall results indicated that HCl acid has obviously effect on significant change in surface morphologies and its roughness varied in the range of 0.5 nm to 4.9 nm.

Abstract: In this paper, two aspects in the wet glass etching, the pre-annealing of the glass and the mask process, are taken into consideration to achieve the deep and defect-free wet etching of Pyrex glass. Compared with the conventional strategies, i.e., HF solution component and mask kinds, our experiment results prove the pre-annealing is another key role to obtain theoretical isotropy character in wet etching. Besides, the high temperature pre-annealing dramatically improves the structure profiles and reduces the notching defects. Additionally, a novel multilayer mask process is proposed. With 1.5μm PR/ 100nm Au/ 100 nm Au/ 20 nm Cr mask and > 450 °C pre-annealing, > 150 μm deep and non-pin-holes Pyrex glass structures are achieved and the roughness of etched surface is lower than 1 nm.

Abstract: Polyimide is often used as a sacrificial layer material to make floating structure. Polyimide is also divided into photosensitive and non-photosensitive type; photosensitive polyimide currently has more negative photoresist and poor performance in many ways. Compared with photosensitive polyimide, the non-photosensitive type has low stress, stable performance and other advantages, so non-photosensitive polyimide has been chosen as a sacrificial layer material. To achieve the graphical function and release sacrificial layer, A deeply research was made in this dissertation makes on wet etching and dry etching. By controlling the wet etching process of prebake condition, exposure and developing time, and oxygen dry etching process of etching power, bias voltage and other key process parameters, a good sacrificial layer graph and etching effect have been got. Finally, it can be concluded that when the prebake conditions for 105°C, 8min and times of exposure and developing were 11s and 29s, the non-photosensitive polyimide wet etching effect is the best; when the etching power is 1000w, an oxygen flux rate is 50sccm, the reaction pressure is 30mTorr, the bias voltage is 140v, oxygen dry etching has a good effect.

Abstract: Sacrificial layer release is the key process step of cavity structure formation of Film Bulk Acoustic Resonator (FBAR), the degree of sacrificial layer release directly determines how good or bad the resonance characteristic of FBAR is. The Constant Diffusion Coefficient (CDC) model numerical iteration of sacrificial layers etching process was simulated with MATLAB, and the etching process was also simulated with Silvaco. According to the simulation results, put forward optimum design of release window. The resonance simulations of FBAR with/without release window have been done by FEA software. The simulation results show that the aperture cavity type FBAR, i.e. the cavity type FBAR with release holes, still has distinct resonant characteristic, but the frequency of impedance zero point and impedance pole of the novel type FBAR are all drifted to higher frequency, and the effective electromechanical coupling coefficient and the quality factor are all reduced.

Abstract: Chemical etching is still preferred to plasma etching in numerous integrated circuits manufacturing steps. Indeed, it enables a better surface smoothness control, which is critical to obtain sufficient carrier mobility. During these steps, photoresist patterns protect underlying materials from etching. It is therefore mandatory to: 1) guarantee photoresist adhesion and keep patterns from being etched away; and 2) prevent surface degradation from etchants penetration down to the photoresist / material interface. To avoid this latter phenomenon, it is therefore crucial to know if etchants penetrate into the photoresist, and at which diffusion rate.

Abstract: The microminiaturization of semiconductor devices has made it necessary to control the wet etching process on the nanometer order. It is therefore extremely important to understand wet etching reactions in the nanoscale region of solid-liquid interfaces, in order to assist in optimizing process conditions to satisfy the severe demand for semiconductor devices. Simulations performed to analyze the behavior of liquid molecules in the nanoscale region have been reported ^[1], but there have been few reports of detailed experimental results. We here report detailed experimental results on the wet etching behavior of SiO₂ film in the nanoscale region between Si materials.

Abstract: A kind of hill-like black silicon have been designed and fabricated by using the combination method of KOH anisotropic etching and gold-assisted HF etching. Pillars array on the surface of a silicon sample was obtained by KOH etching with a SiN_x film dots pattern used as a mask. The sample was then etched in the oxidant HF solution catalyzed by Au nanoparticles for 5 minutes. The etched sample appears dark black. This black silicon is orderly hill-like textures in micro-scale with density nanopores on them. It can suppress the reflection to less than 4% in wavelength range from 250nm to 1000nm, and to about 2.5% at the wave number of 2000-4000 cm^-1. It also has high additional absorption in IR range.