Papers by Author: Dong Ling Li

Abstract: A micro piezoelectric cantilever beam array is designed for vibration energy harvesting. A single degree of freedom analytical model is developed to predict the properties of the device and is verified by finite element method. The piezoelectric material Aluminum Nitride was chosen for the compatibility with the CMOS process. The devices consisting of 5 piezoelectric cantilever beams and one proof mass were fabricated using micromachining technology. The resonance frequency, voltage and power were tested at excitation acceleration of 5.0 g. The maximum output power of the device is 9.13 μW at the resonance frequency of 1315 Hz when piezoelectric beams are connected in parallel.

Abstract: It is presented a fabrication processing of a two step method in deep silicon etching for MEMS applications using an the UK company Surface Technology Systems plc (STS), inductively-coupled plasma (ICP) etch technique STS ICP deep dry etching system. A brief introduction of schematic process of etching deep trenches on silicon substrate is first given, then with two step method for etching deep trenches. The film bulk acoustic resonator (FBAR) devices have been fabricated using STS ICP deep dry etching system with maximum etch rate of 4.6μ m/min, depth more than 450μm and sidewall roughness no more than 0.14μm. At the end of the second step process, the etch selective ratio of silicon to silicon oxygen is enhanced to ensure the device yield. At the same time, the negative effects such as microloads effects, footing effects, lag effects and micrograss effects are suppressed effectively.

Abstract: It is known that the wet chemical etching of silicon in alkaline solution has attracted wide attention due to its advantages such as lower cost, simpler setup, higher rate, smoother surface at micro level, higher degree of anisotropy, and lower pollution. In this paper, the key processes of fabricating vacuum microelectronic accelerometer and slits are presented. The cone curvature radius of the silicon tip arrays less than 30nm was fabricated with wet anisotropic etching of silicon in 33wt. % KOH solution at 70°C added potassium iodine (KI) and Iodine (I2) as additive and the cone aspect ratio was about 0.7. Smooth surface after etching in 33wt. %KOH solution added isopropyl alcohol (IPA) at 80°C was obtained and lateral etching was less than 5um after etching several hours for etching depth over 400um. Scalar slits with bottom width 25um and depth 500um were attained. A constant etch rate lead to precise and reproducible production. The test result reveals that the process to a specific occasion can reach practical requirements.

Abstract: This paper presents a simple but reliable fabrication process for microfluidic devices on glass substrate using wet etching technology. Instead of using expensive Pyrex glasses as substrates and depositing expensive metal or polysilicon/amorphous silicon as etch masks in conventional method, glass slide is used as substrate and a single-layer negative photoresist RFJ-220 is used as the etching mask. The etch rates, generation of defects, undercut ratio and surface roughness are studied. In order to achieve high etching depth and smooth surface, buffered oxide etching with hydrochloric acid as additive is proposed. By proper cleaning and long-time hard baking, the undercut ratio can approach to 1. An 110μm depth microchannel with smooth surface is achieved. This fabrication process leads to a considerable reduction of process steps, fabrication time and material consumption. With this technique, we successfully fabricated a microfluidic device, which is used in the capture of hepatoma cells HepG2.