Gandi Sugandi

Electrochemically deposited and etched membranes with precisely sized micropores for biological fluids microfiltration

This paper presents simple and economical, yet reliable techniques to fabricate a micro-fluidic filter for MEMS lab-on-chip (LoC) applications. The microporous filter is a crucial component in a MEMS LoC system. Microsized components and contaminants in biological fluids are selectively filtered using copper and silicon membranes with precisely controlled microsized pores. Two techniques were explored in microporous membrane fabrication, namely copper electroplating and electrochemical etching (ECE) of silicon. In the first technique, a copper membrane with evenly distributed micropores was fabricated by electroplating the copper layer on the silicon nitride membrane, which was later removed to leave the freestanding microporous membrane structure. The second approach involves the thinning of bulk silicon down to a few micrometers thick using KOH and etching the resulting silicon membrane in 5% HF by ECE to create micropores. Upon testing with nanoparticles of various sizes, it was observed that electroplated copper membrane passes nanoparticles up to 200?nm wide, while porous silicon membrane passes nanoparticles up to 380?nm in size. Due to process compatibility, simplicity, and low-cost fabrication, electroplated copper and porous silicon membranes enable synchronized microfilter fabrication and integration into the MEMS LoC system.

Fabrication of MEMS Based Microspeaker Using Bulk Micromachining Technique

The advantages of micromachining over conventional fabrication include precise dimensional control, integration of on-chip circuits and potential low cost owning to batch processing. Fabrication microspeaker for hearing instrument application using MEMS technology is challenging because of certain critical requirements, including their small size, low driving voltage, high output sound pressure level, flat frequency response and low energy consumption. A small in size, lightweight, and low cost microspeaker is demanded for application such as cellular phones and hearing aids. The device consist of two part; first parts is a micromachined polyimide membrane as the sound generating plate, where thevoice coil placed on the top of membrane, and the coil is a single loop voice coil. The second part is back plate permanent magnet. The disc permanent magnet bonded on acoustic hole plate is Neodymium-Iron-Boron (NdFeB) with magnetization of 1.45 T, diameter 1.6 mm, and thickness 0.8 mm. The fabrication process and performance of the first result device is discussed, and the thickness of electroplated single loop voice coil copper 10 mm and acoustic hole bonded together. The total size of the microspeaker chip is 5 mm x 5 mm x 1.5 mm, polyimide membrane thickness 2 mm.

Effects of material and membrane structure on maximum temperature of microheater for gas sensor applications

The material selection for membrane is important in designing a microheater. A membrane is used as an insulator layer to prevent heat dissipation from the microheater to the substrate. At the same time, the thermal characteristic of the microheater is influenced by the insulator layer. A study on the effects of material and membrane structure on the maximum temperature of the microheater for gas sensor applications has been carried out using Heat Transfer Module of COMSOL 4.2. Three different membrane materials namely silicon nitride (Si3N4), silicon dioxide (SiO2) and polyimide and two types of membrane structures namely full-membrane and bridgemembrane have been chosen for the study. Their effects on the microheater temperature are presented. The resistive meander type of microheater is used in this study. The heater material is platinum. The thickness and the area of the heater are 2 μm and 600 μm × 680 μm respectively. The thickness of each membrane is 5 μm. The area of the full-membrane and the bridgemembrane are 2500 μm × 2500 μm and 850 μm × 850 μm respectively.

Compact electrodynamics MEMS-speaker

This paper describes the design, fabrication and characterization of an electrodynamic MEMS speaker. The miniaturized speaker consists of a deposited single turn microcoil on a 25 µm thick suspended polyimide diaphragm with a 2.5 mm diameter and a small volume permanent magnet Neodymium-Iron-Boron (Nd-Fe-B). A significant improvement of frequency response to sound pressure level of MEMS-speaker in sealed condition was achieved. The sealed measurement performed in a 1500 mm3 silicon rubber tube resulted in a peak amplitude of 90 dB-SPL at a frequency range of 1, 5 and 10 kHz and experienced magnitude boosting with a value of 25 to 30 dB at frequency below 1 kHz compared to unsealed condition. Peak magnitude level of 92.5 dB-SPL and 110 dB-SPL were achieved at the frequency of 200–500 Hz and 20–60 Hz respectively. The results shows that the fabricated MEMS speaker can be applied in ear canal applications such as hearing aids and music player earphones.

Effect of temperature on the etching rate of nitride and oxide layer using Buffered Oxide Etch

This paper presents the effect of temperature to the etch rate of nitride and oxide layers in Buffered Oxide Etch (BOE) solution. Either nitride or oxide layer is commonly used in the semiconductor fabrication process as a mask for the next wet etching process. A well-defined frame structure and reduced etching time will increase the productivity of the fabrication process. The approach starts with patterning the silicon nitride to study the frame structure that formed after the BOE process. Then, the patterned silicon nitride is dipped in BOE solution at two different temperatures, which are 25 °C and 80 °C. The structures that formed are compared, and it was evident that 80 °C gives a better mask structure. Next, the effect of temperature on the etching rate for oxide and nitride layers is further studied by varying the temperature from 40 °C up to 90 °C. At the end of experiment, it was found that temperature will improve the BOE etching process in terms of both time needed and the mask structure.

Physical characteristic analysis of solenoid-based coil structure

Measurement of low magnetic field has played an important role in many electronics applications such as military, non-destructive test, medical diagnosis and treatment. The presence of magnetic field, particularly the strength and direction, can be measured using magnetometer. Fluxgate magnetometer is one of the prominent type among many types of magnetometer due to its simple operating principle, robustness and durability. The main components of fluxgate magnetometer consisting of Driving Coils, Sensing Coils and Magnetic Core. In recent years, fluxgates are increasingly made into micro-scale through MEMS silicon processing technology. Physical characteristics of fluxgate coils such as width of the coil; distance between successive coil; and gap between top and bottom coils have an effect towards device miniaturization and performance. Therefore, physical characteristic analysis of coils is significant. This paper highlights analysis on physical characteristics of solenoid-based coil structure for a micro-scaled fluxgate magnetometer by means of finite element method (FEM) simulations. The results of this analysis can be used to design proper coils that could improve the performance of the device.