The development of compact light modulators integrated on the same chip as the signal processing opens many opportunities for combining inter-chip optical communications with standard silicon circuitry. The use of surface micromachining allows high speed of operation and small size integration with other circuitry. The optical and mechanical requirements for the devices also have to be considered, to ensure compatability with standard silicon processing. A surface micromachining process, using an oxide sacrificial layer and poly/nitride/poly membranes, has been developed. This paper presents the optical and mechanical considerations in the development of a compact micromachined silicon Fabry-Perot interferometer. Initial tests have shown that these micromachined membranes represent a compact and effective light modulating method.

Surface micromachined tuneable interferometer array

Design, development and reliability testing of a low power bridge-type micromachined hotplate

A MEMS hotplate consisting of a double spiral platinum-based element was designed and simulated using MEMS-CAD tool COVENTORWARE. A platinum resistor of 115  Ω was fabricated on a 0.6  μm-thickSiO2 membrane of size 120  μm×120  μm. The hotplate consumes 54 mW when heated up to 756°C. The temperature coefficient of resistance of platinum was measured and found to be 2.19×10−3/°C. The fabrication and reliability testing of the hotplate are described. The test results show that the hotplate can continuously operate at 580°C for 5.5 h and it can sustain at least 60 cycles of pulse-mode operation at 530°C with very low temperature and resistance drifts. The maximum current capability of the hotplate was found to be 13.4 mA without any damage to the structure.

Fabrication and reliability study of a double spiral platinum-based MEMS hotplate

Recently, there has been high demand on miniaturizations of bio-instruments and wide range gas flux measurement in the field of chemistry and mechanics. This paper presents the design, fabrication, and characterization of a silicon-glass-based thermal distribution gas flow meter (20 mm × 10 mm × 1.6 mm) with a wide detection range. To facilitate the fabrication and maintain the stability of the sensor, a platinum (Pt) thin film was adopted as the heater and thermometers. Both the thermal property and temperature sensitivity of Pt thin film were characterized. SiO 2 passivation layers were deposited on top of the Pt film to prevent thermal and electrical shift of sensitive elements. Three pairs of thermometers were constructed beside the heater. Sensitivity and gas flux range of the gas flow meter can be increased by alternate use of these three sensor pairs. We also introduced a specific hardware control circuit system for real-time gas flux monitoring through the connection with a computer interface. The proposed gas flow sensor device was capable of measuring gas flux within the range of 0.8–2800 ml/min, thus demonstrating the potential for a wide range of applications.

A silicon-glass-based microfabricated wide range thermal distribution gas flow meter

A glass-based continuous-flow polymerase chain reaction (PCR) chip has been designed and fabricated. The device consists of a glass microfluidic channel, three NiCr heaters, and three Ni thermometers on the silicon substrate. An intelligent temperature-control circuit system has been designed to achieve desirable temperature control (95, 72, and 55°C) at the three temperature zones of the PCR chip. Simulation underneath the microfluidic channel using the finite element method shows that the temperature distribution through the three temperature zones are relatively uniform. A mixture of DNA samples for PCR was allowed to flow through the microfluidic channel under different flow rates. The amplified sample of the target DNA obtained from the PCR chip was then separated by electrophoresis and was analyzed using an ultraviolet analyzer. The result indicates that DNA amplification can be achieved and that its amplification factor depends greatly on the injection rate of the sample. The optimum sample-flow rate is 0.6 μl/min.

Glass-Based Continuous-Flow PCR Chip With a Portable Control System for DNA Amplification

The development of PCR chip shortens the reaction time of DNA amplification, reduces the bulk of reaction reagents; therefore, it is widely applied to biomedicine and other related fields. Since PCR reaction is completed through three different precise temperature zones periodically, the sensitivity of temperature measurement and the heating property of the metal membrane must be highly regarded. In this paper, three kinds of membranes, Ni, Pt, and Ni–Cr, were fabricated on silicon substrates; their resistance–temperature characteristics and heating properties are discussed. The results show that Ni and Pt films have good linear resistance–temperature relationship; the heating property of Pt film is superior to that of Ni–Cr film. The PCR chip with Pt film microheater can reach 150°C in a short time with 25 V voltage.

Weiping Yan

Papers

Study on metal membrane temperature sensor and microheater for pcr chip