S. H. Kong

Infrared micro-spectrometer based on a diffraction grating

The optical properties of crystalline silicon in the IR spectral range have been used for the realisation of a grating type micro-spectrometer. An aluminium metallisation on a double side polished silicon wafer is used for fabrication of the multi-slit gratings. The dispersed spectrum propagates through this silicon wafer and is projected on an array of polysilicon thermopiles, integrated in a second bulk micromachined silicon wafer. The two wafers are bonded at low temperature. An IR spectrometer results, which is simple to fabricate and remains compatible with standard IC processing.

Design and fabrication of on-chip integrated polySiGe and polySi Peltier devices

Abstract On-chip integration of Peltier devices introduces a number of new fabrication considerations and yields a device with increasingly complex operating characteristics, when compared to the discrete device. Due to fabrication compatibility, polycrystalline SiGe (polySiGe) and polycrystalline Si (polySi) are the thermoelectric materials of choice. Device performance is compared for different thermoelectric materials, and the impact of the non-idealities on performance is analysed, interpreting the results in a graphical manner. The primary conclusion from this study is that, although often ignored, the contact resistance of the device is the most prominent non-ideality. Using a fully compatible process, various Peltier devices have been fabricated. The initial values from the measurements performed on both polySi and polySiGe correspond well to those found in literature, validating the design concept, although further optimisation is required.

Single-chip CMOS optical microspectrometer

Abstract Numerous applications, e.g., systems for chemical analysis by optical absorption and emission line characterization, will benefit from the availability of low-cost single-chip spectrometers. A single-chip CMOS optical microspectrometer containing an array of 16 addressable Fabry–Perot etalons (each one with different resonance cavity length), photodetectors and circuits for read-out, multiplexing and driving a serial bus interface has been fabricated. The result is a chip that can operate using only four external connections (including Vdd and Vss) covering the visible spectral range of the spectrum with FWHM=18 nm. Frequency output and serial bus interface allow easy multi-sensor, multi-chip interfacing using a microcontroller or a personal computer. Power consumption is 1250 μW for a clock frequency of 1 MHz.

Spectral performance of a silicon IR microspectrometer

The performance of an optical IR microspectrometer fabricated in silicon using IC-compatible micromachining is presented. The components are distributed over two silicon wafers. One contains an aluminum-based grating and the other an array of poly-silicon thermocouples with readout circuits. The optical path is defined after low-temperature aligned wafer-to-wafer bonding. Design considerations, fabrication and performance are presented. Measurements confirm an IR operating range between 1 and 9 /spl mu/m and a half-power spectral resolution of 0.5 /spl mu/m.

Performance of integrated silicon infrared microspectrometers

The performance of a microspectrometer fabricated in silicon using micromachining techniques is presented. The optical system is composed of two bonded silicon wafers, which have been subjected to microelectronic process compatible micromachining to co-integrate the optical components (an aluminum based grating, an optical path in crystalline silicon and array of poly-silicon thermo-couples) with readout circuits in silicon. Design considerations, fabrication and performance are presented. Measurements confirm an IR operating range between 1 and 9 µm and a half-power spectral resolution of 0.5 µm.

Thermophysical Characterisation of PolySi 0.7 Ge 0.3 for Use in Thermoelectric Devices

Polycrystalline silicon germanium (polySiGe) provides a good balance between thermoelectric performance and fabrication compatibility, making it highly suitable for use in integrated Peltier elements. Unfortunately, the performance of integrated Peltier elements does not only depend on the properties of polySiGe, but also on other properties like contact resistance and thermal conduction through supporting layers. Although the primary intent of this paper is to present the first of the thermophysical properties of polySiGe, the other properties required to determine the performance of polySiGe Peltier elements are also addressed.

Study on the Behaviour of Various Substrate Geometries for Use As Passive Heat Sink

Performance of many high-accuracy (electronic) applications is reduced by thermal fluctuations within the application. The simplest and most common technique to reduce those effects is compensation, e.g. by dynamic element matching [1]. Although such techniques can significantly reduce the effect of fluctuations, they do not remove the error source, which is still preferable from a viewpoint of metrology.

Fabrication and Optical Measurements of Multi-slit Grating Based Infrared micro-spectrometer

Multi-slit diffraction grating based integrated silicon micro-spectrometers for various infrared wavelength ranges have been realised using bulk micromachining and low temperature silicon-silicon fusion bonding [1]. The transparent optical property of silicon for infrared wavelength range provides a good optical path for incident infrared light. In addition, the high reflectance of aluminium for infrared results in an efficient multi-slit type grating. The grating fabrication by a normal metal deposition with a high accuracy on a double side polished wafer makes the fabrication process simple and compatible with standard IC processing.

Dry Release of Metal Structures in Oxygen Plasma

A surface micromachining fabrication scheme based on organic sacrificial layers and dry-release in oxygen plasma is presented. Free-standing metal structures are formed using conventional photoresists as a sacrificial layer on which a metal structural layer is evaporated and patterned. Structures are subsequently dry-released in an oxygen plasma. For the HPR504 and HiPR6517 photoresists, the lateral under-etching rate (power 1000 W) of about 1 μm/min was found. The presented dry-release technique is fully compatible with standard silicon IC processing and can be applied as an post-processing process module. The technique eliminates any sticking problem and simplifies the processing.