Infrared absorption photoinduced by visible light in a-SixC1-x:H is characterized by in guide pump and probe measurements in order to test its applicability to a low-cost micromodulator, fully integrable as a post-processing on-top of a standard microelectronic chip. The Photoinduced Absorption phenomenon in amorphous silicon arises from an alteration of the defect state population by decay of carriers photogenerated by visible light. These levels, deep in the gap, are strongly involved in interactions with IR radiation, and then the VIS illumination modifies their optical properties by increasing the IR absorption coefficient value. Test waveguiding devices are fabricated by Plasma Enhanced Chemical Vapour Deposition on silicon wafers, at temperatures lower than 180°C, and consist of a a-SiC:H/oxide stack. In particular, devices having a-SixC1-x:H cores with different doping and different carbon concentration are characterized. The 1.55 μm probe radiation generated by a DFB laser diode is efficiently transmitted through the a-SixC1-x core thanks to the step index waveguide structure. The pump system consists of low cost AlInGaP LEDs pulsed by a function generator, for an illumination intensity ranging from 0.15 up to 0.85 mW/mm2. Results show that the modulation effect increase for longer pump penetration depth and for higher doping concentration. The phenomenon strongly depends on the carbon introduction in a-Si:H. Digital transmissions tests at 300 kbit/s were performed.
A characterization of low temperature silicon-glass anodic bonding (AB) parameters is presented here. Silicon-glass couples are bonded at temperature and voltage in the ranges of (200-430)°C and (0.2-2.5)kV, respectively. Two different electrodes are used for applying voltage, single point and planar. Low voltage, low temperature and short bonding time are investigated for different glass thickness and electrode type. The results show that the planar electrode provides a bonding time reduced to less than 5min against the few hours obtained by point electrode, and only slightly dependent on glass thickness. The bond strength of the bonded couples starts to be over the bulk glass strength at 300°C, when using planar electrode, and the high quality bond does not show voids. These results are particularly interesting in case of low temperature, and can be considered better than others presented in literature considering the simpler set-up and the novel electrode type used here.
In addition, employment of above mentioned works are demonstrated for the fabrication of sensing microcomponents in lab-on-chip applications. The compatibility of porous silicon (PSi) and the very quick AB process, performed at low temperatures in order to prevent silicon pore filling with thermal oxides, is confirmed here. Satisfactory strength and bond quality was obtained at temperatures as low as 200°C, at voltages of 2500V, with process times lower than 1,5 minutes.
In this communication, the compatibility of porous silicon and anodic bonding technologies for the realization of sensing microcomponents in lab-on-chip applications has been demonstrated. The two techniques have been combined for the fabrication of a microsensor with biological and chemical molecules sensing capability, in view of its miniaturization and integration with smart micro-dosage systems.
A gas analyzer based on chromatography method using silicon- glass components has been built. Its main components were made by using MAMS-like technology, and its conception is concurrent to the idea of an integrated silicon chromatography proposed by SC Terry.