Microfabrication has gained immense importance in hardware based industries as most companies dealing with Integrated Circuit (IC) manufacturing find it to be of utmost importance. However, microfabrication techniques are critical and require specialized instruments dedicated to the development of high-end products.
In India, majority of the hardware based companies do not have a manufacturing unit and hence, the hardware implementation of a design is carried out in specialized laboratories situated abroad. Very few laboratories in India are equipped with the facility of microfabrication tools, but are dedicated towards academic research purpose only. Devices fabricated from such laboratories lack industry precision and do not cater to the batch processing techniques.
Tools or equipment for microfabrication include those like oxidation furnace, laser writing tool, lithography tool or mask aligner, diffusion tool, thin film deposition tools, RF sputtering tool, thermal evaporator, electron beam evaporator, chemical vapour deposition tools, dry/plasma etching tools, to name a few. These equipment require very high precision and are necessary to be installed in a clean room environment having very low particle count. Also, the internal temperature, pressure and humidity of the clean room are to be monitored at a regular basis such that the factors are maintained at an optimum level. Higher temperature or humidity conditions may lead to malfunctioning of the instruments and the device fabricated would not meet the dimension criteria as desired. It is important to note here that microfabrication techniques are employed to fabricate devices having highly miniaturized dimensions of micrometer (10-6) order or even less. The dust particles in air or even the diameter of a human hair is of the order of a few microns and is thus comparable to the size of the fabricated device. Hence, it is of utmost importance for the laboratory users to wear aprons concealing a major part of their body along with protective goggles and chemical resistant gloves to minimize contamination issues and assure maximum safety from chemical spillage. Also, a maximum limit to the total number of workers entering the clean room in a definite period should be set, since, presence of many individuals contribute to contamination risks resulting in gradual increase of the surrounding temperature and humidity.
Microfabrication consists of fabrication of several devices implemented on a particular substrate platform. Semiconductor substrates are used which are available in the form of wafers which are flat (250-500 microns thick), disc like structures available in different diameter sizes. Most widely used substrate is silicon, since it is less expensive and naturally available. Silicon substrates of low resistivity values (0.1-100Ω-cm) are employed for electronic device implementation whereas a higher resistivity alternative (>10kΩ-cm) is required for devices operating at Radio Frequency (RF) ranges. Low resistivity silicon substrates are lossy since the substrate conductivity is high and contributes to sufficient leakage current. High resistivity substrates on the other hand, have minimal substrate conductivity and are less lossy. But the huge expense associated with the procuring of high resistivity silicon substrates has urged to bring in alternative substrate materials to address the present cause. Glass, quartz and fused silica are well known low-loss substrates which are widely used to fabricate devices operating at the RF range. Germanium or III-V compounds like Gallium Arsenide (GaAs) or Indium Phosphide (InP) are also being used to fabricate limited number of devices dedicated towards a very specialized application.