JAWAHARLAL NEHRU TECHNOLOGICAL UNIVERSITY HYDERABAD B.Tech IV MEMS DESIGN Previous Question Paper (September - 2022 - R18)

RF MEMS refers to the integration of micro-electromechanical systems technology into radio frequency circuits. These devices utilize mechanical movement at the micro-scale to perform signal processing functions, such as switching, tuning, or filtering. Key advantages include low insertion loss, high isolation, and superior linearity compared to solid-state components like PIN diodes or FETs. Common examples include MEMS switches, tunable capacitors, and micro-machined inductors.

Microfluidic systems involve the manipulation and control of fluids in channels with dimensions ranging from tens to hundreds of micrometers. These systems leverage unique physical phenomena at the micro-scale, such as laminar flow, high surface-to-volume ratios, and capillary forces. They are widely used for lab-on-a-chip applications, chemical analysis, and biological sensing, allowing for precise control of reagents, reduced sample consumption, and rapid analysis times.

Photolithography is the fundamental process used in MEMS fabrication to transfer geometric patterns from a mask onto a substrate, typically a silicon wafer coated with a light-sensitive material called photoresist.

1. Surface Preparation: The wafer is cleaned and dehydrated to ensure proper adhesion of the photoresist.
2. Spin Coating: A liquid photoresist is applied to the wafer and spun at high speeds to create a uniform, thin layer of precise thickness.
3. Soft Bake: The wafer is heated to evaporate solvents from the photoresist, improving its stability.
4. Alignment and Exposure: The wafer is aligned with a photomask containing the desired pattern. UV light is passed through the mask, exposing the photoresist. In positive resist, exposed areas become soluble; in negative resist, exposed areas become insoluble.
5. Development: The wafer is immersed in a developer solution that dissolves the soluble portions of the photoresist, leaving behind the patterned relief structure.
6. Hard Bake: A final heating step hardens the remaining photoresist to withstand subsequent etching or deposition processes.