SESSION 2

1. LINEAR CIRCUIT DESIGN Unit 1 – IC FABRICATION Dr. I. Raja rajeswari Assistant Professor Department of EEEAdithya Institute of Technology Coimbatore

2. Session Plan Unit I – IC FABRICATION IC classification - fundamental of monolithic IC technology - epitaxial growth - masking and etching - diffusion of impurities - Realisation of monolithic ICs and packaging - Fabrication of diodes - capacitance, resistance, FETs and PV cell. Course Outcome CO1 – Outline monolithic IC fabrication process and fabrication of diodes, capacitance, resistance, FETs and PV Cell Dr. I. Raja rajeswari, Asst. Prof- EEE

3. Fundamental of monolithic IC technology • The most important process in IC fabrication is the formation of a silicon wafer through crystal growth. • Czochralski method is used for silicon crystal growth from which ultimately silicon wafers are produced. • The apparatus used for the crystal growth is called Czochralski crystal growth apparatus or puller. • The puller has four important subsystems namely furnace, crystal pulling mechanism, ambient control and control systems. • The furnace consists of a crucible, crucible support, rotation mechanism and heating element housed in a chamber. Dr. I. Raja rajeswari, Asst. Prof- EEE

4. Contd., This process is subdivided into number of sub processes as follows: 1. Slicing crystal Ingots The grown single-crystal silicon ingot is prepared and cut into thin circular slices called wafers using precision wire-sawing techniques. 2. Ingot trimming and grinding The ingot’s uneven ends are trimmed off, and its outer surface is ground to a precise diameter to meet standard wafer size specifications and improve uniformity. 3. Ingot slicing The cylindrical ingot is sliced into thin wafers using multi-wire saws. This step introduces surface damage and thickness variation, which must be corrected later. Dr. I. Raja rajeswari, Asst. Prof- EEE

5. Contd., Dr. I. Raja rajeswari, Asst. Prof- EEE

6. Contd., 4. Wafer etching Chemical etching removes damaged surface layers, residual stress, and micro-cracks created during slicing and grinding, improving crystal quality. 5. Wafer polishing Chemical Mechanical Polishing (CMP) produces an ultra-flat, mirror-smooth surface, essential for high-precision IC and solar cell fabrication. 6. Wafer cleaning Final cleaning removes particles, organic contaminants, and metal ions, resulting in device-ready wafers. Dr. I. Raja rajeswari, Asst. Prof- EEE