MODEL RELEASED. Integrated circuit manufacture. Technician in clean-room clothing holds newly- manufactured integrated circuits, in this case for use in an high-frequency sound (ultrasound) sensor The technician processed part of the circuit's surface (substrate) using the machine in the background. The substrate is mainly made of a semiconductor such as silicon. The concentration and distribution of chemical impurities in the substrate determine what properties the circuit will have. Integrated circuits can be much smaller than those made of individual components connected together.