What architectural advancement enabled the function of integrated circuits?

The function of integrated circuits is fundamentally enabled by semiconductor materials. Semiconductors, such as silicon and germanium, have electrical properties that can be modified by the addition of impurities, a process known as doping. This property allows semiconductors to effectively switch and amplify electronic signals, which is essential for the operation of integrated circuits that consist of numerous interconnected components, such as transistors and resistors, all fabricated on a single chip.

Unlike the other options, semiconductor materials provide the necessary control over electrical conductivity that makes the dense packing and functionality of integrated circuits possible. This capability is what revolutionized the electronics industry, enabling the miniaturization of circuits and the creation of complex electronic devices. While copper wires are indeed used to connect various components within an integrated circuit, they do not provide the foundational property necessary for the integrated circuit's operation on their own. Fiber optic cables relate to data transmission rather than internal circuit function, and glass vacuum tubes are an older technology that predates integrated circuits and does not facilitate their operation.