Exposition
Technological Evolution
Silicon Wafers
The manufacture of an integrated circuit is a complex process consisting of successively depositing and removing thin layers of conductor, insulator and semiconductor materials to produce a complex sandwich that contains all the interconnected circuits of a system.
The first step is to form a highly pure, silicon substrate, a wafer-like slice of silicon polished until it is as smooth as a mirror.
Most of the successive layers that are deposited on the wafer set out the shape and arrangement of the transistors and other elements. The process of marking the circuit on the wafer is called photolithography (carving using light). This is like projecting the image of the circuit design on a piece of photographic film, in this case the wafer.
Thousands of identical integrated circuits are created on the same wafer simultaneously. They are then cut, connected to the external pins and packaged. The components of an integrated circuit are so small and precise that they can be destroyed by a grain of microscopic dust.
They are manufactured in what are known as clean rooms, because the filtered air is almost completely dust free.
La mayoría de las sucesivas capas que se depositan sobre la oblea se corresponden con la forma y disposición de los transistores y otros elementos. El proceso de grabación del circuito sobre la oblea se denomina fotolitografiado (escribir sobre una piedra con luz). Equivale a convertir la oblea en un trozo de película fotográfica y proyectar sobre la misma la imagen del circuito deseado.
Sobre una misma oblea se crean simultáneamente cientos de circuitos integrados iguales, que posteriormente son cortados, conectados a los pines externos y encapsulados. Los componentes de un circuito integrado son tan pequeños y precisos que una mota de polvo microscópica puede destruirlos.
Los lugares donde se fabrican se denominan salas limpias, porque el aire se somete a un filtrado exhaustivo y está prácticamente libre de polvo.