10.1.2 Masks

The masks used in the following lithography step are high contrast positive masks, i.e., black on clear masks. They are made of glass covered by a thin film of opaque metal and they are directly produced from a digitized description of the layout of the integrated circuit, where usually an electron beam is used to transfer the patterns onto the masks.

The masks are also called reticles and are generally five times as large as the size of the chip to be produced. During the photolithographic process the opaque parts of the reticles prevent light of high frequency from reaching the wafer, which is covered with a photosensitive layer.