Silicon dioxide, nitride and polysilicon layers are formed on the wafer during a number
of high-temperature furnace processes. The wafers are exposed to various gases,
which either react with the silicon, causing it to oxidize and form an SiO2 layer, or react
with each other to form poly and nitride deposits. These layers are patterned using
photolithography and form the layers of the diodes, transistors, and capacitors of the
circuit. High-temperature furnaces are also used to introduce and diffuse dopants into
the wafers.