Kokusai DD 853 V Diffusion

The Hitachi Kokusai DD 853 V is a diffusion furnace. The furnace is manufactured by Hitachi Kokusai.^[1]

A diffusion furnace operates by creating a precisely controlled high-temperature environment within a horizontal quartz tube. The furnace is divided into multiple independently controlled heating zones to achieve a uniform temperature profile, or hot zone, across the load area.

Process gases are introduced into the tube to carry dopants or reactants to the wafer surfaces. The high temperature drives chemical reactions such as the thermal diffusion of dopant atoms into the wafer lattice or the growth of an oxide layer on the wafer surface.

In the semiconductor fabrication process, diffusion furnaces are employed in the front-end-of-line stage for core material modification. Wafers typically enter a diffusion furnace after cleaning and inspection and prior to the deposition of most thin films and patterning layers.

After thermal processing, wafers move to metrology stations for verification of process results, such as oxide thickness or sheet resistance. The wafers then proceed to subsequent deposition or lithographic steps to continue device construction.

The primary application of diffusion furnaces is the doping of semiconductor wafers to create regions of controlled electrical conductivity, such as p-type and n-type areas. A further key application is the thermal oxidation of wafers to grow insulating layers of silicon dioxide.