Metallization and Wafer Testing

In metallization, metal films are used for interconnecting the components to form an integrated circuit.

After all diffusion and oxidation steps are completed, metal is deposited onto the surface of the wafer to 'wire' the device fabricated in the silicon together.

The metallization process involves putting the wafer into a large chamber and pumping air out of the system.

For Example: A piece of aluminium located on a tungsten 'boat' in the system is heated to high temperature, causing the aluminium to melt and evaporate. The evaporated aluminium will solidify into a thin film when it touches the silicon wafer.

After metallization, the wafer is completely covered by the aluminium. The wafer must be patterned and etched to form the actual 'wires' connecting individual devices into a circuit.
The wafer is covered with silicon dioxide, the various metal layers are interconnected by etching holes called 'vias' and depositing tungsten in them. Other metals besides aluminium can be used too.

Wafer Testing

The equipment for wafer testing marks each bad chip with a drop of dye. The proportion of the devices on the wafer found to perform properly is referred to as yield. The wafer with low yield are discarded because it has many bad chips.



 

culled from Introduction to Semiconductor Devices by Engr. Dr. Mrs. Gloria Chukwudebe