Metals are deposited on the semiconductor devices in order to make electrical contact to the devices. Metals used are typically aluminum or gold and are deposited by thermal evaporation in a bell jar evaporator.
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1. Wafer chips are loaded into a specially-designed holder that slides into a slot in the evaporator. |
| 2. The holder is placed in the evaporator, metal is loaded into a tungsten boat or onto a tungsten filament. The shutter is rotated into place and the bell jar replaced. |  |
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3. Once the bell jar is replaced and a seal made between its o-ring and the evaporator's baseplate, the system is evacuated. Once a low pressure is attained, current is run through the boat or filament containing the metal to be evaporated. The metal melts and then evaporates coating the chips in the holder. The thickness of the film is measured by a quartz crystal monitor inside the jar. |