The VPE consists of a reaction chamber and a lid. A heating element is integrated in the lid. It controls the temperature of the substrate to be etched. Wafer clamping can be achieved in two ways: Wafers can be clamped mechanically by using the clamping ring. The screwing is done from the backside of the apparatus, which is never in contact with the HF vapor. The 3 nuts are easy to handle with protection gloves. The other option is electrostatic clamping. Single chips (longer than 10 mm) as well as wafers can be clamped to the heating element. The backside of the wafer is protected from etching.
Liquid HF is filled into the reaction chamber. The reaction chamber is closed with the lid. The HF vapor is created at room temperature and the etching process starts spontaneously. The etch rate is controlled by the wafer temperature that can be adjusted from 35°C to 60 °C.
After processing, the acid can be stored in a reservoir for re-use in a sealable container. Liquid transfer is simply done by lowering the communicating reservoir with a handle. Due to gravity, the acid flows into the reservoir and can be closed by two valves. Refilling the reaction chamber is done by opening the valves and lifting the handle. The acid flows into the reaction chamber. The acid can be re-used for multiple etchings until it has to be replaced.
The VPE system has a small footprint and can easily be integrated into an existing flow box.