Wafer holder

A method of setting a critical distance dc between a base arrangement and a wafer carrier plate mounted on a drive shaft,

• the method comprising:
• determining an average distance dcA by measuring an actual critical distance dc several times in different positions of the wafer carrier plate in relation to the base arrangement, calculating a mean value thereof, and setting the average distance dcA to be equal to the mean value;
• comparing the average distance dcA to a nominal distance dcN, and in case of a difference between the average distance dcA and the nominal distance dcN surmounting a predetermined differential step:
• demounting said drive shaft together with said wafer carrier plate and said distance setting device from the base arrangement;
• adjusting the critical distance dc by said distance setting device to the nominal distance dcN in a demounted state of the drive shaft and the wafer carrier plate and locking the distance setting device on the drive shaft;
• mounting said drive shaft together with said wafer carrier plate and said distance setting device to the base arrangement.

A rotary drive shaft and vacuum feedthrough having a drive shaft and a distance setting device, the drive shaft comprising

• a shaft head and a shaft foot, wherein the shaft head is configured to mount a wafer carrier plate on the shaft head;
• a power coupling area at or near the shaft foot;
• an elongated sealing surface on an outer circumference of the drive shaft;
• wherein the distance setting device and is mounted lockable to the drive shaft and has a gliding surface to support the distance setting device and the drive shaft when the distance setting device is locked to the drive shaft.