Producing high quality Si-wafers for monocrystalline solar cells or electronic semiconductor devices is a complex process with critical thermodynamic parameters. A common technique to stabilize the thermodynamic conditions in Cz crystal pullers is using a heat shield around the growing ingot. Especially in the region of the transition of the liquid Silicon melt to the solid ingot, very stable conditions are necessary to guarantee highest crystal quality and therefore highest quality end products. The thermodynamic conditions in the critical transition area from the liquid to the solid Silicon are strongly influenced by the gap distance of the heat shield and the hot Silicon melt. This gap distance will change during the grow process of the ingot and has to be readjusted. Therefore it is essential to measure and control this distance accurately and reliable.

NXT offers new, unique and patent applied equipment to measure the exact gap distance between a hot silicon melt and the lower edge of heat shield in a crystal puller.