Stacked silicon wafers about to go into furnace for annealing. Furnace annealing is a process used in semiconductor device fabrication which consist of heating multiple semiconductor wafers in order to affect their electrical properties. Heat treatments are designed for different effects. Wafers can be heated in order to activate dopants, change film to film or film to wafer substrate interfaces, densify deposited films, change states of grown films, repair damage from implants, move dopants or drive dopants from one film into another or from a film into the wafer substrate. Furnace anneals may be integrated into other furnace processing steps, such as oxidations, or may be processed on their own. Furnace anneals are performed by equipment especially built to heat semiconductor wafers. Furnaces are capable of processing lots of wafers at a time but each process can last between several hours and a day. Increasingly, furnace anneals are being supplanted by Rapid Thermal Anneal (RTA) or Rapid Thermal Processing (RTP). The reason for this is the relatively long thermal cycles of furnaces causes dopants that are being actived, especially boron, to diffuse farther than is intended. RTP or RTA fixes this by having thermal cycles for each wafer that is of the order of minutes rather than hours for furnace anneals.