Conduction Heating in RTP Fast, and Pattern-Independent

Various types of conduction-based RTP systems are discussed. It is shown that simple hot plate systems suffer from severe bow of the wafer, when placed directly on the susceptor. This results in non-uniform heating. A solution is to place the wafer on pins; however, this considerably reduces the heat-up rate. An effective way to heat wafers through conduction fast and wellcontrolled is by placing it in a so-called gas bearing, an arrangement in which the wafer floats in between two hot blocks, at a well-controlled, small distance from both blocks. The heat-up rate in this so-called Levitor system is very high (~900ºC/s) and uniform. It is demonstrated that this conduction-based system does not suffer from non-uniformities caused by variations in emissivity and/or pattern density across-wafer or within-die. In a direct comparison on pattern-dependent heating effects, substrates with trenches with varying dimensions are spike-annealed in a state-ofthe- art lamp system and in the Levitor. It was shown that temperature non-uniformities in the lampbased and the conduction-based systems are > 40ºC and < 1ºC, respectively. The conclusion is that the Levitor provides emissivity and pattern-independent heating.