Derivation and Experimental Validation of a Stacked Working Coil Structure for High-Speed Heating in Semiconductor Wafer Induction Heating Systems

This paper derives an optimal stacked working coil structure for high-speed heating in a semiconductor wafer induction heating (IH) system. The eddy current loss of the susceptor (Peddy) is proportional to the square of the switching frequency (fsw) and the maximum magnetic flux density (Bm). However, the equivalent parameters vary with the number of turns (N). A lower N results in lower equivalent inductance (Leq) and Bm, but requires higher fsw to meet the target equivalent resistance (Req). In contrast, increasing N increases Bm but reduces the fsw range satisfying Req. Therefore, the working coil design must consider the trade-off between fswand Bm. Finite element analysis (FEA) based JMAG simulations are used to design single layer and double layer stacked coils and analyze heating characteristics. A 1kW half bridge-series resonant inverter (HB-SRI) based 12-inch class wafer IH system is implemented to experimentally verify the proposed coil selection.