Heating of Low-Resistivity Semiconductor Ribbons and Wafers with Traveling Microwaves

A technique for using traveling microwaves to heat low-resistivity semiconductor ribbons (which are rectangular or nearly so) or wafers (which are round or nearly so) without a susceptor is described. The technique is believed to hold promise for uniformly heating as many as thirty samples simultaneously. The applicator is essentially a section of rectangular waveguide. Its relatively simple geometry facilitates the formulation of an appropriate boundary-value problem. Solution of this problem by numerical methods leads to values for the complex propagation constant as a function of various parameters of interest. Theory indicates that the absorption of microwave energy in the samples can be nearly uniform if the width of the waveguide is properly chosen. Measurements of attenuation constant, and voltage-standing-wave-ratio made at 2.45 Ghz are in satisfactory agreement with theoretical predictions. Preliminary measurements of temperature distributions using temperature sensitive lacquers are consistent with theoretical predictions.