Thermocouple guide and ceramic heater

1. A ceramic heater comprising:

a ceramic plate formed in a disk-like shape and having a wafer placement surface;

a tubular shaft bonded to a rear surface of the ceramic plate on an opposite side to the wafer placement surface;

an inner-peripheral-side resistance heating element embedded in an inner peripheral zone of the ceramic plate;

an outer-peripheral-side resistance heating element embedded in an outer peripheral zone of the ceramic plate;

associated components including a pair of terminals of the inner-peripheral-side resistance heating element and a pair of terminals of the outer-peripheral-side resistance heating element;

an elongate hole extending from a start point in a region of the rear surface of the ceramic plate, the region being positioned within the tubular shaft when viewed from below, to an end position in an outer peripheral portion of the ceramic plate;

an elongate groove defining an inlet portion of the elongate hole; and

a thermocouple guide comprising a straight tube portion; and a curved tube portion formed in continuation with the straight tube portion to turn an extension direction from the straight tube portion, wherein a cross-section of a tip-side part of the curved tube portion, the tip-side part occupying a predetermined range including a tip end of the curved tube portion, has an external shape that is obtained by linearly cutting both sides of a circle with the tip-side part of the curved tube portion being arranged in the elongate groove, and

further comprising a thermocouple inserted through both the thermocouple guide and the elongate hole, and

wherein a horizontal length of the elongate groove is set to be equal to a length of the tip-side part of the curved tube portion, and

wherein a width of the elongate groove is substantially the same as the tip side part of the curved tube portion.

2. The ceramic heater according to claim 1 , wherein the external shape of the cross-section of the tip-side part is a shape that is obtained by cutting both sides of a circle along two parallel chords having the same length.

3. The ceramic heater according to claim 1 , wherein the thermocouple guide is a seamless tube.

4. The ceramic heater according to claim 1 ,

wherein a curvature radius of the curved tube portion is 15 mm or more and 50 mm or less,

a stroke length of the curved tube portion is 15 mm or more and 50 mm or less, and

an angle through which the extension direction from the straight tube portion is turned by the curved tube portion is 50° or more and 90° or less.

5. The ceramic heater according to claim 1 , wherein the tip-side part of the curved tube portion is fitted into the elongate groove.