Electrostatic-chuck heater
An electrostatic-chuck heater is a Johnsen-Rahbek electrostatic-chuck heater and is used in a process of forming a conductive film on a wafer. The electrostatic-chuck heater includes a disc-shaped ceramic base including an electrostatic electrode and a heating resistor, and a hollow shaft attached to a side of the ceramic base that is opposite a wafer-mounting surface. A protruding ring is provided on the wafer-mounting surface and having an outside diameter smaller than a diameter of the wafer. A through-hole extends in a peripheral wall of the hollow shaft from a lower end through to an area of the wafer-mounting surface that is on an inner side with respect to the protruding ring. The through-hole allows gas to be supplied from the lower end of the hollow shaft into a below-wafer space enclosed by the wafer-mounting surface, the protruding ring, and the wafer mounted on the wafer-mounting surface.
1. A Johnsen-Rahbek electrostatic-chuck heater comprising:
a disc-shaped ceramic base having on one side a wafer-mounting surface on which the wafer is to be mounted, the disc-shaped ceramic base including an electrostatic electrode and a heating resistor;
a hollow ceramic shaft attached to a side of the disc-shaped ceramic base that is opposite to the one side having the wafer-mounting surface;
a protruding ring provided on the wafer-mounting surface and having an outside diameter smaller than a diameter of the wafer;
a through-hole extending in a peripheral wall of the hollow ceramic shaft from a lower end through to an opening formed in an area of the wafer-mounting surface that is on an inner side with respect to the protruding ring, the through-hole allowing gas to be supplied from the lower end of the hollow ceramic shaft into a below-wafer space enclosed by the wafer-mounting surface, the protruding ring, and the wafer mounted on the wafer-mounting surface; and
wherein an area of the wafer mounting surface on an outer side with respect to the protruding ring is a surface without openings formed therein.
2. The Johnsen-Rahbek electrostatic-chuck heater according to claim 1 ,
wherein the wafer-mounting surface has a plurality of embossed parts provided in the area on the inner side with respect to the protruding ring and that are to come into contact with the wafer.
3. The Johnsen-Rahbek electrostatic-chuck heater according to claim 1 ,
wherein the protruding ring has a slit through which the inner side and an outer side with respect to the protruding ring communicate with each other.
4. The Johnsen-Rahbek electrostatic-chuck heater according to claim 1 ,
wherein an opening of the through-hole in the wafer-mounting surface includes a plurality of small holes each having a smaller diameter than the through-hole.
5. The Johnsen-Rahbek electrostatic-chuck heater according to claim 1 ,
wherein a force with which the gas supplied into the below-wafer space pushes up the wafer is smaller than a sum of a wafer-chucking force generated by energizing the electrostatic electrode and a force with which atmosphere above the wafer pushes down the wafer.
6. The Johnsen-Rahbek electrostatic-chuck heater according to claim 1 ,
wherein the electrostatic electrode is also used as a plasma electrode.
7. The Johnsen-Rahbek electrostatic-chuck heater according to claim 1 , further comprising:
a ring-shaped groove and/or a plurality of radially arranged grooves on the inner side with respect to the protruding ring.
8. The Johnsen-Rahbek electrostatic-chuck heater according to claim 1 ,
wherein the protruding ring has a surface roughness Ra of 1 μm or greater.
9. The Johnsen-Rahbek electrostatic-chuck heater according to claim 1 ,
wherein the through-hole has openings in the area of the wafer-mounting surface that is on the inner side with respect to the protruding ring and both in a central part and in an outer peripheral part, respectively, of the wafer-mounting surface.