Polycrystalline silicon reactor

1. A polycrystalline silicon reactor in which the polycrystalline silicon is deposited by supplying raw-material gas to a heated silicon seed rod comprising:

a bottom plate on which the silicon seed rod stands, having a dished upper surface formed in a recessed shape so as to descend toward a center thereof;

an opening of a path penetrating the bottom plate from the upper surface to a lower surface, being provided at a lowest part of the upper surface; and

a plug which is detachably attached to the opening.

2. The polycrystalline silicon reactor according to claim 1 , wherein

the plug has a protruded portion which protrudes from the upper surface of the bottom plate, and a through hole which opens at an upper surface of the protruded portion and connects the path to an inner of the reactor.

3. The polycrystalline silicon reactor according to claim 2 , wherein

a sloped annular portion which is higher than the upper surface of the bottom plate is provided at an outer peripheral part of the bottom plate along a circumferential direction, and

the plug is formed so that the upper surface of the protruded portion is higher at least than a top end of the sloped annular portion in a state in which the plug is attached to the opening.

4. The polycrystalline silicon reactor according to claim 1 , wherein the plug is made of carbon.

5. The polycrystalline silicon reactor according to claim 2 , wherein the path is connected to a raw-material gas supply source which supplies the raw-material gas.

6. The polycrystalline silicon reactor according to claim 1 , wherein a sloped annular portion which is higher than the upper surface of the bottom plate is provided at an outer peripheral part of the bottom plate along a circumferential direction.

7. The polycrystalline silicon reactor according to claim 1 , further comprising a cylindrical coolant path surrounding an outer peripheral of the path.