Polycrystalline silicon manufacturing apparatus

1. A polycrystalline silicon manufacturing apparatus which supplies raw gas to the inside of a reaction furnace and supplies a current from an electrode to a silicon seed rod in a state where the vertically extending silicon seed rod is uprightly stood on each of the plural electrodes disposed in a bottom plate portion of the reaction furnace so as to heat the silicon seed rod and thus to deposit polycrystalline silicon on a surface of the silicon seed rod by means of the reaction of the raw gas,

wherein at least a part of the plural electrodes is configured as a two-holding electrode which holds two silicon seed rods;

each two-holding electrode includes only one electrode holder which is inserted in a perforation hole formed in the bottom plate portion and a pair of seed rod holding portions which are formed in an upper end portion of the electrode holder so as to have an interval therebetween;

the pair of seed rod holding portions are supported by the electrode holder with respect to the bottom plate;

a cooling passageway is formed in the inside of the electrode holder so as to flow a cooling medium; and

a lower end portion of the electrode holder perforating the bottom plate portion is connected to a cooling pipe communicating with the cooling passageway.

2. The polycrystalline silicon manufacturing apparatus according to claim 1 , wherein the silicon seed rods are formed into seed assemblies in which upper end portions of two silicon seed rods are connected to each other,

wherein both seed rod holding portions of each two-holding electrode respectively hold each one of silicon seed rods of two pairs of the seed assemblies; and

the two seed rod holding portions of each two-holding electrode are electrically connected to each other through the electrode holder of the each two-holding electrode.

3. The polycrystalline silicon manufacturing apparatus according to claim 2 , wherein plural pairs of seed assemblies are held by a pair of one-holding electrodes and the two-holding electrode disposed between the one-holding electrodes so as to be connected to each other in series in the form of one unit,

wherein a power source circuit which supplies a current to the seed assemblies is connected to the one-holding electrode and the two-holding electrode; and

a current supply to the one unit and a current supply to separated units obtained by separating the one unit into plural units are configured to be switched.

4. The polycrystalline silicon manufacturing apparatus according to claim 2 , wherein each seed assembly has a pair of silicon seed rods and a connecting member connecting the upper end portions of the pair of silicon seed rods.

5. The polycrystalline silicon manufacturing apparatus according to claim 1 , wherein the electrode holder of each two-holding electrode is branched into two branched parts at the upper end portion thereof, and the pair of seed rod holding portions are respectively formed on the branched parts.

6. The polycrystalline silicon manufacturing apparatus according to claim 5 , wherein the electrode holder of each two-holding electrode has a T-shape as a whole.