Polycrystalline silicon reactor
A polycrystalline silicon reactor which can prevent polycrystalline silicon which deposits on the surface of an electrode holding a silicon seed rod from being peeled off is provided. In a polycrystalline silicon reactor which applies an electric current to a silicon seed rod provided within a furnace, thereby heating the silicon seed rod, brings a source gas supplied into the furnace into reaction, and deposits polycrystalline silicon on the surface of the silicon seed rod, the reactor includes, at a bottom plate of the furnace, an electrode holder provided so as to be electrically insulated from the bottom plate, and a seed rod holding electrode connected to the electrode holder, and holding the silicon seed rod toward the upside. Concavo-convex portions exposed to a furnace atmosphere is provided at an outer peripheral surface of the seed rod holding electrode.
1. A polycrystalline silicon reactor in which an electric current is applied to a silicon seed rod provided within a furnace, thereby heating the silicon seed rod, a source gas supplied into the furnace is brought into reaction, and polycrystalline silicon is deposited on the surface of the silicon seed rod, comprising;
at a bottom plate of the furnace, an electrode holder provided so as to be electrically insulated from the bottom plate,
a seed rod holding electrode connected to the electrode holder, and holding the silicon seed rod upward, wherein a concavo-convex portions exposed to a furnace atmosphere is provided at an outer peripheral surface of the seed rod holding electrode, and
a cylindrical lock nut screwed on the concavo-convex portion of the seed rod holding electrode and surrounding a portion of the seed rod holding electrode for fixing the seed rod holding electrode, wherein
an upper end of the seed rod holding electrode is provided with a tapered portion whose width decreases upward, and the taper angle of the tapered portion is equal to or more than 70° and equal to or less than 130°,
an outer surface of the seed rod holding electrode exposed to the furnace atmosphere is composed of the tapered portion and the concavo-convex portions, and
a lower boundary of the tapered portion is directly connected with an upper boundary of the concavo-convex portions.
2. The polycrystalline silicon reactor according to claim 1 , wherein the concavo-convex portions exposed to a furnace atmosphere is provided along most of the outer peripheral surface of the silicon seed rod holding electrode.
3. The polycrystalline silicon reactor according to claim 1 , wherein the concavo-convex portions exposed to a furnace atmosphere is provided along the outer peripheral surface of the silicon seed rod holding electrode not including the tapered portion.
4. The polycrystalline silicon reactor according to claim 1 , wherein the cylindrical lock nut has concavo-convex portions respective to the concavo-convex portions provided at the outer peripheral surface of the silicon seed rod holding electrode and connects to both the silicon seed rod holding electrode and the electrode holder.
5. The polycrystalline silicon reactor according to claim 1 , wherein the silicon seed rod holding electrode comprises:
an opening at the tip of the tapered portion of the silicon seed rod holding electrode, one end of the silicon seed rod being held by the opening; and
a locking screw, which is inserted and fitted through a screw hole provided at the lateral side of the tapered potion; and
the silicon seed rod is pressed from the lateral side by the locking screw.