Method for continual preparation of polycrystalline silicon using a fluidized bed reactor

A method for preparation of polycrystalline silicon using a fluidized bed reactor for preparation of granular polycrystalline silicon,

• wherein a reaction gas outlet of a reaction gas supplying means, that supplies a silicon-containing reaction gas so that silicon deposition may occur while a bed of silicon particles formed inside a reactor tube remains fluidized, is located inside of the bed of silicon particles;
• wherein the reaction gas outlet extends into the reactor tube through its lower end and comprises an outlet end that establishes a reference height separating an upper and lower spaces in the reactor tube;
• and
• wherein the upper space comprises a reaction zone that provides for silicon deposition by the reaction gas, and the lower space comprises a heating zone that provides for heating the silicon particles:
• the method comprising:
• (i) a silicon particle preparation step, wherein the reaction gas is supplied by the reaction gas supplying means so that silicon deposition occurs on the surface of the silicon particles in contact with the reaction gas, while silicon deposit is accumulated on an inner wall of the reactor tube encompassing the reaction zone;
• (ii) a silicon particle partial discharging step, which follows the silicon particle preparation step, wherein, without requiring the supply of the reaction gas, a part of the silicon particles, which are comprised in the bed of silicon particles remaining inside the reactor tube after the silicon particle preparation step, is discharged out of the fluidized bed reactor by a particle discharging means so that the height of the bed of the silicon particles does not exceed the height of the reaction gas outlet;
• (iii) a silicon deposit removal step, which follows the silicon particle partial discharging step, wherein, without requiring the supply of the reaction gas, the silicon deposit is removed by supplying an etching gas into the reaction zone, which reacts with the silicon deposit to form gaseous silicon compounds;
• and
• (iv) a silicon article replenishing step, wherein, after removing the silicon deposit and terminating the supply of the etching gas, silicon particles are replenished into the reactor tube.