Abstract:
Siemens CVD reactors are sealed in a manner which facilitates long production campaigns without refurbishing the seals, by the use of at least two seals, and an electrically insulating member having a thermal conductivity of from 1 to 200 W/mK, a sustained use temperature of at least 400° C., and a resistivity of more than 1-109 Ωcm.
Abstract:
Electrode support seals in a Siemens reactor for the deposition of polycrystalline silicon are protected against thermal stress and degradation, and shorting by falling fragments is prevented by shielding having a high resistivity and also a high thermal conductivity.
Abstract:
The yield and quality of polysilicon rods produced in the Siemens process are increased by preventing pieces of silicon too large to be removed by flushing with gas from entering reaction gas inlets and offgas outlets by means of protective elements installed in the inlets and/or outlets.
Abstract:
Reflective silver coatings on the inside surfaces of a Siemens reactor for polycrystalline silicon production are improved by a cold forming after-treatment of the silver coating.
Abstract:
Electrode assemblies useful, inter alia, for mounting thin rods in Siemens reactors for manufacture of polysilicon, have a base segment which receives a holder segment, and an insert, interfacial surface(s) of which have depressions and/or elevations which reduce contact surface area, allowing the holder, base segment, insert, and optional intermediate segments to be constructed of materials having different thermal conductivities.
Abstract:
Improved sealing of Siemens reactor electrodes which results in improved reactor campaign times, is accomplished by use of an electrically insulating ring in combination with two seals, a first seal located in a groove in the insulating ring or in a groove in the reactor base plate adjacent the insulating ring, and a second seal not contained in a groove.
Abstract:
Deposition on a sightglass in a reactor for CVD deposition of silicon is reduced by conducting a first purge gas stream substantially parallel to the reactor end surface of the sightglass, and conducting a second purge gas stream within the sightglass tube at an angle from the sightglass surface toward the interior of the reactor.
Abstract:
The invention provides a polycrystalline silicon rod having a total diameter of at least 150 mm, including a core A having a porosity of 0 to less than 0.01 around a thin rod, and at least two subsequent regions B and C which differ in porosity by a factor of 1.7 to 23, the outer region C being less porous than region B.
Abstract:
Deposition on a sightglass in a reactor for CVD deposition of silicon is reduced by conducting a first purge gas stream substantially parallel to the reactor end surface of the sightglass, and conducting a second purge gas stream within the sightglass tube at an angle from the sightglass surface toward the interior of the reactor.
Abstract:
The deposition of polycrystalline silicon onto heated filament rods in a Siemens process is improved by supplying reaction gas at least partially through nozzles in the vertical wall of the deposition reactor, at an angle of 0° to 45° to the reactor wall, towards the base plate of the reactor.