Device for insulating and sealing electrode holders in CVD reactors

• US 10,562,778 B2
• Filed: 10/10/2016
• Issued: 02/18/2020
• Est. Priority Date: 10/15/2015
• Status: Active Grant

• Current Assignee: Wacker Chemie AG (Dr. Alexander Wacker Familiengesellschaft Mit Beschrã¤Nkter Haftung)
• Original Assignee: Wacker Chemie AG (Dr. Alexander Wacker Familiengesellschaft Mit Beschrã¤Nkter Haftung)
• Inventors: Rennschmid, Dominik, Kraus, Heinz, Kutza, Christian
• Primary Examiner(s): Burkhart, Elizabeth A
• Application Number:
  US15/744,180
• Publication Number:
  US 20180208469A1
• Time in Patent Office: 1,226 Days
• CPC Class Codes: C01B 33/035 by decomposition or reduction of gaseous or vaporised silicon compounds in the presence of heated filaments of silicon, carbon or a refractory metal, e.g. tantalum or tungsten, or in the presence of heated silicon rods on which the formed silicon is deposited, a silicon rod being obtained, e.g. Siemens process
• CPC Class Codes: C23C 16/24 Deposition of silicon only
• CPC Class Codes: C23C 16/4409 characterised by sealing means
• CPC Class Codes: C23C 16/4418 Methods for making free-standing articles C23C16/01 takes precedence
• CPC Class Codes: C23C 16/46 characterised by the method used for heating the substrate C23C16/48, C23C16/50 take precedence

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.

Claims

1. An apparatus for insulating and sealing electrode holders in CVD reactors having an electrode suitable for accommodating a filament rod disposed atop an electrode holder made of an electrically conductive material and mounted in a recess in a floor plate, comprising:

an electrically insulating ring made of a material of construction having a specific thermal conductivity at room temperature of 0.2-50 W/mK, a minimum flexural strength of greater than 120 MPa, and a specific electrical resistance at room temperature of greater than 10⁹ Ω

cm, located between the electrode holder and the floor plate,

wherein at least two ring-shaped sealing elements for sealing between the electrode holder and the floor plate are present, wherein the electrically insulating ring or the electrode holder or the floor plate comprises at least one groove in which a first sealing element is secured, wherein at least one second sealing element not secured in a groove is present between the electrically insulating ring and the floor plate or between the electrically insulating ring and the electrode holder, and wherein the at least two ring-shaped sealing elements are not located on the same side of the electrically insulating ring.

2. The apparatus of claim 1, wherein the material of construction of the electrically insulating ring is selected from the group consisting of aluminum oxide, silicon nitride, boron nitride, zirconium oxide, and yttrium-oxide-, magnesium-oxide- or calcium-oxide-stabilized zirconium oxide.

3. The apparatus of claim 2, wherein the first sealing element is a graphite foil ring.

4. The apparatus of claim 1, wherein the first sealing element is a graphite foil ring.

5. The apparatus of claim 1, wherein the first sealing element is a metallic O-ring or a metallic seal having an open profile having a spring action.

6. The apparatus of claim 5, wherein the metallic seal has a C-profile and is coated with silver.

7. The apparatus of claim 1, wherein the second sealing element is a gasket comprising graphite or PTFE.

8. The apparatus of claim 7, wherein the gasket is chambered on the reactor-side seal circumference as a result of metal or silver foil being flanged around the reactor-side sealing surface of the gasket.

9. A process for producing polycrystalline silicon, comprising introducing a reaction gas comprising a silicon-comprising component and hydrogen into a CVD reactor comprising at least one filament rod which is disposed atop an apparatus of claim 1, the filament rod supplied with current via the electrode and thus heated by direct passage of current to a temperature at which polycrystalline silicon deposits on the filament rod.