DE10244667B4 - Apparatus and method for the production of a synthetic quartz glass blank - Google Patents

Abstract

An apparatus for producing a synthetic quartz glass blank comprising a media container for containing a hydrolyzable siliceous raw material, a heater for heating the raw material in the media container, a deposition burner for producing SiO ₂ particles from the raw material, and a deposition burner and Media container connecting media line for transporting the raw material, which is in contact with a heating means, characterized in that the media line is designed as a flexible inner tube (1), and that the heating means comprises a flexible outer tube (2), the inner tube (1) under Forming a composite hose with a gap (5) through which a temperature-controllable fluid (7) flows between inner hose (1) and outer hose (2), wherein an additional heater (6) acting on the outer hose (2) heats the fluid (7) is provided outside.

Description

The invention relates to a device for producing a synthetic quartz glass blank, comprising a media container for receiving a hydrolyzable silicon-containing raw material, a heating device for heating the raw material in the media container, a deposition burner for producing SiO ₂ particles from the raw material, and a the media burner connecting the Abscheidebrenner and the media container for transporting the raw material, which is in contact with a heating means.

Furthermore, the invention relates to a method for the production of a blank made of synthetic quartz glass; wherein a hydrolyzable silicon-containing raw material heated in a media container, the heated raw material transported to a deposition burner, produced by means of this from the raw material SiO ₂ particles and the SiO ₂ particles are deposited on a rotating support to form the blank in layers.

method and device according to the present invention Invention can For example, for the production of semi-finished synthetic quartz glass for optical Fibers or for the manufacture of quartz glass components and equipment for the optics and the semiconductor device be used.

From the EP 0 669 287 A1 (corresponding DE 695 16 197 T2 ), a device and a method of the type mentioned are known by means of which several users are supplied with vapor, silicon-containing raw material from a common reservoir. For this purpose, the present in the reservoir as a liquid silicon-containing raw material (SiCl ₄ ) is evaporated by means of a heater and fed with the aid of a carrier gas under pressure via a piping system to the consumers. To avoid condensation in the piping system, it is necessary that the pipes are thermally insulated to the outside.

It is also known media leading To heat pipes. The heating is usually done by wrapping the media line with an electric heater. This heater is set by means of temperature measurement and an associated control to a preset Temperature value regulated. Through vibrations or movements of the media line can result in incorrect measurements at the temperature measuring point, whereby the entire electric heater with too high or one too low temperature is operated.

From the DE 36 03 886 A1 a heat exchanger for heating flowing gases or liquids is known, wherein a fluid tube is provided, through which a medium to be heated flows and wherein the fluid tube is heated from the outside with a heat source. For example, the fluid tube is surrounded by an outer jacket tube, so that in the space between the fluid tube and the jacket tube, a heat transfer medium in the form of water, steam or a heat transfer oil surrounds.

In the DE 694 24 302 T2 a device for adhesive processing is described, which comprises a heatable tubular casing, by means of which a predetermined viscosity of an adhesive transported in the hose is to be maintained. For this purpose, a double-walled hose is provided, which consists of a flexible inner tube and a flexible outer tube. Within a housing, a water heater is provided, from which tempered water is pumped in circulation through the annular gap.

Of the present invention is based on the object, a reproducible Process for the production of a blank from quartz glass by flame hydrolysis and provide a simple and reliable device for the feed of vaporous, provide silicon-containing raw material to a deposition burner, which is reversibly moved along an axis.

These Task is with regard to the device starting from a device of the type mentioned above solved according to the invention that the media line is designed as a flexible inner tube, and that the heating means comprises a flexible outer tube, the Inner tube forming a composite tube with one of a tempered fluid permeable gap between the inner tube and outer tube surrounds, with one acting on the outer tube Additional heating for heating the fluid from the outside is provided.

• • Zur Medienversorgung des Abscheidebrenners wird ein Verbundschlauch eingesetzt, der einen Innenschlauch zum Transport des dampfförmigen Rohstoffes aufweist und der unter Bildung eines Spalts von einem Außenschlauch umgeben ist. Innerhalb des Spalts strömt ein temperierbares Fluid. Damit ist es möglich, den Innenschlauch und damit den im Innenschlauch transportierten dampfförmigen Rohstoff zu erwärmen oder auf einer vorgegebenen Temperatur zu halten. Auf diese Weise werden Temperatursenken oder Temperaturspitzen, wie sie beispielsweise beim Zusammenschieben von Heizwicklungen entstehen können, vermieden. Es ergibt sich somit insgesamt eine Homogenisierung des Temperaturverlaufs über der Länge des Innenschlauches.
• • Dadurch, dass der Innenschlauch von einem mit Fluid durchströmten Außenschlauch umgeben ist, wird die Gefahr eines Austritts von dampfförmigem Rohstoff in die Umgebung vermindert. Denn aus dem Innenschlauch austretender Rohstoff wird mit dem strömenden Fluid abtransportiert. Da es sich bei dem hier relevanten dampfförmigen, siliziumhaltigen Rohstoff häufig um chlorhaltige Substanzen handelt, die chemisch sehr aggressiv sind und beim Austritt in die Umgebung zu Vergiftungen oder Korrosionsschäden führen können, trägt dies zur Betriebssicherheit der Vorrichtung bei.
• • Weiterhin ist sowohl der Innenschlauch als auch der ihn umgebende Außenschlauch flexibel ausgebildet, so dass sich demgemäß ein flexibler Verbundschlauch ergibt. Infolge der Flexibilität kann der Verbundschlauch Bewegungen des Abscheidebrenners folgen. Somit ist es möglich, den Verbundschlauch direkt oder mittelbar mit dem sich bewegenden Abscheidebrenner zu verbinden, ohne dass durch diese Bewegung die notwendige Dichtheit der Leitung beeinträchtigt ist. Durch die Beweglichkeit bedingte Veränderungen der Beheizung des Rohstoffes werden durch das im Spalt fließende Fluid vermieden oder kompensiert.
• • Außerdem ist erfindungsgemäß ein auf den Außenschlauch einwirkende Zusatzheizung zur Erwärmung des Fluids von außen vorgesehen. Die Zusatzheizung wirkt einer Abkühlung des Fluids auf seinem Weg zum Abscheidebrenner entgegen. An die Homogenität der Zusatzheizung über die Länge des Außenschlauches werden dabei geringe Anforderungen gestellt. Es ist kaum erheblich, wenn es – etwa bei einer mehrere Wicklungen aufweisenden Schlauchheizung – zu einer einem Verrutschen der Zusatzheizung und infolge davon zu lokal inhomogener Erwärmung kommt. Denn derartige Inhomogenitäten werden durch das erwärmte Fluid kompensiert.

In the device according to the invention, several aspects contribute to the solution of the above-stated problem:

• • For media supply of the deposition burner, a composite hose is used, which has an inner tube for transporting the vaporous raw material and which is surrounded by a gap to form an outer tube. Within the gap flows a temperature-controllable fluid. This makes it possible to heat the inner tube and thus the transported in the inner tube vaporous raw material or to keep at a predetermined temperature. In this way, temperature sinks or Tempe Rature peaks, as they may arise, for example, when pushing together Heizwindlungen avoided. This results in a total homogenization of the temperature profile over the length of the inner tube.
• • The fact that the inner tube is surrounded by a flow-through outer tube, the danger of leakage of vaporous raw material is reduced in the environment. Because emerging from the inner tube raw material is removed with the flowing fluid. Since the vaporous, silicon-containing raw material relevant here is frequently chlorine-containing substances which are chemically very aggressive and can lead to poisoning or corrosion damage on leaving the environment, this contributes to the operational reliability of the device.
• Furthermore, both the inner tube and the outer tube surrounding it are designed to be flexible, thus resulting in a flexible composite tube. Due to the flexibility, the composite tube can follow movements of the deposition burner. Thus, it is possible to connect the composite hose directly or indirectly with the moving Abscheidebrenner without the necessary tightness of the line is affected by this movement. Due to the mobility related changes in the heating of the raw material are avoided or compensated by the fluid flowing in the gap.
• In addition, according to the invention, an additional heater acting on the outer tube is provided for heating the fluid from the outside. The additional heating counteracts a cooling of the fluid on its way to Abscheidebrenner. At the homogeneity of the additional heating over the length of the outer tube while low demands are made. It is hardly significant if, for example in the case of a hose heating system having a plurality of windings, the auxiliary heater slips and, as a result, there is local inhomogeneous heating. Because such inhomogeneities are compensated by the heated fluid.

Preferably the heating device comprises a heating cabinet within which the media container and a tempering arranged for controlling the temperature of the fluid are.

through of the warming cabinet becomes the media container and thus the silicon-containing raw material contained in a warmed up given temperature in which the raw material evaporates sufficiently. Besides that is in the warming cabinet too a tempering provided by means of which the gap flowing through Fluid is brought to the predetermined temperature. In the simplest Case this is the same temperature to which also heats the media container becomes.

Especially proven It has to be the tempering as a metallic pipe for the fluid formed with a fluid reservoir and with a fluid inlet the gap is connected.

by virtue of the good thermal conductivity From metal, the metallic pipe quickly takes the temperature inside the warming cabinet and passes them on to the fluid. This can be done without further Heating device and control are ensured that the Fluid has the predetermined tempering temperature.

When very cheap a pipe has proven to be a stainless steel pipe spiral is formed.

By the spiral shape of the pipeline becomes a sufficiently long heating section and provided a large surface, so that ensures is that the fluid flowing in the pipeline is the pre-set Temperature can take.

advantageously, the gap has an inlet located within the heating cabinet for the Fluid on. Become cold bridges so avoided.

When particularly advantageous in terms of reliability has an embodiment the device according to the invention proved, in which the inner tube with a media connection of the deposition burner connected, wherein the media connection in a closed, heated housing is arranged.

Of the Media connection of the deposition burner for the raw material is located inside a closed housing. This is heated, so that cold spots in avoided in this area and ensures a constant temperature is. Furthermore reduces the closed housing to the media connection the risk of leakage of raw material in the environment.

A Further improvement results from the fact that the gap in a the housing ending outlet for having the fluid.

The outer tube is thus brought up to the heatable housing, or he ends in the same. Cold bridges are avoided. Within the housing, an outlet for the fluid is provided from the gap, which is preferably connected to a lead-out from the housing. By flushing the housing may be exiting components of the raw material fes or the fluid being removed.

In Connection with the additional heating, it is also advantageous that the Gap an average gap width in the range between 0.2 mm and 2 mm, preferably at most 1 mm. Due to the small gap width Even with low fluid flow, a high flow rate is achieved reached the gap that for a homogeneous heating of the Raw material in the inner tube is sufficient. Apart from the cost factor can small amounts of fluid are also easier to temper than larger amounts.

It has proved its worth, for drying the fluid to provide a drying plant, the - in the flow direction seen the fluid - the Split is arranged upstream.

at the raw material is common Chlorine-containing substances that react in conjunction with water to hydrochloric acid and corrosion damage to lead can. This risk is reduced by the drying of the fluid.

to Achieving the required flexibility of the composite tube an inner tube in the form of a flexible smooth tube than proved appropriate. The smooth tube is the after many cycles of motion Leakage still guaranteed however, a sufficiently large bending radius of more than 20 times the outside diameter of the outer tube is to be provided. Such a large bending radius would be at one Although corrugated hose is not required, however, this allows in contrast for smooth hose no efficient cleaning of the inner tube by gas flushing. Also the outer tube is advantageously designed in the form of a smooth tube.

Out Purity reasons, for reasons the chemical resistance as well as the temperature resistance Perfluoroalkoxy (PFA) has proven to be a suitable material for training of the inner tube proved. The outer tube is preferably made of the same material or polytetrafluoroethylene (Teflon).

Out establish In terms of operational safety, the fluid is advantageously an inert gas, for cost reasons Nitrogen is preferred here.

to Preparation of a blank with doped quartz glass has proven to be proven advantageous, within the oven, a second, connected to the inner tube media container for receiving a second hydrolyzable and vaporizable raw material to form a Provide dopant.

Preferably is for the connection of the first media container and the second media container with the Media hose provided within the heating cabinet fork piece, the with the inner tube and each with a raw material extraction line to the respective media container connected is.

through of the fork piece can the two vaporizing raw materials are fed into the inner tube become. Before the inlet into the fork are advantageously each provided gas flow regulator, so that the desired mixing ratio of Raw materials can be adjusted.

Regarding of the method, the above object is based on the The aforementioned method according to the invention achieved in that for warming of the raw material and to transport the raw material to Abscheidebrenner a device according to the invention is used.

By Use of the device according to the invention become temperature inhomogeneities avoided in the raw material supply to Abscheidebrenner and so the Re producibility of the deposition improved. On the above explanations to the device according to the invention is referred to.

following the invention with reference to an embodiment and a drawing explained in more detail. When single figure shows:

1 a schematic representation of an embodiment of the erfindungsge MAESSEN device for producing a SiO ₂ blank.

The apparatus for producing a synthetic quartz glass blank according to 1 shows a Mehrdüsigen Abscheidebrenner 18 for producing a SiO ₂ blank by the known Außenabscheideverfahren (OVD method). For this purpose, the Abscheidebrenner 18 Fuel gases in the form of hydrogen and oxygen and a glass starting material in the form of SiCl ₄ supplied. In a the separator burner 18 associated burner flame (in 1 not shown), SiO ₂ particles are formed and these are deposited in layers by reversing the deposition burner along a carrier rotating about its longitudinal axis to form the SiO ₂ blank.

The device of the invention serves - with particular attention to the SiCl ₄ supply - to a constant media supply to the Abscheidebrenner 18 and to prevent uncontrolled release of this substance into the environment.

The glass starting material SiCl ₄ is placed in a closed media container 10 is heated therein and heated as SiCl ₄ vapor via a composite hose, which will be described in more detail below, the deposition burner 18 fed.

The media container 10 for the glass source SiCl ₄ is within a means of heating 4 temperature controlled and with blower 3 provided heat Shrink kes 8th arranged. The temperature inside the heating cabinet 8th is set to a temperature in the range between 110 ° C to 120 ° C In the media container 10 the mentioned composite hose protrudes to transport the glass starting material to the deposition burner 18 , The composite hose consists of a flexible inner hose 1 , a flexible outer tube 2 that the inner tube 1 by far with the formation of a flow-through gap 5 surrounds, one of the outer tube 2 warming hose heating 6 and one the hose heater 6 enveloping outer insulation 28 made of silicone foam together.

The inner tube 1 lies as a smooth tube made of PFA (perfluoroalkoxy) from Daikin Ind., Ltd. This material is characterized by a low diffusion for vaporous SiCl ₄ and is chemically resistant to SiCl _4. The inner tube i has an outer diameter of 8 mm and loosens through the outer tube 2 , which is also designed as a smooth PFA hose made of said material with an inner diameter of 9.5 mm, passed. The resulting composite hose has a substantially annular gap 5 with a mean gap width of 0.75 mm.

The inner tube 1 serves to transport the from the media container 10 as a vapor escaping glass starting material SiCl ₄ to the deposition burner 18 , The inner tube 1 is at a connecting piece 11 of the closed media container 10 (Evaporator) connected. From the connecting piece 11 the vaporous SiCl ₄ passes through a withdrawal line 32 to a flow regulator 29 and a fork 30 that with the inner tube 1 directly connected. By means of the flow regulator 29 gets into the inner tube 1 fed controlled amount of SiCl ₄ vapor. From the fork piece 30 runs the inner tube 1 to a pipe connector in the form of an inlet T-piece 12 made of stainless steel, also inside the heating cabinet 8th is installed. The inlet tee 12 has a continuous strand 13 on, at its front end by means of cutting ring 14 the inner tube 1 is taken.

The inner tube 1 is heated over its entire length and kept at a constant temperature, on the one hand to avoid condensation of SiCl ₄ and on the other hand to achieve stable deposition conditions.

For this purpose, the inner tube 1 in the area outside the warming cabinet 8th tempered by passing through the gap 5 between inner tube 1 and outer tube 2 a heated stream of nitrogen is passed continuously at about 3 l / min. For temperature control is in the oven 8th a pipe spiral 9 built of stainless steel tube, through which a nitrogen flow 7 from a compressed gas cylinder 21 over a drying plant 23 continuously in the gap 5 is fed. On his way through the pipe spiral 9 takes the dried nitrogen stream 7 essentially those in the warming cabinet 8th prevailing temperature.

In addition, the outer tube 2 by means of electric hose heating 6 brought to the preset temperature in the range of 110 ° C and 120 ° C and this setpoint temperature by means of a thermocouple 26 and a regulator 27 held. The temperature of the inner tube 1 through the heated nitrogen stream 7 is a safety measure that ensures that even in case of a shift of hose heating 6 , or as a result of insulation faults, the inner tube 1 no significant temperature change undergoes.

The dried and heated nitrogen stream 7 is from the pipe spiral 9 over a stainless pipe 15 the turnoff 16 of the inlet tee 12 supplied and here with the cutting ring 14 sealed. The turnoff 16 of the inlet tee 12 stands with the rear end of the continuous strand 13 of the inlet tee 12 in which the front end of the outer tube 2 inserted and also by means of cutting ring 14 is sealed, in conjunction. Thus lies the front opening 24 of the gap 5 between inner tube 1 and outer tube 2 inside the inlet tee 12 and thus also within the heating cabinet 8th ,

From the front opening 24 of the gap 5 the heated nitrogen flows in the gap 5 over the entire length of the composite hose towards another pipe connection element in the form of an outlet T-piece 17 , The flow of the hot, dried nitrogen is thereby by the gas pressure of the nitrogen cylinder 21 causes.

The outlet tee 17 is - like the inlet tee 12 - with continuous strand 13 and diversion 16 fitted. The outer tube 2 is at the input side of the continuous strand 13 by means of cutting ring 14 sealed and taken, leaving the rear opening 25 of the gap 5 escaping hot, dry stick material flow 7 in the turnoff 16 of the outlet tee 17 arrives. The gap 5 thus ends within the outlet tee 17 , At the junction 16 is a mobile PFA pipeline 22 connected, avoid the used, dry nitrogen 7 in an exhaust system (not shown in the figure) derived.

The inner tube 1 becomes on the opposite side of the continuous strand 13 through the cutting ring 14 sealed and held. In continuation of the inner tube 1 via a hose connection 19 a connecting piece 31 for the media nozzle of the deposition burner 18 fed.

The outlet tee 17 and the hose connection 19 are in a housing 20 housed, by means of heating 4 is heated and with a fan 3 is provided. The heated housing 20 is at the separator burner 18 fixed and movable with this in two spatial directions, as indicated by the directional arrows x, y.

For the absorption of starting substances (such as GeCl ₄ ) as dopant to the deposition burner 18 a second media container (not shown in the figure) is provided, wherein the supply via a supply line 33 and another flow regulator to the fork 30 he follows. The fork piece 30 that with the inner tube 1 is directly connected, is supplied by means of the two flow rate regulator a predetermined ratio of SiCl ₄ - and GeCl ₄ vapors and immediately into the inner tube 1 fed.

Other burner gases, such as hydrogen and oxygen, become the corresponding nozzles of the deposition burner 18 fed, however, the supply hoses are made without heating.

Because of the mobility of the Abscheidebrenner 18 All hose connections must be provided with sufficiently rounded lines of the supply hoses.

With this arrangement it is achieved that the vaporous reactants, such as SiCl ₄ or GeCl ₄ , without condensation to the deposition burner 18 can be supplied. The separation of the inner tube 1 from the outer tube 2 through the heated gap 5 also causes, possibly through the wall of the inner tube 1 through diffusing or leaking gases or vapors in the nitrogen stream 7 be absorbed and removed.

1

inner tube

2

outer tube

3

fan

4

heater

5

gap

6

tube heater

7

nitrogen stream

8th

hot cabinet

9

pipe spiral

10

media container

11

spigot

12

Inlet Tee

 13

continuous strand

14

cutting ring

15

pipeline

16

diversion

17

Outlet tee

18

deposition

19

hose connection

20

casing

21

gas bottle

22

PFA tubing

23

drying plant

24

front gap opening

25

rear gap opening

26

thermocouple

27

regulator

28

external insulation

29

Flow regulator

30

forked piece

31

spigot

32 33

withdrawal line

Claims (15)

An apparatus for producing a synthetic quartz glass blank comprising a media container for containing a hydrolyzable siliceous raw material, a heater for heating the raw material in the media container, a deposition burner for producing SiO ₂ particles from the raw material, and a deposition burner and Media container connecting the media line for transporting the raw material, which is in contact with a heating means, characterized in that the media line as a flexible inner tube ( 1 ) is formed, and that the heating means a flexible outer tube ( 2 ) comprising the inner tube ( 1 ) to form a composite tube with one of a temperature-controlled fluid ( 7 ) through-flowable gap ( 5 ) between inner tube ( 1 ) and outer tube ( 2 ), with one on the outer tube ( 2 ) acting auxiliary heating ( 6 ) for heating the fluid ( 7 ) is provided from the outside. Apparatus according to claim 1, characterized in that the heating device is a Wär cabinet ( 8th ) within which the media container ( 10 ) and a tempering device ( 9 ) for temperature control of the fluid ( 7 ) are arranged. Apparatus according to claim 2, characterized in that the tempering device ( 9 ) as a metallic conduit for the fluid ( 7 ) formed with a fluid reservoir ( 21 ) and with a fluid inlet ( 24 ) of the gap ( 5 ) connected is. Device according to claim 3, characterized in that that the pipe is formed as a pipe spiral made of stainless steel is. Device according to one of claims 2 to 4, characterized in that the gap ( 5 ) one inside the heating cabinet ( 8th ) inlet ( 24 ) for the fluid ( 7 ) having. Device according to one of claims 1 to 5, characterized in that the inner tube ( 1 ) with a hose connection ( 19 ) of the deposition burner ( 18 ), wherein the hose connection ( 19 ) within a closed, heatable housing ( 20 ) is arranged. Device according to claim 6, characterized in that the gap ( 5 ) one in the housing ( 20 ) ending outlet ( 25 ) for the fluid ( 7 ) having. Device according to claim 7, characterized in that the outlet ( 25 ) for the fluid ( 7 ) with one out of the housing ( 20 ) led derivative ( 22 ) connected is. Device according to claim 7, characterized in that the gap ( 5 ) has an average gap width in the range between 0.2 mm and 2 mm, preferably around 1 mm. Device according to one of the preceding claims, characterized in that for drying the fluid ( 7 ) a drying plant ( 23 ) is provided, which - in the flow direction of the fluid ( 7 ) - the gap ( 5 ) is arranged upstream. Device according to one of the preceding claims, characterized in that the inner tube ( 1 ) consists of polyfluoroalkoxy (PFA). Device according to one of the preceding claims, characterized in that the fluid ( 7 ) is an inert gas, preferably nitrogen. Device according to claim 2, characterized in that inside the heating cabinet ( 8th ) a second, with the inner tube ( 1 ) is provided for receiving a second hydrolyzable and vaporizable raw material for forming a dopant connected media container. Apparatus according to claim 13, characterized in that for the connection of the first media container ( 10 ) and second media container with the inner tube ( 1 ) within the heating cabinet ( 8th ) arranged fork piece ( 30 ) provided with the inner tube ( 1 ) and each with a raw material withdrawal line ( 32 . 33 ) is connected to the respective media container. A method of making a synthetic quartz glass blank wherein a hydrolyzable siliceous raw material heats in a media vessel, transports the heated raw material to a deposition burner, generates SiO ₂ particles therefrom from the raw material, and forms the SiO ₂ particles on a rotating carrier of the blank are deposited in layers, characterized in that for heating the raw material and for transporting the raw material to Abscheidebrenner ( 18 ) A device according to one of claims 1 to 14 is used.