GB2084988A - Methods of Etching Materials Containing Silicon - Google Patents
Methods of Etching Materials Containing Silicon Download PDFInfo
- Publication number
- GB2084988A GB2084988A GB8031741A GB8031741A GB2084988A GB 2084988 A GB2084988 A GB 2084988A GB 8031741 A GB8031741 A GB 8031741A GB 8031741 A GB8031741 A GB 8031741A GB 2084988 A GB2084988 A GB 2084988A
- Authority
- GB
- United Kingdom
- Prior art keywords
- deposited
- freon
- layer
- silicon
- compound
- Prior art date
- Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
- Granted
Links
Classifications
-
- C—CHEMISTRY; METALLURGY
- C03—GLASS; MINERAL OR SLAG WOOL
- C03B—MANUFACTURE, SHAPING, OR SUPPLEMENTARY PROCESSES
- C03B37/00—Manufacture or treatment of flakes, fibres, or filaments from softened glass, minerals, or slags
- C03B37/01—Manufacture of glass fibres or filaments
- C03B37/012—Manufacture of preforms for drawing fibres or filaments
- C03B37/014—Manufacture of preforms for drawing fibres or filaments made entirely or partially by chemical means, e.g. vapour phase deposition of bulk porous glass either by outside vapour deposition [OVD], or by outside vapour phase oxidation [OVPO] or by vapour axial deposition [VAD]
- C03B37/018—Manufacture of preforms for drawing fibres or filaments made entirely or partially by chemical means, e.g. vapour phase deposition of bulk porous glass either by outside vapour deposition [OVD], or by outside vapour phase oxidation [OVPO] or by vapour axial deposition [VAD] by glass deposition on a glass substrate, e.g. by inside-, modified-, plasma-, or plasma modified- chemical vapour deposition [ICVD, MCVD, PCVD, PMCVD], i.e. by thin layer coating on the inside or outside of a glass tube or on a glass rod
- C03B37/01861—Means for changing or stabilising the diameter or form of tubes or rods
- C03B37/01869—Collapsing
-
- C—CHEMISTRY; METALLURGY
- C03—GLASS; MINERAL OR SLAG WOOL
- C03B—MANUFACTURE, SHAPING, OR SUPPLEMENTARY PROCESSES
- C03B37/00—Manufacture or treatment of flakes, fibres, or filaments from softened glass, minerals, or slags
- C03B37/01—Manufacture of glass fibres or filaments
- C03B37/02—Manufacture of glass fibres or filaments by drawing or extruding, e.g. direct drawing of molten glass from nozzles; Cooling fins therefor
- C03B37/025—Manufacture of glass fibres or filaments by drawing or extruding, e.g. direct drawing of molten glass from nozzles; Cooling fins therefor from reheated softened tubes, rods, fibres or filaments, e.g. drawing fibres from preforms
- C03B37/027—Fibres composed of different sorts of glass, e.g. glass optical fibres
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- C—CHEMISTRY; METALLURGY
- C03—GLASS; MINERAL OR SLAG WOOL
- C03C—CHEMICAL COMPOSITION OF GLASSES, GLAZES OR VITREOUS ENAMELS; SURFACE TREATMENT OF GLASS; SURFACE TREATMENT OF FIBRES OR FILAMENTS MADE FROM GLASS, MINERALS OR SLAGS; JOINING GLASS TO GLASS OR OTHER MATERIALS
- C03C15/00—Surface treatment of glass, not in the form of fibres or filaments, by etching
Landscapes
- Chemical & Material Sciences (AREA)
- Engineering & Computer Science (AREA)
- Life Sciences & Earth Sciences (AREA)
- Geochemistry & Mineralogy (AREA)
- Materials Engineering (AREA)
- Organic Chemistry (AREA)
- General Life Sciences & Earth Sciences (AREA)
- Manufacturing & Machinery (AREA)
- Chemical Kinetics & Catalysis (AREA)
- General Chemical & Material Sciences (AREA)
- Manufacture, Treatment Of Glass Fibers (AREA)
Abstract
A method of manufacturing glass fibres for optical communication in which layers of doped silica are deposited on the inside of a tubular substrate, which is subsequently collapsed to forms preform for a fibre; during the collapse stage a gaseous material which reacts with the deposited surface is introduced into the tube to remove a layer of previously deposited material, which would otherwise be incorrectly doped due to evaporation. Gaseous materials exemplified are CCl2F2, CFCl3, CF3Cl, CF4, F2 and SF6.
Description
SPECIFICATION
Methods of Etching Materials Containing
Silicon
This invention relates generally to methods of etching materials containing silicon.
In one aspect the present invention relates particularly to the chemical vapour deposition method of producing glass fibres for transmission.
In this method a vaporised silicon compound, usually SiCI4, together with vapourised dopants is passed through a heated, pure silica substrate tube. Thermal reactions cause layers of doped silica to be deposited and the dopant levels are controlled and varied by controlling the concentration of the dopant vapours. After the deposition of the required number of layers the tube is heated causing it to collapse into a solid preform from which the optical fibre is drawn.
A problem that arises during the collapse stage is that at the temperature required, 17000-- 1 9000, dopants in the last deposited layers inside the tubular substrate tend to evaporate. This is clearly undersirable since it produces a dip at the centre of the refractive index profile of the fibre which, in the case of a multimode fibre, corresponds to a reduction in bandwith. It has been proposed to overdope these inner deposited layers to allow for evaporation, but this has not met with much success since it is difficult to compute the correct amount of additional dopant with consistency.
It is an object of the present invention in a first aspect to provide an alternative method for alleviating the effect of the evaporated layers.
According to the invention in a first aspect, there is provided a method of manufacturing glass fibre for optical communication in which layers of doped silica are deposited on the inside of a tubular substrate, the substrate tube being subsequently collapsed to form a preform for a fibre, the method including the step of introducing a gaseous material into the tube during the collapse stage, which gaseous material reacts with the inner deposited surface to remove a layer of previously deposited material.
It has been found particularly advantageous to use gaseous compounds from the class commonly referred to under the trade name Freon (Registered Trade Mark).
The inventors have also appreciated that the advantages accruing from the use of Freons can be obtained in a number of other situations where it is required to remove a surface layer from a silicon-containing material. Such situations are quite common in that it is often necessary to remove a layer of contaminated silicon-containing material when a high degree of purity is required.
One such application, again in the field of optical fibres is during the process of fibre drawing, where imperfections in the outer surface can effect the resultant fibre strength.
Therefore, according to the invention, in a second aspect there is provided a method of removing a layer from the surface of siliconcontaining compound comprising applying a vapour containing a Freon compound to the surface.
In chemical vapour deposition processes for producing optical fibres the deposition mechanism is thermal oxidation in which the solid products of a vapour phase reaction or condension products are sintered to a glass layer.
To reduce the deposition and sintering temperature P2O5 has been added in small quantities to the deposited inner cladding layer and to compensate for the resultant increase in refractive index, fluorine is added as an additional dopant. This process is described in detail in the article published by the present inventors and others in Electronics Letters, 5th July 1979, vol.
15 No. 14,pp411-413.
The fluorine is derived from dichlorodifluoromethane (CCl2F2), also known as
Freon 12, which is heated to 1 5500C with oxygen and silicon tetrachloride vapour. The simplified reaction is described by the equation:-
In a method according to the present invention more core layers are deposited than are finally required, and in one method twice the required thickness is deposited. After deposition is complete and during the collapse of the substrate tube unoxidised Freon vapour and oxygen is passed through the tube. The temperature used to collapse the tube is in the region of 1 9000C which is higher than that required to oxidise the
Freon as described above.A reaction takes place between the Freon and the silicon of the innermost surface of the tube possibly in accordance with the simplified equation:- Sio2+o2+2CCl2F24SiF4+2Co2+2Cl2 In any event a volatile silicon fluoride is produced.
Thus the inner silicon layers are vapourised.
Any dopants present are also converted into vapours which are then removed. By suitable experimentation an amount of silica is removed to leave the required core thickness. It is not necessary to use Freon as the etchant and, for example, sulphur hexafluoride SF8, fluorine F2, carbon tetrafluoride CF4 could be used, as could other Freon type compounds such as CFCI3 or
CF3CI. It is required merely that the vapour provides fluorine in such a form that under certain conditions the volatile compound SiF4, or a similar compound, results when it reacts with the deposited silica.
Amongst the undesirable impurities that can occur in the material of optical fibres, those which introduce an OH group are of the most importance since the bond between this group and other components absorbs strongly in or adjacent the most favoured transmission band.
The presence of freed chlorine vapour as a result of the reaciton between the silica and Freon during substrate collapse is advantageous since this then acts as a drying agent to remove water vapour. The OH concentration of the inner layers of deposited glass has previously been found to particularly increase during the collapse stage, probably as a result of water vapour present or introduced by back diffusion. The freed chlorine vapour is therefore produced at the appropriate stage in the process.
This in situ production of a drying agent simultaneous with the fluorine etching which results from the use of a Freon is envisaged as being advantageous in many processes in which silica is etched.
Claims (7)
1. A method of manufacturing glass fibres for optical communication in which layers of doped silica are deposited on the inside of a tubular substrate, the substrate tube being subsequently collapsed to form a preform for a fibre;
the method including the step of introducing a gaseous material into the tube during the collapse stage, which gaseous material reacts with the inner deposited surface to remove a layer of previously deposited material.
2. A method as claimed in claim 1 in which the gaseous material includes a fluorine compound such that the reaction with the deposited surface comprises the formation of a volatile silicon fluoride.
3. A method as claimed in claim 2 wherein the fluorine compound is a Freon.
4. A method as claimed in claim 3 wherein the
Freon is dichlorodifluoromethane.
5. A method of removing a layer from the surface of a silicon containing compound comprising applying a vapour containing a Freon compound to the surface to produce a volatile silicon fluoride and chlorine vapour.
6. A method of manufacturing glass fibres as claimed in claim 1 and substantially as hereinbefore described.
7. A method of removing a layer from the surface of a silicon-containing compound as claimed in claim 5 and substantially as hereinbefore described.
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| GB8031741A GB2084988B (en) | 1980-10-02 | 1980-10-02 | Methods of etching materials containing silicon |
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| GB8031741A GB2084988B (en) | 1980-10-02 | 1980-10-02 | Methods of etching materials containing silicon |
Publications (2)
| Publication Number | Publication Date |
|---|---|
| GB2084988A true GB2084988A (en) | 1982-04-21 |
| GB2084988B GB2084988B (en) | 1984-06-06 |
Family
ID=10516428
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| GB8031741A Expired GB2084988B (en) | 1980-10-02 | 1980-10-02 | Methods of etching materials containing silicon |
Country Status (1)
| Country | Link |
|---|---|
| GB (1) | GB2084988B (en) |
Cited By (11)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| EP0086533A1 (en) * | 1982-02-15 | 1983-08-24 | Philips Patentverwaltung GmbH | Method of making fluordoped optical fibres |
| EP0091173A1 (en) * | 1982-04-06 | 1983-10-12 | Koninklijke Philips Electronics N.V. | Method of producing optical fibres |
| DE3230199A1 (en) * | 1982-08-13 | 1984-02-16 | Siemens AG, 1000 Berlin und 8000 München | METHOD FOR PRODUCING A FIBERGLASS WITH A RADIAL CRUSH PROFILE |
| GB2134897A (en) * | 1983-02-14 | 1984-08-22 | Western Electric Co | Manufacture of optical fibres and preforms with reduced hydroxyl content |
| EP0117009A1 (en) | 1983-02-22 | 1984-08-29 | Koninklijke Philips Electronics N.V. | Method of making a solid preform for drawing optical fibres |
| US4539033A (en) * | 1982-09-10 | 1985-09-03 | British Telecommunications | Method for drying oxide glasses |
| EP0182250A1 (en) * | 1984-11-13 | 1986-05-28 | Sumitomo Electric Industries Limited | Method for producing glass preform for optical fiber |
| DE3521119A1 (en) * | 1985-06-13 | 1986-12-18 | Heraeus Quarzschmelze Gmbh, 6450 Hanau | METHOD FOR PRODUCING A PREFORM FOR OPTICAL FIBERS AND USE OF A QUARTZ GLASS OR TUBE. DOPED QUARTZ GLASS FOR PRODUCING SUCH A PREFORM |
| US5152816A (en) * | 1989-10-16 | 1992-10-06 | Corning Incorporated | Method of enlarging end of capillary tube bore |
| EP1035083A1 (en) * | 1999-03-08 | 2000-09-13 | Spectran Corporation | Method of collapsing preforms for optical fibers |
| WO2006135098A1 (en) * | 2005-06-14 | 2006-12-21 | Asahi Glass Co., Ltd. | Method of finishing pre-polished glass substrate surface |
-
1980
- 1980-10-02 GB GB8031741A patent/GB2084988B/en not_active Expired
Cited By (15)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| EP0086533A1 (en) * | 1982-02-15 | 1983-08-24 | Philips Patentverwaltung GmbH | Method of making fluordoped optical fibres |
| EP0091173A1 (en) * | 1982-04-06 | 1983-10-12 | Koninklijke Philips Electronics N.V. | Method of producing optical fibres |
| DE3230199A1 (en) * | 1982-08-13 | 1984-02-16 | Siemens AG, 1000 Berlin und 8000 München | METHOD FOR PRODUCING A FIBERGLASS WITH A RADIAL CRUSH PROFILE |
| EP0100998A1 (en) * | 1982-08-13 | 1984-02-22 | Siemens Aktiengesellschaft | Method of making a glass fibre with a radial refraction profile |
| US4539033A (en) * | 1982-09-10 | 1985-09-03 | British Telecommunications | Method for drying oxide glasses |
| GB2134897A (en) * | 1983-02-14 | 1984-08-22 | Western Electric Co | Manufacture of optical fibres and preforms with reduced hydroxyl content |
| EP0117009A1 (en) | 1983-02-22 | 1984-08-29 | Koninklijke Philips Electronics N.V. | Method of making a solid preform for drawing optical fibres |
| EP0182250A1 (en) * | 1984-11-13 | 1986-05-28 | Sumitomo Electric Industries Limited | Method for producing glass preform for optical fiber |
| US4668263A (en) * | 1984-11-13 | 1987-05-26 | Sumitomo Electric Industries, Ltd. | Method for producing glass preform for optical fiber |
| AU578983B2 (en) * | 1984-11-13 | 1988-11-10 | Sumitomo Electric Industries, Ltd. | Method for producing glass preform for optical fiber |
| DE3521119A1 (en) * | 1985-06-13 | 1986-12-18 | Heraeus Quarzschmelze Gmbh, 6450 Hanau | METHOD FOR PRODUCING A PREFORM FOR OPTICAL FIBERS AND USE OF A QUARTZ GLASS OR TUBE. DOPED QUARTZ GLASS FOR PRODUCING SUCH A PREFORM |
| US5152816A (en) * | 1989-10-16 | 1992-10-06 | Corning Incorporated | Method of enlarging end of capillary tube bore |
| EP1035083A1 (en) * | 1999-03-08 | 2000-09-13 | Spectran Corporation | Method of collapsing preforms for optical fibers |
| US6718800B2 (en) * | 1999-03-08 | 2004-04-13 | Fitel Usa Corp. | Method of collapsing a tube for an optical fiber preform |
| WO2006135098A1 (en) * | 2005-06-14 | 2006-12-21 | Asahi Glass Co., Ltd. | Method of finishing pre-polished glass substrate surface |
Also Published As
| Publication number | Publication date |
|---|---|
| GB2084988B (en) | 1984-06-06 |
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Legal Events
| Date | Code | Title | Description |
|---|---|---|---|
| 732 | Registration of transactions, instruments or events in the register (sect. 32/1977) | ||
| 732E | Amendments to the register in respect of changes of name or changes affecting rights (sect. 32/1977) | ||
| PE20 | Patent expired after termination of 20 years |
Effective date: 20001001 |