JP2005187847A - Method for forming glass film, apparatus for manufacturing the same, and method for forming waveguide - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a method for forming a glass film, in which the glass film having the same composition and the same thickness is formed on both the top and under surfaces of a substrate, and an apparatus for manufacturing the same. <P>SOLUTION: In the method for forming the glass film, an upper electrode 5 and a lower electrode 4 are arranged in such a manner that these electrodes face each other within a reaction vessel 11, applying a high voltage to the electrodes 4 and 5, the substrate 25 is arranged apart a gap 17 on the lower electrode 4, forming an open space 26 on the under surface of the substrate 25, and for forming the glass film on the top and under surfaces of the substrate 25, a halogen lamp heater 8 is positioned at the upper electrode 5 and the gas becoming a glass raw material is introduced into the reaction vessel 11 while heating the electrodes 4 and 5 to a prescribed temperature by the halogen lamp heater 8 to cause a pyrosis reaction under a plasma atmosphere, thereby forming the glass film on the top and under surfaces of the substrate 25. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to a method for forming a glass film on a substrate, a manufacturing apparatus for the glass film, and a method for forming a waveguide.

  In the conventional glass film manufacturing apparatus 60 shown in FIG. 6, an upper electrode 63 and a lower electrode 64 with a heater are disposed opposite to each other in a reaction vessel 61, and a high frequency power supply 66 is connected between the electrodes 63 and 64. The substrate 68 is disposed on the lower electrode 64. Further, an exhaust device 62 that keeps the inside of the reaction vessel 61 in a vacuum state and a supply pipe 67 that supplies a raw material gas and the like are connected.

When the glass film is formed, the upper electrode 63 and the lower electrode 64 are heated, high-frequency power is applied, and an alcoholate liquid source ([Si (OC ₂ H ₂ H) heated in the thermostat 72 is used. _{5) 4] 69, [Ge} (OCH 3) 4] 70, [P (OCH 3) 3] 71 , etc.) is O ₂ gas supplied through the gas and O ₂ tube 73 was vaporized, the supply pipe 67 , And is sprayed from the gas shower 65 onto the substrate 68 and undergoes a thermal decomposition reaction in a plasma atmosphere, and a glass film is formed on the substrate 68. Reference numeral 74 denotes a side surface protection plate for forming a uniform glass film on the substrate 68.

JP-A-11-288289 JP 2001-348236 A JP 2002-141342 A

  However, the above glass film forming method has the following problems.

  In the above forming method, a glass film can be formed only on one side of the substrate. Therefore, when forming glass films on both sides of the substrate, after forming the glass film on one side (surface) of the substrate, break the inside of the reaction vessel once to atmospheric pressure, place the substrate upside down, A glass film had to be formed on the back surface under vacuum.

  However, this method has a problem that it takes time to form a glass film. Furthermore, since the film is separately formed on the front surface and the back surface of the substrate, the characteristics (optical, thermal, mechanical characteristics, etc.) between the front and back glass films may be different. In addition, when the substrate is turned over on the lower electrode, the glass film on the substrate surface is damaged or contaminated.

  Further, when a glass film is formed on one surface (front surface) of the substrate, the substrate is warped due to a difference in thermal expansion coefficient between the glass film and the substrate. When the warped substrate is heat-treated at a high temperature, the warpage of the substrate increases. When a warped glass film is processed to form a waveguide, a waveguide having a large loss difference between the TE mode and the TM mode and having a large so-called polarization dependency is obtained. The warpage of the substrate causes a distribution in the dimension of the exposure pattern in the substrate plane in the photolithography process, and further degrades the processing dimension accuracy in the subsequent dry etching process.

  When the thermal expansion coefficient and the softening temperature of the substrate and the glass film are greatly different, the above problem occurs remarkably, so that the substrate is warped when the glass film is first formed on the substrate surface. Further, even if a glass film is formed on the back surface of the warped substrate, the generated warp does not return. The above problem also occurs remarkably when the relative refractive index difference between the core layer and the clad layer of the waveguide is large.

  Accordingly, an object of the present invention is to solve the above-described problems and provide a glass film forming method and a manufacturing apparatus for forming glass with the same composition and the same film thickness on both upper and lower surfaces of a substrate.

  In order to achieve the above object, according to the first aspect of the present invention, an upper electrode and a lower electrode are arranged to face each other in a reaction vessel, a high voltage is applied to the electrode, and a gap is formed on the lower electrode. When the substrate is placed, an open space is formed on the lower surface of the substrate, and a glass film is formed on the upper and lower surfaces of the substrate, a halogen lamp heater is provided on the upper electrode, and the electrode is brought to a desired temperature by the halogen lamp heater. This is a glass film forming method in which a gas serving as a glass raw material is introduced into a reaction vessel while being heated, and a glass film is formed on the upper and lower surfaces of a substrate by causing a thermal decomposition reaction in a plasma atmosphere.

  According to the invention of claim 2, the upper electrode and the lower electrode are arranged to face each other in the reaction vessel, a high voltage is applied to the electrode, and a substrate is arranged on the lower electrode with a gap therebetween. When an open space is formed on the lower surface of the substrate and a glass film is formed on the upper and lower surfaces of the substrate, a halogen lamp heater is provided on the lower electrode, a quartz window is provided on the upper portion of the halogen lamp heater, and the halogen lamp heater In this glass film forming method, a gas serving as a glass raw material is introduced into a reaction vessel while heating an electrode to a desired temperature, and a thermal decomposition reaction is caused in a plasma atmosphere to form glass films on upper and lower surfaces of a substrate.

  The invention according to claim 3 is the glass film forming method according to claim 1 or 2, wherein the electrode is heated from 300 ° C. to 600 ° C. by a halogen lamp heater.

  The invention of claim 4 is the glass film forming method according to any one of claims 1 to 3, wherein the temperature of the electrode facing the electrode provided with the halogen lamp heater is heated from 300 ° C to 450 ° C.

  A fifth aspect of the present invention is the glass film forming method according to any one of the first to fourth aspects, wherein the upper electrode and the lower electrode are heated to the same desired temperature.

  The invention according to claim 6 is the glass film forming method according to claim 1 or 2, wherein the height of the gap is in the range of 5 mm to 40 mm.

Invention of Claim 7 forms the glass film in the upper and lower surfaces of a board | substrate using the glass film formation method in any one of Claim 1-6,
A step of high-temperature heat treatment of the substrate on which the glass film is formed at a temperature in the range of 800 ° C. to 1350 ° C.
Forming a waveguide pattern having a rectangular cross section by photolithography and dry etching on the glass film;
And a high-temperature heat treatment of the waveguide pattern at a temperature in the range of 800 ° C. to 1350 ° C.

  The invention according to claim 8 is a reaction vessel for forming a glass film, a means connected to the reaction vessel for evacuating the inside of the reaction vessel to a high vacuum, and an upper electrode and a lower electrode arranged in the reaction vessel opposite to each other. A means for applying high-frequency power; a substrate fixing member that forms a space on the lower surface of the substrate; and a halogen lamp heater built in the upper electrode; A glass film manufacturing apparatus provided with a gas ejection shower plate provided on the lower electrode side and means for introducing a gas or the like as a glass raw material into the reaction vessel via the gas ejection shower plate.

  The invention of claim 9 comprises a reaction vessel for forming a glass film, a means connected to the reaction vessel for exhausting the inside of the reaction vessel to a high vacuum, and an upper electrode and a lower electrode disposed in the reaction vessel opposite to each other. Means for applying high-frequency power, a substrate fixing member for disposing a substrate on the lower electrode through a gap and forming an open space on the lower surface of the substrate, a halogen lamp heater built in the lower electrode, and the halogen lamp A quartz glass window provided in the upper part of the heater, a gas ejection shower plate provided on the lower electrode side of the upper electrode, and a gas serving as a glass raw material in the reaction vessel through the gas ejection shower disc A glass film manufacturing apparatus provided with a means for introducing.

  According to the present invention, an excellent effect that glass films having the same composition and the same film thickness can be formed on the upper and lower surfaces of the substrate is exhibited.

  Hereinafter, a preferred embodiment of the present invention will be described in detail with reference to the accompanying drawings.

  FIG. 1 shows a schematic diagram of a manufacturing apparatus 1 used in the glass film forming method of the present embodiment.

  The manufacturing apparatus 1 is provided in a clean booth 10 maintained in a class 100 by a clean unit 40.

  A reaction vessel 11 is provided in the clean booth 10, and an upper electrode 5 and a lower electrode 4 are arranged opposite to each other at a predetermined interval inside the reaction vessel 11. The lower electrode 4 is provided with a nichrome wire heater (resistance heater) 18, and the upper electrode 5 has a built-in halogen lamp heater 8 that can be heated to a temperature range of at least 300 to 600 ° C.

  Large capacity exhaust devices 13 and 13 are provided at the bottom of the reaction vessel 11 as high vacuum exhaust means via two exhaust ports 12 and 12, respectively. The large capacity exhaust device 13 includes a mechanical booster pump 14 and a dry pump 15.

  The displacement of the mechanical booster pump 14 is 8200 l / min or more, and the displacement of the dry pump 15 is 1200 l / min or more.

  The lower electrode 4 and the upper electrode 5 are connected to a high frequency power source 22 that applies high frequency power via lead wires 21 and 21. A substrate 25 (three in the figure) is disposed on the lower electrode 4 via a substrate fixing member 24, whereby a gap 17 is formed between the lower electrode 4 and the substrate 25. An open space 26 is formed between the lower electrode 4 and the substrate 25. In the present embodiment, a quartz substrate is used as the substrate 25.

  Here, the open space 26 formed on the lower surface of the substrate 25 will be described.

  As shown in FIG. 2, the substrate fixing member 24 is formed in a columnar shape and is provided at the periphery of the substrate 25, and fixes the substrate 25 in parallel with the lower electrode 4. Each substrate fixing member 24 is provided at three locations where the peripheral edge of one substrate 25 is substantially equally divided to fix the substrate 25. Further, glass, porcelain or the like was used as a material for forming the substrate fixing member 24.

  The gap 17 between the substrate 25 and the lower electrode 4 is preferably 5 mm to 40 mm. This is because if the gap 17 is smaller than 5 mm, it is difficult for plasma to wrap around the lower surface of the substrate 25 during the formation of the glass film. Furthermore, the gas introduced into the reaction vessel 11 also hardly flows around the lower surface of the substrate 25, and the composition and film thickness of the glass films formed on the upper surface and the lower surface of the substrate 25 are different. On the other hand, if the gap is larger than 40 mm, the difference in the composition and optical characteristics of the glass film in the plane between the upper surface of the substrate 25 and the lower surface of the substrate 25 will increase, and the composition of the glass film formed on the upper and lower surfaces of the substrate 25 will increase. This is because the film thickness distribution is non-uniform.

  In the present embodiment, three columnar substrate fixing members 24 are provided on the lower side of the substrate 25 in one substrate 25, but four or more may be used. The substrate fixing member 24 may include a mechanism for sandwiching the substrate 25 and may be fixed to the upper side (the upper electrode 5, the upper wall, etc.) or the side wall of the reaction vessel 11 to hold the substrate 25. At that time, the substrate fixing member 24 is not limited to the columnar shape, but may be two or more.

  Returning to FIG. 1, on the lower electrode 4 side of the upper electrode 5, there is provided a quartz glass shower disc 19 for gas ejection for injecting gas into the reaction vessel 11. The shower disk 19 is formed with a large number of jet outlets (gas jet mechanisms) 20, and a gas supply pipe 23 for supplying the jetted gas is connected to the upper side of the shower disk 19. The gas supply pipe 23 is provided with a tape heater 45 for setting the gas passing through the gas supply pipe 23 to the same temperature.

The reaction container 11 is adjacent to a reaction container front chamber 42 through which a substrate 25 is taken in and out through a substrate entrance 41. The reaction vessel front chamber 42, the gas shower 44 blowing N ₂ gas is provided on the substrate surface, N ₂ gas pipe 43 for introducing the N ₂ gas is connected to the gas shower 44.

The gas introduced into the reaction vessel 11 is a gas obtained by vaporizing an alcoholate liquid source that is a raw material for the glass film, and a gas such as O ₂ , N ₂ , NH ₃ , C ₂ F _6, etc. that reacts with the gas. Is used.

As the alcoholate-based liquid source, a Si-based liquid source 28 such as [Si (OC ₂ H ₅ ) ₄ ] is used and heated and vaporized in a thermostatic chamber 29. The temperature of the thermostatic chamber 29 was 75 ° C. higher than the melting point of the liquid source 28 and lower than the boiling point. A Si-based gas supply pipe 27 that supplies gas obtained by vaporizing the Si-based liquid source 28 is connected to the gas supply pipe 23.

In addition to the Si-based liquid source 28, a Ge-based liquid source 31 such as [Ge (OCH ₃ ) ₄ ] and a P-based liquid source 34 such as [P (OCH ₃ ) ₄ ] may be used. , 35 to heat and vaporize. A Ge-based gas supply pipe 30 that supplies gas vaporized from the Ge-based liquid source 31 and a P-based gas supply pipe 33 that supplies gas vaporized from the P-based liquid source 34 are also connected to the gas supply pipe 23. .

_{Also, O 2, N 2, NH} 3, C 2 F 6 and O ₂ gas supply pipe 36 for supplying to the reaction vessel 11, respectively, N ₂ gas supply pipe 37, NH ₃ gas supply pipe 38, C ₂ F ₆ gas supply A pipe 39 is connected to the gas supply pipe 23.

  Next, a method for forming a glass film will be described.

  The inside of the reaction vessel 11 in which the substrate 25 is disposed is evacuated to a high vacuum by the large capacity exhaust devices 13, 13, high frequency power is applied to the lower electrode 4 and the upper electrode 5 by the high frequency power source 22, and Heating is performed by the supplied halogen lamp heater 8, and the lower electrode 4 is heated by the nichrome wire heater 18.

  The applied high frequency power is 13.56 MHz and 1 kW, and the heating temperature of the upper electrode 5 is in the range of 300 to 600 ° C. In addition, the heating temperature of the upper electrode 5 and the lower electrode 4 was made into the same temperature within the range of 300-450 degreeC here.

  The degree of vacuum in the reaction vessel 11 is preferably several Pa to several tens Pa. If the degree of vacuum is low, the amount of the glass film formed on the lower surface of the substrate 25 is reduced, and a non-uniform glass film tends to be formed. If the degree of vacuum is too high, the film forming rate is reduced and the glass film is oxygen-defected. This is because it is easy.

Next, steam, O ₂ gas, and C ₂ F ₆ gas, which are vaporized by heating the Si-based liquid source 28 to 75 ° C. in the thermostat 29, are mixed in the gas supply pipe 23 heated by the tape heater 45. Superposed and introduced into the reaction vessel 11. The introduced gas is ejected from the ejection port 20 of the shower disk 19 and is uniformly diffused in the reaction vessel 11.

The O ₂ gas is flowed in order to cause a sufficient thermal decomposition reaction of the gas obtained by vaporizing the Si-based liquid source 28 in a plasma atmosphere, and the C ₂ F ₆ gas is F (fluorine) in the SiO ₂ glass film. Used to add.

The temperature in the gas supply pipe 23 is preferably in the range of 80 ° C to 120 ° C. When the temperature in the tube is higher than 120 ° C., hydrolysis reaction occurs in the tube, and glass fine particles adhere to the tube. When the temperature is lower than 80 ° C., adhesion due to liquefaction of the Si-based liquid source 28, C ₂ F ₆ gas, This is because the liquid reaction occurs.

In the reaction vessel 11, plasma is generated between the upper electrode 5 and the lower electrode 4 by high-frequency power and kept at a high vacuum, so that F is formed on the upper and lower surfaces of the substrate 25 by a thermal decomposition reaction in a plasma atmosphere. Thus, a glass film having a low refractive index of SiO ₂ added thereto is formed.

When taking out the substrate 25 on which the glass film has been formed from the reaction vessel 11, the inside of the reaction vessel 11 is broken to atmospheric pressure and then taken out from the substrate inlet / outlet 41. At this time, N ₂ gas is sprayed onto the substrate 25 from the gas shower 44 in the reaction chamber front chamber 42 to remove dust and the like adhering to the upper and lower surfaces of the substrate 25.

  Further, when glass films having different compositions are laminated on the upper and lower surfaces of the substrate 25, the glass films may be continuously formed without taking out the substrate 25 from the reaction vessel 11.

  As described above, according to the glass film forming method of the present embodiment, the upper surface and the lower surface of the substrate 25 are sufficiently heated by the radiant heat (infrared radiant heat) from the lower electrode 4 and the upper electrode 5, and the plasma is also the upper surface of the substrate 25. Not only the bottom surface of the substrate 25 but also the gas of the glass raw material and the gas that reacts to the gas can also flow into the bottom surface of the substrate 25. At the same time, a glass film having almost the same composition can be formed.

  Further, since the open space 26 is formed between the lower surface of the substrate 25 and the lower electrode 4 and the glass film is manufactured on the upper surface and the lower surface of the substrate 25, the time for forming the glass film can be shortened, which is extremely efficient and economical. It is.

  Further, by using the halogen lamp heater 8 as a heat source for heating the substrate, the upper surface and the lower surface of the substrate can be heated substantially uniformly by infrared radiation heat. A uniform glass film can be formed.

  Since the halogen lamp heater 8 is used to heat the substrate 25, high-speed heating and high-speed temperature reduction become easy. In the temperature range from 300 ° C to 600 ° C, the apparatus is started up in a short time to form a glass film. Is possible. Furthermore, there is almost no generation of particles and dust from the halogen lamp heater 8, and extremely clean heating can be performed, and a glass film with almost no contamination of particles and dust can be obtained.

  Further, the lower electrode 4 on the side facing the halogen lamp heater 8 is also heated to the same temperature as the halogen lamp heater 8 in the temperature range of 300 ° C. to 450 ° C. with a nichrome wire heater or the like, thereby further increasing the temperature of the substrate. It can be kept stable.

  Further, by using quartz glass as the material of the shower disk 19 that ejects gas, the upper and lower surfaces of the substrate 25 can be heated substantially uniformly by infrared radiation heat, and the lower surface of the halogen lamp heater 8 is a glass film. Clouding can be prevented.

  Further, even if there is a large difference between the thermal expansion coefficient and the softening temperature between the substrate 25 and the glass film, a glass film having substantially the same composition can be simultaneously formed not only on the upper surface of the substrate 25 but also on the lower surface of the substrate 25. The warpage to the substrate 25 hardly occurs.

  In this embodiment, since an alcoholate-based liquid source is vaporized, gas can be circulated into a slight gap, and not only on the substrate surface but also on the lower surface of the substrate 25. Glass films having the same composition can be formed simultaneously.

  Further, since the substrate 25 hardly warps, it is possible to easily form a plurality of glass films having different glass compositions on the upper and lower surfaces of the substrate 25.

  In order to form the glass film by heating the upper electrode 5 and the lower electrode 4 to the same desired temperature, the glass films formed on the upper surface and the lower surface of the substrate 25 should be formed with substantially the same composition and almost the same film thickness. Can do.

  As long as the substrate 25 can withstand the heating temperature, any of glass materials such as quartz glass and multicomponent glass, semiconductor materials (Si, GaAs, InP, etc.), ceramics, polymer materials, and ferroelectric materials can be used. Good.

  By selecting a material for forming the substrate 25 in a wide range, it can be applied to glass films such as a reflection mirror glass film, a filter glass film, a deflection mirror glass film, an insulating glass film, and a light diffusion glass film.

As the glass raw material gas, an SiH ₄ -based gas may be used in addition to a gas obtained by vaporizing an alcoholate-based liquid source.

  Further, the high frequency power may be higher than 13.56 MHz, or may be a microwave frequency.

  The heating temperature of the lower electrode 4 may be in the temperature range of 300 ° C. to 450 ° C., and may be infrared heating in addition to resistance heating. This is because if the electrode temperature is lower than 300 ° C., it is difficult to obtain a uniform and low-loss glass film, and if it is higher than 450 ° C., it is difficult to provide a member or device for maintaining a vacuum.

Further, in addition to the Si-based liquid source 28, O ₂ gas, and C ₂ F ₆ gas, a Ge-based liquid source 31, a P-based liquid source 34, N ₂ gas, and NH ₃ gas are used so that the upper and lower surfaces of the substrate 25 are formed. SiO ₂ film, SiO ₂ film containing GeO _2, SiO ₂ film containing P ₂ O _5, may be further formed a glass layer which N is added.

The mechanical booster pump 14 and the dry pump 15 that are the large-capacity exhaust devices 13 provided in the manufacturing apparatus 1 are not limited to two sets, and two or more sets may be provided. However, the exhaust device 13 needs to have a large exhaust amount. This is because gases such as N ₂ , C ₂ F ₆ , and NH ₃ are used to add a large amount of N and F into the glass film of SiO ₂ , but there are few oxygen defects and little OH group contamination. In order to form a glass film, it is necessary to flow at least 100 sccm. When the flow rate of a gas such as N ₂ , NH ₃ , C ₂ F ₆ is increased, the flow rate of O ₂ needs to be increased accordingly.

  Therefore, in order to introduce a large flow of gas and keep the inside of the reaction vessel 11 at a high vacuum level, a large capacity exhaust device is required. Thereby, a glass film can be formed in a high vacuum while flowing a large amount of gas into the reaction vessel 11.

  Furthermore, you may use the board | substrate 25 by which at least one of both surfaces was grind | polished in the mirror surface state. By using a substrate polished in a mirror state, a glass film with a more uniform distribution of film thickness, refractive index, and the like can be formed.

  Next, a glass film forming method and a manufacturing apparatus thereof according to another embodiment will be described.

  As shown in FIG. 3, the glass film manufacturing apparatus 2 of the present embodiment is basically the same as the glass film manufacturing apparatus 1 of FIG. 1 described above. The upper electrode 7 is provided with a nichrome wire heater 18, the lower electrode 6 is provided with a halogen lamp heater 8, and a quartz window 9 is provided on the upper surface of the lower electrode 6. Different.

  The quartz window 9 is a lid made of quartz, and is provided to prevent the heating surface of the halogen lamp heater 8 from becoming cloudy due to the adhesion of the glass film.

  As shown in FIG. 4, a substrate fixing member 24 on which the substrate 25 is placed is provided on the quartz window 9. An open space 26 is formed between the substrate 25 and the quartz window 9, and the gap 17 (height from the quartz window 9 to the lower surface of the substrate 25) is 5 to 40 mm, as in the manufacturing apparatus 1.

  The manufacturing apparatus 2 and the glass film forming method formed by the manufacturing apparatus 2 have the same effects as the above-described embodiment. Furthermore, by providing the halogen lamp heater 8 on the lower electrode 6, the upper surface and the lower surface of the substrate 25 can be heated more uniformly. In addition, since the halogen lamp heater 8 is built in the lower electrode 6 and the quartz window 9 is provided to protect the heating surface of the heater 8, the gas ejection mechanism 20 of the gas ejection shower disk 19 is used instead of quartz glass. You may comprise with a metal-type material.

  Furthermore, a halogen lamp heater 8 may be provided on both the lower electrode 6 and the upper electrode 7. At this time, the heating temperature range of the lower electrode 6 and the upper electrode 7 can be set to 300 to 600 ° C., and the temperature in the reaction vessel 11 can be made uniform at a higher temperature.

  Next, a method for forming a waveguide using the above glass film forming method will be described with reference to FIGS.

  First, as shown in FIG. 5A, a glass film to be a lower clad layer having a low refractive index is formed on the upper and lower surfaces of a quartz glass substrate 50 having a diameter of 4 inches. Hereinafter, <Example 1a> describes the film formation conditions and the characteristic results of the formed glass film. <Example 2a> is obtained by changing the film forming conditions of <Example 1a>.

<Example 1a>
In a state where the upper electrode 5 and the lower electrode 4 in the manufacturing apparatus 1 are heated to the same 400 ° C., a gas obtained by vaporizing [Si (OC ₂ H ₅ ) ₄ ], an O ₂ gas, and a C ₂ F ₆ gas are used as a tape heater. In the gas supply pipe 23 heated to a desired temperature in 45, the gas flow ratio O ₂ : C ₂ F ₆ is mixed and superposed so as to be 4: 1, then introduced into the reaction vessel 11, and plasma is supplied for 35 minutes. First glass films 51 and 52 to be a lower clad are formed in an atmosphere.

  In this step, for example, a glass film 51 having a refractive index of 1.4381 ± 0.0008 at a wavelength of 632.8 nm and a thickness of 2.0 μm ± 0.2 μm can be formed on the upper surface of the substrate 50. A glass film 52 having a refractive index of 1.4378 ± 0.0006 at the same wavelength could be formed with a thickness of 1.9 μm ± 0.3 μm.

  Since the first glass films 51 and 52 are obtained by forming the first glass films 51 and 52 on the upper and lower surfaces of the quartz glass substrate 50 while being heated to approximately 400 ° C., the first glass films 51 and 52 are glass films that are stable with respect to temperature. Even when the glass film was heat-treated at a higher temperature in the range of 800 to 1350 ° C., the refractive index of the glass film remained almost unchanged and was a stable glass film.

<Example 2a>
The heating temperature of the upper electrode 5 and the lower electrode 4, using gas and the film forming time is the same, the flow ratio of O ₂ gas and C ₂ F ₆ gas _{O 2: C 2 F 6 =} 13: set to 1. Thereby, for example, a glass film having a refractive index of 1.4146 ± 0.0012 at a wavelength of 632.8 nm can be formed on the upper surface of the substrate with a thickness of 1.8 μm ± 0.42 μm, and the refractive index at the same wavelength can be formed on the lower surface of the substrate. A glass film having a thickness of 1.4142 ± 0.0015 could be formed with a thickness of 1.8 μm ± 0.52 μm.

  Next, as shown in FIG. 5B, a second glass film that forms a core layer on the upper surface of the substrate 50 is formed on the first glass films 51 and 52. Hereinafter, <Example 1b> describes the film formation conditions and the characteristic results of the formed glass film. <Example 2b> is obtained by changing the film forming conditions of <Example 1b>.

<Example 1b>
While the upper electrode 5 and the lower electrode 4 are heated to the same temperature of 400 ° C., steam, O ₂ gas, and N ₂ gas vaporized by heating [Si (OC ₂ H ₅ ) ₄ ] to 75 ° C. in a constant temperature bath. Is introduced into the gas supply pipe 23 heated at 80 ° C. by the tape heater 45. The gas flow ratio was N ₂ : O ₂ = 10: 1 mixed and superimposed, and then introduced into the reaction vessel 11 to form second glass films 53 and 54 in a plasma atmosphere for 35 minutes.

  Thus, for example, the second glass film 53 having a refractive index of 1.47014 ± 0.0007 at a wavelength of 632.8 nm is formed on the upper layer of the first glass film 51 on the upper surface of the substrate 50 with a thickness of 1.8 μm ± 0.53 μm. A second glass film 54 having a refractive index of 1.4696 ± 0.0016 at the same wavelength is 1.7 μm ± 0 on the upper layer (lower side in the figure) of the first glass film 52 on the lower surface of the substrate 50. It was possible to form with a thickness of 61 μm.

<Example 2b>
With the upper electrode 5 and the lower electrode 4 heated to 400 ° C., the flow rate of [Si (OC ₂ H ₅ ) ₄ ] is set to 6 sccm and the flow rate of [Ge (OCH ₃ ) ₄ ] is set to 0.8 sccm, and the temperature is kept constant. Steam vaporized by heating to 75 ° C. in the tank, and O ₂ gas and N ₂ gas are introduced into the supply pipe 23 heated to 80 ° C. by the tape heater 45. The gas flow ratio N ₂ : O ₂ was mixed at 14: 1 and superimposed, and then introduced into the reaction vessel 11 to form a second glass film in a plasma atmosphere for 35 minutes.

  Thereby, for example, a second glass film having a refractive index of 1.499 ± 0.0005 at a wavelength of 632.8 nm can be formed on the first glass film upper layer on the upper surface of the substrate with a thickness of 1.94 μm ± 0.06 μm. On the upper surface of the first glass film on the lower surface of the substrate, a second glass film having a refractive index of 1.498 ± 0.0008 at the same wavelength could be formed with a thickness of 1.93 μm ± 0.18 μm.

  Next, as shown in FIG. 5C, a second glass film 53 is formed on the core layer 55 having a rectangular cross section by photolithography and dry etching.

The second glass film 53 on the upper surface of the substrate 50 is heat-treated at 1000 ° C. for 2 hours in an oxygen atmosphere, then lowered to room temperature, and then a photoresist is applied onto the second glass film 53 and baked. A photomask on which the waveguide pattern of the core layer 55 is drawn is placed on the resist film, and ultraviolet rays are irradiated from above the photomask. After the ultraviolet irradiation, development is performed to obtain the same photoresist pattern as the waveguide pattern of the core layer 55 on the second glass film 53. Next, using the photoresist pattern as an etching mask, the second glass film 53 is patterned while a CHF ₃ gas is allowed to flow as an etching gas in a dry etching process using a reactive ion etching apparatus (RIE). A core layer 55 having a shape is obtained.

  Next, as shown in FIG. 5D, the substrate having the core layer 55 is put into the apparatus 1 again, and the third glass films 56 and 57 having the same composition as the first glass films 51 and 52 are replaced with the cores. On the layer 55, the upper layer of the first glass film 51 and the upper layer of the second glass film 54 (lower side in the figure) were formed with a film thickness of about 10 μm.

  Thereafter, the substrate is subjected to high-temperature heat treatment at 1100 ° C. in an oxygen atmosphere for 2 hours to complete the waveguide 58. In addition, what is necessary is just to give high temperature heat processing within the range of 800 to 1350 degreeC.

  Next, the measurement results of the warpage and optical characteristics of the waveguide 58 manufactured by the above-described forming method will be described.

  The warpage of the waveguide 58 occurs when the quartz glass substrate 50 having a diameter of 4 inches before the glass film formation is about 7 μm, whereas the warpage of the glass substrate after the formation of the waveguide 58 is about 9 μm. There is almost no warpage due to the waveguide formation. This is because glass films having the same composition and the same film thickness are formed on the upper and lower surfaces of the substrate 50 under the same conditions by the above-described glass film forming method.

  Propagation loss at a wavelength of 1550 nm in the TE mode and TM mode was measured in the waveguide 58 composed of a waveguide pattern composed of a straight line having a length of 30 cm and an S-shaped curve. As a result, the difference in loss between the TE and TM modes was almost 0.04 dB or less, and a waveguide with extremely small polarization dependence could be formed. The propagation loss of the waveguide 58 is 0.007 dB / km at a wavelength of 1550 nm, and an ultra-low loss waveguide can be formed.

  Furthermore, in the method for forming a waveguide according to the present embodiment, glass films are formed on the upper and lower surfaces of the substrate 50. Therefore, the glass film on the upper surface side of the substrate 50 is formed in the core pattern of the waveguide by photolithography or dry etching. Even if it fails, the waveguide pattern can be processed using the first and second glass films 52 and 54 laminated on the lower surface of the substrate 50. As a result, it is possible to reduce the waste of the substrate, improve the production yield of the waveguide, and reduce the cost of the waveguide.

  Further, even if a waveguide is manufactured in the steps shown in FIGS. 5A to 5D using the manufacturing apparatus 2, there is almost no warpage equivalent to the waveguide 58, and the optical characteristics with respect to temperature change are stable. In addition, a waveguide with very small transmission loss and polarization dependent loss can be produced.

It is the schematic which shows the manufacturing apparatus of the glass film of this Embodiment. The structure which fixes a board | substrate to the lower electrode of the manufacturing apparatus of FIG. 1 is shown, (a) is the top view, (b) is a side view. It is the schematic which shows the manufacturing apparatus of the glass film of other embodiment. The structure which fixes a board | substrate to the lower electrode of the manufacturing apparatus of FIG. 3 is shown, (a) is the top view, (b) is a side view. (A)-(d) is process sectional drawing which forms a glass film in both surfaces of a board | substrate, and forms a waveguide. It is the schematic which shows the manufacturing apparatus of the glass film by the conventional CVD method.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Manufacturing apparatus 4 Lower electrode 5 Upper electrode 8 Halogen lamp heater 9 Quartz window 11 Reaction container 13 Large capacity exhaust apparatus 17 Gap 19 Gas injection shower disk 22 High frequency power supply 23 Gas supply pipe 24 Substrate fixing member 25 Substrate 26 Open space

Claims (9)

  In the reaction vessel, the upper electrode and the lower electrode are arranged to face each other, a high voltage is applied to the electrode, and a substrate is arranged on the lower electrode with a gap, and an open space is formed on the lower surface of the substrate. When a glass film is formed on the upper and lower surfaces of the substrate, a halogen lamp heater is provided on the upper electrode, and a gas serving as a glass raw material is introduced into the reaction vessel while heating the electrode to a desired temperature by the halogen lamp heater. A glass film forming method comprising causing a thermal decomposition reaction in a plasma atmosphere to form glass films on the upper and lower surfaces of a substrate.   In the reaction vessel, the upper electrode and the lower electrode are arranged to face each other, a high voltage is applied to the electrode, and a substrate is arranged on the lower electrode with a gap, and an open space is formed on the lower surface of the substrate. When a glass film is formed on the upper and lower surfaces of the substrate, a halogen lamp heater is provided on the lower electrode, a quartz window is provided on the upper portion of the halogen lamp heater, and the electrode is heated to a desired temperature by the halogen lamp heater. A glass film forming method comprising introducing a gas as a glass raw material into a reaction vessel and causing a thermal decomposition reaction in a plasma atmosphere to form glass films on the upper and lower surfaces of the substrate.   The glass film forming method according to claim 1 or 2, wherein the electrode is heated from 300 ° C to 600 ° C by the halogen lamp heater.   The glass film forming method according to any one of claims 1 to 3, wherein a temperature of an electrode facing the electrode provided with the halogen lamp heater is heated from 300 ° C to 450 ° C.   The glass film forming method according to claim 1, wherein the upper electrode and the lower electrode are heated to a desired same temperature.   The glass film forming method according to claim 1, wherein a height of the gap is in a range of 5 mm to 40 mm. Forming a glass film on the upper and lower surfaces of the substrate using the glass film forming method according to claim 1;
A step of high-temperature heat treatment of the substrate on which the glass film is formed at a temperature in the range of 800 ° C. to 1350 ° C.
A step of forming a waveguide pattern having a rectangular cross section by photolithography and dry etching on the glass film, and a step of high-temperature heat-treating the waveguide pattern at a temperature in the range of 800 ° C. to 1350 ° C. A method for forming a waveguide.   A reaction vessel for forming a glass film, a means connected to the reaction vessel for evacuating the inside of the reaction vessel to a high vacuum, and a means for applying high-frequency power by disposing the upper electrode and the lower electrode oppositely in the reaction vessel; A substrate fixing member for disposing a substrate on the lower electrode through a gap and forming an open space on the lower surface of the substrate; a halogen lamp heater built in the upper electrode; and a lower electrode side of the upper electrode. An apparatus for producing a glass film, comprising: a gas ejection shower plate; and means for introducing a gas or the like as a glass raw material into the reaction vessel through the gas ejection shower plate. A reaction vessel for forming a glass film, a means connected to the reaction vessel for evacuating the inside of the reaction vessel to a high vacuum, and a means for applying high-frequency power by disposing the upper electrode and the lower electrode oppositely in the reaction vessel; A substrate fixing member for disposing a substrate on the lower electrode through a gap and forming an open space on the lower surface of the substrate; a halogen lamp heater built in the lower electrode; and an upper portion of the halogen lamp heater. A quartz glass window, a gas ejection shower plate provided on the lower electrode side of the upper electrode, and means for introducing gas or the like as a glass raw material into the reaction vessel through the gas ejection shower plate are provided. A glass film manufacturing apparatus characterized by the above.

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