JPH1164661A - Formation of optical waveguide film - Google Patents

Abstract

PROBLEM TO BE SOLVED: To reduce the cost per sheet of substrates by making it possible to efficiently execute a transparent vitrification treatment of porous glass films. SOLUTION: This method includes a stage for depositing glass particles on the substrates 23 by an oxyhydrogen flame burner to form the porous oxide glass films, then forming the transparent oxide glass films by heating the same and an optical waveguide is formed. At this time, plural sheets of the substrates 23 formed with the porous glass films described above are erected and are arranged in parallel with each other along the perpendicular direction on a sintering jig 21 of a flat planar shape apart prescribed intervals from each other by inserting the one-side edges of the substrates 23 into grooves 22 formed in parallel on the jig. Further, plural sheets of the substrates 23 supported at the jig described above are introduced into the furnace and are integrally subjected to the sintering treatment, by which the transparent vitrification of the porous glass films is executed.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

TECHNICAL FIELD The present invention relates to a flame deposition (Fla)
me Hydrolysis Deposition,
The present invention relates to a method for forming an optical waveguide film including a step of forming a porous oxide film on a substrate by an FHD (FHD) method, and then performing a vitrification process by sintering the film.

[0002]

2. Description of the Related Art An optical waveguide has a structure in which an under cladding layer, a core layer, and an over cladding layer are laminated, and Si or quartz is used for a substrate on which the optical waveguide is formed. . Optical waveguide devices include a beam splitter that splits light into a number of parts, an optical switch that switches signals to desired lines, and
In the optical subscriber system, each home is expected to be introduced into an optical circuit in an ONU that integrates an LD, a PD, etc. together with an optical waveguide having a function of demultiplexing / combining an optical signal on a Si substrate. For example, Y. Yamada et al. , “Ap
application of planar light
wave circuit platform to
hybrid integrated optical
WDM transmitter / receiver
module "Electron. Lett. 31
(16), 1366-1367 (1995).

The manufacturing process of such an optical waveguide will be described by taking a case where a Si substrate is used as an example.
In order to fabricate an optical waveguide on an i-substrate, first, a glass layer having a thickness of about 20 μm serving as an under clad is formed, a light-guiding core layer is formed thereon, and this core layer is lithographically and anisotropically formed. This is performed by forming a glass layer having a thickness of 30 μm or more to be an over clad after processing into a light waveguide pattern by reactive etching. As a means for forming these glass layers, a flame deposition method, an electron beam evaporation method, a sputtering method, a plasma CVD method, and the like are known, but the flame deposition method is generally used for producing a glass film having a thickness of several tens of μm. Used.

[0004] The flame deposition method is described in, for example, M. Kawach
i, “Silica waves on si
licon and theair applicati
onto integrated-optic com
ponents ", Optical and Quan
tum Electronics 22, 391-41
As shown in FIG. 6 (1990), in an apparatus as shown in FIG. 1, a halide such as Si, Ge, Br, or P is supplied to an oxyhydrogen flame burner to generate glass fine particles, which are then placed on a table. After being deposited on the substrate placed thereon to form a porous glass fine particle film,
This is a method of producing a transparent glass film by sintering at a temperature of 0 to 1400 ° C.

In FIG. 1, reference numeral 11 denotes a rotary table, reference numeral 12 denotes a substrate, and reference numeral 13 denotes an oxyhydrogen flame burner, which is movable in the direction of the arrow in the figure. Reference numeral 14 denotes an exhaust pipe.

In recent years, cost reduction of waveguide devices and PLC optical circuit modules has been demanded.
In C optical circuits and the like, researches on mounting optical components such as LDs and PDs on a waveguide circuit and reducing the cost of alignment with a fiber connected to the waveguide have been actively conducted. Of course, in consideration of cost reduction, if the cost related to the production of the waveguide can be reduced, it has not been met. Considering the process of forming an optical waveguide by the flame deposition method described above, regarding the deposition, a plurality of substrates are mounted on a single table in an apparatus as shown in FIG. It is possible to form a substrate on which a porous glass fine particle film is formed. But,
1200-140 for vitrification of the deposited film
It is necessary to perform sintering at a temperature of 0 ° C., and it is preferable that sintering is also performed in batches.

In this case, in the sintering step, the glass film or the glass film layer is kept low when air bubbles are actually used as a waveguide, for example, by preventing remaining bubbles and deformation of the substrate. The lossy nature must be maintained. Therefore, for example, in Japanese Patent Application Laid-Open Nos. 5-273424 and 7-27938, the atmosphere during sintering is controlled by the temperature. Japanese Patent Application Laid-Open No. 7-104139 describes that bubbles are prevented from remaining by devising the structure of a sintering furnace.

As described above, the sintering process has been studied on how to suppress the residual air bubbles, but at present, much has not been studied on reducing the cost.

The present invention has been made in view of the above circumstances,
It is an object of the present invention to provide a method for forming an optical waveguide film, which can advantageously perform a sintering process on a plurality of substrates collectively and reduce a sintering process cost.

[0010]

Means for Solving the Problems and Embodiments of the Invention The present inventors have made intensive studies to achieve the above object, and as a result, have reached the present invention.

That is, the present invention comprises a step of forming a porous oxide glass film by depositing glass fine particles on a substrate by an oxyhydrogen flame burner, and then heating this to form a transparent oxide glass film. In the method for forming an optical waveguide including a plurality of substrates on which the porous glass film is formed, one edge of the substrate is placed in grooves formed in parallel at predetermined intervals on a flat sintering jig. By inserting the parts respectively, they stand upright on the jig along the vertical direction, are arranged in parallel with each other, and introduce a plurality of substrates supported by the jig into the furnace and collectively sinter Further, the present invention provides a method for forming an optical waveguide film in which the above-mentioned porous glass film is formed into a transparent glass. In this case, it is preferable to arrange the dummy substrates along the vertical direction before and after the group of a plurality of substrates to be subjected to the sintering process, which are supported in parallel in the vertical direction by the jig.

Hereinafter, the present invention will be described in more detail.
In the present invention, silicon, quartz, or the like is used as a substrate. As a method for forming a porous oxide glass film on a substrate, an apparatus as shown in FIG. Can be followed.

According to the present invention, when the substrates on which a plurality of porous glass films are formed are subjected to a sintering process collectively, the number of substrates that can be processed is limited if the substrates are arranged horizontally.
As shown in FIG. 2, the substrates are oriented in a vertical line with the substrates oriented vertically.

Here, in FIG. 2, reference numeral 21 denotes a plate-shaped sintering jig. It is preferable that the sintering jig does not deform or react in an atmosphere containing O ₂ at a processing temperature of 1200 to 1400 ° C. and does not generate foreign matter, and quartz or SiC is used.

The surface of the jig 21 has a predetermined distance from each other, preferably 3 to 9 mm, more preferably 5 to 7 mm.
A large number of grooves 22 are arranged in parallel in the same direction at an interval of. The ends of a substrate 23 on which the porous glass film is formed are inserted into these grooves 22, whereby a large number of substrates 23 are respectively formed. They are erected along the vertical direction and are arranged side by side with the above-mentioned spacing therebetween. In this case, if the distance between the substrates 23 is small, the substrates may come into contact with each other and the deposited layer may be peeled off, and if the distance is large, the transparency may be insufficient. There is. Preferably, the depth of the groove 22 is about 3 to 5 mm. The number of the substrates 23 is not limited, and is appropriately selected depending on the size of the substrates and the furnace for performing the sintering process. Usually, 8 to 100 substrates, and particularly about 10 to 50 substrates, can be collectively processed.

In this case, as shown in FIG. 2, one or more, preferably 2 to 10, and especially 4 to 8 dummy substrates 24 are respectively provided before and after the substrate group including the plurality of substrates. It is preferable to arrange them in parallel at the above-mentioned intervals along the vertical direction. That is, as described above, a number of substrates are erected in the jig along the vertical direction and are arranged in parallel with each other, but when this is subjected to heat treatment in a furnace as it is, the substrate arranged at the forefront and the rearmost at the rear Since there is nothing on the front or rear of the arranged substrate, the manner in which heat is applied differs from other substrates. Therefore, before and after the porous glass film forming substrate arranged above, the substrate on which the porous glass film is not formed is arranged as a dummy, and the manner in which heat is applied is as similar as possible to all the porous glass film forming substrates. Is to do so. If sintering is performed without this dummy substrate, for example, for the topmost substrate, there is nothing in front, so that the transparent portion and the non-transparent portion reflect the temperature distribution in the substrate surface, and May occur within In addition, as the dummy substrate, a substrate formed of silicon, silicon carbide, or the like can be used.

The jig on which the substrate and the dummy substrate are arranged as described above is inserted into a furnace, and sintering is performed at a temperature of about 1200 to 1400 ° C., for example, in a mixed atmosphere of a hydrogen gas and an oxygen gas. This is to make the film transparent vitrification. The furnace to be used is preferably a material that is less contaminated and hardly deteriorates at the above temperature, and is preferably made of quartz or SiC.

In the present invention, as described above, a substrate having a plurality of porous glass films formed thereon is subjected to a sintering process collectively by, for example, an apparatus as shown in FIG.
As shown in FIG. 2, the substrate on which the porous glass film is formed is set upright and placed on a sintering jig. A plurality of substrates are similarly arranged in a line. This jig is inserted into a furnace core tube for sintering, and is treated at a temperature of 1200 to 1400 ° C. for a predetermined time in an appropriate atmosphere, for example, a mixed atmosphere of He and O ₂ , to form a transparent vitrification. Processing is performed.

In this case, conventionally, the substrate has been placed horizontally so as not to make any contact with the deposited porous glass layer and sintering has been performed. However, in the horizontal installation, the area occupied by the substrates in the furnace is large. For example, when processing a plurality of substrates arranged in a horizontal line, the furnace becomes extremely large, and it is necessary to perform the same temperature processing on all the substrates. For this reason, it is necessary to increase the soaking length, but it is technically very difficult and is not practical for heat treatment of a large number of sheets. As shown in FIG. 6, for example, as shown in FIG. 6, a jig that can withstand a treatment at 1200 to 1400 ° C., for example, a jig such as SiO ₂ or SiC, is arranged in the vertical direction, and introduced into the furnace core tube. Although it is conceivable that the sintering jig is also a source of foreign matter, it is not preferable because the number of sources of dust increases in an atmosphere for performing vitrification. In FIG. 6, 31 is a jig, 32 is a porous glass film deposition substrate, 33
Is a ring-shaped spacer.

On the other hand, in the present invention, since the porous glass film formed on the substrate is formed up to the edge of the substrate, when sintering is performed as shown in FIG.
In order to arrange the substrates upright on a jig, they are inserted into grooves formed in the jig in advance. At this time, the contact between the groove and the substrate surface causes peeling of the deposited porous glass film layer, foreign particles generated due to the peeled glass fine particles and rubbing with the groove of the sintering jig adhere to the substrate surface, and the transparent glass Although it is conceivable that the adhered foreign matter may remain as it is after the sintering process, in fact, regarding the separation due to the contact between the groove provided in the sintering jig and the porous glass film layer, the density of the porous glass film is reduced. If it is high, no peeling is particularly observed. The density value is preferably 0.2 g / cm ³ or more. If the density value is lower than 0.2 g / cm ^3, there is a possibility that a scratch may occur or peeling may occur when contact is made to insert into the groove of the sintering jig. Regarding foreign matter, about 10 to 100 foreign matter having a size of 0.1 μm or more were confirmed in the portion that was in contact with the groove of the sintering jig. There is no problem because it is not the area where the wave circuit is manufactured. Actually, adhesion of foreign matter is not confirmed in the area where the waveguide circuit is formed, and there is no problem in the present sintering method, especially on the foreign matter surface. However, the appearance of the substrate after the sintering process is, as shown in FIG.
Portion (41 in the figure) was slightly unsintered compared to the inside. This was common for all substrates when a plurality of substrates were heat treated. As a representative example, FIG. 4 shows the result of measuring the distribution of the average surface roughness Ra of the glass film surface within the substrate surface.
Shown in The average surface roughness Ra is measured by DEKTAK800
This was performed by the stylus method using 0. The scanning distance is 1 mm, and the Ra value is calculated after subtracting the contribution of the warpage as the background. In the range of 4 cm from the center of the substrate, the Ra value was about 10 to 20 °. On the other hand, the Ra value became larger toward the outside, and the region was observed to be slightly unsintered in appearance, that is, 1 to 2 mm from the substrate end. In the region, the Ra value was about 300 °. This is because the substrate is located in front of the porous glass film layer in the vicinity of the center of the substrate when the porous glass film is sintered, and the contribution of radiant heat is sufficiently obtained. It is considered that sintering did not proceed sufficiently compared with the vicinity of the center because the contribution of the radiant heat from the steel became small and the heat easily escaped.

As described above, in the range of 1 to 2 mm from the edge of the substrate, there is a defect that the surface roughness is large compared to the vicinity of the center and the sintering is insufficient. However, this region is a region that is not used for manufacturing an optical circuit. There is no particular problem.

From the above, it has been confirmed that a glass film can be formed without causing any problem in the actual formation of an optical waveguide circuit even when the transparent vitrification treatment is performed with the arrangement of the substrates as shown in FIG. In the arrangement of FIG. 2, the number of substrates to be processed is reduced from about 10 to about 100 by setting the length of the sintering jig and the interval between the grooves for setting the substrates provided on the sintering jig to a desired value. It is possible to produce about 10 to 100 glass films by one sintering process. This makes it possible to reduce costs associated with sintering per substrate.

In the method of forming an optical waveguide film according to the present invention, the steps other than the formation of the porous film and the vitrification thereof can be performed by a known method to form an optical waveguide.

[0024]

EXAMPLES The present invention will be described below in detail with reference to examples and comparative examples, but the present invention is not limited to the following examples.

Example First, the deposition of the oxide glass fine particles on the substrate was performed as follows. A 10 cm diameter, 1 mm thick Si is placed on the outer periphery of a 80 cm diameter rotary table.
Multiple substrates were mounted. In the present embodiment, 12 sheets were mounted. At this time, the temperature of the substrate was heated to about 600 ° C. by a heater provided below the rotary table. The glass material was supplied to the oxyhydrogen flame burner while rotating the table on which the substrate was placed, and the glass particles were deposited on the substrate while the burner was reciprocated in the radial direction of the table. The height of the burner from the substrate was 2 cm, the distance between the burner and the exhaust pipe was 6.6 cm, and the angle to the normal direction of the burner was 70 °. Glass raw material is SiCl ₄ , BB
r ₃ and POCl ₃ were supplied at a rate of 50 cc /
min, 20 cc / min and 20 cc / min.
O ₂ was used as a carrier gas at this time. Regarding the flow rates of the other gases used, H ₂ = 8 L / min, O ₂ = 6
L / min and seal Ar = 1 L / min. The burner reciprocates while rotating the substrate, and the exhaust pipe also reciprocates in conjunction with the burner so as not to change the positional relationship with the burner. The stroke length of the burner and the exhaust pipe during the reciprocating motion was 16 cm, the moving speed was 1 cm / min, and the rotation speed of the table was 5 rpm. The deposition was performed for about 90 minutes.

After the deposition was completed, the substrates were taken out, and the deposited substrates were placed upright on a sintering jig as shown in FIG. 2, and each substrate was arranged in a line. A quartz jig was used as the sintering jig, and the distance between the substrates was 6 mm. Further, five dummy substrates were arranged in front of the first substrate and behind the rearmost substrate of the stacked and arranged substrates. An Si substrate having a diameter of 10 cm and a thickness of 0.5 mm was used as a dummy substrate.

The substrate and the jig thus arranged were inserted into an electric furnace and vitrified. Inner diameter 1 for furnace tube
A 6 cm quartz material was used. The atmosphere during processing is He
And a mixed atmosphere of O ₂ , and the respective flow rates are He =
2.5 L / min and O ₂ = 0.3 L / min. The processing temperature was 1350 ° C., and the temperature was maintained for 2 hours. The heating rate and the cooling rate were set sufficiently low so as not to slip into the Si substrate.
/ Min.

FIG. 3 shows all appearances of the glass films of the sintered samples.
At the outer circumference of 1 to 2 mm.
The a value was about 300 °, and the Ra value near the center of the substrate was about 20 °. FIG. 4 shows a representative example of the Ra distribution.

The adhesion of foreign matter was checked by visual observation by irradiating the surface of the substrate with a halogen lamp in a dark field. As a result, no adherence of foreign matter was observed near the center of each of the substrates. However, although foreign matter was found to adhere to the groove of the sintering jig, the depth of the groove was 4 mm, and almost all of the foreign matter adhered was 5 mm from the edge of the substrate.
mm, which is an area where there is no problem in actual optical circuit formation. Further, the number of foreign substances visually counted was in the range of 4 to 20 each.

FIG. 5 shows a typical example of the thickness distribution of the formed glass film. The film thickness is Metricconmodel 201
0 by the prism coupling method.
Maximum film thickness 20.2201 μm, minimum film thickness 19.7965
μm, and the film thickness distribution was ± 1.1%, confirming that a good glass film was obtained.

In the above method, when the dummy substrate was not disposed, the appearance of the glass film on the substrate disposed at the forefront was different from the appearance shown in FIG. It was observed that the area of the tied portion was widened to about 1 cm. Further, despite the same deposition and sintering conditions as described above, the average surface roughness Ra near the center of the substrate was about 100 °, and the radius from the center of the substrate was 4 mm.
Ra values were distributed between 100 and 200 ° in the range of cm. In the range of 1 cm from the edge of the substrate, the Ra value was 300 ° or more.

[Comparative Example] For comparison, sintering was performed with the arrangement of substrates shown in FIG. The method of depositing the glass particles on the substrate is exactly the same as the method described in the embodiment. A plate and a ring made of quartz were used to stack and arrange the deposited substrates. The quartz plate is a square plate of 12 cm × 12 cm, and the thickness of the plate is 2 mm. The deposited substrate is placed on the plate, and the quartz plate is placed via a quartz ring.
The substrates were stacked by a method of mounting the deposited substrate thereon and mounting a quartz plate via a ring. A quartz ring having a height of 1 cm was used. Using a plate and a ring of this size, the inner diameter 16 cm described in the example
When trying to insert into the furnace core tube, the maximum number of substrates that can be laminated was eight. On the other hand, when the substrates were arranged vertically and the interval between the substrates was set to 6 mm as described in the embodiment, it was possible to process 20 substrates with the same volume, so that the difference in the number of processed substrates was confirmed.

When the glass film of the sample which was actually sintered and transparent vitrified was examined, the surface roughness was slightly unsintered at a portion of 1 to 2 mm from the substrate end as shown in FIG. Area did not exist, and the surface roughness was almost uniform over the entire surface of the substrate.
However, with regard to the adhered foreign matter, the adhesion of the foreign matter was found to be insignificant over the entire surface by visual observation. The reason for this is that when the laminated sample and the sintering jig as shown in FIG. It is considered that foreign matter was generated due to rubbing with the jig. Further, such foreign substances could not be removed by air blowing or washing on the glass film surface after sintering. Therefore, in order to remove foreign substances, it is conceivable to etch or polish the surface, but this leads to an increase in the number of steps and an increase in cost.

[0034]

According to the present invention, the transparent vitrification treatment of the porous glass film can be efficiently performed, and the cost per substrate can be reduced.

[Brief description of the drawings]

FIG. 1 is a schematic perspective view of an apparatus for manufacturing a porous glass film.

FIG. 2 is a partially omitted front view showing a state where a substrate is set up on a sintering jig.

FIG. 3 is a plan view showing the appearance of a sintered substrate surface obtained according to an example.

4A and 4B are graphs showing typical distributions of average surface roughness Ra of a glass surface after sintering, where FIG. 4A is a distribution of Ra in the Y-axis direction, and FIG. FIG. 6 shows an Ra distribution in the X-axis direction, and FIG. 7C is an explanatory diagram of a measurement position on the substrate.

5 (a) and 5 (b) are graphs showing typical distributions of the film thickness distribution on the glass surface after sintering, (a) being a film thickness distribution in the Y-axis direction, and (b) being a X-axis film. Shows the axial thickness distribution,
(C) is an explanatory view of the measurement position of the substrate.

FIG. 6 is a partially omitted front view showing a state of disposing a substrate on a sintering jig of a comparative example.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 11 Rotary table 12 Substrate 13 Oxy-hydrogen flame burner 14 Exhaust pipe 21 Flat plate 22 Groove 23 Substrate 31 Jig 32 Porous glass film deposition substrate 33 Ring spacer

Continuing from the front page (72) Inventor Masatake Ejima 2-13-1, Isobe, Annaka-shi, Gunma Prefecture Shin-Etsu Kagaku Kogyo Co., Ltd. Precision Functional Materials Research Laboratory (72) Inventor Kazuo Kamiya 2--13 Isobe, Annaka-shi, Gunma Prefecture No. 1 Shin-Etsu Chemical Industry Co., Ltd.

Claims (3)

[Claims] 1. An optical waveguide comprising a step of depositing glass particles on a substrate by an oxyhydrogen flame burner to form a porous oxide glass film, and then heating the porous oxide glass film to form a transparent oxide glass film. In the forming method, a plurality of substrates on which the porous glass film is formed are inserted into grooves formed in parallel at predetermined intervals on a flat sintering jig, and one edge of the substrate is inserted into each groove. In this way, the jigs are erected vertically along the jig, arranged in parallel with each other, and a plurality of substrates supported by the jigs are introduced into a furnace, sintering is performed at once, and the porous A method for forming an optical waveguide film in which a transparent glass film is made vitrified. 2. A dummy substrate is arranged along a vertical direction before and after a group of a plurality of substrates to be subjected to a sintering process, which are supported in parallel along the vertical direction on the jig. 2. The forming method according to 1. 3. The forming method according to claim 1, wherein said jig is made of quartz or silicon carbide.