JPH0616429A - Method for producing oxide glass thin film and device therefor - Google Patents

Abstract

PURPOSE:To obtain an oxide glass thin film low in loss and having a desired refractive index structure by suppressing the volatilization of the additive in the deposited porous film when the film is vitrified in the production of the oxide glass thin film. CONSTITUTION:A fine glass particle contg. an additive and consisting essentially of SiO2 is deposited on a substrate to form a porous thin film, and then the thin film is heated and vitrified. In this case, the vapor of the oxide of an additive is mixed into the heating and vitrifying atmosphere, hence the additive in the deposited porous film is not volatilized, the additive added to a core layer is not diffused, and the volatilization of the component having a vitrification temp. lower than that of the additive (P2O5, B2O3, GeO2, etc.) is effectively prevented. As a result, a desired refractive index structure is obtained, and an oxide glass thin film low in light scattering loss, etc., due to bubbles is produced since the film is not sintered.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method and an apparatus for manufacturing an oxide glass thin film used for forming an optical waveguide or the like.

[0002]

2. Description of the Related Art A glass optical waveguide formed on a quartz glass substrate or a silicon substrate is used as an optical communication component or the like because it has good compatibility with an optical fiber. As a method for forming a glass optical waveguide on a substrate, glass microparticles are deposited on the substrate by a vapor phase method using an oxyhydrogen burner to form a porous glass thin film (FIG. 1). There is a method of heating to a high temperature in an electric furnace or the like to form transparent glass. Normally, a silicon wafer is used as the substrate, and Si
A waveguide containing O ₂ as a main component is formed. In this case,
Since the melting point of silicon is lower than the vitrification temperature of pure SiO ₂ , addition of additives such as P ₂ O ₅ , B ₂ O ₃ and GeO _{2 to} SiO ₂ has lowered the vitrification temperature. The specific contents of the conventional example are disclosed in JP-A-58-58.
105111, JP-A-1-192732, and US
It is described in detail in Patent 4263031 and the like.

[0003]

When glass fine particles are deposited on the above-mentioned substrate to form a porous thin film and heated to a high temperature in an electric furnace or the like to be transparent vitrified, the vitrification temperature is lowered. Therefore, volatilization of the additive components added to the oxide glass thin film causes the following problems.

First, P ₂ O which easily volatilizes in the additive component
₅ , the devitrification of B ₂ O _3, etc. raises the vitrification temperature of the volatilized glass part, so that the unsintered part, that is, the part that does not become vitrified, remains in the produced glass film.
Therefore, the loss becomes large when the waveguide is formed. Further, the volatilization of the additive component changes the refractive index of the glass film surface,
Since the desired refractive index structure cannot be obtained, it becomes difficult to design the waveguide structure.

In view of the above problems, the present invention has a desired refractive index structure with a low loss by suppressing the volatilization of the additive of the deposited porous glass thin film in the work of transparent vitrification. The purpose is to obtain an oxide glass thin film.

[0006]

In order to solve the above problems, in the present invention, glass fine particles containing an additive and containing SiO ₂ as a main component are deposited on a substrate to form a porous thin film. In the method for producing an oxide glass thin film, which is then heated to be transparent vitrified, the oxide vapor of the additive component is mixed in the atmosphere at the time of heating to be transparent vitrified.

Further, as a method of introducing the oxide vapor,
(A) Vapor component simple substance (P ₂ O ₅ , B ₂ O ₃ , Ge0
₍₂ etc.) by heating and evaporating and introducing into the heating region of the substrate, (a) chloride (PCl ₃ , POCl ₃ , BCl ₃ ,
There is a method of oxidizing the vapor of GeCl ₄ etc.) with 0 ₂ gas and introducing it into the heating region of the substrate. At this time, the heating region temperature of the vapor component in the method (a) or the oxidation in the method (a) is used. The region temperature is characterized in that the vapor pressure of the introduced oxide at the heating region temperature of the substrate is set to a temperature which is 50 to 150% of the saturated vapor pressure at that temperature.

Further, as an apparatus for realizing the above method, an apparatus for converting a porous glass thin film containing glass particles containing an additive and having SiO ₂ as a main component on a substrate into transparent glass has two ends. A spatially continuous pipe, a supply means at one end of the pipe for introducing a supply gas into the pipe from the outside, an exhaust means at the other end of the pipe for emitting an exhaust gas from the inside of the pipe to the outside, A first heating means for heating the first area to a first temperature; a second heating means for heating a second area on the other end side of the first area to a second temperature; And a control means for separately controlling the second heating means and the second heating means.

[0009]

The volatilization of the additive is represented by the chemical formula 1 or the chemical formula 2.

[0010]

[Equation 1]

[0011]

[Equation 2]

As the above reaction progresses, volatilization of additive components occurs. This volatilization reaction depends on the chemical equilibrium at the processing temperature. Therefore, if the vapor pressure of the additive component in the processing gas is equal to or higher than the equilibrium vapor pressure at the substrate heating region temperature (in this case, the saturated vapor pressure), the reaction indicated by the arrow (a) in the chemical formulas 1 and 2 is performed. Does not proceed and volatilization of additive components does not occur. However, in the actual process, if the vapor pressure of the additive component is 50 to 150% of the saturated vapor pressure at the heating temperature of the substrate, a practically sufficient effect can be obtained.

Further, the heating region temperature of the steam component, or
If the oxidation region temperature is kept higher than the heating region temperature of the substrate, the vapor pressure of the additive component becomes equal to or higher than the saturated vapor pressure of the chemical formulas 1 and 2, and the effect of preventing the volatilization of the additive component is enhanced.

As a component which easily volatilizes, P ₂
O ₅ , B ₂ O ₃ , GeO _{2 and the} like are listed, and their saturated vapor pressures are shown in FIG.

[0015]

EXAMPLES Examples of the present invention will be specifically described below.

As Example 1, using the apparatus shown in FIG. 1, a glass fine particle deposition film containing SiO ₂ as a main component was used as a Si film.
Form on a substrate.

Now, the apparatus for depositing the glass particles shown in FIG. 1 will be described. A plurality of substrates 1 on which glass particles from the torch 3 are to be deposited are arranged in a reaction vessel 6 whose bottom surface is a rotatable turntable 2. The glass particles and the exhaust gas not deposited on the substrate 1 are sucked into the exhaust pipe 4. The turntable 2 on which the substrate 1 is placed is rotationally driven with respect to the reaction container 6 by a motor (not shown),
The torch 3 reciprocates parallel to the radial direction of the turntable 2. As a result, glass particles can be uniformly deposited on the substrate 1. Further, the turntable 2 is provided with a lower heater 5 to uniformly heat the substrate 1 placed on the turntable 2.

Glass fine particles for an optical waveguide film were deposited by this apparatus. The substrate 1 is arranged on the turntable 2, the turntable 2 is rotated, and the lower heater 5
The temperature of the substrate 1 was raised by. Next, 0 torch 3
₂ gas and H ₂ gas were supplied, and an oxyhydrogen flame was formed at the blowout portion of the torch 3 and was blown onto the substrate 1. At the same time, the torch 3 was reciprocated in parallel in the radial direction of the turntable 2. After the substrate temperature reached a predetermined temperature, when a glass raw material was sent to the torch 3, a hydrolysis reaction occurred in the flame and glass fine particles were deposited on the substrate 1.

The deposition conditions of the glass particles are as follows: the rotation speed of the turntable 2 is 10 [rpm], the moving speed of the torch 3 is 120 [mm / min], and the moving amount of the torch 3 is 200.
[Mm] and the O ₂ gas supplied to the torch 3 is 8 [l /
min] and H ₂ gas at 10 [l / min]. The glass raw materials were supplied to the torch 3 under the following conditions. (First deposition condition) Glass fine particles for lower clad layer (deposition time: 30 minutes) SiCl ₄ : 250 [cc / min] BCl ₃ : 10 [cc / min] PCl ₃ : 25 [cc / min] (first 2 deposition conditions) Glass fine particles for core layer (deposition time: 20 minutes) SiCl ₄ : 250 [cc / min] GeCl ₄ : 40 [cc / min] PCl ₃ : 20 [cc / min] BCl ₃ : 5 [ cc / min] After that, the glass particles deposited on the substrate 1 are heated in a heating furnace 10
Was used for heat treatment. A schematic configuration of the apparatus used in Example 1 is shown in FIG. 3 and will be described. Heating furnace 10
Is composed of a furnace core tube 15 and heaters 13 and 14.
Then, a gas supply device 17 for introducing gas into the furnace core tube 15, an exhaust device 18 for discharging gas outside the furnace core tube 15, and a control device for independently controlling the temperatures of the heaters 13 and 14 respectively. It is composed of 19. Furnace core tube 15
Is a spatially continuous tube. And this furnace core tube 15
Has a heating region 11 of the vapor component upstream of the gas flow and a heating region 12 of the substrate downstream thereof. The temperatures of these two regions are independently controlled by heaters 13 and 14, respectively. A platinum crucible 16 is placed in the heating region 11 for vapor components, and P ₂ O ₅ , B ₂ is placed therein.
O ₃ and GeO ₂ simple substances were charged and heated. The substrate 1 was placed on the heating region 12 of the substrate.

First, the heating area 11 for the vapor component is set to 850.
[° C.], after setting the heating region 12 of the substrate to 800 [° C.], O ₂ is 5 [l / min] and He is 5 [l / min].
The mixed gas of was supplied. Then, the temperature rising rate is 5 [° C./mi
n], the temperature of the heating region 11 of the vapor component is 1300 [° C.], and the temperature of the heating region 12 of the substrate is 12
After maintaining the temperature at 50 [° C.] for 1 hour, the temperature of the vapor component heating region 11 was lowered to 850 [° C.] and the temperature of the substrate heating region 12 was lowered to 800 [° C.] (FIG. 4). After the supply of the mixed gas was stopped, the substrate 1 was taken out. In this heat treatment operation, the temperature of the vapor component heating region 11 was always set to 50 [° C.] higher than the temperature of the substrate heating region 12. No residual bubbles were observed in the glass film obtained on the substrate 1, and the EP
When the elemental components were analyzed by MA (electron probe microanalyzer), element volatilization and diffusion in the interface between the core layer and the lower clad layer and in the outermost core layer were not observed.

As Example 2, as in Example 1, the apparatus of FIG. 1 was used to form a glass fine particle deposited film containing SiO ₂ as a main component on the Si substrate 1. The conditions for depositing the glass fine particle film are the same as in Example 1. A schematic configuration of the apparatus used in Example 2 is shown in FIG. 5 and will be described.
The heating furnace 20 includes a furnace core tube 25 and heaters 23 and 24. Then, a gas supply device 27 that introduces gas into the furnace core tube 25, an exhaust device 28 that discharges gas outside the furnace core tube 25, and a control device that independently controls the temperatures of the heaters 23 and 24. It is composed of 29.
The furnace core tube 25 is a spatially continuous tube. The furnace core tube 25 has a steam component heating region 21 upstream of the gas flow and a substrate heating region 22 downstream thereof. These two areas are heaters 23 and 24, respectively.
Controls the temperature independently. The substrate 1 was placed on the heating region 22 of the substrate.

First, the temperature of the oxidized region 21 is set to 1350.
[° C.], the temperature of the heating region 22 of the substrate is set to 800 [° C.], then GeCl ₄ is 5 [cc / min], POCl
₃ is 10 [cc / min], BCl ₃ is 10 [cc / m]
in] chloride vapor and O ₂ is 5 [l / min], He
Mixed gas of 5 [l / min] was introduced into the heating furnace.
Here, the chloride vapor introduced into the heating furnace has been previously oxidized in the oxidation region 21. Then, the temperature of the heating region 22 of the substrate is raised at a rate of temperature increase rate of 5 [° C./min], maintained at 1250 [° C.] for 1 hour, and then lowered to 800 [° C.] (FIG. 6). . After the supply of the mixed gas was stopped, the substrate 1 was taken out. No residual bubbles were observed in the glass film on the substrate 1 obtained in this example.

Further, a glass particle deposition layer containing SiO ₂ as a main component was formed on the Si substrate 1 under the same deposition conditions as in Example 1. Then, in the electric furnace 10 shown in FIG. 3, the same heat treatment as in Example 1 was performed without vapor components (P ₂ O ₅ , B ₂ O ₃ , GeO ₂ ), and the glass obtained on the substrate 1 was obtained. The outermost surface of the film was cloudy. Further, as a result of elemental analysis by EPMA, the amounts of P, B and Ge on the outermost surface were reduced to 1/4 of the internal amounts.

The present invention is not limited to the above-mentioned embodiment, but the embodiment 1
It is also possible to use a manufacturing method and a manufacturing apparatus in which the above and Example 2 are combined.

The oxide vapor of the additive component introduced has little influence on the diffusion of the additive on the surface and inside of the glass film, and prevents the volatilization of the additive component from the outermost surface of the glass film at high temperature. The effect of doing is greater.

Using the method for producing a glass thin film of the present invention,
A schematic process for producing an optical waveguide will be described with reference to the sectional views shown in FIGS.

A first porous glass film 50a to be a lower clad layer is deposited on the Si substrate 1 (FIG. 7). Then, the second porous glass film 60a to be the core layer is deposited on the first porous glass film 50a (FIG. 8). The first and second porous glass films 50a,
The deposition conditions for 60a are the same as those shown in Example 1.

Then, the first and second porous glass films 50a, 60a are heated by a heating furnace into which oxide vapor is introduced.
Of the lower cladding layer 5 by heating
0 and the core layer 60 (FIG. 9). The core layer is etched leaving a desired region to obtain an optical waveguide 61 (FIG. 10).

Further, a third porous glass film 70a to be an upper clad layer is deposited on the lower clad layer 50 and the optical waveguide 61 (FIG. 11). At this time, the deposition condition of the third porous glass film 70a is the same as the deposition condition of the first porous glass film 50a, that is, the first deposition condition shown in the first embodiment. Then, the third porous glass film 70a is again heated by the heating furnace in which the vapor pressure of the oxide is introduced.
Is heated to be a transparent glass, and the upper clad layer 70 is formed (FIG. 12).

The loss of the buried type optical waveguide thus prepared was measured and found to be 0.1 [dB / cm] or less.
It was very good.

Finally, the relationship between the magnitude of the pressure of the introduced oxide vapor and its effect will be described. FIG. 13 shows a schematic cross-sectional view when a porous glass film is deposited on the substrate 1 and heated to be a transparent vitrified glass layer 80. The parameter Δ on the lower side of the glass layer 80, that is, the substrate side is defined as a, and the parameter Δ on the upper side of the glass layer 80, that is, the surface side is defined as b.

Here, the parameter Δ is the relative refractive index difference with respect to quartz glass, n ₀ is the refractive index of quartz glass, and n
_{When 1} is the refractive index of the target object, it is defined by the following formula.

Δ = (n ₀ ² −n ₁ ² ) / 2n ₀ ² to (n ₀ −n ₁ ) / n ₀ Ratio of the introduced oxide vapor pressure (P _i ) to the saturated vapor pressure (P _is ). (P _i / P _is ), and the surface side parameter Δ with respect to the substrate side parameter Δ (a) of the glass layer 80.
FIG. 1 shows a measurement example in which the relationship between the ratio (b) and (b / a) of (b) is examined.
4 shows. This measurement example is based on GeO ₂ and P ₂ O.
_Although shown for ₅ , almost the same results are obtained with other additives.

The graph of FIG. 14 will be briefly described. When the pressure (P _i ) of the oxide vapor to be introduced _is 40% of the saturated vapor pressure (P _is ), the parameter Δ (b) on the surface side is The parameter Δ (a) is about 0.93 times, and when P _{i is} 160% of Pis, b is about 1.06 times a. During this time,
When the pressure (P _i ) of the introduced oxide vapor increases,
Accordingly, the parameter Δ (b) on the surface side also gradually increases.

As the characteristics of the optical waveguide, it is most desirable that the surface side parameter Δ (b) and the substrate side parameter Δ (a) match (b / a = 1). In order to stabilize the characteristics of the optical waveguide, the ratio (b
/ A) is preferably within 0.95 to 1.05. Therefore, the pressure (P _i ) of the introduced oxide vapor
_Is preferably 50 to 150% of the saturated vapor pressure (P _is ).

Although the silicon substrate is used in the embodiment, the substrate may be a quartz glass substrate. Further, the additives added when forming the porous glass film are not limited to those described in the examples, and various additives that volatilize when heated to become transparent vitrification can be used in the present invention. Can be used.

[0037]

EFFECTS OF THE INVENTION According to the present invention, when an oxide glass thin film used for forming an optical waveguide or the like is produced, a vaporizable oxide component vapor is introduced into an atmosphere for heat-transparent vitrification treatment. As a result, the volatilization of the additive of the deposited porous film does not occur, the diffusion of the additive added to the core layer is prevented, and the additives (P ₂ O ₅ , B ₂ O ₃ , GeO _{2) are} prevented.
Etc.) is effective in preventing volatilization of the vitrification temperature lowering component. With these, it is possible to obtain a desired refractive index structure and to obtain an oxide glass thin film with less loss such as light scattering due to bubbles or the like due to unsintering.

The saturated vapor pressure of the oxide component of the additive can be determined in advance. Therefore, the control of the vapor pressure of the oxide component of the additive can be replaced with the control of the temperature of the oxidation reaction of the introduced oxide component of the additive or the control of the temperature of generating vapor from a solid. That is, the present invention can be realized by a simple control device that does not need to directly control the vapor pressure but instead controls the temperature.

[Brief description of drawings]

FIG. 1 is a schematic view showing an apparatus for depositing glass particles.

FIG. 2 is a diagram showing saturated vapor pressures of main additive components.

FIG. 3 is a schematic diagram showing an apparatus according to Example 1 of the present invention.

FIG. 4 is a schematic diagram showing temperature control according to the first embodiment of the present invention.

FIG. 5 is a schematic view showing an apparatus of Example 2 of the present invention.

FIG. 6 is a schematic diagram showing temperature control according to a second embodiment of the present invention.

FIG. 7 is a cross-sectional view showing a schematic process in the case of producing an optical waveguide by the method for producing a glass thin film of the present invention.

FIG. 8 is a cross-sectional view showing a schematic process when an optical waveguide is produced by the method for producing a glass thin film of the present invention.

FIG. 9 is a cross-sectional view showing a schematic process for producing an optical waveguide by the method for producing a glass thin film of the present invention.

FIG. 10 is a cross-sectional view showing the schematic steps in producing an optical waveguide by the method for producing a glass thin film of the present invention.

FIG. 11 is a cross-sectional view showing a schematic process for producing an optical waveguide by the method for producing a glass thin film of the present invention.

FIG. 12 is a cross-sectional view showing a schematic process for producing an optical waveguide by the method for producing a glass thin film of the present invention.

FIG. 13 is a sectional view for explaining the effect of the present invention.

FIG. 14 _is a ratio (P _i / P _is ) of the pressure (P _i ) of the oxide vapor to be introduced to the saturated vapor pressure (P _is ) and the parameter Δ (b) on the surface side to the parameter Δ (a) on the substrate side. )
It is a figure which shows the relationship with the ratio (b / a) of.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 ... Substrate, 10, 20 ... Heating furnace, 11 ... Steam component heating area, 21 ... Oxidation area, 12, 22 ... Substrate heating area,
13, 14, 23, 24 ... Heater, 15, 25 ... Furnace core tube, 16 ... Platinum crucible, 17, 27 ... Gas supply device, 1
8, 28 ... Exhaust device, 19, 29 ... Control device.

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Satoshi Hirose, Satoshi Hirose, 1 Taya-cho, Sakae-ku, Yokohama-shi, Kanagawa Sumitomo Electric Industries, Ltd. Yokohama Works (72) Inventor Hiroo Kanamori, 1 Taya-cho, Sakae-ku, Yokohama, Kanagawa Sumitomo Electric Industrial Co., Ltd. Yokohama Works (72) Inventor Masahide Saito 1 Tayacho, Sakae Ward, Yokohama City, Kanagawa Sumitomo Electric Co., Ltd. Yokohama Works

Claims (15)

[Claims] 1. A method for producing an oxide glass thin film, the first step of forming a porous glass thin film by depositing glass microparticles containing an additive and having SiO ₂ as a main component on a substrate, and the glass. In order to prevent volatilization of the additive contained in the fine particles, the porous glass thin film is heated in an atmosphere containing a predetermined concentration or more of the oxide vapor of the additive component to form a transparent glass. And a step of manufacturing an oxide glass thin film. 2. The method for producing an oxide glass thin film according to claim 1, wherein the substrate is a quartz glass substrate or a silicon substrate. 3. The oxide vapor is GeO _x , PO _x ,
The method for producing an oxide glass thin film according to claim 1, wherein at least one of BO _x is contained. 4. The oxide vapor has a saturated vapor pressure of oxide of the additive component of 5 at a temperature of the second step.
The method for producing an oxide glass thin film according to claim 1, wherein the oxide glass thin film is introduced at a pressure of 0 to 150%. 5. The method for producing an oxide glass thin film according to claim 1, wherein the oxide vapor is generated by an oxidation reaction of chloride vapor of the additive and O ₂ . 6. The oxidation reaction is carried out at a saturated vapor pressure of 50 to 50% of the saturated vapor pressure of the oxide of the additive component at the temperature of the second step.
The method for producing an oxide glass thin film according to claim 5, wherein the temperature is 150%. 7. The method for producing an oxide glass thin film according to claim 6, wherein the oxidation reaction is performed at a temperature higher than the temperature of the second step. 8. The method for producing an oxide glass thin film according to claim 1, wherein the oxide vapor is obtained by generating vapor from a solid oxide as a component of the additive. 9. The generation of the vapor is the saturated vapor pressure of the oxide of the additive component at 50 at the temperature of the second step.
The method for producing an oxide glass thin film according to claim 8, which is carried out by placing the oxide of the additive component at a temperature of about 150%. 10. The oxide according to claim 9, wherein the generation of the vapor is performed by placing the oxide of the additive component at a temperature higher than the temperature of the second step. Method for manufacturing glass thin film. 11. An apparatus for vitrifying a porous glass thin film, in which glass particles containing an additive and having SiO ₂ as a main component, are deposited on a substrate, and a spatially continuous tube having two ends, A supply unit at one end of the pipe for introducing a supply gas into the pipe from the outside; an exhaust unit at the other end of the pipe for emitting an exhaust gas from the inside of the pipe to the outside; A first heating means for heating to a first temperature, and a second region on the other end side of the first region,
Pores characterized by comprising: a second heating means for heating to a second temperature; a first heating means; and a control means for separately controlling the second heating means. A device for converting a thin glass film into transparent glass. 12. The inspiratory gas contains O ₂ and an inert gas, the porous glass thin film is disposed in the second region, and the first temperature is the temperature at the second temperature. The temperature which is 50 to 150% of the saturated vapor pressure of the oxide of the additive component, and the second temperature is a temperature at which the porous glass thin film becomes transparent vitrified. An apparatus for converting the described porous glass thin film into a transparent glass. 13. The solid material containing the component of the additive is disposed in the first region.
An apparatus for converting the porous glass thin film described in 2 into transparent glass. 14. The inspiratory gas further contains a gas having a component of the additive, and in the first region,
The gas is an oxide vapor.
An apparatus for converting the porous glass thin film described in 2 into transparent glass. 15. The apparatus for vitrifying a porous glass thin film according to claim 11, wherein the first temperature is higher than the second temperature.