JP4379023B2 - Nitrogen-added glass film and waveguide manufacturing method using the same - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a glass film and a method for manufacturing a waveguide using the same, and more particularly to a nitrogen-added glass film having a high relative refractive index difference and a low loss and a method for manufacturing a waveguide using the same.
[0002]
[Prior art]
As a conventional manufacturing method, there is a method of manufacturing a glass film and a waveguide using the same by a liquid source plasma CVD method using the CVD apparatus 81 shown in FIG.
[0003]
Specifically, the reaction vessel (reaction chamber) 82 is evacuated to high vacuum by the exhaust devices 83, 83, and a high frequency power source is supplied to the upper electrode 84 and the lower electrode 85 that are vertically opposed to each other in the reaction chamber 82 at a predetermined interval. A high-frequency voltage (for example, a frequency of 13.56 MHz and an output of 1 kW) is applied by 86, and the upper electrode 84 and the lower electrode 85 are set to predetermined temperatures (upper electrode: Max. 400 ° C., lower electrode: Max. 500 ° C.). Heat to.
[0004]
In this state, a plurality of quartz glass substrates 87 are arranged on the lower electrode 85, and an alcoholate-based liquid source [Si (OC ₂ H _Five ) _Four ] (TEOS) 88, [Ge (OCH _Three ) _Four ] (TMG) 89, [P (OCH _Three ) _Three ] (TMP) 90 steam, O ₂ Together with the gas 91, it is supplied into the reaction chamber 82 as a mixed gas 93 through a gas supply line 92.
[0005]
The mixed gas 93 is supplied to a shower plate (shower electrode) 94 for gas ejection composed of concentric multiple rings provided at the lower part of the upper electrode 84, and a large number of holes 95 formed in the shower electrode 94 form the substrate 87. Sprayed on top. A side protection plate 96 for forming (depositing) a uniform glass film on the substrate 87 is provided on the side surface of the upper electrode 84. Here, the distance between the substrate 87 and the shower plate 94 is set to a predetermined interval s8.
[0006]
At this time, a thermal decomposition reaction of the mixed gas 93 is performed in the reaction chamber 83 in a high vacuum and plasma atmosphere, whereby a glass film serving as a core is formed on the substrate 87. Furthermore, when a glass film of a predetermined shape is formed by performing photolithography and dry etching on this glass film, and the glass film of the predetermined shape is covered with a low refractive index glass film serving as a cladding, a slab waveguide or a buried waveguide Is obtained.
[0007]
On the other hand, as a conventional manufacturing method, SiH _Four Gas and NH _Three Gas or SiH _Four Gas and N ₂ There is also a method of manufacturing a nitrogen-added glass film and a waveguide using the same by a plasma CVD method using O gas.
[0008]
The prior art document information related to the invention of this application includes the following.
[0009]
[Patent Document 1]
JP 2001-348236 A
[0010]
[Problems to be solved by the invention]
However, the manufacturing method by the conventional liquid source plasma CVD method has the following problems.
[0011]
{Circle around (1)} When a slab waveguide is formed by increasing the refractive index of the glass film formed on the substrate 87, the light propagation loss tends to increase. For example, taking the light propagation loss at a wavelength of 1550 nm as an example, the relative refractive index difference (Δ) with respect to the quartz glass substrate 87 is 0.005 dB / cm at 1% and 0.01 dB / cm at 3% and 3%. Then, it increases to 0.1 dB / cm. An example of this phenomenon is shown in FIG.
[0012]
(2) Further, as Δ increases, the refractive index deviation and film thickness deviation of the glass film tend to increase. When Δ is 3%, the refractive index deviation is ± 0.6% and the film thickness deviation is about ±±. It will be 7%. That is, it is difficult to form a uniform glass film. The increase in refractive index deviation and film thickness deviation is to obtain desired optical characteristics in realizing a photonic circuit (filter, splitter, resonator, etc.) for wavelength division multiplex transmission in which the wavelength and phase are precisely controlled. It is a big problem because it makes it difficult.
[0013]
(3) In the formation of a high Δ glass film, even when a plurality of substrates 87 are placed on the lower electrode 85 to form a glass film, the refractive index deviation between the substrates 87 on which the glass films are formed Is increased to ± 0.9% and the film thickness deviation is increased to about ± 9%.
[0014]
(4) In order to realize a glass film having a higher Δ, it is necessary to use a plurality of alcoholate-based liquid sources. However, these vapors are sufficiently mixed and reacted so that the surface of each substrate 87 and each substrate 87 are mixed. It is difficult to obtain a glass film having a uniform composition.
[0015]
On the other hand, the conventional plasma CVD method is SiH. _Four Gas and NH _Three Gas or SiH _Four Gas and N ₂ Due to the thermal decomposition reaction of O gas, Si—H groups and N—H groups are mixed in the glass film and the waveguide, and the wavelength of light absorbed by these absorbing groups exists in the wavelength band for communication. There is a problem that optical propagation loss increases. These absorbing groups are difficult to remove, and as a result, it is difficult to reduce the loss of the glass film and the waveguide. In addition, since OH groups are also mixed, the optical propagation loss in the communication wavelength band is further increased.
[0016]
Accordingly, an object of the present invention is to solve the above problems and provide a nitrogen-added glass film having a high relative refractive index difference and a low loss and a method for manufacturing a waveguide using the same.
[0017]
[Means for Solving the Problems]
The present invention was devised to achieve the above object, and the invention of claim 1 applies a high-frequency voltage to the upper electrode and the lower electrode in the reaction chamber evacuated to a high vacuum, and the upper electrode. And the lower electrode is heated to a predetermined temperature, the substrate is carried into the reaction chamber and placed on the lower electrode or the upper electrode, While using a mechanical booster pump connected in series (exhaust speed is 8400 l / min or more) and a dry pump (exhaust speed is 1200 l / min or more), A plurality of alcoholate liquid sources were vaporized in the reaction chamber. Of a predetermined flow rate (about several sccm) Raw material gas, A flow rate greater than the flow rate of the source gas, and N mixed at the specified mixing ratio ₂ gas (100 sccm or more) And O ₂ gas (400-1500sccm) Of the nitrogen-added glass film that is set together so that the pressure in the reaction chamber is within a range of 25 to 40 Pa, undergoes a thermal decomposition reaction in a plasma atmosphere, and forms a nitrogen-added glass film on the surface of the substrate. It is a manufacturing method.
[0019]
Claim 2 In the invention, the gas supply port in the reaction chamber is provided with a diffusion plate for uniformly diffusing each gas into the substrate. 1 It is a manufacturing method of the nitrogen addition glass film of description.
[0020]
Claim 3 The invention of N ₂ Gas and O ₂ Gas mixing ratio (N ₂ / O ₂ ) Is 4-15 1 or 2 It is a manufacturing method of the nitrogen addition glass film as described in 1 above.
[0021]
Claim 4 According to the present invention, the plurality of alcoholate liquid sources are SiO ₂ GeO ₂ Or SiO ₂ GeO ₂ And P ₂ O ₅ Claims using raw materials to which and are added 1-3 It is a manufacturing method of the nitrogen addition glass film in any one.
[0024]
Claim 5 The invention of claim 1 uses a quartz glass substrate as the substrate. 4 It is a manufacturing method of the nitrogen addition glass film in any one.
[0025]
Claim 6 According to the present invention, the nitrogen-doped glass film has a relative refractive index difference larger than 1% with respect to the quartz glass substrate. 5 It is a manufacturing method of the nitrogen addition glass film of description.
[0026]
Claim 7 The invention of claim 1 to claim 1 6 After forming the nitrogen-added glass film using any of the manufacturing methods described above, the nitrogen-added glass film is subjected to photolithography and dry etching to form a nitrogen-added glass film having a predetermined shape. This is a method for manufacturing a waveguide in which an additive glass film is covered with a low refractive index glass film.
[0029]
DETAILED DESCRIPTION OF THE INVENTION
DESCRIPTION OF EXEMPLARY EMBODIMENTS Hereinafter, preferred embodiments of the invention will be described with reference to the accompanying drawings.
[0030]
First, a waveguide manufactured using the manufacturing method according to the present embodiment will be described with reference to FIGS.
[0031]
As shown in FIG. 4, the waveguide 41 is formed in a slab shape by forming a nitrogen-added glass film on the surface of the quartz glass substrate 42 and performing photolithography and dry etching on the nitrogen-added glass film. The formed nitrogen-added glass film 43 serving as a core is covered with a low refractive index glass film 44 serving as a cladding. The waveguide 41 is also called a slab waveguide.
[0032]
Further, as shown in FIG. 5, the waveguide 51 is formed by forming a nitrogen-added glass film on the surface of the quartz glass substrate 42, and subjecting the nitrogen-added glass film to photolithography and dry etching to form a core having a substantially rectangular cross section. A pattern 52 is formed, and the pattern 52 and the surface of the substrate 42 are covered with a low refractive index glass film 44. The waveguide 51 is also called a buried type waveguide.
[0033]
As a constituent material of the nitrogen-added glass film 43 and the pattern 52, for example, SiO ₂ GeO ₂ That only added, or SiO ₂ GeO ₂ And P ₂ O _Five The one to which is added is used. In this case, the GeO is set so that the relative refractive index difference (Δ) between the substrate 42 and the glass film 43 and between the substrate 42 and the pattern 52 is greater than 1%. ₂ Or GeO ₂ And P ₂ O _Five (The flow rate of the raw material gas vaporized by the liquid sources 3, 4, and 5 described later in FIG. 1) is adjusted. As a constituent material of the low refractive index glass film 44, for example, SiO ₂ Or SiO ₂ The one to which F is added is used.
[0034]
Next, a CVD manufacturing apparatus used for the manufacturing method according to the present embodiment will be described.
[0035]
As shown in FIG. 1, a CVD manufacturing apparatus 1 that manufactures a nitrogen-added glass film and a waveguide using the same by a liquid source plasma CVD method includes a reaction vessel (reaction chamber) 2 and a reaction chamber 2 with Si N gas obtained by mixing a plurality of alcoholate-type liquid sources composed of a system source 3, a Ge system source 4 and a P system source 5 at a predetermined mixing ratio. ₂ Gas 6 and O ₂ Supply means 9 for supplying the gas 7 together with the gas 7, a class 100 clean unit 10 in which the quartz glass substrate 42 before being carried into the reaction chamber 2 is temporarily stored, and a class 100 for storing the entire apparatus main body. The clean booth 11 is mainly composed.
[0036]
In this example, [Si (OC ₂ H _Five ) _Four ] (TEOS) as a Ge-based source 4 [Ge (OCH _Three ) _Four ] (TMG) as P source 5 [P (OCH _Three ) _Three ] (TMP) was used.
[0037]
The supply means 9 includes a thermostatic chamber for storing the sources 3, 4 and 5, respectively, ₂ Gas supply source and O ₂ Connects between gas supply source, each thermostat and reaction chamber 2 and N ₂ Gas supply source and O ₂ The gas supply line 12 connects the gas supply source and the reaction chamber 2.
[0038]
Connected to the reaction chamber 2 are two sets of large capacity exhaust devices 13 and 13 having a predetermined exhaust speed for exhausting the reaction chamber 2 to a high vacuum. Each large-capacity exhaust device 13 is configured by connecting a mechanical booster pump 14 and a dry pump 15 in series. As the mechanical booster pump 14, a pump with an exhaust speed of 8200 l / min or more is used, and as the dry pump 15, a pump with an exhaust speed of 1200 l / min or more is used.
[0039]
In the reaction chamber 2, an upper electrode 16 and a lower electrode 17 are arranged vertically opposite to each other at a predetermined interval. A high frequency power source 18 that applies a high frequency voltage between the electrodes 16 and 17 is connected to the upper electrode 16 and the lower electrode 17. The upper electrode 16 and the lower electrode 17 may be connected to a heating means (not shown) for heating and raising the temperature of the upper electrode 16 and the lower electrode 17. A plurality of substrates 42 carried into the reaction chamber 2 are arranged on the lower electrode 17.
[0040]
Below the upper electrode 16 in the reaction chamber 2, a gas ejection shower plate (shower electrode) 19 comprising concentric multiple rings is provided, and the gas supply line 12 is connected to the shower plate 19. The shower plate 19 is formed with several hundred gas ejection nozzles (diameter 0.4 mmφ) 20 concentrically at a predetermined pitch. A side surface protection plate 21 for forming a uniform glass film on the substrate 42 is provided on the side surface of the upper electrode 16. In this example, the distance between the surface of the substrate 42 and the lower surface of the shower plate 19 is set to a predetermined interval s.
[0041]
The gas supply line 12 is provided in the reaction chamber 2 so as to penetrate the center of the upper electrode 16. A diffusion plate 22 for uniformly diffusing each gas (mixed gas 8) to the substrate 42 is located above the gas supply port 12a at one end of the gas supply line 12 so as to be positioned between the upper electrode 16 and the shower plate 19. Provided integrally with the electrode 16.
[0042]
Between the reaction chamber 2 and the clean unit 10, an opening / closing means 23 such as a valve or a shutter for airtightly loading / unloading the substrate 42 to / from the reaction chamber 2 is provided. The clean unit 10 is provided with a gas shower chamber 25 that carries the substrate 42 into and out of the clean unit 10 and also blows the cleaning gas 24 onto the substrate 42 in a shower to clean the substrate 42. As the cleaning gas 24, for example, N ₂ Use gas. The clean unit 10 is provided with a heating means 26 for heating and raising the temperature in the clean unit 10. The clean unit 10 may be provided with an exhaust device (not shown) that exhausts the inside of the clean unit 10 to a high vacuum.
[0043]
Next, a method for manufacturing a nitrogen-added glass film and a waveguide according to the present embodiment will be described.
[0044]
First, the large-capacity exhaust devices 13 and 13 are operated with the opening / closing means 23 closed, and the reaction chamber 2 is evacuated to a predetermined pressure (degree of vacuum), for example, 25 to 40 Pa. As the mechanical booster pump 14, a pump with an exhaust speed of 8400 l / min or more is used, and as the dry pump 15, a pump with an exhaust speed of 1200 l / min or more is used.
[0045]
The mechanical booster pump 14 having an exhaust speed of 8400 l / min or more and the dry pump 15 having an exhaust speed of 1200 / min or more are used in the reaction chamber 2 with a flow rate larger than the flow rate of the raw material gas, as will be described later. N ₂ Gas 6 and O ₂ The gas 7 is supplied at this time in order to prevent the degree of vacuum in the reaction chamber 2 from being lowered and the nitrogen-added glass film from becoming a porous glass film.
[0046]
The reason why the pressure in the reaction chamber 2 is set to 25 to 40 Pa is that if the pressure in the reaction chamber 2 is larger than 40 Pa, the nitrogen-added glass film becomes a porous glass film and it is difficult to reduce the loss of light propagation loss. It is. Further, if the pressure in the reaction chamber 2 is less than 25 Pa, an exhaust device having a larger capacity than that of the large-capacity exhaust devices 13 and 13 is required. Therefore, the cost of the exhaust device becomes very high, and N ₂ This is because the amount of gas 6 used increases.
[0047]
In parallel with this, a high frequency voltage (for example, a frequency of 13.56 MHz and an output of 1 kW) is applied between the electrodes 16 and 17 by the high frequency power source 18 and the upper electrode 16 is connected to the Max. 400 ° C. (for example, 350 ° C.), the lower electrode 17 is connected to Max. Heat and raise the temperature to 500 ° C. (eg, 400 ° C.).
[0048]
On the other hand, each substrate 42 is cleaned with the cleaning gas 24 in the gas shower chamber 25, each cleaned substrate 42 is carried into the clean unit 10, and the temperature in the clean unit 10 is set to the temperature in the reaction chamber 2 by the heating means 26. Heat and raise the temperature equally (for example, 350 to 400 ° C.). At this time, an exhaust apparatus (not shown) may be operated with the opening / closing means 23 closed, and the vacuum degree in the clean unit 10 may be evacuated until the degree of vacuum in the reaction chamber 2 is equal to the degree of vacuum in the reaction chamber 2. Thereafter, the opening / closing means 23 is opened, each substrate 42 is carried into the reaction chamber 2 and placed on the lower electrode 16, and the opening means 23 is closed again.
[0049]
Next, a raw material gas having a predetermined flow rate (about several sccm) made of vapor vaporized from the alcoholate liquid sources 3, 4, and 5 is mixed at a predetermined flow rate that is larger than the flow rate of the raw material gas. N ₂ Gas 6 and O ₂ Together with the gas 7, the gas is supplied as a mixed gas 8 into the reaction chamber 2 through a gas supply line 12.
[0050]
N ₂ Gas 6 and O ₂ Mixing ratio of gas 7 (N ₂ / O ₂ ) Is 4-15. N ₂ / O ₂ 4 to 15 is that the high Δ of the nitrogen-added glass film and the waveguide is realized, and the generation of the Si group and the N—H group is suppressed, and the Si group and the N in the nitrogen-added glass film and the waveguide are suppressed. This is because it is considered that the -H group is suppressed from mixing to realize low loss characteristics, and the nitrogen-added glass film and the waveguide are suppressed from mixing OH groups.
[0051]
That is, O ₂ The flow rate of the gas 7 is sufficient to cause a thermal decomposition reaction of the raw material gas composed of the vapors of the liquid sources 3, 4, 5 in a high vacuum and plasma atmosphere, and has no oxygen defects and little OH group contamination. In order to realize the nitrogen-added glass film and the waveguide, it is necessary to set the thickness to 100 sccm or more.
[0052]
N ₂ The flow rate of the gas 6 is preferably in the range of 400-1500 sccm. N ₂ When the flow rate of the gas 6 is less than 400 sccm, N is not added in a desired amount into the glass film, and a high Δ cannot be obtained. N ₂ If the flow rate of the gas 6 exceeds 1500 sccm, oxygen defects in the glass film are likely to occur. Therefore, N ₂ The flow rate of the gas 6 needs to be 400-1500 sccm.
[0053]
The mixed gas 8 supplied into the reaction chamber 2 is sprayed onto the diffusion plate 22 and is uniformly diffused into a space (cavity) defined between the upper electrode 16 and the shower plate 19. It is uniformly ejected from the ejection nozzle 20 and is uniformly diffused on the surface of each substrate 42. At this time, a nitrogen-added glass film 43 (see FIG. 4) that becomes a core of uniform composition on each substrate 42 by performing a thermal decomposition reaction of the mixed gas 8 in the reaction chamber 2 in a high vacuum and plasma atmosphere. Is formed (film formation).
[0054]
After the glass film 43 is formed, the temperature in the clean unit 10 is made equal to that in the reaction chamber 2 with the opening / closing means 23 closed. At this time, the degree of vacuum in the clean unit 10 may be equal to that in the reaction chamber 2. In this state, the opening / closing means 23 is opened, and each substrate 42 is unloaded from the reaction chamber 2 to the clean unit 10. After unloading each substrate 42, the opening / closing means 23 is closed again, each substrate 42 is cleaned with the cleaning gas 24 in the gas shower chamber 25, and each cleaned substrate 42 is unloaded from the clean room 10.
[0055]
Here, each substrate 42 on which the nitrogen-added glass film 43 is formed may be heat-treated at a temperature higher than 1000 ° C. Thereafter, photolithography and dry etching are performed on the glass film 43 to form a glass film having a predetermined shape, and when the glass film having the predetermined shape is covered with a low refractive index glass film 44 (see FIGS. 4 and 5) serving as a cladding, A slab waveguide 41 or a buried waveguide 51 is obtained. Further, the slab waveguide 41 or the embedded waveguide 51 may be heat-treated at a temperature higher than 1000 ° C.
[0056]
For example, the low refractive index glass film 44 is formed by using the apparatus 1 again and the source gas and the O 2 vaporized from the liquid source 3 in the reaction chamber 2. ₂ By supplying the gas 7, it can be formed in the same manner as the glass film 43.
[0057]
Next, the characteristics of the slab waveguide 41 manufactured as described above were measured. In the following description, the slab waveguide 41 will be mainly described, but the same applies to the buried waveguide.
[0058]
FIG. 2 shows N ₂ / O ₂ The relative refractive index difference and N of the slab waveguide 41 manufactured by changing variously ₂ / O ₂ The horizontal axis is N ₂ / O ₂ FIG. 5 is a diagram showing the relative refractive index difference Δ (%) on the vertical axis.
[0059]
The manufacturing conditions are as follows: the output of the high frequency power supply 18 is maintained at 600 W, the upper electrode 16 and the lower electrode 17 are heated to 350 ° C. and 400 ° C., the exhaust speed of the mechanical booster pump 14 is 8400 l / min, and the exhaust speed of the dry pump 15 Was 1200 l / min, and the pressure in the reaction chamber 2 was 35 Pa. The composition of the glass film 43 is SiO with N added. ₂ -GeO ₂ -P ₂ O _Five It is a glass film. However, N ₂ / O ₂ Is 0, SiO on which N is not added on the substrate 42 ₂ -GeO ₂ -P ₂ O _Five A glass film is formed.
[0060]
The measurement results of the slab waveguide 41 manufactured with TEOS3, TMG4, and TMP5 steam flow rates of 6, 0.8, and 0.8 sccm, respectively, are indicated by solid lines in FIG. The measurement results of the slab waveguide 41 manufactured as 6, 1.8, and 0.8 sccm, respectively, are shown by dotted lines in FIG.
[0061]
As shown in FIG. ₂ / O ₂ As the value of SiO increases ₂ -GeO ₂ -P ₂ O _Five It can be seen that a large amount of N is added to the glass film, and Δ of the slab waveguide 41 is increased. The Δ of the slab waveguide 41 could be increased up to about 2.5 times as compared with the case where N is not added. N ₂ / O ₂ If the value is 4 to 15, the value of Δ of the slab waveguide 41 can be about 2 to 3.5%.
[0062]
In the conventional manufacturing method, SiO2 is formed on a quartz glass substrate. ₂ -GeO ₂ -P ₂ O _Five When a glass film is formed to realize a slab waveguide having a Δ of about 3%, GeO ₂ The addition amount of 20 mol% or more must be added. Thus GeO ₂ When high concentration is added, quartz glass substrate and SiO ₂ -GeO ₂ -P ₂ O _Five Mismatching between the thermal expansion coefficient and the softening temperature with the glass film increases, causing problems such as the quartz glass substrate being warped by stress and optically polarization dependent.
[0063]
On the other hand, in the slab waveguide 41 manufactured by the manufacturing method according to the present embodiment, since N is added, as can be understood by comparing the solid line and the dotted line in FIG. ₂ Even if the addition amount of TMG4 (flow rate of TMG4) is reduced, the Δ becomes high, and the conventional problem hardly occurs. In addition, since the quartz glass substrate does not easily warp due to stress, the surface of the waveguide can be kept flat, and a semiconductor laser or a light receiving element can be mounted with high dimensional accuracy on the upper surface or end surface thereof. P ₂ O _Five Even if the addition amount is reduced, the same effect can be obtained.
[0064]
Subsequently, the loss characteristic of the slab waveguide 41 was measured.
[0065]
FIG. 3 shows N ₂ / O ₂ Propagation loss and relative refractive index difference and N of the slab waveguide 41 manufactured by variously changing ₂ / O ₂ The horizontal axis is N ₂ / O ₂ FIG. 5 is a graph showing the relative refractive index difference Δ (%) on the left vertical axis and the light propagation loss (dB / cm) on the right vertical axis. The measurement was performed at a wavelength of 1550 nm and a TE mode. The dotted line in FIG. ₂ / O ₂ The solid line in the figure shows Δ and N ₂ / O ₂ Shows the relationship.
[0066]
The measured slab waveguide 41 is manufactured by setting the vapor flow rates of TEOS3, TMG4, and TMP5 to 6, 0.8, and 0.8 sccm, respectively, and other manufacturing conditions are the same as those in FIG. The thickness of the glass film 43 is about 5 μm, and the composition of the glass film 43 is SiO with N added. ₂ -GeO ₂ -P ₂ O _Five It is a glass film.
[0067]
As shown in FIG. ₂ / O ₂ As is increased, Δ of the slab waveguide 41 can be increased, and the light propagation loss does not increase so much. That is, the slab waveguide 41 is a low loss value with a value of Δ being close to 3% and an optical propagation loss of about 0.01 dB / cm, and the loss value of a slab waveguide manufactured by a conventional manufacturing method (0 at Δ3% of 0). Loss of .1 dB / cm).
[0068]
Next, the refractive index characteristics and film thickness characteristics of the nitrogen-added glass film 43 were measured.
[0069]
In order to make it easy to measure the refractive index characteristics and the film thickness characteristics, three Si substrates having a diameter of 4 inches are used in place of the quartz glass substrate 42, and nitrogen is formed on these three Si substrates by the manufacturing method described above. An additive glass film 43 was formed. As a result, the refractive index deviation of the glass film 43 was ± 0.01%, and the film thickness deviation was ± 1.4%. The refractive index deviation between the Si substrates on which the glass film 43 is formed is ± 0.02%, and the film thickness deviation is ± 2.1%. The deviation was about ± 0.9% and the film thickness deviation was about ± 9%).
[0070]
The number of particles (impurity particles) in the glass film 43 (number of particles having a size of 1 to 3 μm: 3, number of particles having a size of 3 to 5 μm: 2 and number of particles having a size of 5 μm or more: 2) Also, it was possible to reduce it to less than half of the conventional number of particles (32).
[0071]
Thus, according to the manufacturing method according to the present embodiment, the raw material gas vaporized by the plurality of alcoholate liquid sources 3, 4, 5 in the reaction chamber 2 is larger in flow rate than the flow rate of the raw material gas. N mixed at a predetermined mixing ratio ₂ Gas 6 and O ₂ Nitrogen-added glass film 43 containing very little Si—H groups, N—H groups, and OH groups by supplying a gas 8 together with the gas 7 and carrying out a thermal decomposition reaction in a high vacuum and plasma atmosphere. The waveguides 41 and 51 using can be easily manufactured.
[0072]
In particular, N ₂ Gas 6 and O ₂ Mixing ratio of gas 7 (N ₂ / O ₂ ) Of 4 to 15, the glass film 43 and the waveguides 41 and 51 having a high relative refractive index difference (high Δ) and low loss can be manufactured. Further, the refractive index and film thickness of the glass film 43 and the waveguides 41 and 51 can be made uniform.
[0073]
In the present embodiment, the mixed gas 8 supplied into the reaction chamber 2 is uniformly diffused to the surface of the substrate 42 by the diffusion plate 22, so that the refractive index and film thickness of the glass film 43 and the waveguides 41 and 51. Can be achieved.
[0074]
A large flow of N in the reaction chamber 2 ₂ When the gas 6 is allowed to flow, the life of the dry pump 15 can be extended significantly. Conventionally, in the dry pump 15, the exhaust gas such as the liquid source 3, 4, 5 or the like corrodes the motor or the rotating part, or the exhaust material such as a polymer adheres to each part to cause clogging. In the present embodiment, a failure occurred in about a month or the life has expired. ₂ Since each component is protected by the gas 6, the failure of each component can be reduced, and the life of the dry pump 15 can be greatly prolonged.
[0075]
In addition, a large flow rate of N in the reaction chamber 2 ₂ Gas 6 and O ₂ When the gas 7 is flowed, the gas ejection nozzle 20 is not clogged by particles, and as a result, the glass film 43 can be formed with good reproducibility, and the adhesion of particles to the gas ejection nozzle 20 can be suppressed. .
[0076]
Large flow rate N ₂ Gas 6 and O ₂ In order to evacuate the gas 7 while maintaining a predetermined degree of vacuum, the nitrogen-added glass film cannot be formed while maintaining the inside of the reaction chamber 2 at a predetermined pressure unless a large-capacity exhaust gas and a purge gas are used.
[0077]
In this embodiment, the mechanical booster pump 14 and the dry pump 15 are connected in series, the exhaust speed of the mechanical booster pump 14 is 8400 l / min or more, and the exhaust speed of the dry pump 15 is 1200 / min or more. The dense glass film 43 and the waveguides 41 and 51 can be formed while maintaining the inside of the chamber 2 at a predetermined high degree of vacuum. Also, a large flow rate of N ₂ Gas 6 and O ₂ Since the gas 7 is exhausted by the large capacity exhaust device (mechanical booster pump 14 and dry pump 15) 13, particles are not easily mixed into the glass film 43 and the waveguides 41 and 51, and the low-loss glass film 43 and the conductive film are introduced. Waveguides 41 and 51 can be manufactured.
[0078]
Since the relative refractive index difference between the glass film 43 and the quartz glass substrate 42 of the waveguides 41 and 51 is larger than 1%, a waveguide type optical component manufactured using this can be miniaturized.
[0079]
Furthermore, if the substrate 42 on which the nitrogen-added glass film 43 is formed and the waveguides 41 and 51 are heat-treated at a temperature higher than 1000 ° C., the glass film 43 and the waveguides 41 and 51 with even lower loss can be manufactured. . In addition, since nitrogen is added into the glass film 43 and the waveguides 41 and 51, the warpage of the substrate 42 can be suppressed to a low level even if heat treatment is performed at a high temperature.
[0080]
In particular, since the embedded waveguide 51 has a higher light confinement effect than the slab waveguide 41, it is possible to achieve an ultra-low loss, an ultra-high Δ, and an ultra-small size. Can be applied.
[0081]
A second embodiment will be described.
[0082]
As shown in FIG. 6, in the reaction chamber 2, the CVD apparatus 61 is provided with the gas supply line 12 penetrating through the central portion of the lower electrode 17 and positioned between the lower electrode 17 and the shower plate 19. The diffusion plate 22 is provided integrally with the lower electrode 17. Other configurations of the device 61 are the same as those of the device 1 of FIG.
[0083]
In order to manufacture the glass film 43 and the waveguides 41 and 51 of FIGS. 4 and 5 using this apparatus 61, the above-described method is the same as that described above except that a plurality of substrates 42 are attached to the lower surface of the upper electrode 16. What is necessary is just to make it the same as the manufactured method.
[0084]
If the apparatus 61 is used, since the substrate 42 is placed above the reaction chamber 2, particles are less likely to be mixed into the glass film 43, and there are fewer particles and defects compared to using the apparatus 1. Therefore, the glass film 43 and the waveguides 41 and 51 with lower loss can be manufactured.
[0085]
A third embodiment will be described.
[0086]
As shown in FIG. 7, the CVD apparatus 71 is provided with a preliminary chamber 72 for temporarily storing the substrate 42 in the vicinity of the reaction chamber 2, and the preliminary chamber 72 exhausts the inside of the preliminary chamber 72 to a high vacuum (for example, Dry pump) 73 is provided. The preliminary chamber 72 and the reaction chamber 2 are communicated with each other through a communication portion 74, and the communication portion 74 is provided with an opening / closing means 23 for opening and closing the communication portion 74 in an airtight manner. In the preliminary chamber 72, a heating means (not shown) for heating and raising the temperature in the preliminary chamber 72 may be provided.
[0087]
The apparatus 71 is provided with a transport mechanism 75 that transports the substrate 42 from the outside of the preliminary chamber 72 to the gas shower chamber 25, the preliminary chamber 72, the communication portion 74, and the reaction chamber 2. Other configurations of the device 71 are the same as those of the device 1 of FIG.
[0088]
In order to manufacture the glass film 43 and the waveguides 41 and 51 of FIGS. 4 and 5 using this apparatus 71, the substrate 42 is carried into the reaction chamber 2 from the preliminary chamber 72 or from the reaction chamber 2 to the preliminary chamber. When unloading the substrate 42 to 72, the degree of vacuum in the preliminary chamber 72 may be made equal to the degree of vacuum in the reaction chamber 2 by the exhaust device 73. Other manufacturing methods are the same as those described above.
[0089]
If the apparatus 71 is used, the substrate 42 can be taken in and out of the reaction chamber 2 while maintaining a high vacuum. Therefore, compared with the case where the apparatus 1 is used, the glass film 43 and the waveguides 41 and 51 with lower loss can be obtained. It can be manufactured and productivity can be increased.
[0090]
In the above embodiment, the glass film 43 is formed on the surface of the substrate 42. However, the relative refractive index difference with the substrate 42 is −0.5% on the surface of the substrate 42, and F is added. SiO ₂ Glass film (SiO ₂ A glass film having a lower refractive index than the glass film) may be formed in advance.
[0091]
SiO with F added ₂ For the glass film, for example, in the process before forming the glass film 43, the apparatus 1 of FIG. ₂ F ₆ Source gas consisting of gas and O ₂ It can be formed by supplying the gas 7. In the step before forming the glass film 43, the same device as the device 1 may be used.
[0092]
As a result, SiO added with F ₂ On the surface of the glass film The glass film 43 to be formed, On the surface of the glass film 43 Additive for controlling the low refractive index of the low refractive index glass film 44 to be formed, for example, GeO ₂ Or P ₂ O ₅ Can be further reduced. Therefore, the mismatch of the thermal expansion coefficient and softening temperature of the substrate 42, the glass film 43, and the low refractive index glass film 44 can be reduced.
[0093]
Instead of forming the nitrogen-added glass film 43 on the surface of the quartz glass substrate 42, SiO added with nitrogen is used. ₂ Further, a nitrogen-added glass film to which at least one dopant such as Ge, P, Ti, B, F, Ta, or Sn is added may be formed. In addition, SiO with nitrogen added ₂ Nitrogen-added glass film added with at least one rare earth element or SiO with nitrogen added ₂ A nitrogen-added glass film in which a metal material or a semiconductor material is added may be formed.
[0094]
Although the example using the quartz glass substrate 42 has been described as the substrate, a multicomponent glass substrate, a semiconductor substrate (for example, Si, GaAs, InP, etc.), a ferroelectric substrate, a magnetic material substrate, or the like can be used. . In this case, on the surface of these substrates, a glass film having a lower refractive index than the glass film to be formed (for example, the above-described SiO doped with F) ₂ A glass film) may be formed in advance.
[0095]
The frequency of the high-frequency power source 18 is not limited to 13.56 MHz, and may be higher than that, for example, a microwave frequency (for example, 2.4 GHz).
[0096]
The heating temperature of the upper electrode 16 and the lower electrode 17 should just be the range of 100-800 degreeC. The heating method of the upper electrode 16 and the lower electrode 17 may be infrared heating in addition to resistance heating.
[0097]
The large-capacity exhaust devices 13, 13 are not limited to two sets, and may be more than two sets.
[0098]
【The invention's effect】
As is apparent from the above description, according to the present invention, an excellent effect that a nitrogen-added glass film having a high relative refractive index difference and a low loss and a waveguide using the same can be produced.
[Brief description of the drawings]
FIG. 1 is a schematic view showing an example of a CVD manufacturing apparatus used in a manufacturing method according to the present embodiment.
FIG. 2 shows the relative refractive index difference and N of a slab waveguide manufactured by the manufacturing method according to the present embodiment. ₂ / O ₂ It is a figure which shows the relationship.
FIG. 3 shows the light propagation loss and relative refractive index difference of the slab waveguide manufactured by the manufacturing method according to the present embodiment, and N ₂ / O ₂ It is a figure which shows the relationship.
FIG. 4 is a cross-sectional view of a slab waveguide manufactured by the manufacturing method according to the present embodiment.
FIG. 5 is a cross-sectional view of an embedded waveguide manufactured by the manufacturing method according to the present embodiment.
FIG. 6 is a schematic view showing an example of a plasma CVD manufacturing apparatus used in the manufacturing method according to the present embodiment.
FIG. 7 is a schematic view showing an example of a plasma CVD manufacturing apparatus used in the manufacturing method according to the present embodiment.
FIG. 8 is a schematic view showing a CVD manufacturing apparatus used in a conventional manufacturing method.
FIG. 9 is a diagram showing loss characteristics of a slab waveguide and a buried waveguide manufactured by a conventional manufacturing method.
[Explanation of symbols]
1 CVD equipment
2 reaction chamber
3,4,5 alcoholate liquid source
6 N ₂ gas
7 O ₂ gas
16 Upper electrode
17 Lower electrode
18 High frequency power supply
22 Diffuser
42 Quartz glass (substrate)

Claims (7)

A high frequency voltage is applied to the upper electrode and the lower electrode in the reaction chamber evacuated to a high vacuum, the upper electrode and the lower electrode are heated to a predetermined temperature, the substrate is carried into the reaction chamber, and the lower electrode or the A plurality of alcoholate-based liquid sources are placed in the reaction chamber using a mechanical booster pump (exhaust speed of 8400 l / min or more) and a dry pump (exhaust speed of 1200 l / min or more) connected in series with the upper electrode. N ₂ gas (100 sccm or more) and O ₂ gas (400-1500 sccm) obtained by mixing the raw material gas at a predetermined flow rate (about several sccm), which is vaporized, at a flow rate larger than the flow rate of the raw material gas and at a predetermined mixing ratio And is set so that the pressure in the reaction chamber is within a range of 25 to 40 Pa, and a thermal decomposition reaction is performed in a plasma atmosphere. Performed, a manufacturing method of a nitrogen-doped glass film and forming a nitrogen-doped glass film on the surface of the substrate.   The method for producing a nitrogen-added glass film according to claim 1, wherein a diffusion plate for uniformly diffusing each gas to the substrate is provided at a gas supply port in the reaction chamber. Method for manufacturing a nitrogen-doped glass film according to claim 1 or 2 mixing ratio of the _{N 2} gas and _{O 2} gas _(N 2 / _{O 2)} is 4 to 15. The plurality of alcoholate based liquid source, the SiO ₂ of GeO _2, or a nitrogen-doped glass film according to any one of claims 1 to 3 using a raw material and GeO ₂ and _P 2 _{O 5} is added to SiO ₂ Production method. The method for producing a nitrogen-added glass film according to claim 1 , wherein a quartz glass substrate is used as the substrate . 6. The method for producing a nitrogen-added glass film according to claim 5, wherein the nitrogen-added glass film has a relative refractive index difference larger than 1% with respect to the quartz glass substrate . After forming the nitrogen-added glass film using the manufacturing method according to any one of claims 1 to 6, the nitrogen-added glass film is subjected to photolithography and dry etching to form a nitrogen-added glass film having a predetermined shape, A method of manufacturing a waveguide, wherein the nitrogen-doped glass film having a predetermined shape is covered with a low refractive index glass film.

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