JP2003149437A - Device and method for manufacturing multilayer film optical filter - Google Patents

Abstract

PROBLEM TO BE SOLVED: To solve a problem that the characteristics of a DWDM multilayer film optical filter having many layers are deteriorated due to the variation of a filming speed or the ruggedness or the like of a deposition material by dropping a deposition substrate stuck to a shutter on the deposition material at the time of preliminary heating of the evaporation material during the filming of the filter. SOLUTION: Since a part 30 at least opposed to the evaporation material 20 out of the shutter 10 covering the material 20 is constituted of the same substance of the material 20, the variation of the filming speed and the ruggedness of the deposition material are not generated because a deposited substance dropped at the time of preliminary heating is constituted of the same material as the desposition material. Consequently the multilayer film optical filter having high characteristics can be stably manufactured.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for manufacturing a dielectric multilayer optical filter used in an optical communication system, and more particularly to a vapor deposition apparatus for a multilayer optical filter.

[0002]

2. Description of the Related Art With the recent development of high-speed communication networks,
A large amount of information has been transmitted at high speed. Development of a wavelength division multiplexing optical communication system has been actively carried out as one of methods for making this possible. In this wavelength division multiplexing optical communication system, optical signals of a plurality of wavelengths are superposed and transmitted on one glass fiber, and the transmission capacity per fiber can be dramatically increased. In particular, DWDM (Dense Wavelength D) with increased density of multiplexed wavelengths
In the ivision multiplexing) system, the wavelength spacing between adjacent channels is narrowing to about 1 nm, and it becomes necessary to narrow the wavelength spacing in order to cope with the increasing information traffic in the future.

In the wavelength division multiplexing optical communication system, it is necessary to connect an optical multiplexer / demultiplexer before and after the glass fiber.
The dielectric multilayer optical filter is a narrow band filter (NBPF, Narrow Band Pass Filter) that constitutes an optical multiplexer / demultiplexer.
er) and various optical filters used in optical communication systems.

In these multilayer optical filters, a high refractive index dielectric film and a low refractive index dielectric film are alternately laminated on a glass substrate to form a multilayer film ranging from several tens to 200 layers. , Its film thickness reaches several tens of μm. An example of the structure of this multilayer optical filter is disclosed in Japanese Patent Laid-Open No. 10-197721.
It is described in Japanese Patent Publication No. Further, FIG. 7 shows, as an example, a multilayer film structure that constitutes a multi-cavity bandpass filter. That is, a basic multilayer optical filter is a mirror layer 1 in which high-refractive-index dielectric layers having an optical film thickness of ¼ wavelength and low-refractive-index dielectric layers having an optical film thickness of ¼ wavelength are alternately laminated. , And the cavity layer 2 having an optical film thickness of ½ wavelength or an integral multiple thereof, the film-forming substrate 3, and the antireflection film 4. However, in order to improve optical characteristics, various film thicknesses are changed based on this structure to obtain desired characteristics.

When a multilayer optical filter is used as the NBPF which constitutes the optical multiplexer / demultiplexer, the band width of the transmission band becomes narrower as the number of cavities increases. Eg 1
In the NBPF for DWDM of 00 GHz pitch, it is necessary to form a multi-layer film having four cavities and more than 130 layers including the mirror layer.

A vapor deposition apparatus is used for forming such a multilayer optical filter. A method is used in which a shutter is opened and a vaporized material is deposited on a substrate after a predetermined preheating time has elapsed.

Preheating of the evaporation source must be performed before film formation for the two purposes of degassing the vapor deposition material and creating a stable molten state in advance. In the case of a multilayer optical filter, each layer must be preheated. Preheating is performed every time before film formation. 1
The time of the preliminary heating for each time is about several minutes although it varies depending on the material and the device. However, the DWD targeted by the present invention
In the NBPF for M, the number of layers is 60 to 60 per vapor deposition material.
Since it reaches 70 layers, preheating is repeated 60 to 70 times per batch, and during that time, a large amount of evaporated material is attached to the shutter.

Since the shutter is heated by receiving the radiant heat from the vapor deposition material, the evaporation material attached to the shutter reacts with the material of the shutter and changes into another kind of compound.
The deposits may fall onto the vapor deposition material during repeated preheating, and as a result, the deposits diffuse into the vapor deposition raw material and the impurities resulting from the shutter material are taken into the film or the vapor deposition raw material. When the above deposit remains undissolved, a protrusion is formed starting from that and unevenness occurs on the surface of the vapor deposition material. The impurities deposited on the substrate optically cause absorption and cause a decrease in transmittance. on the other hand,
The irregularities generated in the vapor deposition material change the evaporation rate and cause a non-homogeneous film, and also change the distribution of the evaporated material in the scattering direction, which causes a film thickness distribution on the substrate, and eventually a multilayer optical filter. It also leads to deterioration of the product acceptance rate.

[0009]

As described above, the DWDM
In the multilayer optical filter for dealing with the above, since the number of layers increases, the evaporation material that reacts with the shutter material from the shutter of the vapor deposition material drops to the vapor deposition material more frequently. It was difficult to form a stable body layer.

[0010]

According to the present invention, the surface of the shutter facing the vapor deposition material is made of the same material as the evaporation source to prevent the reaction between the shutter and the evaporated material, and to prevent evaporation on the shutter. Even if an object peels off and mixes into the vapor deposition material, the problem of impurities and unevenness can be avoided. Also, if it is difficult to use the material of the vapor deposition material itself for the shutter due to price, strength, processability, etc., select the appropriate element from the vapor deposition raw material to configure the vapor deposition raw material side of the shutter. This makes it possible to avoid problems such as the mixing of impurities in the vapor deposition material and the unevenness.

That is, the apparatus for manufacturing a multilayer optical filter of the present invention is a manufacturing apparatus for a multilayer optical filter comprising a dielectric multilayer film in which a plurality of high refractive index films and low refractive index films are alternately laminated. At least a portion of the shutter provided between the substrate and the substrate facing the vapor deposition material is made of the same material as the vapor deposition material. The shutter may be installed between the vapor deposition material and the substrate to control vapor deposition by moving a part of the shutter, or may be configured to control the vapor deposition by moving the shutter itself between the vapor deposition material and the substrate. .

Another manufacturing apparatus for a multilayer optical filter according to the present invention is a manufacturing apparatus for a multilayer optical filter including a dielectric multilayer film in which a plurality of high refractive index films and low refractive index films are alternately laminated. It is characterized in that at least a portion of the shutter provided between the raw material and the substrate facing the vapor deposition raw material is made of a material containing one or more kinds of elements contained in the vapor deposition raw material.

Another manufacturing apparatus for a multilayer optical filter according to the present invention is a multilayer optical filter manufacturing method using silicon oxide as a low refractive index film, wherein a vapor deposition material of silicon oxide (SiO ₂ ) and a substrate are used. It is characterized in that at least a portion of the shutter provided between and facing the vapor deposition material is made of silicon oxide.

Another manufacturing apparatus for a multilayer optical filter of the present invention is a manufacturing apparatus for a multilayer optical filter which uses M oxide (M is tantalum, titanium or niobium) as a high refractive index film. , M oxide deposition material and a shutter provided between the substrate and at least a portion facing the deposition material is composed of the M or M oxide. More preferably, a part of the shutter is made of M. For example, tantalum oxide (Ta ₂ O
₅ ) At least a portion of the shutter provided between the vapor deposition material and the substrate facing the vapor deposition material is tantalum (Ta).
It is good to be composed.

The method for producing a multilayer optical filter of the present invention is a method for producing a multilayer optical filter comprising a dielectric multilayer film in which a plurality of high refractive index films and low refractive index films are alternately laminated, And a step of forming a dielectric multilayer film by opening and closing a shutter provided between the vapor deposition raw material and the substrate, and at least a portion of the shutter facing the vapor deposition raw material is equivalent to the vapor deposition raw material. It is characterized by being composed of the material. Here, the “equivalent material” corresponds to a material containing any one or more of the elements contained in the vapor deposition material, or more preferably the same material.

[0016]

BEST MODE FOR CARRYING OUT THE INVENTION The present invention will be described in detail with reference to Examples. Example 1 FIG. 1 is a schematic diagram showing the structure of a vapor deposition device.
The vapor deposition apparatus has a shutter 10 shaped to cover the vapor deposition raw material 20. When the vapor deposition raw material is preheated, the shutter 10 is closed to prevent the vaporized substance 24 from adhering to the substrate 12 (glass substrate). After the lapse of a predetermined preheating time, the shutter 10 is opened to deposit the evaporation material 24 on the substrate 12, and when the required film thickness is obtained, the shutter 10 is closed. Only one evaporation source is shown in Fig. 1 to facilitate the explanation of the details of the structure. However, when forming a multilayer filter, two evaporation materials, a high refractive index material and a low refractive index material, are placed in the chamber. There is a source, and the desired multilayer film is obtained by alternately opening and closing each shutter. The vapor deposition material 20 is usually loaded into the Cu hearth 19 and heated by an electron gun 22 or the like. Further, the film is formed while irradiating the substrate 12 with oxygen atoms and the like by the ion gun 21 during the film formation.

A general outline of the vapor deposition apparatus will also be described. This vapor deposition apparatus includes an evaporation source unit that blows vapor deposition material, a vapor deposition unit that deposits vapor deposition material on a substrate, a chamber 18, a vacuum exhaust unit (not shown), and a carry-in port (a door on the right side of the drawing, etc.). The details are omitted). The evaporation source portion has a Cu hearth 19 having a ring-shaped recess for mounting the vapor deposition material.
A drive device 19b for rotating a Cu hearth corresponding to an evaporation crucible, an electron gun 22 for irradiating an electron beam on a vapor deposition material to perform heating for preheating / evaporation, and a shutter for controlling the progress of an evaporated material 24. Have 10. In the vapor deposition section, a substrate holder 13 that supports the substrate 12 facing the vapor deposition material in the chamber 18, a substrate rotation motor 14 that can rotate the substrate holder 13 at high speed, and a film thickness monitor light receiving unit 15. And a substrate heater 17 for heating the substrate during film formation. A vacuum is held between the chamber and the substrate holder by a bearing and a magnetic fluid, and other members are also sealed so as not to hinder the exhaust of the chamber.

With such a vapor deposition apparatus, the low refractive index material is made into Si.
A multilayer optical filter was formed using O ₂ and Ta ₂ O ₅ as the high refractive index material. The structure of the shutter used is shown in FIG. This figure is a schematic diagram when the shutter is seen from the vapor deposition material. Shutter 10 for SiO ₂ vapor deposition material
A disk 30 of SiO ₂ (diameter 150 mm, thickness 1 mm) was attached to a portion facing the vapor deposition material, and fixed with a stopper 31. Ta ₂ O ₅ in the shutter 10 for the evaporation source Ta ₂
Disk 30 of O ₅ sintered body (diameter 150 mm, thickness 2.0 m
m) was attached and similarly fixed with a stopper 31. The shutter 10 is connected to a shutter mounting block 32 via a shutter arm 11. By swinging the shutter 10 around the shutter mounting block 32, the shutter 10 was taken in and out (opened and closed) between the vapor deposition material and the substrate. Illustration of a drive mechanism for rotating the shutter mounting block 32 is omitted. Note that parts having similar shapes will be described using the same reference numerals.

A multilayer optical filter was formed by the following steps using these shutters. A cleaning glass substrate with a plate thickness of 10 mm having an antireflection film formed on the back surface was loaded in a film forming apparatus, the vacuum degree was evacuated to 5 × 10 ⁻⁶ Torr or less, and the vapor deposition raw material was preheated, and then film formation was performed. Started. The film thickness during film formation is monitored by directly transmitting the light emitted from the film thickness monitor light projecting unit 23 to the multilayer film under film formation and detecting the transmitted light by the film thickness monitor light receiving unit 15. I went. Specifically, the transmitted light repeats transmission and reflection for each quarter wavelength of the optical thickness of the multilayer film, so the end point is detected by monitoring the light intensity of the transmitted light, and the shutter is opened and closed. It becomes possible to form different films alternately. The wavelength of the monitor light was 1550 nm, which is a typical value of C band.

The layer structure of the formed multilayer filter is (H
L) ^ 6H6LH (LH) ^ 6L (HL) ^ 7H6LH (LH) ^ 7L (HL) ^
It is 8H8LH (LH) ^ 8L (HL) ^ 6H6LH (LH) ^ 62L. Here, H and L are S corresponding to the film thickness of 1/4 wavelength.
The layers of iO ₂ and Ta ₂ O ₅ are shown. Also, (HL) ^ 6
Is that the laminated structure of H and L is repeated 6 times, 6L is 6
Si having a film thickness of × (1/4 wavelength) (that is, 1.5 wavelengths)
It is a layer of O ₂ . Pre-heating of Ta ₂ O ₅ was carried out for 4 minutes under the condition of an electron gun of 6 kV270 mA and SiO 2.
_The preheating of No. ₂ was carried out for 3 minutes under the condition of the electron gun 6 kV 200 mA.

During film formation, the vapor deposition material adhered to the shutter during the preheating was partly peeled off and dropped to the evaporation source, but the fallen material was quickly dissolved and the film formation rate did not change. It was In addition, FIG. 3 is a photograph showing the state of the SiO ₂ vapor deposition raw material after the film formation is completed, but as seen in this, the convex portion due to the unmelted residue of the falling matter did not occur. This is because even if the evaporate adheres to the shutter, the same substances are basically in contact with each other, so that no impure compound is generated and the original substance is maintained, so even if it falls, it contaminates the vapor deposition material. This is because it does not cause bumping or unevenness.

The characteristics of the formed multilayer optical filter are shown in FIG. As shown in this figure, the insertion loss of the embodiment is 0.5.
Less than dB, other filter characteristics are 100GH
It showed good optical properties applicable to z-spacing DWDM systems.

Example 2 Ta ₂ O used in Example 1
The sintered body of No. ₅ has weak mechanical strength and may be damaged if repeatedly used. Also, the price is relatively high. Alternatively, a pure Ta plate (purity 99.9%; diameter 15
0 mm thickness 0.5 mm) was used. Since the Ta plate has mechanical strength and can be repeatedly used, it is more practical than the sintered body of Ta ₂ O ₅ . Other film forming conditions are the same as in Example 1.

As a result, even in this case, the deposits sometimes dropped from the shutter during film formation, but the deposited substances were quickly dissolved, the film formation speed did not fluctuate, and unevenness did not occur. Further, the characteristics of the formed multilayer optical filter are insertion loss of 0.5 dB or less, and it is considered that there is no problem such as mixing of impurities.

As the high refractive index material, TiO ₂ or Nb ₂ O ₅ may be used in addition to Ta ₂ O ₅ mentioned above. In these cases, however, the respective sintered bodies, Ti or Nb may be used.
The metal plate of can be used.

Comparative Example As a comparative example, a shutter having no lining on the side of the vapor deposition material (material SUS304) was used to form a multilayer optical filter similar to those in Examples 1 and 2. Other film forming conditions are the same as those in Examples 1 and 2. During film formation, the deposits that dropped onto the vapor deposition material during preheating are difficult to dissolve, and in both cases of SiO ₂ and Ta ₂ O ₅ , large fluctuations in film formation rate of up to ± 30% were observed when deposits dropped. It was FIG. 5 is a photograph of the SiO ₂ vapor deposition raw material after the film formation in the comparative example. 5 will be described with reference to the schematic diagram of FIG. As shown in this figure, the attached matter 40 that fell down had a brown color due to the reaction with the shutter, and was left unmelted to form a convex portion with that point as the apex.

As shown in FIG. 4, the optical characteristics of the formed multilayer optical filter had an insertion loss of 1 dB or more, and it was suspected that absorption due to fluctuations in the film formation rate or inclusion of impurities was generated. Further, the band width was widened, and the optical characteristics of the comparative example could not be used as the NBPF for DWDM.

[0028]

As described above, according to the manufacturing method of the present invention, it is possible to stably manufacture a multilayer optical filter for DWDM having a large number of layers.

[Brief description of drawings]

FIG. 1 is a schematic diagram showing the structure of a multilayer optical filter vapor deposition device.

FIG. 2 is a schematic view showing a structure of a shutter according to the present invention.

FIG. 3 is a photograph of a structure of a ceramic material showing a state of a SiO ₂ vapor deposition raw material after film formation in an example.

FIG. 4 is a graph showing optical characteristics of an example and a comparative example.

FIG. 5 is a photograph of a structure of a ceramic material showing a state of a SiO ₂ vapor deposition raw material after film formation in a comparative example.

FIG. 6 is a schematic diagram illustrating FIG.

FIG. 7 is a cross-sectional view showing a multilayer film structure that constitutes a multi-cavity bandpass filter.

[Explanation of symbols]

1 mirror layer, 2 cavity layer, 3 deposition substrate,
4 Antireflection Film, 10 Shutter, 11 Shutter Arm, 12 Substrate, 13 Substrate Holder, 1
4 substrate rotation motor, 15 film thickness monitor light receiving part,
16 Crystal type film thickness monitor, 17 Substrate heater,
18 chamber, 19 Cu hearth, 19b drive device, 20 evaporation material, 21 ion gun, 22
Electron gun, 23 Film thickness monitor projecting part, 24 Evaporated material, 30 Disc for covering shutter evaporation material side, 31
Stopper, 32 Shutter mounting block, 40
Objects falling from the shutter.

   ─────────────────────────────────────────────────── ─── Continued front page    (72) Inventor Toshio Kobayashi             5200 Mikkajiri, Kumagaya-shi, Saitama Hitachi Metals Co., Ltd.             Inside the Advanced Electronics Research Laboratory F-term (reference) 2H048 GA04 GA33 GA60                 4K029 BA43 BA46 BA48 BB02 BC07                       CA09 DA12

Claims (5)

[Claims] 1. A manufacturing apparatus of a multilayer optical filter comprising a dielectric multilayer film in which a plurality of high refractive index films and low refractive index films are alternately laminated, wherein at least a shutter provided between a vapor deposition material and a substrate is vapor deposited. An apparatus for manufacturing a multilayer optical filter, characterized in that the portion facing the raw material is made of the same material as the vapor deposition raw material. 2. In a manufacturing apparatus of a multilayer optical filter comprising a dielectric multilayer film in which a plurality of high refractive index films and low refractive index films are alternately laminated, at least a vapor deposition of a shutter provided between a vapor deposition material and a substrate. An apparatus for manufacturing a multilayer optical filter, wherein a portion facing the raw material is made of a material containing one or more kinds of elements contained in the vapor deposition raw material. 3. In a manufacturing apparatus of a multilayer optical filter using silicon oxide as a low refractive index film, at least a portion of a shutter provided between a silicon oxide vapor deposition material and a substrate is opposed to the vapor deposition material. An apparatus for manufacturing a multilayer optical filter, which is composed of an oxide. 4. A multilayer optical filter manufacturing apparatus using M oxide (M is any one of tantalum, titanium, and niobium) as a high-refractive index film, between a deposition material of M oxide and a substrate. An apparatus for producing a multilayer optical filter, wherein at least a portion of a shutter provided facing the vapor deposition material is made of the M or M oxide. 5. A method of manufacturing a multilayer optical filter comprising a dielectric multilayer film in which a plurality of high-refractive index films and low-refractive index films are alternately laminated, comprising a step of preheating a vapor deposition raw material, and a vapor deposition raw material. And a step of forming a dielectric multilayer film by opening and closing a shutter provided between the substrate and the substrate, wherein at least a portion of the shutter facing the vapor deposition material is made of a material equivalent to the vapor deposition material. And a method for producing a multilayer optical filter.