JPH0827408B2 - Method for manufacturing optical multilayer film filter device - Google Patents

Description

TECHNICAL FIELD The present invention relates to a method for manufacturing an optical multilayer film filter element. In particular, the present invention relates to a method for manufacturing an ultra-small and ultra-thin optical multiplexing / demultiplexing filter element used for optical communication and the like.

[Conventional technology]

In general, an optical multilayer film filter element selectively transmits or reflects only light in a specific wavelength region by utilizing light interference of multilayer films. The optical multilayer film filter element has a laminated structure in which non-metallic optical materials having different refractive indexes are superposed, and has been conventionally formed on a glass substrate by vacuum vapor deposition. By changing the film thickness and the refractive index of each layer, it is possible to obtain a filter having an arbitrary half-width with respect to an arbitrary center wavelength.

Such an optical multilayer film filter element is widely used as an optical multiplexing / demultiplexing filter in optical multiplex communication and the like. That is,
The optical multiplexing / demultiplexing filter is inserted at a branch point of an optical waveguide network composed of an optical fiber or the like to separate and combine each wavelength component. Therefore, the optical multiplexing / demultiplexing filter has a very small size, and has an ultrathin size of about several tens of μm in order to prevent light loss.

A conventional optical multiplexing / demultiplexing filter has a structure in which optical substances having different refractive indexes are alternately laminated by a vacuum deposition method on a glass substrate having a thickness of several tens of μm. In order to manufacture such a filter, after vacuum-depositing a multilayer film on a conventional glass substrate,
The glass substrate was ground to several tens of μm and cut into squares of several mm. Alternatively, it is manufactured by depositing a large number of films on a glass chip that has been polished to several tens of μm in advance.

[Problems to be solved by the invention]

However, since the conventional optical multiplexing / demultiplexing filter has a multilayer film structure deposited by the vacuum evaporation method, there is a problem that the film quality is porous and the weather resistance and the moisture resistance are poor. That is, since the multilayer film is porous, water or alcohol is adsorbed and the transmission frequency characteristic of the filter fluctuates, and accurate optical multiplexing / demultiplexing cannot be performed, and noise is mixed into multiplex communication. was there. In view of such a problem, the inventor has obtained an optical multilayer having a non-adsorptive dense structure against moisture and the like in order to obtain an ultra-small and ultra-thin optical multilayer filter element having excellent weather resistance and moisture resistance. Focused on the use of membranes.

By the way, as in the conventional case, when a multilayer film having a dense composition is fixed on a glass substrate and then the glass substrate is polished to a thickness of several tens of μm to manufacture an ultrathin optical filter, the dense multilayer film is formed into a glass. Since the glass substrate exhibits a strong compressive internal stress, the glass substrate is damaged during polishing. what if,
Even if it is polished without breaking, the glass substrate is deformed due to the strong compressive internal stress, which makes it difficult to use. In view of such difficulties, a general object of the present invention is to manufacture an ultra-thin optical filter element composed of a dense multilayer film alone and having excellent weather resistance, without damage or deformation. A characteristic object of the present invention is to manufacture an ultra-thin optical filter element in which a dense multilayer film is subdivided accurately and easily with high yield.

[Means for Solving Problems] In order to achieve the above object, the method for producing an optical filter thin film element according to the present invention utilizes a carrier soluble in a solvent. Increasingly, a dense optical filter thin film that is non-adsorptive to moisture etc. by alternately stacking and stacking high refractive index optical material and low refractive index optical material by using acceleration energy on the surface of a soluble carrier. A film forming step for forming is performed. Next, a non-contact division step of forming a plurality of element sections separated from each other by a non-contact processing process is performed on the formed optical filter thin film. Finally, a step of dissolving the soluble carrier in a solvent to peel off the optical filter thin film to obtain an optical filter thin film piece for each element section is performed to obtain a single optical filter element.

Characteristically, the non-contact division step includes a step of forming a separation groove by irradiating a laser beam spot along the boundary of the element division. Alternatively, a step of applying a photoresist film to the formed optical filter thin film,
You may use the process of patterning a photoresist film according to an element division by non-contact exposure, and the process of etching an optical filter thin film through a patterned photoresist film to form a separation groove.

[Action]

According to the method for manufacturing an optical filter thin film element according to the present invention, a dense optical filter thin film is obtained as a single-type multilayer film that is separated from the carrier in each element section. Therefore, unlike the conventional case, the compressive internal stress between the glass substrate and the multilayer film does not pose a problem, and the optical filter thin film element can be manufactured with high yield. By the way, when the dense optical filter thin film is deposited on the surface of the carrier, the carrier undergoes compressive strain or warpage due to the stress of the dense optical filter thin film. In view of this point, in the present invention, a plurality of element sections separated from each other are formed by a non-contact processing process on the formed optical filter thin film. Since it is non-contact processing, there is no physical contact with the carrier and there is no influence of warpage occurring in the carrier, so that the element sections can be provided accurately and easily. Even if the carrier is warped, it is difficult to accurately and easily process the element sections by dicing for contact processing or photolithography for contact exposure.

〔Example〕

Hereinafter, preferred embodiments of the present invention will be described in detail with reference to the drawings. FIG. 1 is a process drawing showing a first embodiment of a method for manufacturing an optical multilayer filter element.

In the step shown in FIG. 1 (A), a carrier 1 soluble in a predetermined solvent is prepared. In this embodiment, a bulk flat plate carrier is used, and its surface is kept smooth by precision polishing finish. The flat plate carrier is made of a material composed of a metal or a metal compound such as a metal oxide. These materials are used because smooth finish is easy and inexpensive commercially available acids, alkalis or etchants can be used as a solvent.

Subsequently, in the step shown in FIG. 1 (B), the flat plate carrier 1
On the other hand, an optical material having a high refractive index and an optical material having a low refractive index are alternately deposited to form a laminated optical filter multilayer film 2. As a deposition method, an ordinary vacuum vapor deposition method can be used, but in this case, the multilayer film has porosity and is adsorbable to moisture. Therefore, it is preferable to use the ion assisted vacuum deposition method, the ion plating vacuum deposition method, or the sputtering method in order to deposit the multilayer film 2 having a dense composition that is non-adsorbing to water. These deposition methods can form a dense refraction layer that is non-adsorptive to moisture by utilizing accelerated energy particles. In addition,
In this embodiment, a substance evaporated by electron beam heating is accelerated in plasma by using the ion plating vacuum deposition method to be deposited on the surface of the carrier. As the high refractive index optical material forming a high refractive index, for example, Ta ₂ O ₅ can be used,
Examples of the low refractive index optical material forming the low refractive layer include Si
O ₂ can be used. When a film is formed by utilizing acceleration energy particles, a dense optical filter thin film can be formed, but the strong internal compressive stress inevitably causes the flat carrier 1 to warp.

In the step shown in FIG. 1 (C), the optical filter thin film 2 is cut while being held on the soluble carrier 1 to be subdivided into element sections having desired dimensions. This cutting is performed in a non-contact manner using a laser beam spot LBS that is scanned in the X and Y directions as shown in the figure. Therefore, even if the flat plate carrier 1 is warped, the element sections can be formed with high dimensional accuracy without being affected by the warp. Alternatively, X- for a fixed laser beam spot LBS
The flat carrier 1 may be moved using a Y feed table to perform the cutting process. At this time, as shown in the figure, it is preferable that the cutting line is set slightly deeper than the thin film of the multilayer film 2 so that the surface portion of the soluble carrier 1 is also cut.

Finally, in the step shown in FIG. 1 (D), the soluble carrier 1 is immersed in a specific solvent to be dissolved, and the subdivided optical filter multilayer film 2 is peeled off. As a result, the individual optical filter multilayer film pieces that have been subdivided can be separated to obtain a single-type optical filter element 3.

FIG. 2 is a schematic diagram of a YAG laser processing apparatus used in a non-contact partition process using a laser beam spot. As shown in the figure, this processing apparatus has a YAG laser light source 20 capable of continuously emitting a high energy laser beam having an average output value of about 1000W. A first scanning galvanometer mirror 21 is arranged in front of the laser light source 20, and scans the laser beam in the X direction. Further, a second scanning galvanometer mirror 22 is arranged in the traveling direction of the laser beam, and scans the laser beam in the Y direction. The laser beam scanned in the X and Y directions in this manner is collected by the condenser lens 23.
Then, the surface of the carrier 1 on which the optical filter multilayer film is formed is irradiated as a laser beam spot LBS.
The laser beam spot has a spot diameter on the order of micrometer and gives extremely high density energy. When the laser beam spot is detailed along the preset device division boundary line, the irradiated portion of the multilayer filter thin film is heated to a temperature equal to or higher than the melting point and evaporated to be removed to form a cut groove.

As shown in the figure, since this cutting process is performed by non-contact process through the laser beam spot, it is accurately performed along the element section without being affected by the warp of the carrier 1. Further, the cut end surface is extremely flat, and an optical filter multilayer film element having high dimensional accuracy can be manufactured.

On the other hand, if the separation groove is formed by dicing using the rotating blade used for cutting the semiconductor wafer, the rotating blade physically contacts the carrier surface,
It is difficult to perform accurate dicing under the influence of warpage. In addition, chipping occurs on the end faces of the optical filter multilayer film during the cutting process, which reduces the yield.

Further, if the above-mentioned dicing is used, it may be considered that the separation groove forming process is performed on the surface of the carrier in a state where the carrier is not warped before the deposition of the optical filter multilayer film. However, in this case, since the film forming process is performed from the top of the separation groove in a later step, sagging occurs around the deposited film at the end of the separation groove, and desired dimensional accuracy cannot be obtained.

FIG. 3 is a process chart showing a second embodiment of the method for manufacturing a single-piece optical filter thin film element according to the present invention. In the step shown in FIG. 3A, a temporary substrate 4 made of an insoluble substance is prepared.

In the step shown in FIG. 3B, the surface of the temporary substrate 4 is coated with the film carrier 1 made of a soluble substance. This coated carrier 1 can be obtained by, for example, sputtering of metal nickel or vacuum deposition. And this soluble film carrier 1
Is soluble in a particular etching solution.

In the step shown in FIG. 3C, the optical material having a high refractive index and the optical material having a low refractive index are alternately deposited on the coating film carrier 1 to form the laminated optical filter multilayer film 2. This deposition process is performed in the same manner as the first embodiment shown in FIG.
Further, the temporary substrate 4 is inevitably warped for the same reason as described in the first embodiment.

In the step shown in FIG. 3D, the photoresist film 5 is uniformly coated on the surface of the optical filter multilayer film 2. Further, the photomask 6 on which the element division pattern having a desired size and shape is formed is separated from the photoresist film 5 and a non-contact exposure process is performed, and then the element division 7 is formed by a step shown in FIG. 3 (E). Then, the photoresist film 5 is removed. Since the photolithography is performed in a non-contact manner even when the temporary substrate 4 is subjected to a strong stress that causes warping or deformation, the element section 7 can be formed accurately and easily without being adversely affected by warping or deformation. The non-contact photolithography is used especially when a highly precise device dimension standard is required or when a disc-shaped device shape is desired. Contact exposure is not appropriate when the temporary substrate is warped.

Next, in the step shown in FIG. 3 (F), the exposed portion of the optical filter multilayer film 2 through the patterned photoresist film 5, the film carrier 1 and the temporary substrate 4 thereunder.
Dry etching is performed to form a separation groove. That is, the isolation groove is formed so as to surround each element section 7. Dry etching is performed by sputtering using argon cations, for example.

Finally, in the step shown in FIG. 3 (G), after removing the photoresist film 5, in the step shown in FIG. 3 (II), the optical carrier multilayer film partitioned by dissolving the film carrier 1 in a solvent. 2 is peeled off. At this time, since the film carrier 1 has a notch and the end face thereof is exposed, dissolution of the film carrier 1 is promoted by the effect of side etching. In this way, the partitioned optical filter multilayer film 2 is separated from the temporary substrate 4 and individual optical filter elements 3 can be obtained.

Finally, the features of the optical filter element obtained by the above-described manufacturing method will be described. FIG. 4 is a perspective view showing an example of such an optical filter element. As shown in the figure, the optical filter element 3 is composed of a single type multilayer film 2. However, it goes without saying that it can be used in combination with other optical members or optical components in actual use. The multilayer film 2 has a multilayer structure in which high-refractive layers 8 and low-refractive layers 9 are alternately laminated. The high refractive layer 8 is made of an optical material having a relatively high refractive index, has a dense composition that is adsorbed to moisture, and exhibits a certain compressive internal stress. The low refractive layer 9 is made of an optical material having a relatively low refractive index, has a dense composition that is non-adsorptive to moisture, and exhibits a compressive internal stress substantially equal to that of the high refractive layer 8. By appropriately setting the refraction layer and thickness of each refraction layer, it is possible to obtain the optical filter multilayer film 2 having a desired light selection frequency characteristic. In this example, since the optical filter element 3 is used as an optical multiplexing / demultiplexing filter element used for optical multiplex communication or the like, it has an area of several mm square and a film thickness of several tens of μm. For example, by stacking 60 high-refractive layers 8 and low-refractive layers 9 having a layer thickness of 0.25 μm, a multilayer film 2 having a film thickness of 15 μm can be obtained. According to the manufacturing method of the present invention, since the end face of the optical filter element 3 is formed by cutting using a laser beam spot or dry etching by sputtering, it is extremely flat and has an appearance without chipping or sagging. Also excellent in dimensions.

For example, Ta ₂ O ₅ can be used as the high refractive index optical material forming the high refractive layer 8, and SiO ₂ can be used as the low refractive index optical material forming the low refractive layer 9. These optical materials are stacked by a deposition process using accelerated energy particles and have a dense composition that is non-adsorptive to a solvent component such as water or alcohol. As the deposition process using the acceleration energy particles, for example, an ion assisted vacuum deposition method is used.

FIG. 5 is a perspective view showing another example of the optical filter element obtained by the manufacturing method according to the present invention. As shown in the figure, the optical filter element 3 is composed of a single type multilayer film 2. In this example, the multilayer film 2 has an adjustment layer 10 in addition to the laminated portion of the high refractive index layer 8 and the low refractive index layer 9. The adjustment layer 10 has a layer thickness that is adjusted to obtain a desired film thickness of the multilayer film 2. That is, the optical filter element 3
In addition to the laminated portion having the filtering function, has an adjusting layer having only the function of adjusting the thickness of the multilayer film 2. The adjustment layer 10 is made of, for example, the same optical material as that of the low refractive index layer 9, and preferably has a dense composition that is non-adsorptive to moisture, like the laminated portion.

Next, the separating characteristics of the above-described optical filter element will be described with reference to FIG. FIG. 6 is a graph showing the internal stress of a single-layer film formed by depositing various optical substances on a glass substrate by an ion assisted vacuum deposition method. The vertical axis represents the magnitude of the internal stress of the single-layer deposited film, with the 0 level as a reference, the upper side represents the compressive internal stress and the lower side represents the tensile internal stress. The compressive internal stress acts in such a direction as to apply compressive strain to the bonding surface of the glass substrate, and the tensile stress acts in the opposite direction to apply tensile strain to the bonding surface of the glass substrate. The horizontal axis represents the ion current density of assist ions used in the ion assisted vacuum deposition method. The ion-assisted vacuum deposition method is for densifying a deposition film by irradiating the deposition surface with ions that are heating energy particles during vacuum deposition. Therefore, the higher the ion current density, the more the densification progresses. By using such an ion-assisted vacuum deposition method, it is possible to form an optical film including a refraction layer having a dense composition that is non-adsorptive to moisture.
When an optical oxide is used as the material of the refraction layer, oxygen ions are preferable as the accelerated ion particles. As shown in FIG. 6, when the ion current density is 0, that is, when the normal vacuum deposition method is performed, the high refractive index material TiO ₂ exhibits tensile internal stress and the low refractive index material SiO ₂ Exhibit a compressive internal stress having approximately the same magnitude. Therefore, in the past, Ti
An optical filter element was manufactured by laminating O ₂ and SiO ₂ on a glass substrate using a normal vacuum vapor deposition method. The tensile internal stress of TiO ₂ and the compressive internal stress of SiO ₂ do not cancel each other out, and the stress is not substantially applied to the glass substrate to the extent that it does not cause a problematic deformation. However, when the usual vacuum vapor deposition method is used, the vapor deposition deposition layer is not densified and is porous. Therefore, there is a problem with respect to moisture resistance because of its adsorptivity to moisture. On the other hand, in the present invention, the deposition layer is densified by using, for example, the ion assisted vacuum deposition method. As shown in FIG. 6, as the densification progresses, the refraction layers composed of various optical materials all exhibit compressive internal stress. Therefore, it has been extremely difficult to deposit a refractive layer having a strong compressive internal stress on the glass substrate as in the conventional case. This is because the compressive internal stress causes damage or deformation of the glass substrate. Therefore, in the present invention, the optical filter element is manufactured as a single type multilayer film separated from the substrate. In particular, by controlling the ion current density under conditions such that the compressive internal stress of the high-refractive layer and the compressive internal force of the low-refractive layer become substantially equal, and forming each layer film by using the ion assisted vacuum deposition method, Distortion can be eliminated, and a single-piece optical filter multilayer film that is dimensionally stable can be obtained. For example, when Ta ₂ O ₅ is used as the high-refractive index material and SiO ₂ is used as the low-refractive index material, it is clear from FIG. It is possible to produce a single-type optical filter multilayer film that is equally and substantially free of distortion.

〔The invention's effect〕

As described above, according to the present invention, by separating the densified optical filter multilayer film from the glass substrate, the compressive internal stress of the multilayer film with respect to the glass substrate, which has been a problem in the past, is released, and deformation such as warpage occurs. There is an effect that it is possible to obtain an ultra-thin optical filter element having good weather resistance and moisture resistance. Further, according to the present invention, there is an effect that the manufacturing yield can be remarkably improved without the conventional glass substrate being damaged during polishing due to the compressive internal stress of the multilayer film or being deformed due to the compressive internal stress. Further, since the separation groove is formed in the optical filter multilayer film by the non-contact processing, there is an effect that the division or separation of the element can be easily performed with high dimensional accuracy.

[Brief description of drawings]

FIG. 1 is a process diagram showing a first embodiment of the optical filter element manufacturing method, FIG. 2 is a schematic diagram of a laser processing apparatus used in the first embodiment of the optical filter element manufacturing method, and FIG. FIG. 4 is a perspective view showing an example of an optical filter element, FIG. 5 is a perspective view showing another example of the optical filter element, and FIG. 6 is a deposited film. 5 is a graph showing the relationship between internal stress and ion current density. 1 ... Soluble carrier 2 ... Optical filter multilayer film 3 ... Optical filter element, 4 ... Temporary substrate 5 ... Photoresist film, 6 ... Photomask 7 ... Element section

Claims (4)

[Claims] 1. A preparatory step of preparing a carrier that is soluble in a predetermined solvent, and an optical material having a high refractive index and an optical material having a low refractive index are alternated by using acceleration energy with respect to the surface of the soluble carrier. A film forming step of forming a dense optical filter thin film that is non-adsorptive to moisture and the like by depositing and stacking on a film, and a plurality of films separated from each other by a non-contact processing process on the formed optical fill thin film. The non-contact division step comprises a non-contact division step of forming the element section and a peeling step of dissolving the soluble carrier in a solvent to peel the optical filter thin film to obtain an optical filter thin film piece for each element section. A method for manufacturing a single-type optical filter thin film element, which is a step of forming a separation groove by irradiating the element along a boundary between element sections. 2. A preparatory step of preparing a carrier that is soluble in a predetermined solvent, and an optical material having a high refractive index and an optical material having a low refractive index are alternated by using acceleration energy on the surface of the soluble carrier. A film forming step of forming a dense optical filter thin film that is non-adsorptive to moisture and the like by depositing and stacking on a film, and a plurality of films separated from each other by a non-contact processing process on the formed optical filter thin film. It comprises a non-contact partitioning step of forming element compartments, and a peeling step of dissolving the soluble carrier in a solvent to peel off the optical filter thin film to obtain an optical filter thin film piece for each element compartment. The step of applying a photoresist film to the optical filter thin film, the step of patterning the photoresist film according to the element section by non-contact exposure, and the step of applying the patterned photoresist film Of a single type optical filter thin film element, which comprises a step of etching the optical filter thin film to form a separation groove. 3. The method according to claim 1, wherein the preparing step is a step of preparing a flat plate carrier made of a soluble substance. 4. The manufacturing method according to claim 1, wherein the preparing step is a step of forming a film carrier made of a soluble substance on the surface of a temporary substrate made of an insoluble substance.