KR20210152773A - Optical filter and manufacturing method of the optical filter - Google Patents

Abstract

The present invention relates to an optical filter and a manufacturing method thereof. According to an embodiment of the present invention, provided is a method of manufacturing the optical filter, which includes the steps of: forming a protective layer on one surface of a wafer; cutting the wafer using a laser to process the wafer into an optical filter; and cleaning the wafer. The wafer may include a substrate and the filter layer formed on both surfaces of the substrate. The protective layer may be formed to have a thickness equal to or greater than or equal to a depth of an upper portion of the heat-affected region due to heat of the laser. The upper portion of the heat-affected region may have a wide width on the surface of the wafer, and may become narrower toward a lower portion. Also, the lower portion of the heat-affected region may have a narrower width than the upper portion. The laser may be irradiated toward the protective layer. Therefore, it is possible to manufacture the optical filter in which the heat-affected region by the laser is minimized by using the protective layer.

Description

Optical filter and optical filter manufacturing method

The present invention relates to an optical filter and a method for manufacturing an optical filter.

An optical filter is an optical device that transmits or blocks light of a required wavelength band. For example, applications that require the frequency or color of a selected area, such as a camera module, need to limit the wavelength range of light. For this, an optical filter that selectively reflects, refractions, diffraction, or absorbs light of an unwanted wavelength and transmits light of the remaining wavelength may be used.

On the other hand, as one of the key components in VR (Virtual Reality), AR (Augmented Reality), autonomous vehicles, drones, face recognition, iris recognition, gesture recognition, etc., an optical filter for controlling the wavelength of the infrared region is attracting attention. In applying functions such as face recognition, iris recognition, and gesture recognition to smart devices, it is required to develop an optical filter having a low thickness while having high transmission performance for a specific infrared region and high blocking performance for the remaining regions. have.

In general, an optical filter is formed through a laser cutting process after a substrate and a filter layer are manufactured in a wafer state.

At this time, when the wafer is cut with a laser, a heat affected zone (HAZ) is generated on the wafer by the heat of the laser. In the heat-affected area due to the heat of the laser, the structure or mechanical properties of the material constituting the optical filter are changed, causing problems such as deterioration of toughness and ductility, and cracks.

SUMMARY OF THE INVENTION An object of the present invention is to provide an optical filter and a method for manufacturing an optical filter in which a heat-affected region by a laser is minimized.

In addition, an object of the present invention is to provide an optical filter and a method for manufacturing an optical filter having improved durability and reliability by minimizing a heat-affected region.

According to an embodiment of the present invention, forming a protective layer on one surface of a wafer, cutting the wafer using a laser to process the wafer into an optical filter, and cleaning the wafer. A method of manufacturing a filter is provided.

The wafer may include a substrate and filter layers formed on both surfaces of the substrate.

The passivation layer may be formed to have a thickness that is at least equal to or greater than a depth of an upper portion of a heat-affected region due to the heat of the laser.

An upper portion of the heat-affected region may have a wide width on the surface of the wafer, and may become narrower toward a lower portion. In addition, the lower portion of the heat affected region may have a narrower width than the upper portion.

The laser may be irradiated toward the protective layer.

According to another embodiment of the present invention, there is provided an optical filter including a substrate and a filter layer formed on the substrate and composed of at least one layer.

A heat affected region may be formed on at least one of at least one side of the substrate and at least one side of the filter layer. In this case, the width of the heat-affected region may be less than 10 μm.

The method of manufacturing an optical filter according to an embodiment of the present invention may use a protective layer to manufacture an optical filter in which a heat-affected region by a laser is minimized.

Accordingly, durability and reliability of the optical filter manufacturing method and the optical filter according to the embodiment of the present invention can be improved by minimizing the heat-affected region.

1 is a flowchart schematically illustrating a method of manufacturing an optical filter according to an embodiment of the present invention.
2 to 10 are exemplary views for explaining a method of manufacturing an optical filter according to an embodiment of the present invention.
11 is an exemplary view illustrating a heat-affected region generated when a wafer is laser processed without a protective layer according to a conventional manufacturing method.
12 is an exemplary view illustrating a heat-affected region generated when a wafer is laser processed after forming a protective layer according to a manufacturing method according to an embodiment of the present invention.

Hereinafter, embodiments of the present invention will be described in detail with reference to the accompanying drawings. The embodiments introduced below are provided as examples so that the spirit of the present invention can be sufficiently conveyed to those skilled in the art. Accordingly, the present invention is not limited to the embodiments described below and may be embodied in other forms. And in the drawings, the width, length, thickness, etc. of the components may be exaggerated for convenience. Throughout the specification, like reference numbers indicate like elements and like reference numbers indicate corresponding like elements.

The method of manufacturing an optical filter according to an embodiment of the present invention includes forming a protective layer on one surface of a wafer, cutting the wafer using a laser to process the wafer into an optical filter, and cleaning the wafer includes

The wafer may include a substrate and filter layers formed on both surfaces of the substrate.

The passivation layer may be formed to have a thickness that is at least equal to or greater than a depth of an upper portion of a heat-affected region due to the heat of the laser.

An upper portion of the heat-affected region may have a wide width on the surface of the wafer, and may become narrower in a lower direction, and a lower portion of the heat-affected region may have a narrower width than the upper portion.

In addition, the laser may be irradiated toward the protective layer.

The protective layer may have a thickness of at least 10 μm.

The protective layer may be made of a water-soluble material.

In the step of forming the passivation layer, the passivation layer may be formed by applying an aqueous solution on the wafer by spin coating.

In the step of cutting the wafer, the laser may be a picosecond laser or a femtosecond laser.

In the step of cleaning the wafer, the protective layer may be removed.

In this case, in the step of cleaning the wafer, the wafer may be cleaned with deionized water.

The substrate may be made of a material that transmits light in a specific wavelength band. In addition, the filter layer may be made of a material that transmits light in the specific wavelength band and reflects or absorbs light in a wavelength band different from the specific wavelength band.

For example, the optical filter may be an infrared cut filter.

Accordingly, the substrate may transmit light in a visible wavelength band. In addition, the filter layer may reflect or absorb light in an infrared wavelength band and transmit light in a visible light wavelength band.

A width of the heat affected region of the optical filter may be 10 μm or less.

The optical filter according to an embodiment of the present invention may include a substrate and a filter layer formed on the substrate and composed of at least one layer.

In this case, a heat affected region may be formed on at least one of at least one side of the substrate and at least one side of the filter layer.

The width of the heat affected region may be 10 μm or less.

The substrate may be made of a material that transmits light in a specific wavelength band. In addition, the filter layer may be made of a material that transmits light in the specific wavelength band and reflects or absorbs light in a wavelength band different from the specific wavelength band.

For example, the substrate and the filter layer may form an infrared cut-off filter.

Accordingly, the substrate may transmit light in a visible wavelength band. In addition, the filter layer may reflect or absorb light in an infrared wavelength band and transmit light in a visible light wavelength band.

Hereinafter, the light treatment device of the present invention will be described in detail with reference to the drawings.

1 is a flowchart schematically illustrating a method of manufacturing an optical filter according to an embodiment of the present invention.

2 to 10 are exemplary views for explaining a method of manufacturing an optical filter according to an embodiment of the present invention.

Referring to step S110 of FIG. 1 , first, a wafer is prepared.

The wafer 10 is in a state before the plurality of optical filters 100 are individually separated as shown in FIG. 2 . For example, the optical filter 100 may be an ultraviolet blocking filter.

FIG. 3 is an exemplary view schematically illustrating cross-sections A1-A2 of the wafer 10 of FIG. 2 . Referring to FIG. 3 , the wafer 10 includes a substrate 110 and a filter layer 120 formed on both surfaces of the substrate 110 .

The substrate 110 may be made of a material that transmits light in a specific wavelength band.

For example, the substrate 110 may be made of a material that absorbs light in an infrared wavelength band and transmits light in a visible light wavelength band.

The substrate 110 may be glass or a film.

The substrate 110 may be made of an inorganic material such as quartz or glass. In addition, the substrate 110 may include polyester resin, polyolefin resin, norbornene resin, acrylic resin, urethane resin, vinyl chloride resin, fluorine resin, polycarbonate resin, polyvinyl butyral resin, polyvinyl alcohol resin, etc. It may be made of an organic material. However, the material of the substrate 110 is not limited thereto, and is not particularly limited as long as it blocks infrared rays and transmits visible light.

The filter layer 120 may reflect or absorb light in a specific wavelength band. Accordingly, the filter layer 120 may block light of a specific wavelength band from being transmitted.

For example, the filter layer 120 may reflect or absorb light in an infrared wavelength band and transmit light in a visible light wavelength band.

The filter layer 120 may be formed by stacking at least two layers made of materials having different refractive indices. For example, each layer constituting the filter layer 120 may be made of a material including at least one of SiOx, TiOx, NbOx, TaOx, and AlOx.

The filter layers 120 formed on both surfaces of the substrate 110 may have the same configuration as each other. Alternatively, the filter layers 120 formed on both surfaces of the substrate 110 may be formed in different configurations.

The filter layer 120 may be formed by being deposited on the substrate 110 by a PVD (Physical Vapor Deposition) method or a sputtering method. However, the method in which the filter layer 120 is formed is not limited thereto. For example, the filter layer 120 may be formed on the substrate 110 by being deposited on the temporary member and then attached to the substrate 110 and removing the temporary member.

The wafer 10 shown in FIG. 2 has a rectangular cross section. However, the shape of the wafer 10 is not limited thereto. The wafer 10 may have a circular cross-section as shown in FIG. 5 . In addition, the wafer 10 may have various shapes as well as a rectangular or circular cross-section.

Referring to step S120 of FIG. 1 , a protective layer is formed on the wafer.

The protective layer 130 may be formed to cover one surface of both surfaces of the wafer 10 in the direction in which the laser is irradiated in the wafer 10 cutting process. Referring to FIG. 4 , the protective layer 130 may be formed to cover the upper surface of the wafer 10 .

For example, the protective layer 130 may be formed by a spin coating method.

5 and 6 show examples of forming the protective layer 130 by a spin coating method.

Referring to FIG. 5 , the wafer 10 is mounted on the rotating body 21 of the spin coater 20 .

Thereafter, the aqueous solution 131 is dropped on the upper surface of the wafer 10 . The aqueous solution 131 is a material forming the protective layer 130 .

Referring to FIG. 6 , the rotating body 21 is rotated at high speed while the aqueous solution 131 is dropped on the upper surface of the wafer 10 .

When the wafer 10 rotates at a high speed along the rotating body 21 , the aqueous solution 131 is diffused over the entire upper surface of the wafer 10 by centrifugal force.

The aqueous solution 131 may be coated on the wafer 10 by spin coating, and may be anything that can be removed with DI water in a cleaning process.

For example, the aqueous solution may include at least one of ether and alcohol in ultrapure distilled water.

As described above, the protective layer 130 may be formed by applying the aqueous solution 131 to the entire upper surface of the wafer 10 by a spin coating method.

Although the wafer 10 has a circular cross-section in FIG. 5 , the protective layer 130 may be formed on the wafer of FIG. 2 with a rectangular cross-section or other types of wafers by spin coating.

Thereafter, a process of cutting the wafer 10 is performed.

When the wafer 10 is cut using a laser, a heat-affected region by the heat of the laser is generated on the wafer 10 .

Referring to FIG. 7 , when the laser 40 is irradiated to the base material 30 , the base material 30 is melted and removed by the heat of the laser 40 . At this time, a heat affected zone (HAZ) 35 is generated around the molten portion.

The heat-affected region 35 may be a portion that is not melted although the structure or mechanical properties of the base material 30 are changed by the heat of the laser 40 . Alternatively, the heat affected region 35 may be a re-solidified portion after melting by the laser 40 . In the heat-affected region 35 , toughness or ductility is reduced, and cracks may occur.

As shown in FIG. 7 , the heat-affected region 35 is formed wider from the cut surface 31 near the surface of the base material 30 , and is formed to be relatively narrow compared to the surface in the lower direction as shown in FIG. 7 . Also, the further down the downward direction, the more nearly constant with the small width of the heat affected region 35 . For better explanation and understanding, a portion formed to have a wide width W near the surface of the base material 30 among the heat-affected region 35 is referred to as the upper portion 36 of the heat-affected region. In addition, a portion located below the upper portion 36 of the heat-affected region and having a narrower width than the upper portion 36 is referred to as a lower portion 37 of the heat-affected region. The lower portion 37 of the heat affected region 35 may be a portion formed to have a substantially constant width as shown in FIG. 7 .

According to an embodiment of the present invention, the protective layer 130 is formed to minimize the heat-affected region 35 generated when the wafer 10 is cut using a laser.

The protective layer 130 may be formed to have a thickness equal to or greater than the depth H of the upper portion of the heat-affected region 35 . For example, the upper portion of the heat affected region 35 may have a width of about 30 μm and a depth of about 10 μm.

Accordingly, the protective layer 130 may be formed to have a thickness of 10 μm or more.

Alternatively, the thickness of the protective layer 130 may be set based on an arbitrary width of the heat affected region 35 . That is, the protective layer 130 may be formed to have a thickness greater than the maximum depth of the heat affected region 35 having a width greater than a reference value.

For example, the width of the heat affected region 35 serving as a reference value may be 10 μm.

Accordingly, the passivation layer 130 may be formed to have a thickness greater than the maximum depth of a portion having a width exceeding 10 μm in the heat affected region 35 .

The thickness of the protective layer 130 has been described with reference to two examples. However, the standard of the thickness of the protective layer is not limited to two examples. The thickness of the protective layer 130 may be formed to be thicker than the depth of the upper portion of the heat affected region 35 .

Referring to step S130 of FIG. 1 , a plurality of optical filters is formed by cutting the wafer.

According to this embodiment, the wafer 10 may be cut with a laser.

The laser may cut the wafer 10 in various shapes. That is, by using a laser, the optical filter can be easily implemented in various forms than when the cutting process is performed using a blade.

Referring to FIG. 8 , the wafer 10 may be mounted on the stage 61 of the cutting equipment using the temporary tape 50 . Accordingly, the protective layer 130 is formed on the upper surface of the wafer 10 , and the temporary tape 50 may be attached to the lower surface of the wafer 10 .

After the wafer 10 is mounted on the stage 61 , a cutting process of the wafer 10 is performed by irradiating a laser to the wafer 10 . The laser may be irradiated toward the protective layer 130 of the wafer 10 .

For example, the laser may be a picosecond laser or a femtosecond laser.

By laser processing, the protective layer 130 and the wafer 10 may be cut to be divided into a plurality of regions.

As described above, each part of the wafer 10 cut into a plurality by the laser cutting process becomes the optical filter 100 .

Referring to FIG. 9 , during the laser cutting process, a heat-affected region 35 is generated around the protective layer 130 and a portion of the wafer 10 cut by the laser.

The protective layer 130 is formed to have a thickness equal to or greater than the depth of the upper portion 36 having a larger width among the heat affected regions 35 . Therefore, the upper portion 36 of the heat-affected region 35, which is mainly a problem in the laser cutting process, may be formed in the protective layer 130 . Accordingly, the heat-affected region 35 generated on the wafer 10 by the protective layer 130 can be minimized.

Referring to step S140 of FIG. 1 , the wafer on which the cutting process has been performed is cleaned.

The cleaning of the wafer 10 is performed using deionized water (DI water).

Since the protective layer 130 is formed of the aqueous solution 131, it is dissolved in ultrapure distilled water. Therefore, as shown in FIG. 10 , when the wafer 10 is washed with DI water, the protective layer 130 is also removed. When the protective layer 130 is removed, the upper portion 36 of the large-width heat affected region 35 formed in the protective layer 130 is also removed.

Accordingly, only the minimal heat affected region 35 remains in the cleaned wafer 10 .

The temporary tape 50 attached to the lower surface of the wafer 10 may be removed before or after the wafer 10 is cleaned. When the temporary tape 50 is removed, each region of the cut wafer 10 may be completely separated to form a plurality of optical filters 100 .

As described above, in the optical filter 100 manufactured according to the embodiment of the present invention, the heat affected region 35 may be formed on at least one of one side of the substrate 110 and one side of the filter layer 120 . Referring to FIG. 10 , the heat-affected region 35 is formed on one side of the substrate 110 and one side of the filter layer 120 corresponding to the laser cut surface. At this time, the width of the heat affected region 35 is 10 μm or less.

11 shows a heat-affected region 35 generated when the wafer 10 is laser processed without the protective layer 130 according to a conventional manufacturing method. 12 shows a heat-affected region 35 generated when the wafer 10 is laser processed after the protective layer 130 is formed according to the manufacturing method according to an embodiment of the present invention.

Referring to FIG. 11 , when the wafer 10 is cut with a laser without a protective layer, the width of the heat affected region 35 generated on the wafer 10 is about 22.318 μm to 23.462 μm. In addition, it can be seen that cracks having a width of 17.740 μm and a length of 30.329 μm occurred around the cut surface. In addition, it can be confirmed that many cracks have occurred around the cut surface.

Referring to FIG. 12 , when the wafer 10 is cut with a laser after forming the protective layer according to an embodiment of the present invention, the width of the heat affected region 35 generated on the wafer 10 is about 5.150 μm to about 5.150 μm It appears as 8.010 μm. That is, in the case of the method of manufacturing an optical filter according to an embodiment of the present invention, the width of the heat affected region 35 generated in the optical filter is 10 μm or less. In addition, as compared with FIG. 11 , it can be seen that the occurrence of cracks is significantly reduced.

As such, the method of manufacturing an optical filter according to an embodiment of the present invention may reduce a heat-affected region generated in the optical filter.

Accordingly, the method for manufacturing an optical filter according to an embodiment of the present invention can prevent a defect in the optical filter due to a heat-affected region, and improve durability and reliability of the optical filter.

Although the optical filter manufacturing method has been described using the UV cut filter as an example in this embodiment, the optical filter is not limited to the UV cut filter. The method of manufacturing the optical filter according to the present embodiment may be applied to other types of optical filters as well as the UV blocking filter.

In addition, the method of manufacturing the optical filter according to the present embodiment may further include a step of inspecting for defects in the optical filter after the protective layer is removed.

As described above, the detailed description of the present invention has been made by the embodiments with reference to the accompanying drawings, but since the above-described embodiments have only been described with preferred examples of the present invention, the present invention is not limited only to the above embodiments. It should not be understood, and the scope of the present invention should be understood as the following claims and their equivalents.

10: wafer
20: spin coater
21: rotating body
30: base material
31: cut plane
35: heat affected zone
36: top of heat affected zone
37: lower part of the heat affected zone
40: laser
50: temporary tape
61: stage
100: optical filter
110: substrate
120: filter layer
130: protective layer
131: aqueous solution

Claims (15)

forming a protective layer on one surface of the wafer;
cutting the wafer using a laser to process the wafer into an optical filter; and
Including; cleaning the wafer;
The wafer includes a substrate and filter layers formed on both surfaces of the substrate,
The protective layer is formed to have a thickness equal to or greater than or equal to the depth of the upper portion of the heat-affected region by the heat of the laser,
The upper portion of the heat-affected region has a wider width on the surface of the wafer, and the width becomes narrower in the lower direction, and the lower portion of the heat-affected region has a narrower width than the upper portion,
The method of manufacturing an optical filter in which the laser is irradiated toward the protective layer.
The method according to claim 1,
The thickness of the protective layer is at least 10 ㎛ optical filter manufacturing method.
The method according to claim 1,
The protective layer is an optical filter manufacturing method made of a water-soluble material.
4. The method according to claim 3,
In the step of forming the protective layer,
The protective layer is an optical filter manufacturing method formed by applying an aqueous solution on the wafer in a spin coating method.
The method according to claim 1,
In the step of cutting the wafer,
The laser is a picosecond laser or a femtosecond laser optical filter manufacturing method.
The method according to claim 1,
In the step of cleaning the wafer, the optical filter manufacturing method in which the protective layer is removed.
7. The method of claim 6,
In the step of cleaning the wafer
The method of manufacturing an optical filter in which the wafer is cleaned with deionized water.
The method according to claim 1,
The substrate is made of a material that transmits light in a specific wavelength band,
The filter layer transmits light in the specific wavelength band and is made of a material that reflects or absorbs light in a wavelength band different from the specific wavelength band.
9. The method of claim 8,
The optical filter is an infrared cut filter.
10. The method of claim 9,
The substrate transmits light in the visible wavelength band,
The filter layer reflects or absorbs light in an infrared wavelength band and transmits light in a visible light wavelength band.
The method according to claim 1,
The width of the heat-affected region of the optical filter is 10 μm or less.
Board; and
a filter layer formed on the substrate and comprising at least one layer;
A heat affected region is formed on at least one of at least one side of the substrate and at least one side of the filter layer,
An optical filter wherein the width of the heat affected region is 10 μm or less.
13. The method of claim 12,
The substrate is made of a material that transmits light in a specific wavelength band,
The filter layer transmits light in the specific wavelength band, and an optical filter made of a material that reflects or absorbs light in a wavelength band different from the specific wavelength band.
14. The method of claim 13,
An optical filter in which the substrate and the filter layer form an infrared cut-off filter.
15. The method of claim 14,
The substrate transmits light in the visible wavelength band,
The filter layer is an optical filter that reflects or absorbs light in an infrared wavelength band and transmits light in a visible light wavelength band.

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