Optical filter, sensor system comprising same, and preparation method of halogenated amorphous silicon film for optical filter

Abstract

The invention provides an optical filter and a sensor system including the same. The optical filter has a high refractive index and shows a low extinction coefficient in a narrow band of about 800 nm to 1100 nm.

Description

[0001] This application is a divisional application based on the Chinese patent application with application number 202080053757.0 (international application number PCT / KR2020 / 009630), application date July 22, 2020, and invention name "Optical filter and sensor system including the same, and method for preparing halogenated amorphous silicon film for optical filter". Technical Field

[0002] The invention relates to an optical filter and a sensor system comprising the same, and a method for preparing a halogenated amorphous silicon film for the optical filter. Background Art

[0003] Gesture recognition and facial recognition, which are commonly used in smartphones, game consoles, and car interiors, shine light from a lighting device using LD or LED as a light source toward a subject and use information about the subject contained in the light reflected from the subject.

[0004] In this way, the reflected light is converted into an electrical signal by the sensor, and the 3D information of the subject is obtained after analysis and processing. Among them, the light reflected from the light source is reflected by the subject and detected by the sensor, and the amount of light decreases inversely proportional to the square of the distance from the light source to the subject and from the subject to the sensor. In addition, due to the low reflectivity of the subject to the light source, the light reaching the sensor has a very low light intensity compared to the amount of light emitted from the light source. In addition, the ambient light distributed around the sensor system makes the sensor system have high noise characteristics. Therefore, a filter is needed that only transmits narrowband wavelengths in the range of about 800nm ​​to 1100nm according to the type and characteristics of the light source. Among them, the filter must have high transmission characteristics in the narrow band used, and can block other frequency bands through reflection or absorption processes.

[0005] Existing optical filters use TiO2, Nb2O5, Ta2O5, Si3N4, etc. as high-refractive optical deposition materials on a base material such as glass with high transmittance in the region of about 800nm ​​to 1100nm, and use SiO2, MgF2, Al2O3, etc. as low-refractive optical deposition materials. There is also a method of alternately depositing high-refractive optical materials and low-refractive optical materials with a mixture of high-refractive optical deposition materials to prepare a filter that transmits or reflects light within the required frequency band. Recently, attempts are being made to use hydrogenated silicon to obtain a high refractive index.

[0006] Since the incident angle of light reflected from the subject and incident on the sensor is distributed in a wide angle range from 0 to 180 degrees, it is necessary to prepare a filter that allows high AOI (Angle of Incidence) in order to configure a high-performance sensor system. However, in the existing filters using high-refractive materials and low-refractive materials, it is difficult to maintain the optical characteristics obtained at vertical incidence because the refractive index changes according to polarized light in AOIs above ±15 degrees. Therefore, in order to prepare a filter with high optical characteristics at a wide angle of AOI above 15 degrees, a deposition material with a high refractive index and a low extinction coefficient is required.

[0007] In the past few decades, there have been many studies on silicon, especially in the field of large-area flat panel displays such as LCDs and solar cells. The band gap of solid silicon, one of hydrogenated amorphous silicon, is about 1.12eV (@300K), and its absorption edge is located at about 1100nm. Since it absorbs light in the near-infrared region of about 800nm ​​to 1100nm, it is difficult to use it in filters that require high transmittance. The band gap of hydrogenated amorphous silicon (a-Si:H) moves the absorption edge to about 1.75eV-2.0eV depending on the amount of hydrogen atoms in amorphous silicon and the state of silicon crystals. It can obtain the characteristics of optically low absorption coefficient in the near-infrared region above about 700nm, and it has recently been tried to be used in filters.

[0008] At this time, in order to minimize the absorption of light (extinction coefficient is below about 0.001), a hydrogen concentration of about 20% or more is injected into the amorphous silicon to adjust the localized states and band tail of the amorphous silicon. In addition to the expected hydrogenated amorphous silicon (a-Si:H), this also produces Si:H2, (Si:H2)n, voids and chain or network Si:H2+(Si:H2)n compounds, resulting in a lower refractive index, so it is necessary to lower it.

[0009] In addition, the molecular weight of hydrogen atoms in hydrogenated amorphous silicon is small and the size of atoms is very small, so it is easy to obtain them through the diffusion process in the PVD or CVD process. However, since the diffusion coefficient easily changes with temperature, it is difficult to accurately control the amount of hydrogen. During the process or after the process is completed, the movement of hydrogen in the silicon is accompanied by changes in physical properties as the temperature rises.

[0010] Especially in optical filters, the characteristics of each layer of designed optical film are determined by the optical thickness nd (n: optical refractive index, d: physical thickness). Therefore, even if the physical thickness d is constant, when the optical refractive index n changes, the characteristics of the filter will also change, and problems may occur in the sensor system including the filter. Summary of the invention

[0011] Problems to be solved by the invention

[0012] An object of one embodiment of the present invention is to provide an optical filter and a sensor system including the same, wherein the optical filter has a high refractive index and exhibits a characteristic of a low extinction coefficient in a narrow band of about 800 nm to 1100 nm.

[0013] In addition, an object of an embodiment of the present invention is to provide an optical filter that can accommodate a wide range of incident angles and a sensor system including the same.

[0014] In addition to the above-mentioned problems, the implementation examples according to the present invention can be used to solve other problems not specifically mentioned.

[0015] Solutions for solving problems

[0016] An embodiment of the present invention provides an optical filter, characterized by comprising: a first mirror layer, which is formed by alternately laminating a first high-refractive material layer and a first low-refractive material layer; a spacer layer, which is continuously laminated on one side of the first mirror layer and includes a plurality of second high-refractive material layers; and a second mirror layer, which is formed by alternately laminating a third high-refractive material layer and a third low-refractive material layer with the spacer layer placed in the middle and arranged opposite to the first mirror layer.

[0017] At least one of the first high-refractive material layer, the first low-refractive material layer, the second high-refractive material layer, the third high-refractive material layer, and the third low-refractive material layer may include halogenated amorphous silicon.

[0018] In the wavelength range of about 800 nm to 1100 nm, at least one of the first high-refractive material layer, the second high-refractive material layer, and the third high-refractive material layer has a refractive index of about 3.0 or more and an extinction coefficient of 0.001 or less.

[0019] A ratio of (optical thickness of the first high refractive substance layer / optical thickness of the first low refractive substance layer) or (optical thickness of the third high refractive substance layer / optical thickness of the third low refractive substance layer) may be about 1.5 to 3.0.

[0020] The halogenated amorphous silicon may contain F or Cl.

[0021] The filter may have a transmission band in the wavelength range of about 800 nm to 1100 nm, and a maximum shift of the central wavelength of 950 nm by less than about 25 nm according to a change in the incident angle from 0 degrees to 45 degrees.

[0022] The filter may have a transmission band in the wavelength range of about 800 nm to 1100 nm, and a maximum shift of a central wavelength of 950 nm is less than about 38 nm according to a change in an incident angle of 0 degrees to 60 degrees.

[0023] The first high-refractive material layer, the second high-refractive material layer and the third high-refractive material layer have the same refractive index, and the first low-refractive material layer and the third low-refractive material layer may have the same refractive index.

[0024] At least one of the first high-refractive material layer, the first low-refractive material layer, the second high-refractive material layer, the third high-refractive material layer, and the third low-refractive material layer may include halogenated amorphous silicon.

[0025] Halogenated amorphous silicon is prepared using a PVD method including the steps of injecting an inert gas, a halogen gas and a carrier gas into a chamber, and the ratio of the halogen gas volume / (halogen gas volume+carrier gas volume) injected into the chamber at the same time can be approximately greater than 0 and less than 0.375.

[0026] The first low-refractive material layer and the third low-refractive material layer may include any one or more of TiO2, Nb2O5, Ta2O5, Si3N4, SiO2, MgF2, Al2O3, halogenated amorphous silicon compounds or mixtures thereof.

[0027] One embodiment of the present invention provides a method for preparing a halogenated amorphous silicon film for a filter. The method is prepared using a PVD method including the steps of injecting an inert gas, a halogen gas and a carrier gas into a chamber. The ratio of the volume of the halogen gas injected into the chamber at the same time to (the volume of the halogen gas + the volume of the carrier gas) can be approximately greater than 0 and less than 0.375.

[0028] An embodiment of the present invention provides a sensor system, which includes: an optical filter according to an embodiment of the present invention; a light source, which emits light in a wavelength range of approximately 800nm ​​to 1100nm to generate reflected light that can reach the optical filter; and a sensor, which is arranged on a path through which the reflected light passes through the optical filter and is used to receive 3D information about a subject contained in the reflected light.

[0029] Effects of the Invention

[0030] The optical filter and the sensor system including the same according to an embodiment of the present invention have a high refractive index and can show a characteristic of a low extinction coefficient in a narrow band of about 800 nm to 1100 nm.

[0031] According to the method for preparing a halogenated amorphous silicon thin film for an optical filter according to an embodiment of the present invention, an optical filter having a high refractive index and a low extinction coefficient in a narrow band of about 800nm ​​to 1100nm can be prepared.

[0032] In addition, the optical filter and the sensor system including the same according to an embodiment of the present invention can accommodate a wide range of incident angles. BRIEF DESCRIPTION OF THE DRAWINGS

[0033] Figure 1 is a cross-sectional view showing a laminated structure of an optical filter according to an embodiment of the present invention.

[0034] Figure 2 is a diagram showing a basic configuration of a sensor system according to an embodiment of the present invention.

[0035] Figure 3 This is a diagram showing the data in Table 8 in this specification in a graphical form.

[0036] Figure 4 This is a diagram showing the data in Table 9 in this specification in a graphical form. DETAILED DESCRIPTION

[0037] The terms used herein are for describing specific embodiments only and are not intended to be limiting of the present invention. Unless otherwise clearly indicated in the context, singular forms used herein also include plural forms.

[0038] The term “comprising” as used in this specification means to specify specific features, regions, integers, steps, operations, elements and / or components, but does not exclude the existence or addition of other specific features, regions, integers, steps, operations, elements, components and / or groups.

[0039] In the figures of this specification, the thickness is magnified to clearly indicate multiple layers and regions. When referring to a part of a layer, film, region, plate, etc. being "above" another part, it includes not only the case where the other part is "directly above" but also the case where there is another part in between. However, when referring to a part being "directly above" another part, it means that there is no other part in between. On the contrary, when referring to a part of a layer, film, region, plate, etc. being "below" another part, it includes not only the case where the other part is "directly below" but also the case where there is another part in between. However, when referring to a part being "directly below" another part, it means that there is no other part in between.

[0040] Although not otherwise defined, all terms used herein, including technical and scientific terms, have the same meaning as those commonly understood by those skilled in the art to which the present invention belongs. Terms defined in common dictionaries have meanings consistent with relevant technical documents and currently disclosed contents, and unless otherwise defined, should not be understood as idealized or very formulaic meanings.

[0041] The design formula of the optical filter in this specification can be expressed as follows.

[0042]

Design formula

[0043] Glass / (HL)^n 2mH(LH)^n / Air, or Glass / (LH)^n 2mL(HL)^n / Air

[0044] (H is a high-refractive material layer, L is a low-refractive material layer, n represents the number of times the high-refractive material layer and the low-refractive material layer are laminated repeatedly, and m is an integer greater than or equal to 1)

[0045] In addition, the optical thickness of the high-refractive material layer or the low-refractive material layer in this specification can be expressed by the following mathematical formula 1.

[0046]

Mathematical formula 1

[0047] nd=(1 / 4)λ0

[0048] (n is the refractive index, d is the physical thickness, and λ0 is the central wavelength of light passing through the filter)

[0049] The optical thickness of the spacer layer in this specification can be expressed by the following mathematical formula 2.

[0050]

Mathematical formula 2

[0051] nd=(1 / 2)mλ0

[0052] (n is the refractive index, d is the physical thickness, m refers to the m in the above design formula, and λ0 is the central wavelength of the light passing through the filter)

[0053] The meanings of "high refractive index" and "low refractive index" in this specification should be understood as the concept of relative refractive index between optical materials located in each layer in order to control the transmission and reflection characteristics of light, which is commonly understood by technicians in the field of filters with a general structure composed of multiple optical material layers.

[0054] Figure 1 is a cross-sectional view showing a laminated structure of an optical filter 1020 according to an embodiment of the present invention.

[0055] Figure 2 is a diagram showing a basic configuration of a sensor system 1000 according to an embodiment of the present invention.

[0056] refer to Figure 1 and Figure 2 An embodiment of the present invention provides an optical filter 1020, comprising: a first mirror layer 100, which is formed by alternately laminating first high-refractive material layers 110 and first low-refractive material layers 120; a spacer layer 200, which is continuously laminated on one side of the first mirror layer 100 and includes a plurality of second high-refractive material layers; and a second mirror layer 300, which is formed by alternately laminating third high-refractive material layers 310 and third low-refractive material layers 320 by placing the spacer layer 200 in the middle and arranged opposite to the first mirror layer 100.

[0057] According to an embodiment of the present invention, the optical filter 1020 can be composed of Figure 1 The single cavity structure shown may be formed, or a multi-cavity structure may be formed by repeatedly laminating two or more structures each having a single cavity structure as a unit.

[0058] First, the incident light entering the optical filter 1020 may be transmitted or reflected in the order of the first mirror layer 100, the spacer layer 200, and the second mirror layer 300 according to the wavelength region, or in the reverse order.

[0059] The spacer layer 200 as a layer located between the first mirror layer 100 and the second mirror layer 300 may include a high-refractive substance layer.

[0060] When the incident light is incident obliquely instead of vertically, the P-polarized light and the S-polarized light will separate, and as the incident angle increases, the center wavelengths of the two polarized lights move toward the short wavelength, and the two polarized lights become different transmittances according to the wavelength, which eventually becomes the reason for reducing the performance of the optical filter. In order to improve this problem, when one or more of the first high-refractive material layer 110, the third high-refractive material layer 310 and the spacer layer 200 are composed of materials with high optical refractive index, the variation of the transmittance according to the wavelength of the S-polarized light and the P-polarized light with a larger incident angle is reduced, and a larger incident angle can be allowed. Therefore, compared with the spacer layer 200 using a low-refractive material layer, a filter that allows a larger incident angle can be prepared when a high-refractive material layer is used.

[0061] At least one of the first high-refractive material layer 110 , the first low-refractive material layer 120 , the second high-refractive material layer, the third high-refractive material layer 310 , and the third low-refractive material layer 320 may include halogenated amorphous silicon.

[0062] The halogenated amorphous silicon may contain F or Cl.

[0063] Specifically, chlorine (the atomic radius of Cl is 100pm) or fluorine (the atomic radius of F is 50pm) with an atomic radius similar to that of silicon (the atomic radius of Si is 111pm) is placed in a dangling bond, and the electron density of state (DOS) in the band gap of amorphous silicon is adjusted. In the near-infrared band of about 800nm-1100nm, a high optical refractive index of about 3.0 or more and a low extinction coefficient of about 0.001 or less can be obtained. Compared with hydrogen atoms, filters requiring high-temperature reliability can be prepared by using a low diffusion coefficient according to temperature.

[0064] In summary, in the wavelength range of about 800nm ​​to 1100nm, the refractive index of at least one of the first high-refractive material layer 110, the second high-refractive material layer and the third high-refractive material layer 310 may be about 3.0 or more, and have an extinction coefficient of about 0.001 or less. However, when the refractive index of the first high-refractive material layer 110, the second high-refractive material layer and the third high-refractive material layer 310 exceeds about 4.0, light absorption occurs, and it is difficult to manufacture a filter with high actual transmittance.

[0065] The first high-refractive material layer 110 , the first low-refractive material layer 120 , the second high-refractive material layer, the third high-refractive material layer 310 , and the third low-refractive material layer 320 including halogenated amorphous silicon may be prepared by PVD or CVD methods, respectively.

[0066] For example, when prepared by PVD, silicon is placed on a cathode and DC-sputtered or rf-sputtered to deposit it on a substrate facing the silicon cathode. At this time, argon (Ar) is used as an inert gas to generate plasma. In addition, to prepare halogenated amorphous silicon, chlorine (Cl) or a compound gas containing chlorine or fluorine (SiCl4, SiF4) is injected as a reaction gas to form a plasma, and halogenated silicon can be formed on the substrate by reacting with the sputtered silicon. At this time, highly reactive hydrogen (H2) or gaseous hydrochloric acid (HCl) can also be used as a carrier gas. The refractive index of halogenated amorphous silicon can be controlled by adjusting the amount of gas containing halogen substances injected, the temperature of the substrate, and the DC or rf power related to the deposition rate of amorphous silicon. In order to improve the chemical bonding between the halogen-containing substance and silicon, a separate plasma source or ion source with a large plasma density is used to increase the density of halogen (Cl, F) located in the dangling bond of amorphous silicon, so that an extinction coefficient of about less than 0.0005 can be obtained. In addition, with the halogen element located at the dangling bond, the effect of reducing the compressive stress existing in the filter film can also be simultaneously achieved.

[0067] When halogenated amorphous silicon is prepared into a thin film shape using a PVD method including the steps of injecting an inert gas, a halogen gas and a carrier gas into a chamber, the ratio of the volume of the halogen gas injected into the chamber at the same time / (the volume of the halogen gas + the volume of the above-mentioned carrier gas) can be approximately greater than 0 and less than 0.375.

[0068] When the volume ratio of the gas injected into the chamber at the same time is within the above range, the filter including halogenated amorphous silicon according to an embodiment of the present invention has a higher refractive index than the filter using hydrogenated amorphous silicon, and can simultaneously show the same level of extinction coefficient.

[0069] At this time, the halogen gas as the reaction gas can be chlorine (Cl) or a compound gas containing chlorine or fluorine (SiCl4, SiF4), etc., and the carrier gas can be highly reactive hydrogen (H2) or gaseous hydrochloric acid (HCl), etc. Such a halogenated amorphous silicon film can be used to prepare an optical filter.

[0070] The ratio of (optical thickness of the first high-refractive material layer 110 / optical thickness of the first low-refractive material layer 120) or (optical thickness of the third high-refractive material layer 310 / optical thickness of the third low-refractive material layer 320) can be about 1.5 to 3.0. Within the above range, a wide range of incident angles can be accommodated, and the internal stress of the material layer film is minimized, so that an economical optical filter can be manufactured using a thin substrate.

[0071] Specifically, the optical filter 1020 according to an embodiment of the present invention has a transmission band in the wavelength range of about 800nm ​​to 1100nm in the near infrared region, and the central wavelength of 950nm can be shifted (Band Shift) by less than 25nm at most according to the change of the incident angle from about 0 to 45 degrees. In addition, according to the change of the incident angle from about 0 to 60 degrees, the maximum shift can be less than 38nm.

[0072] The first high-refractive material layer 110, the second high-refractive material layer and the third high-refractive material layer 310 have the same refractive index, and the first low-refractive material layer 120 and the third low-refractive material layer 320 may have the same refractive index. Although the first high-refractive material layer 110, the second high-refractive material layer and the third high-refractive material layer 310 or the first low-refractive material layer 120 and the third low-refractive material layer 320 may be selected to have materials with different refractive indices, multiple material sources are required in the preparation stage of the optical filter (multiple different cathodes are required during sputtering), which may bring about problems in the complexity of the preparation equipment, the operation process and the cost, so this problem can be improved by using materials with the same refractive index.

[0073] The first low-refractive material layer 120 and the third low-refractive material layer 320 may include any one or more of TiO 2 , Nb 2 O 5 , Ta 2 O 5 , Si 3 N 4 , SiO 2 , MgF 2 , Al 2 O 3 , halogenated amorphous silicon compounds or mixtures thereof.

[0074] Generally speaking, the refractive index of TiO2, Nb2O5, Ta2O5, and Si3N4 is in the range of about 2.0 to 2.3, and they can usually be classified as high-refractive materials. However, since the refractive index of the halogenated amorphous silicon of the optical filter 1020 according to an embodiment of the present invention is very high (about 3.0 to 4), TiO2, Nb2O5, Ta2O5, Si3N4 or a mixture thereof can be used as a low-refractive material. Therefore, in addition to the generally used low-refractive materials such as SiO2, Al2O3, and MgF2, one or more of Nb2O5, Ta2O5, and Si3N4 can be selected and used, so that the material selection range of the optical filter becomes wider. In addition, by adjusting the process conditions of the thin film deposition step containing the halogenated amorphous silicon compound, different refractive indices can be prepared, so that not only a high-refractive material layer containing the halogenated amorphous silicon compound can be prepared, but also a low-refractive material layer can be prepared.

[0075] Figure 2 is a diagram showing a basic configuration of a sensor system 1000 according to an embodiment of the present invention.

[0076] refer to Figure 2 An embodiment of the present invention provides a sensor system 1000, which includes: an optical filter 1020 according to an embodiment of the present invention; a light source 1010, which emits light in a wavelength range of about 800nm ​​to 1100nm to generate reflected light that can reach the optical filter 1020; and a sensor 1030, which is arranged on the path through which the reflected light passing through the optical filter 1020 flows, and is used to receive 3D information about a subject 1040 included in the reflected light.

[0077] To simplify the illustration, other elements typically included in the sensor system 1000, such as optics, are omitted.

[0078] The light source 1010 emits light with a wavelength in the range of about 800 nm to 1100 nm. The light source 1010 emits modulated light such as light pulses. Preferably, the light source 1010 may be a light-emitting diode (LED), an LED array, a laser diode or a laser diode array.

[0079] The light source 1010 emits light toward the subject 1040, and the subject 1040 then reflects the emitted light to the sensor system 1000. When the sensor system 1000 is a gesture recognition system, the subject 1040 is a user of the gesture recognition system.

[0080] The optical filter 1020 is configured to receive light emitted after being reflected by the object 1040. The optical filter 1020 includes an emission wavelength and has a wavelength range of about 800nm ​​to 1100nm and a transmission band that at least partially overlaps. The optical filter 1020 may be a band transmission filter, and preferably, may be a narrow-band transmission filter as described above. The optical filter 1020 transmits light emitted from the light source 1010 while substantially blocking ambient light. For example, the optical filter 1020 receives light emitted by the light source 1010 that is reflected by the object 1040, and transmits the emitted light to the sensor 1030.

[0081] The sensor 1030 is configured to receive the light transmitted by the optical filter 1020, that is, the sensor 1030 may be disposed behind the optical filter 1020. Depending on circumstances, the optical filter 1020 may be directly formed on the sensor 1030 or disposed above the sensor 1030.

[0082] When the sensor system 1000 is a proximity sensor system, the sensor 1030 is a proximity sensor, which can sense the proximity of the subject 1040 by detecting the emitted light according to methods known in the technical field of the present invention. When the sensor system 1000 is a 3D imaging system or a gesture recognition system, the sensor 1030 is a 3D image sensor, such as a charge-coupled device (CCD) chip or a complementary metal oxide semiconductor (CMOS) chip, which detects the emitted light and provides a 3D image of the subject 1040, which can be a user according to the situation. For processing by a processing system such as an application-specific integrated circuit (ASIC) or a digital signal processing device (DSP), the 3D image sensor can convert the optical signal into an electrical signal according to methods known in the art. For example, when the sensor system 1000 is a gesture recognition system, the processing system can recognize the user's gesture after processing the user's 3D image.

[0083] By including the optical filter 1020 according to an embodiment of the present invention, it can not only have a high refractive index but also show a low extinction coefficient characteristic in a narrow band ranging from about 800nm ​​to 1100nm, and can also accommodate a wide range of incident angles from about 0 degrees to 60 degrees.

[0084] The preferred embodiments of the present invention are described in detail above, but the scope of the present invention is not limited thereto but should be defined by the claims. Various modifications made by technicians using the basic concept of the present invention also fall within the scope of the present invention.

[0085] [Example 1] Design of filter

[0086] By using an optical thin film design software program currently commonly used in research or industry, the following optical filters were designed as comparative examples and embodiments.

[0087] Comparative Examples 1 to 4 and Examples 1 to 4 were designed according to the following filter design formula.

[0088]

Design formula

[0089] Glass(1.52) / (HL)^n 2mH(LH)^n / Air(1.0),(H:a@λ1nm,L:b@λ2nm)

[0090] (H is a high refractive material layer, L is a low refractive material layer, n represents the number of times the high refractive material layer and the low refractive material layer are laminated, m is an integer from 1 to 4, a is the refractive index of the high refractive material layer at a wavelength of λ1, b is the refractive index of the low refractive material layer at a wavelength of λ2, the refractive index of Glass is 1.52, the refractive index of Air is set to 1.0, and the optical thickness ratio of H and L is 1:1.)

[0091] Comparative Example 1 is Glass (1.52) / (HL)^4 2mH(LH)^4 / Air (1.0), (H: 3.6@950nm, L: 2.5@950nm), the high refractive material layer uses halogenated silicon oxide (a-Si:Cl:H), and the low refractive material layer uses halogenated silicon oxide (a-SiOx:Cl).

[0092] Comparative Example 2 is Glass(1.52) / (1.1H0.9L)^4(2m+0.0783)H(0.9L1.1H)^4 / Air(1.0), which is designed under the same conditions as Comparative Example 1 except that the ratio of the optical thickness of the high-refractive material layer and the low-refractive material layer is changed. The value of 0.0783 in the above design formula is a compensation value, which is used to compensate for the change of the resonant wavelength according to the change of the mirror layer located before and after the spacer layer, so that resonance is generated at the required central wavelength to minimize the loss. Specifically, the corresponding compensation value can be obtained by calculating the optical admittance of each layer constituting the mirror layer, or it can be derived using a program. In addition, it can also be applied to the following Comparative Examples 3 and 4, and the design formulas of Examples 1 to 4.

[0093] Comparative Example 3 is Glass(1.52) / (1.15H0.85L)^4(2m+0.1173)H(0.85L1.15H)^4 / Air(1.0), and is designed under the same conditions as Comparative Example 1 except that the ratio of the optical thickness of the high-refractive material layer and the low-refractive material layer is changed.

[0094] Comparative Example 4 is Glass(1.52) / (1.75H0.25L)^4(2m+0.5597)H(0.25L1.1.75H)^4 / Air(1.0), and is designed under the same conditions as Comparative Example 1 except that the ratio of the optical thickness of the high-refractive material layer and the low-refractive material layer is changed.

[0095] Example 1 is Glass(1.52) / (1.2H0.8L)^4(2m+0.1560)H(0.8L1.2H)^4 / Air(1.0), and is designed under the same conditions as Comparative Example 1 except that the ratio of the optical thickness of the high-refractive material layer and the low-refractive material layer is changed.

[0096] Example 2 is Glass(1.52 / (1.25H0.75L)^4(2m+0.1945)H(0.75L1.25H)^4 / Air(1.0), and is designed under the same conditions as Comparative Example 1 except that the ratio of the optical thickness of the high-refractive material layer and the low-refractive material layer is changed.

[0097] Example 3 is Glass(1.52) / (1.3H0.7L)^4(2m+0.2325)H(0.7L1.3H)^4 / Air(1.0), and is designed under the same conditions as Comparative Example 1 except that the ratio of the optical thickness of the high-refractive material layer and the low-refractive material layer is changed.

[0098] Example 4 is Glass(1.52) / (1.5H0.5L)^4(2m+0.3727)H(0.5L1.5H)^4 / Air(1.0), and is designed under the same conditions as Comparative Example 1 except that the ratio of the optical thickness of the high-refractive material layer and the low-refractive material layer is changed.

[0099] [Experimental Example 1] Comparative experiment on filter performance based on design changes

[0100] By using an optical film design software program commonly used in current research or industry, a test was conducted to compare and measure the shift effect (Band shift) at the 950nm center wavelength and the difference in improvement effect relative to Comparative Example 1 (Band shift value difference, and %) of the filters designed for Comparative Examples 1 to 4 and Examples 1 to 4.

[0101] Table 1 below shows the results of measuring the Band Shift (nm) values ​​at various incident angles when m of the spacer layer is 1.

[0102]

Table 1

[0103]

[0104] Table 2 below shows the results of measuring the offset values ​​at various incident angles when m of the spacer layer is 2.

[0105]

Table 2

[0106]

[0107] Table 3 below shows the results of measuring the offset values ​​at various incident angles when m of the spacer layer is 3.

[0108]

Table 3

[0109]

[0110] Table 4 below shows the results of measuring the offset values ​​at various incident angles when m of the spacer layer is 4.

[0111]

Table 4

[0112]

[0113] According to the above experimental results, in Examples 1 to 4, when the incident angle changes in the range of 0 to 45 degrees, it can be seen that the offset value is limited to less than 25nm (24.98nm at 45 degrees in Example 1), and when the incident angle changes in the range of 0 to 60 degrees, it can be seen that the offset value is limited to less than 38nm (37.59nm at 60 degrees in Example 1). At this time, the ratio of (optical thickness of the high-refractive material layer / optical thickness of the low-refractive material layer) corresponding to Examples 1 to 4 changes in the range of 1.5 to 3.0.

[0114] However, the ratio of (optical thickness of high refractive material layer / optical thickness of low refractive material layer) in Comparative Examples 1 to 3 is 1 (Comparative Example 1), about 1.2 (Comparative Example 2), and about 1.35 (Comparative Example 3), respectively. The actually prepared optical filter should have a certain degree of tolerance for large incident angles of transmitted light, but under the same conditions, Comparative Examples 1 to 3 show a low degree of improvement in deviation compared to Examples 1 to 4.

[0115] For example, under the condition of m=1 in Comparative Example 3, with an incident angle of 30 degrees as the reference, the value of the center wavelength shift (Band Shift) % relative to Comparative Example 1 is (%) is 0.08 which is less than 0.1, and this level is difficult to be applied in terms of the effect of preparing optical filters.

[0116] In addition, although the most excellent offset value is shown in Comparative Example 4, the ratio of (optical thickness of the high-refractive material layer / optical thickness of the low-refractive material layer) is 7. Therefore, the filter (Band Pass Filter) used in the sensor system needs to form an additional mirror layer in terms of characteristics, and more layers of optical thin film layers are required, resulting in an increase in the process time and cost required for manufacturing the filter and a decrease in productivity.

[0117] [Example 2] Preparation of halogenated amorphous silicon

[0118] METAMODE is a process based on reactive magnetron sputtering (RPS), a type of PVD (Physical Vapor Deposition), to produce hydrogenated amorphous silicon and halogenated amorphous silicon thin films. The material was prepared by magnetron sputtering.

[0119] The Si cathode is placed on the left and right sides of the substrate carrier (Substrate Carrier) rotating around the center of the chamber as the axis, and silicon (Si) is coated on the glass substrate in angstroms by magnetron sputtering. Then, high-density plasma is obtained by injecting Ar into the ICP (Induction Coupled Plasma) Source, in which Cl2 as a reaction gas and H2 as a carrier gas are injected. H+ and Cl+ react with the deposited Si to obtain hydrogenated silicon (a-Si:H), halogenated silicon (Si:Cl) or its composite SiClxH (1-x), and a film of the required optical thickness is obtained by repeating this process. Before the process, in order to minimize the gas remaining in the coating chamber except for the required process gas (Ar, Cl, H2, etc.), the process gas is injected after exhausting to about 1.0*10^-6mbar to start the process. The DC (Pulsed DC) magnetron process can be achieved by controlling the conductivity of Si as the sputtering cathode. In order to keep the temperature of the base material within a certain range during the process, a Sheath Heater is used as a heating source. In addition, in order to obtain a uniform film, the rotation speed of the substrate carrier on which the mother material is located is set to above about 100 rpm, and an optical monitoring system (InsituOptical Monitoring System) that can optically measure the change in film thickness during the process is used to measure the light transmittance of the film in real time during the process.

[0120] Other specific process conditions are shown in Table 5.

[0121]

Table 5

[0122] Process pressure (mbar) 1.3～1.4E-3 Ar as Si cathode 80sccm Deposition rate 0.4nm / sec Plasma source rf-6Kw Ar as plasma source 100sccm <![CDATA[H2 as a plasma source]]> 25~40sccm Cl as plasma source 0~15sccm Substrate temperature 180℃

[0123] As a result, hydrogenated amorphous silicon and halogenated amorphous silicon films were prepared according to the conditions of Comparative Examples 1 and 2 and Examples 1 to 3 by changing the flow rates of H2 gas and Cl2 gas injected into the chamber as shown in Table 6. The film prepared by Comparative Example 1 was hydrogenated amorphous silicon (a-SiH), and the films prepared by Examples 1 to 3 and Comparative Example 2 were halogenated amorphous silicon (a-SiClH).

[0124]

Table 6

[0125]

[0126] [Experimental Example 2] Comparative Experiment on Optical Properties of Halogenated Amorphous Silicon

[0127] In order to compare the optical properties of the films prepared according to Comparative Examples 1 and 2 and Examples 1 to 3, the transmittance and the refractive index of each prepared film at a transmission wavelength were measured using a spectrophotometer.

[0128] The transmittance measurement results are summarized in Table 7 below, and the refractive index measurement results are summarized in Table 8 below.

[0129]

Table 7

[0130]

[0131] Figure 3 This is a diagram showing the data in Table 8 in a graph format. The X-axis is the wavelength (nm), and the Y-axis is the refractive index.

[0132]

Table 8

[0133]

[0134] Refer to Table 8 and Figure 3 Compared with hydrogenated amorphous silicon (Comparative Example 1), it can be seen that Examples 1 to 3 show excellent optical refractive indices of about 3.593 to 3.861 (800 nm to 1100 nm). However, as in Comparative Example 2, when the flow rate ratio of the Cl2 gas injected into the chamber exceeds 37.5%, a refractive index similar to that of hydrogenated amorphous silicon in Comparative Example 1 is shown.

[0135] In order to compare the optical properties of the films prepared according to Comparative Example 1, Example 2 and Comparative Example 2, the results of measuring the extinction coefficient of each prepared film according to the transmission wavelength are summarized in the following Table 8.

[0136] Figure 4 This is a graph showing the data in Table 9. The X-axis is the wavelength (nm), and the Y-axis is the extinction coefficient (K).

[0137]

Table 9

[0138]

[0139] Refer to Table 9 and Figure 4 In the wavelength region of about 800 nm to 1100 nm, hydrogenated amorphous silicon (Comparative Example 1) and halogenated amorphous silicon (Example 2 and Comparative Example 2) show extinction coefficient values ​​at the same level.

Claims

1. A filter, characterized in that: include: Multiple layers of highly refractive material; and Multiple layers of low-refractive material, At least a part of the plurality of high-refractive material layers and at least a part of the plurality of low-refractive material layers are alternately laminated with each other, At least one of the plurality of high-refractive substance layers has a refractive index of 3.0 or more in a wavelength range of 800 nm to 1100 nm and an extinction coefficient of 0.001 or less.

2. The optical filter according to claim 1, characterized in that At least one of the plurality of high-refractive substance layers or the plurality of low-refractive substance layers includes halogenated amorphous silicon.

3. The optical filter according to claim 2, characterized in that The plurality of high-refractive material layers include a first high-refractive material layer and a third high-refractive material layer, The plurality of low-refractive material layers include a first low-refractive material layer and a third low-refractive material layer, The first high-refractive material layer and the first low-refractive material layer are alternately laminated to form a first mirror layer. The third high-refractive material layer and the third low-refractive material layer are alternately laminated to form a second mirror layer.

4. The optical filter according to claim 3, characterized in that The plurality of high-refractive material layers further include a plurality of second high-refractive material layers, The plurality of second high-refractive material layers are continuously laminated on one side of the first mirror layer to form a spacer layer.

5. The optical filter according to claim 4, characterized in that At least one of the first high-refractive material layer, the first low-refractive material layer, the second high-refractive material layer, the third high-refractive material layer or the third low-refractive material layer contains halogenated amorphous silicon, At least one of the first high-refractive material layer, the second high-refractive material layer, or the third high-refractive material layer has a refractive index of 3.0 or more and an extinction coefficient of 0.001 or less in a wavelength range of 800 nm to 1100 nm.

6. The optical filter according to claim 4, characterized in that The optical filter has a ratio of (optical thickness of the first high-refractive substance layer / optical thickness of the first low-refractive substance layer) or (optical thickness of the third high-refractive substance layer / optical thickness of the third low-refractive substance layer) of 1.5 to 3.

0.

7. The optical filter according to claim 2, characterized in that The halogenated amorphous silicon contains F or Cl.

8. The optical filter according to claim 1, characterized in that The optical filter has a transmission band in the wavelength range of 800 nm to 1100 nm, and a maximum shift of a central wavelength of 950 nm is less than 25 nm according to a change in an incident angle of 0 to 45 degrees.

9. The optical filter according to claim 1, characterized in that The optical filter has a transmission band in the wavelength range of 800 nm to 1100 nm, and a maximum shift of a central wavelength of 950 nm is less than 38 nm according to a change in an incident angle of 0 to 60 degrees.

10. The optical filter according to claim 4, characterized in that The first high-refractive material layer, the second high-refractive material layer and the third high-refractive material layer have the same refractive index. The first low-refractive material layer and the third low-refractive material layer have the same refractive index.

11. The optical filter according to claim 2, characterized in that The halogenated amorphous silicon is prepared using a PVD method including the steps of injecting an inert gas, a halogen gas and a carrier gas into a chamber, The ratio of the volume of the halogen gas injected into the chamber at the same time / (the volume of the halogen gas+the volume of the carrier gas) is greater than 0 and less than 0.

375.

12. The optical filter according to claim 4, characterized in that The first low-refractive material layer and the third low-refractive material layer include any one or more of TiO2, Nb2O5, Ta2O5, Si3N4, SiO2, MgF2, Al2O3, halogenated amorphous silicon compounds or mixtures thereof.

13. A method for preparing a halogenated amorphous silicon thin film for an optical filter, characterized in that: The method is prepared using a PVD method including the steps of injecting an inert gas, a halogen gas and a carrier gas into a chamber, The ratio of the volume of the halogen gas injected into the chamber at the same time / (the volume of the halogen gas+the volume of the carrier gas) is greater than 0 and less than 0.

375.

14. A sensor system, characterized in that: include: The optical filter according to any one of claims 1 to 12; a light source that emits light in the wavelength region of 800 nm to 1100 nm to generate reflected light that can reach the optical filter; and The sensor is arranged on a path through which the reflected light passing through the filter flows, and is used to receive 3D information about the subject contained in the reflected light.

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