JP2015007718A - High reflective mirror and fabry-perot filter having the high reflective mirror - Google Patents

Abstract

PROBLEM TO BE SOLVED: To reduce noise by incident light passing through an etching hole in a high reflective mirror in which an optical multilayer film mirror is formed.SOLUTION: The high reflective mirror includes an optical multilayer film mirror formed in at least a part of the mirror. The optical multilayer film mirror includes: a first high refractive index film and a second high refractive index film having a first refractive index; and a first low refractive index layer having a second refractive index smaller than the first refractive index. The first high refractive index film and the second high refractive index film are disposed opposing to each other via the first low refractive index layer; and the first high refractive index film has a first through-hole that penetrates the first high refractive index film and communicates an outside space with the first low refractive index layer. A first light-shielding zone is formed on one surface side of the second high refractive index film opposite to the first high refractive index film; and the first light-shielding zone is selectively formed in such a manner that, in a part where the optical multilayer film mirror is formed, neither incident light in a direction along the stacked direction of the first and second high refractive index films and the first low refractive index layer, nor diffracted light of the incident light pass through the first through-hole.

Description

  The present invention relates to a high reflection mirror including a mirror portion having an optical multilayer film structure in which a high refractive index film and a low refractive index layer are laminated, and a Fabry-Perot filter including the high reflection mirror.

Conventionally, Patent Document 1 proposes a Fabry-Perot interferometer composed of a high-reflection mirror in which a mirror portion having an optical multilayer film structure is partially constructed. The Fabry-Perot interferometer has a pair of high reflection mirrors (a lower mirror and an upper mirror) provided with a mirror portion, and the lower mirror and the upper mirror are arranged to face each other via an air gap, for example. . The mirror part has a structure in which two high refractive index films are arranged to face each other via a low refractive index layer. Conventionally, a configuration in which SiO ₂ is employed as the low refractive index layer and Si is employed as the high refractive index film is known. On the other hand, in the Fabry-Perot interferometer of Patent Document 1, holes (etching holes) are formed in the high refractive index film in the region to be the mirror part. By this etching hole, the low refractive index layer communicates with the external space and the air gap above the upper mirror. The low refractive index layer in Patent Document 1 is an air layer. By using the low refractive index layer as air, the refractive index ratio with the high refractive index film can be increased, and a mirror with a wide high reflection band can be realized.

Japanese Patent No. 4784495

  However, when the upper mirror and the lower mirror in Patent Document 1 are each considered as a single high-reflection mirror, since there are etching holes in a region to be a mirror portion, a part of incident light passes through a high refractive index film. Without passing through the high reflection mirror. For this reason, a part of light having a wavelength that should be reflected cannot be reflected, leading to a decrease in reflectance. In other words, light having a wavelength that should be reflected is superimposed as noise on the light that passes through the high reflection mirror.

  Further, in the Fabry-Perot filter and Fabry-Perot interferometer constituted by the upper mirror and the lower mirror, the light that has passed through the etching hole does not receive the interference effect of the upper and lower mirrors. For this reason, the wavelength of the light that has passed through the etching hole is different from that of the light that normally receives the interference effect of the upper and lower mirrors. That is, the light that has passed through the etching hole causes noise, and degrades the spectral characteristics of the Fabry-Perot filter.

  The present invention has been made in view of the above problems, and an object thereof is to reduce noise caused by incident light passing through an etching hole.

  The invention disclosed herein employs the following technical means to achieve the above object. Note that the reference numerals in parentheses described in the claims and in this section indicate a corresponding relationship with specific means described in the embodiments described later as one aspect, and limit the technical scope of the invention. Not what you want.

  In order to achieve the above object, the present invention has a first mirror part (M1) having an optical multilayer film structure at least partially, and the first mirror part has a first refractive index film having a first refractive index. (21) and a second high refractive index film (22), and a first low refractive index layer (23) having a second refractive index smaller than the first folding index, The second high-refractive index film is disposed opposite to each other via the first low-refractive index layer, and the first high-refractive index film penetrates the first high-refractive index film and external space and the first low-refractive index. A high-reflecting mirror having a first through hole (24) communicating with a layer and having a first light-shielding band (40a) on one surface side of the second high-refractive index film opposite to the first high-refractive index film The first light-shielding band is configured to shield the incident light and its diffracted light from the stacking direction of the first high-refractive index film, the second high-refractive index film, and the first low-refractive index layer. I am characterized by being selectively formed in a portion corresponding to the error portion.

  According to this, when light is incident from the first high refractive index film side, direct light that will pass through the first through hole (corresponding to the etching hole described in Patent Document 1), and the first The light diffracted by the through hole can be shielded by the first light shielding band. Further, when light enters from the second high refractive index film side, direct light and light diffracted by the first light shielding band can be prevented from reaching the first through hole. Therefore, noise caused by incident light including diffracted light can be reduced.

It is sectional drawing which shows schematic structure of the Fabry-Perot filter which concerns on 1st Embodiment. It is sectional drawing which shows the geometric conditions of optical simulation. It is a graph which shows the result of an optical simulation, and shows the shading zone diameter with respect to an etching hole diameter. It is sectional drawing which shows the process of preparing a board | substrate in the manufacturing method of a Fabry-Perot filter. It is sectional drawing which shows the process of forming a light-shielding zone. It is sectional drawing which shows the process of forming a lower side mirror. It is sectional drawing which shows the process of forming a sacrificial layer. It is sectional drawing which shows the process of forming an upper side mirror. It is sectional drawing which shows schematic structure of the Fabry-Perot filter which concerns on 2nd Embodiment. It is sectional drawing which shows the geometric conditions of optical simulation. It is a graph which shows the amount of diffraction with respect to the wavelength of incident light which shows the result of an optical simulation. It is a top view which shows the magnitude | size of the light-shielding zone with respect to an etching hole. It is sectional drawing which shows schematic structure of the Fabry-Perot filter which concerns on 3rd Embodiment. It is sectional drawing which shows schematic structure of the Fabry-Perot filter which concerns on 4th Embodiment. It is sectional drawing which shows schematic structure of the highly reflective mirror which concerns on 5th Embodiment. It is sectional drawing which shows schematic structure of the Fabry-Perot filter which concerns on other embodiment. It is sectional drawing which shows the process of forming a lower side mirror. It is sectional drawing which shows the process of forming a sacrificial layer and an upper side mirror. It is sectional drawing which shows the process of forming a light-shielding zone, and the process of removing a board | substrate.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings. In the following drawings, the same reference numerals are given to the same or equivalent parts. Further, the x axis, the y axis orthogonal to the x axis, and the z axis orthogonal to the xy plane defined by the x axis and the y axis are defined as directions.

(First embodiment)
Initially, with reference to FIG. 1, schematic structure of the Fabry-Perot filter which concerns on this embodiment is demonstrated.

  The Fabry-Perot filter is used, for example, as a spectroscope of an infrared absorption type component sensor. As an example, it is used to measure the concentration of organic matter in fuel such as automobiles and the concentration of ethanol in exhaled breath.

  As shown in FIG. 1, the Fabry-Perot filter 10 of this embodiment includes a substrate 100, a lower mirror 20, an upper mirror 30, and a light shielding band 40.

  The substrate 100 is obtained by processing a general semiconductor wafer made of silicon to a predetermined thickness. Hereinafter, the thickness direction of the substrate 100 is defined as the z direction. That is, the substrate 100 has a plate shape along the xy plane. Note that the thickness of the substrate 100 in the present embodiment is approximately 400 μm.

  The lower mirror 20 includes a first high refractive index film 21 having a first refractive index, a second high refractive index film 22 having a first refractive index, and a first low refractive index layer 23 having a second refractive index. And a first mirror portion M1 having an optical multilayer film structure including a part thereof. In the portion where the first mirror portion M1 is formed, the first low refractive index layer 23 is interposed between the first high refractive index film 21 and the second high refractive index film 22 in the z direction, and as a whole, high reflection is achieved. The rate is realized.

  The second refractive index is smaller than the first refractive index. More specifically, the first high refractive index film 21 and the second high refractive index film 22 are made of Poly-Si, and the refractive index thereof is approximately 3.45. The first low refractive index layer 23 is an air layer, and its refractive index is approximately 1.00. Since air has a lower refractive index than other materials, it is useful as a low refractive index layer in an optical multilayer film having a high reflectance. The first low refractive index layer 23 may be a vacuum other than air.

Lower mirror 20 through the insulating film 110 made of SiO _2, is formed on the substrate 100. The insulating film 110 is formed on the entire surface 100 a of the substrate 100. A second high refractive index film 22 is formed on the entire surface on the one surface 100 a side of the substrate 100 via the insulating film 110. A first low refractive index layer 23 is formed in a region of the second high refractive index film 22 that becomes the first mirror portion M1. Then, the first high refractive index film 21 is laminated on the second high refractive index film 22 so as to cover the first low refractive index layer 23. That is, in the first mirror part M1, the first low refractive index layer 23 is sandwiched between the first high refractive index film 21 and the second high refractive index film 22.

  In the region to be the first mirror portion M1, the first high refractive index film 21 is formed with a first through hole 24 that penetrates the first high refractive index film 21 in the z direction. The first through hole 24 is formed so as to communicate the gap AG as an external space and the first low refractive index layer 23. The first through hole 24 is an etching hole, and is provided so that an etching solution or a gas can enter a region to be the first low refractive index layer 23 when the first low refractive index layer 23 is formed by etching. . In addition, the first low refractive index layer 23 has an effect as a vent for making the air layer or the vacuum layer. In addition, the opening of the first through hole 24 in the present embodiment is circular.

  The upper mirror 30 is disposed to face the lower mirror 20 with the gap AG interposed therebetween in the z direction. The upper mirror 30 corresponds to a counter mirror in the claims. The basic configuration of the upper mirror 30 is the same as that of the lower mirror 20. The upper mirror 30 includes a third high refractive index film 31 having a first refractive index, a fourth high refractive index film 32 having the same first refractive index, and a second low refractive index layer 33 having a second refractive index. Are high reflection mirrors in which the second mirror part M2 having an optical multilayer film structure is partially formed. In the z direction, the third high-refractive index film 31 and the fourth high-refractive index film 32 are disposed to face each other with the second low-refractive index layer 33 interposed therebetween.

  In the present embodiment, the third high-refractive index film 31 and the fourth high-refractive index film 32 are made of Poly-Si similarly to the first high-refractive index film 21 and the second high-refractive index film 22, and the refractive index thereof is substantially the same. 3.45. The second low refractive index layer 33 is an air layer like the first low refractive index layer 23, and its refractive index is approximately 1.00. Further, the second low refractive index layer 33 may be vacuumed.

  The fourth high refractive index film 32 in the upper mirror 30 is formed to face the first high refractive index film 21 with the gap AG interposed therebetween. In the fourth high refractive index film 32, a second low refractive index layer 33 is formed in a region to be the second mirror portion M2. A third high refractive index film 31 is laminated on the surface of the fourth high refractive index film 32 so as to cover the second low refractive index layer 33. That is, in the second mirror part M2, the second low refractive index layer 33 has a structure sandwiched between the third high refractive index film 31 and the fourth high refractive index film 32.

  In the region of the upper mirror 30 that becomes the second mirror portion M2, the third high refractive index film 31 is formed with a second through hole 34 that penetrates the third high refractive index film 31 in the z direction. The second through hole 34 is formed to communicate the outside with the second low refractive index layer 33. The fourth high refractive index film 32 is formed with a third through hole 35 that penetrates the fourth high refractive index film 32 in the z direction. The third through hole 35 is formed so as to communicate the air gap AG and the second low refractive index layer 33. The second through hole 34 and the third through hole 35 are also etching holes like the first through hole 24, and are circular in this embodiment. And the 2nd through-hole 34 and the 3rd through-hole 35 are formed in the magnitude | size and position which overlap with the 1st through-hole 24 completely in xy plane. Hereinafter, the first, second, and third through holes 24, 34, and 35 are collectively referred to as etching holes.

The upper mirror 30 is formed on the lower mirror 20 via the gap AG by being supported by the spacer layer 50 made of SiO ₂ . In other words, the spacer layer 50 is formed on a part of the surface of the lower mirror 20 opposite to the substrate 100, and the upper mirror 30 is disposed so as to bridge the spacer layer 50.

  The shading band 40 is a thin film made of tungsten, for example, and can be formed by sputter deposition or CVD. The light shielding band 40 in the present embodiment is formed on the surface layer of one surface 100a that is an interface with the insulating film 110 in the substrate 100, and the shape along the xy plane is circular according to the opening shape of the etching holes 24, 34, and 35. Is done. The light shielding band 40 is formed so as to shield incident light and its diffracted light that will pass through the etching holes 24, 34, and 35. As described above, the second through hole 34 and the third through hole 35 are formed in a size and a position that completely overlap with the first through hole 24 in the xy plane. For this reason, the light shielding band 40 is formed so as to share all of the first light shielding band, the second light shielding band, and the third light shielding band corresponding to the first, second, and third through holes 24, 34, and 35, respectively. The The first light shielding band 40a, the second light shielding band 40b, and the third light shielding band 40c will be described later in the third embodiment.

  Although the diffraction angle of incident light depends on the wavelength and order of incident light, in general, diffracted light travels wider than the diameter of a pinhole where diffraction occurs. For this reason, the diameter of the light shielding band 40 is larger than the diameter of the etching holes 24, 34, and 35. The larger the light shielding band 40 is, the more it can exert its light shielding ability. However, it is not desirable to shield light originally desired to be transmitted. Further, as the diameters of the etching holes 24, 34, and 35 are increased, the diffraction angle of the diffracted light can be reduced, but the direct light is easily transmitted.

  Next, with reference to FIGS. 2 and 3, the relationship between the size of the light-shielding band 40 and the sizes of the etching holes 24, 34, and 35 will be described in detail, and the function and effect will be described. In addition, the inventors calculated the diffraction angle of the diffracted light using an optical simulation taking into consideration the wave nature, and the diffraction angle here refers to the first-order diffracted light.

  The inventors obtained the size of the light shielding band 40 necessary for shielding the diffracted light by simulation using the sizes of the etching holes 24, 34, and 35 as variables.

  In this simulation, as shown in FIGS. 1 and 2, light is incident on the substrate 100 from the upper and lower mirrors 20, 30 side in a direction (stacking direction) perpendicular to the one surface 100 a of the substrate 100. That is, it is assumed that incident light is diffracted by the etching holes 24, 34, and 35 and the diffracted light travels toward the light shielding band 40. Further, as a geometric condition, as shown in FIG. 2, the length between the light receiving surface 30 a in which the second through hole 34 in the upper mirror 30 is formed and the one surface 100 a that is an interface between the insulating film 110 in the substrate 100. The thickness was 10 μm, and the thickness of the substrate 100 was 400 μm. Since the first through hole 24 and the third through hole 35 have a shorter distance from the one surface 100a than the second through hole 34, the diffracted light caused by the first and third through holes 24 and 35 is Compared with the diffracted light caused by the two through holes 34, the projection area onto the one surface 100a is small. Therefore, in this simulation, as shown in FIG. 2, only the second through hole 34 formed in the third high refractive index film 31 in the upper mirror 30 is taken into consideration.

  In this simulation, infrared light having wavelengths of 3 μm and 10 μm was assumed as incident light. This wavelength is set because the peak of the absorption coefficient of water, carbon dioxide, or ethanol contained in the fuel or exhaled air of an automobile or the like exists in the range of 3 μm to 10 μm as the wavelength.

  FIG. 3 shows the result of simulating the diameter of the light shielding band for preventing the first-order diffracted light of the incident light from penetrating the substrate 100 with respect to the diameter of the etching hole (corresponding to the second through hole 34 in this simulation).

  The white triangle marker plot (shown as A in FIG. 3) is for the case where the shading band 40 is arranged on the surface layer of the back surface 100b opposite to the one surface 100a of the substrate 100 for infrared light having a wavelength of 3 μm. is there. The white circle marker plot (shown as C in FIG. 3) is obtained when the light shielding band 40 is arranged on the surface layer 100a of the substrate 100 with respect to an infrared ray having a wavelength of 3 μm. The white square marker plot (shown as B in FIG. 3) is obtained when the light shielding band 40 is disposed on the surface layer 100a of the substrate 100 with respect to an infrared ray having a wavelength of 10 μm.

  In any of the above three plots, the graph is a downwardly convex graph having a minimum value in the diameter of the light shielding band 40 required for light shielding. The spread of incident light due to diffraction is more dominant on the side where the diameter of the etching hole is smaller than the diameter of the etching hole that gives the minimum value. On the other hand, on the side where the etching hole diameter is large, direct light passing directly through the etching hole is superior. That is, on the side where the diameter of the etching hole is large, the diameter of the etching hole and the size of the light shielding band 40 for directly shielding light are in a substantially proportional relationship.

  First, consider the case (plot A) in which the light shielding band 40 is disposed on the surface layer of the back surface 100b opposite to the one surface 100a of the substrate 100 with respect to an infrared ray having a wavelength of 3 μm. In this case, the minimum value of the shading band diameter is approximately 110 μm. That is, in order to shield light of this wavelength including diffracted light, the light shielding band 40 having a diameter of 110 μm or more is necessary. Originally, since it is necessary to transmit as much light as possible, it is preferable that the diameter of the light shielding band 40 is small. In the present embodiment, since the light shielding band 40 is formed on the surface layer of the one surface 100a closer to the lower mirror 20 than the back surface 100b, the diameter of the light shielding band 40 can be 110 μm or less.

  Here, when the light shielding band 40 is disposed on the surface layer 100a of the surface 100a of the substrate 100 with respect to the infrared light having a wavelength of 3 μm (plot B), the light shielding band 40 is disposed on the surface of the substrate 100 with respect to the infrared light having a wavelength of 10 μm. Consider the case (plot C) where the layers are arranged on the surface layer of 100a. Since the diffraction angle becomes larger as the wavelength of the incident light is longer, the plot B is always on the larger side of the shading zone diameter than the plot C. Although not shown in the figure, a wavelength λ satisfying 3 μm <λ <10 μm is drawn between plot B and plot C on the vertical axis in FIG. Therefore, as shown by the broken line in FIG. 3, by setting the diameter of the etching hole to 2 μm or more and 80 μm or less, the diameter of the light shielding band 40 is made 110 μm or less in the incident light wavelength region of 3 μm ≦ λ ≦ 10 μm. be able to.

  Thereby, the direct light and the diffracted light passing through the etching holes 24, 34, and 35 can be shielded while the diameter of the light shielding band 40 is 110 μm or less.

  Further, if the diameter of the etching hole is selected so that the diameter of the light shielding band 40 becomes a minimum value, the necessary light can be sufficiently transmitted while sufficiently securing the light shielding property by the light shielding band 40. Since the diffraction angle increases as the wavelength of incident light increases, the minimum value shifts to the larger etching hole diameter side as shown in plots B and C in FIG. That is, the larger the wavelength, the larger the etching hole diameter that gives the minimum value of the diameter of the light shielding band 40. In the incident light wavelength range of 3 μm ≦ λ ≦ 10 μm, the range of the etching hole diameter that gives the minimum value of the diameter of the light-shielding band 40 is 4 μm or more and 20 μm or less as shown by the one-dot chain line in FIG. By setting the diameter of the etching hole within this range, the diameter of the light shielding band 40 can be set to about 14 μm to 46 μm.

  Thereby, the diameter of the light-shielding zone 40 can be further reduced, and the wavelength component that causes noise can be shielded while ensuring the transparency of a desired wavelength.

  Next, with reference to FIGS. 4-8, the manufacturing method of the Fabry-Perot filter which concerns on this embodiment is demonstrated easily. In addition, since the process except the process of forming the light-shielding zone 40 is the same as the method described in Patent Document 1, description thereof is omitted.

  First, as shown in FIG. 4, a substrate 100 made of Si (silicon) is prepared. The substrate 100 in this embodiment has a thickness of approximately 400 μm.

  Next, as shown in FIG. 5, a step of forming a light shielding band 40 is performed. On the surface layer of one surface 100a perpendicular to the thickness direction (z direction) of the substrate 100, the light shielding band 40 is formed so as to form a circle having the same center as the circular first through hole 24 formed in a later step. The light shielding zone 40 can be formed by depositing tungsten by CVD or the like, for example. It can also be formed by sputter deposition. The diameter of the light shielding band 40 is, for example, 46 μm.

Next, as shown in FIG. 6, a step of forming the lower mirror 20 is performed. An insulating film 110 of SiO ₂ is deposited on the entire surface 100a so as to cover the substrate 100 and the light shielding band 40. Thereafter, the lower mirror 20 is formed on the insulating film 110. In the lower mirror 20, a second high refractive index film 22 is deposited on the insulating film 110 by CVD or the like, and an oxide layer 23 a made of SiO ₂ is formed in a region that later becomes the first low refractive index layer 23. Then, a first high refractive index film 21 is deposited on the second high refractive index film 22 by CVD or the like so as to cover the oxide layer 23a. Thereafter, the first through hole 24 is formed by generally known etching.

Next, as shown in FIG. 7, a step of forming the sacrificial layer 60 is performed. A sacrificial layer 60 made of SiO ₂ is formed on the first high refractive index film 21 of the lower mirror 20 so as to fill the first through holes 24. Since the sacrificial layer 60 is partly etched in a later step and that part becomes the gap AG, the layer thickness of the sacrificial layer 60 is the thickness of the gap AG (distance between the lower mirror 20 and the upper mirror 30 facing each other). Equal to

Next, as shown in FIG. 8, a step of forming the upper mirror 30 is performed. First, the fourth high refractive index film 32 is deposited on the sacrificial layer 60 by CVD or the like. Then, on the surface along the xy plane of the fourth high refractive index film 32, a third through hole 35 having the same center and diameter as the first through hole 24 is formed by etching. Thereafter, an oxide layer 33 a made of SiO ₂ is formed in a region that will later become the second low refractive index layer 33. Then, a third high refractive index film 31 is deposited on the fourth high refractive index film 32 by CVD or the like so as to cover the oxide layer 33a. Thereafter, the second through hole 34 is formed by generally known etching.

  Finally, the oxide layer 23a in the lower mirror 20, the oxide layer 33a in the upper mirror 30, and a part of the sacrificial layer 60 are removed by etching to form the Fabry-Perot filter 10 as shown in FIG. Can do.

(Second Embodiment)
In the present embodiment, a configuration when light is incident from the opposite side to the first embodiment will be described. That is, as shown in FIG. 9, the case where light enters the upper and lower mirrors 20 and 30 from the substrate 100 side will be described.

  Note that the size of the etching hole (similar to the first embodiment, the first through hole 24, the second through hole 34, and the third through hole 35 are collectively referred to as an etching hole) and the Fabry excluding the shape or size of the light shielding band 40 are excluded. Since the configuration of the Perot filter 10 is the same as that of the first embodiment, description thereof is omitted.

  With reference to FIGS. 10 to 12, the relationship between the size of the light-shielding band 40 and the sizes of the etching holes 24, 34, and 35 will be described in detail, and the function and effect will be described. In addition, the inventors calculated the diffraction angle of the diffracted light using an optical simulation taking into consideration the wave nature, and the diffraction angle here refers to the first-order diffracted light.

  The inventors obtained the size of the light shielding band 40 necessary for shielding the diffracted light by simulation using the sizes of the etching holes 24, 34, and 35 as variables.

  The geometric condition of the Fabry-Perot filter 10 assumed in the simulation is the same as that in the first embodiment. As described above, the incident light is incident on the upper and lower mirrors 20 and 30 from the substrate 100 side. That is, as shown in FIG. 10, it is assumed that the incident light is diffracted by the end of the light shielding band 40 and the diffracted light travels to the etching hole (corresponding to the second through hole 34 in this simulation). The wavelengths of incident light used in this simulation are 3 μm, 5 μm, 8 μm, and 10 μm.

  FIG. 11 shows the result of simulating the amount of diffraction of incident light with respect to the wavelength of incident light. As shown in FIG. 10, the amount of diffraction here is that incident light is diffracted at the end of the light shielding band 40, and the diffracted light is closer to the center of the light shielding band 40 from a position corresponding to the end of the light shielding band 40. It is the amount that wraps around. Particularly in this simulation, the diffracted diffracted light is projected onto the surface 30 b of the third high refractive index film 31 facing the one surface 100 a of the substrate 100. The amount of diffraction indicates the distance at which the first-order diffracted light is projected from the portion corresponding to the end of the light shielding band 40.

According to the simulation results shown in FIG. 11, in the assumed incident light wavelength region, the wavelength that gives the maximum value of the diffraction amount is 10 μm, and the maximum value of the diffraction amount is 16 μm. Therefore, if the diameter of the etching hole is R (μm), it is possible to prevent the diffracted light from reaching the etching hole by setting the diameter of the light shielding band 40 to R + 32 (μm) or more. In other words, as shown in FIG. 12, the light shielding band 40 is over the entire surface of the virtual circle 70 having the same center as the etching hole and having a diameter of R ₁ +32 (μm) on one surface 100a of the substrate 100. If it is wrapped, the diffracted light can be prevented from reaching the etching hole. In FIG. 12, an example in which the shape of the light shielding band 40 is a square is shown as an example, but the shape of the light shielding band 40 is arbitrary. In order to minimize the area of the light shielding band 40, the circular light shielding band 40 may be formed so as to completely overlap the virtual circle 70.

(Third embodiment)
In each of the above-described embodiments, the example in which the first through hole 24, the second through hole 34, and the third through hole 35 are located at the same position in the xy plane and form a congruent circle is shown. In contrast, in the present embodiment, an example in which the positions of the through holes 24, 34, and 35 in the xy plane are different will be described. In addition, since the components other than each through-hole 24, 34, 35 and the corresponding light-shielding band 40 are the same as those in the above-described embodiments, the description thereof is omitted. In addition, light is assumed to be incident on the light shielding band 40 from the lower mirror 20 side as in the first embodiment.

  As shown in FIG. 13, the through holes 24, 34, and 35 in the present embodiment are congruent with each other and are formed at different positions in a direction orthogonal to the z direction (direction along the xy plane). In the case of such a configuration, a light shielding band 40 corresponding to each of the through holes 24, 34, and 35 is formed in order to shield the incident light passing through each of the through holes 24, 34, and 35 and the diffracted light thereof. That is, as shown in FIG. 13, the Fabry-Perot filter 10 includes a first light shielding band 40a (broken line in FIG. 13) corresponding to the first through hole 24 and a second light shielding band corresponding to the second through hole 34. 40b (one-dot chain line in FIG. 13) and a third light-shielding band 40c (solid line in FIG. 13) corresponding to the third through hole 35. The light shielding bands 40a, 40b, and 40c of the present embodiment are formed so as to overlap each other, and are formed as an integral light shielding band 40.

  As in the present embodiment, the through holes 24, 34, and 35 can be formed at arbitrary positions, and the light shielding bands 40a, 40b, and 40c are at positions corresponding to the through holes 24, 34, and 35, respectively. By forming, incident light can be shielded. However, if the light shielding bands 40a, 40b, and 40c corresponding to the through holes 24, 34, and 35 are formed separately, the area occupied by the light shielding band 40 with respect to the light receiving surface of the Fabry-Perot filter 10 is increased in the xy plane. Therefore, there is a possibility that the incident light cannot be sufficiently transmitted. Therefore, as described in the first embodiment and the second embodiment, it is preferable that the through holes 24, 34, and 35 have a congruent shape having the same center in the xy plane. As a result, the first light shielding band 40a, the second light shielding band 40b, and the third light shielding band 40c can be made to completely overlap each other, and the area occupied by the light shielding band 40 with respect to the light receiving surface can be minimized. can do.

(Fourth embodiment)
In each of the above-described embodiments, an example in which the first through hole 24, the second through hole 34, and the third through hole 35 are congruent with each other has been described. However, the shape size of each through-hole 24, 34, 35 is arbitrary. In the present embodiment, as shown in FIG. 14, an example in which the first through hole 24, the second through hole 34, and the third through hole 35 have the same center but have different diameters in the xy plane will be described. . Hereinafter, the case where light enters the substrate 100 from the upper mirror 30 side will be described.

  As shown in FIG. 14, the Fabry-Perot filter 10 of this embodiment has through holes 24, 34, and 35 having different diameters. The through holes 24, 34, and 35 have the largest diameter of the second through hole 34 formed in the light receiving surface 30 a of the third high refractive index film 31 of the upper mirror 30. And the 1st through-hole 24 most distant from the light-receiving surface 30a in the incident direction (z direction) of light has the smallest diameter. That is, the diameters of the through holes 24, 34, and 35 are larger in the order of the second through hole 34, the third through hole 35, and the first through hole 24.

  The diffraction of light when passing through a hole has a larger diffraction angle as the diameter of the hole causing the diffraction is smaller. Therefore, even when the first through hole 24, the second through hole 34, and the third through hole 35 have to be formed with different sizes, the diameter of the opening becomes closer to the light incident side. It is preferable to make it large. In other words, it is preferable to make the diameter of the opening larger as the through hole is formed at a position farther from the light shielding band 40. According to this, the diffraction amount of the diffracted light by the through-hole formed in a position far from the light shielding band 40 can be further suppressed. Thereby, the diffracted light of the incident light can be shielded by the light shielding band 40 having a smaller diameter.

(Fifth embodiment)
In each of the above-described embodiments, the effect of the light shielding band 40 is described in relation to the through holes 24, 34, and 35 for the Fabry-Perot filter 10 having the lower mirror 20 and the upper mirror 30. The effect of the light shielding band 40 is exhibited not only as the Fabry-Perot filter 10 but also as a high reflection mirror in which the lower mirror 20 is formed on the substrate 100. That is, even if the configuration does not include the upper mirror 30 as the counter mirror, the effect of the light shielding band 40 can be achieved.

  As shown in FIG. 15, the high reflection mirror 200 exemplified in this embodiment has a configuration in which the upper mirror 30 and the spacer layer 50 are not formed with respect to the Fabry-Perot filter 10 described in the first embodiment. As in the first embodiment, the first low-refractive index layer 23 is sandwiched between the first high-refractive index film 21 and the second high-refractive index film 22 in the portion that becomes the first mirror part M1 of the lower mirror 20. To achieve a high refractive index.

  The high reflection mirror 200 has a light shielding band 40 on the surface layer 100a of the substrate 100 as in the above-described embodiments. The light shielding band 40 is formed corresponding to the first through hole 24 and shields direct light passing through the first through hole 24 and its diffracted light from incident light. Thereby, it is possible to prevent light having a wavelength that should be reflected originally from being transmitted because the first through hole 24 is present. Therefore, it is possible to prevent light having a wavelength that should be reflected from being superimposed on the light transmitted through the high reflection mirror as noise.

(Sixth embodiment)
In each of the above-described embodiments, the example in which the lower mirror 20 is formed over the entire surface on the one surface 100a of the substrate 100 has been described. However, the present invention is not limited to this example. For example, as shown in FIG. 16, a configuration in which the substrate 100 does not exist in a part immediately below the lower mirror 20 can be adopted as compared with the first embodiment.

  In the present embodiment, the mirror corresponding to the high reflection mirror described in the claims is the upper mirror 30, and the counter mirror corresponds to the lower mirror 20. That is, as shown in FIG. 16, the upper mirror 30 includes a first high refractive index film 21, a second high refractive index film 22, and a first low refractive index layer 23. The first high refractive index film 21 has a first through hole 24. The lower mirror 20 includes a third high refractive index film 31, a fourth high refractive index film 32, and a second low refractive index layer 33. The third high refractive index film 31 has a second through hole 34, and the fourth high refractive index film 32 has a third through hole 35. A spacer layer 50 is formed in a part of the facing space between the lower mirror 20 and the upper mirror 30, and a region surrounded by the spacer layer 50, the upper mirror 30, and the lower mirror 20 becomes an air gap AG. Further, in the present embodiment, a part of the third high refractive index film 31 in the lower mirror 20 where the second mirror part M2 is not formed is fixed to the substrate 100 via the insulating film 110. In other words, the third high-refractive-index film 31, and thus the lower mirror 20, becomes a membrane in a portion that does not contact the substrate 100 and becomes the second mirror portion M2. In the upper mirror 30, the light shielding band 40 in the present embodiment is formed on the side of the second high refractive index film 22 opposite to the first high refractive index film 21.

  The sizes of the light shielding band 40 and the through holes 24, 34, and 35 are the same as described in the first embodiment and the second embodiment. That is, when light is incident on the light shielding band 40 from the lower mirror 20 side, the diameter of each through hole 24, 34, 35 is 2 μm or more as described in the first embodiment, and By setting the thickness to 80 μm or less, the diameter of the light shielding band 40 can be set to 110 μm or less in the incident light wavelength region of 3 μm ≦ λ ≦ 10 μm. More specifically, by setting the diameter of each through hole 24, 34, 35 to 4 μm or more and 20 μm or less, the diameter of the light shielding band 40 can be set to about 14 μm to 46 μm.

  Further, when light is incident on the lower mirror 20 from the light shielding band 40 side, the diameters of the through holes 24, 34, and 35 are set to R (μm) as described in the second embodiment. In this case, it is possible to prevent the diffracted light from reaching the through holes 24, 34, and 35 by setting the diameter of the light shielding band 40 to R + 32 (μm) or more.

  A method for manufacturing the Fabry-Perot filter 10 according to the present embodiment will be briefly described. This manufacturing method is substantially the same as that of the first embodiment except for the step of forming the light shielding band 40 and the step of removing the substrate 100 described later, and therefore follows the method described in the first embodiment.

  First, the substrate 100 is prepared as in the first embodiment (FIG. 4).

  Next, as shown in FIG. 17, a step of forming the lower mirror 20 is performed. In the present embodiment, after forming the third high refractive index film 31 corresponding to the first high refractive index film 21 in the first embodiment, the first through hole 24 is formed by etching.

  Next, as shown in FIG. 18, a step of forming the sacrificial layer 60 and a step of forming the upper mirror 30 are performed. Unlike the first embodiment, no through hole is formed in the second high refractive index film 22 corresponding to the fourth high refractive index film 32 in the first embodiment.

  Next, as shown in FIG. 19, the light shielding band 40 is formed on the one surface 22 a of the second high refractive index film 22 in the upper mirror 30. The light shielding band 40 is formed in a portion corresponding to the etching hole, that is, the first through hole 24, the second through hole 34, and the third through hole 35, in the portion that becomes the first mirror portion M 1 of the upper mirror 30. The light shielding band 40 is formed by depositing tungsten as in the first embodiment. Further, the substrate 100 is removed by etching from the side opposite to the one surface 100a on which the lower mirror 20 is formed until it reaches the insulating film 110. Etching of the substrate 100 is partially performed so as to include a portion corresponding to a portion that becomes the second mirror portion M2 of the lower mirror 20 and the first mirror portion M1 of the upper mirror 30. In addition, the process of forming the light-shielding band 40 and the process of removing the substrate 100 do not matter in that order.

Finally, the second low-refractive index layer 33 in the lower mirror 20, the first low-refractive index layer 23 in the upper mirror 30, and the portion of SiO ₂ corresponding to the gap AG are removed by etching, as shown in FIG. A simple Fabry-Perot filter 10 can be formed.

(Other embodiments)
The preferred embodiments of the present invention have been described above. However, the present invention is not limited to the above-described embodiments, and various modifications can be made without departing from the spirit of the present invention.

  In each of the embodiments described above, an example in which the light shielding band 40 is formed by depositing tungsten has been described, but the present invention is not limited to this. For example, when the light shielding band 40 is formed on the substrate 100, it may be formed by ion implantation of phosphorus or boron. Similarly, even when the light shielding band 40 is formed on the high refractive index film (specifically, the second high refractive index film 22) as in the other embodiments described above, ion implantation of phosphorus or boron is performed. Can be formed.

  Moreover, in each above-mentioned embodiment, the example to which the facing distance of the upper side mirror 30 and the lower side mirror 20 was fixed was shown. However, the facing distance can be made variable. For example, an electrode for applying a voltage to the upper mirror 30 is formed on the upper mirror 30, and an electrode for applying a voltage to the lower mirror 20 is formed on the lower mirror 20. A Coulomb force acts between the upper mirror 30 and the lower mirror 20 by applying a potential difference between both electrodes. Thereby, the facing distance between the upper mirror 30 and the lower mirror 20 can be set to a distance corresponding to the potential difference between the upper and lower mirrors 20 and 30.

  As a method of making the facing distance between the upper mirror 30 and the lower mirror 20 variable, there is a method of using the piezoelectric effect by making the spacer layer 50 a generally known piezo element.

DESCRIPTION OF SYMBOLS 10 ... Fabry-Perot filter 20 ... Lower mirror, 21 ... First high refractive index film, 22 ... Second high refractive index film, 23 ... First low refractive index layer, 24 ... First through hole 30... Upper mirror, 31... Third high refractive index film, 32... Fourth high refractive index film, 33. 2nd through-hole, 35 ... 3rd through-hole 40 ... light shielding zone 50 ... spacer layer 100 ... substrate AG ... air gap M1 ... 1st mirror part, M2 ... 2nd Mirror part

Claims (12)

Having at least a part of the first mirror part (M1) having an optical multilayer structure,
The first mirror part is
A first high refractive index film (21) and a second high refractive index film (22) having a first refractive index, and a first low refractive index layer (23) having a second refractive index smaller than the first folding index; Have
The first high-refractive index film and the second high-refractive index film are disposed to face each other via the first low-refractive index layer;
The first high refractive index film is a high reflection mirror having a first through hole (24) that penetrates the first high refractive index film and communicates an external space with the first low refractive index layer,
A first light-shielding band (40a) on one surface side of the second high-refractive index film opposite to the first high-refractive index film;
The first light-shielding band shields incident light from the stacking direction of the first high-refractive index film, the second high-refractive index film, and the first low-refractive index layer and diffracted light thereof. A high-reflection mirror, which is selectively formed in a portion corresponding to the mirror portion. In the case where the incident light is incident from the side where the first through hole is formed rather than the first light shielding band,
2. The high reflection mirror according to claim 1, wherein the opening of the first through hole is circular and has a diameter of 2 μm or more and 80 μm or less.   The high reflection mirror according to claim 2, wherein the diameter of the first through hole is 4 μm or more and 20 μm or less. In the case where the incident light is incident from the side where the first light shielding band is formed rather than the first through hole,
The opening of the first through hole is a circle having a diameter R ₁ (μm),
The first light-shielding band has the same center as the first through-hole in a plane perpendicular to the stacking direction, and overlaps the entire virtual circle having a diameter of R ₁ +32 (μm). The high reflection mirror according to claim 1, wherein   The high reflection mirror according to claim 1, wherein the first low refractive index layer is an air layer or a vacuum. The high reflection mirror (20) according to any one of claims 1 to 5,
In the stacking direction of the first high refractive index film (21) and the second high refractive index film (22) constituting the high reflection mirror, a counter mirror (30) facing the first high refractive index film through a gap. ) And
The counter mirror is
Having a second mirror part (M2) having an optical multilayer film structure at least in part,
The second mirror part is
A third high refractive index film (31) and a fourth high refractive index film (32) having the first refractive index, and a second low refractive index layer (33) having the second refractive index,
The third high refractive index film and the fourth high refractive index film are disposed to face each other with the second low refractive index layer interposed therebetween;
The third high refractive index film has a second through hole (34) that penetrates the third high refractive index film and communicates the external space with the second low refractive index layer, and the fourth high refractive index film. The refractive index film has a third through hole (35) that passes through the fourth high refractive index film and communicates the external space and the second low refractive index layer,
The second high refractive index film has a second light shielding band (40b) and a third light shielding band (40c) on one surface side opposite to the first high refractive index film,
The second light shielding band is selectively formed in a portion corresponding to the second mirror portion so as to shield incident light and its diffracted light from the stacking direction, and the third light shielding band is formed in the stacking direction. The Fabry-Perot filter is selectively formed in a portion corresponding to the second mirror portion so as to shield incident light from the light and diffracted light thereof. In the case where the incident light is incident from the side where the first through hole is formed rather than the first light shielding band,
The Fabry-Perot filter according to claim 6, wherein the openings of the second through hole and the third through hole are circular and have a diameter of 2 µm or more and 80 µm or less.   The Fabry-Perot filter according to claim 7, wherein the diameters of the second through hole and the third through hole are 4 µm or more and 20 µm or less. In the case where the incident light is incident from the side where the first light shielding band is formed rather than the first through hole,
The opening of the second through hole is circular with a diameter R ₂ (μm),
The second light-shielding band has the same center as the second through hole in a plane perpendicular to the stacking direction, and overlaps the entire virtual circle having a diameter of R ₂ +32 (μm).
The opening of the third through hole is a circle having a diameter R ₃ (μm),
The third light-shielding band has the same center as the third through-hole in a plane perpendicular to the stacking direction, and overlaps the entire virtual circle having a diameter of R ₃ +32 (μm). The Fabry-Perot filter according to claim 6,   9. The diameter of the opening of each of the first through hole, the second through hole, and the third through hole increases as the light enters closer to the light incident side. Fabry-Perot filter.   The first through hole, the second through hole, and the third through hole have the same axis, and the first light shielding band, the second light shielding band, and the third light shielding band have a common light shielding band (40). The Fabry-Perot filter according to claim 6, wherein the Fabry-Perot filter is formed as follows.   The Fabry-Perot filter according to any one of claims 6 to 11, wherein the first low refractive index layer and the second low refractive index layer are an air layer or a vacuum.

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