JP6809717B2 - Solid photodetector - Google Patents

Description

The present invention relates to a solid photodetector.

Conventionally, a solid-state image sensor (solid-state photodetector) including a light-receiving unit that outputs a signal according to the intensity of the received light has been disclosed. Such a solid photodetector is disclosed, for example, in US Patent Application Publication No. 2010/014829, Japanese Patent Application Laid-Open No. 2016-58507, and Japanese Patent Application Laid-Open No. 2013-518414.

The surface-incident solid-state image sensor described in U.S. Patent Application Publication No. 2010/014829 is a semiconductor substrate including a light receiving portion that outputs a signal according to the intensity of received light, and a light receiving surface and a light receiving surface. It is provided with a read-out wiring unit to be arranged. Further, the light receiving portion and the reading wiring portion are covered with a surface film, and light is incident on the light receiving portion from the light receiving portion surface (surface) side via the surface film.

However, in the surface-incident solid-state imaging device described in US Patent Application Publication No. 2010/014829, the light reflected on the surface of the light receiving portion and the light incident surface of the surface film are different from each other (the reflected light is incident). There is a problem that the light incident from (a place different from the place where the light is formed) interferes (multiple reflection interference) and the sensitivity becomes unstable.

Further, in the back surface incident type solid-state image sensor of Japanese Patent Application Laid-Open No. 2016-58507, a light-shielding film provided on the surface film on the front surface side of the semiconductor substrate is formed in an uneven shape. As a result, the phase of the light reflected by the light-shielding film changes depending on the uneven shape, so that the phase of the light reflected by the light-shielding film and the phase of the light incident on the light receiving surface (back surface) from different parts of the semiconductor substrate are used. Can be different. As a result, interference between the light incident on the light receiving surface of the light receiving portion and the light reflected on the light shielding film side (multiple reflection interference in the semiconductor substrate) is suppressed. As a result, fluctuations in the intensity of the signal detected by the light receiving unit due to light interference are suppressed.

Further, in the back surface incident type solid-state image sensor of Japanese Patent Application Laid-Open No. 2013-518414, a fringe suppression layer made of a refractory metal oxide or a fluoride dielectric is provided on the light receiving surface (back surface of the semiconductor substrate) of the light receiving portion. .. As a result, the light incident on the light receiving surface (back surface of the semiconductor substrate) of the light receiving portion and the light reflected on the front surface side (the surface opposite to the light receiving surface) of the semiconductor substrate interfere with each other (multiplexing in the semiconductor substrate). Reflection interference) is suppressed by the fringe suppression layer. As a result, fluctuations in the intensity of the signal detected by the light receiving unit due to light interference are suppressed.

U.S. Patent Application Publication No. 2010/014829 Japanese Unexamined Patent Publication No. 2016-58507 Japanese Patent Application Laid-Open No. 2013-518414

However, the method for suppressing interference according to Japanese Patent Application Laid-Open No. 2016-58507 and Japanese Patent Application Laid-Open No. 2013-518414 is for light reflected on a surface opposite to the light receiving surface via the semiconductor substrate and light incident on the light receiving surface. It is a method of suppressing interference (multiple reflection interference in a semiconductor substrate), and for interference (multiple reflection interference) that occurs in a surface film provided on the surface of a light receiving portion in a surface-incident solid-state imaging device, light interference is used. The effect of suppressing is not obtained.

The present invention has been made to solve the above problems, and one object of the present invention is solid-state light capable of suppressing the influence of multiple reflection interference on the surface film that protects the light receiving surface. To provide a detector.

In order to achieve the above object, the solid-state light detector according to one aspect of the present invention is provided in contact with a plurality of light receiving portions that output signals according to the intensity of the received light and on the surface of the light receiving portion. comprises a surface membrane for protecting the light receiving portion, and a functional layer provided on the surface of the surface layer, the functional layer has a region where the plurality of different interference characteristics, added together their different interference characteristics By doing so, it is configured to reduce the influence of interference, and the functional layer has 1 / 3.2 to 1 with respect to the shortest wavelength included in the optical wavelength band that reduces the influence of interference. There is a height difference of / 4 wavelengths.

In the solid-state photodetector according to one aspect of the present invention, the functional layer has a plurality of regions having different interference characteristics, and the influence of interference is reduced by adding the different interference characteristics. ing. As a result, the vibration (ripple) of the interference characteristic is averaged by adding the light incident on the regions having different interference characteristics, and the magnitude of the amplitude of the interference ripple is reduced as compared with the single interference characteristic. Will be done. As a result, the influence of multiple reflection interference on the surface film that protects the light receiving surface can be suppressed. As a result, it is possible to prevent the sensitivity from becoming unstable.

In the solid-state photodetector according to the above one aspect, preferably, the refractive index of the functional layer and the refractive index of the surface film are substantially equal, or the functional layer and the surface film are composed of the same substance. With this configuration, it is possible to suppress the reflection of light at the interface between the functional layer and the surface film. As a result, the influence of multiple reflection interference on the surface film can be further suppressed.

In the solid-state photodetector according to the above one aspect, preferably, the functional layer has a stepped shape including a plurality of surfaces at different height positions formed substantially parallel to the light receiving surface. With this configuration, the interference characteristics of light incident on regions (first region, second region) having different height positions of the stepped functional layer can be made different. As a result, the influence of multiple reflection interference can be suppressed by adding light having different interference characteristics and incident on regions having different height positions.

In the solid-state photodetector according to the above one aspect, preferably, the surface of the functional layer on the side where the light is incident has a smooth uneven shape. With this configuration, unlike a flat surface, the interference characteristics of light incident on a surface having a smooth uneven shape are continuously different. By adding these together, the influence of multiple reflection interference can be further suppressed.

In the solid-state photodetector according to the above one aspect, preferably, a functional layer is provided for each light receiving unit. With this configuration, the influence of multiple reflection interference can be suppressed for each light receiving unit.

In the solid-state photodetector according to the above one aspect, preferably, the surface film and the functional layer are integrally formed. With this configuration, the surface film and the functional layer can be manufactured in the same process, so that the manufacturing process of the solid-state photodetector can be simplified.

It is sectional drawing of the solid-state photodetector by 1st Embodiment. It is a top view of the solid-state photodetector (light receiving part) according to 1st Embodiment. It is a figure for demonstrating the optical interference characteristic of the solid-state photodetector according to 1st Embodiment. It is a figure for demonstrating the interference of light in the surface film of a solid-state photodetector by a comparative example. It is a figure for demonstrating the relationship between wavelength and transmittance. It is a figure for demonstrating that the magnitude of light interference is reduced by adding the interference characteristics different from each other. It is a figure (1) for demonstrating the manufacturing method of the solid-state photodetector by 1st Embodiment. It is a figure (2) for demonstrating the manufacturing method of the solid-state photodetector by 1st Embodiment. It is a figure (3) for demonstrating the manufacturing method of the solid-state photodetector by 1st Embodiment. It is an SEM image of the functional layer manufactured by the manufacturing method of the solid-state photodetector according to 1st Embodiment. It is an AFM image of the functional layer manufactured by the manufacturing method of the solid-state photodetector according to 1st Embodiment. It is a cross-sectional profile of the functional layer of FIG. It is a figure for demonstrating that the magnitude of light interference by the functional layer manufactured by the manufacturing method of the solid-state photodetector by 1st Embodiment is reduced. It is a top view of the area of different film thickness. It is a figure which shows the relationship between the film thickness difference and the amount of change in transmittance. It is a figure which shows the relationship between a wavelength and a transmittance. It is a figure which shows the relationship between the wavelength and the amount of change of a transmittance. It is a figure for demonstrating the manufacturing method of the step shape of an equal area. It is a figure which shows the relationship between the thickness d1 and d2, and the amount of change in transmittance. It is a figure which shows the relationship between a wavelength and a transmittance. It is a figure which shows the relationship between the wavelength and the amount of change of a transmittance. It is a figure for demonstrating the manufacturing method of the step shape of area optimization. It is a figure which shows the relationship between the wavelength and the amount of change of a transmittance. It is sectional drawing of the solid-state photodetector by 2nd Embodiment. It is a figure (1) which shows the functional layer of the solid-state photodetector by 2nd Embodiment. It is a figure (2) which shows the functional layer of the solid-state photodetector by 2nd Embodiment. It is a figure (3) which shows the functional layer of the solid-state photodetector by 2nd Embodiment. It is a figure (4) which shows the functional layer of the solid-state photodetector by 2nd Embodiment. It is a figure (1) for demonstrating the manufacturing method of the solid-state photodetector by 2nd Embodiment. It is a figure (2) for demonstrating the manufacturing method of the solid-state photodetector by 2nd Embodiment. It is a figure for demonstrating the effect of the functional layer of the solid-state photodetector by 2nd Embodiment. It is a top view of the solid-state photodetector according to the third embodiment. It is a top view of the solid-state photodetector according to 4th Embodiment. It is sectional drawing of the solid-state photodetector according to the modification of 1st Embodiment.

Hereinafter, embodiments embodying the present invention will be described with reference to the drawings.

[First Embodiment]
The configuration of the solid-state photodetector 10 according to the first embodiment of the present invention will be described with reference to FIGS. 1 to 6.

(Structure of solid-state photodetector)
The solid-state photodetector 10 includes, for example, a CMOS (complementary metallic accessory sensor) sensor including a light receiving unit 11 (photodiode, see FIG. 2) and a CCD (Charge Coupled Device) sensor. In the first embodiment, the solid-state photodetector 10 is a surface-injection type in which light is incident from the side where the wiring pattern 8 is provided.

As shown in FIG. 1, the surface-incident type solid-state photodetector 10 includes a light receiving unit 11. As shown in FIG. 2, a plurality of light receiving units 11 are provided. The plurality of light receiving units 11 are arranged in a matrix in a plan view (viewed from the direction in which light is incident).

Further, as shown in FIG. 1, the light receiving unit 11 has a light receiving surface 11a. The light receiving unit 11 is configured to output a signal according to the intensity of the light incident from the light receiving surface 11a. Further, the light receiving unit 11 is composed of, for example, a photodiode. The photodiode is configured to generate an electric charge when the PN junction included in the semiconductor substrate 11b is irradiated with light.

Further, a surface film 12 for protecting the light receiving surface 11a is provided on the surface of the light receiving surface 11a. The surface film 12 is made of a light-transmitting material such as silicon oxide, silicon nitride, or sapphire. Further, a wiring pattern 8 is formed in the surface film 12. The thickness d0 of the surface film 12 is substantially constant (flat).

Here, in the first embodiment, the functional layer 13 is provided on the surface of the surface film 12 (the surface opposite to the light receiving portion 11 side). The functional layer 13 has an optical interference characteristic generated between the first region (surface 13a) of light incident on the first region (for example, the surface 13a) and the surface film 12, and a second region (for example, the surface 13a). , The optical interference characteristic generated between the second region (surface 13b or surface 13c) of the incident light on the surface 13b or surface 13c) and the surface film 12 is configured to be different. A detailed description of the function of the functional layer 13 will be described later.

Further, in the first embodiment, the functional layer 13 has a stepped shape. That is, the functional layer 13 includes a plurality of surfaces (surfaces 13a, 13b, and 13c) having different height positions formed substantially parallel to the light receiving surface 11a. Further, the shapes of the functional layers 13 provided in the light receiving units 11 are the same as each other. That is, each light receiving portion 11 is provided with a step including three surfaces 13a, 13b, and 13c. The number and height of the steps of the functional layer 13 are not limited to the example shown in FIG. Further, the boundary of one functional unit of the functional layer 13 and the boundary of the light receiving unit 11 do not necessarily have to coincide with each other. In addition, in FIG. 1, an example in which the functional layer 13 has a one-dimensional step shape along the X direction (that is, the cross section in the X direction at any position of the solid-state photodetector 10 is as shown in FIG. 1). Shown. On the other hand, the surfaces (surface 13a, surface 13b and surface 13c) having different height positions are two-dimensionally arranged in various orders in the X and Y directions (for example, the surfaces 13a, 13b and 13c in the X direction). It may be in the order of the surface 13a, the surface 13c, the surface 13b, etc. in the Y direction).

Further, in the first embodiment, the refractive index of the functional layer 13 and the refractive index of the surface film 12 are substantially equal to each other. Specifically, the functional layer 13 is made of the same material as the surface film 12 (for example, a material such as silicon oxide, silicon nitride, or sapphire). The material of the functional layer 13 and the material of the surface film 12 may be different as long as the refractive index is substantially equal.

(Explanation of the function of the functional layer)
Next, the function of the functional layer 13 will be described with reference to FIGS. 3 to 6.

First, as shown in FIG. 4, in the solid-state photodetector 200 according to the comparative example in which the functional layer 13 is not provided, the light (monochromatic light, light C1) incident on the _first point P1 of the surface film 212 at an incident angle θ ₁ ) Is reflected at a reflection angle θ ₁ on the surface of the surface film 212 (the boundary with the air layer). A part of the light incident on the _first point P1 of the surface film 212 at an incident angle θ ₁ is refracted at a refraction angle θ ₂ and penetrates into the surface film 212. Further, a part of the light that has entered the inside of the surface film 212 is reflected at the reflection angle θ ₂ at the boundary between the surface film 212 and the light receiving portion 211. Further, a part of the light that has entered the inside of the surface film 212 is refracted at the refraction angle θ ₃ , enters the inside of the light receiving unit 211, and is detected by the light receiving unit 211.

Further, a part of the light reflected at the reflection angle θ ₂ at the boundary between the surface film 212 and the light receiving portion 211 is refracted at the boundary between the air layer and the surface film 212 and is incident on the air layer (reflected light). .. On the other hand, a part of the light reflected at the reflection angle θ ₂ at the boundary between the surface film 212 and the light receiving portion 211 is reflected again at the point P2 at the boundary between the air layer and the surface film 212 at the reflection angle θ _2. The process proceeds toward the light receiving portion 211 side via the surface film 212. Here, light C2 is incident on the point P2 from the air layer. A part of the light C2 is refracted at the refraction angle θ ₂ and penetrates into the surface film 212. That is, the light C1 and the light C2 interfere with each other (strengthen each other or weaken each other).

ここで、Ｅ_tおよびＥ_iは、それぞれ、透過光電界強度、および、入射光電界強度を表す。また、ｔ_aは、空気層から表面膜２１２に入射する光の振幅透過率を表す。ｔ_cは、表面膜２１２から受光部２１１に入射する光の振幅透過率を表す。ｒ₁は、空気層から表面膜２１２に入射する光の振幅反射率を表す。ｒ₃は、受光部２１１から表面膜２１２に入射する光の振幅反射率を表す。ｎ₂は、表面膜２１２の屈折率を表す。θ₂は、空気層から表面膜２１２に入射する光の屈折角を表す。ｋ₀（＝２π／λ）は、真空中の波数を表す。λ₀は、真空中の光の波長を表す。ｄは、表面膜２１２の厚みを表す。The case where light interference occurs will be described in detail below. The following equation (1) is based on the intensity of transmitted light with respect to the intensity of incident light when multiple reflection interference occurs in the surface film 212 in a three-layer structure consisting of an air layer, a surface film 212, and a light receiving portion 211. Represents.

Here, _Et and E _i represent the transmitted light electric field strength and the incident light electric field strength, respectively. Also, t _a represents the amplitude transmittance of light incident from the air layer on the surface layer 212. t _c represents the amplitude transmittance of the light incident on the light receiving portion 211 from the surface film 212. r ₁ represents the amplitude reflectance of the light incident on the surface film 212 from the air layer. r ₃ represents the amplitude reflectance of the light incident on the surface film 212 from the light receiving unit 211. n ₂ represents the refractive index of the surface film 212. θ ₂ represents the refraction angle of light incident on the surface film 212 from the air layer. k ₀ (= 2π / λ) represents the wave number in vacuum. λ ₀ represents the wavelength of light in vacuum. d represents the thickness of the surface film 212.

ここで、ｎ₁は、空気層の屈折率を表す。θ₁は、空気層から表面膜２１２に入射する光の入射角を表す。ｍは、整数を表す。この式（２）から、光の光路長（式（２）の左辺）が、波長の整数倍になるときに、多重反射干渉の強め合いが生じることがわかる。すなわち、互いに平行な２つの光Ｃ１および光Ｃ２において、光Ｃ１の光路長と光Ｃ２の光路長との差が波長の整数倍になるとき、２つの光（Ｃ１、Ｃ２）において、多重反射干渉の強め合いが生じる。Then, the condition when the left side of the above equation (1) becomes maximum is the following equation (2).

Here, n ₁ represents the refractive index of the air layer. θ ₁ represents the incident angle of the light incident on the surface film 212 from the air layer. m represents an integer. From this equation (2), it can be seen that when the optical path length of light (the left side of equation (2)) becomes an integral multiple of the wavelength, multiple reflection interferences are strengthened. That is, in two light C1 and light C2 parallel to each other, when the difference between the optical path length of light C1 and the optical path length of light C2 is an integral multiple of the wavelength, multiple reflection interference occurs in the two lights (C1 and C2). Strengthens each other.

Next, with reference to FIG. 5, the interference of light of the SiO ₂ film (surface film) formed on the Si substrate (semiconductor substrate) will be described. In FIG. 5, the horizontal axis represents the wavelength of light, and the vertical axis represents the transmittance of the SiO ₂ film (surface film).

When there is light interference (multiple reflection interference) (solid line), the transmittance vibrates violently (ripples) like a vibration waveform as compared with the case where there is no light interference (broken line). Therefore, the intensity of the light reaching the light receiving unit 211 fluctuates, so that the signal output from the light receiving unit 211 becomes difficult to stabilize.

ここで、θは、平行平板に入射する光の入射角を表す。上記の式（３）から、厚みｄが大きくなる程、同じ波長λに対してΔλが小さくなることがわかる。即ち、異なる干渉特性
となることがわかる。The relationship between the ripple interval (Δλ) and the wavelength λ is expressed by the following equation (3). In the following equation (3), assuming light incident on a parallel plate having a thickness d, the light incident on the first point of the parallel plate and undergoing optical action including reflection and refraction, and the first The condition that the light incident on the second point different from the region of No. 1 intensifies each other is obtained based on the fact that the optical path difference between the two lights becomes an integral multiple.

Here, θ represents the incident angle of the light incident on the parallel plate. From the above equation (3), it can be seen that as the thickness d increases, Δλ decreases for the same wavelength λ. That is, it can be seen that the interference characteristics are different.

Next, with reference to FIG. 3, light interference when the functional layer 13 is provided on the surface of the surface film 12 as in the solid-state photodetector 10 of the first embodiment will be described. Note that FIG. 3 shows a state of light reflection / refraction when the refractive index of the surface film 12 and the refractive index of the functional layer 13 are equal. Further, in FIG. 3, unlike FIG. 1, hatching applied to the surface film 12 and the functional layer 13 is omitted.

As shown in FIG. 3, the thickness d1 (distance between the surface 13a and the light receiving surface 11a of the light receiving unit 11) of the portion corresponding to the surface 13a of the surface film 12 and the functional layer 13 and the light receiving surface 11a of the light receiving unit 11 The thickness d2 of the portion corresponding to the surface 13b of the functional layer 13 and the thickness d3 of the portion corresponding to the light receiving surface 11a of the light receiving portion 11 and the surface 13c of the functional layer 13 are different from each other (d1> d2> d3). Here, as shown in FIG. 4, the light incident on one point of the surface 13a and undergoing optical action including reflection and refraction and the light incident on another point different from one point are mutually emitted. They become parallel and interfere (see FIG. 5). The same applies to the surfaces 13b and 13c. However, since the thicknesses d1, d2, and d3 of the portions corresponding to the surfaces 13a, 13b, and 13c are different from each other, the optical interference characteristics of the surfaces 13a, 13b, and 13c are different from each other.

6 (a) to 6 (d) show the respective optics in the structure provided with the surface film 12 and the functional layer 13 having different thicknesses d11 to d14 on the infinitely thick Si substrate obtained by calculation. Interference characteristics are shown. Here, the material of the functional layer is SiO ₂ , and the thicknesses d11 to d14 are 1770 nm, 1800 nm, 1815 nm, and 1845 nm, respectively. As shown in FIGS. 6A to 6D, the optical interference characteristics (ripple amplitude, period, etc.) are different from each other due to the different thicknesses d11 to d14 of the surface film 12 and the functional layer 13. It was confirmed that they were different. Then, when the optical interference characteristics shown in FIGS. 6 (a) to 6 (d) were added together, it was found that the amplitude of the ripple became smaller as shown by the thick line in FIG. 6 (e). That is, when a plurality of different optical interference characteristics are added together, the vibrations (ripples) of the interference characteristics are averaged, and the amplitude of the interference ripples is reduced as compared with a single interference characteristic. As a result, it was confirmed that the influence of multiple reflection interference on the surface film 12 that protects the light receiving surface 11a is suppressed. Note that FIG. 6 (f) shows an average of the transmittances of FIGS. 6 (a) to 6 (d).

Further, when the influence of the multiple reflection interference on the surface film 12 is large, the signal output from the light receiving unit 11 has a characteristic including a relatively large ripple. That is, the change in the sensitivity of the solid-state photodetector 10 when the wavelength is changed becomes large. That is, even if the wavelength of the incident light is slightly deviated, the sensitivity of the solid-state photodetector 10 changes. Therefore, by providing the functional layer 13 to suppress (reduce) the influence of multiple reflection interference on the surface film 12, the ripple of sensitivity to the wavelength of the solid-state photodetector 10 becomes small. As a result, the sensitivity is less likely to change even if the wavelength of the incident light deviates. That is, it becomes possible to stabilize the sensitivity of the solid-state photodetector 10.

(Manufacturing method of solid-state photodetector)
Next, a method of manufacturing the solid-state photodetector 10 will be described with reference to FIGS. 7 to 9.

As shown in FIG. 7, a light receiving unit 11 having a light receiving surface 11a and outputting a signal corresponding to the intensity of the light received on the light receiving surface 11a is formed. Specifically, by repeating steps such as oxidation on the surface of the semiconductor substrate 11b, driving impurities (boron, arsenic, etc.) into the semiconductor substrate 11b, thermal diffusion of impurities, etching, etc., a light receiving portion made of a photodiode or the like is formed. 11 is formed. Further, a wiring pattern 8 (see FIG. 1) is formed by sputtering on the light receiving surface 11a side of the semiconductor substrate 11b. In addition, a plurality of light receiving units 11 are formed in a matrix.

Next, a surface film (passivation film) 12 for protecting the light receiving surface 11a is formed on the surface of the light receiving surface 11a. The surface film 12 is formed so as to cover the entire area of the plurality of light receiving portions 11 arranged in a matrix.

Next, the layer 250 that is the source of the functional layer 13 is formed on the surface of the surface film 12. The layer 250, which is the basis of the functional layer 13, is made of a material having a refractive index substantially equal to that of the surface film 12, and is, for example, silicon oxide, silicon nitride, sapphire, or the like.

Next, the functional layer 13 is formed by etching the layer 250 that is the source of the functional layer 13 provided on the surface of the surface film 12. Specifically, the functional layer 13 has a stepped shape (see FIG. 1) including a plurality of surfaces (surfaces 13a, 13b, and 13c) having different height positions formed substantially parallel to the light receiving surface 11a. The original layer 250 is etched.

In the etching step, the layer 250 that is the source of the functional layer 13 is partially removed by using a chemical solution or a gas activated by plasma discharge. Etching using a chemical solution is called wet etching, and etching by plasma discharge is called dry etching. Further, the etching includes isotropic etching in which etching proceeds at the same ratio in the horizontal direction and vertical direction at the time of etching, and anisotropic etching in which etching proceeds only in the vertical direction. The progress length of etching (magnitude of removal) increases with the processing time. Therefore, the processing time for obtaining a desired depth (length) is determined based on the progress length per unit time determined by the chemical solution or gas used. Hereinafter, the formation of the functional layer 13 having a stepped shape will be specifically described.

First, as shown in FIG. 7, the polyether 300 (photosensitive resin) is applied onto the surface of the layer 250 which is the base of the functional layer 13.

Next, a photomask 310 (a glass plate on which a metal pattern is formed) is arranged on the surface of the photoresist 300. Then, ultraviolet rays are irradiated from the surface of the photomask 310. If the photoresist 300 is of the positive type, the photoresist 300 changes to a material that is soluble in the developing solution due to depolymerization or the like, and if the photoresist 300 is of the negative type, it is polymerized and cured with respect to the developing solution. Changes to an insoluble material. Then, as shown in FIG. 8, the soluble portion is dissolved with a developing solution. For example, the portion of the layer 250 that is the source of the functional layer 13 corresponding to the surface 13a is covered with the photoresist 300.

Then, by performing etching, the portion not covered by the photoresist 300 is removed. Specifically, as shown in FIG. 9, the surface 13b is formed by removing the portion of the layer 250 that is the source of the functional layer 13 other than the portion corresponding to the surface 13a by, for example, anisotropic etching. Will be done. After that, the photoresist 300 is removed. Further, the portion of the layer 250 that is the source of the functional layer 13 corresponding to the surface 13b (and the surface 13a) is covered with the photoresist 300. As a result, the surface 13c (see FIG. 1) is formed by removing the portion of the layer 250 that is the source of the functional layer 13 other than the portions corresponding to the surfaces 13a and 13b by etching. After that, the photoresist 300 is removed. As a result, the functional layer 13 having a stepped shape is formed.

The functional layer and its effect of reducing the influence of multiple reflection interference in the first embodiment manufactured based on the above method will be described with reference to FIGS. 10 to 13. As shown in FIGS. 10 to 12, the functional layer produced based on the above method has four height positions. FIG. 13 shows the transmittance of the functional layer. However, by providing the functional layer manufactured based on the above method, the influence of interference is affected as compared with the case where the functional layer is not provided. It was confirmed that it could be reduced.

Based on the above method, the functional layer and its effect of reducing the influence of multiple reflection interference in the first embodiment manufactured separately will be described with reference to FIGS. 14 to 17. As shown in FIG. 14, a functional layer having two different height positions with the same area ratio is prepared, and the maximum value of the transmittance change at a wavelength of 200 to 1000 nm when one of the height positions is changed is set. The plot is shown in FIG. As shown in FIG. 15, it was confirmed that the change in transmittance was minimized when the difference between the two height positions was 40 nm. This tendency did not depend on the maximum height position (initial film thickness). FIG. 16 shows the transmittance when the height positions of the functional layers are the same, that is, when they have a flat surface, and when the two height positions have a difference of 40 nm. It was confirmed that the amplitude of the interference ripple was particularly reduced with respect to light having a wavelength of 200 to 400 nm. Further, FIG. 17 shows a plot of the amount of change in transmittance (absolute value of the slope of the transmittance). It can be seen that in the case of one type of film thickness, the rate of change was 1.2% at the maximum, but decreased to 0.4%.

Further, the functional layer according to the first embodiment and the effect of reducing the influence of its multiple reflection interference, which are produced separately from the above, will be described with reference to FIGS. 18 to 21. Here, by superimposing etchings of two types of depths, four types of surfaces having an initial film thickness (−0), −d1, −d2, and − (d1 + d2) are created. The area ratios of these surfaces are equal to each other (1: 1: 1: 1). As a result, a functional layer having four different height positions and having different height differences between d1 and d2 is formed, in which d1 and d2 are different combinations. FIG. 19 is a plot of the maximum value of the change in transmittance at a wavelength of 200 to 1000 nm when the height position differences d1 and d2 are changed in these functional layers. As shown in FIG. 19, it was found that the change in transmittance was minimized when d1 = 30 nm and d2 = 45 nm. The transmittances when the height positions of the functional layers are the same, that is, when they have a flat surface, and when the four height positions have differences of 30 nm, 45 nm, and 75 nm, respectively, are shown in FIG. It was confirmed that the amplitude of the interference ripple was particularly reduced with respect to light having a wavelength of 200 to 400 nm. Further, FIG. 21 shows the amount of change in transmittance as in the case of two different heights, and the transmittance when the four height positions have differences of 30 nm, 45 nm, and 75 nm, respectively. However, it was confirmed that the amount of change in transmittance was small.

In the examples of the two functional layers described with reference to FIGS. 14 to 21, there is a step difference of 1 / 3.2 to 1/4 wavelength with respect to the shortest wavelength (200 nm) of the target wavelength. It was confirmed that the transmittance fluctuation was minimized when it was provided. That is, by providing a step of 1 / 3.2 to 1/4 wavelength with respect to the shortest wavelength in the optical wavelength band in which the influence of interference ripple is desired to be reduced, the influence of interference ripple is most affected in the optical wavelength band. It becomes possible to reduce.

Further, with reference to FIGS. 22 to 23, it is shown that the change in transmittance can be further reduced by changing the area ratio of the four different height regions. This is the result of the calculation, not the experimental value. The four different heights (film thicknesses) of the functional layers are the same as the above experimental results, and are 1800 nm, 1770 nm, 1755 nm, and 1725 nm. "Equal area ratio" is the result when the area ratio of each area is 1: 1: 1: 1 as shown in FIG. 18, and "Area optimization" is the result when the area ratio of each area is changed as shown in FIG. The result of optimization is shown so that the maximum value of the change in transmittance is minimized. As a result of the optimization, it can be seen that the maximum value of the amount of change in transmittance is reduced from about 0.2% to about 0.16% in the equal area ratio (Fig. 6). At this time, the area ratio of the film thickness was 1800 nm: 1770 nm: 1755 nm: 1725 nm = 0.219: 0.277: 0.256: 0.249. As a result of the equal area ratio, the amount of change in transmittance was 0.2% or less above, but it is considered that the reason why it exceeds 0.2% here is due to the difference between the experiment and the calculation. ..

(Effect of the first embodiment)
In the first embodiment, the following effects can be obtained.

In the first embodiment, as described above, on the surface of the surface film, the optical interference characteristic generated between the first region of the light incident on the first region and the surface film 12 and the second A functional layer 13 is provided which is configured so that the optical interference characteristics generated between the second region of the incident light in the region and the surface film 12 are different. As a result, the vibration (ripple) of the interference characteristic is averaged by adding the light incident in the first region and the incident light in the second region, and the interference ripple is compared with the single interference characteristic. The magnitude of the amplitude of is reduced. As a result, the influence of multiple reflection interference on the surface film 12 that protects the light receiving surface 11a can be suppressed. As a result, it is possible to prevent the sensitivity from becoming unstable.

Further, in the first embodiment, as described above, the refractive index of the functional layer 13 and the refractive index of the surface film 12 are substantially equal to each other, or the functional layer 13 and the surface film 12 are composed of the same substance. Will be done. As a result, it is possible to suppress the reflection of light at the interface between the functional layer 13 and the surface film 12. As a result, the influence of multiple reflection interference on the surface film 12 can be further suppressed.

Further, in the first embodiment, as described above, the functional layer 13 has a stepped shape including a plurality of surfaces having different height positions formed substantially parallel to the light receiving surface 11a. As a result, the interference characteristics of the light incident on the regions (surfaces 13a, 13b, and 13c) of the stepped functional layers having different height positions can be made different. As a result, the influence of multiple reflection interference can be suppressed by adding different interference characteristics that occur in regions having different height positions.

Further, in the first embodiment, as described above, the functional layer 13 is provided for each light receiving unit 11. As a result, the influence of multiple reflection interference can be suppressed for each light receiving unit 11.

[Second Embodiment]
Next, the second embodiment will be described with reference to FIGS. 24 to 31. In this second embodiment, the functional layer 73 has a smooth uneven shape.

As shown in FIG. 24, in the solid-state photodetector 70 of the second embodiment, the surface 73a of the functional layer 73 on the side where the light is incident has a smooth uneven shape. For example, the surface 73a has a sin wave shape.

Specifically, as shown in FIG. 25, the functional layer 73 has a sin wave shape along the X direction and is formed so as to extend linearly along the Y direction. Further, as shown in FIG. 26, the functional layer 73 having a sine wave shape along the X direction and the functional layer 73 having a sine wave shape along the Y direction may be mixed. Further, as shown in FIG. 27, a plurality of mountain-shaped functional layers 73 may be arranged in a houndstooth pattern. Further, as shown in FIG. 28, a plurality of mountain-shaped functional layers 73 may be arranged in a matrix.

(Manufacturing method of solid-state photodetector)
Next, a method of manufacturing the solid-state photodetector 70 will be described with reference to FIGS. 29 and 30. The manufacturing process of the light receiving portion 11, the surface film 12, and the layer 260 which is the basis of the functional layer 73 is the same as that of the first embodiment.

The layer 260 that is the source of the functional layer 73 is etched so that the surface 73a on the side where the light of the functional layer 73 is incident has a smooth uneven shape. Specifically, as shown in FIG. 29, first, the photoresist 320 (photosensitive resin) is applied on the surface of the layer 260 which is the base of the functional layer 73.

Next, a photomask 330 (a glass plate on which a metal pattern is formed) is arranged on the surface of the photoresist 320. Then, ultraviolet rays are irradiated from the surface of the photomask 330. Then, as shown in FIG. 30, the developer dissolves the soluble moiety. As a result, of the layer 260 which is the source of the functional layer 73, the portion corresponding to the convex portion of the uneven shape is covered with the photoresist 320.

Then, by performing etching, the portion not covered by the photoresist 320 is removed. For example, in the layer 260 that is the source of the functional layer 73, a portion other than the convex portion of the uneven shape is removed by, for example, isotropic etching. After that, the photoresist 320 is removed. As a result, the functional layer 73 having an uneven shape is formed.

Further, as shown in FIG. 31, it was confirmed that the ripples of the functional layer 73 were reduced (see the dotted line in FIG. 31) from the short wavelength side to the long wavelength side. Further, on the short wavelength side, the ripple amplitude is reduced to 1/2 or less. That is, it was confirmed that the influence of multiple reflection interference was suppressed. Since the thickness of the functional layer 73 changes continuously, the interference characteristics of the light incident on the functional layer 73 also continuously change (change). As a result, the number of interference characteristics different from each other is larger than that of the step-shaped functional layer 13 (see FIG. 1), so that it is considered that the effect of suppressing the influence of multiple reflection interference is higher.

(Effect of the second embodiment)
In the second embodiment, the following effects can be obtained.

In the second embodiment, as described above, the surface 73a of the functional layer 73 on the side where the light is incident has a smooth uneven shape. As a result, unlike a flat surface, the interference characteristics of light incident on the surface 73a having a smooth uneven shape are continuously different. By adding these together, the influence of multiple reflection interference can be further suppressed.

[Third Embodiment]
Next, a third embodiment will be described with reference to FIG. In this third embodiment, a plurality of functional layers 83 having different shapes are provided for one light receiving unit 11.

As shown in FIG. 32, in the solid-state photodetector 80 of the third embodiment, a plurality of functional layers 83 are arranged with respect to one light receiving unit 11 (region surrounded by a thick line). For example, the functional layer 83 includes two functional layers 13 (see FIG. 1) and two functional layers 73 (see FIG. 24). Further, in FIG. 32, the areas of the four functional layers 83 in a plan view are configured to be substantially equal to each other, while the shapes and areas of the four functional layers 83 may be different from each other.

(Effect of Third Embodiment)
In the third embodiment, the following effects can be obtained.

In the third embodiment, as described above, a plurality of functional layers 83 are provided for one light receiving unit 11. As a result, even if one functional layer 83 cannot suppress the influence of multiple reflection interference on the surface film 12, the other functional layer 83 can suppress the influence of multiple reflection interference on the surface film 12.

[Fourth Embodiment]
Next, a fourth embodiment will be described with reference to FIG. 33. In this fourth embodiment, the functional layer 93 having one shape is provided across the plurality of light receiving units 11.

Like the functional layer 93 of the solid-state photodetector 90 shown in FIG. 33, the functional layer 93 has a substantially rectangular shape in a plan view, and a plurality of functional layers 93 having a substantially rectangular shape are formed in a matrix. A plurality of arranged light receiving portions 11 may be partially covered. In this case, the boundaries between the functional layers 93 and the boundaries between the light receiving units 11 do not have to match. The plurality of functional layers 93 may have different shapes from each other.

(Effect of Fourth Embodiment)
In the fourth embodiment, the following effects can be obtained.

In the fourth embodiment, as described above, the functional layer 93 having one shape is provided across the plurality of light receiving units 11. As a result, the size of the functional layer 93 is larger than that in the case where the functional layer 93 is formed for each of the plurality of light receiving units 11, so that the functional layer 93 can be easily formed.

[Modification example]
It should be noted that the embodiments disclosed this time are exemplary in all respects and are not considered to be restrictive. The scope of the present invention is shown by the scope of claims rather than the description of the above-described embodiment, and further includes all modifications (modifications) within the meaning and scope equivalent to the scope of claims.

For example, in the first to fourth embodiments, an example of applying the functional layer of the present invention to a surface-incident type solid-state photodetector has been shown, but the present invention is not limited to this. For example, the functional layer (for example, the functional layer 13) of the present invention may be provided in the back surface incident type solid-state photodetector in which light is incident from the side opposite to the side where the wiring pattern is provided. In that case, the functional layer is provided on the back surface (light incident surface).

Further, in the first to fourth embodiments, the refractive index of the functional layer and the refractive index of the surface film are substantially equal to each other, but the present invention is not limited to this. For example, the refractive index of the functional layer and the refractive index of the surface film may differ to some extent.

Further, in the first to fourth embodiments, the functional layer and the surface film are provided as separate bodies, but the present invention is not limited to this. For example, as in the solid photodetector 150 according to the modification of the first embodiment of FIG. 34, the surface film may be configured to serve as a functional layer.

Further, in the first to second embodiments, an example in which the functional layer is formed by etching is shown, but the present invention is not limited to this. For example, the functional layer may be formed by polishing, vapor deposition, crystal growth, or the like.

8 Wiring pattern 10, 70, 80, 90, 150 Solid-state photodetector 11 Light receiving part 11a Light receiving surface 11b Semiconductor substrate 12 Surface film 13, 73, 83, 93, 153 Functional layer 13a, 13b, 13c surface 73a surface

Claims (6)

A plurality of light receiving portions that output signals according to the intensity of the received light, a surface film provided in contact with the surface of the light receiving portion and for protecting the light receiving portion, and a surface film on the surface of the surface film. With a functional layer to be provided
The functional layer has a plurality of regions having different interference characteristics, and is configured to reduce the influence of interference by adding the different interference characteristics.
The functional layer is provided with a height difference of 1 / 3.2 to 1/4 wavelength with respect to the shortest wavelength included in the optical wavelength band for reducing the influence of interference. Detector. The solid-state photodetector according to claim 1, wherein the refractive index of the functional layer and the refractive index of the surface film are substantially equal to each other, or the functional layer and the surface film are made of the same substance. The solid-state photodetector according to claim 1 or 2, wherein the functional layer has a stepped shape including a plurality of surfaces at different height positions formed substantially parallel to the light receiving surface. The solid-state photodetector according to claim 1 or 2, wherein the surface of the functional layer on the side where light is incident has a smooth uneven shape. The solid-state photodetector according to claim 1 or 2, wherein the functional layer is provided for each light receiving unit. The solid-state photodetector according to claim 1 or 2, wherein the surface film and the functional layer are integrally formed.

Images