JPH0677507A - Photodetector - Google Patents

Abstract

PURPOSE:To obtain a photodetector of high reliability which is excellent in transmittance in the light transmission band region, by setting the optical film thickness of each layer of a multilayered film so as to increase toward the outside arithmetical series-wise or geometrical series-wise. CONSTITUTION:A multilayered film 12 for shielding infrared radiation is formed on a light receiving substrate 11 for photoelectric conversion. The film 12 separates a plurality of lights different in wavelength in different optical paths, and intensively leads out only the light in a desired band region. The film 12 is constituted by laminating a plurality of dielectric films different in refractive index. When the center wavelength of a light which the multilayered film 12 is to transmit is lambda, the optical film thickness of a matched layer 13 is 0.7lambda/4, and the film is used as an antireflection film to the substrate 11. The optical film thickness of a low refractive index layer 14 is set to be 0.82lambda/8. The optical film thickness from a third layer to an eleventh layer is set to be an arithmetic series whose common difference is 0.03lambda/4. Hence the transmittance in the light transmission band region as a filter for cutting off infrared radiation is increased, and the light receiving sensitivity of a photodetector can be improved.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a semiconductor light receiving element used in, for example, an automatic exposure system of a camera.

[0002]

2. Description of the Related Art Conventionally, when a light receiving element such as a photodiode is used in a camera automatic exposure system or the like, it is necessary to measure the light amount in the visible light range of a human, so an infrared cut filter is provided on the silicon light receiving element. It is necessary to provide a photodiode in which the wavelength sensitivity characteristic of silicon is corrected to the luminosity by providing the above. A glass optical absorption filter is generally used for such a conventional photodiode.

FIG. 8 shows a configuration diagram of a conventional light receiving element. In this structure, the light receiving chip 3 is mounted in the concave portion 2 of the ceramic substrate 1 (stem), the resin 4 is coated on the light receiving chip 3, and the glass light absorption filter 5 is further attached. In the figure, 6 is a metal lead pin.

[0004]

FIG. 9 shows a characteristic curve of a general glass optical absorption filter 5. From this characteristic curve, it is clear that the light transmittance of the light absorption filter 5 made of glass is low in the light transmission band. If the light transmittance of the light absorption filter 5 made of glass is low in the light transmission band, it will not be transmitted much even in the light band desired to be transmitted. Then, the light receiving sensitivity of the light receiving chip 3 is lowered and the output characteristic is lowered.

Further, since the glass light absorption filter 5 depends on the coloring material, it is difficult to change the design and it is also difficult to change the wavelength sensitivity of the light receiving chip 3. in addition,
Discoloration of the glass light absorption filter 5 is also a problem.

Further, the cost of the glass optical absorption filter 5 itself is high.

Further, there are the following problems from the viewpoint of visibility.

FIG. 10 shows the wavelength dependence of the light receiving sensitivity of the light receiving element when there is no filter. Further, FIG. 11 shows the luminosity. As shown in the figure, in order to bring the characteristics of the light receiving element having the characteristics shown in FIG.
It can be seen that the wavelength changes gently with respect to the wavelength m, and it is necessary to correct light having a sensitivity of 800 to 1000 nm, which has a high sensitivity of the light receiving element, by a filter having a sufficiently low transmittance.

In view of the above problems, the present invention provides a light receiving element which has a high light transmittance in the light transmission band, can be easily changed in design, can be made relatively inexpensive, and has high reliability without considering discoloration. To aim.

[0010]

As shown in FIGS. 1 and 6, a light receiving substrate 11 for photoelectric conversion and an infrared ray on the light receiving substrate 11 are cut off. A multi-layered film 12 is formed, and the multi-layered film 12 forms the light receiving substrate 1.
An optical matching layer 13 as a first layer on the first matching layer 1 and the matching layer 1
3 is composed of a low-refractive index layer 14 and a high-refractive index layer 15 which are alternately laminated a number of times, and the optical film thickness of each layer of the multi-layered film 12 is a geometric progression or a geometrical ratio toward the outside. It is set to increase in series.

From the viewpoint of luminosity, in the light-receiving element according to the first aspect, it is preferable that the optical film thickness of the multilayer film 12 is made to be an arithmetic series having different stepwise tolerances.

[0012]

In the means for solving the problems according to the above claims 1 and 3, the infrared shielding of the multilayer film 12 is gently performed by changing the optical film thickness of each layer of the multilayer film 12 in a geometric progression or a geometric progression. These characteristics are exhibited, and the light transmittance in the light transmission band is also high. Therefore, the light receiving sensitivity of the light receiving element in the light transmission band is also improved.

Further, in the light receiving element of the present invention, if the optical film thickness of the multilayer film 12 is made to have an arithmetic series having different stepwise tolerances, a light receiving sensitivity close to the luminosity can be obtained.

[0014]

(First Embodiment) FIG. 1 is a side view of a light receiving element showing a first embodiment of the present invention. As shown in the figure, the light receiving element of this embodiment is one in which a multilayer film 12 for blocking infrared rays is formed on a light receiving substrate 11 for photoelectric conversion.

The light receiving substrate 11 is made of a silicon semiconductor or the like, and when the PN junction portion thereof is irradiated with light having an energy larger than the energy band gap, the electron-hole pairs generated in the crystal are diffused, An electric current flows.

The multilayer film 12 is intended to strongly extract only light in a desired band by separating a plurality of lights having different wavelengths into different optical paths. For this reason, it is desirable that a plurality of dielectric films having different refractive indexes be laminated to be configured.
Therefore, as the multilayer film 12, there is used one in which only one matching layer 13 is formed, and a low refractive index layer 14 and a high refractive index layer 15 are alternately laminated in an arithmetic series on the matching layer 13. .

As the matching layer 13, Si ₃ N ₄ or ZrO is used.
_{2 and the} like, SiO _{2 and the} like are used as the low refractive index layer 14, and TiO _{2 and the} like are used as the high refractive index layer 15. These are laminated on the light receiving substrate 11 by an electron beam evaporation method or the like.
When two or more layers are used as the matching layer 13, it goes without saying that not only the above materials but also various combinations are used.

Then, the length of a quarter of the center wavelength of light to be transmitted by the multilayer film 12 is set to λ (for example, 400 to 500).
nm), the optical film thickness of the matching layer 13 as the first layer is 0.6λ, the optical film thickness of the low refractive index layer 14 as the second layer is 0.425λ, and the optical film thickness as the third layer is 0.425λ. High refractive index layer 1
5 has an optical film thickness of 0.85λ, and thereafter, up to the 25th layer is 0.
The low refractive index layer 14 as the 26th layer is increased by 0.25λ.
Is set to 0.7λ.

In this way, the optical film thickness of each layer of the multilayer film 12 is changed by arithmetic progression so that the multilayer film 12 can be obtained.
The characteristic of the infrared cut filter of (1) represents a gentle characteristic having a certain range, and the light transmittance in the entire light transmission band becomes high. Therefore, the light receiving sensitivity in the light transmission band of the light receiving element is improved.

Actually, when the relationship between the light transmittance (%) and the wavelength (nm) at this time is verified by experimental values, FIG.
It became like. Here, the incident angle on the multilayer film 12 is 0.
The center wavelength is set to 800 nm.

Referring to FIG. 2, in particular, the light wavelength is 400 to 60.
It is clear that the light transmittance in the 0 nm light transmission band is higher than that of the conventional glass light absorption filter shown in FIG. Specifically, in the conventional glass light absorption filter of FIG. 9, the light transmittance at a light wavelength of 500 nm is 80.
%, It is close to 100% in the multilayer film 12 filter of this embodiment shown in FIG.

Therefore, it can be seen that the light receiving sensitivity of the light receiving substrate 11 is greatly improved and the output characteristics are improved.

Further, since the infrared cut filter is composed of the multilayer film 12, when it is desired to change the design of the light transmission stop band and the like, the center wavelength λ of the multilayer film 12 and the film of the multilayer film 12 accompanied by this. It can be changed simply by changing the thickness. Therefore, it becomes easy to change the wavelength sensitivity of the light receiving element.

Furthermore, since the multilayer film 12 functions as a protective layer, it is possible to prevent the deterioration of element characteristics due to changes in temperature or humidity.

Furthermore, since the formation of the multilayer film 12 is generally inexpensive, the cost can be improved.

[0026] Incidentally, although this embodiment used ZrO ₂ as a matching layer, constituted by SiO _2, the first layer and the SiO ₂ layer obtained by adding an optical film thickness of the second layer and the first layer second It is also possible to serve as two layers. Further, when the light receiving element is used by being sealed with a resin layer, since the refractive index outside the multilayer film changes, a matching layer is required at the top of the multilayer film.

(Second Embodiment) FIG. 3 is a side view of a light receiving element showing a second embodiment of the present invention. As shown in the figure, the light receiving element of the present embodiment is the first in that the low refractive index layers 14 and the high refractive index layers 15 are alternately laminated in a geometric progression on the matching layer 13 as the first layer. Similar to the example, but in this example, the optical film thicknesses of the low refractive index layer 14 and the high refractive index layer 15 are configured so as to form an arithmetic series having different stepwise tolerances. is there.

That is, when the length of the central wavelength of the light to be transmitted by the multilayer film 12 is λ, the optical film thickness of the matching layer 13 as the first layer is 0.7λ / 4. The matching layer 1
Reference numeral 3 serves as an antireflection film between the multilayer film 12 excluding the matching layer 13 and the light receiving substrate 11. The optical film thickness of the second low refractive index layer 14 is 0.82λ / 8. The optical thickness from the third layer to the eleventh layer has a tolerance of 0.03λ /
It is an arithmetic series of 4. Specifically, the optical film thickness of the high refractive index layer 15 of the third layer is 0.82λ / 4, the optical film thickness of the low refractive index layer 14 of the fourth layer is 0.85λ / 4, and the optical film thickness of the fifth layer is The optical film thickness of the high refractive index layer 15 is 0.88λ / 4, and is increased by 0.03λ / 4 up to the 11th layer, and the optical film thickness of the 11th high refractive index layer 15 is 1.06λ. It is / 4. The optical thickness from the 12th layer to the 27th layer has a tolerance of 0.
It forms an arithmetic series of 018λ / 4. Specifically, the first
The optical thickness of the two low refractive index layers 14 is 1.078λ /
4, the optical thickness of the high refractive index layer 15 of the 13th layer is 1.09
6λ / 4, the optical thickness of the low refractive index layer 14 of the 14th layer is 1.114λ / 4, and up to the 27th layer 0.018λ /
The optical film thickness of the high refractive index layer 15 of the 27th layer is 1.348λ / 4. 27th to 29th layers
The optical film thickness up to the layer is the same, and is 1.348λ / 4.
The optical film thickness of the low refractive index layer 14 of the 30th layer is 1.3.
It is set to 48λ / 8. Since the 27th layer to the 29th layer can be regarded as an arithmetic series having a tolerance of 0, the 3rd layer to the 29th layer are configured to form an arithmetic series having different tolerances stepwise.

Light transmittance (%) and wavelength (nm) at this time
When the relationship between and was verified by experimental values, it became as shown in FIG. Here, the incident angle to the multilayer film is set to 0 ° and the center wavelength is set to 820 nm. As shown, 600-7
At 00 nm, it changes gently, 800-1000 nm
Shows that a filter with low light transmittance is constructed. The light transmittance in the light transmission band is also higher than that of the conventional glass light absorption filter shown in FIG.

As described above, the light receiving element has
At 700 nm, it changes gently, 800-1000n
In m, it is corrected by a filter with low transmittance, so
The characteristic of the light receiving sensitivity shown in FIG. 5 is obtained, and the light receiving sensitivity close to the visual sensitivity shown in FIG. 11 is obtained.

(Third Embodiment) FIG. 6 is a side view of a light receiving element showing a third embodiment of the present invention. As shown in the figure, the light receiving element of this embodiment is similar to the first embodiment in that the low refractive index layers 14 and the high refractive index layers 15 are alternately laminated on the matching layer 13 as the first layer. However, the difference is that the thickness dimensions of the low refractive index layer 14 and the high refractive index layer 15 are set in geometric progression.

That is, the length of a quarter of the center wavelength of the light to be transmitted by the multilayer film 12 is λ (for example, 400 to 50).
0 nm), the optical film thickness of the matching layer 13 as the first layer is 0.6λ, the optical film thickness of the low refractive index 14 as the second layer is 0.427λ, and the third layer is The optical film thickness of the high refractive index layer 15 is 0.853λ, and thereafter, the 29th layer is increased by 1.02 times, and the low refractive index layer 14 as the 30th layer is set to 0.714λ. .

Light transmittance (%) and wavelength (nm) at this time
When the relationship with and was verified by experimental values, it became as shown in FIG. Here again, the angle of incidence on the multilayer film 12 is set to 0 ° and the center wavelength is set to 800 nm. The light transmittance in the light transmission band in FIG. 7 is also higher than that of the conventional glass light absorption filter shown in FIG. Therefore, the light receiving substrate 1
It can be seen that the light receiving sensitivity of 1 is significantly improved and the output characteristics are improved.

The present invention is not limited to the above embodiments, and it goes without saying that many modifications and changes can be made to the above embodiments within the scope of the present invention.

For example, in the above embodiment, Si ₃ N ₄ , ZrO ₂ , SiO ₂ or TiO ₂ was used as the multilayer film 12, but other oxides are not limited to these dielectric materials. It is also possible to choose.

[0036]

As is apparent from the above description, according to claims 1 and 3 of the present invention, the optical film thickness of each layer of the multilayer film is changed in a geometric progression or a geometric progression. The light transmittance in the light transmission band as the infrared cut filter is increased, and the light receiving sensitivity of the light receiving element is increased.

Further, in the light-receiving element of the present invention, if the optical film thickness of the multilayer film is configured to have an arithmetic series having different stepwise tolerances, a light-receiving sensitivity close to the visual sensitivity can be obtained.

Further, when it is desired to change the design of the light transmission stop band of the multilayer film, it can be changed only by changing the film thickness according to the central wavelength of the multilayer film, and the wavelength sensitivity of the light receiving element can be easily changed. Become.

Furthermore, since the multilayer film functions as a protective layer, it is possible to prevent deterioration of device characteristics due to temperature change or humidity change.

Further, since only the multilayer film is required to be formed, there is an excellent effect that the manufacturing cost can be reduced by reducing the number of parts.

[Brief description of drawings]

FIG. 1 is a side view of a light receiving element showing a first embodiment of the present invention.

FIG. 2 is a characteristic diagram showing a light transmittance with respect to a light wavelength of a multilayer film according to the first embodiment of the present invention.

FIG. 3 is a side view of a light receiving element showing a second embodiment of the present invention.

FIG. 4 is a characteristic diagram showing the light transmittance of the multilayer film according to the second embodiment of the present invention with respect to the light wavelength.

5 is a characteristic diagram showing the light receiving sensitivity of the light receiving element shown in FIG.

FIG. 6 is a side view of a light receiving element showing a third embodiment of the present invention.

FIG. 7 is a characteristic diagram showing light transmittance with respect to light wavelengths of a multilayer film according to a third embodiment of the present invention.

FIG. 8 is a sectional view of a conventional light receiving element.

FIG. 9 is a characteristic diagram showing the light transmittance of a glass light absorption filter that has been conventionally used.

FIG. 10 is a characteristic diagram showing the light receiving sensitivity of a light receiving element having no filter.

FIG. 11 is a diagram showing luminosity characteristics.

[Explanation of symbols]

 11 Photoreceptive Substrate 12 Multilayer Film 13 Matching Layer 14 Low Refractive Index Layer 15 High Refractive Index Layer

Claims (3)

[Claims] 1. A light receiving substrate for photoelectric conversion, and a multilayer film for blocking infrared light formed on the light receiving substrate, wherein the multilayer film is an optical matching layer as a first layer on the light receiving substrate. And a low-refractive index layer and a high-refractive index layer, which are alternately laminated many times on the matching layer, and the optical film thickness of each layer of the multilayer film increases in an arithmetic progression toward the outside. A light-receiving element characterized by being set to 2. The light-receiving element according to claim 1, wherein the optical film thickness of the multi-layer film is configured so as to form an arithmetic series having different tolerances stepwise. . 3. A light receiving substrate for photoelectric conversion, and a multilayer film for blocking infrared light formed on the light receiving substrate, wherein the multilayer film is an optical matching layer as a first layer on the light receiving substrate. And a low-refractive index layer and a high-refractive index layer that are alternately laminated many times on the matching layer, and the optical film thickness of each layer of the multilayer film increases in a geometric progression toward the outside. A light-receiving element characterized by being set to