JPH0246887B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a photoelectric converter for illumination meters and a method for manufacturing the same, and the present invention relates to a photoelectric converter for illumination meters and a method for manufacturing the same, and it is possible to easily produce a photoelectric converter having spectral sensitivity characteristics that match the visibility curve, which is extremely important as a photoelectric converter for illumination meters. The aim is to provide it at a low cost.

Photodetectors for illuminance meters that have been known so far can be roughly divided into: A phototube type, B photocell type using selenium photocells or silicon solar cells, and C photoconductor type using photoconductors such as CdS. There is something like that.

However, since the spectral sensitivity characteristics of these devices do not match the visibility curve required for a luminometer, a visibility correction filter is required. In general, phototube type detectors (A) are expensive, while those using selenium photocells (B) are inexpensive, but have problems with fatigue and temperature characteristics, and in C, CdS as a photoconductor is manufactured using a manufacturing method. Moreover, the vapor deposition method, gas phase reaction, and sintering method have the problem that uniform thin films cannot be produced with good reproducibility, in large quantities, and at low cost.

Therefore, among the many light-receiving elements, it is considered most desirable to use a silicon photovoltaic cell as a photodetector for an illumination meter in terms of cost, reliability, and various characteristics.

However, as mentioned above, even with silicon photovoltaic cells,
In order to use it as a photodetector for an illumination meter, a visibility correction filter is required to bring the spectral sensitivity characteristics close to the visibility curve.These filters can be selected from various types, such as gelatin membranes and glass filters, depending on the type of element. There are many different types, and their accuracy varies greatly depending on whether they satisfy JIS standards (JIS-C-1609) or legal standards such as the Measurement Act.

The present invention uses a photovoltaic type PN junction silicon photodiode, which is extremely excellent in aspects other than spectral sensitivity characteristics and is easily available, as a light receiving element, and improves its visibility correction filter, thereby improving its spectral sensitivity characteristics. The object of the present invention is to provide a photoelectric converter for an illuminance meter that closely matches the visibility curve and fully satisfies legal standards.

To describe the present invention in more detail, the light receiving surface of a PN junction type silicon photodiode is coated with a CdS thin film,
By combining this with a commercially available visibility correction filter, such as the cyan blue glass filter C-52S manufactured by Toshiba Glass Co., Ltd., a photoelectric sensor for illumination meters with a spectral sensitivity curve that closely matches the visibility curve can be used. The converter can be easily obtained.

The spectral sensitivity curve obtained by combining a commercially available cyan blue glass filter and a PN junction silicon photovoltaic cell has a maximum sensitivity that relatively matches the peak of the luminous sensitivity line at 550 nm. On the shorter wavelength side, the luminosity curve exhibits a value larger than the relative value of each wavelength, and cannot satisfy the value specified by the legal illuminometer.

The present invention utilizes the synergistic effect of the filter effect of the CdS thin film and the visibility correction filter to reduce the deviation from the visibility curve, especially on the short wavelength side, to the relative sensitivity value at each wavelength of the visibility curve. It is something that can be done. In other words, by using a CdS thin film to cut out the excess sensitivity on the short wavelength side, we have created a photoelectric converter for illumination meters that has extremely high assembly precision, is inexpensive, and has an ideal spectral sensitivity curve. can get.

The CdS thin film used for such purposes is best integrated with a silicon photodiode, and the important requirements for this thin film are to cut only the extra sensitivity on the short wavelength side and reduce the sensitivity on the long wavelength side. The reason is that the transmittance is high. To achieve this, the CdS thin film must be uniform, dense, thin, and have good crystallinity, and considering that it can be easily produced, it is desirable to have a stoichiometric composition. .

Hereinafter, the details of the present invention will be explained with reference to Examples.

Figure 1 shows the photodetector used in the present invention.
A of the figure shows a PN junction type silicon photodiode.
is a top view, and B is a cross-sectional view.

In FIG. 1, the silicon single crystal substrate 1 used for producing the PN junction type silicon photodiode according to the present invention is of N type and has a specific resistance of 1 to 5 Ω.
− cm ² . First, when creating a PN junction type silicon photodiode, we used vapor phase diffusion using PClO ₃ to easily form an ohmic electrode around the silicon single crystal substrate surface, which will serve as the light receiving surface.
Form an N ⁺ diffusion layer 2. Next, in order to form a PN junction layer in a portion other than the N ⁺ diffusion layer, a P-type diffusion layer 3 is formed by vapor phase diffusion using BBr ₃ . The thickness of the PN junction layer formed at this time was approximately 1.0μ.
It is m. Further, the light receiving surface is covered with a thermal oxide film 6 to provide an antireflection effect. Next, in order to attach the electrodes, a frame-shaped electrode was placed on the previously formed N ⁺ diffusion layer, and an electrode was placed near the periphery of the P-type diffusion layer using photoresist and etching methods to equally divide the light-receiving area into four parts. Al shown as 5a, 5b, 5c using
Form an electrode. Furthermore, CdS plays a role as a visibility correction filter, which is an important element of the present invention.
A thin film 7 is formed.

This CdS thin film 7 is formed by the following chemical precipitation method. That is, as shown in FIG. 2, there is a substrate holder 9 in which a silicon photodiode 8 is set, which is masked with a resist such as a photoresist except for the P diffusion layer which becomes the light receiving part of the silicon photodiode, and cadmium chloride, aqueous ammonia, and ammonium chloride. ,
A CdS precipitation solution 10 consisting of CdS and thiourea is placed in a precipitation reaction vessel 11 such as a beaker, and the substrate holder 9 is rotated by a rotating shaft 12 while the precipitation reaction vessel 1 is heated.
Approx.
After dipping for a minute, a CdS thin film with a uniform thickness of 0.1 μm with strong adhesion and no pinholes is formed on the light-receiving surface of the silicon photodiode. This membrane is approximately
It consists of a mixed crystal of oriented cubic and hexagonal crystals consisting of fine crystal grains of 0.08 μm. Note 14
is a bathtub agitator.

The CdS precipitation solution used at this time was an alkaline aqueous solution, and its composition was as follows.

0.1 mol CdCl ₂ aqueous solution 10 parts by volume 14% ammonia water 8.5 parts by volume 2.5 mol NH ₄ Cl aqueous solution 2.5 parts by volume 1 mol thiourea aqueous solution 50 parts by volume In this way, the light-receiving surface is coated with the CdS thin film 7. As shown in FIG. 3, the silicon photodiode 8 is fixed to an insulating stem 16 on which a lead pin 15 is provided in advance, and the ohmic electrode of the diode 8 and the lead pin 15 are connected by bonding with a gold wire 17, and a photoelectric conversion output is obtained. can be taken outside.

As is clear from FIG. 4, an air gap is provided above the silicon photodiode 8 fixed to the stem 16, and a cyan blue glass filter 18, which together with the CdS thin film 7 constitutes a visibility correction filter, is fixed above the air gap. This cyan blue glass filter 18 is a blue transparent glass plate whose main components are phosphorus pentoxide P ₂ O ₅ , aluminum oxide Al ₂ O ₃ , copper carbonate CuCO ₃ , and the like.

The aforementioned P-N junction layer has a silicon photodiode 8 with a thickness of 1.0 μm, a CdS film 7 with a thickness of 0.1 μm, and a thickness of
The spectral transmittance of the 1.0 mm cyan blue filter 18 itself is as shown in FIG. 5 as 8, 7, and 18, respectively, and a unique transmittance curve was obtained for CdS.

Further, the CdS film 7 is deposited on the light receiving surface of the silicon photodiode 8 by the chemical deposition method described above, and the visibility correction filter 18 is set above the photodiode 8 as shown in FIG. When we measured the spectral sensitivity characteristics of the current, we found a spectral sensitivity curve 20 that closely matched the visibility curve 19 in Figure 6.
By combining a silicon photodiode with the CdS film of the present invention coated on its light-receiving surface and a cyan blue glass filter as a visibility correction filter, an extremely excellent photoelectric converter for illumination meters can be obtained. I was able to confirm that it was obtained.

In this way, by depositing the CdS thin film that constitutes the visibility correction filter together with the cyan blue glass filter on the light-receiving surface of the silicon photodiode, the photoelectric converter for the illumination meter can be assembled with high precision, and the filter part It is extremely robust and resistant to moisture, and has ideal spectral sensitivity characteristics by combining the excellent characteristics of silicon photodiodes as photodetectors for illumination meters and the filter performance of visibility correction filters. It is possible to provide a highly sensitive and highly reliable illumination meter.

[Brief explanation of the drawing]

Fig. 1 shows a silicon photodiode as a photoelectric conversion element used in an example of the present invention, A is a top view, B is a cross-sectional view, and Fig. 2 shows a CdS thin film coated on the light-receiving surface of the photodiode. 3 is a perspective view of assembling a photoelectric converter for an illumination meter using the same photodiode, FIG. 4 is a cross-sectional view of the same photoelectric converter, and FIG. 5 is a silicon photodiode, etc. FIG. 6 is a diagram showing a visibility curve and a spectral sensitivity curve of a photoelectric converter for an illumination meter according to the present invention. 1...N-type substrate, 2...N ⁺ diffusion layer, 3...P
Type diffusion layer, 5a, 5b, 5c... Aluminum electrode, 7... CdS thin film, 8... Silicon photodiode, 16... Insulating stem, 17... Gold wire,
18...Cyan blue glass filter.

Claims (1)

[Scope of Claims] 1. A highly concentrated impurity diffusion layer of the same conductivity type as the substrate from which the ohmic electrode is taken out is provided around one main surface of a silicon semiconductor substrate having N or P type conductivity, and A CdS thin film is deposited on one main surface of a P-N junction photodiode, which has an impurity diffusion layer exhibiting P or N type conductivity, which is opposite to that of the substrate, formed in a portion other than the periphery of the main surface. a photoelectric conversion element,
A photoelectric converter for an illumination meter, comprising a cyan blue glass filter placed on the light-receiving surface side of this element. 2. The photoelectric converter for an illumination meter according to claim 1, wherein the CdS thin film deposited on one main surface of the silicon semiconductor substrate has a stoichiometric composition. 3. A step of forming a highly concentrated impurity layer of the same conductivity type as the substrate from which an ohmic electrode is taken out around one main surface of a silicon semiconductor substrate having an N or P type conductivity type, and a step of forming a high concentration impurity layer of the same conductivity type as the substrate from which an ohmic electrode is taken out, and forming a P-N junction as a photodiode by diffusing impurities of a conductivity type opposite to that of the substrate;
a step of forming independent ohmic electrodes on each of the two impurity diffusion layers; a step of depositing a CdS thin film on the one main surface after the electrode formation;
A method for manufacturing a photoelectric converter for an illumination meter, comprising the step of arranging a cyan blue glass filter on a thin film. 4. The method of manufacturing a photoelectric converter for an illumination meter according to claim 3, wherein the CdS film deposited on the one principal surface is formed by a chemical precipitation method.