JPH0685308A - Optical sensor - Google Patents

Abstract

PURPOSE:To provide an optical sensor having a high breakdown voltage against statistic electricity. CONSTITUTION:A third photoelectromotive part, composed of a third electrode film 6, amorphous semiconductor film 4 and metallic electrode 5, is virtually disabled from photoelectric conversion, and a second electrode film 3 is electrically connected with the third electrode film 6. Or, a dielectric film part formed on a first metallic electrode on the amorphous semiconductor film 4 is provided with the electricity accumulation function, and a second photoelectromotive part is connected in parallel with the accumulating part. These constitutions, mentioned above, improve the electrostatic breakdown voltage of the second photoelectromotive part, and thus significantly enhances that of the optical sensor itself.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an optical sensor using a semiconductor film having a photoelectric conversion function.

[0002]

2. Description of the Related Art Currently, most of the materials used as photoelectric conversion materials for photosensors are semiconductor films. Specific examples of this semiconductor film include amorphous materials such as amorphous silicon and CdS. The optical sensor made of these amorphous semiconductors is disclosed in, for example, JP-A-56-13.
There are documents such as No. 5980.

8A and 8B are element structure diagrams of a conventional optical sensor using an amorphous silicon film as a semiconductor film. FIG. 8A is a plan view and FIG. 8B is a view taken along the line AA in FIG. 8A. FIG. In the figure, 1 is a translucent insulating substrate made of glass or the like, 2
Reference numerals 3 and 3 denote a large-area element transparent conductive film (TCO) and a small-area element transparent conductive film (TCO) made of tin oxide, indium tin oxide, or the like serving as a light incident side electrode. Reference numeral 4 denotes a semiconductor film made of an amorphous silicon film having a photoelectric conversion function, which is formed on the transparent conductive films 2 and 3, and is formed by stacking respective conductive semiconductor films of pin parallel to the film surface. To be done.
Reference numeral 5 is a metal film made of aluminum, silver, or the like, which serves as a back electrode of this optical sensor. An equivalent circuit of this optical sensor is shown in FIG.

In the case of such an optical sensor, the thickness of the semiconductor film 4 which is usually used is about 200 as a p-type semiconductor film.
Å, the i-type semiconductor film is about 3000 Å, and the n-type semiconductor film is about 500 Å. Therefore, it is a so-called thin film, which is extremely thin with a total film thickness of less than 1 μm.

[0005]

Although the semiconductor film having the photoelectric conversion function is such a thin film as described above, it has an advantage in cost that only a few raw materials are used, but on the other hand, Many precautions are required in manufacturing and handling.

[0006] Above all, strength against static electricity, so-called breakdown voltage, is an important problem as a result of this thin film. The occurrence of defects due to such static electricity is likely to occur particularly in handling after the final step of forming the back electrode. Also,
Once an accident occurs due to static electricity, the element is almost short-circuited between the light incident side electrodes 2 and 3 and the back electrode 5, and cannot be used as an element.

As a measure against such a problem, conventionally, by increasing the film thickness of a semiconductor film to be used or by forming a metal film which is an electrode on the light incident side more uniformly, for example, a protrusion of the metal film is caused. Attempts have been made to reduce the damage caused by static electricity.

However, the method of increasing the thickness of the semiconductor film cannot be easily implemented because it inherently causes a change in the photosensitivity characteristic which is important as an optical sensor.

Further, in the method of homogenizing the metal film, it is necessary to always strictly control the forming conditions, and it is difficult to carry out the method in terms of mass productivity and reproducibility of the device.

[0010]

The present invention provides an optical sensor having a transparent insulating substrate, a first electrode film, a second electrode film, a third electrode film, an amorphous semiconductor film, and a metal electrode. And
The first electrode film, the second electrode film, and the third electrode film are formed on the transparent insulating substrate, and the first electrode film,
The amorphous semiconductor film is formed on the second electrode film and the third electrode film, and the metal electrode is formed on the amorphous semiconductor film. The electrostatic capacity of the first photovoltaic portion formed by the amorphous semiconductor film and the metal electrode is the second formed by the second electrode film, the amorphous semiconductor film, and the metal electrode. The capacitance is set to be larger than the electrostatic capacity of the photovoltaic portion, and the third photovoltaic portion including the third electrode film, the amorphous semiconductor film, and the metal electrode is substantially photoelectric. The second electrode film and the third electrode film are set in a non-convertible state and electrically connected to each other.

Another aspect of the present invention is a transparent insulating substrate,
In a photosensor having a first electrode film, a second electrode film, an amorphous semiconductor film, a dielectric film, a first metal electrode, and a second metal electrode, on the transparent insulating substrate, The first electrode film and the second electrode film are formed, the amorphous semiconductor film is formed on the first electrode film and the second electrode film, and the amorphous semiconductor film is formed on the amorphous semiconductor film. Has the first metal electrode formed thereon, the dielectric film formed on the first metal electrode, and the second film formed on the dielectric film.
An electrode film is formed, and a capacitance of a first photovoltaic portion formed by the first electrode film, the amorphous semiconductor film, and the first metal electrode is equal to that of the second electrode film and the second electrode film. The capacitance is set to be larger than the capacitance of the second photovoltaic portion composed of the amorphous semiconductor film and the first metal electrode,
A portion composed of the metal electrode, the dielectric film, and the first metal electrode has a function of storing electricity, and the second photovoltaic portion and the portion having the function of storing electricity are connected in parallel. Has a configured configuration.

[0012]

In the photosensor according to the present invention, the first photovoltaic portion is composed of the first electrode film, the amorphous semiconductor film and the metal electrode, and the second electrode film is composed of the amorphous semiconductor film and the metal electrode. Two types of optical sensor units are configured by the second photovoltaic unit. In the plurality of optical sensor units, the first photovoltaic unit is configured for ambient photometry, and the area of the light receiving unit is set to be relatively large. On the other hand, the second photovoltaic section is configured for central photometry and has a relatively smaller area than the first photovoltaic section. As a result, the capacitance of the first photovoltaic section becomes larger than the capacitance of the second photovoltaic section.

With such a configuration, when an electrostatic voltage that destroys the second photovoltaic portion is applied, this portion is electrostatically destroyed because the electrostatic capacitance of the second photovoltaic portion is small. ,
Although the first photovoltaic section functions, it loses its function as an optical sensor.

However, in the present invention, a third electrode film, an amorphous semiconductor film, and a metal electrode are used as the third electrode film.
Since the photovoltaic portion is set to a state in which photoelectric conversion is substantially impossible, and in this state, the second electrode film and the third electrode film are electrically connected, the second photovoltaic film is formed. The electrostatic capacities of the power unit and the third electromotive unit are added, and as a result, the withstand voltage against static electricity of the second photovoltaic unit, which is the rate-determining part of the electrostatic withstand voltage of the photosensor, that is, the electrostatic withstand voltage. Can be increased. As a result, it becomes possible to greatly improve the electrostatic breakdown voltage of the optical sensor.

According to another aspect of the present invention, the dielectric film portion formed on the first metal electrode on the amorphous semiconductor film has a function of storing electricity, and the second photovoltaic portion and the function of storing electricity. Since the part having the structure is connected in parallel,
The electrostatic breakdown voltage of the photovoltaic section can be increased. As a result, the electrostatic breakdown voltage of the optical sensor can be significantly improved.

[0016]

(First Embodiment) FIGS. 1A and 1B are element structure diagrams of an optical sensor according to the present invention. FIG. 1A is a plan view and FIG. 1B is a sectional view taken along line AA of FIG. FIG. Reference numeral 1 in the figure is a transparent insulating substrate made of glass, quartz or the like. Two
Is a transparent conductive film (first electrode film) for a large-area element such as tin oxide or indium tin oxide formed on one main surface of the transparent insulating substrate 1, that is, a first photovoltaic portion, A transparent conductive film (second electrode film) made of a similar material for a small-area element, that is, for a second photovoltaic portion, which is arranged in a circular shape in the central portion so as to measure the central portion of the optical sensor. There is. The large-area element transparent conductive film 2 is arranged and formed so as to surround the small-area element transparent conductive film 3 so that the circumference of the central portion of the photosensor can be measured. Also, 4 is the first
The amorphous semiconductor film is formed so as to cover the photovoltaic portions of the electrode film 2 and the second electrode film 3. The amorphous semiconductor film 4 is substantially a photovoltaic portion, that is, a portion that operates as an optical sensor portion. Here, a p-type amorphous silicon film which is one conductivity type amorphous semiconductor film, an i-type amorphous semiconductor film made of silicon, and another conductivity type semiconductor formed on this amorphous semiconductor film are used. Therefore, the n-type amorphous silicon film is used in this embodiment.

A metal electrode 5 made of a metal material is arranged on the amorphous semiconductor film 4. As a result, the light as an optical sensor uses the incident light from the transparent insulating substrate 1.

Particularly, in this embodiment, the third area photovoltaic element is electrically connected in parallel with the large area element transparent conductive film 2 and the small area element transparent conductive film 3 in parallel with the small area element. An auxiliary electrode film (third electrode film) 6 made of a transparent conductive film is formed and arranged so as to be configured. The auxiliary electrode film 6 surrounds the large-area element transparent conductive film 2 and is arranged and formed around the sensor which is not related to photometry of the optical sensor.

Further, a light shielding film pattern 7 for shielding the power generation region (third photovoltaic portion) formed by the third electrode film 6 from the incident light is provided on the transparent insulating substrate on the incident light side.
That is, it is arranged and formed on the side opposite to the first, second and third electrode film sides with the transparent insulating substrate interposed therebetween. Therefore,
This part is set in a state where photoelectric conversion is substantially impossible.

FIG. 2 is an explanatory diagram of an equivalent circuit of the above-mentioned photosensor, and the reference numerals in the drawing correspond to those in FIG.

Next, a method of manufacturing this optical sensor will be described for each step. First, a glass plate as a transparent insulating substrate 1 is prepared, and a transparent conductive film for a large area element (first
The electrode film 2), the small-area transparent conductive film (second electrode film 3), and the tin oxide to be the auxiliary electrode film (third electrode film 6) are formed by vapor deposition and then patterned.

Then, in the next step, p-type amorphous silicon which is a part of the amorphous semiconductor film 4 is formed by the plasma CVD method, and the large area transparent conductive film 2 and the small area transparent conductive film 3 are formed. Then, patterning is performed so as to cover at least a part of the auxiliary electrode film 6. In the subsequent process, plasma C
A stack of an intrinsic amorphous semiconductor film made of i-type amorphous silicon and a conductive semiconductor film made of n-type amorphous silicon is continuously formed by a VD method.

Further, in the next step, a metal film 5 of aluminum or the like is deposited on the amorphous semiconductor film 4 by a vapor deposition method.
An optical sensor was obtained by forming according to the patterning of the solid line in FIG.

In this embodiment, p-type and n-type conductive semiconductor films are used in view of the structure of the device, but this structure is preferable because the photocarriers can be taken out to the outside more effectively.
However, these conductive semiconductor films are not always necessary. That is, even in the structure in which the n-type conductive semiconductor film is omitted in the embodiment, a so-called pi junction is formed between the p-type and i-type amorphous semiconductors in the channel region, Due to its ability to function as an optical sensor. When the conductive semiconductor films are used, the conductivity type of those semiconductor films needs to be determined in advance in correspondence with the polarity of the applied voltage.

Then, the withstand voltage characteristic against static electricity of the optical sensor obtained as described above was examined. This measurement is shown in FIG.
An optical sensor is arranged in the measuring device shown in (1), a reverse bias voltage is applied to the optical sensor in a pulsed manner, and the defect occurrence rate of the optical sensor for each voltage at this time is investigated.
In the measuring device shown in FIG. 3, V is a DC bias, C is a capacitor having a capacity of 220 PF, S is a changeover switch for changing over to contacts A and B, and PD is an optical sensor.
First, the changeover switch S is set to the contact A side, and the capacitor C is charged with a predetermined voltage by the DC bias V. Next, the changeover switch S is changed over to the contact B side so as to be applied to the arranged test photosensor PD. Then, since a voltage is applied to the photosensor PD in the opposite direction, if the DC bias set at this time is higher than the withstand voltage of the photosensor, the photosensor will be destroyed. The number of photosensors that were destroyed at this time was examined with each sample number being 100, and the number of photosensors that were not destroyed was defined as the non-defective rate (%).

The results are shown in FIG. FIG. 4 is a diagram showing the relationship between the applied voltage to the optical sensor and the non-defective rate. In the optical sensor of FIG. 1 according to this embodiment, the capacitance of the first photovoltaic portion, which is a large-area element, is 450 PF, the electrostatic breakdown voltage of this portion is the broken line A, and the second area is a small-area element. The electrostatic capacity of the photovoltaic portion is 30 PF, and the electrostatic breakdown voltage of this portion is shown by the broken line B. In addition, the electrostatic capacity of the third photovoltaic section composed of the auxiliary electrode is 420 PF. From the results shown in FIG. 4, it can be seen that the conventional photosensor having no third photovoltaic portion coincides with the polygonal line B and has a defect even with an applied voltage of only 50V. On the other hand, the electrostatic breakdown voltage of the photosensor of the present invention is 450 PF, which is simply the sum of the capacitance of the second photovoltaic portion and the capacitance of the third photovoltaic portion, as shown by the broken line X in FIG. It can be understood that the element as a whole is significantly improved as compared with the first photovoltaic section having the electrostatic breakdown voltage capacity.

In the above-mentioned embodiment, light is used from the side of the transparent insulating substrate 1. However, the present invention is not limited to this, and a non-translucent substrate is used as the substrate 1, and a metal electrode is used. By using a transparent conductive film of tin oxide, indium tin oxide, or the like instead of 5, an optical sensor using incident light from the main surface side of the substrate can be obtained.

(Second Embodiment) FIG. 5 is an element structure diagram of another optical sensor according to the present invention. FIG. 5A is a plan view and FIG. 5B is a line BB in FIG. FIG. 1 in the figure
Is a transparent insulating substrate, 2 is a large area element formed on the transparent insulating substrate 1, that is, a transparent conductive film (first electrode film) for the first photovoltaic portion, 3 is a small area element, that is, the first 2 A transparent conductive film (second electrode film) for the photovoltaic portion. The large-area element transparent conductive film 2 and the small-area element transparent electrode film 3 are
Similar to the embodiment, the large-area element transparent conductive film 2 is arranged so as to surround the small-area element transparent conductive film 3 so as to measure the periphery of the central portion of the optical sensor, and the small-area element transparent electrode film 3 is arranged.
Are arranged and formed in a circular shape in the central portion of the optical sensor so as to measure the central portion of the optical sensor. And, 4 is the first electrode film 2
And an amorphous semiconductor film formed so as to cover each electromotive force portion of the second electrode film 3, and is a portion that substantially operates as a photovoltaic portion, that is, an optical sensor portion. Here, a p-type amorphous silicon film that is one conductivity type amorphous semiconductor film, an amorphous semiconductor film made of silicon, and another conductivity type semiconductor formed on this amorphous semiconductor film are used. In the embodiment, an n-type amorphous silicon film is used.

Since the first metal electrode 5 made of a metal material is arranged on the amorphous semiconductor film 4, the light as the photosensor utilizes the incident light from the transparent insulating substrate 1. There is.

In the second embodiment, the large area element transparent conductive film 2 and the small area element transparent conductive film 3 are:
A dielectric film 8 is formed and arranged on the same plane, and on top of this, a dielectric film 8 electrically connected and formed in parallel with the small area element via the first metal electrode 5. The dielectric film 8 is composed of Si ₃ N ₄ . It should be noted that SiC or SiO ₂ can be used as the material forming the dielectric film 8. Second metal electrodes are formed on the dielectric film 8, and these and the first metal electrode film 5 constitute a portion having a function of storing electricity, that is, a capacitor. The portion having the function of storing electricity is electrically connected in parallel with the second photovoltaic portion by the first metal electrode 5 and the second metal electrode 9.

FIG. 6 is an explanatory diagram of an equivalent circuit of the above-mentioned photosensor, and the reference numerals in the drawing are the same as those in FIG.

Next, the method of manufacturing this optical sensor will be described with reference to the first method.
Only parts different from the embodiment will be described. Transparent insulating substrate 1
After forming tin oxide to be the transparent conductive film for the large area element (first electrode film 2) and the transparent conductive film for the small area (second electrode film 3) by vapor deposition on one surface of, the patterning is performed.

In the next step, p-type amorphous silicon which is a part of the amorphous semiconductor film 4 is formed by plasma CVD, and the large area transparent conductive film 2 and the small area transparent conductive film 3 are formed. Patterning is performed so as to cover at least a part thereof. Then, subsequently, a stacked body of an intrinsic amorphous semiconductor film made of n-type amorphous silicon and a conductive semiconductor film made of n-type amorphous silicon is continuously formed by a plasma CVD method.

Further, in the next step, a film of the first metal electrode 5 of aluminum or the like is formed on the amorphous semiconductor film 4 by the vapor deposition method according to the patterning of FIG. 5A. Further, the dielectric film 8 and the second metal electrode 9 were formed in this order by CVD and vapor deposition.

Next, the characteristics of the thus obtained optical sensor against static electricity were examined. For this measurement, the measuring device shown in FIG. 3 was used as in the first embodiment.

The results are shown in FIG. FIG. 7 is a diagram showing the relationship between the voltage applied to the optical sensor and the non-defective rate. In the optical sensor of FIG. 5 which is the second embodiment, the electrostatic capacity of the first photovoltaic portion, which is a large area element, is 450 PF, and the electrostatic breakdown voltage of this portion is the broken line A, which is a small area element. The electrostatic capacity of the second photovoltaic portion is 30 PF, and the electrostatic breakdown voltage of this portion is shown by the broken line B. In addition, the electrostatic capacitance of the sum of the portion having the function of storing electricity with the second photovoltaic portion in the optical sensor of the present invention is 400 PF.

From the results shown in FIG. 7, the conventional photosensor having no third photovoltaic section coincides with the broken line B, and a defect occurs even with an applied voltage of only 50 V. It can be understood that the electrostatic breakdown voltage of the optical sensor of the present invention is significantly improved as shown by the broken line Y in FIG.

In the second embodiment, the portion having the function of storing electricity is formed of the dielectric film, but instead of this, even if the element is formed by using the amorphous semiconductor film, the same applies. Since it operates, this portion can be shielded from light and the withstand voltage and withstand voltage characteristic of the optical sensor can be improved. Further, in the photosensor of the second embodiment, since the portion having the electricity storage function is laminated on the photovoltaic portion, it can be configured without enlarging the element in plan view, which contributes to downsizing of the element. There is a feature that you can do it.

[0039]

According to the optical sensor of the present invention, the third electrode film of the third photovoltaic portion and the second electrode film of the second photovoltaic portion are set in a state in which substantially no photoelectric conversion is possible. Are electrically connected to each other, the electrostatic capacities of the second photovoltaic portion and the third electromotive portion are added to each other, and as a result, it is a rate-determining portion of the electrostatic breakdown voltage of the optical sensor. The withstand voltage against static electricity of the second photovoltaic section, that is, the withstand voltage can be increased.

Further, since the dielectric film portion having the function of storing electricity has a structure in which the second photovoltaic portion is connected in parallel, the electrostatic breakdown voltage of the second photovoltaic portion can be increased. In addition to the above effect, since the dielectric film portion is formed by being laminated, it can contribute to miniaturization of the optical sensor.

As described above, the electrostatic withstand voltage of the optical sensor as a whole can be greatly improved, and its industrial value is extremely large.

[Brief description of drawings]

FIG. 1 is an element structure diagram of an optical sensor of the present invention.

FIG. 2 is an explanatory diagram of an equivalent circuit of the optical sensor of the present invention.

FIG. 3 is a conceptual explanatory view of an electrostatic breakdown voltage measuring device.

FIG. 4 is a diagram showing changes in electrostatic withstand voltage of the optical sensor of the first embodiment.

FIG. 5 is an element structure diagram of another optical sensor of the present invention.

FIG. 6 is an equivalent circuit explanatory diagram of another optical sensor of the present invention.

FIG. 7 is a diagram showing changes in electrostatic breakdown voltage of the optical sensor of the second embodiment.

FIG. 8 is an element structure diagram of a conventional photosensor.

FIG. 9 is an explanatory diagram of an equivalent circuit of a conventional photosensor.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 ... Transparent insulating substrate 2 ... Large area element transparent conductive film (first electrode film) 3 ... Small area element transparent conductive film (second electrode film) 4 ... Amorphous semiconductor Film 5 ... Metal electrode (first metal electrode) 6 ... Auxiliary electrode film (third electrode film) 7 ... Light-shielding film pattern 8 ... Dielectric film 9 ... Second metal electrode

Claims (2)

[Claims] 1. A transparent insulating substrate, a first electrode film, and a second electrode film.
In an optical sensor having an electrode film, a third electrode film, an amorphous semiconductor film, and a metal electrode, the first electrode film, the second electrode film and the third electrode film are provided on the transparent insulating substrate. The amorphous semiconductor film is formed on the first electrode film, the second electrode film, and the third electrode film, and the metal electrode is formed on the amorphous semiconductor film. The first photovoltaic part formed of the first electrode film, the amorphous semiconductor film, and the metal electrode has a capacitance of the second photovoltaic part.
The capacitance is set to be larger than the electrostatic capacity of the second photovoltaic portion composed of the electrode film, the amorphous semiconductor film, and the metal electrode, and the third electrode film, the amorphous semiconductor film, and The third photovoltaic part composed of the metal electrode is set to a state in which substantially no photoelectric conversion is possible, and the second electrode film and the third electrode film are electrically connected. Optical sensor. 2. A transparent insulating substrate, a first electrode film, and a second
An optical sensor having an electrode film, an amorphous semiconductor film, a dielectric film, a first metal electrode, and a second metal electrode, wherein the first electrode film and the second electrode are provided on the transparent insulating substrate. An electrode film is formed, the amorphous semiconductor film is formed on the first electrode film and the second electrode film, and the first metal electrode is formed on the amorphous semiconductor film. Is formed, the dielectric film is formed on the first metal electrode, the second electrode film is formed on the dielectric film, the first electrode film and the The capacitance of the first photovoltaic portion formed by the amorphous semiconductor film and the first metal electrode is formed by the second electrode film, the amorphous semiconductor film, and the first metal electrode. Is set to be larger than the electrostatic capacity of the second photovoltaic section, and the second metal electrode, the dielectric film, and the An optical sensor in which a portion including the first metal electrode has a function of storing electricity, and the second photovoltaic portion and the portion having the function of storing electricity are connected in parallel.