JPS6260819B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION Field of Industrial Application The present invention relates to an amorphous thin film photoelectric conversion element applied to photoelectric encoders and the like.

1. Configuration of Conventional Example and Its Problems FIG. 1 is a configuration diagram of a photoelectric encoder using a conventional photodiode 4. As shown in FIG. light emitting diode,
A photodiode 4, which is a light receiving element, is arranged facing a light source 1 such as an incandescent lamp, and a shield plate 3 having continuous apertures 2 at an appropriate pitch is arranged therebetween.
The photodiode 4 is a PN junction diode made of single crystal silicon, and a voltage is applied to lead wires 4a and 4b so that a reverse bias is applied to the PN junction. When the shielding plate 3 moves laterally in the figure, intermittent light enters the PN junction of the photodiode 4, and the generated carrier generates a photocurrent signal in the lead wires 4a and 4b as shown in FIG. 2. That is, Shiyahei board 3
A number of pulses are generated according to the amount of movement of the object, and the analog displacement can be quantified. The disadvantage of this conventional example is that the generated photocurrent is small and pulsating, has low sensitivity, and is susceptible to noise.

Further, the photodiode 4 has a large shape, for example, the outer diameter is about 3 mmφ, and the light receiving part is about 1 mmφ, and its resolution with respect to displacement is poor. Furthermore, the thickness of the photodiode element is 2 to 3 mm, making it impossible to reduce the thickness of the entire encoder. The distance between the shield plate 3 and the light source 1 and photodiode 4 is 0.5 to 1 mm, respectively.
That's about it.

OBJECTS OF THE INVENTION The present invention provides a photoelectric conversion element for an encoder that is small and has extremely high sensitivity.

Structure of the Invention The present invention provides a photoelectric transformer using an amorphous silicon thin film that can simultaneously form a plurality of microphotovoltaic element patterns on a single substrate and also provide differential electrical coupling. It is a magnetic element.

DESCRIPTION OF EXAMPLE FIG. 3 shows an example. glass, ceramic,
Two lower electrodes 5a and 5b are formed on an insulating substrate 5 such as a heat-resistant polymer film. The formation method is
Nickel, nickel-chromium alloy, chromium, aluminum, titanium, ITO (In _x Sn ₁ - _x O ₂ ), SnO ₂ , etc. are deposited in vacuum by electron beam evaporation or by sputtering equipment. Next is prozma
An amorphous silicon semiconductor thin film 6 is formed on a substrate 4 heated to 150 to 300° C. by generating glow discharge in silane gas at a pressure of 0.1 to 4 Torr using a CVD device. In this amorphous silicon, unbonded dangling bonds are generated by decomposition of silane (SiH ₄ ).
The localized levels in the band gap are significantly reduced due to atomic compensation. Therefore, if a gas containing an impurity element is mixed during discharge, the impurities can be controlled to a P-type or N-type semiconductor. Therefore, we first formed a 100-500 Å P-type amorphous silicon layer in silane gas containing 0.2-2% diborane (B ₂ H ₆ ), and then a 3000-5000 Å i-type amorphous silicon layer containing no impurities. Finally, an N-type amorphous silicon layer with a thickness of 50 to 5000 Å is formed in a silane gas containing 0.2 to 2% of phosphine (PH ₃ ) to form an amorphous silicon semiconductor thin film 6 having a PiN structure. Furthermore, upper electrodes 7a and 7b are formed in the same manner as the lower electrode. In the case of the embodiment shown in FIG. 3, the upper electrodes 7a and 7b serving as the light-receiving surfaces must be at least transparent electrodes, and are made of ITO or SnO ₂ . FIG. 4 is a sectional view of the embodiment of the photoelectric conversion element shown in FIG. 3. In FIG. 3, two photovoltaic elements are simultaneously formed on one insulating substrate 5, the transparent upper electrode 7a is electrically contacted with the lower electrode 5b of the adjacent photovoltaic element, and the transparent The upper electrode 7b is also patterned to electrically contact the lower electrode 5a of the adjacent photovoltaic element. Therefore, as shown in the circuit diagram of FIG. 5, two photovoltaic elements are connected in series. In FIG. 3, the distance between the transparent upper electrodes 7a and 7b is half the pitch of the aperture 2, so
When the shield plate 3 moves laterally, the upper electrodes 7a and 7
Light is alternately incident on the photovoltaic elements b, and photovoltaic forces are generated alternately in the two photovoltaic elements. Therefore, the lead wires 8a, 8
An alternating current photocurrent as shown by the dotted line in FIG. 8 flows through b. Since the two photovoltaic elements are, so to speak, the same as solar cells, there is no need for a bias power source as in the conventional example.

As is clear from the above description, it is very easy to form two or more photovoltaic elements on a single insulating substrate, and an example thereof is shown in FIG. A comb-shaped common lower electrode 10, 11 is provided on a single insulating substrate 9, an amorphous silicon thin film 12 is provided as a common film in a plasma CVD apparatus, and transparent upper electrodes 13, 14, 15 are further provided. The common lower electrode 10 of adjacent photovoltaic elements is brought into electrical contact, and the transparent upper electrodes 16, 17, 18 are also brought into electrical contact with the common lower electrode 11 of adjacent photovoltaic elements. FIG. 7 is an electrical circuit diagram of the element shown in FIG. 6. Since every other photovoltaic element is connected in parallel and the light is turned on and off at the same time, the photocurrent is integrated, and the lead wires 19 and 20 are connected to a highly sensitive alternating current as shown by the solid line in Figure 8. photocurrent flows.

The upper electrodes 13 to 18 in FIG. 6 can be formed into a fine pattern with a width of 50 μm by photo-etching a transparent electrode deposited on the entire surface. If you make the width 50μ by photo etching, the stiff plate 3 will become
An extremely high-resolution encoder that generates one pulse signal every 0.1 mm of movement can be easily realized. The insulation plate 3 is made into a disk, and the apertures 2 are arranged on its circumference, and photovoltaic elements are placed at a pitch of 0.1 mm to 50 μ on the outer circumference of a circular insulating substrate so as to face it. It is also possible to create an encoder that detects displacement due to rotation. Even if the photoelectric conversion element shown in Fig. 6 has a large opening of 5 mm, for example, 100
By forming an amorphous silicon thin film and photoetching electrodes on a substrate size of mm, 400 elements can be obtained from one substrate, making it mass-producible and inexpensive. Since it is photoetched, the dimensional accuracy of the element arrangement is also high.

In FIG. 4, if the insulating substrate 5 is made of transparent glass and the lower electrodes 5a and 5b are made of transparent electrodes, it is possible to face the thin plate 3 so that light enters from the substrate side. Further, as in the embodiment shown in FIG. 9, a thin insulating film 21 such as SiO ₂ or SiN is provided on a metal plate 25 made of stainless steel or aluminum to form a substrate, which improves the workability of the substrate and improves electromagnetic induction. It can also be used casually.

In addition, in the above example, a continuous amorphous silicon thin film was formed for multiple electromagnetic waves.
A separate amorphous silicon thin film may be used for each electrode.

Effects of the Invention As described above, according to the present invention, sensitivity is high because multiple photovoltaic elements are coupled in a differential type, and since it is made of amorphous silicon, mass production is possible, low cost, and small size. Since a pattern can be formed by photoetching, an excellent photoelectric conversion element for an encoder with high resolution can be obtained.

[Brief explanation of the drawing]

Figure 1 is a block diagram of an encoder using a conventional photodiode, Figure 2 is a diagram showing the photocurrent of the photodiode in Figure 1, and Figure 3 is an encoder using a photoelectric conversion element according to an embodiment of the present invention. A configuration diagram of an encoder, FIG. 4 is a sectional view of the photoelectric conversion element in FIG. 3, FIG. 5 is an electric circuit diagram of FIG. 3, and FIG. 6 is a top view of the photoelectric conversion element according to an embodiment of the present invention. 7th
6 is an electrical circuit diagram of FIG. 6, FIG. 8 is a diagram showing photocurrents generated at terminals 19 and 20 in FIG. 7, and FIG. 9 is a cross-sectional view of a photoelectric conversion element according to a different embodiment of the present invention. . 5... Insulating plate, 5a, 5b... Lower electrode, 6...
...Amorphous silicon thin film, 7a, 7b... Upper electrode.

Claims (1)

[Claims] 1. A plurality of lower electrodes are provided on an insulating substrate, an amorphous silicon thin film is formed thereon, a plurality of upper electrodes are provided thereon facing the lower electrode, and at least one of the upper electrode and the lower electrode is formed. One side is a transparent electrode, and a plurality of photovoltaic elements are formed by the amorphous silicon thin film and the lower and upper electrodes sandwiching it, and the electrode pattern is formed so that the polarities of adjacent photovoltaic elements are connected in reverse order. The formed photoelectric conversion element.