JPH0770754B2 - Method for forming resistance layer in semiconductor optical position detector - Google Patents

Description

The present invention relates to a method for forming a resistance layer in a semiconductor optical position detector.

(Prior Art) The applicant previously proposed a semiconductor optical position detector according to Japanese Patent Application No. 161470/1982.

This semiconductor photo-position detector includes a photovoltaic layer made of amorphous silicon, a resistive layer is formed on one or both surfaces of the photovoltaic layer, and a collector pole is arranged on the resistive layer. It has the configuration

(Problems to be Solved by the Invention) The resistance layer of the semiconductor optical position detector according to the above-mentioned prior application is formed by a manufacturing method such as a sputtering method or a vacuum deposition method, and its material is ITO (indium-tin-oxide). ) Is used.

By the way, in order to enhance the detection sensitivity of this type of detector, it is desirable to increase the resistance value of the resistance layer.
When is used as the material of the resistance layer, the sheet resistance stably obtained is several + Ω / □, and it is difficult to obtain the sheet resistance of several hundreds Ω / □ or more with good reproducibility.

That is, FIG. 7 illustrates the relationship between the oxygen partial pressure and the sheet resistance value when the resistance layer of ITO having a film thickness of about 1000 Å is formed by the sputtering method using the substrate temperature as a parameter. It is difficult to obtain a sheet resistance of several hundred Ω / □ or more because it is necessary to form the resistance layer under an oxygen partial pressure where the change in sheet resistance value is gentle in order to obtain a layer.

The sheet resistance can be increased by reducing the film thickness. For example, if the film thickness (1000Å) is set to 1/10 or less, a sheet resistance of several hundred Ω / □ can be obtained. However, this method is not practical because the reproducibility is extremely poor in terms of manufacturing technology.

(Means for Solving Problems) The present invention relates to a photovoltaic layer having a pin structure made of amorphous silicon, a light-transmissive resistance layer formed on at least the light receiving surface side of the photovoltaic layer, It is applied to a semiconductor optical position detector equipped with a collecting electrode for extracting a position signal arranged in a resistance layer, and the resistance layer is a substrate temperature of 300 to 400 ° C using a material mainly containing tin oxide, and oxygen. Partial pressure 5 × 10 ^-4 ~
The feature is that the film is formed by a sputtering method under the condition of 5 × 10 ⁻⁵ Torr.

(Function) Since the resistance layer is formed by using a material mainly containing tin oxide under a predetermined temperature and an oxygen partial pressure, a high in-plane average resistance value can be obtained and the in-plane resistance distribution can be improved. A relatively uniform resistance layer is formed with good reproducibility.

(Example) Hereinafter, an example of the present invention will be described in detail with reference to the accompanying drawings.

FIG. 1 (a) is a plan view showing an example of a semiconductor optical position detector to which the present invention is applied, and FIGS. 1 (b) and (c) are lines AA 'and B- in FIG. 1 (a), respectively. It is sectional drawing by the B'line.

In this semiconductor optical position detector, a resistance layer 2 (transparent conductive film) containing tin oxide (SnO ₂ ) as a main material is formed on a substrate 1 made of glass or the like by a sputtering method. A photovoltaic layer 3 is formed on the upper surface of the resistance layer 2, and a resistance layer 4 made of the same material as the resistance layer 2 is formed on the upper surface of the resistance layer 2 by the same method.

The photovoltaic layer 3 has a three-layer structure, and although not shown, the upper layer, the middle layer and the lower layer are formed of P-type amorphous silicon, i-type amorphous silicon and n-type amorphous silicon, respectively. Note that these layers are CVD
It is formed by the method.

A pair of rod-shaped x-direction collector electrodes 5a, 5b are arranged opposite to each other at both ends of the resistance layer 2, and a pair of y-direction collector electrodes 6a, 6b are similarly arranged at both ends of the resistance layer 4. It is arranged opposite.

The equivalent circuit of this position detector is represented as shown in FIG. That is, at the light irradiation position 7, the current source 8 and the ideal diode 9 are formed between the resistance layers 2 and 4, and the resistor 10 and the junction capacitance 11 are formed between the resistance layers 2 and 4 except the light receiving surface. The resistance layers 2 and 4 are composed of distributed resistances 12 and 14, respectively.

Here, the position detecting action of the semiconductor optical position detector will be described.

As shown in FIGS. 4A, 4B and 4C, when the light beam A is incident on the semiconductor optical position detector, a photo-generated current is generated at the incident position P. At this time, in the resistance layer 2, the current is divided by the resistances r _x1 and r _x2 between the incident position P and the electrodes 5a and 5b, and in the resistance layer 4, the resistances r _y1 and r between the position P and the electrodes 6a and 6b. _{Since the} current is divided by _y2 , the currents I _x1 and I _x2 from the electrodes 5a and 5b and the electrodes 6a and 6b, respectively.
The currents I _y1 and I _y2 are taken out from each.

The divided currents I _x1 , I _x2 , I _y1 , I _y2 are usually input to a signal processing circuit as illustrated in FIG.

This processing circuit includes a preamplifier 13 to which the above currents are input.
16, adders 17 and 18 for obtaining current sums I _x1 + I _x2 and I _y1 + I _y2 , and subtractors for obtaining current differences I _x1 −I _x2 and I _y1 −I _y2
19 and 20, and a divider 21 and a ratioer which obtains a ratio between the outputs of the adder 17 and the subtractor 19 and a ratio between the outputs of the adder 18 and the subtractor 20.
22 and each of the dividers 21 and 22 outputs a light incident position signal P _{x in the} x direction shown in the following formula (1) and a light incident position signal P _{y in the} y direction shown in the following formula (2). .

According to this processing circuit, a position signal that is not affected by the intensity of incident light and its change can be obtained.

Here, focusing on the position detection only in the x direction, the resistance between the electrodes 5a and 5b in the resistance layer 2 is r, the distance L between the electrodes 5a and 5b is L,
Each load resistance connected to electrodes 5a and 5b (amplifier 13,14
If the input resistance of is equal to R, the equivalent circuit shown in FIG. 6 is obtained.

According to this equivalent circuit, I _x1 and I _x2 are respectively _calculated based on Kirchhoff's law of division. However, ρ is expressed as the resistivity of the resistance layer 2, and when these I _x1 and I _x2 are substituted into the above equation (1), A relationship is obtained. In order to increase the output of the position signal P _x from the equation (5), (R / r) should be made as small as possible. The same applies to the output of the position signal P _y .

In order to reduce (R / r), it is sufficient to reduce R or increase r, but the load resistance R cannot be reduced unnecessarily due to the restriction of the processing circuit.

In this embodiment, the resistance layer is formed by the sputtering method using a material mainly containing tin oxide. At that time, the substrate temperature is in the range of 300 to 400 ° C., and the oxygen partial pressure value is 5
It is set in the range of × 10 ^{-4 to} 5 × 10 ^-5 Torr.

If the resistance layer is formed under such conditions, as shown in FIG. 2, the resistance layer to be formed can have an extremely high sheet resistance value (100Ω / □ or more at a film thickness of 1000Å). .

Therefore, according to the present embodiment, the value of (R / r) can be reduced and the output of the position detection signal can be dramatically increased, and the S / N ratio can be improved accordingly.

Further, as is clear from the fact that the sheet resistance change characteristics in the temperature range of 300 to 400 ° C are close to each other, it is clear that within the above temperature range, a sheet resistance close to each other can be obtained, and the above characteristics are not so sharp. Since it has not risen rapidly, high sheet resistance can be obtained under a wide oxygen partial pressure range of 5 × 10 ^{−4 to} 5 × 10 ⁻⁵ Torr. Therefore, a resistance layer having a relatively uniform in-plane resistance distribution can be formed with good reproducibility.

FIG. 8 exemplifies the output characteristics of the semiconductor optical position detector in which the resistance layers 2 and 4 are formed of the above-mentioned material mainly containing tin oxide. In the figure, the broken line shows the irradiation position of the light beam, and the solid line shows the position detected by this detector.

If the resistance layers 2 and 4 are formed by using 100% tin oxide, the resistance value becomes unnecessarily large. Therefore, as the material for the resistance layer, tin oxide mixed with an appropriate amount of impurities such as antimony is used. Is used.

The semiconductor photo-position detector has a structure in which resistance layers are arranged on both sides of the photovoltaic layer 3, but the present invention is a detector having a structure in which the resistance layer is formed only on one side of the photovoltaic layer. Of course, in this case, the resistance layer is provided with collector electrodes 5a, 5b, 6a, 6b in the x and y directions, and a common electrode is provided on the other surface of the photovoltaic layer. To be

The present invention can also be effectively applied to a one-dimensional detector. It is not necessary to make the resistance layer 2 transparent in the embodiment, but if the resistance layer 2 is made transparent, the light incident position from the substrate 1 side can be detected.

(Effects of the Invention) According to the present invention, it is possible to form a resistance layer having a high average in-plane resistance value and a relatively uniform in-plane resistance distribution with good reproducibility, which results in high reliability. It becomes possible to mass-produce semiconductor optical position detectors.

[Brief description of drawings]

FIG. 1 shows an example of a semiconductor optical position detector to which the present invention is applied. FIG. 1 (a) is a plan view thereof, and FIG. 1 (b) and FIG. -A 'line and BB'
FIG. 2 is a cross-sectional view taken along a line, and FIG. 2 is a graph illustrating the relationship between the film-forming conditions of the resistance layer containing tin oxide as a main material and the sheet resistance
FIG. 3 is an equivalent circuit diagram of the position detector shown in FIG. 1, FIG. 4 is a diagram explaining the operation of the position detector shown in FIG. 1, and FIG. 5 is an output signal of the two-dimensional semiconductor optical position detector. FIG. 6 is a block diagram showing an example of a circuit for processing the above, FIG. 6 is an equivalent circuit diagram showing the action at the time of detecting in the x direction, and FIG. 7 is an example of the relationship between the film forming conditions of the ITO resistance layer and the sheet resistance. Graph, No. 8
The drawing is a graph illustrating the output characteristic of the semiconductor optical position detector to which the present invention shown in FIG. 1 is applied. 1 ... Substrate, 2, 4 ... Resistor layer, 3 ... Photovoltaic layer, 5a, 5
b, 6a, 6b …… Current collecting poles.

Claims (1)

[Claims] 1. A photovoltaic layer having a pin structure made of amorphous silicon, a translucent resistance layer formed on at least the light-receiving surface side of the photovoltaic layer, and a position signal extraction provided on the resistance layer. The present invention is applied to a semiconductor optical position detector equipped with a collector electrode for use as a substrate, and the resistance layer is made of a material mainly composed of tin oxide at a substrate temperature of 300 to 400 ° C. and an oxygen partial pressure of 5 × 10 ^{−4 to} 5 A method for forming a resistance layer in a semiconductor optical position detector, characterized in that a film is formed by a sputtering method under a condition of × 10 ^-5 Torr.