JPH0864793A - Photoelectric conversion device - Google Patents

Abstract

PURPOSE: To enable a photoelectric conversion device to be enhanced in an S/N ratio without providing an injection blocking layer and lessened in cost by a method wherein devices of the same laminar constitution are formed of the same material on the same insulating board, and wiring layers are formed of common films at the same time with the electrodes of the devices. CONSTITUTION: A first electrode layer 102, a first insulating layer 107 which stops carriers of both first conductivity-type and second conductivity-type from passing, a photoelectric conversion semiconductor layer 104, a second insulating layer 117, a gate electrode layer 202 of a switching element, a third insulating layer 203, a semiconductor layer 204, and a main electrode are formed of common films on the same substrate 1 through the same process, and important films very conducive to characteristics are formed in the same vacuum. By this setup, a photoelectric conversion device of this constitution is enhanced in degree of freedom of design, simplified in manufacturing process, and lessened in cost, possessed of multiple functions, and enhanced in performance.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a photoelectric conversion device,
In particular, the present invention relates to a photoelectric conversion device that is formed by using a large-area process, for example, a photoelectric conversion device that is suitably used for a one-dimensional or two-dimensional photoelectric conversion device that performs a normal-size reading such as a facsimile, a digital copy, or an X-ray imaging device.

[0002]

2. Description of the Related Art Conventionally, a reading system using a reduction optical system and a CCD type sensor has been used as a reading system for a facsimile, a digital copy or an X-ray image pickup device. , A-
Through the development of photoelectric conversion semiconductor material represented by Si), it is remarkable to develop a so-called contact type sensor in which a photoelectric conversion element and a signal processing unit are formed on a large-area substrate and read by an optical system of the same size as the information source. . In particular, a-Si is not only used as a photoelectric conversion material, but also as a field effect transistor (hereinafter referred to as T
Since it can also be used as an FT), it has an advantage that the photoelectric conversion semiconductor layer and the semiconductor layer of the TFT can be simultaneously formed.

8A to 8C are diagrams showing the structure of a conventional photosensor, FIGS. 8A and 8B show the layer structure of two types of photosensors, and FIG. ) Indicates a common typical driving method. 8A and 8B both show a photo diode type optical sensor, and FIG. 8A shows a PIN.
The mold, FIG. 8B, is called a Schottky type. FIG.
In (a) and (b), 1 is an insulating substrate, 2 is a lower electrode, and 3 is p.
A type semiconductor layer (hereinafter referred to as p layer), 4 is an intrinsic semiconductor layer (hereinafter referred to as i layer), 5 is an n type semiconductor layer (hereinafter referred to as n layer), and 6 is a transparent electrode. In the Schottky type of FIG. 8B, the material of the lower electrode 2 is appropriately selected, and the Schottky barrier layer is formed so that electrons are not injected from the lower electrode 2 to the i layer 4. In FIG. 8C, reference numeral 10 denotes an optical sensor that is a symbolic representation of the above optical sensor, 11 denotes a power source, and 12 denotes a detection unit such as a current amplifier. The direction indicated by C in the optical sensor 10 is the transparent electrode 6 side in FIGS. 8A and 8B, the direction indicated by A is the lower electrode 2 side, and the power source 11 is on the C side with respect to the A side. It is set to apply a positive voltage. The operation will be briefly described here. FIG.
As shown in (a) and (b), when light is incident from the direction indicated by the arrow and reaches the i layer 4, the light is absorbed and electrons and holes are generated. Since an electric field is applied to the i layer 4 by the power source 11, the electrons move to the C side, that is, the n layer 5 and move to the transparent electrode 6, and the holes move to the A side, that is, the lower electrode 2. Therefore, the photocurrent has flowed through the optical sensor 10. When no light is incident, neither electrons nor holes are generated in the i layer 4, and the holes in the transparent electrode 6 are n.
The layer 5 functions as a hole injection blocking layer, and the electrons in the lower electrode 2 are generated by the p-type layer 3 in the PIN type shown in FIG.
In the Schottky type of, the Schottky barrier layer acts as an electron injection blocking layer, and neither electrons nor holes can move,
No current flows. Therefore, the current changes depending on whether light is incident or not, and if this is detected by the detection unit 12 in FIG. 8C, it operates as an optical sensor.

[0004]

However, it has been difficult to produce a low-cost photoelectric conversion device having a high SN ratio with the above-mentioned conventional photosensor. The reason will be described below.

The first reason is that both the PIN type shown in FIG. 8A and the Schottky type shown in FIG. 8B require an injection blocking layer at two locations. In the PIN type shown in FIG. 8A, the n layer 5 which is an injection blocking layer needs to have a property of guiding electrons to the transparent electrode 6 and at the same time blocking holes from being injected into the i layer 4. If either characteristic is lost, the photocurrent will decrease,
A current (hereinafter referred to as dark current) is generated when no light is incident,
This causes an increase and causes a decrease in the SN ratio. This dark current includes fluctuations called shot noise, which is considered to be noise at the same time, and includes so-called quantum noise. Even if the dark current is subtracted by the detection unit 12, the quantum noise associated with the dark current is reduced. It is not possible. In order to improve this characteristic, it is usually necessary to optimize the conditions for forming the i-layer 4 and the n-layer 5 and the conditions for annealing after formation. However, another injection blocking layer, p-layer 3
In the case of, the electron and the hole are opposite, but equivalent characteristics are required, and similarly, optimization of each condition is required. Normal,
The optimization conditions for the former n-layer and the latter p-layer are not the same, and it is difficult to satisfy both conditions at the same time. That is, the need for two injection blocking layers in the same optical sensor makes it difficult to form an optical sensor with a high SN ratio. This also applies to the Schottky type of FIG. 8B. Further, in the Schottky type of FIG. 8B, a Schottky barrier layer is used for one of the injection blocking layers, but this utilizes the difference in work function between the lower electrode 2 and the i layer 4, and the lower electrode It is more difficult to satisfy the conditions because the materials of No. 2 are limited or the effect of the localized level of the interface greatly affects the characteristics. It has also been reported that a thin silicon or metal oxide film or nitride film of about 100 angstrom is formed between the lower electrode 2 and the i layer 4 in order to further improve the characteristics of the Schottky barrier layer. , Which uses the tunnel effect to guide holes to the lower electrode 2
It improves the effect of blocking the injection into the layer 4, and since the difference in work function is also used, it is necessary to limit the material of the lower electrode 2, and the blocking of the injection of electrons and the formation of holes by the tunnel effect. Since the reverse property of movement is used, the oxide film and the nitride film are limited to a very thin area of about 100 angstroms, and it is difficult to control the thickness and film quality, and the productivity is lowered.

Further, the fact that two injection blocking layers are required reduces productivity and increases cost. This is because the injection blocking layer is important in terms of characteristics, and if a defect occurs due to dust or the like even at one of the two locations, the characteristics as an optical sensor cannot be obtained.

The second reason will be described with reference to FIG. Figure 9
Shows the layer structure of a field effect transistor (TFT) formed of a thin semiconductor layer. The TFT may be used as part of the control unit in forming a photoelectric conversion device. In the figure, the same parts as those in FIG. 8 are indicated by the same numbers. In FIG. 9, 7 is a gate insulating film, and 60 is an upper electrode. The forming method will be described step by step. The lower electrode 2, which functions as a gate electrode (G), the gate insulating film 7, the i layer 4, the n layer 5, the source and drain electrodes (S, D) on the insulating substrate 1.
An upper electrode 60 serving as a film is sequentially formed, the upper electrode 60 is etched to form source and drain electrodes, and then the n layer 5 is etched to form a channel portion.

This TFT enables the operation of a switch for turning on and off between the source and drain electrodes formed of the upper electrode 60 by controlling the potential of the lower electrode 2 which functions as a gate electrode. The characteristics of this TFT Is
It is greatly influenced by the state of the interface between the gate insulating film 7 and the i layer 4. For example, if there are many impurities at the above interface,
The threshold voltage for turning on or off the TFT greatly deviates from the design value, the resistance value when the TFT is on becomes high, and the resistance value when the TFT is off becomes low. Good characteristics cannot be obtained.

Further, even if desired TFT characteristics are obtained in the initial stage, there is a problem that the above-mentioned threshold voltage largely changes while the TFT is repeatedly turned on and off, causing malfunction.

Usually, in order to obtain good TFT operation characteristics, that is, to form a good interface between the gate insulating film 7 and the i layer 4, the gate insulating film 7 and the i layer 4 of this TFT are formed in the same vacuum. It is preferable to form continuously.

However, when the conventional photosensor is formed on the same substrate as this TFT, this layer structure poses a problem, resulting in an increase in cost and deterioration in characteristics. The reason is that the structure between the lower electrode and the i layer of the conventional photosensor shown in FIG.
Whereas the PIN type of (a) has an electrode / p layer / i layer and the Schottky type of FIG. 8 (b) has an electrode / i layer, T
FT differs in the structure of electrode / insulating film / i layer,
In order to form the TFT by sharing the i layer of the conventional optical sensor, it is impossible to continuously form the gate insulating film 7 of the TFT and the i layer 4 in the same vacuum. Both of the operating characteristics of the TFT cannot be obtained well.
This requires the process for forming each element of the photosensor and the TFT to be sequentially performed for each element, which leads to a decrease in yield and an increase in cost due to the complicated process.

Further, in order to make the i layer / n layer common, an etching process of the gate insulating layer 7 and the p layer 3 is required, and the p layer 3 of the injection blocking layer which is an important layer of the optical sensor described above is required. And the i-layer 4 cannot be formed in the same vacuum, or contamination due to etching of the gate insulating film at the interface between the important gate insulating film 7 of the TFT and the i-layer 4 causes deterioration of the characteristics and the SN ratio. .

In order to improve the above-mentioned Schottky type characteristic of FIG. 8B, the oxide film or the nitride film formed between the lower electrode 2 and the i layer 4 has the same film order. However, as described above, the oxide film or the nitride film needs to have a thickness of about 100 Å and is shared with the gate insulating film, and it is difficult to obtain good characteristics of both the optical sensor and the TFT. FIG. 10 shows the results of our experiments on the yields of the gate insulating film and the TFT. Gate insulation film thickness is 10
The yield drops sharply below 00 angstroms,
Yield is about 30% at 800 Å, 500
The yield was 0% at angstrom, and even the operation of the TFT could not be confirmed at 250 angstrom. It is clear that it is difficult to share an oxide film or a nitride film of a photosensor utilizing the tunnel effect with a gate insulating film of a TFT which must insulate electrons and holes, and the data show that.

Such poor matching in terms of process or characteristics with the TFT, which is an important element in constructing the photoelectric conversion device, poses a problem in constructing the entire system, and is low in cost and high in performance. It was a serious problem in making a multifunctional device.

[0015]

A photoelectric conversion device according to the present invention is a first photoelectric conversion device that prevents passage of a first electrode layer, a carrier of a first conductivity type and a carrier of a second conductivity type different from the first conductivity type. An insulating layer, a photoelectric conversion semiconductor layer, a second insulating layer that blocks passage of the first conductivity type carrier and the second conductivity type carrier, and a photoelectric conversion element in which a second electrode layer is laminated, and a gate An electrode layer, a third insulating layer, a semiconductor layer, a pair of first and second main electrode layers that separate a part of the semiconductor layer to be a channel region, and between the main electrode layer and the semiconductor layer. A switch element in which an ohmic contact layer is laminated, and a wiring layer that electrically connects the first or second electrode layer of the photoelectric conversion element and the first main electrode layer of the switch element on the same substrate. I have.

[0016]

The present invention provides a low-cost photoelectric conversion device having a high SN ratio and capable of detecting the amount of incident light without providing an injection blocking layer in the photoelectric conversion element.

Further, on the same substrate, the first electrode layer of the photoelectric conversion element, the first insulating layer, the photoelectric conversion semiconductor layer, and the second electrode layer, and the gate electrode layer of the switch element, the third insulating layer. , The semiconductor layer, and the main electrode can be composed of a common film in the same process, and the film structure that is important in terms of characteristics can be formed in the same vacuum, which improves design flexibility and simplifies the process. It can be applied to high-performance application products with multiple functions at a cost.

If the third electrode layer of the capacitive element, the intermediate layer having the fourth insulating layer, and the fourth electrode layer are provided on the same substrate, the amount of light incident on the photoelectric conversion element can be obtained in addition to the above-mentioned function. It is possible to provide a photoelectric conversion device in which high functions for outputting the integrated value of are integrated on the same substrate.

[0019]

Embodiments of the present invention will now be described in detail with reference to the drawings. [Embodiment 1] FIG. 1A is a layer configuration diagram of a photoelectric conversion element 100, a TFT 200 and a wiring layer 400 in a photoelectric conversion device according to a first embodiment of the present invention, and FIG. 1B is a photoelectric conversion device. It is a circuit diagram of. In FIG. 1A, 1 is an insulating substrate made of glass, and 102 is a lower electrode made of Al or Cr. Reference numerals 107 and 117 denote lower and upper insulating layers formed of silicon nitride SiN that prevent passage of both electrons and holes, and have a thickness of 500 angstroms or more, which is a thickness such that electrons and holes cannot move due to a tunnel effect. Is set to. Reference numeral 104 is a photoelectric conversion semiconductor layer formed of an intrinsic semiconductor i layer of hydrogenated amorphous silicon a-Si, 105 and 106 are upper electrodes, 105 is a transparent electrode portion formed of an a-Si n layer, and 106 is a transparent electrode portion. It is an opaque electrode portion formed of Al or Cr. In this embodiment, the lower electrode 102 and the upper electrode 106 are opaque electrodes, and the upper electrode is
The opaque electrode portion 106 has a two-layer structure that does not completely cover the transparent electrode portion 105 and allows light to enter. However, it is also possible to form the upper electrode with only a transparent electrode such as ITO. If the lower electrode is formed of a transparent electrode, the opaque electrode portion 106 of the upper electrode may cover the transparent electrode portion 105, or the transparent electrode portion 105 may not be provided.

Further, 202 is a gate electrode formed of Al, Cr or the like, 203 is a gate insulating layer formed of silicon nitride SiN, and 204 is hydrogenated amorphous silicon a.
A semiconductor layer formed of an intrinsic semiconductor i-layer of —Si, 205
Is an ohmic contact layer formed of an n-layer of a-Si for moving electrons between the semiconductor layer 204 and the source electrode 206 and the drain electrode 207, and 217 is a surface of the semiconductor layer 204 formed of silicon nitride SiN. The protective layer 217 covers the semiconductor layers 204 and n.
Contact holes are provided for connection to layer 205. The source electrode 206 and the drain electrode 207 are formed of Al or Cr. The upper electrode 106 of the photoelectric conversion element 100 and the source electrode 206 of the TFT 200 are made of Al.
And a wiring 406 of Cr. As is clear from the drawing, the layer structure of each element is the same, and the same material can be simultaneously formed on the same insulating substrate 1. Also, the wiring layer can be formed at the same time as the electrodes of each element. FIG.
In FIG. 1B, 100 is a symbolic representation of the photoelectric conversion element shown in FIG. 1A, where U is the upper electrode 106 side and B is the lower electrode 102 side electrode. 120 is a detection unit,
110 is a power supply unit, and the power supply unit 110 is a positive power supply 111 that gives a positive potential to the U electrode, and GN that has the same potential as the B electrode
It is composed of a connection 112 for giving a D potential. Also,
In the figure, 210 and 211 symbolize the TFT shown in FIG. 1A, and g, s and d indicate the gate electrode 202, the source electrode 206 and the drain electrode 207, respectively. Although only one TFT 200 is shown as a representative in FIG. 1A, both the TFT 210 and the TFT 211 are actually formed on the same insulating substrate as shown in FIG. 1B. Each gate electrode is connected to the control unit 130, and the control unit 130 controls the refresh-TFT 210 in the refresh mode and the read-TFT 211 in the photoelectric conversion mode to turn on. The operation of this embodiment will be described below with reference to FIGS.

2 (a) and 2 (b) are energy band diagrams of the photoelectric conversion element showing the operation in the refresh mode and the photoelectric conversion mode of this embodiment, respectively. The lower electrode 102 to the upper electrode 105 in FIG. 1 (a) are shown. Up to the state of each layer in the thickness direction. In FIG. 2A in the refresh mode, the U electrode is supplied with the GND potential which is the same potential as the B electrode, and therefore the holes indicated by black circles at the interface between the i layer 104 and the lower insulating layer 107 are diffused. i layer 104
Disperse throughout. At the same time, i layer 104 and upper insulating layer 117
Electrons indicated by white circles at the interface with and are also dispersed in the entire i layer 4. In this state, holes and electrons are generated in the i layer 104.
Recombine at, and if this condition persists for a long enough time i
The holes and electrons in the layer 104 disappear and only the minute electrons and holes that are thermally excited in the i-layer 104 become. In this state, when the photoelectric conversion mode shown in FIG.
Since the electrode is given a positive potential with respect to the B electrode, i layer 1
The small holes and electrons in 04 are B electrode,
It is guided to the U electrode side and reaches the interface between the i layer 104 and the lower insulating layer 107 and the interface between the i layer 104 and the upper insulating layer 117. However, electrons and holes existing in the B electrode and the U electrode cannot pass through the lower insulating layer 107 and the upper insulating layer 117, respectively, and thus are not guided to the i layer 104. When light enters the i-layer 104 in this state, the light is absorbed and electron-hole pairs are generated. These electrons move in the i-layer 104 by the electric field and are guided to the interface with the upper insulating layer 117, and similarly holes move in the i-layer 104 and move to the i-layer 1.
04 and the lower insulating layer 107. However, since holes and electrons cannot move into the upper and lower insulating layers 117 and 107, holes are at the interface between the i layer 104 and the lower insulating layer 107, and electrons are between the i layer 104 and the upper insulating layer 117. Since it stays at the interface, a current flows from the B electrode to the detection unit 120 in order to maintain electrical neutrality in the element. This current corresponds to the electron-hole pair generated by light and is therefore proportional to the incident light. After maintaining the photoelectric conversion mode of FIG. 2B for a certain period, the refresh mode of FIG.
In the state of (a), the holes and electrons remaining in the i layer 104 are dispersed in the i layer 104 as described above, and at the same time, currents corresponding to the holes and electrons flow to the detection unit 120. The amount of the holes corresponds to the total amount of light incident during the photoelectric conversion mode period, and the current flowing through the detection unit 120 corresponds to the total amount of light. That is, the photoelectric conversion element 100 in this embodiment can output the amount of light that is incident in real time, and at the same time, can output the total amount of light that is incident during a certain period. This can be said to be a major feature of this embodiment. The detection unit 120 may detect either one or both depending on the purpose.

Here, referring to FIGS. 1, 2 and 3,
The operation of the detection unit 120 of this embodiment will be described. FIG.
3 is a timing chart of the operation of the photoelectric conversion device of FIG. In FIG. 3, V _UB is the potential of the U electrode with respect to the B electrode of the photoelectric conversion element 100, P indicates the state of incident light, ON is the state of incident light, OFF is no incident of light,
That is, it shows a dark state. Is represents the current flowing into the detection unit 120, and the horizontal axis direction represents the passage of time. First, the refresh-TFT 210 and the read-T
When the refresh-TFT 210 is turned ON by the control unit 130 from the state where both FT211 are OFF, the refresh mode is entered, V _UB becomes GND potential 0 V, and electrons and holes diffuse in the i layer 4 as shown in FIG. 2 (a). At the same time, since they are recombined, a negative rush current E shown in FIG.
After that, the refresh mode ends and the refresh-T
When the FT 210 is turned off and the read-TFT 211 is turned on at the same time, V _UB becomes a positive voltage, and a positive inrush current E ′ that charges the equivalent capacitance in the photoelectric conversion element flows to enter the photoelectric conversion mode. At this time, when light is incident, a photocurrent A indicated by A flows. If the same operation is performed in the dark state, no current flows as indicated by A '. Therefore, the incident light can be detected by directly integrating the photocurrent A or the photocurrent A for a certain period. In addition, read from the state of A
-At the same time as turning off the TFT 211, the refresh-T
When the FT 210 is controlled to be ON, the inrush current B flows.
This is an amount reflected in the total amount of light incident in the immediately preceding photoelectric conversion mode period, and the light incident can be detected by integrating this rush current B or obtaining a value corresponding to the integral. If no light is incident in the immediately preceding photoelectric conversion mode, the inrush current becomes small as indicated by B ', and the incident light can be detected by detecting the difference. Since the inrush currents E and E ′ described above are approximately equal to the inrush current B ′, they may be subtracted from the inrush current B.

Further, if the state of incident light changes even in the same photoelectric conversion mode period, Is changes like C and C '. Even if this is detected, the incident state of light can be detected. That is, it is not always necessary to set the refresh mode for each detection opportunity.

However, if the period of the photoelectric conversion mode is long for some reason or the illuminance of the incident light is strong, the current may not flow although the light is incident as in D. This is i, as shown in FIG.
Many holes and electrons are retained in the layer 104, and the electric field in the i layer 104 is reduced due to the holes and electrons.
This is because the generated electrons are not guided to the interface between the i layer 104 and the upper insulating layer 117 and are recombined with the holes in the i layer 104. When the light incident state changes in this state, the current may flow unstablely, but if the refresh mode is set again, the holes and electrons in the i layer 104 disappear, and in the next photoelectric conversion mode, A ″ Thus, a current equal to A is obtained, which is also a feature of this embodiment.

In the above description, the incident light was explained as being constant, but the currents A, B, and C all change continuously depending on the intensity of the incident light, and the intensity of the incident light is not limited to the detection, and the intensity is also quantified. Needless to say, it can be detected automatically.

Further, in the above description, when the holes and electrons in the i layer 104 are to be erased in the refresh mode, it is ideal that all the holes and electrons are eliminated, but even if only some holes are eliminated. There is an effect, and the value is the same as when all of the photocurrents A or C are extinguished, and there is no problem. Further, if the light is made to disappear so that a constant amount always remains, the amount of light can be quantitatively detected also by the current of B. That is, it is sufficient if the current value is not in the state of D, that is, the state of FIG. 2C at the next detection opportunity in the photoelectric conversion mode, and if the voltage of V _UB in the refresh mode and the period of the refresh mode are determined. Good. Further, in the refresh mode, the voltage of V _UB is not limited to 0V. When a large number of holes and electrons remain in the i layer 104, even if V _UB is a positive voltage, the electric field in the i layer is applied in the direction of guiding holes to the U electrode side and electrons to the B electrode side. And the holes can be dispersed in the i-layer 4 and disappear. Further, by appropriately setting V _UB to a negative voltage, an electric field is applied in a direction that promotes dispersion of electrons and holes in the i-layer 4, and the annihilation speed of electrons and holes can be increased.

7 (a) and 7 (b) are energy band diagrams of the photoelectric conversion element section showing the operation when the voltage V _{UB in} the refresh mode is a positive voltage and a negative voltage, respectively. 2 and is the same as FIG. 2 except for the potential relationship applied to the U electrode and the B electrode.

As shown in FIG. 2C, in the photoelectric conversion mode, a large number of electrons and holes remain in the i-layer 104, the electric field in the i-layer 104 is small, and the current does not flow even though light is incident. With no flow, V _{UB as} shown in Fig. 7 (a)
Voltage is made smaller than that in the photoelectric conversion mode, that is, V
_In the refresh mode when the voltage of _UB is positive, even if the voltage of V _UB does not become 0V, the electrons and holes in the i layer 104 remaining at the respective interfaces are in the A portion shown in FIG. 7A. It moves to the center side of the i-layer 104 except for the electrons and the holes in the B part. Further, electrons and holes are recombined near the center of the i-layer 104, and if this state continues for a sufficiently long time, the electrons and holes in the i-layer 104 are the electrons in the A portion and the B
Excludes by recombination except for some holes. In this state, if the voltage of V _UB is increased, that is, the photoelectric conversion mode is set as shown in FIG. 2B, it is apparent that the photocurrent corresponding to the incident light can be detected. In this case, in the refresh mode and the photoelectric conversion mode, the interface between the upper insulating layer 117 on the U electrode side and the i layer 104 is shown in FIG.
Electrons always stay in the area A in the middle of the figure, and similarly, it is the interface between the lower insulating layer 107 and the i layer 104 on the side of the B electrode.
A hole is always retained in the portion B shown in (a). This has an effect that a photoelectric conversion device having a fast optical response can be realized without adverse effects due to a change in the state of the interface state that causes a slow transient response in switching between the refresh mode and the photoelectric conversion mode.

Further, in the refresh mode as shown in FIG. 7B, when a voltage is applied so that the voltage of V _UB becomes a negative voltage, in the direction shown by the thick arrow A ′ in FIG. 7B. An electric field is applied to the i-layer 10 in the directions in which holes and electrons move.
4, the electrons and holes disperse more quickly throughout the i-layer 4 and recombine the holes and electrons in the i-layer 104 (FIG.
The arrow B ′ in (b) can be made to disappear. In this case, the movement of holes and electrons in the i-layer 104 is positively performed not only by thermal diffusion but also by an electric field, so that the i-layer 104 can move faster and the holes and electrons can disappear more quickly. This has the effect of shortening the time.

4 (a), (b), (c), and (d) show the structure of the detection section, respectively. 121 is an ammeter represented by current Amp, 122 is a voltmeter, 123 is a resistor, 124 is a capacitor, 125 is a switch element,
Reference numeral 126 is an operational amplifier. FIG. 4A is for directly detecting the current, and the output of the ammeter 121 is the voltage or the amplified current. In FIG. 4B, a current is passed through the resistor 123 and the voltage is detected by the voltmeter 122. In FIG. 4C, electric charge is accumulated in the capacitor 124 and the voltage is stored in the voltmeter 122.
Is detected in. In FIG. 4D, the integrated value of the current is detected as a voltage by the operational amplifier 126. FIG. 4 (c),
In (d), the switch element 125 plays a role of giving an initial value to each detection, and it may be replaced with a high resistance resistor depending on the detection method. Ammeters and ammeters are transistors and operational amplifiers that combine them.
It is possible to use a resistor, a capacitor, and the like that operate at high speed, and these ammeters and voltmeters themselves may include an integration function and a subtraction function. The detection unit has 4
It is not limited to the kind, but it is sufficient if current or charge can be detected directly or the integrated value can be detected.A detector for detecting the current or voltage value and a resistor, capacitor, or switch element are combined, and a plurality of photoelectric conversion elements are simultaneously or sequentially arranged. It can also be configured to output. When configuring a line sensor or an area sensor, the potentials of 1000 or more photoelectric conversion elements are controlled and detected in combination with the wiring of the power supply section and the switch elements. In this case, it is advantageous in terms of SN ratio and cost if the switch element, the capacitor, and a part of the resistor are formed on the same substrate as the photoelectric conversion element. In this case, the photoelectric conversion element of this embodiment is a typical switch element T
Since the layer structure between the FT and the lower electrode is the same film structure between the i layers, they can be simultaneously formed by a simple process, and a low cost photoelectric conversion device with a high SN ratio can be realized. [Embodiment 2] FIG. 5 is a circuit diagram showing a second embodiment of the photoelectric conversion device of the present invention. The same parts as those in FIG. 1B are designated by the same reference numerals. Photoelectric conversion element 100 and T
The layer structure of the FTs 220 to 222 is the same as that in FIG.

As shown in FIG. 5, in this embodiment, the capacitor 300, which is a capacitive element, is the photoelectric conversion element 1.
00 is connected between the B electrode and the GND potential, and 114 is a power supply V _U , 11 for applying a positive potential to the U electrode.
Reference numeral 5 is a power source V _B that applies a predetermined potential to the B electrode in the refresh mode of the photoelectric conversion element. Power supply 11 at this time
5 is set equal to or lower than the power source 114. The ON / OFF states of the gate electrodes of the TFTs 220 to 222 are controlled by the control units 131 to 133, respectively.
The part surrounded by the broken line is the detection part, and detects the light incident on the photoelectric conversion element 100 as described below.

This embodiment has four modes in detail,
The photoelectric conversion element refresh mode, the B electrode initialization mode, the accumulation mode, and the detection mode, respectively.
The photoelectric conversion element refresh mode of 1 corresponds to the refresh mode of the first embodiment, and the B electrode initialization mode, storage mode, and detection mode of 2 correspond to the photoelectric conversion mode of the first embodiment. An electric field is applied to each layer in the same direction, and the operation of the photoelectric conversion element 100 is basically the same. Each mode will be sequentially described below. After the three TFTs 220 to 222 are turned off, in the photoelectric conversion element refresh mode, the control unit 131 causes T
The FT 220 is turned on, and the power supply 115 applies the potential V _B to the B electrode. A positive potential V _U is applied to the U electrode by the power supply 114, that is, the potential V _UB of the U electrode with respect to the potential of the B electrode is (V _U −V _B ). Then, the holes and electrons in the photoelectric conversion element 100 disappear and are refreshed. Next, after the TFT 220 is turned off, the control unit 132 turns on the TFT 221.
The B electrode initialization mode is entered, and the B electrode is given a GND potential. At this time, V _UB becomes a positive voltage, and the photoelectric conversion element 100 enters the photoelectric conversion mode after the inrush current flows.
Next, the TFT 221 is turned off and the B electrode is opened in terms of direct current. However, the capacitor 300 maintains the potential. Here, when light is incident on the photoelectric conversion element 100, a corresponding current flows out from the B electrode, and the potential of the B electrode rises. That is, the incident information of light is accumulated in the capacitor 300 as electric charges. After a certain accumulation time, the control unit 133 turns on the TFT 222 to shift to the detection mode.
At this time, the charge accumulated in the capacitor 300 is the TFT 22.
2 flows to the side of the operational amplifier 126 through 2, and this charge corresponds to the integrated value of the current flowing out of the photoelectric conversion element 100 in the accumulation mode, that is, is composed of the operational amplifier 126, the capacitor 124, and the switch element 125 as the total amount of incident light. It is detected by the integrator. This integrator is initialized by switching on the switch element 125 and discharging the capacitor 124 by a control unit (not shown) before shifting to the detection mode. Further, after turning off the TFT 222, the control unit 131 turns on the TFT 220 again, and the following operation is repeated.

As described above, the feature of the present embodiment is a high cost operational amplifier, in which the integrated value of the current flowing during a constant long storage time can be obtained in a short period of the detection mode by a simple combination of elements. It is shown that the photoelectric conversion device having a high SN ratio, which has a light load and a plurality of photoelectric conversion elements, can be constructed at low cost. The operation of the photoelectric conversion element of this embodiment is basically the same as that of the first embodiment, but the difference is that the potential of B potential increases and V _UB decreases during the photoelectric conversion mode. This is likely to result in the state shown in FIG. 2C with a small amount of incident light, which may limit the amount of incident light in normal operation, but this can be improved by making the capacitor 300 sufficiently large. On the contrary, when only a small amount of light needs to be detected, the stray capacitance Cs of the photoelectric conversion element 100 indicated by the dotted line does not have to be formed as the capacitor 300 as an active element.
Can operate as a capacitive element. This stray capacitance C
s can be adjusted by the area of the opaque electrode 106 of the upper electrode of the photoelectric conversion element 100 shown in FIG.

6A is a plan view of the photoelectric conversion device shown in FIG. 5, and FIG. 6B is a plan view of FIG. 6A.
The sectional view between -B is shown. In FIG. 6A, parts that cannot be shown in detail are indicated by the same symbols as in FIG. 100
Is a photoelectric conversion element, and 220 to 222 are TFTs, and the connection between the semiconductor layer and the main electrode via the ohmic contact layer is connected through a contact hole 410 formed in the protective layer. Reference numeral 300 is a capacitor, and reference numerals 402 and 406 are wirings that electrically connect the respective elements.
8 are connected. 412 in FIG.
A reference numeral 416 is a wiring connecting to other components.

The photoelectric conversion element 100 and the TFT 220-
222 has the same layer configuration as that of FIG. 1A of the first embodiment. The layer structure of the capacitor 300 used in this example is shown in FIG.

The capacitor 300 used in this embodiment is shown in FIG.
As shown in (c), 302 is a lower electrode of a capacitor formed of Al, Cr or the like, 307 is a lower insulating layer formed of silicon nitride SiN, 304 is an intrinsic semiconductor i layer of hydrogenated amorphous silicon a-Si. , 317 is an upper insulating layer formed of silicon nitride SiN, 305 and 306 are upper electrode layers, and 305 is an upper electrode layer.
Is a transparent electrode portion formed of an n-layer of a-Si, and 306 is A
It is an opaque electrode portion formed of 1 or Cr. Here, the lower insulating layer 307 / semiconductor layer 304 / upper insulating layer 317 acts as an intermediate layer of the capacitor 300 and includes the upper and lower insulating layers 307 and 317, so that a good capacitor with less leakage is formed. Further, as shown in FIGS. 6A and 6B, the lower electrode 2 of the photoelectric conversion element 100 and the lower electrode 302 of the capacitor are connected by the wiring 402 of Al or Cr.

As is apparent from FIGS. 6 (c) and 1 (a), the layer structure of each element used in this embodiment is the same, and the same material can be simultaneously formed on the same insulating substrate 1. Also, the wiring layer can be formed at the same time as the electrodes of the respective elements, and the wiring layer is formed by a simple process by using a common film.

Next, a method of forming each element of this embodiment will be described with reference to FIGS.

First, about 500 angstroms of Cr is deposited as the lower metal layer 2 on the glass substrate 1 which is an insulating material by sputtering or the like, and then patterning is performed by photolithography to etch unnecessary areas.
As a result, the lower electrode of the photoelectric conversion element 100, the TFT 22
Gate electrodes 0 to 222, a lower electrode of the capacitor 300, and lower electrodes 402 and 412 are formed.

Next, SiN is formed by the CVD method in the same vacuum.
Each of (7) / i (4) / SiN (17) layers is about 20
00/5000/2000 Angstrom deposited.
These layers are the lower insulating layer / photoelectric conversion semiconductor layer / upper insulating layer of the photoelectric conversion element 100, the gate insulating film / semiconductor layer / protective layer of the TFTs 220 to 222, and the capacitor 300.
Will be the middle layer of. It is also used as a cross insulation layer for upper and lower wiring. The thickness of each layer is not limited to these, and is optimally designed according to the voltage, current, charge, incident light amount, etc. used as a photoelectric conversion device, but at least SiN cannot pass electrons and holes, and as a gate insulating film of a TFT. It is preferable that the thickness is 500 angstroms or more so that it can function.

After depositing each layer, the contact hole of SiN 17 and the area to be 410 are etched, and then CV is applied.
N layer 5 is deposited to 500 angstrom by D method,
Subsequently, the n layer 5 in the unnecessary portion is patterned by photolithography, removed by etching, and further SiN (7) / i (4) / in the area to be the contact hole 408.
SiN (17) is removed by etching. As a result, the transparent electrode portion on the upper part of the photoelectric conversion element 100, the TFT 200 to.
The ohmic contact layer 222, the transparent electrode portion of the intermediate electrode / upper electrode of the capacitor 300, and the contact hole 408 are formed, and the semiconductor layers of the TFTs 220 to 222 and the ohmic contact layer are connected via the contact hole 410.

Next, the upper metal layer 6 is sputtered to about 1
Deposit 10,000 Angstroms. Further, the upper metal layer 6 is patterned by photolithography to etch unnecessary areas, and the opaque electrode portion of the upper electrode of the photoelectric conversion element 100, the source and drain electrodes which are the main electrodes of the TFTs 220 to 222, and the capacitor 300.
Opaque electrode portion which is the upper electrode of the
And 416 are formed. Contact hole 408 at the same time
In, the lower wiring 402 and the upper wiring 406 are connected.

Further, unnecessary SiN (7) / i
The (4) / SiN (17) layer is etched to separate each element. With this, the photoelectric conversion element 100 and the TFTs 220 to 2
22, lower wirings 402 and 412, upper wirings 406 and 41
6 and contact holes 408 and 410 are completed. Although not shown, the upper portion of each element is usually covered with a passivation film such as SiN in order to improve durability.

As described above, in this embodiment, the photoelectric conversion element 100, the TFTs 220 to 222, the capacitor 300,
And the wiring part 400, the common lower metal layer 2 and SiN (7) / i (4) / SiN (17) which are simultaneously deposited.
It can be formed only by etching the layers, the n-layer 5, the upper metal layer 6 and each layer. Further, the photoelectric conversion element 100 does not have an injection blocking layer and can be formed in the same vacuum.
Further, the gate insulating film / i layer interface, which is important in the characteristics of the TFT, can be formed in the same vacuum, and the TFT of this embodiment is formed in the same vacuum as the gate insulating film and the semiconductor layer. SiN17 having the same material and thickness as the upper insulating layer
By forming the protective layer with, each element and wiring can be formed without exposing the semiconductor surface corresponding to the channel of the TFT, and it is always stable without being affected by various damages and contamination during the process. A characteristic TFT can be obtained.

Furthermore, since the intermediate layer of the capacitor 300 includes an insulating layer which is less likely to leak due to heat, a capacitor having good characteristics is formed. As described above, this embodiment makes it possible to produce a high-performance photoelectric conversion device at low cost.

As is clear from the above description, the photoelectric conversion element is not limited to those shown in the first and second embodiments. That is, the first electrode layer, the first insulating layer that blocks the movement of holes and electrons, the photoelectric conversion semiconductor layer, the second insulating layer that blocks the movement of holes and electrons,
It suffices if there is a second electrode layer. Further, the photoelectric conversion semiconductor has only to have a photoelectric conversion function of generating a pair of electrons and holes upon incidence of light. The layer structure may not be a single layer but may be a multilayer structure, and the characteristics may be continuously changed.

Similarly, a TFT may have a gate electrode, a gate insulating film, a semiconductor layer capable of forming a channel, an ohmic contact layer, and a main electrode. For example, a structure in which a protective layer covering the semiconductor surface is not provided, or the ohmic contact layer may be a p layer, in which case the holes may be used as channels by reversing the control voltage of the gate electrode.

Similarly, a capacitor may have a lower electrode, an intermediate layer including an upper or lower insulating layer, and an upper electrode. For example, a transparent electrode portion of the upper electrode,
Even if the upper insulating layer and the semiconductor layer are not provided and only the upper electrode (opaque electrode portion), the lower insulating layer, and the lower electrode are used, or the photoelectric conversion element and the TFT are not specially separated from each other, they may also be used as the electrode portion of each element. good.

Furthermore, the insulating substrate does not have to be an insulating material, but may be a conductor or a semiconductor on which an insulating material is deposited.

[0050]

As described above, according to the present invention,
The incident amount of light can be detected without providing an injection blocking layer in the photoelectric conversion element in the photoelectric conversion device, the process can be optimized easily, the yield can be improved, and the manufacturing cost can be reduced. It is possible to provide a high-cost and low-cost photoelectric conversion device.

Further, since the tunnel effect or the Schottky barrier is not used between the first electrode or the second electrode and the photoelectric conversion semiconductor layer, the electrode material can be freely selected and the thickness of the insulating layer and the Other controls have a high degree of freedom.
Further, since the gate electrode, the semiconductor layer, and the main electrode of the switching element such as a field effect transistor (TFT) formed at the same time can have the same film structure, they can be simultaneously formed as a common film, and the photoelectric conversion element, the TFT, Important film configurations for both switch elements can be formed simultaneously in the same vacuum, and further, there is an effect that the photoelectric conversion device can have high SN and low cost.

In addition, since the photoelectric conversion element itself stores optical information as a carrier and has a property of flowing a current in real time at the same time, there is an effect that a photoelectric conversion device having a complex structure and a complex function can be formed.

[Brief description of drawings]

1A is a layer configuration diagram of a photoelectric conversion element and a TFT in a first embodiment according to the present invention, and FIG. 1B is an overall circuit diagram.

2A to 2C are energy band diagrams in each operation mode of the photoelectric conversion element.

FIG. 3 is a time chart of a current flowing through a detector.

4A to 4D are configuration diagrams of a detector.

FIG. 5 is an overall circuit diagram of a second embodiment according to the present invention.

6A is a plan view of a second embodiment according to the present invention, FIG. 6B is a sectional view, and FIG. 6C is a layer configuration diagram of a capacitor.

7 (a) and 7 (b) are energy band diagrams of the photoelectric conversion element showing an operation for each of a positive voltage and a negative voltage of V _{UB in} the refresh mode.

8A to 8C are configuration diagrams of a conventional optical sensor.

FIG. 9 is a layer configuration diagram of a TFT.

FIG. 10 is a graph showing the yield of TFT with respect to the thickness of a gate insulating film.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Insulating substrate 100 Photoelectric conversion element 102 Lower electrode 104 Photoelectric conversion semiconductor layer (i layer) 105, 106 Upper electrode 107 Lower insulating layer 110 Power supply section 117 Upper insulating layer 120 Detection section 130 Control section 200 TFT 202 Gate electrode 203 Gate insulating film 204 semiconductor layer (i layer) 205 ohmic contact layer (n layer) 206 source electrode 207 drain electrode 217 protective layer 300 capacitor 302 capacitor lower electrode 304 semiconductor layers 305 and 306 capacitor upper electrode 307 lower insulating layer 317 upper insulating layer 400 wiring

 ─────────────────────────────────────────────────── ─── Continued Front Page (72) Inventor Hidemasa Mizutani 3-30-2 Shimomaruko, Ota-ku, Tokyo Canon Inc.

Claims (7)

[Claims] 1. A first electrode layer, a first conductivity type carrier, and a first insulating layer that blocks passage of a second conductivity type carrier different from the first conductivity type, a photoelectric conversion semiconductor layer, and the first layer. A photoelectric conversion device in which a conductive type carrier and a second insulating layer that blocks passage of the second conductive type carrier, and a second electrode layer are stacked, a gate electrode layer, a third insulating layer, a semiconductor layer, A pair of first and second main electrode layers that separate a part that becomes a channel region of the semiconductor layer, and a switch element in which an ohmic contact layer is laminated between the main electrode layer and the semiconductor layer; A photoelectric conversion device comprising: a wiring layer electrically connecting the first or second electrode layer of the conversion element and the first main electrode layer of the switch element on the same substrate. 2. A control means for controlling ON / OFF of the switch means, wherein the control means, in the refresh mode, includes the carrier of the first conductivity type and the second carrier in the photoelectric conversion semiconductor layer. In order to promote recombination with a conductive type carrier, a potential difference is applied between the first electrode layer and the second electrode layer of the photoelectric conversion element, or the first electrode layer and the second electrode layer are formed. At the same potential, in the photoelectric conversion mode, the first and second conductivity type carriers generated by the light incident on the photoelectric conversion semiconductor layer are respectively formed at the interface between the second insulating layer and the photoelectric conversion semiconductor layer. , A potential difference is provided between the first electrode layer and the second electrode layer of the photoelectric conversion element so as to be guided to the interface between the first insulating layer and the photoelectric conversion semiconductor layer, and the photoelectric conversion mode, The first insulating layer and the photoelectric conversion In order to detect the carrier of the second conductivity type guided to the interface with the semiconductor layer or the carrier of the first conductivity type guided to the interface between the second insulating layer and the photoelectric conversion semiconductor layer, The photoelectric conversion device according to claim 1, which is a means for controlling the switch element. 3. The first electrode layer and the gate electrode layer of the photoelectric conversion element and the switch element, the first insulating layer and the third insulating layer, the photoelectric conversion semiconductor layer and the semiconductor layer, The said 2nd electrode layer and the said 1st and 2nd main electrode layer are each comprised by the common film | membrane or Claim 2 or Claim 2.
The photoelectric conversion device described in 1. 4. A capacitive element including a third electrode layer, a fourth electrode layer, and an intermediate layer between the third electrode layer and the fourth electrode layer, the intermediate layer having at least a fourth insulating layer. And a wiring layer electrically connecting the first or second electrode layer of the photoelectric conversion element and the third or fourth electrode layer of the capacitive element on the same substrate. The photoelectric conversion device according to claim 3. 5. The first electrode layer and the third electrode layer of the photoelectric conversion element and the capacitor, the second electrode layer and the fourth electrode layer, the first or second insulation The photoelectric conversion device according to claim 4, wherein the layer and the fourth insulating layer are formed of a common film. 6. The photoelectric conversion device according to claim 1, wherein at least a part of the photoelectric conversion semiconductor layer and the semiconductor layer is amorphous hydrogenated amorphous silicon. . 7. The photoelectric conversion according to claim 1, further comprising a detection unit that detects an integrated value of the first or second conductivity type carriers generated in the photoelectric conversion mode. apparatus.