JP2578954B2 - Semiconductor device - Google Patents

Description

Description: BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a semiconductor device such as an optical sensor, and more particularly to an improvement in insulation between conductors stacked via a semiconductor layer.

[Conventional technology]

2. Description of the Related Art In recent years, techniques for forming a plurality of thin film semiconductor elements on a substrate have been developed as semiconductor devices such as ICs, LSIs, liquid crystal displays, and optical sensors. For this reason, a plurality of intersections are required for wiring between elements.

In particular, thin film transistors (TF
T) with 10000 or more, 1x line sensor for A4 reading
It is necessary to form 8 sensor elements per 1 mm, that is, 1728 optical sensor element elements and TFTs corresponding to each sensor element element on the same substrate.

For this reason, more intersecting portions are required for the wiring between the elements. For example, when adopting matrix wiring to reduce the number of TFTs and downsize the device, the number of intersections is 10
000 places or more.

In order to form such a large number of intersections, in order to simplify the process and reduce the cost, it is necessary to use a semiconductor layer or an insulating layer for forming an element without providing a dedicated insulating layer. A configuration that insulates the part is preferably adopted.

FIG. 5A is a schematic plan view of an example of a semiconductor device,
FIG. 5 (B) is a schematic sectional view taken along line II of FIG.
For convenience of explanation, a part of other accessory parts is also shown. Since the present invention is suitably used for a contact-type photoelectric conversion device using a photoconductive line sensor using electrons as a carrier, a description will be given based on an example of the device as shown in FIG. Here, matrix wiring is employed for the signal readout system. 1, a common wiring 4 and a shield wiring 11 are formed on a substrate 1, and an insulating layer 5, an intrinsic semiconductor layer (hereinafter, referred to as “i layer”) 6 and an n ⁺ layer 7 for ohmic contact are formed thereon. Are laminated. Then, the individual electrode wiring 8 from the optical sensor 9 is formed, and is connected to the common wiring 4 through the contact hole 10b.

In such a matrix wiring, the shield wiring 11
Is supplied with a constant positive voltage by the power supply Va.
This is to prevent crosstalk caused by capacitive coupling between the common lines 4.

The common wiring 4 is connected to a current-voltage conversion circuit (not shown) composed of an operational amplifier or the like, and converts the photocurrent from the optical sensor 9 into a voltage and outputs it to the outside. Note that the connection potential of the common wiring 4 in this configuration is used as a reference potential.

[Problems to be solved by the invention]

However, as a result of many experiments by the present inventors, it has been found that the above-described semiconductor device has the following problems.

FIG. 6 is a schematic sectional view taken along line II-II in FIG. 5 (A).

As described above, the shield wiring 11 is supplied with a positive voltage from the power supply Va, and the individual electrode wiring 8 is connected to the common wiring 4, so that the reference voltage is almost the ground voltage. That is, in FIG. 6, the shield wiring 11 has a higher potential than the individual electrode wiring 8.

In this state, can supply electrons to the i layer 6 through n ⁺ layer 7 here because the individual electrode wiring 8 is lower potential than the shielding wire 11, the insulating layer side electrons through the n ⁺ layer 7 and the i layer 6 Move to.

For this reason, if the insulating layer 5 has a defect or is locally thinned due to a variation in the manufacturing process or the like, the electric field in that portion becomes strong, and there is a possibility that dielectric breakdown may occur during operation. In addition, the electric field between the arrows A in the figure also becomes strong, and if impurity ions, water, and the like are present on the side surface of the insulating layer 5 and the surface of the wiring 11, there is a high possibility that the lower wiring 11 is dissolved by electrolysis to break. It became clear that it had the problem of becoming.

In addition, since the insulating layer 5 is insulated depending on the thickness of the insulating layer 5, the over-etching 19 or the like at the time of manufacturing is liable to cause a decrease in electric breakdown voltage, which leads to a decrease in yield and reliability. Had also.

Such a problem is caused not only at the intersection between the shield wiring 11 and the individual electrode wiring 8 but also at the intersection 22 ″ between the wiring 22 to which the positive voltage is applied by the power supply Vb and the wiring 22 ′ grounded.
(See FIG. 5 (A)).

[Means for Solving the Problems] In a semiconductor device according to the present invention, two conductors are opposed to each other across a laminated body including an insulating layer and a semiconductor layer, and an average potential of a first conductor bonded to the semiconductor layer is provided. The average potential of the second conductor bonded to the insulating layer with respect to the direction is such that the supply of carriers that can be supplied from the first conductor to the semiconductor layer is blocked.

In addition, a semiconductor device according to the present invention includes a plurality of photoelectric conversion elements each having a semiconductor layer for performing photoelectric conversion on a substrate and an individual electrode electrically connected to the semiconductor layer for performing photoelectric conversion; Matrix wiring connected to
A semiconductor device having a wiring provided between the matrix wirings and maintained at a constant potential, wherein a crossing portion between the individual electrode and the wiring maintained at the constant potential is provided with a semiconductor layer and an insulating layer interposed therebetween. The average potential of the individual electrodes is a potential for preventing supply of carriers that can be supplied to the semiconductor layer.

[Action]

In the present invention, by setting the average potential of the first and second conductors as described above, the semiconductor layer as well as the insulating layer contributes to insulation, and the thickness of the layer serving as an insulating layer can be substantially increased. it can.

For this reason, even if the insulating layer is locally thin, no strong electric field is generated there, and the insulation and durability between the two conductors are greatly improved as compared with the conventional one, so that a highly reliable semiconductor device can be manufactured. Can be provided.

〔Example〕

Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings.

 First, an embodiment of the present invention will be described.

One of the preferred embodiments of the present invention includes a conductive layer forming two wirings that are connected to each other through a stacked body including an insulating layer and a semiconductor layer, and each of the conductive layers has an average potential of at least one. There is a semiconductor device which is configured so as to block supply of carriers to a semiconductor layer.

For example, as shown in FIG. 1A, a first wiring 101 as a conductive layer, an insulating layer 102, an i-type semiconductor layer 103, an n ⁺ -type semiconductor layer 104, and a second wiring 110 as a conductive layer. In the case of a semiconductor device having a structure, the potential of the first wiring 101 is lower than that of the second wiring 110.

Note that when the semiconductor layer 104 is a P ⁺ -type layer, the first wiring 101 may have a higher potential than the second wiring 110.

As shown in FIG. 1B, the first wiring 201 and the insulating layer 2
02, a semiconductor device having an i-type semiconductor layer 203 and a second wiring 210, wherein the second wiring 210 is made of Al or Cr and forms a Schottky barrier with respect to the i-layer 203. 1
The wiring 201 may be set to a higher potential than the second wiring 210.

As described above, the average potential of the conductive layer can be appropriately selected depending on the configuration, conductivity type, carrier concentration, and the like of the semiconductor layer.

Next, a most preferred embodiment to which the present invention is applied will be described in detail with reference to the drawings.

FIG. 2 (A) is a schematic plan view of one embodiment of the semiconductor device according to the present invention, and FIG. 2 (B) is a schematic sectional view taken along line III-III.

This embodiment is a contact-type photoelectric conversion device, and uses a line sensor in which a plurality of photoconductive sensors using electrons as carriers are arranged in the vertical direction on the paper surface of FIG. However, in the figure, only a configuration for two bits is shown for simplification.

[Preparation of Sample 1] As shown in each figure, 0.1 μm of Al / Cr was deposited on a cleaned glass plate 1 as a translucent insulating substrate by a vacuum deposition method.
Next, a resist pattern is formed by photolithography and wet etching is performed to form a light-shielding layer 2 having an illumination window 3, a wiring 22 'for fixing the light-shielding layer 2 to a ground potential, and a matrix individual electrode wiring 23. Then, a light-transmitting insulating layer 5 made of silicon nitride was formed to a thickness of 0.3 μm by RF glow discharge using a SiH ₄ gas and an NH ₃ gas as film forming materials by a plasma CVD method.

Subsequently, an i-layer 6 of a-Si or the like serving as a photoconductive layer was formed to a thickness of 1 μm using SiH ₄ gas as a film forming material. Further, an n ⁺ layer 7 for an ohmic contact was laminated to a thickness of 0.1 μm using SiH ₄ gas and PH ₃ gas as raw materials for film formation. Then, a resist pattern is formed by photolithography, reactive ion etching is performed as dry etching using CF ₄ gas, and the n ⁺ layer 7, i layer 6, and insulating layer 5 are partially removed to form contact holes 10b and 10c. Was formed.

Thereafter, Al was deposited to a thickness of 1.0 μm by a vacuum deposition method, a resist pattern was formed by photolithography, and wet etching was performed to partially remove Al. Further, the n ⁺ layer was removed by dry etching to form the upper wirings 4, 11, 8, 22 and the like. Further, each element was independently separated by the same dry etching as described above.

Finally, a light-transmitting protective film 15 made of polyimide and epoxy resin was formed and completed.

Thus, a photoelectric conversion device according to the present invention was produced. This photoelectric conversion device has electrodes 8 of both terminals of an optical sensor 9,
Wiring 2 for supplying a positive voltage from power supply Vb to optical sensor 9
2. It has a matrix common wiring 4 and a shield wiring 11, and a positive voltage is applied to the shield wiring 11 from a power supply Va to prevent cross stall.

The individual electrode wirings 23 from each optical sensor 9 are connected to the common wiring 4 through the contact holes 10b to form a matrix wiring.

Further, the insulating layer 5, the i-layer 6, and the n ⁺ layer 7 between the common wiring 4 and the shield wiring 11 are removed by etching.

[Preparation of Sample 2] Sample 2 was prepared using the same method as sample 1 described above.
It was created. Sample 2 is the photoelectric conversion device shown in FIG. 5 as described above, and is different from sample 1 in that the arrangement of the matrix common wiring 4, the shield wiring 11 and the individual electrode wiring 23, and the arrangement of the wirings 22 and 22 'are upside down. All the layers were formed by the same film formation and etching method as in Sample 1.

Here, the operation of the contact type image sensor will be briefly described with reference to FIG. 2 (B).

The present embodiment is brought into close contact with a document 17 to be read by a roller 16 or the like, and light is emitted from the light source (not shown) to the document 17 through the illumination window 3. When the reflected light is incident on the optical sensor 9, the resistance value of the i-layer 6 of the optical sensor 9 changes according to the intensity of the incident light, and the information on the document 17 is converted into an electric signal.

The output signal of the optical sensor 9 appears on the common wiring 4 through the individual wiring 23 and is output to the outside through a current-voltage conversion circuit (not shown).

[Experiment I]

As an example in which the voltage applied to the shield wiring is fixed and the positions of the shield wiring and the individual electrode wiring are different, the following experiment was performed on a plurality of prepared samples 1 and a plurality of samples 2.

First, at a temperature of 80 ° C. and a relative humidity of 85%, the intersection 23 ′ is observed with a microscope while a voltage of 5 V is applied to the shield wiring 11 and a voltage of 3 V is applied to the individual electrode wiring 23 of each of the samples 1 and 2. While light incident on the photoelectric conversion
The output signal from was observed.

As a result, in Sample 2, corrosion occurred in all of Sample 2 after 150 hours from the start of the experiment, and the output signal was disturbed.

However, it was 500 hours after the first disturbance of the output signal due to corrosion was observed in Sample 1.

(Experiment II)

Next, another experiment was performed using a plurality of samples 2 prepared as an example in which the positions of the shield wiring and the individual electrodes were the same.

First, a voltage of 3 V is applied to the individual electrode wiring 23 at an environmental temperature of 80 ° C. and an environmental humidity of 85%, and the voltage applied to the shield wiring 11 is 0 V, 3 V, 5 V, and the intersection 23 ′ The output signal was observed while observing.

 The following table shows the results.

As described above, the sample 2-1 and the sample 2-2 according to the present invention obtained good results.

(Experiment III)

Further, another experiment was performed using the plurality of samples 2 thus prepared. A withstand voltage test was performed by changing the direction of the voltage applied to the individual electrode wiring 23 and the shield wiring 11.

As a result, the withstand voltage when the potential of the individual electrode wiring 23 was higher than the potential of the shield wiring 11 was 30 V.

On the other hand, when the potential of the individual electrode wiring 23 was lower than the potential of the shield wiring 11, the withstand voltage was 250V.

The contact type photoelectric conversion device according to the present embodiment described above is suitably used for, for example, a facsimile device.

FIG. 3 is a schematic configuration diagram of a facsimile apparatus using the photoelectric conversion device according to the above embodiment.

In the figure, at the time of document transmission, a document 1205 is pressed on a contact image sensor 1201 as a photoelectric conversion device by a platen roller 1203, and is moved in the direction of the arrow by a platen roller 1203 and a feed roller 1204. The surface of the document is illuminated by a xenon lamp 1202 as a light source, and the reflected light is incident on a sensor 1201 to be converted into an electric signal corresponding to image information of the document and transmitted.

At the time of reception, the recording paper 1206 is
And the thermal head 1208 reproduces an image corresponding to the received signal.

The entire apparatus is controlled by a controller of a system control board 1209, and power is supplied from a power supply 1210 to each drive system and each circuit.

As a result of carrying out image communication by mounting the photoelectric conversion device according to the present invention on the facsimile apparatus described above, the communication image was favorably maintained even when used for a long time.

Hereinafter, an operation according to the present invention in the above-described contact type photoelectric conversion device of the present embodiment will be described.

FIG. 4 is an enlarged schematic cross-sectional view of a portion of the shield wiring 11 in FIG. 2 (B).

According to the present embodiment, as described above, the shield wiring 11
Is supplied with a positive voltage from the power supply Va. The individual electrode wiring 23 is a wiring for passing the output signal of the optical sensor, and its reference potential is set to the ground potential. Therefore,
As the average potential, the individual electrode wiring 23 has a lower potential than the shield wiring 11.

As a result, the i-layer 6 is depleted of electrons, and cannot move between the n ⁺ layer 7 and the i-layer 6 even if a hole is generated, so that the i-layer 6 functions as an insulator. That is, the substantial thickness of the insulating layer in this embodiment is
Thus, the insulation and the durability are both significantly improved as compared with the prior art. In other words, for example, if the insulating layer 5 is over-etched or locally thinned at the time of manufacture, the i-layer 6 is also an insulator, so that the over-etched portion 19 reduces the withstand voltage. In addition, it is possible to prevent dielectric breakdown or the like due to concentration of an electric field on the thin portion 24.

Further, since the substantial insulating layer is thicker, the electric field between the arrows B in the drawing becomes weaker than before, and as a result, promotion of electrolysis on the side surfaces of the insulating layer 5 and the i-layer 6 is suppressed. Thus, the situation where the wiring 23 is melted can be prevented. Similarly, since the intersection of the wirings 22 and 22 'in FIG. 2A has the same structure, the insulation and durability between the wirings can be improved. Therefore, according to the present invention, high reliability can be obtained even when a large number of wiring intersections exist in the entire device as in such a photoelectric conversion device.

In this embodiment, the configuration is shown in FIG. 2, but the configuration is not limited to this. As described above, for example, even in the configuration of the intersection of the shield wiring 11 and the individual electrode wiring 8 shown in FIG. 5, if the polarity of the power supply Va can be reversed in the circuit configuration, the shield wiring 11 is connected to the individual electrode wiring. If the average potential is lower than that of the i.sup.8, the i-layer 6 is depleted of electrons serving as carriers, and cannot move between the n ⁺ layer 7 and the i-layer 6 even if holes are generated. It functions as an insulator, and an effect equivalent to that of this embodiment can be obtained.

Furthermore, as described above, the ohmic contact layer 7 is formed using an optical sensor using holes as carriers.
Is formed in the p ⁺ layer, when the potential relationship with the counter electrode at the wiring intersection is the relationship between the shield wiring 11 and the individual electrode wiring 8 shown in FIG. A certain hole is in a depletion state, and even if electrons are generated, it cannot move between the p ⁺ layer and the i layer. Therefore, the i layer 6 functions as an insulator, and the same effect as that of the present embodiment can be obtained.

As described above, if a material that forms a Schottky barrier between the i layer 6 and at least one of carriers of electrons and holes is used as an electrode, the n ⁺ layer and the p ⁺ layer become This is unnecessary, and the same effect as that of the present embodiment can be obtained by setting the average potential between the common electrode and the counter electrode so as to prevent the supply of carriers capable of supplying the i-layer.

In this embodiment, the structure includes the i-layer. However, the present invention is not limited thereto. To summarize the above, if the average potential of the counter electrode for any semiconductor layer is such that the supply of carriers that can be supplied to some or all of the semiconductor layers is prevented, at least the carrier supply The layer in which is prevented functions as an insulator, and the same effect as that of the present embodiment is obtained, thereby achieving the object of the present invention.

Further, in the present embodiment, a DC voltage is applied to the shield wiring 11, but the present invention is not limited to this. The shield wiring 11 has a similar laminated structure, and a pulse-like voltage is applied to upper and lower wirings. Even in this case, if the average potential is set as described above, the same effect as that of the present embodiment can be obtained.

In addition, the present invention can be preferably applied to the contact type photoelectric conversion device as in the present embodiment, but is not limited thereto. The present invention is applicable to a general semiconductor device having a multilayer structure requiring an insulating region. That is, by applying the present invention to an information processing apparatus such as a facsimile apparatus, the yield can be improved at low cost, and a highly reliable information processing apparatus can be realized.

〔The invention's effect〕

As described in detail above, in the semiconductor device according to the present invention, the average potential of the first and second conductors is set so as to block the supply of carriers that can be supplied from the first conductor to the semiconductor layer. Therefore, the semiconductor layer together with the insulating layer also contributes to the insulation, and the thickness of the insulating layer is substantially increased.

For this reason, even if the insulating layer is locally thin, a strong electric field is not generated there, and the insulation and durability between the two conductors are greatly improved, and the reliability and durability of the device are high. Become.

[Brief description of the drawings]

1 (A) and 1 (B) are schematic sectional views showing a preferred embodiment of the present invention. FIG. 2 (A) is a schematic plan view of one embodiment of the semiconductor device according to the present invention, and FIG. 2 (B) is a schematic sectional view taken along line III-III. FIG. 3 is a schematic configuration diagram of a facsimile apparatus using the photoelectric conversion device according to the above embodiment. FIG. 4 is an enlarged schematic cross-sectional view of a portion of the shield wiring 11 in FIG. 2 (B). FIG. 5A is a schematic plan view of an example of the semiconductor device, and FIG. 5B is a schematic cross-sectional view taken along the line II. FIG. 6 is a schematic sectional view taken along line II-II in FIG. 5 (A). 101, 201: first wiring, 102, 202: insulating layer, 103, 203: i-type semiconductor layer, 104: n ⁺ type semiconductor layer, 110, 210: second wiring.

Claims (11)

(57) [Claims] A second conductor joined to the insulating layer with respect to an average potential of the first conductor joined to the semiconductor layer; A semiconductor device, wherein an average potential is in a direction in which supply of carriers that can be supplied from the first conductor to the semiconductor layer is prevented. 2. The semiconductor device according to claim 1, wherein said semiconductor layer has an i-layer and an n ⁺ ohmic contact layer, and an average potential of said first conductor is higher than an average potential of said second conductor. . 3. The semiconductor device according to claim 1, wherein said semiconductor layer has an i-layer and a p ⁺ ohmic contact layer, and an average potential of said first conductor is lower than an average potential of said second conductor. . 4. The semiconductor device according to claim 1, wherein said first conductor forms a Schottky barrier with respect to said semiconductor layer. 5. The semiconductor device according to claim 1, wherein said semiconductor layer is made of hydrogenated amorphous silicon. 6. A plurality of photoelectric conversion elements each having a semiconductor layer for performing photoelectric conversion on a substrate and individual electrodes electrically connected to the semiconductor layer for performing photoelectric conversion, and a matrix electrically connected to the photoelectric conversion elements. In a semiconductor device having a wiring and a wiring provided between the matrix wirings and held at a constant potential, a portion where the individual electrode intersects with the wiring held at the fixed potential sandwiches a semiconductor layer and an insulating layer. Wherein the average potential of the individual electrodes is a potential for preventing supply of carriers that can be supplied to the semiconductor layer. 7. The intersecting portion includes the individual electrode, the semiconductor layer provided on the individual electrode via the insulating layer, and the wiring provided on the semiconductor layer via an n ⁺ layer. The semiconductor device according to claim 6, wherein the average potential of the individual electrodes is lower than the potential of the wiring. 8. The intersecting portion includes the individual electrode, the semiconductor layer provided on the individual electrode via the insulating layer, and a wiring provided on the semiconductor layer via a p ⁺ layer. 7. The semiconductor device according to claim 6, wherein the average potential of the individual electrodes is higher than the potential of the wiring. 9. The semiconductor device according to claim 1, wherein the crossing portion is formed between the wiring and the semiconductor layer provided on the wiring with the insulating layer interposed therebetween.
7. The semiconductor device according to claim 6, further comprising an individual electrode provided through an n ⁺ layer, wherein an average potential of the individual electrode is higher than an electric potential of the wiring. 10. The intersecting portion includes the wiring, the semiconductor layer provided on the wiring via the insulating layer, and the individual electrode provided on the semiconductor layer via a p ⁺ layer. The semiconductor device according to claim 6, wherein the average potential of the individual electrodes is lower than the potential of the wiring. 11. The semiconductor device according to claim 6, wherein said semiconductor layer is made of hydrogenated amorphous silicon.