JPS63199458A - Light-receiving device and one-dimensional image sensor using this device and manufacture of said device - Google Patents

Abstract

PURPOSE:To obtain a light receiving device with high yield and a few manufacturing processes and to make this device have excellent characteristics even when a protective film of Si3N4 or the like is formed on insular a-Si:H semiconductors, by making a transparent electrode in contact with only an upper surface part of longitudinal struc ture of insular hydrogenated amorphous silicon semiconductors and not in contact with the side part. CONSTITUTION:Insular hydrogenated amorphous silicon semiconductors 3' and 8', a transparent electrode 12, and a transmissive protective film are serially laminated on an electrode 2' which is made of a conductor on an insulating substrate 1'. Such a light-receiving device is composed so that a transparent electrode 12 is made in contact with only an upper surface of longitudinal structure of the insular hydrogenated amorphous silicon semiconductors 3' and 8' and not in contact with the side part. For example, an insular lower electrode 2' is formed on the insulating substrate 1', and an (i) layer 3' of an a-Si:H film and a P layer 8' of an a-Si:H film are formed on the electrode 2'. Thereafter, when Cr is disposed all over the surface, the transmis sive conductor layer 12 is formed by an interfacial reaction of a-Si:H 3' and 8' to Cr. In succession, Cr is etched to form an upper electrode 11, and next a-Si:H 3' and 8' are etched into an insular shape.

Description

[Detailed Description of the Invention] [Field of Industrial Application] The present invention relates to a one-dimensional image sensor, which is an image reading device such as a facsimile, and a photoelectric conversion element (hereinafter referred to as a light-receiving device) made of hydrogenated amorphous silicon used therein. A light-receiving element that is suitable for preventing the occurrence of crosstalk and eliminating characteristic deterioration in order to expect highly reliable and high performance, and a one-dimensional image sensor that uses this light-receiving element. The present invention relates to a method of manufacturing the light receiving element.

[Conventional technology]

Conventionally, a light receiving element made of hydrogenated amorphous silicon used in a -dimensional image sensor is manufactured by Nikkei Electronics <NIXXEI ELECTRONIC3) 19
As described in April 28, 1982, pages 149 to 161, metal/hydrogenated amorphous silicon (hereinafter a-
3i:H)/indium thene oxide (In
-dium Tin Oxide) (hereinafter referred to as ITO) has been proposed.

That is, as shown in FIG. 4, a metal electrode 2, a-3i:■] film 3, I
It has been proposed that the TO electrodes 4 are formed in this order.

[Problem that the invention seeks to solve]

In putting the above-mentioned conventional technology into practical use, as shown in FIG.
A device covered with a protective film 5 made of O7 or the like is used.

However, when covered with this protective film 5, there is a problem that the characteristics are significantly deteriorated.

In other words, the voltage in the dark that forms the protective film 5 at 70°C, which is the upper limit temperature at which the -dimensional image sensor is used, and the reverse current (current flowing from the metal electrode 2 to the protective film 5) As shown in FIG. 6, the characteristics of the reverse current 6 before forming the protective film 5 and the reverse current 7 after forming the protective film 5 are shown in FIG. has increased by about three orders of magnitude. The reverse current in a normal-dimensional image sensor is 1. Xl,
Since it is said that 0-'A/C- or less is desirable, the characteristics of the light-receiving element will deteriorate even though the protective film 5 is formed. This characteristic deterioration is thought to be caused by the deterioration of the bonding characteristics between the hydrogenated amorphous silicon and the rTO interface due to the formation of the 5jN4 or SiO□ film.

This characteristic deterioration is caused by hydrogenated amorphous silicon (
(hereinafter abbreviated as a-3i:H) 3 as shown in FIG.
a obtained by glow discharge decomposition of only S i Ha gas
-3i:H first layer (hereinafter abbreviated as 'r layer) 3 and SiH
<B-added a-3i:H obtained by glow discharge decomposition of a mixed gas of gas and B2H6 gas which is a doping gas
It has been found that this problem can be solved by creating a two-layer structure consisting of a second layer (hereinafter abbreviated as P layer) 8. This is shown in FIG.

In other words, FIG. 8 shows the characteristics of the photoelectric conversion element having the structure shown in FIG. 7 in the dark before and after the formation of the protective film.
At 0° C., there is no difference between the reverse current 9 before the protective film is formed and the reverse current 10 after the protective film is formed, and there is no characteristic deterioration due to the protective film formation. At this time, P which is the second layer of a-3i:H
The layer was formed by glow discharge decomposition of a mixed gas of B2H6/SiH, = 0.04% by volume, and the film thickness was 250 mm.
It's a person.

However, if this hydrogenated amorphous silicon is formed into an island shape as shown in FIG. It has been found that under a certain voltage, some elements exhibit characteristic deterioration in which the current increases over time. This is shown in FIG.

In other words, FIG. 10 shows the photoelectric conversion element of a-3i:H formed in an island shape as shown in FIG. 9 after formation of a protective film at 70° C. when a constant voltage of 5 V is applied in a dark place. It shows the change in reverse current over time. This characteristic is not practical. This characteristic deterioration is caused by a
-3t:H was processed into an island shape, a-3i:
The cause is thought to be that the layer 3 is exposed on the side surface of the H, and the bonding characteristics between the layer 3 and the TTO interface deteriorate due to the formation of the protective film, resulting in current leakage. This can be fully considered from the following facts.

In other words, the increase in the reverse current before and after forming the protective film for only one layer 3 is approximately 2Xl when 5V is applied, as shown in Figure 6.
0-5A/afl. The pixel size of a-3t:H formed in an island shape showing the characteristics shown in Fig. 10 is 100 μm
The film thickness is 150 μm, and the film thickness is 1 μm. Therefore, side 1
The area of the exposed portion of layer 3 is approximately 3% of the surface area of a-3i:I(.
/cta, so the side surface is approximately 6X10-'A/
The reverse current increases by d, which almost matches the value of the reverse current increasing over time shown in FIG. Moreover, this characteristic deterioration is caused by not processing a-3i:H into an island shape, but with one layer 3 and P
This does not occur as long as the two-layer structure of layer 8 is used.

However, if a-3i:H is not formed like an island like this, each pixel will be electrically connected due to this a-3i: Charge flows into the pixel, causing a phenomenon in which a pixel that is not receiving light appears to be receiving light, that is, large loss talk, which causes a problem in that the characteristics of the -dimensional image sensor, particularly the resolution, deteriorate.

In addition, in the case where a-3t:H is sandwiched between a metal electrode and an ITO electrode as described above, if a pinhole occurs in a-3i:H, the metal electrode and ITO electrode are connected through the pinhole. There is a problem in that the yield is significantly reduced due to short-circuiting.

An object of the present invention is to provide a light receiving element that solves the problems of the prior art and enables high reliability and high performance, a one-dimensional image sensor using this light receiving element, and a method for manufacturing the light receiving element. It's about doing.

[Means for solving problems]

The above purpose is to form a photodetector by sequentially laminating a hydrogenated amorphous silicon semiconductor formed in an island shape on an electrode made of a conductor on an insulating substrate, a transparent electrode, and a transparent protective film. This is achieved by configuring the light-receiving device consisting of a hydrogenated amorphous silicon semiconductor formed in an island shape so that only the top surface of the vertical structure is brought into contact with the transparent electrode, and the transparent electrode is not provided on the side surface. , for a one-dimensional image sensor using the above-mentioned light-receiving element, a hydrogenated amorphous silicon semiconductor formed in an island shape on a lower electrode formed in an island shape of a conductor, a transparent electrode, and a light-transmitting Protective films are sequentially laminated, and a light-receiving element formed in such a way that only the top surface of the vertical structure of the island-shaped hydrogenated amorphous silicon semiconductor contacts the transparent electrode and does not contact the side surface is placed on an insulating substrate. This is achieved by arranging a plurality of bonding bats in a one-dimensional direction and connecting them to the protective film, and connecting the bonding bats to the scanning integrated element by wire bonding. Regarding the manufacturing method, a layer of hydrogenated amorphous silicon semiconductor is formed by glow discharge decomposition of only monosilane gas on a lower electrode formed in an island shape of a conductor, and a layer is formed by glow discharge decomposition of a mixed gas of monosilane gas and doping gas. A step of forming two or more layers with the formed layer, a step of forming an insulating layer such as an oxide film on the side surface of each layer of the hydrogenated amorphous silicon, and a step of forming the hydrogenated amorphous silicon with the hydrogenated amorphous silicon. forming a transparent conductor for light incidence through an interfacial reaction with a metal film directly formed on crystalline silicon;
a step of forming the remaining portion of the metal film after removing the region of the transparent conductor for light incidence as an upper electrode; and a step of forming each layer of the hydrogenated amorphous silicon into an island shape;
This is accomplished by including the step of forming a protective mask on the required portions of the hydrogenated amorphous silicon.

[Effect]

As mentioned above, the characteristic deterioration due to the formation of the protective film is a-3.
The problem in the vertical direction can be solved by making the vertical structure of i:H into two layers, the i layer and the P layer.

Further, characteristic deterioration in the lateral direction, that is, in the side surface portion of a-3t:H exposed by processing a-3i:H into an island shape, does not occur unless the side surface portion and the transparent electrode are bonded.

However, as long as the transparent electrode is made of ITO, a −3i:H
Bonding of the side surface of the ITO to the ITO cannot be avoided.

Therefore, in the present invention, the transparent electrode is made into a transparent conductive layer formed by an interfacial reaction between a-3i:H and a metal film directly formed on this a-3i:H, and then the a- 3
t:H was processed into an island shape so that there was no connection between the side surface and the transparent electrode, so that the a-3i
It is possible to prevent short circuits between the transparent electrode and the metal electrode, which is the lower electrode formed on the substrate, through the pinholes that occur during the formation of :H.

In addition, the transparent electrode is drawn out using a conductive layer formed from the remaining portion of the metal film after removing the area that should be used as the transparent electrode, so the remaining metal film doubles as a light-shielding film and crosses. Talk can be prevented.

〔Example〕

Hereinafter, FIG. 1 (
al, (bl, (c)) will be explained.

As shown in FIG. 1 (al, (bl, (C1)), a lower electrode 2' processed into an island shape is provided on an insulating substrate 1'.

This lower electrode 2' is formed of Cr by a 1000-person sputtering method, and is formed into an island shape by a photoetching process.

Next, the substrate 1' is placed in a reaction chamber of a plasma CVD apparatus (not shown) and heated in a vacuum state.
After forming layer 3' with a thickness of about 1 μm, the hydrogen-diluted 82F+6 gas was introduced to form a-3i with a thickness of about 250λ.
: Form the P layer 8' of the H film.

Next, the substrate 1' is taken out from the plasma CVD apparatus, and in order to remove the oxide film caused by natural oxidation of a-3t:H3', 8', light etching is performed using a fluoro-nitric acid aqueous solution, and then approximately Cr is removed by a sputtering method. 0.1
It is formed on the entire surface of the substrate 1 to a thickness of μm. At this time, the temperature of the substrate 1 is preferably in the range of 100°C to 250°C.

As a result, a-3t:H3', 8' and this a-3t
: A translucent conductor 112 is formed by an interfacial reaction with Cr formed on H3' and 8'.

Next, the region 13 to be formed as the transparent conductor layer 12 for the water-immersion elbow is removed by photoetching Cr, and at the same time, Cr is left in the region 13 to be formed as the extraction electrode of the transparent electrode, which is the transparent conductor layer I2. and pattern the upper electrode 1.
1, a photoresist is laminated on the remaining upper electrode 11 and the region 13, which is a transparent conductor layer for light incidence, to form a-3i:H3'.

Etch 8'. This etching is Mazua-3
i:H3', 8' and this a-3i:H3'.

The transparent conductor layer 12 formed by an interfacial reaction with Cr formed on 8' is formed using a fluoro-nitric acid aqueous solution, and the 1 layer 3' of H is formed using a hydrazine aqueous solution. As a result, a-3i:H3', 8' is formed into an island shape.

Therefore, there is no connection between the side parts of a-3i: H3', 8' and the transparent electrode, and the transparent electrode and the lower electrode are connected through the pinholes that occur when forming a-3i: H3', 8'. It is possible to create a structure in which short circuits with certain metal electrodes 2 do not occur.

Further, since the upper electrode 11 also serves as a light shielding film, crosstalk can be prevented.

Next, FIG. 2 shows a one-dimensional image sensor using the light receiving element shown in FIG.
Figure [bl is AA' sectional view of Figure 2 (al), Figure 2 (C
) is a BB' sectional view of FIG. 2 (al).

As shown in FIGS. 2(a), (b), (cl), a lower electrode 2'' is formed on an insulating substrate 1'' made of glass or the like by the same method as the metal electrode 2' described in FIG. In this case, the island pitch of the lower electrode 2'' is 8 pixels/
In a one-dimensional image sensor of mm, the thickness is 125 μm.

Then, in the same manner as described in FIG. 1, a-5i:H
After forming the I-layer 3' and P-layer 8' of the film, plasma CV
A protective film I5 of 5LNa having a thickness of 2 μm is deposited on required portions using a mask by glow discharge decomposition using 5iHa, N Hs, and N 2 by method D.

After that, NiCr16. A
U'17 is sequentially laminated by sputtering and formed by photoetching to form a ponding pad. This bonding pad and the scanning integrated element 18 bonded to the substrate 1'' are connected by wire bonding 19.

Next, Flexible Printed Surkisoto (Flex
By connecting FPC (hereinafter referred to as FPC) 20, a one-dimensional image sensor is completed.

As shown in Fig. 3, when a constant voltage of 5 cm is applied to the light receiving element of the above-mentioned -dimensional image sensor in a dark place, the temperature is 70°C.
As a result of an experiment on the change in reverse current over time after the protective film was formed, no characteristic deterioration was observed. In this case, although Figure 3 shows data for one pixel, it is possible to obtain characteristics with good reproducibility and no characteristic deterioration for all pixels as a -dimensional image sensor, and the light sensitivity and response speed are the same as conventional ones. characteristics can be obtained.

In addition, in the present invention, since ITO is not used as the transparent electrode, ITO, which is a problem when using ITO, is not used.
Damage to a-3t:H during TO formation, good quality ITO
ITO due to its difficulty in obtaining and poor chemical resistance.
It is possible to eliminate problems such as dissolution of

Furthermore, in the present invention, the metal electrode can be formed by simply stacking and removing the metal film after forming the a-3i:H film, so the manufacturing process is reduced compared to when ITO is used for the transparent electrode. In addition, it is possible to eliminate the short circuit between the metal electrode, which is the lower electrode, and the transparent electrode through the bottle ball that occurs when forming a-3i:H, so the yield can be greatly improved. can.

〔Effect of the invention〕

According to the present invention, it is possible to obtain a high-yield light-receiving element with few manufacturing steps that has good characteristics even when a protective film such as 51g4 is formed in an island-shaped a-8i:H semiconductor. Reliable, with good resolution
This has the effect of enabling a low-cost one-dimensional image sensor using a-8i:H.

[Brief explanation of the drawing]

FIG. 1 shows a light receiving element which is an embodiment of the present invention.
Figures (al is a plan view thereof, Figure 1 (bl is a sectional view, Figure 2 is a one-dimensional image sensor using the light receiving element shown in Figure 1), Figure 2 (al is a plan view thereof, Figure 2 (bl is Figure 2 f8) A-A' sectional view, Figure 2 fc) is Figure 2 (a) B-B' sectional view, Figure 3 is the protection of the light receiving element shown in Figure 1. Figure 4 is a cross-sectional view of a conventional light-receiving element before forming a protective film, Figure 5 is a cross-sectional view of a conventional light-receiving element after forming a protective film, and Figure 6 is a graph of the change in reverse current over time after film formation. is a reverse current curve diagram of a conventional light-receiving element, and FIG. 7 is a diagram of a conventional a-
3i: A cross-sectional view showing a light-receiving element with a two-layer structure consisting of H. Figure 8 is a reverse current curve diagram of the conventional light-receiving element shown in Figure 7 before and after the formation of a protective film. Figure 9 is a diagram showing the conventional island-shaped The cross-sectional view of the processed light-receiving element, FIG. 1O, is a reverse current curve diagram of the conventional light-receiving element shown in FIG. 1'... Insulating substrate, 2', 2''... Lower electrode, 3
'---a-3t:H i-layer, 3'-・-a-3i:H
P layer, 11...metal film, 12...transparent conductive layer,
13... Light incidence area, 14... Upper electrode, 15...
...Protective film, 16...NiCr, 17...Au, 1
8...Scanning integrated element, 19...Wire bonding, 19...FPCo Agent Patent attorney Tadashi Akimoto Figure 1 (b) 3'; j%) 12:j
1 Likelihood conductive layer 8': 41 layers) 1
3: Input elbow standard area 11: Metal film - 1k Fig. 3 Clearance (seconds) Fig. 4 Fig. 5 Fig. 6 Voltage (V) Fig. 7 Fig. 8 t /Th (V) Between legs 0 )

Claims (1)

[Scope of Claims] 1. Light receiving device formed by sequentially laminating a hydrogenated amorphous silicon semiconductor formed in an island shape on an electrode made of a conductor on an insulating substrate, a transparent electrode, and a transparent protective film. A light-receiving element characterized in that only the top surface of the vertical structure of the hydrogenated amorphous silicon semiconductor formed in the island shape is brought into contact with the transparent electrode, and the side surfaces thereof are not brought into contact. 2. The transparent electrode is composed of a transparent conductor layer formed by an interfacial reaction between the hydrogenated amorphous silicon and a metal film formed directly on the hydrogenated amorphous silicon. A light-receiving element according to claim 1, characterized in that: 3. The hydrogenated amorphous silicon semiconductor is composed of two or more layers: a layer obtained by glow discharge decomposition of only monosilane gas, and a layer obtained by glow discharge decomposition of a mixed gas of monosilane gas and doping gas. A light receiving element according to claim 1 or 2, characterized in that: 4. The light receiving device according to claim 1, 2, or 3, wherein the hydrogenated amorphous silicon semiconductor has a side surface formed of an insulating layer such as an oxide film. element. 5. A hydrogenated amorphous silicon semiconductor formed in an island shape, a transparent electrode, and a transparent protective film are sequentially laminated on a lower electrode formed in an island shape of a conductor, and the island shape is formed. A plurality of light-receiving elements formed in such a way that only the top surface of a vertical structure of a hydrogenated amorphous silicon semiconductor contacts the transparent electrode and does not contact the side surfaces are arranged one-dimensionally on an insulating substrate, and a plurality of light receiving elements are arranged in one dimension on an insulating substrate, and A one-dimensional image sensor characterized in that a connecting bonding bat is formed, and the bonding bat is configured to be connected to a scanning integrated element by wire bonding. 6. The transparent electrode is composed of a transparent conductive layer formed by an interfacial reaction between the hydrogenated amorphous silicon and a metal film formed directly on the hydrogenated amorphous silicon. A one-dimensional image sensor according to claim 5, characterized in that: 7. The hydrogenated amorphous silicon semiconductor is composed of two or more layers: a layer obtained by glow discharge decomposition of only monosilane gas, and a layer obtained by glow discharge decomposition of a mixed gas of monosilane gas and doping gas. A one-dimensional image sensor according to claim 5 or 6, characterized in that: 8. The primary device according to claim 5, 6, or 7, wherein the hydrogenated amorphous silicon semiconductor has a side surface formed of an insulating layer such as an oxide film. Former image sensor. 9. A layer formed of a hydrogenated amorphous silicon semiconductor by glow discharge decomposition of only monosilane gas on a lower electrode formed in an island shape of a conductor, and a layer formed by glow discharge decomposition of a mixed gas of monosilane gas and doping gas. a step of forming two or more layers of the hydrogenated amorphous silicon, a step of forming an insulating layer such as an oxide film on the side surface of each layer of the hydrogenated amorphous silicon, and a step of forming the hydrogenated amorphous silicon and the hydrogenated amorphous silicon. A step of forming a light-transmitting conductor for light incidence by an interfacial reaction with a metal film directly formed on the metal film, and a step of forming a remaining portion of the metal film after removing the region of the light-transmitting conductor for light incidence. It is characterized by comprising the steps of forming an upper electrode, forming each layer of the hydrogenated amorphous silicon into an island shape, and forming a protective mask at a required portion on the hydrogenated amorphous silicon. A method for manufacturing a light receiving element.