JPH05145054A - Photodiode and image sensor using the same - Google Patents

Abstract

PURPOSE:To reduce a leakage current between upper and lower electrodes of a photoconductive layer and to improve a manufacturing yield in a photodiode PD and an image sensor using the same. CONSTITUTION:A leakage current preventing insulating layer 5 is formed except a continuity region 2Ba between a lower electrode 2B and a photoconductive layer 7 on an upper surface of the electrode 2B of a photodiode PD, and the layer 7 is formed on the region 2Ba and the layer 5 around the region 2Ba. Since the layer 5 is formed before the layer 7 having a low manufacturing temperature is formed, the layer 5 is treated at a high temperature to provide excellent insulation.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a structure of a photodiode in which a photoconductive layer and an upper electrode are sequentially laminated on a lower electrode, and a thin film transistor for forming the photodiode and its light receiving amount detection circuit. And to an image sensor (so-called hybrid image sensor) arranged on an insulating substrate.

[0002]

2. Description of the Related Art Recently, an image sensor of the type described above is C
It has been attracting attention as an image reading device such as a FAX instead of a CD. In addition, the driving circuit unit is also a thin film transistor (TF
T), among others, high performance and low cost can be achieved by integrating with poly-Si TFT (polysilicon thin film transistor). "Development of TFT drive perfect contact type image sensor" (1990, 21st Image Optical Conference) , P11, Itagaki, etc.).

FIG. 23 is an example of a circuit diagram of a conventional image sensor. The image sensor Im includes a plurality of light receiving elements Si (i = 1, 2,
, N). Each of the light receiving elements Si has a capacitive component and is charged according to the amount of light received by each light receiving element Si.
The output signal from the output terminal of the shift register SRi (i = 1, 2, ...) Is transferred to the signal buffer SBi (i = 1, 2, hand).
The signal inverted by is input to the gate of the analog switch SWi (i = 1, 2, ...) As a received light amount read signal. Then, the electric charge charged in the capacitance component of each of the light receiving elements Si is detected as a current pulse signal by the received light amount read signal input to the gate of the analog switch SWi (i = 1, 2, ...), and signal processing is performed. It is converted into a voltage signal by the circuit. This voltage signal is output to a shading correction circuit or the like of an image reading circuit (not shown).

FIG. 24 is a schematic explanatory view of the structure of a conventional image sensor, and shows the structures of a thin film transistor TFT and a photodiode PD in a device formed on an insulating substrate. In FIG. 24, poly is placed on the insulating substrate 01.
A source / drain electrode 02 made of -Si material is formed. A gate insulating film (SiO 2 film) 03 is formed on the source / drain electrodes 02, and the gate insulating film 03 is formed.
A gate electrode (poly-Si) 04 is formed on the top.
A lower interlayer insulating film (SiO2) 0 is formed on the gate electrode 04.
5 is formed, and a photodiode (sensor portion) PD that detects the amount of received light is formed on the lower interlayer insulating film 05. The photodiode PD has a base electrode 0
6, a-Si sensor layer 07, transparent electrode (ITO) 08,
It is composed of an upper interlayer insulating film 09 and the like. TFT
And contact holes B1 and B2 communicating with the electrodes 02 and 04 of the TFT are formed in the lower interlayer insulating film 05 and the upper interlayer insulating film 09 which separate the photodiode PD from each other. A contact hole B3 communicating with the transparent electrode 08 is formed in the upper interlayer insulating film 09. Each of the contact holes B1, B
The electrodes 02 and 04 of the TFT communicating with 2 and B3 and the transparent electrode 08 of the photodiode PD are connected to the wiring 010 of Al (aluminum). The wiring 010
Is covered with an element protective film (polyimide film) 011.

[Problems to be Solved by the Invention]

In the conventional image sensor Im shown in FIG.
As shown by arrows A1 and A2 in FIG.
There is a problem that a leak current is likely to occur on the side portion of. This is considered to be due to the following reasons. That is, since the a-Si sensor layer 07 has a thick film thickness of about 1 μm, and the film deposition temperature is low at 200 ° C. to 300 ° C., and the subsequent process temperature is limited to the lower temperature, the upper interlayer insulating film 09 is formed. It is difficult to have good insulation. That is, there is a problem that a short circuit occurs between the upper transparent electrode 08 and the lower electrode 06 due to poor coverage, and the yield is reduced.

In view of the above problems, the present invention has the following (A)
The items listed in 1) and (A2) are the subjects. (A1) Prevent the generation of leakage current between the upper and lower electrodes of the photoconductive layer. (A2) To improve the manufacturing yield of image sensors.

[0007]

The present invention devised to solve the above problems will now be described. The elements of the present invention are to facilitate correspondence with the elements of the embodiments described later. , The reference numerals of the elements of the embodiments are enclosed in parentheses. The reason why the present invention is described in association with the reference numerals of the embodiments described below is to facilitate understanding of the present invention.
It is not intended to limit the scope of the invention to the examples.

In order to solve the above problems, the first aspect of the present application
The photodiode (PD) of the invention has a lower electrode (2B,
22) and a photoconductive layer (7, 24) and an upper electrode (8, 25) are sequentially laminated on the photoconductive layer (22), and an interlayer insulating film (9, 26) is provided on a side surface of the photoconductive layer (7, 24). In the provided photodiode (PD), a conduction region (2Ba, 22a) between the lower electrode (2B, 22) and the photoconductive layer (7, 24) is formed on the upper surface of the lower electrode (2B, 22).
And a leakage current preventing insulating layer (5, 23) is formed, and the photoconductive layer (7, 24) is formed in the conductive region (2Ba,
22a) and its conductive region (2Ba, 22a) are formed on the upper surface portion of the leakage current preventing insulating layer (5, 23).

The photodiode (PD) of the second invention of the present application is the photodiode (P) of the first invention.
In D), the insulating layer for preventing leakage current (5, 2)
3) is characterized in that it is formed by the interlayer insulating film (5, 23) deposited on the upper surface of the lower electrode (2B, 22).

The photodiode (PD) of the third invention of the present application is the photodiode (P) of the first invention.
In D), the leakage current preventing insulating layer (23)
Is formed of an oxide insulating film on the upper surface of the lower electrode (2B, 22).

Further, the image sensor of the fourth invention of the present application comprises a photoconductive layer (7) and an upper electrode (8) sequentially laminated on the lower electrode (2B), and the photoconductive layer (7). A photodiode (PD) having an interlayer insulating film (9) disposed on its side surface, and a gate electrode (4) and a source / drain electrode (2A) disposed above and below the gate insulating film (3). And the photodiode (PD)
Thin film transistor (TF
T) and an image sensor disposed on an insulating substrate (1), leaving a conduction region (2Ba) between the lower electrode (2B) and the photoconductive layer (7) on the upper surface of the lower electrode (2B). An insulating layer (5) for preventing leakage current is formed, and the photoconductive layer (7) includes the conductive region (2Ba) and the insulating layer (5) for preventing leakage current around the conductive region (2Ba).
It is characterized in that it is formed on the upper surface portion.

In the image sensor of the present invention, the gate electrode (4) of the thin film transistor (TFT).
And the electrode (2A) disposed below the source / drain electrode (2A), and the photodiode (P
The lower electrode (2B, 22) of D) can be formed on the same surface.

Next, the operation of the present invention having the above-mentioned features will be described. The photodiode (PD) of the first invention of the present application having the above-mentioned characteristics is provided on the upper surface of the lower electrode (2B, 22) and the lower electrode (2B, 22) and the photoconductive layer (7,
24), the insulating layer (5, 23) for preventing leakage current is formed, leaving the conduction region (2Ba, 22a) between the photoconductive layers (7, 24) and the conduction region (2Ba, 22a). It is formed on the upper surface portion of the leak current preventing insulating layer (5, 23) around the region (2Ba, 22a). In the photodiode (PD) having such a structure, since the leakage current preventing insulating layers (5, 23) are formed before the photoconductive layers (7, 24) having a low manufacturing temperature are formed, the leakage currents are prevented. The treatment performed in the process of forming the insulating layer (5, 23) does not affect the characteristics of the photoconductive layer (7) formed thereafter. Therefore, the leakage current preventing insulating layer (5, 2
When forming 3), there are less restrictions on heat treatment and ion implantation. In this way, the conditions for forming the leakage current prevention insulating layers (5, 23) are relaxed, so that various kinds of processing (high temperature processing or the like) can be performed. In this case, it is possible to form the insulating layer (5, 23) for preventing leakage current that has excellent insulating properties. Therefore, even if the insulation property of the interlayer insulating film (9) arranged in contact with the side surface of the photoconductive layer (7, 24) of the photodiode (PD) is poor, the insulation for leakage current prevention is excellent. The upper electrode (8, 25) and the lower electrode (2) of the photodiode (PD) are formed by the layers (5, 23).
The generation of a leak current between B and 22) is prevented.

In the photodiode (PD) of the second invention of the present application having the above-mentioned features, the insulating layer (5) for preventing leakage current is an interlayer insulating film formed on the upper surface of the lower electrode (2B, 22). It is formed by the membrane (5, 23). Since the interlayer insulating films (5, 23) are formed before the photoconductive layers (7, 24) having a low manufacturing temperature are formed, they can be processed at a high temperature. By treating the interlayer insulating film (5, 23) at a high temperature, the leak current preventing insulating layer (5, 23) having excellent insulating properties can be formed.

In the photodiode (PD) of the third invention of the present application having the above-mentioned features, the insulating layer (23) for preventing leakage current is formed of an oxide insulating film on the upper surface of the lower electrode (22). .. Since it is easy to form the oxide insulating film (23) having excellent insulating properties, the leak current preventing insulating layer (23) having excellent insulating properties can be formed. According to the third aspect of the present invention, the leak current preventing insulating layer (23) can be easily formed by providing a simple step of oxidizing the upper surface of the lower electrode (22). Since this method does not involve an increase in the film forming step, it is effective in shortening the manufacturing time, lowering the manufacturing cost, and the like.

The image sensor of the fourth invention of the present application having the above-mentioned characteristics is leaked on the upper surface of the lower electrode (2B), leaving a conductive region between the lower electrode (2B) and the photoconductive layer (7). A current preventing insulating layer (5) is formed, and the photoconductive layer (7) is formed on the upper surface portion of the leak current preventing insulating layer (5) around the conductive region. In the case of such a structure, since the leakage current preventing insulating layer (5) is formed before the photoconductive layer (7) having a low manufacturing temperature is formed, the influence on the photoconductive layer (7) is not taken into consideration. Without doing so, the insulating layer (5) for preventing leakage current can be manufactured. Therefore, the leak current preventing insulating layer (5) having excellent insulating properties can be easily obtained. Therefore, the photoconductive layer (7) of the photodiode (PD).
Even if the insulating property of the interlayer insulating film (9) disposed in contact with the side surface of the photodiode (PD) is poor, the leakage current preventing insulating layer (5) having excellent insulating property prevents the upper electrode (8) of the photodiode (PD) and Generation of a leak current between the lower electrodes (2B) is prevented. The manufacturing yield of the image sensor having the photodiode (PD) having such a structure is improved.

Further, in the image sensor of the present invention having the above-mentioned structure, the gate electrode (4) and the source / drain electrodes (2) of the thin film transistor (TFT) are provided.
When the lower electrode (2A) of A) and the lower electrode (2B) of the photodiode (PD) are formed on the same surface, both electrodes (2A, 2B) on the same surface.
Can be formed simultaneously. Therefore, in that case, the number of manufacturing steps of the image sensor can be reduced.

[0017]

Embodiments of the present invention will be described below with reference to the drawings. [Embodiment 1] FIG. 1 is a sectional view of an essential part of an image sensor according to Embodiment 1 of the present invention, and FIGS. In FIG. 1, a source / drain electrode 2A of a thin film transistor TFT and a lower electrode 2B of a photodiode PD are formed on an insulating substrate 1 by poly-Si. A gate insulating film (SiO2 film) 3 is formed on the source / drain electrodes 2A and a part of the upper surface of the insulating substrate 1, and a gate electrode (poly-Si) 4 is formed on the gate insulating film 3.

A lower interlayer insulating film (SiO2) 5 is formed on the gate electrode 4 of the thin film transistor TFT and the lower electrode 2B of the photodiode PD, and corresponds to the lower electrode 2B on the lower interlayer insulating film 5. Thus, the opening 5a is formed. The opening 5a of the lower interlayer insulating film 5 and the upper surface portion of the lower interlayer insulating film 5 around the opening 5a are
A photoconductive layer 7 is formed. A portion of the lower interlayer insulating film 5 in contact with the bottom surface region 7a of the photoconductive layer 7 has a function as a leakage current preventing insulating layer. The lower electrode 2B facing the opening 5a forms a conduction region 2Ba with the photoconductive layer 7. A transparent electrode (upper electrode of the photodiode PD) 8 is formed on the upper surface of the photoconductive layer 7.

An upper interlayer insulating film 9 is formed on the lower interlayer insulating film 5 having a function as the transparent electrode 8 and the leak current preventing insulating layer. Contact holes B1 and B2 connected to the source / drain electrodes 2A of the TFT are formed in the lower and upper interlayer insulating films 5 and 9. A contact hole B3 connected to the transparent electrode 8 is formed in the upper interlayer insulating film 9. Further, a contact hole B4 connected to the lower electrode 2B of the photodiode PD is formed in the lower and upper interlayer insulating films 5 and 9. In addition, the electrodes 2A connected to the contact holes B1 to B4,
8, 2B are connected to an Al (aluminum) wiring 10. The wiring 10 is an element protection film (polyimide film) 11
Is covered by.

Next, a method of manufacturing the image sensor of the first embodiment having the above-mentioned structure will be described. 2 (A) to (J)
FIG. 3A is an explanatory diagram of a manufacturing process of the image sensor Im shown in FIG. 1, and is a cross-sectional view of a main part of the image sensor Im.
3 to 8 are respectively shown in FIGS. 2 (A), 2 (C),
It is a top view corresponding to (E), (G), (I), and (J). 2 (A) and FIG. 3, on the insulating substrate 1
By poly-Si, the source / drain electrodes 2A of the plurality of thin film transistors TFT, the lower electrode 2B of the photodiode PD, and the plurality of electrodes 2C for matrix wiring are formed. In FIG. 2B, the gate insulating film layer (SiO2)
3L and the gate electrode layer 4L are sequentially laminated. As the gate electrode 4, poly-Si, a metal thin film of Ta, Ti, Cr or the like or a silicide of Pt-Si or the like can be used. 2C and 4, the gate electrode layer 4L and the gate insulating film layer 3L are patterned using the same mask (not shown) to form the gate insulating film 3 and the gate electrode 4. In FIG. 2D, the source / drain electrode 2A is selectively implanted with P (phosphorus) and B (boron) by a method such as ion implantation or shower doping to form a source portion 2As and a drain portion 2Ad. ..

2 (E) and FIG. 5, the lower interlayer insulating film 5 is formed at a temperature high enough to obtain sufficient insulation, and the photodiode P is formed on the lower interlayer insulating film 5.
A tapered opening 5a connecting to the lower portion 2B of D is formed.
In FIG. 2F, the photoconductive layer 7L and the transparent electrode layer (ITO) 8 are sequentially laminated. 2G and 6, the transparent electrode layer 8L is wet-etched and the photoconductive layer 7L is dry-etched using the same resist pattern as a mask. Then, the transparent electrode 8 and the photoconductive layer 7 are formed. The etching conditions for the photoconductive layer (a-Si layer) 7L are, for example, SF6, 200SCCM, F115,
200 SCCM, pressure 0.2 Torr, RF power 1.0 Ke
By setting V, a selection ratio sufficient to use SiO 2 as an etching stopper can be obtained.

In FIG. 2H, the upper interlayer insulating film 9 is deposited. In general, since the deposition temperature of the a-Si layer (the photoconductive layer 7) is as low as 200 ° C., the upper interlayer insulating film 9 formed after the photoconductive layer 7 has a high temperature at which sufficient insulation can be obtained. Insulation is insufficient because it cannot be treated with. However, since the lower interlayer insulating film 5 is treated at a high temperature at which sufficient insulation is obtained as described above, the lower electrodes 2 disposed above and below the photoconductive layer 7 are treated.
The insulating property between B and the transparent electrode 8 is the lower interlayer insulating film 5
Guaranteed by. 2 (I) and 7,
The interlayer insulating films 5 and 9 are etched to form contact holes B1 to B4 and B5 (see FIG. 7). The actual shape of the contact hole Bi has a depth of 0.5 μm.
The diameter is about 5 μm with respect to about m, and the diameter is formed about 10 times larger than the depth. 2J and 8, an Al wiring 10 is provided on the upper surface of the upper interlayer insulating film 9. Then, a polyimide film having a thickness of 1.2 μm is formed and then patterned to form a protective film 11, thereby completing the image sensor Im having the structure shown in FIG.

In the first embodiment, the thin film transistor TF is used.
Since the source / drain electrode 2A of T and the lower electrode 2B of the photodiode PD are formed on the same surface,
It can be formed at the same time. Therefore, the manufacturing process can be reduced.

[Second Embodiment] Next, an image sensor according to a second embodiment of the present invention will be described with reference to FIG. In the description of the second embodiment, constituent elements corresponding to the constituent elements of the first embodiment shown in FIG. 1 are designated by the same reference numerals, and duplicated detailed description will be omitted. Image sensor Im of the second embodiment
Is different from Example 1 (see FIG. 1) formed in a narrow portion in that the gate insulating film 3 is formed in a wide portion of the surface of the insulating substrate 1. Therefore, the photoconductive layer 7 is connected to the lower electrode 2B through the contact hole Bo formed in the gate insulating film 3 and the lower interlayer insulating film (insulating film having a function as a leak current preventing insulating layer) 5. Has been done. Since the gate insulating film 3 and the lower interlayer insulating film 5 are formed before the photoconductive layer 7 is formed, they can be processed at a high temperature at which sufficient insulation can be obtained. Therefore, the lower electrodes 2B disposed above and below the photoconductive layer 7
The insulation between the transparent electrode 8 and the transparent electrode 8 is ensured by the gate insulating film 3 and the lower interlayer insulating film 5. Therefore, the insulating property is further improved.

[Third Embodiment] Next, a photodiode (PD) according to a third embodiment of the present invention will be described with reference to FIGS. FIG. 10 is a sectional view of a principal part of a photodiode PD of the third embodiment, and FIGS. 11 to 17 are photodiodes P shown in FIG.
It is explanatory drawing of the manufacturing process of D. In FIG. 10, the lower electrode 22 of the photodiode PD is formed of poly-Si on the insulating substrate 21. A lower interlayer insulating film 23 (that is, a leakage current preventing insulating layer) is formed on the lower electrode 22 while leaving a conduction region 22a with a photoconductive layer (described later). A photoconductive layer 24 is formed on the conductive region 22a and on the upper surface portion of the leak current preventing insulating layer 23 around the conductive region 22a. A region 24a on the bottom surface of the photoconductive layer 24 has a shape larger than the conductive region 22a between the lower electrode 22 and the photoconductive layer 24. A transparent upper electrode 2 is formed on the upper surface of the photoconductive layer 24.
5 is formed.

An upper interlayer insulating film 26 is formed on the transparent electrode 25 and the lower interlayer insulating film 23.
The transparent upper electrode 25 is formed on the upper interlayer insulating film 26.
A contact hole B6 is formed so as to be connected to. Further, a contact hole B7 connected to the lower electrode 23 of the photodiode PD is formed in the lower and upper interlayer insulating films 23 and 26. In addition, the electrodes 23 and 25 connected to the contact holes B6 and B7, respectively.
Is connected to a wiring 27 of Al (aluminum).
The wiring 27 is covered with an element protection film (polyimide film) 28.

Next, a method of manufacturing the photodiode PD of the third embodiment having the above-mentioned structure will be described with reference to FIGS. In FIG. 11, the lower electrode 22 is formed on the insulating substrate 21.
And a resist pattern R1 is formed by using the same mask as the mask for forming the upper electrode 25 and the photoconductive layer 24.
To form. Since the resist pattern R1 determines the shape of the conductive region 22a between the lower electrode 22 and the photoconductive layer 24, it must be formed smaller than the bottom shape of the photoconductive layer 24. Therefore, it is necessary to form the resist pattern R1 smaller than a resist pattern R2 for forming the upper electrode 25 and the photoconductive layer 24, which will be described later, using the mask for forming the upper electrode 25 and the photoconductive layer 24.

In the third embodiment, since two kinds of resist patterns R1 and R2 having different sizes are formed using the same mask, the resist pattern R1 is formed under the following conditions. The conditions for forming the resist pattern R1 are such that the heating time or temperature of the resist is decreased, the exposure time is decreased, or the development time is increased in comparison with the conditions for forming the resist pattern R2. Specifically, by making the exposure time twice or more and the developing time 1.5 times or more, the region of the resist pattern R1, that is, the conduction region 22a between the lower electrode 22 and the photoconductive layer 24, The size can be made smaller than the area 24a on the bottom surface of the photoconductive layer 24. Further, by reducing the heating time of the resist for forming the resist pattern R1 or raising the heating temperature, the conductive region 22a between the lower electrode 22 and the photoconductive layer 24 can be formed with good reproducibility.

Next, the lower interlayer insulating film 23 is deposited on the insulating substrate 21 (the insulating substrate 21 having the lower electrode 22 and the resist pattern R1 formed on the upper surface) shown in FIG. 11 (see FIG. 12).

Next, when the resist pattern R1 on the insulating substrate 21 is peeled off and the lower interlayer insulating film 23 is lifted off, the conduction region 22 between the lower electrode 22 and the photoconductive layer 24 is formed.
a is exposed (see FIG. 13).

Next, a photoconductive layer 24 and an upper electrode 25 are sequentially deposited on the insulating substrate 21 where the conductive region 22a is exposed (see FIG. 14).

Next, a resist pattern R2 is formed on the upper surface of the upper electrode 25 by using the same mask as that used for forming the resist pattern R1 (see FIG. 15).
The resist pattern R2 is formed larger than the resist pattern R1 formed under the above conditions.

Using the resist pattern R2, the upper electrode 25 and the photoconductive layer 24 are sequentially etched, and the upper electrode 25 is etched again (see FIG. 16). The bottom surface area 24a of the photoconductive layer 24 is the conductive area 22a.
Since it has a larger shape than the photoconductive layer 24,
Are formed on the conductive region 22a and the upper surface portion of the lower interlayer insulating film (insulating layer for preventing leakage current) 23 around the conductive region 22a.

Next, the resist pattern R2 is peeled off (see FIG. 17). An upper interlayer insulating film 26 (see FIG. 10) is formed on the upper surface of the one shown in FIG. Next, the interlayer insulating films 23 and 26 are etched to form contact holes B6 and B7 (see FIG. 10) in the same manner as described with reference to FIGS. 2I and 2J of the first embodiment. To do.
The Al wiring 27 is formed on the upper surface of the upper interlayer insulating film 26.
To provide. Next, form a 1.2μ thick polyimide film,
When the protective film 28 is formed, the photodiode PD having the structure shown in FIG. 10 is completed. Also in the photodiode PD of the third embodiment, since the lower interlayer insulating film (leakage current preventing insulating layer) 23 is formed between the lower electrode 22 and the outer peripheral portion of the bottom surface region of the photoconductive layer 24, Conductive layer 2
The side surface 4 and the lower electrode 22 are not in contact with each other. With such a structure, it is possible to prevent generation of a leak current on the side surface of the photoconductive layer 24. This Example 3
In the above, the same mask is used to form resist patterns R1 and R2 having different sizes, and the forming conditions are changed. Thus, by changing the forming conditions and using the same mask, the required number of masks can be saved.

[Fourth Embodiment] Next, a photodiode (PD) according to a fourth embodiment of the present invention will be described with reference to FIGS. FIG. 18 is a cross-sectional view of an essential part of the photodiode PD of the fourth embodiment, and FIGS. 19 to 22 are explanatory views up to the middle of the manufacturing process of the photodiode PD. In the description of the fourth embodiment, constituent elements corresponding to those of the third embodiment are designated by the same reference numerals, and detailed description thereof will be omitted.
In this Example 4, the leakage current preventing insulating layer 23 between the outer peripheral portion of the bottom surface region of the photoconductive layer 24 and the lower electrode 22 is formed of an oxide insulating film on the surface of the lower electrode 22, and thus the upper surface of the lower electrode 22 is higher. Example 3 in which a lower interlayer insulating film is deposited on
Is different from The fourth embodiment is configured similarly to the third embodiment in other points.

Next, a method of manufacturing the photodiode PD of the fourth embodiment having the above-mentioned structure will be described with reference to FIGS. In FIG. 19, the lower electrode 22 is formed on the insulating substrate 21.
And a resist pattern R1 is formed by using the same mask as the mask for forming the upper electrode 25 and the photoconductive layer 24.
To form. This resist pattern R1 is the same as in the third embodiment.
It is formed under the same conditions as.

Next, the upper surface of the lower electrode 22 of the insulating substrate 21 (the insulating substrate 21 having the lower electrode 22 and the resist pattern R1 formed on the upper surface) shown in FIG. An oxide insulating film (leakage current preventing insulating layer) 23 is formed on the upper surface of the electrode 22 (see FIG. 20).

Next, the insulating substrate 21 resist pattern R1
When peeled off, the conductive region 22a between the lower electrode 22 and the photoconductive layer 24 is exposed (see FIG. 21).

Next, a photoconductive layer 24 and an upper electrode 25 are sequentially deposited on the insulating substrate 21 where the conductive region 22a is exposed (see FIG. 22). The state shown in FIG. 22 corresponds to FIG. 14 of the third embodiment.

After that, if the manufacturing process similar to that described in the third embodiment with reference to FIGS. 15 to 18 is performed, the photodiode PD of the fourth embodiment shown in FIG. 18 is obtained. Like the photodiode PD of the third embodiment, the photodiode PD of the fourth embodiment can prevent the generation of the leak current on the side surface of the photoconductive layer 24. This Example 4 is
Since the leakage current preventing insulating layer 23 can be formed by providing the oxidation process of the upper surface of the lower electrode 22,
The manufacturing process can be simplified as compared with the third embodiment which requires the film forming process of the lower interlayer insulating film 23.

Although the embodiments of the image sensor according to the present invention have been described in detail above, the present invention is not limited to the above embodiments, and does not deviate from the present invention described in the claims. It is possible to make various design changes.

For example, the photoconductive layer 7 of the photodiode PD has a P + layer into which monovalent ions of P (phosphorus) are implanted (doped) instead of the a-Si layer, and i (intr
It is also possible to use a pin type formed of two layers including an insic) layer. Further, the wiring 10 can be formed of two layers of Al / Mo to reduce the contact resistance with the transparent electrode (ITO) instead of using only Al. Further, in the thin film transistor TFT, the gate electrode 4 may be arranged on the lower side and the source / drain electrode 2A may be arranged on the upper side.

[0043]

In the above-described photodiode and image sensor of the present invention, the photodiode is the photoconductive layer 2
Since a leak current preventing insulating layer having excellent insulating properties is formed between the outer periphery of the bottom surface region of 4 and the lower electrode 22,
The side surface of the photoconductive layer is not in contact with the lower electrode. With such a structure, it is possible to prevent the occurrence of leakage current on the side surface of the photoconductive layer. Moreover, the manufacturing yield of the image sensor having such a photodiode can be improved.

Further, not only the upper interlayer insulating film but also excellent insulating property is provided between the electrode arranged below the thin film transistor TFT and the photodiode PD and the wiring formed on the upper surface of the upper interlayer insulating film. Since the leakage current preventing insulating layer is provided, the insulation between the electrodes and the wiring is improved. Then, it is possible to prevent a short circuit due to a pinhole or the like. Therefore, the manufacturing yield of the image sensor can be improved.

In the image sensor of the present invention, the electrode disposed below the gate electrode and the source / drain electrode of the thin film transistor and the lower electrode of the photodiode are formed on the same surface. Since both electrodes can be simultaneously formed on the same surface, the number of manufacturing steps of the image sensor can be reduced.

[Brief description of drawings]

FIG. 1 is a structural explanatory diagram of a main part of an image sensor according to a first embodiment of the present invention.

FIG. 2 is an explanatory diagram of the method of manufacturing the image sensor of the embodiment, in which (A) to (J) are cross-sectional views of the main part in each manufacturing process.

FIG. 3 is an explanatory view of the manufacturing method of the embodiment, which is the same as FIG.
It is a top view corresponding to (A).

FIG. 4 is an explanatory view of the manufacturing method of the embodiment, which is the same as FIG.
It is a top view corresponding to (C).

FIG. 5 is an explanatory view of the manufacturing method of the embodiment, which is the same as FIG.
It is a top view corresponding to (E).

FIG. 6 is an explanatory view of the manufacturing method according to the embodiment, which is the same as FIG.
It is a top view corresponding to (G).

FIG. 7 is an explanatory view of the manufacturing method of the embodiment, which is the same as FIG.
It is a top view corresponding to (I).

FIG. 8 is an explanatory view of the manufacturing method of the embodiment, which is the same as FIG.
It is a top view corresponding to (J).

FIG. 9 is a structural explanatory view of a main part of the image sensor according to the second embodiment of the present invention.

FIG. 10 is a photodiode PD according to a third embodiment of the present invention.
It is a structure explanatory view of the principal part of.

FIG. 11 is an explanatory diagram of a manufacturing process of the photodiode according to the third embodiment.

FIG. 12 is an explanatory view of the manufacturing process of the photodiode of the third embodiment, which is an explanatory view of the next process of FIG. 11;

FIG. 13 is an explanatory diagram of the manufacturing process of the photodiode of the third embodiment, which is an explanatory diagram of the next process of FIG. 12;

FIG. 14 is an explanatory view of the manufacturing process of the photodiode of the third embodiment, which is an explanatory view of the next process of FIG. 13;

FIG. 15 is an explanatory view of the manufacturing process of the photodiode of the third embodiment, which is an explanatory view of the next process of FIG. 14;

FIG. 16 is an explanatory diagram of the manufacturing process of the photodiode of the third embodiment, which is an explanatory diagram of the next process of FIG. 15;

FIG. 17 is an explanatory view of the manufacturing process of the photodiode of the third embodiment, which is an explanatory view of the next process of FIG. 16;

FIG. 18 is an explanatory view of the manufacturing process of the photodiode of the third embodiment, which is an explanatory view of the next process of FIG. 17;

FIG. 19 is a photodiode PD of the fourth embodiment of the present invention.
It is a structure explanatory view of the principal part of.

FIG. 20 is an explanatory diagram of the manufacturing process of the photodiode according to the fourth embodiment.

FIG. 21 is an explanatory view of the manufacturing process of the photodiode of the fourth embodiment, which is an explanatory view of the next step of FIG. 20.

FIG. 22 is an explanatory diagram of the manufacturing process of the photodiode of the fourth embodiment, which is a schematic view of the next process of FIG. 21;

FIG. 23 is a circuit diagram of a conventional image sensor.

FIG. 24 is a structural explanatory view of a conventional image sensor.

[Explanation of symbols]

PD: photodiode, TFT: thin film transistor,
DESCRIPTION OF SYMBOLS 1 ... Insulating substrate, 2A ... Source / drain electrode, 2B ... Lower electrode, 2Ba ... Conductive region, 3 ... Gate insulating film, 4 ... Gate electrode, 5 ... Leakage current preventing insulating layer (lower interlayer insulating film), 5a ... Aperture, 7 ... Photoconductive layer, 8 ... Upper electrode (transparent electrode), 9 ... Upper interlayer insulating film, 21 ... Insulating substrate, 22 ...
Lower electrode, 22a ... Conductive region, 23 ... Leakage current preventing insulating layer (lower interlayer insulating film, oxide insulating film), 24 ... Photoconductive layer, 25 ... Upper electrode, 26 ... Upper interlayer insulating film,

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Hiroyuki Hotta 2274 Hongo, Ebina City, Kanagawa Prefecture Fuji Zero Tux Co., Ltd.

Claims (4)

[Claims] 1. A photodiode in which a photoconductive layer and an upper electrode are sequentially stacked on a lower electrode and an interlayer insulating film is provided on a side surface of the photoconductive layer, wherein the lower electrode is provided on an upper surface of the lower electrode. An insulating layer for preventing leakage current is formed leaving a conductive region between the electrode and the photoconductive layer,
The photodiode is characterized in that the photoconductive layer is formed on the conductive region and on an upper surface portion of the leakage current preventing insulating layer around the conductive region. 2. The photodiode according to claim 1, wherein the leakage current preventing insulating layer is formed of an interlayer insulating film deposited on the upper surface of the lower electrode. 3. The photodiode according to claim 1, wherein the insulating layer for preventing leakage current is formed of an oxide insulating film on the upper surface of the lower electrode. 4. A photodiode having a photoconductive layer and an upper electrode sequentially stacked on a lower electrode and having an interlayer insulating film disposed on the side surface of the photoconductive layer, and a photodiode above and below the gate insulating film. An image sensor in which a thin film transistor having a gate electrode and a source / drain electrode arranged and forming a light receiving amount detection circuit of the photodiode is provided on an insulating substrate, wherein the lower electrode and the lower electrode are provided on an upper surface of the lower electrode. An insulating layer for preventing leakage current is formed leaving a conductive region between the photoconductive layers,
The image sensor, wherein the photoconductive layer is formed on the conductive region and on an upper surface portion of the leakage current preventing insulating layer around the conductive region.