JP2000031524A - Manufacture of photoelectric conversion element - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a manufacturing method of a photoelectric conversion element which can prevent the short circuit between the first electrode and the second electrode by simple process, concerning the manufacture of a photoelectric conversion element. SOLUTION: This manufacture includes a process of forming the first electrode 2 on an insulating substrate 1, a process of forming a photoelectric conversion film 3 on the first electrode 2, a process of forming an interlayer insulating film 4 so as to cover the first electrode 2 and the photoelectric conversion film 3 exclusive of the top of the photoelectric conversion film 3 to serve as the contact section with the second electrode 5, a process of dry-oxidizing the whole substrate where the first electrode 2, the photoelectric conversion film 3 and the interlayer insulating film 4 are made, and a process of forming the second electrode 5 having light permeability on the interlayer insulating film 4 and the photoelectric conversion film 3.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a method for manufacturing a photoelectric conversion element, and more particularly to a method for manufacturing a photoelectric conversion element including a step for preventing a short circuit between electrodes of the photoelectric conversion element.

[0002]

2. Description of the Related Art With an increase in the area of a solar cell, an image sensor, and the like, a thin-film photoelectric conversion element using a photoelectric conversion film of amorphous silicon or the like that can be deposited over a large area is being developed. In particular, in the case of an image sensor, by forming a sensor portion having the same width as the document, one-to-one image formation is possible, the document and the sensor portion can be brought into close contact, and a reduction optical system is not required. Thus, the size of the document reading unit can be easily reduced.

FIG. 4 shows a structure of a conventional general photoelectric conversion element. This photoelectric conversion element is manufactured by the following steps. First, a first electrode 2 made of metal is formed and patterned on an insulating substrate 1 having a light transmitting property, and a photoelectric conversion film 3 is formed and patterned on the first electrode 2. Thereafter, an interlayer insulating film 4 for preventing a short circuit between the first and second electrodes in the vertical direction is formed and patterned, and then a second electrode 5 made of a transparent electrode is formed.
And patterning. After that, a surface protection film 8 is formed on the second electrode 5.

As a material of the photoelectric conversion film 3, hydrogenated amorphous silicon or the like is used. This hydrogenated amorphous silicon layer is deposited on the first electrode 2 by glow discharge decomposition of monosilane gas (SiH ₄ ) or the like. It is difficult to form a layer, and the generation of pinholes cannot be avoided. This is because dust in the manufacturing apparatus adheres to the substrate surface. Further, when patterning the hydrogenated amorphous silicon layer, a pinhole may be generated due to a photo defect.

Similarly, pinholes may be generated in the interlayer insulating film 4. For example, the interlayer insulating film 4
As a material for the above, hydrogenated amorphous silicon nitride or the like is used, but pinholes may be generated due to adhesion of dust during film formation, photo defects, and the like. Here, in the case where the photoelectric conversion film includes only one diode, a change in function as an element caused by the presence of a pinhole in the photoelectric conversion film or the interlayer insulating film will be considered.

First, considering the simplest equivalent circuit of this photoelectric conversion element, it is as shown in FIG. Series resistance Rs
Is the sum of the contact resistance of the electrodes and the resistance of the external circuit,
The parallel resistance Rsh is a resistance component caused by a leakage current.
Here, if there is no pinhole in the photoelectric conversion film or the interlayer insulating film and no short circuit occurs between the first electrode and the second electrode, the parallel resistance Rsh may be considered to be infinite (∞). In FIG. 5, I _L is a photocurrent proportional to the intensity of incident light, I _j is a current flowing through the diode, and I _sh is a leakage current due to a short circuit or the like. Now the current flowing through the external circuit and _{I, I = -I L + I} j + I sh ... (1) is satisfied.

FIG. 7 shows an ideal photoelectric conversion element having no pinhole in the photoelectric conversion film or interlayer insulating film, that is, a current-voltage characteristic curve (IV curve) when the parallel resistance Rsh = ｓ and Rs = 0. ). Here, I ₁ is a characteristic curve when light is incident, and I ₂ is a characteristic curve when dark. Rsh = because it is ∞ is I _sh ~0, photocurrent I _L becomes dominant at the time of light incidence, in the dark, the current through the diode I _j
Becomes dominant.

Here, if a pinhole is formed in a portion where the first electrode 2 and the second electrode 5 overlap in the photoelectric conversion film 3 or the interlayer insulating film 4, a part between the first electrode and the second electrode is partially removed. A short circuit occurs, and the parallel resistance Rsh is greatly reduced. FIG. 8 shows a current-voltage characteristic curve in this case. Here, Rs = 0 is set. I ₃ is a characteristic curve when light is incident, and I ₄ is a characteristic curve when dark.

In this case, for example, the diode currents I _j to
In a zero bias region, the above relational expression (1) becomes as follows. From _{I~-I L + Ish = -I} L + V / Rsh ... (2) This equation (2), even in the dark even during light irradiation, as evidenced by a large voltage V dependence of current I, The characteristics of I ₃ and I ₄ are significantly lower than the characteristics (I ₁ and I ₂ ) of the ideal photoelectric conversion element shown in FIG. That is, in a solar cell, a forward bias region, that is, a region of V> 0 is used. However, as compared with an ideal photoelectric conversion element, the conversion efficiency is poor when a pinhole is provided.

Next, consider an image sensor having a structure in which a photoelectric conversion film in a photoelectric conversion element is formed by laminating a photodiode and a blocking diode having a polarity opposite to that of the photodiode.

FIG. 9 shows current-voltage characteristics during light irradiation when there is no pinhole in the photoelectric conversion film or the interlayer insulating film. Here, the on voltage is set to -0.5 as the read voltage.
Assuming that the V and off voltages are 1.0 V, the ratio of the current value at the on voltage to the current value at the off voltage is large, so that the image can be read. On the other hand, FIG. 10 shows that the first electrode and the second
4 shows current-voltage characteristics when a pinhole occurs in a portion where an electrode overlaps. Here, as the reading voltage,
As described above, when the on voltage is -0.5 V and the off voltage is 1.0 V, the S / N is small and the image cannot be read.

As described above, the occurrence of pinholes in the photoelectric conversion film or the interlayer insulating film of the photoelectric conversion element causes a reduction in conversion efficiency and open voltage in a solar cell, and a reading of an optical image in an image sensor. Invites a decline in ability. That is, the pinhole is a fatal defect, and a problem arises in that the production yield as an element is reduced.

First electrode 2 and second electrode 5 by pinhole
As a method for preventing a short circuit between the first electrode 2 and the first electrode 2 formed on a substrate, a photoelectric conversion film 3 is deposited on a first electrode and a second electrode formed on a substrate. Even if a pinhole is generated in the photoelectric conversion film 3 by the anodic oxidation, the underlying first electrode 2 exposed in the film is insulated by the pinhole, and the second electrode formed on the photoelectric conversion film 3 is formed. A technique that can prevent a short circuit between the first electrode and the first electrode is disclosed. FIG. 6 shows a flowchart of a conventional process for manufacturing a photoelectric conversion element according to this technique.

In FIG. 6, the first electrode is formed (S10).
1), patterning (S102), formation of a photoelectric conversion film (S103), patterning (S104), formation of a second electrode (S108), and patterning (S109) are the same as those in the above-described manufacturing process. After patterning (S104), anodic oxidation (S105),
The difference is that the steps of washing (S106) and drying (S107) are performed.

[0015]

However, in the prior art shown in FIG. 6, a wet process is performed in which the underlying first electrode exposed in the film by the pinhole of the photoelectric conversion film is insulated by anodic oxidation. Therefore, after anodic oxidation (S105), cleaning (S106) and drying (S10)
7) is required, and the number of steps is increased. Also, anodizing step (S105)
In order to prevent the electrolyte solution from coming into contact with the portion of the first electrode exposed from the photoelectric conversion film (that is, the lead portion of the first electrode) and to prevent the photoelectric conversion film from being anodized, Oxidation had to be performed. When there are a plurality of photoelectric conversion elements on the same substrate, the first
There is a problem that it is necessary to connect the electrodes and perform anodic oxidation, which requires a very complicated operation.

The present invention has been made in consideration of the above points, and has as its object to provide an easy manufacturing process capable of preventing a short circuit between a first electrode and a second electrode of a photoelectric conversion element. I do.

[0017]

SUMMARY OF THE INVENTION The present invention comprises a step of forming a first electrode on an insulating substrate, a step of forming a photoelectric conversion film on the first electrode, and a contact portion with the second electrode. Forming an interlayer insulating film so as to cover the first electrode and the photoelectric conversion film except on the photoelectric conversion film to be formed, and dry the entire substrate on which the first electrode, the photoelectric conversion film, and the interlayer insulating film are formed. An object of the present invention is to provide a method for manufacturing a photoelectric conversion element, comprising: a step of performing an oxidation treatment; and a step of forming a second electrode having optical transparency on the interlayer insulating film and the photoelectric conversion film. Examples of the dry oxidation treatment (dry process) include a standing treatment at a raised temperature in an oxidizing gas atmosphere for a predetermined time, a plasma treatment in a gas containing oxygen, and the like. The first electrode is made of Ta, Al, Cr, T
Any metal of i, Nb, or Zr may be used.

According to the present invention, the portion of the first electrode exposed for the pinhole formed in the photoelectric conversion film or the interlayer insulating film is oxidized by the dry oxidation treatment, so that a complicated process is not performed. A short circuit between the first electrode and the second electrode can be easily prevented.

[0019]

In the method of manufacturing a photoelectric conversion element according to the present invention, when the step of performing the dry oxidation treatment comprises a treatment in which the temperature is raised in an oxidizing gas atmosphere and left for a predetermined time, the temperature to be raised is , 150 ° C. or more and 350 ° C. or less, and the standing time may be about 1 hour. Further, when the step of performing the dry oxidation treatment comprises a plasma treatment in a gas containing oxygen, the pressure of the gas used for the plasma treatment may be set to 0.1 Torr or more and 1 Torr or less.
Further, in the present invention, after the step of performing the dry oxidation treatment, a step of removing an oxidized upper layer portion of the photoelectric conversion film that is in contact with the second electrode by etching may be provided.

Hereinafter, the present invention will be described in detail based on an embodiment shown in the drawings. Note that the present invention is not limited to this.

First Embodiment A process for manufacturing a photoelectric conversion element according to a first embodiment of the present invention will be described. FIG. 1 shows a cross-sectional view of the photoelectric conversion element of the present invention. FIG. 2 shows a flowchart of the manufacturing process according to the first embodiment. As shown in FIG.
The present invention is characterized in that, in the manufacturing process of the first embodiment, after the patterning of the interlayer insulating film (step S6), a step of raising the temperature and leaving it in an oxygen atmosphere (step S7) is provided.

First, in step 1, the first electrode 2 is formed. Here, Ta is placed on the insulating glass substrate 1.
Is formed by DC sputtering (FIG. 1A). For example, Ar pressure: 0.2 Torr
r, Ta of 300 nm under the condition of input power of 300 W
Form a film. Next, a photoresist is formed on the first electrode 2 made of Ta, and patterned in a line shape.
Dry etching is performed under the condition of (CF ₄ + O ₂ ) gas: 0.15 Torr to pattern the linear first electrode 2.

Next, a photoelectric conversion film 3 is formed on the first electrode 2 under the conditions shown in Table 1 by using plasma CVD (step S3). Table 1 below shows conditions for forming the photoelectric conversion film.

[0024]

[Table 1]

Thereafter, resist patterning is performed in the same manner as the first electrode 2, and patterning is performed in a dot shape by dry etching (step S4, FIG. 1B). At this time, a pinhole that becomes a short-circuit defect may occur.
Reference numeral 6 in FIG. 1B indicates a pinhole in the photoelectric conversion film.

Thereafter, as shown in FIG. 1C, to prevent a short circuit between the upper and lower electrodes, an interlayer insulating film 4 made of a-SiN: H is formed to a thickness of 200 nm (step S5), and an upper contact portion is formed. Patterning is performed so that only the openings are formed (step S6). In FIG. 1C, reference numeral 6 in the interlayer insulating film also indicates a pinhole.

Next, in step S7, the temperature is raised to 230 ° C. in an oxygen atmosphere and left for about one hour. At this time, the pinhole 6 of the photoelectric conversion film 3 or the interlayer insulating film 4 is formed.
The exposed portion of the first electrode 2 is oxidized to form a Ta ₂ O ₃ film 7 which is an electrically insulating oxide insulating film as shown in FIG.

Thereafter, as shown in FIG.
A second electrode 5 made of 400 nm is formed by sputtering (step S8), and the Ta electrode 2 is formed by wet etching.
Is performed in a line shape so as to be orthogonal to (step S9). Finally, a surface protection film 8 is formed (step S
10), the photoelectric conversion element is completed (FIG. 1 (f)).

When a photoelectric conversion element is manufactured by the above-described steps, processing such as heating and standing as shown in step S7 is required. This step is performed by conventional anodic oxidation (S105) and cleaning. The work is easier than the processing of (S106).

Second Embodiment FIG. 3 shows a flowchart of a process for manufacturing a photoelectric conversion element according to a second embodiment of the present invention. Here, the feature is that oxygen plasma processing S11 is performed instead of the processing of step S7. 3, steps S1 to S6 are the same as the steps shown in FIG.

After step S6, O_TwoFlow rate 20SCC
M, substrate temperature 200 ° C, pressure 0.2 Torr, input power
Oxygen plasma treatment is performed for 1 minute at 100 W
Step S11). Thereby, the photoelectric conversion film 3 or the layer
The exposed portion of the first electrode 2 due to the pinhole of the inter-insulating film 4 is
Oxidized, as shown in FIG.
_TwoO_ThreeThe coating 7 is formed.

Next, as in the first embodiment, the ITO
(Step S8), patterning (Step S9), and formation of the surface protection film 8 (Step S10), the photoelectric conversion element is completed.

In the above steps, the oxygen plasma treatment in step S11 is required, but the first electrode can be oxidized more easily and in a shorter time than the conventional anodic oxidation and cleaning treatments.

Note that the present invention is not limited to the above-described embodiment, and the materials and temperature conditions may be changed as necessary. For example, the first electrode 2
Examples of the material include Al, Cr, Ti, Nb,
Zr or the like can be used. The photoelectric conversion film 3 may be made of arsenic, in addition to hydrogenated amorphous silicon.
A selenium-tellurium-based amorphous semiconductor, cadmium sulfide, or the like can be used. As the interlayer insulating film 4, a-Si
In addition to N: H, SiO ₂ or the like can be used. Second
Although the electrode 5 is a transparent electrode, a transparent material may be used, and ZnO or the like may be used in addition to ITO.

Further, the temperature of the first electrode 2 exposed in the film by the pinholes of the photoelectric conversion film 3 or the interlayer insulating film 4 is increased in an oxidizing gas atmosphere such as oxygen (step S7), or a gas containing oxygen atoms is used. (Step S11), a step (etching step) of removing the thin silicon oxide film formed on the surface of the hydrogenated amorphous silicon, which is the photoelectric conversion film, using several percent of HF is added. Is also good.

[0036]

According to the present invention, since the dry oxidation process is used, an oxide film can be formed on at least the first electrode at the position of the short-circuit defect formed in the photoelectric conversion film and the interlayer insulating film. The first electrode and the second electrode are easily manufactured.
A short circuit between the electrodes can be prevented.

[Brief description of the drawings]

FIG. 1 is a cross-sectional view showing a step of manufacturing a photoelectric conversion element according to a first embodiment of the present invention.

FIG. 2 is a flowchart of a manufacturing process of the photoelectric conversion element according to the first embodiment of the present invention.

FIG. 3 is a flowchart of a manufacturing process of a photoelectric conversion element according to a second embodiment of the present invention.

FIG. 4 is a cross-sectional view showing a structure of a conventional general photoelectric conversion element.

FIG. 5 is an equivalent circuit diagram of a photoelectric conversion element including one diode.

FIG. 6 is a flowchart of a manufacturing process of a conventional photoelectric conversion element.

FIG. 7 is a diagram showing a current-voltage characteristic curve of an ideal photoelectric conversion element including one diode.

FIG. 8 is a diagram illustrating a current-voltage characteristic curve of a photoelectric conversion element including one diode when a pinhole occurs in a photoelectric conversion film or an interlayer insulating film.

FIG. 9 is a diagram illustrating a current-voltage characteristic curve of a photoelectric conversion element including two diodes having opposite polarities when there is no pinhole in the photoelectric conversion film or the interlayer insulating film.

FIG. 10 shows current-voltage characteristics of a photoelectric conversion element including two diodes having opposite polarities when a pinhole occurs in a portion where a first electrode and a second electrode overlap in a photoelectric conversion film or an interlayer insulating film. It is a curve.

[Explanation of symbols]

 Reference Signs List 1 insulating substrate 2 first electrode 3 photoelectric conversion film 4 interlayer insulating film 5 second electrode 6 pinhole 7 oxide insulating film 8 surface protective film

 ────────────────────────────────────────────────── ─── Continued on the front page (72) Inventor Katsushi Kishimoto 22-22 Nagaikecho, Abeno-ku, Osaka-shi, Osaka F-term (reference) 4M118 AA08 AA10 AB10 BA05 CA14 CA32 CB05 CB06 CB14 EA01 5F049 AB05 BB03 CA11 CA14 CA15 CA18 DA01 FA05 FA11 GA01

Claims (8)

[Claims] A step of forming a first electrode on an insulating substrate; and a step of forming a photoelectric conversion film on the first electrode.
Forming an interlayer insulating film so as to cover the first electrode and the photoelectric conversion film except on a photoelectric conversion film which is to be a contact portion with the second electrode; and forming the first electrode, the photoelectric conversion film, and the interlayer insulating film. A process of dry-oxidizing the entire substrate on which is formed, and a step of forming a second electrode having optical transparency on the interlayer insulating film and the photoelectric conversion film. . 2. The method for manufacturing a photoelectric conversion element according to claim 1, wherein the step of performing the dry oxidation treatment comprises raising the temperature in an oxidizing gas atmosphere and leaving the substrate to stand for a predetermined time. 3. The method according to claim 1, wherein the temperature is raised to 150 ° C. or more and 35 ° C.
3. The method according to claim 2, wherein the temperature is set to 0 ° C. or lower. 4. The method according to claim 1, wherein the step of performing the dry oxidation comprises performing a plasma treatment in a gas containing oxygen.
The manufacturing method of the photoelectric conversion element of Claim. 5. The method for manufacturing a photoelectric conversion element according to claim 4, wherein a pressure of a gas used for the plasma processing is set to 0.1 Torr or more and 1 Torr or less. 6. The method according to claim 1, further comprising, after the step of performing the dry oxidation treatment, a step of removing an oxidized upper layer portion of the photoelectric conversion film that is in contact with the second electrode by etching. A method for manufacturing a photoelectric conversion element. 7. The method according to claim 1, wherein the first electrode is made of Ta, Al, Cr, T
The method according to any one of claims 1, 2, 3, 4, 5, and 6, wherein the method is made of any one of i, Nb, and Zr. 8. The method according to claim 7, wherein the photoelectric conversion element is an image sensor.