JP2023069531A - Manufacturing method for solid state imaging element, and solid state imaging element - Google Patents

Abstract

To provide a manufacturing method for a solid state imaging element capable of reducing dark current.SOLUTION: A manufacturing method for a solid state imaging element includes the steps of: forming a Te film 12 and a first amorphous Se film 13a sequentially on a substrate 11 including a signal readout circuit; forming a transparent electrode 15, a metal oxide film 14, and a second amorphous Se film 13b sequentially on a transparent substrate 16; and bonding with pressure the first amorphous Se film 13a and the second amorphous Se film 13b. The metal oxide is an n-type semiconductor. In the manufacturing method for a solid state imaging element, when the first amorphous Se film 13a and the second amorphous Se film 13b are bonded with pressure, the first amorphous Se film 13a and the second amorphous Se film 13b are heated to form a crystal Se film 13.SELECTED DRAWING: Figure 1

Description

The present invention relates to a solid-state imaging device manufacturing method and a solid-state imaging device.

In recent years, as the number of pixels of a solid-state image pickup device has increased, the pixel area has been reduced, so there is a problem that the sensitivity of the solid-state image pickup device is lowered. Therefore, a stacked solid-state imaging device using a crystalline Se film as a p-type semiconductor film constituting a photoelectric conversion film has been studied (see Non-Patent Documents 1 and 2). The stacked solid-state imaging device has a Ga ₂ O ₃ film (n-type semiconductor film), a Te film, a crystalline Se film and an ITO film which are sequentially stacked on a substrate having a signal readout circuit. Here, the crystalline Se film is formed by crystallizing an amorphous Se film, but it is necessary to insert a Te film as a base film.

However, because the carriers traveling toward the substrate having the signal readout circuit are electrons, and the visible light incident from the transparent electrode side is absorbed in the crystalline Se film before reaching the depletion layer, Inability to obtain sufficient sensitivity.

Therefore, a Te film and a first amorphous Se film are formed on a substrate having a signal readout circuit, a transparent electrode, a metal oxide film and a second amorphous Se film are formed on a transparent substrate, and a first amorphous Se film is formed. and a second amorphous Se film are pressure-bonded, and then the first amorphous Se film and the second amorphous Se film are heated to form a crystalline Se film (see Patent Document 1).

JP 2017-208376 A

S. Imura et al. IEDM Tech. Dig. , (2014) 88 S. Imura et al. Appl. Phys. Lett. 104, (2014) 242101

However, since the crystalline Se film has a bonding interface, crystal defects (voids) occur, resulting in an increase in dark current.

An object of the present invention is to provide a method for manufacturing a solid-state imaging device capable of reducing dark current.

According to one aspect of the present invention, there is provided a method for manufacturing a solid-state imaging device, in which a step of sequentially forming a Te film and a first amorphous Se film on a substrate having a signal readout circuit; sequentially forming a film and a second amorphous Se film; and pressure bonding the first amorphous Se film and the second amorphous Se film, wherein the metal oxide is an n-type semiconductor; During the pressure bonding, the first amorphous Se film and the second amorphous Se film are heated to form a crystalline Se film.

In the solid-state imaging device manufacturing method described above, a Te film may be further formed between the metal oxide film and the second amorphous Se film.

In the method for manufacturing a solid-state imaging device, instead of sequentially forming a transparent electrode, a metal oxide film and a second amorphous Se film on the transparent substrate, the transparent electrode is formed on one surface of the metal oxide substrate. and the second amorphous Se film may be formed on the other surface of the metal oxide substrate.

In the solid-state imaging device manufacturing method described above, a Te film may be further formed between the metal oxide substrate and the second amorphous Se film.

Another aspect of the present invention is a solid-state imaging device manufactured by the method for manufacturing a solid-state imaging device described above.

According to the present invention, it is possible to provide a method for manufacturing a solid-state imaging device capable of reducing dark current.

It is a cross-sectional schematic diagram which shows an example of the manufacturing method of the solid-state image sensor of this embodiment. It is a cross-sectional schematic diagram which shows the solid-state image sensor manufactured by the manufacturing method of the solid-state image sensor of FIG. 4 is an electron microscope image of a cross section of an evaluation sample of the solid-state imaging device of Example 1. FIG. 10 is an electron microscope image of a cross section of an evaluation sample of the solid-state imaging device of Example 2. FIG. 4 is an electron microscope image of a cross section of an evaluation sample of the solid-state imaging device of Comparative Example 1. FIG. 10 is an electron microscope image of a cross section of an evaluation sample of the solid-state imaging device of Comparative Example 2. FIG. 4 is a graph showing the relationship between the absolute value of dark current density and the reverse bias voltage; 4 is a graph showing the relationship between the reverse bias voltage and the absolute value of photocurrent density.

BEST MODE FOR CARRYING OUT THE INVENTION Hereinafter, embodiments of the present invention will be described with reference to the drawings.

FIG. 1 shows an example of a method for manufacturing the solid-state imaging device of this embodiment.

First, a Te (tellurium) film 12 and a first amorphous Se (selenium) film 13a are sequentially formed on a substrate 11 having a signal readout circuit (see FIG. 1(a)), and a transparent electrode 15 is formed on a transparent substrate 16. , a metal oxide film 14 and a second amorphous Se film 13b are sequentially formed (see FIG. 1B). Here, the metal oxide forming the metal oxide film 14 is an n-type semiconductor. Next, the first amorphous Se film 13a and the second amorphous Se film 13b are pressure-bonded (see FIG. 1(c)). Here, when the first amorphous Se film 13a and the second amorphous Se film 13b are pressure-bonded, the first amorphous Se film 13a and the second amorphous Se film 13b are heated to form the crystal Se film 13 (Fig. 1(d)). Here, the crystalline Se forming the crystalline Se film 13 is a p-type semiconductor.

Note that the Te film 12 serves as a starting point for the growth of Se crystals, in addition to preventing the separation of amorphous Se during crystallization.

In the manufacturing method of the solid-state imaging device of the present embodiment, the first amorphous Se film 13a and the second amorphous Se film 13b are heated when the first amorphous Se film 13a and the second amorphous Se film 13b are pressure-bonded. Since the crystalline Se film 13 is formed, the crystalline Se film 13 suppresses the generation of voids and reduces the dark current generated from the defect level.

On the other hand, when the first amorphous Se film and the second amorphous Se film are pressure-bonded and then the first amorphous Se film and the second amorphous Se film are heated to form a crystalline Se film, the crystalline Se film is Since it has a bonding interface, voids are generated.

Further, in the manufacturing method of the solid-state imaging device of this embodiment, the Te film 12 and the first amorphous Se film 13a are sequentially formed on the substrate 11 having the signal readout circuit, and the metal oxide film 14 is formed on the transparent substrate 16. and the second amorphous Se film 13b are sequentially formed, the amount of Te in the crystalline Se film 13 is reduced. As a result, it becomes possible to efficiently apply a voltage to the crystalline Se in the crystalline Se film 13, thereby improving the multiplication factor.

A method for forming the Te film 12 is not particularly limited, but for example, a heating vapor deposition method can be used.

A method for forming the amorphous Se films 13a and 13b is not particularly limited, but examples thereof include a heating vapor deposition method.

A method for forming the transparent electrode 15 is not particularly limited, but examples thereof include a sputtering method.

The pressure applied to pressure-bond the first amorphous Se film 13a and the second amorphous Se film 13b is not particularly limited, but is, for example, 1 kN or more and 30 kN or less.

Although the temperature for heating the first amorphous Se film 13a and the second amorphous Se film 13b is not particularly limited, it is, for example, 100° C. or higher and 200° C. or lower.

A Te film may be further formed between the metal oxide film 14 and the second amorphous Se film 13b.

Further, when the first amorphous Se film 13a and the second amorphous Se film 13b are pressure-bonded, the temperatures of the first amorphous Se film 13a and the second amorphous Se film 13b are maintained for a predetermined time without heating. The first amorphous Se film 13a and the second amorphous Se film 13b may be heated. In this case, the applied pressure for maintaining the temperature of the first amorphous Se film 13a and the second amorphous Se film 13b is the same as the applied pressure for heating the first amorphous Se film 13a and the second amorphous Se film 13b. They may be the same or different.

FIG. 2 shows a solid-state imaging device manufactured by the solid-state imaging device manufacturing method of FIG.

The solid-state imaging device 10 has a Te film 12, a crystalline Se film 13, a metal oxide film 14, a transparent electrode 15 and a transparent substrate 16 which are sequentially laminated on a substrate 11 having a signal readout circuit.

The substrate 11 having the signal readout circuit is not particularly limited, but is, for example, a Si substrate having a CMOS (Complementary Metal Oxide Semiconductor) structure and electrodes formed thereon. The electrode is connected to the negative electrode of power supply 17 .

The electrodes may be transparent electrodes or opaque electrodes.

The material forming the transparent electrode is not particularly limited, but examples thereof include ITO (indium tin oxide), IZO (indium zinc oxide), and AZO (aluminum-doped zinc oxide).

The material forming the opaque electrode is not particularly limited, but examples thereof include Au (gold), Cu (copper), Al (aluminum), W (tungsten), Mo (molybdenum), and the like.

The film thickness of the electrode is not particularly limited, but is, for example, 10 nm or more and 100 nm or less.

A method for forming the electrodes is not particularly limited, but examples thereof include a sputtering method.

Although the film thickness of the Te film 12 is not particularly limited, it is, for example, 0.1 nm or more and 10 nm or less.

Although the film thickness of the crystalline Se film 13 is not particularly limited, it is, for example, 100 nm or more and 5 μm or less.

Since the metal oxide film 14 is an n-type semiconductor film, a depletion layer is formed between it and the crystalline Se film 13, which is a p-type semiconductor. Therefore, light incident from the transparent substrate 16 side generates a large number of carriers in the depletion layer, and holes travel toward the substrate 11 . Further, holes are multiplied by colliding with Se atoms in the crystalline Se film 13 .

The metal oxide forming the metal oxide film 14 is not particularly limited as long as it is an n-type semiconductor. Examples include Ga ₂ O ₃ (gallium oxide), ZnO (zinc oxide), CeO ₂ (cerium oxide), Y ₂ O ₃ (yttrium oxide), In ₂ O ₃ (indium oxide), and the like. Among these, Ga ₂ O ₃ is preferred.

Although the film thickness of the metal oxide film 14 is not particularly limited, it is, for example, 1 nm or more and 100 nm or less.

A method for forming the metal oxide film 14 is not particularly limited, but an example thereof includes a sputtering method.

The transparent electrode 15 is connected to the positive electrode of the power source 17 .

The material forming the transparent electrode 15 is not particularly limited, but examples thereof include ITO (indium tin oxide), IZO (indium zinc oxide), and AZO (aluminum-doped zinc oxide).

Although the film thickness of the transparent electrode 15 is not particularly limited, it is, for example, 10 nm or more and 100 nm or less.

The material forming the transparent substrate 16 is not particularly limited, but examples thereof include sapphire, soda lime glass, quartz, alkali-free glass, silicoborate glass, and the like.

In the manufacturing method of the solid-state imaging device of this embodiment, instead of sequentially forming the transparent electrode 15, the metal oxide film 14 and the second amorphous Se film 13b on the transparent substrate 16, one surface of the metal oxide substrate A transparent electrode may be formed on the substrate, and a second amorphous Se film may be formed on the other surface of the metal oxide substrate. In this case, a Te film may be further formed between the metal oxide substrate and the second amorphous Se film.

(Example 1)
An evaluation sample of the solid-state imaging device was produced by the method described below. Specifically, after forming an ITO film with a thickness of 20 nm on a silicon substrate by a sputtering method, a Te film with a thickness of 0.2 nm and an amorphous Se film with a thickness of 150 nm were sequentially formed by a vacuum deposition method. filmed. Next, an ITO film with a thickness of 20 nm and a Ga ₂ O ₃ film with a thickness of 20 nm were sequentially formed on the sapphire substrate by sputtering, and then an amorphous Se film with a thickness of 150 nm was formed by vacuum deposition. bottom. Next, the amorphous Se films were faced to each other and pressure-bonded with a pressure of 2 kN. At this time, pressurization was started at a pressurization pressure of 2 kN and then maintained at room temperature for 1 minute, then the temperature was raised to 160° C. in about 10 minutes, and the temperature was lowered to room temperature in about 1 hour.

(Example 2)
A solid-state imaging device evaluation sample was prepared in the same manner as in Example 1, except that a Te film having a thickness of 0.2 nm was further formed between the Ga ₂ O ₃ film and the second amorphous Se film by vacuum deposition. made.
(Example 3)
An evaluation sample of a solid-state imaging device was produced in the same manner as in Example 1, except that the thickness of the Te film was changed to 0.4 nm.

(Comparative example 1)
Amorphous Se films were faced to each other, and after starting pressurization with a pressurization pressure of 2 kN, it was maintained at room temperature for 1 minute. A solid-state imaging device evaluation sample was prepared in the same manner as in Example 2, except that the temperature was lowered to room temperature in about 1 hour.

(Comparative example 2)
Example 2 except that the amorphous Se films were opposed to each other, the pressure was started at a pressure of 2 kN, the pressure was maintained at room temperature for 1 minute, and after pressure bonding, the pressure was stopped and no heating was performed. An evaluation sample of the solid-state imaging device was produced in the same manner as in the above.

(cross-section observation)
Using an electron microscope, the cross section of the evaluation sample of the solid-state imaging device was observed.

3 to 6 show cross-sectional electron microscope images of evaluation samples of the solid-state imaging devices of Examples 1 and 2 and Comparative Examples 1 and 2, respectively. Although the magnification of the electron microscope images in FIGS. 4 and 5 is not shown, it is the same as the magnification of the electron microscope images in FIGS.

In the evaluation sample of the solid-state imaging device of Example 1, voids were not observed in the crystalline Se film because Se crystals grew starting from the Te film formed on one side when the amorphous Se film was pressure-bonded. No (see Figure 3).

In the evaluation sample of the solid-state imaging device of Example 2, voids were not observed in the crystalline Se film because Se crystals grew starting from the Te films formed on both sides when the amorphous Se film was pressure-bonded. No (see Figure 4).

In the evaluation sample of the solid-state imaging device of Comparative Example 1, after the amorphous Se film was press-bonded, the Se crystals grew from the Te films formed on both sides as starting points, so voids were observed at intermediate points (FIG. 5). reference).

The evaluation sample of the solid-state imaging device of Comparative Example 2 was not heated after the amorphous Se film was pressure-bonded, so the amorphous Se was not crystallized (see FIG. 6).

From the above, it can be seen that when the amorphous Se film is pressure-bonded, the generation of voids is suppressed by the growth of Se crystals starting from the Te film.

(dark current density and photocurrent density)
A negative voltage was applied to the ITO film on the silicon substrate side, a positive voltage was applied to the ITO film on the sapphire substrate side, and current-voltage characteristics were measured.

FIG. 7 shows the relationship between the absolute value of the dark current density and the reverse bias voltage. Also, FIG. 8 shows the relationship between the absolute value of the photocurrent density and the reverse bias voltage.

The evaluation sample of the solid-state imaging device of Example 2 was compared with the evaluation sample of the solid-state imaging device of Comparative Example 1 manufactured under the same conditions except that the amorphous Se film was pressure-bonded and then heated. Low density (see Figure 7).

The evaluation sample of the solid-state imaging device of Example 1 was compared with the evaluation sample of the solid-state imaging device of Example 2, which was manufactured under the same conditions except that Te films were formed on both sides. Since the concentration is low and the resistance is high, a voltage can be efficiently applied to the crystalline Se in the crystalline Se film, resulting in a high multiplication factor (see FIG. 8).

Further, the evaluation sample of the solid-state imaging device of Example 1 was compared with the evaluation sample of the solid-state imaging device of Example 3 manufactured under the same conditions except that the thickness of the Te film was doubled. Since the Te concentration in the film is low and the resistance is high, a voltage can be efficiently applied to the crystalline Se in the crystalline Se film, resulting in a high multiplication factor (see FIG. 8).

From the above, it can be seen that when the amorphous Se film is pressure-bonded, dark current is reduced by the growth of Se crystals starting from the Te film. Furthermore, it can be seen that the multiplication factor is improved by forming the Te film on one side.

REFERENCE SIGNS LIST 10 solid-state imaging device 11 substrate having a signal readout circuit 12 Te film 13 crystalline Se film 13a first amorphous Se film 13b second amorphous Se film 14 metal oxide film 15 transparent electrode 16 transparent substrate 17 power supply

Claims (5)

sequentially forming a Te film and a first amorphous Se film on a substrate having a signal readout circuit;
sequentially forming a transparent electrode, a metal oxide film and a second amorphous Se film on a transparent substrate;
pressure bonding the first amorphous Se film and the second amorphous Se film,
the metal oxide is an n-type semiconductor,
A method for manufacturing a solid-state imaging device, wherein the first amorphous Se film and the second amorphous Se film are heated to form a crystalline Se film when the pressure bonding is performed. 2. The method of manufacturing a solid-state imaging device according to claim 1, further comprising forming a Te film between said metal oxide film and said second amorphous Se film. Instead of sequentially forming a transparent electrode, a metal oxide film and a second amorphous Se film on the transparent substrate, the transparent electrode is formed on one surface of the metal oxide substrate and 2. The method of manufacturing a solid-state imaging device according to claim 1, wherein said second amorphous Se film is formed on the surface. 4. The method of manufacturing a solid-state imaging device according to claim 3, further comprising forming a Te film between said metal oxide substrate and said second amorphous Se film. A solid-state imaging device manufactured by the solid-state imaging device manufacturing method according to claim 1 .

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