JP2001168314A - Solid-state image pick-up device and its manufacturing method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a solid-state image pick-up device which is capable of meeting requirements such as high sensitivity, high transfer performance, a low dark current and the like at the same time and a method of manufacturing the same. SOLUTION: A P-type well region 2 is formed on the surface of an N-type Si substrate 1. An N-type CCD channel region 3 is provided in the P-type well region 2 and divided in a vertical direction by P+-type channel blocking regions 12. An ONO gate insulating film G of three-layered structure composed of Si oxide film 6/Si nitride film 5/Si oxide film 4 is formed on the surface of an N-type CCD channel region 3, and a poly-Si transfer electrode 7 is provided on the ONO gate insulating film G. An anti-reflection film F of two-layered structure of Si nitride film 9/Si oxide film 8 is formed on the surface of the poly-Si transfer electrode 7. The upper Si oxide film and the Si nitride film 5 inside the ONO gate insulating film G are separated from the Si nitride film 9 inside the anti-reflection film F in a region over the P+-type channel blocking regions 12. The Si oxide film 6/Si nitride film 5 inside the ONO gate insulating film G and the anti-reflection film F are separated by a gap between the poly-Si transfer electrode 7 and the other poly-Si transfer electrode 7.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a television camera, a video camera, a still camera, and the like.
The present invention relates to a solid-state imaging device used in a visible light region and a method for manufacturing the same.

[0002]

2. Description of the Related Art Conventionally, this type of solid-state image pickup device is called a frame transfer type solid-state image pickup device or a full frame type solid-state image pickup device. A conventional example of the frame transfer type solid-state imaging device will be described below based on a report by Okada et al. (Television Society Journal, Vol. 49, No. 2, pp. 176-181, 1995).

FIG. 3 is a diagram showing the overall configuration of the above-mentioned conventional frame transfer type solid-state imaging device. This solid-state image sensor performs photoelectric conversion of incident light, and temporarily converts an image pickup region 15 formed from a vertical charge-coupled device array for reading out generated signal charges, and a signal charge generated in the image pickup region 15. It comprises a storage region 16 composed of a column of vertical charge-coupled devices for storing and sequentially transferring the charges, a horizontal charge-coupled device 17 for scanning the charges line by line, and an output unit 18 composed of a plurality of transistors for converting the charges into voltages. ing.

[0006] A region R indicating the pixel plane structure of the imaging region 15
In FIG. 3, the channels of the vertical charge-coupled device row are separated in the vertical direction in FIG. 3 by the p ⁺ type channel blocking region 14, and the poly-Si (polycrystalline silicon) transfer electrode 13 is formed by a two-layer poly-Si process. The poly-Si transfer electrode 13 has no opening, and receives light transmitted through the poly-Si transfer electrode 13. According to this conventional example, the gate insulating film under the poly-Si transfer electrode 13 is a Si oxide film, and when the thickness of the poly-Si transfer electrode 13 is about 70 nm and the thickness of the gate oxide film is about 180 nm, It has been shown that high sensitivity to the visible light region can be obtained. The configuration of the full-frame solid-state imaging device is obtained by removing the accumulation region from the entire configuration of the frame transfer-type solid-state imaging device.

[0005]

In the above-described conventional frame transfer type solid-state imaging device, the thickness of the poly-Si transfer electrode 13 is about 70 nm, and the thickness of the gate oxide film is about 1 nm.
The reason for the high sensitivity at about 80 nm is that poly-Si
In addition to reducing the light absorption of the transfer electrode 13, a high refractive index material (poly-Si transfer electrode 13 sandwiched between Si oxide films) sandwiched between low refractive index materials and a low refractive index material sandwiched between high refractive index materials Refractive index substance
When the optical length of the thickness of the (gate oxide film sandwiched between the poly-Si transfer electrode 13 and the Si substrate) is about の of the wavelength, it becomes a condition for reducing the reflectance of incident light. is there.

However, the thickness of 180 nm of the Si oxide film is extremely large as a gate insulating film in a charge-coupled device. In the charge-coupled device, in order to have high charge transfer capability, it is better to make the gate insulating film thin, and it is preferable that the thickness of the silicon oxide film be at most 100 nm or less at most. However, it is shown in the above-mentioned conventional example that the sensitivity is reduced when the Si oxide film is 100 nm.
As a solution to this problem, a two-layer film of Si ₃ N ₄ (silicon nitride) / SiO ₂ (silicon dioxide) frequently used as a gate insulating film other than the Si oxide film, and an ONO film (S
It is conceivable to use a gate insulating film including a Si nitride film, such as a three-layer film of iO ₂ / Si ₃ N ₄ / SiO ₂ ).

[0007] Alternatively, the Si oxynitride film also has characteristics close to those of the Si nitride film, and thus can be used. The Si nitride film and the Si oxynitride film have higher refractive indices and dielectric constants than the Si oxide film. (Si nitride film has a refractive index of 2, relative dielectric constant of 7, and Si oxynitride film has a refractive index of 1.45 to 2, relative dielectric constant of 3.8.) ~ 7, Si oxide film has a refractive index of 1.
45, the relative dielectric constant of 3.8), the optical length can be increased even if the physical thickness is the same, and the electrically converted film thickness of the Si oxide film can be reduced.

[0008] However, the gate insulating film is made of a silicon oxide film.
When formed from a combination with a Si nitride film (or a Si oxynitride film), since the Si nitride film (or a Si oxynitride film) has a large residual stress, an interface state between the gate insulating film and the CCD channel region is formed. Is increased, and another problem that the dark current is increased as compared with the case of using only the Si oxide film occurs. Therefore, the conventional solid-state imaging device has a problem that high performances such as high sensitivity, high transfer capability, and low dark current cannot be satisfied at the same time for the reasons described above.

The present invention has been made under such a background, and provides a solid-state imaging device capable of simultaneously satisfying high performance such as high sensitivity, high transfer capability, and low dark current, and a method of manufacturing the same. It is in.

[0010]

According to the first aspect of the present invention,
At least, an imaging region that performs a photoelectric conversion of incident light and reads a signal charge generated by the photoelectric conversion, and an image pickup region including a vertical charge-coupled device row, and a horizontal charge-coupled device that receives the signal charges of the vertical charge-coupled device row and sequentially transfers the signal charges And a signal-to-voltage conversion of the signal charge and an output unit for outputting the signal charge as a voltage signal, wherein the gate insulating film (for example, ONO of one embodiment) of the vertical charge-coupled device is provided.
The gate insulating film G) is a Si nitride film (for example, of one embodiment)
Si nitride film 5) or Si oxynitride film or both (Si nitride film and Si oxynitride film) and Si oxide film (for example,
The Si nitride film and / or the Si oxynitride film in the gate insulating film, or both of them (the Si nitride film and the Si oxynitride film). ) Is divided into minute portions below each electrode.

According to a second aspect of the present invention, there is provided the solid-state imaging device according to the first aspect, wherein the Si nitride film, the Si oxynitride film, or both of them (Si nitride film and Si oxynitride film) are combined with the Si oxide film. The synthetic optical length of the gate insulating film made of is between 200 nm and 275 nm, and the electrically converted film thickness of the Si oxide film is 100 nm or less.

According to a third aspect of the present invention, in the solid-state imaging device according to the first or second aspect, a transfer electrode (for example, a poly-Si film according to an embodiment) constituting the vertical charge-coupled device is provided.
The insulating film (for example, the antireflection film F in one embodiment) on the transfer electrode 7) is a Si nitride film (for example, the Si nitride film 9 in one embodiment) or a Si oxynitride film or both (Si nitride film and Si nitride film). Si oxynitride film), the Si nitride film or the Si oxynitride film in the insulating film, or both of them (the Si oxynitride film).
The nitride film and the Si oxynitride film are divided into minute portions on each electrode.

According to a fourth aspect of the present invention, in the solid-state image pickup device according to any one of the first to third aspects, the insulating film functioning as an anti-reflection film on the transfer electrode constituting the vertical charge-coupled device is provided. , A composite optical length from the outermost Si nitride film or Si oxynitride film to the transfer electrode, including Si nitride film or Si oxynitride film or both (Si nitride film and Si oxynitride film) But 100 nm to 13
It is characterized by being between 7.5 nm.

According to a fifth aspect of the present invention, in the solid-state imaging device according to any one of the first to fourth aspects, the transfer electrode constituting the vertical charge-coupled device is a single-layer polycrystalline structure.
It is characterized by being formed by patterning a Si film.

According to a sixth aspect of the present invention, at least an image pickup area comprising a vertical charge-coupled device array for performing photoelectric conversion and reading out generated signal charges, and receiving and transferring the signal charges of the vertical charge-coupled device sequence. In a method for manufacturing a solid-state imaging device including a horizontal charge-coupled device and an output unit that converts a signal charge into a charge-voltage (a charge amount is converted into a voltage) and outputs the converted charge, the gate insulating film of the vertical charge-coupled device includes: A first step of forming a Si oxide film and depositing a Si nitride film or a Si oxynitride film or both (the Si nitride film and the Si oxynitride film); and a deposited Si nitride film or the Si oxide film. Nitride film or both (Si
A second step of etching and removing the nitride film and the Si oxynitride film on the channel blocking region to form a band, a polycrystalline Si film being deposited and patterned into a shape of a transfer electrode, and a gap between the transfer electrodes is formed. A third step of etching and removing the Si nitride film, the Si oxynitride film, or both (the Si nitride film and the Si oxynitride film).

According to a seventh aspect of the present invention, in the method of manufacturing a solid-state imaging device according to the sixth aspect, the third step comprises: depositing the polycrystalline Si film, and then depositing the polycrystalline Si film on the surface of the polycrystalline Si film. Si
Nitride film and / or Si oxynitride film
A fourth step of depositing an insulating film including a nitride film and the Si oxynitride film, and at least the Si nitride film, the Si oxynitride film, or both (the Si nitride film and the Si oxide film) in the insulating film. Removing the nitride film) on the channel blocking region by etching to form a band-like shape. When the polycrystalline Si film is patterned into a transfer electrode shape, the The insulating film including the Si nitride film, the Si oxynitride film, or both of them (the Si nitride film and the Si oxynitride film) on the film is simultaneously removed by etching.

According to an eighth aspect of the present invention, in the solid-state imaging device according to any one of the first to fifth aspects, the gate insulating film of the vertical charge-coupled device has a Si nitride film or a Si nitride film on a Si oxide film. The insulating film, which is formed of a two-layer film including an oxynitride film and functions as an antireflection film on the transfer electrode constituting the vertical charge-coupled device, is a single layer made of a Si nitride film or a Si oxynitride film. Features.

In the solid-state imaging device of the present invention, the gate insulating film of the vertical charge-coupled device for performing photoelectric conversion is the Si oxide film and the Si nitride film (or the Si oxynitride film, or both, ie, the Si nitride film and the Si nitride film). Since the gate insulating film has a long optical length and a small electrical equivalent oxide thickness, the gate insulating film further includes a Si nitride film (or Si nitride film) in the gate insulating film. Oxynitride film or both) is divided into minute portions under each electrode, so that the residual stress is lower than that of a single Si nitride film or Si oxynitride film extending under many electrodes as in the past. Are dispersed, and the effect is made small.

The thickness condition of the gate insulating film (ONO gate insulating film G or the like) composed of a combination of the Si oxide film and the Si nitride film (or the Si oxynitride film or both) is as follows.
It is desirable that the combined optical length is between 200 nm and 275 nm, and the electrical equivalent Si oxide film thickness is 100 nm or less. Here, the optical length of 200 nm to 275 nm corresponds to the wavelength of 400 nm to 55 nm.
It is equivalent to λ / 2 of 0 nm and has a center wavelength of 550 in the visible light region.
This means that the film thickness condition is such that the reflectance is suppressed for wavelengths shorter than nm.

According to the results of the study (simulation and experiment) by the inventor, the gate insulating film is made of Si nitride (or Si
Oxynitride film or both), the reflectance reduction condition λ / 2 is different from the case of only Si oxide film.
It has been found that the reflectance is reduced in a wide wavelength band on the long wavelength side from the wavelength to be obtained. Therefore, in order to increase the sensitivity in a wide range of the entire visible light region, a combined optical length of λ / 2 for a wavelength shorter than the center wavelength of 550 nm is advantageous. Here, the relative dielectric constant of the Si oxide film is about 7, while the relative dielectric constant of the Si oxide film is about 7, and the Si oxynitride film takes a value between 3.8 and 7 depending on the ratio of oxygen and nitrogen. A gate insulating film composed of a combination of a SiN film and a Si nitride film (or a Si oxynitride film or both) can reduce the electrical film thickness even if the synthesized optical length is long, and can reduce the charge coupling. It is possible to realize a silicon oxide film equivalent thickness of 100 nm or less that allows the device to have a high charge transfer capability.

Normally, a pixel of a conventional solid-state image sensor is
Before the surface flattening film is formed, a low-refractive-index insulating film layer thick enough to eliminate the interference effect is formed by laminating a surface flattening film and a color filter exhibiting the same low refractive index as the oxide film. The outermost high refractive index film (Si nitride film or Si
Up to an oxynitride film) contributes to the interference effect or the antireflection effect.

In the solid-state image pickup device of the present invention, the Si nitride film (or Si oxynitride film or Si oxynitride film or Both), which exhibit an anti-reflective effect. Since the Si nitride film (or Si oxynitride film or both) is formed by being divided into minute portions on each electrode, the residual stress of the Si nitride film (or Si oxynitride film or both) is also reduced. Decentralized, with minimal impact.

The thickness condition from the outermost Si nitride film (or Si oxynitride film) in the insulating film functioning as an antireflection film on the transfer electrode constituting the vertical charge coupled device to the transfer electrode is defined as It is desirable that the optical length is 100 nm to 137.5 nm. For optical lengths from 100 nm to 137.5 nm, wavelengths from 400 nm to
It is equivalent to λ / 4 of 550 nm, and has a center wavelength of 55 in the visible light region.
This means that the film thickness is such that the reflectance is suppressed for wavelengths shorter than 0 nm.

According to the results of the study (simulation and experiment) by the inventor, the insulating film including the Si nitride film (or the Si oxynitride film or both) on the transfer electrode also has the Si nitride film (or the Si oxynitride film or It is similar to the case of the gate insulating film including both of them, and it has been found that the reflectance is reduced in a wide wavelength band on the long wavelength side from the wavelength satisfying the reflectance reduction condition λ / 4. Therefore, in order to increase the sensitivity in a wide range of the entire visible light region, a combined optical length of λ / 4 for a wavelength shorter than the center wavelength of 550 nm is advantageous.

Furthermore, if the transfer electrodes constituting the vertical charge-coupled device are formed by patterning one layer of a poly-Si film, the transfer electrodes formed when the transfer electrodes are formed from two or more layers of the poly-Si film are overlapped. There is no portion, and light loss at that portion can be reduced. Therefore, the solid-state imaging device of the present invention can simultaneously satisfy high performance such as high sensitivity, high transfer capability, and low dark current.

In the method of manufacturing a solid-state imaging device according to the present invention, as described above, a Si oxide film is formed as a gate insulating film of a vertical charge coupled device, and a Si nitride film (or a Si oxynitride film or both) is formed. Depositing, etching and removing the deposited Si nitride film (or the Si oxynitride film or both) on a channel blocking region, and depositing a poly-Si film and patterning it into a transfer electrode shape And the Si in the gap between the transfer electrodes
Nitride film (or the above-mentioned Si oxynitride film or both)
Includes the step of etching and removing the Si nitride film (or Si oxynitride film or both) in the gate insulating film
Is divided into minute parts under each electrode, and on the CCD channel of the vertical charge-coupled device that performs photoelectric conversion and charge transfer, the transfer electrode end and the Si nitride film (or Si oxynitride film or both) The edges can be perfectly matched.

In the method for manufacturing a solid-state imaging device according to the present invention, after depositing a poly-Si film as described above,
Depositing an insulating film including a Si nitride film (or a Si oxynitride film or both) on the Si film, and forming at least a Si nitride film in the insulating film including the Si nitride film (or the Si oxynitride film or both); Etching a film (or a Si oxynitride film or both) on a channel blocking region, and patterning the poly-Si film into a transfer electrode shape; Since the insulating film including the Si nitride film (or Si oxynitride film or both) on the film is also removed by etching,
The Si nitride film (or Si oxynitride film or both) on the poly-Si transfer electrode is divided into minute portions on each electrode, and the transfer voltage is transferred on the CCD channel of the vertical charge-coupled device that performs photoelectric conversion. The extreme and the end of the Si nitride film (or Si oxynitride film or both) for antireflection can be completely matched.

The gate insulating film of the vertical charge coupled device is
A two-layer film having a Si nitride film (or Si oxynitride film) on a Si oxide film, that is, Si ₃ N ₄ (silicon nitride) / S
In the case where the insulating film composed of a two-layer film of iO ₂ (silicon dioxide) and functioning as an antireflection film on the transfer electrode constituting the vertical charge coupled device is a single layer composed of a Si nitride film or a Si oxynitride film Is a solid-state imaging device of the present invention,
Since the simplest (simple) laminated structure is obtained, the manufacturing process can be shortened and the cost is more economical. Here, the gate insulating film is
What can not be a single layer of nitride film or Si oxynitride film
Si nitride film or Si oxynitride film is a vertical charge coupled device CC
This is because a dark current component generated in the CCD becomes extremely large when the structure is in direct contact with the D channel.

[0029]

Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 is a diagram illustrating a configuration example of a solid-state imaging device according to an embodiment of the present invention. Here, FIG. 1A shows a vertical cross-sectional structure of an imaging region in the solid-state imaging device when cut along the charge transfer direction, and FIG. 3 is a vertical sectional structure of an imaging region in the solid-state imaging device of FIG.

In a solid-state imaging device according to an embodiment described below, a transfer electrode constituting a vertical charge-coupled device has a single-layer transfer electrode.
It employs a so-called single layer electrode CCD (Charge Coupled Device) type formed by patterning a Si film. n
A p-type well region 2 is formed on the surface side of a type Si substrate 1. An n-type CCD channel region 3 is provided in the p-type well region 2.

Here, for example, the n-type Si substrate 1 has a phosphorus concentration as an impurity of about 10 ¹³ cm ⁻³ to 10 ¹⁵ cm ⁻³ .
The p-type well region 2 has a depth of 1 μm to 5 μm,
The concentration of boron as an impurity is about 10 ¹⁵ cm ⁻³ to 10 ¹⁷ cm ⁻³ . Further, the n-type CCD channel region 3 has a depth of 0.1
μm to 2 μm, and either phosphorus or arsenic is used as an impurity, and the concentration is 10 ¹⁶ cm ⁻³ to 10 ¹⁷ cm.
It is about ^-3 .

The n-type CCD channel region 3 is vertically divided by the p ⁺ -type channel blocking region 12. This p ⁺
The channel blocking region 12 has a depth of 1 μm to 4 μm, for example.
And the concentration of boron as an impurity is 10 ¹⁷ cm ⁻³ to 10
It is about ¹⁹ cm ^-3 . On the surface side of the n-type CCD channel region 3, an ONO gate insulating film G having a laminated structure composed of three layers of a Si oxide film 6, a Si nitride film 5, and a Si oxide film 4 is formed. Here, the Si oxide film 4 is formed by a thermal oxidation method, and the Si nitride film 5 and the Si oxide film 6 on the surface of the Si oxide film 4 are
It is formed by a CVD method.

On the surface side of the ONO gate insulating film G, that is, on the surface of the Si oxide film 6, a poly-Si transfer electrode 7 is provided. On the surface of the poly-Si transfer electrode 7, a Si nitride film 9 / S
An anti-reflection film F having a two-layer structure of the i-oxide film 8 is formed. Further, as shown in FIG. 1B, the Si oxide film 6 and the Si nitride film 5 in the ONO gate insulating film G are cut off in a region on the p ⁺ type channel blocking region 12, and the anti-reflection film F is formed. Are separated from each other by a region on the p ⁺ type channel blocking region 12 in the same manner.

In the charge transfer direction, as shown in FIG. 1A, the Si oxide film 6 and the Si nitride film 5 on the ONO gate insulating film G and the antireflection film F having a two-layer structure are The transfer electrode 7 is cut off as a pattern completely coincident with the transfer electrode 7.
According to the method for manufacturing a solid-state imaging device of the present invention, the Si oxide film 6
And the Si nitride film 5 is patterned before depositing the poly-Si film.
The nitride film 9 is patterned before patterning the poly-Si film. Thus, the Si oxide film 6, the Si nitride film 5, and the Si nitride film 9 are cut off in the region above the p ⁺ -type channel blocking region 12, and are band-shaped in the transfer direction of the vertical charge-coupled device. And
In the step of etching and removing the gap portions P between the respective poly-Si transfer electrodes 7 in the formation of the poly-Si transfer electrode 7, all the layers from the Si nitride film 9 to the Si nitride film 5 are collectively patterned. The structure of the vertical charge-coupled device can be realized.

The thickness of the ONO gate insulating film G depends on the combined optical length of the wavelength at which the reflection of visible light is desired to be suppressed, particularly the wavelength of 400 nm to 55 nm.
1/2 of 0 nm, 100 n in terms of electrical Si oxide film thickness
m or less. At this time, if the synthetic optical length of the ONO gate insulating film G is to be reduced to, for example, half the wavelength around 420 nm, the Si oxide film 6 (thickness is 15 nm) / Si nitride film 5 (thickness is 65 n
m) / Si oxide film 4 (having a thickness of 40 nm) is one example.
Here, since the refractive index of each layer is 1.45 for the Si oxide film and 2 for the Si nitride film, the combined optical length is 209.75 nm.
Since the relative permittivity of the Si oxide film is about 3.8 and that of the Si nitride film is about 7, the ONO gate insulating film G has a thickness equivalent to an electrical Si oxide film of 90.29 nm.

The thickness of the antireflection film F having a two-layer structure of the Si nitride film 9 / Si oxide film 8 on the poly-Si transfer electrode 7 is
The optical length of the composite is set to a wavelength at which the reflection of visible light is desired to be suppressed, in particular, 波長 of the wavelength of 400 to 550 nm. For example, if the synthetic optical length of the antireflection film F is to be reduced to 1/4 near the wavelength of 420 nm, the Si nitride film 9 (42 nm thick) / Si oxide film 8
(Thickness: 15 nm) is an example of such a structure.
Has an optical length of 105.75 nm.

The poly-Si transfer electrode 7 has a high concentration (10 ¹⁸ cm ⁻³ to
10 ²¹ cm ^-3 ) is doped with phosphorus or arsenic,
It is about 30 nm to 300 nm. However, it is preferable that the poly Si transfer electrode 7 be as thin as possible in order to reduce light absorption loss with respect to incident light. For example, if the poly-Si transfer electrode 7 has a thickness of 60 nm, the optical characteristics at this time are as shown in FIG. FIG. 2 shows the transmittance, the reflectance and the absorptance, and the wavelength of the incident light when the ON-gate insulating film G and the antireflection film F of the above-described example are provided and the poly-Si transfer electrode 7 is 60 nm thick. 6 is a graph showing a relationship with the graph.

In the graph of FIG. 2, the transmittance refers to the multilayer structure (the antireflection film F, the poly-Si transfer electrode 7 and the ONO
N-type CCD channel region 3, p
This is the ratio of light incident on the mold well region 2 and the n-type Si substrate 1. The reflectance is a ratio of the light reflected from the light receiving portion composed of the multilayer structure and the Si substrate in the above-described vertical charge-coupled device to the light incident from the outside. The absorptance is a ratio of light absorbed by the poly-Si transfer electrode 7 to light incident from the outside.

In the graph of FIG. 2, the reflectance is minimized near the wavelength of 420 nm, and starts to act to increase the transmittance. However, the reflectance increases over a wide wavelength band from the nearby wavelength to the long wavelength side. The state of low transmittance and high transmittance is maintained. Therefore, in order to increase the sensitivity in a wide range of the entire visible light region, it is effective to set the reflection reduction condition for a shorter wavelength.

However, this is the case where the gate insulating film G includes the Si nitride film 5 and / or the Si oxynitride film, and the antireflection film F includes the Si nitride film 9 and / or the Si oxynitride film. This is also the case when the Si oxynitride film contained in both has a high nitrogen content and a refractive index close to 2. That is, in the case of a solid-state imaging device having a transfer electrode made of poly-Si (poly-Si transfer electrode 7) on the light receiving section as described above, the gate insulating film G and the antireflection film F have a refractive index of about 2 Interweaving the materials enhances consistency over a wide range of visible light.

The poly-Si transfer electrode 7 and another poly-Si transfer electrode 7
In the n-type CCD channel region 3 in the gap portion P between
A boron added region 10 is formed. The boron-added region 10 has a structure peculiar to the single-layer electrode CCD type.
Countermeasures for reducing the potential barrier or potential dip generated in the channel region of the gap portion P between the i transfer electrode 7 and another poly-Si transfer electrode 7 and ensuring the transfer efficiency of charges (in this case, electrons). It is.

Boron ion implantation using the poly-Si transfer electrode 7 (including the Si nitride film 5, the Si oxide film 6, the Si oxide film 8 and the Si nitride film 9) as a part of the mask allows the boron-added region 1 to be formed.
0 is formed by self-alignment. At this time, the concentration of boron added to the boron-added region 10 is set to about half of the phosphorus concentration (or arsenic concentration) of the n-type CCD channel region 3. The outermost part of the imaging region is protected by a thick insulating film 11 having a low refractive index. When the resistance is high due to the small thickness of the poly-Si transfer electrode 7 and it is difficult to transmit a drive signal, a backing metal wiring is provided at a position on the p ⁺ Through the poly-Si transfer electrode 7
To supply a drive signal.

As described above, the gate insulating film G and the poly-Si
The insulating film (the antireflection film F) on the transfer electrode 7 includes a Si nitride film (or a Si oxynitride film or both), and these Si nitride films (or a Si oxynitride film or both) are Since the charge-coupled device is divided into minute portions for each electrode, the influence of the residual stress of the Si nitride film (or the Si oxynitride film or both) is extremely small. For this reason, the dark current level in the charge-coupled device of one embodiment is suppressed to about the same level as when all of the gate insulating film G and the antireflection film F are formed of a Si oxide film.

By including the Si nitride film 5 (or the Si oxynitride film or both) in the gate insulating film G, the charge-coupled device can be provided with an optical length sufficient to reduce the reflection in the visible light region. It is configured as an electrical thickness capable of having a high charge transfer capability. Therefore, the solid-state imaging device according to an embodiment of the present invention is configured to have high sensitivity to incident light, low noise at the time of photoelectric conversion and charge transfer, and a large saturated charge amount. .

Although the solid-state imaging device according to the above embodiment is a single-layer electrode CCD type, the solid-state imaging device of the present invention may have a two-layer electrode configuration similar to the conventional example. However, in this case, the separation position on the CCD channel of the Si nitride film or the Si oxynitride film or both, and the position of the inter-electrode gap between the poly-Si transfer electrode and another poly-Si transfer electrode, Care must be taken because a deviation of the order of magnitude of the alignment error occurs.

In the above-described embodiment, the case where the gate insulating film G is composed of three layers and the antireflection film F is composed of two layers has been described. Accordingly, even in the case of a multi-layer structure, the present invention has the effects described above. The structure having a small number of layers means that the gate insulating film G in FIG. 1 has the uppermost Si oxide film 6 removed.
This is a two-layer film composed of the Si nitride film 5 / Si oxide film 4 and the antireflection film F is a single film composed of the Si nitride film 9 from which the lowermost Si oxide film 8 is removed. Since the laminated structure is used, the manufacturing process can be shortened, so that productivity can be further improved, the manufacturing cost can be reduced, and the cost is more economical.

Further, in the conductivity type of the semiconductor material included in the above-described embodiment, if the p-type and the n-type are all exchanged, that is, the n-type Si substrate 1 is changed to the p-type Si substrate, The well region 2 is an n-type well region, the n-type CCD channel region 3 is changed to a p-type CCD channel region, the boron-doped region 10 is changed to a phosphorus-doped region or an arsenic-doped region,
By changing the p ⁺ -type channel blocking region 12 to the n ⁺ -type channel blocking region, a solid-state imaging device having holes as signal charges instead of electrons is obtained.

[0048]

Next, an embodiment will be described with reference to FIG. Effective single-layer electrode CCD type with 4-phase drive vertical CCD method 640
A full-frame solid-state imaging device with (H) × 480 (V) pixels and a pixel size of 6 μm □ was manufactured. With a phosphorus concentration of about 2 × 10 ¹⁴ cm ^-3 and an n-type Si substrate surface orientation (100), the same phosphorus concentration
Using an epitaxial Si substrate (n-type Si substrate 1) on which an epitaxial Si layer with a thickness of about 20 μm is formed, a depth of 3 μm
P-type well region 2 with boron concentration of about 5 × 10 ¹⁵ cm ^-3
Was formed.

In this p-type well region 2, an n-type CCD channel region 3 having a depth of about 1 μm and a phosphorus concentration of about 5 × 10 ¹⁶ cm ⁻³ was formed. The n-type CCD channel region 3 is vertically divided by p ⁺ -type channel blocking regions 12 provided at a pitch of 6 μm. This p ⁺ -type channel blocking region 12 has a width of 1
The depth is about 2 μm, and the concentration of boron as an impurity is about 8 × 10 ¹⁷ cm ⁻³ .

On the surface of the n-type CCD channel region 3, a Si oxide film 6 (thickness: 15 nm) / Si nitride film 5 (thickness: 65 nm) / Si oxide film 4
An ONO gate insulating film G (having a thickness of 40 nm) is provided. Then, the Si oxide film 6 of this ONO gate insulating film G and S
The i-nitride film 5 is divided on the p ⁺ -type channel blocking region 12 with a gap of 0.5 μm.

On the ONO gate insulating film G, a 60 nm thick poly-Si
The transfer electrode 7 is formed with an electrode length of 1.2 μm and a gap (gap portion P between electrodes) of 0.3 μm. Phosphorus is added as an impurity to the poly-Si transfer electrode 7 at a concentration of about 5 × 10 ²⁰ cm ⁻³ . Also, the surface of the poly-Si transfer electrode 7 has Si
An antireflection film F of a nitride film 9 (42 nm in thickness) / Si oxide film 8 (15 nm in thickness) is provided, and the Si nitride film 9 has a thickness of 0.5 μm on the p ⁺ type channel blocking region 12. It is divided by opening a gap.

The silicon oxide film 6 / Si in the ONO gate insulating film G
Since the separation of the nitride film 5 and the antireflection film F on the n-type CCD channel region 3 is performed at the same time as the patterning of the poly-Si transfer electrode 7, the edges of the layers in the gap portion completely match. Therefore, the size of one piece of the Si nitride film in the ONO gate insulating film G and the antireflection film F is 1.2 μm ×
It is extremely small, 5.5 μm in width.

Boron-added region 10 in gap P between electrodes
Are the antireflection film F, the poly-Si transfer electrode 7 and the ONO gate
Part of implantation mask using Si oxide film 6 / Si nitride film 5 in edge film G
Boron by ion implantation
After the subsequent heat treatment, the n-type CCD channel region 3
3 × 10 electrically active phosphorus concentration near the surface¹⁶ cm
^-3It is formed so that it becomes about.

After the insulating film (low refractive index) 11 is formed by CVD (chemical vapor deposition) or the like, a metal light shield for limiting the metal internal wiring and the image pickup portion is formed, and the outermost device is formed of a protective film (low). (Refractive index). The above-described ONO gate insulating film G has a gate insulating film consisting of only a Si oxide film equivalent in electrical thickness, and the above-described anti-reflection film F has an optical reflection length consisting of only a Si oxide film having an optical length equivalent to the gate insulating film. The antireflection effect is lost when a thick insulating film with a low refractive index is formed, so the antireflection effect is not provided.) A full-frame solid-state imaging device of the same type having the same type was also manufactured, and the effect of the present invention was verified by comparison with this. .

Since the electrical thicknesses of the two gate insulating films are equivalent, the amount of charge that can be handled in charge transfer was equal. Also, as an effect of dividing the Si nitride film into minute portions for each electrode, it was confirmed that the dark current was almost the same as when the gate insulating film was formed only of the Si oxide film. Furthermore, the sensitivity of the full-frame solid-state imaging device of the present invention is extremely superior with respect to the sensitivity in photoelectric conversion with respect to incident light, and both the gate insulating film and the antireflection film are compared with the full-frame solid-state imaging device having only the Si oxide film. And blue
(Wavelength 450 nm) 4.47 times, green (wavelength 550 nm) 1.45 times, red
(Wavelength 650 nm) was 2.77 times.

The embodiment of the present invention has been described in detail with reference to the drawings. However, the specific configuration is not limited to this embodiment, and a design change or the like may be made without departing from the gist of the present invention. The present invention is also included in the present invention.

[0057]

As described above, according to the solid-state imaging device of the present invention, the thickness condition of the gate insulating film including the Si nitride film or the Si oxynitride film, or both, is controlled optically and electrically. In addition, the insulating film containing the Si nitride film or the Si oxynitride film or both has a high antireflection effect on the poly-Si transfer electrode, and the gate insulating film and the poly-Si
Since the Si nitride film or Si oxynitride film or both included in the insulating film on the transfer electrode is divided into small portions for each electrode to prevent dark current increase, high sensitivity, high transfer capability, low dark current, etc. There is an effect that a solid-state imaging device that simultaneously satisfies high performance can be provided.

Further, in the method for manufacturing a solid-state imaging device according to the present invention, the Si nitride film or the silicon nitride film in the gate insulating film and the antireflection film may be used.
The gap portion (gap) on the vertical charge-coupled device channel of the Si oxynitride film or both can be completely matched with the gap portion between the vertical charge-coupled device transfer electrodes. There is an effect that it can be manufactured with extremely small performance variations.

[Brief description of the drawings]

FIG. 1 is a diagram illustrating a configuration example of a solid-state imaging device according to an embodiment of the present invention.

FIG. 2 is a graph showing the relationship between the transmittance, the reflectance, and the absorptance, and the wavelength of incident light.

FIG. 3 is a diagram showing an overall configuration of a frame transfer type solid-state imaging device according to a conventional example.

[Explanation of symbols]

Reference Signs List 1 n-type Si substrate 2 p-type well region 3 n-type CCD channel region 4 Si oxide film 5 Si nitride film 6 Si oxide film 7 Poly Si transfer electrode 8 Si oxide film 9 Si nitride film 10 Boron added region 11 Insulating film (low (Refractive index) 12 p ⁺ channel blocking region G gate insulating film F antireflection film P gap between electrodes 13 poly-Si transfer electrode 14 p ⁺ channel blocking region 15 imaging region 16 storage region 17 horizontal charge-coupled device 18 output unit R Area showing the pixel plane structure

Claims (8)

[Claims] 1. An image pickup area comprising at least a vertical charge-coupled device array for performing photoelectric conversion of incident light and reading out signal charges generated by photoelectric conversion, and receiving and sequentially transferring the signal charges of the vertical charge-coupled device array A horizontal charge-coupled device, and an output unit for converting the signal charge into a voltage and outputting the signal charge as a voltage signal, wherein the gate insulating film of the vertical charge-coupled device is a Si nitride film or a Si oxynitride film or The gate insulating film is formed by dividing the silicon nitride film and / or the silicon oxynitride film or both into small portions under one electrode. Solid-state imaging device. 2. The synthetic optical length of a gate insulating film composed of a combination of a Si nitride film or a Si oxynitride film or both and a Si oxide film is between 200 nm and 275 nm, and the Si oxide film 2. The solid-state imaging device according to claim 1, wherein a film thickness converted into an electric field is 100 nm or less. 3. An insulating film on a transfer electrode constituting the vertical charge-coupled device functions as an anti-reflection film, and the insulating film includes a Si nitride film, a Si oxynitride film, or both thereof. 3. The solid-state imaging device according to claim 1, wherein the Si nitride film or the Si oxynitride film or both are divided into minute portions on one electrode. 4. An insulating film functioning as an anti-reflection film on a transfer electrode constituting the vertical charge-coupled device includes a Si nitride film, a Si oxynitride film, or both, and the outermost Si nitride film. 4. The solid-state imaging device according to claim 1, wherein a combined optical length from the Si oxynitride film to the transfer electrode is between 100 nm and 137.5 nm. 5. 5. The solid according to claim 1, wherein the transfer electrode forming the vertical charge-coupled device is formed by patterning a single-layer polycrystalline Si film. Imaging device. 6. At least photoelectric conversion is performed, and
An imaging region including a vertical charge-coupled device array for reading out generated signal charges; a horizontal charge-coupled device for receiving and transferring the signal charges of the vertical charge-coupled device array; and an output unit for converting the signal charges into charge-voltage signals and outputting the converted signal charges A method for manufacturing a solid-state imaging device, comprising: forming a Si oxide film as a gate insulating film of the vertical charge-coupled device, and depositing a Si nitride film or a Si oxynitride film or both; A second step of removing the deposited Si nitride film and / or the Si oxynitride film or both by etching on the channel blocking region to form a band; and depositing a polycrystalline Si film and patterning it into a transfer electrode shape. A third step of etching and removing the Si nitride film and / or the Si oxynitride film in the gap between the transfer electrodes. Method of manufacturing a solid-state imaging device according to. 7. The method according to claim 7, wherein, after depositing the polycrystalline Si film, the third step comprises:
A fourth step of depositing an insulating film including a Si nitride film or a Si oxynitride film or both; and forming at least the Si nitride film or the Si oxynitride film or both in the insulating film on a channel blocking region. A fifth step of forming the polycrystalline Si film into a band shape by etching and removing, when the polycrystalline Si film is patterned into a shape of a transfer electrode, the Si on the polycrystalline Si film in a gap portion between the transfer electrodes is formed.
7. The method according to claim 6, wherein the insulating film including the nitride film or the Si oxynitride film or both of them is simultaneously removed by etching. 8. The vertical charge-coupled device, wherein the gate insulating film is formed of a two-layer film including a Si nitride film or a Si oxynitride film on a Si oxide film, and is formed on a transfer electrode constituting the vertical charge-coupled device. 6. The solid-state imaging device according to claim 1, wherein the insulating film functioning as an antireflection film is a single layer made of a Si nitride film or a Si oxynitride film.