JPH11121728A - Solid-state image pick-up device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a solid-state image pick-up device capable of enhancing the sensitivity in the range from blue color visible light to near ultraviolet light and the whole sensitivity from the near ultraviolet light to near infrared light. SOLUTION: At least one element out of an antireflection film 17 for reducing the reflection of a light having wavelengths below the wavelength of blue color visible light or an SiN film 18 as a passivation film hardly absorbing a light having a wavelength less than that of the blue color visible light is adopted. Accordingly, this adoption is combined with a well known structure capable of enhancing the sensitivity from red color visible light to near infrared light thereby enabling the whole sensitivity from near ultraviolet light to near infrared light to be enhanced.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a solid-state image pickup device for picking up light by making light incident on a photosensitive section.

[0002]

2. Description of the Related Art In order to enhance the sensitivity of a solid-state imaging device, the depth from the surface of a photosensitive portion to the overflow barrier is increased when the semiconductor substrate is N-type, or the semiconductor is increased when the semiconductor substrate is P-type. 2. Description of the Related Art A structure that lowers the impurity concentration of a substrate to easily expand a depletion layer from a photosensitive portion has been conventionally known.

[0003]

However, although these structures can increase the sensitivity from red visible light to near infrared light, the sensitivity from blue visible light to near ultraviolet light almost increases. It is not suitable as a structure for increasing the sensitivity of a solid-state imaging device used for a visible light color camera or the like.

Accordingly, the present invention has high sensitivity from blue visible light to near ultraviolet light, and when combined with the above-described conventionally known structure, the overall sensitivity from near ultraviolet light to near infrared light is high. It is an object of the present invention to provide a solid-state imaging device capable of increasing sensitivity.

[0005]

In the solid-state imaging device according to the first aspect, since a film for increasing transmission of light having a wavelength equal to or less than the wavelength of blue visible light is provided on the photosensitive portion, The amount of incident blue visible light and near ultraviolet light.

In the solid-state imaging device according to the second aspect, since the film that increases the transmission of light having a wavelength equal to or less than the wavelength of blue visible light is an antireflection film, by using an antireflection film having a multilayer structure or the like, The amount of incident light of a wide range of wavelengths from blue visible light to near ultraviolet light can be increased.

In the solid-state imaging device according to the third aspect, the film that increases the transmission of light having a wavelength equal to or less than the wavelength of blue visible light is a passivation film, and the passivation film is a film originally provided on the photosensitive portion. Therefore, the amount of blue visible light or near-ultraviolet light incident on the photosensitive portion is large even though the number of manufacturing processes has not increased.

In the solid-state imaging device according to the fourth aspect, since the film that increases the transmission of light having a wavelength equal to or less than the wavelength of blue visible light is both the antireflection film and the passivation film, an increase in the number of manufacturing steps is suppressed. In addition, the amount of incident light having a wide range of wavelengths from blue visible light to near ultraviolet light can be further increased.

[0009]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention applied to a CCD solid-state imaging device using an N-type semiconductor substrate will be described below with reference to FIGS. C of this embodiment
In order to manufacture a CD solid-state imaging device, as shown in FIG. 1A, a P ^- well 12 as an overflow barrier is formed on the surface of an N-type Si substrate 11 and then has a high resistance and a thickness. A Si epitaxial layer 13 of 3 μm or more is formed on the Si substrate 11.

Next, as shown in FIG. 1B, an SiO ₂ film 14 as a gate oxide film is
And the polycrystalline Si film 15 is processed on the SiO ₂ film 14 into a pattern such as a transfer electrode. Then, by introducing impurities using the polycrystalline Si film 15 as a mask, an N ⁺ diffusion layer 16 as a photosensitive portion is formed on the Si epitaxial layer 13.

Next, as shown in FIG. 1C, an antireflection film 17 for reducing reflection of light having a wavelength equal to or less than the wavelength of blue visible light is formed on the N ⁺ diffusion layer 16. Anti-reflection film 1
7 is, for example, SiO ₂ film / SiN film / SiO ₂
Although a multilayer film as a film can be used, other multilayer films that include a polycrystalline Si film and the like in addition to the SiO ₂ film and the SiN film and cause multiple interference of light may be used.

Next, as shown in FIG. 1D, a SiN film 18 as a passivation film is deposited on the entire surface by a plasma CVD method. FIG. 2 shows a thickness 2 formed on a quartz substrate.
2 shows the transmittance when light of various wavelengths is incident on the 00 nm film, and the SiN film 18 has the transmittance A in FIG.
have. As is apparent from the transmittance A, the wavelength D
The SiN film 18 has a high transmissivity, that is, a low absorptivity not only for the i-line but also for the KrF excimer laser light having the wavelength E.

On the other hand, a SiN film conventionally used as a passivation film has a transmittance C. As is clear from the transmittance C, the conventional SiN film has only a low transmittance for the i-line and does not transmit the KrF excimer laser light at all. It is considered that the transmittances of the SiN films are different from each other because the ratio of N in the SiN films, the density of the SiN films, and the like are different.

The SiO 2 formed by the plasma CVD method
The N film has a transmittance B, and the SiON film has a higher transmittance than the conventional SiN film.
An iON film may be used instead of the SiN film 18. After that, an Al film 19 and the like as a light shielding film are formed to complete the CCD solid-state imaging device of the present embodiment.

The CC of the present embodiment manufactured as described above
In the D solid-state imaging device, since the Si epitaxial layer 13 has a high resistance and a thickness of 3 μm or more, the depletion layer from the N ⁺ diffusion layer 16 extends over 3 μm and extends from red visible light to near infrared light. High sensitivity.

Moreover, in the CCD solid-state imaging device of the present embodiment, the reflection of light having a wavelength equal to or less than the wavelength of blue visible light is small due to the anti-reflection film 17, and the wavelength of blue visible light or less is small due to the SiN film 18. Absorption of light having a wavelength of Therefore, sensitivity from blue visible light to near ultraviolet light is high.

As a result, the CCD solid-state imaging device of this embodiment has the relative sensitivity a shown in FIG. 3, and as is apparent from the relative sensitivity a, the CCD solid-state imaging device of this embodiment has near-ultraviolet light. The overall sensitivity from to near infrared light is high. Therefore, the CCD solid-state imaging device according to the present embodiment can be applied to a surveillance camera shared between day and night.

In FIG. 3, the relative sensitivity b is SiN
This is the case where a conventional SiN film is used instead of the film 18, and the relative sensitivity c is that of the conventional SIN film instead of the SiN film 18.
In the case where the iN film is used and the anti-reflection film 17 is not used, the relative sensitivity d is such that a conventional SiN film is used instead of the SiN film 18, the anti-reflection film 17 is not used, and N ⁺ In this case, the depletion layer from the diffusion layer 16 does not extend beyond 3 μm.

Therefore, in the above embodiment, the antireflection film 1 is used.
Although both the SiN film 7 and the SiN film 18 are used, it is possible to have higher sensitivity than the conventional CCD solid-state imaging device by using only one of them. In the above embodiments, the present invention is applied to a CCD solid-state imaging device using an N-type semiconductor substrate. However, a solid-state imaging device other than a CCD solid-state imaging device using a P-type semiconductor substrate or a CCD solid-state imaging device is used. The invention of the present application can be applied to the element.

[0020]

In the solid-state imaging device according to the first aspect, since the amount of incident blue visible light or near ultraviolet light to the photosensitive portion is large, the sensitivity of blue visible light or near ultraviolet light is high.

In the solid-state imaging device according to the second aspect, by using an anti-reflection film having a multilayer structure or the like, the amount of incident light of a wide range of wavelengths from blue visible light to near ultraviolet light can be increased. The sensitivity of light having a wide range of wavelengths from blue visible light to near ultraviolet light can be increased.

In the solid-state imaging device according to the third aspect, although the number of manufacturing steps is not increased, the amount of blue visible light or near-ultraviolet light incident on the photosensitive portion is large, so that the manufacturing cost is not increased. Nevertheless, the sensitivity to blue visible light and near ultraviolet light is high.

In the solid-state imaging device according to the fourth aspect, the amount of incident light of a wide range of wavelengths from blue visible light to near ultraviolet light can be further increased while suppressing an increase in the number of manufacturing steps. The sensitivity of light having a wide range of wavelengths from blue visible light to near-ultraviolet light can be further increased while suppressing an increase in the wavelength.

[Brief description of the drawings]

FIG. 1 is a side sectional view showing a manufacturing method according to an embodiment of the present invention in the order of steps.

FIG. 2 is a graph showing a relationship between wavelength and transmittance in a passivation film used in one embodiment and a conventional example.

FIG. 3 is a graph showing a relationship between wavelength and relative sensitivity in various solid-state imaging devices including one embodiment and a conventional example.

[Explanation of symbols]

16 ... N ⁺ diffusion layer (photosensitive portion), 17 ... anti-reflection film, 18
... SiN film (passivation film)

Claims (4)

[Claims] 1. A solid-state imaging device, wherein a film for increasing transmission of light having a wavelength equal to or less than the wavelength of blue visible light is provided on a photosensitive portion. 2. The solid-state imaging device according to claim 1, wherein the anti-reflection film for the light is the film. 3. The solid-state imaging device according to claim 1, wherein the passivation film transmitting the light is the film. 4. The solid-state imaging device according to claim 1, wherein the antireflection film for the light and the passivation film for transmitting the light are the films.