JP2000196051A - Solid-state image sensor and manufacture thereof - Google Patents

Abstract

PROBLEM TO BE SOLVED: To enable an incident light of specific wavelengths to be sufficiently lessened in loss, by a method wherein a photodetective part is provided inside a semiconductor substrate, and an anti-reflection film composed of multilayered films that include two high refractive index layers whose refractive indexes are larger than specified is provided over the photodetective part. SOLUTION: A photodiode is formed as a photodetective part 12 inside a silicon substrate, and an anti-reflection multilayered film 20 is formed on a silicon oxide film 13 over the photodetective part 12. The anti-reflection multilayered film 20 is composed of a first high-refractive index layer 21, a first low-refractive index layer 22, a second high-refractive index layer 23, and a second low-refractive index layer 24 which are successively laminated in this sequence. Metal compound films whose refractive indexes each larger than 1.9 are used as the high-refractive index layers 21 and 23, and on the other hand, metal compound films whose refractive indexes are smaller than those of the high-refractive index layers 21 and 23 are used as the low-refractive idex layers 22 and 24.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a solid-state imaging device, and more particularly, to a solid-state imaging device having improved image quality and sensitivity of an output image and a method of manufacturing the same.

[0002]

2. Description of the Related Art At present, as a solid-state imaging device, a device using a CCD (Charge Coupled Device) for reading out signal charges is mainly used. Then, as the number of pixels and the size of the solid-state imaging device increase in order to achieve higher resolution and downsizing of the optical system, improvement in sensitivity has become an issue.

In general, a solid-state image sensor has a semiconductor substrate (silicon substrate) on which a photodiode is formed as a light receiving portion.
On top of this, a transfer electrode is formed via an insulating film, and further, an interlayer insulating film, a light shielding film having an opening above the light receiving section, and a surface protective film are sequentially laminated. In such a solid-state imaging device, multiple rays of reflected light are generated at the surface of the silicon substrate or at the interface of the thin film with respect to the light incident on the light receiving unit, so that the light reaching the photodiode is reduced and the sensitivity is reduced. There was a problem of doing.

In order to solve this problem, it has been proposed that an anti-reflection film such as a silicon nitride film is formed on a light receiving portion to reduce the loss of incident light and improve the sensitivity (Japanese Patent Laid-Open Publication No. H11-163873). JP-A-63-14466, JP-A-4-14-1
No. 52,674).

[0005]

However, it is difficult for the above-described conventional antireflection film to sufficiently reduce the reflected light and sufficiently reduce the loss of the incident light near the wavelength of 550 nm having high visibility. Was.

SUMMARY OF THE INVENTION It is an object of the present invention to provide a solid-state imaging device in which the loss of incident light having a wavelength of about 550 nm is sufficiently reduced, and a method of manufacturing the same.

[0007]

In order to achieve the above object, a solid-state imaging device according to the present invention comprises a semiconductor substrate, a light receiving portion formed in the semiconductor substrate, and a light receiving portion formed above the light receiving portion. A solid-state imaging device comprising an antireflection film,
The antireflection film is a multilayer film including at least two high refractive index layers having a refractive index of 1.9 or more.

According to the present invention, the sensitivity of the solid-state imaging device can be further improved. Further, the loss of incident light can be reduced over the entire visible light range, and in particular, the loss of incident light near a wavelength of 550 nm can be sufficiently reduced.

In the solid-state imaging device according to the present invention, the antireflection film preferably includes a low refractive index layer having a lower refractive index than the high refractive index layer between the high refractive index layers. The refractive index of the low refractive index layer is, for example, less than 1.9. Further, the solid-state imaging device of the present invention, between the antireflection film and the semiconductor substrate,
Preferably, a silicon oxide film is provided.

As described above, the solid-state imaging device of the present invention preferably includes a semiconductor substrate, and a light receiving portion formed in the semiconductor substrate, wherein the silicon oxide film formed on the light receiving portion, An antireflection film formed on a silicon oxide film, wherein the antireflection film has a first high refractive index layer, and a first low refractive index layer formed on the first high refractive index layer. , A second high refractive index layer formed on the first low refractive index layer, and a second low refractive index layer formed on the second high refractive index layer. However, the first and second high refractive index layers have a refractive index of 1.9 or more, and the first and second high refractive index layers have a refractive index of 1.9 or more.
The low refractive index layer has a lower refractive index than each of the adjacent high refractive index layers.

Hereinafter, preferred thicknesses of the respective layers constituting the antireflection film will be exemplified. The thickness of the first high refractive index layer is 30 nm
６０60 nm, the thickness of the first low refractive index film is 80 nm〜１０10
0 nm, and the thickness of the second high refractive index layer is 90 nm to 130 n.
m, the thickness of the second low refractive index layer is 130 nm to 700 nm
Is preferred. The thickness of the second low refractive index layer is 130
nm-170 nm or 500-700 nm is more preferred.

Further, in the solid-state imaging device of the present invention,
It is preferable that a surface protective film is further provided above the antireflection film. This surface protective film preferably has a refractive index and a film thickness so that the antireflection effect is further improved as compared with the case where no surface protective layer is provided. Note that the thickness is preferably 110 nm to 140 nm.

In the solid-state imaging device according to the present invention, the first and second high refractive index layers are made of titanium, zirconium, tantalum,
It is preferable that the main component be an oxide of at least one metal selected from indium and niobium, or a nitride of silicon.

According to the method of manufacturing a solid-state imaging device of the present invention, a step of forming a light receiving portion in a semiconductor substrate and at least two high refractive index layers having a refractive index of 1.9 or more above the light receiving portion are provided. Forming an anti-reflection film that is a multilayer film including the same.

[0015]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Preferred embodiments of a solid-state imaging device and a method of manufacturing the same according to the present invention will be described with reference to the drawings.

FIG. 1 is a cross-sectional view of one embodiment of the solid-state imaging device of the present invention. The light receiving unit 1 is provided inside the silicon substrate 11.
2, a photodiode is formed. On the silicon substrate 11, a silicon oxide film 13 is formed as an insulating film. On the silicon oxide film 13, a transfer electrode 14 is formed in a predetermined pattern.

On the transfer electrode 14, an interlayer insulating film 16, a light shielding film 17, and a surface protection film 18 are formed in this order. The interlayer insulating film 16 and the surface protection film 18 are
2, the light-shielding film 17 is patterned so that the opening above the light-receiving portion 12 is an opening region.

In this solid-state imaging device, an antireflection multilayer film 20 is formed on the silicon oxide film 13 above the light receiving section 12. As shown in FIG. 2, the antireflection multilayer film 20 includes a first high refractive index layer 21, a first low refractive index layer 22, a second high refractive index layer 23, and a second low refractive index layer 24. It has a structure laminated in this order. But at least 2
The film configuration of the antireflection multilayer film is not particularly limited as long as the layer includes a high refractive index layer (refractive index: 1.9 or more).

As the first and second high refractive index layers 21 and 23, a film made of a metal compound having a refractive index of 1.9 or more (for example, an oxide, a nitride or an oxynitride) is preferably used. Can be. As a material of the high refractive index layer, for example,
Titanium oxide (refractive index 2.2 to 2.7; hereinafter, the refractive index is indicated in parentheses), zirconium oxide (2.0 to 2.
1), tantalum oxide (1.9 to 2.2), indium oxide (1.9 to 2.1), niobium oxide (2.1 to 2.2)
2.3), silicon nitride (2.0) is preferred.

Oxides are superior in permeability to hydrogen as compared with nitrides, so that dark current treatment can be effectively performed. In addition, each of the oxide films has a smaller internal stress than the silicon nitride film, so that the output image is less likely to cause so-called “white scratches”. From such a viewpoint, it is preferable to use an oxide as a material for the high refractive index layer.

On the other hand, the first and second low refractive index layers 22,
The first and second high refractive index layers 21 and 23
A film made of a metal compound having a lower refractive index (particularly, oxide or oxynitride) can be used. As a material of the low refractive index layer, silicon oxide (refractive index: 1.46) and various fluorides are preferable.

In the embodiment shown in FIGS. 1 and 2,
The second low-refractive-index layer 24 includes the interlayer insulating film 16.
In this embodiment, since the interlayer insulating film 16 and the low-refractive-index film 25 are made of the same low-refractive-index material (for example, a silicon oxide film), these two layers function as one low-refractive-index layer 24. As described above, some or all of the layers constituting the antireflection multilayer film 20 may be formed of other thin films required for forming the solid-state imaging device.

The high refractive index layer or the low refractive index layer of the antireflection multilayer film 20 may be formed by laminating two or more layers made of different substances. The antireflection multilayer film 20 may include a layer made of a metal compound other than the above, such as aluminum oxide, as long as it has two or more high refractive index layers.

In the above embodiment, on the antireflection multilayer film 20,
A surface protection film 18 is formed. The surface protection film 18
It is preferable to use a silicon nitride film, a silicon oxynitride film or a silicon oxide film. Further, in order to further improve the antireflection effect, it is preferable to form the film with a higher refractive index than the second low refractive index layer 24.

The preferred thickness of each layer of the reflective multilayer anti-reflective coating 20 is as described above. However, the second low refractive index layer 24
For the two layers constituting the above, the thickness of the interlayer insulating film 16 is 3
0 nm to 600 nm, and the thickness of the low refractive index film 25 is set to 20 nm.
It is preferable to set it to 100 nm. The thickness of the silicon oxide film 13 is preferably 50 nm or less, and the thickness of the surface protection film 18 is preferably 110 nm to 140 nm.

For the other films, substances conventionally used can be used. For example, the light shielding film 17
For example, a metal film such as aluminum or tungsten is used.

Hereinafter, an example of a method for manufacturing the solid-state imaging device will be described with reference to FIG. The light receiving section 12 and the silicon oxide film 13 can be formed by an ion implantation method and a thermal oxidation method, respectively, as conventionally performed. The transfer electrode 14 can also be formed by patterning a polycrystalline silicon film formed by a CVD method (chemical vapor deposition) by dry etching. The surface of the transfer electrode 14 is covered with a silicon oxide film by further applying a thermal oxidation method (FIG. 3).
(A)).

Subsequently, a first high refractive index layer 21, a first low refractive index layer 22, and a second high refractive index layer 23 are formed in this order as an anti-reflection multilayer film. A low refractive index film 25 constituting a part of the refractive index layer 24 is formed (FIG. 3B). The method for forming each layer is not particularly limited, and for example, a low pressure CVD method or a plasma CVD method can be used.

Further, a resist 30 is formed in a portion above the light receiving section 12 where the antireflection multilayer film 20 is to be formed.
(C)). Etching is performed sequentially using the resist 30.

The etching may be either dry etching such as reactive ion etching or wet etching. Further, both may be used in combination. For example, a silicon oxide film formed as a low refractive index layer (film) may be patterned by wet etching, and a silicon nitride film formed as a high refractive index layer may be patterned by reactive ion etching.

For example, when a silicon oxide film (low-refractive index layer) and a silicon nitride film (high-refractive index layer) are laminated on a multilayer film, the silicon oxide film is removed by wet etching and the silicon nitride film is removed by dry etching. A phenomenon in which the nitride film remains on the side wall of the silicon oxide film is observed (FIG. 3D). However, the film 31 remaining on the side wall is
The silicon oxide film can be removed (lifted off) by wet etching applied in the next step.

After the high refractive index layer and the low refractive index layer are patterned by etching (FIG. 3E), an interlayer insulating film 16 is formed (FIG. 3F). In this embodiment,
The interlayer insulating film 16 forms a part of the antireflection multilayer film 20 as described above. As shown in FIG. 1, the interlayer insulating film 16
A surface protective film 11 is further formed thereon. Low pressure CVD is also used for forming the interlayer insulating film 16 and the surface protection film 11.
Method, a plasma CVD method, or the like can be applied.

The interlayer insulating film 16 is formed on the transfer electrode 14
And a concave portion between the high refractive index layer and the low refractive index layer laminate. The width of the concave portion (d in FIG. 3F) is preferably 0.2 μm to 0.4 μm.

[0034]

EXAMPLES Hereinafter, the present invention will be described more specifically with reference to examples, but the present invention is not limited to the following examples. As described below, in this example, a solid-state imaging device having the same configuration as that shown in FIGS. 1 to 3 was manufactured, and the antireflection effect of the antireflection multilayer film was confirmed.

First, a photodiode is formed by ion-implanting an n-type impurity such as phosphorus into a p-type silicon substrate, and a 20 nm-thick film is formed on this substrate by thermal oxidation.
An insulating film made of a silicon oxide film was grown. next,
A 300-nm-thick polysilicon film was grown by CVD (vapor phase deposition), and a transfer electrode having a predetermined pattern was formed by dry etching.

Next, the electrodes were covered with a silicon oxide film by thermal oxidation. Further, on the insulating film on the photodiode, a 40-nm-thick silicon nitride film as a first high-refractive-index layer and an 84-nm-thick silicon oxide film as a first low-refractive-index layer by a low-pressure CVD method. A silicon nitride film having a thickness of 109 nm is used as a second high-refractive-index layer to form a
Was formed as a low refractive index film constituting a part of the second low refractive index layer.

A resist was formed above the stacked body of the silicon oxide film and the silicon nitride film. Using this resist, the laminated body was sequentially etched by applying wet etching for the silicon oxide film and dry etching for the silicon nitride film.

Further, a silicon oxide film was formed as an interlayer insulating film. The thickness of the interlayer insulating film was 110 nm.
The interlayer insulating film becomes a second low refractive index layer having a thickness of 130 nm together with the previously formed silicon oxide film above the light receiving section. Thus, an antireflection multilayer film was formed above the light receiving section. Note that the width of the concave portion of the interlayer insulating film corresponding to d in FIG.

Thereafter, a film thickness of 4
An aluminum film having a thickness of 00 nm was formed, and patterning was performed by dry etching so that an opening was formed above the light receiving portion to form a light shielding film. Further, a silicon nitride film having a thickness of 120 nm was formed by a plasma CVD method to form a surface protective film.

FIG. 4 shows a spectral reflectance curve of the solid-state imaging device thus formed. As shown in FIG. 4, in the solid-state imaging device, it was possible to more reliably reduce the reflected light in a region having a high luminosity of 550 nm while obtaining a good antireflection effect.

[0041]

As described above, according to the present invention,
By forming an antireflection film which is a multilayer film including at least two high refractive index layers having a refractive index of 1.9 or more, loss of incident light is reduced over the entire visible light region, and wavelengths with particularly high luminosity are provided. It is possible to provide a solid-state imaging device in which the loss of incident light near 550 nm is sufficiently reduced.

[Brief description of the drawings]

FIG. 1 is a cross-sectional view illustrating one embodiment of a solid-state imaging device of the present invention.

FIG. 2 is a diagram illustrating a film configuration above a light receiving unit of the solid-state imaging device illustrated in FIG. 1;

FIG. 3 is a process chart showing one embodiment of a method for manufacturing a solid-state imaging device of the present invention.

FIG. 4 is a spectral reflectance curve of light incident on a light receiving section of one embodiment of the solid-state imaging device of the present invention.

[Explanation of symbols]

 Reference Signs List 11 silicon substrate 12 light receiving portion 13 silicon oxide film 14 transfer electrode 16 interlayer insulating film 17 light shielding film 18 surface protection film 20 antireflection multilayer film 21 first high refractive index layer 22 first low refractive index layer 23 second high Refractive index layer 24 Second low refractive index layer 25 Low refractive index film

 ──────────────────────────────────────────────────続 き Continuing on the front page (72) Inventor Yuji Matsuda 1006 Kazuma Kadoma, Osaka Prefecture F-term in Matsushita Electronics Industrial Co., Ltd. 4M118 AA10 AB01 BA10 CA03 CA34 FA06 GB03 GB07 GB11 5C024 AA01 CA31 EA08 FA01 FA11 GA11

Claims (10)

[Claims] 1. A solid-state imaging device comprising: a semiconductor substrate; a light receiving portion formed in the semiconductor substrate; and an antireflection film formed above the light receiving portion, wherein the antireflection film comprises: A solid-state imaging device comprising a multilayer film including at least two high refractive index layers having a refractive index of 1.9 or more. 2. The solid-state imaging device according to claim 1, wherein the antireflection film includes a low refractive index layer having a lower refractive index than the high refractive index layer between the high refractive index layers. 3. The solid-state imaging device according to claim 1, further comprising a surface protection film above the antireflection film. 4. The solid-state imaging device according to claim 1, further comprising a silicon oxide film between the antireflection film and the semiconductor substrate. 5. A semiconductor device comprising: a semiconductor substrate; a light receiving portion formed in the semiconductor substrate; a silicon oxide film formed on the light receiving portion; and an anti-reflection film formed on the silicon oxide film. Wherein the antireflection film is formed on a first high refractive index layer, a first low refractive index layer formed on the first high refractive index layer, and on the first low refractive index layer. A second high refractive index layer formed on the second high refractive index layer and a second high refractive index layer formed on the second high refractive index layer.
Solid-state imaging device comprising: a low-refractive-index layer. However, the refractive index of the first and second high refractive index layers is 1.9 or more,
The refractive index of the second low-refractive-index layer is lower than that of any of the high-refractive-index layers adjacent to each other. 6. The thickness of the first high refractive index layer is 30 nm to 6 nm.
0 nm, and the thickness of the first low refractive index layer is 80 nm to 100 n.
m, the thickness of the second high refractive index layer is 90 nm to 130 nm,
The solid-state imaging device according to claim 5, wherein the thickness of the second low refractive index layer is 130 nm to 700 nm. 7. The solid-state imaging device according to claim 6, further comprising a surface protective film above the antireflection film. 8. The surface protective layer has a thickness of 110 nm to 140 nm.
The solid-state imaging device according to claim 3, wherein the thickness is set to nm. 9. The method according to claim 1, wherein the first and second high-refractive-index layers are mainly composed of an oxide of at least one metal selected from titanium, zirconium, tantalum, indium and niobium, or a nitride of silicon. 9. The solid-state imaging device according to any one of claims 1 to 8. 10. A step of forming a light receiving portion in a semiconductor substrate, and forming an antireflection film, which is a multilayer film including at least two high refractive index layers having a refractive index of 1.9 or more, above the light receiving portion. Forming a solid-state imaging device.