JP2003046074A - Solid-state image pickup device and producing method therefor - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a solid-state image pickup device and a producing method therefor, with which stable sensitivity characteristics can be provided, while enhancing the sensitivity by improving the convergence efficiency. SOLUTION: In the solid-state image pickup device having a light receiving part 5, with which a light incident region is specified by a light-shielding film 17, formed on a wafer 11, this device has a transparent film 21 formed on the light incident region of the light-receiving part 5, while having a first refraction factor and having a light-transmitting function and a planarized film 22 formed to surround the sidewall of the transparent film 21, having a second refraction factor which is lower than the first refraction factor of the transparent film 21.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to, for example, a solid-state image pickup device having a structure for guiding incident light to a light receiving part between a light receiving part and an on-chip lens, and a manufacturing method thereof.

[0002]

2. Description of the Related Art At present, there is a strong demand for improvement in image quality of CCD solid-state image pickup devices. In order to meet the demand, it is necessary to increase the number of pixels to increase the resolution and to improve the sensitivity. Therefore, it is necessary to further reduce the pixel size while increasing the pixel array density. is there.

However, when the pixel size is reduced, the amount of light incident on the unit pixel is reduced, and the sensitivity characteristic of the light receiving portion of each pixel is deteriorated. here,
Increase the aperture of the light receiving part for the purpose of improving sensitivity, that is,
If the opening of the light-shielding film is made large, smear is likely to occur due to the mixing of light into the charge transfer section, so there is a limit to making the opening of the light-receiving section large.

From this point of view, an on-chip lens is provided on the on-chip color filter provided above the light receiving portion to improve the efficiency of light collection on the light receiving portion. But,
For example, in a CCD solid-state imaging device having a pixel size of 4 × 4 μm or less, increasing the light-collecting efficiency by using an on-chip lens alone is almost at its limit.

Therefore, as a new technique for improving the above-mentioned light-collecting efficiency and suppressing the occurrence of smear, another technique of forming a film of a light-transmitting material in the layer between the on-chip lens and the light-receiving portion is proposed. By forming a lens (in-layer lens), the light collection efficiency is further improved.

This in-layer lens is a lens formed in the interlayer film immediately above the light receiving portion that performs photoelectric conversion.
Similar to the on-chip lens, the light incident on the in-layer lens is refracted at the interface on the upper surface side or the lower surface side of the in-layer lens and guided to the light receiving portion.

Therefore, by using such an in-layer lens together with the above-mentioned on-chip lens, the light that has been condensed by the on-chip lens and has entered can be condensed again by the in-layer lens. The light collection efficiency of the solid-state image sensor as a whole can be further increased.

However, in the case of forming a conventionally proposed intralayer lens, an interlayer film having a reflow shape such as a BPSG film is formed on a light-shielding film, and is formed between transfer electrodes, that is, directly above a light receiving portion. In general, a process of embedding a high-refractive-index material in the recess formed in and forming the embedded high-refractive-index material as an in-layer lens is adopted.

However, in this process, since the shape of the intralayer lens is determined by the shape of the interlayer film,
It is difficult to obtain a desired shape, that is, an optimum shape for condensing light. Therefore, even though the in-layer lens is provided, it is still difficult to obtain a sufficiently high condensing efficiency.

[0010]

Therefore, in Japanese Patent Laid-Open No. 10-326885 and Japanese Patent Laid-Open No. 11-121725, as an alternative technique to the in-layer lens, a hole is formed in the flattening film immediately above the light receiving portion. There is disclosed a technique in which a high refractive index material is formed and then embedded in a hole to totally reflect light at an interface between the high refractive index film and the planarizing film and to capture the light in a light receiving portion.

However, with further miniaturization of the solid-state image pickup device in recent years, the area of the light-receiving portion has been reduced, and as a result, the aspect ratio of the hole formed on the light-receiving portion is increased, resulting in high refraction. There is a problem that the coverage of the material has deteriorated, and voids (voids) have been generated so that the holes cannot be completely filled.

As described above, when a void or the like is generated in the high refractive index film, it causes deterioration of the sensitivity characteristic and variation of the sensitivity characteristic.

The present invention has been made in view of the above circumstances, and an object of the invention is to provide a solid-state image pickup device capable of obtaining stable sensitivity characteristics while improving the light collection efficiency and sensitivity, and a method of manufacturing the same. To provide.

[0014]

In order to achieve the above object, the solid-state image pickup device of the present invention is a solid-state image pickup device having a light-receiving portion formed on a substrate and having a light-incident region specified by a light-shielding film. Formed on the light incident region of the light receiving portion,
An optically transparent first film having a first refractive index and having a light guiding function, and formed to surround a side wall of the first film,
A second film having a second index of refraction lower than the first index of refraction of the first film.

The first film is formed so as to be higher than the height of the light shielding film.

The upper surface of the first film and the upper surface of the second film are formed so as to be flush with each other.

The first film is formed above the first film, and the first film is formed.
It further has an on-chip lens that collects light toward the film.

According to the above-described solid-state image pickup device of the present invention, since the refractive index of the first film is larger than that of the second film, the first film is obliquely incident on the surface of the first film. Light reaching the interface between the first film and the second film is totally reflected at the interface due to the difference in refractive index between the first film and the second film, and enters the light receiving portion. In addition, since the second film is formed around the first film as described above, it is less affected by the shape of the step of the underlying layer as compared with an in-layer lens or the like. Variability is reduced. Also,
Since the second film is formed so as to surround the side wall of the first film, a void or the like is generated in the first film, unlike the case where the first film is embedded in the hole of the second film. Nothing.

Further, in order to achieve the above-mentioned object, a method of manufacturing a solid-state image pickup device of the present invention comprises a step of forming a light receiving portion on a substrate, and a light shield having an opening on the substrate above the light receiving portion. Forming a film, forming an optically transparent first film having a first refractive index on the substrate at least in the opening, and surrounding a side wall of the first film. Forming a second film having a second refractive index lower than the first refractive index of the first film.

Preferably, in the step of forming the first film, the step of depositing the first film material on the substrate in the opening and on the light shielding film, and on the first film material. And a step of forming a mask layer having a pattern of the first film, and a step of removing the first film material with the mask layer as a mask until the light shielding film is exposed.

In the step of forming the light-shielding film, the light-shielding film is formed of a material having an etching selection ratio to the first film material, and in the step of removing the first film material, the first film material is etched. Remove.

The step of forming the second film includes the step of forming the first film.
Coating the second film material on the light-shielding film to cover the first film, and leaving the second film material deposited on the sidewall of the first film on the first film. And a step of removing the formed second film material.

In the step of removing the second film material, the second film material is removed so that the upper surface of the first film and the upper surface of the second film are on the same plane.

After the step of forming the second film, there is a step of forming an on-chip lens for condensing light toward the first film above the first film.

In the solid-state imaging device manufacturing method of the present invention described above, the optically transparent first film having the first refractive index is formed on at least the substrate in the opening, and the side wall of the first film is formed. A second film having a second refractive index lower than the first refractive index of the first film is formed so as to surround the. Therefore,
In the present invention, the above-described total reflection action can be performed at the interface between the first film and the second film, and by increasing the film thickness of the first film, the first film that performs total reflection can be obtained. The height of the interface between the second film and the second film can be easily increased. Even if the area of the light receiving portion is small, the first film is formed on the light receiving portion instead of forming the hole portion in the second film and forming the first film in the hole portion. By forming the second film so as to cover the side surface of the first film, it is possible to eliminate adverse effects due to the aspect ratio of the holes, etc., and to easily obtain a desired height without being affected by the area of the light receiving part. The first film and the second film having a can be formed.

[0026]

BEST MODE FOR CARRYING OUT THE INVENTION Embodiments of a solid-state image pickup device and a method of manufacturing the same according to the present invention will be described below with reference to the drawings.

First Embodiment FIG. 1 is a diagram showing a main configuration of a solid-state image pickup device according to the present embodiment. The solid-state imaging device 1 according to this embodiment includes an imaging unit 2, a horizontal transfer unit 3, and an output unit 4. The output unit 4 is
For example, it has a charge-voltage conversion unit 4a composed of a floating gate.

The image pickup section 2 is constructed by arranging a large number of pixels 8 each consisting of a light receiving section 5, a reading gate section 6 and a vertical transfer section 7 in a planar matrix. Each pixel 8 is separated by a channel stopper (not shown) so as not to electrically interfere with each other.

The vertical transfer sections 7 are commonly provided for each column of the light receiving sections 5 and arranged in a predetermined number. The four-phase clock signals φV1 and φV for driving the vertical transfer unit 7 are provided to the image pickup unit 2.
2, φV3 and φV4 are input. Two-phase clock signals φH1 and φH2 for driving the horizontal transfer unit 3 are input to the horizontal transfer unit 3.

The above horizontal transfer section 3 and vertical transfer section 7
Is a potential well of minority carriers formed by introducing impurities on the surface side of a semiconductor substrate, and a plurality of electrodes (transfer electrodes) that are repeatedly formed by being insulated and separated from each other on a substrate with an insulating film interposed. It consists of The clock signals φV1, φV2, φV3, φV4, φH1, and the above-mentioned clock signals for the transfer electrodes are provided in the transfer units 3 and 7.
φH2 is applied with a periodic phase shift.
These transfer units 3 and 7 are controlled by the clock signal applied to the transfer electrodes to sequentially change the potential distribution of the potential well described above, and transfer the charges in the potential well in the phase shift direction of the clock signal. Functions as a shift register.

FIG. 2 is an enlarged plan view of an essential part of the image pickup section 2 shown in FIG. As shown in FIG. 2, a plurality of rectangular light receiving portions 5 are arranged in a matrix in the horizontal and vertical directions.

A first transfer electrode 15 made of polysilicon of the first layer is formed to extend in the horizontal direction between the light receiving portions 5 arranged in a matrix. The first transfer electrode 15 has a rectangular shape that slightly extends in the vertical direction on both sides of the light receiving unit 5.

On the first transfer electrode 15, a second transfer electrode 16 made of second layer polysilicon is extendedly formed. The second transfer electrode 16 has a rectangular shape extending on both sides of the light receiving unit 5 so as to overlap the first transfer electrodes 15 which are vertically adjacent to each other.

FIG. 3A shows a sectional view taken along the line AA 'in FIG. 2, and FIG. 3B shows a sectional view taken along the line BB' in FIG. As shown in FIG. 3, for example, a p-type well (hereinafter referred to as a substrate) 11 formed on a silicon substrate or a silicon substrate is composed of, for example, an n-type impurity region, and a pn junction with the substrate 11 is mainly formed. A light receiving unit 5 is formed which performs photoelectric conversion in a region to generate signal charges and accumulates the signal charges for a certain period.

As shown in FIG. 3A, a charge transfer portion 13 mainly made of an n-type impurity region is formed in a region adjacent to one side of the light receiving portion 5 at a predetermined distance, and the illustration thereof is omitted. However, between the light receiving portion 5 and the charge transfer portion 13, a read gate portion formed of a p-type impurity region forming a variable potential region is formed. Further, in the other adjacent region of the light receiving unit 5, a charge transfer unit 13 'composed of an n-type impurity region is formed at a predetermined distance, and although not shown, the light receiving unit 5 and the charge transfer unit 13 are not shown. , A channel stopper formed of a high-concentration p-type impurity region is formed deep in the substrate.

An insulating film 14 made of silicon oxide or the like is formed on the substrate 11, and a first transfer electrode 15 made of polysilicon or the like is formed on the charge transfer portions 13 and 13 'via the insulating film 14. ing. Further, the second transfer electrode 16 is formed on the first transfer electrode 15 via the insulating film 14, and the first and second transfer electrodes 15 and 16 are formed on the insulating film 14.
Is formed by being embedded in. The charge transfer units 13 and 13 'and the transfer electrodes 15 and 16 shown in FIG. 3 correspond to the vertical transfer unit 7 shown in FIG.

A light shielding film 17 made of a refractory metal such as tungsten (W) is formed on the insulating film 14 so as to cover the transfer electrodes 15 and 16. An opening 17a is formed above the light receiving section 5. Further, the light shielding film 17 is formed so as to slightly project into the light receiving section 5. In this way, the light shielding film 17 is formed so as to cover the transfer electrodes 15 and 16 and to slightly project into the light receiving portion 5 because the light shielding property of the light shielding film 17 with respect to the charge transfer portions 13 and 13 ′. This is to increase smear and suppress smear.

A transparent film 21 made of a material having a high refractive index, for example, silicon nitride having a refractive index of about 2.0 is formed in a columnar shape (in this example, a quadrangular prism) on the opening 17a of the light shielding film 17. There is. In addition, in addition to the transparent film 21, DLC (Diamond like Carbon) having a refractive index of about 3.0,
A polyimide resin having a refractive index of about 1.7 may be used.

The side wall of the transparent film 21 is covered to form the transparent film 21.
Material having a refractive index lower than that of the flattening film 22 made of, for example, silicon oxide having a refractive index of about 1.45.
Is formed, and the flattening film 22 is formed so as to extend also on the light shielding film 17.

The surfaces of the transparent film 21 and the flattening film 22 are flattened, and the upper surfaces of the transparent film 21 and the flattening film 22 are processed so that they are on the same plane. A passivation film 30 made of, for example, silicon nitride is formed on the entire surfaces of the transparent film 21 and the planarizing film 22 so as to cover the surfaces.

An on-chip color filter (OCCF) 40 is formed on the passivation film 30. The on-chip color filter 40 is colored in any one of red (R), green (G), and blue (B) in the primary color coding system, and in the complementary color system, for example, cyan (Cy),
It is colored magenta (Mg), yellow (Ye), green (G), or the like.

An on-chip lens (OCL) 50 made of a light-transmitting material such as a negative photosensitive resin is formed on the on-chip color filter 40. On-chip lens 5
0 is used to effectively utilize the light above the light-shielding film and make it enter the transparent film 21, so that it is formed so as to minimize the gap serving as an ineffective region. Also, the on-chip lens 50
Is formed to have a curvature so that incident light can be condensed on the transparent film 21 whose side wall is surrounded by the flattening film 22.

Here, both the on-chip color filter 40 and the on-chip lens 50 described above have a refractive index of 1.
It is formed of a material of about 5 to 1.6.

The operation of the solid-state image pickup device according to the present embodiment having the above configuration will be described with reference to FIG. In the solid-state imaging device according to the present embodiment, incident light is focused on the transparent film 21 by the on-chip lens 50, transmitted through the transparent film 21, and guided to the light receiving unit 5.

When the incident light enters the light receiving portion 5, it is photoelectrically converted by the photodiode (light receiving portion 5) reversely biased with respect to the substrate 11, and an amount of electric charge according to the amount of incident light is generated.
This charge is accumulated in the high-concentration n-type impurity region in the light receiving section 5 for a certain period. After that, the read voltage is applied to the second transfer electrode 16, and the charges are transferred to the charge transfer unit 13. Further, a transfer voltage is applied to the transfer electrodes 15 and 16 with their phases periodically shifted, and the charges are transferred in the vertical direction and sent to the horizontal transfer section 3. Then, the charges sent to the horizontal transfer unit 3 are transferred in the horizontal direction, and are taken out from the output unit 4 as a time-series image signal.

In the above operation, in the solid-state image pickup device according to this embodiment, as shown in FIG. 4, the light is obliquely incident on the surface of the transparent film 21 and reaches the interface between the transparent film 21 and the flattening film 22. Light is also reflected at the interface and enters the light receiving unit 5.

With respect to the above operation, the surface of the transparent film 21 and the surface of the light receiving portion 5 are parallel to each other, and the angle formed between the surface of the transparent film 21 and the side surface of the flattening film 22 (interface with the transparent film 21). The right angle, and the refractive index n1 of the transparent film 21 is 2.0,
A case where the flattening film 22 has a refractive index n2 of 1.45 will be described as an example.

In this case, the curvature of the on-chip lens 50, the on-chip lens 50, the color filter 4
0 and the refractive index of the passivation film 30 is the angle θ of the light incident on the transparent film 21 with respect to the surface of the transparent film 21.
1 is pre-adjusted to be an angle larger than 46.5 °.

Then, as described above, the angle θ1 is 46.5 °.
The angle of incidence θ1 (see FIG. 4) on the interface between the transparent film 21 and the planarizing film 22 is adjusted by adjusting the angle to be larger.
In (a), the angle between the incident light L1 and the normal line to the side surface of the flattening film 22 shown by the broken line is larger than 46.5 °. The refractive index n1 of the transparent film 21 is 2.0, and the flattening film 22
Since the refractive index n2 of the transparent film 21 is 1.45, the interface between the transparent film 21 and the flattening film 22 is transmitted through the transparent film 21 as described above according to Snell's law shown in the following formula (1). All of the light that reaches the above point is totally reflected and is incident on the light receiving unit 5.

[0050]

[Equation 1] n1 · sin θ1 = n2 · sin θ2 (1)

That is, as shown in FIG. 4B, if the light is totally reflected when the refraction angle θ2 exceeds 90 °, 90 ° is substituted for θ2 in the above equation (1), and n1 =
By setting 2.0 and n2 = 1.45, the following expression (2) is obtained,

[0052]

[Equation 2] 2.0 × sin θ1 = 1.45 × sin 90 ° (2)

Since sin 90 ° = 1, sin
The value of θ1 is given by the following equation (3),

[0054]

[Equation 3] sin θ1 = 1.45 / 2.0 (3)

From this, θ1 = 46.5 °, which is a critical angle for total reflection, can be obtained.

Therefore, as described above, the angle θ1 of the light incident on the transparent film 21 with respect to the surface of the transparent film 21 becomes larger than the critical angle of 46.5 °, and thus the transparent film 21. All the light that has passed through and reaches the interface between the transparent film 21 and the flattening film 22 is totally reflected and enters the light receiving unit 5.

In the above example, the case where the transparent film 21 has a refractive index n1 of 2.0 and the flattening film 22 has a refractive index n2 of 1.45 has been described. However, the present invention is not limited to this. Membrane 2
The larger the difference between the refractive index n1 of 1 and the refractive index n2 of the planarizing film 22, the more effectively the above-described action of total reflection is performed.

FIG. 5 shows a simulation result of the light collection rate of the solid-state image pickup device according to the present embodiment. In FIG. 5, the film thickness from the silicon substrate 11 to the lower surface of the on-chip lens 50 is fixed to 5.0 μm, in which the refractive index of the transparent film 21 and the film thickness of the on-chip lens 50 are variously changed. Is shown. That is, the result when the refractive index of the transparent film 21 is 1.9 is graph A, the result when the refractive index is 1.8 is graph B, and the result when the refractive index is 1.7. The result is graph C. Note that in all of the above, the refractive index of the flattening film 22 is 1.45 of silicon oxide. Further, as a conventional structure, a graph D shows a result when an in-layer lens is formed by embedding a high refractive index material in the recess of the interlayer insulating film.

As shown in FIG. 5, in the conventional example (graph D), even if the film thickness of the on-chip lens is changed, the light collection ratio does not exceed 65%. However, in this embodiment, the transparent film 21 is used.
Whichever refractive index is used, the light collection rate exceeds 65%. Further, in the present embodiment, it is found that the light collection rate is improved as the refractive index of the transparent film 21 is increased, and further, by optimizing the thickness of the on-chip lens 50 (in this example, In the case of 1.4 μm), for example, when the transparent film 21 has a refractive index of 1.9, the light collection rate exceeds 80%, which is a very high value. In this example, by increasing the thickness of the on-chip lens 50, the focus of the on-chip lens 50 tilts to the upper layer side, and light can be guided further into the transparent film 21. Is 1.4, the effect of this structure is most apparent.

As described above, according to the solid-state image pickup device of this embodiment, the light incident on the transparent film 21 is transparent because the light from the on-chip lens 50 is effectively condensed on the transparent film 21. The light is totally reflected at the interface between the film 21 and the flattening film 22 and is effectively guided to the light receiving unit 5 as described above, so that the light collection efficiency on the light receiving unit 5 can be improved and the sensitivity is improved. Can be made.

Further, the obliquely incident light which is incident from the adjacent pixel is reflected at the interface between the transparent film 21 and the flattening film 22 because the angle with the surface of the transparent film 21 is smaller than the critical angle. However, since the incidence on the light receiving unit 5 is limited,
Unnecessary incidence from adjacent lenses is suppressed, color mixture and the like are less likely to occur, and similarly, since the incident angle of incident light is limited, the occurrence of smear is reduced, and the charge transfer units 13 and 13 '. The light shielding property of is enhanced.

Since the transparent film 21 and the surface of the flattening film 22 are substantially on the same plane, the step due to the first transfer electrode 15 and the second transfer electrode 16 is eliminated, and the transparent film 21 and the flattening film 22 are formed on them. The processing uniformity of the on-chip color filter 40, the on-chip lens 50, and the like can be improved, and smear increase and minute sensitivity unevenness can be suppressed.

Further, immediately above the light receiving portion 5 which is the light incident path, from the outside of the on-chip lens 50, air having a refractive index of 1.0 and a refractive index of approximately 1.5 to 1.6. On-chip lens 50 and color filter 40 of
A passivation film 30 having a refractive index of 2.0 and a transparent film 21, a light receiving portion 5 made of silicon having a refractive index of 3.8,
Since the refractive index increases toward the light receiving portion 5 side, total reflection does not occur even in the obliquely incident light when passing through the interface between layers of different materials in the path of these light, The light is refracted so that the light is incident on the surface of the light receiving unit 5 at a more vertical angle. Therefore, it is possible to obtain a higher light-collecting efficiency and prevent deterioration of the characteristics due to reflection.

Next, a method of manufacturing the solid-state image pickup device according to this embodiment will be described with reference to FIGS. 6 (a) to 9 (h). 6 (a) to 9 (h) are cross-sectional views corresponding to FIG. 3 (a).

Processes up to FIG. 6A will be described. First, various impurity regions in a silicon substrate are formed according to a known method. That is, a p-type impurity is ion-implanted at a high concentration into a p-type silicon substrate or a p-type well (hereinafter referred to as a substrate) 11 formed on a silicon substrate to form a channel stopper (not shown) and n-type impurities are removed. Ion implantation is performed under predetermined conditions to form the light receiving portion 5,
Charge transfer unit 1 by ion-implanting n-type impurities under predetermined conditions
3 and 13 'are formed, and p-type impurities are ion-implanted between the charge transfer sections 13 and 13' and the light receiving section 5 under a predetermined condition to form a read gate section (not shown). Then, thermal oxidation or CVD is performed on the substrate 11 on which various impurity regions are formed.
An insulating film 14 is formed by depositing a silicon oxide film or the like by (Chemical Vapor Deposition) method. Subsequently, polysilicon with an impurity added to increase conductivity is deposited on the insulating film 14 by a CVD method, and the polysilicon is patterned to form a first transfer electrode (not shown). Then, the first transfer electrode and the light receiving portion 5 are covered to form an insulating film 14 made of, for example, silicon oxide, silicon nitride, or the like, and the second film is formed on the first transfer electrode via the insulating film 14. The transfer electrode 16 is formed, and the second transfer electrode 1 is formed.
The insulating film 14 is formed so as to cover the insulating film 6. Further, tungsten (W) is formed on the insulating film 14 so as to cover the transfer electrodes.
A refractory metal such as the above is deposited by the CVD method, and the refractory metal film is patterned so as to have the opening 17a above the light receiving portion 5 to form the light shielding film 17. With the above, FIG.
The structure shown in (a) is formed.

Next, as shown in FIG. 6B, the light shielding film 1
A material having a high refractive index, for example, silicon nitride having a refractive index of about 2.0 is deposited on the surface 7 and the opening 17a thereof by the plasma CVD method to form the transparent film 21a.
Regarding the film thickness of the transparent film 21a, the opening 17a of the light-shielding film is used.
The height of the portion deposited above is the height d of the light shielding film 17 that covers the first and second transfer electrodes 15 and 16 (FIG. 3B).
Refer to the above).

Next, as shown in FIG. 7C, the transparent film 2
A resist is applied on 1a, and patterning is performed so that the resist is left in the portions which will be the sensor openings, to form a resist film R1.

Next, as shown in FIG. 7D, the transparent film 21a is patterned by performing anisotropic plasma dry etching using the resist film R1 as a mask to form a quadrangular prism shape. The transparent film 21 is formed and the resist film R1 is removed. Here, in the present embodiment, the light incident region is defined by the opening 17a of the light shielding film 17, and when the transparent film 21 is formed only in the opening 17a, it is formed later due to the positional shift of the resist pattern and the like. Since an interface for performing total reflection is formed in the opening 17a of the light-shielding film 17 and variations in sensitivity characteristics may occur between the pixels, the interface not only overlaps the light-receiving portion 5 but also slightly on the light-shielding film 17. By patterning in the above manner, variations in sensitivity characteristics among pixels due to positional deviation can be suppressed. In the step of etching the transparent film 21a, the light shielding film 17 is used as an etching stopper film, so that the etching selection ratio between the transparent film 21a made of silicon nitride and the light shielding film 17 made of tungsten or the like becomes sufficiently large. Etching conditions.

Next, as shown in FIG. 8E, the light shielding film 1
7 and the transparent film 21 are covered, and a material having a lower refractive index than the transparent film 21, for example, silicon oxide having a refractive index of about 1.45 is deposited on the entire surface by the CVD method, and the flattening film 22 is formed. To form. As the flattening film 22,
It may be a silicon oxide film formed by an atmospheric pressure ozone oxidation method, or a silicon oxide film formed by a plasma CVD method using TEOS as a raw material. The thickness of the flattening film 22 is set so that the height of the portion deposited on the light shielding film 17 is the same as or higher than the height of the transparent film 21.

Next, as shown in FIG. 8F, the flattening film 22 is covered and a resist film R2 is applied on the entire surface. The resist film R2 is formed to have a film thickness that can absorb the height of the flattening film 22 formed on the transparent film 21.

Next, as shown in FIG. 9 (g), for example,
The entire surface is etched by anisotropic etching such as RIE (Reactive Ion Etching) to remove the flattening film 22 formed on the transparent film 21 together with the resist film R2, and further, the transparent film 21 and the flattening film 22. Flatten the surface of. Here, etching is performed under the condition that the etching selection ratio between the resist film R2 and the material forming the flattening film 22 is close to 1. As a result, the flattening film 22 is formed on the sidewall of the transparent film 21.
And the upper surface of the transparent film 21 and the upper surface of the flattening film 22 are in the same plane.

Next, as shown in FIG. 9H, the transparent film 2
1 and the flattening film 22 to cover the entire surface with plasma CV
Silicon nitride is deposited by the D method to form the passivation film 30.

In the subsequent steps, the on-chip color filter 40 is formed on the passivation film 30 by, for example, a dyeing method. In the dyeing method, a polymer such as casein is added with a photosensitizer and applied, and exposure, development, dyeing and fixing are repeated for each color. Alternatively, the on-chip color filter 40 may be formed using a dispersion method, a printing method, an electrodeposition method, or the like.

Finally, the on-chip lens 50 is formed by processing a light-transmissive resin such as a negative photosensitive resin by etching, for example, using a lens-shaped resist pattern having a predetermined curvature as a mask. Then, Fig. 3
The solid-state imaging device shown in can be manufactured.

According to the method of manufacturing the solid-state image pickup device according to the present embodiment described above, after the transparent film 21 which is a high refractive index material is formed by patterning, the flattening film 22 that covers the transparent film 21 is formed, and the transparent film 21 is formed. By removing the flattening film 22 formed on the surface of the transparent film 21 and flattening the surfaces of the transparent film 21 and the flattening film 22, a hole is formed in the interlayer film made of a conventional low refractive index material. As compared with the method of embedding a high-refractive-index material in the portion, there is no adverse effect such as generation of voids due to an increase in the aspect ratio of the hole due to the further reduction of the area of the light receiving portion 5, The structure having the same can be stably manufactured. This makes it possible to manufacture a solid-state imaging device having stable sensitivity characteristics.

Further, by increasing the film thickness of the transparent film 21, the height of the interface between the transparent film 21 and the flattening film 22 for total reflection can be increased, which further improves the light collection efficiency. It can also be increased. In this case, even if the area of the light receiving portion 5 is further reduced, in the present embodiment, since the transparent film 21 is formed by patterning using the resist as a mask, the thickness of the transparent film can be easily increased. can do. On the other hand, in the manufacturing method in which the hole is formed and then the high refractive index material is embedded in the hole, if the area of the light receiving portion 5 becomes small, the film thickness of the interlayer film forming the hole is increased. Since the aspect ratio of the hole is further increased and voids are generated due to insufficient coverage as described above, there is a limit on the interface height for performing total reflection.

Further, as compared with the conventional manufacturing condition of the in-layer lens in which the curvature is greatly influenced by the step of the base and the light collecting function thereof is affected, the shape of the base is not affected. Control of manufacturing conditions for obtaining a desired structure can be simplified, and a solid-state imaging device having substantially the same sensitivity characteristic in a plurality of pixel portions can be manufactured.

The present invention is not limited to the above description of the embodiments. For example, in the present embodiment, in order to flatten the surface of the transparent film 21 and the surface of the flattening film 22 so that they are flush with each other, a resist is applied in the steps shown in FIGS. 8F and 9G. Then, the entire surface is etched back, but not limited to this, for example, after the planarizing film 22 is deposited on the entire surface, CMP (Chemical Mechanical Polishing) is performed.
By the method, the surface of the transparent film 21 may be polished until it is exposed, and the surfaces of the transparent film 21 and the planarizing film 22 may be planarized.

In addition, in this embodiment, the transparent film 21.
By forming the flattening film 22 so as to surround the side wall of, the light from the on-chip lens 50 is effectively condensed to the light receiving section 5, but if the same principle is adopted,
The shape of the transparent film and the shape of the flattening film surrounding the side wall are
There is no particular limitation. The materials for the transparent film and the flattening film are not particularly limited as long as they have a refractive index difference that allows total reflection. Besides, various modifications can be made without departing from the scope of the present invention.

[0080]

According to the present invention, it is possible to obtain stable sensitivity characteristics while improving light collection efficiency and sensitivity.

[Brief description of drawings]

FIG. 1 is a schematic configuration diagram of a solid-state imaging device according to this embodiment.

FIG. 2 is an enlarged plan view of an essential part of an imaging section of the solid-state imaging device according to the present embodiment.

3A and 3B are cross-sectional views of the solid-state imaging device according to the present embodiment, FIG. 3A is a cross-sectional view taken along the line AA ′ of FIG. 2, and FIG.
FIG. 3 is a sectional view taken along the line BB ′ of FIG.

FIG. 4 is a diagram for explaining a light collecting action of the solid-state imaging device according to the present embodiment.

FIG. 5 is a diagram showing a simulation result for explaining the effect of the solid-state imaging device according to the present embodiment.

FIG. 6 is a cross-sectional view showing the steps up to the step of forming a transparent film in the manufacturing of the solid-state imaging device according to the present embodiment.

FIG. 7 is a cross-sectional view showing a transparent film patterning step in the manufacturing of the solid-state imaging device according to the embodiment.

FIG. 8 is a cross-sectional view showing a step of forming a flattening film in the manufacturing of the solid-state imaging device according to the present embodiment.

FIG. 9 is a cross-sectional view showing a step of forming a passivation film in the manufacturing of the solid-state imaging device according to the present embodiment.

[Explanation of symbols]

1 ... Solid-state imaging device, 2 ... Imaging unit, 3 ... Horizontal transfer unit, 4 ...
Output section, 4a ... Charge-voltage conversion section, 5 ... Light receiving section, 6 ... Read gate section, 7 ... Vertical transfer section, 8 ... Pixel, 11 ... Substrate, 13, 13 '... Charge transfer section, 14 ... Insulating film, 15 ...
First transfer electrode, 16 ... Second transfer electrode, 17 ... Light-shielding film, 1
7a ... Opening part, 21 ... Transparent film, 22 ... Flattening film, 30 ...
Passivation film, 40 ... On-chip color filter, 50 ... On-chip lens, R1, R2 ... Resist film.

   ─────────────────────────────────────────────────── ─── Continued front page    F-term (reference) 4M118 AA01 AB01 BA13 CA02 CA32                       FA06 GB03 GB11 GC07 GD04                       GD07 GD14                 5C024 CY48 EX43 GX03 GY01

Claims (10)

[Claims] 1. A solid-state imaging device having a light-receiving portion formed on a substrate and having a light-incident region specified by a light-shielding film, the solid-state imaging device being formed on the light-incident region of the light-receiving portion and having a first refractive index. An optically transparent first film having a mochi light guiding function, and a second refraction film formed so as to surround a sidewall of the first film and having a refractive index lower than the first refractive index of the first film. Solid-state imaging device having a second film having an index. 2. The solid-state imaging device according to claim 1, wherein the first film is formed to be higher than the height of the light shielding film. 3. The solid-state imaging device according to claim 1, wherein the upper surface of the first film and the upper surface of the second film are formed so as to be flush with each other. 4. The first film formed above the first film,
The solid-state imaging device according to claim 1, further comprising an on-chip lens that collects light toward the film. 5. A step of forming a light-receiving portion on a substrate, a step of forming a light-shielding film having an opening above the light-receiving portion on the substrate, and a step of forming a light-shielding film on the substrate at least in the opening. Forming an optically transparent first film having a refractive index of 1. and a second film having a lower refractive index than the first film of the first film so as to surround a side wall of the first film. And a step of forming a second film having a refractive index. 6. The step of forming the first film, the step of depositing a first film material on the substrate in the opening and on the light-shielding film, and on the first film material, 6. The method comprises: forming a mask layer having a pattern of the first film; and removing the first film material using the mask layer as a mask until the light shielding film is exposed.
A method for manufacturing the described solid-state imaging device. 7. In the step of forming the light-shielding film, the light-shielding film is formed of a material having an etching selection ratio with respect to the first film material, and the first film material is removed in the step of removing the first film material. The method for manufacturing a solid-state imaging device according to claim 6, wherein the solid-state imaging device is removed by etching. 8. The step of forming the second film comprises the steps of covering the first film and depositing a second film material on the light-shielding film; and depositing on a sidewall of the first film. 6. The method for manufacturing a solid-state imaging device according to claim 5, further comprising the step of removing the second film material formed on the first film so as to leave the second film material. 9. In the step of removing the second film material, the second film material is removed so that the upper surface of the first film and the upper surface of the second film are on the same plane. The method for manufacturing a solid-state imaging device according to claim 8. 10. The method further comprises, after the step of forming the second film, forming an on-chip lens for condensing light toward the first film above the first film. Item 5. A method for manufacturing a solid-state imaging device according to item 5.