JP2001230401A - Solid-state image sensing device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To solve the problem that the ratio of scattered light that enters the surface of the end part of a photoelectric conversion element with a large incidence angle increases as the size of the photoelectric conversion element in a solid-state image sensing device becomes smaller, and smear caused by the incidence of the scattered light onto the surface of the end part of the photoelectric conversion element cannot be reduced easily even if a light- shielding film is formed by a material with a relatively high light absorption capacity. SOLUTION: When the solid-state image sensing device is to be manufactured by forming a photoelectric conversion element or the like at one surface side of a semiconductor substrate, a step is formed between a light incidence surface out of the surfaces of the photoelectric conversion element and the surface of the semiconductor substrate around the photoelectric conversion element.

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 a photoelectric conversion element formed on one surface side of a semiconductor substrate.

[0002]

2. Description of the Related Art A solid-state imaging device is formed by forming a large number of photoelectric conversion elements (photodiodes) and charge transfer paths for transferring signal charges accumulated in these photoelectric conversion elements on one surface side of a semiconductor substrate. Can be obtained.

In a CCD (charge coupled device) type solid-state imaging device, a charge transfer path is formed by the CCD. MOS
The solid-state imaging device of the type includes a switching element (for example, a transistor) provided for each photoelectric conversion element and a predetermined number of output signal lines connected to the switching element. An electric signal corresponding to the accumulated signal charge amount is generated on a predetermined output signal line.

In both solid-state imaging devices of the CCD type and the MOS type, the upper surfaces of the photoelectric conversion elements are substantially flat. The upper surface of the photoelectric conversion element is located on substantially the same plane as the surface of the semiconductor substrate around the photoelectric conversion element.

[0005] Such a solid-state imaging device is used for a line sensor used in a copy machine, a facsimile machine, or the like, or an area image sensor used in a video camera, an electronic still camera, or the like.

[0006] Conventionally, in a solid-state imaging device, a light shielding film has been used in order to prevent unnecessary photoelectric conversion from being performed in a region other than the photoelectric conversion element. This light shielding film is generally made of aluminum, chromium, tungsten,
A metal thin film made of titanium, molybdenum, or the like, an alloy thin film made of two or more of these metals, or a multi-layer metal thin film formed by combining the metal thin films or a combination of the metal thin film and the alloy thin film. You.

In order to prevent conduction between the light shielding film and the semiconductor substrate or the charge transfer path or the output signal line, the light shielding film and the semiconductor substrate or the charge transfer path or the output signal line are electrically connected by an electric insulating film. Insulated. The electric insulating film is usually also formed on the upper surface of each photoelectric conversion element.
The thickness of the electric insulating film on the photoelectric conversion element is, for example, 0.1
０．３0.3 μm.

Of course, if the photoelectric conversion element is completely covered with the light shielding film in plan view, it becomes impossible to perform desired photoelectric conversion. For this reason, the light shielding film has one opening above each photoelectric conversion element so that desired photoelectric conversion is performed in the photoelectric conversion element.

This opening is usually located above a region inside the edge when the photoelectric conversion element is viewed in plan.
That is, the light shielding film usually covers the edge of the photoelectric conversion element in plan view.

[0010] The photoelectric conversion element performs photoelectric conversion by light incident through the opening of the light shielding film. Hereinafter, in this specification, a photoelectric conversion element surface that is exposed in a plan view through an opening formed in a light shielding film is referred to as a “light incident surface” of the photoelectric conversion element.

[0011]

The light incident on the solid-state imaging device is scattered before reaching the photoelectric conversion element.
This scattering tends to increase as the size of the photoelectric conversion element decreases.

In the conventional solid-state imaging device, when the scattering of light increases, the light enters between the lower surface of the light shielding film (the surface on the semiconductor substrate side; the same applies hereinafter) and the edge surface of the photoelectric conversion element. The amount of scattered light to be emitted also increases. The scattered light that has entered between the lower surface of the light shielding film and the edge surface of the photoelectric conversion element is
Multiple reflection occurs between the light shielding film and the edge surface of the photoelectric conversion element or the surface of the semiconductor substrate.

[0013] When the multiply reflected light is absorbed in a region other than the photoelectric conversion element, it may cause smear. In particular, in the case of a CCD type solid-state imaging device, when light is absorbed in the charge transfer path, it causes an increase in smear.

By forming the light-shielding film with a material having a relatively high light-absorbing ability, for example, tungsten or chromium, it is possible to suppress an increase in smear caused by multiple reflected light for the following reasons.

That is, when the light-shielding film has a relatively high light-absorbing ability, light is repeatedly incident on the lower surface of the light-shielding film by multiple reflection, and each time a part of the multiple reflected light becomes light. Absorbed by the shielding film. As a result, the amount of light absorbed by the semiconductor substrate in a region other than the photoelectric conversion element decreases, and an increase in smear is suppressed.

For example, when the light shielding film is formed of tungsten, the smear can be reduced to about て compared to the case where the light shielding film is formed of a material having a relatively high reflectance such as aluminum. is there.

However, as the size of the photoelectric conversion element decreases, the width of the edge of the photoelectric conversion element covered in plan view by the light shielding film decreases. In addition, light scattering increases. As a result, the ratio of scattered light incident on the edge surface of the photoelectric conversion element at a large incident angle increases.

When the incident angle of the scattered light incident on the edge surface of the photoelectric conversion element increases, the number of times that the light is incident on the lower surface of the light shielding film due to multiple reflection decreases. Therefore, even if the light shielding film is formed of a material having a relatively high light absorbing ability, it becomes difficult to reduce smear caused by scattered light incident on the edge surface of the photoelectric conversion element.

An object of the present invention is to provide a solid-state imaging device capable of reducing smear.

[0020]

According to one aspect of the present invention, there is provided a photoelectric conversion element formed on one surface side of a semiconductor substrate, wherein a light incident surface of the photoelectric conversion element surface and the photoelectric conversion element are separated from each other. A photoelectric conversion element having a step between the surface of the semiconductor substrate around the element, a light shielding film formed above the photoelectric conversion element and having an opening on the light incident surface, and close to the photoelectric conversion element. And a charge transfer path for transferring the signal charges stored in the photoelectric conversion element.

For example, an inclined surface (including a curved surface and a vertical surface) having an upward slope from the photoelectric conversion element to the outside thereof is formed at the edge of the light incident surface when the photoelectric conversion element is viewed in a plan view. It is possible to reduce the amount of scattered light that enters between the lower surface of the light shielding film and the edge surface of the photoelectric conversion element.

For example, an inclined surface (including a curved surface and a vertical surface) having a downward slope from the photoelectric conversion element toward the outside thereof is formed on the semiconductor substrate around the photoelectric conversion element. It is possible to reduce the amount of scattered light entering between the lower surface of the transfer electrode forming the charge transfer path and the semiconductor substrate (charge transfer channel).

For example, a concave portion or a convex portion is provided between the light incident surface of the photoelectric conversion element and the edge of the photoelectric conversion element in plan view. The amount of scattered light that enters between the lower surface of the light shielding film and the edge surface of the photoelectric conversion element, or between the lower surface of the transfer electrode forming the charge transfer path and the semiconductor substrate (charge transfer channel) is reduced. It becomes possible. Further, in the concave portions or the convex portions, scattered light is incident on the photoelectric conversion element or the light shielding film at an incident angle different from a case where the concave portions or the convex portions are not provided. Therefore, even if the light-shielding film is formed of a material having relatively high light-absorbing ability, scattered light that could not be absorbed by the light-shielding film in the conventional solid-state imaging device can be reflected by high-frequency multiple reflection. Expected to be absorbed by the light shielding film. In addition, it can be expected to increase the amount of scattered light which becomes too small to reach the semiconductor substrate (charge transfer channel) due to the shallow reflection angle.

For these reasons, it is possible to reduce smear.

[0025]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, a solid-state imaging device according to an embodiment will be described with reference to the drawings.

FIG. 1 is a sectional view schematically showing a CCD type solid-state imaging device 1 according to a first embodiment.

As shown in FIG. 1, the solid-state imaging device 1 has n
A semiconductor substrate 2 composed of a p-type silicon substrate 2a and a p-type semiconductor epitaxial layer or well 2b (hereinafter referred to as "p-type well 2b") formed on one surface side of the n-type silicon substrate 2a. Have.

An n-type region 3a is formed at a predetermined portion of p-type well 2b.
Or by providing an n-type region 3a at a predetermined position in the p-type well 2b and providing ap ⁺ -type layer thereon, thereby forming the photoelectric conversion element 3 composed of a photodiode. The impurity concentration in the p ⁺ -type layer is higher than the impurity concentration in the p-type well.

In a solid-state imaging device for a line sensor, a predetermined number of photoelectric conversion elements 3 are formed, for example, in one or three rows. In a solid-state imaging device for an area sensor, a predetermined number of photoelectric conversion elements 3 are formed, for example, in a matrix.

The planar shape of the n-type region 3a constituting the photoelectric conversion element 3 is a rectangle, a polygon not less than a pentagon in which all internal angles are obtuse angles, and a pentagon or more in which the internal angles include an acute angle and an obtuse angle. Polygons, shapes in which corners of these polygons are rounded, and the like can be appropriately selected.

In the solid-state imaging device 1, the surface of a region in which the photoelectric conversion element 3 enters at a constant width from the edge when viewed in plan is formed substantially on the same plane as the surface of the surrounding semiconductor substrate 2. Have been. This region is hereinafter referred to as “the edge of the photoelectric conversion element 3”.

The area inside the edge of the photoelectric conversion element 3 is
It is concave like a dish. Hereinafter, this concave portion is referred to as a “dish-shaped concave portion”.

The surface of the dish-shaped recess is substantially flat except for its edge in plan view. The edge in plan view of the dish-shaped concave portion is a slope (however, a curved surface) with an upward slope toward the outside.

The depth of the dish-shaped recess is determined, for example, by the thickness of the electric insulating film 6 below the transfer electrode 4b (for example, 0.1 to
0.3 [mu] m) or more and about 0.5 [mu] m or less, which does not easily cause a problem in the manufacturing process of the solid-state imaging device. The planar shape of the dish-shaped concave portion is a rectangle, a pentagon or more polygon in which all interior angles are obtuse angles, a pentagon or more polygon in which the interior angles include acute angles and obtuse angles, and corners of these polygons. The rounded shape of the portion can be appropriately selected.

An n-type region 4a for a charge transfer path (hereinafter referred to as "charge transfer channel 4a") is formed in the p-type well 2b near the n-type region 3a of the photoelectric conversion element 3. The n-type region 4a has a linear shape or a band shape in plan view.

The n-type region 3a and the charge transfer channel 4a are separated from each other by a channel stop 5 composed of, for example, a p ⁺ -type region, except for a read gate region not shown. The impurity concentration in the channel stop 5 is higher than the impurity concentration in the p-type well 2b. The channel stop 5 is a region for electrically isolating the n-type region 3a from the surroundings, and an insulating region may be used instead of the p ⁺ -type region.

The electric insulating film 6 is formed on the upper surface of the photoelectric conversion element 3 and on the surface of the semiconductor substrate 2 around the photoelectric conversion element 3. The electrical insulating film 6 is formed, for example, by a thermal oxide film formed by thermally oxidizing the semiconductor substrate 2, a thermal oxide film and a nitride film (ON film) formed thereon, and a thermal oxide film and a thermal oxide film formed thereon. Nitride film and oxide film (ON
O film).

The transfer electrode 4b made of, for example, polysilicon
Are provided above the charge transfer channel 4a via the electric insulating film 6. The transfer electrode 4b traverses the charge transfer channel 4a in plan view and forms one charge transfer stage at the intersection with the charge transfer channel 4a in plan view. For example, two or three charge transfer stages are provided for one photoelectric conversion element 3. One charge transfer channel 4a and each transfer electrode 4b intersecting the same in plan view constitute one charge transfer path 4 composed of a CCD.

A read gate (not shown) is provided to control reading of signal charges from the photoelectric conversion element 3 to the charge transfer path 4. The read gate has, for example, a read gate electrode composed of a part of the transfer electrode 4b or a part of a transfer electrode different from the transfer electrode 4b. The readout gate electrode is provided via an electric insulating film 6 on a region of the p-type well 2b interposed between the photoelectric conversion element 3 (n-type region 3a) and the charge transfer channel 4a.

When a predetermined read pulse is applied to the read gate electrode, the signal charges stored in the photoelectric conversion element 3 are read to a charge transfer stage adjacent to the read gate. That is, the signal charges are read out to the charge transfer path 4.

The electric insulating film 7 is provided on the surface of the transfer electrode 4b. The electrical insulating film 7 is formed, for example, by thermally oxidizing the surface of the transfer electrode 4b.

A light shielding film 8 for preventing unnecessary photoelectric conversion from being performed in a region other than the photoelectric conversion element 3 covers the electric insulating films 6 and 7 so as to cover these electric insulating films. Is provided.

The light shielding film 8 is formed on the photoelectric conversion element 3 in plan view.
Has an opening 8a above the dish-shaped recess. The outline in plan view of the opening 8a substantially matches the outline in plan view of the dish-shaped recess. The shape of the opening 8a in plan view is appropriately selected according to the shape of the dish-shaped concave portion of the photoelectric conversion element 3 in plan view. The edge of the photoelectric conversion element 3 is covered with the light shielding film 8 on a plane.

In the photoelectric conversion element 3, the surface of the dish-shaped concave portion corresponds to the light incident surface. As described above, the edge of the light incident surface is an inclined surface (however, a curved surface) having an upward slope.

The light shielding film 8 is made of, for example, a metal thin film made of aluminum, chromium, tungsten, titanium, molybdenum, or the like, an alloy thin film made of two or more of these metals, It is composed of a multilayer metal thin film or the like obtained by combining a thin film and the above alloy thin film. In order to suppress smear, tungsten,
It is preferable that the light shielding film 8 is formed of a material having a relatively high light absorbing ability such as chromium.

When a microlens is used, a focus adjusting layer 9 for flattening the base surface and adjusting the distance between the microlens and the photoelectric conversion element 3 is provided. The focus adjustment layer 9 is formed by applying a transparent resin such as a photoresist to a desired thickness by a method such as a spin coating method so as to cover the light shielding film 8 and the electric insulating film 6 exposed from the opening 8a. Formed by

Even when a microlens is not used, a protective layer made of a silicon nitride film or the like is provided as necessary in order to prevent moisture and the like from entering the light shielding film 8 and layers below the light shielding film 8. This protective layer is formed by, for example, a chemical vapor deposition method (CVD method) or a physical deposition method (PVD method) so as to cover the light shielding film 8 and the electric insulating film 6 exposed from the opening 8a. .

The focus adjusting layer 9 may be provided on the above-mentioned protective layer. Further, an inner lens can be formed on the focus adjustment layer 9.

In a solid-state image pickup device such as a line sensor solid-state image pickup device in which a microlens is not an essential component, a solid-state image pickup device for monochrome image pickup can be obtained by providing the above-mentioned protective layer. it can. If a color filter array described below is provided on this protective layer, a solid-state imaging device for color imaging can be obtained.

In a solid-state image pickup device for color image pickup using a micro lens, a color filter array is formed on a focus adjusting layer 9, and a micro lens array is provided thereon via a flattening film 12. .

The color filter array is a color filter 11 of a desired color which is disposed one by one above each photoelectric conversion element 3.
Composed of The color filter array includes a color filter array of three primary colors (red, green, and blue) and a so-called complementary color filter array.

A complementary color filter array is, for example,
(i) green (G), cyan (Cy) and yellow (Ye) color filters; (ii) cyan (Cy), yellow (Ye) and white or colorless (W) color filters; (iii) cyan (C)
y), magenta (Mg), yellow (Ye) and green (G) color filters, or (iv) cyan (Cy), yellow (Y
e), green (G) and white or colorless (W) color filters.

The color filter array can be manufactured by, for example, forming a layer of a resin (color resin) to which a pigment or dye of a desired color is added by a method such as a photolithography method at a predetermined position.

The flattening film 12 formed on the color filter array fills the unevenness of the surface of the color filter array to form a flat surface. The flattening film 12 is formed by applying a transparent resin such as a photoresist to a desired thickness by a method such as a spin coating method.

The microlens array formed on the flattening film 12 is constituted by microlenses 13 arranged one by one above the individual photoelectric conversion elements 3. The shape of each microlens in plan view is a rectangle (including a rhombus), a shape with rounded corners, a pentagon or more polygon in which all interior angles are obtuse, A shape with a rounded corner, a circle, an ellipse, or the like can be appropriately selected.

Each of the microlenses 13 is formed, for example, by partitioning a layer made of a transparent resin (including a photoresist) having a refractive index of about 1.3 to 2.0 into a predetermined shape by a photolithography method or the like. It is obtained by melting the transparent resin layer of the section by heat treatment, rounding the corners by surface tension, and then cooling.

In the solid-state imaging device 1 described above,
The surface of the dish-shaped recess formed in the photoelectric conversion element 3 is a light incident surface of the photoelectric conversion element 3. The light incident surface is recessed from the surface of the semiconductor substrate 2 around the photoelectric conversion element 3, and the edge of the light incident surface is an inclined surface (a curved surface) having an upward slope toward the outside. That is, there is a step between the light incident surface of the photoelectric conversion element 3 and the surface of the semiconductor substrate 2 around the photoelectric conversion element 3.

For this reason, even if the light incident from the microlenses 13 is scattered, the light is more illuminated than when the upper surface of the photoelectric conversion element 3 and the surface of the semiconductor substrate 2 around the photoelectric conversion element 3 are on the same plane. Scattered light hardly enters between the lower surface of the shielding film 8 and the edge surface of the photoelectric conversion element 3. As a result,
Reduction of smear is expected.

Next, FIG. 2A, FIG. 2B, FIG.
An example of a method for manufacturing the photoelectric conversion element 3 shown in FIG. 1 will be described with reference to (c) and FIG.

FIGS. 2A to 2D are cross-sectional views of a substrate for describing main steps in manufacturing the photoelectric conversion element 3 shown in FIG.

First, a p-type semiconductor epitaxial layer 2b (p-type well 2b) is formed on one surface of an n-type silicon substrate 2a.
Is formed to obtain the semiconductor substrate 2. A stacked film is formed by stacking a silicon oxide film having a thickness of, for example, about 0.02 μm and a silicon nitride film having a thickness of, for example, about 0.05 μm on the p-type well 2b in this order. . The thickness of the silicon oxide film forming the laminated film is preferably, for example, about 0.01 to 0.05 μm, and the thickness of the silicon nitride film is, for example, preferably about 0.02 to 0.1 μm.

A resist pattern having a predetermined shape is formed on the laminated film by a method such as a photolithography method.

As shown in FIG. 2A, a through hole 21 is formed at a predetermined position in the laminated film 20 including the silicon oxide film 20a and the silicon nitride film 20b.
This through-hole 21 can be formed, for example, by dry-etching the laminated film 20 using a resist pattern formed on the laminated film 20 as an etching mask. Instead of dry etching, wet etching can be applied. The through hole 21 is formed on a portion where a light incident surface of the photoelectric conversion element is to be formed.

As shown in FIG. 2B, the surface of the p-type well 2b exposed through the through hole 21 is thermally oxidized to form a silicon oxide film 22. Silicon oxide film 22
Is, for example, about 0.05 μm. The thickness of the silicon oxide film 22 is preferably, for example, about 0.02 to 0.1 μm.

As shown in FIG. 2C, the silicon oxide film 22 is removed by a method such as wet etching or dry etching. A dish-shaped concave portion 23 is formed at the position where the silicon oxide film 22 was located. The two-dot chain line in the figure indicates the surface of the semiconductor substrate 2 before the silicon oxide film 22 is formed.

The silicon nitride film 20b and the silicon oxide film 20a are respectively removed by wet etching to expose the entire upper surface of the p-type well 2b.

As shown in FIG. 2D, an impurity serving as a donor is implanted into a predetermined portion of the p-type well 2b by ion implantation using a mask M such as a resist pattern.
Activated by heat treatment to form n-type region 3a for a photoelectric conversion element. At this time, the impurities serving as donors are doped at the bottom of the dish-shaped recess 23 and around the dish-shaped recess 23. The photoelectric conversion element 3 having the dish-shaped recess 23 is obtained.

In the state shown in FIG. 2A, even if impurities serving as donors are implanted into predetermined portions of the p-type well 2b by ion implantation using the laminated film 20 as a mask, dish-shaped recesses are formed. 23 can be obtained. In this case, after ion implantation of impurities, FIG.
The steps shown in FIG. 2B and FIG. 2C are sequentially performed, and thereafter, the laminated film 20 is removed. When the silicon oxide film 22 is formed, the ion-implanted impurity is activated to form the n-type region 3a.

The implantation depth of the ion-implanted impurity is substantially constant in the entire region where the ion is implanted. However, if heat treatment for activation is performed after ion implantation,
Deforms due to diffusion. FIG. 2D schematically shows a boundary between the p-type well 2 and the n-type region 3a. The same applies to the drawings referred to in the later-described modifications or other embodiments.

In manufacturing the solid-state imaging device 1 shown in FIG. 1, after manufacturing the photoelectric conversion element 3 as described above, or before manufacturing the photoelectric conversion element 3, the channel stop 5 and the charge transfer A charge transfer channel 4a for the path 4 is formed. When the channel stop 5 and the charge transfer channel 4a for the charge transfer path 4 are formed before the photoelectric conversion element 3 is manufactured, the photoelectric conversion element 3 is manufactured next. After that, the electric insulating film 6, the transfer electrode 4b, the electric insulating film 7, the light shielding film 8, the focus adjusting layer 9, the color filter 11, the second planarizing film 12, and the microlens 13 are sequentially formed.

Next, a modification of the first embodiment will be described with reference to FIG.

FIG. 3 shows a modification of the first embodiment.
FIG. 2 is a cross-sectional view schematically illustrating a CD-type solid-state imaging device 1a.

In the solid-state imaging device 1a of this modification, the shape of the n-type region 3a in the photoelectric conversion element 3 is different from the shape of the n-type region 3a in the solid-state imaging device 1 of the first embodiment.
That is, unlike the photoelectric conversion element 3 in the first embodiment, the edge of the dish-shaped recess itself of the photoelectric conversion element 3 coincides with the edge of the n-type region 3a when the photoelectric conversion element 3 is viewed in plan. I have.

The opening 8a of the light shielding film 8 is open on the inner side in plan view from the edge of the dish-shaped recess itself. The light incident surface of the photoelectric conversion element 3 is defined as a flat surface serving as the bottom surface of the dish-shaped concave portion.

However, the layer configuration of the solid-state imaging device is the same as that of the first embodiment. Therefore, among the components and locations shown in FIG. 3, those corresponding to the components and locations shown in FIG. 1 are given the same reference numerals as those used in FIG. 1, and description thereof will be omitted.

In the illustrated solid-state imaging device 1a, the first
For the same reason as in the solid-state imaging device 1 of the embodiment, reduction of smear is expected.

The solid-state imaging device 1a shown in FIG. 3 has the first configuration except that the photoelectric conversion element 3 is manufactured, for example, as follows.
It can be manufactured in the same manner as the solid-state imaging device 1 of the embodiment.

First, after performing the step shown in FIG. 2A in the same manner as in the case of manufacturing the photoelectric conversion element 3 shown in FIG. 1, the silicon nitride film 20b (see FIG. 2C) is removed. Using the impurity serving as a donor as a mask,
b is ion-implanted. Next, the through holes 21 (FIG. 2A)
2) is thermally oxidized to form a silicon oxide film 22 (see FIG. 2A). At this time, the ion-implanted impurity is activated to form n-type region 3a. After that, the silicon oxide film 22 is removed, and the laminated film 20 (see FIG. 2A) is removed to obtain the photoelectric conversion element 3 shown in FIG.

Next, another modified example of the first embodiment will be described with reference to FIG.

FIG. 4 is a sectional view schematically showing a CCD type solid-state imaging device 1b according to another modification of the first embodiment.

The solid-state imaging device 1b of the present modification is different from the first embodiment in that the opening 8a of the light shielding film 8 is open on the bottom surface of the dish-shaped concave portion of the photoelectric conversion element 3 in plan view. This is different from the solid-state imaging device 1 of the example. Other points are the same as those of the solid-state imaging device 1 of the first embodiment.

Therefore, among the constituent members and locations shown in FIG. 4, those corresponding to the constituent members or locations shown in FIG. 1 are given the same reference numerals as those used in FIG. Omitted.

As shown in FIG. 4, the photoelectric conversion element 3 in the solid-state imaging device 1b has the same shape as the photoelectric conversion element 3 in the solid-state imaging device 1 of the first embodiment. However, the shape of the light shielding film 8 is selected such that the opening 8a opens on the bottom surface of the dish-shaped concave portion as described above.

In the solid-state imaging device 1a shown in FIG.
For the same reason as in the solid-state imaging device 1 of the embodiment, reduction of smear is expected.

Further, since the periphery of the opening 8a in the light shielding film 8 is inclined down toward the opening 8a, the light enters between the lower surface of the light shielding film 8 and the surface of the photoelectric conversion element 3. The following are expected for scattered light. That is, the incident angle or the reflection angle of the scattered light may change on the lower surface of the light shielding film 8 forming the slope around the opening 8a or on the surface of the photoelectric conversion element 3 facing the lower surface. Be expected. Accordingly, the following is expected.

As shown in FIG. 5A, scattered light (a broken line L _{1 in the} figure) incident at a small incident angle between the lower surface of the light shielding film 8 and the surface of the photoelectric conversion element 3 (n-type region 3a). After several multiple reflections, the light is reflected under a large reflection angle on the lower surface of the light shielding film 8 forming the slope around the opening 8a. As a result, it is expected that scattered light will not enter the charge transfer channel 4a (see FIG. 4).

Further, as shown in FIG. 5B, the scattered light incident at a large incident angle between the lower surface of the light shielding film 8 and the surface of the photoelectric conversion element 3 (n-type region 3a) (in the figure, , Broken line L
Indicated by ₂ . ) Is reflected by the edge slope of the dish-shaped recess in the photoelectric conversion element 3. As a result, the scattered light is applied to the light shielding film 8 above the edge surface of the photoelectric conversion element 3 (n-type region 3a).
It is expected that the light will be incident on the lower surface under a small incident angle. At this time, if the light shielding film 8 is formed of a material having a relatively high light absorbing ability, the light shielding film 8 is formed between the edge surface of the photoelectric conversion element 3 (the n-type region 3a) and the lower surface of the light shielding film 8 thereabove. It is expected that the light will be absorbed by the light shielding film 8 during multiple reflections.

The solid-state imaging device 1b shown in FIG. 4 is similar to the solid-state imaging device 1b of the first embodiment except that the shape of a resist pattern used as an etching mask when forming the opening 8a in the light shielding film 8 is appropriately selected. It can be formed in the same manner as the solid-state imaging device 1.

Next, still another modification of the first embodiment will be described with reference to FIG.

FIG. 6 is a sectional view schematically showing a CCD type solid-state image pickup device 1c according to still another modification of the first embodiment.

The solid-state imaging device 1c according to the present modification is configured such that: (i) light shielding is performed so that the contour of the opening 8a of the light shielding film 8 substantially matches the contour of the photoelectric conversion element 3 in plan view. The point where the film 8 is formed, and (ii) the silicon oxide film 22 (see FIG. 2B) formed in the p-type well 2b to obtain the photoelectric conversion element 3 having the dish-shaped concave portion are removed. This is different from the solid-state imaging device 1a shown in FIG. Other points are the same as those of the solid-state imaging device 1a shown in FIG.

For this reason, among the components and locations shown in FIG. 6, those corresponding to the components and locations shown in FIG. 2B or FIG. 3 are used in FIG. 2B or FIG. The same reference numerals as the reference numerals are used, and the description is omitted.

As shown in FIG. 6, the photoelectric conversion element 3 in the solid-state imaging device 1c of the present modification has the same shape as the photoelectric conversion element 3 shown in FIG. For this reason, in the illustrated solid-state imaging device 1c, reduction of smear is expected for the same reason as in the solid-state imaging device 1 of the first embodiment.

Further, since the silicon oxide film 22 has a weak lens effect even though the silicon oxide film 22 is weak, the lower surface of the light shielding film 8 and the surface of the photoelectric conversion element 3 are located more than in the solid-state imaging device 1a shown in FIG. Light is hard to enter. As a result, smear is expected to be further reduced as compared with the solid-state imaging device 1a shown in FIG.

The solid-state imaging device 1c shown in FIG. 6 has the same structure as that of FIG.
Can be manufactured in the same manner as the solid-state imaging device 1a shown in FIG.

First, an impurity serving as a donor is ion-implanted into the p-type well as in the case of obtaining the photoelectric conversion element 3 in the solid-state imaging device 1a shown in FIG. Is thermally oxidized to form a silicon oxide film. At this time, the thickness of the silicon oxide film is, for example, 0.2 μm. The thickness of the silicon oxide film is preferably, for example, about 0.1 to 0.3 μm. Next, the photoelectric conversion element 3 shown in FIG. 6 is obtained by removing only the laminated film used as a mask at the time of ion implantation without removing the silicon oxide film.

The solid-state imaging device 1c shown in FIG. 6 can be manufactured by, for example, the following method in addition to the above-described method.

First, similarly to the case of manufacturing the solid-state imaging device 1a shown in FIG. 3, the steps up to the step shown in FIG. 2C are performed. Next, an impurity serving as a donor is ion-implanted into the dish-shaped concave portion 23 using the laminated film 20 as a mask. The p-type well 2b exposed through the through hole 21 (FIG. 2A)
Reference) The surface portion is thermally oxidized to form a silicon oxide film 22. At this time, the ion-implanted impurities are activated, and an n-type region for a photoelectric conversion element is formed. This n-type region has a substantially constant thickness, unlike n-type region 3a shown in FIG. Next, the laminated film 20 is removed by wet etching. Thereafter, the solid-state imaging device 1c is operated in the same manner as when the solid-state imaging device 1 shown in FIG. 1 is obtained.
To manufacture.

Next, a second embodiment will be described with reference to FIG.

FIG. 7 is a sectional view schematically showing a CCD type solid-state imaging device 30 according to the second embodiment.

The solid-state imaging device 30 of this modification is different from the solid-state imaging device 30 in that the photoelectric conversion element 33 does not have a dish-shaped recess, and its light incident surface protrudes from the surface of the semiconductor substrate 2 around the photoelectric conversion element 33. Are significantly different from the solid-state imaging device 1 of the first embodiment. However, the layer configuration of the solid-state imaging device 30 is the same as that of the first embodiment.

Therefore, among the constituent members and locations shown in FIG. 7, those corresponding to the constituent members or locations shown in FIG. 1 include a photoelectric conversion element and an n-type region constituting the photoelectric conversion element, respectively. Except for this, the same reference numerals as those used in FIG.

As shown in FIG. 7, in the photoelectric conversion element 33, the upper surface of the n-type region 33a protrudes from the surface of the semiconductor substrate 2 around the photoelectric conversion element 33. n-type region 33
The upper surface of a is substantially flat. N-type region 33 based on the surface of semiconductor substrate 2 around photoelectric conversion element 33
The height of the upper surface a is preferably, for example, about 0.01 to 0.05 μm.

The opening 8a of the light shielding film 8 is n
It is open inside the edge of the mold region 33a. Therefore, the light incident surface of the photoelectric conversion element 33 is
3a is defined on the upper surface.

Therefore, between the light incident surface of the photoelectric conversion element 33 and the surface of the semiconductor substrate 2 around the photoelectric conversion element 33,
There are steps. Light incident surface of photoelectric conversion element 33 and transfer electrode 4
The lower surface of “b” is located on substantially the same plane.

In the solid-state imaging device 30 of this embodiment,
Reduction of smear is expected for the following reasons.

That is, even if the light incident from the microlens 13 is scattered, the upper surface of the photoelectric conversion element 33 and the surface of the semiconductor substrate 2 around the photoelectric conversion element 33 are positioned on substantially the same plane. In comparison, scattered light is less likely to enter between the transfer electrode 4b and the charge transfer channel 4a. As a result, reduction of smear is expected.

Next, FIG. 8A, FIG. 8B, FIG.
An example of a method for manufacturing the photoelectric conversion element 33 shown in FIG. 7 will be described with reference to (c) and FIG.

FIGS. 8A to 8D are cross-sectional views of a substrate for explaining main steps in manufacturing the photoelectric conversion element 33. FIG.

First, a p-type semiconductor epitaxial layer 2b (p-type well 2b) is formed on one surface of an n-type silicon substrate 2a.
Is formed to obtain the semiconductor substrate 2. A stacked film is formed by stacking a silicon oxide film having a thickness of, for example, about 0.02 μm and a silicon nitride film having a thickness of, for example, about 0.05 μm on the p-type well 2b in this order. . The thickness of the silicon oxide film constituting the laminated film is preferably, for example, 0.01 to 0.05 μm, and the thickness of the silicon nitride is, for example, preferably 0.02 to 0.1 μm.

A resist pattern having a predetermined shape is formed on the laminated film by a method such as photolithography. Then, the laminated film is dry-etched using the resist pattern as an etching mask.

As shown in FIG. 8A, the photoelectric conversion element 3
The mask laminated film 40 is left only on the portion where the layer 3 is to be formed. As described above, the laminated film 40 includes the silicon oxide film 40a and the silicon nitride film 40b formed thereon.

In forming the mask laminated film 40, a method such as wet etching can be applied instead of dry etching.

As shown in FIG. 8B, the exposed p
The surface of the mold well 2b is thermally oxidized to form a silicon oxide film 41.
To form The thickness of the silicon oxide film 41 is preferably, for example, about 0.02 to 0.1 μm.

As shown in FIG. 8C, the mask laminated film 40 is removed by a method such as wet etching or dry etching. The surface of the p-type well 2b covered with the mask laminated film 40 is exposed.

As shown in FIG. 8D, an impurity serving as a donor is implanted into the p-type well 2b by ion implantation using the silicon oxide film 41 as a mask, and then heat-treated to form an n-type for a photoelectric conversion element. The region 33a is formed. At this time, an impurity serving as a donor is injected into a region covered with the mask stack film 40. n-type region 33a
The photoelectric conversion element 33 whose upper surface protrudes from the surface of the surrounding semiconductor substrate 2 is obtained. Thereafter, the silicon oxide film 41
Is removed by, for example, wet etching.

After the photoelectric conversion element 33 is manufactured as described above, the channel stop 5 and the charge transfer channel 4a for the charge transfer path 4 are formed. Thereafter, similarly to the first embodiment, the electric insulating film 6, the transfer electrode 4b, the electric insulating film 7, the light shielding film 8, the focus adjusting layer 9, the color filter 11, the second
Are sequentially formed.

Next, a modification of the second embodiment will be described with reference to FIG.

FIG. 9 shows C according to a modification of the second embodiment.
FIG. 3 is a cross-sectional view schematically illustrating a CD-type solid-state imaging device 30a.

In the solid-state imaging device 30a of this modification, a dish-shaped recess is formed in the n-type region 33a of the photoelectric conversion element 33.
The difference from the solid-state imaging device 30 of the second embodiment is that the surface of the concave portion is a light incident surface. Other points are the same as those of the solid-state imaging device 30 of the second embodiment.

Therefore, among the constituent members and locations shown in FIG. 9, those corresponding to the constituent members or locations shown in FIG. 7 are denoted by the same reference numerals as those used in FIG. Omitted.

As shown in FIG. 9, the n-type region 33a of the photoelectric conversion element 33 has the same vertical sectional shape as the n-type region 3a of the photoelectric conversion element 3 in the solid-state imaging device 1 of the first embodiment. have. The bottom surface of the dish-shaped recess formed in the n-type region 33 a is located on substantially the same plane as the surface of the semiconductor substrate 2 around the photoelectric conversion element 33. The upper surface of the edge of the photoelectric conversion element 33 protrudes from the surface of the semiconductor substrate 2 around the photoelectric conversion element 33.

The outline in plan view of the opening 8a formed in the light shielding film 8 substantially coincides with the outline in plan view of the dish-shaped recess formed in the n-type region 33a. Therefore, there is a step between the light incident surface of the photoelectric conversion element 33 and the surface of the semiconductor substrate 2 around the photoelectric conversion element 33. The edge of the photoelectric conversion element 33 is covered with the light shielding film 8 in plan view.

In the illustrated solid-state imaging device 30a, reduction of smear is expected for the same reason as in the solid-state imaging device 30 of the second embodiment. Further, for the same reason as in the solid-state imaging device 1 of the first embodiment, reduction of smear is expected.

The solid-state imaging device 30a shown in FIG. 9 can be manufactured in the same manner as the solid-state imaging device 30 of the second embodiment except that the photoelectric conversion element 33 is manufactured as follows.

First, a multilayer film 40 for a mask is formed on a semiconductor substrate 2 in the same manner as in the case of manufacturing the photoelectric conversion element 33 shown in FIG. 7 (see FIG. 8). At this time, FIG.
As in the step shown in FIG. 3A, a through hole for forming a dish-shaped recess in the p-type well 2b is provided in the laminated film 40. The planar shape of the stacked film 40 corresponds to the planar shape of the edge of the photoelectric conversion element 33 to be manufactured.

Next, using the laminated film 40 as a mask, an impurity serving as a donor is implanted into the p-type well 2b by ion implantation. An impurity implantation region is formed in p-type well 2b.

The surface of the p-type well 2b exposed from the through hole of the laminated film 40 and the p-type well 2 around the laminated film 40
b The surface is thermally oxidized to form a silicon oxide film. At this time, the ion-implanted impurities are activated, and an n-type region 33a for the photoelectric conversion element 33 is formed.

The silicon oxide film formed on n-type region 33a and the silicon oxide film around laminated film 40 are removed by wet etching. Further, the laminated film 40 is removed by a method such as wet etching or dry etching. The intended photoelectric conversion element 33 is obtained.

Next, a third embodiment will be described with reference to FIG.

FIG. 10 is a sectional view schematically showing a CCD type solid-state imaging device 50 according to the third embodiment.

The solid-state imaging device 50 of this embodiment is different from the solid-state imaging device 50 in that the light incident surface of the photoelectric conversion element 53 is located on substantially the same plane as the surface of the semiconductor substrate 2 around the photoelectric conversion element 53.
It has a common point with the solid-state imaging device 30a shown in FIG. However, the solid-state imaging device 30a shown in FIG. 9 is different from the solid-state imaging device 30a shown in FIG. 9 in that a concave portion that is recessed from the surface of the semiconductor substrate 2 around the photoelectric conversion element 53 is formed at the edge of the photoelectric conversion element 53 in plan view. Other points are the same as those of the solid-state imaging device 30a.

Therefore, of the components and locations shown in FIG. 10 corresponding to the components and locations shown in FIG. 9, except for the photoelectric conversion element and its n-type region, respectively, The same reference numerals are given to the same reference numerals, and the description is omitted.

As shown in FIG. 10, the photoelectric conversion element 53
N-type region 53a includes a flat portion having a surface substantially on the same plane as the surface of semiconductor substrate 2 around photoelectric conversion element 53. The outer periphery of this flat portion is a concave portion that is recessed from the surface of the semiconductor substrate 2.

The outline in plan view of the opening 8a formed in the light shielding film 8 substantially matches the outline in plan view of the flat portion in the n-type region 53a. Therefore, the photoelectric conversion element 5
There is a step between the light incident surface 3 and the surface of the semiconductor substrate 2 around the photoelectric conversion element 53. The edge portion (outer periphery of the flat portion) of the photoelectric conversion element 53 is covered with the light shielding film 8 in plan view.

In the illustrated solid-state imaging device 50, a concave portion is formed on the outer periphery of the light incident surface of the photoelectric conversion element 53, and the light shielding film 8 enters the concave portion. Even if the light is scattered, the scattered light hardly enters between the transfer electrode 4b and the charge transfer channel 4a.
As a result, reduction of smear is expected.

The solid-state imaging device 50 shown in FIG. 10 can be manufactured in the same manner as the solid-state imaging device 1 of the first embodiment, except that the photoelectric conversion element 53 is manufactured, for example, as follows.

First, the n-type region 53a of the photoelectric conversion element 53
A mask pattern having a through-hole at a position where a is to be formed is formed on the semiconductor substrate 2, and in this state, an impurity serving as a donor is implanted into the p-type well 2b by an ion implantation method. An impurity implantation region is formed in p-type well 2b.
The mask pattern is removed. Next, similarly to the step shown in FIG. 8A, a laminated film 40 having a predetermined shape is formed on the semiconductor substrate 2. This laminated film 40 is formed by n of the photoelectric conversion element 53.
It has an annular through hole corresponding to the position and shape in plan view of the concave portion to be formed in the mold region 53a.

The surface of the impurity-implanted region exposed from the through hole of the laminated film 40 is thermally oxidized to form a silicon oxide film. At this time, the ion-implanted impurity is activated, and an n-type region 53a for the photoelectric conversion element 53 is formed.

The silicon oxide film formed on n-type region 53a is removed by wet etching. Further, the laminated film 40 is removed by a method such as wet etching or dry etching. Desired photoelectric conversion element 5
3 is obtained.

Each of the solid-state imaging devices 1, 1a, 1
b, 1c, 30, 30a, 50 are area image sensors used in video cameras, electronic still cameras, etc.
Alternatively, it can be used for a line sensor used in a copying machine, a facsimile machine, or the like.

Next, an embodiment of the solid-state imaging device for an area sensor will be described with reference to FIG.

FIG. 11 is a plan view schematically showing an example of a plane arrangement of main members in the solid-state imaging device 100 for an area sensor provided with the photoelectric conversion element 3 shown in FIG.
Among the components and locations shown in the figure, those corresponding to the components and locations shown in FIG. 1 are denoted by the same reference numerals as those used in FIG. 1, and description thereof will be omitted. In FIG. 11, illustration of a microlens array, a second planarizing film, a color filter array, a focus adjusting layer, a protective layer, an electric insulating film formed on a semiconductor substrate surface, a channel stop region, and the like is omitted. I have.

The solid-state imaging device 100 shown in FIG.
A predetermined number of photoelectric conversions formed in a row on one surface of the body substrate 2
Photoelectric conversion element group 6 composed of elements (photodiodes) 3
0 has a plurality of groups. Photoelectric conversion element group shown
The number of 60 is 3 groups in total including those partially shown
It is. Each of the photoelectric conversion element groups 60 has a fixed direction D _V 
(Indicated by an arrow in FIG. 11). Elia Sen
In the entire solid-state imaging device 100, the number of photoelectric conversion elements
Child 3 is a square matrix (including those with different numbers of rows and columns)
No. ).

Each of the photoelectric conversion elements 3 constituting the photoelectric conversion element group 60 has an n-type region 3a (see FIG. 1) having a rectangular shape in plan view.

In an actual solid-state imaging device for an area sensor, the total number of photoelectric conversion elements 3 is, for example, several hundred thousand to several hundreds.
Reach ten thousand.

One charge transfer channel 4a per group of photoelectric conversion element groups 60 is formed on the left side of the corresponding photoelectric conversion element group 60 in the drawing. Individual charge transfer channel 4a extends in a direction D _V.

For one photoelectric conversion element row, one transfer-only transfer electrode 4b and one read-only transfer electrode 4c are alternately formed one by one in this order from the upstream side.

Here, in this specification, the movement of electric charges in the electric charge transfer path is regarded as one flow, and the relative positions of the individual members and the like are set to “any upstream”, It shall be specified as "any downstream".

On the downstream side of the most downstream photoelectric conversion element row,
One auxiliary transfer electrode 4d is formed.

Each of transfer electrodes 4b, 4c and 4d extends in the row direction (indicated by arrow _DH in the figure).

[0152] Each of the transfer forwarding electrodes 4b are each intersection of a plan view of the charge transfer channel 4a, has a rectangular transfer stage forming part 4b ₁ projecting to the downstream side. The same applies to the auxiliary transfer electrode 4d. The transfer stage forming part of the auxiliary transfer electrodes 4d that transfer stage forming section 4d _1.

Each of the read-out / transfer electrodes 4c is provided at each intersection of each charge transfer channel 4a in plan view.
The rectangular transfer stage forming part 4c ₁ projecting to the upstream side has.

Each transfer-only transfer electrode 4b and auxiliary transfer electrode 4d are made of, for example, a second polysilicon layer. Each read / transfer electrode 4c is made of, for example, a first polysilicon layer. The transfer electrode made of the first polysilicon layer and the transfer electrode made of the second polysilicon layer are electrically connected to each other by a surface oxide film (silicon oxide film) formed on the transfer electrode made of the first polysilicon layer. Insulated.

Arranged on one charge transfer channel 4a
Transfer stage forming unit 4b₁ , 4c ₁ Are respectively
A charge transfer stage together with the load transfer channel 4a.
You. The electric charge lined up along one charge transfer channel 4a
Each of the load transfer stages includes one charge transfer path 4 composed of a CCD.
Is configured. Each of the charge transfer paths 4 is, for example, driven in four phases.
It is.

The read gate region, which is a part of the p-type well 2b (see FIG. 1), corresponds to the n-type region 3 of the photoelectric conversion element 3.
a (see FIG. 1) and the charge transfer channel 4a. Individual readout gate region is covered in a plan view by the transfer step formation 4c ₁ in the read combined transfer electrode 4c.

A drive pulse for charge transfer is applied to the read / transfer electrode 4c, and a read pulse for reading signal charges from the photoelectric conversion element 3 to the charge transfer path 4 is applied to the read / transfer electrode 4c. Portion which covers a plan view of the readout gate region in each transfer stage forming part 4c ₁ serves as the readout gate electrode. This part, hereinafter referred to as the readout gate electrode 4c _2. The readout gate electrode 4c ₂ the readout gate region thereunder, constituting the readout gate.

[0158] In Figure 11, hatched individual readout gate electrode 4c _2, are easy understanding readout gate electrode 4c _2.

[0159] The downstream end of each charge transfer path 4 is connected to an output transfer path 70 composed of, for example, a two-phase drive type CCD.

An output section 80 is connected to one end of the output transfer path 70.

A light shielding film 8 having one rectangular opening 8 a above each photoelectric conversion element 3 covers each photoelectric conversion element 3 and each charge transfer path 4. The light shielding film 8 covers almost all of the individual transfer electrodes 4b, 4c, 4d, almost all of the output transfer path 7, and almost all of the output section 80.

In the illustrated solid-state imaging device 100, signal light is accumulated in the photoelectric conversion element 3 when light enters the photoelectric conversion element 3 through the opening 8 a of the light shielding film 8. When a read pulse is applied to the read / transfer electrode 4c, the signal charges stored in the photoelectric conversion element 3 are read to the charge transfer path 4 via the read gate.
The read pulse is applied to every other read / transfer electrode 4.
c are simultaneously applied. That is, the solid-state imaging device 100
Are interlaced.

The signal charge read out to the charge transfer path 4 is
By driving the charge transfer path 4, for example, in four phases, the charge transfer stages are sequentially transferred to the output transfer path 70.

The signal charge transferred to the output transfer path 70 is
For example, by driving the output transfer path 70 in two phases, the charge transfer stages in the output transfer path 70 are sequentially transferred to the output unit 80.

The output section 80 converts the signal charge sent from the output transfer path 70 into a signal voltage by, for example, a floating capacitor (not shown), and converts this signal voltage to, for example, a source follower circuit (not shown). Amplify using. The charge after detection (conversion) is absorbed by a power supply (not shown) via a reset transistor (not shown).

Illustrated solid-state imaging device 1 for area sensor
00 has the photoelectric conversion element 3 shown in FIG. Therefore, reduction of smear can be expected for the same reason as described in the description of the first embodiment.

Next, a modification of the solid-state imaging device for an area sensor will be described with reference to FIG.

FIG. 12 is a partially enlarged plan view schematically showing an area sensor solid-state imaging device 100a according to this modification.

The solid-state image pickup device 100a for area sensor shown in the figure includes (i) the point that the individual photoelectric conversion elements 3 are "pixel-shifted" and (2) the transfer electrodes 4b,
4c has a meandering shape.
This is different from the sensor solid-state imaging device 100. Other points are the same as those of the solid-state imaging device for area sensor 100. For this reason, among the components and locations shown in FIG.
11 correspond to those shown in FIG.
The same reference numerals are used as those used in, and the description is omitted.

Here, the “pixel shift arrangement” referred to in this specification means that each of the photoelectric conversion elements 3 forming the odd-numbered photoelectric conversion element group 60 corresponds to each of the even-numbered photoelectric conversion element groups 60. Each of the photoelectric conversion elements 3 is about の of the pitch P ₁ between the photoelectric conversion elements 3 in each photoelectric conversion element group 60 (see FIG. 12), and the arrangement direction of the photoelectric conversion elements in the photoelectric conversion element group. D _V (see FIG. 12), each of the photoelectric conversion elements 3 constituting the odd-numbered photoelectric conversion element rows is different from each of the photoelectric conversion elements 3 constituting the odd-numbered photoelectric conversion element rows. The pitch P ₂ (see FIG. 12) between the photoelectric conversion elements 3 in the element row is about 1
/ 2, shifted in the row direction D _H (refer to FIG. 12), which means an arrangement of photoelectric conversion element groups in which each of the photoelectric conversion element groups 60 includes only the odd-numbered or even-numbered row of photoelectric conversion elements 3.

[0171] In addition, "about one half of the pitch P ₁ between the photoelectric conversion element", in addition to containing a P _1/2, the manufacturing error, the cause rounding errors such pixel location occurring on design or mask fabrication although the out of the P _1/2, is intended to include a value that can be regarded as substantially equivalent to P _1/2 when viewed from the image quality of the performance and the image of the solid-state imaging device obtained. The same applies to “approximately の of the pitch P ₂ between photoelectric conversion elements” in this specification.

As shown in FIG. 12, in the solid-state imaging device for area sensor 100a, when the transfer electrode 4b and the read-only transfer electrode 4c adjacent to each other cross one certain photoelectric conversion element group 60, Overlap each other. When crossing the photoelectric conversion element group 60 adjacent to the photoelectric conversion element group 60, they are separated from each other and surround one of the photoelectric conversion elements 3 constituting the photoelectric conversion element group 60 in plan view.

The adjacent transfer-only transfer electrode 4b and read-out transfer electrode 4c extend in the direction _DH as a whole while repeating the above separation.

Although not shown, the solid-state imaging device for area sensor 100a includes an output transfer path 70 and an output section 80 (see FIG. 11), similarly to the solid-state imaging device for area sensor 100 shown in FIG. Have.

Next, an embodiment of a solid-state imaging device for a line sensor will be described with reference to FIG.

FIG. 13 is a plan view schematically showing an example of a plane arrangement of main members in the solid-state imaging device 110 for a line sensor provided with the photoelectric conversion element 3 shown in FIG.
Among the components or locations shown in FIG. 1, those corresponding to the components or locations shown in FIG. 1 or FIG. 11 are given the same reference numerals as those used in FIG. 1 or FIG.
The description is omitted.

The line sensor solid-state imaging device 110 shown in FIG. 13 is a solid-state imaging device for black-and-white imaging. Therefore, no color filter array is provided. Further, the microlens array is also an optional component and is not shown. When a microlens is not used, the planarizing film and the focusing layer are also optional components.

The solid-state imaging device 110 shown in the figure has one photoelectric conversion element group 60 composed of a predetermined number of photoelectric conversion elements (photodiodes) 3 formed in a row on one surface side of the semiconductor substrate 2. ing. The number of the illustrated photoelectric conversion elements 3 is a total of five including those partially shown.

In an actual line sensor for monochrome image capturing,
For example, one photoelectric conversion element array including one or two groups of photoelectric conversion element groups is formed. In a line sensor for color imaging, for example, one or three rows of photoelectric conversion elements, each of which includes one or two groups of photoelectric conversion elements, are formed. The total number of photoelectric conversion elements is, for example, about 1000 to 20,000.

When a predetermined number of photoelectric conversion elements are divided into two groups and arranged in a line, for example, each of the odd-numbered photoelectric conversion elements constitutes one group, and each of the even-numbered photoelectric conversion elements constitutes another group. Constitute a group.

The solid-state imaging device 1 for a line sensor shown in the figure
In 10, a transfer channel 4a is formed near the photoelectric conversion element group 60 on the left side in the figure. The charge transfer channel 4a extends in a certain direction D _V (indicated by an arrow in FIG. 13).

A total of two transfer electrodes 4e and a total of two transfer electrodes 4f are alternately formed for one photoelectric conversion element 3 in this order from the upstream side.

Each of the transfer electrodes 4e shown is made of, for example, a first polysilicon layer, and each of the transfer electrodes 4f is made of, for example, a second polysilicon layer. The adjacent transfer electrodes 4e and 4f are electrically insulated from each other by a surface oxide film (silicon oxide film) formed on the surface of the transfer electrode 4e. Each transfer electrode 4e, 4f is a charge transfer channel 4 in plan view.
a.

The charge transfer channel 4a and each transfer electrode 4e,
4f constitutes the CCD type charge transfer path 4. One transfer electrode 4e and the underlying charge transfer channel constitute one potential barrier region, and one transfer electrode 4f and the underlying charge transfer channel constitute one potential well region.

The illustrated charge transfer path 4 is composed of, for example, a two-phase drive type CCD. At this time, the transfer electrodes 4e and 4f on the upstream side corresponding to the individual photoelectric conversion elements 3 form a set and are electrically connected to one current terminal. Also,
Downstream transfer electrode 4 corresponding to each photoelectric conversion element 3
e and 4f form a set and are electrically connected to another current terminal. One potential barrier region and one potential well region immediately downstream thereof are simultaneously driven.

Each photoelectric conversion element 3 and charge transfer channel 4a
One readout gate electrode 90a is formed for each photoelectric conversion element 3 in plan view. An end of each read gate electrode 90a on the side of the charge transfer channel 4a is overlapped with a separate transfer electrode 4f in plan view.

Each of the read gate electrodes 90a is composed of a part of one read gate electrode line 90. The read gate electrode line 90 is made of, for example, a first polysilicon layer. A surface oxide film (silicon oxide film) is formed on the surface of the readout gate electrode line 90.

Each read gate electrode 90a, together with the underlying p-type well 2b (see FIG. 1), constitutes one read gate.

A single drain region 91 is formed near the photoelectric conversion element group 60 on the right side in the figure.
Discharge drain region 91 extends in a strip shape in the direction D _V.

One sweeping gate electrode line 92 is provided between each photoelectric conversion element 3 and the draining drain region 91 in plan view. Swept gate electrode line 92
Extend in strip shape in the direction D _V. The discharge gate electrode line 92 is made of, for example, a first polysilicon layer. A surface oxide film (silicon oxide film), not shown, is formed on the surface of the sweep gate electrode line 92.

The discharged drain region 91 and the discharged gate electrode line 92 constitute a horizontal overflow drain together with the semiconductor substrate 2.

The output section 80 is connected downstream of the charge transfer path 4.

A light shielding film 8 having one rectangular opening 8 a is formed above each photoelectric conversion element 3 so as to cover each photoelectric conversion element 3, charge transfer channel 4 a and draining drain region 91. I have. The light shielding film 8 covers almost all of the individual transfer electrodes 4e and 4f, almost all of the output section 80, almost all of the readout gate electrode line 90, and almost all of the sweeping gate electrode line 92. .

The illustrated solid-state imaging device 1 for a line sensor
In 10, light is incident on the photoelectric conversion element 3 through the opening 8 a of the light shielding film 8, so that signal charges are accumulated in the photoelectric conversion element 3. When a read pulse is applied to the read gate electrode line 90, the signal charges stored in each photoelectric conversion element 3 are simultaneously read out to the charge transfer path 4 via the corresponding read gate.

The signal charge read out to the charge transfer path 4 is
The charge transfer path 4 is transferred to the output unit 80 by, for example, driving the charge transfer path 4 in two phases.

The output section 80 converts the signal charge sent from the charge transfer path 4 into a signal voltage using, for example, a floating capacitor (not shown), and converts this signal voltage into, for example, a source follower circuit (not shown). Amplify using. The charge after detection (conversion) is absorbed by a power supply (not shown) via a reset transistor (not shown).

The illustrated solid-state imaging device 1 for a line sensor
Reference numeral 10 includes the photoelectric conversion element 3 shown in FIG. Therefore, reduction of smear can be expected for the same reason as described in the description of the first embodiment.

Although the solid-state imaging device according to the embodiment has been described above, the present invention is not limited to the above-described embodiment. It will be apparent to those skilled in the art that various modifications, improvements, combinations, and the like can be made.

[0199] For example, a photoelectric conversion element (photodiode) is, n in n-type silicon substrate ^- -type region, p-type region,
It can also be manufactured by sequentially forming an n ⁻ type region and an n type region. Such a photoelectric conversion element,
For example, it can be obtained as follows. First, an n-type semiconductor epitaxial layer is formed on an n-type silicon substrate. Next, a p-type impurity is implanted into the epitaxial layer by a high energy ion implantation method. An n ⁻ -type region, a p-type region, and an n ⁻ -type region are formed in this order on an n-type silicon substrate. Thereafter, the uppermost the n ^- n-type region is formed at a predetermined position of the mold area, to obtain a photoelectric conversion element of interest. n
^- impurity concentration in the type region is lower than the impurity concentration in the n-type region.

[0200] A photoelectric conversion element can also be manufactured by forming an n-type region on a p-type silicon substrate.

Furthermore, a photoelectric conversion element (photodiode) can also be obtained by forming a desired semiconductor layer on the surface of an electrically insulating substrate and forming a predetermined impurity region in this semiconductor layer.

In the present specification, the term “semiconductor substrate” also includes a substrate made of a material other than a semiconductor and provided with a semiconductor layer for forming a photoelectric conversion element (photodiode), a charge transfer channel, and the like on one surface. Shall be

When the photoelectric conversion element is a photodiode, the photodiode can be embedded. For example, an n-type region is formed in a p-type well,
By forming the p ⁺ -type layer on the surface of the mold region, a buried photodiode can be obtained.

In each of the examples, a predetermined portion of the p-type well was thermally oxidized to form a photoelectric change element having a step between the surrounding semiconductor substrate surface and the light incident surface. The step can also be formed by, for example, forming a film having a predetermined shape serving as an etching stopper on an n-type silicon substrate in advance and then directly etching the n-type silicon substrate.

The driving method of the charge transfer path is not limited to the driving method described in the embodiment. The driving method is
It can be appropriately selected according to the intended use of the solid-state imaging device. The same applies to the output transfer path.

In the solid-state imaging device of each embodiment, a photoelectric conversion element (photodiode) is formed on a p-type well formed on an n-type semiconductor substrate. Therefore,
In these solid-state imaging devices, a vertical overflow drain structure can be provided. Accordingly, an electronic shutter can be additionally provided. In order to attach a vertical overflow drain structure to the solid-state imaging device of each embodiment, a p-type well formed in the semiconductor substrate and a lower portion of the n-type semiconductor substrate constituting the semiconductor substrate (a region below the p-type well) are required. ) Is added to allow a reverse bias voltage to be applied. By providing the overflow drain structure, blooming can be easily suppressed.

The solid-state imaging device is not limited to a CCD-type solid-state imaging device, but may be a MOS-type solid-state imaging device. As described above, the MOS-type solid-state imaging device includes a plurality of photoelectric conversion elements, a switching element (for example, a transistor) provided for each photoelectric conversion element, and a predetermined number of output signal lines connected thereto. Have.
With the operation of the switching element, an electric signal corresponding to the signal charge amount accumulated in the photoelectric conversion element is generated on a predetermined output signal line.

In addition, various changes, improvements, combinations, and the like can be made.

[0209]

As described above, according to the present invention,
It is possible to reduce smear in a solid-state imaging device such as a CCD type or a MOS type. Accordingly, it is possible to improve the performance of the solid-state imaging device.

Furthermore, since the surface of the photoelectric conversion element and the surface of the semiconductor substrate around the photoelectric conversion element are three-dimensionally arranged, the degree of freedom in designing the solid-state imaging device is also increased to three dimensions. For example,
The distance between the microlens and the photoelectric conversion element is adjusted not only by the thickness of the focus adjustment layer but also by the size of the step between the light incident surface of the photoelectric conversion element and the surface of the surrounding semiconductor substrate. Becomes possible.

[Brief description of the drawings]

FIG. 1 is a cross-sectional view schematically illustrating a solid-state imaging device according to a first embodiment.

FIGS. 2A to 2D are cross-sectional views of a substrate for describing main manufacturing steps of the photoelectric conversion element shown in FIG. 1;

FIG. 3 is a cross-sectional view schematically illustrating a solid-state imaging device according to a modification of the first embodiment.

FIG. 4 is a cross-sectional view schematically illustrating a solid-state imaging device according to another modification of the first embodiment.

5A illustrates an example of a reflection path when scattered light is incident at a small incident angle between a lower surface of a light shielding film and a surface of a photoelectric conversion element of the solid-state imaging device illustrated in FIG. 4; FIG. 5B is a cross-sectional view illustrating a reflection path when scattered light is incident at a large incident angle between the lower surface of the light shielding film and the surface of the photoelectric conversion element of the solid-state imaging device illustrated in FIG. It is sectional drawing which shows an example.

FIG. 6 is a sectional view schematically showing a solid-state imaging device according to still another modification of the first embodiment.

FIG. 7 is a cross-sectional view schematically illustrating a solid-state imaging device according to a second embodiment.

8 (a) to 8 (d) are cross-sectional views of a substrate for describing main manufacturing steps of the photoelectric conversion element shown in FIG. 7;

FIG. 9 is a cross-sectional view schematically illustrating a solid-state imaging device according to a modification of the second embodiment.

FIG. 10 is a sectional view schematically showing a solid-state imaging device according to a third embodiment.

FIG. 11 is a plan view schematically showing a solid-state imaging device for an area sensor according to an embodiment.

FIG. 12 is a plan view schematically showing a solid-state imaging device for an area sensor according to a modification.

FIG. 13 is a plan view schematically illustrating a solid-state imaging device for a line sensor according to an embodiment.

[Explanation of symbols]

1, 1a, 1b, 1c, 30, 30a, 50: solid-state imaging device, 2: semiconductor substrate, 2a: n-type silicon substrate,
2b: p-type well; 3, 33, 53: photoelectric conversion element (photodiode); 3a, 33a, 53a: n-type region of photoelectric conversion element (photodiode); 4: charge transfer path; 4a: charge transfer channel; 4b, 4c, 4
e, 4f transfer electrode, 4d, 90a readout gate electrode, 8 light shielding film, 11 color filter, 13 microlens, 70 output transfer path, 80 output section,
90 ... Reading gate electrode line, 100, 100a
... solid-state imaging device for area sensor, 110 ... line
Solid-state imaging device for sensors.

 ──────────────────────────────────────────────────続 き Continued on the front page F term (reference) 4M118 AA05 AB01 BA08 BA10 BA11 BA14 CA03 CA04 DB03 DB06 DB08 FA06 FA08 FA13 FA35 GB03 GB07 GB11 GC08 GD04 GD07 5C024 CX13 CY48 CY49 EX43 GX03 GZ34 GZ36

Claims (5)

[Claims] 1. A photoelectric conversion element formed on one surface side of a semiconductor substrate, wherein a step is formed between a light incident surface of the photoelectric conversion element surface and the semiconductor substrate surface around the photoelectric conversion element. A light-shielding film formed above the photoelectric conversion element and having an opening on the light incident surface, formed near the photoelectric conversion element, and accumulated in the photoelectric conversion element. A solid-state imaging device having a charge transfer path for transferring signal charges. 2. The solid-state imaging device according to claim 1, wherein the light incident surface is recessed from a surface of the semiconductor substrate around the photoelectric conversion element. 3. The solid-state imaging device according to claim 1, wherein the light incident surface protrudes from a surface of the semiconductor substrate around the photoelectric conversion element. 4. The light incident surface is substantially on the same plane as the surface of the semiconductor substrate around the photoelectric conversion element, and the surface of the photoelectric conversion element around the light incident surface is recessed from the surface of the semiconductor substrate. The solid-state imaging device according to claim 1. 5. The light incident surface is substantially on the same plane as the surface of the semiconductor substrate around the photoelectric conversion element, and the surface of the photoelectric conversion element around the light incident surface protrudes from the surface of the semiconductor substrate. The solid-state imaging device according to claim 1.