JP2002110953A - Solid-state imaging device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a solid-state imaging device of high optical sensitivity, where the degree of convergence of the light which enters a light-receiving surface obliquely is increased and a received optical image can be converted into an electric signal with high efficiency. SOLUTION: This solid-state imaging device is provided with a photodiode 102 formed on a substrate 101, a first interlayer insulating film 105 formed on the photodiode 102, a second interlayer insulating film 109 which is formed on the first interlayer insulating film 105 and has a trench part 111 having a concave lens shape at a position on a light-receiving region of the photodiode 102, and a third interlayer insulating film 110 which is formed on the second interlayer insulating film 109 and has a refractive index larger than that of the second interlayer insulating film 109.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

[0001] 1. Field of the Invention [0002] The present invention relates to a solid-state imaging device, and more particularly to a solid-state imaging device having high light sensitivity capable of converting a received optical image into an electric signal with high efficiency.

[0002]

2. Description of the Related Art Solid-state imaging devices for obtaining image signals from optical images are used in video cameras, digital cameras, and the like, and in recent years, further miniaturization has been required.

[0003] Solid-state image sensors are mainly used as image sensors, and charge-coupled devices (CCs) are roughly classified into solid-state image sensors.
D) type and MOS type. Each of these sensors uses a photodiode as a light-electric conversion element, and when configuring a two-dimensional image input sensor,
A large number of micro-sized photodiodes are arranged in a matrix, and the entire photodiode arrangement surface of the matrix arrangement constitutes a light receiving surface. An optical image is formed on the light receiving surface, and an image signal for each pixel is obtained by each photodiode.

In the case of the CCD type, the image signal from each photodiode is transferred to a line register in units of a matrix line, and is shifted serially at a predetermined reading timing and output serially. In the case of the MOS type, an arbitrary line and an arbitrary column are activated by controlling a transistor switch provided for each pixel, and an image signal of the pixel is read.

[0005] The MOS type solid-state imaging device (image sensor) requires various wirings such as a signal output wiring, a row selection wiring, a power supply wiring, and a signal read driving wiring in an imaging area. The number of wirings in the imaging area is much larger than that of the CCD type, and the MOS type image sensor has many types of wiring, so it has a multi-layer layout, and the number of wiring layers is also required by the number of interlayer insulating films Becomes As the number of interlayer insulating films increases, the height from the photodiode to the uppermost upper surface of the interlayer insulating film increases.

FIG. 8 shows a structure of a conventional MOS type solid-state imaging device. Photodiode 8 on semiconductor substrate 801
02 is formed. The photodiode 802 forms an N-type channel region as a formation region of the photodiode 802 in a P-type well region formed on the semiconductor substrate 801 which is an N-type substrate;
The P-type channel region is formed in the N-type channel region. (Not shown)
Further, the semiconductor substrate 801 is provided with S
TI (Shallow Trench Isolati
on), an element isolation region 803 is formed,
A gate wiring 804 is formed thereon.

A first interlayer insulating film 8 using an insulating film such as SiO 2 is formed on the entire surface of the photodiode 802.
05, on which signal wiring 806 and power supply wiring 807 are provided.
Wiring layer 808 is formed. The wiring layer 80
A second interlayer insulating film 809 using an insulating film is further provided on the entire surface on the substrate 8. On the second interlayer insulating film 809,
A flattening film is formed, and a microlens is formed thereon. A solid-state imaging device (not shown) includes a solid-state imaging device including the photodiode 802, a transistor for reading out charges (accumulated in the photodiode 802 by light conversion), a transistor for amplifying a readout signal, and resetting signal charges. Transistors and the like are formed in the periphery (not shown) to constitute a unit cell. A large number of the unit cells are arranged in a two-dimensional matrix. Since each photodiode constitutes a unit pixel, in order to secure a signal level, it is necessary to guide 100% of the light arriving at the light-receiving surface of the unit pixel to convert the light into electricity and convert it into an image signal. There is.

[0008]

In the solid-state imaging device described above, each photodiode 8 has recently been required due to the demand for miniaturization.
The area of No. 02 is further miniaturized. Photodiode 8
When the area of 02 is reduced, the light 810 obliquely incident becomes difficult to enter the light receiving surface of the photodiode 802, and there is a problem that the light condensing degree is reduced.

When a large number of wirings are formed as in a MOS solid-state image pickup device, it is necessary to arrange the wirings in multiple layers, and an interlayer insulating film for the wiring layers is required for the number of wiring layers. The imaging device has a multilayer structure.

Further, a multilayer film may be formed according to a demand for miniaturization. When a multilayer film is formed, the photodiode 8
02, the height from the semiconductor substrate 801 on which the upper layer 02 is formed to the upper surface of the uppermost interlayer insulating film is increased, and light obliquely incident on the photodiode 802 There is a problem that it is difficult to enter the light receiving surface, and the degree of condensing is reduced.

SUMMARY OF THE INVENTION The present invention has been made to solve the above-mentioned problems, and has a structure in which obliquely incident light can be condensed more on a light receiving surface of a photodiode. It is intended to provide.

[0012]

According to a first aspect of the present invention, there is provided a solid-state imaging device, comprising: a photoelectric conversion element formed on a substrate; and a photoelectric conversion element formed on the photoelectric conversion element. Having a groove at a position on the light receiving area of the first
Formed on the first interlayer insulating film and the first interlayer insulating film;
A second interlayer insulating film having a refractive index larger than that of the first interlayer insulating film.

A photoelectric conversion element formed on the substrate, a first interlayer insulating film formed on the photoelectric conversion element, and a photoelectric conversion element formed on the first interlayer insulating film; A second interlayer insulating film having a groove at a position on the light receiving region, a third interlayer insulating film formed on the second interlayer insulating film and having a higher refractive index than the second interlayer insulating film. , Are provided.

A photoelectric conversion element formed on a substrate, a first interlayer insulating film formed on the photoelectric conversion element, and a second part having a groove at a position on a light receiving region of the photoelectric conversion element. And a third interlayer insulating film formed on the second interlayer insulating film and having a higher refractive index than the second interlayer insulating film.
And an insulating film structure comprising: an insulating film structure comprising: a plurality of the insulating film structures formed on the first interlayer insulating film;

Further, the groove portion is a concave lens-shaped arc-shaped groove portion.

According to the present invention, more light obliquely incident (light that has not conventionally entered the light receiving surface of the photodiode formed below and has not been able to contribute as a signal component) is collected on the light receiving surface. Can light.

Further, the groove is characterized in that its edge is a groove having an arc shape.

Alternatively, the groove is a groove having a substantially inverted triangular shape.

Further, the photoelectric conversion elements are photodiodes, and a plurality of the photoelectric conversion elements are two-dimensionally arranged on the substrate.

[0020]

Embodiments of the present invention will be described below in detail with reference to the drawings. (First Embodiment) A solid-state imaging device according to a first embodiment of the present invention will be described in detail with reference to FIG.

FIG. 1 shows a structure of a solid-state image sensor (image sensor) of a MOS type solid-state image sensor according to the present embodiment. In FIG. 1, a pixel including a photodiode 102 is formed on a semiconductor substrate 101. The photodiode 102 forms an N-type channel region as a formation region of the photodiode 102 in a P-type well region formed on the semiconductor substrate 101 which is an N-type substrate. It is configured by further forming a P-type channel region in the region. (Not shown) Also, an STI (Shallow Trench) is formed on the semiconductor substrate 101 by a trench technique.
(Isolation), an element isolation region 103 is formed, and a gate wiring 104 is formed thereon. The element isolation region 103 has a LOCOS (Loc
al Oxidation of Silicon).

On the entire surface of the photodiode 102, a first interlayer insulating film 1 using an insulating film such as SiO2 is formed.
05, on which the signal wiring 106 and the power wiring 107
Is formed. The wiring layer 10
A second interlayer insulating film 109 and a third interlayer insulating film 110 using an insulating film are further provided on the entire surface on the upper surface 8. The second
Is, for example, TEOS, and has a refractive index n
2 is 1.4. Further, the third interlayer insulating film 110 is, for example, SiH4, and the refractive index n3 is 1.5.

The refractive index n3 of the third interlayer insulating film 110
Is formed to be larger than the refractive index n2 of the second interlayer insulating film 109. That is, it is sufficient that n3> n2, and the constituent material is not particularly limited. In such a case, when light enters the substance n2 from the substance n3 according to Snell's law, the relational expression of θ3 <θ2 holds. The second interlayer insulating film 109 is formed on the photodiode 10
Groove 111 having a bottom at a position above the center of 2
(Dent) is formed thereon, and the third interlayer insulating film 1 is formed thereon.
10 have been deposited.

On the third interlayer insulating film 110, a filter or a flattening film such as SiO2 is formed, and a microlens is formed thereon. The solid-state imaging device (not shown) includes a solid-state imaging device including the photodiode 102 and a charge (the photodiode 10 is converted by light conversion).
A transistor for reading out (accumulated in 2), a transistor for amplifying a read signal, a transistor for resetting signal charges, and the like are formed in the periphery (not shown) to constitute a unit cell. A large number of the unit cells are arranged in a two-dimensional matrix.

Next, in the solid-state imaging device, of the manufacturing method, the second interlayer insulating film 109 having a depression is formed.
And a method of forming the third interlayer insulating film 110 formed thereon will be described with reference to FIG. First, FIG.
1A, a photodiode 102 and an element isolation region 103 are formed on a semiconductor substrate 101, and a gate wiring 104 is formed on the element isolation region. further,
A first interlayer insulating film 105 is formed on the substrate 101.

Next, as shown in FIG. 2B, a signal wiring 106 and a power wiring 107 are formed on the first interlayer insulating film 105.
Is formed. The wiring layer 108 includes
In order not to block incident light, the photodiode 1
It is not formed in the area above the reference numeral 02. The first interlayer insulating film 1
A second interlayer insulating film 109 made of TEOS (n2 = 1.4) is formed on the substrate 05. Subsequently, a resist pattern 201 having an opening near the center of the photodiode 102 is formed, and isotropic etching such as wet etching or chemical dry etching is performed, thereby forming a substantially arc-shaped groove 111 (dent). To form

Next, as shown in FIG. 2C, the resist pattern 201 is removed, and SiH4 (n3 = 1...) Is formed on the second interlayer insulating film 109 where the groove 111 is formed.
5) depositing a third interlayer insulating film 110 consisting of
(Chemical Mechanical Poli
(shing) process or etch-back process to planarize.

In the present embodiment, in the solid-state imaging device shown in FIG.
2 an interlayer insulating film (10
9 and 110), two-layer films having different refractive indices are used. Of the two-layer film, the lower interlayer insulating film has a lower refractive index than the upper interlayer insulating film, and has a concave lens-shaped groove 111 having a bottom at a position above the center of the photodiode 102. Depression) is formed. Therefore, the obliquely incident light 11
2 (conventionally, light that did not enter the light receiving surface of the photodiode formed below and could not contribute as a signal component) was converted from the photodiode 1 by Snell's law.
The light is refracted in a direction that allows the light to enter the area No. 02, and more light can be collected on the light receiving surface.

Since the groove 111 has a concave lens shape,
Light that is obliquely incident on a position outside the center of the groove 111 is refracted in a direction such that it is incident on the center of the photodiode 102, so that more light can be collected.

Therefore, by applying the present embodiment, it is possible to provide a solid-state imaging device capable of increasing the light condensing degree and obtaining a high-quality signal with high light sensitivity. Further, since the semiconductor device can be further miniaturized, a chip area can be formed small, and cost reduction, miniaturization, and low power consumption can be achieved.

As a first modification of the present embodiment, FIG.
As shown in the figure, even if the shape of the groove (depression) formed in the second interlayer insulating film 109 is formed as follows, the effect of the lens can be obtained similarly, and more light is collected. It becomes possible.

First, as shown in FIG. 4A, a photodiode 102 and an element isolation region 103 are formed on a semiconductor substrate 101, and a gate wiring 104 is formed on the element isolation region 103. Further, a first
Is formed.

Next, as shown in FIG. 4B, a signal wiring 106 and a power wiring 107 are formed on the first interlayer insulating film 105.
Is formed. The wiring layer 108 includes
In order not to block incident light, the photodiode 1
It is not formed in the area above the reference numeral 02. The first interlayer insulating film 1
A second interlayer insulating film 109 is formed on the substrate 05. The second
Is, for example, TEOS, and has a refractive index n
2 is 1.4.

The second interlayer insulating film 109 is formed on the wiring layer 10
8 is formed on the step-shaped insulating film, and thus the photodiode 1 without the wiring layer 108 is formed.
02 is formed in a shape as if a groove 301 was formed. The edge 302 of the groove 301 is rounded and has a substantially arc shape.

Next, as shown in FIG.
A third interlayer insulating film 110 is deposited on the second interlayer insulating film 109 on which 1 is formed, and is planarized by performing a CMP process or an etch-back process. The third interlayer insulating film 11
0 is SiN, and the refractive index n3 is 2.0. The third interlayer insulating film 110 is formed so that the refractive index n3 of the third interlayer insulating film 110 is higher than the refractive index n2 of the second interlayer insulating film 109. That is, it is sufficient that n3> n2, and the constituent material is not particularly limited.

Also in the first modification, a two-layer film having a different refractive index is used for the interlayer insulating films (109 and 110) between the wiring layers 108 provided above the photodiodes 102 constituting the image sensor. Of the two-layer film, the lower interlayer insulating film has a refractive index smaller than that of the upper interlayer insulating film, and has a groove 301 (dent) having a bottom above the center of the photodiode 102. Are formed.

Since the edge portion 302 of the groove portion 301 is rounded and formed into an arc shape, the obliquely incident light 112 (conventionally does not enter the light receiving surface of the photodiode formed below) due to the lens effect. , The light that could not contribute as a signal component) is refracted in a direction that makes it possible to enter the region of the photodiode 102 according to Snell's law, and more light is collected on the light receiving surface. It is a structure that can be done.

In the first modification, it is not necessary to perform an additional step when forming the groove, so that the groove 301 can be easily formed and more light can be collected. Therefore, similar effects can be obtained by applying the first modification.

Further, as a second modification of the present embodiment, as shown in FIG. 5, the shape of the groove 501 (dent) formed in the second interlayer insulating film 109 may be formed as follows. Similarly, the effect of the lens can be obtained, and more light can be collected.

First, as shown in FIG. 6A, a photodiode 102 and an element isolation region 103 are formed on a semiconductor substrate 101, and a gate wiring 104 is formed on the element isolation region 103. Further, a first
Is formed.

Next, as shown in FIG. 6B, a signal wiring 106 and a power supply wiring 107 are formed on the first interlayer insulating film 105.
Is formed. The wiring layer 108 includes
In order not to block incident light, the photodiode 1
It is not formed in the area above the reference numeral 02. The first interlayer insulating film 1
A second interlayer insulating film 109 is formed on the substrate 05. The second
The interlayer insulating film 109 is TEOS, and the refractive index n2 is 1.4.

Subsequently, a resist pattern 6 having an opening near the center of the photodiode 102 is formed.
RIE (Reactive Io) using a deposition gas so that a sidewall protective film is deposited on the sidewalls.
n Etching) to form the second interlayer insulating film 1
At 09, a groove 501 having a tapered side wall is formed. The groove 501 is formed to have a substantially inverted triangular shape having a bottom at a position above the center of the photodiode 102.

Next, as shown in FIG.
A third interlayer insulating film 110 is deposited on the second interlayer insulating film 109 on which 1 is formed, and is planarized by performing a CMP process or an etch-back process. The third interlayer insulating film 11
0 is SiN, and the refractive index n3 is 2.0. The third interlayer insulating film 110 is formed so that the refractive index n3 of the third interlayer insulating film 110 is higher than the refractive index n2 of the second interlayer insulating film 109. That is, it is sufficient that n3> n2, and the constituent material is not particularly limited.

Also in the second modification, a two-layer film having a different refractive index is used as the interlayer insulating film (109 and 110) on the wiring layer 108 provided above the photodiode 102 constituting the image sensor. Of the two-layer film, the lower interlayer insulating film has a smaller refractive index than the upper interlayer insulating film,
A groove 501 (dent) having a bottom is formed above the center of the photodiode 102.

Therefore, due to the effect of the lens, the obliquely incident light 112 (light which has not conventionally entered the light receiving surface of the photodiode formed below and has not been able to contribute as a signal component) is transmitted by the Snell. According to the law, the light is refracted in a direction that allows the light to enter the region of the photodiode 102, and more light can be collected on the light receiving surface. Therefore, similar effects can be obtained by applying the second modification.

The first embodiment and its modifications have been described above. However, the present invention is not limited to the device having the structure described in the embodiment, and it is needless to say that the present invention can be implemented with various devices. .

As shown in FIG. 7, a wiring layer 108 is further formed on the third interlayer insulating film 110 and the first
The same two-layer film structure as any one of the second interlayer insulating film 109 and the third interlayer insulating film 110 described in the embodiment and the modification thereof (the first embodiment in the figure). From the fourth interlayer insulating film 701 and the fifth interlayer insulating film 70
2, it may be further formed thereon.

At this time, similarly to the two-layer film of the second interlayer insulating film 109 and the third interlayer insulating film 110, for example, the fourth interlayer insulating film 701 has a refractive index n4 of 1.4. The fifth interlayer insulating film 702 is made of SiN having a refractive index n5 of 2.0. The fifth
Is formed such that the refractive index n5 of the interlayer insulating film 702 is larger than the refractive index n4 of the fourth interlayer insulating film 701. That is, it is sufficient that n5> n4, and the constituent material is not particularly limited.

A plurality of the two-layer film structures can be formed according to a demand for a multilayer film. As described above, even if the wiring layer is formed into a two-layer film or a three-layer film, the light 112 obliquely incident on the wiring layer (conventionally does not enter the light receiving surface of the photodiode formed below) due to the effect of the lens. , Which could not contribute as a signal component) can be focused on the light receiving surface.

As an example of the solid-state imaging device, a MOS
Although the type of image sensor has been described as an example, the present invention is applicable to image sensors in general. Also, the photodiode is used as a light receiving element for photoelectric conversion,
The light-receiving element can be formed on a semiconductor substrate, and is not limited to a photodiode. The invention is not limited to a two-dimensional image sensor, and may be a one-dimensional image sensor (line sensor).

[0051]

As described above in detail, in the solid-state imaging device of the present invention, a two-layer film having a different refractive index is used as an interlayer insulating film between wiring layers provided above a photodiode constituting an imaging device. Of the two-layer film, the interlayer insulating film formed below has a low refractive index, and has a concave lens-shaped groove (dent) having a bottom at a position above the center of the photodiode. Since an interlayer insulating film having a large (relatively large) refractive index is deposited thereon, light obliquely incident on the light receiving surface (conventionally, a light incident on a light receiving surface of a photodiode formed below) is formed by the effect of the lens. Light that could not contribute as a signal component) can be collected more on the light receiving surface.

As described above, since the degree of light collection can be further increased, it is possible to provide a solid-state imaging device capable of obtaining a high-quality signal with high light sensitivity. Further, since the semiconductor device can be further miniaturized, a chip area can be formed small, and cost reduction, miniaturization, and low power consumption can be achieved.

[Brief description of the drawings]

FIG. 1 is a fragmentary cross-sectional view showing a partial structure of a solid-state imaging device according to a first embodiment of the present invention;

FIG. 2 is a fragmentary cross-sectional view showing some steps of a method for manufacturing the solid-state imaging device according to the first embodiment of the present invention.

FIG. 3 is a fragmentary cross-sectional view illustrating a structure of a part of a solid-state imaging device according to a first modification of the first embodiment of the present invention.

FIG. 4 is a fragmentary cross-sectional view showing some steps of a method for manufacturing a solid-state imaging device according to a first modification of the first embodiment of the present invention.

FIG. 5 is a fragmentary cross-sectional view showing a partial structure of a solid-state imaging device according to a second modification of the first embodiment of the present invention;

FIG. 6 is an essential part cross sectional view showing some steps of a method for manufacturing a solid-state imaging device according to a second modification of the first embodiment of the present invention.

FIG. 7 is a fragmentary cross-sectional view showing a partial structure of the solid-state imaging device according to the first embodiment of the present invention;

FIG. 8 is a cross-sectional view of a main part showing a partial structure of a conventional solid-state imaging device.

[Explanation of symbols]

101: semiconductor substrate, 102: photodiode, 10
3: Element isolation region, 104: Gate wiring, 105: First
, Signal wiring, 107 power supply wiring,
108 ... wiring layer, 109 ... second interlayer insulating film, 110 ...
Third interlayer insulating film, 111: groove, 112: incident light, 2
01 ... resist pattern, 301 ... groove, 302 ... edge, 501 ... groove, 601 ... resist pattern, 701
... Fourth interlayer insulating film, 702 ... Fifth interlayer insulating film, 80
1 ... semiconductor substrate, 802 ... photodiode, 803 ...
Element isolation region, 804 gate wiring, 805 first interlayer insulating film, 806 signal wiring, 807 power supply wiring, 80
8 wiring layer, 809 second interlayer insulating film, 810 incident light

 ──────────────────────────────────────────────────続 き Continued on the front page F term (reference) 4M118 AA10 AB01 BA14 CA03 EA01 FA06 FA08 FA28 GD04 GD06 GD07 GD08 5C024 CX41 CY47 GX03 5F088 AA01 BA01 BA16 BB03 EA04 JA12 JA20

Claims (7)

[Claims] A photoelectric conversion element formed on a substrate; a first interlayer insulating film formed on the photoelectric conversion element and having a groove at a position on a light receiving region of the photoelectric conversion element; A second interlayer insulating film formed on the first interlayer insulating film and having a refractive index larger than that of the first interlayer insulating film. 2. A photoelectric conversion element formed on a substrate, a first interlayer insulating film formed on the photoelectric conversion element, and a photoelectric conversion element formed on the first interlayer insulating film. A second interlayer insulating film having a groove at a position on the light receiving region, a third interlayer insulating film formed on the second interlayer insulating film and having a higher refractive index than the second interlayer insulating film; , A solid-state imaging device. 3. A photoelectric conversion element formed on a substrate, a first interlayer insulating film formed on the photoelectric conversion element, and a second groove having a groove at a position on a light receiving region of the photoelectric conversion element. And a third interlayer insulating film formed on the second interlayer insulating film and having a higher refractive index than the second interlayer insulating film. Are formed on the first interlayer insulating film in a plurality of layers. 4. The solid-state imaging device according to claim 1, wherein the groove is an arc-shaped groove having a concave lens shape. 5. The solid-state imaging device according to claim 1, wherein the groove is a groove having an arc-shaped edge. 6. The solid-state imaging device according to claim 1, wherein the groove is a substantially inverted triangular groove. 7. The solid-state imaging device according to claim 1, wherein the photoelectric conversion elements are photodiodes, and a plurality of the photoelectric conversion elements are two-dimensionally arranged on the substrate.