JP2001320034A - Solid-state image sensing element and its manufacturing method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a solid-state image sensing element in which sensitivity and stability are improved by preventing 'vignetting' of a condensed light which is to be caused by an anti-reflection pattern, and a manufacturing method of the element. SOLUTION: This solid-state image sensing element is provided with the anti-reflection pattern 31 having an aperture 31 a on a photo sensor 11 between a light shielding film 16 opening a part above the photo sensor 11 on a substrate 10 surface and a microlens 18 for condensing a light in a light receiving part 11. An inner wall upper part of the aperture part 31 a of the anti-reflection pattern 31 is molded in an R-shaped tapered form. Consequently, a condensed light (h) condensed by the microlens 18 can be prevented from being 'shaded' by an aperture upper part of the pattern 31, without increasing an aperture diameter of the aperture part 31a on the photo sensor 11 side.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a solid-state imaging device and a method of manufacturing the same, and more particularly, to a solid-state imaging device having an antireflection pattern for preventing occurrence of flare and a method of manufacturing the same.

[0002]

2. Description of the Related Art FIG. 7 shows a configuration diagram of an interline transfer type solid-state imaging device. The solid-state imaging device shown in this figure is provided with photo sensors 11 (that is, light receiving portions) in a matrix on the surface side of a substrate, and a vertical transfer CCD 12 is provided alongside the photo sensors 11 along the column direction. I have. A horizontal transfer CCD 13 provided along the column direction is connected to an end of each vertical transfer CCD 12.
The output unit 14 is connected to the last stage.

FIG. 8 is a cross-sectional view (a cross-sectional view taken along the line AA 'in FIG. 7) of a main part of an interline transfer type solid-state imaging device. As shown in this figure, a vertical transfer CCD beside each photo sensor 11 provided on the front side of the substrate 10
Reference numeral 12 denotes a diffusion layer 12a provided on the front surface side of the substrate 10 and a transfer electrode 12b on the diffusion layer 12a. The opening 16 is formed on the photosensor 11 on the substrate 10.
The light shielding film 16 having a is provided so as to cover the transfer electrode 12b. The light shielding film 16 is made of, for example, Al (aluminum). Then, a flattening insulating film 17 is formed on the substrate 10 in a state where these are buried, and a microlens 18 for condensing light on each photosensor 11 is provided on the flattening insulating film 17. .

However, in the solid-state image pickup device having such a configuration, not all light incident from the microlens side is condensed on the photosensor 11 by the microlens 18, and a part of the light is irradiated on the light shielding film 16. Is done. Here, Al constituting the light shielding film 16 has a reflectance of about 90% for light having a wavelength of 600 nm and a high reflectance for visible light.
Therefore, when strong light is incident on the solid-state imaging device, the light applied to the light-shielding film 16 is reflected on the surface thereof, and is further reflected on the seal glass above the microlens 18 (not shown), and again solid-state imaging is performed. The light enters the element to generate flare. Therefore, the quality of the image is significantly impaired.

Therefore, in the solid-state imaging device shown in FIG. 9, an anti-reflection pattern 21 is provided between the light shielding film 16 and the microlens 18, for example, on the flattening insulating film 17 to prevent flare. ing. The anti-reflection pattern 17 is formed by patterning a transparent resin and dyeing it with a black pigment, or by patterning a photoresist containing a black pigment by photolithography technology. It is formed in substantially the same shape, and the opening 21
a.

[0006]

However, in the solid-state imaging device shown in FIG. 9, the condensed light h condensed by the microlenses 18 is blocked by the corners of the antireflection pattern 21.
There is a problem that a so-called "blur" easily occurs and the sensitivity is lowered. In addition, variations in processing of the anti-reflection pattern 21 and the microlenses 18 cause variations in the amount of “blur”, resulting in non-uniform sensitivity.

In particular, with the miniaturization of the pixel size of the solid-state imaging device, the distance d between the photo sensor 11 and the micro lens 18 needs to be reduced in order to reduce the dependence of the CCD sensitivity on the change in the F value of the camera lens. Has occurred.
Accordingly, the anti-reflection pattern 21 and the micro lens 1
Since the distance d1 with respect to the line 8 is also reduced, the occurrence of "blur" is more likely to occur.

In order to prevent the occurrence of such "blur", if the width of the anti-reflection pattern 21 is simply reduced and the opening diameter of the opening 21a is increased, the anti-reflection pattern 21 The anti-reflective effect of
The effect of preventing the occurrence of flare is reduced. Moreover, since the adhesion area of the anti-reflection pattern 21 to the base (here, the planarization insulating film 17) is reduced, the anti-reflection pattern 2
There is also a problem that 1 is easily peeled off.

SUMMARY OF THE INVENTION It is an object of the present invention to provide a solid-state image pickup device capable of preventing "blurring" of condensed light by an anti-reflection pattern and improving and stabilizing sensitivity, and a method of manufacturing the same. .

[0010]

According to the present invention, there is provided a solid-state imaging device comprising: a light-shielding film having an opening on a light-receiving portion on a substrate surface; In a solid-state imaging device provided with an antireflection pattern having an opening on a light receiving portion between the lens and the lens, an upper portion of an inner wall of the opening of the antireflection pattern is formed in a tapered shape.

In the solid-state image pickup device having such a configuration, the opening of the antireflection pattern has a larger diameter toward the microlens. For this reason, it is possible to prevent the condensed light condensed by the microlens from being “blown” at the upper portion of the opening of the antireflection pattern without increasing the diameter of the opening on the light receiving portion side. Therefore, it is possible to easily make the light condensed by the microlens incident on the light receiving unit while ensuring the antireflection effect of the antireflection pattern.

Further, according to the method of manufacturing a solid-state imaging device of the present invention, an antireflection pattern having an opening on the light receiving portion is formed above a light shielding film opening on the light receiving portion on the substrate surface.
In a method for manufacturing a solid-state imaging device in which a microlens for condensing light on a light receiving portion is formed above an antireflection pattern, a first method is to perform a reflow process on the formed antireflection pattern. , A micro lens is formed.

In the first method, since the antireflection pattern having the opening is subjected to the reflow process,
The anti-reflection pattern softens and its corners are rounded. Therefore, the upper part of the inner wall of the opening of the antireflection pattern is formed in a tapered shape.

According to a second method, in the step of forming an anti-reflection pattern, first, an anti-reflection film is formed above the light-shielding film, and a resist pattern having an opening on the light receiving portion is formed on the anti-reflection film. After that, a reflow process is performed on the resist pattern, and then the resist pattern and the anti-reflection film are etched from above the resist pattern to transfer the shape of the resist pattern to the anti-reflection film to form an anti-reflection pattern. It is characterized by forming.

In the second method, a reflow process is performed on a resist pattern having an opening.
The resist pattern softens and its corners are rounded,
The upper part of the inner wall of the opening is formed in a tapered shape. Therefore, the antireflection pattern formed by transferring the shape of the resist pattern to the antireflection film has an opening in which the upper portion of the inner wall is formed in a tapered shape.

[0016]

Embodiments of the present invention will be described below in detail with reference to the drawings. First, prior to describing the method for manufacturing the solid-state imaging device of the present invention, the solid-state imaging device of the present invention will be described. Note that the same components as those of the conventional solid-state imaging device described with reference to FIG.
Duplicate description will be omitted.

FIG. 1 is a diagram showing an embodiment of a solid-state image sensor according to the present invention. The solid-state imaging device shown in this figure is similar to the solid-state imaging device described in the related art with reference to FIG. , A light-shielding film 16 covering the transfer electrode 12a constituting the vertical CCD 12 and having an opening 16a on the photosensor 11, and a planarization insulating film formed on the substrate 10 in a state where these are embedded. Film 17, light shielding film 16
An antireflection pattern 31 having an opening 31a patterned in the same manner as described above, and a microlens 18 for condensing light on each photosensor 11 are provided.

The solid-state imaging device shown in FIG.
The difference from the solid-state imaging device shown in FIG. 9 lies in the shape of the antireflection pattern 31. That is, in the antireflection pattern 31, the upper part of the inner wall of the opening 31a is formed in a tapered shape, and the opening diameter of the opening 31a is gradually increased toward the upper part. Here, the anti-reflection pattern 31
Is formed in such a shape that the upper corner of the inner wall of the opening (21a) in the antireflection pattern (21) of the conventional solid-state imaging device shown in FIG. However, the diameter of the opening 31a at the bottom of the opening is the same as in the conventional case.

The tapered shape of the upper portion of the inner wall of the opening 31a is determined by the distance d1 between the antireflection pattern 31 and the microlens 18, and the closer the distance is, the larger R is, that is, the larger the opening is toward the upper portion. And However, the opening edge portion of the anti-reflection pattern 31 has a certain thickness so that the anti-reflection effect of the anti-reflection pattern 31 is maintained.

The anti-reflection pattern 3 thus formed
In the solid-state imaging device provided with 1, the opening diameter of the opening 31a of the antireflection pattern 31 is wider toward the microlens 18 side. For this reason, it is possible to prevent the condensed light h condensed by the microlens 18 from being “blown” over the opening of the antireflection pattern 31 without increasing the opening diameter of the opening 31 a on the photosensor 11 side. . Therefore, it is possible to easily make the condensed light h by the microlens 18 incident on the photosensor 11 while securing the substantial anti-reflection effect of the anti-reflection pattern 31 by securing the substantial opening diameter of the opening 31a. As a result, it is possible to improve and stabilize the sensitivity of the solid-state imaging device.

In the above-described embodiment, the case where the upper portion of the inner wall of the opening 31a of the antireflection pattern 31 has an R-shaped tapered shape has been described. However, the solid-state imaging device of the present invention may have an anti-reflection pattern as shown in FIG. 2 or FIG.

That is, the antireflection pattern 32 of the solid-state imaging device shown in FIG. 2 is formed in a lens shape, and the entire inner wall of the opening 32a is formed in an R-shaped taper shape.

In the anti-reflection pattern 33 as shown in FIG. 3, the entire inner wall of the opening 33a is formed in a tapered shape having a fixed angle. In other words, the inner wall of the opening 33a is formed of a flat surface.

The anti-reflection patterns 32 and 33 formed in such a shape have a smaller thickness at the edges of the openings 32a and 33a than the anti-reflection pattern 31 shown in FIG. Although the effect of prevention is slightly reduced, the spread of the opening diameter from the photosensor 11 side to the microlens 18 side is increased, so that the effect of preventing the "concentration" of the condensed light h at the shoulders of the openings 32a and 33a is prevented. Becomes larger.

In the above embodiment, the case where the antireflection patterns 31 (32, 33) are provided on the planarizing insulating film 17 has been described. However, the solid-state imaging device of the present invention may have a configuration in which an anti-reflection pattern 34 is provided immediately above the light shielding film 16 as shown in FIG. As the shape of the antireflection pattern 34, the shapes of the antireflection patterns 31, 32, and 33 described with reference to FIGS.

In the solid-state image pickup device having such a configuration,
Since the distance d1 between the microlens 18 and the anti-reflection pattern 34 can be increased as compared with the solid-state imaging device described with reference to FIGS.

Next, embodiments of the method for manufacturing a solid-state imaging device according to the present invention will be described. In each embodiment, a method of manufacturing the solid-state imaging device described with reference to FIG. 1 will be described as an example. Since the steps before the formation of the planarization insulating film 17 are the same as those in the related art, the method of forming the antireflection pattern 31 thereafter will be described in detail.

FIG. 5 is a sectional process view showing a first embodiment of a method for manufacturing a solid-state imaging device. In the manufacturing method of the first embodiment shown in this figure, first, as shown in FIG.
A PSG (phospho silicate glass) is formed in a state of covering each component such as the photo sensor 11, the transfer electrode 12b, and the light shielding film 16.
ss) or a BPSG (boro phospho silicate glass), a planarizing insulating film 17 is formed on the substrate 10, and the opening 3 is formed on the photosensor 11 on the planarizing insulating film 17.
1a, the antireflection pattern 31 colored black is formed.

The anti-reflection pattern 31 is made of a resin material, such as a photoresist, which is softened by a reflow process. The resist pattern formed by lithography is dyed with a black pigment, or a photoresist containing a black pigment is used. It is obtained by patterning by lithography technology. In addition, after the resin film is pattern-etched using a resist pattern as a mask, the resin film is formed by dyeing the resin film with a black pigment, or by pattern-etching a resin film containing a black pigment using the resist pattern as a mask. You may.

Next, as shown in FIG. 5 (b), the anti-reflection pattern 31 is softened by subjecting the anti-reflection pattern 31 to a reflow treatment, and the surface tension of the anti-reflection pattern 31 causes the upper portion of the inner wall of the opening 31a to be in a predetermined position. To a tapered shape. At this time, the reflow temperature is set according to the material constituting the anti-reflection pattern 31, and is set in the range of 110 ° C. to 180 ° C. in the case of, for example, a positive photoresist containing a novolak resin as a main component. You. By setting the reflow temperature within this temperature range, the upper portion of the inner wall of the opening 31 is formed into a tapered shape having a predetermined curvature.

After the above, as shown in FIG. 5C, a microlens 18 is formed above the antireflection pattern 31 by a known technique, thereby completing a solid-state imaging device.

According to the manufacturing method described above, FIG.
As described with reference to (b), since the anti-reflection pattern 31 having the opening 31a is subjected to the reflow treatment, the anti-reflection pattern 31 is softened, and the corners thereof are rounded due to surface tension. Therefore, it is possible to form the upper portion of the inner wall of the opening 31a of the antireflection pattern 31 into a tapered shape. Therefore, it is possible to obtain a solid-state imaging device in which the antireflection effect of the antireflection pattern is sufficient and the sensitivity can be improved and stabilized.

In the first embodiment of the manufacturing method, the anti-reflection pattern 31 described with reference to FIG.
By setting the reflow temperature in the reflow process of
The shape of the opening 31a can be controlled from a shape in which only the upper part of the inner wall of the opening 31a of the antireflection pattern 31 is rounded to a shape in which the entire antireflection pattern 31 is rounded due to surface tension. For this reason, the temperature of the reflow process is set to be higher and the anti-reflection pattern 31 is set.
Is sufficiently softened, the lens-shaped antireflection pattern 32 as described with reference to FIG. 2 can be formed, and the entire inner wall of the opening can be tapered.

FIG. 6 is a sectional process view showing a second embodiment of the method for manufacturing a solid-state image sensor. In the manufacturing method of the second embodiment shown in this figure, first, as shown in FIG.
A planarizing insulating film 17 made of PSG or BPSG is formed on the substrate 10 in a state of covering the components such as the photosensor 11, the transfer electrode 12b, and the light shielding film 16, and then the planarizing insulating film 17 is colored. The anti-reflection film 30 made of the resin material is formed. At this time, the anti-reflection film 30 is formed by applying a transparent resin and then dyeing with a black pigment or applying a resin containing a black pigment. Note that the antireflection film 30 does not need to be a photosensitive material.

Next, a resist pattern 41 is formed on the antireflection film 30 by lithography. The resist pattern 41 is made of, for example, a positive resist and is formed in a shape having an opening 41 a on the photosensor 11.

Thereafter, a reflow process is performed on the resist pattern 41 to soften the resist pattern 41, and the upper surface of the inner wall of the opening 41a is formed into a tapered shape having a predetermined curvature by the surface tension. At this time, the reflow temperature is set depending on the material constituting the resist pattern 41. For example, in the case of a positive type photoresist mainly containing a novolak resin or the like, 110 ° C.
To 180 ° C. Then, by setting the reflow temperature within this temperature range, the opening 4
The upper portion of the inner wall 1a is formed into a tapered shape having a predetermined curvature.

Next, as shown in FIG. 6B, the antireflection film 30 is etched using the resist pattern (41) after the reflow treatment as a mask. The etching conditions at this time are set so that the etching rate for the resist pattern (41) and the etching rate for the antireflection film 30 are substantially equal. This etching is performed until the planarizing insulating film 17 on the photosensor 11 is exposed in a predetermined area. After the etching is completed, the thickness of the antireflection film 30 is adjusted so that the resist pattern (41) does not remain on the antireflection film 30.
It is assumed that the thickness is set to be thicker than the film thickness.

By etching as described above, the antireflection film 30 is shaved according to the shape of the resist pattern (41), and the shape of the resist pattern (41) is transferred to the antireflection film 30. 31 are formed.

After the above, as shown in FIG. 6C, a microlens 18 is formed above the antireflection pattern 31 by a known technique, thereby completing a solid-state imaging device.

According to the manufacturing method described above, the opening 4
Since the resist pattern 41 having 1a is subjected to the reflow treatment, the resist pattern 41 is softened, its corners are rounded, and the upper portion of the inner wall of the opening 41a is formed into a tapered shape. Therefore, this resist pattern 41
In the anti-reflection pattern 31 obtained by transferring the shape of the anti-reflection film 30 to the anti-reflection film 30, an opening 31a in which the upper portion of the inner wall is formed in a tapered shape is provided. Therefore, it is possible to obtain a solid-state imaging device in which the anti-reflection effect of the anti-reflection pattern 31 is sufficient and the sensitivity can be improved and stabilized.

In the second embodiment of the manufacturing method, the resist pattern 41 explained with reference to FIG.
By setting the reflow temperature in the reflow process of
The shape of the opening 41a can be controlled from a shape in which only the upper portion of the inner wall of the opening 41a of the resist pattern 41 is rounded to a shape in which the entire resist pattern 41 is rounded due to surface tension. For this reason, the temperature of the reflow process is set to be higher and the resist pattern 41
Is sufficiently softened to form the lens-shaped resist pattern 41, so that the lens-shaped antireflection pattern 32 as described with reference to FIG. 2 can be formed.

In the first and second embodiments of the manufacturing method, the method of forming the anti-reflection patterns 31 (32) on the planarization insulating film 17 has been described. However, the method for manufacturing a solid-state imaging device of the present invention is also applicable to the manufacture of a solid-state imaging device in which the antireflection pattern 34 is provided immediately above the light-shielding film 16 as described with reference to FIG. In this case, after forming the light shielding film 16 and before forming the planarizing insulating film 17, the steps described with reference to FIGS. 5A and 5B and FIGS. 6A and 6B are used. Is performed, and then the planarizing insulating film 17 and the microlens 18 are formed.
Is formed.

[0043]

According to the solid-state imaging device of the present invention described above, the upper portion of the inner wall of the opening of the anti-reflection pattern is tapered, so that the diameter of the opening on the light receiving portion side can be increased without increasing the diameter of the opening. It is possible to prevent the condensed light condensed by the lens from being “blurred” above the opening of the antireflection pattern. Therefore, it is possible to improve and stabilize the sensitivity of the solid-state imaging device without lowering the antireflection effect of the antireflection pattern.

According to the method of manufacturing a solid-state image pickup device of the present invention, the antireflection pattern having the opening is subjected to the reflow treatment, so that the antireflection pattern is softened and the upper part of the inner wall of the opening is formed. Can be formed into a tapered shape. Therefore, it is possible to obtain a solid-state imaging device in which the antireflection effect of the antireflection pattern is sufficient and the sensitivity can be improved and stabilized.

Further, according to the method of manufacturing a solid-state imaging device according to the third aspect of the present invention, the resist pattern having the opening is subjected to a reflow process to form the upper portion of the inner wall of the opening into a tapered shape, which is used as a mask. By etching the anti-reflection film, an anti-reflection pattern having an opening in which the inner wall upper portion is formed in a tapered shape can be formed. Therefore, it is possible to obtain a solid-state imaging device in which the antireflection effect of the antireflection pattern is sufficient and the sensitivity can be improved and stabilized.

[Brief description of the drawings]

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

FIG. 2 is a cross-sectional view showing a modification (part 1) of the antireflection pattern in the solid-state imaging device of the present invention.

FIG. 3 is a cross-sectional view showing a modification (part 2) of the antireflection pattern in the solid-state imaging device of the present invention.

FIG. 4 is a sectional view showing a modified example of the solid-state imaging device of the present invention.

FIG. 5 is a sectional process view showing a first embodiment of a method for manufacturing a solid-state imaging device of the present invention.

FIG. 6 is a sectional process view showing a second embodiment of a method for manufacturing a solid-state imaging device of the present invention.

FIG. 7 is a configuration diagram of an interline transfer type solid-state imaging device.

FIG. 8 is a cross-sectional view of a conventional solid-state imaging device.

FIG. 9 is a cross-sectional view of a conventional structural image sensor having an anti-reflection pattern.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 10 ... board | substrate, 11 ... light receiving part, 16 ... light shielding film, 17 ... micro lens, 31, 32, 33, 34 ... antireflection pattern, 31a, 32a, 33a, 34a ... opening part, 30 ...
Antireflection film, 41: resist pattern, 41a: opening

Claims (3)

[Claims] An anti-reflection pattern having an opening on the light receiving portion is provided between a light shielding film that opens on the light receiving portion on the substrate surface and a microlens for condensing light on the light receiving portion. In the solid-state imaging device, the opening of the anti-reflection pattern is formed such that an upper portion of an inner wall thereof is tapered. 2. An anti-reflection pattern having an opening on the light receiving portion is formed above a light-shielding film opening on the light receiving portion on the substrate surface, and a microlens for condensing light on the light receiving portion is provided. A method for manufacturing a solid-state imaging device formed above an anti-reflection pattern, comprising: performing a reflow process on the anti-reflection pattern; and then forming the microlens. 3. An anti-reflection pattern having an opening on the light receiving portion is formed above a light shielding film opening on the light receiving portion on the substrate surface, and a microlens for condensing light on the light receiving portion is provided. In the method for manufacturing a solid-state imaging device formed above an anti-reflection pattern, in the step of forming the anti-reflection pattern, a resist pattern having an opening on the light-receiving portion includes forming an anti-reflection film above the light-shielding film. Is formed on the antireflection film, a reflow process is performed on the resist pattern, and then the resist pattern and the antireflection film are etched from above the resist pattern to change the shape of the resist pattern into the antireflection film. A method for manufacturing a solid-state imaging device, comprising forming an anti-reflection pattern transferred to a film.