JPH1022484A - Solid image pick-up device and formation of its lens element - Google Patents

Abstract

PROBLEM TO BE SOLVED: To reduce smear of a solid image pick-up device and prevent a phenomen of mixing light of neighboring picture elements and reduction of sensitivity. SOLUTION: In this picture image pick-up device, a region A where two vertically transfer resistors 7 are adjacent back to back through a channel stopper 5 and a region B, where two photodetecting element vertical arrays 3 are adjacent back to back through a channel stopper, are alternately arranged along a horizontal direction and light-shielding films 11 with an opening for every photodetecting element 3 are formed above transfer electrodes 9 on the surface of the substrate 1. In this case, a film width on the part covering the intervals between the photodetecting elements of the light-shielding film 11 is made thickner than the film thickness of the other parts.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a solid-state image sensing device, in particular, a light receiving element is arranged vertically and horizontally on the surface of a semiconductor substrate, and a vertical transfer register is provided corresponding to each vertical column of the light receiving element. A region having a read gate between a light receiving element and a corresponding vertical transfer register, wherein two light receiving element columns are adjacent via a channel stopper, and two vertical transfer registers are adjacent via a channel stopper. Are arranged alternately along the horizontal direction, and a light-shielding film having an opening for each light-receiving element is formed so as to cover the vertical transfer electrode above the substrate surface, and a light-collecting efficiency thereof. The present invention relates to a method for forming a lens element that enhances the image quality.

[0002]

2. Description of the Related Art FIGS. 5A and 5B show one conventional example of a solid-state imaging device, in which FIG. 5A is a sectional view and FIG. 5B is a plan view. In the drawing, reference numeral 1 denotes an N-type semiconductor substrate, 2 denotes a first P-type well, 2a denotes a second P-type well, which is shallower than the first P-type well 2 and is located below a vertical transfer register (7) to be described later. Located on the side. 3 is an N-type light receiving element, 4
Is a P ⁺⁺ type accumulator formed on the surface of the light receiving element 3, 5 is a P ⁺ type channel stopper, and 6 is a light receiving element 3
A read gate, which is a gate for reading the signal charges (electrons) from the gate to the vertical transfer register (7) described below, vertically transfers the signal charges (electrons) read through the read gate 6. A vertical transfer register, 8 is a gate insulating film formed on the surface of the semiconductor substrate 1, 9 is a vertical transfer electrode made of polysilicon, 10 is an interlayer insulating film, and 11 is a light shielding film made of aluminum. Correspondingly, it has an opening 12 and is provided in order to prevent light from entering other than the light receiving element 3 as much as possible. 13 is an overpassivation film, 14 is a flattening film, and 15 is a substantially dome-shaped lens element provided corresponding to each light receiving element 3.

As is apparent from FIG. 5, a conventional solid-state image sensor generally has a vertical transfer register 7, a readout gate 6, a light receiving element 3, a channel stopper 5, and a vertical transfer register arranged in a horizontal (horizontal scanning) direction. 7, reading gate 6, light receiving element 3, channel stopper 5,.
・ ・ It was a regular arrangement.

[0004]

However, according to the conventional solid-state imaging device as shown in FIG. 5, there is a limitation in reducing smear. This will be described in detail.

That is, the light-shielding film 11 made of aluminum completely covers the vertical transfer electrode 9 made of polysilicon, and further projects outward from the vertical transfer electrode 9. Light obliquely entering the opening 12 of the light-shielding film 11 is reflected by the light-shielding film 11. It is unavoidable that the light enters the area under the overhang of the light-receiving layer 11, travels through repeated reflection between the bottom surface of the light-shielding film 11 and the surface of the semiconductor substrate 1, and then enters the register 7 as light leakage. I mean,
This is because the light-shielding film 11 is formed on the surface of the semiconductor substrate 1 via the gate insulating film 8, and the gate insulating film 8 has transparency.

The light thus incident enters the vertical transfer register 7, where it is photoelectrically converted to generate electric charges (electrons), which is a main cause of the generation of smear. When such a smear captures a high-brightness subject, the smear creates a white and vertically extending tail on the monitor screen, so that the image quality is remarkably reduced.
Therefore, its reduction is strongly required.

In the prior art, as described above, the vertical transfer register 7, the read gate 6, the light receiving element 3, the channel stopper 5, the vertical transfer register 7, the read gate 6, the light receiving element 3, the channel stopper 5,.
.., The light leakage from the read gate 6 side and the light leakage from the channel stopper 5 side enter each vertical transfer register 7.
For this reason, the amount of leaked light was inevitably increased, and it was difficult to reduce smear. And in the past,
Smear could not be improved except by reducing both as much as possible while balancing the light leakage on both sides.

SUMMARY OF THE INVENTION The present invention has been made to solve such problems, and aims to reduce the smear of a solid-state image sensor and to prevent the phenomenon that light from adjacent pixels is mixed and the sensitivity from decreasing. Aim.

[0009]

According to a first aspect of the present invention, there is provided a solid-state imaging device, wherein two vertical columns of light receiving elements are adjacent to each other via a channel stopper back to back, and two vertical transfer registers are back to back via a channel stopper. Adjacent regions are alternately arranged along the horizontal direction, and a light-shielding film having an opening for each light-receiving element is a solid-state imaging device formed above a transfer electrode on the surface of the substrate; It is characterized in that the film thickness at the portion covering the upper portion between the light receiving elements is made thicker than the film thickness at the other portions.

Therefore, according to the solid-state imaging device of the first aspect, each vertical transfer register is adjacent to the adjacent vertical transfer register via the channel stopper, that is, the adjacent vertical transfer registers are back to back via the channel stopper. Therefore, light leaks into each vertical transfer register only from the read gate side. Therefore, the amount of leaked light is reduced, and smear can be reduced.

In addition, since the thickness of the portion of the light-shielding film that covers the space between the adjacent light receiving elements is made larger than the thickness of the other portions, the light of the pixel adjacent to the light receiving element is inclined to enter each light receiving element. Can be prevented by a thick light shielding film. Therefore, it is possible to prevent light from adjacent pixels from being mixed due to the proximity of adjacent light receiving elements. Accordingly, smear can be reduced without causing a phenomenon (for example, color mixture) in which light from adjacent pixels is mixed.

In the solid-state imaging device according to the second aspect, a region where two light receiving element vertical columns are adjacent to each other back to back via a channel stopper and a region where two vertical transfer registers are adjacent to each other back to back via a channel stopper are horizontal. A plurality of light receiving elements adjacent to each other via a channel stopper, wherein a light-shielding film having an opening for each light receiving element is alternately arranged along the direction and formed above the transfer electrode on the substrate surface. , One lens element is provided.

Therefore, according to the solid-state imaging device of the present invention, each vertical transfer register is adjacent to the adjacent vertical transfer register via the channel stopper, that is, the adjacent vertical transfer registers are back to back via the channel stopper. Therefore, light leaks into each vertical transfer register only from the read gate side. Therefore, the amount of leaked light is reduced, and smear can be reduced.

Further, since the lens element is provided for each of a plurality of pixels adjacent in the horizontal direction, one of the lens elements is provided.
The effective aperture area per pixel (the area contributing to light collection)
The size can be made wider than the case where a lens element is provided for each pixel, and the light collection efficiency can be increased. Accordingly, smear can be reduced while increasing sensitivity.

According to a third aspect of the present invention, there is provided the solid-state imaging device according to the second aspect, wherein a portion of a lens element provided for each of a plurality of pixels adjacent in the horizontal direction on a portion between adjacent light receiving elements is provided.
A separation portion for separating the lens element into right and left is formed.

Therefore, according to the solid-state image pickup device of the third aspect, since the separating portion for separating the lens element into the left and right is formed in the portion above the light receiving element adjacent to each lens element, the light receiving element is adjacent to the light receiving element. It is possible to prevent the light of the pixel from trying to enter obliquely by the separating portion. Therefore, the light of adjacent pixels is mixed and one light is received, such as color mixing caused by the light of two pixels entering one lens element by covering a plurality of adjacent pixels with one lens element. The phenomenon of entering the element can be prevented. Accordingly, it is possible to reduce smear without causing a phenomenon in which light of adjacent pixels is mixed, for example, color mixing.

According to a fourth aspect of the present invention, there is provided the lens element forming method according to the third aspect, wherein the resist film formed on the lens material film is provided with a separation groove for separating a portion corresponding to each lens element from the others. Forming, forming a lens element-like portion by softening the resist film by heat treatment, and then exposing a portion where a separation portion of each lens element-like portion made of the resist is to be formed, forming a slit by development, Thereafter, a lens element made of the lens material film is formed by etching back the resist film and the lens material film.

Therefore, according to the lens element forming method of the present invention, each lens element-shaped portion is formed by softening the resist film separated for each lens element on the lens material film, and then exposed and developed. Since the slit is formed and then etched back, it is possible to form a lens element having a separating portion composed of the slit.

[0019]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, the present invention will be described in detail with reference to the illustrated embodiments. 1A and 1B show a first embodiment of the solid-state imaging device of the present invention, wherein FIG. 1A is a sectional view and FIG. 1B is a plan view.

In the drawings, reference numeral 1 denotes an N-type semiconductor substrate, 2 denotes a first P-type well, 2a denotes a second P-type well, which is shallower than the first P-type well 2 and has a vertical transfer register (7 ) Is located below. 3 is an N-type light receiving element, 4
Is a P ⁺⁺ type accumulator formed on the surface of the light receiving element 3, 5 is a P ⁺ type channel stopper, and 6 is a light receiving element 3
A gate for reading out signal charges (electrons) from the gate to a vertical transfer register (7) described below; 7 is a vertical transfer register for vertically transferring the signal charges (electrons) read through the read gate 6; Is a gate insulating film formed on the surface of the semiconductor substrate 1, 9 is a vertical transfer electrode made of polysilicon, and 10 is an interlayer insulating film.

Reference numeral 11 denotes a light-shielding film made of aluminum, which has an opening 12 corresponding to each light-receiving element 3 and is provided to prevent light from entering other than the light-receiving element. The light-shielding film 11 is formed such that the thickness of the portion 11a covering the space between the adjacent light receiving elements 3 is larger than the thickness of the other portions. 13 is an overpassivation film.

The present solid-state image pickup device differs from the solid-state image pickup device shown in FIG.
Horizontal (horizontal scanning or horizontal transfer) of vertical transfer register 7
The arrangement order in the direction is different. That is, as described above, the conventional solid-state imaging device includes the vertical transfer register 7, the readout gate 6, the light receiving element 3, the channel stopper 5, the vertical transfer register 7, the readout gate 6, the light receiving element 3, the channel stopper 5,.・ It had a regular arrangement.

On the other hand, in the solid-state image pickup device of the present embodiment, as is apparent from FIG. 1, two vertical transfer registers 7.7 are adjacent to each other back to back via the channel stopper 5, and two The light receiving elements 3, 3 have an arrangement order in the horizontal direction in which regions B adjacent to each other back to back via the channel stopper 5 are alternately arranged along the horizontal direction. That is, the vertical transfer register 7, the channel stopper 5,
Vertical transfer register 7, read gate 6, light receiving element 3,
The channel stopper 5, the light receiving element 3, the read gate 6, the vertical transfer register 7, the channel stopper 5, and the vertical transfer register 7 are arranged in this order.

Therefore, since each vertical transfer register 7 is adjacent to the adjacent vertical transfer register 7 via the channel stopper 5, in other words, the adjacent vertical transfer registers 7 are adjacent to each other.
Since 7 is back-to-back via the channel stopper 5, light leaks into each vertical transfer register 7 only from the read gate 6 side. Therefore, the amount of leaked light is reduced, and smear can be reduced.

The solid-state image pickup device of this embodiment is different from the conventional solid-state image pickup device shown in FIG. The difference is that the film thickness is larger than the film thickness of the portion.

Therefore, according to the present embodiment, it is possible to prevent the light of the adjacent pixel from obliquely entering each light receiving element 3 by the thick light shielding film 11. Therefore, it is possible to prevent the light of the adjacent pixels from being mixed (in the case of a color solid-state imaging device, color mixing is brought about, so that it is often called color mixing).

That is, it is the light that enters obliquely that causes color mixing or the like. By increasing the thickness of the light-shielding film 11, the light-shielding effect against the oblique light is enhanced. Therefore, by making the film thickness of the portion 11a of the light-shielding film 11 that covers the space between the adjacent light receiving elements 3 larger than the thickness of the other parts, the adjacent pixels generated due to the closeness of the adjacent light receiving elements such as color mixing can be obtained. Can be prevented from being mixed and incident on one light receiving element 3.

Thus, according to the present embodiment, it is possible to reduce smear without causing a phenomenon that light of adjacent pixels is mixed.

[0029]

FIG. 2 shows a second embodiment of the solid-state imaging device according to the present invention.
It is sectional drawing which shows embodiment. In the present embodiment, a lens element (on-chip lens) is provided in the first embodiment shown in FIG. 1, and the other points are common to the first embodiment and common points. Since has already been described, the description thereof will be omitted, and only the lens element will be described.

Reference numeral 15 denotes a lens element, and the passivation film 1
The light receiving element 3 is formed on a flat film 14 formed on the light receiving element 3.

As described above, the solid-state imaging device of the present invention can be applied to a solid-state imaging device having a lens element.

[0032]

FIG. 3 shows a third embodiment of the solid-state imaging device according to the present invention.
It is sectional drawing which shows embodiment. This embodiment is obtained by improving the characteristics of the second embodiment, mainly the sensitivity, and differs from the second embodiment only in the lens element. In other respects, there is no difference from the second embodiment. Only the differences will be described.

Are lens elements, and one lens element 16 is formed so as to cover two pixels where the light receiving elements 3.3 are adjacent to each other via the channel stopper 5. . More specifically, the left end of one lens element 16 is located at the left end of the left and right adjacent two pixels (two adjacent vertical transfer registers 7 on the left side).
7), and the right end is located near the right end (on the portion between the two adjacent vertical transfer registers 7 on the right side) of the area composed of the two pixels.

Reference numeral 17 denotes a slit formed in a portion above each adjacent light receiving element 4 of each lens element 16 provided for each of a plurality of pixels adjacent in the horizontal direction so as to separate the lens element 16 from side to side. It is.

According to such a solid-state imaging device, first, each lens element 16 is formed so as to cover two adjacent pixels to which the adjacent light receiving elements 3.3 belong. The surface area of one lens element 16 per light receiving element can be made larger than that of the solid-state imaging device shown in FIG. That is, in the case of the solid-state imaging device shown in FIG.
Since the lens element 15 is provided on each light receiving element 3 and the lens element 15 is not provided on the vertical transfer register 7, the light incident thereon is not received. Therefore, it is not difficult to raise the sensitivity.

However, according to the solid-state imaging device shown in FIG.
The lens element 16 is also provided above each vertical transfer register 7, and light incident thereon can also be incident on the light receiving element 3 by the lens effect of the lens element 16. Therefore, the sensitivity of the solid-state imaging device can be higher than that of the solid-state imaging device shown in FIG.

According to such a solid-state image pickup device, a slit 1 for separating the lens element 16 to the left and right is provided in a portion above the adjacent light receiving elements 3.3 of each lens element 16.
Since the separating portion made of 7 is formed, even if a plurality of adjacent pixels are covered by one lens element 16, a problem such as color mixing does not occur.

That is, since a plurality of pixels adjacent in the horizontal direction (horizontal scanning direction) are covered by one lens element 16, the sensitivity can be improved. There is a possibility that light from adjacent pixels may be mixed and incident on one light receiving element 3 such as color mixing due to the incidence of light.

However, according to the solid-state image pickup device, since the slit 17 is formed at the center of each lens element 16 in the horizontal direction to separate the lens element 16 from side to side, problems such as color mixing hardly occur. That is, light obliquely entering the central portion in the left-right direction of each lens element 16 causes color mixing and the like, but the slit 17 serves to prevent color mixing and the like since the slit 17 eliminates oblique light. Elimination of oblique light also leads to reduction of smear.

Accordingly, it is possible to further reduce smear without causing a problem such as color mixing.

[0041]

4A to 4E are cross-sectional views showing one embodiment of a method of manufacturing the lens element 16 of the third embodiment shown in FIG. 3 in the order of steps.

(A) As shown in FIG. 4A, a resist film 21 is formed on the microlens material film 20 by coating.

(B) Next, as shown in FIG. 4B, separation grooves 22 for separating each lens element formation region from other lens element formation regions are formed by exposing and developing the resist film 20. The separation groove 22 is formed between a pair of light receiving elements 16.
The area formed by two pixels to which 16 belongs is formed as one section and separated from the other. Therefore,
Each section is rectangular, and the lens element is formed with a rectangular section containing two pixels as a base.

(C) Next, the resist film 21 is softened by heat treatment, so that the surface tension of the softened resist film 21 itself is reduced to a dome in each section as shown in FIG. 4C. The lens element-like portion 23 having a shape is formed. This is the micro lens material 20 by the etch back.
, But not the lens element itself.

(D) Next, by exposing and developing the lens element-like portion 23 made of the resist 21, FIG.
As shown in (1), a slit 14 is formed at the center in the horizontal (horizontal scanning) direction.

(E) Thereafter, the lens element-like portion 23
Then, the lens element 16 made of the microlens material 20 is formed by etching back the microlens material film 20. Since the lens element 16 is formed by etching back the lens element-shaped portion 23 having the slit 24, the lens element 16 has the same dome-shaped portion as the lens element-shaped portion 23 and has the same shape as the slit 24. The slit 17 is provided at the same position.

Thus, according to the method of manufacturing the present lens element, the lens element 16 having the slit 17 of the solid-state imaging device shown in FIG. 3 can be formed.

[0048]

According to the solid-state imaging device of the first aspect, each vertical transfer register is adjacent to the adjacent vertical transfer register via the channel stopper, that is, the adjacent vertical transfer registers are back to back via the channel stopper. Therefore, light leaks into each vertical transfer register only from the read gate side. Therefore, the amount of leaked light is reduced, and smear can be reduced.

Further, the thickness of the portion of the light-shielding film that covers the space between the adjacent light receiving elements is made larger than the thickness of the other portions, so that the light of the pixel adjacent to the light receiving element is inclined to enter each light receiving element. Can be prevented by a thick light shielding film. Therefore, it is possible to prevent a phenomenon such as color mixing in which light from adjacent pixels is mixed due to the proximity of adjacent light receiving elements and is incident on one light receiving element. Therefore, it is possible to reduce smear without causing a phenomenon that light of adjacent pixels is mixed.

According to the solid-state imaging device of the second aspect, each vertical transfer register is adjacent to the adjacent vertical transfer register via the channel stopper, that is, the adjacent vertical transfer registers are back to back via the channel stopper. Light leaks into each vertical transfer register only from the read gate side. Therefore, the amount of leaked light is reduced, and smear can be reduced.

Further, since the lens element is provided for each of a plurality of pixels adjacent in the horizontal direction, one of the lens elements is provided.
The effective aperture area per pixel (the area contributing to light collection)
The size can be made wider than the case where a lens element is provided for each pixel, and the light collection efficiency can be increased. Accordingly, smear can be reduced while increasing sensitivity.

According to the solid-state image pickup device of the third aspect, since the separation section for separating the lens element to the left and right is formed in the portion above the light receiving element adjacent to each lens element, the adjacent light receiving element is formed in the light receiving element. The light can be prevented from entering obliquely by the separating portion. Therefore, the light of adjacent pixels is mixed and one light is received, such as color mixing caused by the light of two pixels entering one lens element by covering a plurality of adjacent pixels with one lens element. Phenomena such as color mixing incident on the element can be prevented. Therefore, it is possible to reduce smear without causing a phenomenon that light of adjacent pixels is mixed.

According to the lens element forming method of the present invention, after each lens element-shaped portion is formed by softening the resist film separated for each lens element on the lens material film,
Since a slit is formed by exposure and development, and then etched back, it is possible to form a lens element having a separating portion composed of the slit.

[Brief description of the drawings]

FIGS. 1A and 1B show a first embodiment of a solid-state imaging device of the present invention, in which FIG. 1A is a cross-sectional view and FIG. 1B is a plan view.

FIG. 2 is a sectional view showing a second embodiment of the solid-state imaging device of the present invention.

FIG. 3 is a cross-sectional view showing a third embodiment of the solid-state imaging device of the present invention.

4A to 4E are cross-sectional views illustrating a method of manufacturing the lens element according to the third embodiment shown in FIG. 3 in the order of steps.

FIGS. 5A and 5B show one conventional example of a solid-state imaging device, where FIG. 5A is a cross-sectional view and FIG. 5B is a plan view.

[Explanation of symbols]

3 ... light receiving element, 5 ... channel stopper, 6.
..Read gate, 7 ... vertical transfer register, 11
.., A light-shielding film, 11a, a portion where the film thickness of the light-shielding film is made thicker than the others, 12, an opening of the light-shielding film, 16, a lens element, 17, a separating portion (slit).

Claims (4)

[Claims] 1. A light receiving element is vertically and horizontally disposed on a surface portion of a semiconductor substrate, and a vertical transfer register is provided corresponding to each vertical column of the light receiving element. With a read gate between them, the area where two light receiving element vertical columns are adjacent via a channel stopper and the area where two vertical transfer registers are adjacent via a channel stopper are alternately arranged along the horizontal direction A solid-state imaging device formed such that a light-shielding film having an opening for each light-receiving element covers and protrudes from the vertical transfer electrode above the substrate surface, and a portion of the light-shielding film covering between adjacent light-receiving elements. A solid-state imaging device characterized in that the film thickness is larger than the film thickness of other parts. 2. A light receiving element is vertically and horizontally disposed on a surface portion of a semiconductor substrate, and a vertical transfer register is provided corresponding to each vertical column of the light receiving element. With a read gate between them, the area where two light receiving element vertical columns are adjacent via a channel stopper and the area where two vertical transfer registers are adjacent via a channel stopper are alternately arranged along the horizontal direction A solid-state imaging device formed so that a light-shielding film having an opening for each light-receiving element covers and protrudes from the vertical transfer electrode above the surface of the substrate; A solid-state imaging device, wherein one lens element is provided on the surface correspondingly. 3. The solid-state image pickup device according to claim 2, wherein a separation portion for separating the lens element from side to side is formed in a portion above the light receiving element adjacent to each lens element. 4. A resist film is formed on the lens material film,
A lens element having a curved surface in a region surrounded by the separation groove by softening the resist film by heat treatment to form a separation groove for partitioning a portion corresponding to each lens element in the resist film. Then, a slit is formed in the portion of the lens element-shaped portion of the resist to be formed where the separation portion is to be formed by exposure and development. Thereafter, the resist film and the lens material film are etched. 4. The method for forming a lens element of a solid-state imaging device according to claim 3, wherein the lens element is formed of a lens material film by backing.