JPH09270501A - Solid-state image pickup device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To improve the accuracy of an image by forking each of pixel having a square light receiving opening symmetric in the vertical and horizontal directions and having equal vertical and horizontal width to reduce the distortion due to the resolution difference depending in the direction. SOLUTION: The light receiving opening 12 has equal widths Wv and Hv in the vertical and horizontal directions V and H and made symmetric in these directions, this makes equal the quantities of a regular light L and oblique light L' and limits of incident lights in the directions V and H and hence equal the resolutions in both directions. This it is possible to form the receiving opening 12 in such square shape to make equal the resolutions in the directions H and V, resulting in reduction of the distortion of an input image.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a charge transfer type (so-called CCD) solid-state image sensor suitable for use in image reading, for example.

[0002]

2. Description of the Related Art As a structure of a CCD solid-state image sensor, in order to detect light in the vertical and horizontal directions of a pixel,
Conventionally, each pixel has a square shape.

The structure of this CCD solid-state image pickup device is shown in FIG. The figure shows the main part of the imaging area. CC shown in FIG.
In the D solid-state imaging device 40, a plurality of light receiving portions 61 are arranged in a matrix, and a vertical transfer register 44 having a CCD structure is formed on one side of each light receiving portion row via a read gate portion 62. An OCL (on-chip lens) 41 for condensing light is formed on the upper part of each light receiving portion 61, whereby the condensed light enters the light receiving portion 61 through the light receiving portion opening 42,
The signal charge that is photoelectrically converted and corresponds to the amount of light is stored in the charge storage unit 43.
Is accumulated in The signal charges of the light receiving section 61 are read out to the vertical transfer register 44 via the read gate section 62 and then sequentially transferred in the vertical transfer register 44. This C
In the CD solid-state imaging device 40, a square unit cell 50 corresponding to each pixel is formed.

FIG. 5A shows the horizontal direction (H direction) of FIG.
B is a cross-sectional view in the vertical direction (V direction) of FIG. Although not shown, the semiconductor substrate 51 is provided with a semiconductor region forming the charge storage section 43, a transfer channel region forming the vertical transfer register 44, a read gate region, a channel stop region, and the like. The gate insulating film 4 is formed on the transfer channel region and the read gate region of the semiconductor substrate 51.
5, the transfer electrode layer 46 is formed, and the interlayer insulating layer 47 is entirely formed so as to cover the transfer electrode layer 46. The transfer electrode layer 46, the gate insulating film 45, and the transfer channel region form a vertical transfer register 44 having a CCD structure. On the interlayer insulating layer 47, a light shielding metal layer 48 for blocking light to other portions except the light receiving portion 61, the passivation film 4
9 are sequentially formed, and the transparent layer 52 is formed thereon. The upper portion of the transparent layer 52 is processed into a spherical shape to form an OCL (on-chip lens) 41 that collects light.

An opening 48a is formed in a portion of the light shielding metal layer 48 corresponding to the light receiving portion 61, and this opening is formed in the light receiving portion opening 4.
It is equivalent to 2.

In this CCD solid-state image pickup device 40, a pixel (pixel) and a unit cell 50 corresponding to the pixel are formed in a square shape, but the light receiving portion opening 42 has an opening width in order to increase the amount of light received. It is formed as wide as possible, and as a result, it is a rectangle having a long vertical direction (V direction) as shown in FIG.

[0007]

By the way, in a CCD solid-state image pickup device with an on-chip lens, an on-chip lens is formed so as to collect parallel light. Some light is not concentrated. That is, as shown in FIG. 5, there is oblique light L ′ that is not condensed with respect to the ordinary light L that is condensed.

Therefore, in the CCD solid-state image pickup device 40 having the above-mentioned conventional structure, the light receiving portion opening 42 has a rectangular shape, and the light receiving portion opening 42 has an opening width WH in the _H direction and an opening width WV in the _V direction. Therefore, the amount of oblique light L ′ that is incident and the limit of the incident direction of the incident light are different between the H direction and the V direction. As a result, the image resolutions in the H direction and the V direction are different from each other, so that the image is distorted.

In particular, when a CCD solid-state image pickup device is used for optical reading such as OCR (Optical Chracter Recognition) as recently performed, it is preferable to increase the amount of received light or increase the brightness of an image. It is desired to increase the resolution of the light receiving section to improve the reading accuracy. However, if the image is distorted as described above,
It was not possible to read with high accuracy.

As described above, in the CCD solid-state image sensor having square-shaped pixels, the H direction and the V direction
There has been a demand for a method of reducing the distortion due to the difference in resolution from the direction.

In order to solve the above-mentioned problem, the present invention provides a solid-state image pickup device which eliminates the distortion caused by the difference in resolution depending on the direction and has a high image accuracy.

[0012]

According to the present invention, a light receiving portion opening of each pixel has a square shape, or has a shape which is symmetrical in the vertical direction and the horizontal direction and has the same width in the vertical direction and the width in the horizontal direction. Solid-state image sensor.

According to the above-described structure of the present invention, the light receiving portion openings of each pixel are symmetrical in the vertical direction and the horizontal direction, and the width in the vertical direction is equal to the width in the horizontal direction. And the amount of incident light in the horizontal direction can be matched.

[0014]

BEST MODE FOR CARRYING OUT THE INVENTION The solid-state image pickup device of the present invention is a solid-state image pickup device in which a unit cell corresponding to each pixel has a square shape, and a light receiving portion opening of each pixel has a square shape, or a vertical direction and a horizontal direction. The shape is symmetrical with respect to the direction, and the width in the vertical direction is equal to the width in the horizontal direction.

An embodiment of the CCD solid-state image pickup device of the present invention will be described below with reference to the drawings. In this example, the aperture of the light receiving portion has a square shape. As shown in FIG. 1 (only the main part of the imaging region), in the CCD solid-state imaging device 1 of the present embodiment, a plurality of light receiving parts 31 are arranged in a matrix, and a read gate part 32 is provided on one side of each light receiving part row. A vertical transfer register 14 having a CCD structure is formed via the. Each light receiving unit 31
OCL (on-chip lens) that collects light on the top of the
11 is formed, and the light condensed by this is formed in the light receiving portion opening 1
The light is incident on the light receiving portion 31 through 2, is photoelectrically converted, and signal charges corresponding to the amount of light are accumulated in the charge accumulating portion 13. The signal charges of the light receiving section 31 are read out to the vertical transfer register 14 via the read gate section 32 and then sequentially transferred in the vertical transfer register 14.

FIG. 2A is a sectional view in the horizontal direction (H direction) of FIG. 1, and FIG. 2B is a sectional view in the vertical direction (V direction) of FIG. Although not shown in the figure, the semiconductor substrate 2 includes a semiconductor region forming the charge storage unit 13, and a vertical transfer register 14.
, A transfer channel region, a read gate region, a channel stop region, and the like are formed. A transfer electrode layer 16 is formed on the transfer channel region and the read gate region of the semiconductor substrate 2 with a gate insulating film 15 interposed therebetween.
An interlayer insulating layer 17 is entirely formed so as to cover the transfer electrode layer 16. The transfer electrode layer 16, the gate insulating film 15, and the transfer channel region form a vertical transfer register 14 having a CCD structure. The light receiving portion 3 is formed on the interlayer insulating layer 17.
A light shielding metal layer 18 for blocking light to other portions except 1 and a passivation film 19 are sequentially formed, and a transparent layer 3 is formed thereon. The upper portion of the transparent layer 3 is processed into a spherical shape, and OCL (on-chip lens) 11 that collects light
Is composed.

The transfer electrode layer 16 is the gate insulating film 15
The transfer electrode layer 16 of the adjacent unit cell 20
Since they are formed above and below each other, they are shown as two upper and lower transfer electrode layers 16 in the sectional view in the V direction.

An opening 18a is formed in a portion of the light shielding metal layer 18 corresponding to the light receiving portion 31, and this opening 18a corresponds to the light receiving portion opening 12.

In the CCD solid-state image pickup device 1 of this embodiment, in particular, each pixel (pixel) and the unit cell 20 corresponding thereto have a square shape, and the light receiving portion opening 12 has a square shape. .

According to the solid-state image pickup device 1 of this embodiment, the width W _{V of} the light receiving portion opening 12 in the vertical direction (V direction) is equal to the width W _H of the light receiving portion opening 12 in the horizontal direction (H direction), and the light receiving portion opening 12 has a width V. By the symmetry in the direction H and the direction H, the light amount of the normal light L and the oblique light L ′ and the limit of the incident direction of the incident light become equal in the vertical direction and the horizontal direction, and the resolution in both directions becomes the same.

Therefore, by forming the light receiving portion opening 12 in a square shape in this way, the resolutions in the H direction and the V direction can be made the same, so that the distortion of the input image can be reduced.

Further, since the area of the light receiving portion opening 12 is smaller than that of the conventional rectangular shape, the light receiving amount is reduced. On the other hand, since the image is clearly distinguished from the adjacent unit cells, the image can be recognized more finely and the resolution can be improved especially in the optical reading of the image.

The CCD solid-state image pickup device 1 is manufactured, for example, as follows. First, similarly to the manufacturing process of a conventional CCD solid-state image pickup device, a semiconductor region forming the charge storage unit 13 and a transfer channel region forming the vertical transfer register 14 are formed on the semiconductor substrate 2 by an ion implantation method.

Next, the gate insulating film 15 is subjected to thermal oxidation and CV.
It is formed by the D (chemical vapor deposition) method.

Next, a polysilicon film is formed over the entire surface by a CVD method so as to cover the surface, and this is etched by a RIE (reactive ion etching) method to form the transfer electrode layer 16.

Further, an interlayer insulating layer 17 is formed over the entire surface by CVD so as to cover the surface. After that, the light shielding metal layer 18 is formed thereon by the sputtering method.

Then, the light shielding metal layer 18 is pattern-etched by the photo process and the RIE method to form the opening 18a. This opening 18a becomes the light receiving portion opening 12. At this time, by making the pattern square, the light receiving portion opening 12 can be made square.

Next, the passivation film 1 is entirely covered.
9 is formed. Further, the transparent layer 3 is formed, and the transparent layer 3 is formed into a lens shape by etching back using a resist or the like to form an OCL (on-chip lens) 11. In this way, the CCD solid-state image sensor 1 of FIG. 1 can be manufactured.

In the above example, the light receiving portion opening 12 has a square shape, but other light receiving portion openings are symmetrical in the vertical and horizontal directions and have the same opening width in both directions, for example, a circle, a regular octagon or a corner is removed. A configuration of a square or a square with rounded corners can also be adopted. Among these, FIG. 3 shows an embodiment in which the light receiving portion opening is circular.

The CCD solid-state image pickup device 21 shown in FIG. 3 has the same structure as the CCD solid-state image pickup device 1 of the embodiment shown in FIG. 1, and the light-receiving portion opening 22 is formed in a circular shape. Since other configurations are the same as those of the CCD solid-state image pickup device 1 of FIG. 1, the same reference numerals are given and description thereof will be omitted.

[0031] Since the light receiving opening 22 also in this case is in circular, as well as H and V directions of the opening width W _H, W _V is equal, therefore since the two-way resolution equal,
The distortion of the input image can be reduced.

The solid-state image pickup device of the present invention is not limited to the above-mentioned example, and various other structures can be adopted without departing from the gist of the present invention.

[0033]

According to the above-described solid-state image pickup device of the present invention, the light receiving portion opening is formed in a square shape or in a shape symmetrical with respect to the vertical direction and the horizontal direction and having the same opening width in both directions, so that the resolution in both directions is improved. Will be equal.

As a result, the distortion of the input image can be reduced, and the image reading accuracy of the solid-state image pickup device can be improved.

[Brief description of drawings]

FIG. 1 is a schematic plan view of an embodiment of a CCD solid-state image sensor of the present invention.

FIG. 2A is a cross-sectional view of the CCD solid-state image sensor of FIG. 1 in the H direction. B is a cross-sectional view of the CCD solid-state image sensor of FIG. 1 in the V direction.

FIG. 3 is a schematic plan view of another embodiment of the CCD solid-state imaging device of the present invention.

FIG. 4 is a schematic plan view of a conventional CCD solid-state imaging device.

5 is a sectional view of the CCD solid-state image sensor of FIG. 4 in the H direction. B is a cross-sectional view of the CCD solid-state image sensor of FIG. 4 in the V direction.

[Explanation of symbols]

1, 21, 40 CCD solid-state imaging device, 2, 51 semiconductor substrate, 3, 52 transparent layer, 11, 41 OCL (on-chip lens), 12, 22, 42 light receiving portion opening, 1
3,43 charge storage unit, 14,44 vertical transfer register,
15,45 Gate insulating film, 16,46 Transfer electrodes, 1
7,47 Interlayer insulating layer, 18,48 Light shielding metal layer, 1
9,49 passivation film, 20, 50 unit cells, 31 and 61 receiving unit, 32 and 62 reading gate portion, W _H, W _V opening width, L normal light, L 'oblique light

Claims (1)

[Claims] 1. A solid-state imaging device in which a unit cell corresponding to each pixel has a square shape, and a light receiving portion opening of each pixel has a square shape, or is symmetrical in a vertical direction and a horizontal direction, and the vertical direction is the same. And a width in the horizontal direction are equal to each other.