JPH1074926A - Solid-state image pickup element - Google Patents

Abstract

PROBLEM TO BE SOLVED: To improve the sensitivity of a solid-state image pickup element by increasing substantially the numerical apertures of picture elements by respectively providing photosensitive sections, corresponding to the light condensing sections of on-chip lenses and lens gap sections between adjacent on-chip lenses." SOLUTION: A solid-state image pickup element has image pickup areas composed of photosensitive sections 11 which become pixels and vertical transfer registers 12a and 12b which are formed on one side of the photosensitive sections 11 as signal reading-out sections and have CCD structures. On the image pickup area, a first photosensitive section 11a is formed at the position, corresponding to the light-condensing sections of on-chip lenses 19 composed of micro-lenses correspondingly to each picture element. At the same time, second photosensitive sections 11b are formed at the positions, corresponding to the lens gap sections 20 between the adjacent on-chip lenses 19. Since the lenses 19, lens gap section 20, and photosensitive sections 11 are arranged in the above-mentioned manner, the image pickup element may also receive light which pass through the lens gap sections 20. Therefore, the numeral apertures of the picture elements and, accordingly, the sensitivity of the image pickup elements can be improved.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention
The present invention relates to an amplification type solid-state imaging device.

[0002]

2. Description of the Related Art Normally, in a solid-state imaging device, an on-chip lens is arranged on a photosensitive portion for performing photoelectric conversion, and the aperture ratio of a pixel is increased by converging incident light.

FIGS. 7 and 8 show examples of a CCD type solid-state imaging device having an on-chip lens. FIG. 7 is a sectional view of the imaging region, and FIG. 8 is a top view thereof. This solid-state imaging device 4
Numeral 0 denotes a so-called vertical overflow structure in which, for example, a first p-type semiconductor well region 42 is formed on a semiconductor substrate 41 made of, for example, n-type silicon. An n-type impurity diffusion region 43 for forming a photosensitive portion (that is, a light receiving portion) 51 on the surface.
In addition, a p-type positive charge storage region 44 is formed thereon.
Further, a p-type second semiconductor well region 45 and an n-type transfer channel region 46 for forming a vertical transfer register are formed in the first semiconductor well region 42 at a position distant from the photosensitive portion 51. Channel stop region 5
4 are formed. Here, the first semiconductor well region 42
Becomes a so-called overflow barrier region.

The gate insulating film 5 is formed on the transfer channel region 46, the channel stop region 54, and the read gate portion 52.
5, a transfer electrode 5 made of, for example, polycrystalline silicon.
6 are formed. The transfer channel region 46, the gate insulating film 55, and the transfer electrode 56 constitute a vertical transfer register 53 having a CCD structure. Then, a read gate section 52 is formed between the photosensitive section 51 and the transfer register 53.

[0005] An interlayer insulating layer 57 covering the transfer electrode 56
The Al light-shielding film 18 is formed on the entire surface except for the opening of the photosensitive section 51 through the opening. Further, an on-chip lens 59 made of a transparent microlens is formed on the flattening insulating layer 50 via the flattening insulating layer 50 so as to correspond to each photosensitive portion 11. The photosensitive section 51 is a pixel, and a plurality of photosensitive sections 51 are arranged in a matrix, and an on-chip lens 59 is formed corresponding to each pixel.

In the solid-state image pickup device 40, the light L condensed by the on-chip lens 59 is received by the photosensitive portion 51, and is photoelectrically converted.
1 is stored. The signal charges of the photosensitive section 51 are read out to the charge transfer register 53 through the readout gate section 52, and further transferred to the vertical transfer register 53, and output through a horizontal transfer register (not shown).

[0007]

However, in such a conventional solid-state imaging device 40, the adjacent lenses 59
Since the light incident on the portion between the lens and the lens 59 (the lens gap portion 60) cannot be received, the substantial aperture ratio has been reduced by the lens gap portion 60.

In a solid-state image pickup device having an on-chip lens, it is desired to further increase the sensitivity by increasing the substantial aperture ratio of pixels.

In order to solve the above-mentioned problem, the present invention makes it possible to receive light in a portion other than the portion focused by the lens, thereby increasing the substantial aperture ratio of the pixel and improving the sensitivity. And a solid-state imaging device.

[0010]

The solid-state imaging device according to the present invention is provided with a photosensitive portion corresponding to a condensing portion of an on-chip lens and a lens gap portion between adjacent on-chip lenses.

According to the configuration of the present invention described above, by providing the photosensitive portion below the lens gap, light incident on the lens gap can be photoelectrically converted, and the aperture ratio can be increased. The sensitivity can be improved.

[0012]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS A solid-state imaging device according to the present invention has an on-chip lens corresponding to each pixel, and corresponds to a condensing portion of the on-chip lens and a lens gap between adjacent on-chip lenses. In this configuration, each of the photosensitive units is provided.

According to the present invention, in the solid-state image pickup device, one pixel is constituted by a photosensitive portion corresponding to a condensing portion of an on-chip lens and a photosensitive portion corresponding to a lens gap portion.

According to the present invention, there is provided the above-mentioned solid-state imaging device.
A pixel is provided with two photosensitive units and two signal readout units, and one set of the photosensitive unit and the readout unit is used for light reception of the light-collecting unit.
The other set is used for light reception at the lens gap.

According to the present invention, in the solid-state image pickup device, one pixel is constituted by a photosensitive portion corresponding to a condensing portion of an on-chip lens and a photosensitive portion corresponding to a lens gap portion. And a signal reading unit is provided.

According to the present invention, in the solid-state image pickup device, a signal reading section is provided between a photosensitive section corresponding to a condensing section of an on-chip lens and a photosensitive section corresponding to a lens gap section.

Hereinafter, embodiments of the solid-state imaging device of the present invention will be described with reference to the drawings. FIGS. 1 and 2 show one embodiment of the solid-state imaging device according to the present invention. In this embodiment, the embodiment is applied to a CCD solid-state imaging device having a vertical overflow structure. FIG. 1 is a cross-sectional view of the imaging region, and FIG. 2 is a top view thereof.

The CCD solid-state image pickup device 1 of this embodiment has an image pickup device comprising a photosensitive section (light receiving section) 11 serving as a pixel and a vertical transfer register 12 having a CCD structure serving as a signal reading section formed on one side thereof. On the region, a first photosensitive portion 11a is formed at a position corresponding to a light collecting portion of an on-chip lens 19 composed of a micro lens corresponding to each pixel, and a so-called lens gap between adjacent on-chip lenses 19 is formed. A second photosensitive portion 11b is formed at a position corresponding to the portion 20, and transfers signal charges from the corresponding photosensitive portions 11a and 11b to one side of each of the first and second photosensitive portions 11a and 11b. A first vertical transfer register 12a and a second vertical transfer register 12b having a CCD structure are formed, and one pixel is constituted by the first and second photosensitive units 11a and 11b. Photosensitive unit 11 which is composed, 1 by the first and second vertical transfer registers 12a and 12b
A vertical transfer register constituting a pixel is constituted.

That is, as shown in FIG. 1, this solid-state imaging device 1 has a semiconductor substrate 2 made of silicon of a first conductivity type, for example, n-type silicon, and a first semiconductor well region 3 of a second conductivity type, for example, a p-type silicon. Are formed on the surface of the first p-type semiconductor well region 3, and an n-type impurity diffusion region 4 for forming two photosensitive portions, that is, a first photosensitive portion 11a and a second photosensitive portion 11b, respectively. And the p-type positive charge storage region 5 thereon
Is formed. Further, in order to form the p-type second semiconductor well region 6 and the vertical transfer registers 12a and 12b in the first semiconductor well region 3 slightly away from the one side of each of the photosensitive portions 11a and 11b. Is formed, and a p-type channel stop region 14 is further formed. Here, the first semiconductor well region 3 becomes a so-called overflow barrier region.

A transfer electrode 16 made of, for example, polycrystalline silicon is formed on the transfer channel region 7, the channel stop region 14, and the read gate portions 13a and 13b via a gate insulating film 15, and the transfer channel region 7, the gate insulating film The first and second vertical transfer registers 12a and 12b having a CCD structure are constituted by the transfer electrodes 15 and the transfer electrodes 16. Then, read gate sections 13a and 13b are formed between the respective photosensitive sections 11a and 11b and the corresponding vertical transfer registers 12a and 12b, respectively.

Interlayer insulating layer 17 covering transfer electrode 16
An Al light-shielding film 18 is formed on the entire surface except for the openings of the photosensitive portions 11a and 11b via the. Further, the planarization insulating layer 1
An on-chip lens 19 made of a transparent microlens is formed on the photosensitive portion 11 via the first photosensitive portion 11 and the condensing portion of the on-chip lens 19 corresponds to each first photosensitive portion 11a. And each adjacent on-chip lens 19
A lens gap portion 20 is formed so as to correspond to each second photosensitive portion 11b. Two photosensitive units 11a and 11b
A single pixel is constituted by a plurality of photosensitive units 11 (11a, 11b) arranged in a matrix (see FIG. 2).

As described above, in this example, two photosensitive units 11a and 11b and two vertical transfer registers 12a,
12b, one set of the photosensitive portion 11a and the vertical transfer register 12a is a light L condensed by the on-chip lens 19.
Used in the _first light receiving detection, used for receiving the detection light L ₂ having passed through the groove-shaped lens gap 20 between pairs of the other photosensitive portion 11b and the vertical transfer register 12b is the on-chip lens 19.

In the transfer method of this embodiment, as shown in a schematic configuration diagram in FIG. 3, one pixel (unit cell) U includes two sets (11 sets) of a photosensitive section, a read gate section, and a vertical transfer register.
a, 13a, 12a and 11b, 13b, 12b),
The two vertical transfer registers 12a and 12b transfer charges in the vertical direction in parallel with other pixels in the vertical direction.

According to the CCD solid-state imaging device 1 according to the above-described embodiment, the light L condensed by the on-chip lens 19
₁ is received by the first photosensitive portion 11a, light L ₂ transmitted through the lens gap portion 20 is received by the second photosensitive portion 11b, and signal charges by photoelectric conversion in the respective light receiving portions 11a and 11b correspond to each other. Then, the signal is transferred through the first and second vertical transfer registers, and is then output as an added signal of one pixel. Therefore, the light incident on the imaging unit by the first and second photosensitive units 11a and 11b can be used without waste, and the aperture ratio as one pixel can be improved, and the sensitivity can be improved.

In the solid-state imaging device 1, since the electric charge due to the light L ₁ condensed by the on-chip lens 19 and the electric charge due to the light L ₂ passing through the lens gap can be separately obtained, two types of strong and weak are available. Another feature is that a signal can be obtained.

In this case, the light L ₁ condensed by the on-chip lens 19 and the light L ₂ having passed through the lens gap have different light condensing degrees (light condensing degree L ₁ > L ₂ ). Of the high-sensitivity photosensitive section, and the second photosensitive section 11b
Can be configured as low-sensitivity photosensitive sections, respectively. Therefore, a high dynamic range in which a gradation is obtained over a wide range from a small light quantity to a large light quantity by adding the signals of both photosensitive sections 11a and 11b having different sensitivities. A range of CCD solid-state imaging devices is obtained.

The signal processing in the solid-state imaging device 1 is as follows.
A signal from the photosensitive unit 11a for receiving the condensed light L _1, a signal from the photosensitive unit 11b that receives light L ₂ having passed through the lens gap can be directly added. In this example, the location where signal addition is performed can be a horizontal transfer register or a signal processing circuit beyond it.

The signal from the photosensitive section 11a and the signal from the photosensitive section 11b are converted by a signal processing circuit or the like at the subsequent stage.
The addition may be performed after the gains of the respective signals are made equal.

Further, in the solid-state imaging device 1 of the above example, the vertical transfer registers 12a and 12b are provided for the two photosensitive units 11a and 11b, respectively. 11b, it is also possible to adopt a configuration in which one vertical transfer register is provided, and a readout gate portion is provided between them. In this case, the signals in the two photosensitive units 11a and 11b are added as they are in the vertical transfer register.

FIGS. 4 and 5 show another embodiment of the solid-state imaging device according to the present invention. This example performs photoelectric conversion by incident light, accumulates signal charges obtained by photoelectric conversion,
This is a case where the present invention is applied to a so-called amplifying type solid-state imaging device constituted by pixels (light receiving elements) having a function of outputting a signal according to the accumulated signal charge amount.

FIGS. 4 and 5 are schematic structural views of another embodiment of the solid-state imaging device of the present invention. FIG. 4 is a cross-sectional view of the solid-state imaging device, FIG. 5A is a perspective view with a partial cross section, and FIG. 5B is a top view.

In this amplification type solid-state imaging device 21, a second conductivity type, ie, an n-type semiconductor layer (overflow barrier layer) 23 and a p-type semiconductor well region 24 are formed on a first conductivity type, for example, a p-type silicon semiconductor substrate 22. A ring-shaped gate electrode 28 capable of transmitting light is formed on the p-type semiconductor well region 24 via a gate insulating film 27, and is surrounded by the ring-shaped gate electrode 28 in the p-type semiconductor well region 24. An n-type source region 25 is formed in the separated internal region, and a drain region 26 common to other pixels is formed in an outer peripheral region of the gate electrode 28. Here, a MOS transistor (hereinafter, referred to as a pixel MOS transistor) serving as one pixel is formed. ). For the ring-shaped gate electrode 28, a thin material or a transparent material is selected so as to absorb light as little as possible.

The source region 25 is formed in the source contact portion 2
The drain region 26 is connected to a drain power supply line (not shown), and the gate electrode 28 is connected to a vertical selection line (not shown).

In this embodiment, the planarizing insulating layer 3 covers the pixel MOS transistor and the vertical signal line 30.
An on-chip lens 32 composed of a semi-cylindrical microlens is formed on 1. In this case, the on-chip lens 32 includes the gate electrode 28 divided into two parts by the vertical signal line 30 and the photosensitive parts 28a and 28b including the area below the gate electrode 28.
Is focused on one of the photosensitive portions 28a, and the other photosensitive portion 28a.
The lens gap 33 is formed so as to correspond to “b”.

FIG. 6 shows a schematic configuration diagram of the transfer system in this case. In this case, one pixel (unit cell) U has two photosensitive portions 28a and 28b.
a, a single vertical signal line 3 as a read section
0 is provided, and signals from the two photosensitive units 28a and 28b are output by the vertical signal line 30.

In the above-mentioned amplification type solid-state imaging device 21, the ring-shaped gate electrode 2 of the pixel MOS transistor is used.
8 pass through photoelectric conversion in silicon to generate electron-holes. One of these charges, in this example, the hole h, is used as a signal charge in the p-type semiconductor well region 24 below the gate electrode 28. It is stored in the formed potential well, and the modulation of the substrate bias by this charge is taken out as a signal. That is, when a high-level potential is applied to the gate electrode 28 through the vertical selection line and the pixel MOS transistor is turned on, a channel current (source / drain current) flows through the surface channel, and this channel current is modulated by the signal charge h. Therefore, this channel current is output through the vertical signal line 30, and the amount of change is used as a signal output.

In this embodiment, the above-described on-chip lens 32 is provided, and the photosensitive section 28b is disposed below the lens gap section 33. As in the example, since light passing through the lens gap 33 can be received, the aperture ratio can be improved, and the sensitivity can be improved.

The solid-state image pickup device of the present invention is not limited to the above-described example, and may take various other configurations without departing from the gist of the present invention.

[0039]

According to the above-described solid-state imaging device of the present invention, by making the light incident on the lens gap also enter the photosensitive portion, the aperture ratio can be increased and the sensitivity can be improved.

Further, a condensing part by an on-chip lens,
Since the photosensitive area is formed corresponding to the lens gap,
Two types of strong and weak signals can be obtained separately. Therefore,
When the signals of the two photosensitive units having different sensitivities are added, a solid-state imaging device having a high dynamic range capable of obtaining gradations over a wide range from a small light amount to a large light amount is obtained.

[Brief description of the drawings]

FIG. 1 is a schematic configuration diagram (cross-sectional view) of an embodiment of a solid-state imaging device according to the present invention.

FIG. 2 is a top view of the solid-state imaging device of FIG. 1;

FIG. 3 is a configuration diagram of a transfer system of the solid-state imaging device of FIG. 1;

FIG. 4 is a schematic configuration diagram (cross-sectional view) of another embodiment of the solid-state imaging device of the present invention.

FIG. 5A is a perspective view showing a part of the solid-state imaging device of FIG. 4 in section; B is a top view of the solid-state imaging device of FIG.

FIG. 6 is a configuration diagram of a transfer system of the solid-state imaging device of FIG. 4;

FIG. 7 is a schematic configuration diagram (cross-sectional view) of a conventional solid-state imaging device.

FIG. 8 is a top view of the solid-state imaging device of FIG. 7;

[Explanation of symbols]

REFERENCE SIGNS LIST 1 solid-state imaging device, 2, 22 semiconductor substrate, 3 first semiconductor well region, 4 impurity diffusion region, 5 positive charge accumulation region, 6 second semiconductor well region, 7 transfer channel region, 10, 31 planarization insulating layer , 11, 11a, 11
b, 28a, 28b Photosensitive section, 12a, 12b Vertical transfer register, 13a, 13b Read gate section, 14
Channel stop region, 15 gate insulating film, 16
Transfer electrode, 17 interlayer insulating layer, 18 Al light shielding film, 1
9, 32 on-chip lens, 20, 33 lens gap portion, 21 amplifying solid-state imaging device, 23 semiconductor layer (overflow barrier layer), 24 semiconductor well region, 25 source region, 26 drain region, 27 gate insulating film, 28 gate Electrode, 29 source contact portion, 30 vertical signal line, 40 solid-state imaging device, 41
Semiconductor substrate, 42 first semiconductor well region, 43 impurity diffusion region, 44 positive charge accumulation region, 45 second semiconductor well region, 46 transfer channel region, 50 planarization insulating layer, 51 photosensitive portion, 52 readout gate portion, 5
3 vertical transfer register, 54 channel stop area,
55 gate insulating film, 56 transfer electrode, 57 interlayer insulating layer, 58 Al light shielding film, 59 on-chip lens, 60
Lens gap, U 1 pixel (unit cell)

Claims (4)

[Claims] An on-chip lens corresponding to each pixel is provided, and a photosensitive portion is provided corresponding to a condensing portion of the on-chip lens and a lens gap between adjacent on-chip lenses. A solid-state imaging device characterized by comprising: 2. The solid-state imaging device according to claim 1, wherein one pixel is constituted by a photosensitive portion corresponding to a condensing portion of the on-chip lens and a photosensitive portion corresponding to the lens gap portion. . 3. A pixel is constituted by a photosensitive portion corresponding to a condensing portion of the on-chip lens and a photosensitive portion corresponding to the lens gap portion, and a signal readout portion corresponding to each of the photosensitive portions. The solid-state imaging device according to claim 1, further comprising: 4. A signal reading section is provided between a photosensitive section corresponding to a condensing section of the on-chip lens and a photosensitive section corresponding to the lens gap section. 3. The solid-state imaging device according to item 1.