JPS6251254A - Solid-state image pickup device - Google Patents

Abstract

PURPOSE:To obtain a device having a CCD, which can perfectly transfer charge generated in a light sensitive region without decreasing a dynamic range, by forming a plurality of electrodes in parallel with the inner surface of a recess part formed in the main surface of a substrate, and forming a channel region formed by a charge transfer means in parallel with the inner surface of the recess part, thereby making an optical vignetting factor large. CONSTITUTION:A plurality of electrodes 20 for transferring charge accumulated in light sensitive regions 10 are formed in parallel with the inner surface of a recess part 24 formed in the main surface of a substrate 12. A channel region 26 formed by a charge transfer means is formed in parallel with the inner surfdeeof the recess part 24. For example, the side surface of the recess part 24 is formed vertically in the main surface of the substrate 12. Each electrode 20 is provided along the inner side surface and the bottom surface of the recess part 24. The electrode 20 is provided along the main surface of the substrate 12 at the outside of the recess part 24. Thus an (n) channel 26 of a CCD is formed along the recess part 24 based on the shape of the electrode 20. The electrodes 20 are constituted so that every other electrode 20 is overlapped on the end part of the neighboring electrode 20. Every other electrode 20 has a gate electrode 28 for transferring the optical charge accumulated in the light sensitive region 10 to the (n) channel 26 of the CCD.

Description

DETAILED DESCRIPTION OF THE INVENTION Technical Field The present invention relates to a solid-state imaging device, and more particularly to a solid-state imaging device using a charge-coupled device (CCD), which is a charge transfer type solid-state imaging device.

For example, in the case of an interline transfer method, a solid-state imaging device using COD vertically transfers photocharges accumulated in photosensitive areas arranged in a matrix using a CC port for vertical transfer.
In step 5, the image is transferred horizontally using a CCD for horizontal transfer and output.

A photosensitive region is formed on one main surface of the semiconductor substrate, and photocharges excited in the photosensitive region in response to incident light are transferred to a CCD, and vertically and horizontally transferred by the CCD.

Recently, solid-state imaging devices using COD have improved resolution and φ
Therefore, the density has been increased, and compared to the previous 200,000 pixels per chip, higher density ones, for example, 1 chip with 300,000 or 400,000 pixels, have been manufactured. on the other hand,
The size of the chip has been reduced to improve yield and reduce cost, and is now 1/2 inch or 81 degrees square.

Therefore, it is necessary to reduce the area of the photosensitive region and the transfer electrode of the CC port, but if the area where the photosensitive region is formed is made smaller, the amount of charge that can be accumulated decreases, resulting in a reduction in the dynamic range. Furthermore, if the area of the GCD transfer electrode is made smaller, the capacitance of the channel formed along the electrode becomes smaller, making it impossible to completely transfer the charges generated in the photosensitive area, resulting in unread accumulated charges. As a result, the readout signal becomes incomplete, and a process is required to sweep out the charge left unread in the photosensitive area, for example, during the vertical blanking period.

Purpose The present invention eliminates the drawbacks of the prior art, and provides a solid-state imaging device having a CCD that can increase the optical aperture ratio without reducing the dynamic range, and can completely transfer the charges generated in the photosensitive area. The purpose is to provide equipment.

DISCLOSURE OF THE INVENTION According to the present invention, a plurality of photosensitive elements are formed on one main surface of a semiconductor substrate and a conductor substrate and are arranged to receive incident light and excite photocharges corresponding to the incident light. and a charge transfer means having a plurality of electrodes arranged adjacent to the photosensitive area to transfer the charges accumulated in the photosensitive area, and the photocharge excited by the incident light is passed through the charge transfer means. In the solid-state imaging device for reading, a plurality of electrodes are formed parallel to the inner surface of a recess formed on the main surface of the substrate, and a channel region formed by the charge transfer means is formed parallel to the inner surface of the recess.

DESCRIPTION OF EMBODIMENTS Next, embodiments of a solid-state imaging device according to the present invention will be described in detail with reference to the accompanying drawings.

An embodiment of the present invention is shown in FIGS. 1 and 2. FIG. A large number of imaging cells each including a photosensitive area 1O are arranged in a matrix, and 2
It constitutes a three-dimensional imaging cell array. This photosensitive area 1
At zero, photocharges are excited and accumulated by the incident light.

As can be seen from FIG. 1, which shows a cross-sectional view taken along the line II in FIG. The photosensitive region IO is formed by diffusing n-type impurities on this p-type layer 14 to form an n÷ region 16, and forming an n+ region 16 and a p-type layer 1.
4 forms a pn junction.

Photocharges excited by light incident on the photosensitive region IO are accumulated in this junction region.

A plurality of electrodes 20 are arranged adjacent to the photosensitive area 10 in the column direction of FIG. 2 (in a direction perpendicular to the paper plane of FIG. 1), forming a GCD for vertical transfer. Electrode 20 is advantageously formed of polycrystalline silicon and has leads 22 as shown in FIG.
is connected to other electrodes 20 in the row direction. As can be seen from FIG. 1 and FIG. 3 showing the electrode 20, the substrate 1
A recess 24 is formed in the substrate 12, and the side surface of the recess 24 is connected to the substrate 12.
It is formed perpendicular to the main surface of. The electrode 20 is placed in this recess 2
It is formed parallel to the inner surface of 4. That is, the electrode 20 is provided along the side and bottom surfaces of the recess 24 inside the recess 24, and is provided along one side of the substrate 12 outside the recess 24.
It is formed in a substantially V shape so as to be provided along the surface.

Due to the shape of the electrode 20, the GCD n-channel 26 is formed in a substantially square shape along the recess 24, as shown in FIG.

The electrodes 20 are configured such that every other electrode 20 overlaps the end of an adjacent electrode 20, as shown in FIGS. 2 and 3, and every other electrode 20 is accumulated in the photosensitive area lO. It has a gate electrode portion 28 for transferring the photocharges generated by the photoelectric charge to the n-channel 26 of the CC port.

An insulating layer 18 of SiO2 is provided between the electrode 20 and the p-type layer 14 and on the surface of the n+ region 16. A p-type layer 1 is provided between the CC port and the photosensitive region IO of another adjacent pixel.
A p-type region 30 is formed at 5 to form a channel stopper for element isolation. In FIG. 1, the p+ region 30 of the channel stopper is formed under the LOGOS field oxide film, but it may be only the p+ region 30 that does not form the LOGO3 structure.

PSG (
An insulating layer 40 (silicate glass containing phosphorus) is formed, and a shield layer 42 is formed of a material such as metal that does not allow light to pass through the insulating layer 40 for pixel separation.

Next, the operation of this embodiment will be explained.

Photocharges are excited by the light incident on the photosensitive region IO and are accumulated in the pn junction region as described above. Gate electrode part 2
When a positive pulse is applied to the electrode 20 with 8, an n-channel (not shown) is formed in the p-type layer 14 below the gate electrode portion 28, and the photosensitive region! The charges accumulated at 0 pass through this n-channel and are transferred to the n-channel 2B of the COD.

Next, a drive clock signal is applied to the plurality of electrodes 20, and C
The charges accumulated in the n-channel 26 of the C port pass through the n-channel 26 all at once and are transferred vertically (in the column direction). When all the charges for one pixel are transferred vertically, the charges for one pixel at the end on the cCn (not shown) side for horizontal transfer are transferred to the COD for horizontal transfer, and then to the GCD for horizontal transfer.
is transferred horizontally (in the row direction). CC for horizontal transfer
When all the charges transferred to D are transferred horizontally and output, the driving clock signal is applied again to the plurality of electrodes 20, and all the charges are transferred vertically by one pixel, and the CCD side for horizontal transfer is transferred vertically by one pixel. The charge for one pixel at the edge of is transferred to the horizontal transfer COD, and then horizontally transferred and outputted by the horizontal transfer CC port. By repeating similar operations, an output signal corresponding to the light irradiated onto the photosensitive area 10 is obtained.

According to this embodiment, since the transfer electrode 20 of the COD is formed parallel to the inner surface of the recess 24 formed on the main surface of the substrate 12 as described above, the n-channel 2B of the CCD is formed along this electrode 20. It is formed parallel to the side and bottom surfaces of the recess 24. Therefore, a channel having a large capacity can be formed with respect to the area of the main surface of the substrate 12.

In order to clarify the effects of this embodiment, it will be explained in comparison with a conventional example.

FIG. 4 shows a sectional view of a conventional example.

A plurality of electrodes 2 constituting a CCD adjacent to the photosensitive area IO
00 is formed parallel to the main surface of the substrate 12. In this conventional example, since the COD n-channel 280 is formed under the electrode 200, it is formed broadly parallel to the main surface of the substrate 12. Therefore, since a large area of the main surface of the substrate 12 is required to form the n-channel 260, if the area of the main surface for forming the n-channel 260 is reduced by increasing the density of the device, the amount of light accumulated in the photosensitive region IO can be reduced. If the area of the main surface for forming the n-channel 260 is increased in order to completely transfer the charges, the optical aperture ratio becomes smaller and the photosensitive area 10
Since the area in which the photoelectric charge is formed becomes smaller, the photocharge storage capacity becomes smaller and the dynamic range becomes smaller.

On the other hand, according to this embodiment, as described above, the substrate 12
Since a large-capacitance CCD channel can be formed in a small area of the main surface of the CCD, the charges generated and accumulated in the photosensitive area 10 can be completely transferred even in the case of a fine imaging cell structure. Since the capacitance of the channel is small as shown in FIG.

In addition, since the optical aperture ratio is improved and the area of the photosensitive region IO can be increased, a fine imaging cell structure can be used to obtain high resolution while having a large photocharge storage capacity and achieving a large dynamic range. Ru.

The depth of the first part 24 is preferably about 0.5 to 2.0' pm, and by providing the recess 24 of this extent, the electrode 20 can be placed in one of the recesses 24! By arranging them in parallel to , the surface area of the n-channel increases by about 10 to 50 μm. Therefore 1, n
If the capacity of the channel is the same as that of the conventional one, the channel width can be reduced to 25 to 70%, the optical aperture ratio can be reduced to -1, and the area of the photosensitive region 10 can be increased. , the dynamic range is 1. ．． It can be increased by 5 to 2.5 times.

For example, if the i of the recess 24 is 2Bm, and the length of the n-channel is 17pm, the increased area of the n-channel is 2Bm.
m17x2=B4 ILm.

Note that in the above embodiment, the shape of the recess 24 is different from that of the substrate 12.
The substrate 12 has side surfaces perpendicular to the main surface of the substrate 12, but there are cases in which the central portion of the recess 24 is the deepest point and the cross section formed by the inclined bottom surface is triangular, and a curved surface that is convex toward the deeper part of the substrate 12. It is sufficient if the electrodes are arranged so that the n-channel 26 is formed in a direction other than the direction parallel to the main surface of the substrate 12, such as one having the following.

Further, the CC port may have a p-channel instead of an n-channel.

Effect As described above, in the present invention, since the electrode of the CCD is formed parallel to the inner surface of the recess formed on the main surface of the substrate, and the channel of the CCD is formed parallel to the inner surface of the recess, the capacitance of the channel can be reduced. It can be made larger. Therefore, the charges accumulated in the photosensitive area can be completely transferred. In addition, since the optical aperture ratio can be improved, even when a fine cell structure is used to obtain high resolution, the photosensitive region has a large charge storage capacity and a large dynamic range can be obtained.

[Brief explanation of the drawing]

FIG. 1 is a sectional view taken along the line II in FIG. 2 showing the structure of an embodiment of the solid-state imaging device according to the present invention, and FIG. 2 is a top view showing the structure of the embodiment of the solid-state imaging device according to the invention. , FIG. 3 is a perspective view showing the electrode of FIG. 1, and FIG. 4 is a sectional view showing the structure of a conventional 11III body imaging device. Explanation of symbols of main parts 10, . . . Photosensitive region 12, . . . Substrate 14...p layer 1f1. ,,n+ region 0,,,electrode 24,,,concavity 2B,,,n channel 28,,,gate electrode section Patent applicant Fuji Photo Film Co., Ltd. 1 agent
Takao Katori

Claims (1)

[Claims] 1. A semiconductor substrate, and a plurality of photosensitive regions formed on one main surface of the semiconductor substrate and arranged so as to receive incident light and excite photocharges according to the incident light. , a charge transfer means having a plurality of electrodes arranged adjacent to the photosensitive area in order to transfer the charges accumulated in the photosensitive area, and the photoelectric charge excited by the incident light is transferred to the photosensitive area. A solid-state imaging device that performs readout through means, wherein the plurality of electrodes are formed parallel to the inner surface of a recess formed on the main surface of the substrate, and the channel region formed by the charge transfer means is parallel to the inner surface of the recess. A solid-state imaging device characterized by being formed parallel to. 2. A solid-state imaging device according to claim 1, wherein the recess has a side surface perpendicular to the main surface of the substrate.