JPH01201954A - Solid-state color image pickup device - Google Patents

Abstract

PURPOSE:To obtain high resolution and high accuracy while making image reproduction having excellent picture quality possible by making a sensitive layer of a pixel of the first kind of laminated construction directly connecting to a semiconductor substrate for detecting light of two colors, detecting a signal for color reproduction with the picture element of the first kind and detecting a signal for brightness reproduction with the picture element of the second kind. CONSTITUTION:The plural number of pixels P11, P12... are formed in the shape of a matrix on a semiconductor substrate in a light receiving region. For instance, in the pixel P11 of the first kind, a transfer gate TR11 is formed between the transfer gates G1, G3... and impurities 20g, while a transfer gate TL11 is formed between the transfer gate electrodes G2, G4 and one end of floating diffusion 21 for being transferred to a prescribed charge transfer element of the charge transfer lines H1 and H2 on both sides by impressing a prescribed high voltage control signal on the transfer gate electrodes. On the other hand, in the pixel P12 of the second kind, a transfer gate TR12 is formed between the electrodes G1, G2... and one end impurities 27 for transfer signal charge to a prescribed transfer element of a charge transfer line by impressing a prescribed high voltage control signal.

Description

DETAILED DESCRIPTION OF THE INVENTION (Industrial Application Field) The present invention relates to a solid-state color imaging device, and particularly to a solid-state color imaging device that detects a plurality of hues per pixel to achieve high resolution.

(Prior Art) A conventional stacked solid-state color imaging device that detects a plurality of colors per pixel is shown in FIG.

First, to explain the structure of the light receiving area, 1
2 is an n-type semiconductor substrate, 2 is a P-well layer formed on the upper surface of the semiconductor substrate 1, and a plurality of CCD charge transfer lines 3 made of n-type impurities are formed on the surface of the P-well layer 2. are formed in parallel at predetermined intervals.

As is well known, between these charge transfer lines 3, n1
A plurality of impurity layers 4 made of type impurities are formed in a matrix, and electricity is transmitted between each impurity layer 4 and a corresponding predetermined charge transfer line 4 via a transfer gate 5 provided at one end of each impurity layer 4. It is designed to be electrically conductive. That is, each of the above transfers
A so-called transfer gate electrode layer 6 is laminated above the gate 5 and the charge transfer line 3, and the signal charge is transferred and read out to the outside by a charge transfer method such as a so-called four-phase drive method.

Further, on the upper surface of the transfer gate electrode layer 6, a photosensitive layer 7, which is buried in the silicon oxide film layer 9 and electrically insulated from each other, is provided.
8 are formed so as to overlap each other, and these photosensitive layers 7.8 are arranged corresponding to the arrangement of the impurity layers 4. The first photosensitive layer 7 on the side closer to the semiconductor substrate has a sandwich structure in which the upper surface of an intermediate layer 10 made of amorphous silicon is sandwiched between a transparent electrode layer 11 and the back surface sandwiched between a conductive layer 12 having a light-shielding property. One end of the conductor layer 12 is electrically connected to a predetermined impurity layer 4 via a connection layer 13. On the other hand, the second photosensitive layer 8 on the top has a sandwich structure in which the top and back surfaces of the intermediate layer 14 made of amorphous silicon are sandwiched between transparent electrode layers 15 and 16, and the transparent electrodes on the back side are sandwiched between transparent electrode layers 15 and 16. In an imaging device having such a structure in which one end of the layer 16 is electrically connected to another impurity layer 4 via the connection layer 17, the signal generated by the photoelectric conversion effect of the second photosensitive layer 8 is Charge connection layer 1
7. Send to a predetermined charge transfer line 3 via a predetermined impurity layer 4 and transfer gate 5, and read out to the outside by further predetermined charge transfer. On the other hand, the light transmitted through the second photosensitive layer 8 is photoelectrically converted in the first photosensitive layer 7, and the signal charges generated thereby are transferred to a predetermined transfer gate via a connection layer 13, a predetermined impurity layer 4, and a transfer gate 5. It is sent to the charge transfer line 3 and read out to the outside by a predetermined charge transfer.

By arranging a plurality of such photosensitive layer structures in a mosaic pattern, it is possible to form a multi-pixel, ie, high-resolution, imaging device.

(Problems to be solved by the invention) However, in such conventional imaging devices,
The manufacturing process is complicated, and it is difficult to manufacture each pixel with high precision, resulting in a large amount of variation. For example, as a specific example of the problem, forming a connection layer in the vertical direction as shown in FIG. For example, it is extremely difficult to process.

(Means for Solving the Problems) The present invention has been made in view of the above problems, and it is an object of the present invention to provide a solid-state color imaging device with a novel structure that can realize high resolution and high precision. purpose.

In order to achieve this object, the present invention forms a plurality of pixels and a plurality of charge transfer lines arranged between these pixels on a semiconductor substrate for reading out respective signal charges generated in these pixels to the outside. In the solid-state color imaging device, each pixel includes an impurity layer buried in a predetermined depth of the semiconductor substrate, a floating diffusion layer formed on a surface portion of the semiconductor substrate opposite to the impurity layer, and a first transfer gate that transfers signal charges generated in the impurity layer to the predetermined charge transfer line; and a photosensitive layer stacked directly on the surface of the floating diffusion layer; a first type of pixel comprising a second transfer gate for transferring signal charges to the predetermined charge transfer line or another predetermined charge transfer line; and forming an impurity layer in the semiconductor substrate. It has a photosensitive element consisting of
and a second type of pixel comprising a transfer gate that transfers signal charges generated by the photoelectric conversion action of the photosensitive element to a predetermined charge transfer line (function). By using this structure, the photosensitive layer of the first type of pixel is a laminated structure that is directly connected to the semiconductor substrate, which simplifies the structure, so it is possible to achieve high precision with relatively basic semiconductor manufacturing technology. Furthermore, since the first type of pixel can detect two colors of light, it is possible to achieve high resolution in addition to the above-mentioned high precision.

Furthermore, if the arrangement and configuration is such that the first type of pixel is a pixel for detecting blue and red light, and the second type of pixel is a pixel for detecting green light, - When resolution is particularly important, such as when forming a luminance signal based on a green detection signal, the structure of the second type of pixel makes it possible to obtain high resolution. It becomes possible to perform excellent image reproduction. That is, the first type of pixel can detect a signal for reproducing color, and the second type of pixel can detect a signal for reproducing brightness, which requires high frequency components. be.

(Embodiment) Hereinafter, one embodiment of the solid-state color imaging device according to the present invention will be described based on the drawings. Fig. 1 is a plan view of the main structure of the light-receiving area when viewed from above, Fig. 2 is a vertical sectional view of the main part when cut along the imaginary line x-x in Fig. 1, and Fig. 3 and FIG. 4 are explanatory diagrams showing the arrangement of pixels.

First, in FIG. 1, a plurality of pixels Pz, P+□, P131, . . . are arranged in a matrix in the light receiving area.

Pl-, PHI, P2□+PZ3t・pa・, Pz%
, P 111 +P7□lP+131...+pH
ll is formed on a semiconductor substrate (not shown). As shown in FIG. 2, these pixels consist of two types of pixels with different structures, which are arranged alternately. In FIG. 1, pixel pHl P131 P2□ is the first
Pixel of type P1□.

P21+P23 is the second type of pixel. Therefore, the structure of the first type of pixel will be explained using pixel pH as a representative.

1 and 2, a well-known P-well layer 19 is diffused into an n-type semiconductor substrate 18, and a P-well 1
An n-type impurity layer 20 is formed at a predetermined depth Ll from the surface of 9 (in the region indicated by multiple points surrounded by solid lines in FIG. 1).
is buried, and one end 20g thereof extends to the surface of the P-well 19. Since this manufacturing method is formed by a well-known diffusion technique, etc., a description thereof will be omitted.

Further, on the upper surface of the impurity layer 20, that is, on the surface of the P-well 19, there is a floating diffusion 21 (in FIG. (within the indicated area)
is formed. On the surface of the floating diffusion 21, a photosensitive layer 24 consisting of an n-type amorphous silicon layer 9 = 22 of a predetermined thickness and a p-type amorphous silicon [23] layered on the upper surface is directly exposed to electricity. A transparent electrode 25 is laminated on the upper surface of the photosensitive layer 24.

Note that the substrate is covered with a light-shielding layer 26 such as an aluminum layer except for a predetermined area where the impurity layer 20, floating diffusion 21, and photosensitive layer 24 are stacked on each other. That is, only the rectangular area indicated by the dotted line 26 in FIG. 1 is opened, and the opened portion becomes the pixel P++.

On the other hand, the structure of the second type of pixel will be explained using pixel P1□ as a representative. As shown in FIG. 2, a photosensitive element (photodiode) is provided by forming an n-type impurity layer 27 on the surface of the P-well 19.

These pixels with different structures are arranged alternately in a matrix, and a charge transfer line H1, Hz of the CCD structure is used to read out the signal charges generated in these pixels to the outside.
, H3, H4... are formed. That is, to explain again using the pixel Pl+ as a representative, a channel stopper (not shown) is used to electrically insulate the pixel Pl+ from the impurity layer 20, etc. and the floating diffusion 21, etc.
N-type charge transfer lines H,, H2, H3,
H4 mountain is formed. Then, a comb-shaped transfer gate electrode G1. G
2. G 3. G a.

・"' + G (2n-11, Gf2n) is stacked on the charge transfer lines H1゜H2, H3, H4 through an insulating layer, and performs the so-called 4-phase drive method 2 signal charge transfer.
Transfer gate electrodes c, , c3 . with odd subscripts. ...,
A transfer gate T is connected between the transfer element formed by Gtzn-n and one end 20g of the impurity layer 20.
On the other hand, a transfer gate electrode is formed between the transfer element formed by z +11 and one end of the floating diffusion 21. Gates TLI+ are formed, and by applying a predetermined high voltage control signal to the transfer gate electrodes, these transfer gates become conductive and the charge transfer lines H1, H2 on both sides are made conductive.
to a predetermined charge transfer element (not shown). Although the structure of the pixel P11 and its surroundings has been described as a representative, the first type of pixel group corresponding to the pixel pH has a similar structure. Note that the above layer 23.
24 may be a short wave absorbing film such as CdS, Cd5-3e, a-3i:H, etc.

On the other hand, if the structure for charge transfer regarding the second type of pixel is described using the pixel P1□ as a representative, the transfer gate electrodes G, G3, . ...+ A transfer gate TR12 is formed between the transfer element formed by G(in-11) and one end of the impurity layer 27, and is made conductive by applying a predetermined high voltage control signal, as shown in the figure. The signal charge is transferred to a predetermined transfer element of the charge transfer line H3 located on the right side.Other second type pixels also have the same structure.

With this structure, if the thickness of the photosensitive layer of the first type of pixel and the depth of the impurity layer buried thereunder are designed according to predetermined conditions, blue will be produced in the photosensitive layer and red will be produced in the impurity layer. By detecting each hue of , and setting the second type of pixel under the same conditions, green can be detected, and the three desired primary colors can be detected. Then, as shown in Part 3, the first type of pixels (indicated by R/B in the figure) and the second type of pixels (indicated by G in the figure) are arranged in a mosaic pattern. Therefore, higher resolution can be obtained than in the past. Further, as shown in FIG. 4, it is possible to arrange them in a striped pattern, or to have a configuration corresponding to a conventional incline arrangement, Bayer arrangement, or the like.

In this way, according to this embodiment, the first type of pixel has two
Since color can be detected, higher density and higher resolution are possible. Furthermore, as shown in FIG. 2, the photosensitive layer of each pixel is formed so as to be directly connected to the charge transfer line via the transfer gate, so that the conventional connection layer (13.17 in FIG. ) is no longer necessary, making it possible to simplify the manufacturing process and improve manufacturing accuracy.

Furthermore, in this embodiment, a signal related to hue that does not require a relatively high frequency component is detected by the first type of pixel,
Since the second type of pixel detects a signal related to high frequency luminance, it is possible to obtain a clear reproduced image.

For convenience of explanation, an example has been described in which the two transfer gates in the first type of pixel are arranged diagonally as shown in FIG. 1, but the embodiment is not limited to this. They may be provided in the same row position in the lateral direction.

Furthermore, the transfer gates of the second type of pixels are the transfer gate electrodes Gz, G4. "".

It may be provided at a position controlled by G (21); in any case, changes in the formation position of the transfer gate of each pixel are all included in the present invention.

Further, as an example of design conditions regarding the composition and thickness of the photosensitive layer in the first type of pixel, the photosensitive layer is set to 0.0
A-3i:H having a thickness of 5 μm to 0.5 μm is formed to detect blue, and an impurity layer is formed to a depth of 0.5 μm to 5 μm to detect red, and the impurity layer of the second type of pixel is They are each formed to have a thickness of 0.2 μm to 5 μm so as to detect green.

(Effects of the Invention) As explained above, according to the present invention, since it has the first type of pixel that generates color signals of two colors in one pixel, it is possible to achieve high resolution. Since the photosensitive layer is directly electrically connected to the floating diffusion, the structure is simple and the manufacturing process is simple. In addition to the above effects, it is possible to realize a color solid-state imaging device with a high degree of integration. Furthermore, if the first type of pixel is a pixel for detecting blue and red light, and the second type of pixel is a pixel for detecting green light, then It is possible to obtain a signal and a signal related to the luminance of a high frequency component, and as a result, it is possible to reproduce a reproduced video with excellent image quality.

[Brief explanation of the drawing]

FIG. 1 is a plan view partially showing the main structure of the light receiving area for explaining an embodiment of the solid-state color imaging device according to the present invention, and FIG. 2 is a plan view taken along the virtual line χ-X in FIG. FIGS. 3 and 4 are explanatory diagrams showing the arrangement of pixels, and FIG. 5 is a vertical sectional view showing the structure of a conventional stacked solid-state color imaging device. 20: Impurity layer 21: Floating diffusion 22.23:
Amorphous silicon layer 24: Photosensitive layer 25: Transparent electrode layer 26: Light shielding layer 27: Impurity layer p, 1 to P: Pixel H, H2, H3, H, -゛-: Charge transfer line G1 to G
zr,: Transfer gate electrode 5 concave Figure 5 Figure 5

Claims (2)

[Claims] (1) In a solid-state color imaging device in which a plurality of pixels and a plurality of charge transfer lines arranged between these pixels and for reading out respective signal charges generated in these pixels to the outside are formed on a semiconductor substrate. , each pixel includes: an impurity layer buried in a predetermined deep part of the semiconductor substrate;
It has a floating diffusion layer formed on the surface portion of the semiconductor substrate opposite to the impurity layer, and a photosensitive layer laminated directly on the surface of the floating diffusion layer, and a signal charge generated in the impurity layer is transferred. A first transfer gate for transferring to the predetermined charge transfer line and a second transfer gate for transferring signal charges generated in the photosensitive layer to the predetermined charge transfer line or another predetermined charge transfer line. and a photosensitive element formed by forming an impurity layer in the semiconductor substrate, and which transfers signal charges generated by the photoelectric conversion action of the photosensitive element to a predetermined charge transfer line. a second type of pixel comprising a transfer gate; and a second type of pixel comprising a transfer gate. (2) In the solid-state color imaging device according to claim 1, the first type of pixel includes: the photosensitive layer formed to a predetermined thickness that photoelectrically converts light of a predetermined short wavelength; The impurity layer is formed in a predetermined deep part of the semiconductor substrate so as to photoelectrically convert light of a predetermined long wavelength that has passed through the photosensitive layer.