JPH04278584A - Solid-state image device and manufacture and drive method thereof - Google Patents

Abstract

PURPOSE:To offer a solid-state image sensing device to facilitate a reduction in the dimension of pixels, the manufacture method of the device and the drive method of the device. CONSTITUTION:A plurality of photoelectric transducers 1 are arranged, transfer channels are provided adjoining the elements 1 via isolation parts 3 and 11 and charge readout means 10a for reading out charge from the elements 1 are provided at side parts, where the channels 2 are not provided, between the elements 1 and photoelectric transducers 1' adjacent to the elements 1. As regions for the means 10a can be made narrow, the open areas of the elements 1 can be increased.

Description

[Detailed description of the invention]

0001

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a solid-state imaging device used in a video camera, a method of manufacturing the same, and a method of driving the same.

0002

2. Description of the Related Art Solid-state imaging devices using charge transfer devices such as charge-coupled devices (CCDs) have been put into practical use rapidly in recent years due to their superiority in low noise characteristics.

The structure of a conventional solid-state imaging device will be described below with reference to the drawings. FIG. 5 shows the configuration of a conventional solid-state imaging device. This figure shows the main parts of a so-called interline transfer type CCD. 1 is a photoelectric conversion element;
Reference numeral 2 denotes a transfer channel forming a part of a vertical CCD which is a charge transfer means; 3 and 4 are separating parts between the photoelectric conversion element 1 and the transfer channel 2 forming a part of the charge transfer means; 5 and 6;
, 7 and 8 are transfer electrodes forming part of the charge transfer means;
5 and 7 are lower layer transfer electrodes, and 6 and 8 are upper layer transfer electrodes. As shown by the arrow 9, the region where the separating section 4 and the transfer electrode 5 overlap is the charge reading means 9a, and the photoelectric conversion element 1
The charges generated are read out to the transfer channel 2 via the charge reading means 9a.

0004

[Problems to be Solved by the Invention] Such conventional solid-state imaging devices have had the following problems.

[0005] The isolation section 4 must electrically completely isolate the photoelectric conversion element 1 and the transfer channel 2 under the voltage applied during a normal vertical transfer period. On the other hand, when a charge readout voltage is applied, the charges in the photoelectric conversion element 1 must be completely read out to the transfer channel 2 without leaving them behind. The photoelectric conversion element 1 and the transfer channel 2 are generally n-type, and the separation section 4 is p-type. In order to satisfy both of these requirements, the separation section 4 between the photoelectric conversion element 1 and the transfer channel 2 needs to have an appropriate relationship between concentration and width. That is, a narrow width requires a high concentration, and a low concentration requires a wide width. However, when the concentration is high, the width of the separating section 4 must be narrowed, and it is difficult to manage the width because it is sensitive to even the slightest fluctuation. Further, when the concentration is high, the width of the separation section 4 increases due to thermal history, and the regions of the transfer channel 2 and the photoelectric conversion element 1 are eroded, thereby deteriorating the element characteristics such as sensitivity and saturation of the solid-state imaging device. On the other hand, when the concentration is low, a large width is required. All of these factors become more influential as the pixel dimensions are reduced due to smaller elements and increased number of pixels, and have a large impact on the reduction of pixel size.

[0006] Also, as a means to improve the sensitivity of solid-state imaging devices with fine pixels, the on-chip lens method, in which a fine lens is formed directly on the element for each pixel, has recently been frequently used. Even if the area of the photoelectric conversion element 1 is the same, the height will be higher if the shape is closer to a square than if it is an elongated rectangle. However, in recent high-resolution solid-state imaging devices (with a large number of horizontal pixels), the horizontal dimension of the pixel becomes smaller, so the horizontal dimension of the photoelectric conversion element becomes smaller and its shape becomes vertically elongated, reducing the effectiveness of the on-chip lens. It's getting harder to get.

The present invention has been made to solve the above-mentioned conventional problems, and an object of the present invention is to provide a solid-state imaging device with reduced pixel dimensions, a method of manufacturing the same, and a method of driving the same.

[0008]

[Means for Solving the Problems] In order to achieve this object, the solid-state imaging device of the present invention has a charge readout means from the photoelectric conversion elements on the side where the charge transfer means between adjacent photoelectric conversion elements is not provided. It has a configuration that forms.

[0009]

[Operation] With this configuration, a sufficient distance between the charge reading means can be secured, so that the pixel size can be easily reduced.

0010

DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described below with reference to the drawings.

FIG. 1 shows the configuration of a solid-state imaging device according to a first embodiment of the present invention. The difference from the conventional structure shown in FIG. 5 is that the charge readout means 10a is provided not on the transfer channel 2 side but on the vertically separated portion of the photoelectric conversion element 1. The signal charges are read out through the vertical separation section as indicated by arrow 10. According to this structure, since the separation section 11 does not require a readout function, it is not necessary to satisfy the conditions for the charge readout means described in the conventional example, and therefore it may have a low concentration and a narrow width, making it easy to reduce the pixel size. .

Furthermore, even with the same pixel size, the width of the aperture of the photoelectric conversion element 1 can be increased, and the sensitivity can be improved. Furthermore, since the shape of the opening of the photoelectric conversion element 1 can be approximated to a square, the light focusing effect of the on-chip lens can be improved and the sensitivity can be improved.

[0013] Furthermore, the CCD type solid-state imaging device is shown in FIG. 1(b).
As shown in the cross-sectional view taken along line A1-A2 in FIG. 1(a), a low concentration p- layer 1 formed on an n-type substrate 15
Generally, elements are formed within 6. In this case, the transfer channel 2 is formed in the p-layer 17, which has a slightly higher concentration. However, the area p near the center of the gap in transfer channel 2
Since the - layer 18 has a low concentration, when a voltage is applied to the lower electrode 19, the surface potential of the p-layer 18 easily increases.
In addition, since the depletion layer also tends to spread deep, the photoelectric conversion element 1
It becomes possible to read out the electric charge from the cell at a low voltage. In addition, 2
0 is an electrode on the upper layer side.

In order to realize this structure, the transfer electrode of the transfer channel 2 and the part connecting between the transfer electrodes on the adjacent transfer channels 2 used as the electrodes of the charge readout means 10a are simultaneously formed of the same material. This can be achieved by using this method.

Next, a second embodiment of the present invention will be explained using FIG. 2. In the first embodiment shown in FIG. 1, the charges of the photoelectric conversion elements 1 in the odd rows are read by applying a read voltage to the transfer electrode 5, and the charges of the photoelectric conversion elements 1 in the even rows are read by applying a read voltage to the transfer electrode 7. The electric charge of the conversion element 1' is read out. Thereafter, a voltage is applied to the transfer electrodes 5, 6, 7, and 8 to mix the charges within the charge transfer means as necessary. On the other hand, in the second embodiment shown in FIG. 2, by applying a readout voltage to the transfer electrode 5, the charges of the photoelectric conversion elements 1 in the odd rows and the photoelectric conversion elements 1' in the even rows are simultaneously mixed, and Read in the direction of 30, 31, transfer electrode 7
By applying a read voltage to , the charges of the photoelectric conversion elements 1' in the even-numbered rows and the photoelectric conversion elements 1' in the odd-numbered rows are read out in the directions of arrows 32 and 33 by changing the mixing partners. Accordingly, the read operation can be completed with a simple read voltage and in a short time.

Next, the element structure for realizing the operations of the first and second embodiments will be explained with reference to FIGS. 3(a) and 3(b).

FIG. 3(a) shows the element structure for realizing the operation of the first embodiment.
It is a sectional view taken along two lines. 5 is the lower layer transfer electrode, 8
is the upper layer transfer electrode, the n- layer 40 is an impurity layer forming the odd-numbered photoelectric conversion elements, the n- layer 40' is an impurity layer forming the even-numbered photoelectric conversion elements, and the p+ layers 41, 41
' is an impurity layer for reducing dark current formed on the n-layers 40, 40', and 43 is an insulating layer such as silicon dioxide. As shown in FIG. 3(a), the n-layer 40 is connected to the transfer electrode 5.
Although the n-layer 40' is located outside of the edge of the transfer electrode 5, the charge on the n-layer 40' is easily reduced for the same voltage because the n-layer 40' penetrates directly under or a part of the edge of the transfer electrode 5. However, the charges on the n-layer 40 will not be read out. Such a structure can be realized by forming the n-layer 40' by a self-alignment method after forming the transfer electrode 5, and forming the n-layer 40 separately from the transfer electrode 5.

Next, a second embodiment will be explained. Figure 3
(b) shows an element structure for realizing the operation of the second embodiment, and is a sectional view taken along the line C1-C2 in FIG. In the second embodiment, both the n-layers 40 and 40' penetrate directly under the transfer electrode 5 or a part thereof, so that the voltage applied to the transfer electrode 5 easily causes the n-layers 40 and 40' to
- the charges on layers 40 and 40' can be read out; Further, such a structure can be realized by a manufacturing method in which, after forming the transfer electrode 5, the n-layers 40 and 40' are simultaneously formed by a self-alignment method.

1 as in the second embodiment shown in FIG. 3(b).
When a plurality of charge readout means are formed in each photoelectric conversion element, no matter which charge readout means is used to read the signal charge, if the potential state of the photoelectric conversion element immediately after being read out is not equal, so-called fixed pattern noise will occur. Become. Therefore, it is necessary that the photoelectric conversion element be completely depleted immediately after being read. Next, an example of the applied clock in the second embodiment will be explained with reference to FIG. 4.

In FIG. 4, clocks 51, 52, 53, and 54 are clocks applied to transfer electrodes 5, 8, 7, and 6, respectively. Period T160 is A field period, period T261
is the B field period, period T362 is the vertical retrace period of the A field period, period T363 is the vertical retrace period of the B field period, period T464 is the photoelectric conversion element 1 of the odd row
The period T565 is a period during which a pulse is applied to the transfer electrode 5 to read the charge from the even-numbered photoelectric conversion element 1'.
This is the period during which a pulse is applied to the transfer electrode 7 to read out charges from the transfer electrode 7. Further, the clock indicated by 55 is a period during which the clock is applied for transferring the charge in the charge transfer means, and the clocks 51, 52, 53, and 54 are not the same clock during this period. By using such a clock, signals from two photoelectric conversion elements can be read out by applying only one pulse.

[0021] The above is a p-type substrate formed in an n-type substrate.
Although we have explained an example in which a photoelectric conversion element is provided in the mold layer, p
It goes without saying that a similar effect can be obtained when a photoelectric conversion element is provided on the mold substrate. It goes without saying that the same effect can be obtained even if the polarity of the conductivity type is reversed and the polarity of the applied voltage is reversed. Furthermore, although a two-dimensional CCD solid-state imaging device has been described here, it is clear that a so-called one-dimensional CCD solid-state imaging device can also have similar effects.

[0022]

As described above, the present invention provides charge reading means from the photoelectric conversion elements on the sides where the charge transfer means between adjacent photoelectric conversion elements is not provided, thereby reducing the area of the photoelectric conversion elements. Accordingly, it is possible to realize a solid-state imaging device in which the light-condensing effect of the on-chip lens can be increased, and the device can be miniaturized.

In particular, in a so-called frame transfer type CCD imaging device, the charge transfer section also serves as a photoelectric conversion section, and variations in dark current from the charge transfer section directly become fixed pattern noise, which significantly deteriorates the reproduced image quality. Therefore, the use of the solid-state imaging device according to the present invention, which generates very little dark current, has a very large effect of improving image quality.

[Brief explanation of the drawing]

FIG. 1(a) is a block diagram of a solid-state imaging device according to a first embodiment of the present invention; FIG. 1(b) is a sectional view taken along line A1-A2 in FIG. 1(a);

[
FIG. 2 is a configuration diagram of a solid-state imaging device according to a second embodiment of the present invention

[Figure 3] (a) is a cross-sectional view of Figure 1 (a) taken along line B1-B2; (b) is a cross-sectional view of Figure 2 taken along line C1-C2;

[Figure 4]
Application clock diagram in the second embodiment of the present invention

[Figure 5]
Configuration diagram of conventional solid-state imaging device

[Explanation of symbols]

1 Photoelectric conversion element 2 Transfer channel (charge transfer means) 3 Separation section 10a Charge reading means 11 Separation part

Claims (11)

[Claims] 1. A side in which a plurality of photoelectric conversion elements are arranged, a charge transfer means is provided adjacent to the photoelectric conversion elements via a separation part, and a charge transfer means between adjacent photoelectric conversion elements is not provided. What is claimed is: 1. A solid-state imaging device, comprising: a means for reading out charges from the photoelectric conversion element; 2. The solid-state imaging device according to claim 1, wherein one charge reading means is a means for reading charges from a plurality of adjacent photoelectric conversion elements. 3. The solid-state imaging device according to claim 1, wherein one charge reading means is a charge reading means from only one photoelectric conversion element among a plurality of adjacent photoelectric conversion elements. Device. 4. A plurality of photoelectric conversion elements are arranged, a charge transfer means is provided adjacent to the photoelectric conversion element via a separation section or a charge readout means, and a plurality of charge readout elements are provided to one photoelectric conversion element. A solid-state imaging device characterized in that a means is formed. 5. The solid-state imaging device according to claim 1, wherein the photoelectric conversion element is depleted when reading charges from the photoelectric conversion element. 6. A claim characterized in that the transfer electrode of the charge transfer means is formed of a plurality of layers, and the charge readout means is formed of the same electrode material as the transfer electrode of the lowest layer of the charge transfer means. 3. The solid-state imaging device according to item 1 or 3. 7. Charge transfer means is formed adjacent to a plurality of photoelectric conversion elements and the photoelectric conversion element via a separation section, and photoelectric conversion means is formed adjacent to the photoelectric conversion element on the side where the charge transfer means is not provided between adjacent photoelectric conversion elements. A charge readout means from the conversion element is formed, a transfer electrode of the charge transfer means is formed in a plurality of layers, and the charge readout means and the transfer electrode of the lowest layer of the charge transfer means are simultaneously formed by the same process. A method for manufacturing a solid-state imaging device. 8. A charge transfer means is formed adjacent to a plurality of photoelectric conversion elements via a separation section, and a photoelectric conversion means is formed adjacent to the photoelectric conversion element on the side where the charge transfer means is not provided between adjacent photoelectric conversion elements. After forming an electrode constituting a charge reading means from a conversion element, the electrode is used as a mask material when forming a plurality of photoelectric conversion elements adjacent to the electrode, or a mask material that determines the shape of the electrode is used. A method of manufacturing a solid-state imaging device, comprising forming a photoelectric conversion element using a mask material. 9. A charge transfer means is formed adjacent to a plurality of photoelectric conversion elements via a separation section, and a photoelectric conversion means is formed adjacent to the photoelectric conversion element on a side where the charge transfer means is not provided between adjacent photoelectric conversion elements. After forming an electrode constituting a charge reading means from a conversion element, the electrode is used as a mask material when forming a plurality of photoelectric conversion elements adjacent to the electrode, or a mask material that determines the shape of the electrode is used. A photoelectric conversion element formed using the electrode as a mask material and a photoelectric conversion element formed using the electrode as a mask material or without using a mask material that determines the shape of the electrode as a mask material are formed at the same time. A method for manufacturing a solid-state imaging device. 10. A side where a plurality of photoelectric conversion elements are arranged, a charge transfer means is provided adjacent to the photoelectric conversion elements via a separation part, and a charge transfer means between adjacent photoelectric conversion elements is not provided. A charge readout means from the photoelectric conversion element is formed in a solid-state imaging device equipped with a plurality of electrically independent charge readout means. A method for driving a solid-state imaging device, the method comprising applying a read voltage. 11. A plurality of photoelectric conversion elements are arranged, and a charge transfer means is provided adjacent to the photoelectric conversion element via a separation section or a charge readout means, and a plurality of charge readout elements are provided to one photoelectric conversion element. 1. A method for driving a solid-state imaging device, comprising depleting a photoelectric conversion element when reading charges from the photoelectric conversion element of the solid-state imaging device in which the means is formed.