JPS607432B2 - solid state imaging device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION '11 Field of Application of the Invention The present invention relates to improving the performance of a solid-state imaging device that reads out optical information accumulated in a plurality of optical diodes formed on the surface of a semiconductor.

'2) Prior Art A conventional solid-state imaging device includes an element as shown in FIG.

In FIG. 1, 10 is a CCD shift register for horizontal reading, 11 is a vertical MOS shift register, 12 is a photoelectric conversion portion, and 13 is one picture element. Conventional devices include those in which the photoelectric conversion portion 12 is composed of a MOS transistor and a photodiode, and those in which the photoelectric conversion portion 12 is composed of a MOS transistor and a photodiode, and a
Some systems have been announced that consist only of ``pledDevfce'' or a combination of these. Furthermore, a device with only one-dimensional array (in that case, Fig. 1
Although there are devices in which a single shift register is unnecessary) and devices in which a two-dimensional array is used, the principle of the present invention is not influenced by these devices and can be applied to any solid-state image sensor. In this specification, for convenience of explanation, a conventional example of a combination of a MOS transistor and a photodiode shown in FIG. 2 will be described. In FIG. 2, 14 is a switching MOS transistor, and 15 is a photodiode consisting of a pn junction. By the way, in the solid-state imaging device shown in FIG. 1, signals that are thermally generated from other parts of the semiconductor substrate and are indistinguishable from optical information diffuse into the image area and mix with the optical information. Put it away.

This causes the device to read erroneous signals and increases the non-uniformity of the signals, which is a major problem in camera equipment that handles analog signals. A conventional example for solving this problem is shown in FIG. In Figure 3, the shaded area 3M indicates a diffusion layer that absorbs heat signals from the surroundings, and is an n0 diffusion layer in a device that uses electrons as optical information, and a p+ diffusion layer in a device that uses holes as a signal. It is a layer. In FIG. 3, if the device is formed by the usual method, the clock line 33 of the horizontal CCD shift register 10 is made of polycrystalline Si, so as shown in FIG.
) To form the diffusion layer 3, it is necessary to provide a photoetching process just for forming the diffusion layer 30, which results in an increase in mask cost (increase in cost) and a decrease in yield.

'3' Object of the Invention The object of the present invention is to form a portion that removes heat signals from the surroundings without providing any extra photo-etching process.

[4- General Description of the Invention The essence of the present invention is that another CCD shift register is provided in parallel with the horizontal reading CCD shift register, and the CCD diffuses from the surroundings.

The purpose of this method is to remove signals generated by heat or light (hereinafter referred to as thermal signals or thermoelectrons). [5} Examples Hereinafter, the present invention will be explained in detail with reference to examples.

FIG. 4 is a diagram showing an embodiment of the present invention.

In FIG. 4, 10 is a CCD shift register for horizontal reading, 11 is a vertical MOS shift register, and 12 is a photoelectric conversion section shown in FIG. 40 is a CCD shift register according to the present invention, and 41 and 42 are diffusion layers for absorbing thermal signals. In the structure shown in FIG. 4, in addition to the horizontal readout CCD register 0, there are two other CCD registers above and below
A D register 40 is formed, and the same clock 43
It is driven by.

The sources 41 and drains 42 of the upper and lower CCD registers 40 serve as diffusion layers for absorbing thermal signals. For example, in an n-channel device in which electrons serve as optical information, the source 41 and drain 42 in FIG. is applied. In the structure shown in Figure 4,
Thermionic electrons diffusing from the left and right directions of the device are source 41
Alternatively, it is absorbed by the drain 42. Further, thermoelectrons diffusing from above and below are transferred by the CCD register 40 to the drain 42 side along with the transfer of the CCD register, and finally absorbed by the drain saw 42. Therefore, it spreads from above and below and from left and right. All electrons generated due to heat etc. will be absorbed. By the way, the absorbing CCD register 40 can be formed in exactly the same process as the horizontal readout CCD register of the image sensor, and the absorbing source 41 and drain 42 can also be formed in the same process as for forming a normal source and drain. Because of the formation process, embodiments according to the present invention do not require additional masks or photo-etching steps.

In FIG. 4, the output line 32 of the vertical MOS shift register 1 is made of metal such as aluminum, and the n1 diffusion layer 41 can be formed in the same process as the source and drain formation of other parts. However, if the output line 32 of the MOS shift register 11 is made of transferred crystal silicon due to process considerations, forming the n+ diffusion layer 41 outside the MOS shift register 11 will not interfere with the principle of the present invention. There isn't. Moreover, there is no problem with the essence of the present invention whether the output circuit of the horizontal output CCD register 0 is formed inside or outside the absorption n+ diffusion layer 72.

Of course, considering the original purpose, it is desirable that the vertical MOS shift register 1 and the output circuit be formed outside the absorption n+ diffusion layer. FIG. 5 shows another embodiment of the invention.

While FIG. 4 shows a two-dimensional imaging device, FIG. 5 shows an example of a one-dimensional imaging device.

In this case, no vertical MOS register is required. FIG. 6 shows another embodiment of the invention.

FIG. 6 shows that the photoelectric conversion section 12 is a CCD or a CCD.
This shows a combination of a photodiode and a photodiode. At this time, the transfer direction of the CCD of the photoelectric conversion unit 12 is vertical. The present invention in FIG. 6 consists in the formation of a CCD register 40 for horizontal blotting as well as a CCD register 60 for vertical blotting. In this case, a part of the suction gate n10 diffusion layer shown in FIG. 4 is made into a CCD, but the number of masters and the number of process steps are reduced, which is the same as in FIG. 4.

In addition, in FIGS. 4 to 6, the horizontal readout CC
The present invention was applied to a device having two D registers, upper and lower, but the CCD register for horizontal reading is
There is only one on either side, or conversely, there are two on the top and bottom.
It is possible to apply the present invention to a device having one book at a time or three at a time; for example, in the embodiment shown in FIG. 7, there is only one CCD register for reading at the bottom, and in the case of In the example, there are three reading Cs at the bottom.
This shows the case where there is a CD register.

The case shown in FIG. 8 is effective for single-chip color cameras.
In the above embodiments, the size (channel width) of the absorbing CCD register 40 is unrelated to the size of the reading CCDIO, but it is considered that the smaller the size, the better the yield.

[61 Summary As stated above] According to the present invention, it is possible to reduce the number of masks and manufacturing process steps, absorb heat signals gushing out from the surroundings, and produce a low-cost, high-performance solid material. An image sensor can be realized.

In the above explanation, it was expressed as a CCD register, but this is
BCD (Bhlk Charge-Ua orderferDev
ice), BBD (Buchet Brigade D
evice), BCCD (Bnried Channe)
1 Charge Coupled, Device).

Furthermore, although the description has been made using an n-channel device, the principle of the present invention will not be affected by the use of a p-channel device.

As described above, the principle of the present invention is not affected by the structure of the photoelectric conversion unit or the arrangement method (one-dimensional or two-dimensional).

It is also possible to improve the S/N ratio by taking a differential between the output of the absorbing CCD register and the output of the horizontal reading CCD register.

[Brief explanation of drawings]

Figures 1 and 3 are diagrams showing a conventional example, Figure 2 is a diagram showing a specific example of a light conversion section, and Figures 4, 5, 6, 7, and 8 are diagrams showing a conventional example. It is a figure showing an example of the present invention. Fig. 7 Fig. 2 Fig. 3 Chrysanthemum Fig. 6

Claims (1)

[Claims] 1. In a semiconductor conversion device consisting of a photoelectric conversion unit including a plurality of photo-sensing diodes provided on a semiconductor substrate and a charge transfer device as a signal readout device, the outside of the signal readout charge transfer device or the photoelectric conversion portion A solid-state imaging device characterized in that another charge transfer device is arranged and formed near the device so as to remove signals from the surroundings other than optical information.