JPH06260630A - Solid-state image pickup device - Google Patents

Abstract

PURPOSE:To provide a solid-state image pickup device which can reduce the flare caused by the irregular reflection of an incoming light. CONSTITUTION:In a solid-state image pickup device which has a plurality of light receiving elements 4, which receive light from the object of image pickup, being arranged on a semiconductor substrate of a first conductivity type, a plurality of vertical transfer elements 5, which transfer the charge generated in a plurality of light receiving elements in vertical direction, and a horizontal transfer means 2, which outputs charge to output end 7, being connected between a plurality of vertical transfer means and the output end, a plurality of vertical transfer means are made of a semiconductor diffusion layers of a second conductivity type.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a solid-state image pickup device.

[0002]

2. Description of the Related Art Conventionally, solid-state image pickup devices are roughly classified into a MOS type and a CCD type.
There is a combination of a mold and a CCD type. The conventional solid-state imaging device shown in FIG. 5 is an example of a combination of the MOS type and the CCD type, and is shown by an image area. A conventional solid-state imaging device will be described with reference to FIG.

The conventional solid-state image pickup device shown in FIG. 5 has a vertical transfer pulse generation circuit 1, a horizontal transfer section 2, an output amplifier 3 and an output terminal 7, and a light receiving section 4, a silicon gate 6, a diffusion layer 8 and a metal. It is mainly configured by combining a plurality of wirings 9 and a plurality of contact holes 10.

FIG. 6 is an explanatory view showing an end surface of a cross section of Xa-Xb shown in FIG. As shown in FIG.
The light receiving portion 4, the silicon gate 6, the diffusion layer 8, and the contact hole 10 indicated by are arranged on the silicon substrate 11. The light receiving section 4 shown in FIG. 5 is composed of the diffusion layer 13 and the photoelectric conversion section 12. Further, the silicon gate 6 shown in FIG. 6 is arranged in the silicon oxide film 14 of the insulator, and the silicon oxide film 14 on the diffusion layer 8 has a contact for inserting the metal wiring 9 shown in FIG. Hall 10
Is being worn.

Next, these operations will be described with reference to FIGS. The solid-state imaging device shown in FIGS. 5 and 6 will be described as a back-illuminated infrared solid-state imaging device.

First, in FIG. 6, when light is incident from the back surface of the silicon substrate 11, the photoelectric conversion portion 12 (light receiving portion 4).
Due to this, a part of the incident light is photoelectrically converted, and charges are accumulated in the diffusion layer 13.

Then, as shown in FIG. 5, the charges generated in the light receiving portion 4 by the vertical transfer pulse generation circuit 1 as described in FIG. 6 move from the diffusion layer 13 to the diffusion layer 8 through the silicon gate 6. To do. The charges moved to the diffusion layer 8 are sent to the horizontal transfer unit 2 through the contact hole 10 and the metal wiring 9 made of aluminum or the like, and output from the output terminal 7 via the output amplifier 3.

[0008]

However, in the solid-state image pickup device having the above structure, for example, the light incident from the back surface may be irregularly reflected by the metal wiring 9 that vertically transfers the generated charges. There is a problem that flare occurs due to the light incident on the light-receiving unit 4 having a plurality of lights.

That is, to explain in more detail with reference to FIGS. 5 and 6, in FIG. 6, for example, the silicon substrate 1 is used.
When the light is incident from the back surface of No. 1, the incident light is received by the photoelectric conversion unit 12 (light receiving unit 4) as described above, but the incident light is reflected by the metal wiring 9. The incident light is transmitted through the silicon oxide film 14 and is absorbed by the silicon gate 6.

Therefore, in FIG. 5, since the light reflected by the metal wiring 9 is incident on the light receiving portion 4 in the vicinity, there is a problem that flare occurs.

In view of the above problems, it is an object of the present invention to obtain a solid-state image pickup device capable of reducing flare caused by irregular reflection of incident light.

[0012]

In order to achieve the above object, a solid-state image pickup device according to the present invention comprises a plurality of two-dimensionally arranged on a first conductivity type semiconductor substrate and receives light from an image pickup object. Of light receiving elements, a plurality of vertical transfer means for vertically transferring the charges generated by the plurality of light receiving elements, and a plurality of vertical transfer means connected between the plurality of vertical transfer means and an output end, and the charge to the output end. In a solid-state imaging device having horizontal transfer means for outputting, the plurality of vertical transfer means are formed by a second conductive type semiconductor diffusion layer.

[0013]

According to the solid-state image pickup device of the present invention, a plurality of light receiving elements, which are two-dimensionally arranged on the first conductivity type semiconductor substrate and receive light from an object to be imaged, and charges generated by the plurality of light receiving elements are provided. A plurality of vertical transfer means for transferring in the vertical direction, and a horizontal transfer means connected between the plurality of vertical transfer means and the output end for outputting the electric charges to the output end. The vertical transfer means was formed of the second conductivity type semiconductor diffusion layer.

That is, since the plurality of vertical transfer means for vertically transferring the charges generated by the plurality of light receiving elements are made of a material having a high reflectance of light, the plurality of vertical transfer means diffusely reflect the light from the object to be imaged. The plurality of vertical transfer means are formed by semiconductor diffusion layers having a low light reflectance because they affect the light receiving element.

Therefore, the semiconductor diffusion layer can transfer charges generated in a plurality of light receiving elements in the vertical direction, and can significantly reduce diffused reflection of light from the object to be imaged, thereby reducing the occurrence of flare. Can be made.

[0016]

1 is a plan view showing an image area of a solid-state image pickup device according to an embodiment of the present invention, and FIG.
FIG. 7 is a diagram showing an end face of a cross section of Ya-Yb in FIG. Figure 1
In FIG. 1, a configuration example of 3 × 3 9 pixels in the horizontal direction and the vertical direction is shown, but the actual number of pixels is several tens to several hundreds of thousands. In the present embodiment, a back illuminated infrared solid-state imaging device will be described below.

First, FIG. 2 will be described. As shown in FIG. 2, the light receiving section 4 including the diffusion layer 13 and the photoelectric conversion section 12 each having a concentration of 1 × 10 ¹⁸ cm ⁻³ or more for lowering the resistivity on the silicon substrate 11, and the resistivity. The diffusion layer 5 having a concentration of 1 × 10 ¹⁸ cm ⁻³ or more to reduce the temperature, the silicon oxide film 14 of an insulator located on the light receiving portion 4 and the upper surface in the vertical direction of the diffusion layer 5, and the silicon oxide film. It is mainly composed of a gate 6 formed of polysilicon which is enclosed by 14 and is insulated from the silicon substrate 11.
The photoelectric conversion unit 12 is made of platinum silicide (P _t S _i ).
When the photoelectric conversion portion 12 is formed of platinum silicide, the silicon substrate 11 is P-type and the diffusion layers 5 and 13 are N-type.

Next, FIG. 1 will be described based on the description of FIG. As shown in FIG. 1, a solid-state imaging device according to an embodiment of the present invention includes a vertical transfer pulse generation circuit 1, a horizontal transfer unit 2, an output amplifier 3, an output terminal 7, a light receiving unit 4, a polysilicon gate 6, and a vertical gate. The transfer unit 5 is mainly configured, and the light receiving unit 4, the polysilicon gate 6, and the vertical transfer unit 5 are
As described above, the structure is as shown in FIG. 2, and a plurality of these are combined to form one solid-state imaging device. The vertical transfer unit 5 corresponds to the diffusion layer 5 in FIG.

Next, the operation of this embodiment shown in FIGS. 1 and 2 will be described. As described above, since the solid-state imaging device in this embodiment is a back-illuminated infrared imaging device, light rays are incident from below the silicon substrate 11 in FIG. A part of the incident light beam is received by the photoelectric conversion unit 12 and photoelectrically converted by the photoelectric conversion unit 12 to generate electrons and holes. Of the electrons and holes generated in the photoelectric conversion unit 12, the electrons are accumulated in the diffusion layer 13 and transferred to the diffusion layer 5 by the action of the polysilicon gate 6. Light rays incident from below the silicon substrate 11 are transmitted through the silicon substrate 11 and the diffusion layers 5 and 13 due to the characteristics of the silicon substrate 11 and the diffusion layer 5, and the polysilicon gate 6
Will be absorbed.

Here, the diffusion layer 5 corresponds to the vertical transfer unit 5 in FIG. Therefore, the electrons accumulated in the diffusion layer 13 in FIG. 2 are transferred to the vertical transfer unit 5 in FIG.
The electrons have been transferred to. Therefore, the vertical transfer pulse generation circuit 1 transfers the signal to the horizontal transfer unit 2 located vertically upward, and the horizontal transfer unit 2 transfers the output signal to the output terminal 7 via the output amplifier 3 for output.

FIG. 3 is a diagram showing a circuit diagram of the solid-state image pickup device according to the present embodiment, which will be described below in correspondence with FIGS. The photodiode 4 corresponds to the light receiving unit 4 in FIGS. Therefore, electrons and holes are generated in the photodiode 4. Of these, the generated electrons are accumulated in the diffusion layer 13 in FIG. 2 and transferred to the diffusion layer 5 (vertical transfer unit 5 in FIG. 1) by the action of the polysilicon gate 6. This is because the vertical transfer pulse applied from the vertical transfer pulse generation circuit 1 to the polysilicon gate 6 at an appropriate timing opens the MOS transistor 30 shown in FIG. Therefore, in FIG. 3, the electrons generated in the photodiode 4 are
It is transferred to the vertical transfer path 34 via the transistor 30.

The electrons transferred to the vertical transfer path 34 shown in FIG. 3 are turned on by the vertical transfer pulse generation circuit 1 and by applying a transfer pulse to the pulse input terminal 35.
Horizontal transfer unit 3 via transistor 31 and amplifier 32
3 is transferred. The MOS transistor 31 and the amplifier 32 are for efficiently transferring the electrons transferred to the vertical transfer path 34 to the horizontal transfer unit 33. The horizontal transfer unit 33 is composed of, for example, a CCD.

The electrons transferred to the horizontal transfer unit (CCD) 33 are sequentially output to the output terminal 7 via the output amplifier 3, and an infrared image is obtained in time series.

The circuit diagram shown in FIG. 3 can also be applied to FIGS. 5 and 6 shown in the conventional example. That is, conventionally, the electrons were transferred to the horizontal transfer unit 2 by the metal wiring 9 in FIGS. 5 and 6, but in one embodiment according to the present invention, the metal wiring 9 in FIGS. 1 and 2, the present invention differs from the prior art in that electrons are transferred to the horizontal transfer section 2 by a diffusion layer (vertical transfer section) 5, as shown in FIG. Therefore,
If shown as a circuit diagram, one embodiment according to the present invention and the conventional example have the same circuit diagram.

FIG. 4 is a circuit diagram showing another embodiment according to the present invention, which is a circuit diagram of a so-called MOS type solid-state image pickup device in which the horizontal transfer means is a MOS type. In the conventional MOS type solid-state image pickup device, the horizontal transfer pulse generation circuit 22 is used to generate electrons generated in the photodiode 4 in FIG. 4 by the metal wiring 9 as shown in FIGS.
However, the MOS type solid-state imaging device can also be configured by configuring the vertical transfer path 23 for transferring the electrons by the diffusion layer 5 shown in FIGS. 1 and 2.

[0026]

As described above, according to the present invention, since the vertical transfer portion is composed of the diffusion layer, it is possible to reduce the occurrence of flare even when a strong spot light or the like is incident.

Further, since the vertical transfer portion is composed of the diffusion layer, it is not necessary to process the contact hole for each pixel as in the conventional case, so that the cost for processing the contact hole is reduced and the manufacturing is further improved. Since it becomes easier, there is also an effect that a higher yield can be obtained as compared with the conventional one.

Further, since the vertical transfer path is conventionally formed of aluminum or the like, so-called grain may occur in the aluminum, so that if the width of the transfer path is made too thin, the transfer path is broken. However, since the transfer path is composed of a diffusion layer, disconnection does not occur even if the width of the transfer path is narrowed to the limit of the so-called design rule, and the opening area of the light receiving portion is increased by the amount of narrowing the width of the vertical transfer path Therefore, there is also an effect that the device can be configured with high sensitivity.

[Brief description of drawings]

FIG. 1 is a plan view showing an image area of a solid-state imaging device according to an embodiment of the present invention.

FIG. 2 is a diagram showing an end face of a cross section of Ya-Yb in FIG.

FIG. 3 is a circuit diagram of the present embodiment when the horizontal transfer unit is a CCD type.

FIG. 4 is a circuit diagram of the present embodiment when the horizontal transfer unit is a MOS type.

FIG. 5 is a diagram showing an image area of a conventional solid-state imaging device.

6 is a diagram showing a cross section of an end surface of Xa-Xb in FIG.

[Explanation of symbols]

 1: Vertical transfer pulse generation circuit 2: Horizontal transfer part 3: Output amplifier 4: Light receiving part 5: Vertical transfer part 6: Polysilicon gate 7: Output terminal 8: Diffusion layer 9: Metal wiring 10: Contact hole 11: Silicon substrate 12: Photoelectric conversion unit 13: Diffusion layer 14: Silicon oxide film 20, 21, 30, 31: MOS transistor 23, 34: Vertical transfer path 22: Horizontal transfer pulse generation circuit 32: Amplifier 33: Horizontal CCD 35: Pulse input terminal

Claims (1)

[Claims] 1. A plurality of light receiving elements, which are two-dimensionally arranged on a first conductivity type semiconductor substrate and receive light from an imaging target, and a plurality of which transfer charges generated in the plurality of light receiving elements in a vertical direction. A vertical transfer means, and a horizontal transfer means connected between the plurality of vertical transfer means and an output end and outputting the electric charge to the output end. A solid-state imaging device comprising a two-conductivity-type semiconductor diffusion layer.