JPH0794694A - Solid state image sensor - Google Patents

Abstract

PURPOSE:To provide a CCD solid state image sensor in which the incidence of light to a charge detecting part is blocked, the dark current is reduced, the output dynamic range is prevented from lowering, and the operation of peripheral circuit is stabilized by laminating the dye layers of respective colors of an on-chip filter at least on the charge detecting part of solid state image sensor thereby forming a shading film. CONSTITUTION:Dye layers of three colors M, Cy, Y of an on-chip color filter 19 at an image pick-up part 14 are superposed to form a shading film 27 on the output part 18 of a solid state image sensor including a signal charge detecting part 16 and the peripheral circuit part 20 thereof. Consequently, when a bright light source such as the sun is sensed, incidence of light to the output part 18, especially to the signal charge detecting part 16 thereof, is blocked thus retarding generation of dark current through photoelectric conversion. This structure reduces the dark current with no adverse effect on the high sensitivity and high operating speed and without sacrifice of the output dynamic range of solid state image sensor.

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 As a CCD solid-state image pickup device, an IT (interline transfer) type CCD solid-state image pickup device is known. FIG. 3 shows the overall configuration of the IT type CCD solid-state image sensor. The IT type CCD solid-state image pickup device 1 has a large number of light receiving parts 2 which are arranged in a matrix, and an image pickup part 4 in which a vertical transfer register 3 having a CCD structure is provided on one side of each light receiving part row, and a CCD structure. Horizontal transfer register 5
And a signal charge detection unit 6 such as a floating diffusion region or a floating gate connected to the final stage of the horizontal transfer register 5 and an output unit 8 including an output amplifier 7 connected to the signal charge detection unit 6.

A light shielding film made of, for example, Al is formed on the vertical transfer register 3 and the horizontal transfer register 5 so that light is not incident thereon. A so-called on-chip color filter 9 is formed on the image pickup section 4. For example, in the case of a complementary color filter, magenta (M), cyan (Cy) and yellow (Y) respectively corresponding to each light receiving section 2 are formed. The dyed layer is formed. Although not shown, peripheral circuits are formed in the peripheral portion of the imaging unit 4.

In the image pickup device 1, the signal charges from the respective light receiving portions 2 are read out to the vertical transfer register 3, and the signal charges for each line are transferred from the vertical transfer register 3 to the horizontal transfer register 5 and then horizontally. The signals are sequentially transferred in the transfer register 5, converted into charge-voltage by the signal charge detection unit 6, and CCD output is obtained from the output amplifier 7.

[0005]

By the way, the above-mentioned C
In the CD solid-state image pickup device 1, that is, in the solid-state image pickup device for general use, the output unit 8 and the peripheral circuit unit 10 have not been shielded from light. This is because there is a problem in processing the wiring, and when the Al light-shielding film is formed, the capacity between the Al light-shielding film and the signal charge detection unit 6 increases, which is disadvantageous in achieving higher sensitivity and higher speed.

However, in the case where the light is not shielded, for example, when a bright light source such as the sun is photographed, the output portion, especially the signal charge detection portion 6 outside the image pickup area happens to be exposed to strong light, and photoelectric conversion is performed there to generate dark current. May be. This phenomenon is remarkable especially when the driving frequency is low.

For example, the drive frequency of an auto-focus sensor of a camera is lower than the drive frequency of a normal television image sensor, for example, about 100 KHz. In this case, since the signal charge is accumulated in the charge detection portion, for example, the floating diffusion region 6 for a long time, the time for photoelectric conversion in the floating diffusion region 6 is increased, and the dark current is significantly increased. It will be.

In such a case, the black level of the pixel being output at that time increases, so that the pixel appears darker than it should be. For the same reason, the output dynamic range becomes smaller.

On the other hand, when the transistor of the peripheral circuit section 10 is exposed to light, that is, when light is incident under the gate, it is modulated, for example, the current at the cutoff increases and the circuit operation becomes unstable.

In view of the above points, the present invention provides a solid-state image pickup device capable of reducing dark current.

[0011]

According to the present invention, the on-chip filter 1 is provided on at least the charge detection portion 16 of the solid-state image pickup device.
The light-shielding film is formed by the laminated film 27 in which the respective colors M, Cy, and Y of 9 are stacked.

[0012]

In the present invention, at least the charge detector 16
Each color M, Cy, Y of the on-chip color filter 19
By forming the light-shielding film 27 made of a laminated film in which light is overlapped, the incidence of light on the charge detection unit 16 is blocked. Therefore, the generation of dark current due to photoelectric conversion in the charge detection unit 16 is suppressed, and the dark current of the solid-state image sensor can be reduced. At the same time, it is possible to prevent a decrease in the output dynamic range.

Since the light shielding film 27 is formed of a laminated film for each color of the on-chip color filter 19, no capacitance is formed between the on-chip color filter 19 and the diffusion layer of the charge detection unit 16, and the solid-state image pickup device High sensitivity and high speed are not impaired.

Similarly, when the light-shielding film 27 made of a laminated film in which the respective colors of the on-chip color filter 19 are overlapped is formed on the peripheral circuit section 20, light incidence on the transistors of the peripheral circuit section 20 is blocked, A reliable transistor operation can be performed without an increase in current at the cutoff.

[0015]

Embodiments of the solid-state image pickup device according to the present invention will be described below with reference to the drawings.

FIG. 1 shows an example of an IT type CCD solid-state image pickup device according to the present invention. CCD solid-state image sensor 11 of this example
Is an image pickup section 14 in which a large number of light receiving sections 12 to be pixels are arranged in a matrix, and a vertical transfer register 13 having a CCD structure for vertically transferring signal charges is provided on one side of each light receiving section row. And a horizontal transfer register 15 having a CCD structure for horizontally transferring the signal charges to the lower end of the imaging unit 14.
And a signal charge detection unit 16 such as a floating diffusion region and a floating gate connected to the final stage of the horizontal transfer register, and an output unit 18 including an output amplifier 17, and a peripheral circuit such as a drive circuit in the peripheral portion. Are formed.

A light shielding film made of, for example, Al is formed on the vertical transfer register 13 and the horizontal transfer register 15 so that light is not incident thereon. An on-chip color filter 19 is formed on the image pickup unit 14. For example, in the case of a complementary color system filter, magenta (M) and M are respectively provided on the corresponding light receiving units 12.
Cyan (Cy) and yellow (Y) dyed layers are formed.

That is, as shown in the sectional view of FIG. 2, in the image pickup section 14, for example, a photodiode (photoelectric conversion element) which constitutes the light receiving section 2, a semiconductor substrate in which a transfer channel region of the vertical transfer register 13 and the like are formed. Transfer electrode 22 made of polycrystalline silicon on the surface of 21 via a gate insulating film.
Is formed, and an Al light-shielding film 23 is formed so as to cover the transfer electrode 22 via an insulating film. Then, the flattening film 2
An on-chip color filter 19 composed of corresponding dyed layers of magenta (M), cyan (Cy) and yellow (Y) is formed on each of the light-receiving units 12 through 4, and incident light is further incident on the color filter 19. An on-chip microlens 25 for condensing light on each light receiving unit 12 is formed.

Since the operation of the CCD solid-state image pickup device 11 (reading of signal charges) is the same as that described above, duplicated description will be omitted.

In the present embodiment, in particular, all the colors of the on-chip color filter 19, that is, magenta (M), on the entire output section 18 and the peripheral circuit section 20, as shown by the diagonal lines in FIG.
A light shielding film 27 is formed by a laminated film in which dye layers of three colors of cyan (Cy) and yellow (Y) are stacked.

That is, in the process of forming the on-chip color filter, exposure is performed by using the mask expanded to the output section 18 and the peripheral circuit section 20, and the process is repeated for each dyed layer of each color to output as shown in FIG. Simultaneously with the formation of the color filter 19 of the imaging unit 14, the dye layers of three colors of magenta (M), cyan (Cy), and yellow (Y) are all overlaid on the unit 18 (the peripheral circuit unit 20 is the same). Shading film 2
7 is formed. A protective film 28 made of the same material as the on-chip microlens 25 is formed on the light shielding film 27.

According to the above-described embodiment, the dye layer of the on-chip color filter 19 in the image pickup section 14 is used on the output section 18 and the peripheral circuit section 20 of the solid-state image pickup element to obtain the three colors (M). , (Cy), (Y) dyeing layers are all stacked to form the light-shielding film 27, so that the output unit 1
8 and the peripheral circuit section 20 are prevented from entering the light. In case of commonly used complementary color on-chip color filter,
The transmittance of the laminated film 27 in which the three colors are overlapped is as low as 0 to 30%.

Therefore, even when a bright light source such as the sun is photographed, light is blocked from entering the signal charge detecting section 16 (eg, floating diffusion region, floating gate, etc.) 16 of the output section 18, and is darkened by photoelectric conversion. It is possible to suppress the generation of electric current. Therefore, the dark current of the solid-state image sensor can be reduced.

Since the light-shielding film 27 of this example is not a conductive film of Al or the like but a light-shielding film utilizing the on-chip color filter 19, the light-shielding film 27 is formed between the signal charge detecting portion 16 and the floating diffusion region. No capacitance is formed, and there is no hindrance to higher sensitivity and higher speed. At the same time, it is possible to prevent a decrease in the dynamic range of the output of the solid-state image sensor. This embodiment is particularly suitable for application to a camera autofocus sensor.

Further, in the peripheral circuit section 20 as well, since the light shielding film 27 does not illuminate the transistors in the peripheral circuit, the circuit operation can be stabilized without an increase in the current at the cutoff, for example.

In the above example, the light-shielding film 27 is formed by superimposing three colors of complementary color on-chip color filters. However, when using red, green, and blue on-chip color filters, the red and green colors are used. It is also possible to use a light-shielding film in which dye layers of three colors of blue are stacked.

In the above example, the present invention is applied to the IT type CCD solid-state image pickup device, but it is also applicable to, for example, an FIT (frame interline transfer) type CCD solid-state image pickup device.

[0028]

According to the present invention, the dark current can be reduced by forming the light-shielding film formed by superimposing the respective colors of the on-chip color filter on at least the signal charge detecting portion of the solid-state image sensor. It is possible to prevent a decrease in the output dynamic range. Therefore, a highly reliable solid-state image sensor can be provided.

[Brief description of drawings]

FIG. 1 is a configuration diagram showing an example of a CCD solid-state imaging device according to the present invention.

FIG. 2 is a sectional view of essential parts showing an example of a CCD solid-state imaging device according to the present invention.

FIG. 3 is a configuration diagram of a conventional CCD solid-state imaging device.

[Explanation of symbols]

 1, 11 CCD solid-state imaging device 2, 12 light receiving part 3, 13 vertical transfer register 4, 14 imaging part 5, 15 horizontal transfer register 6, 16 signal charge detection part 7, 17 output amplifier 8, 18 output part 19 on-chip color Filters 10, 20 Peripheral circuit part 21 Semiconductor substrate 22 Transfer electrode 23 Al light-shielding film 24 Flattening film 25 On-chip microlens 27 Light-shielding film 28 Protective film M Magenta Cy Cyan Y Yellow

Claims (1)

[Claims] 1. A solid-state image sensor, comprising a solid-state image sensor having a light-shielding film formed on at least a charge detection portion, the light-shielding film being a laminated film in which respective colors of an on-chip color filter are overlapped.