JPH0669481A - Solid-state image pickup and its production - Google Patents

Abstract

PURPOSE:To prevent the generation of false signal due to light leaking into light-receiving and charge transfer parts formed on a semiconductor board and reduce smear failures. CONSTITUTION:A peripheral part of photodiode 12 as a light-receiving part and an N-type embedded channel 14 as a charge transfer part that are formed on a P-type semiconductor board 11 are covered with WSi films 17 of 100mmu in thickness, and upper sides of the films 17 on the channels 14 are covered with Al films 18 of 800mmu in thickness and further TiN films 19 of 200mmu cover the films 17 and 18. Therefore, a light shielding film of 300mmu in thickness is formed on the upper side of the peripheral part of the photodiode 12, while a light shielding film of 1100mmu in thickness is formed on the channel 14.

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 for detecting an optical signal.

[0002]

2. Description of the Related Art A sectional structure of a conventional solid-state image pickup device is shown in FIG. In the figure, 31 is a P-type semiconductor substrate, and 32, 3
2 is an N-type photodiode for performing photoelectric conversion, 33,
Reference numeral 33 is a P-type channel stopper that prevents charges from flowing into other pixels, and 34 and 34 are N-type buried channels for transferring charges. Reference numeral 35 is a polysilicon electrode for transferring charges, 36 is an insulating film covering the polysilicon electrode 35, 37 is a light-shielding film made of an Al film for preventing light from entering the N-type buried channel 34, and 38 is a light-shielding film. 37
And a protective film that covers the exposed portion of the insulating film 36.

The operation of the solid-state image pickup device configured as described above will be described.

When light is incident on the photodiode 32 as a light receiving portion, charges are generated from the P-N junction portion according to the amount of incident light. The charge is read out to the N-type buried channel 34 as the charge transfer portion by changing the voltage of the polysilicon electrode 35 and lowering the potential of the N-type buried channel 34. The charge transfer is performed by applying a clock signal to the polysilicon electrode 35.

[0005]

By the way, in the above-mentioned conventional structure, when strong light is incident, the incident light is transmitted through the polysilicon electrode 35 and the N type buried channel 3 is formed.
The first phenomenon (indicated by an arrow A in the figure) invading the light source 4 or the incident light is the light shielding film 37 of the photodiode 32.
The second phenomenon (indicated by an arrow a in the figure) that is reflected on the side wall of the opening of the photo diode 32 and enters the photodiode 32, or the incident light repeatedly diffuses between the semiconductor substrate 31 and the light shielding film 37 to cause photo A third phenomenon (shown by c in the figure) that enters the diode 32 occurs. The charges generated by the leakage of light into the light receiving unit and the charge transfer unit become false signals, and vertical stripes are generated (smear defect) on the screen, resulting in deterioration of image quality.

In order to suppress the above first phenomenon, the light shielding film 3
7 may be made thicker, but in the conventional structure, if the light shielding film 37 is thickened, the side wall of the opening of the light shielding film 37 also becomes thicker, so that the second phenomenon due to reflection on the side wall increases. There is a problem such as that, and variation in processing becomes large.

In view of the above, the present invention solves the above-mentioned problems of the prior art, prevents a false signal generated by light leaking into the light receiving portion and the charge transfer portion, and can sufficiently cope with miniaturization. And to ensure that such a solid-state imaging device can be manufactured by a simple process.

[0008]

In order to achieve the above object, the means for solving the problems according to the invention of claim 1 is to increase the thickness of the light shielding film covering the upper side of the charge transfer portion, while at the same time, to the periphery of the light receiving portion. The thickness of the light-shielding film that covers the portion is reduced.

Specifically, the means for solving the problems according to the invention of claim 1 is a solid-state imaging device having a light receiving portion and a charge transfer portion formed on a semiconductor substrate, and is intended for a peripheral portion of the light receiving portion and the charge transfer portion. A first light-shielding film is formed on the portion, and a second light-shielding film is formed on a portion of the first light-shielding film above the charge transfer portion. The third light shielding film is formed on the second light shielding film.

Further, according to the invention of claim 2, in order to further reduce the light passing through the light shielding film and penetrating into the charge transfer portion, in the structure of claim 1, the film thickness of the second light shielding film is the above. A configuration in which the thickness of the first light-shielding film and the thickness of the third light-shielding film are set to be thicker than the total is added.

According to the invention of claim 3, in order to prevent irregular reflection of light between the light-shielding film and the semiconductor substrate, the first light-shielding film is formed of a material having a low reflectance in the structure of claim 1. The configuration that is done is added.

Further, the invention of claim 4 is a method for manufacturing the solid-state image pickup device according to claim 1,
Specifically, after forming the first light shielding film over the entire surface on the light receiving portion and the charge transfer portion formed on the semiconductor substrate,
A second light-shielding film is selectively formed on the first light-shielding film on the upper side of the charge transfer portion, and then over the entire surface of the first light-shielding film and the second light-shielding film. The third light-shielding film is formed, and thereafter, the upper portion of the central portion of the light-receiving portion in the first and third light-shielding films is selectively removed.

[0013]

According to the structure of claim 1, since the thick light-shielding film composed of the first, second and third light-shielding films is formed on the charge transfer portion, the incident light is incident on the first to third light-shielding films. Since it is blocked by the light shielding film, it does not enter the charge transfer portion.

Since a thin light-shielding film composed of the first and second light-shielding films is formed on the peripheral portion of the light-receiving portion, incident light is less likely to be reflected by the side walls of the openings of the first and second light-shielding films. Therefore, the incident light reflected by the side wall is less likely to enter the light receiving portion.

According to the structure of claim 2, since the film thickness of the second light shielding film is set to be thicker than the sum of the film thickness of the first light shielding film and the film thickness of the third light shielding film, The phenomenon that light penetrates into the charge transfer portion and the phenomenon that incident light is reflected by the side walls of the openings of the first and second light shielding films and penetrates into the light receiving portion are further reduced.

According to the structure of claim 3, since the first light-shielding film is made of a material having a low reflectance, irregular reflection of light between the light-shielding film and the semiconductor substrate is prevented,
It is possible to prevent a phenomenon in which light diffusely reflected between the light shielding film and the semiconductor substrate enters the light receiving portion.

According to the structure of claim 4, first to third light shielding films are formed on the charge transfer portion formed on the semiconductor substrate.

The second light shielding film is not formed on the light receiving portion formed on the semiconductor substrate, and after the first and third light shielding films are formed on the upper side of the light receiving portion, the light receiving portion is formed. Since the first and third light shielding films on the upper side of the central portion of the light receiving portion are selectively removed, the light shielding film is not formed on the upper side of the central portion of the light receiving portion, while the first and third light shielding films are formed on the upper side of the peripheral portion of the light receiving portion. First and third light shielding films are formed.

[0019]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The structure of a solid-state image pickup device according to an embodiment of the present invention will be described below with reference to FIG.

In the figure, 11 is a P-type semiconductor substrate, 1
Reference numerals 2 and 12 are N-type photodiodes as a light-receiving portion for performing photoelectric conversion, 13 and 13 are P-type channel stoppers that prevent an electric charge from flowing into other pixels, and 14 and 14 are N-type buried portions as a charge transfer portion. Channels, 15 and 15 are polysilicon electrodes for transferring charges, 16 is an insulating film that covers the polysilicon electrodes 15, and 17 is a first light-shielding film that covers the peripheral portion of the photodiode 12 and the N-type buried channel 14. Is formed on the WSi film 17 and covers the N-type buried channel 14.
Al film as a light-shielding film of, WSi film 17 and Al
A TiN film as a third light-shielding film formed on the film 18 and covering the peripheral portion of the photodiode 12 and the N-type buried channel 14, and 20 covers the exposed portions of the TiN film 19 and the insulating film 16. It is a protective film.

A method of manufacturing the solid-state image pickup device according to the above embodiment will be described below with reference to FIGS.

First, on the P-type semiconductor substrate 11, the N-type photodiode 12, the P-type channel stopper 13,
After each of the N-type buried channel 14, the polysilicon electrode 15 and the insulating film 16 is formed, a WSi film 17 is formed on the entire surface of the insulating film 16 as shown in FIG.
The film is formed to a film thickness of 0 mμ, and then the Al film 18 is formed to a film thickness of 800 mμ on the entire surface of the WSi film 17.

Next, as shown in FIG. 3, since only the Al film 18 on the upper side of the polysilicon electrode 15 is left, the Al film 18 on the peripheral side of the Al film 18 on the upper side of the polysilicon electrode 15 is removed. Etching treatment is selectively performed.

Next, as shown in FIG. 4, a TiN 19 film is formed over the entire surface of the Al film 18 and the WSi film 17 above the polysilicon electrode 15 to a thickness of 200 mμ.

Next, as shown in FIG. 5, the TiN film 19 and the WSi film 17 are simultaneously etched to form a photodiode opening 21 between the polysilicon electrodes 15, and then the insulating film 16 and the TiN 19 film are formed. A protective film 20 is formed on the entire surface of the above.

As a result of selectively forming the multilayer light-shielding film as described above, the WSi film 17 of 100 mμ, the Al film 18 of 800 mμ and the 200 mμ are formed on the upper side of the polysilicon electrode 15.
Since a light-shielding film made of the TiN film 19 having a thickness of 1100 mμ is formed, the light passes through the polysilicon electrode 15 and the N
Intrusion into the mold buried channel 14 can be sufficiently prevented.

Further, 1 is provided above the photodiode 12.
A situation in which only a 300 mμ light-shielding film composed of a 00 mμ WSi film 17 and a 200 mμ TiN film 19 is formed, and light is reflected by the side wall of the opening of the light-shielding film of the photodiode 12 and enters the photodiode 12. Is reduced.

Further, since the WSi film 17 having a low reflectance is formed in the lower layer of the light shielding film which covers the peripheral portion of the photodiode 12, irregular reflection of light between the semiconductor substrate 11 and the light shielding film is prevented. As a result, the situation in which the irregularly reflected light enters the photodiode is prevented.

In addition, a 100 μm WSi film 17 and 8
By combining the Al film 18 of 00 mμ and the TiN film 19 of 200 mμ, generation of silicon nodules in the Al film 18 is prevented, so that the light shielding property can be improved. Further, since the TiN film 19 having a low reflectance is used as the uppermost layer, halation when forming an on-chip filter can be reduced.

In the present invention, the WSi film 17 is used as the lower layer of the light-shielding film and the TiN film 18 is used as the upper layer, but it is clear that the same effect can be obtained by using other refractory metals instead. Is.

[0031]

As described above, according to the solid-state image pickup device of the first aspect of the present invention, the first,
Since a thick light-shielding film including the second and third light-shielding films is formed, and a thin light-shielding film including the first and second light-shielding films is formed on the peripheral portion of the light receiving portion, incident light Is blocked by the thick light-shielding film composed of the first to third light-shielding films, so that it is difficult to enter the charge transfer portion, and the side walls of the openings of the first and second light-shielding films are thinned and reflected by the side walls. Since it is less likely to be incident, the incident light reflected by the side wall is less likely to enter the light receiving portion.

Therefore, according to the first aspect of the present invention, the false signal generated by the leakage of the light into the light receiving portion and the charge transfer portion is prevented, so that the smear defect can be prevented and the miniaturization can be sufficiently dealt with. .

According to the solid-state imaging device of the second aspect of the present invention, the film thickness of the second light-shielding film is set to be thicker than the sum of the film thickness of the first light-shielding film and the film thickness of the third light-shielding film. Because
Since the light that passes through the light shielding film and enters the charge transfer portion is further reduced, smear defects can be more surely prevented.

According to the solid-state imaging device of the third aspect of the invention, since the first light-shielding film is made of a material having a low reflectance, irregular reflection of light between the light-shielding film and the semiconductor substrate is prevented, Light that diffusely reflects between the light-shielding film and the semiconductor substrate and enters the light receiving portion is reduced, so that smear defects can be more reliably prevented.

According to the method of manufacturing a solid-state image pickup device according to the fourth aspect of the present invention, the first light-shielding film is formed over the entire surface of the light-receiving portion and the charge transfer portion, and the charge on the first light-shielding film is formed. A second light-shielding film is selectively formed on the upper portion of the transfer portion,
Since the third light-shielding film is formed over the entire surfaces of the first and second light-shielding films and the upper portion of the central portion of the light-receiving portion in the first and third light-shielding films is selectively removed, the charge Since the thick light-shielding portion including the first to third light-shielding films is formed on the transfer portion, and the thin light-shielding portion including the first and third light-shielding films is formed on the peripheral portion of the light receiving portion. The solid-state imaging device according to the invention of claim 1 can be reliably manufactured by a simple process.

[Brief description of drawings]

FIG. 1 is a sectional view of a solid-state imaging device according to an embodiment of the present invention.

FIG. 2 is a cross-sectional view showing steps of a method for manufacturing the solid-state imaging device.

FIG. 3 is a cross-sectional view showing steps of a method for manufacturing the solid-state imaging device.

FIG. 4 is a cross-sectional view showing steps of a method for manufacturing the solid-state imaging device.

FIG. 5 is a cross-sectional view showing a step in a method for manufacturing the solid-state imaging device.

FIG. 6 is a sectional view of a conventional solid-state imaging device.

[Explanation of symbols]

 11 P-type semiconductor substrate 12 Photodiode (light-receiving part) 13 P-type channel stopper 14 N-type buried channel (charge transfer part) 15 Polysilicon electrode 16 Insulating film 17 WSi film (first light-shielding film) 18 Al film ( Second light-shielding film 19 TiN film (third light-shielding film) 20 Protective film 21 Photodiode opening

Claims (4)

[Claims] 1. A solid-state imaging device having a light receiving portion and a charge transfer portion formed on a semiconductor substrate, wherein a first light shielding film is formed on a peripheral portion of the light receiving portion and the charge transfer portion. A second light shielding film is formed on the upper portion of the first light shielding film above the charge transfer portion.
A solid-state imaging device, wherein a third light-shielding film is formed on the light-shielding film and the second light-shielding film. 2. The film thickness of the second light shielding film is set to be thicker than the sum of the film thickness of the first light shielding film and the film thickness of the third light shielding film. The solid-state imaging device according to claim 1. 3. The solid-state imaging device according to claim 1, wherein the first light-shielding film is formed of a material having a low reflectance. 4. A first light-shielding film is formed over the entire surface of a light-receiving portion and a charge-transfer portion formed on a semiconductor substrate, and then above the charge-transfer portion on the first light-shielding film. A second light-shielding film is selectively formed on the portion, and then a third light-shielding film is formed over the entire surfaces of the first light-shielding film and the second light-shielding film, and then the first light-shielding film is formed. And a method for manufacturing a solid-state imaging device, wherein an upper portion of the central portion of the light receiving portion in the third light shielding film is selectively removed.