JPH04225565A - Solid state image sensor - Google Patents

Abstract

PURPOSE:To obtain an image of high quality having small roughness and white damage due to a shielding film. CONSTITUTION:An N<+> type layer 3 for forming a photodiode, a channel stopper 4, a buried channel 5 are selectively formed on a surface in a P-type well 2. A transfer gate 6 is disposed on the channel 5. An insulating layer 7 and a shielding film 8 for controlling a photosensor 8 are formed on the gate 6. The film 8 is formed by forming an Al-Si alloy film 8a and a high melting point metal film 8b. Even is silicon nodule 11 is generated in the film 8a, a light passing therethrough is interrupted by the film 8b, and a decrease in the quality of an image due to the nodule 11 can be prevented. Further, the films 8a, 8b are formed thereby to alleviate stress, to suppress generation of a hillock 10, and to prevent roughness of an image.

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.

0002

2. Description of the Related Art In recent years, the number of pixels in solid-state imaging devices has been increased, the dynamic range has been improved, and the image quality has been improved at low or high illuminance.

FIG. 8 shows a conventional solid-state imaging device below.
Explain using. Note that this figure is a cross-sectional view of a unit pixel.

In FIG. 8, 1 is an N-type silicon substrate, 2
3 is a P-type well, and 3 is an N+ layer, which together with the P-type well 2 constitutes a photodiode section. 4 is the channel stopper,
It is composed of a P+ layer to avoid crosstalk with other pixels. 5 is a buried channel for transferring charge;
It is composed of N+ layers. 6 is a transfer gate to which a transfer clock signal is supplied, and an insulating layer 7 is provided on the buried channel 5.
is located through. Reference numeral 8 denotes a light-shielding film for regulating the light-receiving section 9, and conventionally an Al--Si alloy film has been used.

The operation of the solid-state imaging device configured as described above will be explained below. First, the light receiving section 9
According to the amount of light incident thereon, charges are accumulated in the depletion layer from the PN junction by the N+ layer forming the photodiode section 3 and the P-type well 2. Readout of charges to the buried channel 5 is performed by applying a voltage to the transfer gate 6 to lower the potential on the buried channel 5 side. A transfer clock signal that changes the potential sequentially is sent toward the front in FIG. 8, and the amount of light incident on each light receiving section is detected.

[0006]

However, in this solid-state imaging device, since the light-shielding film 8 is made of an Al--Si alloy, hillocks (mound-like protrusions) 10 occur thereon. When this extends in the lateral direction, the incident light on the light receiving section 9 is partially blocked, causing roughness in the reproduced image. Further, when there is a silicon nodule (small lump of silicon) 11 in the light shielding film 8, light is transmitted to the buried channel 5 through it. This transmitted light causes white scratches to appear on the reproduced image. The presence of such image roughness and white scratches on the image causes deterioration of the image quality.

SUMMARY OF THE INVENTION An object of the present invention is to provide a solid-state imaging device in which roughness and white scratches in reproduced images are reduced.

[0008]

[Means for Solving the Problems] In the solid-state imaging device of the present invention, the light-shielding film that regulates the aperture of the light-receiving section includes a film in which a plurality of light-shielding materials are laminated.

[0009]

[Function] By laminating multiple light shielding materials in the light shielding film, the light that enters the inclined area other than the light receiving part is significantly reduced, and
The influence of hillocks and nodules that occur in some of the light shielding materials constituting the light shielding film is reduced.

0010

DESCRIPTION OF THE PREFERRED EMBODIMENTS Solid-state imaging devices according to embodiments of the present invention will be described below with reference to FIGS. 1 to 7.

FIG. 1 is a sectional view of a main part of the first embodiment. In the solid-state imaging device of this embodiment, a P-type well 2 is formed on one surface side of an N-type silicon substrate 1. On the surface of this P-type well 2, there is an N+ layer 3 for forming a photodiode section, a channel stopper 4 made of a P+ layer for avoiding crosstalk with other pixels, and a channel stopper 4 for transferring charge. A buried channel 5 made of an N+ layer is selectively formed. A transfer gate 6 to which a transfer clock signal is supplied is arranged on the buried channel 5 with an insulating layer 7 interposed therebetween. An insulating layer 7 and a light shielding film 8 are laminated on the transfer gate 6. The light shielding film 8 is for regulating the light receiving part 9, and is formed by laminating an Al-Si alloy film 8a and a high melting point metal film 8b.

FIG. 2 is a sectional view of a main part of the second embodiment. The solid-state imaging device of this embodiment is most different from the first embodiment in that the stacking order of the Al-Si alloy film 8a and the high melting point metal film 8b that constitute the light shielding film 8 is reversed. be. That is, an Al--Si alloy film 8a and a high melting point metal film 8b are sequentially laminated on the transfer gate 6 with an insulating layer 7 interposed therebetween. The base portion of the high melting point metal film 8b extends toward the light receiving section 9, and the Al-Si alloy film 8a
has a structure in which its tip does not protrude toward the light receiving section 9 side.

FIG. 3 is a sectional view of a main part of the third embodiment. In the solid-state imaging device of this embodiment, the light shielding film 8 has a so-called sandwich structure in which a high melting point metal film 8b is sandwiched between Al--Si alloy films 8a.

FIG. 4 is a sectional view of the main part of the fourth embodiment. The solid-state imaging device of this embodiment has the structure of the second embodiment shown in FIG.
A high melting point metal film 8b is deposited thereon.

FIG. 5 is a sectional view of a main part of the fifth embodiment. In the solid-state imaging device of this embodiment, the base of the high melting point metal film 8b is further extended toward the light receiving section 9 side compared to the second embodiment shown in FIG. This is to prevent the hem from protruding.

As described above, by constructing the light shielding film 8 as a laminated film of the Al-Si alloy film 8a and the high melting point metal film 8b, the silicon nodules 1 are formed on the Al-Si alloy film 8a.
Even if 1 occurs, the light passing through it is blocked by the high melting point metal film 8b, and the deterioration in image quality caused by the silicon nodules 11 can be improved. Further layering relieves stress,
The occurrence of hillocks 10 can be reduced.

FIG. 6 is a sectional view of a main part of the sixth embodiment. In the solid-state imaging device of this embodiment, the base of the high-melting point metal film 8b is expanded toward the light-receiving part 9 side, and the Al-Si alloy film 8
The side wall of a is inclined and tapered forward. With such a structure, even if horizontal hillocks 10 occur in the Al--Si alloy film 8a, they do not significantly affect the amount of light incident on the light receiving section 9. Furthermore, the amount of incident light reflected from the side walls of the light shielding film 8 is also reduced.

Note that reactive ion etching (RIE)
When forming a forward taper by a method, etc., in order to strengthen anisotropic etching, CH, a gas system that can form a polymer, is used.
Obtain the optimal shape using F3, CHCl3, or CCl4, etc. Further, by forming the light shielding film 8 into a laminated structure, the difference in etch rate between each layer is increased, and the base of the high melting point metal film 8b can be easily formed to be larger than the Al-Si alloy film 8a.

FIG. 7 is a sectional view of a main part of the third embodiment. In the solid-state imaging device of this embodiment, a light-shielding film 8 having a uniform thickness and high reflectance is formed on a color filter (on-chip color filter) 12 formed directly on the surface. Note that an Al--Si alloy film 8a may be formed on the surface of the solid-state imaging device, and a high-melting point metal film may be formed at a low temperature by selective CVD on the color filter 12.

[0020]

As described above, in the solid-state imaging device of the present invention, the range of material selection is expanded by laminating a plurality of light-shielding materials as the light-shielding film. Light transmitted through the silicon nodules can be blocked, and the stress relaxation caused by lamination can suppress the occurrence of hillocks, making it possible to greatly improve the quality of reproduced images. .

Furthermore, the structure according to the present invention can suppress a decrease in processing accuracy due to light halation during the photolithography process in the manufacturing process, and improve the uniformity of image quality and dynamic range of the completed solid-state imaging device. can be done.

[Brief explanation of the drawing]

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

FIG. 2 is a cross-sectional view of main parts of a solid-state imaging device according to a second embodiment of the present invention.

FIG. 3 is a sectional view of main parts of a solid-state imaging device according to a third embodiment of the present invention.

FIG. 4 is a sectional view of main parts of a solid-state imaging device according to a fourth embodiment of the present invention.

FIG. 5 is a sectional view of main parts of a solid-state imaging device according to a fifth embodiment of the present invention.

FIG. 6 is a cross-sectional view of main parts of a solid-state imaging device according to a sixth embodiment of the present invention.

FIG. 7 is a sectional view of main parts of a solid-state imaging device according to a third embodiment of the present invention.

[Figure 8] Cross-sectional view of a unit pixel of a conventional solid-state imaging device

[Explanation of symbols]

1 Silicon substrate 6 Transfer gate section 8. Light shielding film 8a Al-Si alloy film (light shielding material) 8b High melting point metal film (light shielding material) 9 Light receiving section

Claims (4)

[Claims] 1. A light receiving section for converting incident light into charges and a transfer gate section for transferring the charges are formed on a semiconductor substrate, and a plurality of light shielding films regulating an opening of the light receiving section are formed. A solid-state imaging device is a film made of laminated light-shielding materials. 2. The solid-state imaging device according to claim 1, wherein the tip of the base of the first layer constituting the light-shielding film extends closer to the light-receiving section than the tip of the second layer formed thereon. 3. The solid-state imaging device according to claim 1, wherein the angle between the side wall of the light shielding film and the surface of the light receiving section is an obtuse angle. 4. The solid-state imaging device according to claim 1, wherein a second light-shielding film is formed on the surface of the color filter provided in the solid-state imaging device.