JPH0395968A - Solid-state image pick-up element - Google Patents

Abstract

PURPOSE:To prevent scattering of the area of a light-receiving window even after going through annealing treatment at 300-450 deg.C and irregular reflection from a ground when forming a pattern of film on the light-receiving window by using a high melting- point metal film as a light-screening film for isolating each light-receiving element and by using the high melting-point metal film and an aluminum film which is placed above it as a means for screening light at a charge transfer region. CONSTITUTION:The title item consists of a high melting-point metal film 9 with a light-receiving window 11 on a light-receiving element and a light-screening aluminum film 1 covering only the area above an n-type diffusion layer 5. An aluminum film is superposed onto the high melting-point metal film at a CCD requiring light-screening property. The high melting-point metal film does not produce any hillock as in an aluminum film even though an annealing process at 300-450 deg.C, thus preventing the area of the light-receiving window from scattering if this high melting-point metal film is used as a film determined the light-receiving window. Use of a high melting- point metal film with lower reflectivity than that of the aluminum film prevents irregular reflection generated due to level difference in the ground on exposure and enables patterning to be made accurately.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a solid-state image sensor, and particularly to a charge-coupled device (C
Regarding solid-state imaging devices using OD). C. Prior Art] A plan view of a conventional image sensor of this type is shown in FIG.
A line sectional view is shown in Fig. 5. As shown in Figure 4,
In a conventional solid-state image sensor, a light-shielding aluminum film 1a having light-receiving windows 11 opened in a matrix is formed on a semiconductor substrate. Under the light-shielding aluminum film 1a, as shown in FIG.
In the surface area of the type well region 2, an n-type diffusion layer 3 of the photodiode is separated by a channel stop region 6.
and an n-type diffusion layer 5 which is a charge transfer region of the CCD. Further, on the semiconductor substrate under the light-shielding aluminum film 1a, there is a gate voltage f! surrounded by an insulator M7. 4 is formed. The characteristics required of the light-shielding film of such a solid-state image sensor are: ■ The film must be sufficiently light-shielding to prevent light from leaking into the COD, and ■ It must be precisely processed so that the area of the light-receiving window does not vary. There are two points to mention: the membrane is capable of forming Aluminum film is widely used as a film that satisfies these two points. [Problems to be Solved by the Invention] The light-shielding film of the conventional solid-state image sensing device described above has the following two drawbacks due to the use of an aluminum film as the light-shielding film. First, in the manufacturing process of solid-state image sensors, after processing the light-shielding film, it is necessary to perform annealing treatment at 300 to 450°C in a hydrogen atmosphere to reduce the surface unit of the semiconductor substrate. This annealing process produces protrusions called ridges on the surface of the film. These protrusions that partially form on the sidewalls and surface of the light-shielding film cause variations in the area of the light-receiving window. The second drawback is that the aluminum film has a high light reflectance. In the conventional solid-state image sensor shown in FIG.
By coating an emulsion such as gelatin or casein on each light-receiving window, buttering it, and dyeing it to have the desired spectral characteristics, a solid-state imaging device with color sensitivity can be realized. Butterning is carried out using ultraviolet rays with a wavelength of 300 to 400 nm, but if there is a highly reflective film under the film to be patterned, diffuse reflection will occur during exposure, making it difficult to perform accurate patterning. becomes difficult. [Means for Solving the Problems] The solid-state image sensor of the present invention includes a plurality of periodically arranged light receiving elements and a charge transfer region for reading out signals from each light receiving element on the entire surface of a semiconductor substrate. A light-shielding film is provided to separate each light-receiving element and completely shield the charge transfer region from light, using a high-melting point metal film (or a high-melting-point metal silicide film) as the light-shielding film that separates each light-receiving element.
The high melting point metal film and the aluminum film placed on top of the high melting point metal film are used as a means for shielding the charge transfer region from light. [Example] Next, an example of the present invention will be described with reference to the drawings. FIG. 1 is a sectional view showing one embodiment of the present invention. This figure shows the same cross-sectional portion as FIG. 5, and the same parts as in FIG. 5 are given the same reference numerals. The difference between this embodiment and the conventional example shown in FIG. It is constructed of a melting point metal film 9 and a light-shielding aluminum film 1 covering only the n-type diffusion layer 5 of the CCD, and is otherwise the same as the conventional example. Figure 2 shows a graph of the transmittance of the high-melting point metal film and aluminum film for light at each optical wavelength. High melting point metal films are inferior to aluminum films in terms of light shielding properties. Therefore, in the present invention, in the CCD section where light-shielding properties are required, an aluminum film is layered on a high-melting point metal film. On the other hand, unlike aluminum films, high melting point metal films do not generate hills even after undergoing an annealing process at 300 to 450°C. The area of the light-receiving window can be made uniform. In addition, in the color filter forming process, reflection near the light receiving window is a problem, but since a high melting point metal film with a lower reflectance than an aluminum film is used here, it prevents diffused reflection that occurs at the step of the base during exposure. This allows for accurate patterning. In the process of forming a light shielding film according to the present invention, a selectivity with respect to the high melting point metal film 9 is required when etching the light shielding aluminum film 1, but this can be easily achieved by using a phosphoric acid solution at around 60°C. can do. FIG. 3 is a sectional view showing another embodiment of the present invention. In this embodiment, a polysilicon film 1 is placed under a high melting point metal film 9.
It has a structure in which 0 is arranged. This polysilicon film 10
This increases the adhesion of the high-melting point metal M9 and improves the conductivity of the light-shielding film, so use the light-shielding film! Improves reliability when used as a pole. Note that even if a high melting point metal sisoside film is used in place of the high melting point metal film used in each of the above embodiments, the present invention can achieve the same efficiency as in each of the above embodiments. [Effects of the Invention] As explained above, in the solid-state image sensor of the present invention, the light-shielding aluminum film is used only for shielding light from COD, and the high-melting point metal film or high-melting point metal silicide film forming the light-receiving window allows each light to be received. Since the elements are separated, according to the present invention, the area of the light-receiving window does not vary even after annealing at 300 to 450°C, and when forming a filter film pattern on the light-receiving window, It is possible to prevent diffused reflection from the surface and form accurate patterns.

[Brief explanation of drawings]

FIG. 1 is a sectional view showing one embodiment of the present invention, and FIG. 2 is a sectional view showing an embodiment of the present invention.
3 is a sectional view showing another embodiment of the present invention, FIG. 4 is a plan view showing a conventional example, and FIG. 5 is a sectional view taken along the line AA' in FIG. 4. It is. DESCRIPTION OF SYMBOLS 1, 1a... Light-shielding aluminum film, 2... P-type well region, 3... N-type diffusion layer (photodiode), 4... Gate electrode, 5... N-type diffusion layer (t-type well region),... transfer region), 6... channel stop region, 7... insulating film, 8... n-type semiconductor substrate,
9... High melting point metal film, 10... Polysilicon film, 11... Light receiving window.

Claims (1)

[Claims] a plurality of light-receiving elements regularly arranged on one principal surface of a semiconductor substrate; and a charge transfer region formed on one principal surface of the semiconductor substrate for receiving and transferring signal charges photoelectrically converted in the light-receiving elements. and a light-shielding film formed on the semiconductor substrate with an insulating film in between, which separates the plurality of light-receiving elements and blocks light from the charge transfer region, wherein the light-shielding film covers each light-receiving element. 1. A solid-state imaging device comprising a refractory metal film or a refractory metal silicide film having an opening thereon, and an aluminum film formed on the charge transfer region.