JPH02140978A - Solid state image sensor - Google Patents

Abstract

PURPOSE:To prevent sensitivity from decreasing by forming the aluminum particles of a thin aluminum film for forming a light shielding film smaller than those of a thin aluminum film formed as signal wirings in a solid state image sensor. CONSTITUTION:An N-type diffused layer 2 is formed on one main face of a P-type silicon substrate 1, a reading electrode 3 of polycrystalline silicon is formed through an oxide film, an interlayer film 4 is then formed, covered with a thin aluminum film thereon, and formed in a pattern to form a light shielding film 5. Further, it is covered with an interlayer film 6 made of a silicon oxide film, and formed with a thin aluminum film in a predetermined pattern, thereby forming signal wirings 7. The aluminum particle size of the film 5 is formed smaller than those of the wirings 7. Accordingly, if particles are emitted during the annealing after the formation, the particles entering a photodetector are small, and thus, the influence on the photodetecting area of the photodetector is substantially eliminated. In this manner, it can prevent its sensitivity from decreasing.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to one-dimensional and two-dimensional solid-state imaging devices, and particularly to a device that achieves uniformity of sensitivity.

[Conventional technology]

Conventionally, in solid-state imaging devices, an aluminum thin film that constitutes signal wiring and an aluminum thin film that constitutes a light-shielding film that defines a light-receiving area are formed in the same process. For this reason,
The grain size (dalein size) of each aluminum thin film is the same, and in order to prevent electromigration in signal wiring where large currents flow, the grain size is relatively large (
approximately 3.0 μm or more).

[Problem to be solved by the invention]

In the conventional solid-state imaging device described above, the following problem occurs because the grain size of the aluminum thin film of the light shielding film is the same as the grain size of the aluminum thin film of the signal wiring.

That is, as shown in FIG. 3, a part of the plane of the light receiving element area,
In the solid-state imaging device, after forming a light-shielding film 5' to define alternately arranged light receiving elements 8 and channel cut regions 9, annealing is performed at about 400 to 450°C. At this time, the aluminum undergoes thermal movement due to the annealing temperature, and a phenomenon occurs in which the particles 5b fly out along the boundary toward the light receiving element, as shown by diagonal lines in the figure.

For this reason, this flying particle 5b makes the light receiving area of the light receiving element 8 in this part smaller than the light receiving area of other light receiving elements, causing a problem that the sensitivity of the light receiving element in this part is reduced.

An object of the present invention is to provide a solid-state imaging device that prevents such a decrease in sensitivity.

[Means to solve the problem]

In the solid-state imaging device of the present invention, the aluminum particles of the aluminum thin film constituting the light-shielding film that defines the light-receiving area of the light-receiving element have a particle size smaller than that of the aluminum particles of the aluminum thin film formed as signal wiring in the solid-state imaging device. is formed.

C Effect] In the above-described configuration, the aluminum grain size of the aluminum thin film in the signal wiring is increased to ensure electromigration resistance, and at the same time, a decrease in the area of the light receiving element due to the phenomenon of aluminum grains flying out from the light shielding plate is suppressed.

〔Example〕 Next, the present invention will be explained with reference to the drawings.

FIGS. 1(a) and 1(b) are cross-sectional views showing an embodiment of the present invention in the order of manufacturing steps, and FIG. 2 is a plan view thereof.

That is, as shown in FIG. 1(a), an N-type diffusion layer 2 is formed on the entire surface of a P-type silicon substrate 1, and a readout electrode 3 made of polycrystalline silicon is formed with an oxide film interposed therebetween. Thereafter, a glabellar film 4 is formed, and an aluminum thin film is deposited thereon and patterned to form a light shielding film 5. At this time,
The aluminum thin film is formed so that the grain size is about 1.0 μm or less. Further, the film thickness is approximately 0.5 μm.

Next, as shown in FIG. 1(b), annealing is performed in a range of approximately 400 to 450 DEG C., and an interlayer film 6 made of a silicon oxide film is deposited by CVD. The film thickness is approximately 0.5 μm.

Thereafter, a contact hole (not shown) is opened in the glabellar membrane, and an aluminum thin film is formed in a desired pattern thereon to form the signal wiring 7. This signal wiring 7 is about 3
．． It is formed to have a large particle size of 0 μm or more to obtain an anti-electromigration effect.

In the solid-state imaging device manufactured in this way, the light shielding film 5
The aluminum grain size of the signal wiring 7 is considered to be extremely smaller than that of the signal wiring 7. Therefore, even if particles fly out due to annealing after forming the light-shielding film, the particles will fly out into the light-receiving element section where the light-receiving elements 8 and channel cut regions 9 are alternately arranged, as shown by diagonal lines in FIG. 5a is extremely small and has almost no effect on the light-receiving area of the light-receiving element 8. Therefore, the sensitivity of the light-receiving element in this part is not lowered than that of other light-receiving elements, and the solid-state imaging device has high sensitivity. can be configured.

〔Effect of the invention〕

As explained above, in the present invention, the aluminum particles of the aluminum thin film constituting the light shielding film have a smaller particle size than the particles of the aluminum thin film constituting the signal wiring, so the aluminum grain size of the aluminum thin film in the signal wiring is increased. This has the effect of ensuring electromigration resistance while suppressing a reduction in the area of the light receiving element due to the phenomenon of aluminum particles flying out from the light shielding plate, thereby improving light receiving sensitivity and its uniformity.

[Brief explanation of the drawing]

1(a) and 1(b) are cross-sectional views showing an example of the manufacturing method of the solid-state imaging device of the present invention in the order of manufacturing steps, FIG. 2 is a plan view of essential parts of an embodiment of the present invention, and FIG. 1 is a plan view of a portion of a conventional solid-state imaging device. 1... P type silicon substrate, 2... N type diffusion layer, 3...
...Reading electrode, 4...Interlayer film, 5.5'...Light shielding film, 5a, 5b...Aluminum particles, 6...Interlayer film, 7...Signal wiring, 8...Light receiving Element, 9...Channel cut region. Figure 2

Claims (1)

[Claims] 1. In a solid-state imaging device in which light-receiving elements are arranged on a semiconductor substrate and the light-receiving area of the light-receiving elements is defined by a light-shielding film made of an aluminum thin film, the aluminum particles of the aluminum thin film constituting the light-shielding film are A solid-state imaging device characterized in that the aluminum particles are formed to have a smaller particle size than the aluminum particles of the aluminum thin film formed as signal wiring therein.