JPH02232967A - Solid-state image sensor - Google Patents

Abstract

PURPOSE:To prevent a solid-state image sensor of this design from deteriorating in smear and sensitivity nonuniformity property by a method wherein a slope whose angle of inclination is 45 deg. or more and a horizontal or nearly horizontal pent-roof-like part are provided to the end of an optical shielding film. CONSTITUTION:A photoelectric conversion region and a change transfer region are formed on a semiconductor substrate 1. An optical shielding film 5 of Al is provided with a slope 9 whose angle of inclination is 45 deg. or more to a horizontal plane and a horizontal pent-roof-like part 10 so as to prevent the reflected light from the film 5 being incident on a part nearby a poly-Si electrode 3 to deteriorate a solid-state image sensor of this design in smear property. By this setup, light 2 incident on the slope 9 of the film 5 is reflected twice and sent outside, so that it never deteriorate the image sensor in smear and sensitivity nonuniformity property.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a solid-state imaging device, and particularly to the structure of a light shielding film of a solid-state imaging device.

[Conventional technology]

Conventionally, the structure of the light shielding film of this type of solid-state imaging device was as shown in FIG. 1 is a semiconductor substrate on which a photoelectric conversion region and a charge transfer region are formed; 2, 4, and 6 are oxide films; 3 is a charge transfer electrode made of polysilicon; and 5 is a light shielding film made of aluminum.

During imaging, the light incident on the light receiving section 7 is photoelectrically converted into electrons, which are read out under the polysilicon electrode where the potential potential is deeper when the potential potential changes, which is normally given at a constant cycle. Polysilicon electrodes 5 usually have two or more types of shapes and functions arranged alternately, and by applying potential alternately, electrons generated by photoelectric conversion are sequentially sent to the output section and taken out to the outside. , it is regenerated into image data by an external circuit.

[Problem to be solved by the invention]

In the conventional solid-state imaging device described above, the polysilicon electrode 3
Since aluminum, which has an extremely high reflectance, is used for the light-shielding film 5 formed on the charge transfer region having a There is a drawback that the light enters the periphery of charge transfer regions facing each other across adjacent pixels, deteriorating smear characteristics and sensitivity unevenness characteristics.

[Means to solve the problem]

In the solid-state image sensing device of the present invention, the end portion of the light-shielding film has an inclined portion having an inclination of 45° or more with respect to the horizontal, and a horizontal or nearly horizontal eave-shaped portion following the inclined portion. That is, according to the present invention, an inclined part having an inclination of 45 degrees or more with respect to the horizontal is provided at the end of the light-shielding film on the polysilicon electrode, and a horizontal part for re-reflecting the light once reflected at this inclined part. Since the eaves portion is formed to protrude above the eaves, the light incident on the inclined portion is reflected to the outside twice, which has the effect of preventing deterioration of smear characteristics and sensitivity unevenness characteristics.

〔Example〕

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

FIG. 1 is a longitudinal sectional view of an embodiment of the present invention.

In the figure, 1 is a semiconductor substrate, on which a photoelectric conversion region and a charge transfer region are formed by impurity diffusion. 2 and 4 are oxide films that function as insulating films. 3 is a polysilicon electrode, which plays a main role in charge transfer. Reference numeral 5 denotes an aluminum light-shielding film to prevent light reflected by the aluminum light-shielding film 5 from entering the vicinity of the polysilicon electrodes (hereinafter referred to as counter electrodes) facing each other across the pixels and worsening the smear characteristics. It has an inclined part 9 having a certain slope and a horizontal eave-like eave part 10. The theory and actual structure of the function of this slope and eaves section are shown below. FIG. 2 is an explanatory diagram of this embodiment. In the figure, reference numeral 5 denotes an aluminum light-shielding film having an inclined portion 9 and an eaves portion 8 . Here, the horizontal lengths of the slope part 9 and the eaves part 10 are respectively Ll,
L2, and the angle of inclination of the inclined part 9 is θ. If the horizontal length L2 of the eaves part 10 is long enough, if θ>45°, the light that is perpendicularly incident on the solid-state imaging device will be reflected once at the inclined part 9. The light is necessarily reflected once more by the eaves part 10. In reality, it is impossible to take the horizontal length L2 of the eaves part 10 to infinity, so the length of the eaves part required to fully reflect the light once reflected by the slope part 9 is L 2 (MAX). Therefore, by configuring the horizontal eaves portion with a length L 2 (MAX) <sm) expressed by θ2=2θ−90° or more, it is effective to improve smear characteristics, uneven sensitivity of the device, etc.

? Figure 3 is a graph of the equation. Figure 4 shows an example actually designed using this method and the light path at that time. As is clear from this example, the light beam incident on the inclined portion of the aluminum light-shielding film 5 is reflected to the outside by two reflections, so that the smear characteristics and sensitivity unevenness characteristics are not deteriorated. In actual device tests, it was confirmed that the smear value was reduced by approximately 40%.
[Effects of the Invention] As described above, the present invention provides a solid-state imaging device in which the shape of the end of an aluminum light-shielding film formed on a polysilicon electrode is formed into an inclined part having an inclination of 45 degrees or more, and this inclined part. When the inclination angle is θ and the horizontal length is Lc■,

[Brief explanation of the drawing]

Fig. 1 is a longitudinal sectional view of one embodiment of the present invention, Fig. 2 is a sectional view of the end of the light shielding film for explaining the same embodiment, and Fig. 3 is the length of the sloped part and the eaves part and the incidence of light. A graph showing the relationship with the angle, Fig. 4 is a sectional view of an embodiment using actual values, and Fig. 5 is a sectional view of a conventional example. 1... Semiconductor substrate, 2... Oxide film, 3
...Polysilicon electrode, 4 ... Oxide film, 5 ... Light shielding film, 6 ... Cover oxide film, 7 ... Light receiving part , 8... Incident light, 9.
...Slope part, 10...Eave part. Agent Patent Attorney Susumu Uchihara OS / t. 5 it (7ttn)

Claims (1)

[Claims] In a solid-state imaging device having a plurality of photoelectric conversion regions and a plurality of charge transfer regions on one main surface of a semiconductor substrate, the shape of the end of the light shielding film covering the upper part other than the photoelectric conversion region is inclined at an angle of 45° or more with respect to the horizontal. What is claimed is: 1. A solid-state imaging device, characterized in that it has a structure having a horizontal or nearly horizontal eave portion following the structure.