JPH03165063A - Solid-state image sensor - Google Patents

Abstract

PURPOSE:To prevent false signals by sliding an electrode which reads or transfers charges with a thin light-shielding side wall made of a metal film or the like. CONSTITUTION:After a p-type well 2 is formed in an n-type semiconductor substrate 1 by ion implantation and diffusion heat treatment of a p-type, a p<+> type channel stop 5, an n-type photoelectric conversion region 3, and an n-type charge transfer region 4 are formed by ion implantation of p-type and n-type impurities. This step is followed by the formation of a charge transfer electrode 7 made of polysilicon via an insulating film 6 and then of an insulating film 6 on the surface of polysilicon under thermal oxidation. A light-shielding metal film 8 is uniformly grown from top of the film 6 by a method such as sputtering an organic metal CVD and anisotropically etched, thereby remaining in self-alignment on the side wall of the charge transfer electrode 7. The final step is to form an insulating film 6 as the interlayer film and an aluminum film 9 as its overlayer. This design allows the effective shield of oblique incident light incoming to the cell inner region other than photodetectors.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a CCD type or MOS type solid-state image sensor, and particularly relates to a solid-state image sensor that reduces false signals such as smear.

[Prior Art] A cross-sectional view of a conventional solid-state imaging device of this type is shown in FIG. 4. This is an example of a CCD type two-dimensional solid-state imaging device, and in the same figure, 1 is an n-type semiconductor substrate, 2 is a p-type well, 3 is an n-type photoelectric conversion region, 4 is an n-type charge transfer region, 5 is a p + type channel stop, 6 is an insulating film, 7 is a charge transfer electrode made of polysilicon, and 9 is an aluminum light shielding film. be.

In this solid-state image sensor, incident light to the image sensor is regulated by an aluminum light-shielding film 9 so that it is incident only on the photoelectric conversion region 4 . Signal charges generated in the photoelectric conversion region are read out to the charge transfer region 4 by applying readout pulses and transfer pulses to the charge transfer electrode 7, and are directed within the region toward the horizontal charge transfer element relative to the paper surface. Transferred vertically.

[Problems to be Solved by the Invention] In the conventional solid-state image sensor described above, the aluminum light-shielding film 9 is effective for incident light perpendicular to the element.

However, in an actual imaging device, since obliquely incident light other than vertically incident light exists, the obliquely incident light 13 enters a region other than the photoelectric conversion region 3 as shown in FIG. In this case, a part of the photoelectrically converted charge 14 due to the obliquely incident light is collected in the charge transfer region 4 and becomes a smear component. When a conventional solid-state image sensor captures an image of a high-brightness object, the image becomes distorted due to a smear component caused by this obliquely incident light component.

As a method for preventing obliquely incident light from entering areas other than the photoelectric conversion area, as shown in FIG. A possible method is to cover it with a film 9a. However, with this method, when patterning the aluminum light-shielding film, a sufficiently large margin must be provided to prevent the sides of the charge transfer electrode 7 from being exposed even if misalignment occurs. A problem arises in that the area becomes narrower and the sensitivity is significantly lowered. In particular, it is difficult to employ this method in recent solid-state image sensing devices in which the device density has been increased.

[Means for Solving the Problems] A solid-state imaging device of the present invention includes a plurality of photoelectric conversion regions of a second conductivity type provided within a semiconductor region of a first conductivity type, and a plurality of photoelectric conversion regions provided adjacent to each photoelectric conversion region. a charge readout region of a first conductivity type; a signal charge receiving region that receives signal charges generated in the photoelectric conversion region via the charge readout region; and a signal charge receiving region formed on the charge readout region with an insulating film interposed therebetween. a gate electrode, a metal light-shielding film formed on a semiconductor substrate so as to cover the gate electrode, and a film thickness thinner than the metal light-shielding film and formed on a sidewall of the gate electrode to be separated from the metal light-shielding film. The light shielding film is provided with a light shielding film.

[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. In this figure, the same reference numerals are given to parts that are common to the parts of the conventional example shown in FIG. A light-shielding metal film 8 having a film thickness of 0° and 1 μm is formed.

Since the tungsten film having the above-mentioned thickness has a light transmittance of 0.1% or less, obliquely incident light entering the film can be almost completely blocked. Therefore, in the image sensor of this example, even when capturing an image of a high-brightness object, image distortion does not occur to the extent that it becomes a problem.In addition, the thick light-shielding metal film described above hardly reduces the aperture area. There is no decrease in sensitivity.

Next, the manufacturing method of this example will be explained with reference to FIGS. 2(a) to 2(d).

After forming a p-type well 2 in an n-type semiconductor substrate 1 by ion implantation of p-type impurities and diffusion heat treatment by a conventional method, a p+-type channel stop 5 and an n-type photoelectric conversion region are formed by ion implantation of p-type and n-impurities. 3 and an n-type charge transfer region 4 are formed.

Subsequently, a charge transfer electrode 7 made of polysilicon is formed via the insulation M6 [FIG. 2(a)].

Next, an insulating film 6 is formed on the surface of the polysilicon by thermal oxidation, and a light-shielding metal film 8 is uniformly formed thereon by a method such as a sputtering method or an organometallic CVD method, as shown in FIG. 2(b). to grow. Subsequently, the light-shielding metal film 8 is anisotropically etched to leave the light-shielding metal film 8 on the side wall of the charge transfer electrode 7 in a self-aligned manner, as shown in FIG. 2(c).

Next, as shown in FIG. 2(d), an insulating film 6 is formed as a glabellar film, and an aluminum light-shielding film 9 is formed thereon to obtain the solid-state imaging device shown in FIG. 1.

FIG. 3 is a sectional view showing another embodiment of the present invention. This is connected to the MO3 type solid-state image sensor, and in this device, the signal charge generated within the photoelectric conversion region 3 is
By applying a read pulse to the gate electrode 11, the signal is read to the n-type drain region 10 and taken out via the signal line 12.

In this embodiment as well, since the thin light-shielding metal film 8 is provided on the side walls of the gate electrode 11 and the signal line 12, light does not leak into areas other than the photoelectric conversion area, and images caused by false signal charges are prevented. Collapse is suppressed.

In the above embodiments, tungsten was used as the material for the sidewall light-shielding film, but the present invention is not limited thereto, and other metal materials or silicides thereof may be used.

[Effects of the Invention] As explained above, in the present invention, a thin light-shielding sidewall made of a metal film or the like is formed on the side wall of an electrode that performs charge readout or charge transfer. , it is possible to effectively block obliquely incident light that is about to enter the cell internal region other than the light receiving element without substantially reducing the aperture area of the light receiving element. Therefore, according to the present invention, it is possible to prevent the generation of false signals due to obliquely incident light components, which is a problem when imaging a high-brightness subject, without reducing sensitivity, and to prevent image distortion caused by false signals. Can be suppressed.

[Brief explanation of the drawing]

FIG. 1 is a sectional view showing one embodiment of the present invention, and FIG.
) to (d) are cross-sectional views for explaining the manufacturing process,
FIG. 3 is a sectional view showing another embodiment of the present invention, FIG.
FIG. 5 is a sectional view showing each conventional example. 1... N-type semiconductor substrate, 2... P-type well, 3
...n-type photoelectric conversion region, 4...n-type charge transfer region, 5...p1-type channel stop, 6.
...Insulating film, 7...Charge transfer electrode, 8...
・Light-shielding metal film, 9... Aluminum light-shielding film,
DESCRIPTION OF SYMBOLS 10... N-type drain region, 11... Gate electrode, 12... Signal line, 13... Oblique incident light,
14...Photoelectric conversion charge.

Claims (1)

[Claims] a plurality of second conductivity type photoelectric conversion regions provided within the first conductivity type semiconductor region; a first conductivity type charge readout region provided adjacent to each photoelectric conversion region; A signal charge receiving region that receives generated signal charges via the charge readout region, a gate electrode provided on the charge readout region with an insulating film interposed therebetween, and a signal charge receiving region formed on the semiconductor substrate so as to cover the gate electrode. a metal light-shielding film having an opening over the photoelectric conversion region; and a light-shielding film formed on a side wall of the gate electrode to be thinner than the metal light-shielding film and separated from the metal light-shielding film. Solid-state image sensor.