JPH03161970A - Solid-state image sensing device - Google Patents

Abstract

PURPOSE:To obtain a solid-state image sensing device of high reliability wherein the generation of smear is restrained, by preventing a light from leaking into a semiconductor substrate part under the vicinity of a transferring part by using a shielding film. CONSTITUTION:A recessed part 23 is formed by caving the surface of a P-type well region 22 where an N-type layer 25 corresponding with a light receiving window 32 is formed. The surface level of said part 23 is positioned at a part lower than the surface of the P-type well region 22. In this manner, the end portion of a light shielding film 31 positioned on the periphery of the light receiving window 32 is set at the same level as the surface of an N-type buried layer 26 constituting a CCD transferring part, or positioned at a part lower than the surface of the layer 26. As the result, when a lot of light enters from the light receiving window 32, the light entering the well region 22 under the vicinity of the buried layer 26 turning to a transferring part is blocked by the shielding film 31, and the light can be prevented from leaking into the region 22 part. Hence an image signal led out from the rear end of the transferring part becomes large, and so-called smear generation is restrained.

Description

[Detailed description of the invention] [Purpose of the invention] (Industrial application field) The present invention relates to a solid-state imaging device.

(Prior Art) As a conventional solid-state imaging device, one having a structure shown in FIG. 3 is known. FIG. 3 is a sectional view showing a light receiving section, a transfer section, and a field shift gate section therebetween, and l in the figure is an n-type silicon substrate. On the surface of this substrate 1,
A p-well region 2 is selectively provided. This p-
A p+ type channel stopper region 3 is formed on the surface of the well region 2 to electrically isolate the light receiving section, the transfer section, and the field shift gate section therebetween from other regions. On the surface of the well region 2 surrounded by the channel stopper region 3, an n-type layer 4 serving as a light receiving portion is formed. A CCD is provided on the surface of the well region 2.
An n-type buried layer 5 constituting a transfer section is formed at a desired distance from the n-type layer 4. A gate electrode 8 made of polycrystalline silicon is provided on the well region 2 including the channel region 6 between the n-type layer 4 and the n-type buried layer 5 with a thin oxide film 7 interposed therebetween. A plurality of transfer electrodes (not shown) constituting a CCD transfer section are provided on the oxide film 7 in a direction perpendicular to the channel length of the channel region 6. An insulating film 9 made of Si02, for example, is coated on the oxide film 7 including the gate electrode B and the transfer electrode (not shown). This insulating film 9 is covered with a shielding film lO made of aluminum, for example, and the n
The shielding film 10 corresponding to a part of the mold layer 4 has a light receiving window 1l.
is drilled.

However, in the conventional solid-state imaging device described above, when a large amount of light is received, it also enters the well region 2 of the buried layer 5 which serves as a transfer section other than the n-type layer 4 through the light receiving window l1 of the shielding film lO. Ru. When light is incident on the well region 2,
Electrons are generated in the region 2, reach the buried layer 5, and the image signal taken out at the rear end of the transfer section increases.
There was a problem of so-called smearing.

For this reason, the thickness of the insulating film 9 coated on the n-type layer 4 is reduced and the shielding film In is extended 71:. However, there is a limit to the ability of the shielding film 10 to prevent light from leaking into the well region 2 near the transfer section, and the amount of smear can be reduced. There was naturally a limit to reducing this.

(Problems to be Solved by the Invention) The present invention has been made in order to solve the above-mentioned conventional problems, and prevents light from leaking into the semiconductor substrate portion under the vicinity of the transfer section by a shielding film, thereby causing smearing. The purpose of this invention is to provide a highly reliable solid-state imaging device that suppresses this.

[Structure of the Invention] (Means for Solving the Problems) The present invention provides a semiconductor substrate, an impurity layer of one conductivity type formed on the surface of the substrate that acts as a light receiving portion, and a semiconductor substrate separated from the impurity layer by a desired distance. a buried layer of one conductivity type as a transfer portion formed on the surface portion of the base; and an electrode formed on the base including a channel region between the impurity layer and the buried layer via a thin insulating film; A solid-state imaging device comprising an insulating film coated on the base including the electrode, and a shielding film coated on the insulating film and having a light receiving window opened at a location corresponding to a part of the impurity layer. In the solid-state imaging device, the semiconductor substrate surface corresponding to the light-receiving window is located further away from the semiconductor substrate surface on which the buried layer is formed.

(Function) According to the present invention, the surface of the semiconductor substrate corresponding to the light receiving window is located below the surface of the semiconductor substrate on which the buried layer is formed (for example, the surface of the semiconductor substrate containing an impurity layer of one conductivity type corresponding to the light receiving window By recessing the buried layer and relatively protruding the buried layer serving as the transfer portion, the shielding film can block light that is about to enter the semiconductor substrate region under the vicinity of the buried layer serving as the transfer portion. As a result, it is possible to obtain a highly reliable solid-state imaging device in which the shielding film prevents light from leaking into the semiconductor substrate portion below the vicinity of the transfer section and suppresses the occurrence of smear.

5 (Example) Hereinafter, an example of the present invention will be described in detail with reference to FIG.

21 in the figure is an n-type silicon substrate. A p-well region 22 is selectively provided on the surface of this substrate 21. The portion of the p-well region 22 where the n-type layer is to be formed is depressed by etching to form four portions 23. A p+ type channel stopper region 2 is provided on the surface of the p-well region 22 to electrically isolate the light receiving section, the transfer section, and the field shift gate section therebetween from other regions.
4 is formed. This channel stopper area 24
An n-type layer 25 that functions as a light receiving section is formed on the surface of the recess 23 of the well region 22 surrounded by. On the surface of the well region 22, there is a
A type buried layer 26 is formed at a desired distance from the n-type layer 25. A gate electrode 29 made of polycrystalline silicon is provided on the well region 22 including the channel region 27 between the n-type layer 25 and the n-type buried layer 26 with a thin oxide film 28 interposed therebetween. A plurality of transfer electrodes (not shown) constituting a CCD transfer section are provided on the oxide film 628 in a direction perpendicular to the channel length of the channel region 27. For example, Si is formed on the oxide film 28 including the gate electrode 29 and the transfer electrode (not shown).
An insulating film 30 made of n2 is coated. A shielding film 31 made of aluminum, for example, is coated on the insulating film 30, and a light receiving window 32 is formed in the shielding film 31 corresponding to a part of the n-type layer 25.

According to such a configuration, the surface of the p-well region 22 where the n-type layer 25 corresponding to the light-receiving window 32 is formed is depressed to form the recess 23, and the surface level is leveled with the p-well region 22 where the n-type layer 25 is formed. - The shielding film 3l located around the light receiving window 32 by being located below the surface of the well region 22
The end portion of the CCD transfer section can be located at the same level as or below the surface of the n-type buried layer 26 constituting the CCD transfer section. As a result, when a large amount of light is received from the light receiving window 32, the shielding film 3l can block the light that is about to enter the well region 22 near and below the buried layer 26, which becomes the transfer section. Therefore, the shielding film 31 prevents light from leaking into the well region 22 under the vicinity of the transfer section, increasing the image signal taken out at the rear end of the transfer section, and achieving high reliability by suppressing so-called smear generation. A solid-state imaging device can be obtained.

Note that the solid-state imaging device according to the present invention is not limited to the above-described large-scale embodiment, and may have the structure shown in FIG. 2.

That is, the solid-state imaging device shown in FIG. 2 has a structure in which a portion of the p-well region 22 where the n-type layer is to be formed is depressed by etching to form a deep groove portion 33. According to the solid-state imaging device having such a structure, the light-receiving window 32 can be formed at the bottom of the groove 33, and the end of the shielding film 81 located around the light-receiving window 32 can be formed into an n-type folding layer 26 constituting a CCD transfer section. When a large amount of light is received from the light-receiving window 82, the shielding film 8l causes it to enter the well region 22 near and below the buried layer 26, which becomes the transfer section. Since the light can be blocked more reliably, the shielding film 31 prevents light from leaking into the well region 22 under the vicinity of the transfer section, and the image signal taken out at the rear end of the transfer section becomes larger. can be prevented.

[Effects of the Invention] As described in detail above, the present invention provides a highly reliable solid-state imaging device in which the shielding film prevents light from leaking into the semiconductor substrate portion under the vicinity of the transfer section and suppresses the occurrence of smear. Can be provided.

[Brief explanation of the drawing]

FIG. 1 is a sectional view of a solid-state imaging device showing one embodiment of the present invention, FIG. 2 is a sectional view of a solid-state imaging device showing another embodiment of the invention, and FIG. 3 is a sectional view of a conventional solid-state imaging device. FIG. 2l...n-type silicon substrate, 22...p-well region, 23...recess, 25...n-type layer, 26...n
Mold buried layer, 29... Gate electrode, 31... Shielding film, 32... Light receiving window, 33... Groove.

Claims (1)

[Claims] A semiconductor substrate, an impurity layer of one conductivity type formed on the surface of this substrate and acting as a light receiving section, and a buried layer of one conductivity type as a transfer section formed on a portion of the surface of the substrate separated by a desired distance from this impurity layer. an electrode formed on a base including a channel region between the impurity layer and the buried layer via a thin insulating film; an insulating film coated on the base including this electrode; In the solid-state imaging device, the buried layer is formed on the surface of the semiconductor substrate corresponding to the light-receiving window. A solid-state imaging device characterized in that it is located below the surface of a semiconductor substrate.