JPH01283961A - Solid state image sensor - Google Patents

Abstract

PURPOSE:To avoid generation of smear by arranging position of a contact hole sufficiently apart from end of an electrode so that the contact hole do not give influence on a recess to be formed on surface of an photoconductive film. CONSTITUTION:On a surface of photoconductive film 15, a recess 20 which corresponds height difference between ends of pixel electrodes 181 and 182 is formed. There are provided contact holes 191 and 192 at more than predetermined distances apart form the pixel electrodes 181 and 182. Therefore, a recess 20 shape formed on the surface of photoconductive film 15 by the height difference between ends of pixel electrodes 181 and 182 becomes independent to height differences of contact holes 191 and 192 thereby the recess produced by the height differences of pixel electrodes 181 and 182 is protected from going out of shape due to influence by height difference of contact holes 191 and 192. Thus, refraction by lens effect of recess 20 can be enhanced so that lights are protected from reaching to chips in lower layers through a gap between the pixel electrodes 181 and 182 so that the generation of smear can positively be prevented.

Description

DETAILED DESCRIPTION OF THE INVENTION [Object of the Invention] (Industrial Application Field) The present invention relates to a solid-state imaging device, and particularly to a solid-state imaging device that suppresses the occurrence of smear.

(Prior art) Conventionally, as shown in the tAs diagram, a photoconductive film stacked solid-state imaging device uses an interline transfer method to transfer the leading conductive film HJ.
An amorphous silicon stacked COD image sensor using an amorphous silicon film (a-3i) is known.

In FIG. 5, on the surface of a P-type silicon substrate 1, an N++ type first impurity layer 5 and an N+ type second impurity layer 2, which are diodes for accumulating signal charges generated by incident light, are formed. N for forming a channel in a vertical CCD for reading out signal charges accumulated at 5°2
+ type third impurity layer 3 (31, 32), further P+ type fourth impurity layer channel stopper 4 (4+, 42
) is formed. An insulating film 6 (6+
, 6□) are formed, and within this insulation H6, a first polycrystalline silicon gate electrode 7 (71, 7□) and a second polycrystalline silicon gate electrode 8 (8+, 82) are formed stepwise at a predetermined distance. The first AI electrode (signal input electrode) 17 (
17,, 17□) are provided.

Then, a smoothing layer 10 (10,.

After depositing the contact hole 19 (19,
, 19□) are formed. On the smoothing layer 10 and the contact hole 19, for example, an AN electrode (
Pixel electrode) 18 (18+.

18□, 183) are formed, an amorphous silicon photoconductive film 15 is formed thereon, and finally an ITO electrode 16 is formed as a transparent electrode.

In the interline transfer type amorphous silicon laminated COD image sensor having the above-described structure, smear caused by a portion of incident light penetrating into the substrate poses a problem. That is, a part of the light incident on the photoconductive film 15 reaches the substrate 1 through the gap between the pixel electrodes 18. Here, the surfaces of the photoconductive film 15 and the ITO electrode 16 have four parts 20 (201) due to the step difference at the end of the pixel electrode 18, which is the lower layer, depending on the method of manufacturing them.

20□) is formed. Since the recess 20 functions as a lens, the light incident on the ITO film 16 above the gap between the pixel electrodes 18 is refracted by the recess 20. This results in a reduction in smear caused by light reaching the silicon substrate 1.

However, in the COD image sensor shown in FIG. 5, the contact hole 19 is formed near the end of the pixel electrode 18. Therefore, the shape of the recess 20 is disturbed by the step of the contact hole 19 and becomes nearly flat.In other words, due to the influence of the contact hole 19, the lens effect of the recess 20 is weakened, and smear reduction is insufficient. There is.

(Issue 8 to be Solved by the Invention) As described above, conventionally, there is a problem in that light enters the chip below from the end of the pixel electrode, causing smear. Even if four parts are formed in the photoconductive film to correspond to the step difference at the end of the pixel electrode, if the contact hole is located close to the end of the pixel electrode, the concave part will be flattened and the smear reduction effect will not be sufficiently achieved. .

The present invention has been made in consideration of the above-mentioned circumstances, and its purpose is to reliably form four parts that perform a lens function on the portion of the photoconductive film located on the end of the pixel electrode. An object of the present invention is to provide a solid-state imaging device that can reliably suppress the occurrence of smear.

[Structure of the Invention] (Means for Solving the Problems) The gist of the present invention is to position the contact hole sufficiently far from the electrode end so that the contact hole does not affect the four parts formed on the surface of the photoconductive film. It's about letting go.

That is, the present invention provides a charge reading scanning chip, a smoothing layer provided on the chip and having a contact hole formed in a part thereof opening to a signal input electrode of the chip, and a smoothing layer provided in the smoothing layer and the contact hole. A picture 51S electrode provided and separated corresponding to one pixel, a photoconductive film provided on this pixel electrode and the smoothing layer, and a transparent electrode provided on this photoconductive film. In the solid-state imaging device, a concave portion reflecting the step difference at the end of the pixel electrode is formed on the surface of the photoconductive film, and the contact hole is formed from the end of the pixel electrode so that the shape of the concave portion does not collapse. They are formed at a distance of a predetermined distance or more (generally 0.5 μm or more).

(Function) According to the present invention, the shapes of the recesses on the surface of the photoconductive film caused by the steps of the pixel electrode and the contact hole become independent, and the recesses caused by the steps of the pixel electrode are prevented from collapsing due to the steps of the contact hole. can. Therefore, it is possible to increase the refraction due to the lens effect in the concave portion and prevent light from reaching the underlying chip through the gap between the pixel electrodes, thereby making it possible to reliably prevent the occurrence of smear. .

(Example) Hereinafter, the details of the present invention will be explained with reference to illustrated embodiments. Fig. 1 is a sectional view showing a schematic configuration of a solid-state imaging device according to an embodiment of the present invention, and Fig. 2 is a sectional view of the same device during its manufacture. is a cross-sectional view of , showing the state after the smoothing layer is formed.

First, as shown in FIG. 2, the surface of the P-type silicon substrate 1 is selectively diffused, etched, etc. by a well-known method, and an Nla layer is formed to accumulate the signal charge generated by the pre-injection into the photodiode. 2, an N1 type third impurity layer 3 (31) for reading signal charges accumulated in the photodiode and forming a channel in the vertical CCD.

3.), P″″ type fourth impurity layer channel stopper 4
(4+, 4°) was formed. Subsequently, an insulating film 6 (6+, 62) is formed on the substrate 1, and a first polycrystalline silicon gate electrode 7 (71, 72) is formed in the insulating film 6.
and a second polycrystalline silicon gate electrode 8 (8+,
82) was formed.

Next, a part of the insulating film 6 on the N+ type first impurity layer 2 was etched to the surface of the silicon substrate 1, and an N++ type first impurity layer 5 was formed by ion implantation to form a storage diode. The first electrode 17 (17,) functions as a signal input electrode.

17□) was formed using, for example, an AIN pole. Here, the first
The structure up to the state in which the electrodes 17 are formed is a charge reading scanning chip, and a smoothing insulating film 10 (
101,10□) was formed. Note that the structure shown in FIG. 2 is similar to the conventional device.

Next, as shown in FIG. 1, a part of the insulating film 10 is opened and the second electrode 18 (181) becomes the pixel electrode.

18□), for example, an AfI electrode was formed. Note that this electrode 18 is formed using a mask having the layout shown in FIG. Subsequently, an H-type amorphous silicon photoconductor 815 is deposited by the CVD method, and then an ITO electrode 16 is deposited and patterned by a known method to complete a photoconductive film stacked solid-state imaging device.

At this time, a recess 2o is formed on the surface of the photoconductive film 15 and the ITO electrode 16 due to the step at the end of the pixel electrode 18.

With such a configuration, the IT on the gap between the pixel electrodes 18
The light incident on the O electrode 16 passes through the electrode 18 and the photoconductive film 1.
The light is refracted by the recess 20 + formed on the surface of the light beam 5, and almost never enters directly below the incident position. Therefore, it is possible to prevent light from entering the substrate 1 side through the gap between the pixel electrodes 16 and causing smear. Moreover, the contact hole 19 is located at the center of the pixel electrode 18, and the pixel electrode 18
Since it is sufficiently far away from the end of the contact hole 19, the recess 20 is not affected by the step of the contact hole 19.
can be reliably provided with a lens function. Further, since the recess 20 is formed in a self-aligned manner on the gap between the electrodes 18 reflecting the step difference at the end of the pixel electrode 18, no special process is required for forming the recess, and it can be easily realized. There are advantages such as

Note that the present invention is not limited to the embodiments described above. For example, the position of the contact hole does not have to be in the center of the pixel electrode as shown in FIG. , it is sufficient that the distance is at least a certain distance from the end of the pixel electrode. According to the experiments of the present inventors,
As shown in FIG. 4, it has been confirmed that if the contact hole is spaced apart from the edge of the pixel electrode by about 0.5 μm, the influence of the contact hole will hardly appear on the recess. Therefore, the contact hole is ii! il/: It may be provided at a position 0.5 μm or more away from the end of the electrode.

Further, the amorphous silicon photoconductive film stacked CCD image sensor according to the present invention is not limited to the interline transfer method, but may also be a frame transfer method or a frame/interline transfer method. In addition, various modifications can be made without departing from the gist of the present invention.

[Effects of the Invention] As detailed above, according to the present invention, the contact hole is positioned sufficiently away from the electrode end so that the contact hole does not affect the recess formed on the surface of the photoconductive film. Therefore, a concave portion that functions as a lens can be reliably formed in the portion of the photoconductive film located above the end of the pixel electrode.
It becomes possible to realize a solid-state imaging device that can reliably suppress the occurrence of smear.

[Brief explanation of the drawing]

FIG. 1 is a cross-sectional view showing a schematic configuration of a solid-state imaging device according to an embodiment of the present invention, and FIG. 2 is a cross-sectional view showing the construction of a charge reading scanning chip section showing the manufacturing process of the same embodiment device. FIG. 3 is a plan view showing a layout of contact holes and pixel electrodes in the same embodiment, FIG. 4 is a plan view showing a modified example of the layout of contact holes and pixel electrodes, and FIG. 5 is a conventional device. FIG. 6 is a cross-sectional view showing a schematic configuration of the conventional device, and FIG. 6 is a plan view showing the layout of contact holes and pixel electrodes in a conventional device. DESCRIPTION OF SYMBOLS 1... P type silicon substrate, 2... N+ type second impurity layer, 3... N+ type third impurity layer, 4... P1 type fourth
Impurity layer, 5... N+ type first impurity layer, 6... Insulating film, 7... First polycrystalline silicon gate, 8... Second
Polycrystalline silicon gate, 10... Insulating film for smoothing, 1
5...Amorphous silicon photoconductive film, 16...I
TO electrode, 17...first electrode (signal input electrode), 18
. . . second electrode (pixel electrode), 19 . . . contact hole, 20 . . . recess. Applicant's representative Patent attorney Takehiko Suzue Incident light 81 Figure g#2 Figure 3 Figure 4

Claims (2)

[Claims] (1) A charge reading scanning chip, a smoothing layer provided on this chip and in which a contact hole opening to the signal input electrode of the chip is formed, and a smoothing layer provided in the smoothing layer and the contact hole. A solid comprising a pixel electrode separated corresponding to one pixel, a photoconductive film provided on the pixel electrode and the smoothing layer, and a transparent electrode provided on the photoconductive film. In the imaging device, a recess reflecting a step at the end of the pixel electrode is formed on the surface of the photoconductive film, and the contact hole is formed at a distance of at least a predetermined distance from the end of the pixel electrode so that the shape of the recess does not collapse. A solid-state imaging device characterized by being formed separately. (2) Claim 1, wherein the contact hole is spaced from an end of the pixel electrode by 0.5 μm or more.
The solid-state imaging device described.