JPH09213924A - Solid-state imaging device - Google Patents

Abstract

(57) Abstract: When applied to a transfer register adjacent to a light receiving part of a solid-state image sensor, it is possible to reduce the frequency of “vignetting” of incident light due to a light shielding film formed on the transfer register. (EN) Provided is a solid-state image sensor capable of improving the light receiving sensitivity. In a solid-state imaging device of the present invention, a buffer layer 8 is formed via a transfer electrode 12 made of a polycrystalline silicon layer and a thermal oxide film. As a feature of the present invention, the flattening film 100 for the purpose of insulation and flattening is formed so that the portion where the flattening film 100 and the interlayer insulating film 14 overlap (the portion marked with a circle) becomes thin. On top of that, an Al light-shielding film 15 is formed via a shunt wiring layer 9 made of an Al layer and an interlayer insulating film 14.
Are formed. As a result, it is possible to prevent “vignetting” of incident light due to the Al light-shielding film 15.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a solid-state image pickup device used in, for example, a high-definition television camera device, and more specifically, it improves the electrode structure of a vertical transfer gate electrode so as to "cut off" incident light. The present invention relates to a solid-state imaging device that prevents

[0002]

2. Description of the Related Art Recently, for example, high-definition television (HD
In a solid-state image pickup device for TV), in order to prevent a propagation delay of a transfer clock applied to a vertical transfer register to enable a high speed operation, it has a shunt structure by Al wiring or the like and further reduces smear. C covered with Al for shading
A CD solid-state image pickup device has been proposed by the present applicant and is disclosed as a "charge transfer device" in Japanese Patent Laid-Open No. 7-106552.

A CCD solid-state image sensor having a shunt wiring structure according to the present invention will be described with reference to FIGS. 3 to 5. First, an outline of a conventional solid-state image sensor will be described with reference to FIG. FIG. 3 is a plan view showing a schematic configuration of a CCD solid-state imaging device having a shunt wiring structure.

A CCD solid-state image pickup device having a shunt wiring structure has a light receiving section 1 for photoelectrically converting incident light and accumulating it, a signal arranged in each vertical column of these light receiving sections 1 and read through a read gate. The imaging region 3 is formed by a vertical transfer register 2 that transfers charges in the vertical direction. The vertical transfer register 2 is driven by, for example, a 4-phase transfer clock.

The signal charges read out to the vertical transfer register 2 are transferred to the horizontal transfer register 4 for each scanning line.
In the horizontal transfer register 4, the signal charges for one scanning line transferred from the vertical transfer register 2 are transferred in the horizontal direction by, for example, two-phase driving. At the output end of the horizontal transfer register 4, for example, an output unit 5 having an FDA (Floating Diffusion Amplifier) configuration is arranged. The output section 5 detects the signal charge transferred by the horizontal transfer register 4 and derives it as a voltage signal.

Next, referring to FIG. 4, CC according to the present invention
The wiring structure of the D solid-state image sensor will be described. FIG. 4 is a plan view schematically showing an image portion of a CCD solid-state image pickup device to which the vertical transfer register according to the present invention is applied.

In the CCD solid-state image pickup device shown in FIG. 4, a large number of light receiving portions 1 formed by photodiodes are arranged in a matrix on an N-type silicon substrate, and among these many light receiving portions 1 are arranged in the column direction. A vertical transfer register 2 is commonly configured for the arrayed light receiving units 1. The transfer electrode of the vertical transfer register 2 extends in the horizontal direction and is also used as a wiring. In particular, the transfer electrode of the vertical transfer register 2 is a region between the light receiving units adjacent to each other in the vertical direction of the light receiving unit 1 (a region for separating the light receiving unit 1, In addition, in one region, the first transfer electrode 6 made of the first polycrystalline silicon layer and the second transfer electrode 7 made of the second polycrystalline silicon layer are formed in one region.
Are formed by overlapping.

A buffer layer 8 made of a polycrystalline silicon layer is formed on each transfer electrode for the purpose of preventing potential shift (potential fluctuation due to contact between Al and polycrystalline silicon).
Is formed. Further, a shunt wiring layer 9 made of an Al (aluminum) layer is formed so as to extend in the vertical direction through a thick flattening film (details will be described later), and on the shunt wiring layer 9. A light-shielding film made of an Al layer is formed through the interlayer insulating film so as to open the light receiving portion 1.

In each shunt wiring layer 9, the first and second transfer electrodes 6 and 7 corresponding to each column and the buffer layer 8 are connected by the first contact hole 10, and the buffer layer 8 is formed.
And the shunt wiring layer 9 are connected by the second contact hole 11. Then, for example, four-phase transfer clocks φ1 to φ4 are selectively applied to each shunt wiring layer, and the first to fourth transfer electrodes are respectively applied to the first to fourth transfer electrodes through these shunt wiring layers. Transfer clock φ1
~ Φ4 are applied individually. This 4-phase transfer clock φ
By applying 1 to φ4, the signal charges read from the light receiving unit 1 during the read period are transferred to the horizontal transfer register 4 shown in FIG. 3 in units of rows along the vertical transfer register.

Now, referring to FIG. 5, the C according to the present invention will be described.
The cross-sectional structure of the vertical transfer register of the CD solid-state image sensor will be described. FIG. 5 is a sectional view taken along line AA in FIG.

In the vertical transfer register sectional shape shown in FIG. 5, a transfer electrode 12 made of a polycrystalline silicon layer is formed on an N-type silicon substrate, and the transfer electrode 12 is buffered by the polycrystalline silicon layer via a thermal oxide film. Layer 8 is formed. In addition, PS is used for the following purposes via a thermal oxide film,
The leveling film 13 such as G (phosphorus silicate glass) is 30
It is formed with a film thickness of about 0 nm. That is, the flattening film 13
(1). Al laid on top of the transfer electrode to reduce the level difference
Improve step coverage. (2). It can be considered that it plays a role of an insulating material between the transfer electrode and an Al light-shielding film described later.

A shunt wiring layer 9 made of an Al layer is formed thereon with a film thickness of about 400 nm. An Al light-shielding film 15 made of an Al layer is formed on the shunt wiring layer 9 via an interlayer insulating film 14. Note that in the cross-sectional view shown in FIG. 5, for simplicity, the protective film, the flattening film, the color filter, the micro condenser lens, and the like on the Al light-shielding film 15 are omitted.

However, in the shunt structure CCD solid-state image pickup device to which the present invention is applied, for example, two films of the planarizing film 13 and the interlayer insulating film 14 overlap between the transfer electrode 12 and the Al light shielding film 15. There is a part that exists. Of course, this portion has a sufficient margin in terms of pressure resistance, and rather, since the total film thickness is thick, the upper Al light-shielding film 15 may overhang, which may cause "vignetting" of incident light.

That is, in the conventional CCD solid-state image pickup device, the potential shift in the transfer channel region (not shown) can be prevented by forming the buffer layer 8 for buffering. However, this buffer layer 8 and the shunt. The wiring layer 9 for use is required. Therefore, the ratio of the opening width of the light receiving portion to the height of the vertical transfer register, that is, the aspect ratio becomes large, and the peripheral edge of the light receiving portion opening in the Al light-shielding film 15 (the flattening film and the interlayer insulating film indicated by a circle are There is a problem in that the frequency of incident light reflected to the outside at the overlapped portion), that is, so-called “vignetting” becomes large, and the light receiving sensitivity is lowered.

[0015]

SUMMARY OF THE INVENTION The present invention has been made in view of the above problems, and the problem is that when the present invention is applied to a transfer register adjacent to a light receiving portion of a solid-state image pickup device, the flattening film is mainly used. To provide a solid-state image sensor capable of reducing the frequency of “vignetting” of incident light due to a light-shielding film formed on a transfer register due to the film thickness and improving light-receiving sensitivity. is there.

[0016]

The solid-state image pickup device of the present invention is proposed to solve the above-mentioned problems.
A transfer channel region for transferring charges is formed on a semiconductor substrate, transfer electrode groups are arranged in one direction along the transfer channel region, and a shunt wiring layer is formed to shunt the corresponding transfer electrode in the transfer electrode group. In the solid-state imaging device, a buffer layer for preventing potential shift in the transfer channel region and a flattening film (insulating film) for insulation / flattening are provided between the transfer electrode and the shunt wiring layer.
Is formed, and the film thickness of this flattening film is made thinner, for example, 100 nm or more and 200 nm or less at the peripheral edge facing the transfer channel region, compared to other portions.

Preferably, the thinned portion of the flattening film is a portion where the flattening film and the interlayer insulating film formed above the shunt wiring layer overlap. .

In the solid-state image sensor according to the present invention,
Since the flattening film under the shunt wiring layer is formed so as to be thin at the peripheral edge facing the transfer channel region, that is, the peripheral edge (shoulder portion) of the light receiving portion opening, it is formed in the upper layer portion thereof. Prevents unnecessary overhang of the Al light-shielding film,
The frequency of “shaking” of incident light can be reduced, and the light receiving sensitivity can be improved.

In addition to that, Al is formed in the shape surrounding the light receiving portion.
It becomes easy to form the light-shielding film, and accordingly, the light-shielding between the light-receiving portions can be surely performed, and smear can be effectively reduced.

[0020]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, specific embodiments of the present invention will be described with reference to the accompanying drawings.

First, the sectional structure of the vertical transfer register of the CCD solid-state image pickup device of the present invention will be described. FIG. 1 shows an A- of a CCD solid-state image pickup device to which the vertical transfer register of the present invention is applied.
It is sectional drawing on the A line. The planar structure of the CCD solid-state image pickup device of the present invention is substantially the same as that shown in FIG. 4 described above, and therefore the description thereof will be omitted.
A sectional view on line A is shown. Further, the same reference numerals are attached to the portions common to the above-mentioned matters.

In the vertical transfer register sectional shape of the CCD solid-state image pickup device of the present invention shown in FIG. 1, a transfer electrode 12 made of a polycrystalline silicon layer is formed on an N-type silicon substrate, and a thermal oxide film is formed on the transfer electrode 12. A buffer layer 8 made of a polycrystalline silicon layer is formed through the. Further, as a feature of the present invention, for example, PS for the purpose of insulation and flattening
A flattening film 100 made of G or the like is formed.

A shunt wiring layer 9 made of an Al layer is formed thereon, and an Al light-shielding film 15 is formed on the shunt wiring layer 9 with an interlayer insulating film 14 interposed therebetween. In the figure, for simplicity, the protective film on the Al light-shielding film, the flattening film, the color filter, the micro condenser lens, etc. are omitted.

Here, the planarizing film 100 and the interlayer insulating film 14
In the overlapping portion (marked with a circle), the flattening film 100 is thinned to about 100 nm to 200 nm within a range where the breakdown voltage between the transfer electrode 12 and the Al light-shielding film 15 does not matter, and the upper Al light-shielding layer 15 is formed. Are formed so as not to overhang the light receiving portion. Therefore, in the interlayer insulating film 14 and the Al light-shielding film 15 formed thereon, the flattening film 10
Since the peripheral edge of 0 is formed thin, it is formed close to the buffer layer 8 side. Along with this, the Al light-shielding film 15 is gently formed, so that “vignetting” of incident light due to the Al light-shielding film is eliminated.

That is, according to the present invention, the film thickness of the flattening film 100 at least in the portion where the interlayer insulating film 14 exists between the shunt wiring layer 9 and the Al light shielding film 15 is made thinner than other portions, so that the Al The main purpose is to prevent unnecessary protrusion of the light shielding film 15.

Next, the manufacturing process of the solid-state image pickup device to which the vertical transfer register according to the present invention is applied will be sequentially described with reference to FIG. 2A to 2D are process sectional views for explaining the manufacturing process of the CCD solid-state imaging device of the present invention.

First, as shown in FIG. 2A, for example, N
After forming the transfer electrode 12 of the polycrystalline silicon layer on the silicon substrate of the shape, the transfer electrode 1 is patterned.
A buffer layer 8 is formed on 2. After that, through the thermal acid film,
A flattening film 100 is deposited on the entire surface by a CVD method or the like, and reflowed to form the film. The manufacturing process up to this point is the same as the method used conventionally.

Next, as shown in FIG. 2B, a photoresist film (not shown) is formed on the entire surface, and then exposure and development processes are performed to pattern the photoresist film.
Then, as shown in FIG. 3C, the flattening film 100 is subjected to, for example, reactive ion etching (RIE).
etching to remove the resist. At this time, the flattening film 100 is formed on the peripheral edge of the buffer layer 8 by 1
Etching is selectively advanced to a thickness of about 00 nm to 200 nm to form a thin film.

Turning to FIG. 1D, after shunt Al is vapor-deposited by, for example, a sputtering method, patterning and
After etching, the interlayer insulating film 14 is deposited on the entire surface including the Al shunt wiring layer 9 by, for example, the CVD method. At this time, since the peripheral edge portion of the lower leveling film 100 is thinned, the interlayer insulating film 14 is also deposited without protruding. After that, the interlayer insulating film 14 is patterned and etched so as to surround the shunt wiring layer 9. Further, although not shown, an Al light-shielding film is deposited by a sputtering process, and a patterning / etching process is performed to form an Al film.
The present structure is obtained in which the effect of “vignetting” of incident light due to the light shielding film is eliminated.

The present invention is not limited to the above embodiment,
Various embodiments can be adopted. For example, in the above-mentioned embodiment, the CCD solid-state image pickup device having the shunt wiring structure of the interline transfer system (IT) is exemplified.
In addition, vertical transfer registers for solid-state imaging devices such as frame interline transfer system (FIT),
It goes without saying that the present invention can be appropriately applied to the charge transfer register of the CCD delay line.

[0031]

As described above, in the solid-state imaging device of the present invention, the flattening film under the shunt wiring layer is
Since it is formed so as to be thin at the peripheral edge of the light-receiving portion opening, the frequency of “vignetting” of incident light due to the light-shielding film formed in the upper layer can be reduced, and the light-receiving sensitivity can be improved. It will be possible.

Further, it becomes easy to form a light-shielding film in a shape surrounding the light-receiving portion, and accordingly, light-shielding between the light-receiving portions can be surely performed, and smear can be effectively reduced. Become.

[Brief description of drawings]

FIG. 1 is a CC to which a vertical transfer register of the present invention is applied.
It is sectional drawing on the AA line of a D solid-state image sensor.

FIG. 2 is a process sectional view for explaining the manufacturing process of the CCD solid-state imaging device of the present invention.

FIG. 3 is a plan view showing a schematic configuration of a CCD solid-state imaging device having a shunt wiring structure.

FIG. 4 is a plan view schematically showing an image portion of a CCD solid-state image sensor to which a vertical transfer register according to the present invention is applied.

FIG. 5 is a sectional view taken along line AA in FIG. 4;

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Light-receiving part 2 Vertical transfer register 3 Imaging area 4 Horizontal transfer register 5 Output part 6 1st transfer electrode 7 2nd transfer electrode 8 Buffer layer 9 Shunt wiring layer 10 1st contact hole 11 2nd contact hole 12 Transfer electrode 13,100 Flattening film 14 Interlayer insulating film 15 Al Light shielding film

Claims (3)

[Claims] 1. A transfer channel region for transferring charges is formed on a semiconductor substrate, and transfer electrode groups are arranged in one direction along the transfer channel region, and corresponding transfer electrodes in the transfer electrode group are respectively shunted. In the solid-state imaging device in which the wiring layer for shunt is formed, a buffer layer for preventing potential shift in the transfer channel region is provided between the transfer electrode and the wiring layer for shunt, and the purpose is for insulation / planarization. A solid-state imaging device, wherein a flattening film is formed, and a film thickness of the flattening film is formed thinner at a peripheral edge facing the transfer channel region than at other portions. 2. An interlayer insulating film is formed on the upper layer of the shunt wiring layer, and the flattening film and the interlayer insulating film overlap each other in a portion where the film thickness of the flattening film is thin. The solid-state image sensor according to claim 1, which is a portion where 3. The solid-state imaging device according to claim 1, wherein the flattening film has a thickness of 100 nm or more and 200 nm or less.