JP3399484B2 - Solid-state imaging device - Google Patents

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 sensor, and more particularly to a solid-state image sensor capable of reducing smear.

[0002]

2. Description of the Related Art Generally, a CCD type solid-state image pickup device is shown in FIG.
It has a sectional structure shown in. In the drawings, 1 is a silicon semiconductor substrate, 2 is a vertical transfer register, 3 is a photosensor for photoelectric conversion, 4 is a read gate portion interposed between the photosensor 3 and the vertical transfer register 2, and 5 is polysilicon. Is a transfer electrode, 6 is an interlayer film, and 7 is a light-shielding film made of, for example, aluminum, which shields a portion other than the photosensor 3 in the imaging region. Reference numeral 8 denotes an overhang portion that overhangs the light shielding film 7 from above the transfer electrode 5 toward the photosensor 3 side.

Meanwhile, the interlayer film 6 is case were often formed by only SiO _2, and aluminum and SiO ₂ forming the light-shielding film 7 that generation of white in the underlying photosensor third interlayer film 6 so that the reaction There was a problem. Therefore, in order to prevent the SiO ₂ forming the interlayer film 6 from directly contacting the light shielding film 7 made of aluminum, the interlayer film 6 is made of polysilicon or titanium oxynitride having a thickness of 100 nm and SiO 2 having a thickness of 200 nm, for example. _An attempt was made to form a two-layer structure with _two films. The upper layer of the double-layered interlayer film 6 is made of polysilicon or titanium oxynitride, and the lower layer is made of a SiO ₂ film. FIG. 4 is an enlarged cross-sectional view showing the interlayer film 6 of such a solid-state image pickup device in an enlarged manner.

FIG. 5 is a sectional view showing another conventional solid-state image pickup device. This solid-state image sensor is basically the same as the solid-state image sensor shown in FIGS. 3 and 4, but the upper layer 6a of the interlayer film 6 is made of PSG, and the transfer electrode 5 made of polysilicon and the semiconductor substrate 1 (of The gate insulating film for insulating between the resistor) is a silicon oxide film (SiO ₂ ),
The difference is that a silicon nitride film (Si ₃ N ₄ ) and a silicon oxide film (SiO ₂ ) are formed in a three-layer structure. 6d shows the silicon nitride film.

In FIG. 5, 1 is an n-type semiconductor substrate,
1a is a first p-type well, 1b is an n-type light receiving element, 1c
Is a second p-type well shallower than the first p-type well and is formed below the vertical transfer register 2. 1d
Is a p ^{+ +} type hole accumulated region, 1e is a p ⁺ type channel stopper, 12 is a passivation film,
Sensor is a sensor, ROG is a read gate unit, V-
reg is a vertical transfer register, and CS is a channel stopper.

[0006]

By the way, in the solid-state imaging device shown in FIGS. 3 and 4 in which the upper layer 6a of the interlayer film 6 is formed of polysilicon or titanium oxynitride and the lower layer 6b is formed of SiO2, the interlayer The light 9 obliquely incident on the end face of the film 6 is reflected at the interface 10 between the interlayer film 6 and the end face of the semiconductor substrate 1, and is also reflected at the interface 11 between the lower layer 6b and the upper layer 6a. ,
That is, there is a problem in that the light travels while undergoing multiple reflections, enters the vertical transfer register 2, and becomes a smear.

That is, the light 9 obliquely incident on the lower layer 6b
Is reflected by the interface 10 at about several tens of percent (for example, 50%), and the rest is absorbed by the semiconductor substrate 1. Therefore, each time the light is reflected once at the interface, the oblique light is attenuated by, for example, one half, but in the end, it is a fraction to a few tens of minutes of the light obliquely incident on the interlayer film 6. 1 enters the vertical transfer register 2 and becomes a smear. Further, in the solid-state imaging device shown in FIG. 5, the obliquely incident light 9 repeats multiple reflection between the silicon semiconductor surface and the lower surface of the light shielding film 7 made of aluminum, enters the vertical transfer register 2, and becomes a smear. Of.

Such a smear is not preferable because it produces an image with a white tail on the monitor screen when a high-luminance object is imaged. Therefore, it is necessary to reduce it. First, the overhanging portion 8 of the light shielding film 7 is
It is conceivable to increase the length b of the optical path to the vertical transfer register 2 from the boundary between the light-sensitive sensor section and the light-shielding section that becomes smear. This is because the longer the optical path length is, the more the number of times the smeared light is reflected, and the greater the number of reflections, the more the smeared light is attenuated. However, lengthening the overhanging portion 8 of the light shielding film 7 leads to a reduction in the aperture ratio of the sensor and lowers the sensitivity, which is not preferable.

Further, the thickness a of the portion where the obliquely incident light 9 repeats multiple reflections (the thickness of the lower layer 6b of the interlayer film 6 in the case of the solid-state image pickup device shown in FIGS. 3 and 4 is shown in FIG. 5). In the case of a solid-state image sensor, it may be possible to reduce the thickness of the interlayer film 6). This is because as the thickness a is reduced, the number of times that the light obliquely incident on the lower layer 6 is reflected before reaching the transfer register 2, and the light that becomes a smear before entering the register 2 is attenuated more. Because.

However, in the solid-state image pickup device shown in FIGS. 3 and 4, there is a limitation in thinning the lower layer 6b of the interlayer film 6. The difference in etching rate between the aluminum forming the light-shielding film 7 and the polysilicon or titanium oxynitride forming the upper layer 6a of the interlayer film 6 is small, and the interlayer film 6 is selectively etched using the light-shielding film 7 as a mask. Since the upper layer 6a of the interlayer film 6 has electrical conductivity, it must be completely selectively etched in order to prevent short circuits, and the surface of the semiconductor substrate 1 must be prevented in order to prevent white scratches and dark current. However, it is necessary to make the lower layer 6b of the interlayer film 6 thicker, for example, to 200 nm so as to cope with variations in etching thickness. Further, when the thickness of the interlayer film 6 is reduced, the effect of preventing the invasion of unnecessary impurities such as sodium is weakened, and white scratches are easily generated, which is also a constraint on the thickness reduction of the interlayer film 6. Further, also in the solid-state imaging device shown in FIG. 5, if the interlayer film 6 is made thin, the effect of preventing the invasion of unnecessary impurities such as sodium becomes weak and white scratches easily occur. There is a limit. The reduction of the pixel size accompanying the increase in the number of pixels also makes it more difficult to prevent smear.

The present invention has been made to solve the above problems, and smear can be reduced without causing white scratches, dark currents, and electrical shorts between light-shielding films. The purpose is to plan.

[0012]

A solid-state image pickup device according to claim 1, wherein an interlayer film between at least the overhanging portion of the light-shielding film and the semiconductor substrate has a three-layer structure, and the interlayer film is an intermediate layer thereof. Has a higher refractive index than its lower and upper layers, and the intermediate layer is
It is characterized in that it is a silicon film, titanium oxynitride, tantalum oxide, aluminum oxide or titanium nitride. A solid-state image pickup device according to a second aspect is the solid-state image pickup device according to the first aspect, wherein the silicon film is a polysilicon film.

A solid-state image pickup device according to a third aspect of the present invention is the solid-state image pickup device according to the first aspect, characterized in that the lower and upper layers of the interlayer film are oxide films. The solid-state imaging device according to claim 4 has a light-shielding film formed on a transfer electrode via an interlayer film having a three-layer structure, the interlayer film extending to a portion below the overhang portion of the light-shielding film, and an intermediate layer thereof. Has a higher refractive index than the lower layer and the upper layer, and the lower layer is formed thinner than the upper layer. The solid-state imaging device according to claim 5 has a light-shielding film formed on a transfer electrode formed on the surface of a semiconductor substrate via an insulating layer via an interlayer film having a three-layer structure, and the interlayer film is the light-shielding film. The intermediate layer has a refractive index larger than those of the lower layer and the upper layer, and the lower layer is thinner than the insulating layer on the surface of the semiconductor substrate.

[0014]

According to the solid-state imaging device of the first aspect, since the interlayer film has a three-layer structure, a material having an etching selection ratio with the light-shielding film can be used as the upper layer to selectively etch the light-shielding film. At this time, the upper layer can serve as an etching stopper. Since the upper layer is interposed between the light-shielding film and the intermediate layer and there is no risk of short-circuiting between the light-shielding films by the intermediate layer, the selective etching is an etching that completely removes the intermediate layer. It does not have to be, and etching that stops in the interlayer is sufficient.

Therefore, even if the lower layer is not formed thick in consideration of variations in etching depth, the selective etching prevents the surface of the semiconductor substrate from being etched to cause white scratches and dark current. can do.
Therefore, it is not necessary to make the lower layer thick, and it is possible to make it thin. Since the intermediate layer made of one of the silicon film, titanium oxynitride, tantalum oxide, aluminum oxide and titanium nitride has a higher refractive index than the lower layer and the upper layer, it is obliquely incident on the lower layer. The reflected light is repeatedly reflected at the interface between the semiconductor substrate and the lower layer and at the interface between the lower layer and the intermediate layer many times to be attenuated to form a smear, so that the smear can be reduced.

According to the solid-state image pickup device of the second aspect, since the silicon film is a polysilicon film, it is possible to eliminate the risk of white scratches on the surface of the semiconductor substrate. This is because, since polysilicon originally has a property of blocking the reaction between aluminum and a silicon oxide film, and the light-shielding film is generally made of aluminum, when the lower layer of the interlayer film is formed of a silicon oxide film, the intermediate By using the polysilicon film as the layer, the polysilicon film can suppress the reaction between the aluminum forming the light-shielding film and the underlying silicon oxide film. Therefore, it is possible to prevent white scratches from occurring on the surface of the semiconductor substrate.

According to the third aspect of the solid-state image pickup device, the upper layer and the lower layer of the interlayer film are made of an oxide film capable of obtaining a large etching selection ratio with respect to the light-shielding film, and the oxide film is a silicon film or titanium which originally forms an intermediate layer. Since the refractive index is higher than that of oxynitride, tantalum oxide, aluminum oxide, or titanium nitride, the upper layer functions as an etching stopper when etching the interlayer film using the light shielding film as a mask, and the intermediate layer and the lower layer are It is possible to prevent the semiconductor substrate from being damaged by being corroded, and the fact that the light-shielding film and the oxide film react with each other to affect the semiconductor substrate to cause white damage. It can be prevented by an intermediate layer composed of a nitride, tantalum oxide, aluminum oxide or titanium nitride. That. Since the light incident on the upper layer is repeatedly reflected in the upper layer, most of the light cannot enter the register and does not smear. The light incident on the lower layer is repeatedly reflected in the lower layer and is attenuated each time. Only a part becomes smear. Therefore, smear can be reduced.

According to the solid-state image pickup device of the fourth aspect, the interlayer film having a three-layer structure between the transfer electrode and the light-shielding film extends below the overhang portion of the light-shielding film, and the intermediate layer thereof is the lower layer and the upper layer thereof. Since it has a higher refractive index than the above, at least a part of the light obliquely incident on the lower end surface of the light-shielding film overhang portion is multiply reflected at the interface between the lower layer and the intermediate layer and the interface between the lower layer and the semiconductor substrate, and the remaining A part is multiply reflected at the interface between the upper layer and the intermediate layer and the interface between the upper layer and the light shielding film, and attenuates. Therefore, most of the light obliquely incident on the lower end surface of the light-shielding film overhang portion cannot enter the register and cannot become a smear. Therefore, smear can be significantly reduced. Further, since the upper layer is thinner than the lower layer of the interlayer film, the number of reflections repeated in the lower layer can be increased until the light obliquely incident on the lower layer travels and enters the transfer register to become a smear. Since more light can be attenuated, smear can be reduced from that point as well. Further, the light incident on the upper layer is repeatedly reflected between the interface between the upper layer and the light-shielding film on the upper side thereof and the interface between the intermediate layer and the upper layer thereof, so that it hardly penetrates into the lower layer, and smear does not occur. I won't.

According to the solid-state image pickup device of the fifth aspect, the interlayer film having a three-layer structure between the transfer electrode and the light-shielding film extends to below the overhanging portion of the light-shielding film, and the intermediate layer is the lower layer and the upper layer. Since it has a higher refractive index than the above, at least a part of the light obliquely incident on the lower end surface of the light-shielding film overhang portion is multiply reflected at the interface between the lower layer and the intermediate layer and the interface between the lower layer and the semiconductor substrate, and the remaining A part is multiply reflected at the interface between the upper layer and the intermediate layer and the interface between the upper layer and the light shielding film, and attenuates. Therefore, most of the light obliquely incident on the lower end surface of the light-shielding film overhang portion cannot enter the register and cannot become a smear. Therefore, smear can be significantly reduced. Further, since the lower layer of the interlayer film is thinner than the insulating film below the transfer electrode, the number of times of reflection of light traveling in the lower layer can be increased, and the attenuation can be increased. From that point, the smear can be remarkably reduced.

[0020]

The solid-state image pickup device of the present invention will be described in detail below with reference to the illustrated embodiments. 1A and 1B show a first embodiment of the solid-state image pickup device of the present invention. FIG. 1A is a sectional view, and FIG. 1B is an enlarged sectional view showing a part of FIG. It is a figure. The present solid-state image sensor is substantially different from the conventional solid-state image sensor shown in FIGS. 3 and 4 in the structure of the interlayer film 6, but is common in other points, and the common points have already been described. It will be omitted and only the differences will be described. Further, common parts are denoted by common reference numerals throughout the drawings.

In this solid-state imaging device, the interlayer film 6 has a three-layer structure, and the upper layer 6a is made of SiO ₂ , and has a thickness of, for example, 200 nm.
It has a certain thickness. The intermediate layer 6b is made of, for example, polysilicon and has a thickness of 100 nm, for example. The lower layer 6c is made of SiO2 and has a thickness of 10 nm, for example.

According to such a solid-state image pickup device, smear can be effectively reduced. Because the upper layer 6
Since a and the lower layer 6c are made of SiO ₂ and have a smaller refractive index than the polysilicon forming the intermediate layer 6c (polysilicon has a refractive index of 3.9, SiO _{2 has} a refractive index of 1.45).
As shown in (B), light incident on the thick upper layer 6a of the interlayer film 6 is first reflected by about 50% at the interface between the upper layer 6a and the intermediate layer 6b, and the remaining about 50% enters the intermediate layer 6b. . Upper layer 6
The light reflected at the interface between a and the intermediate layer 6b is reflected at the interface between the upper layer 6a and the light shielding film 8 made of aluminum, and about 50% is reflected at the interface between the upper layer 6a and the intermediate layer 6b, and the remaining about 50%. % Enters the middle layer 6b.

The light thus entering the upper layer 6a travels in the upper layer 6a while repeating reflection, and does not become smear. Further, only the light that has entered the intermediate layer 6b from the upper layer 6a enters the lower layer 6c, and the lower layer 6c and the semiconductor substrate 1
About 50% is reflected at the interface with and the rest is absorbed in the semiconductor substrate 1. The light reflected at the interface is reflected at the interface between the lower layer 6c and the intermediate layer 6b, travels in the lower layer 6c while repeating reflection thereafter, and eventually enters the vertical transfer register 2 to become a smear. However, the light that becomes smear is attenuated by about 50% each time it is reflected by the above interface, and the lower layer 6c has 10
Since it is as thin as nm, the number of reflections repeated until reaching the vertical transfer register 2 is large. Therefore, the amount of light that causes smear is extremely small.

Of course, light obliquely incident directly into the lower layer 6c or light obliquely incident directly into the intermediate layer 6b is first reflected at the interface between the lower layer 6c and the semiconductor substrate 1, and then the lower layer 6c and the intermediate layer. After reflection at the interface with 6b, this reflection is alternately repeated to proceed in the lower layer 6c, and is attenuated at each reflection. Since the lower layer 6c is as thin as 10 nm, the number of reflections repeated until reaching the register 2 is inevitably increased. As a result, the number of times of attenuation increases, and the amount of attenuation of light that causes smear also increases. Therefore, smear can be reduced.

2A and 2B are cross-sectional views showing a method of manufacturing the solid-state image pickup device shown in FIG. 1 in the order of steps. First, as shown in FIG. 2A, an interlayer film 6 having a three-layer structure is formed by, for example, continuous sputtering on the surface of the substrate 1 of the CCD type solid-state imaging device on which the transfer electrodes 5, 5, ... Are formed. . Next, an aluminum film 7 is entirely formed on the interlayer film 6, and the aluminum film 7 is formed as shown in FIG.
Is selectively etched and patterned to form a light shielding film.

After that, when the sensor opening is formed by continuing the selective etching until the etching depth reaches at least the intermediate layer 6b of the interlayer film 6 using the light shielding film 7 as a mask, the solid-state imaging device shown in FIG. 1 is obtained. Middle layer 6b
Is made of polysilicon and has conductivity, but the light-shielding film 5
Since the upper layer 6a made of SiO ₂ having an insulating property is interposed between and, the problem of short circuit between the light shielding films 7 and 7 cannot occur even if the intermediate layer 6b is not completely removed. Therefore, it suffices to etch the interlayer film 6 to a depth reaching the intermediate layer 6b. Therefore, the lower layer 6c is allowed to be formed as thin as 10 nm. This is nothing but the reduction of smear without fear of the occurrence of white scratches.

Further, the intermediate layer 6b made of polysilicon is present on the lower layer 6c, and since the polysilicon plays a role of blocking the reaction between aluminum and SiO ₂ forming the light shielding film 7, the lower layer 6c shields the light. There is no risk of reacting with the film 7 and causing white scratches on the surface of the semiconductor substrate 1. If polysilicon is present in the sensor opening, it causes an optical problem, so it is better to remove it. However, if it is carried out by etching with CF type plasma species or radical species, it can be done with almost no damage to the base. .

In the above embodiment, the upper layer 6 of the interlayer film 6 is
The thickness of a is 200 nm, and the thickness of the intermediate layer 6b is 100 nm.
However, it is not limited to this,
For example, the thickness of the upper layer 6a may be 50 nm, and the thickness of the intermediate layer 6b may be 50 nm. The thickness of the lower layer 6c is
As described above, the thinner the thickness, the better in terms of reducing smear. Further, the electric potential of the sensor surface is close to the ground level, and the light-shielding film 7 is at the ground level, so the electric field strength does not become strong. Therefore, the thickness is as thin as 10 nm. It's done.

The polysilicon forming the intermediate layer 6b of the interlayer film 6 may or may not be one in which n-type or p-type impurities are diffused. Further, when n-type or p-type impurities are diffused, there is no particular problem regarding smear even if the polysilicon is electrically floated or a certain potential is applied. The three-layer structure of the interlayer film 6 may be provided in the protruding portion of the interlayer film 6 to the sensor, and need not be provided in the entire area of the interlayer film 6. That is, except for the overhang portion 8, the interlayer film 6 may have a single-layer structure composed of only the lower layer 6c. Further, in the above embodiment, the intermediate layer 6b of the light-shielding film 6 is formed of polysilicon, but the invention is not limited to this, and any material having a higher refractive index than the upper layer 6a and the lower layer 6c may be used. For example, the intermediate layer 6b may be formed of TiON (titanium oxynitride), TaO ₂ , SiN, Al ₂ O ₃ , TiN or the like.

[0030]

According to the solid-state imaging device of the first aspect, the interlayer film between at least the overhanging portion of the light-shielding film and the semiconductor substrate has a three-layer structure, and the interlayer film includes the intermediate layer as the lower layer and the intermediate layer as the lower layer. It has a larger refractive index than the upper layer, and the intermediate layer is characterized by being a silicon film, titanium oxynitride, tantalum oxide, aluminum oxide or titanium nitride.

Therefore, according to the solid-state imaging device of the first aspect, since the interlayer film has a three-layer structure, by using a material having an etching selection ratio with the light-shielding film as an upper layer, the light-shielding film can be selectively selected. The upper layer can serve as an etching stopper during etching. Since the upper layer is interposed between the light-shielding film and the intermediate layer and there is no risk of short-circuiting between the light-shielding films by the intermediate layer, the selective etching is an etching that completely removes the intermediate layer. It does not have to be, and etching that stops in the interlayer is sufficient.

Therefore, even if the lower layer is not formed thick in consideration of the variation in etching depth, the selective etching prevents the surface of the semiconductor substrate from being etched to cause white scratches and dark current. can do.
Therefore, it is not necessary to make the lower layer thick, and it is possible to make it thin. Since the intermediate layer made of one of the silicon film, titanium oxynitride, tantalum oxide, aluminum oxide and titanium nitride has a higher refractive index than the lower layer and the upper layer, it is obliquely incident on the lower layer. The reflected light is repeatedly reflected at the interface between the semiconductor substrate and the lower layer and at the interface between the lower layer and the intermediate layer many times to be attenuated to form a smear, so that the smear can be reduced.

A solid-state image pickup device according to a second aspect is the solid-state image pickup device according to the first aspect, characterized in that the silicon film is a polysilicon film. Therefore, according to the solid-state imaging device of the second aspect, since the silicon film is a polysilicon film, it is possible to eliminate the possibility of causing white scratches on the surface of the semiconductor substrate. This is because, since polysilicon originally has a property of blocking the reaction between aluminum and a silicon oxide film, and the light-shielding film is generally made of aluminum, when the lower layer of the interlayer film is formed of a silicon oxide film, the intermediate By using the polysilicon film as the layer, the polysilicon film can suppress the reaction between the aluminum forming the light-shielding film and the underlying silicon oxide film. Therefore, it is possible to prevent white scratches from occurring on the surface of the semiconductor substrate.

A solid-state image pickup device according to a third aspect is the solid-state image pickup device according to the first aspect, characterized in that the lower and upper layers of the interlayer film are oxide films. Therefore, according to the solid-state imaging device of the third aspect, the upper layer and the lower layer of the interlayer film are made of an oxide film capable of obtaining a large etching selection ratio with respect to the light-shielding film, and the oxide film is a silicon film or titanium oxide which originally forms an intermediate layer. Since it has a higher refractive index than nitride, tantalum oxide, aluminum oxide, or titanium nitride, the upper layer acts as an etching stopper when etching the interlayer film using the light-shielding film as a mask, and the intermediate layer and lower layer are eroded. The silicon film and the titanium oxynitride can be prevented from being scratched even on the semiconductor substrate, and the light-shielding film and the oxide film react with each other to affect the semiconductor substrate to cause white scratches. , Tantalum oxide, aluminum oxide or titanium nitride can be prevented. And
Since the light incident on the upper layer is repeatedly reflected in the upper layer, most of the light cannot enter the register and does not become a smear. The light incident on the lower layer is repeatedly reflected in the lower layer and attenuates each time, and only a small part is generated. Only smear. Therefore, smear can be reduced.

A solid-state image pickup device according to a fourth aspect of the present invention has a light-shielding film formed on the transfer electrode via an interlayer film having a three-layer structure, the interlayer film extending below a protruding portion of the light-shielding film, The intermediate layer has a larger refractive index than the lower layer and the upper layer, and the lower layer is formed thinner than the upper layer.

Therefore, according to the solid-state image pickup device of the fourth aspect, the interlayer film of the three-layer structure between the transfer electrode and the light-shielding film extends to below the overhang portion of the light-shielding film, and the intermediate layer is the lower layer. And, since it has a larger refractive index than the upper layer, at least a part of the light obliquely incident on the lower end surface of the light-shielding film overhang portion is multiply reflected at the interface between the lower layer and the intermediate layer and the interface between the lower layer and the semiconductor substrate, The remaining part is multiply reflected at the interface between the upper layer and the intermediate layer and the interface between the upper layer and the light shielding film, and attenuates. Therefore,
Most of the light obliquely incident on the lower end surface of the light-shielding film overhang portion cannot enter the register and cannot become a smear. Therefore,
Smear can be significantly reduced.

Furthermore, since the upper layer is thinner than the lower layer of the interlayer film,
Since the number of reflections repeated in the lower layer can be increased until the light obliquely incident on the lower layer travels into the transfer register and becomes a smear, it is possible to further attenuate the light that becomes a smear. From that point as well, smear can be reduced. Further, the light incident on the upper layer is repeatedly reflected between the interface between the upper layer and the light-shielding film on the upper side thereof and the interface between the intermediate layer and the upper layer thereof, so that it hardly penetrates into the lower layer, and smear does not occur. I won't.

According to a fifth aspect of the present invention, a solid-state imaging device has a light-shielding film formed on a transfer electrode formed on a surface of a semiconductor substrate via an insulating layer via an interlayer film having a three-layer structure. Is extended to below the overhanging portion of the light-shielding film, the intermediate layer has a higher refractive index than the lower layer and the upper layer, and the lower layer is thinner than the insulating layer on the surface of the semiconductor substrate. And

Therefore, according to the solid-state imaging device of the fifth aspect, the interlayer film of the three-layer structure between the transfer electrode and the light-shielding film extends to below the overhang portion of the light-shielding film, and the intermediate layer thereof is the lower layer. And, since it has a larger refractive index than the upper layer, at least a part of the light obliquely incident on the lower end surface of the light-shielding film overhang portion is multiply reflected at the interface between the lower layer and the intermediate layer and the interface between the lower layer and the semiconductor substrate, The remaining part is multiply reflected at the interface between the upper layer and the intermediate layer and the interface between the upper layer and the light shielding film, and attenuates. Therefore,
Most of the light obliquely incident on the lower end surface of the light-shielding film overhang portion cannot enter the register and cannot become a smear. Therefore,
Smear can be significantly reduced. Further, since the lower layer of the interlayer film is thinner than the insulating film below the transfer electrode, the number of times of reflection of light traveling in the lower layer can be increased, and the attenuation can be increased. From that point, the smear can be remarkably reduced.

[Brief description of drawings]

1A is a sectional view, and FIG. 1B is an enlarged sectional view showing a part of FIG.

2A and 2B are cross-sectional views showing a method of manufacturing the solid-state imaging device shown in FIG. 1 in order of steps.

FIG. 3 is a cross-sectional view showing one conventional example.

FIG. 4 is a cross-sectional view showing a part (main part) of FIG. 3 in an enlarged manner.

FIG. 5 is a cross-sectional view showing another conventional example.

[Explanation of symbols]

1 Semiconductor substrate 2 Transfer register 5 Vertical transfer register 6 Interlayer film 6a Upper layer of interlayer film 6b Intermediate layer of interlayer film 6c Lower layer of interlayer film 7 Light-shielding film 7a, 7b Multi-layered light-shielding film 8 Overhanging part of light-shielding film 13 Low reflective film

─────────────────────────────────────────────────── ─── Continuation of the front page (56) References JP-A-5-67767 (JP, A) JP-A-5-167052 (JP, A) JP-A-3-108761 (JP, A) JP-A-3- 190272 (JP, A) JP 5-152557 (JP, A) JP 3-194969 (JP, A) JP 4-280675 (JP, A) JP 4-137763 (JP, A) JP-A-4-225565 (JP, A) JP-A-6-151793 (JP, A) (58) Fields investigated (Int.Cl. ⁷ , DB name) H01L 27/148

Claims (5)

(57) [Claims] 1. An interlayer film between at least an overhang portion of a light-shielding film and a semiconductor substrate has a three-layer structure, and the interlayer film has an intermediate layer having a larger refractive index than its lower and upper layers. The solid-state imaging device, wherein the intermediate layer is one of a silicon film, titanium oxynitride, tantalum oxide, aluminum oxide, and titanium nitride. 2. The solid-state image sensor according to claim 1, wherein the silicon film is a polysilicon film. 3. The solid-state image sensor according to claim 1, wherein the lower layer and the upper layer of the interlayer film are oxide films. 4. A light-shielding film formed on a transfer electrode via an interlayer film having a three-layer structure, wherein the interlayer film extends below a protruding portion of the light-shielding film, and the interlayer film is an intermediate layer thereof. There the solid-state imaging device characterized by the lower layer and have a higher refractive index than the upper, lower of the interlayer film is formed thinner than the upper layer. 5. Formed on the surface of a semiconductor substrate via an insulating layer
Is formed on the transferred electrode via a three-layered interlayer film.
A light-shielding film, the interlayer film extends below the overhang portion of the light-shielding film, and the interlayer film has an intermediate layer larger than the lower layer and the upper layer.
Has a Do refractive index, the insulating layer of the lower layer of the interlayer film is the semiconductor substrate of the surface
A solid-state image sensor characterized by being made thinner .