JPH0645569A - Solid-state image pick-up device and its manufacturing method - Google Patents

Abstract

PURPOSE:To stop the flaring light by oblique incident light or inner reflected light for avoiding the transmission of false signals. CONSTITUTION:Light shielding films 54 are formed on transfer channels 44. The stepped parts about 2-4mum high are formed on a semiconductor substrate 41 by transfer gate electrodes 51 and the light shielding films 54. Next, an underneath flattening layer 55 is formed to flatten these stepped parts and then the first light shielding layer 56, the first transparent film 57, the second flare stopping layer 58, the second transparent film 59, the third flare stopping layer 60 and the third transparent film 61 are successively formed and finally, microlenses 62 are formed on the whole surface.

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 having a plurality of light shielding layers and a method of manufacturing the same.

[0002]

2. Description of the Related Art In recent years, in order to colorize and use a solid-state image pickup device, there is a filter bonding method in which a color filter layer formed on a glass plate is bonded to a solid-state image pickup device.
However, as the process becomes complicated and the element becomes finer, it has become mainstream to use a so-called on-chip color filter system in which a color filter layer is directly formed on a semiconductor substrate on which a solid-state image sensor is formed. Further, in a small-sized solid-state image pickup device, a microlens is formed on the color filter layer, and incident light is focused on the light receiving portion to improve the light receiving sensitivity.

A conventional solid-state image pickup device will be described below. FIG. 23 is a sectional view of a main part of a conventional solid-state imaging device,
An example of a color filter bonding method is shown.

Since the surface of the semiconductor substrate 1 on which the solid-state image pickup device is formed has a large amount of irregularities, first of all, the surface of the semiconductor substrate 1 is ground flattening layer 4 first.
Then, the transparent film 6 is formed. After this,
Color filter 13 using color filter adhesive layer 12
Is glued. The light shielding layer 14 is a light absorbing layer or a light reflecting layer formed on the glass substrate surface of the color filter 13, and covers the vertical CCD 10 to prevent stray light (hereinafter referred to as flare light) incident on the photodiode 2. It is arranged. The incident light 8 that has passed through the optical system of the video camera reaches the photodiode 2 through the color filter 13 and the light energy is converted into an electric signal.

24 and 25 are cross-sectional views of the main part of another conventional solid-state image pickup device, showing an example of an on-chip filter system.

Generally, the on-chip filter system is shown in FIG.
As shown in FIG. 1, a semiconductor substrate 1 on which a solid-state image sensor is formed
An underlying flattening layer 4, a light-shielding layer 5 and a transparent film 6 are provided on top of this, and a condenser lens (referred to as an on-chip lens) 11 is formed thereon. In this way, the incident light 8 condensed by the on-chip lens 11 is efficiently guided to the photodiode 2, but is blocked so that the flare light which is the internal reflected light 9 does not enter the photodiode 2 as a false signal. The layer 5 is formed in the transparent film 6.

In the conventional solid-state image pickup device shown in FIG. 25, the thickness of the light shielding layer 5 is thicker than that in the conventional solid-state image pickup device shown in FIG. 24. By controlling this thickness, flare light can be more completely removed. It is something to try to prevent.

[0008]

However, the above-mentioned conventional structure has the following problems and cannot sufficiently prevent flare light.

In the filter-adhesion type solid-state image pickup device shown in FIG. 23, obliquely incident light rays of the incident light 8 are reflected by the light-shielding film 3, and are repeatedly reflected on the surface of the color filter 13 and the transparent film 6. The internally reflected light 9 reaches the photodiode 2 which should not be originally incident, which causes a false signal.

In the on-chip filter type solid-state image pickup device shown in FIG. 24, when the incident light 8 enters from an oblique direction, the light shielding layer 5 cannot absorb and block flare light sufficiently because the light shielding layer 5 has a thin single layer structure. Internal reflection is repeated at 3 and the like to reach the photodiode 2 which should not be incident, which causes generation of a false signal.

Further, in the on-chip filter type solid-state image pickup device shown in FIG. 25, the thickness of the light-shielding layer 5 which is a light absorption layer is increased so that the incident light 8 which obliquely enters can be blocked and absorbed. Of the incident light 8 that has passed through the on-chip lens 11, the light that passes through the periphery of the lens is blocked by the thick light-shielding layer 5 and the light that should originally reach the photodiode 2 is absorbed, and the sensitivity is reduced. When the light shielding layer 5 is formed by photolithography, a negative type natural protein material is mainly used. However, in this case, if the film thickness of the light shielding layer 5 is large, the resolution is not sufficiently achieved, and the film remaining of the light shielding layer 5 is likely to occur. As a result, the periphery of the photodiode 2 is partially covered, and the sensitivity of the photodiode 2 decreases. Furthermore, when the light-shielding layer 5 has a large film thickness, the material may be dissolved in the developing step after exposure, and stains may occur on the image.

The present invention solves the above-mentioned conventional problems by preventing flare light due to obliquely incident light or internally reflected light,
It is an object of the present invention to provide a solid-state imaging device which is excellent in image characteristics without generating a false signal and a manufacturing method thereof.

[0013]

In order to achieve this object, a solid-state image pickup device of the present invention has a light-shielding film in a region other than a photodiode of the solid-state image pickup device on a semiconductor substrate on which the solid-state image pickup device is formed. The flattening layer is formed on the light-shielding film, and two or more light-shielding layers are formed on the flattening layer.

The method of manufacturing the solid-state image pickup device of the present invention is
Forming a matrix of photodiodes and vertical CCDs on a semiconductor substrate; forming a transfer gate electrode on the semiconductor substrate on the vertical CCD via an insulating film; and a light-shielding film on the transfer gate electrode. Forming, a step of forming a base flattening layer for flattening the surface of the semiconductor substrate, a step of forming a first light shielding layer on the base flattening layer on the transfer gate electrode, Forming a first transparent film on the first light-shielding layer and planarizing it; forming a second light-shielding layer on the first transparent film; and secondly forming a second light-shielding layer on the second light-shielding layer. Forming a transparent film and flattening it.

Further, a step of forming photodiodes and vertical CCDs in a matrix on a semiconductor substrate, a step of forming a transfer gate electrode on the semiconductor substrate on the vertical CCD via an insulating film, and the transfer gate. Forming a light-shielding film on the electrode, forming a base planarizing layer for planarizing the surface of the semiconductor substrate, and forming a first light-shielding layer on the base planarizing layer on the transfer gate electrode. A step of forming a first transparent film on the first light-shielding layer and planarizing it, a step of forming a second light-shielding layer on the first transparent film, and a second light-shielding step Forming a second transparent film on the layer and planarizing it, forming a third light-shielding layer on the second transparent film, and forming a third transparent film on the third light-shielding layer Forming and flattening, and forming a microlens on the third transparent film. And a step of forming a.

[0016]

With this structure, flare light that is likely to occur when light obliquely enters the solid-state image pickup device and flare light that is internally reflected by the light-blocking metal layer or the like of the incident light can be efficiently blocked and absorbed. Also when applied to a solid-state imaging device equipped with an on-chip lens, it is possible to obtain a good screen without reducing the amount of light collection and without developing stains caused by increasing the thickness of the light shielding layer.

[0017]

DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described below with reference to the drawings.

FIG. 1 is a sectional view of a main part of a solid-state image pickup device according to the first embodiment of the present invention, showing an example of an on-chip filter system.

Hereinafter, the CCD (char
A cross-sectional view of a ge coupled device) type solid-state imaging device will be described.

First, the N-type semiconductor substrate 41 has a surface orientation (10
0) and the impurity concentration is about 10 ¹⁴ cm ⁻³ . A first P-type diffusion layer 42 is formed on the N-type semiconductor substrate 41. The depth of the first P-type diffusion layer 42 is about 5 μm. The impurity concentration of the first P-type diffusion layer 42 is about 10 ¹⁵ cm.
^-3 . The first P-type diffusion layer 42 is the photodiode 4
It is provided for discharging unnecessary electric charges at 3. That is, the photodiode 43 is formed on the N-type semiconductor substrate 41 as an N-type diffusion layer. In the photodiode 43, an electric charge (photocarrier) is formed by the light incident from the outside and is temporarily stored inside. When the charge is generated in a large amount and becomes larger than the charge that can be accumulated in the photodiode 43, the charge flows from the photodiode 43 to another region. Such charges cause blooming when they enter the transfer channel 44 formed of the N-type diffusion layer. The occurrence of such blooming can be prevented by forming the first P-type diffusion layer 42.
The first P-type diffusion layer 42 is fixed to zero volt. Therefore, in the potential distribution formed in those regions, the charges generated in the photodiode 43 pass through the first P-type diffusion layer 42 and are discharged to the N-type semiconductor substrate 41. When the impurity concentration of the first P-type diffusion layer 42 is set to the above value, the photodiode 43 can be easily depleted and the photoelectric conversion signal amount can be increased when the solid-state imaging device operates. it can. The depth of the first P-type diffusion layer 42 is determined by the depth of the photodiode 43 and the breakdown voltage between them. The depth of the photodiode 43 is required to be about 2 μm in order to obtain sufficient photoelectric conversion efficiency when light in the visible light region is incident.

An N-type diffusion layer, which is a photodiode 43, is formed on the first P-type diffusion layer 42. When light is incident on the photodiode 43, electron pairs of electrons and holes are generated in the depletion layer of the photodiode 43. The electrons pass through the adjacent transfer channel 44 and become signal charges. The holes are taken out of the N-type semiconductor substrate 41 through the first P-type diffusion layer 42. In this way
The photodiode 43 converts incident light into signal charge. A second P-type diffusion layer 45 is formed on the surface of the photodiode 43.

Here, the second P-type diffusion layer 45 is formed.
The reason is that the photodiode 43 of the N-type diffusion layer is a semiconductor substrate.
Formed in contact with the interface between the plate 41 and the gate insulating film 48
Current, the current is generated due to the effect of the interface states existing at the interface.
Occurs, and the characteristics of the element deteriorate. Depletion layer is silicon
Relatively high concentration so that it does not reach the insulating film interface
A second P-type diffusion layer 45 having a high temperature is formed. This second P
The type diffusion layer 45 has 10 ¹⁷cm^-3With impurity concentration exceeding
Ron is needed. This much impurity concentration is
Ion implantation method,
Therefore, an injection defect occurs on the surface of the semiconductor substrate 41, and a leak occurs.
Cause current. As a result, to prevent the generation of dark current
However, the improvement effect is not sufficient.
Yes. Prevents the occurrence of implantation defects due to such ion implantation
In order to do so, there is a method of performing hydrogen annealing. But water
Hydrogen source introduced into the semiconductor substrate 41 by elementary annealing
When heat or light is applied to the semiconductor substrate 41, the
There is no effect because it escapes from the interface between the recon substrate and the oxide film.
The stability is poor. Therefore, the element manufactured using this
There is a problem in the reliability of the child after being left for a long time.

A third P-type diffusion layer 47 is formed in the first P-type diffusion layer 42. Third P-type diffusion layer 4
7 has a function of preventing charge, which is noise, of signals generated in the N-type semiconductor substrate 41 from diffusing into the transfer channel 44. Here, the diffusion depth of the third P-type diffusion layer 47 is about 1 μm. The impurity concentration of the third P-type diffusion layer 47 is 10 ¹⁶ cm ^-3 . The third P-type diffusion layer 47 is used to surround the transfer channel 44 formed of the N-type diffusion layer. Generally, such a structure is called a Hi-C structure. Third
When the diffusion depth of the P-type diffusion layer 47 is deepened by heat treatment, the diffusion in the lateral direction simultaneously proceeds. Therefore, the third
The P-type diffusion layer 47 of (1) penetrates to the N-type diffusion layer of the photodiode 43. If the third P-type diffusion layer 47 enters the photodiode 43, the photoelectric conversion output will decrease. The transfer channel 44 is a transfer area for transferring the signal charge formed by the photodiode 43 to a predetermined area.

Here, the diffusion depth of the transfer channel 44 is about 0.5 μm. The impurity concentration of the transfer channel 44 is 10 ¹⁶ to 10 ¹⁷ cm ⁻³ .

In order to realize the above Hi-C structure, it is necessary to make the third P-type diffusion layer 47 wider than the transfer channel 44.

When the signal charges generated in the photodiode 43 are read out to the transfer channel 44, the potential of the transfer channel 44 is made lower than the potential of the photodiode 43. Further, when the signal charge carried to the transfer channel 44 flows back to the photodiode 43 or when the signal charge exists in the transfer channel 44, the signal charge formed in the photodiode 43 is transferred to the transfer channel 44. It needs to be prevented from flowing. Therefore, the fourth P-type diffusion layer 48 that controls the potential at the time of reading is formed between the photodiode 43 and the transfer channel 44. When the signal charge is transferred from the photodiode 43 to the transfer channel 44, the potential in the fourth P-type diffusion layer 48 is set lower than the potential of the photodiode 43 and is equal to or slightly higher than the potential of the transfer channel 44. Controlled by. When the signal charge is accumulated in the transfer channel 44, the potential of the fourth P-type diffusion layer 48 is higher than the potential of the photodiode 43 and higher than the potential of the transfer channel 44 so that the signal charge does not flow back to the photodiode 43. Controlled to be high.

Here, the diffusion layer depth of the fourth P-type diffusion layer 48 is about 1 μm. The surface concentration of the fourth P-type diffusion layer 48 on the surface of the silicon substrate 41 is 10 ¹⁶ to 10 ¹⁷ cm ^−3.
Is. When the driving pulse voltage for operating the solid-state imaging device is 0 V or 15 V, it is possible to prevent the charge from flowing backward from the transfer channel 44 to the photodiode 43, or
Alternatively, it is necessary that the charges flow from the photodiode 43 into the transfer channel 44. Therefore, the diffusion layer depth and the impurity concentration of the fourth P-type diffusion layer 48 are set so that the threshold voltage can have the optimum potential distribution in each state. The width of the fourth P-type diffusion layer 48 is preferably about 1 μm or less. If the width of the fourth P-type diffusion layer 48 is larger than 1 μm, the gm characteristic of the transistor deteriorates. If the gm characteristic deteriorates, it becomes impossible to completely read out the signal charges accumulated in the photodiode 43. On the contrary, when the width of the fourth P-type diffusion layer 48 is smaller than about 1 μm, the short channel effect occurs. Punch-through easily occurs due to the short channel effect, and as a result, the photoelectric conversion output value of the photodiode 43 becomes small.

The solid-state image pickup device has a pair of photodiodes 43 and transfer channels 44, which are formed in a matrix. A fifth P-type diffusion layer 49 is formed to electrically separate this pair from the adjacent pair. The fifth P-type diffusion layer 49 is formed by ion implantation. Here, the depth of the fifth P-type diffusion layer 49 is about 1 μm. The surface concentration of the fifth P-type diffusion layer 49 is 10 ¹⁷
It is -10 ¹⁸ cm ^-3 .

The surface concentration of the fifth P-type diffusion layer 49 needs to be set within the above range so that the signal charges accumulated in the adjacent photodiode 43 do not flow in. If the surface concentration is less than 10 ¹⁷ cm ^-3 ,
The signal charge of the adjacent photodiode 43 flows in.
Further, when the surface concentration is higher than 10 ¹⁸ cm ^-3 , the narrow channel effect occurs in the adjacent transfer channels 44.
When the narrow channel effect occurs, the transfer capacity of the transfer channel 44 decreases. For this reason, the dynamic range of the solid-state imaging device becomes small, and the transfer efficiency deteriorates.

The width of the fifth P-type diffusion layer 49 is preferably about 1 μm or less. If the width of the fifth P-type diffusion layer 49 is 1
If it is larger than μm, the transfer area of the transfer channel 44 is reduced. That is, it becomes impossible to completely read out the signal charges accumulated in the photodiode 43. On the contrary, when the width of the fifth P-type diffusion layer 49 is smaller than 1 μm, the short channel effect occurs. Due to the short channel effect, punchthrough easily occurs between the adjacent photodiode 43 and the transfer channel 44. As a result, the information of the adjacent photodiodes 43 is read and the resolution is lowered. Furthermore, the output of the photodiode 43 is reduced.

A gate insulating film 50 is grown on the N-type semiconductor substrate 41 by a silicon oxide film. The gate insulating film 50 is formed by a pyro oxidation method. Gate insulating film 5
The film thickness of 0 is about 50 nm or more. The film thickness of the gate insulating film 50 is preferably set to 50 nm or more in order to improve the transfer efficiency by utilizing the fringing effect.

The transfer gate electrode 51 is formed by patterning polysilicon grown by the low pressure CVD method. The sheet resistance of the transfer gate electrode 51 is several tens Ω. The film thickness of the transfer gate electrode 51 is about 500 nm. The transfer gate electrode 51 is used as an electrode for applying a drive pulse for reading out and transferring the signal charge formed by the photodiode 43 to the transfer channel 44. As described above, it is desirable that the transfer gate electrode 51 has as low resistance as possible. However, if the phosphorus doping amount is increased for the purpose of lowering the resistance, the breakdown voltage of the interlayer film 52 formed by oxidizing the surface of the transfer gate electrode 51 is deteriorated, so the phosphorus doping amount is preferably set to the above value. An interlayer film 52 made of a polysilicon oxide film is grown on the surface of the transfer gate electrode 51.

The interlayer film 52 is grown by oxidizing the surface of the transfer gate electrode 51 by a pyrooxidation method. Interlayer film 5
The film thickness of 2 is about 200 nm. The interlayer film 52 is formed to secure the breakdown voltage of the interlayer film. Further, due to the etching residue of the polysilicon film generated by the etching when forming the transfer gate electrode 51, a leak is generated through the etching residue of the polysilicon film when a drive voltage is applied. Leakage can be prevented by burning off such a polysilicon etching residue when the interlayer film 52 is formed. Since the four-phase driving pulse applied to the transfer gate electrode 51 changes the level of -7V, 0V and + 15V, the interlayer film 52 has a breakdown voltage of 22V or more of the maximum voltage difference.

An interlayer film 53 is formed of a silicon oxide film on the surface of the interlayer film 52. The film thickness of the interlayer film 53 is about 100 nm. The interlayer film 53 is formed by the CVD method. The interlayer film 53 is formed to prevent the breakdown voltage from locally weakening due to the presence of pinholes or the like in the polysilicon oxide film forming the interlayer film 52.

In order to prevent light from entering the transfer channel 44 and becoming a smear component, a light shielding film 54 made of a metal vapor deposition film such as an aluminum film is formed. As described above, a step of about 2 to 4 μm is formed on the semiconductor substrate 41 of the transfer channel 44 by the transfer gate electrode 51 and the light shielding film 54. An underlying flattening layer 55 is formed to flatten the surface step, and the first light shielding layer 5 is formed on the underlying flattening layer 55.
6 is formed. The base flattening layer 55 has a film thickness of 3 to 5
Acrylic transparent resin of about μm is used. The first light shielding layer 56 formed on the underlying flattening layer 55
Also, since a layer mainly composed of an acrylic resin may be used, when the first light shielding layer 56 is processed, the base flattening layer 5 is used.
After forming the base flattening layer 55 so that 5 does not deform, 2
The base leveling layer 55 is baked and solidified by baking at a temperature of about 00 ° C. The underlying flattening layer 55 needs to be sufficiently flattened in order to accurately form the upper light-shielding layer. The bottom surface and the convex portion of the concave and convex portions formed on the surface after the underlying flattening layer 55 is formed. The difference from the top surface of is less than 0.1 μm. If this difference is 0.1 μm or more, the pattern of the light-shielding layer formed in the upper layer has uneven distribution in the regions to be shielded from light depending on the location. As a result, the resolution of the finally manufactured solid-state imaging device varies from place to place. For the first light-shielding layer 56, gelatin, casein, or acrylic resin is used by dyeing black. Thus, the first light-shielding layer 56 is an organic film and is a negative-type sensitive organic film that can be formed by ordinary photolithography. Gelatin and casein are exposed by g-line in photolithography, but their resolution is low. For this reason, the pattern cannot be miniaturized as the element is miniaturized, and the resolution is low, so that it affects the region other than the desired region. In this embodiment, acrylic resin is used. Acrylic resin is a transparent resin that is insensitive to light. However, the diazo compound is added to the acrylic copolymer, and further dimethylaminoethyl methacrylate (DMAEMA) is added in order to have a dyeing group so that dyeing is possible. This makes it possible to dye, and even in photolithography i
It is a negative type material that is sensitive to lines. Therefore, it is possible to miniaturize the pattern accompanying the miniaturization of the element, and it is expected that the resolution will be improved. When gelatin or casein is dyed in black, a material containing chromic acid as a main component is used, which causes adverse effects on the environment such as contamination. However, in the case of acrylic resin, such a material is used. It is safe because it has no adverse effects on the human body.

Next, the first light shielding layer 56 is formed so as not to block the light incident on the photodiode 43.
The film thickness of the first light shielding layer 56 is 0.3 μm to 0.1 μm in this embodiment.
It is used at 5 μm. However, the film thickness cannot be 0.8 μm or more. Because this acrylic resin is a negative type, swelling of a pattern called so-called swelling in which the resin absorbs the developing solution occurs during development. This is removed by the rinse after development and shrinks, but the film thickness is 0.8μ.
If it is more than m, the pattern will be uneven during contraction. Further, a skirt called scum is formed at the skirt of the pattern at the time of developing peculiar to the negative type. Such scum is formed in a region that should not be shielded from light.
As described above, the swelling and scum cause variations in the sensitivity of the manufactured solid-state imaging device, and the image has a stain.
In order to prevent this, it is necessary to use the film with a thickness of 0.8 μm or less. Further, the cross-sectional width of the first light-shielding layer 56 needs to be dimensioned so as to cover the light-shielding film 54 and not to block the light collecting path by the on-chip lens, and here it is set to 2 μm.

A transparent film 57 is formed on this, and a third light shielding layer 60 is formed on the transparent film 57 with a second light shielding layer 58 and a transparent film 59 interposed therebetween. Transparent film 57, 5
A transparent acrylic resin is baked and hardened to be used as 9. The film thickness is 0.5 to 2 μm and the surface of the substrate is flattened.
The second and third light shielding layers 58 and 60 are made of the same material and have the same film thickness as those of the first light shielding layer 56 described above. Second light shielding layer 58
As for the cross-sectional width of the third light-shielding layer 60, the cross-sectional width is made smaller toward the top so as not to block the light collection path of the on-chip lens. Further, the third light shielding layer 60 is covered with the transparent film 61 having the same material and the same film thickness as the transparent film 57 to be planarized. An on-chip lens 62 is formed on it.

With the above configuration, the light 63 incident on the on-chip lens 62 from the direction perpendicular to the photodiode 43 is the microlens 62 and the transparent films 57, 59, 61.
Then, the light passes through the underlying flattening layer 55 and enters the photodiode 43. Such light 63 directly reaches the photodiode 43, whereas light 6 that enters the microlens 62 from an oblique direction at an acute angle with respect to the surface of the semiconductor substrate 41.
Some of the parts 4, 65 do not reach the photodiode 43. The light 64, 65 incident from an oblique direction is refracted by the lens or the transparent film, but the optical path of the light 64, 65 travels toward the transfer gate electrode 51. Therefore, the transfer gate electrode 5
It reaches the light-shielding film 54 formed on 1 and is reflected. The reflected light is returned to the underlying flattening layer 55 and the transparent films 57 and 59,
The so-called flare light is transmitted through 61, reflected at the boundary between the transparent film 61 and the microlens 62, and incident on the adjacent photodiode 43. As in the present embodiment, by forming the light shielding layers 56, 58 and 60 other than the optical path of the light 63 which is directly incident on the photodiode 43 from the microlens 62, the reflected light is shielded and absorbed. Therefore, flare light is not generated.

FIG. 2 is a sectional view of the essential parts of a solid-state image pickup device according to the second embodiment of the present invention. The portions where the light-shielding film is formed on the respective diffusion layers formed in the semiconductor substrate 71 and the transfer gate electrodes 72 on the semiconductor substrate 71 are the same. The difference from the first embodiment is that the second light shielding layer 74 and the third light shielding layer 75 are directly formed on the first light shielding layer 73 without a transparent film. In this case, the cross-sectional width of the light-shielding layers of the second light-shielding layer 74 and above is formed so that the upper layer does not obstruct the light collection path of the on-chip lens 76. At this time, the respective light shielding layers 73 and 7
The material and film thickness of 4, 75 may be the same as in the first embodiment. However, since the three light-shielding layers 73, 74, and 75 have a multi-layered structure, the step difference caused by them is as large as about 1.5 to 6 μm, so that the substrate surface is flattened before the on-chip lens 76 is provided. The film thickness of the transparent film 77 must be correspondingly about 2.5 to 7 μm. In the second embodiment, the number of steps is smaller than that in the first embodiment, but when the second and third light shielding layers 74 and 75 are formed, the step difference of the base becomes large and the light shielding layer pattern is formed. Since the precision of the above becomes poor, the effect is small especially when the device is miniaturized.

As described above, in the first and second embodiments, the three light-shielding layers are provided along the optical paths passing through the on-chip lenses 62 and 76, so that they do not enter the photodiode 43 and are scattered inside. Even if there is light, there is no flare light that penetrates into the adjacent photodiode 43, so that uneven sensitivity occurs, and as a result, bleeding does not occur in the image.

Here, the reason why the three light-shielding layers of the first and second embodiments are used is determined by their light-shielding ability. As described above, the film thickness of the light shielding layer can be used only up to about 0.8 μm due to the limitation of the forming process. A single light-shielding layer using such an acrylic resin can block only 60% of the intensity of incident light with a film thickness of 0.8 μm. Therefore, as in this embodiment, 3
When the three-layer light-shielding layer is used, the light transmitted through the three-layer light-shielding film can be reduced to about 6.4% of the incident light. As described above, the number of light shielding layers to be used depends on the comparison with the required characteristics.

The arrangement of the light shielding layer will be described with reference to FIG. The drawing shows a sectional view of a portion corresponding to one pixel of the solid-state imaging device. The light emitted from the subject enters the microlens 80 through the aperture. The microlens 80 includes light that is incident from the direction perpendicular to the substrate and light that is incident at an arbitrary angle with respect to the direction perpendicular to the substrate. This arbitrary angle is determined by the optical path of the light incident from the aperture. Light incident from the vertical direction passes through the microlens 80, and the focal point forms an image forming point A on the surface of the photodiode 81. For this purpose, the photodiode 81
It is realized by changing the distance from the surface of the micro lens 80 to the micro lens 80 or the curvature of the micro lens 80. On the other hand, the light incident from the direction inclined at an arbitrary angle from the vertical direction is
It is formed apart from the image forming point A formed by the light incident from the vertical direction. Considering all of these lights, the width of the photodiode is set so as to cover the area of the image forming point imaged by these lights as shown in the figure. That is, the light always passes through the region sandwiched by the line segments CD and EF that connect both ends of the microlens 80 to both ends of the photodiode. For this reason, the light shielding layer needs to be arranged outside the line segment along the line segment. Here, when the width of the photodiode 81 is r, the width of the microlens 80 is R, and the distance from the surface of the photodiode 81 to the bottom surface of the microlens L is L, this line segment is the origin of the center of the photodiode 81. The line segment EF is expressed by the following equation.

Y = [L (2X-r)] / (R-r) From this, the height from the end G to the end G on the photodiode side above the first light-shielding layer 82 is d ₁ . 2 light shielding layer 8
The height to the photodiode end H on top of 3 is d
₂ , the height from the end H to the end I on the photodiode side above the third light shielding layer 84 is d ₃ , from the center point of a specific microlens 80 to the center point of the adjacent microlens 80. If the distance is P, the positions of the ends G, H, and I on the substrate are [d ₁ (R−r) + rL] from the origin, respectively.
/ 2L, _{[(d 1 + d 2) (} R-r) + rL ] / 2L,
[(D ₁ + d ₂ + d ₃ ) (R−r) + rL] / 2L. At this time, the width W of each light-shielding layer is calculated by the same formula, and the width of the first light-shielding layer 82 is [d ₁ (R
−r) + L (P−R)] / L, the width of the second light shielding layer 83 is [(d ₁ + d ₂ ) (R−r) + L (P−R)] / L, the third
The width of the light shielding layer 84 of [(d ₁ + d ₂ + d ₃ ) (R−r) +
Ideally, L (P-R)] / L. However, in this case, as shown in the drawing, the distance between one microlens 80 and the adjacent microlens 80 is R. That is, it is necessary that the end portion of the microlens 80 and the end portion of the adjacent microlens 80 are in contact with each other.

FIG. 4 is a sectional view of a main part of a solid-state image pickup device according to the third embodiment of the present invention, showing an example of a filter bonding method. However, in the description, the configuration after the light shielding film is formed will be described. A photodiode 91 and a vertical CCD section 92 are formed on the semiconductor substrate 90. The transfer gate electrode 93 is formed on the semiconductor substrate 90, and the light shielding film 9 is formed on the transfer gate electrode 93.
4 are formed. A base flattening layer 95 is formed to flatten the surface step on the semiconductor substrate 90, and a first light shielding layer 96 is formed thereon so as not to block light incident on the photodiode 91. Has been done.
The cross-sectional width of the first light-shielding layer 96 is set so as to cover the light-shielding film 94, and the thickness of the first light-shielding layer 96 is preferably 0.8 μm or less so that stains do not occur after development. A transparent film 97 is formed on the first light shielding layer 96, and a second light shielding layer 98 is formed thereon so as not to block light incident on the photodiode 91. In this case, since the chief ray passing through the color filter 99 is substantially perpendicular to the color filter 99, the cross-sectional width of the second light-shielding layer 98 and the light-shielding layers is the first.
It may be about the same as or slightly smaller than the light shielding layer 96. Further, the thickness of the second light-shielding layer 98 does not cause stains after development.
8 μm or less is desirable. The transparent film 100 is formed by including the second light-shielding layer 98 thus formed, and the color filter 99 is adhered thereon by using the filter adhesive layer 101. The color filter 99 is formed on a glass substrate. In addition, the light-shielding film 1 is made of a chromium film on the glass substrate.
02 is formed. This glass substrate and semiconductor substrate 9
The position 0 is aligned by alignment marks provided on both sides and bonded via the filter adhesive layer 101. Such a method is called a filter glass bonding method. In this method, unlike the first and second embodiments, since the light incident on the photodiode 91 is incident substantially perpendicular to the substrate surface, it is not necessary to change the width of the light shielding layer depending on its position. Even in such a solid-state imaging device, there is light 108 incident from an oblique direction. Such light is reflected by the light shielding film 94 on the transfer gate electrode 93, and the underlying flattening layer 95,
Penetrates through the transparent films 97, 100 and the filter adhesive layer 101,
It is reflected on the upper surface of the color filter 99. The reflected light 108 enters the adjacent photodiode 91. In this embodiment, the light reflected by the light shielding film 94 and the light reflected by the glass substrate surface are shielded and absorbed by the light shielding layers 96, 98 and 102, so that flare light is not generated.

Next, a method of manufacturing a solid-state image pickup device according to an embodiment of the present invention will be described with reference to the drawings.

5 to 16 are process sectional views for explaining the manufacturing method. First, as shown in FIG. 5, a photodiode 111 and a vertical CCD 112 are formed on a semiconductor substrate 110 on which a solid-state image sensor is formed. After that, vertical CCD1
A transfer gate electrode 113 is formed on the surface 12. A light shielding film 114 that prevents light from entering the vertical CCD 112 is formed on the transfer gate electrode 113 so as to cover the vertical CCD 112.

Next, as shown in FIG. 6, the semiconductor substrate 110
A transparent synthetic resin, such as an acrylic resin, which has a sufficient transmittance in the visible light range, is applied to the surface of the surface by a spin coating method in which the rotation speed is set according to the viscosity, and the base is flattened to flatten the surface irregularities. The layer 115 is formed.

Next, as shown in FIG. 7, the underlying flattening layer 11
The material of the first light-shielding layer 116 is applied onto the layer 5 by spin coating. As the material of the first light-shielding layer 116, a natural protein containing a light absorbing dye, such as gelatin or casein, or an acrylic resin containing a light absorbing dye is used. Instead of using dye-containing materials, spin coat natural protein or synthetic resin with dyeability, then dye it in a light-absorption color (often black), and add tannic acid to prevent color loss. It may be fixed using tartar.

Next, as shown in FIG. 8, the first light shielding layer 116 is left on the light shielding film 114. In this step, for example, when using a resin material having photosensitivity with chromic acid, diazo, azide, etc., the portion irradiated by lithography with ultraviolet light or far ultraviolet light is resin-crosslinked, and the unirradiated portion is used as a developing solution. It is rinsed off and the first light shielding layer 116 is formed.
When a resin material having no photosensitivity is used, a photosensitive resist is spin-coated on the material to be the first light-shielding layer 116, and the photosensitive resist is exposed to ultraviolet rays or the like in a desired pattern, After development, the portion without the resist pattern is dry-etched or wet-etched. After that, the remaining resist is removed by ashing to form a first light shielding layer 116 having a predetermined pattern.

Next, as shown in FIG. 9, a transparent film 117 is formed on the entire surface by using acrylic resin or the like for flattening.
Next, as shown in FIG. 10, the material used for forming the first light shielding layer 116 is spin-coated.

Next, as shown in FIG. 11, the second light shielding layer 118 having a predetermined pattern is formed by the same process as that of FIG. When forming an on-chip lens, the cross-sectional width of the second light-shielding layer 118 is smaller than the cross-sectional width of the first light-shielding layer 116 so as not to block light collection of the on-chip lens onto the photodiode 111. Keep it. When the on-chip lens is not formed, the first light shielding layer 116
The cross-sectional width of the second light shielding layer 118 may be the same.

Next, as shown in FIG. 12, a transparent film 119 is applied to the entire surface. Next, as shown in FIG. 13, the material used for forming the first light-shielding layer 116 is spin-coated on the transparent film 119 by the same process as in FIG.

Next, as shown in FIG. 14, a third light shielding layer 120 having a predetermined pattern is formed by the same process as that of FIG. Next, the transparent film 121 is applied to the entire surface. The transparent films 117, 119, and 121 applied in the above steps are optically integrated. When the on-chip lens is not required, there are one that ends in the step of FIG. 15 and one that adheres the color filter. In the case of forming an on-chip lens, the on-chip lens 122 is formed right above the photodiode 111 as shown in FIG.

Next, a manufacturing method in which a transparent film is not sandwiched between the first, second and third light shielding layers will be described with reference to the drawings.

17 to 22 are process sectional views for explaining the manufacturing method. The steps leading to FIG. 17 are shown in FIGS.
The description is omitted because it is the same as the above process. Next in FIG.
As shown in FIG. 8, a material similar to that shown in FIG. 7 is used as a material for forming the second light shielding layer 118, and this is spin-coated. Next, as shown in FIG. 19, the second light shielding layer 118 is formed by the same process as in FIG. Second light shielding layer 118
The cross-section width of the
The first light shielding layer 116 so as not to interfere with the collection of light to the first
Smaller than the cross-sectional width of. Similarly, as shown in FIG. 20, a third light shielding layer 120 having a smaller cross-sectional width than the second light shielding layer 118 is formed. Next, as shown in FIG. 21, the surface is planarized with the transparent film 123. Next, as shown in FIG.
After the transparent film 124 is formed by spin coating, the on-chip lens 122 is formed so as to match the photodiode 111.

[0056]

As described above, according to the present invention, two or more light-shielding layers are formed in a region other than the photodiode of a solid-state image pickup device formed on a semiconductor substrate with or without a transparent film sandwiched therebetween. By doing so, flare light generated when light obliquely enters the solid-state imaging device and flare light internally reflected by a light-shielding metal layer or the like of incident light are efficiently blocked and absorbed, and a film per light-shielding layer is provided. Since the thickness can be reduced, it is possible to realize an excellent solid-state imaging device that can obtain a good screen without generating stains after development. Further, by decreasing the cross-sectional width of each light-shielding layer in order from the semiconductor substrate side, it is possible to realize a solid-state imaging device that does not interfere with light collection from the on-chip lens to the photosensitive portion even when the on-chip microlens is formed.

Further, according to the present invention, an on-chip filter system in which a color filter is directly formed on a solid-state image pickup substrate, a filter adhesion system in which a color filter previously formed on a glass substrate is adhered, and a system in which no filter is attached are used. Even when applied to a device, an excellent effect can be obtained.

[Brief description of drawings]

FIG. 1 is a sectional view of an essential part of a solid-state imaging device according to a first embodiment of the present invention.

FIG. 2 is a sectional view of an essential part of a solid-state imaging device according to a second embodiment of the present invention.

FIG. 3 is a diagram illustrating the arrangement of a light shielding layer.

FIG. 4 is a sectional view of a main part of a solid-state imaging device according to a third embodiment of the present invention.

FIG. 5 is a process cross-sectional view that is a first embodiment of the method for manufacturing a solid-state imaging device according to the present invention.

FIG. 6 is a process cross-sectional view which is a first embodiment of a method for manufacturing a solid-state imaging device according to the present invention.

FIG. 7 is a process cross-sectional view that is a first embodiment of the method for manufacturing a solid-state imaging device of the present invention.

FIG. 8 is a process cross-sectional view which is a first embodiment of the method for manufacturing a solid-state imaging device of the present invention.

FIG. 9 is a process cross-sectional view that is a first embodiment of the method for manufacturing a solid-state imaging device of the present invention.

FIG. 10 is a process cross-sectional view that is a first embodiment of the method for manufacturing a solid-state imaging device of the present invention.

FIG. 11 is a process cross-sectional view that is a first embodiment of the method for manufacturing a solid-state imaging device of the present invention.

FIG. 12 is a process cross-sectional view that is a first embodiment of the method for manufacturing a solid-state imaging device of the present invention.

FIG. 13 is a process cross-sectional view that is a first embodiment of the method for manufacturing a solid-state imaging device of the present invention.

FIG. 14 is a process cross-sectional view that is a first embodiment of the method for manufacturing a solid-state imaging device according to the present invention.

FIG. 15 is a process sectional view showing a first embodiment of a method for manufacturing a solid-state imaging device according to the present invention.

FIG. 16 is a cross-sectional view illustrating a process of forming an on-chip lens.

FIG. 17 is a process sectional view showing a second embodiment of the method for manufacturing the solid-state imaging device of the present invention.

FIG. 18 is a process sectional view showing a second embodiment of the method for manufacturing the solid-state imaging device of the present invention.

FIG. 19 is a process sectional view showing a second embodiment of the method for manufacturing the solid-state imaging device of the present invention.

FIG. 20 is a process sectional view showing a second embodiment of the method for manufacturing the solid-state imaging device of the present invention.

FIG. 21 is a process sectional view showing a second embodiment of the method for manufacturing the solid-state imaging device of the present invention.

FIG. 22 is a process sectional view showing a second embodiment of the method for manufacturing the solid-state imaging device of the present invention.

FIG. 23 is a cross-sectional view of a main part of a conventional solid-state imaging device.

FIG. 24 is a cross-sectional view of main parts of another conventional solid-state imaging device.

FIG. 25 is a cross-sectional view of main parts of another conventional solid-state imaging device

[Explanation of symbols]

 41 semiconductor substrate 43 photodiode 55 underlying flattening layer 56 first light-shielding layer 57 transparent film 58 second light-shielding layer 59, 61 transparent film 60 third light-shielding layer 62 microlens

Claims (11)

[Claims] 1. A light-shielding film is formed on a region other than a photodiode of the solid-state image sensor on a semiconductor substrate on which the solid-state image sensor is formed, and a flattening layer is formed on the light-shielding film. A solid-state imaging device, comprising two or more light-shielding layers formed on the flattening layer. 2. The solid-state image pickup device according to claim 1, wherein a transparent film is formed between the light shielding layers. 3. The solid-state image pickup device according to claim 1, wherein a transparent film is formed on the light-shielding layer which is formed by stacking two or more layers. 4. The solid-state imaging device according to claim 1, wherein the light-shielding layer has a cross-sectional width that becomes narrower in order from the semiconductor substrate side. 5. The solid-state image pickup device according to claim 4, wherein a microlens is formed on the uppermost transparent film in accordance with the position of the photodiode of the solid-state image pickup device. 6. The cross-sectional width W of the light-shielding layer is r, the width of the photodiode is R, the width of the microlens is R, the distance from the surface of the photodiode to the bottom of the microlens is L, and the photodiode is the light-shielding layer. Is d and the distance from the center point of the photodiode to the center point of the photodiode next to the photodiode is P, then W = [d (R-r) + L (P-R)] / L The solid-state imaging device according to claim 5, wherein 7. The light-shielding layer has a negative photosensitive property,
The solid-state imaging device according to claim 1, wherein an acrylic resin to be dyed is used. 8. The solid-state imaging device according to claim 7, wherein the light-shielding layer has a thickness of 0.3 to 0.8 μm. 9. The light-shielding layer comprises an acrylic copolymer, a diazo compound and dimethylaminoethyl methacrylate (DMA).
8. The solid-state imaging device according to claim 7, wherein EMA) is added. 10. A photodiode and a vertical C on a semiconductor substrate.
Forming the CD with a matrix, and the vertical C
Forming a transfer gate electrode on the semiconductor substrate on the CD via an insulating film; forming a light-shielding film on the transfer gate electrode; and forming a base flattening layer for flattening the semiconductor substrate surface. And a step of forming a first light shielding layer on the underlying flattening layer on the transfer gate electrode,
Forming a first transparent film on the first light-shielding layer and planarizing it; forming a second light-shielding layer on the first transparent film; and forming a second light-shielding layer on the second light-shielding layer. And a step of forming a second transparent film and planarizing the second transparent film. 11. A photodiode and a vertical C on a semiconductor substrate.
Forming the CD with a matrix, and the vertical C
Forming a transfer gate electrode on the semiconductor substrate on the CD via an insulating film; forming a light-shielding film on the transfer gate electrode; and forming a base flattening layer for flattening the semiconductor substrate surface. And a step of forming a first light shielding layer on the underlying flattening layer on the transfer gate electrode,
Forming a first transparent film on the first light-shielding layer and planarizing it; forming a second light-shielding layer on the first transparent film; and forming a second light-shielding layer on the second light-shielding layer. Forming a second transparent film and flattening it; forming a third light shielding layer on the second transparent film; forming a third transparent film on the third light shielding layer; A method of manufacturing a solid-state imaging device, comprising: a planarizing step; and a step of forming a microlens on the third transparent film.