JPH09116127A - Solid-state image sensor - Google Patents

Abstract

PROBLEM TO BE SOLVED: To set the balance of light quantity entering the light sensing parts for respective colors within a desired range by varying the input light quantity for the light sensing parts corresponding to the respective colors of on-chip color filter layer by using a light shielding layer, a protection layer and an on-chip micro lens. SOLUTION: As for the plane shape of an on-chip micro lens 9, that corresponding to a G on-chip color filter layer 8 is the largest and those corresponding to R and B on-chip color filters 8 become smaller in order. Such a shape of the lens 9 makes it possible to change the plane shape of a resist pattern formed on the organic polymeric material layer for on-chip micro lens formation to be smaller or large, and it can be formed easily through reflow. Thus, the quantity of light transmitted through the lens 9 corresponding to the layers 8 can be changed so as to control the incident light quantity.

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, and more particularly, to a color solid-state image pickup device having high color reproducibility in which the balance of the amount of light incident on the photosensor portion corresponding to each color is highly controlled.

[0002]

2. Description of the Related Art CCD (Charge Coupled)
Solid-state image pickup devices such as devices are roughly classified into area sensors used for video cameras and camera-integrated video tape recorders, and line sensors used for facsimiles and bar code readers. Has become an indispensable device for the electronic eyes of. There is a strong demand for miniaturization and high resolution of the CCD, and the occupied area per unit pixel is reduced with the progress of high integration, and at the same time, the opening area of the sensor portion is also being reduced.

Due to the reduction of the opening area of the sensor section,
The amount of light taken into the sensor section is insufficient, and it has become difficult to generate sufficient photo-induced charges to secure the S / N ratio. Therefore, an on-chip microlens is a structure adopted in view of the requirements of satisfying both the characteristics of high integration and high sensitivity. A schematic cross-sectional view in the vertical register direction of a pixel portion of a single-plate type color solid-state imaging device that employs an on-chip microlens will be described with reference to FIG.

By forming a first-layer polysilicon gate 3 and a second-layer polysilicon gate 4 on a semiconductor substrate 1 made of silicon or the like, and performing self-aligned ion implantation and activation heat treatment using these gate electrodes as a mask. The optical sensor unit 2 is formed. Next, a metal film such as aluminum is deposited on the entire surface, and the upper portion of the optical sensor portion 2 is opened to form the light shielding layer 5. The opening plane shape of the light shielding layer is, for example, a rectangle of 1.5 μm × 2.5 μm. After this Si ₃
A protective layer 6 such as N ₄ is formed on the entire surface to have a uniform thickness, and is further flattened with acrylic resin or SiO ₂ to fill the step formed by the first-layer polysilicon gate 3 and the second-layer polysilicon gate 4. The conversion layer 7 is formed, and the on-chip color filter layer 8 corresponding to each color is further formed.
The planar arrangement of each color of the on-chip color filter layer 8 will be described later. After that, the on-chip microlens 9 having a larger area than the planar shape of the optical sensor unit 2 is formed so as to be located above the optical sensor unit 2. With such a structure, the light incident on the on-chip microlens 9 is condensed on the sensor unit 2, and the utilization efficiency of the incident light can be improved several times or more to secure the S / N ratio of the solid-state imaging device. Become.

As a method of manufacturing the on-chip microlens 9, the applicant of the present invention has previously filed Japanese Patent Application Laid-Open No. 1-1066.
As disclosed in Japanese Patent Publication No. 6, an organic polymer material layer is formed on the on-chip color filter layer 8, a resist pattern is selectively formed on the organic polymer material layer, and then heat treatment is applied to this resist pattern. Is reflowed to form a reflow resist pattern having a surface shape forming a part of a substantially spherical surface. At this stage, the shape of the on-chip microlens is determined, but for the reason described later, the reflow resist pattern and the organic polymer material layer are both etched back over the entire surface, the reflow resist pattern is etched off, and the shape of the reflow resist pattern is changed. Transfer to the organic polymer material layer, which is the on-chip microlens material layer, to complete the on-chip microlens 9.

The reason why the reflow resist pattern is not directly used as an on-chip microlens is that the lower on-chip color filter layer 8 is not thermally fading, for example, 180.
This is because it is difficult to select a resist material having both the property of being reflowable at a temperature of not higher than 0 ° C. and the property of not being reflowed at a temperature of about 150 ° C. which is applied during wire bonding or resin molding in the post-treatment process. Also 150 ℃
Even if a resist material that can be reflowed in a narrow temperature range from 1 to 180 ° C. can be selected, the actual process window is narrow in terms of temperature control, and it is difficult to use. Therefore, a resist material having excellent low temperature reflow properties and an organic polymer material layer having excellent heat resistance and optical characteristics are individually selected and used.

The plane shape of the on-chip microlens 9 thus formed and having an excellent shape is shown in FIG. 6 (b).
FIG. 6B is a view of the on-chip microlens group 9 formed on the surface of the CCD solid-state imaging device from the object side, and the AA cross section of FIG. 6A corresponds to FIG. 6A. As shown in the figure, the on-chip microlenses 9 are formed to have the same planar shape and sectional shape.
It is designed so that the amount of light incident on the optical sensor unit 2 of each color is constant.

By the way, the on-chip color filter layer 8
Is R (red), G (green) and B (blue) for primary colors
Is a complementary color system, Mg (magenta), C
A combination of y (cyan), G (green) and Y (yellow) is used as a structural unit, and this is periodically arranged in, for example, a checkered pattern. The arrangement of each color in the structural unit differs depending on the color coding of frame reading or field reading, but since it is not directly related to the gist of the present invention, detailed description thereof will be omitted. The color coding of the solid-state image pickup device of the RGB three-primary color field read is described in detail in, for example, Japanese Patent Publication No. 5-72796.

[0009]

In a solid-state image pickup device having such an on-chip color filter layer, in order to obtain a good white balance, for example, the amount of light that passes through the B color filter layer and enters the photosensor, It is necessary to keep the ratio of the amount of light that passes through the G color filter layer and enters the photosensor and the amount of light that passes through the R color filter layer and enters the photosensor within a certain range.
This will be described with reference to FIGS.

First, FIG. 5A shows the spectral sensitivity characteristic of the sensitivity of the optical sensor using the Si photoelectric conversion element. In addition,
The spectral sensitivity characteristic shown in FIG. 5A is a characteristic including an infrared cut filter for smear prevention and the like.

On the other hand, the color image of a color television is
As shown in FIG. 5C, the optical sensor sensitivity after mounting the on-chip color filter layers of B: G: R is 0.11:
It is designed so that an accurate white balance can be obtained at a ratio of 0.59: 0.30. Then, the filter characteristics of each color of the on-chip color filter layer of the solid-state image pickup device are given the light transmittance characteristics shown in FIG. 5B, for example, and the spectral sensitivity characteristics of the optical sensor by the Si photoelectric conversion element The output voltage from the optical sensor is just 0.1
It is designed to have a ratio of 1: 0.59: 0.30. When the ratio of the output voltage from the photosensor for each color deviates from this value by a certain range or more, the white balance is lost, and it is difficult to faithfully reproduce the color of the subject only by electrical circuit correction.

As a method of keeping the balance of the amount of light incident on the photosensors of the respective colors within a certain fixed range and setting the ratio of the output voltage from the photosensors of the respective colors to the constant value as described above, for example, on A method of selecting the dyeing density depending on the dyeing condition of the chip color filter layer is adopted. That is, the color filter light transmittance is controlled as shown in FIG. 4B by controlling the dye concentration, dyeing temperature, dyeing time, etc. when fixing each color dye to the coating film mainly composed of gelatin or the like, and controlling each color. The balance of the amount of transmitted light is ensured. However, only the dyeing conditions of the on-chip color filter layer may reduce the degree of freedom in designing the solid-state image pickup device, and a satisfactory result may not be obtained.

The present invention is proposed in view of the above-mentioned problems of the prior art, and surely keeps the balance of the amount of light incident on the photosensor portion of each color within a desired fixed range, and is excellent in color reproducibility. It is an object of the present invention to provide a solid-state imaging device.

[0014]

A solid-state image pickup device according to the present invention includes a light-shielding layer having openings selectively formed on a plurality of photosensor portions, and a plurality of photosensor portions and the light-shielding layer. A protective layer formed on the entire surface, a plurality of on-chip color filter layers periodically formed on the planarization layer formed on the protective layer so as to face the plurality of photosensor parts, and an on-chip color An on-chip microlens formed on a filter layer, wherein at least one of the light-shielding layer, the protective layer, and the on-chip microlens is an on-chip color filter layer. It is characterized in that the amount of light incident on the optical sensor unit is made different for each color.

In a preferred embodiment of the present invention, the planar shape of the on-chip microlens is different in the area corresponding to each color of the on-chip color filter layer so that the amount of incident light is different. And

In another preferred embodiment of the present invention, the cross-sectional shape of the on-chip microlens is made different in height according to each color of the on-chip color filter layer, so that the amount of incident light is made different. It is characterized by

In still another preferred embodiment of the present invention, the cross-sectional shape of the protective layer is made different in thickness depending on each color of the on-chip color filter layer so that the amount of incident light is made different. Is characterized by.

In still another preferred embodiment of the present invention, the planar shape of the light shielding layer is made different from that of the on-chip color filter layer by making the opening areas thereof different so as to make the incident light amount different. Is characterized by.

In the conventional solid-state image pickup device, the shapes of the on-chip microlens, the protective layer and the light-shielding layer have all been designed with a focus on uniform formation. Therefore, the control of the amount of light incident on the photosensor portion corresponding to each color of the on-chip color filter layer depends only on the dyeing density condition of the on-chip color filter layer, and thus it is not always possible to perform sufficient control. .

In any of these embodiments of the present invention, it becomes possible to control the amount of incident light corresponding to each color of the on-chip color filter layer, and the degree of freedom in designing the solid-state image pickup device is dramatically improved. Each embodiment may be adopted individually or a plurality of them may be combined. Further, it can be used in combination with a method of selecting the dyeing density of the on-chip color filter layer.

[0021]

BEST MODE FOR CARRYING OUT THE INVENTION Embodiments of the present invention will be described below with reference to the accompanying drawings. Note that, in the following embodiments, the same reference numerals are given to the same constituent elements as those shown in FIG.

Embodiment 1 This embodiment is an example in which the planar shape of an on-chip microlens is made different in area corresponding to each color of an on-chip color filter layer, and this is shown in FIG. ) ~
This will be described with reference to FIG.

FIG. 1A is a schematic sectional view of the pixel portion of the solid-state image pickup device according to the present embodiment in the vertical register direction.
Then, a schematic plan view of the solid-state imaging device viewed from the subject side is shown in FIG. The AA cross section of FIG. 1B is shown in FIG.
Is equivalent to As can be seen in the figure, the planar shape of the on-chip microlens 9 is the largest corresponding to the G on-chip color filter layer 8 and is smaller in the order corresponding to the R and B on-chip color filter layers 8. . The shape of such an on-chip microlens 9 is
The resist pattern formed on the organic polymer material layer for forming the on-chip microlens described above can be easily formed by giving the resist pattern a large and small shape and reflowing it.

By adopting such a planar shape of the on-chip microlenses 9, it becomes possible to control the incident light quantity by making the transmitted light quantity of the on-chip microlenses 9 corresponding to the respective on-chip color filter layers 8 different, thereby achieving white balance. An excellent solid-state imaging device can be obtained.

Embodiment 2 This embodiment is an example in which the cross-sectional shape of the on-chip microlens is made different in height according to each color of the on-chip color filter layer, and this is shown in FIG. a) ~
This will be described with reference to FIG.

FIG. 2A shows a schematic cross-sectional view of the solid-state image pickup device according to the present embodiment in the vertical register direction, and FIG. 2B shows a schematic plan view of the solid-state image pickup device viewed from the subject side. The AA cross section of FIG. 2B corresponds to FIG. As shown in the figure, the height of the cross-sectional shape of the on-chip microlens 9 is, for example, largest corresponding to the G on-chip color filter layer 8 and corresponding to the R and B on-chip color filter layers 8. It becomes smaller in order of what you do. Such a shape of the on-chip microlens 9 can be easily formed by varying the thickness of the resist pattern formed on the organic polymer material layer for forming the on-chip microlens described above.

As one of the manufacturing methods thereof, an upper layer resist film is further applied after the resist pattern is formed, the upper layer resist pattern is left only on the resist pattern requiring a thickness, and these are reflowed together to form a reflow resist. A pattern may be formed, and this may be etched back and transferred to the organic polymer material layer. At this time, it is of course necessary to take care not to mix with the resist pattern of the lower layer when the resist film of the upper layer is applied, and the solvent of the coating solution for the upper resist film is selected and the prebaking conditions of the resist film of the lower layer are appropriately set. As another manufacturing method, after forming a reflow resist pattern having a uniform thickness, an upper layer resist film is further applied, and the upper layer resist pattern is left only on the reflow resist pattern requiring a thickness. A two-step reflow method of reflowing the pattern may be used. Then, the entire surface is etched back to transfer the reflow resist pattern shape to the organic polymer material layer which is the on-chip microlens material layer.

By adopting such a cross-sectional shape of the on-chip microlens 9, it becomes possible to easily control the incident light quantity by making the transmitted light quantity of the on-chip microlens 9 different for each on-chip color filter layer 8.
It is possible to obtain a solid-state imaging device having an excellent white balance.

Embodiment 3 This embodiment is an example in which the thickness of the protective layer on the photosensor is made different for each color, which will be described with reference to FIG.

FIG. 3 is a schematic sectional view of the pixel portion of the solid-state image pickup device according to this embodiment in the vertical register direction. As shown in the figure, the protective layer 6 on the optical sensor 2 has the thinnest thickness corresponding to the G on-chip color filter layer 8 and the thinnest corresponding to the R and B on-chip color filter layers. Get thicker. To control the thickness of the protective layer 6 as described above, the protective layer 6 made of Si ₃ N ₄ or the like is formed thick,
It can be easily formed by selectively etching the protective layer 6 on the upper portion of the optical sensor which is desired to be thin. Etching is
Either wet etching or plasma etching may be used.

By controlling the thickness of the protective layer 6 as described above, it becomes possible to control the amount of light incident on the optical sensor section by making the multiple interference modes of the transmitted light of each protective layer 6 different and to control the solid-state image pickup excellent in white balance. The device can be obtained.

Embodiment 4 This embodiment is an example in which the planar shape of the light shielding layer is made different in the opening area corresponding to each color of the on-chip color filter layer, and this is shown in FIG. Description will be made with reference to (d).

FIG. 4A is a schematic sectional view of the pixel portion of the solid-state image pickup device according to the present embodiment in the vertical register direction.
4B to 4D are schematic plan views of the solid-state imaging device viewed from the subject side. A BB cross section of FIG. 4B corresponds to FIG. As shown in the figure, the light shielding layer 5
The area corresponding to the G on-chip color filter layer is the largest and the area corresponding to the R and B on-chip color filter layers is smaller in that order. FIG.
FIG. 4B is an example in which the opening widths in the vertical direction are made different, and FIG.
FIG. 4C shows an example in which the opening widths in the horizontal direction are made different, and FIG.
(D) is an example in which the opening widths in both the vertical and horizontal directions are made different. The design of these opening shapes is appropriately selected according to the lower layer structure such as the photosensor portion and the polysilicon gate.

The plane shape of the light shielding layer can be easily realized by designing a resist pattern exposure mask for patterning the light shielding layer. Even by controlling the opening area of the light-shielding layer as described above, it becomes possible to control the amount of light incident on the optical sensor section by making the amount of light transmitted through each light-shielding layer different, and to obtain a solid-state imaging device with excellent white balance. it can.

Although the present invention has been described with reference to the four examples, the present invention is not limited to these examples. Although all of the above-described embodiments have been described using the example of the primary color on-chip color filter layer, the present invention can be similarly applied to the complementary color on-chip color filter layer.

Further, in addition to making the light transmission amount different for each of the light shielding layer, the protective layer and the on-chip microlens, a plurality of these are combined to make the light transmission amounts different,
The amount of light incident on the optical sensor unit may be controlled. By greatly expanding the degree of freedom in designing the solid-state imaging device in this manner, it is possible to obtain a solid-state imaging device structure having a better white balance.

[0037]

As is apparent from the above description, according to the solid-state image pickup device of the present invention, the balance of the amount of light incident on the photosensor portion of each color is surely kept within a desired fixed range, and the color reproducibility is improved. It is possible to provide an excellent solid-state imaging device.

[Brief description of the drawings]

1A and 1B show a solid-state imaging device according to a first embodiment to which the present invention is applied, FIG. 1A is a schematic cross-sectional view of a pixel portion in a vertical register direction, and FIG. 1B is a schematic plan view of the solid-state imaging device viewed from a subject side. FIG. 6 is a diagram showing a layout of an on-chip microlens group.

2A and 2B show a solid-state imaging device according to a second embodiment to which the present invention is applied, FIG. 2A is a schematic cross-sectional view of a pixel portion in a vertical register direction, and FIG. 2B is a schematic plane view of the solid-state imaging device viewed from a subject side. FIG. 6 is a diagram showing a layout of an on-chip microlens group.

FIG. 3 is a schematic sectional view of a pixel portion of a solid-state imaging device according to a third embodiment of the present invention in a vertical register direction.

4A and 4B show a solid-state imaging device according to a fourth embodiment of the present invention, in which FIG. 4A is a schematic cross-sectional view of a pixel portion in a vertical register direction, and FIGS. 4B to 4D are schematic plane views of a light shielding layer. It is a figure.

5A and 5B are graphs showing spectral characteristics, where FIG. 5A is a spectral characteristic of Si photosensor sensitivity, FIG. 5B is a light transmittance of an on-chip color filter layer of each color, and FIG. 5C is an on-chip color filter. The respective Si optical sensor sensitivities after the layers are mounted are shown.

6A and 6B show a conventional solid-state imaging device, FIG. 6A is a schematic cross-sectional view of a pixel portion in a vertical register direction, and FIG. 6B is a schematic plan view of the solid-state imaging device as viewed from the subject side. It is a figure which shows the layout of a lens group.

[Explanation of symbols]

 1 Semiconductor Substrate 2 Optical Sensor Section 3 First Layer Polysilicon Gate 4 Second Layer Polysilicon Gate 5 Light Shielding Layer 6 Protective Layer 7 Flattening Layer 8 On-Chip Color Filter Layer 9 On-Chip Microlens

Claims (5)

[Claims] 1. A light-shielding layer having openings selectively formed on a plurality of optical sensor portions, a protective layer formed on the entire surface of the plurality of optical sensor portions and the light-shielding layer, and the protection. On-chip color filter layers of a plurality of colors that are periodically formed facing the plurality of photosensor units on a flattening layer formed on the layer, and on-chip formed on the on-chip color filter layer. A solid-state imaging device comprising: a microlens, wherein at least one of the light-shielding layer, the protective layer, and the on-chip microlens corresponds to each color of the on-chip color filter layer, A solid-state imaging device having a structure in which the amount of light incident on the optical sensor unit is different. 2. The plane shape of the on-chip microlens is different in the area corresponding to each color of the on-chip color filter layer, so that the incident light amount is different. The solid-state imaging device described. 3. The cross-sectional shape of the on-chip microlens is different in height depending on each color of the on-chip color filter layer so that the incident light amount is different. 1. The solid-state imaging device according to 1. 4. The cross-sectional shape of the protective layer is characterized in that the incident light amount is made different by making the thickness different corresponding to each color of the on-chip color filter layer.
The solid-state imaging device according to claim 1. 5. The planar shape of the light-shielding layer is different in the incident light amount by making the opening area of the on-chip color filter layer different for each color. Solid-state imaging device.