JP2008034521A - Solid-state imaging apparatus, and manufacturing method thereof - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To solve the conventional problem that a step difference of the thickness of a color filter occurs between an effective pixel region having each color filter formed thereon and a neighboring region having no color filter, resulting in variation of coating when a resist is spin-coated in a subsequent step, because the color filters of a solid-state imaging apparatus are formed only on the effective pixel region. <P>SOLUTION: First, a green (G) color filter is formed on an effective pixel region. Then, simultaneously with forming a blue (B) color filter on the effective pixel region, a blue (B) color filter is formed also on a neighboring circuit as one part of a neighboring region. Further, simultaneously with forming a red (R) color filter on the effective pixel region, a red (R) color filter is formed on a bonding pad on the neighboring region. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a solid-state imaging device and a manufacturing method thereof, and more particularly to a solid-state imaging device in which a peripheral region located around an effective pixel region is flattened and a manufacturing method thereof.

  Solid-state imaging devices such as CCD solid-state imaging devices and MOS solid-state imaging devices are used in various image input devices such as video cameras, digital still cameras, and facsimiles.

  In order to obtain a color image by the solid-state imaging device, it is necessary to divide the light incident on the effective pixel region into color components, and then make the dispersed color components enter a light receiving unit that performs photoelectric conversion. In general, a color filter is used as a means for separating color components from incident light. It is also well known that a microlens is further provided on the upper layer of the color filter as a method for collecting light incident on the effective pixel region more efficiently.

  By the way, since the structures of the effective pixel region and the peripheral region of the solid-state imaging device are different, the surface of the solid-state imaging device before the color filter formation is not necessarily flat. Therefore, when manufacturing a solid-state imaging device having a color filter, prior to the color filter formation step, in order to avoid the occurrence of problems in the subsequent color filter formation step due to the step between the effective pixel region and its peripheral region. A technique for planarizing the surface of the peripheral region using a polymer material is known (hereinafter referred to as “first planarization technique”). According to the first planarization technique, the uneven step in the peripheral region is planarized in advance before the color filter is formed, so that uneven application of the color filter resist is suppressed, and a high-quality color solid-state imaging device without color unevenness Can be obtained (see, for example, Patent Document 1).

In addition, there is also known a technique for flattening the uneven step in the peripheral region by forming an antireflection film made of an organic compound dyed black (hereinafter referred to as “second flattening technique”). According to the second planarization technique, the antireflection and planarization can be realized by one antireflection film, and therefore, when other layers are formed in the subsequent process, uneven application of the layer forming material occurs. Therefore, it is possible to prevent a decrease in sensitivity and a yield due to the coating unevenness (see, for example, Patent Document 2).
Japanese Patent No. 2786647 JP-A-5-299625

  However, the conventional method for manufacturing a solid-state imaging device has the following problems.

  Usually, in a color solid-state imaging device, the color filter is formed only on the effective pixel region and not in the peripheral region. Therefore, even if the conventional first and second planarization techniques are applied and the surface is planarized before the color filter is formed, the effective pixel region and its peripheral region are not colored after the color filter is formed. A step of about 1 micron is generated due to the thickness of the filter. As a result, in the step of forming the microlens on the upper layer of the color filter, when the resist for microlens formation is spin-coated on the surface of the color filter, resist brushing (unevenness of coating) occurs due to the step of the color filter, resulting in a yield. Decrease in image quality and image quality.

  In order to eliminate the level difference of the color filter, it may be possible to form a black antireflection film as in the second planarization technique, but a process different from the formation of the color filter is provided. Since it is necessary, the cost increase accompanying the increase in the number of processes is inevitable.

  Therefore, the present invention has been made to solve the above-described problems, and an object of the present invention is to realize a color solid-state imaging device that has high image quality and is inexpensive.

  In order to achieve the above object, the method for manufacturing a solid-state imaging device according to the present invention is characterized in that color filters are formed using the same material in the pixel region and its peripheral region.

  That is, the present invention includes a pixel region having a plurality of light receiving portions, a peripheral region disposed around the pixel region and having bonding pads formed thereon, and at least two color filters arranged in a predetermined pattern. The present invention relates to a method for manufacturing a solid-state imaging device, and includes a step of forming a color filter that does not include at least a metal component in a peripheral region, and a color filter that does not include a metal component formed above a bonding pad in the peripheral region. Forming an opening by removing the portion by etching.

  In this case, the step of forming the color filter includes the step of forming the first color filter on the pixel region and the first region in the peripheral region, the first region in the peripheral region, and the first region in the peripheral region. Preferably, the method includes forming a second color filter having a color different from that of the first color filter on a different second region.

  Specifically, when the arrangement format of the color filters in the pixel area is a primary color Bayer arrangement of green, blue, and red, in the color filter forming process, a blue color filter is used as the first color filter in the pixel area. Simultaneously with the formation, the blue color filter is also formed in the first region of the peripheral region excluding the bonding pad and the alignment recognition portion. Subsequently, as the second color filter, a red color filter is formed in the pixel region, and at the same time, the red color filter is applied to the second region in the peripheral region where the blue color filter is not formed (that is, Bonding pad and alignment recognition part).

  After the color filter is formed in both the pixel area and the peripheral area, the surface of the substrate is almost flattened. Then, in a subsequent process, an on-chip microlens resist is applied by spin coating, and is subjected to exposure and development. A microlens is formed in the pixel region. Furthermore, an opening is provided on the bonding pad and the alignment recognition portion by partially removing the red color filter formed in the second region of the peripheral region by the etching process.

  In the method for manufacturing a solid-state imaging device according to the present invention, the same material as the color filter formed on the pixel region is used, and the color filter is formed on the peripheral region simultaneously with the formation of the color filter on the pixel region. Therefore, the surfaces of the pixel region and the peripheral region are planarized at the same time. Therefore, the uneven step between the pixel region and the peripheral region, which has been caused by providing the color filter only in the conventional pixel region, is not formed. Therefore, uneven coating (so-called scratch defect) in the subsequent spin coating process of the microlens resist. Can be fundamentally resolved. Therefore, according to the method for manufacturing a solid-state imaging device according to the present invention, a solid-state imaging device with high image quality and low cost can be realized.

  In addition, it is preferable that a material having at least one kind of metal atom is used for the green and blue color filters, and a material containing no metal atom is used for the red color filter. In this case, the red color filter is part of the etching process without causing defects (so-called metal contamination) that cause deterioration of the oxide film breakdown voltage due to crystal defects and an increase in leakage current, which adversely affects device characteristics and yield. Removed.

  In addition, when the color filter of the pixel area is a primary color Bayer array, a third color filter having a different color from the first and second color filters, that is, a green color filter is replaced with a first color filter of the first and second color filters. It is preferable to form it before.

  Further, in the method for manufacturing a solid-state imaging device according to the present invention, after the green color filter is formed in a checkered pattern in the pixel region, the bonding pad and the alignment recognition unit are excluded when forming the blue color filter in the pixel region. It is preferable to form a blue color filter simultaneously in most of the peripheral region. Finally, when the red color filter is formed in the pixel area, the red color filter is simultaneously formed in the peripheral area where the blue color filter is not formed (the area on the bonding pad and the alignment recognition portion). As a result, the peripheral region is flattened. After the formation of the microlens, the red color filter formed on the bonding pad and the alignment recognition part is partially removed by etching, so that most of the peripheral region can be formed with a blue color filter.

  With such a configuration, due to the spectral characteristics of the blue color filter, long wavelength light among the light incident on the peripheral region is absorbed. It is also possible to reduce flare.

  The bonding pads are preferably formed along the outer periphery of each of the solid-state imaging devices formed on the semiconductor substrate. In this case, it is more desirable to form a U-shaped opening in plan view on the bonding pad by partially removing the red color filter on the peripheral region in the etching process. Therefore, the part along the outer periphery of the solid-state imaging device in the upper part of the bonding pad is opened.

  According to such a configuration, by forming a blue color filter on the peripheral region, it is possible to obtain a flare reduction effect due to an increase in the area occupied by the blue color filter on the peripheral region. The color filter thus made does not cause a problem of poor wiring adhesion in the wire bonding process.

  According to the method for manufacturing a solid-state imaging device according to the present invention, a high-quality color solid-state imaging device can be realized at low cost.

  Hereinafter, a solid-state imaging device and a manufacturing method thereof according to an embodiment of the present invention will be described using a CCD solid-state imaging device as an example.

  FIG. 1 is a plan view showing a schematic configuration of a solid-state imaging device according to an embodiment of the present invention.

  The solid-state imaging device according to the present embodiment includes an effective pixel region having a plurality of light receiving portions and a peripheral region formed around the effective pixel region. In the peripheral area, peripheral circuits such as a horizontal transfer unit (for example, a horizontal CCD) and an amplifier unit (for example, a floating diffusion amplifier) schematically shown by broken lines, and a plurality of bonding pads to which signal lines are connected Is formed.

  As shown in FIG. 1, the solid-state imaging device according to the embodiment of the present invention is characterized in that the opening shape of the upper part of the bonding pad (the shape of the portion from which the color filter is removed) is a “U-shaped”. Have

  With such a structure, the solid-state imaging device according to the embodiment of the present invention has, for example, a square shape (rectangular shape) in which the opening shape of the upper part of the bonding pad (the shape of the portion from which the color filter is removed) is surrounded by the color filter. Compared with the case where it does, removal of the foreign material which entered the opening part at the time of dicing can be performed easily, and also adhesion of the foreign material in a wire bonding process can be prevented.

  2-17 is sectional drawing which shows the manufacturing process of the solid-state imaging device concerning this embodiment.

  2 to 17, (A) shows a Red pixel surrounded by Green pixels in the primary color Bayer array in the effective pixel area, and (B) shows the Green pixels in the primary color Bayer array in the effective pixel area. (C) shows a peripheral circuit such as a horizontal CCD and FDA formed in the peripheral region, and (D) shows a bonding pad formed in the peripheral region. For convenience of explanation, FIGS. 2 to 17 (A), (B), and (D) show the vertical cross-sectional structure shown in FIG. 1, and FIGS. 1 shows a horizontal sectional structure shown in FIG. Further, in FIG. 3 to FIG. 8, for convenience of explanation, three colors of the color filter resist and the formed color filter are indicated by R (red), G (green), and B (blue).

  First, as shown in FIG. 2, an effective pixel region and a peripheral region are formed on a semiconductor substrate, and the surfaces of the effective pixel region and the peripheral region are planarized by a planarizing film.

  Specifically, the effective pixel region is made of, for example, polysilicon and a plurality of light receiving units 25 arranged in a matrix on a semiconductor substrate, and transfers charges generated by photoelectric conversion by the light receiving unit 25 in the vertical direction. A vertical transfer electrode (transfer electrodes 10 and 11), a light-shielding film 17 made of, for example, tungsten, and shielding the vertical transfer electrode, and a first transparent flat surface for flattening irregularities on the vertical transfer electrode and the light-shielding film 17 The inner layer lens 18 is formed around the chemical film 13.

  In the peripheral region, peripheral circuits and bonding pads are formed. The peripheral circuit is made of, for example, polysilicon, and is formed of a horizontal transfer electrode (transfer electrodes 26 and 27) that transfers charges output from the vertical transfer electrode in the horizontal direction, and a metal such as aluminum or copper. A light-shielding film 14 that shields light and an amplifier unit that converts the charges transferred in the horizontal direction by the horizontal transfer electrode into a voltage. The bonding pad is a terminal used to input a power source and a control signal for driving the solid-state imaging device and to output the solid-state imaging device to the outside.

  In FIG. 2, the insulating films 12, 15 and 16 are shown together, but the structure and manufacturing method of the effective pixel region and the peripheral region are not particularly limited, and any structure and manufacturing method can be used. Applicable.

  Next, as shown in FIG. 3, a green color filter resist is applied by spin coating on the effective pixel region and the peripheral region whose surfaces are flattened.

  Next, as shown in FIG. 4, a part of the applied green color filter resist is exposed to ultraviolet rays using a mask having a checkered pattern in the effective pixel region. After the exposure, a green color filter is formed in the effective pixel region through a development process.

  Next, as shown in FIG. 5, a blue color filter resist is applied to the effective pixel region patterned with the green color filter and the peripheral region by a spin coating method.

  Next, as shown in FIG. 6, a part of the applied blue color filter resist is exposed using a mask having a predetermined pattern. After the exposure, a blue color filter is formed above a part of the effective pixel region and the peripheral circuit through a development process.

  Next, as shown in FIG. 7, a red color filter resist is applied to the effective pixel region patterned with the green and blue color filters, the peripheral circuit on which the blue color filter is formed, and the bonding pad. Apply by spin coating.

  Next, as shown in FIG. 8, a part of the red color filter resist applied by ultraviolet irradiation is exposed using a predetermined mask pattern. After the exposure, a red color filter is formed above a part of the effective pixel region and the bonding pad in the peripheral region through a development process.

  Next, as shown in FIG. 9, a second transparent planarizing film 19 is formed on the surfaces of the effective pixel region and the peripheral region. Although the material of the 2nd transparent planarization film | membrane 19 is not specifically limited, For example, acrylic resin can be utilized. As a result, fine irregularities on the color filter surface of each color are further flattened.

  Next, as shown in FIG. 10, a microlens forming material 20 is applied on the second transparent planarizing film 19 in order to form a microlens for improving the light collection efficiency. As a specific example of the microlens forming material 20, a photosensitive resist made of an acrylic resin using melamine as a binder is applied on the second transparent planarizing film 19 by a spin coating method.

  Next, as shown in FIG. 11, a part of the applied microlens forming material 20 is exposed by ultraviolet irradiation using a mask having a predetermined pattern. After the exposure, a microlens forming resist pattern 21 corresponding to each light receiving portion in the effective pixel region is formed through a development process.

  Next, as shown in FIG. 12, the microlens forming resist patterned in the effective pixel region is processed into a lens shape by a heating flow to form a plurality of microlenses 22.

  Next, as shown in FIG. 13, a low refractive index transparent film 23 is applied to the peripheral region and the effective pixel region where the microlenses 22 are formed by a spin coating method. As a specific example, the low-refractive-index transparent film 23 is a fluorine-containing resin film, which can suppress the reflection of light on the surface of the microlens 22 and increase the amount of light incident on the light receiving unit 25.

  Next, as shown in FIG. 14, a photosensitive resist 24 is applied on the low refractive index transparent film 23 by a spin coating method.

  Next, as shown in FIG. 15, a part of the applied photosensitive resist 24 is exposed by ultraviolet irradiation using a mask having a predetermined pattern. After the exposure, a photosensitive resist is formed in the effective pixel region and the portion other than the upper portion of the bonding pad in the peripheral region through a development process.

  Next, as shown in FIG. 16, dry etching using a CF-based gas is performed using the patterned photosensitive resist as a mask. As a result of the dry etching, an opening is formed in a part not covered with the resist film, that is, a part above the bonding pad.

  Then, as shown in FIG. 17, the solid-state imaging device according to the present embodiment is obtained by removing the photosensitive resist.

  As described above, the method of manufacturing the solid-state imaging device according to the present embodiment is characterized in that the color filter is formed on the peripheral region in the same process as that for forming the color filter on the effective pixel region. Have.

  More specifically, a blue color filter is formed on a peripheral circuit which is a part of the peripheral region at the same time as the blue color filter is formed on the effective pixel region (FIGS. 5 and 6). At the same time as the red color filter is formed on the effective pixel region, the red color filter is formed on a bonding pad different from the peripheral circuit in the peripheral region (FIGS. 7 and 8).

  When the color filter is formed only on the effective pixel region and not on the peripheral region as in the conventional case, the unevenness caused by the thickness of the color filter is generated between the effective pixel region and the peripheral region. This leads to uneven application of resist in the lens forming process.

  On the other hand, according to the manufacturing method according to the present embodiment, since the color filter is formed in the effective pixel region and the peripheral region at the same time, the surfaces of the effective pixel region and the peripheral region after the color filter formation are substantially flat. It becomes. Therefore, in the subsequent process (FIG. 10), it is possible to prevent uneven application when spin-coating the microlens forming resist, and to improve yield and image quality. Further, since a separate process for forming the color filter on the peripheral region is not necessary, an economical manufacturing method can be realized in terms of manufacturing cost.

  Further, in the present embodiment, as shown in FIG. 1, a blue color filter is formed in most of the peripheral region except for the bonding pads. The blue color filter can absorb light having a long wavelength due to its spectral characteristics. Of the incident light to the peripheral region, the long wavelength light is absorbed by the blue color filter. As a result, flare caused by reflection of the long wavelength light (particularly, red light) in the peripheral region can be reduced.

  Further, in the method for manufacturing a solid-state imaging device according to the present invention, the red color filter formed in the peripheral region is partially removed by etching using a mask in which the opening of the bonding pad is open at the side in the chip outer peripheral direction. Thus, a step of forming a U-shaped opening is included. As a result of such a process, as shown in FIG. 1, a part of the outer periphery of the color filter above the bonding pad is formed in a U-shape in plan view. That is, a part including the outer periphery of the chip is opened above the bonding pad. Therefore, even if the color filter is formed on the peripheral region where the conventional color filter has not been formed, problems such as poor wiring adhesion do not occur in the wire bonding process.

  In the present embodiment, the peripheral area is flattened by blue and red color filters, but the peripheral circuit may be flattened by green and red color filters.

  In this embodiment, the color filters are formed in the order of green, blue, and red. However, the order of forming the color filters for each color is not necessarily limited to this.

  Furthermore, in the present embodiment, an example in which the color filter formed in the effective pixel region has a primary color Bayer array composed of three colors of green, blue, and red has been described. The present invention can also be applied in the same manner even when an array pattern other than the primary color Bayer array is provided, and the same operational effects as in the present embodiment can be achieved.

  Furthermore, although the case where the color filter is a primary color filter of three colors is described in the present embodiment, the number of colors of the color filter is not particularly limited. Further, the manufacturing method according to the present invention can be similarly applied to a complementary color filter other than the primary color filter.

  Further, in this embodiment, two color filters are formed on the peripheral region in order to eliminate the step between the effective pixel region and the peripheral region, but one color is formed above both the peripheral circuit and the bonding pad. Only the color filter may be formed.

  Furthermore, in the present embodiment, an example of a method for manufacturing a CCD solid-state imaging device has been described, but it goes without saying that the manufacturing method according to the present invention can be similarly applied to a MOS-type solid-state imaging device.

  According to the method for manufacturing a solid-state imaging device according to the present invention, a solid-state imaging device with high image quality and low cost can be realized.

1 is a plan view schematically showing a solid-state imaging device according to an embodiment of the present invention. Sectional drawing which shows the manufacturing process of the solid-state imaging device which concerns on one Embodiment of this invention. Sectional drawing which shows the process following FIG. Sectional drawing which shows the process following FIG. Sectional drawing which shows the process following FIG. Sectional drawing which shows the process following FIG. Sectional drawing which shows the process following FIG. Sectional drawing which shows the process following FIG. Sectional drawing which shows the process following FIG. Sectional drawing which shows the process following FIG. Sectional drawing which shows the process following FIG. Sectional drawing which shows the process following FIG. Sectional drawing which shows the process of following FIG. Sectional drawing which shows the process of following FIG. Sectional drawing which shows the process of following FIG. Sectional drawing which shows the process following FIG. Sectional drawing which shows the process of following FIG.

DESCRIPTION OF SYMBOLS 10 Transfer electrode 11 Transfer electrode 12 Insulating film 13 1st transparent planarization film 14 Light-shielding film 15 Insulating film 16 Insulating film 17 Light-shielding film 18 Inner lens 19 Second transparent planarizing film 20 Microlens formation material 21 Microlens formation resist Pattern 22 Micro lens 23 Low refractive index transparent film 24 Photosensitive resist 25 Light receiving part 26 Transfer electrode 27 Transfer electrode

Claims (11)

Manufacture of a solid-state imaging device including a pixel region having a plurality of light receiving portions, a peripheral region disposed around the pixel region and formed with a bonding pad, and at least two color filters arranged in a predetermined pattern A method,
Forming a color filter not containing at least a metal component in the peripheral region;
And a step of forming an opening by removing a part of the color filter not including the metal component formed above the bonding pad in the peripheral region by etching. The step of forming the color filter includes:
Forming a first color filter on the pixel region and on the first region in the peripheral region;
Forming a second color filter having a color different from that of the first color filter on the pixel region and on a second region different from the first region in the peripheral region. A manufacturing method of a solid-state imaging device according to Item 1. The first and second regions are disposed adjacent to each other;
A peripheral circuit is formed in the first region;
3. The method of manufacturing a solid-state imaging device according to claim 2, wherein the bonding pad is formed in the second region.   4. The method of manufacturing a solid-state imaging device according to claim 3, wherein in the step of forming the opening, a part of the second color filter formed above the bonding pad is removed by etching. A plurality of the solid-state imaging devices are formed on a semiconductor substrate,
The method of manufacturing a solid-state imaging device according to claim 4, wherein the bonding pad is disposed along an outer periphery of the solid-state imaging device.   4. The method for manufacturing a solid-state imaging device according to claim 3, wherein at least one of the first and second color filters is formed of a material that does not include a metal component.   4. The method for manufacturing a solid-state imaging device according to claim 3, wherein at least one of the first and second color filters is formed of a material that absorbs light having a wavelength in the near infrared region.   4. The method for manufacturing a solid-state imaging device according to claim 3, wherein at least one of the first and second color filters is formed of a material containing a pigment.   4. The method of manufacturing a solid-state imaging device according to claim 3, wherein the array of color filters formed in the effective pixel region is a primary color Bayer array composed of three colors of green, blue, and red. Before the step of forming the first and second color filters, further comprising the step of forming a third filter having a color different from that of the first and second filters in the pixel region;
The first color filter is blue;
The second color filter is red;
The method of manufacturing a solid-state imaging device according to claim 9, wherein the third color filter is green. A solid-state imaging device,
A pixel region disposed on a semiconductor substrate and having a plurality of light receiving portions;
On the semiconductor substrate, a peripheral region disposed around the pixel region;
A first color filter formed on the pixel region and on a first region in the peripheral region;
A solid-state imaging device comprising: a second color filter formed on the pixel region and a second region different from the first region in the peripheral region, and having a color different from the first color filter .

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