JP5773582B2 - Pattern forming method and method for manufacturing solid-state imaging device - Google Patents

Description

  The present invention relates to a pattern forming method using a photolithography technique, and more particularly to alignment during pattern formation.

  Conventionally, in a method for manufacturing a solid-state imaging device or a liquid crystal display device which is an optical functional device, there is a step of forming a pattern such as a blue filter or a black filter using a photolithography technique. A blue filter, a black filter, and the like are made of a material having low transmittance at many wavelengths of light. At the time of alignment (positioning) for forming a pattern such as a blue filter or a black filter, the following problem may occur. The alignment light for detecting the alignment mark must pass through the material of the blue filter or the black filter, and the light reflected from the alignment mark becomes weak. As a result, it becomes difficult to detect the alignment mark.

  In order to solve such a problem, in Patent Document 1, an alignment mark is newly formed using a material having a high alignment light transmittance. There has been proposed a method of performing alignment for pattern formation of a material having a low light transmittance by using this new alignment mark.

  Japanese Patent Application Laid-Open No. 2004-228620 proposes a method of detecting an alignment mark after selectively removing a material having low light transmittance existing on the alignment mark.

JP-A-11-2111908 JP 2007-004082 A

  When the technique described in Patent Document 1 is used, since a new alignment mark is recreated, the new alignment mark includes a deviation component from the original alignment mark. Furthermore, since the pattern is formed based on the new alignment mark, the alignment accuracy is deteriorated.

  Further, when the technique described in Patent Document 2 is used, a material with low light transmittance existing on the alignment mark is removed by a photolithography technique. For example, a photoresist mask pattern for removal is formed. A process is required. In other words, the technique described in Patent Document 2 increases the number of processes.

  Therefore, an object of the present invention is to provide a pattern forming method for a material having a high alignment accuracy and a low number of steps and a low light transmittance for alignment. It is another object of the present invention to provide an alignment mark structure capable of forming a pattern of a material having low alignment light transmittance with high alignment accuracy and a small number of steps.

The pattern forming method of the present invention includes a step of forming a first pattern including an alignment mark having a concave portion or a convex portion on a substrate, a step of forming a planarizing layer on the first pattern, A step of removing a part of the planarization layer formed on the alignment mark; a step of forming a layer to be processed on the planarization layer from which the part has been removed; A step of optically detecting the position from above the layer to be processed using light, and a step of aligning; and a step of patterning the layer to be processed based on the position of alignment to form a second pattern. And in the step of forming the processed layer, the processed layer is a material having an average spectral transmittance in the wavelength region of the light in the alignment step of 5% or less, and the processed layer The upper surface is the above It is formed to have a step which follows the shape of the line placement marks. Furthermore, in the pattern forming method of the present invention, in the step of forming the second pattern, a portion formed on the alignment mark of the processed layer is removed, or the first pattern is formed. And a step of forming a passivation film between the step of forming and the step of forming the planarizing layer.

  According to the present invention, it is possible to form a pattern of a material with low alignment light transmittance with high alignment accuracy and a small number of steps.

6 is a schematic cross-sectional view illustrating a pattern forming method of Example 1. FIG. 3 is a schematic cross-sectional view of a pattern in Example 1. FIG. 6 is a schematic cross-sectional view illustrating a pattern forming method of Example 2. FIG. It is a plane schematic diagram of a solid-state imaging device.

  Hereinafter, it will be described in detail with reference to the drawings.

Example 1
In this embodiment, a CMOS type solid-state imaging device applied to a three-plate camcorder will be described as an example with reference to FIG. 1, FIG. 2, and FIG.

  First, FIG. 4 is a schematic plan view illustrating the solid-state imaging device of the present embodiment. In FIG. 4, 100 is a three-plate solid-state imaging device, 101 is an effective pixel area, 102 is outside the effective pixel area, 103 is a light shielding pattern, and 104 is a pad. In the effective pixel region, a plurality of pixels including a photoelectric conversion unit (for example, a photodiode) are arranged. The effective pixel area outside 102 is an area other than the effective pixel area 101. Outside the effective pixel region 102, an optical black portion (OB portion) where pixels are shielded from light, a peripheral circuit portion that performs driving for reading out signals from the solid-state imaging device, signal processing, and the like are arranged. The light shielding pattern 103 is disposed outside the effective pixel region 102 and shields the OB portion and the peripheral circuit portion disposed outside the effective pixel region 102. Further, the light shielding pattern 103 is not disposed on the pad 104 because the pad 104 is connected. The light shielding pattern 103 may be disposed in the effective pixel region 101 so that light does not enter other than the photoelectric conversion unit. Here, the pattern made of a material having low light transmittance in this embodiment is the light shielding pattern 103. Next, a method for forming the light shielding pattern 103 will be described with reference to FIG.

  FIG. 1 is a schematic cross-sectional view for explaining the pattern forming method of this embodiment. Each cross-sectional schematic diagram of FIG. 1 corresponds to the AA ′ line of FIG. 4 and only a part of the main part of the solid-state imaging device is extracted.

  In FIG. 1A, reference numeral 105 denotes an insulating layer, 106 denotes a passivation layer, 107 denotes an alignment mark, and 108 denotes a metal pattern existing outside the effective pixel region 102. A semiconductor substrate (substrate) on which a plurality of wiring layers, insulating layers, and elements are formed is disposed below the insulating layer 105 (not shown). The insulating layer 105 is, for example, a silicon oxide film, and the passivation layer 106 is, for example, a silicon nitride film. The metal pattern 108 is, for example, a pattern mainly composed of aluminum. The passivation layer 106 has an inner lens in the effective pixel region 101. Here, the alignment mark 107 is the same layer as the wiring layer (metal pattern) used in the effective pixel region 101 and the effective pixel outside region 102 on the insulating layer 105. Therefore, the alignment mark 107 can be formed simultaneously with the formation of the wiring layer (metal pattern) or the like (formation of the first pattern).

  In the configuration of FIG. 1A, the upper surface of the insulating layer 105 may be uneven due to a wiring layer (not shown). Further, on the upper surface of the passivation layer 106, there may be irregularities at the boundary between the effective pixel region 101 and the outside of the effective pixel region 102 depending on the presence or absence of the metal pattern 108 between the effective pixel region 101 and the outside of the effective pixel region 102. Further, when the passivation layer 106 has an inner lens, the upper surface of the passivation layer 106 has irregularities. In order to stably form various patterns after the next step, it is necessary to fill the unevenness and make it flat (flattening).

  In FIG. 1B, a planarization layer 109 is formed in order to planarize the above-described uneven upper surface. The planarizing layer 109 is a photosensitive material. As long as it is a photosensitive material, it may be a positive type or a negative type, and the photosensitive wavelength of the photosensitive material is not limited.

  In FIG. 1C, the planarization layer 109, which is a photosensitive material, is patterned using a photolithography technique, and the planarization layer 109 formed over the alignment mark 107 is selectively removed. For example, when a positive resist is used for the planarizing layer 109, exposure is performed using a photomask having a mask pattern in which exposure light is irradiated on the alignment mark 107, and development is performed. By such treatment, the planarization layer 109 on the alignment mark 107 can be selectively removed.

  Next, a material (layer to be processed) having a low light transmittance for alignment is formed. The material having a low alignment light transmittance is, for example, a material with T ≦ 5%, where T is the average spectral transmittance in the wavelength region of the alignment light. This is the case where a He—Ne laser is used as the alignment light (wavelength around 633 nm). The material having an average transmittance T of 5% or less when this He—Ne laser is used is, for example, a blue resist or a black resist. In this embodiment, a blue resist is used, and a blue resist layer 110 is formed in the effective pixel region 101 and outside the effective pixel region 102 as shown in FIG.

  Then, the alignment mark 107 is detected by alignment light from the upper part of the blue resist layer 110 in FIG. Since the planarization layer 109 has been removed around the alignment mark 107, a step following the shape of the alignment mark 107 exists on the upper surface (front surface) of the blue resist layer 110. When alignment light is incident on the surface step (surface step) of the blue resist layer 110, the incident light is scattered and the alignment mark 107 can be detected. After that, alignment is performed based on the detection result of the alignment mark 107, and the blue resist layer 110 is exposed and developed using a photolithography technique and patterned. Then, a blue light shielding pattern 103 (second pattern) is formed outside the effective pixel region 102 (FIG. 1E).

Here, the detection method of the alignment mark 107 will be described in detail with reference to FIG. FIG. 2 is an enlarged cross-sectional view of the periphery of the alignment mark 107 in FIG. As shown in FIG. 2, since the flattening layer 109 on and around the alignment mark 107 is removed, a step (t1> 0) is formed on the surface of the blue resist layer 110. Then, as shown in FIG. 2, the light is optically detected from above the blue resist layer 110. That is, when alignment light is incident on a portion of the blue resist layer 110 where the surface step is generated, the alignment light is scattered by the surface step. This scattering can improve the contrast of the contour of the alignment mark 107 in the alignment mark detection optical system of the exposure apparatus. Therefore. The alignment mark 107 can be detected.

  This alignment mark detection method is not a method using reflected light of alignment light transmitted through the material deposited on the alignment mark 107, but a surface shape (surface) of the material deposited on the alignment mark 107. This is a method using scattered light due to a step. Therefore, the alignment mark 107 can be correctly detected regardless of the transmittance of the material deposited on the alignment mark 107. Therefore, even when the blue resist layer 110 having a low alignment light transmittance is formed on the alignment mark 107, the alignment mark 107 can be detected correctly.

  As described above, according to the present embodiment, it is possible to easily perform alignment (positioning) of a material having low light transmittance for alignment in the three-plate solid-state imaging device. In addition, since the process is simple, high throughput can be secured at low cost. Furthermore, when patterning a material having low light transmittance for alignment, it is possible to use the original alignment mark 107 instead of the newly provided alignment mark, thereby suppressing a decrease in alignment accuracy. It becomes possible.

  In addition, the alignment mark structure of this embodiment, that is, the structure in which the planarizing layer 109 is removed around the alignment mark 107 can be formed with a high number of alignment accuracy and a small number of steps, and a high alignment accuracy can be obtained. .

  Further, although the alignment mark 107 of this embodiment is disposed on the insulating layer 105, the arrangement location is not limited to this. Further, the alignment mark 107 may be disposed on the outer periphery of the solid-state imaging device 100 with respect to the pad 104 in FIG. 4, for example, may be disposed in a scribe region. When the alignment mark 107 is arranged in the scribe region, it can be removed when the solid-state imaging device 100 is completed.

(Example 2)
In this embodiment, a single-plate CMOS solid-state imaging device will be described as an example. The present embodiment is different from the first embodiment in having a plurality of color filter layers. The pattern made of a material having low light transmittance in this embodiment is a blue resist pattern included in a plurality of color filter layers. Hereinafter, the description of the same configuration as that of the first embodiment is omitted.

  The solid-state imaging device of the present embodiment has a schematic plan view of FIG. 4 similar to that of the first embodiment. A pattern forming method in such a solid-state imaging device will be described with reference to FIG. 3 and a part of FIG. FIG. 3 is a schematic cross-sectional view for explaining the pattern forming method of the present embodiment. Similar to the first embodiment, only a part of the main part of the solid-state imaging device is extracted corresponding to the line AA ′ of FIG. It is.

  The pattern forming method of this example is the same as that of Example 1 up to the step of removing the planarizing layer 109 on the insulating layer 105 and then removing it (FIG. 1C).

  Next to FIG. 1C, as shown in FIG. 3A, a material having a high alignment light transmittance is formed. Examples of the material having high light transmittance for alignment include a green resist and a red resist. In this embodiment, a green resist is used, and a green resist layer 111 is formed in the effective pixel region 101 and outside the effective pixel region 102 as shown in FIG.

  Then, the green resist layer 111 is exposed and developed using photolithography technology and patterned to form a green resist pattern 112 in the effective pixel region 101 (FIG. 3B). In the case of the green resist layer 111, since the transmittance of alignment light is high, there is no problem even if the alignment mark 107 is detected by a general method.

  Next, a film having a low light transmittance for alignment is formed. A material having low light transmittance for alignment is a blue resist as in the first embodiment. As shown in FIG. 3C, a blue resist layer 110 is formed on the effective pixel region 101 and outside the effective pixel region 102 so as to cover the green resist pattern 112.

  Then, the blue resist layer 110 is exposed and developed using photolithography technology and patterned to form a blue light-shielding pattern 103 outside the effective pixel region, and at the same time, a blue resist pattern 113 is formed in the effective pixel region (FIG. 3). (D)). Here, when detecting the alignment mark, it is possible to form the blue resist pattern 113 with high accuracy by using the surface level difference of the blue resist layer 110 as in the first embodiment.

  As described above, even in a single-plate solid-state imaging device, the pattern forming method of the present invention can perform alignment with high accuracy without increasing the number of steps. In addition, the structure of the alignment mark of the present invention can be formed with a small number of steps with high alignment accuracy even in a single-plate solid-state imaging device, and high alignment accuracy can be obtained.

  In this embodiment, the blue resist layer is patterned after the patterning of the green resist layer. However, the order of this step may be changed. In addition, although a green resist is taken as an example of a material having high light transmittance for alignment, other colors (red, complementary color) may be used as a matter of course. Similarly, a blue resist is taken as an example of a material with low light transmittance for alignment. However, if the average spectral transmittance in the wavelength region of exposure alignment light is T, the material is T ≦ 5%. Other color materials may be used. Further, the color filter layer has not only two colors of green and blue, but may be two or more colors.

  In Examples 1 and 2, a photosensitive material is used as an example of a material having a low alignment light transmittance. However, the present invention can also be applied to a light-shielding metal such as aluminum. For example, when aluminum is used, a surface step formed after the aluminum layer is formed may be used as in the first and second embodiments. The alignment mark is not limited to a convex shape (convex portion) such as a metal pattern, but may be a concave portion formed by etching the insulating layer. In the first and second embodiments, the material having low light transmittance for alignment disposed on the alignment mark is removed, but it may be left as it is.

  Further, the present invention is not limited to a solid-state imaging device such as a CCD or CMOS type, but can be applied to other optical function devices having a color filter layer and a light shielding layer, for example, a display device such as a liquid crystal display device. Can be applied.

101 Effective pixel region 102 Outside effective pixel region 103 Light shielding pattern 105 Insulating layer 106 Passivation layer 107 Alignment mark 108 Metal pattern 109 Flattening layer 110 Blue resist layer

Claims (9)

Forming a first pattern including an alignment mark having a concave portion or a convex portion on a substrate;
Forming a planarization layer on the first pattern;
Removing a part of the planarization layer formed on the alignment mark;
Forming a layer to be processed on the planarized layer from which the part has been removed;
A step of optically detecting the position of the alignment mark from above the layer to be processed using light, and performing alignment;
Patterning the work layer based on the alignment to form a second pattern,
In the step of forming the processing layer, the processing layer is a material having an average spectral transmittance in the wavelength region of the light in the alignment step of 5% or less, and the upper surface of the processing layer Is formed to have a step following the shape of the alignment mark ,
In the step of forming the second pattern, a part of the layer to be processed formed on the alignment mark is removed . The planarization layer is a photosensitive material;
The pattern forming method according to claim 1, wherein the step of removing the part includes a step of exposing the planarizing layer and a step of developing the planarized layer after the exposure.   The pattern forming method according to claim 1, wherein the processing layer is a blue resist layer.   The pattern forming method according to claim 1, wherein the processing layer is a light-shielding metal layer.   The pattern forming method according to claim 1, wherein the first pattern is a wiring layer. A pattern different from the first pattern is flattened based on the alignment using the alignment mark between the step of removing the part of the flattening layer and the step of forming the layer to be processed. Forming on the oxidization layer,
The pattern forming method according to claim 1 , wherein in the step of forming the processing layer, the processing layer is formed as a sex film so as to cover the another pattern . Forming a first pattern including an alignment mark having a concave portion or a convex portion on a substrate;
Forming a planarization layer on the first pattern;
Removing a part of the planarization layer formed on the alignment mark;
Forming a layer to be processed on the planarized layer from which the part has been removed;
A step of optically detecting the position of the alignment mark from above the layer to be processed using light, and performing alignment;
Patterning the work layer based on the alignment to form a second pattern,
In the step of forming the processed layer, the processed layer is a material having an average spectral transmittance in the wavelength region of the light in the aligning step of 5% or less, and the upper surface of the processed layer Is formed to have a step following the shape of the alignment mark,
A pattern forming method comprising a step of forming a passivation film between the step of forming the first pattern and the step of forming the planarizing layer. A method for manufacturing a solid-state imaging device using the pattern forming method according to claim 7,
In the step of forming the first pattern, the substrate has a photoelectric conversion unit,
8. The manufacturing of the solid-state imaging device according to claim 7, wherein in the step of forming the passivation film, the passivation film is formed including an inner lens provided corresponding to the photoelectric conversion unit. Way . Forming a first pattern including an alignment mark having a concave portion or a convex portion on a substrate having an effective pixel region in which a plurality of photoelectric conversion portions are arranged and an outside of the effective pixel region other than the effective pixel region ; When,
Forming a planarization layer on the first pattern;
Removing a part of the planarization layer formed on the alignment mark;
After the step of removing the part, forming a blue resist layer on the planarization layer;
Optically detecting the position of the alignment mark from above the blue resist layer using light, and performing alignment;
Patterning the blue resist layer based on the alignment to form a second pattern including a blue light-shielding pattern, and
In the step of forming the blue resist layer, the blue resist layer is formed so that the upper surface of the blue resist layer has a step following the shape of the alignment mark ,
In the step of forming the second pattern, the light shielding pattern is formed outside the effective pixel region, and a blue resist pattern is formed in the effective pixel region simultaneously with the light shielding pattern . Production method.

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