JPH07122720A - Image sensor and manufacturing method thereof - Google Patents

Abstract

(57) [Summary] [Purpose] Prevents film cracking and peeling of filters. [Structure] A filter 3 formed of a multilayer film on a flattening processing plane on a photoelectric conversion unit for converting an optical signal into an electric signal.
And an image sensor in which the adhesive layer 4 is interposed between the image sensor and the image sensor.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an image sensor and a method for manufacturing the same, and more particularly to an image sensor for converting an optical signal not only in visible light but also in a non-visible light region into an electric signal and a method for manufacturing the same. The present invention is a facsimile machine,
It is preferably used for an image sensor used in an image information processing apparatus such as an image scanner or a copying machine.

[0002]

2. Description of the Related Art In recent years, the applications of solid-state imaging devices have been diversified, and new functions are required. For example, in addition to high image quality of a copying machine, it has been required to recognize an invisible image, reproduce it, and record it. As such an image, that is, an invisible light image, there is, for example, an image formed of ink having a property of absorbing infrared rays. As a sensor technology for recognizing such an image, in order to use both a sensor for detecting visible light and a sensor for detecting invisible light, a technology of putting both sensors in one semiconductor chip has been found. . Generally, such a sensor is provided with an organic flattening film for flattening irregularities such as wiring and a selective transmission color filter on a pixel. Then, a dielectric multilayer film is provided on a necessary portion of the upper layer of the flattening film for the purpose of removing invisible light.
As a method of manufacturing such a sensor, a photoelectric conversion element is formed on a silicon substrate, a filter for realizing a function is formed, and then a flattening film treatment is performed. Then, a dielectric multilayer film is provided thereon, and unnecessary portions are removed by the RIE method (reactive ion etching method), leaving the dielectric multilayer film on the visible region sensor section. After that, A1
After patterning and etching the electrode pad portion and the scribing portion, wire bonding is further performed after dicing, and a sensor chip can be obtained by glass sealing. At this time, heating at ˜220 ° C. is required mainly in the heating process for patterning, bonding, and glass sealing.

The structure of the image sensor and the manufacturing method thereof will be described in more detail with reference to the drawings.

FIG. 5 is a schematic plan view showing an example of the image sensor. The image sensor 8 includes a photoelectric conversion element (R, G, B) for converting an optical signal in the visible light region into an electric signal and a photoelectric conversion element (iR) for converting an optical signal in the invisible light region into an electric signal. They are arranged side by side in a 4-line configuration. Here, as the photoelectric conversion element, a photovoltaic element such as a photodiode or a phototransistor or a photoconductive element is used. The photoelectric conversion element used for the visible light region has a laminated filter (iR cut filter) made of a dielectric multilayer film that transmits the visible light region and blocks light in the invisible light region. Further, in order to obtain a signal in a specific region of the visible light region, a filter that selectively transmits only the specific region is also included. That is,
Each of the R (red), G (green), and B (blue) photoelectric conversion elements has a unique filter that transmits only a specific wavelength region of visible light and a common filter that blocks an invisible light region. .

On the other hand, as a photoelectric conversion element (iR) for converting an optical signal in the invisible light region into an electric signal, a material having sensitivity in a wide wavelength region including the invisible light region is used for light in the invisible light region. On the other hand, it is configured by combining filters having selective transmittance.

As described above, by combining with each filter, it is possible to obtain a specific optical signal in each visible light region and invisible light region. FIG. 6 shows a schematic sectional view of an example of the image sensor. A filter for realizing a function is formed on the photodiodes 13a to 13d formed on one Si substrate 9. CCDs 14a to 14d for transferring optical signals are arranged adjacent to the photodiodes 13a to 13d.
Filters 12e, 12d, 12c for selectively transmitting only specific wavelength regions on the photodiodes 13a to 13c.
And a filter 11 for blocking the invisible light region are provided, and an optical signal in the visible light region is obtained by a combination of the filters 12e, 12d, 12c and the filter 11. Also, on the photodiode 13d, R,
Filters 12a and 1 for selectively transmitting only the wavelength region of B
2b is provided to obtain an optical signal in the invisible light region. Reference numerals 10a and 10b are flattening films.

The filter 11 is formed of a dielectric multi-layer film and is usually composed of alternating layers of a high refractive index film and a low refractive index film. TiO ₂ , ZnS, Ta ₂ O for the high refractive index film
₅ , Nb ₂ O ₃ , ZrO ₂ , HfO ₂ , Y ₂ O ₃ , Ce
O _{2 and the} like and mixtures thereof are used. Further, as the low refractive index film, Al ₂ O ₃ , SiO ₂ , MgF ₂ , Na _{2 is used.}
AlF _6, etc. and mixtures thereof are used. The substrate heating temperature during film formation is poor in heat resistance because the planarization films 10a and 10b are usually formed of an organic resin such as an acrylic polymer, and is preferably in the temperature range of room temperature to 220 ° C.

FIG. 7 shows a schematic diagram of a post-process of the sensor. However, a detailed schematic diagram of the steps until the planarization films 10a and 10b of FIG. 6 are formed is omitted. Flattening film 15
After the processing (corresponding to the flattening films 10a and 10b in FIG. 6), a dielectric multilayer film 17 is provided, and a pattern is formed by a resist so that unnecessary portions can be removed while leaving the multilayer film on the visible region sensor section. 18 is formed and etched by the RIE method. Further, after the aluminum electrode pad 16 and the scribing portion are patterned and etched, dicing and wire bonding are performed, and the glass chip 19 is sealed to manufacture a sensor chip. At this time, heat of about 220 ° C. is mainly applied in the steps of patterning, bonding and glass sealing.

[0009]

However, in the above manufacturing process, after the dielectric multilayer film 17 is formed, the process of
Since heat of about 20 ° C. is applied, when an attempt is made to obtain a sensor having a structure in which the iR cut filter 11 shown in FIG. 6 is laminated, there arises a problem that film cracking occurs in a later step.

In addition, in the above manufacturing process, when the sensor chip provided with the dielectric multilayer film is heated, the organic flattening film undergoes surface deformation, which causes a problem that surface accuracy is deteriorated. (Object of the Invention) An object of the present invention is to provide an image sensor for preventing defective film cracking and peeling. Another object of the present invention is to provide a manufacturing method for manufacturing such an image sensor at low cost.

[0011]

According to the image sensor of the present invention, a filter composed of a multilayer film is provided with an adhesive layer interposed on a flattening treated plane on a photoelectric conversion portion for converting an optical signal into an electric signal. It is provided.

The method of manufacturing the image sensor of the present invention comprises:
A step of providing a layer having a flattened surface on a first substrate provided with a photoelectric conversion part for converting an optical signal into an electric signal;
A step of providing a filter composed of a multilayer film on a second substrate via a release agent layer; a step of adhering the flattening surface and the filter surface with an adhesive layer interposed; By peeling the second substrate from the interface of the agent layer,
And a step of providing the filter on the flattened surface with an adhesive layer interposed.

[0013]

According to the image sensor of the present invention, by interposing an adhesive layer between the flattening plane and the multilayer filter, heat shrinkage or the like of the flattening plane is suppressed to prevent film cracking and peeling. It is about to be resolved.

An organic flattening film can be used as the film forming the flattening surface, but is made of a material having a higher rigidity and / or a smaller coefficient of thermal expansion than the organic flattening film as the adhesive layer. By selecting one, it is possible to suppress the shrinkage and the like of the organic flattening film with respect to the temperature change and prevent film cracking and film peeling of the multilayer film.

In the image sensor manufacturing method of the present invention, after the multilayer filter is provided on the second substrate having excellent surface accuracy, the multilayer filter is transferred onto the flattening plane with the adhesive layer interposed. By doing so, the multilayer filter is formed on the flattened flat surface by a simple manufacturing process, and the surface accuracy of the image sensor is improved.

[0016]

Embodiments of the present invention will be described below with reference to the drawings. The present invention is not limited to the following examples, as long as the object of the present invention is achieved,
It is possible to select the multilayer film structure and materials within the range. (Example 1) After cleaning the glass substrate 1 shown in FIG. 1 which has been polished to 10 Newtons or less, it is immersed in a fluorine-based mold release agent (a solution in which perfluoroalkylsilane is diluted with a solvent such as triethane or dichloromethane) for 10 seconds. 70 mm /
The release agent layer 2a was formed by pulling up at a pulling speed of a minute. A dielectric multilayer film 3 was formed on the release agent layer 2a by a vacuum vapor deposition method. When the dielectric multilayer film 3 is transferred onto the sensor, it suppresses the transmittance of near-infrared light, which is a non-visible light region, and has the transmittance of the visible light region.
On the release agent layer 2a, a multilayer film iR cut filter of 21 layers of TiO ₂ and SiO ₂ was formed such that the layer arranged on the sensor side was the outermost layer so as to obtain the above characteristics at the time of transfer. The degree of vacuum during formation is 1 × 10 ^-2 Pa and the substrate temperature is 50 ° C. The spectral characteristics of this iR cut filter are shown in FIG.

On the other hand, a photodiode (PD) serving as a photoelectric conversion element and a C for transferring a signal to the Si wafer 6.
On the substrate where the CD and Al electrodes are arranged adjacent to each other, B
Selective transmission color filters of (blue), G (green), R (red) and B (blue) are formed by printing. Next, after forming the acrylic polymer flattening film 5b, an R filter is formed by printing only on the photoelectric conversion element portion in the infrared light region of the B filter (the B + R filter absorbs visible light, Having a spectral characteristic of transmitting infrared light (iR portion), an acrylic polymer flattening film 5a is then formed.

[0018] A thermosetting adhesive (epoxy two-component adhesive,
Product name: Cemedine 1565) is dropped and adhered to the adhesive layer 4 so as not to entrap air bubbles.
It is cured for a period of time, and the glass substrate is peeled from the release agent layer. The spectral characteristics of the iR cut filter on the silicon wafer at this time are shown in FIG.

An image sensor is formed on the thus obtained image sensor substrate through patterning of the iR portion and Al electrode pad portion, etching, dicing, wire bonding and glass sealing for packaging. did. In the image sensor thus obtained, no defects such as cracks or peeling were observed in the dielectric multilayer film, and both visible light and near-infrared light showed good sensor functions. (Example 2) Si as a substrate for dipping a release agent
An image sensor was obtained in the same manner as in Example 1 except that a wafer was used. The image sensor thus obtained has no visible defects such as cracks or peeling in the dielectric multilayer film.
Both near infrared light showed good sensor function. Example 3 A carbon film was formed as a release agent layer 2b on the acrylic film 7 having a thickness of 50 μm shown in FIG. As a film forming method at this time, discharge was performed at a CH ₄ gas pressure of 0.4 Pa and an RF power of 200 w for 10 minutes to obtain a carbon film as a release agent layer having a thickness of 50 nm. A dielectric multilayer film 3 was formed on this release agent layer by a sputtering method. The dielectric multilayer film 3 has the same structure as that of the first embodiment. The degree of vacuum during formation is 0.15 Pa (Ar / O ₂ = 9/1), the RF power is 1 kW, and the substrate temperature is 80 ° C.

On the other hand, as in Example 1, after the selective transmission filter and the acrylic flattening film 5c are formed on the Si wafer 6 on which the PD and the like are formed, the (B) filter as the iR portion is provided and the selection is performed. A transmission filter (R) is provided for the purpose of visible cut (no acrylic flattening film is provided on the upper layer).

A thermosetting adhesive (epoxy two-component adhesive, trade name: Cemedine 1565) was dropped on the bonding surface of the Si substrate thus prepared, and acrylic was used so that air bubbles were not caught in the adhesive layer 4. After laminating the films, a glass substrate having 10 or less Newton and a thickness of 10 mm and having the same shape as the silicon substrate is laminated, and then at 100 ° C. for 1 hour.
It is cured for a time, and the acrylic film 7 is peeled off from the release agent layer.

An image sensor is formed on the thus obtained image sensor substrate through patterning of the iR portion and the Al electrode pad portion, etching, dicing, wire bonding and glass sealing for packaging. did.

In the image sensor thus obtained, no defects such as cracks and peeling were observed in the dielectric multilayer film, and both visible light and near-infrared light showed good sensor functions.
Further, in the present embodiment, it is not necessary to form the acrylic flattening film into two layers, and the release substrate is in the shape of a film and has a small rigidity and easy release, which is advantageous in manufacturing.

[0024]

As described in detail above, according to the present invention, it becomes possible to provide a dielectric multilayer film having excellent heat resistance and strong adhesion on the image sensor, and the function and application of the image sensor can be improved. It is useful for diversification. In particular, by providing an adhesive layer having a lower coefficient of thermal expansion and a higher elastic modulus than that of the flattening film between the flattening film and the dielectric multilayer film, it is possible to prevent film cracking and film peeling in the subsequent process. The image sensor and its manufacturing method can be provided.

[Brief description of drawings]

FIG. 1 is a schematic cross-sectional view of a first embodiment of an image sensor of the present invention.

FIG. 2 is a spectral characteristic diagram of an iR cut filter on glass according to a first embodiment of the image sensor of the present invention.

FIG. 3 is a spectral characteristic diagram of an iR cut filter according to a first embodiment of the image sensor of the present invention.

FIG. 4 is a schematic cross-sectional view of a third embodiment of the image sensor of the present invention.

FIG. 5 is a schematic plan view showing an example of an image sensor.

FIG. 6 is a schematic cross-sectional view of an example of an image sensor.

FIG. 7 is a schematic cross-sectional view of the image sensor manufacturing process.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Glass substrate 2a, 2b Release agent layer 3,11,17 Multilayer film 4 Adhesive layer 5a, 5b, 5c, 10a, 10b, 15 Flattening film 6,9 Si substrate 7 Acrylic film 8 Image sensor 12a-12e Filter 13a to 13d Photodiodes 14a to 14d CCD 16 Al electrode pad 18 Mask 19 Sealing glass

Front Page Continuation (72) Inventor Fukasawa Jobu 3-30-2 Shimomaruko, Ota-ku, Tokyo Canon Inc.

Claims (9)

[Claims] 1. An image sensor in which a filter composed of a multilayer film is provided with an adhesive layer interposed on a flattening plane on a photoelectric conversion unit for converting an optical signal into an electric signal. 2. The image sensor includes a plurality of sensor arrays including a plurality of photoelectric conversion elements for color-separating a light signal in a visible light region and converting the light signal into an electric signal, and color-separating the light signal in an invisible light region. A plurality of sensor arrays including a plurality of photoelectric conversion elements for converting into an electric signal, and an image sensor in which the filters are arranged in a visible light region and a non-visible light region. The image sensor according to claim 1, wherein the image sensor is a filter formed as an element of a sensor array for separating light. 3. The image sensor according to claim 1, wherein the flattened surface is an organic resin layer surface, and the linear thermal expansion coefficient of the adhesive layer is smaller than that of the organic resin layer. 4. The image sensor according to claim 1, wherein the flattened surface is an organic resin layer surface, and the elastic modulus of the adhesive layer is larger than that of the organic resin layer. 5. A step of providing a layer having a flattened surface on a first substrate provided with a photoelectric conversion part for converting an optical signal into an electrical signal, and a release agent layer on the second substrate via a release agent layer. A step of providing a filter constituted by a multilayer film, a step of adhering the flattened surface and the filter surface with an adhesive layer interposed, and peeling the second substrate from the interface of the release agent layer. The method of manufacturing an image sensor according to claim 1, further comprising a step of providing the filter on the flattening surface with an adhesive layer interposed. 6. The image sensor includes a plurality of sensor arrays including a plurality of photoelectric conversion elements that color-separate a light signal in a visible light region into an electric signal and color-separate a light signal in an invisible light region. An image sensor in which a plurality of sensor arrays including a plurality of photoelectric conversion elements for converting into electric signals are arranged in parallel, and the filter composed of the multi-layered film includes an optical signal in the visible light region and an invisible light signal. The method of manufacturing an image sensor according to claim 5, wherein the filter is a filter formed as an element of a sensor array for separating an optical signal in an optical region. 7. The method of manufacturing an image sensor according to claim 5, wherein the second substrate is glass. 8. The method of manufacturing an image sensor according to claim 5, wherein the second substrate is a synthetic resin sheet. 9. The method of manufacturing an image sensor according to claim 5, wherein the second substrate is a silicon wafer.