JP2018157605A - Imaging apparatus and camera - Google Patents

Abstract

PROBLEM TO BE SOLVED: To reduce deterioration of reliability and degradation of imaging performance due to stress generated by bimetal effect caused by difference between a linear expansion coefficient of a semiconductor chip having an imaging region and a linear expansion coefficient of a wiring board joined to the semiconductor chip via a bump.SOLUTION: A solid-state imaging apparatus 1 includes: a semiconductor chip 2 having an imaging region 2a; and a wiring board 3 which is joined to the semiconductor chip 2 via a bump 5 having elasticity.SELECTED DRAWING: Figure 1

Description

  The present invention relates to a solid-state imaging device and an electronic camera using the same.

  A conventional packageless solid-state imaging device includes, for example, a silicon chip having an imaging region and a wiring board bonded to the silicon chip via bumps. As the bumps, metal bumps made of metal such as solder, Au or Cu are used. As an example of such a conventional solid-state imaging device, FIG. 4E of Patent Document 1 below discloses a solid-state imaging device having a so-called COG (Chip on glass) structure in which gold balls are used as the bumps. ing.

JP-A-11-121653

  However, in the conventional solid-state imaging device, the reliability caused by the poor connection due to the stress caused by the bimetal effect resulting from the difference between the linear expansion coefficient of the silicon chip and the linear expansion coefficient of the wiring board, and the imaging surface of the silicon chip This results in a decrease in imaging performance due to the warp.

  The present invention has been made in view of such circumstances, and an object thereof is to provide a solid-state imaging device with improved reliability and imaging performance, and an electronic camera using the same.

  The following aspects are presented as means for solving the problems. A solid-state imaging device according to a first aspect includes a semiconductor chip having an imaging region, and a wiring board bonded to the semiconductor chip via elastic bumps.

  A solid-state imaging device according to a second aspect is the solid-state imaging device according to the first aspect, wherein the semiconductor chip and the wiring board are joined to each other by an elastic adhesive disposed so as to surround the adhesive. It is.

  In the solid-state imaging device according to the third aspect, in the second aspect, the Young's modulus of the adhesive is 1.0 Gpa or less. This Young's modulus is preferably 0.1 Gpa or less, and more preferably 0.05 Gpa or less.

  The solid-state imaging device according to a fourth aspect is the solid-state imaging device according to any one of the first to third aspects, wherein the wiring board has an opening in a region including a region facing the imaging region. A translucent member bonded to the surface of the semiconductor chip on the imaging region side and bonded to the surface of the wiring board opposite to the semiconductor chip so as to close the opening is provided.

  A solid-state imaging device according to a fifth aspect is the solid-state imaging device according to any one of the first to third aspects, wherein the wiring board has translucency, and the wiring board covers the imaging chip so as to cover the imaging area. It has been joined.

  A solid-state imaging device according to a sixth aspect includes, in any one of the first to fifth aspects, another semiconductor chip mounted on the wiring board and electrically connected to the semiconductor chip. .

  In the solid-state imaging device according to a seventh aspect, in the sixth aspect, the another semiconductor chip is bonded to the wiring board via an elastic bump.

  In the solid-state imaging device according to an eighth aspect, in any one of the first to seventh aspects, the elastic bump is made of a composite material of a fluorinated copolymer polymer and a carbon nanotube, or It is composed of a conductive rubber material.

  An electronic camera according to a ninth aspect includes the solid-state imaging device according to any one of the first to eighth aspects.

  A solid-state imaging device with improved reliability and imaging performance, and an electronic camera using the solid-state imaging device can be provided.

1 is a schematic cross-sectional view schematically showing a solid-state imaging device according to a first embodiment of the present invention. It is a schematic perspective view which shows typically an example of an elastic bump. It is a schematic sectional drawing which shows typically the electronic camera by the 2nd Embodiment of this invention. It is a schematic sectional drawing which shows typically the solid-state imaging device by the 3rd Embodiment of this invention. It is a schematic sectional drawing which shows typically the solid-state imaging device by the 4th Embodiment of this invention.

  Hereinafter, a solid-state imaging device and an electronic camera according to the present invention will be described with reference to the drawings.

[First Embodiment]
FIG. 1 is a schematic cross-sectional view schematically showing a solid-state imaging device 1 according to the first embodiment of the present invention.

  The solid-state imaging device 1 according to the present embodiment includes a semiconductor chip 2 having an imaging region 2a, a wiring board 3, and a translucent plate 4 as a translucent member.

  In the present embodiment, the semiconductor chip 2 is an image sensor such as a CMOS or CCD configured as a chip, and a plurality of pixels (not shown) are two-dimensionally arranged in the imaging region 2a. The semiconductor chip 2 photoelectrically converts incident light incident on the imaging region 2a via the translucent plate 4 and outputs an image signal. For example, a read circuit (not shown) that reads the image signal by driving the pixel and a processing circuit (for example, an AD conversion circuit) that processes the output signal may be mounted on the semiconductor chip 2.

  In the present embodiment, the substrate material of the semiconductor chip 2 is silicon, and the semiconductor chip 2 is a so-called silicon chip. However, in the present invention, the substrate material of the semiconductor chip 2 is not necessarily limited to silicon.

  In the present embodiment, a rigid substrate is used as the wiring substrate 3. A circuit component may be mounted on the wiring board 3 so as to mount a predetermined circuit, or only the relay wiring may be mounted without mounting the circuit component. The wiring board 3 has an opening 3 a formed in a region including a region facing the imaging region 2 a of the semiconductor chip 2.

  An electrode pad (not shown) is formed on the upper surface (surface on the imaging region 2 a side) near the outer periphery of the semiconductor chip 2, and an electrode pad (not shown) is formed on the lower surface around the opening 3 a in the wiring substrate 3. These are joined by bumps 5. An adhesive 6 is formed between the vicinity of the outer periphery of the semiconductor chip 2 and the periphery of the opening 3a in the wiring board 3 (including the vicinity of the bumps 5), whereby the imaging region 2a, the translucent plate 4 and The airtightness of the space between them is maintained. Further, the bonding by the bumps 5 is reinforced by the adhesive 6.

  Examples of the substrate material of the wiring board 3 include glass and ceramic. In this embodiment, as will be described later, even if the difference between the linear expansion coefficient of the substrate material of the wiring substrate 3 and the linear expansion coefficient of the substrate material of the semiconductor chip 2 is relatively large, the bimetal resulting from the difference is used. For example, a glass epoxy substrate can be used as the wiring substrate 3 because a decrease in reliability and a decrease in imaging performance due to the stress caused by the effect can be reduced. The glass epoxy substrate has a larger difference from the linear expansion coefficient of the substrate material (generally silicon) of the semiconductor chip 2 than an LTCC (Low Temperature Co-fired Ceramics) substrate or a non-alkali glass substrate for liquid crystal. Although it has a linear expansion coefficient, there are advantages that it is inexpensive and multilayer wiring and fine wiring are possible. However, in the present invention, an LTCC substrate, a non-alkali glass substrate for liquid crystal, or the like may be used as the wiring substrate 3, and in that case, reliability and imaging performance are further deteriorated due to stress caused by the bimetal effect. Can be reduced.

  The translucent plate 4 is bonded to the upper surface of the wiring substrate 3 (the surface opposite to the wiring substrate 3) with an adhesive 7 so as to close the opening 3a of the wiring substrate 3. The adhesive 7 is provided over the entire circumference of the opening 3a in the wiring board 3, and the translucent plate 4 is maintained so that the airtightness of the space between the imaging region 2a and the translucent plate 4 is maintained. And the wiring board 3 are sealed.

  As a material of the translucent plate 4, for example, glass for measures against α rays (glass in which the amount of α rays emitted is sufficiently reduced), quartz that is an optical low-pass filter, or the like can be used.

  In this embodiment, a bump having elasticity (hereinafter referred to as “elastic bump”) is used as the bump 5. FIG. 2 is a schematic perspective view schematically showing an example of the elastic bump. The elastic bump of this example is composed of a composite material in which carbon nanotubes 12 are mixed in a base material 11 having elasticity. The base material 11 is, for example, a rubber material such as an elastomer material, specifically, a fluorine copolymer. The carbon nanotubes 12 are blended in the base material 11 so as to extend in a needle shape, a thread shape, or the like and become entangled with each other to be electrically connected. In the example illustrated in FIG. 2, the elastic bump is configured in a quadrangular prism shape, but the shape is not limited thereto, and may be configured in a cylindrical shape, for example. Specifically, the elastic bump shown in FIG. 2 is obtained by using, for example, a carbon nanotube rubber paste obtained by a manufacturing method disclosed in International Publication No. 2009/102077 pamphlet, a semiconductor chip 2 or a wiring substrate 3. Further, it can be manufactured by patterning by screen printing, die-cutting printing, ink jet printing or dispensing. If such a manufacturing method is adopted, high-temperature heat treatment is not required, and carbon nanotubes are generated during and after manufacture of the solid-state imaging device 1 and adhere to the imaging region 2a of the semiconductor chip 2 and the like. Thus, it is possible to avoid the situation that causes the image quality degradation of the captured image.

  The elastic bump used in the present invention is not limited to an elastomer material mixed with carbon nanotubes, and may be elastic and conductive. The elastic bump used in the present invention may be, for example, an elastic conductive resin, conductive rubber, or paste. The elastic bump used in the present invention may be one in which a conductor (for example, solder or silver paste) other than carbon nanotubes is mixed in the base material 11 having elasticity. In this case, the conductivity of the elastic bump is borne by a relatively rigid conductor, and the elasticity of the elastic bump is borne by the substrate 11.

  The Young's modulus (the Young's modulus at room temperature of 25 ° C.) of the adhesive 6 is preferably 1.0 Gpa or less, more preferably 0.1 Gpa or less, and even more preferably 0.05 Gpa or less. . As an adhesive having a Young's modulus of 0.05 Gpa or less, an acrylic resin or a silicon resin is generally used, but an epoxy resin with a resin filler is also included. Silicone resins often generate siloxane, and acrylic resins, especially when exposed to high temperatures of 100 ° C or more, generally have a large amount of outgas. Due to siloxane and other outgases generated from the resin in the sealed semiconductor chip surface, Insufficient energization, gas condensation, etc., electrical characteristics failure, especially in the case of an image sensor, condensation can occur on the sealed glass surface, which can be reflected in the captured image and degrade the image quality. There is sex. In addition, acrylic and silicon resins have high hygroscopicity and moisture permeability of the resin, and moisture absorbed by the resin or moisture that has passed through the resin into the sealed imaging surface is not contained within the sealing surface. There is a possibility that the image quality deteriorates due to condensation on the imaging surface or the glass surface, or the Al pad of the element or the metal in the connection portion is corroded by the condensed moisture, and electrical characteristics such as disconnection may occur. Therefore, it is desirable to use an adhesive made of an epoxy resin having low hygroscopicity and moisture permeability and low outgas as the adhesive 6 as compared with the case of using an adhesive made of a silicon resin or an acrylic resin.

  According to the present embodiment, even if the difference between the linear expansion coefficient of the semiconductor chip 2 having the imaging region 2a and the linear expansion coefficient of the wiring substrate 3 bonded to the semiconductor chip 2 via the bumps 5 is relatively large, Since an elastic bump is used as the bump 5, the stress generated by the bimetal effect due to the difference in the linear expansion coefficient is relieved by the elasticity of the bump 5. Therefore, according to the present embodiment, the possibility that the bumps 5 are peeled off from the semiconductor chip 2 or the wiring substrate 3 to cause a connection failure in electrical connection is reduced, and the reduction in reliability is reduced. In addition, the warp of the imaging surface of the semiconductor chip 2 due to the temperature change can be reduced, and the deterioration of the imaging performance can be reduced.

[Second Embodiment]
FIG. 3 is a schematic cross-sectional view schematically showing an electronic camera 100 according to the second embodiment of the present invention.

  The solid-state imaging device 1 according to the first embodiment is incorporated in the body 101 of the electronic camera 100 according to the present embodiment. The electronic camera 100 according to the present embodiment is configured as a single-lens reflex type electronic still camera. However, the solid-state imaging device 1 according to the first embodiment is different from other electronic still cameras, video cameras, and mobile phones. You may incorporate in various electronic cameras, such as a camera mounted in.

  In electronic camera 100 according to the present embodiment, body 101 is provided with interchangeable photographic lens 102. The subject light that has passed through the photographing lens 102 is reflected upward by the quick return mirror 103 and forms an image on the screen 104. The subject image formed on the screen 104 is observed from the finder observation window 107 through the eyepiece lens 106 from the penta roof prism 105. When the release button (not shown) is fully pressed, the quick return mirror 103 jumps upward, and the subject image from the photographing lens 102 enters the solid-state imaging device 1 described above.

  The solid-state imaging device 1 is positioned and fixed in the body 101 by being attached to the body 101 via a bracket (not shown) and a position adjusting mechanism (not shown).

  According to the present embodiment, since the solid-state imaging device 1 according to the first embodiment is used, it is possible to reduce reliability and imaging performance.

[Third Embodiment]
FIG. 4 is a schematic cross-sectional view schematically showing a solid-state imaging device 11 according to the third embodiment of the present invention, and corresponds to FIG. 4, elements that are the same as or correspond to those in FIG. 1 are given the same reference numerals, and redundant descriptions thereof are omitted.

  The solid-state imaging device 11 according to the present embodiment is different from the solid-state imaging device 1 according to the first embodiment in that the wiring board 3, the translucent plate 4 and the adhesive 7 are replaced with a translucent wiring. A substrate 12 is used, and a flexible wiring substrate 13 is bonded to the wiring substrate 12 via bumps 14 to have a COG structure.

  As the wiring board 12, for example, a glass plate made of glass for preventing α rays (glass with a sufficiently reduced amount of α rays emitted) can be used. A general glass contains a trace amount of radioactive elements such as uranium and thorium, and generates α rays when the radioactive elements decay. When a glass plate made of general glass is used as the wiring substrate 12, the generated α rays are incident on the imaging region 2a of the semiconductor chip 2, and noise that becomes a sudden white spot is generated. Therefore, it is preferable to use a glass plate made of glass for preventing α rays as the wiring board 12. In general, the linear expansion coefficient of the glass for preventing α rays is, for example, about twice the linear expansion coefficient of the substrate material (generally silicon) of the semiconductor chip 2, and the difference between the two is large.

  An electrode pad (not shown) is formed on the upper surface (surface on the imaging region 2a side) near the outer periphery of the semiconductor chip 2, and the electrode pad (not shown) is formed on the lower surface of the wiring board 12 at a position corresponding to the electrode pad. They are formed and joined between them by bumps 5 made of elastic bumps. The adhesive 6 described above is formed between the vicinity of the outer periphery of the semiconductor chip 2 and the wiring board 12 (including the vicinity of the bumps 5), and thereby the airtightness of the space between the imaging region 2a and the wiring board 12 is formed. Sex is to be maintained. Further, the bonding by the bumps 5 is reinforced by the adhesive 6.

  Although not shown in the drawing, on the lower surface of the wiring board 12, in addition to the electrode pads bonded by the bumps 5, there are electrode pads to which the bumps 14 are bonded and wirings connecting these electrode pads. Is formed. The semiconductor chip 2 is connected to the outside via bumps 5, electrode pads and wirings on the lower surface of the wiring board 12, bumps 14, and the flexible wiring board 13. As the bumps 14, metal bumps such as Au stud bumps may be used, but elastic bumps are preferably used. Instead of joining with the bumps 14 or with joining with the bumps 14, an ACF (Anisotropic Conductive Film) is formed between the electrode pads on the lower surface of the wiring board 12 and the electrode pads (not shown) of the flexible wiring board 13. The conductive film may be joined.

  Also in the present embodiment, as in the first embodiment, the linear expansion coefficient of the semiconductor chip 2 having the imaging region 2a and the linear expansion coefficient of the wiring substrate bonded to the semiconductor chip 2 via the bumps 5 Even if the difference is relatively large, since the elastic bumps are used as the bumps 5, it is possible to reduce deterioration in reliability and imaging performance. In particular, when a glass plate made of glass for preventing α rays is used as the wiring board 12, the difference becomes large, so the effect of the present embodiment is remarkable.

  Further, in the present embodiment, the COG structure is adopted, and the wiring board 12 in which the wiring board 3 and the translucent plate 4 in FIG. 1 are integrated is used. Compared to the form, it is possible to realize low cost by reducing the number of parts.

  The solid-state imaging device 11 according to the present embodiment can be used in place of the solid-state imaging device 1 in the electronic camera 100 according to the second embodiment. This also applies to the solid-state imaging device 21 described later.

[Fourth Embodiment]
FIG. 5 is a schematic sectional view schematically showing a solid-state imaging device 21 according to the fourth embodiment of the present invention, and corresponds to FIG. 5, elements that are the same as or correspond to those in FIG. 4 are given the same reference numerals, and redundant descriptions thereof are omitted. The difference between the present embodiment and the third embodiment is the point described below.

  In the present embodiment, two semiconductor chips 22 that are electrically connected to the semiconductor chip 2 are mounted on the lower surface of the wiring board 12 in addition to the semiconductor chip 2 having the imaging region 2a. In the present embodiment, for example, the semiconductor chip 2 includes a plurality of pixels and a readout circuit that drives these to read out an image signal, and one semiconductor chip 22 outputs one signal output from the semiconductor chip 2. A processing circuit for performing processing such as AD conversion on the image signal of the part is mounted, and processing for performing processing such as AD conversion on the remaining image signal output from the semiconductor chip 2 is mounted on the other semiconductor chip 22. A circuit is installed. The output signal output from each semiconductor chip 22 is output to the outside via each flexible wiring board 13.

  In the first and third embodiments, the circuits mounted on the two semiconductor chips 22 in the present embodiment may be mounted on the semiconductor chip 2 or mounted on the two semiconductor chips 22. The circuit may be mounted on a circuit board or the like provided outside the solid-state imaging device 21.

  In the present embodiment, the electrode pads (not shown) on the lower surface of the wiring substrate 12 and the electrode pads (not shown) on the upper surface of the semiconductor chip 22 are joined by the bumps 23 and 24. Although not shown in the drawing, on the lower surface of the wiring substrate 12, wiring connecting the electrode pads joined by the bumps 5 and the electrode pads joined by the bumps 23, and the electrodes joined by the bumps 24 A wiring for connecting between the pad and the electrode pad bonded to the bump 14 is formed. Metal bumps such as Au stud bumps may be used as the bumps 23, 24, and 14, but elastic bumps are preferably used. Instead of joining by the bumps 23, 24, and 14, or together with joining by the bumps 23, 24, and 14, an ACF is formed between the electrode pad on the lower surface of the wiring board 12 and the electrode pad (not shown) of the flexible wiring board 13. May be joined.

  At locations including the vicinity of the bumps 23 and 24, the wiring substrate 12 and the semiconductor chip 22 are bonded to each other by adhesives 25 and 26, and the bonding by the bumps 23 and 24 is reinforced. As the adhesives 25 and 26, it is preferable to use an adhesive similar to the adhesive 6 described above.

  This embodiment can provide the same advantages as those of the third embodiment.

  Although the embodiments of the present invention have been described above, the present invention is not limited to these embodiments.

DESCRIPTION OF SYMBOLS 1,11,21 Solid-state imaging device 2 Semiconductor chip 2a Imaging area 3 Wiring board 5 Bump (elastic bump)
6 Adhesive

Claims (9)

A first semiconductor chip that generates a signal by photoelectrically converted charges;
A bump for outputting the signal generated by the first semiconductor chip;
A second semiconductor chip having a processing circuit for converting the signal from the bump into a digital signal;
The said bump is an imaging device comprised with the composite material by which the carbon nanotube was mixed in the base material of a fluorine-type copolymer polymer.   The imaging device according to claim 1, further comprising a substrate connected to the bump and having a wiring for outputting the signal from the bump to the second semiconductor chip. The first semiconductor chip has an imaging region in which a plurality of pixels are arranged,
The imaging device according to claim 2, wherein the substrate has translucency and is disposed at a position facing the imaging region.   The imaging device according to claim 3, wherein the bump is disposed between the first semiconductor chip and the substrate so as to join the first semiconductor chip and the substrate.   The solid-state imaging device according to claim 3, further comprising an adhesive disposed so as to surround the bump between the first semiconductor chip and the substrate.   The imaging apparatus according to claim 5, wherein the adhesive is an epoxy resin containing a resin filler.   The imaging device according to any one of claims 3 to 5, wherein a Young's modulus of the adhesive is 1.0 Gpa or less.   The imaging device according to claim 1, wherein the bump has elasticity.   The camera provided with the imaging device as described in any one of Claims 1-8.

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