JP6051636B2 - Image sensor - Google Patents

Description

  The present invention relates to an image sensor and a method for manufacturing the image sensor.

An imaging device in which an imaging area in which a plurality of pixels for photoelectrically converting a received subject image and an AD converter that receives an analog signal output from the imaging area and converts it into a digital signal are formed on the same chip It has been known.
[Prior art documents]
[Patent Literature]
[Patent Document 1] Japanese Patent Laid-Open No. 7-2222063

  As the imaging area increases, there is a problem that the chip becomes larger.

  The imaging device according to the first aspect of the present invention includes an imaging chip including an imaging region in which a plurality of pixels are arranged, an optical element fixed to the imaging chip and sealing the imaging region, and an optical element adjacent to the imaging chip. And a signal processing chip including at least an AD converter that receives an analog signal output from the pixel and converts the analog signal into a digital signal.

  An image pickup device manufacturing method according to a second aspect of the present invention includes: an attaching step of attaching an optical element to each of the image pickup regions on a wafer on which a plurality of image pickup regions in which a plurality of pixels are arranged are formed; Divide each unit circuit area including the imaging area into individual imaging steps to which the optical element is attached, and an AD that receives the analog signal output from the pixel and converts it into a digital signal A fixing step of fixing the signal processing chip including at least the converter to the imaging chip adjacent to the optical element.

  It should be noted that the above summary of the invention does not enumerate all the necessary features of the present invention. In addition, a sub-combination of these feature groups can also be an invention.

It is a figure which shows the structure of the image pick-up element of this embodiment. It is a figure which shows typically the state by which the 1st signal processing chip and the 2nd signal processing chip were fixed to the fixed plate. It is a figure explaining the manufacturing method of an image sensor. It is a figure explaining the manufacturing method of an image sensor.

  Hereinafter, the present invention will be described through embodiments of the invention, but the following embodiments do not limit the invention according to the claims. In addition, not all the combinations of features described in the embodiments are essential for the solving means of the invention.

  FIG. 1 is a diagram illustrating a configuration of an image sensor 10 according to the present embodiment. FIG. 1A is a schematic top view of the image sensor 10. FIG.1 (b) is sectional drawing which shows typically the AA cross section of Fig.1 (a). In FIG. 1A, the imaging region 101, the adhesive layer 400, and the adhesives 501 and 502, which will be described later, are the same as those in FIG. 1B in order to clarify the correspondence with each element in FIG. Has been hatched. The imaging element 10 includes an imaging chip 100, an optical element 200, and a signal processing chip 300.

  As shown in FIG. 1A, the imaging chip 100 is rectangular when viewed from above, and has an imaging region 101 at the center. In the imaging region 101, a plurality of pixels that photoelectrically convert a received subject image are arranged. The imaging region 101 may include pixels that form an optical black region. The shape of the imaging region 101 is a rectangle as shown in FIG.

  The imaging chip 100 includes electrode pads 104 and 105 at outer edges of a pair of opposing sides in the imaging region 101. As shown in FIGS. 1A and 1B, the electrode pad 104 is provided on the outer edge portion of the first side 102 of the imaging region 101, and the electrode pad 105 is formed on the second side 103 facing the first side. Provided at the outer edge. The electrode pads 104 and 105 are used for electrical connection with a signal processing chip 300 described later.

  An adhesive layer 400 is formed on the periphery of the imaging region 101 so as to surround the imaging region 101. The adhesive layer 400 adheres the imaging chip 100 and the optical element 200. A thermosetting adhesive or the like is used as a material for the adhesive layer 400.

  The optical element 200 is disposed on the adhesive layer 400 so as to face the imaging region 101, and is bonded to the imaging chip 100 via the adhesive layer 400. The area of the optical element 200 is larger than the area of the imaging region 101, and the optical element 200 covers the entire imaging region 101. The adhesive layer 400 is interposed between the imaging chip 100 and the optical element 200 and is formed so as to surround the imaging region 101. Therefore, the optical element 200 can seal the imaging region 101 while being separated from the imaging chip 100 by the thickness of the adhesive layer 400.

  Specifically, the optical element 200 is a cover glass that covers the imaging region 101 of the imaging chip 100. As the cover glass, borosilicate glass, quartz glass, non-alkali glass, heat-resistant glass, or the like can be used.

  The signal processing chip 300 is fixed to the imaging chip 100 adjacent to the optical element 200. The signal processing chip 300 includes at least an AD converter that receives an analog signal output from the imaging chip 100 and converts it into a digital signal. In addition to the AD converter, the signal processing chip 300 includes a readout circuit that reads out an analog signal generated by the imaging chip, a timing control circuit that drives the readout circuit, a removal circuit that removes noise in the readout signal, and the like. But you can.

  The number of signal processing chips is appropriately determined according to the pixel signal readout method. In the present embodiment, two-channel reading is adopted as a pixel signal reading method. Therefore, in the present embodiment, the signal processing chip 300 includes the first signal processing chip 310 and the second signal processing chip 320. In the following description, when there is no particular distinction between the first signal processing chip 310 and the second signal processing chip 320, they may be collectively expressed as a signal processing chip 300. The first signal processing chip 310 includes a first AD converter. The second signal processing chip 320 includes a second AD converter. The first AD converter and the second AD converter receive different pixel signals. Thereby, the AD conversion process can be speeded up.

  The first signal processing chip 310 is fixed to the outer edge portion of the first side 102 of the imaging region 101. Specifically, the electrode pad 311 of the first signal processing chip is electrically connected to the electrode pad 104 of the imaging chip via the bump 601. The imaging chip 100 and the first signal processing chip 310 are bonded by an adhesive 501 formed so as to surround the connection portion.

  The second signal processing chip 320 is fixed to the outer edge portion of the second side 103 facing the first side. Specifically, the electrode pad 321 of the second signal processing chip is electrically connected to the electrode pad 105 of the imaging chip via the bump 602. The imaging chip 100 and the second signal processing chip 320 are adhered by an adhesive 502 formed so as to surround the connection portion.

  As described above, in the imaging device 10 of the present embodiment, the imaging region and the circuit region are formed on separate chips. Therefore, processes suitable for the imaging chip 100 and the signal processing chip 300 can be employed in the manufacturing stage. As a result, for example, a higher voltage is used for the imaging chip 100 than the signal processing chip 300 from the viewpoint of performance improvement, while the signal processing chip 300 can achieve power saving using a lower voltage than the imaging chip. Further, the degree of freedom in design increases in the line width of the wiring pattern.

  The first signal processing chip 310 and the second signal processing chip 320 are fixed to the imaging chip 100 adjacent to the optical element 200. That is, not only the optical element 200 but also the optical element 200 and the signal processing chip 300 are arranged on the imaging chip 100. Therefore, compared with the case where the signal processing chip 300 and the optical element 200 are stacked, the height of the entire image sensor 10 can be suppressed.

  The imaging chip 100 is provided with the formation region of the electrode pads 104 and 105 in the peripheral part away from the imaging region 101. Therefore, it is easy to secure a bump area, and bonding via the bumps is facilitated. The imaging chip 100, the first signal processing chip 310, and the second signal processing chip 320 are partially overlapped and fixed. Therefore, the width of the image sensor can be reduced as compared with the case where the image area and the circuit area are formed on the same chip.

  In the imaging device 10, the first signal processing chip 310 and the second signal processing chip 320 may each be connected to an external circuit via a flexible substrate. In this case, the space around the imaging chip 100 can be used for connection between the first signal processing chip 310 and the second signal processing chip 320 and the flexible substrate.

  The imaging device may further include a fixing plate for fixing the first signal processing chip and the second signal processing chip. FIG. 2 is a diagram schematically showing a state in which the first signal processing chip 310 and the second signal processing chip 320 are fixed to the fixing plate 700. Further, as shown in FIG. 2, the flexible substrate 810 may be connected to the first signal processing chip 310, and the flexible substrate 820 may be connected to the second signal processing chip 320.

  As shown in FIG. 2, the fixed plate 700 is rectangular as a whole, and has a rectangular opening 701 at the center. That is, the fixed plate 700 is a square ring. The fixed plate 700 has a first peripheral edge 703 along the first side 702 of the rectangular opening 701 and a second peripheral edge 705 along the second side 704 facing the first side 702.

  The fixed plate 700 is installed on the first signal processing chip 310 and the second signal processing chip 320. Specifically, the first peripheral edge 703 of the fixed plate 700 is in contact with the first signal processing chip 310, and the second peripheral edge 705 of the fixed plate 700 is in contact with the second signal processing chip 320. The lower surface of the first peripheral edge 703 of the fixing plate 700 and the upper surface of the first signal processing chip 310 are fixed by being bonded with an adhesive. Similarly, the lower surface of the second peripheral edge 705 of the fixing plate 700 and the upper surface of the second signal processing chip 320 are fixed by being bonded with an adhesive. Since the fixing plate 700 is fixed to the first signal processing chip 310 and the second signal processing chip 320, a frame-like structure is formed. Therefore, the first signal processing chip 310 and the second signal processing chip 320 are more robust against external force than when the first signal processing chip 310 and the second signal processing chip 320 have a cantilever structure.

  The opening 701 of the fixed plate 700 is formed at least in a portion corresponding to the imaging region when the fixed plate 700 and the first signal processing chip 310 and the second signal processing chip 320 are fixed. Here, the area of the opening 701 of the fixed plate 700 is formed wider than the area of the optical element 200. The optical element 200 is exposed from the opening 701 of the fixed plate 700. In the configuration of the imaging element 20, since the portion corresponding to the imaging area is opened in the fixed plate 700, the incidence of the subject image on the imaging area is not hindered.

  The material of the fixing plate 700 is, for example, metal or ceramic. Since the first signal processing chip 310 and the second signal processing chip 320 generate heat, heat dissipation can be improved by using a material having high thermal conductivity as the material of the fixed plate 700. Further, the first signal processing chip 310 and the second signal processing chip 320 may be connected to an external circuit via flexible substrates 810 and 820, respectively.

  FIG. 3 is a diagram illustrating a method for manufacturing an image sensor. Specifically, FIG. 3 shows the process steps at the wafer level. In FIG. 3, the electrode pads 104 and 105 formed on the wafer in the step prior to FIG. 3A are omitted from the viewpoint of simplification.

  First, as shown in FIG. 3A, a wafer 110 having a plurality of imaging regions 101 in which a plurality of pixels that photoelectrically convert a received subject image is formed is prepared, and an adhesive material layer 210 is formed on the wafer 110. Form. For example, the adhesive material layer 210 is formed by uniformly applying an adhesive on the wafer 110. Further, the adhesive material layer 210 may be formed by attaching a die attach sheet on the wafer 110.

  Next, by removing a part of the adhesive material layer 210, as shown in FIG. 3B, an adhesive layer 400 surrounding each of the plurality of imaging regions 101 is formed (adhesive layer forming step). The adhesive layer 400 is formed by patterning the adhesive material layer 210 using, for example, photolithography.

  Next, the optical element 200 is attached to each of the plurality of imaging regions 101 by, for example, thermocompression bonding (attaching step). As a result, as shown in FIG. 3C, each of the plurality of imaging regions 101 is sealed by the optical element 200 via the adhesive layer 400, so in the steps after the sticking step, particles are captured in the imaging region 101. Can be prevented from adhering.

  Next, the wafer is cut out for each unit circuit area including the imaging area 101, and as shown in FIG. 3D, the wafer is singulated into the imaging chip 100 to which the optical element 200 is attached (individualization). Process).

  FIG. 4 is a diagram for explaining a method of manufacturing an image sensor. Specifically, the steps after separation are shown. Since the processes after the singulation are common to the respective imaging chips, the description will be given focusing on one imaging chip.

  As shown in FIG. 4A, an adhesive 501 is formed on the electrode pad 104 on the left side of the imaging chip 100 by a dispenser. A thermosetting resin can be used as the adhesive 501. After the imaging chip 100 on which the adhesive 501 is formed and the first signal processing chip 310 on which the bump 601 is formed on the electrode pad 311 are aligned in advance, the first signal processing chip 310 is bonded onto the imaging chip 100. . Bonding of the imaging chip 100 and the first signal processing chip 310 is performed in a heated state. As a result, as shown in FIG. 4B, the first signal processing chip 310 is electrically connected to the imaging chip 100 via the bumps 601 and is fixed to the imaging chip 100 by the adhesive 501 ( Fixing process).

  Similarly, an adhesive 502 is formed on the electrode pad 105 on the right side of the imaging chip 100 with a dispenser. Then, after aligning the imaging chip 100 on which the adhesive 502 is formed and the second signal processing chip 320 in which the bumps 602 are previously formed on the electrode pads 321, the second signal processing chip 320 is placed on the imaging chip 100. to paste together. Bonding of the imaging chip 100 and the second signal processing chip 320 is also performed in a heated state. As a result, as shown in FIG. 4C, the second signal processing chip 320 is electrically connected to the imaging chip 100 via the bumps 602 and is fixed to the imaging chip 100 by the adhesive 502 ( Fixing process).

  Next, as shown in FIG. 4D, a fixed plate 700 having an opening 701 corresponding to the imaging region 101 of the imaging chip is installed on the first signal processing chip 310 and the second signal processing chip 320 (installation process). ). Specifically, the fixing plate 700, the first signal processing chip 310, and the second signal processing chip 320 are bonded together with an adhesive.

  Further, as shown in FIG. 4E, the flexible substrate 810 connected to the external circuit is connected to the first signal processing chip 310, and the flexible substrate 820 is connected to the second signal processing chip 320 (connection process). Specifically, the flexible substrate 810 having the bumps 603 previously formed on the electrode pads 811 and the electrode pads 312 of the first signal processing chip 310 are aligned, and then the flexible substrate 810 and the first signal processing chip 310 are bonded together. . The flexible substrate 810 and the first signal processing chip 310 are bonded together in a heated state. Further, the flexible substrate 810 and the first signal processing chip 310 are bonded with an adhesive 503.

  Similarly, after the flexible substrate 820 having the bumps 604 formed on the electrode pads 821 in advance and the electrode pads 322 of the second signal processing chip 320 are aligned, the flexible substrate 820 and the second signal processing chip 320 are bonded together. The flexible substrate 820 and the second signal processing chip 320 are also bonded together in a heated state. Further, the flexible substrate 820 and the second signal processing chip 320 are bonded with an adhesive 504.

  In the above description, the linear expansion coefficient of the imaging chip and the optical element is not particularly mentioned. However, glass having a linear expansion coefficient substantially the same as the linear expansion coefficient of the imaging chip may be used as the optical element. By using a cover glass having a linear expansion coefficient substantially the same as the linear expansion coefficient of the imaging chip, it is possible to suppress warping of the imaging element.

  Further, as the optical element, a cover glass that has been subjected to processing for suppressing α-ray emission can also be used. The processing for suppressing α-ray emission applied to the cover glass is realized by removing uranium and thorium in the cover glass. For example, when the α-ray emission amount of the cover glass is 0.01 count / (cm · hr) or less and the thickness is 20 μm or more, the emission of α-rays can be effectively suppressed. Therefore, by using a cover glass that has been subjected to processing for suppressing α-ray emission, occurrence of pixel defects due to the influence of α-rays can be suppressed.

  The linear expansion coefficient of the cover glass that has been subjected to the processing for suppressing the emission of α-rays may be different from the linear expansion coefficient of the imaging chip. Therefore, when a cover glass that has been subjected to processing for suppressing α-ray emission is employed, an elastic adhesive may be used as the adhesive layer. Examples of the elastic adhesive include acrylic resins, silicone resins, and epoxy resins. By using an elastic adhesive as the adhesive layer, it is possible to reduce stress applied to the imaging chip 100 due to warpage caused by a difference in linear expansion coefficient between the cover glass and the imaging chip. Accordingly, it is possible to suppress warping of the image sensor. When the imaging surface of the image sensor is warped, the image is distorted and the image quality is deteriorated.However, in this embodiment, since the warp of the imaging surface of the image sensor is suppressed, good imaging can be realized, and the image quality is improved. Deterioration can be prevented.

  In the above description, the optical element is fixed to the imaging chip via the adhesive layer, but the optical element may be fixed to the imaging chip via a spacer. When the optical element is fixed via the spacer, it is preferable that the spacer has an annular shape so as to surround the optical element as in the case where the optical element is fixed via the adhesive layer. Accordingly, the optical element can seal the imaging region while being separated from the imaging chip by the thickness of the spacer. The spacer preferably has elasticity. When the spacer has elasticity, it is possible to absorb the stress caused by the difference in the linear expansion coefficient between the optical element and the imaging chip, as in the case where the elastic adhesive is used. The elastic spacer can be formed by, for example, a rubber member.

  In the above description, two signal processing chips are fixed to the imaging chip. However, the number of signal processing chips is not limited to two, and may be one. Three or more signal processing chips may be fixed. When three or more signal processing chips are fixed, the signal processing chips can be fixed to the outer edge portion of the side orthogonal to the first side 102 of the imaging region 101.

  In the above description, the imaging chip 100 and the imaging region 101 have been described as having a rectangular shape, but other shapes may be used. For example, the shapes of the imaging chip 100 and the imaging region 101 may be square. In addition, although the fixing plate 700 and the opening 701 have been described as rectangular, other shapes may be used as long as the signal processing chip 300 can be fixed and an area corresponding to the imaging area is opened. . For example, the fixed plate 700 and the opening 701 may be square.

  As mentioned above, although this invention was demonstrated using embodiment, the technical scope of this invention is not limited to the range as described in the said embodiment. It will be apparent to those skilled in the art that various modifications or improvements can be added to the above-described embodiment. It is apparent from the scope of the claims that the embodiments added with such changes or improvements can be included in the technical scope of the present invention.

  Although the steps of the manufacturing process in the claims, the description, and the drawings are described using “first”, “next”, etc. for convenience, it is essential to carry out in this order. Does not mean.

DESCRIPTION OF SYMBOLS 10 Image sensor, 20 Image sensor, 100 Image pick-up chip, 101 Image pick-up area, 102 1st edge | side, 103 2nd edge | side, 104 Electrode pad, 105 Electrode pad, 110 Wafer, 200 Optical element, 210 Adhesive material layer, 300 Signal processing chip , 310 First signal processing chip, 320 Second signal processing chip, 400 Adhesive layer, 501 Adhesive, 502 Adhesive, 503 Adhesive, 504 Adhesive, 601 Bump, 602 Bump, 603 Bump, 604 Bump, 700 Fixed plate , 701 Opening, 702 First edge, 703 First peripheral edge, 704 Second edge, 705 Second peripheral edge, 810 Flexible substrate, 820 Flexible substrate, 311 Electrode pad, 312 Electrode pad, 321 Electrode pad, 322 Electrode pad , 811 Electrode pad, 821 Very pad

Claims (10)

An imaging chip including an imaging region in which a plurality of pixels are arranged;
An optical element fixed to the imaging chip and sealing the imaging area;
A first signal processing chip that is fixed to the imaging chip and converts a pixel signal output from a pixel arranged in the imaging region into a digital signal;
A second signal processing chip that is fixed to the imaging chip and is arranged in the imaging area and that converts a pixel signal output from a pixel different from a pixel that outputs a pixel signal to the first signal processing chip into a digital signal; With
The optical element is disposed between the first signal processing chip and the second signal processing chip in the imaging chip,
The imaging chip, the first signal processing chip, and the second signal processing chip have a rectangular shape,
The imaging element in which the length of the short side of the imaging chip is the same as the length of the long side of the first signal processing chip and the second signal processing chip .   The imaging element according to claim 1, wherein the optical element is fixed to the imaging chip via an adhesive layer, and seals the imaging region while being separated from the imaging chip by the thickness of the adhesive layer.   The imaging element according to claim 1, wherein the optical element is fixed to the imaging chip via a spacer and seals the imaging region while being separated from the imaging chip by the thickness of the spacer.   The first signal processing chip is fixed to an outer edge portion of a first side of the imaging region having a rectangular shape, and the second signal processing chip is fixed to an outer edge portion of a second side facing the first side. The imaging device according to any one of claims 1 to 3.   5. The apparatus according to claim 1, further comprising: an opening that allows a subject image to be incident on the imaging region, and a fixing plate provided on the first signal processing chip and the second signal processing chip. Image sensor.   The imaging device according to claim 5, wherein the fixed plate conducts heat generated in the first signal processing chip and the second signal processing chip.   The image sensor according to claim 5 or 6, wherein a material of the fixing plate is metal or ceramic.   The image sensor according to any one of claims 5 to 7, wherein an area of the opening is larger than an area of the optical element. The first signal processing chip is connected to an external circuit through a first flexible substrate,
The imaging device according to claim 1, wherein the second signal processing chip is connected to an external circuit via a second flexible substrate. The first signal processing chip is disposed between the fixed plate and the first flexible substrate,
The imaging device according to claim 9, wherein the second signal processing chip is disposed between the fixed plate and the second flexible substrate.

Images