JP2009176949A - Backside irradiation-type solid state image pickup device and its production process - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To reduce loss and color mixture of an incident light quantity in a backside irradiation-type solid state image pickup device. <P>SOLUTION: Two or more light receiving elements 12 are two-dimensionally arranged within a semiconductor substrate 11, and wiring layers 15 and electrode pads 16 are formed at a front surface 11b side of the semiconductor substrate 11. The semiconductor substrate 11 is made so laminar as to receive light from its backside surface 11a side. A light-shielding film 18 having an opening 18a at a right above region of each light receiving element 12 is prepared on the backside surface 11a side of the semiconductor substrate 11, and a color filter 19 is prepared within the openings 18a of the light-shielding film 18 and on the same plane as the light-shielding film 18. A supporting substrate 22 is pasted onto the front surface 11b side of the semiconductor substrate 11. The electrode pads 16 are partially exposed on the backside surface 11a side of the semiconductor substrate 11. Further, the upper surfaces of the light-shielding film 18 and the color filter 19 are on the same level through planarization. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to a backside illuminated solid-state imaging device that receives light from the backside where no wiring layer is formed, and a method for manufacturing the same.

  In an electronic camera such as a digital camera, a CCD (Charge Coupled Device) type or CMOS (Complementary Metal Oxide Semiconductor) type solid-state imaging device made of a semiconductor chip is used. These electronic cameras are required to be miniaturized as well as to have high functions. Along with this, in the solid-state imaging device, higher pixels and smaller pixels are being promoted. If the pixel is simply miniaturized, the amount of incident light (sensitivity) to the light receiving element in the pixel decreases, so the aperture ratio of each pixel (the ratio of the amount of incident light to the light receiving element to the amount of incident light to the pixel) is increased. This is an issue.

  Usually, a solid-state imaging device is configured to receive light incident from the surface side of a semiconductor substrate on which a wiring layer is formed by a light receiving element formed in the semiconductor substrate, and the incident light is blocked by the wiring layer. This is a factor that hinders improvement of the aperture ratio (that is, high sensitivity). Therefore, in recent years, it has been proposed to use a back-illuminated solid-state imaging device in order to achieve high sensitivity (see, for example, Patent Documents 1 and 2). The back-illuminated solid-state imaging device is configured so that a light receiving element receives light irradiated on the back side where a wiring layer is not formed by thinning a semiconductor substrate.

Also in such a back-illuminated solid-state imaging device, a light shielding film for opening an effective pixel region and shielding a dark pixel region (optical black region) for obtaining a black signal is formed. This light-shielding film is formed on the back side that is the light incident surface, a color filter is formed on the light-shielding film via an insulating film, and a microlens is formed on the color filter (see Patent Document 3). ).
Japanese Patent Laid-Open No. 9-82852 JP 2002-222936 A JP 2006-019653 A

  However, in the backside illumination type solid-state imaging device described in Patent Document 3, since the color filter is provided on the light-shielding film, the thickness from the light incident surface to the color filter is large. There is a concern that the amount of incident light is absorbed and a loss occurs. In addition, since the thickness from the light incident surface to the color filter is large, there is a concern that light obliquely incident on adjacent pixels may enter (that is, color mixing).

  The present invention has been made in view of the above problems, and an object of the present invention is to provide a back-illuminated solid-state imaging device that can reduce loss of incident light quantity and color mixing, and a method for manufacturing the same.

  In order to achieve the above object, in the backside illumination type solid-state imaging device of the present invention, a plurality of light receiving elements are two-dimensionally arranged in a semiconductor substrate, a wiring layer is formed on the surface side of the semiconductor substrate, In the backside illuminated solid-state imaging device in which the semiconductor substrate is thinned so as to receive light from the opposite backside, a light shielding film having an opening in the region directly above each light receiving element on the backside of the semiconductor substrate A color filter formed in the opening of the light-shielding film and on the same plane as the light-shielding film, a support substrate attached to the surface side of the semiconductor substrate, and a surface side of the semiconductor substrate. And a plurality of electrode pads partially exposed on the back side of the semiconductor substrate.

  The upper surfaces of the light shielding film and the color filter are preferably flush with each other.

  Moreover, it is preferable that the light shielding film is electrically connected to any one of the electrode pads by a through electrode penetrating the semiconductor substrate.

  Further, it is preferable that the support substrate is fixed on a package base, and the electrode pad and a lead terminal of the package base are connected via a wire.

  It is also preferable that a part of the electrode pads and the lead terminals are connected by flip-mounting peripheral circuit elements.

  According to another aspect of the present invention, there is provided a backside illumination type solid-state imaging device, comprising: preparing a semiconductor substrate in a wafer state; forming a light receiving element in the semiconductor substrate; and then providing a wiring layer and an electrode pad on the surface of the semiconductor substrate. A step of forming, a step of laminating a support substrate on the front side of the semiconductor substrate, polishing the back side of the semiconductor substrate to make a thin plate, and a light shielding film material layer made of a conductive material on the back side of the semiconductor substrate And forming a light shielding film having an opening in a region immediately above each light receiving element by patterning the light shielding film material layer, and a color filter forming material so as to fill the opening of the light shielding film And forming a color filter by patterning the applied forming material, polishing the surface of the color filter, and forming the color filter and the light shielding film A step of flattening the surfaces to be the same plane, a step of excavating a position directly above the electrode pad from the back side of the semiconductor substrate to partially expose the electrode pad, and an element region as a solid-state imaging device And cutting the semiconductor substrate and the support substrate into individual pieces.

  According to the present invention, since the light shielding film and the color filter are formed on the same plane and the thickness from the light incident surface to the color filter is reduced, it is possible to reduce the loss of incident light quantity and color mixing.

  In FIG. 1, a back-illuminated solid-state imaging device 10 according to the present invention is formed on the basis of a semiconductor substrate (silicon substrate) 11, and light receiving elements 12 made of photodiodes are arranged at a pitch of several μm in the semiconductor substrate 11. Two-dimensional array. The semiconductor substrate 11 is thinned to a thickness of 30 μm or less (preferably about 10 μm) so that light can be incident from the back surface 11a side. The light receiving element 12 generates and accumulates signal charges by photoelectrically converting incident light.

  On the front surface 11 b side of the semiconductor substrate 11, signal charges accumulated in the light receiving element 12 are transferred to a charge transfer path (when the backside illumination type solid-state imaging device 10 is a CCD type) or an amplifier (the backside illumination type solid-state imaging device 10 is a CMOS type). A transfer electrode (gate electrode) 13 is provided. The transfer electrode 13 is made of polysilicon or the like, and its periphery is covered with a protective insulating film 14 made of silicon oxide or the like. A wiring layer 15 made of aluminum or the like and an electrode pad 16 made of the same material as the wiring layer 15 are formed on the surface layer of the protective insulating film 14.

  On the other hand, on the back surface 11 a side of the semiconductor substrate 11, a light shielding film 18 having an opening 18 a is formed in a region immediately above the light receiving element 12 via an insulating film 17 made of silicon oxide or the like. A color filter 19 for separating incident light is formed in the portion 18a. That is, the light shielding film 18 and the color filter 19 are formed on the same plane. The light shielding film 18 is made of, for example, aluminum, and the color filter 19 is made of, for example, a pigment dispersion type color resist in which a pigment is dispersed in a photoresist material. Further, the upper surfaces of the light shielding film 18 and the color filter 19 are flush with each other by planarization, and an insulating film 20 for protecting the surface is formed thereon.

  A through electrode 21 is formed so as to penetrate from the back surface 11 a side to the front surface 11 b side of the semiconductor substrate 11, and the through electrode 21 connects the light shielding film 18 to one electrode pad 16. And the support substrate 22 is affixed on the surface of the protective insulating film 14 in which the wiring layer 15 and the electrode pad 16 were formed.

  The electrode pad 16 is provided at the peripheral portion, and the protective insulating film 14, the semiconductor substrate 11, the insulating film 17, the light shielding film 18, and the insulating film 20 stacked directly thereon are partially exposed so as to be exposed to the light incident side. Has been removed.

  The support substrate 22 is made of, for example, the same silicon as the semiconductor substrate 11 in order to prevent the occurrence of warping due to the difference in thermal expansion coefficient with the semiconductor substrate 11.

  FIG. 2 is a plan view of the light shielding film 18 and the color filter 19. The light shielding film 18 shields light between pixels and shields a dark pixel region (optical black region) 23 for obtaining a black signal. The color filter 19 includes three color segments 19a to 19b having different spectral characteristics. The color segment 19a is a filter that allows red light to pass through, and is indicated with a symbol R. The color segment 19b is a filter that transmits green light, and is indicated by a reference symbol G. The color segment 19c is a filter that transmits blue light, and is denoted by reference numeral B. The arrangement of the color segments 19a to 19c is a so-called Bayer arrangement.

  In the back-illuminated solid-state imaging device 10 configured as described above, since the light shielding film 18 and the color filter 19 are formed in the same plane, the thickness from the light incident surface (back surface 11a) to the color filter 19 is large. Since it is small, the absorption rate of the incident light in the meantime decreases, and the loss of the incident light amount is reduced. This also reduces the incidence (that is, color mixing) of the light incident on the adjacent pixel (light that has passed through the color filter 19 of the adjacent pixel) and incident on the light receiving element 12.

  Since the back-illuminated solid-state imaging device 10 has the electrode pads 16 formed as described above, it can be mounted on the package substrate 30 by a normal wire bonding method as shown in FIG. The package base 30 has an open container shape with an open top, and is made of, for example, ceramic. A plurality of lead terminals 31 are formed on the side of the package base 30.

  The backside illumination type solid-state imaging device 10 is fixed via an adhesive layer 32 so that the support substrate 22 faces the bottom surface of the package base 30. The electrode pad 16 is connected to a portion (inner lead portion) exposed in the package base 30 of the lead terminal 31 via a wire 33. The upper opening of the package base 30 is sealed with a cover glass 34, and the periphery of the cover glass 34 is bonded to the upper end of the package base 30 with an adhesive layer 35.

  Thereby, since the light shielding film 18 is connected to any one of the lead terminals 31, it can be set to a constant potential such as a ground potential.

  Next, a manufacturing method of the backside illumination type solid-state imaging device 10 will be described with reference to manufacturing process diagrams shown in FIGS. First, a semiconductor substrate 11 in a wafer state is prepared, and a light receiving element 12 and the like are formed in the semiconductor substrate 11 by a well-known semiconductor wafer process technique, as shown in FIG. A transfer electrode 13 and a protective insulating film 14 covering the transfer electrode 13 are formed, and a wiring layer 15 and an electrode pad 16 are formed on the surface layer of the protective insulating film 14. The transfer electrode 13 is made of polysilicon, the protective insulating film 14 is made of silicon oxide, and the wiring layer 15 and the electrode pad 16 are made of aluminum. Note that a plurality of element regions as solid-state imaging devices are formed in a matrix on the semiconductor substrate 11.

  Next, as shown in FIG. 4B, the semiconductor substrate 11 is turned upside down, and the surface on which the wiring layer 15 and the electrode pad 16 are formed is bonded to a support substrate 22 made of silicon. With the semiconductor substrate 11 supported by the support substrate 22 in this way, the back surface 11a side of the semiconductor substrate 11 is polished by the back grinding method, and the semiconductor substrate 11 is thinned as shown in FIG. 4C. Thereby, the semiconductor substrate 11 is set to a thickness (30 μm or less (preferably about 10 μm)) that allows light to be incident on the light receiving element 12 from the back surface 11a side.

  Next, after depositing silicon oxide on the back surface 11a of the semiconductor substrate 11 by a CVD (Chemical Vapor Deposition) method to form an insulating film 17, as shown in FIG. A resist mask 40 having an opening in the region immediately above the electrode pad 16 is formed on the insulating film 17 by photolithography, and etching (anisotropic etching) is performed based on the resist mask 40 to thereby form the electrode pad from the back side. 16 is formed.

  Next, the resist mask 40 is removed, and the through-hole 41 is filled with a conductive material such as aluminum, thereby forming the through-electrode 21 as shown in FIG. 5B, and the insulating film 17 is formed on the insulating film 17 by sputtering. A light shielding film material layer 42 made of a conductive material such as aluminum is formed. At this time, the formed light shielding film material layer 42 is bonded to the through electrode 21.

  Next, as shown in FIG. 5C, a resist mask 43 having an opening in the color filter 19 formation region (a region immediately above the light receiving element 12) is formed on the light shielding film material layer 42 by photolithography. The light shielding film 18 is formed by etching (anisotropic etching) the light shielding film material layer 42 based on the resist mask 43.

  Next, the resist mask 43 is removed, and a photosensitive photoresist material 44 in which a green pigment is dispersed is applied by spin coating as shown in FIG. ), A color segment 19b that transmits green light is formed in the color filter 19 described above. Similarly, application of a photoresist material in which a pigment is dispersed and photolithography are repeated to form a color segment 19a that transmits red light and a color segment 19b that transmits blue light, as shown in FIG. 6C.

  At this time, since the thickness of each color segment 19a to 19c varies, the upper surface of the color filter 19 is then polished by CMP (Chemical Mechanical Polishing) as shown in FIG. And the light shielding film 18 are flattened so that they are flush with each other. At the time of polishing by this CMP method, the light shielding film 18 is used as a stopper to stop the polishing.

  Next, as shown in FIG. 7B, an insulating film 20 is formed so as to cover the upper surfaces of the light shielding film 18 and the color filter 19 by the CVD method. Then, the position immediately above the electrode pad 16 is excavated from the insulating film 20 side by etching or dicing, and an opening for partially exposing the electrode pad 16 is formed as shown in FIG. 7C.

  Thereafter, although not shown, the backside irradiation type solid-state imaging device shown in FIG. 1 is obtained by cutting the semiconductor substrate 11 and the support substrate 22 into individual pieces for each element region as a solid-state imaging device by a dicing method. 10 is completed.

  In the above embodiment, the color filter 19 is formed of a pigment dispersed color resist material having photosensitivity, but the present invention is not limited to this, and the color filter 19 is formed of a non-photosensitive resin film. It may be formed. In this case, a resist mask may be formed on the formed resin film by a photolithography technique, and the resin film may be patterned based on the resist mask.

  In the above embodiment, the color filter 19 is formed as a so-called Bayer array of RGB color segments 19a to 19c. However, the present invention is not limited to this, and the color segment arrangement method and each color segment are not limited thereto. The spectral characteristics may be changed as appropriate.

  Moreover, in the said embodiment, although the light shielding film 18 is formed with aluminum, this invention is not limited to this, You may form the light shielding film 18 with other metal materials, such as copper and tungsten. Furthermore, the light shielding film 18 may have a multilayer structure composed of a plurality of types of metal layers.

  Moreover, in the said embodiment, as shown in FIG. 3, although each electrode pad 16 of the backside illumination type solid-state imaging device 10 is connected to each lead terminal 31 of the package base | substrate 30 via the wire 33, this invention However, the present invention is not limited to this, and as shown in FIG. 8, the peripheral circuit element 50 may be connected by flip-chip mounting between some of the electrode pads 16 and the lead terminals 31. The peripheral circuit element 50 is a monolithic IC (semiconductor integrated circuit) element, and is a signal that performs signal processing of a drive circuit that drives the backside illumination type solid-state imaging device 10 and an imaging signal output from the backside illumination type solid-state imaging device 10. A processing circuit is built in. The flip-chip mounting of the peripheral circuit element 50 is performed between the electrode pad (not shown) of the peripheral circuit element 50 and the electrode pad 16 of the backside illumination type solid-state imaging device 10 and the electrode pad (not shown) of the peripheral circuit element 50. ) And the lead terminal 31 of the package base 30 are connected by solder balls 51, respectively.

  Further, in the above embodiment, the backside illumination type solid-state imaging device 10 is sealed by the open container-shaped package base 30 and the cover glass 34. However, the present invention is not limited to this, and the package base 30 is used. Instead, a cover glass may be attached to the back surface 11a side (on the insulating film 20) of the back-illuminated solid-state imaging device 10. The cover glass is preferably attached in a wafer state before the step of FIG.

  In the above embodiment, the microlens is not provided, but the present invention is not limited to this, and the microlens may be formed on the insulating film 20 so as to correspond to each light receiving element 12.

It is a longitudinal cross-sectional view of a back irradiation type solid-state imaging device. It is a top view which shows the structure of a color filter. It is a longitudinal cross-sectional view which shows the form which packages a back irradiation type solid-state imaging device. It is process drawing (the 1) which shows the manufacturing method of a back irradiation type solid-state imaging device. It is process drawing (the 2) which shows the manufacturing method of a back irradiation type solid-state imaging device. It is process drawing (the 3) which shows the manufacturing method of a back irradiation type solid-state imaging device. It is process drawing (the 4) which shows the manufacturing method of a back irradiation type solid-state imaging device. It is a longitudinal cross-sectional view which shows the 2nd form which packages a backside illumination type solid-state imaging device.

Explanation of symbols

DESCRIPTION OF SYMBOLS 10 Back-illuminated solid-state imaging device 11 Semiconductor substrate 12 Light receiving element 13 Transfer electrode 15 Wiring layer 16 Electrode pad 18 Light shielding film 19 Color filter 21 Through electrode 22 Support substrate 30 Package base 31 Lead terminal 33 Wire 34 Cover glass 40 Resist mask 42 Light shielding Film material layer 44 Resist material 50 Peripheral circuit element

Claims (6)

A plurality of light receiving elements are two-dimensionally arranged in the semiconductor substrate, a wiring layer is formed on the front surface side of the semiconductor substrate, and the semiconductor substrate is thinned so as to receive light from the back surface side opposite to the front surface side. In the backside illuminated solid-state imaging device,
A light shielding film having an opening in a region directly above each light receiving element on the back surface side of the semiconductor substrate;
A color filter formed in the opening of the light shielding film and on the same plane as the light shielding film;
A support substrate attached to the surface side of the semiconductor substrate;
A plurality of electrode pads formed on the front side of the semiconductor substrate and partially exposed on the back side of the semiconductor substrate;
A backside illumination type solid-state imaging device.   The backside illumination type solid-state imaging device according to claim 1, wherein the upper surfaces of the light shielding film and the color filter are flush with each other.   The back-illuminated solid-state imaging device according to claim 1, wherein the light shielding film is electrically connected to any one of the electrode pads by a through electrode penetrating the semiconductor substrate. .   4. The backside irradiation according to claim 1, wherein the support substrate is fixed on a package base, and the electrode pad and a lead terminal of the package base are connected via a wire. Type solid-state imaging device.   5. The backside illumination type solid-state imaging device according to claim 4, wherein a part of the electrode pads and the lead terminals are connected by flip-mounting a peripheral circuit element. 6. Preparing a semiconductor substrate in a wafer state, forming a light receiving element in the semiconductor substrate, and then forming a wiring layer and an electrode pad on the surface of the semiconductor substrate;
Bonding a support substrate to the front surface side of the semiconductor substrate, polishing the back surface side of the semiconductor substrate and thinning;
Forming a light-shielding film material layer made of a conductive material on the back side of the semiconductor substrate, and patterning the light-shielding film material layer to form a light-shielding film having an opening in a region immediately above each light-receiving element; ,
Applying a color filter forming material so as to fill the opening of the light shielding film, and patterning the applied forming material, thereby forming a color filter;
Polishing the surface of the color filter, and flattening the surface of the color filter and the light-shielding film to be in the same plane;
Excavating a position directly above the electrode pad from the back side of the semiconductor substrate, and partially exposing the electrode pad;
Cutting the semiconductor substrate and the support substrate into individual pieces for each element region as a solid-state imaging device; and
A method for manufacturing a backside illumination type solid-state imaging device.

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