JP2009081201A - Method of manufacturing backside irradiation type imaging device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide the method of manufacturing a backside irradiation type imaging device which has high connection reliability, which has less deterioration in sensitivity caused by signal delay, and which has a small package size having a small numbers of steps of extracting an electrode which is connected with an external device. <P>SOLUTION: A backside irradiation type imaging device which has high connection reliability, which has less deterioration in sensitivity caused by signal delay, and which has a small package size can be manufactured by the steps of forming a charge transfer portion such as an electrode pad 15 and a photodiode 14 on the front surface side of a semiconductor substrate 10, adhering a support substrate 17 to the front surface side of the semiconductor substrate 10 with a first adhesive 18, thinning the backside side of the semiconductor substrate 10 and forming an optical layer such as a color filter 20 and an AR layer 19 on the thinned backside side of the semiconductor substrate 10, adhering a protection substrate 22 to the backside side of the semiconductor substrate 10 with a second adhesive 23, and peeling the support substrate 17 off of the semiconductor substrate 10. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to a manufacturing method of a backside illumination type imaging device in which a solid-state imaging device is formed on a front surface side of a semiconductor substrate and light is incident from the back surface side of the semiconductor substrate.

  A solid-state imaging device used for an optical apparatus such as a digital still camera or a video camera generally transfers a solid-state imaging device such as a photodiode formed on the surface side of a semiconductor substrate and a charge generated by the solid-state imaging device. A transfer path, a transfer electrode, and a charge transfer unit such as a wiring. An optical layer such as a color filter, a microlens, and a light shielding film is formed above the solid-state image sensor. Incident light to the solid-state image sensor is irradiated to the solid-state image sensor via the microlens and the color filter, and the solid-state image sensor Converted. The charges generated in the solid-state imaging device by photoelectric conversion are transferred to the outside via the charge transfer unit.

  In recent years, in such a solid-state imaging device, a backside illumination type imaging device that photoelectrically converts light incident from the backside of a semiconductor substrate has been proposed in order to improve sensitivity (see, for example, Patent Document 1 and Patent Document 2). .

In the backside illumination type imaging device, after forming the solid-state imaging device and the charge transfer unit on the surface side of the semiconductor substrate, the support substrate is bonded to the surface side, and the back side is thinned by a method such as back grinding or etching, Light layers such as a light shielding film, a color filter, and a microlens are formed on the back side. In the semiconductor substrate on which the optical layer is formed, an electrode for connecting the charge transfer portion and the external device is formed, and a protective substrate is provided on the optical layer.
JP-A-6-326293 JP-A-2005-353631

  However, in the manufacturing method of the backside illumination type solid-state imaging device described in Patent Document 1, the support substrate remains adhered to the entire front surface side, and in order to form an electrode for connecting to an external device, Since it is necessary to provide an electrode extraction terminal as a charge transfer unit on the back side, the package size of the solid-state imaging device is increased. Also in the method of manufacturing the backside illumination type solid-state imaging device described in Patent Document 2, the package size is increased due to the connection by the bonding wire from the opening.

  Further, in Patent Document 1, a method of forming a through hole that leads to the electrode lead-out terminal with respect to the support substrate in order to reduce the package size can be considered, but in order to form a through hole with respect to a thick support substrate. In addition, the number of processes increases, the number of connection interfaces increases, connection reliability decreases, and there is a problem that sensitivity is lowered due to signal delay due to the capacitance of the through wiring.

  The present invention has been made for such a problem, and it is an object of the present invention to provide a method for manufacturing a backside illumination type solid-state imaging device with a small number of steps for extracting electrodes connected to an external device.

  In order to achieve the above-mentioned object, the present invention provides a method for manufacturing a backside illumination type imaging device in which a solid-state imaging device is formed on the front surface side of a semiconductor substrate, and light is incident on the solid-state imaging device from the back surface side of the semiconductor substrate. Forming a solid-state imaging device on the surface side of the semiconductor substrate and a charge transfer unit for transferring charges generated in the solid-state imaging device to an external device; and a surface of the semiconductor substrate on which the solid-state imaging device is formed Bonding a support substrate to the side with a first adhesive, and thinning the back side of the semiconductor substrate to which the support substrate is bonded, and forming a light layer on the back side of the thinned semiconductor substrate A step of bonding a protective substrate with a second adhesive to the back surface side of the semiconductor substrate on which the optical layer is formed by thinning the back surface, and from the semiconductor substrate to which the protective substrate is bonded Above It is characterized by having the steps of stripping a lifting board.

  According to the present invention, first, a solid-state imaging device such as a photodiode and a charge transfer portion such as a transfer path, a transfer electrode, and a wiring for transferring charges generated in the solid-state imaging device are formed on the surface side of the semiconductor substrate. Subsequently, a support substrate is bonded to the surface side of the semiconductor substrate on which the solid-state imaging element is formed by a first adhesive.

  At this time, in order to ensure the visibility of the alignment mark formed on the surface of the semiconductor substrate or to facilitate the peeling of the support substrate, the support substrate is formed with a light-transmitting material or a plurality of holes. Further, the support substrate is made of a material having a thermal expansion coefficient close to that of the semiconductor substrate. Specific examples of the support substrate material include silicon wafer, quartz glass, non-alkali glass, and borosilicate glass. In addition, as the first adhesive, a resist material or an adhesive having a self-peeling property whose adhesive strength is reduced by ultraviolet light, heat, or the like is used in order to easily peel the support substrate in a later step.

  Subsequently, the semiconductor substrate to which the support substrate is bonded is thinned on the back side by a method such as back grinding or etching, and a light layer such as a light-shielding film, a color filter, or a micro lens is formed on the thinned back side. It is formed. Subsequently, a protective substrate made of low α-ray glass or the like is bonded to the back surface side of the semiconductor substrate on which the optical layer is formed by the second adhesive.

  Subsequently, the support substrate is peeled from the semiconductor substrate to which the protective substrate is bonded. In peeling the support substrate, the adhesive force of the first adhesive is selectively reduced by immersing the support substrate side in a resist developer, irradiating the support substrate side with ultraviolet light, or heating the support substrate side. Is done. An electrode is formed on the front surface side of the semiconductor substrate from which the support substrate has been peeled off to form a backside illumination type solid-state imaging device.

  As a result, the support substrate is easily peeled off after the protective substrate is adhered, and it is possible to take out the electrode to be connected to the external device with a small number of steps, and the connection reliability is high, and the sensitivity is not lowered due to signal delay. It becomes possible to manufacture a small size back-illuminated solid-state imaging device.

  As described above, according to the manufacturing method of the backside illumination type imaging device of the present invention, it is possible to provide the manufacturing method of the backside illumination type solid-state imaging device with a small number of steps of taking out the electrode connected to the external device. .

  Hereinafter, preferred embodiments of a method for producing a solid-state imaging device according to the present invention will be described in detail with reference to the accompanying drawings.

  1 to 11 are cross-sectional views showing the steps of a method for manufacturing a backside illumination type imaging device according to the present invention. FIG. 1 is a cross-sectional view showing a cross-sectional structure of the semiconductor substrate 10 before the support substrate 17 is attached.

  First, in the method for manufacturing a backside illumination type imaging device according to the present invention, as shown in FIG. 1, a photodiode 14 which is a solid-state imaging device, an electrode pad 15, a transfer electrode (not shown), A step of forming a charge transfer section such as a path and a pixel separation layer is performed.

  In the present embodiment, an SOI (Silicon on Insulator) wafer including an SOI substrate 11, an SOI oxide film 12, and an SOI active layer 13 is used as the semiconductor substrate 10, and the SOI active layer 13 on the surface side of the semiconductor substrate 10 is used. A photodiode 14 and an electrode pad 15 for transferring charges to an external device are formed by a conventionally known method. A planarization layer 16 made of silicon nitride, silicon oxide or the like is formed on the photodiode 14 and the pad 15.

  Subsequently, as shown in FIG. 2, the support substrate 17 is bonded to the front surface side of the semiconductor substrate 10 on which the photodiode 14, the electrode pad 15, the planarization layer 16, and the like are formed on the front surface side, with the first adhesive 18. To do.

  When forming each element constituting an optical layer such as a color filter and a microlens on the back surface with reference to an alignment mark (not shown) formed on the front surface side of the semiconductor substrate 10 in a later step, the support substrate 17 is light transmissive. The visibility of the alignment mark is ensured by using a transparent material having a gap. As a method of ensuring the visibility of the alignment mark, a hole for recognizing the alignment mark may be provided in the support substrate 17 on the alignment mark.

  A specific material of the support substrate 17 is a material having a thermal expansion coefficient close to that of the semiconductor substrate 10, and silicon wafer, quartz glass, non-alkali glass, borosilicate glass, or the like is used.

  The support substrate 17 has not only a hole for recognizing the alignment mark, but also a hole for allowing the first adhesive 18 to penetrate into the first adhesive 18 in a later step. There may be multiple open.

  As the first adhesive 18, a resist material or a tape-shaped adhesive having a self-peeling property whose adhesive strength is reduced by ultraviolet light, heat, or the like is used. When the adhesive 18 is a resist material, it is applied onto the support substrate 17 by spin coating, and when it is an adhesive tape-like material, it is adhered to the support substrate 17 for use.

  The first adhesive 18 has an alkali resistance against KOH or the like and has a heat resistance of 150 ° C. or higher, desirably 220 ° C. or higher, and adheres the support substrate 17 and the semiconductor substrate 10. At this time, an object that can visually recognize the alignment mark formed on the surface side of the semiconductor substrate 10 is used.

  As the first adhesive 18, a resist material or an epoxy-based self-peeling adhesive can be preferably used.

  Bonding of the support substrate 17 and the semiconductor substrate 10 is performed by applying a pressure of 0.2 to 0.3 kg / cm 2 in a vacuum. After bonding, when the adhesive 18 is a resist material, resist baking is performed at a temperature of 100 to 200 ° C. for 1 to 3 minutes.

  Subsequently, the semiconductor substrate 10 is inverted and placed on the apparatus as shown in FIG. 3, and the back side of the semiconductor substrate 10 is placed on the SOI substrate 11 by a conventionally known technique such as back grinding or etching as shown in FIG. Is thinned.

  Subsequently, an optical layer made of an antireflection film, a color filter, or the like is formed on the back surface side of the thinned semiconductor substrate 10. For example, in the present embodiment, as shown in FIG. 5, the AR layer 19 is formed on the back surface side of the thinned semiconductor substrate 10 for the purpose of preventing the surface reflection of incident light as the optical layer.

  Subsequently, as shown in FIG. 6, a color filter 20 is formed as an optical layer on the AR layer 19. In forming the color filter 20, the color filter 20 having a desired shape is formed by repeatedly applying each color of the color filter 20, baking, and applying, baking, and developing the photoresist. After the color filter 20 is formed, a light shielding layer 21 is formed around the color filter 20 as shown in FIG.

  Next, as shown in FIG. 8, the protective substrate 22 is bonded to the back surface side of the semiconductor substrate 10 on which the elements constituting the optical layer are formed by a second adhesive 23. The protective substrate 22 is a light-transmitting plate-like member formed of low α-ray glass or the like, and an antireflection layer 24 that prevents reflection of incident light is formed on the surface.

  As the second adhesive, a light transmissive epoxy adhesive or the like can be suitably used.

  Subsequently, as shown in FIG. 9, the support substrate 17 is peeled from the semiconductor substrate 10 to which the protective substrate 22 is bonded. When the first adhesive 18 is a resist material, the support substrate 17 is peeled off by immersing the surface side of the semiconductor substrate 10 in a resist developer and allowing the resist developer to permeate through the holes formed in the support substrate 17. This is done by removing one adhesive 18. In addition, when using an adhesive whose adhesive strength is reduced by ultraviolet rays as the first adhesive 18, when ultraviolet light is irradiated from the support substrate 17 side and an adhesive whose adhesive strength is reduced by heat is used, By heating the surface side of the semiconductor substrate 10, the adhesive force of the adhesive is reduced and the support substrate 17 is peeled off. Thereby, the support substrate 17 can be easily peeled from the semiconductor substrate 10.

  The semiconductor substrate 10 from which the support substrate 17 has been peeled is then formed with a hole 25 in a part of the planarization layer 16 to expose the electrode pad 15 as shown in FIG. On each exposed electrode pad 15, as shown in FIG. 11, bumps 26 for connection to an external device are formed to form a backside illumination type imaging device.

  As described above, according to the manufacturing method of the backside illuminating type imaging device of the present invention, the support substrate can be easily peeled off after the protective substrate is bonded, and the electrode connected to the external device can be taken out with a small number of steps. It becomes.

  Furthermore, since the thick support substrate is peeled off from the semiconductor substrate surface side, the number of connection interfaces is reduced and the capacitance of the wiring does not increase, so the connection reliability is high and the sensitivity is reduced due to signal delay. Therefore, it is possible to manufacture a back-illuminated solid-state imaging device with a small package size.

Sectional drawing which showed the cross-section of the semiconductor substrate of the manufacturing method of the backside illumination type imaging device concerning this Embodiment. Sectional drawing of the state which adhere | attached the support substrate on the semiconductor substrate of the manufacturing method of a back irradiation type imaging device. Sectional drawing of the state which reversed the semiconductor substrate of the manufacturing method of a back irradiation type imaging device. Sectional drawing which showed the thin layer state of the back surface side of the manufacturing method of a back irradiation type imaging device. Sectional drawing of the state in which AR layer of the manufacturing method of the backside illumination type imaging device was formed. Sectional drawing of the state in which the color filter of the manufacturing method of a back irradiation type imaging device was formed. Sectional drawing of the state which formed the light shielding layer of the manufacturing method of a back irradiation type imaging device. Sectional drawing of the state which adhered the protective substrate of the manufacturing method of a back irradiation type imaging device. Sectional drawing of the state which peeled the support substrate of the manufacturing method of a back irradiation type imaging device. Sectional drawing of the state which formed the hole in the planarization layer of the manufacturing method of a back irradiation type imaging device. Sectional drawing of the state in which the bump of the manufacturing method of a back irradiation type imaging device was formed.

Explanation of symbols

DESCRIPTION OF SYMBOLS 10 ... Semiconductor substrate, 11 ... SOI substrate, 12 ... SOI oxide film, 13 ... SOI active layer, 14 ... Solid-state image sensor, 15 ... Electrode pad, 16 ... Planarization layer, 17 ... Support substrate, 18 ... 1st adhesion | attachment 19 ... AR layer, 20 ... color filter, 21 ... light shielding layer, 22 ... protective substrate, 23 ... second adhesive, 24 ... antireflection layer, 25 ... hole, 26 ... bump

Claims (6)

In the manufacturing method of the backside illumination type imaging device in which a solid-state imaging device is formed on the front surface side of the semiconductor substrate and light is incident on the solid-state imaging device from the back surface side of the semiconductor substrate.
Forming a solid-state image sensor on the surface side of the semiconductor substrate and a charge transfer unit for transferring charges generated in the solid-state image sensor to an external device;
Bonding a support substrate with a first adhesive to the surface side of the semiconductor substrate on which the solid-state imaging element is formed;
Thinning the back side of the semiconductor substrate to which the support substrate is bonded, and forming an optical layer on the back side of the thinned semiconductor substrate;
Bonding a protective substrate with a second adhesive to the back side of the semiconductor substrate on which the back surface is thinned and the optical layer is formed;
And a step of peeling the supporting substrate from the semiconductor substrate to which the protective substrate is bonded.   The method of manufacturing a backside illumination imaging apparatus according to claim 1, wherein the first adhesive is a resist material or a self-peeling adhesive.   The method for manufacturing a backside illumination imaging apparatus according to claim 1, wherein the support substrate is light transmissive.   The method for manufacturing a backside illumination type imaging device according to claim 1, wherein the support substrate has a plurality of holes formed therein.   5. The backside illuminated imaging according to claim 1, wherein the support substrate is one of a silicon wafer, quartz glass, non-alkali glass, or borosilicate glass. Device manufacturing method. The support substrate is peeled off by selectively reducing the adhesive force of the first adhesive using any one of ultraviolet light, heat, and a resist developer. 6. A method for manufacturing a backside illumination type imaging device according to any one of 3, 4, and 5.

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