JP5369542B2 - Manufacturing method of solid-state imaging device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To solve the problem that reducing a manufacturing cost is difficult because centering between an imaging lens and an imaging element requires labor. <P>SOLUTION: A plurality of imaging elements (11) are formed on the surface of a semiconductor wafer (10). A resin (35) is arranged on each of imaging elements and then cured to form an imaging lens (35B) of resin. The semiconductor wafer in which imaging lenses are formed is divided into imaging chips where each of the imaging elements are integrated with the imaging lens formed thereon. <P>COPYRIGHT: (C)2010,JPO&amp;INPIT

Description

  The present invention relates to a method for manufacturing a solid-state imaging device in which an imaging semiconductor chip and an imaging lens are integrated.

  In a camera module using a solid-state imaging device such as a CMOS sensor or a CCD, light converged by an imaging lens is guided to an image receiving portion of an imaging chip. The imaging lens is fixed to the image receiving unit by mechanically supporting the lens barrel in front of the image receiving unit. Alternatively, the image receiving unit and the imaging lens are integrated by adhering the imaging lens to a surface of the filter provided on the image receiving unit opposite to the surface facing the image receiving unit (see Patent Document 1). .

Japanese Patent Laid-Open No. 9-130683

  In the structure that mechanically supports the lens barrel, focusing and centering are difficult due to variations in manufacturing of the lens barrel, variations in wearing accuracy, and the like. Because of this difficulty, it is difficult to reduce manufacturing costs.

  Even in the method of adhering the imaging lens to the filter on the image receiving unit, it is difficult to reduce the manufacturing cost because it takes time to center the imaging lens.

A method of manufacturing a fixed imaging device for solving the above-described problem includes a step of forming a plurality of imaging devices on a surface of a semiconductor wafer, and placing and curing a resin on each of the imaging devices, A step of forming a manufactured imaging lens, and a step of dividing the semiconductor wafer on which the imaging lens is formed into an imaging chip in which each of the imaging elements and the imaging lens formed thereon are integrated. And forming the imaging lens includes disposing a frame having an opening corresponding to the imaging element on the semiconductor wafer, and filling a resin in the opening of the frame. And a step of inserting a mold for making the surface of the resin into a convex lens shape into the opening and molding the resin.

  Since the imaging lens is fixed to the imaging element in a semiconductor wafer state before being separated into the imaging chip, it is not necessary to individually position the imaging lens with respect to the imaging element here. For this reason, it is possible to reduce the manufacturing cost.

  Examples 1 to 3 will be described with reference to the drawings.

  With reference to FIGS. 1A to 1H, a method of manufacturing a solid-state imaging device according to the first embodiment will be described.

  As shown in FIG. 1A, a plurality of imaging elements 11 are formed on the surface of a semiconductor wafer 10. The imaging elements 11 are arranged in a matrix on the surface of the semiconductor wafer 10. Each of the imaging elements 11 includes, for example, an image receiving unit such as a CMOS sensor or a CCD, and a peripheral circuit unit. The image receiving unit includes a plurality of pixels including a photodiode and a transistor. Each planar shape of the image sensor 11 is, for example, a square, and the arrangement period in the row direction and the column direction is 4 mm. A scribe region for separating the image sensor 11 into chips is secured between the image sensors 11 adjacent to each other.

  FIG. 1B shows a cross-sectional view of a part of one image sensor 11. A plurality of photodiodes 20 are formed on the surface of the semiconductor wafer 10. One photodiode 20 and three transistors constitute one pixel. Note that illustration of the transistor is omitted. A silicon oxide film 21 is formed on the photodiode 20 and the semiconductor wafer 10. A partial spherical depression is formed on the surface of the silicon oxide film 21 at a position corresponding to the photodiode 20.

  A silicon nitride film 22 is formed on the silicon oxide film 21. The surface of the silicon nitride film 22 is substantially flat. Due to the difference in refractive index between silicon oxide and silicon nitride, a depression formed on the surface of the silicon oxide film 21 acts as the microlens 23.

  As shown in FIG. 1C, the frame 30 is disposed on the semiconductor wafer 10. FIG. 1D is a plan sectional view taken along one-dot chain line 1D-1D in FIG. 1C. A cross-sectional view taken along one-dot chain line 1C-1C in FIG. 1D corresponds to FIG. 1C. The frame 30 has a square lattice-like planar shape along a scribe region secured between the image sensors 11 adjacent to each other. The frame 30 defines an opening 30c. The opening 30 c is disposed at a position corresponding to the image sensor 11 formed on the surface of the semiconductor wafer 10. Each planar shape of the opening 30c is, for example, a square having a side length of 3 mm, and the thickness of the frame 30 separating the openings 30c adjacent to each other is 1 mm. That is, the arrangement period of the openings 30 c in the row direction and the column direction is 4 mm, which is the same as the arrangement period of the image sensor 11. A groove 30d extending in the height direction is formed on one side surface of each opening 30c. The width and depth of the groove 30d are, for example, 0.2 mm.

  The main body 30a of the frame 30 is made of SUS or aluminum. A fluororesin coating is applied to the surface of the main body 30a. An elastic film 30b made of an elastic member is in close contact with the surface of the main body 30a facing the semiconductor wafer 10. The elastic film 30b is made of, for example, a silicone resin and has a thickness of, for example, 100 μm. By providing the elastic film 30b, it is possible to eliminate a gap at the contact portion between the frame 30 and the semiconductor wafer 10.

  As shown in FIG. 1E, a resin container 40 containing a resin 45 is disposed above the semiconductor wafer 10. The resin 45 is kept above the glass transition temperature. An injection port 41 is provided on the bottom surface of the resin container 40 at a position corresponding to the opening 30 c of the frame 30. A piston 42 is inserted into the resin container 40. The resin is injected from the injection port 41 by pressurizing the resin 45 in the resin container 40 with the piston 42. The resin 35 injected from the injection port 41 is filled in the opening 30c.

  As shown in FIG. 1F, a mold 48 is inserted into the opening 30c of the frame 30, and the resin 35 is molded. On the surface of the mold 48 that is in contact with the resin 35, a recess is provided for making the surface of the resin 35 into a convex lens shape. The temperature of the mold 48 is maintained equal to or higher than the glass transition temperature of the resin. By inserting the mold 48, the upper surface of the resin 35 is molded into a convex lens shape. Excess resin leaks to the outside through the groove 30d (FIG. 1D) provided in the frame 30.

  As shown in FIG. 1G, after the temperature of the resin 35 has decreased to the same level as the temperature of the mold 48, the mold 48 and the frame 30 are removed. An imaging lens 35 </ b> A formed by curing the resin remains on the imaging element 11 of the semiconductor wafer 10. On the side surface of the imaging lens 35A, a ridge-like protrusion 35B caused by the groove 30d is formed.

  As shown in FIG. 1H, the semiconductor wafer 10 is diced to be separated into an imaging chip in which the imaging element 11 and the imaging lens 35A are integrated.

As an example, ZEONEX (registered trademark) 480R manufactured by Nippon Zeon Co., Ltd. can be used as the resin for the imaging lens. When ZEONEX 480R is used, the temperature of the resin 45 in the resin container 40 shown in FIG. 1E is 270 ° C., and the pressure at the time of resin injection is 80 kgw / cm ² . The filling amount of the resin into one opening 30c is 25.2 mm ³ . Since the planar shape of the opening 30c is a square with a side length of 3 mm, the height of the filled resin 35 is 2.8 mm. The temperature of the mold 48 shown in FIG. 1F is 120 ° C. The cooling time is, for example, 480 seconds.

  The refractive index of ZEONEX 480R is 1.52. If the radius of curvature of the convex surface of the imaging lens 35A is 1 mm and the height from the image receiving surface to the top of the imaging lens 35A is 2.8 mm, the image receiving surface is focused.

  In the first embodiment, the imaging lens 35A is fixed to each of the imaging elements 11 in a wafer state before separating the solid-state imaging element into chips. Therefore, it is necessary to align the imaging lens for each imaging chip. There is no. Since the lens mounting process for each chip can be omitted, the manufacturing cost can be reduced. Further, the positional accuracy of the imaging lens 35 </ b> A depends on the alignment accuracy between the semiconductor wafer 10 and the mold 48. By increasing the alignment accuracy between the semiconductor wafer 10 and the mold 48, the positional deviation between the imaging lens 35A and the imaging element 11 can be within an allowable range.

  Since the imaging lens 35A is fixed to the imaging device 11 before the camera assembly process, it is possible to prevent contamination such as dust generated during the assembly process.

  In the first embodiment, the microlens 23 is disposed above the photodiode 20, but the microlens 23 is not necessarily disposed. In order to obtain a color image, a color filter may be disposed between the photodiode 20 and the imaging lens 35A. It is preferable to use a material that does not deform, melt, or the like at the heat treatment temperature when forming the imaging lens 35A for the color filter.

  In Example 1, a thermoplastic resin is used as the imaging lens resin, but a thermosetting resin may be used. When using a thermosetting resin, the injected resin 35 is cured by heating the mold 48.

  With reference to FIG. 2A-FIG. 2C, the manufacturing method of the solid-state image sensor by Example 2 is demonstrated.

  The semiconductor wafer 10 and the image sensor 11 shown in FIG. 2A are the same as those of the first embodiment shown in FIG. 1A. A resin container 40 is disposed above the semiconductor wafer 10. The frame 30 used in the process shown in FIG. 1E of Example 1 is not used in Example 2. Resin is dropped onto the image pickup device 11 of the semiconductor wafer 10 from the injection port 41 of the resin container 40. The dropped resin 35 has a convex lens shape on the image sensor 11 due to its surface tension. If the resins dropped on the image sensors 11 adjacent to each other are continuous, a beautiful convex lens shape is not obtained. For this reason, it is preferable that the amount of resin to be dropped is such that the resins dropped on the imaging elements 11 adjacent to each other are not continuous.

  As shown in FIG. 2B, the resin 35 is cooled and hardened to form a resin imaging lens 35A.

  As shown in FIG. 2C, the semiconductor wafer 10 is separated into chips in which the imaging element 11 and the imaging lens 35A are integrated.

  In the second embodiment, the radius of curvature of the imaging lens 35A depends on the viscosity of the resin, the dripping amount of the resin, and the like. When the arrangement period of the imaging lens 35A to be formed, the viscosity of the resin, the dropping amount, etc. on the surface of the semiconductor wafer 10 satisfy the condition that the resins on the imaging elements 11 adjacent to each other do not continue, the method according to the second embodiment Can be adopted.

  Also in Example 2, a color filter may be arranged in the same manner as in Example 1, or a thermosetting resin may be used for the imaging lens.

  With reference to FIG. 3A-FIG. 3D, the manufacturing method of the solid-state image sensor by Example 3 is demonstrated.

  As shown in FIG. 3A, the image sensor 11 is formed on the surface of the semiconductor wafer 10. A resin microlens array 60 is formed on the surface of the image sensor 11.

  FIG. 3B shows an enlarged cross-sectional view of the imaging device 11 and the microlens array 60. The image sensor 11 includes a plurality of photodiodes 20. A silicon oxide film 21 is formed on the photodiode 20 and the semiconductor wafer 10. A microlens array 60 is formed on the surface of the silicon oxide film 21. The microlens array 60 includes a plurality of resin microlenses 61 arranged corresponding to the photodiodes 20. The micro lens 61 condenses incident light at the position of the photodiode 20. The silicon oxide film 21 is exposed in the region where the microlens array 60 is not formed.

  The microlens array 60 is formed, for example, by spin-coating a thermoplastic resin, patterning, and then performing a heat treatment.

  As shown in FIG. 3C, the resin container 40 is disposed above the semiconductor wafer 10, and the resin is dropped on the microlens array 60. The dropped resin 35 has a convex lens shape due to its surface tension. Since the wettability of the resin-made microlens array 60 is higher than the wettability of the surface where the surrounding inorganic material is exposed, the resin 35 is positioned on the microlens array 60 in a self-aligning manner. In addition, the resins dropped on the image sensors 11 adjacent to each other are difficult to continue.

  As shown in FIG. 3D, the imaging lens 35A is formed by cooling and curing the resin 35. Thereafter, as in the case of the first and second embodiments, the semiconductor wafer 10 is separated into chips of the solid-state imaging device.

  In order for the micro lens 61 to act as a convex lens, it is necessary to select materials for the micro lens 61 and the imaging lens 35A so that the refractive index of the micro lens 61 is larger than the refractive index of the imaging lens 35A.

  In Example 3, since the dropped resin 35 is positioned on the microlens array 60 in a self-aligning manner, positioning accuracy can be improved. Instead of the microlens array 60, a film made of a material having a wettability higher than the wettability of the surrounding surface with respect to the resin may be disposed on the imaging element 11. For example, a resin film may be disposed only on the imaging element 11 on the surface where the inorganic material is exposed. In this case, the effect of the micro lens cannot be obtained, but the effect that the imaging lens can be arranged in a self-aligning manner can be obtained.

  In Example 3, a color filter may be disposed in the same manner as in Example 1, or a thermosetting resin may be used for the imaging lens.

  Although the present invention has been described with reference to the embodiments, the present invention is not limited thereto. It will be apparent to those skilled in the art that various modifications, improvements, combinations, and the like can be made.

(1A) is a cross-sectional view of a wafer in the middle of manufacturing of the method for manufacturing a solid-state imaging device according to Example 1, and (1B) is an enlarged cross-sectional view thereof. (1C) is a cross-sectional view of the wafer and the frame in the middle of manufacturing of the method for manufacturing the solid-state imaging device according to Example 1, and (1D) is a plan cross-sectional view of the frame. (1E) is a cross-sectional view of a wafer, a frame, and a resin container in the course of manufacturing of the solid-state imaging device manufacturing method according to the first embodiment. (1F) and (1G) are cross-sectional views of a wafer and a frame in the middle of manufacturing of the method for manufacturing a solid-state imaging device according to Example 1, and (1H) is a view of the device after separating the solid-state imaging device into chips. It is sectional drawing. (2A) is a cross-sectional view of a wafer and a resin container in the course of manufacturing of the method for manufacturing a solid-state imaging device according to Example 2, (2B) is a cross-sectional view of the element after resin curing, and (2C) is FIG. 3 is a cross-sectional view of the element after separation into chips. (3A) is a cross-sectional view of a wafer in the middle of manufacturing of the method for manufacturing a solid-state imaging device according to Example 3, and (3B) is an enlarged cross-sectional view thereof. (3C) is a cross-sectional view of the wafer and the resin container in the course of manufacturing of the method for manufacturing the solid-state imaging device according to Example 3, and (3D) is a cross-sectional view of the element after resin curing.

Explanation of symbols

DESCRIPTION OF SYMBOLS 10 Semiconductor wafer 11 Image pick-up element 20 Photodiode 21 Silicon oxide film 22 Silicon nitride film 23 Micro lens 30 Frame 35 Resin 35A Imaging lens 35B Ridge-like projection 40 Resin container 41 Outlet 42 Piston 45 Resin 48 Mold 60 Micro lens array 61 Micro lens

Claims (2)

Forming a plurality of image sensors on the surface of the semiconductor wafer;
A step of forming a resin imaging lens by disposing and curing a resin on each of the imaging elements;
Dividing the semiconductor wafer on which the imaging lens is formed into an imaging chip in which each of the imaging elements and the imaging lens formed thereon are integrated, and
Forming the imaging lens comprises:
Placing a frame having an opening corresponding to the imaging element on the semiconductor wafer;
Filling the resin into the opening of the frame;
Inserting a mold into the opening to form a convex lens on the surface of the resin, and molding the resin;
A method for manufacturing a solid-state imaging device including : Forming a plurality of image sensors on the surface of the semiconductor wafer;
A step of forming a resin imaging lens by disposing and curing a resin on each of the imaging elements;
Dividing the semiconductor wafer on which the imaging lens is formed into an imaging chip in which each of the imaging elements and the imaging lens formed thereon are integrated, and
Forming the imaging lens comprises:
A resin having fluidity is dropped on the image sensor so that the resins dropped on adjacent image sensors do not continue to each other, and the surface of the dropped resin is caused by the surface tension of the resin. Including a step of convexing,
Before dropping the resin having fluidity, a resinous microlens corresponding to the pixel of the image sensor is formed on each surface of the image sensor, and between the image sensors adjacent to each other, A method for manufacturing a solid-state imaging device in which an inorganic material is exposed.

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