JP2008298872A - Method for manufacturing optical device and optical device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a method for manufacturing an optical device where peripheral-darkening can be effectively corrected at a low cost, and to provide the optical device. <P>SOLUTION: A first flattened layer 28 is formed on a semiconductor substrate 21, and the surface thereof is flattened, thereafter, a flare prevention film 32 is formed on the surface of the first flattened layer 28, in a position located above a wiring layer 24. A color filter 29 is formed above the first flatted layer 28. In this case, the color filter 29 is formed so as to interpose a gap between the color filter 29 and the flare prevention film 32. The surface of the color filter 29 is flattened by chemical mechanical polishing. Since the gap is formed between the color filter 29 and the flare prevention film 32, the thickness of the peripheral part 34 of the color filter 29 becomes thinner than that of the center part 33. At the final process, microlenses 31 are formed above the color filter 29 through the second flattened layer 30. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to an optical element manufacturing method capable of effectively correcting peripheral light reduction, and an optical element.

  As an optical element in which a plurality of pixels are arranged, for example, a solid-state imaging element such as a CCD image sensor or an LCOS (reflection type liquid crystal element) is known. An imaging lens is used in an imaging device that uses such an optical element. However, when the aperture of the imaging lens is opened to the open side, the amount of light in the peripheral portion decreases with respect to the central portion of the lens due to a decrease in aperture efficiency, and the There is a problem of so-called peripheral dimming in which the amount of incident light on the pixels in the peripheral part of the arrangement surface decreases.

Conventionally, various proposals have been made to correct peripheral dimming (see, for example, Patent Document 1). In the method described in Patent Document 1, the area of the peripheral pixel is made larger than that of the central portion, thereby increasing the amount of incident light on the peripheral pixels and obtaining a uniform output between the central portion and the peripheral portion. Yes. In addition to this method, among the microlenses that focus the light on the pixel, the microlens arranged at the periphery is shifted to the center of the array surface with respect to the center of the pixel. Has been proposed.
Japanese Unexamined Patent Publication No. 07-143411

  In the method described in Patent Document 1, in order to change the area of the peripheral pixel, it is necessary to prepare a dedicated mask when forming the pixel, and there is a problem that the manufacturing cost increases. Further, the size of the array surface is increased by increasing the area of the peripheral pixel. Alternatively, if the number of pixels is reduced while the size of the array surface remains the same, the resolution is lowered. In the method of disposing the micro lenses by shifting, it is necessary to prepare a dedicated mask as in the method described in Patent Document 1, and there is still a difficulty in terms of manufacturing cost.

  By the way, it is possible to correct the peripheral dimming by making the color filter arranged on the array surface where the pixels are arrayed thinner in the peripheral portion than in the central portion of the array surface. It is considered possible. However, in the conventional semiconductor substrate manufacturing process, as shown in FIG. 6A, the color filter 103 is formed on the semiconductor substrate 102 so as to be surrounded by the anti-flare film 101 without providing a gap between the anti-flare film 101. Form. Then, chemical mechanical polishing is performed to flatten the flare prevention film 101 and the color filter 103 as shown in FIG. For this reason, it is not easy to make the thickness of the color filter 103 different between the central portion and the peripheral portion.

  The present invention has been made in view of the above problems, and an object of the present invention is to provide an optical element manufacturing method and an optical element that can perform effective peripheral dimming correction at low cost.

  In order to achieve the above object, an optical element manufacturing method according to the present invention is an optical element manufacturing method in which a color filter is provided on an array surface on which a plurality of pixels are arrayed. In comparison, a color filter forming step of forming a color filter so that the thickness of the peripheral portion is reduced is provided.

  In the color filter forming step, it is preferable to perform chemical mechanical polishing on the color filter.

  Further, it is preferable to provide an appropriate gap for controlling the thickness of the peripheral portion of the color filter between the chemical mechanical polishing stopper film and the color filter.

  In addition, it is preferable to form a gap with a width of 1/3 or more and 3 or less of the pixel.

  Further, the stopper film is preferably a flare prevention film that prevents the occurrence of flare, and specifically, is preferably a light shielding film that shields the wiring provided around the arrangement surface.

  The stopper film is preferably a blue filter constituting a color filter.

  The optical element is preferably a solid-state imaging element that photoelectrically converts light incident on the pixel and outputs an imaging signal.

  The optical element of the present invention is an optical element in which a color filter is provided on an arrangement surface on which a plurality of pixels are arranged, and the color filter has a thickness at a peripheral portion as compared with a central portion of the arrangement surface. Is thin.

  According to the method for manufacturing an optical element and the optical element of the present invention, the thickness of the color filter is made thinner compared to the center of the pixel array surface, so that effective peripheral light attenuation correction can be performed. It can be done inexpensively.

  As shown in FIG. 1, the solid-state imaging device 11 is an interline transfer type CCD image sensor, and is arranged in a matrix (two-dimensional matrix) at a predetermined pitch in the vertical (V) direction and the horizontal (H) direction. A plurality of photodiodes (light receiving elements) 12, a vertical CCD (VCCD) 13 provided for each vertical column of photodiodes 12, and a read transfer gate (TG) provided between the photodiodes 12 and VCCD 13. 14, a horizontal CCD (HCCD) 15 to which the final stage of each VCCD 13 is connected in common, an output gate (OG) 16 and a floating diffusion (FD) 17 provided adjacent to the final stage of the HCCD 15, and an FD 17 The source follower type amplifier circuit 18 is connected.

The photodiode 12 receives and photoelectrically converts light incident through the microlens 31 (see FIG. 2), and generates and accumulates signal charges corresponding to the amount of incident light. The TG 14 transfers the signal charge accumulated in the photodiode 12 to the VCCD 13. The VCCD 13 receives the signal charge transferred from the photodiode 12 via the TG 14 and transfers the received signal charge toward the HCCD 15 in the vertical direction line by line. The HCCD 15 receives the signal charges output from the last stage of the VCCD 13 one row at a time, and horizontally transfers the signal charges toward the OG 16 every time one row of signal charges is received. The OG 16 transfers the signal charges sent from the HCCD 15 to the FD 17 in order for each pixel. The FD 17 converts the signal charge transferred from the OG 16 into a voltage signal. The amplifier circuit 18 amplifies the voltage signal generated by the FD 17 and outputs it as an imaging signal _Vout .

In FIG. 2, which shows a cross section taken along line II-II in FIG. 1, the photodiode 12, VCCD 13, and TG 14 are provided in the semiconductor substrate 21. A transfer electrode 23 is formed on the VCCD 13 via an insulating film 22. A voltage for controlling the vertical transfer by the VCCD 13 and the read transfer of the signal charge by the TG 14 is applied to the transfer electrode 23. The insulating film 22 is made of SiO ₂ (silicon dioxide) formed by, for example, a thermal oxidation method or a CVD (Chemical Vapor Deposition) method. The transfer electrode 23 is made of polysilicon formed by, for example, a CVD method.

On the semiconductor substrate 21, a light shielding film 25, an insulating layer 26, a lens layer 27, a first planarizing layer 28, a color filter 29, a second planarizing layer 30, a microlens 31, and flare prevention. A film 32 is formed. The light shielding film 25 is made of a refractory metal such as tungsten formed by sputtering or the like, covers the transfer electrode 23 and shields it from light. The insulating layer 26 is made of a light-transmitting insulating material such as BPSG (boron phosphorus silicate glass) and covers the upper surfaces of the insulating film 22 and the light shielding film 25. The lens layer 27 is made of P-SiN. The lens layer 27 is formed so as to cover the upper side of the insulating layer 26, and the portions respectively positioned above the photodiodes 12 have a convex lens shape in both the upper and lower directions. The first planarization layer 28 is made of, for example, P—SiO ₂ , P—SiN, an organic material, or the like. The surface of the first planarization layer 28 is planarized and has a light transmitting property. Although not shown, an insulating layer made of silicon oxide or the like is formed between the transfer electrode 23 and the light shielding film 25.

  The color filter 29 is formed on the surface of the first planarization layer 28. The color filter 29 is formed, for example, by applying and patterning a color resist material containing pigments corresponding to three colors (R, G, B) or four colors (Mg, G, Cy, Ye). Is done.

  After the color filter 29 is formed on the surface of the first planarization layer 28, the surface is planarized by chemical mechanical polishing. The thickness of the color filter 29 is thinner in the peripheral portion 34 than in the central portion 33 by chemical mechanical polishing. Accordingly, the light transmittance of the color filter 29 is larger in the peripheral portion 34 than in the central portion 33. As a result, the amount of light incident on the peripheral photodiode 12 is increased, and the peripheral dimming is corrected.

  The microlens 31 has a convex lens shape, and is formed on the color filter 29 subjected to chemical mechanical polishing via the second planarizing layer 30 so as to be positioned above each photodiode 12. Has been. The microlens 31 is arranged so that the optical axis passing through the center thereof passes through the center of the photodiode 12 and is perpendicular to the surface of the photodiode 12. The microlens 31 has a curvature that efficiently collects incident light parallel to the optical axis toward the photodiode 12. Note that one pixel 36 is configured by one photodiode 12, the color filter 29, and the microlens 31. In the following description, the surface of the solid-state imaging device 11 on which the pixels 36 are arranged is referred to as an arrangement surface 37.

  A wiring layer 24 is provided on the insulating layer 26 around the arrangement surface 37 (where the pixels 36 are not provided). The wiring layer 24 is made of a metal such as aluminum, for example, and is connected to a bonding pad (not shown) to which the transfer electrode 23 and bonding wires that connect the solid-state imaging device 11 and the external control circuit are connected.

  The flare prevention film 32 is formed on the surface of the first planarization layer 28 so as to be positioned above the wiring layer 24. The flare prevention film 32 is made of a light shielding material having a visible light absorbing group, for example. The flare prevention film 32 prevents incident light from being reflected by the wiring layer 24 and entering the photodiode 12 to cause flare or ghost. A second planarization layer 30 is formed above the anti-flare film 32 and the surface thereof is planarized.

Between the color filter 29 and the flare preventing film 32, the gap d _a is provided. Since the color filter 29 in the peripheral portion 34 is provided with _a gap da, when the chemical mechanical polishing is performed, the color filter 29 is overpolished more than the central portion 33 and is slightly thinner than the central portion 33. The thickness d _b of the color filter 29 in the peripheral portion 34 is set to such a value that the optimal peripheral light attenuation can be corrected by controlling various conditions such as the gap d _a and the polishing time of chemical mechanical polishing. Become. Note that the end portion of the flare prevention film 32 facing the peripheral portion 34 is slightly thinner than the other portions, like the color filter 29 of the peripheral portion 34.

The gap da has _a width of 1/3 or more and 3 or less of the pixel 36. The gap d _a is defined in this way. If the gap d _a is less than 1/3 the width of the pixel 36, the color filter 29 can be flattened, but the thickness d _b cannot be controlled. possible and will, when the gap d _a is the width of more than three pixels 36, too small thickness d _b progressed excessively polished, the color balance of the color filter 29 of the central portion 33 and peripheral portion 34 pixels It is because it collapses to the extent that it affects.

  Hereinafter, the manufacturing process of the solid-state imaging device 11 of the above embodiment will be described with reference to the flowchart of FIG. 3 and FIGS. 4 and 5. The structure below the first planarization layer 28 is formed by a well-known semiconductor device manufacturing process, and a description thereof is omitted here.

  After the first planarization layer 28 is formed and the surface is planarized, as shown in FIG. 4A, flare prevention is provided at a position on the surface of the first planarization layer 28 and above the wiring layer 24. A film 32 is formed. In addition, when forming a flare prevention film with a blue filter, you may carry out simultaneously with the process of forming the blue filter of a pixel part.

  Next, as illustrated in FIG. 4B, the color filter 29 is formed on the first planarization layer 28. At this time, the color filter 29 is formed so that a gap is formed between the anti-flare film 32. The color filter 29 is formed by a known color filter manufacturing method (for example, JP-A-2006-319133).

  Next, the surface of the color filter 29 is flattened by chemical mechanical polishing as shown in FIG. At this time, since a gap is provided between the color filter 29 and the flare prevention film 32, the thickness of the color filter 29 is thinner in the peripheral portion 34 than in the central portion 33.

  Then, a second planarization layer 30 is formed on the color filter 29 and the flare prevention film 32 and planarized. Thereafter, the microlens 31 is formed on the color filter 29. The microlens 31 is formed so as to be positioned above each photodiode 12 by a known microlens manufacturing process. Through the steps as described above, the solid-state imaging device 11 shown in FIG. 2 is completed.

  As described above, in the present embodiment, the thickness of the color filter 29 can be made thinner than the central portion 33 by the chemical mechanical polishing, and the peripheral portion 34 can be made thinner. Thereby, it is possible to effectively correct the peripheral dimming.

  In addition, since chemical mechanical polishing that is generally performed in the manufacturing process of a conventional solid-state imaging device is used, the area of the peripheral pixel is changed or the microlens is shifted and arranged. Compared with the conventional method, manufacturing cost does not start.

Further, the gap d _a pixel 36 1/3 or more, because the 3 or less, it is possible to reliably obtain the effect of the correction of vignetting, color balance of the color filter 29 and does not affect the image quality Can be maintained. Further, since the flare prevention film 32 is also used as a stopper film for chemical mechanical polishing, it is not necessary to provide a dedicated stopper film, and the manufacturing cost can be further reduced.

  In addition, you may use the blue filter which comprises a color filter as a flare prevention film. Since the blue filter is made of a material having a relatively high visible light absorptance, it sufficiently fulfills the role of a flare prevention film. In this case, a blue filter is first formed on the entire surface of the planarization layer. Then, after patterning leaving a portion functioning as a flare prevention film and a portion functioning as a color filter, green and red filters are sequentially formed to complete the color filter. If it does in this way, a manufacturing process will be shortened and it can contribute to the further reduction of manufacturing cost.

  In the above-described embodiment, the solid-state imaging device 11 is described as an example of the optical element. However, the present invention is not limited to this, and for example, a display element such as LCOS (Liquid Crystal On Silicon) is also used. Applicable.

It is the schematic which shows the structure of a solid-state image sensor. It is sectional drawing which follows the II-II line | wire of the solid-state image sensor shown in FIG. It is a flowchart which shows the manufacturing process of a solid-state image sensor. It is explanatory drawing which shows the manufacturing process of a solid-state image sensor, (A) shows when a flare prevention film is formed on a planarization layer, (B) shows when a color filter is formed on a planarization layer, respectively. It is explanatory drawing which shows the manufacturing process of a solid-state image sensor, and shows the time of giving chemical mechanical polishing. It is explanatory drawing which shows the manufacturing process of the conventional solid-state image sensor, (A) shows the time of forming a color filter, (B) shows the time of performing chemical mechanical polishing, respectively.

Explanation of symbols

11 Solid-state imaging device (imaging device)
12 Photodiode (light receiving element)
29 Color filter 31 Micro lens 32 Anti-flare film 33 Center part 34 Peripheral part 36 Pixel 37 Array surface

Claims (9)

In the method of manufacturing an optical element in which a color filter is provided on an arrangement surface where a plurality of pixels are arranged,
A method of manufacturing an optical element, comprising: a color filter forming step of forming the color filter so that a thickness of a peripheral portion is thinner than a central portion of the arrangement surface.   2. The method of manufacturing an optical element according to claim 1, wherein the color filter is subjected to chemical mechanical polishing in the color filter forming step.   3. The method of manufacturing an optical element according to claim 2, wherein a gap is provided between the stopper film for the chemical mechanical polishing and the color filter.   4. The method of manufacturing an optical element according to claim 3, wherein the gap is formed with a width of 1/3 or more and 3 or less of the pixel.   5. The method of manufacturing an optical element according to claim 3, wherein the stopper film is a flare prevention film that prevents flare from occurring.   6. The method of manufacturing an optical element according to claim 3, wherein the stopper film is a light-shielding film that shields wiring provided around the arrangement surface.   The method for manufacturing an optical element according to claim 3, wherein the stopper film is a blue filter constituting the color filter.   The method of manufacturing an optical element according to claim 1, wherein the optical element is a solid-state imaging element that photoelectrically converts light incident on the pixel and outputs an imaging signal. In an optical element in which a color filter is provided on an arrangement surface where a plurality of pixels are arranged,
The optical element is characterized in that a peripheral portion of the color filter is thinner than a central portion of the arrangement surface.

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