JP2006210701A - Solid-state image sensing device and its manufacturing method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To solve the problem of generation of irregularities in the surface of an image sensor due to a thick IR transmitting filter laminated in an IR picture element in a solid-state image sensing element wherein R, G, B picture elements detecting RGB color factors and IR picture element detecting infrared light factor are disposed. <P>SOLUTION: After a transfer electrode and a wiring are formed on a semiconductor substrate 30, a flattened film 32 is formed. A recess 34 is formed by etching the flattened film 32 in a position corresponding to an IR picture element. A B filter 36 is buried in the recess 34 on the IR picture element, and an R filter 42 is further laminated. R, G, B filters are laminated on the R, G, B picture elements using the unetched flattened film 32 as a foundation. The height of the surface of a filter array formed in the RGB picture element and IR picture element becomes even by making the recess part 34 deep by one layer of a color filter. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a solid-state imaging device and a manufacturing method thereof, and more particularly to an on-chip color filter in a solid-state imaging device including a light receiving element having sensitivity in an infrared region.

  A solid-state imaging device (solid-state imaging device) such as a CCD (Charge Coupled Device) image sensor mounted on a video camera or a digital camera has a two-dimensionally arranged light receiving portion (light receiving device), and incident light is received by this light receiving portion. An electrical image signal is generated through photoelectric conversion. The light-receiving unit itself has sensitivity to the near-infrared region having a longer wavelength in addition to the entire visible light region having a wavelength of about 380 to 780 nm. Therefore, in order to acquire a color image, a plurality of types of color filters having different colors of transmitted light, that is, transmitted wavelength regions, are arranged on the light receiving surface. The color filter is laminated on the flattened film after forming a transparent flattened film on the light receiving surface. Further, a separate flattening film and protective film are laminated on the color filter.

  Color filters include primary color filter sets whose transmitted light is red (R), green (G), and blue (B), and complementary color systems that are cyan (Cy), magenta (Mg), and yellow (Ye). There is a filter set. These color filters are configured by, for example, coloring an organic material and transmit visible light of a corresponding color, but also transmit infrared light due to the material. For example, FIG. 5 is a graph showing the wavelength characteristics of the transmittance of each of the RGB filters, and the figure also shows the spectral sensitivity characteristics of the light receiving unit.

  Since the light receiving section is sensitive to infrared light, when an infrared light component is incident, signal charges are generated by the component, and correct color expression cannot be performed. Therefore, conventionally, an infrared cut filter is separately provided between the camera lens and the solid-state imaging device.

  The infrared cut filter cuts infrared light and attenuates visible light by about 10 to 20%. For this reason, there is a problem that the intensity of visible light incident on the light receiving portion is reduced, the S / N ratio of the output signal is lowered accordingly, and the image quality is deteriorated.

  As a countermeasure to this problem, while eliminating the infrared cut filter, a light receiving unit that basically detects only the infrared light component in the incident light is provided, and based on information on the infrared light component obtained from the light receiving unit. A method of performing signal processing for reproducing correct colors can be considered.

The light receiving unit that detects only the infrared light component can be realized by stacking a plurality of types of color filters that transmit visible light of different colors on the light receiving surface. In other words, the color filters stacked on each other prevent visible light from being transmitted by absorbing visible light components transmitted through one color filter with other color filters, while each color filter transmits infrared light components. , Selectively transmits infrared light.
Japanese Patent Application No. 2003-425708

  FIG. 6 is a schematic cross-sectional view of a conventional filter array of the imaging unit. When the light receiving unit 60 that detects each color component of the visible light and the light receiving unit 62 that detects the infrared light component are mixedly arranged in a mosaic shape, the light receiving unit 60 corresponding to the visible light component has an upper surface of the planarizing film 64. On the other hand, only one color filter 66 that transmits the color component is laminated. On the other hand, the light receiving unit 62 corresponding to the infrared light component has a plurality of layers of color filters 66 and 68 on the planarizing film 64. Are stacked. For this reason, there is a difference in the thickness of the filter laminated on the planarizing film 64 between the light receiving unit 62 that detects the infrared light component and the other light receiving unit 60 that detects the visible light component, and a structure is formed on the filter. There was a problem that could interfere with forming. For example, if the thickness of the flattening film 70 formed on the filter is reduced, it is difficult to ensure flatness. On the other hand, if it is attempted to ensure flatness, the film thickness increases.

  The present invention has been made to solve the above problem, and improves the flatness of the surface of the solid-state imaging device after the color filter is formed, and prevents the resolution from being lowered due to the refraction of light in the flattening film on the color filter. Another object of the present invention is to provide a solid-state imaging device that can easily form a microlens array that can be stacked on a color filter.

  The solid-state imaging device according to the present invention selectively includes a plurality of types of visible light component light receiving elements in which color filters that transmit different colors are stacked on a light receiving surface through transparent base layers, and an infrared light component selectively. Infrared light transmission filter that transmits light is arranged with an infrared light component light receiving element laminated on a light receiving surface through the underlayer, and the underlayer receives light of the infrared light component light receiving element. On the surface, the infrared light transmitting filter is formed thinner than the light receiving surface of the visible light component light receiving element, and the infrared light transmitting filter transmits a plurality of types of color filters that transmit infrared light among the color filters on the base layer. It is configured by stacking.

  A preferred aspect of the present invention includes, as the color filter, a red transmission filter that transmits a component corresponding to red, and a blue transmission filter that transmits a component corresponding to blue, and the infrared light transmission filter includes: It is a solid-state imaging device configured by laminating a red transmission filter and the blue transmission filter.

  The method for manufacturing a solid-state imaging device according to the present invention includes a plurality of types of visible light component light receiving elements in which color filters that transmit different colors are stacked on a light receiving surface, and red that selectively transmits infrared light components. In the method of manufacturing a solid-state imaging device in which an infrared light component light receiving element in which an external light transmission filter is laminated on a light receiving surface is arranged, the light reception of each visible light component light receiving element and the infrared light component light receiving element A step of forming a transparent base layer in common on the surface and an infrared light transmission filter forming step of forming the infrared light transmission filter, wherein the infrared light transmission filter formation step comprises An etching step of etching a ground layer to form a concave portion of the underlayer on the light receiving surface of the infrared light-receiving element; and at least one color filter that transmits infrared light among the color filters as a lower filter When A lower filter forming step of laminating in the recess, and an upper filter forming step of laminating on the lower filter using a color filter of the color filter that transmits infrared light and is different from the lower filter as the upper filter. And.

  Another method of manufacturing a solid-state imaging device according to the present invention is to selectively transmit infrared light components and a plurality of types of visible light component light receiving elements in which color filters that transmit different colors are stacked on the light receiving surface. In a method of manufacturing a solid-state imaging device in which an infrared light transmission filter is arranged with an infrared light component light receiving element laminated on a light receiving surface, the visible light component light receiving element and the infrared light component light receiving element Commonly on the light receiving surface, a step of forming a transparent base layer, and an infrared light transmission filter forming step of forming the infrared light transmission filter, the infrared light transmission filter formation step, A recess forming step of forming a recess of the base layer on the light receiving surface of the infrared light receiving element; and at least one type of color filter that transmits infrared light among the color filters as a lower filter. Under laminated A filter forming step, and an upper filter forming step of laminating on the lower filter a color filter of the color filter that transmits infrared light and is different from the lower filter as an upper filter. .

  According to a preferred aspect of the present invention, one of a red transmission filter that transmits a component corresponding to red and a blue transmission filter that transmits a component corresponding to blue is formed as the lower filter, and the other is formed as the upper filter. Manufacturing method.

  According to the present invention, the base layer of the color filter is formed so as to be recessed on the infrared light component light receiving element from on the visible light component light receiving element. An infrared light transmission filter formed by laminating a plurality of color filters is thicker than a color filter on a visible light component light receiving element. However, since the infrared light transmission filter is formed in the depression (concave portion) of the base layer, the surfaces of the infrared light transmission filter and the color filter on the visible light component light receiving element can be flattened.

  Hereinafter, embodiments of the present invention (hereinafter referred to as embodiments) will be described with reference to the drawings.

  FIG. 1 is a schematic plan view showing the configuration of the CCD image sensor according to the present embodiment. This CCD image sensor is of a frame transfer type and includes an imaging unit 2, a storage unit 4, a horizontal transfer unit 6, and an output unit 8 formed on a semiconductor substrate.

  The imaging unit 2 includes a plurality of CCD shift registers (vertical shift registers 10) extending in the column direction (vertical direction), and these vertical shift registers 10 are arranged in the row direction (horizontal direction). Each bit of the vertical shift register 10 constituting the imaging unit 2 functions as a light receiving unit constituting each pixel.

  A color filter is arranged corresponding to each light receiving portion, and a light component having sensitivity to the light receiving portion is determined according to the transmission characteristics of the color filter. Here, an array of 2 × 2 pixels constitutes a unit of an array of light receiving units. For example, the light receiving units 12, 14, 16, and 18 constitute this unit.

  The light receiving units 12, 14, and 16 are respectively provided with a G filter, an R filter, and a B filter. Each of these filters has, for example, the transmission characteristics shown in FIG. For incident light including an infrared light component (IR component), the light receiving unit 12 generates signal charges corresponding to the G component and the IR component. Similarly, the light receiving unit 14 generates a signal charge corresponding to the R component and the IR component, and the light receiving unit 16 generates a signal charge corresponding to the B component and the IR component.

  The light receiving unit 18 is provided with an IR filter (infrared light transmitting filter) that selectively transmits an infrared light component, and generates a signal charge corresponding to the IR component in the incident light. This IR filter can be configured by laminating an R filter and a B filter. This is because, among visible light, the B component that passes through the B filter does not pass through the R filter, while the R component that passes through the R filter does not pass through the B filter. This is because the light component is removed, and the IR component that passes through both filters remains exclusively in the transmitted light.

  In the imaging unit 2, the 2 × 2 pixel configuration is repeatedly arranged in the vertical direction and the horizontal direction.

  The storage unit 4 includes a plurality of vertical shift registers 20 in the same manner as the imaging unit 2. Each vertical shift register 20 is provided corresponding to the vertical shift register 10 of the imaging unit 2, and its input terminal is connected to the output terminal of the vertical shift register 10. The vertical shift register 20 holds the signal charges vertically transferred from the imaging unit 2 by the frame transfer operation at high speed, and vertically transfers the signal charges to the horizontal transfer unit 6 line by line.

  The horizontal transfer unit 6 includes a CCD shift register, and an output terminal of the vertical shift register 20 is connected to each bit. The horizontal transfer unit 6 receives the signal charges for one row output in parallel from the plurality of vertical shift registers 20, and then horizontally transfers the signal charges toward the output unit 8.

  The output unit 8 converts the signal charge output from the horizontal transfer unit 6 into a voltage signal and outputs it as an image signal.

  Each vertical shift register 10 is an impurity diffusion layer formed in a semiconductor substrate and serves as a charge transfer path, and is formed to extend in the row direction on the semiconductor substrate, a channel region that also functions as a light receiving portion, And a plurality of vertical transfer electrodes arranged in the column direction.

  On the semiconductor substrate, a wiring layer formed of, for example, an Al film is further stacked. This is patterned to form a clock wiring or the like extending along a channel stop that separates adjacent channel regions. Here, the clock wiring applies a transfer clock to the vertical transfer electrode. After a planarizing film made of a transparent material is laminated on the wiring layer, a filter array made of the above-described R, G, B filter and IR filter is further formed thereon.

  FIG. 2 is a schematic perspective view showing a method for manufacturing the filter array of the imaging unit. 3 and 4 are schematic cross-sectional views illustrating a method for manufacturing the filter array of the imaging unit. These drawings show the above-described light receiving portions 12 to 18 taken out. 3 shows a state in which the direction of the light receiving parts 12 and 14 is viewed from a vertical section passing through the light receiving parts 16 and 18, and FIG. 4 shows a state of the light receiving parts 12 and 16 from a vertical section passing through the light receiving parts 14 and 18. Shows the direction. As described above, after the transfer electrode and the wiring layer are formed on the semiconductor substrate 30, the planarizing film 32 is formed (FIGS. 2A, 3A, and 4A). 2 to 4, the transfer electrode and the wiring layer are omitted.

  As shown in FIGS. 2A, 3A, and 4A, the planarizing film 32 is once formed to have a flat surface, and then is formed on the light receiving surface of the light receiving unit 18. The part is etched. As a result, a recess 34 is formed on the light receiving surface of the light receiving portion 18 in the planarizing film 32 (FIGS. 2B, 3B, and 4B). This etching is performed, for example, after a mask layer for etching is formed in a portion other than the light receiving portion 18 on the surface of the planarizing film by using a photolithography technique. Further, the etching amount, that is, the depth of the recess is set in accordance with the thickness of the B filter laminated on the recess 34 in the next step.

  A B filter 36 is stacked in the recess 34 on the light receiving unit 18 (FIG. 2C, FIG. 3C, and FIG. 4C). The B filter 36 is formed using, for example, a photosensitive resin colored in blue. For example, the photosensitive resin is applied to the entire surface of the semiconductor substrate by a method such as spin coating, and then exposed and developed using a photomask. By this exposure / development process, the photosensitive resin is patterned so as to remain only in the concave portion 34, and the B filter 36 is formed. The B filter 36 is embedded in the recess 34. For example, the depth of the recess 34 and the film thickness of the B filter 36 are set so that the upper surface of the B filter 36 has the same height as the surface of the planarizing film 32 around the recess 34. Determined.

  Next, the B filter 38 is laminated on the light receiving unit 16 by the same method as that for the B filter 36 (FIGS. 2D, 3D, and 4D). Further, the G filter 40 is laminated on the light receiving unit 12 by the same method as the B filter 36 (FIGS. 2E, 3E, and 4E). Since the B filter 38 and the G filter 40 are formed on the unetched planarizing film 32 adjacent to the concave portion 34, the upper surface thereof is higher than the B filter 36.

  An R filter 42 is laminated on the light receiving unit 14 and the light receiving unit 18. The R filter 42 is stacked on the planarizing film 32 at the position of the light receiving unit 14. On the other hand, the light receiving unit 18 is laminated on the B filter 36. Here, as described above, since the height of the upper surface of the B filter 36 and the surface of the planarizing film 32 at the position of the light receiving unit 14 are basically equal, for example, the R filter 42 includes the light receiving units 14 and 18. (Fig. 2 (f), Fig. 3 (f), Fig. 4 (f)).

  Through the above steps, a color filter is laminated on each light receiving portion. An IR filter is formed by laminating two color filters, a B filter 36 and an R filter 42, in the light receiving unit 18 that detects the IR component, and a recess 34 is provided in the underlying planarization film 32, By embedding the one-layer color filter in the recess 34, the second-layer filter formed on the light-receiving portion 18 is prevented from protruding from the filters of the surrounding light-receiving portions. That is, the flatness of the surface of the filter array formed on each of the light receiving portions 12 to 18 is improved. A planarizing film 44 is laminated on this surface (FIG. 2 (g), FIG. 3 (g), FIG. 4 (g)). Since the undulation of the surface of the filter array serving as the base of the flattening film 44 is suppressed as described above, the flattening film 44 can realize the flattening of the surface of the imaging unit 2 with a relatively thin film thickness.

  Although a frame transfer type CCD image sensor is shown here, the present invention can also be applied to other types such as an interline transfer type and C-MOS image sensors.

  Further, when a set of complementary color filters is used, the IR filter can be configured by stacking three of a Cy filter, an Mg filter, and a Ye filter. In this case, the recess 34 is formed to a depth of two color filter layers. Thereby, the surface height of the color filter of the 3rd layer of the uppermost layer which comprises IR filter, and the surrounding color filter of the light-receiving part for visible light can be arrange | equalized.

It is a typical top view which shows the structure of the CCD image sensor which concerns on embodiment. It is a typical perspective view which shows each process of the manufacturing method of the filter array of an imaging part. It is typical sectional drawing which shows each process of the manufacturing method of the filter array of an imaging part. It is typical sectional drawing which shows each process of the manufacturing method of the filter array of an imaging part. It is a graph which shows the wavelength characteristic of the transmittance | permeability of each RGB filter, and the spectral sensitivity characteristic of a light-receiving part. It is typical sectional drawing of the conventional filter array of an imaging part.

Explanation of symbols

  2 imaging unit, 4 storage unit, 6 horizontal transfer unit, 8 output unit, 10, 20 vertical shift register, 12-18 light receiving unit, 30 semiconductor substrate, 32, 44 planarization film, 34 recess, 36, 38 B filter, 40 G filter, 42 R filter.

Claims (5)

There are a plurality of types of visible light component light receiving elements in which color filters that transmit different colors are laminated on a light receiving surface through transparent underlayers, and an infrared light transmission filter that selectively transmits infrared light components. In a solid-state imaging device in which infrared light component light receiving elements stacked on a light receiving surface through the base layer are arranged,
The underlayer is formed thinner on the light receiving surface of the infrared light component light receiving element than on the light receiving surface of the visible light component light receiving element,
The infrared light transmission filter is configured by laminating a plurality of types of color filters that transmit infrared light among the color filters on the base layer,
A solid-state imaging device. The solid-state imaging device according to claim 1,
As the color filter, a red transmission filter that transmits a component corresponding to red, and a blue transmission filter that transmits a component corresponding to blue,
The infrared light transmission filter is configured by stacking the red transmission filter and the blue transmission filter;
A solid-state imaging device. A plurality of types of visible light component light receiving elements each having a color filter that transmits different colors are stacked on the light receiving surface, and an infrared light transmitting filter that selectively transmits infrared light components are stacked on the light receiving surface. In a method of manufacturing a solid-state imaging device in which infrared light component light receiving elements are arranged,
Forming a transparent base layer in common on the light receiving surfaces of the visible light component light receiving elements and the infrared light component light receiving elements;
An infrared light transmission filter forming step of forming the infrared light transmission filter;
Have
The infrared light transmission filter forming step includes:
An etching step of etching the underlayer to form a recess in the underlayer on the light receiving surface of the infrared light component light receiving element;
A lower filter forming step of laminating at least one type of color filter that transmits infrared light among the color filters as a lower filter in the recess;
An upper filter forming step of transmitting infrared light among the color filters and laminating on the lower filter as a type of color filter different from the lower filter;
The manufacturing method characterized by having. A plurality of types of visible light component light receiving elements each having a color filter that transmits different colors are stacked on the light receiving surface, and an infrared light transmitting filter that selectively transmits infrared light components are stacked on the light receiving surface. In a method of manufacturing a solid-state imaging device in which infrared light component light receiving elements are arranged,
Forming a transparent base layer in common on the light receiving surfaces of the visible light component light receiving elements and the infrared light component light receiving elements;
An infrared light transmission filter forming step of forming the infrared light transmission filter;
Have
The infrared light transmission filter forming step includes:
A recess forming step of forming a recess in the base layer on the light receiving surface of the infrared light receiving element;
A lower filter forming step of laminating at least one type of color filter that transmits infrared light among the color filters as a lower filter in the recess;
An upper filter forming step of transmitting infrared light among the color filters and laminating on the lower filter as a type of color filter different from the lower filter;
The manufacturing method characterized by having. In the manufacturing method of Claim 3 or Claim 4,
One of a red transmission filter that transmits a component corresponding to red and a blue transmission filter that transmits a component corresponding to blue is formed as the lower filter, and the other is formed as the upper filter. Device manufacturing method.

Images