JPH04223371A - Solid-state image sensing device - Google Patents

Abstract

PURPOSE:To enable a solid-state image sensing device to be protected against flare caused by the reflected light by a method wherein a single-layer or a multilayer antireflection film is provided to the outer surface of a micro-lens. CONSTITUTION:An antireflection film 20 of two-layered structure is provided to the outer surface of a micro-lens 19. The antireflection film 20 is so formed as to be smaller than the micro-lens 19 in refractive index, and an outer film 20a is set smaller than an inner film 20b in refractive index. As mentioned above, the antireflection film 20 is provided to the outer surface of the micro- lens 19, whereby a refractive index change can be made small between air and the micro-lens 19 to prevent incident light from being reflected. Therefore, a solid-state image sensing device of this design can be improved in utilization factor of incident light and sensitivity holding down flares caused by the reflected light.

Description

[Detailed description of the invention]

0001

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a solid-state imaging device, and more particularly to a solid-state imaging device having an imaging section in which a microlens is arranged for each unit pixel.

0002

2. Description of the Related Art As an example of a solid-state imaging device, FIG.
Shown below. In the figure, a plurality of photosensitive sections 1 are arranged two-dimensionally in pixel units in the vertical and horizontal directions and accumulate signal charges according to the amount of incident light, and signal charges read out from these photosensitive sections 1 in each vertical column. An imaging section 3 includes a vertical shift register (vertical transfer section) 2 that transfers the data in the vertical direction. The signal charges of all pixels photoelectrically converted in the photosensitive section 1 are instantaneously read out to the vertical shift register 2 for each vertical column during a part of the vertical blanking period. The signal charges transferred to the vertical shift register 2 are sequentially transferred to the horizontal shift register (horizontal transfer section) 4 in portions corresponding to one scanning line during a part of the horizontal blanking period. The signal charges for one scanning line are sequentially transferred in the horizontal direction by the horizontal shift register 4. At the final end of the horizontal shift register 4, FDA (
Floating Diffusion Amplif
An output circuit section 5 is provided, which is made up of a circuit such as a driver. This output circuit section 5 converts the signal charge obtained by photoelectric conversion in the photosensitive section 1 into a voltage and outputs the voltage.

[0003] In this type of CCD solid-state imaging device, the proportion occupied by the photosensitive part (sensor part) in each pixel, that is, the aperture ratio, is generally about 20 to 50%.
The utilization efficiency of light incident on the element surface of the imaging section 3 is poor. In order to improve the utilization efficiency of light incident on the element surface of the imaging section 3 and improve the sensitivity, a solid-state imaging device includes an imaging section in which a microlens is provided as an on-chip microlens for each pixel. is already known.

0004

[Problems to be Solved by the Invention] As mentioned above, in a CCD solid-state imaging device in which a microlens is formed for each unit pixel of the imaging section, although it is possible to improve the utilization efficiency of incident light due to the light condensing action of the microlens. The occurrence of side effects due to periodically arranged microlenses cannot be ignored. A side effect of this microlens is that some of the light incident on the microlens is reflected by the surface of the lens due to the change in refractive index between the air medium and the microlens, which is unrelated to imaging. When the light reaches the light-receiving surface in the form of light, it causes harmful light called "cell ghost" that appears around high-brightness objects in the captured image.

SUMMARY OF THE INVENTION Accordingly, it is an object of the present invention to provide a solid-state imaging device that is capable of suppressing flare (cell ghost) caused by reflected light on the surface of a microlens arranged for each pixel of an imaging section. With the goal.

[0006]

[Means for Solving the Problems] In order to achieve the above object, in the present invention, incident light is In a solid-state imaging device including an imaging section configured with a microlens for condensing light, a single-layer or multilayer anti-reflection film is provided on the outer surface of the microlens.

[0007]

[Operation] In the solid-state imaging device according to the present invention, since the antireflection film disposed on the outer surface of the microlens has a smaller refractive index than the microlens, refraction between the air medium and the microlens is The change in the reflectance becomes smaller, the reflectance decreases, and reflection prevention can be achieved. Thereby, it is possible to improve the utilization efficiency of incident light while suppressing flare (cell ghost) caused by reflected light. In addition, by multilayering the antireflection film, the effective wavelength range for antireflection can be expanded.

[0008]

Embodiments Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings. FIG. 1 is a cross-sectional view showing the structure of a unit pixel in an imaging section of a CCD solid-state imaging device according to the present invention. In the figure, by forming a signal charge accumulation region 12 as an N+ type region on the surface side of a silicon substrate 11, an N
A photosensitive section 1 is constituted by a P-junction photodiode. A channel stop portion 13 is formed adjacent to this signal charge storage region 12 . In addition, silicon substrate 1
1, adjacent to the channel stop part 13, N+
A signal charge transfer region 12 is formed by the mold region, and a silicon oxide film SiO is formed on this signal charge transfer region 12.
A vertical shift register (vertical CCD) 2 is constructed by forming a transfer electrode 16 made of polysilicon through an insulating layer 15 made of 2. Between the photosensitive section 1 and the vertical shift register 2 is a readout gate section 17 for reading out signal charges photoelectrically converted in the photosensitive section 1 to the vertical shift register 2. In this example, the gate electrode of the read gate section 17 and the transfer electrode 16 are made of polysilicon. Vertical shift register 2 excluding photosensitive section 1
A light shielding layer 18 made of aluminum is provided on the read gate portion 17 with an insulating layer 15 interposed therebetween.

Further, above each photosensitive section 1, a microlens 19 is arranged for each unit pixel to condense incident light onto the photosensitive section 1. This microlens 19 is provided in order to improve the utilization efficiency of incident light and improve sensitivity by focusing incident light on the photosensitive section 1 in the imaging section 1, which generally has a low aperture ratio. It is something. For example, a two-layer antireflection film 20 is provided on the outer surface of the microlens 19.
is provided. In this antireflection film 20, the material is selected so that its refractive index is smaller than that of the microlens 19, and further, the refractive index of the outer film 2a is smaller than that of the inner film 2b. .

[0010] By disposing the antireflection film 20 on the outer surface of the microlens 19 in this manner, the change in refractive index between the air medium and the microlens 19 is reduced, and reflection of incident light can be prevented. Therefore, while suppressing flare (cell ghost) caused by reflected light, it is possible to improve the utilization efficiency of incident light and improve sensitivity accordingly.

[0011] In the above embodiment, the antireflection film 20 has a two-layer structure, but it may have a single layer structure or a three or more layer structure. This means that the effective wavelength range for antireflection can be expanded. Further, the present invention is not limited to application to a CCD solid-state imaging device using an interline transfer method, but is also applicable to a solid-state imaging device in which a microlens is arranged for each pixel in order to effectively utilize incident light in the imaging section. Applicable to all devices.

0012

As explained above, in the solid-state imaging device according to the present invention, by providing an anti-reflection film on the outer surface of the microlens arranged for each unit pixel, the gap between the air medium and the microlens is reduced. Since the change in the refractive index is reduced and reflection of incident light can be prevented, flare (cell ghost) caused by reflected light can be suppressed.

[Brief explanation of the drawing]

FIG. 1 is a cross-sectional view showing the structure of a unit pixel in an imaging section of a CCD solid-state imaging device according to the present invention.

FIG. 2 is a schematic configuration diagram of a CCD solid-state imaging device using an interline transfer method.

[Explanation of symbols]

1 Photosensitive part 2 Vertical shift register 3 Imaging section 12 Signal charge accumulation region 14 Signal charge transfer area 16 Transfer electrode 19 Micro lens 20 Anti-reflection film

Claims (1)

[Claims] 1. A solid-state imaging device comprising an imaging section configured such that a microlens for condensing incident light is arranged for each of a plurality of photosensitive sections two-dimensionally arranged in pixel units in the vertical and horizontal directions. 2. A solid-state imaging device according to claim 1, wherein a single-layer or multi-layer anti-reflection film is provided on the outer surface of the microlens.