KR20090068403A - Image sensor and method for fabricating the same - Google Patents

Abstract

An image sensor and a manufacturing method thereof are provided to enhance optical sensitivity by preventing loss of light received through an image sensor and suppressing interference between adjacent pixels. An image sensor includes a semiconductor substrate(10), a metal wiring layer(30), a gap-fill layer, a color filter array, and a micro lens. The semiconductor substrate includes a light receiving element(15). The metal wiring layer includes is formed on the semiconductor substrate. The metal wiring layer includes a trench(37) having a concave bottom corresponding to the light receiving element. The trench is filled with the gap-fill layer. The color filter array is formed on the metal wiring layer including the gap-fill layer. The micro lens is formed on the color filter array.

Description

Image sensor and manufacturing method thereof {IMAGE SENSOR AND METHOD FOR FABRICATING THE SAME}

Embodiments relate to an image sensor and a method of manufacturing the same.

An image sensor is a semiconductor device that converts an optical image into an electrical signal. The image sensor is largely a charge coupled device (CCD) and a complementary metal oxide silicon (CMOS) image sensor. (CIS).

CMOS image sensors are devices that digitize light with IMAGING technology. In the CMOS image sensor, a photo diode and a MOS transistor are formed in a unit pixel to sequentially detect an electrical signal of each unit pixel in a switching manner to implement an image.

The structure of the CMOS image sensor is briefly divided into a light receiving unit, a filter unit, a sensor unit, and a circuit unit. The key to imaging technology is to filter the incoming light and digitize the image without losing any light.

The CMOS image sensor has a thicker metal wiring layer than the CCD type image sensor because the CMOS image sensor has a multilayer structure of an insulating layer, a protective layer, a color filter layer, a planarization layer, and a micro lens on the top of the photodiode.

As a result, in the case of the CMOS image sensor, as the pixel pitch becomes smaller, there is a problem in that the focus does not occur on the photodiode layer even when a microlens having an optimal shape is formed.

This is because the size of the minimum spot that can be condensed under the focus condition of the microlens is proportional to ~ 1 / NA and the focal length in the size of the airy disc. Here NA is the numerical aperture (Numerical Aperture).

In the pixel of the image sensor, the NA corresponds to the pixel pitch and the focal length corresponds to the thickness of the metal wiring layer. Therefore, in order to obtain the same sized focus spot, the thickness of the metal wiring layer must be thinner as the size of the pixel becomes smaller.

However, the conventional structure of the image sensor has a limitation in designing it to be thinner than the minimum required thickness of the metal wiring layer, thereby resulting in a limit pixel pitch in which the pixel size can no longer be reduced.

The embodiment provides an image sensor and a method of manufacturing the same that can improve the optical characteristics of the image sensor and improve the light sensitivity.

The embodiment provides an image sensor and a method of manufacturing the same, which can use the light entering the image sensor without loss and can exclude interference with adjacent pixels.

The image sensor according to the embodiment may include a semiconductor substrate including a light receiving element, a metal wiring layer formed on the semiconductor substrate and having a recessed bottom surface corresponding to the light receiving element, a gap fill film embedded in the trench, and It includes a color filter array formed on the metal wiring layer including a gap fill film and a micro lens formed on the color filter array.

The method of manufacturing an image sensor according to the embodiment may include forming a metal wiring layer on a semiconductor substrate including a light receiving element, forming a preliminary trench in the metal wiring layer, and having the concave profile on the bottom surface of the preliminary trench. Forming an organic layer on the interconnection layer, etching back the organic layer and the metal interconnection layer to form a trench having a concave profile at a bottom surface thereof, and forming a gap fill layer on the metal interconnection layer so that the trench is embedded; Include.

The image sensor and the method of manufacturing the same according to the embodiment have the effect of improving the performance of the image sensor by forming a trench in the metallization layer and changing the profile of the trench bottom to improve the light concentrating degree.

When the image sensor according to the embodiment is incident light toward the metal wiring, the convex profile of the bottom surface of the trench is convex downward, and by filling the trench with a material having a different refractive index can be efficiently focused and improve the image quality It has an effect.

Hereinafter, an image sensor and a method of manufacturing the same according to an embodiment will be described in detail with reference to the accompanying drawings.

In the description of the embodiments, where it is described as being formed "on / under" of each layer, it is understood that the phase is formed directly or indirectly through another layer. It includes everything.

In the description of the embodiment will be described with reference to the structure of the CMOS image sensor (CIS), the present invention is not limited to the CMOS image sensor, it is applicable to all image sensors, such as CCD image sensor.

1 to 6 are process cross-sectional views of a method of manufacturing an image sensor according to an embodiment.

First, as shown in FIG. 1, the circuit layer 20 and the metallization layer 30 are formed on the first substrate 10.

An isolation layer 5 and a light receiving element 15 are formed on the first substrate 10, the circuit layer 20 includes a circuit including a transistor, and the metal wiring layer 30 includes the circuit. It is formed including a wiring 35 connected with.

The light receiving element 15 may be a photo diode.

As shown in FIG. 2, a preliminary trench 37 is formed in the metal wiring layer 30.

The preliminary trench 37 may be formed by forming a photoresist pattern on the metal wiring layer 30 and then performing an etching process.

In the process of etching the metal wiring layer 30, a preliminary trench 37 may be formed with a margin of about 0.1 to 0.7 μm in consideration of an additional etching process for forming a trench later.

The preliminary trench 37 is formed in a region corresponding to the light receiving element 15 of the metal wiring layer 30.

3, the organic layer 40 is formed on the metal wiring layer 30 including the preliminary trench 37.

The organic layer 40 is a planar type material, and when the preliminary trench 37 is gap-filled, the upper surface profile is concave down. Here, the organic layer 40 having such a profile may be used as an etch seed pattern by adjusting the gap fill amount of the organic layer 40.

The organic layer 40 may apply a planar type organic material to the preliminary trench 37. In this case, the amount of the organic material formed in the preliminary trench 37 is appropriately adjusted so that the organic layer 40 may be coated to cover the inner bottom surface of the preliminary trench 37. In this case, the organic layer 40 may be more deposited on the corners of the preliminary trench 37 to form an organic layer 40 having a lens shape in which an upper surface thereof is concave down.

As described above, the organic film 40 having the concave shape of the upper surface profile in the preliminary trench 37 enables the profile to be transferred to the lower insulating film to form the trench 37a.

As shown in FIG. 4, the entire surface of the substrate 10 on which the organic layer 40 is formed is etched back.

When the etch back process is performed, the organic layer 40 and the metal wiring layer 30 are etched so that the top surface profile of the organic layer 40 is transferred to the bottom surface of the trench 37a to have a concave lens shape. .

In this case, all of the organic film 40 on the metal wiring layer 30 and the organic film 40 in the trench 37a are also removed.

Subsequently, as shown in FIG. 5, a gap fill material film 50 is formed on the metal wiring layer 30 to fill the trench 37a.

The gapfill material layer 45 may be formed of an oxide film, a polymer, a photoresist, or the like having excellent light transmittance.

The gap fill material layer 45 is formed to cover the trench 37a and the metal wiring layer 30, and a part of the metal wiring layer 30 is exposed through the planarization process of the gap fill material layer 45, and the trench is exposed. The gap fill material film 45 is formed in 37a.

Thereafter, a process of curing the gapfill material layer 45 may be performed.

The gap fill material layer 45 is formed of a material that is larger than the refractive index of the interlayer insulating material of the metal interconnection layer 30 so that light is refracted at the boundary between the gap fill material layer 45 and the metal interconnection layer 30. (15) to focus light.

For example, the refractive index of the gap fill material film 45 is 1 to 1.6, and the refractive index of the interlayer insulating film is about 1 to 1.4.

The refractive index of the gapfill material layer 45 may be greater than the refractive index of the interlayer insulating layer.

As shown in FIG. 6, a first planarization layer 61 is formed on the metal wiring layer 30, a color filter array is formed on the first planarization layer 61, and the color filter is formed. Micro lenses may be formed on the array.

The heights of the first to third photosensitive color filters 51, 52, and 53 may be different from each other in the color filter array, and the heights may be decreased in the order of red, green, and blue. This is because the first to third photosensitive color filters 51, 52, and 53 have different wavelengths depending on the color of the color filter.

Thereafter, a second planarization layer 62 is formed on the first to third photosensitive color filters 51, 52, and 53, and a microlens is formed on the second planarization layer 62 to correspond to the unit pixel. lens 65 may be formed.

The pad 60 may be formed on the metal wiring layer 30.

The image sensor having the same structure as the embodiment can minimize the loss due to the refraction of light by the guide pattern 45 formed along the inner wall of the trench 37a.

In addition, the image sensor according to the embodiment may effectively fill the photodiode with light entering the image sensor by filling a material having a high refractive index in the trench 37a having a concave bottom surface.

Although described above with reference to the embodiments, which are merely examples and are not intended to limit the present invention. Those skilled in the art to which the present invention pertains are not exemplified above without departing from the essential characteristics of the present invention. It will be appreciated that many variations and applications are possible. For example, each component specifically shown in the embodiment of the present invention can be modified. And differences relating to such modifications and applications will have to be construed as being included in the scope of the invention defined in the appended claims.

1 to 6 are process cross-sectional views of a method of manufacturing an image sensor according to an embodiment.

Claims (6)

A semiconductor substrate including a light receiving element; A metal wiring layer formed on the semiconductor substrate and including a trench in which a bottom surface is concave in correspondence with the light receiving element; A gapfill film embedded in the trench; A color filter array formed on the metal wiring layer including the gap fill layer; And And a micro lens formed on the color filter array. The method of claim 1, The refractive index of the gap fill film is an image sensor, characterized in that greater than the refractive index of the metal wiring layer. Forming a metal wiring layer on a semiconductor substrate including a light receiving element; Forming a preliminary trench in the metal wiring layer; Forming an organic layer on the metallization layer to have a concave profile at the bottom of the preliminary trench; Etching back the organic layer and the metallization layer to form a trench having a concave profile at a bottom surface thereof; And And forming a gap fill layer on the metal wiring layer to fill the trench. The method of claim 3, wherein And the trench is formed in a region corresponding to the light receiving element formed on the semiconductor substrate. The method of claim 3, wherein The refractive index of the gap fill film is a manufacturing method of the image sensor, characterized in that greater than the refractive index of the metal wiring layer. The method of claim 3, wherein After forming the gap fill film, The method of manufacturing an image sensor further comprising the step of curing the gap fill film.

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