KR100731067B1 - Cmos image sensor and method for manufacturing the same - Google Patents

Abstract

A CMOS image sensor and a manufacturing method thereof are provided to improve the sensitivity of the image sensor itself by reducing the thickness of a second planarization layer using trenches with thicknesses corresponding to those of color filters on a first planarization layer. A plurality of photodiodes(102) are formed in a semiconductor substrate(101). A first planarization layer(103) is formed on the entire surface of the resultant structure. A first trench with a first depth is formed on the first planarization layer. A second trench with a second depth is formed on the first planarization layer. A blue color filter layer(106) is formed in the first trench. A green color filter layer(107) is formed in the second trench. A red color filter layer(108) is formed on the first planarization layer. A microlens(110) is formed on each color filter layer. A second planarization layer(109) is formed between the color filter layers and microlenses.

Description

CMOS image sensor and method for manufacturing the same

1 is a cross-sectional view showing a CMOS image sensor of the prior art

2 is a cross-sectional view showing a CMOS image sensor according to the present invention

3A to 3E are cross-sectional views illustrating a method of manufacturing the CMOS image sensor according to the present invention.

Explanation of symbols for the main parts of the drawings

101 semiconductor substrate 102 photodiode

103: first planarization layer 104: first trench

105: second trench 106: blue color filter layer

107: green color filter layer 108: red color filter layer

109: second planarization layer 110: microlens

The present invention relates to an image sensor, and more particularly to a CMOS image sensor and a method of manufacturing the same to improve the sensitivity of the image sensor.

In general, an image sensor is a semiconductor device that converts an optical image into an electrical signal, and may be broadly classified into a charge coupled device (CCD) image sensor device and a complementary metal oxide semiconductor (CMOS) image sensor device.

The CMOS image sensor is composed of a photodiode portion for sensing the irradiated light and a CMOS logic circuit portion for processing the detected light into an electrical signal and converting the data into light. The greater the amount of light received by the photodiode, the higher the photosensitivity of the image sensor. The characteristic becomes good.

In order to increase the optical sensitivity, a technique in which the fill factor of the photodiode in the total area of the image sensor is increased or the path of the light incident to a region other than the photodiode is changed to focus the photodiode. .

A representative example of the focusing technique is to form a microlens, which is a method of irradiating a larger amount of light to a photodiode by refracting the path of incident light by making a convex microlens with a material having a high light transmittance on the photodiode. to be.

In this case, light parallel to the optical axis of the microlens is refracted by the microlens to form a focal point at a predetermined position on the optical axis.

Hereinafter, a CMOS image sensor according to the related art will be described with reference to the accompanying drawings.

1 is a cross-sectional view showing a CMOS image sensor of the prior art.

In the prior art CMOS image sensor, as shown in FIG. 1, at least one photodiode 12 is formed in the surface of the semiconductor substrate 11 to generate charges according to the amount of incident light, and the photodiode 12 First planarization layer 13 formed on the entire surface of the semiconductor substrate 11 and the first planarization layer 13 including the color of R, G, and B formed on the first planarization layer 13 to pass light of a specific wavelength band, respectively. A color filter layer corresponding to the filter layer 14, the second flattening layer 15 formed on the front surface including the color filter layer 14, and a convex shape having a predetermined curvature on the second flattening layer 15. And a microlens 16 that transmits 14 and focuses light to the photodiode 12.

Here, the microlens 16 is determined in consideration of various factors such as the focus of the focused light and the like, the curvature and the formation height is determined, the polymer-based resin is mainly used, patterning by deposition, exposure and development, reflow, etc. It is formed by the process of.

That is, it should be formed with an optimal size, thickness, and radius of curvature determined by the size, position, shape of the unit pixel, the thickness of the photosensitive device, and the height, position, size, etc. of the light blocking layer.

At this time, the shape of the pattern profile changes according to the exposure conditions. For example, process progress conditions change according to the thin film conditions of a semiconductor substrate. Therefore, the microlens also changes. In reality, the pattern forming conditions tend to be very unstable and consequently the light focusing efficiency is lowered.

As described above, the microlens 16 formed to increase the light focusing efficiency in the process for manufacturing the CMOS image sensor of the related art is an important factor that determines the characteristics of the image sensor.

The microlens 16 serves to focus more light onto the photodiode 12 through each color filter layer 14 depending on the wavelength when natural light is irradiated.

Light incident on the image sensor is focused by the microlens 16, and the light filtered through the color filter layer 14 is incident on the photodiode 12 configured to correspond to the lower end of the color filter layer 14.

In this case, the light blocking layer serves to prevent the incident light from escaping to another path.

However, there are the following problems in the conventional CMOS image sensor.

That is, since the color filter layers 14 stack different thicknesses for each filter type, a large number of steps occur. In order to compensate for this, after forming the color filter layer 14, the second planarization layer 15 is formed on the entire surface of at least half the thickness of the color filter.

At this time, light exists as natural light in the second planarization layer 15 before passing through the color filter layer 14, which penetrates between the color filter layers 14 and reaches the photodiode 12, thereby causing noise. do.

More specifically, the difference in the amount of light that reaches the photodiode according to the type and thickness of the lower film quality of the microlens is generated, the focusing efficiency is lowered, thereby causing a problem of deterioration of image quality.

The present invention is to solve the conventional problem as described above, to reduce the thickness of the planarization layer formed between the color filter layer and the microlens to prevent noise caused by the penetration of natural light to improve the sensitivity of the image sensor. It is an object of the present invention to provide a CMOS image sensor and a method of manufacturing the same.

The CMOS image sensor according to the present invention for achieving the above object is formed of at least one photodiode in the surface of the semiconductor substrate and generates a charge according to the amount of incident light, and a semiconductor substrate comprising the photodiodes A first planarization layer formed on the entire surface, a first trench formed at a predetermined depth in the surface of the first planarization layer, and a predetermined distance from the first trench in the surface of the first planarization layer at a predetermined distance from the first trench. On the first planarization layer except for the second trench formed in a thin depth, the blue color filter layer formed in the first trench, the green color filter layer formed in the second trench, and the blue color filter layer and the green color filter layer. A red color filter layer formed and a microlens formed on each of said color filter layers The features.

In addition, the method for manufacturing the CMOS image sensor according to the present invention for achieving the above object comprises the steps of forming a first planarization layer on a substrate on which a plurality of photodiodes are formed, and in a predetermined region of the first planarization layer. Forming a first trench having a predetermined depth from a surface, forming a second trench in the surface with a depth smaller than the first trench, the first planarization layer having a predetermined distance from the first trench, and Forming a blue color filter layer in the first trench, forming a green color filter layer in the second trench, forming a red color filter layer on the first planarization layer except for the first and second trenches; And forming microlenses on each of the color filter layers.

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

2 is a cross-sectional view showing a CMOS image sensor according to the present invention.

As shown in FIG. 2, at least one photodiode 102 is formed in the surface of the semiconductor substrate 101 to generate electric charges according to the amount of incident light, and a semiconductor substrate including the photodiodes 102. The first planarization layer 103 formed on the entire surface of the 101, the first trenches 104 formed at a predetermined depth in the surface of the first planarization layer 103, and a predetermined distance from the first trenches 104. A second trench 105 having a depth smaller than that of the first trench 104 in the surface of the first planarization layer 103, and a blue (B) color filter layer formed in the first trench 104. 106, on the first planarization layer 103 between the green (B) color filter layer 107 formed in the second trench 105, and between the blue color filter layer 106 and the green color filter layer 107. A peninsula including a red (R) color filter layer 108 formed on the substrate and the color filter layers 106, 107, and 108, respectively. And a second flattening layer 109 formed on the entire surface of the sieve substrate 101 and microlenses 110 formed on the second flattening layer 109 to correspond to the respective color filter layers 106, 107, and 108. do.

 Here, the surface heights of the blue color filter layer 106, the green color filter layer 107, and the red color filter layer 108 are the same by the first and second trenches 104 and 105, so that the second planarization layer 109 is formed. Can be made thinner than the conventional one.

In addition, the first and second planarization layers 103 and 109 are formed of a SiN layer.

In addition, although the second planarization layer 109 is formed in the embodiment of the present invention, the second planarization layer 109 may be omitted because the color filter layers 106, 107, and 108 are formed to be flush with the same height. .

3A to 3E are cross-sectional views illustrating a method of manufacturing the CMOS image sensor according to the present invention.

As shown in FIG. 3A, a photodiode 102 is formed in the surface of the semiconductor substrate 101 to generate charges corresponding to the amount of light incident on at least one, and the semiconductor substrate 101 including the photodiode 102. ), An interlayer insulating layer (not shown) and a first planarization layer 103 are sequentially formed on the entire surface.

Here, the interlayer insulating layer may be formed in a multi-layer, but not shown, after forming a light shielding layer for preventing light from being incident to a portion other than the photodiode 102 after the formation of one interlayer insulating layer, the interlayer insulation A layer is formed.

On the other hand, the interlayer insulating layer uses an oxide such as USG (Undoped Silicate Glass).

In addition, the first planarization layer 103 is formed of a SiN film.

As shown in FIG. 3B, a predetermined portion of the first planarization layer 103 is selectively removed through a photo and etching process to form a first trench 104 having a predetermined depth from the surface.

Here, the first trench 104 is a region where a blue color filter will be formed later.

As shown in FIG. 3C, a predetermined portion of the first planarization layer 103 may be selectively removed to have a predetermined distance from the first trench 104 through a photo and etching process, and thus, the first trench 104 may be removed. The second trench 105 is formed to a thin depth.

As shown in FIG. 3D, a blue filter resist is coated on the entire surface including the first and second trenches 104 and 105, and then exposed and developed to expose the blue color filter layer 106 inside the first trench 104. ).

Here, the reticle used when forming the blue color filter layer 106 uses the reticle used when forming the first trench 104 as it is.

Subsequently, after applying a green resist, it is exposed and developed to form a green color filter layer 107 in the second trench 105.

Here, the reticle used when forming the green color filter layer 107 uses the reticle used when forming the second trench 105 as it is.

After the red resist is applied, a red color filter layer 108 is formed on the first planarization layer 103 between the blue color filter layer 106 and the green color filter layer 107 by performing exposure and development processes.

In the embodiment of the present invention, the blue color filter layer 106, the green color filter layer 107, and the red color filter layer 108 are formed in this order. However, the forming order of each color filter layer may be arbitrarily adjusted. .

As shown in FIG. 3E, a second planarization layer 109 is formed on the front surface of the semiconductor substrate 101 including the color filter layers 106, 107, and 108 to adjust the focal length and to secure the flatness for forming the lens layer. do.

On the other hand, the embodiment of the present invention compared to other color filters before forming the color filter layer to reduce the thickness of the second planarization layer 109 so that the natural light passing through the microlenses can directly enter the color filter layer. The thick filters form trenches in the surface of the first planarization layer 103 before forming each color filter layer.

Therefore, the thickness of the second planarization layer 109 can be reduced to a minimum and can even be omitted since the surface of each color filter layer is formed to be planarized as a whole.

Subsequently, a microlens formation material layer is coated on the second planarization layer 109, and then the material layer is patterned by an exposure and development process to form a microlens pattern.

Here, an oxide film such as a resist or TEOS may be used as the material layer for forming the microlens.

Subsequently, the microlens pattern is reflowed to form the microlens 110.

In this case, the reflow process may use a hot plate or a furnace. In this case, the curvature of the microlens 110 is changed according to the shrinkage heating method, and the focusing efficiency is also changed according to the curvature.

Subsequently, the microlens 110 is irradiated with ultraviolet rays and cured. Herein, the microlens 110 may maintain an optimal radius of curvature by irradiating and curing ultraviolet rays to the microlens 110.

Those skilled in the art will appreciate that various changes and modifications can be made without departing from the spirit of the present invention.

Therefore, the technical scope of the present invention should not be limited to the contents described in the embodiments, but should be defined by the claims.

Such CMOS image sensor and its manufacturing method according to the present invention has the following effects.

That is, before forming the color filter layer, the filters thicker than other color filters form trenches in the surface of the first flattening layer in advance, and then form the respective color filter layers to reduce the thickness of the second flattening layer and pass through the microlenses. The sensitivity of the image sensor can be improved by allowing natural light to enter the color filter layer directly.

Claims (5)

At least one photodiode formed in the surface of the semiconductor substrate and generating charges according to the amount of incident light; A first planarization layer formed on an entire surface of the semiconductor substrate including the photodiodes; A first trench formed to a predetermined depth in the surface of the first planarization layer, A second trench formed at a depth smaller than the first trench in the surface of the first planarization layer and having a predetermined distance from the first trench; A blue color filter layer formed in said first trench, A green color filter layer formed in said second trench, A red color filter layer formed on the first planarization layer except for the blue color filter layer and the green color filter layer; And a microlens formed on each of the color filter layers. The CMOS image sensor according to claim 1, further comprising a second planarization layer formed between each of the color filter layers and the microlens. The CMOS image sensor according to claim 1, wherein each of the color filter layers is formed at the same height. Forming a first planarization layer on the substrate on which the plurality of photodiodes are formed; Forming a first trench having a predetermined depth from a surface in a predetermined region of the first planarization layer; Forming a second trench at a depth smaller than the first trench in the surface of the first planarization layer at regular intervals from the first trench; Forming a blue color filter layer in the first trench; Forming a green color filter layer in the second trench; Forming a red color filter layer on the first planarization layer except for the first and second trenches; Forming a microlens on each of the color filter layers. The method of claim 4, further comprising forming a second planarization layer between each of the color filter layers and the microlens.

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