KR20060136072A - CMOS Image sensor and method for manufacturing the same - Google Patents

Abstract

The present invention relates to a CMOS image sensor and a method of manufacturing the same to improve the performance of the image sensor by improving the uniformity of the size of the microlens during the formation of the microlens, and according to the amount of light incident to at least one formed on the semiconductor substrate Photodiode regions for generating charge, an interlayer insulating layer formed on the front surface including the photodiode regions, a plurality of trenches formed at a predetermined depth in the surface of the interlayer insulating layer to correspond to the photodiode regions; And a color filter layer formed in each of the trenches, each of which passes light of a specific wavelength band, and a micro lens formed on the color filter layer and passing through a corresponding color filter layer to focus light into a photodiode region. It is done.

CMOS image sensor, microlens, MUV photoresist, grating

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

2A to 2D are cross-sectional views illustrating a method of manufacturing a CMOS image sensor according to the prior art.

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

4A to 4G are cross-sectional views illustrating a method of manufacturing the CMOS image sensor according to the present invention.

5 is a plan view showing a grating around a microlens made of MUV photoresist in the manufacture of CMOS image sensor according to the present invention;

Explanation of symbols for main parts of the drawings

31 photodiode 32 interlayer insulation layer

33: MUV photoresist 34: Reticle

35 trench 36 color filter layer

37 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 performance of the image sensor by improving the uniformity of the microlens size.

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.

In particular, when forming a plurality of microlenses, it is very important to stably control the exposure conditions and developing conditions for determining between each microlens.

Hereinafter, a CMOS image sensor and a manufacturing method thereof 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 11 is formed on a semiconductor substrate (not shown) and generates charges according to the amount of incident light, and the photodiode (11) an interlayer insulating layer 12 formed on the entire surface including regions, a protective film 13 formed on the interlayer insulating layer 12, and a protective film 13 formed on the protective film 13, respectively. R, G, B color filter layer 14 for passing light, a planarization layer 15 formed on the front surface including the color filter layer 14, and a convex shape having a predetermined curvature on the planarization layer 15 It consists of a micro lens 16 that passes through the corresponding color filter layer 14 and focuses light to the photodiode 11 region.

Although not shown in the figure, an optical shielding layer is formed in the interlayer insulating layer to prevent light from being incident on portions other than the photodiode 11 region.

The device for sensing light is not a photodiode, but may be configured as a photogate.

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. After applying the microlens resist layer, patterning and reflowing by exposure and development, 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 micro lens 16 serves to focus more light onto the photodiode 11 region 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 11 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.

2A to 2D are cross-sectional views illustrating a method of manufacturing a CMOS image sensor according to the prior art.

As shown in FIG. 2A, an interlayer insulating layer 12 is formed on a semiconductor substrate on which a plurality of light sensing elements, for example, photodiodes 11 are formed.

Here, the interlayer insulating layer 12 may be formed in multiple layers, and although not shown, a light shielding layer is formed to prevent light from being incident to portions other than the photodiode 11 after forming one interlayer insulating layer. Later, an interlayer insulating layer is formed again.

Next, a planarized protective layer 13 is formed on the interlayer insulating layer 12 to protect the device from moisture and scratches.

After the coating is applied on the passivation layer 13 using a salty resist, exposure and development processes are performed to form color filter layers 14 for filtering light for each wavelength band.

Subsequently, the planarization layer 15 is formed on the color filter layer 14 to adjust the focal length and to secure the flatness for forming the lens layer.

As shown in Fig. 2B, a microlens resist layer 16a is applied onto the planarization layer 15, and a mask 17 having an opening is arranged on the resist layer 16a.

Subsequently, the resist layer 16a is selectively exposed so as to correspond to an opening of the mask 17 by irradiating a light such as a laser on the entire surface of the mask 17.

As shown in Fig. 2C, the exposed resist layer 16a is developed to form a microlens pattern 16b.

As shown in FIG. 2D, the microlens pattern 16b is reflowed at a predetermined temperature to form the microlens 16.

However, there is a problem in the conventional CMOS image sensor and its manufacturing method as described above.

That is, most of the salt resistant resists forming the color filter are made of negative resists in which a portion where no light is received is developed in a developer. In addition, the kind of viscosity that has a great influence on determining the thickness is also very limited.

Therefore, there are many difficulties in implementing the required thickness freely in the process, and the required thickness can be obtained by using various kinds of resists, but there are disadvantages in that the types of resists increase.

In particular, when the thickness of the blue resist becomes thick, light does not reach the bottom of the blue resist, and thus adhesion to the sub film is poor, and thus pattern peeling occurs frequently.

In addition, after the color filter, there are many difficulties in forming the microlenses, and the microlens sizes are very nonuniform.

In other words, the distance between the microlenses is irregular and curvature is often not formed properly, and since the microlens cannot be formed directly on the color filter, a flattening layer is formed between the color filter and the microlens, thereby making the overall image sensor thicker. The focusing efficiency of light is lowered by the planarization layer.

The present invention has been made to solve the above-mentioned conventional problems, to provide a CMOS image sensor and a method of manufacturing the same to improve the performance of the image sensor by improving the uniformity of the microlens size during the formation of the microlens. The purpose is.

The CMOS image sensor according to the present invention for achieving the above object is formed on at least one photodiode region formed on the semiconductor substrate to generate a charge according to the amount of incident light, and formed on the front surface including the photodiode regions An interlayer insulating layer, a plurality of trenches formed in a predetermined depth in the surface of the interlayer insulating layer, corresponding to each photodiode region, a color filter layer formed in each of the trenches and allowing light to pass through a specific wavelength band, respectively; And a micro lens formed on the color filter layer to transmit a corresponding color filter layer to focus light to the photodiode region.

In addition, the method for manufacturing a CMOS image sensor according to the present invention for achieving the above object is to form an interlayer insulating layer on a semiconductor substrate formed with a plurality of photodiodes, and to apply a photoresist on the interlayer insulating layer And forming a lattice surrounding the microlens region by exposure and development, and selectively removing the interlayer insulating layer using the lattice of the photoresist as a mask to form a plurality of trenches having a predetermined depth from a surface. And removing the photoresist and forming a color filter layer inside each of the trenches, and forming a microlens 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.

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

As shown in FIG. 3, at least one photodiode 31 is formed on a semiconductor substrate (not shown) to generate charges according to the amount of incident light, and includes the photodiode 31 regions. An interlayer insulating layer 32 formed on the front surface of the interlayer, a plurality of trenches 35 formed in a predetermined depth corresponding to each of the photodiode 31 regions in the surface of the interlayer insulating layer 32, and the respective trenches. A color filter layer 36 of R, G, and B formed in 35 to pass light of a specific wavelength band, and a convex shape having a predetermined curvature on the color filter layer 36, and corresponding color filter layer ( It consists of a micro lens 37 that passes through 36 and focuses light to the photodiode 31 region.

Here, the depth of the trench 35 is formed deeper than the thickness of each color filter layer 36, and is formed shallower than the sum of the thicknesses of the microlens 37 and the color filter layer 36.

4A to 4G are cross-sectional views illustrating a method of manufacturing a CMOS image sensor according to the present invention, and FIG. 5 illustrates a grating around a microlens made of MUV photoresist in the manufacture of the CMOS image sensor according to the present invention. Top view.

As shown in FIG. 4A, an interlayer insulating layer 32 is formed on a semiconductor substrate on which a plurality of photosensitive devices, for example, photodiodes 31 are formed.

Here, the interlayer insulating layer 32 may be formed in multiple layers, and although not shown, a light shielding layer is formed to prevent light from being incident on portions other than the photodiode 31 after forming one interlayer insulating layer. Later, an interlayer insulating layer is formed again.

As shown in FIG. 4B, an MUV photoresist 33 is applied onto the interlayer insulating layer 32.

Here, the MUV photoresist 33 is a photoresist that responds to an I-line.

Subsequently, the reticle 34 for forming the microlens is aligned on the MUV photoresist 33, and the MUV photoresist 34 is selectively exposed using the reticle 34 as a mask. .

As shown in Fig. 4C, the exposed portion of the MUV photoresist 33 is developed and patterned. In this case, as shown in FIG. 5, the developed MUV photoresist 33 has a microlens formation region A and a lattice B structure surrounding the surroundings.

Subsequently, the interlayer insulating layer 32 is selectively removed using the patterned MUV photoresist 33 as a mask to form a trench 35 having a predetermined depth from the surface.

Each of the trenches 35 is formed to correspond to the photodiode 31 region, respectively.

As shown in FIG. 4D, the MUV photoresist 33 is removed and coated using a salt resistant resist on the entire surface of the semiconductor substrate including the trench 35, and then exposed and developed. Color filter layers (R, G, B) 36 are formed to filter light for each wavelength band.

Here, each of the color filter layers 36 is formed at the same height as the upper surface height of the interlayer insulating layer 32 in the trench 35.

As shown in FIG. 4E, the color filter layer 36 formed inside the trench 35 is subjected to an etching process such as ashing to selectively remove each color filter layer 36 by a predetermined thickness to the surface. do.

Here, by controlling the etching thickness of the color filter layer 36 it is possible to ensure the formation depth of the microlenses formed later.

As shown in FIG. 4F, a microlens resist 37a is deposited on the entire surface of the interlayer insulating film 32 including the color filter layer 36.

As shown in Fig. 4G, the resist 37a is selectively exposed using the reticle used to form the trench 35 as a mask.

Subsequently, the exposed resist 37a is developed to remove the exposed portion to form a microlens pattern, and the microlens pattern is reflowed to form a hemispherical microlens 37.

In this case, the reflow process may use a hot plate or a furnace. At this time, the curvature of the microlens 37 varies according to the method of shrinkage heating, and the focusing efficiency also varies according to the curvature.

Subsequently, the microlens 37 is irradiated with ultraviolet rays and cured. In this case, the microlens 37 may maintain an optimum radius of curvature by irradiating and curing the microlens 37 with ultraviolet rays.

In addition, the depth of the trench 35 is formed deeper than the thickness of each of the color filter layers 36, and is formed to be shallower than the sum of the thicknesses of the microlens 37 and the color filter layer 36. The curvature of the microlenses can be improved.

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.

First, by forming the color filter and the microlens inside the trench, it is possible to easily control the microlens size without a separate space CD control, it is possible to prevent the pattern collapse of the color filter layer.

Second, the light collecting efficiency and uniformity of the microlens may be improved by removing the planarization layer between the microlens and the color filter layer.

Third, the sensitivity of the color may be improved by improving the uniformity of the microlens size, which is a problem in forming the microlens during the manufacturing process of the image sensor.

Fourth, the exposure conditions for forming the microlenses are stabilized to reduce the rework rate of the microlenses.

Fifth, although the exposure conditions are severely changed according to the state of the lower layer in the related art, in the present invention, the change in the critical dimension of the microlens according to the exposure energy can be reduced.

Claims (11)

Photodiode regions formed on at least one semiconductor substrate and generating charges according to the amount of incident light; An interlayer insulating layer formed on the front surface including the photodiode regions; A plurality of trenches formed in a surface of the interlayer insulating layer with a predetermined depth corresponding to each of the photodiode regions; A color filter layer formed in each of the trenches to pass light of a specific wavelength band, respectively; And a microlens formed on the color filter layer to transmit a corresponding color filter layer to focus light onto the photodiode region. The CMOS image sensor of claim 1, wherein the trench is formed deeper than a thickness of each of the color filter layers. The CMOS image sensor according to claim 1, wherein the trench is formed shallower than the sum of the thicknesses of the microlenses and the color filter layer. Forming an interlayer insulating layer on the semiconductor substrate on which the plurality of photodiodes are formed; Coating, exposing and developing a photoresist on the interlayer insulating layer to form a lattice surrounding the microlens area; Selectively removing the interlayer insulating layer using a lattice of the photoresist as a mask to form a plurality of trenches having a predetermined depth from a surface; Removing the photoresist and forming a color filter layer inside each of the trenches; And forming a microlens on each of the color filter layers. The method of claim 4, further comprising curing the microlens by irradiating ultraviolet light. The method of claim 4, wherein the photoresist uses an MUV photoresist that responds to an I-line. The microlens is formed by coating, exposing and developing a microlens resist on an interlayer insulating film including the color filter layer to form a microlens pattern, and reflowing the microlens pattern. Method of manufacturing a CMOS image sensor. The method of claim 4, further comprising removing a color filter layer formed in the trench from a surface by a predetermined thickness. The method of claim 8, wherein the color filter layer is selectively removed using an ashing process. The method of claim 4, wherein the trench is formed deeper than a thickness of the color filter layer. The method of claim 4, wherein the trench is formed to be shallower than the sum of thicknesses of the color filter layer and the microlens.

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