KR100967744B1 - Cmos image sensor with bi-convex microlense and fabricating method of the same - Google Patents

Abstract

The present invention relates to a CMOS image sensor and a method of manufacturing the same, and more particularly, to a CMOS image sensor and a method of manufacturing the same by applying a double-sided convex lens as a microlens. The present invention for this purpose, the first OCL formed on the substrate is completed, the substructure including a photodiode; A plurality of color filters formed adjacent to each other on the first OCL; A second OCL formed on the color filter; A barrier line formed on the second OCL, the barrier line having a predetermined width only in an adjacent region of the color filter; A fourth OCL formed on the second OCL including the barrier line and having a curved surface that is convex toward the substrate; And a double-sided convex microlens formed on the fourth OCL.

Image sensor, double-sided convex lens, micro lens, overcoating layer

Description

CMOS image sensor with double-sided convex microlens and method for manufacturing the same {CMOS IMAGE SENSOR WITH BI-CONVEX MICROLENSE AND FABRICATING METHOD OF THE SAME}             

1 is a cross-sectional view showing a cross-sectional structure of the CMOS image sensor according to the prior art,

FIG. 2 is a view showing a path through which light is focused in a single-sided convex lens and a double-sided convex lens, respectively;

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

* Description of the symbols for the main parts of the drawings *

21 substrate 22 device isolation film

23 photodiode 24 interlayer insulating film

25: final metal wiring 26: passivation film

27: first OCL 28: color filter

29: second OCL 30: third OCL

31 fourth OCL 32 double-sided convex microlens

The present invention relates to a CMOS image sensor and a method of manufacturing the same, and in particular, by applying a double-sided convex lens as a microlens provided in the image sensor, by increasing the amount of light collected to improve the light sensitivity and improve the characteristics of the image sensor Invention.

In general, an image sensor is a semiconductor device that converts an optical image into an electrical signal. Among them, a charge coupled device (CCD) includes individual metal-oxide-silicon (MOS) capacitors. A device in which charge carriers are stored and transported in a capacitor while being in close proximity to each other. Complementary MOS image sensors use CMOS technology that uses a control circuit and a signal processing circuit as peripheral circuits. A device employing a switching scheme that creates MOS transistors as many as pixels and sequentially detects outputs using the MOS transistors.

CCD (charge coupled device) has many disadvantages such as complicated driving method, high power consumption, high number of mask process steps, complicated process, and difficult to implement one processing chip because signal processing circuit cannot be implemented in CCD chip. In order to overcome such drawbacks, the development of a CMOS image sensor using a sub-micron CMOS manufacturing technology has been studied in recent years. CMOS image sensor realizes image by forming photodiode and MOS transistor in unit pixel and detects signal in turn by switching method.It uses CMOS manufacturing technology, which consumes less power and 30 to 20 masks. Compared to CCD process which requires 40 masks, the process is very simple, and it is possible to make various signal processing circuits and one chip, which is attracting attention as the next generation image sensor.

The image sensor for implementing a color image has an array of color filters on the light sensing portion for generating and accumulating photocharges by receiving light from the outside. The color filter array (CFA) consists of three colors: red, green, and blue, or three colors: yellow, magenta, and cyan. It is made of color.

In addition, the image sensor is composed of a light sensing portion for detecting light and a logic circuit portion for processing the detected light as an electrical signal to make data. The ratio of the area of the light sensing portion in the entire image sensor element is increased to increase the light sensitivity. Efforts have been made to increase the fill factor, but these efforts are limited in a limited area because the logic circuit part cannot be removed.

Therefore, a condensing technology has emerged to change the path of light incident to an area other than the light sensing portion to raise the light sensitivity, and to collect the light sensing portion. For this purpose, the image sensor uses a microlens on the Cali filter. The method of forming is used.

FIG. 1 is a cross-sectional view illustrating a CMOS image sensor including such a color filter and a microlens. Referring to this, first, an isolation layer 12 defining an active region and a field region on a semiconductor substrate 11 is described. The photodiode 13 for receiving light and generating photocharges is formed in each unit pixel. In FIG. 1, each transistor constituting the unit pixel is not shown.

After the device isolation film 12 and related elements including the photodiode 13 are formed, the interlayer insulating film 14 is formed on the semiconductor substrate 11 and the final metal wiring 15 is then formed on the interlayer insulating film 14. ) Is formed. Although FIG. 1 shows the case where one metal wiring 15 is used, more metal wiring may be used, and the metal wiring formed at the top is referred to as the final metal wiring 15. In this case, the metal wires are intentionally laid out so as not to block the light incident on the photodiode 13.

After the final metal wiring 15 is formed in this manner, the passivation film 16 is formed on the final metal wiring 15 to protect the device from moisture, scratches, and the like.

Next, a first OCL (Over Coating Layer) is formed to remove the step by the final metal wiring 15 and the passivation film 16, which is formed on the surface where the color filter 18 to be subsequently formed is flattened. To make it possible. The first OCL 17 is made of a photosensitive film series material.

Next, a color filter 18 for color image realization is formed on the first OCL 17. As a color filter, a dyed photoresist is generally used, and one color filter 18 is formed for each unit pixel. Formed to separate color from incident light.

As shown in FIG. 1, the conventional color filters are formed using photoresist in all three filters of blue, red, and green, and are formed by slightly overlapping neighboring color filters. Since the adjacent color filters are formed to overlap each other slightly in this way, a step occurs and to compensate for this, the second OCL 19 is formed on the color filter 18 in a subsequent process.

The microlenses to be formed in the subsequent process should be formed on the flattened surface, which eliminates the step caused by the color filter. Accordingly, as described above, the second OCL 19 is formed on the color filter 18, and the second OCL 19 is also formed of a photoresist-based film.

After the second OCL 19 is formed above the color filter to remove the step, the microlens 20 is formed on the second OCL 19 having the flattened surface. The microlens 20 is formed by patterning a photoresist film for forming a microlens, and when the microlens is patterned in a rectangular shape through a thermal process, a microlens having a cross-sectional convex lens shape as shown in FIG. Can be formed.

In recent years, the size of an image sensor having such a configuration is gradually miniaturized, and accordingly, the size of a unit pixel is also reduced. If the size of the unit pixel is reduced, the area of the photodiode constituting the unit pixel is also expected to be significantly reduced, but the size of the color filter or microlens may be limited.

In other words, even if the size of the microlens or the color filter is reduced, it is expected that the area of the photodiode is not reduced. In this case, the amount of light that can be irradiated with the reduced photodiode is also reduced. When the single-sided convex microlenses are used, the amount of light decreases more severely. This will be described with reference to FIG. 2.

FIG. 2 is a diagram illustrating paths of light condensed in the case of a double-sided convex lens and a single-sided convex lens. Referring to this, in the case of a single-sided convex lens, light incident from the light source F1 toward the center of the single-sided convex lens is illustrated. Is condensed at the condensing point F2, but light incident on the edge of the cross-sectional convex lens is not condensed at the condensing point F2.

Looking at the case of the double-sided convex lens, not only the light incident from the light source F1 to the center of the double-sided convex lens, but also the light incident on the edge of the double-sided convex lens is condensed at the condensing point F2. Can be.

Therefore, when the double-sided convex lens is applied to the image sensor, it is possible to obtain an image sensor having excellent light sensitivity.

SUMMARY OF THE INVENTION The present invention has been made to solve the above-described problems, and an object thereof is to provide an image sensor and a method of manufacturing the same, which improve light sensitivity by applying a double-sided convex lens as a microlens.

The present invention for achieving the above object, the first OCL formed on the substrate is completed substructure including a photodiode; A plurality of color filters formed adjacent to each other on the first OCL; A second OCL formed on the color filter; A barrier line formed on the second OCL, the barrier line having a predetermined width only in an adjacent region of the color filter; A fourth OCL formed on the second OCL including the barrier line and having a curved surface that is convex toward the substrate; And a double-sided convex microlens formed on the fourth OCL.

In addition, the present invention comprises the steps of forming a first OCL on the substrate on which the formation of the substructure including a photodiode; Forming a plurality of color filters adjacent to each other on the first OCL; Forming a second OCL on the color filter; Forming and patterning a third OCL on the second OCL to form a barrier line having a constant width only on a second OCL corresponding to an area where the color filter is adjacent; Forming a fourth OCL having a curved surface convex toward the substrate on the second OCL including the barrier line; And forming a photoresist film for microlenses on the fourth OCL, patterning and flowing the microlens to form convex microlenses on both sides.

The present invention forms an overcoat layer in addition to the conventional overcoating layer and forms a frame on which the double-sided convex lens is to be formed using the additionally formed overcoating layer, and then the photosensitive film is flowed to form the double-sided convex lens. The invention is improved.                     

Hereinafter, the most preferred embodiments of the present invention will be described with reference to the accompanying drawings so that those skilled in the art can easily implement the technical idea of the present invention.

3A to 3F are cross-sectional views illustrating a method of manufacturing a CMOS image sensor according to an exemplary embodiment of the present invention, and a CMOS image sensor and a method of manufacturing the same according to an exemplary embodiment will be described with reference thereto.

Referring first to FIG. 3A, the process up to forming the second OCL 29 is the same as in the prior art. That is, the device isolation layer 22 defining the active region and the field region is formed on the semiconductor substrate 21, and a photodiode 23 is formed in each unit pixel to receive light to generate photocharges. In FIG. 3A, respective transistors constituting the unit pixel are not shown.

After the related devices including the device isolation layer 22 and the photodiode 23 are formed in this way, the interlayer insulating film 24 is formed on the semiconductor substrate 21 and the final metal wiring 25 is then formed on the interlayer insulating film 24. ) Is formed. Although FIG. 3A illustrates the case where one metal wire 25 is used, more metal wires may be used, and the metal wire formed at the top is referred to as the final metal wire 25. In this case, the metal wires are intentionally laid out so as not to block the light incident on the photodiode 23.

After the final metal wiring 25 is formed in this manner, the passivation film 26 is formed on the final metal wiring 25 to protect the device from moisture, scratches, and the like.                     

Next, a first overcoat layer (OCL) is formed on the passivation layer 26 to remove the step difference between the final metal wiring 25 and the passivation layer 26. 28) is formed on the flattened surface.

The first OCL 27 is formed of a photosensitive film series material, and after the first OCL 27 is applied to the passivation film 26 to a thickness of about 6500 mW, the first OCL 27 is first only in a region corresponding to the color filter. The applied first OCL 27 is patterned using an appropriate mask so that the OCL 27 is formed.

That is, the first OCL 27 is left in the unit pixel region where the color filter is to be formed, and the first OCL 27 applied to the input / output circuit region or the peripheral circuit region is removed using an appropriate mask (not shown). The mask will be referred to as a first mask (not shown). After patterning the first OCL 27 in this manner, a curing process is performed at 220 ° C. for 3 minutes.

Next, a color filter 28 for realizing a color image is formed on the first OCL 27. As a constituent of the color filter, a dyed photoresist is generally used, and one color filter 28 is formed in each unit pixel to separate colors from incident light.

The blue filter illustrated in FIG. 3A has a thickness of about 7000 약, the red filter has a thickness of about 8000 Å and the green filter has a thickness of about 7000 Å. After the color filter is formed in this way, the curing process must be performed at a predetermined temperature, in order to prevent reaction and chemical attack between the color filter materials. In one embodiment of the present invention, the curing process was performed at 220 ° C for 3 minutes.

Referring to FIG. 3A, since the neighboring color filters are formed to overlap slightly, a step is generated. In order to compensate for this, a second OCL 29 is formed on the color filter 28 in a subsequent process.

The microlenses to be formed in the subsequent process should be formed on the flattened surface, which eliminates the step caused by the color filter. Accordingly, as described above, the second OCL 29 is formed on the color filter 28, and the second OCL 29 is formed of a photoresist-based film.

Since the second OCL 29 should be formed only in a region corresponding to the color filter like the first OCL 27, the first mask (not shown) is applied after the second OCL 29 having a thickness of 4000 kPa is applied. ) To pattern.

Next, as shown in FIG. 3B, the third OCL 30 is applied on the second OCL 29 to a thickness of 2400 to 2600 μs, and then shown in FIG. 3C using a second mask (not shown). As described above, the third OCL 30 is patterned to form the barrier line 30.

Referring to FIG. 3C, the third OCL 30 has a width d of about 0.4 to 0.6 μm and remains only in an area corresponding to the boundary between the color filter and the color filter, so that the barrier line 30 remains. ) And the third OCL 30 present in the remaining area is patterned to be removed. The mask used in the third OCL 30 patterning process is referred to as a second mask (not shown). The function of the barrier line 30 is to form a frame in which the double-sided convex lens will be formed in a subsequent process.

After the barrier line 30 is formed in this manner, as shown in FIG. 3D, the fourth OCL 31 is applied to the second OCL 29 including the barrier line 30 in a thickness of 5000 kPa. The fourth OCL 31 is applied to have a curved surface due to the step due to the barrier line 30, which is shown in FIG. 3D. The fourth OCL 31 having the curved surface convex toward the substrate serves as a frame in which the double-sided convex lens will be formed in a subsequent microlens forming process.

Next, as shown in FIG. 3E, a microlens forming photoresist film 32 is applied on the fourth OCL 31 to a thickness of 5500 to 7500 kPa, and patterned to form one microlens 32 for each unit pixel. ). As the photoresist film 32 for forming the microlenses used in the embodiment of the present invention, a silicon oxide film-based photosensitive resist having good light transmittance was used. The microlens 32 shown in Fig. 3E has an angular shape since it has not yet flowed.

Next, when the process of flowing the microlenses is performed, as shown in FIG. 3F, microlenses convex on both sides can be obtained. That is, since the fourth OCL 31 existing under the microlens has a curved surface that is convex toward the substrate 21, when the flow process is performed, the bottom surface of the microlens 32 is also curved in the fourth OCL 31. The convex flows along, and the upper surface of the microlens 32 is convex in the same manner as in the prior art, it is possible to obtain a convex microlens on both sides.

Hereinafter, the flow process according to an embodiment of the present invention will be described in more detail. First, as shown in FIG. 3E, after patterning the photoresist film 32 for forming a microlens formed on the fourth OCL 31, blank exposure using a stepper is performed.

In the above blank exposure step, light having a wavelength of 248 nm is used. Through this exposure process, the PAC (Photo Active Compound) component present in the microlens forming photosensitive film 32 is decomposed, and when the thermal process is subsequently performed, the flow proceeds smoothly.

That is, since the bonding force is reduced when the PAC component is decomposed through the exposure process, through the flow process for 5 minutes at a temperature of 150 ℃, it is possible to obtain a two-sided convex microlens as shown in Figure 3f, After such a flow process, the curing process is further performed at 200 ° C. for 5 minutes to harden the shape of the microlens.

When applied to the CMOS image sensor of the present invention, the size of the photodiode is reduced (for example, 2.0㎛ × 2.0㎛), while the size of the microlens and the color filter is constant (for example, 3.2㎛ × 3.2㎛) The recent trend of decreasing below) has the advantage of improving the light sensitivity of the CMOS image sensor.

In addition, in the exemplary embodiment of the present invention, the case in which the double-sided convex microlens is applied to the CMOS image sensor has been described as an example, but the microlens is also applied to the charge coupled device (CCD) in addition to the CMOS image sensor. Silver can also be applied to charge coupled devices.

As described above, the present invention is not limited to the above-described embodiments and the accompanying drawings, and the present invention may be variously substituted, modified, and changed without departing from the spirit of the present invention. It will be apparent to those of ordinary skill in Esau.

When applying the present invention made as described above, it is possible to form a convex microlens on both sides, there is an effect that the photosensitivity is improved even in the miniaturized image sensor.

Claims (8)

As CMOS image sensor, A first OCL formed on a substrate on which a substructure including a photodiode is completed; A plurality of color filters formed adjacent to each other on the first OCL; A second OCL formed on the color filters; A barrier line formed on the second OCL, the barrier lines having a predetermined width only in an adjacent region of the color filters; A fourth OCL formed on the second OCL including the barrier line, the fourth OCL having a convex curved surface facing toward the substrate; And Double-sided convex microlenses formed on the fourth OCL CMOS image sensor comprising a. The method of claim 1, And the barrier line has a thickness of 2400 m 2 to 2600 m and a width of 0.4 m to 0.5 m. The method of claim 1, The double-sided convex microlens is made of a silicon oxide-based photosensitive film, CMOS image sensor. As a method of manufacturing the CMOS image sensor, Forming a first OCL on the substrate on which the substructure including the photodiode is completed; Forming a plurality of color filters adjacent to each other on the first OCL; Forming a second OCL on the color filters; Forming and patterning a third OCL on the second OCL to form a barrier line having a constant width only on a second OCL corresponding to an area in which the color filter is adjacent; Forming a fourth OCL having a convex curved surface directed toward the substrate on the second OCL including the barrier line; And Forming a double-sided convex microlens by forming a photoresist film for microlenses on the fourth OCL, patterning and flowing the same; Method of manufacturing a CMOS image sensor comprising a. The method of claim 4, wherein Forming a barrier line on the second OCL, And the barrier line is formed to have a thickness of 2400 m 2 to 2600 m and a width of 0.4 m to 0.5 m. The method of claim 5, Forming a fourth OCL having a convex curved surface directed toward the substrate on the second OCL including the barrier line, And the fourth OCL is formed to have a thickness of 5000 kPa. The method of claim 4, wherein Forming and flowing a photoresist film for microlenses on the fourth OCL, Blank exposing the microlens photosensitive film; Flowing the microlens photosensitive film for 5 minutes at a temperature of 150 ° C .; And Curing the photosensitive film for microlenses for 5 minutes at a temperature of 200 ℃ Further comprising, the manufacturing method of the CMOS image sensor. The method of claim 4, wherein In the step of forming a photosensitive film for microlens on the fourth OCL, The microlens photosensitive film is a method of manufacturing a CMOS image sensor is formed to a thickness of 5500 5 to 7500Å.

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