KR101001093B1 - CMOS image sensor with improved characteristics and manufacturing method - Google Patents

Abstract

The present invention relates to a CMOS image sensor and a method of manufacturing the same, and in particular, by forming a third OCL having a guard space on the second OCL to compensate for the step caused by the color filter and forming a microlens on the third OCL, The invention improves the uniformity with respect to the size and height of the lens, and also facilitates the CD measurement to improve the characteristics and yield of the image sensor. 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 third OCL formed on the second OCL corresponding to the color filter, the third OCL having a predetermined space and spaced apart from each other; And a microlens formed on the third OCL.

Image Sensor, Critical Dimension, Micro Lens, Overcoat Layer

Description

CMOS image sensor with improved characteristics and its manufacturing method {CMOS IMAGE SENSOR WITH IMPROVED CHARACTERISTICS AND FABRICATING METHOD OF THE SAME}             

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

1B is a plan view showing an OCL, a color filter, and a microlens in a unit pixel of a CMOS image sensor according to the related art;

2A to 2E are cross-sectional views illustrating a manufacturing process of the CMOS image sensor according to an embodiment of the present invention;

3 is a plan view showing an OCL, a color filter, and a microlens in a unit pixel of 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 microlens

The present invention relates to a CMOS image sensor and a method for manufacturing the same, and to improve the uniformity of the width and height of the microlens, and to facilitate the measurement of the CD (Critical DImension) to improve the characteristics and yield of the image sensor .

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. Recently, in order to overcome such drawbacks, the development of CMOS image sensors using sub-micron CMOS manufacturing techniques has been studied. The CMOS image sensor forms an image by forming a photodiode and a MOS transistor in a unit pixel and sequentially detects signals in a switching method, and implements an image by using a CMOS manufacturing technology, which consumes less power and uses 30 to 40 masks as many as 20 masks. Compared to CCD process that requires two 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.

An image sensor for realizing a color image has an array of color filters on the upper part of the light sensing portion that receives and receives light from the outside to generate and accumulate photocharges. The color filter array (CFA) consists of three colors: red, green, and blue, or three colors: yellow, magenta, and cyan. It is made of collar.

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, in order to increase the light sensitivity, a light converging technology has emerged that changes the path of light incident to the area other than the light sensing part and collects the light into the light sensing part. For this purpose, the image sensor uses a microlens on the color filter. The method of forming is used.

FIG. 1A is a cross-sectional view showing a configuration of 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 which receives light and produces | generates a photocharge is formed in each unit pixel. In FIG. 1A, respective transistors constituting the unit pixel are not shown.

After the related devices including the device isolation layer 12 and the photodiode 13 are formed in this way, the interlayer insulating film 14 is formed on the semiconductor substrate 11, and the final metal wiring 15 is formed on the interlayer insulating film 14. Is formed. Although FIG. 1A illustrates the case where one metal wiring 15 is used, more metal wirings 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 on the passivation film 16 to remove the step by the final metal wiring 15 and the passivation film 16, which is a color filter to be formed subsequently This is to make the 18 be formed on the flattened surface. 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. The color filter is typically a dyed photoresist, and one color filter 18 for each unit pixel. Is formed to separate the color from the incident light.

As shown in FIG. 1A, a conventional color filter is formed using photoresist in all three filters of blue, red, and green, and neighboring color filters are formed to overlap each other slightly. 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.

Microlenses for collecting light must be formed on the flattened surface, which eliminates the step caused by the color filter. Therefore, as described above, the second OCL 19 is formed on the color filter 18 to eliminate the step, and the second OCL 19 also includes a photoresist-based film.

After the second OCL 19 is formed above the color filter 18 to remove the step, the microlens 20 is formed on the second OCL 19 having the flattened surface. A method of forming the microlens 20 will be described below.

First, a photosensitive photoresist of a silicon oxide film series having high light transmittance is applied by using a spin-on-coater. Next, a patterning process using an appropriate mask is performed to form an angular microlens corresponding to each unit pixel.

Next, by applying a thermal process to flow the angular microlens, a dome-shaped microlens as shown in FIG. 1A can be obtained.

Under the recent trend that the size of the microlenses is reduced to 4 μm or less, when the microlenses are manufactured by using the conventional method, there are the following problems, which will be described with reference to FIG. 1B.

FIG. 1B is a plan view showing a first OCL 17, a second OCL 19, a color filter 18, and a microlens 20 in a unit pixel of a CMOS image sensor manufactured by applying a conventional technique. It can be seen that the patterned microlens 20 is formed in a bias or the outer boundary thereof is unclear.

That is, the microlenses according to the prior art are not formed in the portion where the microlenses are to be formed accurately (for example, aligned at the center of the unit pixel), are formed in a biased manner, or the outer boundary of the microlens is unclear. The formation and the uniformity of the size and the height were lowered.

In addition, due to the uncertainty of the pattern as described above, it is difficult to measure the critical dimension, and also due to the instability of the process, the amount of light focused on the photodiode is reduced.

The present invention is to solve the above-mentioned problems, and to provide a CMOS image sensor and a method of manufacturing the same, which improves the uniformity of the size and height of the microlens and CD measurement.

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 third OCL formed on the second OCL corresponding to the color filter, the third OCL having a predetermined space and spaced apart from each other; And a microlens formed on the third 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; Applying and patterning a third OCL on the second OCL to form a third OCL having a predetermined space and spaced apart from each other on a second OCL corresponding to the color filter; Forming a photoresist film for microlenses on the second OCL including the third OCL; Patterning the microlens photoresist so that the microlens photoresist remains only on the third OCL; And forming a hemispherical microlens on the third OCL by flowing the patterned microlens photosensitive film.

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a CMOS image sensor and a method of manufacturing the same, and in particular, a third OCL is formed on a second OCL (Over Coating Layer) functioning to remove a step caused by a color filter, and a guard spacer is formed. By appropriately patterning the third OCL, the uniformity of the width and height of the microlens to be formed on the third OCL in a subsequent process is improved, and the CD (Critical Dimension) measurement is facilitated to facilitate the characteristics of the image sensor. And the invention which improved the yield.

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.

2A to 2E are process 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 embodiment of the present invention will be described with reference thereto.

Referring first to FIG. 2A, 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. 2A, 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. 2A 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 OCL (Over Coating Layer) is formed on the passivation film 26 to remove the step by the final metal wiring 25 and the passivation film 26, which is a color filter to be formed subsequently ( 28) is formed on the flattened surface.

The first OCL 27 is formed of a photosensitive film-based material, and after the first OCL 27 is applied to the passivation film 26 to a thickness of about 6500 mm 3, the first OCL 27 is applied only to 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 only in the unit pixel region where the color filter is to be formed, and the first OCL 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 implementing 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 while being slightly overlapped, 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 a subsequent process should be formed on the flattened surface, which eliminates the step caused by the color filter. Therefore, as described above, the second OCL 29 is formed on the color filter 28. The second OCL 29 is formed of a photoresist film.

Since the second OCL 29 should be formed only in a region corresponding to the color filter like the first OCL 27, after applying the second OCL 29 having a thickness of 5000 kPa, the first mask (not shown) ) To pattern.

Next, as shown in FIG. 2A, the third OCL 30 is applied on the second OCL 29 to a thickness of 1400 to 1600 mm 3, and then the third OCL 30 is patterned using an appropriate mask. The third OCL 30 is patterned to have a guard space d1 of 0.4 to 0.6 mu m, and the mask used at this time will be referred to as a second mask (not shown).

Referring to FIG. 2A, the third OCL 30 corresponds to each color filter 28 and has a guard space d1 of 0.4 to 0.6 μm and is spaced apart from each other. It can be seen that the width d2 is smaller than the width of the color filter. In addition, the third OCL 30 is formed to have a wider width d2 than the width of the microlens in consideration of the width of the microlens to be formed in a subsequent process.

According to one embodiment of the present invention, since the microlenses are formed on the third OCL 30 formed to be spaced apart from each other while having a guard space, uniformity with respect to the size or height of each microlens is improved, and micro The outer boundary of the lens is clearly formed to facilitate CD measurement.

After patterning the third OCL 30 in this manner, as shown in FIG. 2B, a photoresist film for forming a microlens with a high transmittance of silicon oxide film on the second OCL 29 including the third OCL 30 ( 31) is applied to a thickness of 5500 ~ 7500Å.

Subsequently, as shown in FIG. 2C, the microlens forming photosensitive film 31 is patterned such that the microlens forming photosensitive film 31 remains only on the third OCL 30. At this time, the width of the patterned microlens forming photosensitive film 31 is set to be narrower than the width d2 of the third OCL 30 in consideration of a subsequent flow process. The microlens-forming photosensitive film 31 shown in Fig. 2C has an angular shape since it has not yet flowed.

Next, a flow process is performed to change the angled microlenses into hemispherical microlenses. Hereinafter, the flow process according to an embodiment of the present invention will be described in more detail.

First, after patterning the photoresist film 31 for forming a microlens formed on the third OCL 30 as described above, blank exposure using a stepper as shown in FIG. 2D is performed. Proceed. Through this exposure process, the PAC (Photo Active Compound) component present in the microlens forming photosensitive film 31 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, a hemispherical microlens as shown in FIG. 2E can be obtained through the flow process for 5 minutes at a temperature of 150 ° C. After the flow process, the curing process is further performed at 200 ° C. for 5 minutes to harden the shape of the microlens.

Referring to FIG. 2E, since the microlens 31 according to the exemplary embodiment of the present invention is formed on the third OCL 30 formed with the guard space spaced apart from each other, it can be seen that the size and height are uniformly formed. The formed microlens 31 has a thickness of 5500 to 7500 mW.

3 illustrates a first OCL 27, a second OCL 29, a third OCL 30, a color filter 28, and a microlens 31 in a unit pixel of a CMOS image sensor according to an exemplary embodiment of the present invention. Is a plan view showing a state formed.

Referring to FIG. 3, the first OCL 27 in contact with the color filter 28 and formed under the same, and the second OCL 29 in contact with the color filter 28 and formed over the same first mask (not shown). Since it is patterned using), it has the same shape in plan.

When viewed in plan view, the color filter 28 is formed inside the first OCL 27 and the second OCL 29. Also in plan view, a third OCL 30 is formed inside the color filter 28, and the third OCL 30 has the same octagonal shape as the microlens. In addition, the microlens 31 is formed inside the third OCL 30, and the microlens 31 is formed in alignment with the region to be formed without any bias to either side, and the outer boundary surface thereof is also formed. Clearly patterned, there is no difficulty in measuring CD.

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, there is an advantage that the uniformity of the size and height of the microlens is improved to stabilize the characteristics and color characteristics of the device, and the boundary between the microlens and the microlens is CD-SEM (Critial Dimension-Scanning Electron Microscopy) is also clearly distinguished, there is an advantage that does not require CD measurement.

Claims (6)

In the 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 filter; A third OCL formed on the second OCL corresponding to the color filter, the third OCL having a predetermined space and spaced apart from each other; And A microlens formed on the third OCL Including; And the third OCL has an octagonal shape and the width of the microlenses is narrower than the width of the third OCL. The method of claim 1, The spacer, wherein the third OCL is spaced apart from each other, is 0.4 to 0.6 μm, and the third OCL has a thickness of 1400 to 1600 Å. The method of claim 1, The micro lens is a CMOS image sensor having a thickness of 5500 ~ 7500Å. In the 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 filter; Applying and patterning a third OCL on the second OCL to form a third OCL having a predetermined space and spaced apart from each other on the second OCL in correspondence with the color filter; Forming a photoresist film for microlenses on the second OCL including the third OCL; Patterning the microlens photoresist so that the microlens photoresist remains only on the third OCL; And Forming a hemispherical microlens on the third OCL by flowing the patterned photoresist for microlens Including; And the third OCL has an octagonal shape, and after the microlens is formed on the third OCL, the width of the microlens is narrower than the width of the third OCL. The method of claim 4, wherein In the step of applying and patterning a third OCL on the second OCL, The third OCL is patterned to have a width wider than the width of the microlens, and the third OCL is patterned to be spaced apart having a space of 0.4 ~ 0.6㎛ patterned manufacturing method of the CMOS image sensor. The method of claim 4, wherein Flowing the patterned microlens photosensitive film, Blank exposing the patterned microlens photoresist; 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 ° C. Method of manufacturing a CMOS image sensor further comprising.

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