KR100461977B1 - CMOS image sensor 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 in particular, by forming a valley in the lower flattening film and forming a color filter and a microlens inside the prevention bone to prevent bridge phenomenon between adjacent microlenses, and further, an upper leveling film The invention is simplified by omitting the forming step. The present invention for this purpose, the passivation film formed on the semiconductor substrate in which the photodiode is completed; A planarization film formed on the passivation film and having a valley in a region corresponding to the photodiode; And a color filter and a micro lens formed by being stacked in the valley. In addition, the present invention comprises the steps of forming a related element comprising a photodiode and a metal wiring on a substrate; Forming a passivation film on the metal wiring; Forming a planarization film on the passivation film; Patterning the planarization layer to form a valley in an area corresponding to the photodiode; And sequentially forming a color filter and a microlens in the valley.

Description

CMOS image sensor and fabrication method {CMOS image sensor and fabricating method of the same}

The present invention relates to a CMOS image sensor, in particular to form a valley (valley) in the lower flattening film formed on the lower portion of the color filter and to prevent the bridge phenomenon by forming a color filter and a micro lens inside the valley, forming the upper flattening film The invention is a simplified process by omitting the process.

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 signal processing circuit 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. The CMOS image sensor forms an image by forming a photodiode and a MOS transistor in a unit pixel (Pixel) and sequentially detects signals through a switching method.As a CMOS manufacturing technique, the power consumption is low and the number of masks is 20 to 30 to 40. 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 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, 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 showing a cross section of a CMOS image sensor including a color filter and a microlens as described above. First, an element isolation layer 12 defining an active region and a field region is formed on a semiconductor substrate 11, and a photodiode 13 is formed in each unit pixel to receive light to generate photocharges. In FIG. 1, the respective transistors constituting the unit pixel are 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. In FIG. 1, although one metal wire 15 is used, more metal wires may be used. In an embodiment of the present invention, a case in which one metal wire is used has been described as an example. This is called the 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 to protect the device from moisture, scratches, and the like.

Next, the lower leveling film 17 is formed to remove the step difference between the final metal wiring 15 and the passivation film 16, so that the color filter to be formed subsequently is formed on the flattened surface. The lower planarization layer is made of a photoresist-based material, and is also referred to as an under over coating layer (under OCL).

Next, a color filter 18 for forming a color image is formed on the lower planarization layer 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 overlapped portion becomes thicker in the photoresist, light transmittance is weakened, resulting in loss of light.

In addition, since adjacent color filters are formed to overlap each other slightly, a step is generated because it is not easy to control the final thickness of each color filter, and to compensate for this, an upper leveling film is required as a subsequent step, which complicates the process. There was this.

In order for the microlenses to be formed in a subsequent process to be formed on the flattened surface, the step due to the color filter must be eliminated. To this end, an upper planarization film 19 is formed on the color filter 18. The upper planarization film 19 is also made of a photoresist-based film, also referred to as an upper over coating layer (Upper OCL). do.

After forming the upper planarization film 19 to remove the step, the microlens 20 is formed on the upper planarization film 19 having the planarized surface. The microlens 20 may form a dome-shaped microlens by flowing a rectangular photosensitive film.

In the CMOS image sensor having such a structure, the wider the dome-shaped microlens, the larger the amount of light that can be received. Seen in the disadvantages.

In other words, when the width of the microlenses is wide, the light condensing efficiency is increased by increasing the amount of light that is acceptable. However, the wider the width of the microlenses, the narrower the interval between adjacent microlenses, There was a disadvantage in that a bridge phenomenon in which adjacent microlenses were stuck to each other occurred.

The present invention is to solve the above-described problems, forming a valley in the flattening film formed on the lower portion of the color filter and preventing the bridge phenomenon by forming a color filter and a microlens in the valley to prevent the upper planarization film forming process It is an object of the present invention to provide a CMOS image sensor and a method of manufacturing the same by simplifying the process.

1 is a cross-sectional view showing a cross-sectional structure of a conventional CMOS image sensor;

2A to 2E 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: lower flattening film 28: color filter

29 microlens

30: Goal

The present invention for achieving the above object, the passivation film formed on the semiconductor substrate with the photodiode formed on the bottom structure; A planarization film formed on the passivation film and having a valley in a region corresponding to the photodiode; And a color filter and a microlens formed by being stacked in the valley. In addition, the present invention provides a method of manufacturing a CMOS image sensor, comprising the steps of: forming a related element comprising a photodiode and a metal wiring on a substrate; Forming a passivation film on the metal wiring; Forming a planarization film on the passivation film; Patterning the planarization layer to form a valley in an area corresponding to the photodiode; And sequentially forming a color filter and a microlens in the valley.

The present invention is an invention in which a valley is formed on a lower flattening film and a color filter and a microlens are stacked and formed in the valley formed in this way to prevent bridge phenomenon and at the same time simplify the process.

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 manufacturing process of a CMOS image sensor according to an exemplary embodiment of the present invention, and a CMOS image sensor and a manufacturing method thereof according to an exemplary embodiment of the present invention will be described with reference thereto.

Referring first to FIG. 2A, the process up to forming the final metal wiring 25 and the passivation film 26 is the same as in the prior art. That is, after forming the isolation layer 22 defining the active region and the field region on the semiconductor substrate 21, unit pixels including the photodiode 23 are formed in a predetermined region in the substrate. In FIG. 2A, only the photodiode 23 is shown among the elements of the unit pixel, and each transistor constituting the unit pixel is not shown.

After the device isolation film 22, the photodiode 23, and the transistors (not shown) are formed, the interlayer insulating film 24 is formed on the semiconductor substrate 21, and the metal wiring 25 is then formed on the interlayer insulating film ( 24) form. Although FIG. 2A illustrates the case where one metal wire 25 is used, more metal wires may be used. In this case, the metal wires are intentionally laid out so as not to block the light incident on the photodiode 22.

After the final metal wiring 25 is formed in this manner, the passivation film 26 is formed on the interlayer insulating film 24 including the final metal wiring 25 to protect the device from moisture, scratches, and the like. do.

Next, a lower planarization layer 27 is formed on the passivation layer 26 in order to remove the step difference between the final metal wiring 25 and the passivation layer 26. In an embodiment of the present invention, the lower planarization layer 27 is formed. The deposition thickness of (27) is formed to be thicker than before. This is because a valley is formed in the lower planarization layer 27 in a subsequent process, and the color filter and the microlens are overlapped and formed in the valley. The lower planarization film used in one embodiment of the present invention is formed using a positive photoresist.

Next, as shown in FIG. 2B, after the exposure process is performed on the lower planarization layer 27, a patterning process of removing a region corresponding to the photodiode 23 is performed to form the valley 30. Next, after forming such a valley 30, the firing process (curing) is performed. At this time, it is possible to form by adjusting the dose (dose) using a BIM mask in the process of forming a bone, it can be produced by changing the transmittance of HtPSM.

In addition, the mask used to pattern the bone may use the mask to be used to pattern subsequent color filters.

2B to 2C, each valley 30 is formed in the lower planarization layer 27 of the region corresponding to the photodiode 23, and a high wall is formed between the valleys 30 and 30. It exists. In one embodiment of the present invention, since the color filter 27 is formed inside the valley 30, since there is no overlap between adjacent color filters, there is an advantage in that the thickness of the color filter can be easily adjusted.

In the prior art, due to the overlap between adjacent color filters, it is difficult to control the final thickness of the color filter, so a step caused by the color filter is generated. In order to compensate for this, the upper flattening film has to be formed on the upper part of the color filter.

However, in one embodiment of the present invention by removing the overlap between the color filters at the source, it is easy to adjust the thickness of the color filter. Therefore, in one embodiment of the present invention, since the thickness of the color filter can be uniformly formed, it is possible to prevent the generation of the step caused by the color filter, and thus there is an advantage of not having to form the upper leveling film.

When the color filter 28 is formed inside the valley 30 according to an embodiment of the present invention, the thickness of the color filter 28 is set not to exceed the depth of the valley 30. This is to prevent the bridge phenomenon by using the microlens 29 to be formed subsequently also has a structure in which the valleys 30 are formed.

As a constituent of the color filter 28, a dyed organic photoresist is usually used. Such a color filter is formed one by one for each unit pixel through an exposure process using an appropriate reticle, and serves to separate colors from incident light.

As such, after the color filter 28 is formed in the valley 30 to an appropriate thickness, the photoresist film 29 for forming a microlens is formed directly on the color filter 28.

That is, in one embodiment of the present invention, the microlens 29 is patterned as shown in FIG. 2D without forming an upper planarization layer on the color filter 28. At this time, the patterned photosensitive film 29 for forming the microlenses is formed to have a narrower width than the width of the valley 30 in consideration of a subsequent flow process.

Next, as illustrated in FIG. 2E, a dome-shaped microlens 29 may be obtained by flowing a photoresist film for forming a rectangular microlens using a thermal process.

In one embodiment of the present invention, since the microlens 29 is also formed in the valley, there is an advantage that can prevent the bridge phenomenon that is stuck with the adjacent microlenses even if the subsequent flow process, and also, as in the prior art, In consideration of the burden of maintaining the distance between adjacent microlenses over a certain distance, the size of the microlenses can be increased compared to the conventional art.

That is, if the lower planarization film 27 is patterned by setting the thickness of the wall separating the bone 30 and the bone 30 to be thin, the size of the microlenses can be significantly increased.

As described above, the present invention is not limited to the above-described embodiments and the accompanying drawings, and various substitutions, modifications, and changes are possible in the art without departing from the technical spirit of the present invention. It will be clear to those of ordinary knowledge.

The present invention as described above, the step of preventing the step caused by the color filter can be omitted because the step of forming the upper planarization film has the effect of simplifying the process, and also prevents the bridge phenomenon of the microlens and at the same time reduce the size of the microlens Since it can be increased, there is an effect of improving the characteristics of the CMOS image sensor.

Claims (4)

In the CMOS image sensor, A passivation film formed on the semiconductor substrate having the photodiode formed thereon; A planarization film formed on the passivation film and having a valley in a region corresponding to the photodiode; And Color filters and microlenses stacked inside the valley CMOS image sensor comprising a. The method of claim 1, The planarization film is CMOS image sensor, characterized in that consisting of a positive photoresist. In the method of manufacturing the CMOS image sensor, Forming an associated device on the substrate, the photodiode and the associated device comprising a metallization; Forming a passivation film on the metal wiring; Forming a planarization film on the passivation film; Patterning the planarization layer to form a valley in an area corresponding to the photodiode; And Sequentially forming a color filter and a microlens in the valley Method for manufacturing a CMOS image sensor comprising a. The method of claim 3, wherein Patterning the planarization layer to form a valley in a region corresponding to the photodiode; And a mask used for patterning the planarization film is a mask used for patterning a color filter.