KR100729744B1 - Method of manufacturing cmos image sensor - Google Patents

Abstract

A method for manufacturing a CMOS sensor is provided to prevent photon from being scattered to enhance optical properties by minimizing a space between respective micro-lenses. A semiconductor substrate(100) has an understructure including photodiodes(120) and metal wires(150), wherein each photodiode constitutes a unit pixel. A protective layer(160) is formed on the entire surface of the semiconductor substrate in which the understructure of the photodiodes and the metal wires are formed. A selective photolithography process using photoresist pattern is performed on the protective layer to form a trench(180) in each pixel region so that a surface tension induction line(160') is formed near a boundary of each pixel. After the photoresist pattern is removed, each trench is coated and filled with a color filter(190). A micro-lens(200) is formed on each color filter and each surface tension induction line.

Description

Method of manufacturing CMOS image sensor {Method of manufacturing CMOS image sensor}

1 is a cross-sectional structural view of a CMOS image sensor according to the prior art.

FIG. 2 is a schematic plan view of the pixel region a of the CMOS image sensor of FIG.

3 is a partial plan view of a CMOS image sensor according to the prior art.

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

5 is a plan view of FIG. 4d.

6 is a plan view of FIG. 4E.

<Description of the symbols for the main parts of the drawings>

100 semiconductor substrate 110 device isolation film

120: photodiode 130: pixel

140: interlayer insulating film 150: metal wiring

160: protective film 160 ': surface tension induction line

170: photoresist 180: trench

190: color filter 200: micro lens

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a CMOS image sensor, and in particular, to minimize light space between respective microlenses, to prevent light scattering and to prevent cross talk between adjacent pixels, thereby improving reliability of a device. It relates to a manufacturing method.

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, the Complementary MOS image sensor uses CMOS technology that uses a control circuit and a signal processing circuit as peripheral circuits. By using this method, a MOS transistor corresponding to the number of pixels is made, and a switching method of sequentially detecting output using the same is employed.

CCD (charge coupled device) has many disadvantages such as complicated driving method, high power consumption, and complicated process due to the large number of mask process steps, and it is difficult to realize signal processing circuit in CCD chip. Recently, in order to overcome such drawbacks, the development of a CMOS image sensor using a sub-micron CMOS manufacturing technology has been studied a lot.

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.

1 is a cross-sectional structural view of a CMOS image sensor according to the prior art.

As shown in the drawing, the conventional CMOS image sensor may include a peripheral circuit area b in which a signal processing circuit or a logic circuit is formed around the pixel area a in which an image is input, and the pixel area a ), Photodiodes 12 are respectively formed by the device isolation layer 11.

In the conventional CMOS image sensor, a plurality of interlayer insulating layers 14, wires 16, and a color filter array 18 are formed to form a multilayer wiring, and are formed on the color filter 18. The overcoat layer 19 and the micro lens 20 are formed.

The micro lens is formed with a predetermined space between the pixels.

According to the conventional technology, the planarization of the insulating film on which the color filter is formed is performed, and then the overcoating layer is formed on the upper part, followed by the planarization, and then the final microlens is formed. have.

FIG. 2 is a schematic plan view of the pixel area a of the image sensor of FIG. 1, in which a grape diode 12 and a microlens 20 are formed in each pixel 13, and the size of each pixel is greater than 20 pixels. It is classified in the order of micro lens> photo diode.

Looking at the plan view, the space portion A exists between the microlenses 20 adjacent to one side in the pixel, and the space portion B in the diagonal direction exists between the diagonally adjacent microlenses 20. Done.

In this case, the space between the adjacent micro lenses diagonally larger than the space between the adjacent micro lenses 20 is larger.

The unnecessary spaces scatter the photons incident to the lower photodiode through the microlens without focusing on the photodiode.

In addition, even when the pixel size increases, photons cannot be concentrated in the photodiode region because the diagonal space portion C still exists as shown in FIG. 3.

As the pixel size decreases with the development of technology, the microlens size also decreases, thereby increasing the space between the microlenses.

For example, as shown in FIG. 3, if the area occupied by the space portion C when the pixel size is increased is 1%, the area of the space portion when the pixel size is reduced may be 20% or more.

The space between each of the micro lenses interferes with the concentration of photons incident on the photodiode region, and causes a cross-talk phenomenon in which photons are incident to the adjacent photodiode region through the space portion, thereby reducing resolution. There is a problem.

An object of the present invention for solving the problems according to the prior art is to minimize the space between the micro-lenses to prevent scattering of incident photons to reach the corresponding photodiode to the maximum and adjacent photo diodes It is to provide a method of manufacturing a CMOS image sensor that can prevent the cross-talk phenomenon between.

The method of manufacturing the CMOS image sensor of the present invention for solving the above technical problem is a method of manufacturing a CMOS image sensor in which each photodiode, a metal wiring, a color filter, and a microlens constituting a unit pixel of each pixel are formed. Forming a protective film on the entire surface of the semiconductor substrate on which the substructures such as the photodiode and the metal wiring are formed; Forming a surface tension induction line on the portion, removing the photoresist pattern and coating and filling a color filter in each of the trenches, and forming a microlens on top of each color filter and on the surface tension induction line. A step is made.

In the embodiment of the present invention, the micro lens is preferably formed so that the space portion with the neighboring micro lens does not occur.

As described above, in the method for manufacturing the CMOS image sensor of the present invention, scattering of incident photons can be prevented as much as possible by preventing the microlens from generating a space portion with neighboring microlenses through surface tension with the protective film.

The invention will become more apparent through the preferred embodiments described below with reference to the accompanying drawings. Hereinafter will be described in detail to enable those skilled in the art to easily understand and reproduce through embodiments of the present invention.

4A to 4E are cross-sectional views sequentially illustrating a method of manufacturing a CMOS image sensor according to an exemplary embodiment of the present invention. The peripheral circuits are not illustrated and only pixel regions are illustrated.

First, as shown in FIG. 4A, an isolation layer 110 defining an active region and a field region is formed on the entire surface of the semiconductor substrate 100.

Then, the photodiode 120 is formed to receive light in a portion of the active region and convert the light into an electrical signal.

Although only the photodiode 120 and the device isolation layer 110 are illustrated in FIG. 4A, this is for convenience of description and the remaining elements constituting a unit pixel (eg, a plurality of gate electrodes, Source / drain regions, etc.) are not shown.

Subsequently, as shown in FIG. 4B, after forming the photodiode 120, the gate electrode, the source / drain region, and the like, an insulating film 140 and a metal wiring 150 formed of a plurality of layers are formed thereon. The protective layer 160 is formed on the uppermost layer.

The passivation layer 160 is to prevent the elements formed on the metal wire 150 and the semiconductor substrate 100 from being affected by moisture, scratches, etc., and SiO _{2 having a} general oxide film structure and a band structure include Si. All materials and all materials including the "F" concentration in these materials can be used.

Then, a photoresist pattern 170 is formed on the passivation layer 160 to expose a region corresponding to the upper portion of each photodiode 120 as shown in FIG. 4C.

Thereafter, the protective layer 160 is selectively etched using the photoresist pattern 170 to form trenches 180 in each pixel region 130 as shown in FIG. 4D. Remove (170).

The trench 180 is formed to be greater than or equal to the thickness of each color filter array CFA to be formed in a subsequent process.

In this case, as the trench 180 is formed, an oxide film line is formed at a boundary portion of each pixel 130, which is called a surface tension induction line 160 ′.

The surface tension induction line 160 ′ is preferably formed to have a width of 0.15 μm or less, but can be adjusted according to the size of the pixel.

FIG. 5 is a plan view from above of FIG. 4D, where each pixel 130 region is defined by a surface tension inducing line 160 ′, with the spacing between each pixel 130 being very fine.

In this case, each pixel area defined above is illustrated in a square shape in the drawing, but may be patterned into a rectangular shape or other shape.

In addition, the etching process using the photoresist pattern 170 may be a dry etching process using a plasma activated based on C _x F _y / O ₂ / Ar or CHF ₃ / CF ₄ / O ₂ / Ar, In some cases, it may be performed using a plasma in which He, N ₂ , and Co are selectively mixed.

On the other hand, after the trench 180 is formed, a process of coating the color filter 190 including red, green, and blue filling the trench 180 is performed as shown in FIG. 4E.

In this case, when the color filler 190 coating process is performed, the color filter 190 has an upper end portion having a beak shape (D) by the surface tension with the surface tension induction line 160 ′.

Subsequently, a microlens material is formed on the resultant formed color filter 190, and filled into the trench 180 by the surface force induction line 160 ′.

Thereafter, when a flow process is performed, the dome-shaped microlens 200 in which the microlens material exists to the upper portion of the surface tension induction line 160 ′ is formed. When the microlens 200 has a dome shape, light condensing efficiency is increased. At this time, although not shown, a process of forming a low temperature oxide film for protecting the microlens may be further performed.

6 is a plan view after the microlens flow is performed, in which the color filter 19 of each pixel is defined by a surface tension induction line 160 ', and the microlens 200 is connected to the surface tension induction line 160'. It can be seen that the space between each pixel is close to zero because it exists up to the top.

 Accordingly, since the space between the microlenses is close to zero, scattering of incident photons is prevented.

Although the present invention has been described with reference to the accompanying drawings, it will be apparent to those skilled in the art that many different and obvious modifications are possible without departing from the scope of the invention from this description. Therefore, the scope of the invention should be construed by the claims described to include many such variations.

As described above, according to the method of manufacturing the CMOS image sensor of the present invention, each of the neighboring microlenses is formed such that mutual spaces do not occur in the surface tension with the protective film, thereby preventing scattering of incident photons. As a result, the optical characteristics of the device can be improved by allowing the photodiode to reach the photodiode.

In addition, the present invention can improve the reliability of the device by preventing the cross-talk phenomenon in which photons are incident to the adjacent photodiode region through the space portion by preventing the space portion between each micro lens. There is this.

Claims (5)

In the manufacturing method of the CMOS image sensor which forms each photodiode, metal wiring, a color filter, and a micro lens which comprise the unit pixel of each pixel, Forming a protective film on an entire surface of the semiconductor substrate on which the lower structures such as the photodiode and the metal wiring are formed; Forming a trench in each pixel region by forming a trench in each pixel region by a selective photolithography process using a photoresist pattern on the passivation layer; After removing the photoresist pattern, filling each trench by coating a color filter; And And forming a microlens on the color filter and on the surface tension induction line. The method of claim 1, The trench depth is greater than or equal to the thickness of the color filter is formed manufacturing method of the CMOS image sensor. The method of claim 1, The etching process of forming the trench is a method of manufacturing a CMOS image sensor, characterized in that carried out using a plasma activated based on C _x F _y / O ₂ / Ar or CHF ₃ / CF ₄ / O ₂ / Ar. The method of claim 3, wherein The etching process is a method of manufacturing a CMOS image sensor, characterized in that using a plasma further mixed any one selected from He, N ₂ , Co. The method according to any one of claims 1 to 4, The micro lens is a method of manufacturing a CMOS image sensor, characterized in that formed so that the space portion with the neighboring micro lens does not occur.

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