KR100731127B1 - Method for manufacturing cmos image sensor - Google Patents

Abstract

A method for manufacturing a CMOS image sensor is provided to prevent the degradation of sensibility of a sensor by preventing the contamination of a microlens surface and a color filter layer due to the particles caused by a back grinding process and a die sawing process using a protection layer made of a tert-butylalchol layer. A plurality of photodiodes(12) and a variety of transistors(13) are formed on a semiconductor substrate(11) defined with a sensing region, a peripheral region, and a pad region. A plurality of interlayer dielectrics and a plurality of metal lines are formed on the resultant structure. A protection layer(18) is formed thereon. A color filter layer(19) and a microlens(20) are formed on the protection layer of the sensing region. A lens protection layer(21) made of a tert-butylalchol layer is formed on the resultant structure. A grinding process and a die sawing process are performed on a rear surface of the substrate.

Description

Method for manufacturing CMOS image sensor

1 is an equivalent circuit diagram of a typical 3T CMOS image sensor

2 is a layout diagram illustrating unit pixels of a general 3T CMOS image sensor.

3 is a cross-sectional view showing a unit pixel of a conventional CMOS image sensor

4 is a structural cross-sectional view of the CMOS image sensor according to the present invention

Explanation of symbols for the main parts of the drawings

11 semiconductor substrate 12 photodiode

13: transistor 14: first interlayer insulating film

15: second interlayer insulating film 16: third interlayer insulating film

17: fourth interlayer insulating film 18: protective film

19 color filter layer 20 micro lens

21: Tet-butyl alcohol layer

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a CMOS image sensor, and more particularly, to a method for manufacturing a CMOS image sensor for preventing contamination of a microlens formed on a top layer of a CMOS image sensor from foreign matter.

In general, an image sensor is a semiconductor device that converts an optical image into an electrical signal, and includes a charge coupled device (CCD) and a complementary MOS image sensor. Are distinguished.

The charge coupling device includes a plurality of photo diodes (PDs) for converting a signal of light into an electrical signal, arranged in a matrix form, and formed between the photo diodes in each vertical direction arranged in the matrix form. A plurality of vertical charge coupled devices (VCCDs) for vertically transferring charges generated in the diodes and horizontal charge transfers for horizontally transferring charges transferred by the respective vertical charge transfer regions (VCCD) A horizontal charge coupled device (HCCD) and a sense amplifier for outputting an electrical signal by sensing the charge transmitted in the horizontal direction.

However, such a charge coupling device has a disadvantage in that the driving method is complicated, the power consumption is high, and the manufacturing process is complicated because a multi-step photo process is required. In addition, the charge coupling device has a disadvantage in that it is difficult to integrate a control circuit, a signal processing circuit, an analog / digital converter (A / D converter), and the like into a charge coupling device chip, which makes it difficult to miniaturize a product.

Recently, CMOS image sensors have attracted attention as next generation image sensors for overcoming the disadvantages of the charge coupled device. The CMOS image sensor is formed by forming the MOS transistors corresponding to the number of unit pixels on the semiconductor substrate using CMOS technology using a control circuit, a signal processing circuit, and the like as peripheral circuits. The device adopts a switching method for sequentially detecting the output of the. That is, the CMOS image sensor implements an image by sequentially detecting an electrical signal of each unit pixel by a switching method by forming a photodiode and a MOS transistor in the unit pixel.

The CMOS image sensor has advantages, such as a low power consumption, a simple manufacturing process according to a few photoprocess steps, by using CMOS manufacturing technology. In addition, since the CMOS image sensor can integrate a control circuit, a signal processing circuit, an analog / digital conversion circuit, and the like into the CMOS image sensor chip, the CMOS image sensor has an advantage of easy miniaturization. Therefore, the CMOS image sensor is currently widely used in various application parts such as a digital still camera, a digital video camera, and the like.

A general CMOS image sensor will be described with reference to the accompanying drawings.

1 is an equivalent circuit diagram of a general 3T CMOS image sensor.

As shown in FIG. 1, a unit pixel of a general 3T CMOS image sensor includes one photodiode (PD) and three nMOS transistors T1, T2, and T3. The cathode of the photodiode PD is connected to the drain of the first nMOS transistor T1 and the gate of the second nMOS transistor T2.

The sources of the first and second nMOS transistors T1 and T2 are all connected to a power supply line supplied with a reference voltage VR, and the gate of the first nMOS transistor T1 has a reset signal RST. It is connected to the reset line supplied.

Further, the source of the third nMOS transistor T3 is connected to the drain of the second nMOS transistor, the drain of the third nMOS transistor T3 is connected to a read circuit (not shown in the drawing) via a signal line, The gate of the third nMOS transistor T3 is connected to a column select line to which a selection signal SLCT is supplied.

Accordingly, the first nMOS transistor T1 is referred to as a reset transistor Rx, the second nMOS transistor T2 is referred to as a drive transistor Dx, and the third nMOS transistor T3 is referred to as a selection transistor Sx.

2 is a layout diagram illustrating unit pixels of a general 3T CMOS image sensor.

As shown in FIG. 2, in the unit pixel of a general 3T CMOS image sensor, an active region 10 is defined so that one photodiode 100 is formed in a wide portion of the active region 10. Gate electrodes 120, 130, and 140 of three transistors that overlap each other in the active region 10 of the remaining portion are formed.

That is, the reset transistor Rx is formed by the gate electrode 120, the drive transistor Dx is formed by the gate electrode 130, and the selection transistor Sx is formed by the gate electrode 140. Is formed.

Here, impurity ions are implanted into the active region 10 of each transistor except for lower portions of the gate electrodes 120, 130, and 140 to form source / drain regions of each transistor.

Therefore, a power supply voltage Vdd is applied to a source / drain region between the reset transistor Rx and the drive transistor Dx, and a source / drain region on one side of the select transistor Sx is shown in a read circuit (not shown). Not used).

Although not illustrated in the drawings, the gate electrodes 120, 130, and 140 described above are connected to respective signal lines, and each of the signal lines has a pad at one end thereof and is connected to an external driving circuit.

Three photodiodes configured as described above constitute one pixel. That is, red, green, and blue color filter layers are formed on each of the three photodiodes constituting one pixel to form one pixel.

3 is a cross-sectional view illustrating a unit pixel of a general CMOS image sensor, and illustrates only main parts related to condensing.

In the conventional CMOS image sensor, as shown in FIG. 3, a field oxide film (not shown) for defining an active region is formed on a semiconductor substrate 11 defined by a sensing unit and a peripheral driving unit. A plurality of photodiodes (PD) 12 are formed in the semiconductor substrate 11 in the region, and a plurality of transistors 13 are formed on the semiconductor substrate 11 in the active region.

A first interlayer insulating layer 14 is formed on the entire surface of the substrate including the sensing unit including the photodiode 12 and the transistor 13 and the peripheral driving unit, and the first metal wiring M1 is formed on the first interlayer insulating layer 14. ) Is formed.

A second interlayer insulating film 15, a second metal wiring M2, a third interlayer insulating film 16, a third metal wiring M3, and a fourth interlayer insulating film 17 are disposed on the first metal wiring M1. , The fourth metal wiring M4 and the protective film 18 are formed in this order.

The second, third, and fourth metal wires M2, M3, and M4 are disposed in the peripheral driving part so as not to affect the light incident on the photodiode 12.

In addition, R and GB color filter layers 19 for implementing a color image are formed on the planarization layer 18 of the sensing unit, and micro-lens (micro-lens) is formed on each color filter layer 19. 20) is formed.

In this case, the microlens 20 is coated with a photoresist and patterned to remain on the photodiode 12, and then reflowed through the photoresist to obtain a desired curvature.

The micro lens 20 as described above plays an important role of converging incident light to the photodiode 12.

After completing such a structure, although not shown in the drawing, a backgrinding, a die sawing process, and the like that further process the substrate backside are further performed.

However, such a conventional method for manufacturing CMOS image sensor has the following problems.

That is, as described above, after the microlens is formed, foreign matter and other defects occurring during the backgrinding, die sawing, etc., and other defects that cannot be traced to the surface of the microlens and Since it penetrates to the color filter layer, there exists a problem that the sensitivity of the CMOS image sensor falls.

The present invention has been made to solve the above problems, and after forming a micro lens, a method of manufacturing a CMOS image sensor that can prevent contamination from foreign matter by forming a protective film on the sensor surface including the micro lens. The purpose is to provide.

According to an aspect of the present invention, there is provided a method of manufacturing a CMOS image sensor, including: forming a plurality of photodiodes and various transistors on a semiconductor substrate defined by a sensing unit, a peripheral driving unit, and a pad unit; Forming a plurality of interlayer insulating films and a plurality of metal wires on each of the interlayer insulating films in front of the semiconductor substrate; Forming a protective film on an entire surface of the substrate including the metal wires; Forming a color filter layer and a micro lens on the passivation layer on the sensing unit; Forming a protective film for protecting the microlens on the entire surface of the substrate including the microlens; And grinding the back surface of the semiconductor substrate and performing a die sawing process.

Hereinafter, a method of manufacturing the CMOS image sensor according to the present invention having the above characteristics will be described in more detail with reference to the accompanying drawings.

4 is a structural cross-sectional view of the CMOS image sensor according to the present invention.

According to the present invention, a method of manufacturing a CMOS image sensor includes a field oxide film (not shown) for defining an active region on a semiconductor substrate 11 defined as a sensing unit and a peripheral driver as shown in FIG. 4. Form.

A plurality of photodiodes (PD) 12 and a plurality of transistors 13 are formed on the semiconductor substrate 11 of the active region in the semiconductor substrate 11 of the active region.

A first interlayer insulating layer 14 is formed on the entire surface of the substrate including the sensing unit including the photodiode 12 and the transistor 13 and the peripheral driving unit, and a first metal wiring on the first interlayer insulating layer 14. (M1) is formed.

The second interlayer insulating film 15, the second metal wiring M2, the third interlayer insulating film 16, the third metal wiring M3, and the fourth interlayer insulating film 17 are formed on the first metal wiring M1. 4 metal wiring M4 and the protective film 18 are formed in order.

The second, third, and fourth metal wires M2, M3, and M4 may be formed in the peripheral driving part so as not to affect the light incident to the photodiode 12.

In addition, R and GB color filter layers 19 for forming a color image are formed on the protective layer 18 of the sensing unit, and micro-lens 20 is formed on each of the color filter layers 19. To form.

Here, a planarization layer (not shown) may be further formed to smoothly form the microlens on the color filter layer.

In addition, the microlens 20 is coated with a photoresist and patterned to remain on the photodiode 12, and then reflowed through the photoresist to obtain a desired curvature.

The micro lens 20 as described above plays an important role of converging incident light to the photodiode 12.

In addition, a Tet-Butylalchol layer 21 is formed on the surface of the sensor including the microlens 20 as a protective film to a thickness of 500 kPa or more.

The Tet-Butylalchol layer 21 is a (CH3) 3COH component, and has a melting point of about 26 degrees and a boiling point of about 82.41 degrees. As such, it is possible to protect the substrate surface including the microlens in a backgrinding, a die sawing process, and the like, which will be performed later.

In the above, the Tet-butyl alcohol layer (Tert-Butylalchol layer) 21 may be deposited to a thickness of 500 kPa or more and chemical mechanical polishing may be performed with a target of 500 kPa or more.

After completion of the structure as described above, although not shown in the figure, further backgrinding (diegrinding), die sawing process, etc. for processing the back surface of the substrate.

Then, the Tet-Butylalchol layer 21 is removed.

On the other hand, the present invention described above is not limited to the above-described embodiment and the accompanying drawings, it is possible that various substitutions, modifications and changes within the scope without departing from the technical spirit of the present invention. It will be evident to those with ordinary knowledge in Esau.

The manufacturing method of the CMOS image sensor of the present invention as described above has the following effects.

That is, after forming the microlenses, a tet-butyl alcohol layer 21 is formed as a protective film on the surface of the sensor including the microlenses before the backgrinding and die sawing processes. In addition, since the backgrinding and the die sawing process are performed, foreign matter and other defects that cannot be traced due to the backgrinding and the die sawing process are contaminated and contaminate the micro lens surface and the color filter layer so that the sensitivity of the sensor is detected. Can be prevented from lowering.

Claims (5)

Forming a plurality of photodiodes and various transistors on a semiconductor substrate defined by a sensing unit, a peripheral driver, and a pad unit; Forming a plurality of interlayer insulating films and a plurality of metal wires on each of the interlayer insulating films in front of the semiconductor substrate; Forming a protective film on an entire surface of the substrate including the metal wires; Forming a color filter layer and a micro lens on the passivation layer on the sensing unit; Forming a tet-butyl alcohol layer on the entire surface of the substrate including the micro lens using a protective film for protecting the micro lens; Grinding the back surface of the semiconductor substrate and performing a die sawing process. delete The method of claim 1, The tet-butyl alcohol layer (Tert-Butylalchol layer) is a manufacturing method of the CMOS image sensor, characterized in that formed to a thickness of 500Å or more. The method of claim 3, wherein Forming the Tet-butyl alcohol layer (Tert-Butylalchol layer) and the chemical mechanical polishing process further characterized in that the manufacturing method of the CMOS image sensor. delete

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