KR100660329B1 - Cmos image sensor and method for manufacturing the same - Google Patents

Abstract

A CMOS image and a manufacturing method thereof are provided to reduce light loss and crosstalk by shortening a distance between a micro lens and a photo diode. Plural photo diodes(101) and all sorts of transistors(102) are formed on a semiconductor substrate(100) having a sensor unit and a driving unit. A first interlayer dielectric(103) is formed on the whole surface of the semiconductor substrate. A first metal wire(M1) is formed on the sensor unit and the driving unit on the first interlayer dielectric. A second interlayer dielectric(104) is formed on the whole surface of the semiconductor substrate including the first metal wire. A second metal wire(M2) is formed on the sensor unit and the driving unit on the second interlayer dielectric. A third interlayer dielectric(105) and an etch stop layer are formed in turn on the whole surface of the semiconductor substrate including the second wire. A third metal wire(M3) is formed on the etch stop layer. A fourth interlayer dielectric(107) is formed on the driving unit around the semiconductor substrate including the third metal wire. A fourth metal wire(M4) is formed on the fourth interlayer dielectric. A planarization layer(109) is formed on the whole surface of the semiconductor substrate including the fourth metal wire. A color filter layer(110) and a micro lens(111) are formed in turn on the sensor unit of the planarization layer.

Description

CMOS image sensor and method for manufacturing the same

1 is a circuit diagram showing a unit pixel of a conventional CMOS image sensor

2 is a cross-sectional view showing a CMOS image sensor according to the prior art

3 is a cross-sectional view showing a CMOS image sensor according to the present invention

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

Explanation of symbols for the main parts of the drawings

100 semiconductor substrate 101 photodiode

102 transistor 103 first interlayer insulating film

104: second interlayer insulating film 105: third interlayer insulating film

106 nitride film 107 fourth interlayer insulating film

108: photoresist 109: planarization layer

110: color filter layer 111: microlens

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an image sensor, and more particularly, to a CMOS image sensor for improving light condensing characteristics and a manufacturing method thereof.

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) is an individual metal-oxide-metal (MOS). ) Capacitors are in close proximity to each other and charge carriers are stored and transported in the capacitors. Complementary MOS image sensors use control circuits and signal processing circuits as peripheral circuits. It is a device that employs a switching method of making as many MOS transistors as the number of pixels using CMOS technology and sequentially detecting the output using the same.

CCD has many disadvantages such as complicated driving method, high power consumption, complicated process due to the large number of mask process steps, and difficulty in making one chip because signal processing circuit cannot be implemented 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 by switching method, and realizes images by using CMOS manufacturing technology. Compared to CCD process which 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.

FIG. 1 is a circuit diagram illustrating a unit pixel composed of one photodiode (PD) and four MOS transistors in a conventional CMOS image sensor, and includes a photodiode (PD) for generating photocharges upon receiving light. ), A transfer transistor (Tx) for transporting the photocharges collected from the photodiode (PD) to a floating diffusion (FD), and the potential of the floating diffusion (FD) to a desired value and discharge of charge Addressing to the reset transistor Rx for resetting the floating diffusion region FD, the drive transistor Dx serving as a source follower buffer amplifier, and the switching role. It consists of a select transistor Sx. Outside the unit pixel, a load transistor is formed to read an output signal.

2 is a cross-sectional view illustrating a unit pixel of a CMOS image sensor according to the related art, and illustrates only main parts related to condensing.

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

A first interlayer insulating layer 14 is formed on the entire structure including the photodiode 12 and the transistor 13, and a plurality of metal wirings constituting a unit pixel are formed on the first interlayer insulating layer 14. M1, M2, M3, M4) are formed.

Here, the metal wires M1, M2, M3, and M4 are disposed so as not to block light incident on the photodiode 12.

Subsequently, second to fourth interlayer insulating layers 15, 16, 17 and planarization layers 18 are formed between the metal wirings M1, M2, M3, and M4 of the unit pixel of each layer for electrical insulation. It is.

In addition, R and GB color filter layers 19 for forming a color image are formed on the planarization layer 18 of the sensor unit, and photoresist is used as the material on the color filter layer 19. A dome-shaped micro-lens 20 is formed.

Here, 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 microlens 20 as described above plays an important role in converging incident light to the photodiode 12.

However, as the device is highly integrated, the metal wires must be formed on different layers, and as the height of the plurality of interlayer insulating films increases, the distance between the microlens 20 and the photodiode 12 is increased so that the microlens 20 is increased. It was not possible to collect light properly to the photodiode (PD) alone.

That is, although the second to fourth interlayer insulating layers 15, 16, and 17 are stacked in the sensor unit even though the number of layers of the metal wirings M1 and M2 is only two, the microlens 20 receives the actual light. There is a thick film up to the photodiode 12 to weaken the light quality of the image is degraded.

In addition, when the distance between the microlens 20 and the photodiode 12 is far, the incident angle is out of the light, the light enters the adjacent pixel, so that the color interference of crosstalk occurs well to deteriorate the image quality.

Accordingly, in recent years, the thickness of each interlayer insulating film on the photodiode 12 tends to be reduced. However, this increases the intensity of light received by the photodiode 12 and thus improves the quality of the image, but increases the capacitance between the metal wires and increases the possibility of causing various problems such as leakage current.

The present invention has been made in order to solve the above problems, CMOS image sensor and a method of manufacturing the same to increase the intensity of light incident to the photodiode through the microlens and to prevent problems such as leakage current to the peripheral drive unit The purpose is to provide.

CMOS image sensor according to the present invention for achieving the above object is a plurality of photodiodes and various transistors formed on the semiconductor substrate defined by the sensor unit and the peripheral drive unit, and the first interlayer formed on the front surface of the semiconductor substrate An insulating film, a first interlayer insulating film formed on the front surface of the semiconductor substrate including the first metal wiring formed in the sensor unit and the peripheral drive unit on the first interlayer insulating film, and a sensor on the second interlayer insulating film A second metal interconnection formed on the portion and the peripheral driving unit, a third interlayer insulating layer and an etch stop layer sequentially formed on the front surface of the semiconductor substrate including the second metal interconnection, and a third metal interconnection formed on the etch stop layer; A fourth interlayer insulating film formed on a peripheral driving portion of the semiconductor substrate including the third metal wiring, and the fourth interlayer insulating film And the configured including the fourth metal wiring and the fourth front planarization layer formed on the semiconductor substrate including the metal wiring and the color filter layer formed in turn on the sensor portion of the planarization layer and a micro lens formed features.

In addition, the method for manufacturing a CMOS image sensor according to the present invention for achieving the above object comprises the steps of forming a plurality of photodiodes and transistors on a semiconductor substrate defined by a sensor unit and a peripheral drive unit, each of the photodiodes and Forming a first interlayer insulating film on the entire surface of the semiconductor substrate including the transistor; forming a first metal wiring on the sensor unit and the peripheral driving unit on the first interlayer insulating film; and forming a first interlayer insulating film on the first interlayer insulating film. Forming a second interlayer insulating film on the entire surface; forming a second metal wiring on the sensor portion and the peripheral driving portion on the second interlayer insulating film; and a third interlayer insulating film on the entire surface of the semiconductor substrate including the second metal wiring. And sequentially forming an etch stop layer, and forming a third metal wiring on the peripheral driving part on the etch stop layer. Forming a fourth interlayer insulating film on the entire surface of the semiconductor substrate including the third metal wiring, forming a fourth metal wiring on a peripheral driving portion on the fourth interlayer insulating film, and forming a fourth metal wiring on the sensor portion of the semiconductor substrate. Removing the fourth interlayer insulating film, forming a planarization layer on the entire surface of the semiconductor substrate, and sequentially forming a color filter layer and a microlens in the sensor portion of the planarization layer. do.

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

3 is a cross-sectional view showing a CMOS image sensor according to the present invention.

As shown in FIG. 3, a plurality of photodiodes 101 and various transistors 102 formed on the semiconductor substrate 100 defined by a sensor unit and a peripheral driver unit, the photodiodes 101, and the transistors 102 are provided. A first interlayer insulating film 103 formed on the entire surface of the semiconductor substrate 100 including the semiconductor substrate 100, a first metal wiring M1 formed on the sensor unit and the peripheral driving unit on the first interlayer insulating film 103, and the first interlayer insulating film 103. The second interlayer insulating film 104 formed on the entire surface of the semiconductor substrate 100 including the metal wiring M1, and the second metal wiring M2 formed on the sensor unit and the peripheral driving unit on the second interlayer insulating film 104. And a third interlayer insulating film 105 and a nitride film 106 sequentially formed on the entire surface of the semiconductor substrate 100 including the second metal wiring M2, and a third metal wiring formed on the nitride film 106. Peripheral driving portion of the semiconductor substrate 100 including M3 and the third metal wiring M3. On the front surface of the semiconductor substrate 100 including the fourth interlayer insulating film 107 formed, the fourth metal wiring M4 formed on the fourth interlayer insulating film 107, and the fourth metal wiring M4. The planarization layer 109 is formed, and the color filter layer 110 and the microlens 111 are sequentially formed on the sensor portion of the planarization layer 109.

That is, in the CMOS image sensor according to the present invention, the first, second, and third interlayer insulating films 103, 104, and 105 are formed in the sensor unit, and the first to fourth interlayer insulating films 103, 104, 105, and 107 are formed in the peripheral driving unit. 111 is to reduce the distance between the photodiode 101.

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

As shown in FIG. 4A, a field oxide film (not shown) for defining an active region is formed in the semiconductor substrate 100 defined by the sensor unit and the peripheral driving unit, and a plurality of field oxide films are formed in the active region of the semiconductor substrate 100. Photodiodes 101 and transistors 102 are formed.

Subsequently, a first interlayer insulating film 103 is formed on the entire surface of the semiconductor substrate 100 including the photodiodes 101 and the transistors 102, and a first metal film is deposited on the first interlayer insulating film 103. After that, selectively patterning is performed to form the first metal wiring M1 on the sensor unit and the peripheral driving unit.

A second interlayer insulating film 104 is formed on the entire surface of the semiconductor substrate 100 including the first metal wiring M1, and a second metal film is deposited on the second interlayer insulating film 104. By patterning, the second metal wiring M2 is formed on the sensor unit and the peripheral driving unit.

As shown in FIG. 4B, a third interlayer insulating film 105 is formed on the entire surface of the semiconductor substrate 100 including the second metal wiring M2, and an etch preventing nitride film is formed on the third interlayer insulating film 105. Form 106.

As shown in FIG. 4C, a third metal film is deposited on the nitride film 106 and then selectively patterned to form a third metal wiring M3 on the peripheral driving unit.

Subsequently, a fourth interlayer insulating film 107 is formed on the entire surface of the semiconductor substrate 100 including the third metal wiring M3, and a fourth metal film is deposited on the fourth interlayer insulating film 107. By patterning, the fourth metal wiring M4 is formed on the peripheral driving part.

After the photoresist 108 is coated on the entire surface of the semiconductor substrate 100 including the fourth metal wiring M4, the photoresist 108 is patterned such that the photoresist 108 remains only in the peripheral driving unit by an exposure and development process.

As shown in FIG. 4D, the fourth interlayer insulating layer 107 formed on the sensor unit of the semiconductor substrate 100 is selectively removed using the patterned photoresist 108 as a mask.

In this case, the nitride film 106 formed on the third interlayer insulating film 105 is used as an etch stop layer when selectively removing the fourth interlayer insulating film 107.

In addition, the etching process of the fourth interlayer insulating layer 107 uses a wet method, a dry method, or a mixing method.

As shown in FIG. 4E, the photoresist 108 is removed, and a planarization layer 109 is formed by depositing a nitride film or the like on the entire surface of the semiconductor substrate 100.

As shown in FIG. 4F, a color filter layer is coated on the planarization layer 109 and then patterned to form the salt resist by an exposure and development process to filter light for each wavelength band. 110 are formed to have a constant interval.

Subsequently, a microlens formation material layer is coated on the entire surface of the semiconductor substrate 100 including the color filter layer 110, and then the material layer is patterned by an exposure and development process to form a microlens on the color filter layer 110. Form a pattern.

Here, an oxide film such as a resist or TEOS may be used as the material layer for forming the microlens.

Meanwhile, a planarization layer (not shown) may be formed on the color filter layer 110 before applying the microlens material layer.

Subsequently, the microlens pattern is reflowed at a temperature of 150 to 200 ° C. to form the microlens 111.

In this case, the reflow process may use a hot plate or a furnace. At this time, the curvature of the microlens 111 varies depending on the shrinkage heating method, and the focusing efficiency also varies according to the curvature.

Subsequently, the microlens 111 is irradiated with ultraviolet rays and cured. Herein, the microlens 111 may maintain an optimum radius of curvature by irradiating and curing ultraviolet rays to the microlens 111.

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 apparent to those of ordinary skill in Esau.

The CMOS image sensor of the present invention and a method of manufacturing the same have the following effects.

First, the thickness of the interlayer insulating film between the microlens and the photodiode in the sensor unit is reduced in thickness, thereby reducing the loss of light, thereby improving optical sensitivity.

Second, the distance between the microlens and the photodiode is shortened, thereby reducing the crosstalk due to the incident angle.

Third, the image quality can be improved not only in the dark but also in the bright due to the improvement of light sensitivity and prevention of crosstalk.

Fourth, the restriction of the number of layers of metal wiring in the peripheral driving unit is removed, so that the design efficiency can be increased by using more metal wiring layers.

Claims (5)

A plurality of photodiodes and various transistors formed on a semiconductor substrate defined by a sensor unit and a peripheral driver; A first interlayer insulating film formed on the entire surface of the semiconductor substrate; A first metal wiring formed on the sensor portion and the peripheral driving portion on the first interlayer insulating film; A second interlayer insulating film formed on the entire surface of the semiconductor substrate including the first metal wiring; A second metal wiring formed on the sensor portion and the peripheral driving portion on the second interlayer insulating film; A third interlayer insulating film and an etch stop layer sequentially formed on the entire surface of the semiconductor substrate including the second metal wiring; A third metal wiring formed on the etch stop layer; A fourth interlayer insulating film formed on a peripheral driving portion of the semiconductor substrate including the third metal wiring; A fourth metal wiring formed on the fourth interlayer insulating film; A planarization layer formed on an entire surface of the semiconductor substrate including the fourth metal wiring; And a color filter layer and a micro lens, which are sequentially formed on the sensor unit of the planarization layer. The CMOS image sensor of claim 1, wherein the etch stop layer is a nitride film.  Forming a plurality of photodiodes and transistors on a semiconductor substrate defined by a sensor unit and a peripheral driver; Forming a first interlayer insulating film on an entire surface of the semiconductor substrate including each of the photodiodes and transistors; Forming a first metal wiring on the sensor unit and the peripheral driving unit on the first interlayer insulating layer; Forming a second interlayer insulating film on an entire surface of the semiconductor substrate including the first metal wiring; Forming a second metal wiring on the sensor unit and the peripheral driving unit on the second interlayer insulating layer; Sequentially forming a third interlayer insulating film and an etch stop layer on an entire surface of the semiconductor substrate including the second metal wiring; Forming a third metal wiring on the peripheral driving part on the etch stop layer; Forming a fourth interlayer insulating film on an entire surface of the semiconductor substrate including the third metal wiring; Forming a fourth metal wiring on the peripheral driving portion on the fourth interlayer insulating film; Removing a fourth interlayer insulating layer formed on a sensor unit of the semiconductor substrate; Forming a planarization layer on an entire surface of the semiconductor substrate; And forming a color filter layer and a microlens in sequence in the sensor portion of the planarization layer. The method of claim 3, wherein the etch stop layer is formed of a nitride film. The method of claim 3, wherein the fourth interlayer insulating layer is selectively removed by using a wet, dry, or mixed method.

Images