KR20100076254A - Image sensor and method for manufacturing the image sensor - Google Patents

Abstract

PURPOSE: An image sensor and a method for manufacturing the same are provided to optimize the area of a photo diode by transmitting signals from a photodiode to peripheral transistors through connection patterns to metal wiring. CONSTITUTION: A semiconductor substrate is divided into a pixel area(110) and a peripheral area(120). A first to a third epitaxial layers(130,140,150) are successively formed on the top of a semiconductor substrate. A red photo diode(170) is formed in the first epitaxial layer of the pixel area. A green photo diode(174) is formed in the second epitaxial layer of the pixel area. A blue photo diode(172) is formed in the third epitaxial layer of the pixel area. A plurality of vertical connection parts(136a~136f) are respectively connected to the red, the green, and the blue photo diode.

Description

Image sensor and method for manufacturing the image sensor

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to semiconductor devices, and more particularly to a method of manufacturing an image sensor.

An image sensor refers to a semiconductor device that converts an optical image into an electrical signal, and includes a CCD (Charge Coupled Device) device and a CMOS (Complementary Metal-Oxide-Silicon) device. The image sensor is composed of a light receiving area including a photodiode for detecting light and a logic area for processing the detected light into an electrical signal to make data, and efforts are being made to increase light sensitivity.

In the case of a general CMOS image sensor, transistors for driving and the like are formed horizontally, including a photodiode, and a unit pixel uses a color filter of red (R), green (G), and blue (B) color. Will detect the light.

In this case, in the general CMOS image sensor, one unit pixel must include all of the red (R), green (G), and blue (B) color filters formed in a planar shape, and thus the size thereof becomes large. Therefore, for such a general CMOS image sensor, the pixel density decreases.

As such, a vertical image sensor has been proposed to improve the problem of lowering the density of a general image sensor.

To improve this, a vertical image sensor has been developed. The vertical image sensor includes a red, green, and blue photodiode for detecting red (R), green (G), and blue (B) signals per unit pixel. It has a vertical structure.

Hereinafter, a conventional vertical CMOS image sensor will be described with reference to the accompanying drawings.

1 is a cross-sectional view showing a conventional vertical CMOS image sensor.

Referring to FIG. 1, a semiconductor substrate 30 divided into a pixel region 10 and a peripheral region 20, and first to third epitaxial layers 40, 50, and 60 sequentially on the semiconductor substrate 30. ) Is formed.

In this case, photodiodes 45, 55, and 65 are formed on the epitaxial layers 40, 50, and 60, respectively. Specifically, a red (R) photodiode 45 is formed on the first epitaxial layer 40. The green (G) photodiode 55 is formed in the second epitaxial layer 50, and the blue (B) photodiode 65 is formed in the third epitaxial layer 60.

Each of the red (R), green (G), and blue (B) photodiodes (45, 55, 65) is formed to have different depths by controlling the implantation energy of the N-type impurity ions. The wavelength of R) is relatively long, the wavelength of blue (B) is relatively short, and the wavelength of green (G) has an intermediate length between red (R) and blue (B) wavelengths.

Accordingly, the red (R) photodiode 45 is formed at the bottom of the wavelength, and the green (G) photodiode 55 is formed at the bottom, and the blue (B) photodiode 65 is formed at the surface.

Each of the photodiodes 45, 55, and 65 is connected to each other by the plurality of vertical connectors, that is, the first to third vertical connectors 62a, 62b, and 62c, respectively, in the epitaxial layers 40, 50, and 60. It is electrically connected to the signal line.

A shallow trench isolation (STI) 75 is formed in an isolation region of the third epitaxial layer 60 to isolate the devices.

Transistors having a gate electrode 72, sidewall spacers 74, and source and drain regions 80a and 80b are formed on the third epitaxial layer 60 of the pixel region 10 and the peripheral region 20.

Although not shown, an insulating layer and various metal wirings formed in the insulating layer are formed on the lower structure.

In such an image sensor, a transistor for signal transmission and an insulating layer on which metal wirings are formed are formed on a lower structure in which photodiodes 45, 55, and 65 are formed. Therefore, the area of the red or green photodiode 45 and 55 is larger than that of the blue photodiode 65, but as a result, only the area of the blue photodiode 65 of the uppermost layer plays a role. That is, there is a problem in that the area actually used compared with the interview of the photodiode 45, 55, 65 is reduced.

The present invention is to provide an image sensor and a method of manufacturing the same that can maximize the area of the photodiode.

According to an embodiment of the present disclosure, an image sensor includes a semiconductor substrate divided into a pixel region and a peripheral region, first to third epitaxial layers sequentially formed on the semiconductor substrate, and the pixel. A red photodiode formed in the first epitaxial layer in the region, a green photodiode formed in the second epitaxial layer in the pixel region, a blue photodiode formed in the third epitaxial layer in the pixel region, and the red and green A plurality of vertical connections connected to each of the blue photodiodes, a transistor formed on the third epitaxial layer in the peripheral region, and a photo via the vertical connections in the first to third epitaxial layers in the peripheral region. Comprising a connection electrode for transmitting a signal from diodes to said transistor via said semiconductor substrate It characterized.

According to another aspect of the present invention, there is provided a method of manufacturing an image sensor, the method including: forming a first epitaxial layer on a semiconductor substrate divided into a pixel region and a peripheral region; Forming first to third vertical connectors in the epitaxial layer, a red photodiode connected to the second vertical connectors, and a first connection electrode connected to the semiconductor substrate in the first epitaxial layer in the peripheral region; Forming a second epitaxial layer on the first epitaxial layer, a fourth and fifth vertical connectors in the second epitaxial layer of the pixel region, and a green photodiode connected to the fourth vertical connector. Forming a second connection electrode in the second epitaxial layer of the peripheral region so as to be connected to the first connection electrode, and forming a third epitaxial layer on the second epitaxial layer. And a sixth vertical connector in the third epitaxial layer of the pixel region, a blue photodiode connected to the sixth vertical connector, and the second connection electrode in a third epitaxial layer in the peripheral region. Forming a third connection electrode so as to form a third connection electrode; first to sixth vertical connections connected to each of the red, green, and blue photodiodes; and the first to third connections of the peripheral region via the semiconductor substrate. And forming a transistor for signal transmission to the peripheral region through an electrode.

According to an embodiment of the present invention, an image sensor and a method of manufacturing the same transmit a signal from a photodiode to a transistor in a peripheral region through a metal wiring and a connection pattern formed in a semiconductor substrate, not a transistor in a pixel region in which the photodiode is formed. As a result, the area of the photodiode can be optimized by eliminating transistors or metal wires existing in the conventional process, thereby making it possible to fabricate a high pixel image sensor having a small unit pixel size.

Hereinafter, the technical objects and features of the present invention will be apparent from the description of the accompanying drawings and the embodiments. Looking at the present invention in detail.

2 is a cross-sectional view showing a vertical image sensor according to the present invention.

Referring to FIG. 2, a vertical image sensor is divided into a pixel region 110 and a peripheral region 120. In the pixel region 110, N-type impurity ions are implanted into the semiconductor substrate 100 to have different depths. Red (R), green (G), and blue (B) photodiodes 170, 172, and 174 are formed. The peripheral region 120 includes a signal processing transistor having a gate electrode 190, a sidewall spacer 192, and source and drain regions 182a and 182b, and a connection electrode 132 connecting the transistor and the horizontal connection 125. 142 and 152 are formed.

In detail, the image sensor may include a first epitaxial layer 130 formed on the semiconductor substrate 130 including the horizontal connector 125 and a second epitaxial layer 140 formed on the first epitaxial layer 130. ) And a third epitaxial layer 150 formed on the second epitaxial layer 140.

The horizontal connection 125 may be formed by selectively removing a region connected to a photodiode to be formed later through an etching process on the semiconductor substrate 130. The chemical vapor deposition (CVD) may be performed on a plurality of grooves in the semiconductor substrate 100. After the deposition of the tungsten (W) film by a deposition method such as), and the surface of the semiconductor substrate is planarized through a chemical mechanical polishing (CMP) process, the tungsten metal material is formed so that only the grooves in the semiconductor substrate remain.

Here, the photodiodes 170, 172, and 174 are formed on the epitaxial layers 130, 140, and 150, respectively. Specifically, the red (R) photodiode 170 is formed on the first epitaxial layer 130. A green (G) photodiode 172 is formed on the second epitaxial layer 140, and a blue (B) photodiode 174 is formed on the third epitaxial layer 150.

Each of the red (R), green (G), and blue (B) photodiodes (170, 172, 174) is formed by implanting N-type impurity ions, and the wavelength of red (R) is relatively long. The wavelength of blue (B) is relatively short and the wavelength of green (G) has an intermediate length between red (R) and blue (B) wavelengths.

Thus, a red (R) photodiode 170 is formed in the bottommost first epitaxial layer 130 along the length of the wavelength, and then a green (G) photodiode (second) in the second epitaxial layer 140. 172, a blue (B) photodiode 174 is formed on the surface of the third epitaxial layer 150.

Each of the photodiodes 170, 172, and 174 may include first to third vertical connections formed on a plurality of vertical connections, that is, the first epitaxial layer 130, within the epitaxial layers 130, 140, and 150. 136a, 136b, and 136c, the fourth and fifth vertical connectors 136d and 136e formed in the second epitaxial layer 140, and the sixth vertical connector 136f formed in the third epitaxial layer 150. Include.

The plurality of vertical connectors 136a, 136b, 136c, 136d, 136e, and 136f are formed by implanting high concentration ions, i.e., N-type impurities, and are connected to the horizontal connectors 125 inside the semiconductor substrate 100 so as to be connected to the peripheral region. Is electrically connected to the transistor of 120.

Specifically, the red (R) photodiode 170 is connected to the horizontal connection 125 through the second vertical connection 136b, and the green (G) photodiode 172 is connected to the first vertical connection 136a and The blue (B) photodiode 174 is connected to the third vertical connection part 136c, the fifth vertical connection part 136e, and the sixth vertical connection part 136f through the fourth vertical connection part 136d. Is connected to the horizontal connection 125 through. The horizontal connecting portion 125 has a thickness of 6 μm to 10 μm.

Electrical signals generated from the photodiodes 170, 172, 174 are connected to the connecting electrodes 132, 142 of the peripheral region 120 through the verticals 136a, 136b, 136c, 136d, 136e, 136f and the horizontal connection 125, respectively. 152 is transmitted to the signal processing transistor.

The connection electrode may be formed on the first connection electrode 132 formed on the first epitaxial layer 130, the second connection electrode 142 formed on the second epitaxial layer 140, and the second epitaxial layer 150. The third connection electrode 152 formed is integrally formed.

The connecting electrodes 132, 142, and 152 and the horizontal connecting portion 125 are formed of tungsten (W), which is a metal resistant to heat.

Shallow Trench Isolation (STI) 180 for isolation between devices in an isolation region of the third epitaxial layer 150 and first and second conductivity due to implantation of impurity ions into the gate electrode 190. Type impurity regions 182a and 182b are formed.

As such, the signal transmission from the photodiodes 170, 172, and 174 is not connected to the transistors of the pixel region 110 in which the photodiodes 170, 172, and 174 are formed, and the horizontal connection portion 125 formed in the semiconductor substrate 100. Since the signal is transmitted to the transistors in the peripheral region 120 through the connection electrodes 132, 142, and 152, that is, those that may block light such as transistors or metal wires existing in the pixel region 110 in a conventional process. As a result, the area of the photodiodes 170, 172, and 174 may be optimized, thereby manufacturing a high pixel image sensor having a small unit pixel size.

3A to 3D are cross-sectional views illustrating a method of manufacturing the image sensor according to FIG. 2.

Referring to FIG. 3A, horizontal connections are formed in the semiconductor substrate 100.

Specifically, a plurality of grooves are formed by removing a predetermined region of the semiconductor substrate through an etching process using a mask on the semiconductor substrate 100. Subsequently, after depositing a tungsten (W) film on the semiconductor substrate 100 by a deposition method such as chemical vapor deposition (CVD), the semiconductor substrate 100 may be subjected to a chemical mechanical polishing (CMP) process. The planarization of the surface of the semiconductor layer 100 allows the tungsten metal material to remain only in the groove in the semiconductor substrate 100 to form the horizontal connection portion 125. Here, the height from the surface of the semiconductor substrate 100 to the groove, that is, the thickness of the horizontal connection portion 125 is formed to 6㎛ ~ 10㎛.

Referring to FIG. 3B, the first epitaxial layer 130 is formed on the semiconductor substrate 100 having the horizontal connectors 125.

Specifically, after the first epitaxial layer 130 is formed on the semiconductor substrate 100, N-type high concentration ions are injected into the first epitaxial layer 130 so as to be connected to the horizontal connection portion 125. The first to third vertical connecting portions 136a, 136b, and 136c are formed.

Subsequently, after forming a first photoresist pattern (not shown) exposing the first epitaxial layer 130 on which the red (R) photodiode 170 is to be formed, on the first epitaxial layer 130. A red (R) photodiode 170 is formed by implanting N-type impurity ions onto the first epitaxial layer 130 using a first photoresist pattern (not shown).

The second vertical connector 136b electrically connects the red (R) photodiode 170 and the horizontal connector 125.

After forming the first epitaxial layer 130, the peripheral region 120 removes the first epitaxial layer 130 through an etching process so that the horizontal connection portion 125 of the semiconductor substrate 100 is exposed to the first contact hole. After forming the 122, the tungsten material is embedded in the first contact hole 122 to form the first connection electrode 132.

Referring to FIG. 3C, a second epitaxial layer 140 including a green (G) photodiode 172 is formed on the first epitaxial layer 130.

Specifically, after the second epitaxial layer 140 is formed on the first epitaxial layer 130, the second epitaxial layer 140 is connected to each of the first and third vertical connectors 136a and 136c. N-type high concentration ions are implanted into the fourth and fifth vertical connecting portions 136d and 136e.

Subsequently, after forming a second photoresist pattern (not shown) exposing the second epitaxial layer 140 on which the green (G) photodiode 172 is to be formed, on the second epitaxial layer 140. The green (G) photodiode 172 is formed by implanting N-type impurity ions onto the second epitaxial layer 140 using a second photoresist pattern (not shown).

The first vertical connector 136a and the third vertical connector 136c are connected to electrically connect the green (G) photodiode 172 and the horizontal connector 125.

After forming the second epitaxial layer 140, the peripheral region 120 removes the second epitaxial layer 140 through an etching process to expose the first connection electrode 132 of the first epitaxial layer 130. After the second contact hole 124 is formed, a tungsten material is embedded in the second contact hole 124 to form a second connection electrode 142 connected to the first connection electrode 132.

Referring to FIG. 3D, a third epitaxial layer 150 including a blue (B) photodiode 174 is formed on the second epitaxial layer 140.

Specifically, after the third epitaxial layer 150 is formed on the second epitaxial layer 140, the N-type high concentration of the N-type epitaxial layer 150 is connected to the fifth vertical connection portion 136e. Ions are implanted to form the sixth vertical connecting portion 136f.

Subsequently, after forming a third photoresist pattern (not shown) exposing the third epitaxial layer 150 on which the blue (B) photodiode 174 is to be formed, on the third epitaxial layer 150. The blue (B) photodiode 174 is formed by implanting N-type impurity ions onto the third epitaxial layer 150 using a third photoresist pattern (not shown).

The third vertical connector 136c, the fifth vertical connector 136e, and the sixth vertical connector 136f electrically connect the blue (B) photodiode 174 and the horizontal connector 125.

The red (R), green (G), and blue (B) photodiodes 170, 172, and 174 thus formed are arranged vertically to form one pixel.

After the third epitaxial layer 150 is formed, the peripheral region 120 removes the third epitaxial layer 150 through an etching process to expose the second connection electrode 142 of the second epitaxial layer 140. After the third contact hole 126 is formed, a tungsten material is embedded in the third contact hole 126 to form a third connection electrode 152 connected to the second connection electrode 142. Here, the first to third connection electrodes 132, 142, and 152 are integrally formed to form one connection electrode.

In addition, a device isolation film (STI) for isolation between the signal processing transistor on the third epitaxial layer 150 of the peripheral region 120 and the devices in the isolation region of the third epitaxial layer 150. Source and drain regions 182a and 182b are formed at 180 and below the gate electrode 190 as impurity regions of the first and second conductivity types due to the implantation of impurity ions. When the first conductivity type is P type, the second conductivity type is N type.

Here, after forming the first to third epitaxial layers 130, 140, and 150, the first to third connection electrodes 132, 142, and 152 may expose the horizontal connection 125 through one etching process. It may be formed by forming a contact hole of buried with tungsten.

The connecting electrode including the first to third connecting electrodes 132, 142, and 152 is formed of red (R) and green (G) through the verticals 136a, 136b, 136c, 136d, 136e, and 136f and the horizontal connection 125. Signal from the blue (B) photodiode 170, 172, and 174 is transmitted to the signal processing transistor formed in the peripheral region.

As shown in FIG. 4, the horizontal connectors 125 occupy only about 1% of the total area of the unit pixel, and thus the epitaxial layers 130, 140, and 150 on the horizontal connectors 125 are entirely formed. The characteristics of the photodiodes 170, 172, and 174 are not affected.

As such, the signal transmission from the photodiodes 170, 172, and 174 is formed on the semiconductor substrate 100, not the transistors of the pixel region 110 in which the photodiodes 170, 172, and 174 are formed. Since the signal is transmitted to the transistors in the peripheral area through the 136c, 136d, 136e, and 136f and the horizontal connection 125, the photodiode 170, which is capable of blocking light such as transistors or metal wires existing in a conventional process, is removed. The areas 172 and 174 may be optimized, and thus a high pixel image sensor having a small unit pixel size may be manufactured.

It will be apparent to those skilled in the art that various modifications and variations can be made in the present invention without departing from the spirit or scope of the invention. Will be clear to those who have knowledge of. Therefore, the technical scope of the present invention should not be limited to the contents described in the detailed description of the specification but should be defined by the claims.

1 is a cross-sectional view showing a conventional vertical CMOS image sensor.

2 is a cross-sectional view showing a vertical image sensor according to the present invention.

3A to 3D are cross-sectional views illustrating a method of manufacturing the image sensor according to FIG. 2.

4 is a view showing an image sensor in one pixel according to the present invention.

<Description of Symbols for Main Parts of Drawings>

110: pixel area 120: peripheral area

125: horizontal connection 130, 140, 150: epitaxial layer

136a to 136f: vertical connection part 132, 142, 152: connection electrode

170: red photodiode 172: green photodiode

174 blue photodiode

Claims (12)

A semiconductor substrate divided into a pixel region and a peripheral region, First to third epitaxial layers sequentially formed on the semiconductor substrate; A red photodiode formed in the first epitaxial layer of the pixel region; A green photodiode formed in the second epitaxial layer of the pixel region; A blue photodiode formed in a third epitaxial layer of the pixel region; A plurality of vertical connections connected to each of the red, green, and blue photodiodes; A transistor formed on the third epitaxial layer in the peripheral region; And connection electrodes for transmitting a signal from photodiodes to the transistor via the semiconductor substrate through the vertical connections in the first to third epitaxial layers of the peripheral region. The method of claim 1, And at least one horizontal connection portion connected to the vertical connection portion and the connection electrode and formed on a surface of the semiconductor substrate to transmit a signal to the transistor. The method of claim 2, The horizontal connection portion is an image sensor, characterized in that formed in a thickness of 6㎛ ~ 10㎛. The method of claim 2, The horizontal sensor is an image sensor, characterized in that formed by tungsten. The method of claim 1, The connection electrode may include a first connection electrode formed in the first epitaxial layer, A second connection electrode formed in the second epitaxial layer, And a third connection electrode formed in the third epitaxial layer. The method of claim 5, And the connection electrode is formed of tungsten. The method of claim 1, The vertical connection portion may include first to third vertical connection portions formed in the first epitaxial layer; Fourth and fifth vertical connectors formed on the second epitaxial layer; A sixth vertical connection part formed in the third epitaxial layer, The second vertical connection is connected to the red photodiode, The first and fourth vertical connectors are connected to the green photodiode, And the third, fifth and sixth vertical connections are connected with a blue photodiode. Forming a first epitaxial layer on a semiconductor substrate divided into a pixel region and a peripheral region; First to third vertical connectors in the first epitaxial layer of the pixel region, a red photodiode connected to the second vertical connector, and a first connection to the semiconductor substrate in the first epitaxial layer of the peripheral region. Forming an electrode, Forming a second epitaxial layer on the first epitaxial layer; Fourth and fifth vertical connections in the second epitaxial layer of the pixel region, a green photodiode connected to the fourth vertical connection, and a first connection electrode in the second epitaxial layer in the peripheral region. Forming a connecting electrode; Forming a third epitaxial layer on the second epitaxial layer; A third connection electrode connected to a sixth vertical connection part in the third epitaxial layer of the pixel region, a blue photodiode connected to the sixth vertical connection part, and a second connection electrode in the third epitaxial layer of the peripheral area; Forming a, First to sixth vertical connection parts connected to each of the red, green, and blue photodiodes, and the first to third connection electrodes of the peripheral area via the semiconductor substrate, for signal transmission to the peripheral area. A method of manufacturing an image sensor comprising the step of forming a transistor. The method of claim 8, And forming a horizontal connection part through an etching process in the semiconductor substrate so as to be connected to the vertical connection part and the first to third connection electrodes to transmit a signal to the transistor. Way. The method of claim 9, The horizontal connection portion is a manufacturing method of the image sensor, characterized in that formed in a thickness of 6㎛ ~ 10㎛. The method of claim 8, And the horizontal connection part is formed of tungsten. The method of claim 8, The first to the third connection electrode is a manufacturing method of the image sensor, characterized in that formed of tungsten.

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