KR101009393B1 - Vertical CMOS Image Sensor and Manufacturing Method Thereof - Google Patents

Abstract

The present invention relates to a vertical CMOS image sensor capable of improving dark leakage characteristics, and a method of manufacturing the same.

The vertical CMOS image sensor according to the present invention includes a first photodiode formed on a semiconductor substrate having a first epitaxial layer, a second epitaxial layer formed on the first epitaxial layer, and a second formed on the second epitaxial layer. And a photodiode, a third epitaxial layer formed on the second epitaxial layer, a third photodiode formed on the third epitaxial layer, and an isolation layer formed in an isolation region of the third epitaxial layer. The third photodiode may be formed at a portion of the third epitaxial layer lower than the depth of the device isolation layer.

Photodiodes, Epilayers

Description

Vertical type CMOS image sensor and method for fabricating of the same

The present invention relates to a method of manufacturing a vertical CMOS image sensor, and more particularly, to a vertical CMOS image sensor capable of improving dark leakage characteristics and a method of manufacturing the same.

In general, CMOS image sensors are semiconductor devices that convert optical images into electrical signals. Among them, charge coupled devices (CCDs) include 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 one another.

CMOS image sensors, on the other hand, use CMOS technology that uses a control circuit and a signal processing circuit as peripheral circuits to create as many photodiodes as the number of pixels and transistors connected to them to open and close channels. The transistors sequentially detect red, green, and blue optical signals using the transistors and output the same by a switching method.

These CMOS image sensors have many advantages, such as low power consumption, low process costs, and high levels of integration. In particular, recent technological advances have made CMOS image sensors an attractive alternative to charge-coupled devices (CCDs) in many applications.

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 a 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, so that the size of the unit is large. Thus, in the case of such a general CMOS image sensor, the pixel integration degree is lowered.

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

The vertical image sensor has a vertical structure of red (R), green (G), and blue (B) photodiodes to detect red (R), green (G), and blue (B) signals per unit pixel. It is.

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

1 is a cross-sectional view of a unit pixel of a general vertical CMOS image sensor.

As shown in FIG. 1, a conventional vertical CMOS image sensor is formed on a semiconductor substrate 1 on which a first epitaxial layer 2 is grown, and on a predetermined portion of the first epitaxial layer 2. The red photodiode 3, the second epitaxial layer 5 formed on the first epitaxial layer, the green photodiode 6 formed on the second epitaxial layer 5, and the second epitaxial layer ( 5) the third epitaxial layer 7 formed on the second epitaxial layer 7, the blue photodiode 8 formed on the third epitaxial layer 7, and the second epitaxial layer 5 so as to be connected to the red photodiode 3. The first plug 9, the second plug 10 formed on the third epitaxial layer 7 to be connected to the green photodiode 6, and the device isolation layer formed on the third epitaxial layer 7 of the isolation region. (11) is comprised.

However, the red and green photodiodes in the conventional vertical CMOS image sensor recover damage from the implant due to the presence of additional epilayers at the time of implantation. In contrast, the blue photodiode is closest to the silicon surface, causing damage to the silicon surface of the photodiode and associated implants, which causes dark leakage, which is why the blue photodiode is darker. There is a problem that is weak. In addition, defects at the edge of the device isolation layer may affect the blue photodiode and degrade image characteristics.

Accordingly, an object of the present invention is to provide a vertical CMOS image sensor and a method of manufacturing the same that can improve the dark leakage (dark leakage) characteristics.

The vertical CMOS image sensor according to the present invention includes a first photodiode formed on a semiconductor substrate having a first epitaxial layer, a second epitaxial layer formed on the first epitaxial layer, and a second formed on the second epitaxial layer. And a photodiode, a third epitaxial layer formed on the second epitaxial layer, a third photodiode formed on the third epitaxial layer, and an isolation layer formed in an isolation region of the third epitaxial layer. The second epitaxial layer and the third epitaxial layer have grooves in regions corresponding to the third photodiode, and the third photodiode is formed in the third epitaxial layer at a position lower than the depth of the device isolation layer due to the grooves. It features.

The method of manufacturing a vertical CMOS image sensor according to the present invention includes the steps of forming a first photodiode on a semiconductor substrate on which a first epitaxial layer is formed, forming a second epitaxial layer on the first epitaxial layer, Forming a second photodiode on the second epitaxial layer, etching a predetermined region of the second epitaxial layer, forming a third epitaxial layer on the second epitaxial layer, and Forming a third photodiode in an epitaxial layer, and forming a device isolation layer in an isolation region of the third epilayer, wherein the third photodiode portion is lower than the depth of the device isolation layer; And the second epitaxial layer is etched away from the region overlapping with the third photodiode.

As described above, the vertical CMOS image sensor and a method of manufacturing the same according to the present invention form a portion where the blue photodiode is to be formed to be lower than the depth of the device isolation layer, so that the edge between the device isolation layer and the blue photodiode It has the effect of preventing the interference to improve the dark liquidity characteristics.

Hereinafter, a vertical 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.

2 is a cross-sectional view of a unit pixel of a vertical CMOS image sensor according to the present invention.

As shown in FIG. 2, the vertical CMOS image sensor according to the present invention includes a first photodiode 104 formed on a semiconductor substrate 100 on which a first epitaxial layer 102 is formed, and a first photodiode 104. The second epi layer 106 formed on the epi layer 102, the second photodiode 108 formed on the second epi layer 106, and the third epi layer formed on the second epi layer 106 ( 110, a third photodiode 112 formed on the third epitaxial layer 110, and an isolation layer 114 formed in an isolation region of the third epitaxial layer 110.

Here, the second epitaxial layer 106 and the third epitaxial layer 110 have a form in which grooves are formed by etching an area overlapping with the region where the third photodiode 112 is to be formed.

Here, the third photodiode 112 is formed in the third epitaxial layer portion lower than the depth of the device isolation layer 114.

Here, the semiconductor substrate 100 and the first epitaxial layer 102 on the side of the first photodiode 104 to transmit signals generated from the first photodiode 104 and the second photodiode 108 to near the silicon surface. And a second plug 118 formed in the second epitaxial layer 106 on the side of the first photodiode 108 and the first plug 116 formed over.

The first to third photodiodes 104, 108, and 112 are photodiodes of corresponding colors that sense red, green, and blue light, respectively.

3A to 3D are cross-sectional views illustrating a manufacturing process of the vertical CMOS image sensor according to the present invention.

First, as shown in FIG. 3A, a photosensitive film is coated on the semiconductor substrate 100 on which the first epitaxial layer 102 is grown, and the exposed and developed portions of the semiconductor substrate 100 are exposed. Pattern as much as possible. The first photodiode 104 is formed by n-type ion implantation using the patterned photoresist as a mask. Here, the first photodiode 104 is a red photodiode.

Then, the photoresist film is removed, the second epitaxial layer 106 is formed on the first epitaxial layer 102, and then the photosensitive film is applied on the second epitaxial layer 102, and the exposure and development are performed to the second epitaxial layer. Patterned to expose a portion of layer 106. After the patterned photoresist is used as a mask, the first photodiode 104 is patterned to be exposed, and then ion implanted to form the first plug 116. Here, the first plug 116 is formed over the semiconductor substrate 100 and the first epitaxial layer 102 on the side of the first photodiode 104.

Subsequently, as shown in FIG. 3B, after the photoresist film is removed, the photoresist film is coated on the second epitaxial layer 106, and exposed and developed to pattern a portion of the second epitaxial layer 106. The second photodiode 108 is formed by n-type ion implantation using the patterned photoresist as a mask. Here, the second photodiode 108 is a green photodiode.

Next, after the photoresist film is removed, a portion of the second epitaxial layer 106 that overlaps with a portion where the third photodiode 112 to be formed in a subsequent process is to be formed is etched after patterning to have a depth of 4000 to 4500 Å.

Then, as shown in FIG. 3C, a third epitaxial layer 110 is formed on the second epitaxial layer 106. At this time, the depth of the portion where the third photodiode 112 is to be formed while the third epitaxial layer 110 is formed becomes final 3500 ~ 4000Å by the influence of the depth etched in the second epitaxial layer 106, which is a subsequent process It becomes equal to the depth of the device isolation film 114 to be formed in. Thereafter, the second photodiode 108 and the first plug 116 are patterned using the photosensitive film, and then ion implanted to form the second plug 118. Here, the second plug 118 is formed in the second epi layer 106 on the side of the second photodiode 108.

Subsequently, as shown in FIG. 3D, the third photodiode 112 is formed by n-type ion implantation using a photosensitive film as a mask. Here, the third photodiode 112 is a blue photodiode. Thereafter, the device isolation layer 114 is formed through an element isolation process. The third photodiode 112 is formed in the third epitaxial layer 110 at a depth lower than that of the device isolation layer 114.

Meanwhile, although the vertical CMOS image sensor according to the present invention has been described by using the first, second and third photodiodes 104, 108 and 112 as red, green and blue photodiodes, the blue photodiode is referred to as the third photodiode 112. It is applicable to form the red and green photodiodes as the third photodiode 112 as well.

Those skilled in the art will appreciate that various changes and modifications can be made without departing from the technical spirit of the present invention. 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 of a unit pixel of a general vertical CMOS image sensor.

2 is a cross-sectional view of a unit pixel of a vertical CMOS image sensor according to the present invention.

3A to 3D are cross-sectional views illustrating a manufacturing process of the vertical CMOS image sensor according to the present invention.

Claims (14)

A first photodiode formed on the semiconductor substrate on which the first epitaxial layer is formed; A second epitaxial layer formed on the first epitaxial layer, A second photodiode formed on the second epitaxial layer, A third epitaxial layer formed on the second epitaxial layer, A third photodiode formed on the third epitaxial layer, An isolation layer formed in the isolation region of the third epitaxial layer, The second epitaxial layer and the third epitaxial layer have grooves in regions corresponding to the third photodiode, and the third photodiode is formed in the third epitaxial layer at a position lower than the depth of the device isolation layer due to the grooves. Vertical CMOS image sensor, characterized in that. The method of claim 1, And a first plug formed over said semiconductor substrate and said first epi layer on said first photodiode side and a second plug formed on said second epi layer on said second photodiode side. Type CMOS image sensor. The method of claim 1, And the third epitaxial layer has an etched region in which a region where the third photodiode is to be formed has an etch depth equal to that of the device isolation layer. The method of claim 3, wherein The depth of the portion where the third photodiode is to be formed is a vertical CMOS image sensor, characterized in that 3500 ~ 4000Å by the influence of the groove formed in the second epi layer. delete The method of claim 1, And the first, second and third photodiodes are red, green and blue photodiodes, respectively. delete Forming a first photodiode on the semiconductor substrate on which the first epitaxial layer is formed; Forming a second epitaxial layer on the first epitaxial layer, Forming a second photodiode on the second epitaxial layer, Etching a predetermined region of the second epitaxial layer; Forming a third epitaxial layer on the second epitaxial layer, Forming a third photodiode on the third epitaxial layer, Forming an isolation layer in the isolation region of the third epitaxial layer, Wherein the third photodiode is formed in a portion of the third epitaxial layer lower than the depth of the device isolation layer, and the second epitaxial layer etches an overlapping region with the third photodiode. Manufacturing method. The method of claim 8, After forming the second epi layer, forming a first plug over the semiconductor substrate and the first epi layer on the side of the first photodiode; And after forming the third epitaxial layer, forming a second plug on the second epitaxial layer on the side of the second photodiode. The method of claim 8, The third epitaxial layer is a vertical CMOS image sensor manufacturing method, characterized in that the depth of the trench formed by transferring the etching area formed in the second epitaxial layer is 3500 ~ 4000Å. delete The method of claim 8, And the first, second and third photodiodes are red, green and blue photodiodes, respectively. The method of claim 8, The second epitaxial layer is a method of manufacturing a vertical CMOS image sensor, characterized in that for etching to a depth of 4000 ~ 4500Å. delete

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