KR20100079390A - Unit pixel in image sensor and method for manufacturing thereof - Google Patents

Unit pixel in image sensor and method for manufacturing thereof Download PDF

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Publication number
KR20100079390A
KR20100079390A KR1020080137858A KR20080137858A KR20100079390A KR 20100079390 A KR20100079390 A KR 20100079390A KR 1020080137858 A KR1020080137858 A KR 1020080137858A KR 20080137858 A KR20080137858 A KR 20080137858A KR 20100079390 A KR20100079390 A KR 20100079390A
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KR
South Korea
Prior art keywords
gate electrode
photodiode
semiconductor substrate
device isolation
isolation layer
Prior art date
Application number
KR1020080137858A
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Korean (ko)
Inventor
현우석
Original Assignee
주식회사 동부하이텍
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Priority to KR1020080137858A priority Critical patent/KR20100079390A/en
Publication of KR20100079390A publication Critical patent/KR20100079390A/en

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    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01L—SEMICONDUCTOR DEVICES NOT COVERED BY CLASS H10
    • H01L27/00—Devices consisting of a plurality of semiconductor or other solid-state components formed in or on a common substrate
    • H01L27/14—Devices consisting of a plurality of semiconductor or other solid-state components formed in or on a common substrate including semiconductor components sensitive to infrared radiation, light, electromagnetic radiation of shorter wavelength or corpuscular radiation and specially adapted either for the conversion of the energy of such radiation into electrical energy or for the control of electrical energy by such radiation
    • H01L27/144—Devices controlled by radiation
    • H01L27/146—Imager structures
    • H01L27/14601—Structural or functional details thereof
    • H01L27/14609—Pixel-elements with integrated switching, control, storage or amplification elements
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01L—SEMICONDUCTOR DEVICES NOT COVERED BY CLASS H10
    • H01L27/00—Devices consisting of a plurality of semiconductor or other solid-state components formed in or on a common substrate
    • H01L27/14—Devices consisting of a plurality of semiconductor or other solid-state components formed in or on a common substrate including semiconductor components sensitive to infrared radiation, light, electromagnetic radiation of shorter wavelength or corpuscular radiation and specially adapted either for the conversion of the energy of such radiation into electrical energy or for the control of electrical energy by such radiation
    • H01L27/144—Devices controlled by radiation
    • H01L27/146—Imager structures
    • H01L27/14601—Structural or functional details thereof
    • H01L27/14636—Interconnect structures
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01L—SEMICONDUCTOR DEVICES NOT COVERED BY CLASS H10
    • H01L27/00—Devices consisting of a plurality of semiconductor or other solid-state components formed in or on a common substrate
    • H01L27/14—Devices consisting of a plurality of semiconductor or other solid-state components formed in or on a common substrate including semiconductor components sensitive to infrared radiation, light, electromagnetic radiation of shorter wavelength or corpuscular radiation and specially adapted either for the conversion of the energy of such radiation into electrical energy or for the control of electrical energy by such radiation
    • H01L27/144—Devices controlled by radiation
    • H01L27/146—Imager structures
    • H01L27/14683—Processes or apparatus peculiar to the manufacture or treatment of these devices or parts thereof

Abstract

PURPOSE: A unit pixel in image sensor and a method for manufacturing thereof are provided to reduce a contact area of a photo diode by contacting the photo diode and the gate electrode of a drive transistor at the same time. CONSTITUTION: An element isolation film is formed in a semiconductor substrate to define an active region. A gate electrode(140) is extended to a semiconductor substrate and a part of the surface of the element isolation film. A photo diode(120) is formed inside the semiconductor substrate in order to be arranged in the other side of the element isolation film. An insulating layer is formed on the semiconductor substrate including a gate electrode and the photo diode. A contact plug(170) penetrates through an insulating layer and directly connects the photo diode to the gate electrode.

Description

Unit pixel in image sensor and method for manufacturing thereof

An embodiment relates to a unit pixel of an image sensor.

An image sensor is a semiconductor device that converts an optical image into an electrical signal, and is largely a charge coupled device (CCD) and a CMOS (Complementary Metal Oxide Silicon) image sensor. Sensor (CIS).

The CMOS image sensor implements an image by sequentially detecting an electrical signal of each unit pixel in a switching method of forming a photodiode and a MOS transistor in the unit pixel.

The unit pixels of the CMOS image sensor are classified into 3Tr-1PD type, 4TR-1PD type, and 5TR-1PD type according to the number of transistors. The 3TR-1PD type consists of three transistors of one photodiode, and the 4TR-1PD type consists of one photodiode and four transistors.

1 is an equivalent circuit diagram illustrating a unit pixel of a 3Tr type image sensor, and FIG. 2 is a layout diagram illustrating a unit pixel of FIG. 1.

In general, a unit pixel of a 3Tr CMOS image sensor includes one photodiode (PD) and three nMOS transistors T1, T2, and T3, as shown in FIG. 1.

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.

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) through a signal line, The gate of the 3 nMOS transistor T3 is connected to the column select line to which the selection signal SLCT is supplied.

Here, the first nMOS transistor T1 is a reset transistor Rx for resetting photocharges collected in the photodiode PD, and the second nMOS transistor T2 is a source follower buffer amplifier. Source transistor (Dx), and the third nMOS transistor (T3) is a selection transistor (Sx) to enable the addressing (addressing) as a switching (switching) role.

As shown in FIG. 2, one photodiode 20 is formed in a wide portion of the active region 10, and the active region 10 of the remaining portion of the unit pixel of the general 3T CMOS image sensor is shown. The gate electrodes 30, 40, and 50 of three transistors overlapping each other are formed.

That is, a reset transistor Rx is formed by the gate electrode 30, a source floor transistor Dx is formed by the gate electrode 40, and a selection transistor Sx is formed by the gate electrode 50. Is formed.

Here, impurity ions are implanted into the active region 10 of each transistor except for the lower portion of each gate electrode 30, 40, 50 to form a source / drain region of each transistor.

Accordingly, an input terminal Vin to which an external potential is applied is formed in a source / drain region between the reset transistor Rx and the source floor transistor Dx, and a source of one side of the select transistor Sx is formed. An output terminal Vout connected to a read circuit (not shown in the drawing) is formed in the / drain region.

3 is a cross-sectional view taken along the line AA ′ of FIG. 2.

As shown in FIG. 3, the device isolation layer 11 formed in the device isolation region of the semiconductor substrate 10 defined as the active region and the device isolation region, and a portion of the device isolation layer 11 and the active region. The gate electrode 40 of the drive transistor to be formed, the photodiode region PD formed in a part of the active region of the semiconductor substrate 10, and the gate electrode 40 and the photodiode 20 are formed. An insulating layer 60 formed on the entire surface of the semiconductor substrate 10 including the first contact 71 connected to the photodiode 20 and the gate electrode 40 through the insulating layer 60. And a metal line 80 connecting the second contact 72 and the first and second contacts 71 and 72 so that the gate electrode 40 and the photodiode 20 are electrically connected to each other.

As described above, in the 3Tr image sensor, the first contact 71 connected to the photodiode 20 and the second contact 72 connected to the gate electrode 40 are respectively formed and then the metal line 82 is used. Thus, routing with the drive transistor was formed. Accordingly, light incident to the photodiode 20 may be lost due to etching damage of the photodiode 20 and routing of the metal line 80.

In the embodiment, the contact area of the photodiode can be reduced to the minimum area by simultaneously contacting the photodiode and the gate electrode of the drive transistor in the 3Tr transistor.

In an embodiment, a unit pixel of an image sensor may include: an isolation layer formed on a semiconductor substrate to define an active region; A gate electrode extending to one surface of the semiconductor substrate and the device isolation layer corresponding to one side of the device isolation layer; A photodiode formed inside the semiconductor substrate to be aligned with the other side of the device isolation layer; An insulating layer formed on the semiconductor substrate including the gate electrode and the photodiode; And a contact plug penetrating the insulating layer to directly connect the photodiode and the gate electrode.

A method of manufacturing a unit pixel of an image sensor according to an embodiment includes forming an isolation layer on a semiconductor substrate to define an active region; Forming a gate electrode on the semiconductor substrate corresponding to one side of the device isolation film so as to extend on a portion of the surface of the device isolation film; Forming a photodiode in the semiconductor substrate to be aligned with the other side of the device isolation layer; Forming an insulating layer on the semiconductor substrate including the gate electrode and the photodiode; And forming a contact plug penetrating the insulating layer to directly connect the photodiode and the gate electrode.

According to the embodiment, the photodiode and the gate electrode are electrically and physically directly connected by contact plugs, thereby improving the signal transfer speed of the image sensor.

In addition, since the respective contacts for connecting the photodiode and the gate electrode do not have to be formed, the light receiving region of the photodiode can be maximized.

In addition, since the photodiode and the gate electrode are directly connected by the contact plug, it is not necessary to form a separate metal line. Accordingly, the fill factor and sensitivity of the photodiode may be improved.

A unit pixel of the image sensor and a method of manufacturing the same according to an embodiment will be described in detail with reference to the accompanying drawings.

In the description of the embodiments, where described as being formed "on / over" of each layer, the on / over may be directly or through another layer ( indirectly) includes everything formed.

A unit pixel of an image sensor according to an embodiment will be described with reference to FIGS. 4 and 5.

4 is a layout diagram illustrating unit pixels of an image sensor according to an exemplary embodiment, and FIG. 5 is a cross-sectional view taken along line B-B 'of FIG. 4.

Referring to FIG. 4, a unit pixel of an image sensor according to an embodiment includes a photodiode 120 that receives light and generates photocharges, and a reset transistor for resetting photocharges collected by the photodiode 120. Rx (130), drive transistor (Dx) 140 serving as a source follower buffer amplifier, and select transistor (Sx) enabling addressing as a switching role. And 150.

The photodiode 120 and the gate electrode 140 of the drive transistor Dx are electrically and physically directly connected by the contact plug 170.

Specifically, as shown in FIG. 5, the device isolation layer 110 formed on the semiconductor substrate 100 to define an active region, the semiconductor substrate 100 and the device isolation layer corresponding to one side of the device isolation layer 110. A gate electrode 140 extending to a portion of the surface of the substrate 110, a photodiode 120 formed inside the semiconductor substrate 100 to be aligned with the other side of the device isolation layer 110, and the gate electrode 140. And a contact plug directly connecting the photodiode 120 and the gate electrode 140 through the insulating layer 160 and the insulating layer 160 formed on the semiconductor substrate 100 including the photodiode 120. And 170.

That is, the contact plug 170 is formed inside the contact hole 165 which simultaneously exposes the photodiode 120 and the gate electrode 140 of the drive transistor Dx that are formed adjacent to each other with the device isolation layer 110 interposed therebetween. ) Is formed.

According to the embodiment, the photodiode 120 and the gate electrode 140 may be electrically and physically connected directly by the contact plug 170 to improve the signal transfer speed of the image sensor.

In addition, since the contact for connecting the photodiode 120 and the gate electrode 140 does not have to be formed, the light receiving area of the photodiode 120 can be maximized.

In addition, since the photodiode 120 and the gate electrode 140 are directly connected by the contact plug 170, it is not necessary to form a separate metal line. Accordingly, the fill factor and sensitivity of the photodiode may be improved.

Hereinafter, a method of manufacturing a unit pixel of an image sensor according to an embodiment will be described with reference to FIGS. 6 to 7.

Referring to FIG. 6, the device isolation layer 110 is formed on the semiconductor substrate 100.

The semiconductor substrate 100 may be a single crystal or polycrystalline silicon substrate, and may be a substrate doped with p-type impurities or n-type impurities. For example, the semiconductor substrate 100 may be a p-type (p +) substrate, and a low concentration of the p-type epi layer (p-epi) may be formed by performing an epitaxial process on the semiconductor substrate 10. have.

An isolation layer 110 is formed on the semiconductor substrate 100 to define an active region. The device isolation layer 110 may be formed by an STI process. In other words, an active region and an isolation region may be defined by the isolation layer 110.

The gate electrode 140 is formed on the semiconductor substrate 100. The gate electrode 140 may be formed to cover the surface of the semiconductor substrate 100 corresponding to one side of the device isolation layer 110 and a partial region of the device isolation layer 110. Alternatively, the gate electrode 140 may be formed only on the semiconductor substrate 100 on the other side of the device isolation layer 110.

The gate electrode 140 may be formed by depositing a gate insulating film and a gate conductive film on the entire surface of the semiconductor substrate 100 and then selectively patterning the gate insulating film. For example, the gate conductive layer may be formed of a single layer or a plurality of layers of polysilicon, metal, and silicide.

Here, the gate electrode 140 is a gate electrode of the drive transistor Dx, and when forming the gate electrode 140, a gate electrode of another transistor (reset transistor, select transistor) may be formed.

The photodiode 120 is formed on the semiconductor substrate 100. The photodiode 120 is formed inside the semiconductor substrate 100 to be aligned with the other side of the device isolation layer 110. The photodiode 120 may be separated from the gate electrode 140 by the device isolation layer 110.

For example, the photodiode 120 may be formed by forming a photoresist pattern (not shown) defining a photodiode predetermined region on the semiconductor substrate 100 and then performing an ion implantation process. Although not shown, the photodiode 120 may be formed in a PNP structure.

An insulating layer 160 is formed on an entire surface of the semiconductor substrate 100 including the gate electrode 140 and the photodiode 120. The insulating layer 160 may be formed of an oxide film or a nitride film.

A contact hole 165 is formed through the insulating layer 160 to expose the photodiode 120, the gate electrode 140, and the device isolation layer 110. The contact hole 165 may selectively expose a portion of the photodiode 120 and the gate electrode 140 corresponding to both sides of the device isolation layer 110. The contact hole 165 forms a photoresist pattern 200 having an opening wider than the width of the device isolation layer 110 on the insulating layer 160, and then uses the photoresist pattern 200 as an etch mask. It can be formed by selectively etching the insulating layer 160 using. Since the width of the opening of the photoresist pattern 200 has a width wider than that of the device isolation layer 110, the contact hole 165 is adjacent to the device isolation layer 110 and the device isolation layer 110. A portion of the gate electrode 140 and the photodiode 120 may be exposed.

Referring to FIG. 7, a contact plug 170 is formed in the contact hole 165. The contact plug 170 may be formed by filling a metal film in the contact hole 165 and then performing a planarization process. For example, the contact plug 170 may be formed of various conductive materials including copper, aluminum, tungsten, alloy, or silicide.

A contact plug 170 formed of a conductive material is formed in the contact hole 165 so that the photodiode 120 and the gate electrode 140 may be electrically and physically connected directly. Accordingly, the signal transmission speed of the image sensor can be improved.

In addition, since the photodiode 120 and the gate electrode 140 are formed by one contact hole 165 forming process and a metal film deposition process, the process may be simplified. That is, since the metal contacts for connecting the photodiode 120 and the gate electrode 140 do not have to be formed, the process can be simplified.

In addition, the contact plug 170 may contact the partial region of the photodiode 120 to maximize the light receiving region of the photodiode 120.

In addition, since the photodiode 120 and the gate electrode 140 are directly connected by the contact plug 170, it is not necessary to form a separate metal line. Accordingly, the fill factor and the sensitivity may be improved by reducing the etch damage and the loss of light of the photodiode 120.

The above-described embodiments are not limited to the above-described embodiments and drawings, and various substitutions, modifications, and changes can be made without departing from the spirit and scope of the present invention. It will be clear to those who have it.

1 is an equivalent circuit diagram illustrating a unit pixel of a 3Tr image sensor.

2 is a layout diagram illustrating a unit pixel of a 3Tr image sensor.

3 is a cross-sectional view taken along the line AA ′ of FIG. 2.

4 is a layout diagram illustrating unit pixels of an image sensor according to an exemplary embodiment.

5 is a cross-sectional view taken along the line AA ′ of FIG. 4.

6 and 7 are views illustrating a manufacturing process of the image sensor according to the embodiment.

Claims (7)

An isolation layer formed on the semiconductor substrate to define an active region; A gate electrode extending to one surface of the semiconductor substrate and the device isolation layer corresponding to one side of the device isolation layer; A photodiode formed inside the semiconductor substrate to be aligned with the other side of the device isolation layer; An insulating layer formed on the semiconductor substrate including the gate electrode and the photodiode; And And a contact plug directly connecting the photodiode and the gate electrode through the insulating layer. The method of claim 1, And the contact plug is formed inside a contact hole through the insulating layer to simultaneously expose the device isolation layer and the photodiode and gate electrodes on both sides of the device isolation layer. The method of claim 1, The gate electrode is a unit pixel of the image sensor, characterized in that the gate electrode of the drive transistor. The method of claim 1, The photodiode and the gate electrode are applied to a 3Tr transistor unit pixel of the image sensor. Forming an isolation layer on the semiconductor substrate to define an active region; Forming a gate electrode on the semiconductor substrate corresponding to one side of the device isolation film so as to extend on a portion of the surface of the device isolation film; Forming a photodiode in the semiconductor substrate to be aligned with the other side of the device isolation layer; Forming an insulating layer on the semiconductor substrate including the gate electrode and the photodiode; And And forming a contact plug penetrating the insulating layer to directly connect the photodiode and the gate electrode. The method of claim 5, Forming the contact plug, Forming a contact hole including the device isolation layer in the insulating layer and simultaneously exposing a portion of the gate electrode and the photodiode corresponding to both sides of the device isolation layer; And And embedding a metal film in the contact hole and then performing a planarization process. The method of claim 5, The gate electrode is a unit pixel manufacturing method of the image sensor, characterized in that the gate of the drive transistor.
KR1020080137858A 2008-12-31 2008-12-31 Unit pixel in image sensor and method for manufacturing thereof KR20100079390A (en)

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KR1020080137858A KR20100079390A (en) 2008-12-31 2008-12-31 Unit pixel in image sensor and method for manufacturing thereof

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Application Number Priority Date Filing Date Title
KR1020080137858A KR20100079390A (en) 2008-12-31 2008-12-31 Unit pixel in image sensor and method for manufacturing thereof

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KR20100079390A true KR20100079390A (en) 2010-07-08

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