KR20070049409A - Image sensor and method for manufacturing the same - Google Patents

Abstract

The present invention provides an image sensor and a method of manufacturing the same, which can realize a high resolution image having excellent optical characteristics by suppressing light incident to the control unit as much as the unit pixel size is reduced. And a substrate on which a control element for controlling the photocharge of the photodiode is formed, a first interlayer insulating layer formed on the substrate to cover the photodiode and the control element, and to prevent light from being incident on a region where the control element is formed. To provide an image sensor including a light blocking layer formed on the first interlayer insulating film overlapping with the region in which the control element is formed so as not to overlap the region in which the photodiode is formed. In addition, the present invention provides a step of providing a substrate having a photodiode and a control element for controlling the photocharge of the photodiode, forming a first interlayer insulating film on the substrate to cover the control element; And forming a light blocking layer overlapping with the region where the control element is formed so as not to overlap with the region where the photodiode is formed so that light does not enter the region where the control element is formed. .

 Image sensor, control element, photodiode, light blocking layer, LIC.

Description

Image sensor and its manufacturing method {IMAGE SENSOR AND METHOD FOR MANUFACTURING THE SAME}

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

2 (a) and 2 (b) show the area reduction of the photodiode region due to the recent integration of the image sensor.

3 is a plan view showing a CMOS image sensor according to a preferred embodiment of the present invention.

4 is a cross-sectional view taken along the line II ′ of FIG. 3;

5A to 5D are cross-sectional views illustrating a method of manufacturing the image sensor according to the preferred embodiment of the present invention shown in FIG.

<Description of the symbols for the main parts of the drawings>

221: photodiode region 220: control region

100 substrate 102 device isolation film

104: gate electrode 106: etch stop film

108: spacer 11, 111: photodiode

113: junction region 114: floating diffusion region

116, 122, 126: interlayer insulating film

118a, 118b, 123, 128: contact plug

120: light blocking layer 124, 130: metal wiring

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an image sensor and a method for manufacturing the same, and more particularly, to a complementary metal-oxide-semiconductor (CMOS) image sensor including a photodiode and a control element for controlling charge of the photodiode.

Recently, the demand of digital cameras is exploding with the development of video communication using the Internet. Moreover, the demand for small camera modules increases as the popularity of mobile communication terminals such as PDAs equipped with cameras, International Mobile Telecommunications-2000 (IMT-2000), Code Division Multiple Access (CDMA) terminals, etc. increases. Doing.

As a camera module, an image sensor module using a Charge Coupled Device (CCD) or a Complementary Metal-Oxide-Semiconductor (CMOS) image sensor, which are basic components, is widely used.

Such an image sensor is a semiconductor device that converts an optical image into an electrical signal. As described above, a CCD and a CMOS image sensor have been developed and widely commercialized. A CCD is a device in which charge carriers are stored and transported in a capacitor while individual metal-oxide-silicon (MOS) capacitors are in close proximity to each other. On the other hand, a CMOS image sensor uses a CMOS technology that uses a control circuit and a signal processing circuit as peripheral circuits to make MOS transistors by the number of pixels, and uses the switching to detect an output sequentially. It is a device employing the method.

However, CCD has many disadvantages such as complicated driving method, high power consumption, large number of mask processes, complicated process, and difficult to implement signal processing circuit in the CCD chip. Recently, in order to overcome such disadvantages of CCD, researches on the development of CMOS image sensors using sub-micron CMOS manufacturing techniques have been actively conducted.

In general, a CMOS image sensor implements an image by forming a photo diode and a MOS transistor in a unit pixel to sequentially detect signals in a switching manner. The unit pixel of the CMOS image sensor includes one photo. It consists of a diode and four NMOSFETs whose control signals Tx, Rx, Dx and Sx are input to the gate.

1 is a circuit diagram illustrating a unit pixel of a general CMOS image sensor.

Referring to FIG. 1, a unit pixel of a CMOS image sensor may include one photo diode 11 that receives light to generate photocharges, and a controller 20 that controls the photocharges of the photo diodes 11. It is composed. At this time, the control unit 20 resets the transfer transistor 13 for transferring the photocharges collected from the photodiode 11 to the floating diffusion node 12 and the reset transistor 14 for resetting the floating diffusion node 12. ), A drive transistor 15 serving as a source follower buffer amplifier, and a select transistor 16 for addressing in a switching role. Here, the transfer transistor 13 and the reset transistor 14 use a native NMOSFET having a low threshold voltage, and the drive transistor 15 and the select transistor 16 use a normal NMOSFET. . The other transistors not shown are load transistors to which a bias voltage is applied.

The unit pixel of the CMOS image sensor detects light in the visible wavelength band by using the native NMOSFET, and then converts the detected photocharge into the floating diffusion node 12, that is, the drive transistor 15. The amount to be transferred to the gate of the output terminal (Vout) outputs an electrical signal.

On the other hand, in recent years, a lot of human and material investment has been made to reduce the overall chip size by decreasing the unit pixel size with increasing the number of pixels for the high resolution of the image sensor. As such, as the unit pixel size is reduced, the formation area of the photodiode 11 compared to the control unit 20 is reduced. As a result, the amount of light incident on the control unit 20 is relatively increased compared to the amount of light incident on the photodiode 11 that is the light collecting point. As such, a signal generated by the light incident to the controller 20 acts as a noise of the image sensor to deteriorate the optical characteristic. Referring to (a) and (b) of FIG. 2, it can be seen that the area of the photodiode 11 compared to the control unit 20 has recently decreased with the reduction of the unit pixel size.

Accordingly, the present invention has been made to solve the above problems of the prior art, an image sensor capable of realizing a high resolution image having excellent optical characteristics by suppressing the light incident to the control unit as much as possible even if the unit pixel size is reduced and The purpose is to provide a manufacturing method.

According to an aspect of the present invention, there is provided a photodiode, a substrate on which a control element for controlling the photocharge of the photodiode is formed, and a substrate formed on the substrate to cover the photodiode and the control element. A first interlayer insulating film and a light blocking layer formed on the first interlayer insulating film overlapping with the region where the control element is formed so as not to overlap with the region where the photodiode is formed so that light does not enter the region where the control element is formed. It provides an image sensor.

According to another aspect of the present invention, there is provided a substrate on which a photodiode and a control element for controlling photocharge of the photodiode are provided. Forming a first interlayer insulating film on the substrate; and forming a light blocking layer overlapping the region where the control element is formed so as not to overlap with the region where the photodiode is formed so that light does not enter the region where the control element is formed. It provides an image sensor manufacturing method comprising a.

According to the present invention, the light blocking layer is formed on the interlayer insulating film covering the control element so as to overlap the area where the control element is formed, thereby preventing the light incident from the outside from entering the area where the control element is formed. Therefore, a high resolution image having excellent optical characteristics can be realized.

DETAILED DESCRIPTION Hereinafter, exemplary embodiments of the present invention will be described in detail with reference to the accompanying drawings so that those skilled in the art may easily implement the technical idea of the present invention. In addition, in the drawings, the thicknesses of layers and regions are exaggerated for clarity, and in the case where the layers are said to be "on" another layer or substrate, they may be formed directly on another layer or substrate or Or a third layer may be interposed therebetween. In addition, the same reference numerals throughout the specification represent the same components.

Example

3 is a plan view illustrating an image sensor according to a preferred embodiment of the present invention, and FIG. 4 is a cross-sectional view taken along the line II ′ of FIG. 3.

3 and 4, an image sensor according to an exemplary embodiment of the present invention may include a substrate 100 having a photodiode 111 and a control element for controlling photocharge of the photodiode 111 and a photodiode ( The first interlayer insulating film 116 formed on the substrate 100 to cover the 111 and the control element, and the region in which the photodiode 111 is formed so that light does not enter the region (or the controller) on which the control element is formed. And a light blocking layer 120 formed on the first interlayer insulating layer 116 overlapping with the region where the control element is formed so as not to overlap with each other.

At this time, the control element is a photovoltaic charge collected from the gate electrode 104a (hereinafter referred to as a first gate electrode) for the transfer transistor formed on the substrate 100 to be aligned on one side of the photodiode 111 and the photodiode 111. Is formed in the floating diffusion region 114 formed in the substrate 100 on one side of the transfer transistor and the reset transistor for resetting the floating diffusion region 114 so as to be transmitted through the transfer transistor. Drive transistor gate electrode 104b (hereinafter referred to as a second gate electrode) and junction region 113 serving as a source follower buffer amplifier to amplify the potential of the floating diffusion region 114, and the drive transistor. It includes a select transistor (not shown) that performs a switching role for outputting a signal amplified from, for convenience of description For the sake of illustration, only the transfer transistor and the drive transistor are shown.

What is important here is that the floating diffusion region 114 and the second gate electrode 104b are interconnected by the light blocking layer 120. This includes contact plugs 118a (hereinafter referred to as first contact plugs) for electrically connecting the light blocking layer 120 and the floating diffusion region 114, and the light blocking layer 120 and the second gate electrode 104b. It is possible by forming the contact plugs 118b (hereinafter referred to as second contact plugs) for connecting and forming the light blocking layer 120 simultaneously connected to the first and second contact plugs 118a and 118b. As a result, a wider design margin can be secured as compared with forming a separate metal wiring connecting the floating diffusion region 114 and the second gate electrode 104b, respectively. This is because the light blocking layer 120 is formed by using a Local InterConnector (LIC) technology, which is generally applied according to a decrease in memory cell size.

In particular, the light blocking layer 120 is formed of any one selected from Ti, TiN, a laminated film of Ti / TiN, a metal material, and a doped polysilicon.

In addition, the image sensor according to an exemplary embodiment of the present invention further includes a plurality of metal wires 124 for electrically connecting the junction region 113 of the drive transistor with an external circuit, respectively. In particular, the metal wire 124 should not be connected to the light blocking layer 120. For this purpose, the metal wiring 124 is formed on the second interlayer insulating film 122 formed on the first interlayer insulating film 116 to cover the light blocking layer 120. Preferably, the light blocking layer 120 includes a region in which a contact plug 123 (hereinafter referred to as a third contact plug) for electrically connecting the junction region 113 and the metal wiring 124 of the drive transistor is formed. It is formed so as not to overlap. In addition, a contact plug 128 electrically connected to the junction region 113 of the drive transistor through the third contact plug 123 to apply a power supply voltage V _DD to the junction region 113 of the drive transistor; Hereinafter, a third interlayer insulating film 126 through the fourth contact plug) and a metal wiring 130 formed on the third interlayer insulating film 126 to be connected to the fourth contact plug 128 may be further included. Can be.

In FIGS. 3 and 4, undescribed '220' and '221' represent a control unit and a photodiode region, respectively, and '106' protects upper portions of the first and second gate electrodes 104a and 104b from etching. It is an etch stop.

That is, in the image sensor according to the preferred embodiment of the present invention, the light blocking layer 120 is formed on the first interlayer insulating film 116 covering the control element so as to overlap the region (or control unit) on which the control element is formed, thereby preventing from the outside. The incident light may be blocked from entering the control unit. Therefore, it is possible to implement a high resolution image having excellent optical characteristics by preventing image distortion.

5A through 5D are cross-sectional views illustrating a method of manufacturing the image sensor shown in FIG. 4.

First, as shown in FIG. 5A, a photodiode 111 and a control element are formed on a substrate 100 on which an isolation layer 102 having a shallow trench isolation (STI) structure is formed.

For example, first, a plurality of gate electrodes for the transistor are formed on the substrate 100. Here, the gate electrode for a transistor is a gate electrode for a transfer transistor 104a (hereinafter, referred to as a first gate electrode) constituting a unit pixel of an image sensor, and a gate electrode for a drive transistor 104b (hereinafter, referred to as a second gate electrode). And a gate electrode (not shown) for a reset transistor and a gate electrode (not shown) for a select transistor. In the following description, a description of a method of forming a reset transistor and a select transistor will be omitted for convenience of description. In this case, an etch stop layer 106 and a spacer 108 are provided on the upper surface and both side walls of the gate electrode including the first and second gate electrodes 104a and 104b, respectively.

Subsequently, a photodiode 111 is formed in the substrate 100 exposed to one side of the first gate electrode 104a by performing a mask process and an impurity ion implantation process for forming a photodiode.

Subsequently, a mask process and an impurity ion implantation process are performed to form a junction region 113 in the substrate 100 exposed to both sides of the second gate electrode 104b, and to be exposed to the other side of the first gate electrode 104a. A floating diffusion region 114 is formed in the substrate 100.

Subsequently, a first interlayer insulating film 116 is formed on the entire surface of the substrate 100 to cover the control element including the plurality of gate electrodes and the photodiode 111. For example, the first interlayer insulating film 116 is formed of an oxide film-based material. Preferably, the first interlayer insulating film 116 may include a high density plasma (HDP) oxide film, a boron phosphorus silicalicate glass (BPSG) film, a phosphorous Silicate glass (PSG) film, a plasma enhanced tetra ethole ortho silicate (PETOS) film, and a PECVD (PECVD) film. Single layer film using any one of Plasma Enhanced Chemical Vapor Deposition (USG) film, USG (Un-doped Silicate Glass) film, Fluorinated Silicate Glass (FSG) film, Carbon Doped Oxide (CDO) film and Organic Silicate Glass (OSG) film It is formed of a laminated film in which these are laminated.

Subsequently, as shown in FIG. 5B, a portion of the first interlayer insulating layer 116 is etched by performing a mask process and an etching process, thereby forming the floating diffusion region 114 and the second gate electrode in the first interlayer insulating layer 116. A plurality of contact holes (not shown) are formed to expose 104b.

Subsequently, a plurality of contact plugs 118a and 118b which are embedded only in the contact holes are formed, respectively. For example, after the plug material is deposited on the first interlayer insulating layer 116 so as to fill the contact holes, the plug material is planarized to form contact plugs 118a and 118b (hereinafter, referred to as first and second contact plugs).

Subsequently, as illustrated in FIG. 5C, after the light blocking layer 120 is deposited on the first interlayer insulating layer 116, a mask process and an etching process may be performed to overlap the region where the control element is formed. The light blocking layer 120 in the region overlapping with the region where the photodiode 111 is formed is etched so that the light blocking layer 120 remains only on the upper portion. Due to the formation of the light blocking layer 120, light incident to the region (or the controller) on which the control element is formed may be blocked.

Here, the light blocking layer 120 is formed of any one selected from Ti, TiN, a laminated film of Ti / TiN, a metal material and a doped polysilicon.

Subsequently, as illustrated in FIG. 5D, a second interlayer insulating film 122 is deposited on the first interlayer insulating film 116 to cover the light blocking layer 120. In this case, the second interlayer insulating film 122 is formed of the same material as the first interlayer insulating film 116.

Subsequently, a portion of the first and second interlayer insulating films 116 and 122 are etched by performing a mask process and an etching process, thereby exposing a plurality of contact holes to expose the junction regions 113 for the drive transistors, respectively. To form.

Subsequently, a plurality of contact plugs 123 (hereinafter referred to as third contact plugs) embedded only in the contact holes are formed, the metal wiring material is deposited on the second interlayer insulating layer 122, and then etched to form a plurality of contact plugs 123. A plurality of metal wires 124 connected to the third contact plugs 123 are formed, respectively. Preferably, the third contact plug 123 and the metal wire 124 are formed so as not to be connected to the light blocking layer 120.

Subsequently, in order to apply the power supply voltage VDD to the junction region 113 for the drive transistor, for example, the drain of the drive transistor, an upper metal wiring 130 connected to the metal wiring is formed on the metal wiring 124. For example, after the third interlayer dielectric layer 126 is deposited on the second interlayer dielectric layer 122 to cover the metal interconnection 124, the metal line 124 connected to the drain of the drive transistor is performed by performing a mask process and an etching process. A contact hole exposing the contact hole and forming a contact plug 128 (hereinafter, referred to as a fourth contact plug) embedded in the contact hole. Then, the metal wire 130 is formed on the third interlayer insulating film 126 to be connected to the fourth contact plug 128.

Although the technical idea of the present invention has been described in detail according to the above preferred embodiment, it should be noted that the above-described embodiment is for the purpose of description and not of limitation. In addition, those skilled in the art will understand that various embodiments are possible within the scope of the technical idea of the present invention.

As described above, according to the present invention, by forming the light blocking layer on the interlayer insulating film covering the control element so as to overlap the region where the control element is formed, it is possible to block the light incident from the outside incident to the area where the control element is formed. have. Accordingly, it is possible to provide an image sensor and a method of manufacturing the same, which realize a high resolution image having excellent optical characteristics.

In addition, according to the present invention described above, the floating diffusion region and the gate electrode of the drive transistor are interconnected by a light blocking layer, thereby further forming a separate metal wiring connecting the floating diffusion region and the gate electrode of the drive transistor, respectively. A wide design margin can be achieved.

Claims (12)

A substrate on which a photodiode and a control element for controlling the photocharge of the photodiode are formed; A first interlayer insulating film formed on the substrate to cover the photodiode and the control element; And The light blocking layer formed on the first interlayer insulating layer overlapping the region where the control element is formed so as not to overlap the region where the photodiode is formed so that light does not enter the region where the control element is formed. Image sensor comprising a. The method of claim 1, wherein the control element, A transfer transistor formed on the substrate to be aligned on one side of the photodiode; A floating diffusion region formed in the substrate on one side of the transfer transistor to receive the photocharges collected by the photodiode through the transfer transistor; A reset transistor formed on one side of the floating diffusion region to reset the floating diffusion region; A drive transistor functioning as a source follower buffer amplifier to amplify the potential of the floating diffusion region; And Select transistor which performs a switching role to output the amplified signal from the drive transistor Image sensor comprising a. The method of claim 2, And the floating diffusion region and the gate electrode of the drive transistor are interconnected by the light blocking layer. The method according to any one of claims 1 to 3, The light blocking layer is formed of any one selected from Ti, TiN, a laminated film of Ti / TiN, a metal material and a doped polysilicon. The method of claim 2 or 3, A second interlayer insulating film formed on the first interlayer insulating film to cover the light blocking layer; And A plurality of metal interconnections formed on the second interlayer insulating layer to be electrically connected to junction regions of the drive transistors, respectively; Image sensor further including. The method of claim 5, And the metal wiring is not connected to the light blocking layer. Providing a substrate including a photodiode and a control element for controlling photocharge of the photodiode; Forming a first interlayer insulating film on the substrate so as to cover the control device; And Forming a light blocking layer overlapping the region where the control element is formed so as not to overlap the region where the photodiode is formed so that light does not enter the region where the control element is formed; Image sensor manufacturing method comprising a. The method of claim 7, wherein the providing of the substrate on which the photodiode and the control element are formed, Forming a plurality of gate electrodes for the transistor on the substrate; And Forming the photodiode and the floating diffusion region in the substrate exposed to both sides of a gate electrode for a transfer transistor among the gate electrodes for the transistor; Image sensor manufacturing method comprising a. The method of claim 8, The forming of the light blocking layer may include forming the light blocking layer to interconnect a gate electrode for a drive transistor among the gate electrodes for the transistor and the floating diffusion region. The method according to any one of claims 7 to 9, The light blocking layer is formed of any one selected from the group of Ti, TiN, Ti / TiN laminated film, a metal material and doped polysilicon. The method of claim 9, wherein after forming the light blocking layer, Forming a second interlayer insulating film on the first interlayer insulating film so as to cover the light blocking layer; Forming a plurality of contact plugs electrically connected to junction regions of the drive transistors in the first and second interlayer insulating films; And Forming a plurality of metal wires respectively connected to the contact plugs; Image sensor manufacturing method further comprising. The method of claim 11, And the contact plug and the metal wiring are not connected to the light blocking layer.

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