KR20070070428A - Complementary metal oxide semiconductor image sensor and method for manufacturing the same - Google Patents

Abstract

A CMOS image sensor and its manufacturing method are provided to prevent an incident light from penetrating a semiconductor structure including metal lines by illuminating directly a backside of a substrate in which photodiode is formed, thereby restraining image loss, reduction of a light transmitting ratio and noise generation. A photodiode(25) is formed on a substrate(20b). A semiconductor construction layer includes a gate electrode for transistors, a plurality of metal lines and a plurality of interlayer dielectrics for insulating the metal lines. A passivation layer is formed to protect the semiconductor construction layer. An adhesive layer(29) is formed on the passivation layer. A glass substrate(30) is formed on the adhesive layer. A color filter(33) is formed on the backside of the substrate.

Description

CMOS image sensor and its manufacturing method {COMPLEMENTARY METAL OXIDE SEMICONDUCTOR IMAGE SENSOR AND METHOD FOR MANUFACTURING THE SAME}

1 is a cross-sectional view showing a portion of a unit pixel of a CMOS image sensor according to the prior art.

2 is a cross-sectional view showing a portion of a unit pixel of a CMOS image sensor according to an exemplary embodiment of the present invention.

3A to 3D are cross-sectional views illustrating a method of manufacturing a CMOS image sensor according to the embodiment of the present invention shown in FIG.

-Explanation of symbols for the main parts of the drawings-

20, 20a, 20b: substrate

21: gate insulating film

22: gate conductive film

23: gate electrode for transfer transistor

25: photodiode

26: floating diffusion region

27: interlayer insulation film

28: contact plug

29: adhesive layer

30: glass substrate

31: wet etching process

32: antireflection film

33: color filter

The present invention relates to an image sensor and a method of manufacturing the same, and more particularly, to a CMOS (Complementary Metal Oxide Semiconductor) image sensor to apply a backside illumination technology and a method of manufacturing the same.

The CMOS metal sensor is a device widely used in mobile phones, cameras for personal computers (PCs), and electronic devices. CMOS image sensor is simpler to drive than CCD (Charge Coupled Device), which is used as an image sensor, and it is possible to integrate a signal processing circuit into one chip so that a system on chip (SOC) is possible. Allows the module to be miniaturized.

1 is a cross-sectional view illustrating a portion of a unit pixel of a CMOS image sensor according to the related art.

Referring to FIG. 1, a CMOS image sensor according to the related art includes a plurality of transistor gate electrodes (not shown) including a gate transistor 12 (hereinafter, referred to as a transfer gate electrode) formed on a substrate 10. A photodiode 15 formed in the substrate 10 exposed to one side of the transfer gate electrode 12, a floating diffusion region 16 formed in the substrate 10 exposed to the other side of the transfer gate electrode 12, An interlayer insulating film 17 formed through a multi-layered metal wiring (not shown) to cover the transfer gate electrode 12 and a color filter 18 formed on the interlayer insulating film 17 are included.

At this time, the light irradiated from the outside, such as 'A', is focused on the photodiode 13 via a micro lens (not shown) formed on the color filter 18, the color filter 18, the interlayer insulating film 17, and the like. do.

On the other hand, such a CMOS image sensor should be arranged together with a light receiving element, that is, a photodiode 13 and peripheral circuits such as a digital control block (ADC) and an analog digital converter (ADC) in a chip of a limited area. When manufacturing an actual image sensor, the area of a pixel array including a light receiving element that receives and senses light is limited to less than 30% of the total area of a chip.

In this situation, the pixel size has recently been reduced in order to achieve high image quality. Accordingly, the amount of light that can be received by the light receiving element is reduced, resulting in image loss.

In addition, when light enters the photodiode 13, when the interlayer insulating layer and a material having a different refractive index come into contact with the interlayer insulating film, such as metal wiring, reflection of the light occurs, thereby reducing the amount of light (light quantity) incident on the photodiode 13. Problem occurs. This reduction in the amount of light reduces the light transmittance of the image sensor, and the reflection of light causes noise, which is a fatal defect in the image sensor.

The present invention proposed to solve the problems of the prior art as described above, has another object to provide a CMOS image sensor and a method of manufacturing the same that can suppress image loss, light transmittance reduction and noise generation.

According to an aspect of the present invention, there is provided a substrate including a photodiode formed therein, a plurality of gate electrodes for transistors on the substrate, a plurality of metal wirings, and a plurality of metals formed for insulation between the metal wirings. A semiconductor structure layer comprising an interlayer insulating film of the insulating layer, a protective layer formed to cover the semiconductor structure layer to protect the semiconductor structure layer, an adhesive layer formed on the protective layer, a glass substrate formed on the adhesive layer, and It provides a CMOS image sensor comprising a color filter formed on the back of the substrate.

Preferably, the substrate is formed such that the back side has an acid and a valley. In this case, the substrate is formed such that the rear surface has a vertex, not a surface, at a portion where the peak and the valley meet.

According to another aspect of the present invention, there is provided a method of forming a plurality of transistor gate electrodes on a substrate, forming a photodiode locally on the substrate, and forming a plurality of photodiodes on the substrate. Forming a semiconductor structure layer comprising a metal wiring and a plurality of interlayer insulating films for insulation between the metal wirings, forming a protective layer covering the semiconductor structure layer to protect the semiconductor structure layer, and the protection A method of manufacturing a CMOS image sensor includes forming an adhesive layer on an upper layer, forming a glass substrate on the adhesive layer, and forming a color filter on a rear surface of the substrate.

Preferably, after forming the glass substrate, further comprising the step of flattening the back surface of the substrate, and performing a wet etching process.

Preferably, the wet etching process uses a potassium hydroxide solution so that the back side of the substrate has acid and bone, and the back side of the substrate has a vertex at the portion where the acid and bone meet.

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 may be formed directly on other layers or substrates when referred to as being on another layer or substrate. Or a third layer may be interposed therebetween. Also, throughout the specification, the same reference numerals denote the same components.

Example

2 is a cross-sectional view illustrating a portion of a unit pixel of a CMOS image sensor according to an exemplary embodiment of the present invention.

Referring to FIG. 2, a CMOS image sensor according to an exemplary embodiment includes a substrate 20b having a photodiode 25 formed therein and a gate electrode 23 for a transfer transistor on the substrate 20b. A semiconductor structure layer comprising a gate electrode for a transistor (not shown), a plurality of metal wirings (not shown), and a plurality of interlayer insulating films 27 formed for insulating between metal wirings, and a semiconductor to protect the semiconductor structure layer A protective layer (not shown) formed to cover the structure layer, an adhesive layer (Glue layer 29) formed on the protective layer, a glass substrate 30 formed on the adhesive layer 29, and a back surface of the substrate 20b. It includes a color filter 33 formed in.

According to the exemplary embodiment of the present invention, the color filter 33 is formed on the rear surface of the substrate 20b on which the process of forming the semiconductor structure layer including the photodiode 25 and the plurality of metal interconnections is completed, and backside illumination is performed. By applying a light irradiation technique (following an arrow of 'i') on the back surface of the substrate 20b, the light incident from the outside may be directly incident on the photodiode 25.

That is, by directly irradiating light on the back surface of the substrate 20b having the photodiode 25 formed therein, since the light does not pass through the semiconductor structure layer including the metal wiring, the reflection of light can be suppressed. Thus, image loss, light transmittance reduction and noise generation can be suppressed.

In particular, the substrate 20b is formed such that its rear surface has an acid B and a valley C. FIG. Preferably, the substrate 20b is formed such that its rear surface has a vertex at the portion where the peak B and the valley C meet. As such, when the back surface of the substrate 20b is formed in the form having the peaks B and the valleys C, the light condensation rate of the light may be increased more than when the back surface of the substrate 20b is flat. This is because the reflection of light is minimized by the inclined surfaces formed by the mountains B and the valleys C to further increase the light condensation rate to the photodiode 25.

At this time, the color filter 33 is formed by applying along the acid (B) and the valley (C) of the substrate 20b. In addition, an anti-reflective coating (ARC) 32 may be interposed between the color filter 33 and the substrate 20b.

In addition, a contact plug 28 is formed in the semiconductor structure layer to connect the metal wires to each other, wherein the contact plug 28 is formed of tungsten (W) or copper (Cu). In particular, when the contact plug 28 is formed of Cu, any one selected from the group of Ta, TaN, and WN or a lamination thereof is used as a barrier metal for preventing the diffusion of Cu into the interlayer insulating film 27. Laminated film is used. Preferably, the contact plug 28 is formed having a width of 0.2 ~ 5㎛ and a thickness of 0.3 ~ 3㎛.

The metal wiring is formed of any one metal selected from the group of Ti, TiN, and TiW or a laminated film thereof. Preferably, it is formed in thickness of 100-1000 kPa.

The contact plug 28 is connected to an I / O pad 35 formed through the adhesive layer 29 and the glass substrate 30, and the input / output pad 35 is formed of aluminum (Al) wiring or copper bumps. Is formed. At this time, the adhesive layer 29 is formed of any one polymer (Polymer) selected from the group of HSQ, MSQ and BCB of SOG (Spin On Glass).

3A to 3D are cross-sectional views illustrating a method of manufacturing a CMOS image sensor according to an exemplary embodiment of the present invention illustrated in FIG. 2.

First, as shown in FIG. 3A, a gate electrode (not shown) for transistors constituting a peripheral element and a plurality of transistor gate electrodes 23 constituting a pixel are formed on the substrate 20. For example, a gate electrode constituting the pixel includes a gate electrode 23 (hereinafter referred to as a transfer gate electrode) of a transfer transistor, a gate electrode of a reset transistor, a gate electrode of a drive transistor, and a gate electrode of a select transistor.

Here, only the transfer gate electrode 23 is shown for convenience of description, and the transfer gate electrode 23 has a stacked structure of the gate insulating film 21 and the gate conductive film 22. In addition, all the gate electrodes have the same structure.

Subsequently, a photodiode 25 is formed in the substrate 20 exposed to one side of the transfer gate electrode 23 by performing a mask process and an ion implantation process.

Subsequently, a mask diffusion process and a source / drain ion implantation process are performed to form a floating diffusion region 26 in the substrate 20 exposed to the other side of the transfer gate electrode 23 and simultaneously expose both sides of the other gate electrode. Source / drain regions (not shown) are formed in the substrate 20 of the region.

Subsequently, a plurality of interlayer insulating films 27 are formed on the entire upper surface of the substrate 20 so as to cover the transfer gate electrode 23 with multiple metal wirings (not shown) interposed therebetween. For example, the metal wiring is formed of any one metal selected from the group of Ti, TiN, and TiW or a laminated film thereof. Preferably, it is formed in thickness of 100-1000 kPa.

At this time, the interlayer insulating film 27 is formed of an oxide film-based material. For example, the interlayer insulating layer 27 may be a high density plasma (HDP) oxide film, a boron phosphorus silicate glass (BPSG) film, a phosphorus silicate glass (PSG) film, a plasma enhanced tetra thyle ortho silicate (peteos) film, a plasma enhanced chemical vapor (PECVD) film, and the like. A single layer film or a laminate of these layers is laminated using any one of a deposition film, a USG (Un-doped Silicate Glass) film, a Fluorinated Silicate Glass (FSG) film, a Carbon Doped Oxide (CDO) film, and an Organic Silicate Glass (OSG) film. Form into a film.

Then, contact plugs 28 are formed in the interlayer insulating film 27 to connect the metal wires to each other. Here, for convenience of description, the contact plug 28 is illustrated to be directly connected to the floating diffusion region 26 without showing the metal wiring. This indicates that the floating diffusion region 26 is electrically connected to the metallization via the contact plug 28.

For example, the contact plug 28 is formed as follows. First, a mask process and an etching process are performed to form a contact hole (not shown) having a width of 0.2 to 5 μm, and then a plug material is deposited to fill the contact hole. Then, it is planarized to the upper portion of the interlayer insulating film 27 to form a contact plug 28 isolated in the contact hole.

Preferably, tungsten (W) or copper (Cu) is used as the plug material, and when Cu is used, the diffusion material is selected from a group of Ta, TaN, and WN to prevent Cu diffusion into the interlayer insulating film 27. Either one or a laminated film thereof is used. Hereinafter, the contact plug 28, the metal wires, and the interlayer insulating layer 27 will be collectively referred to as a semiconductor structure layer.

Subsequently, a passivation layer (not shown) is deposited to protect the surface of the semiconductor structure layer.

Subsequently, an adhesive layer (Glue Layer) 29 is applied on the protective layer. Here, the adhesive layer 29 is formed by applying a polymer of any one of the HSG, MSQ and BCB of SOG (Spin On Glass) series to a thickness of 0.1 ~ 10㎛.

Subsequently, a glass substrate 30 is formed on the adhesive layer 29, and then a thermal process is performed to enhance adhesion between the interlayer insulating layer 27 and the glass substrate 30. That is, the adhesive property between the interlayer insulating film 27 and the glass substrate 30 is enhanced through the adhesive layer 29. Preferably, a thermal process is performed within the temperature range of 200-500 degreeC.

Subsequently, as shown in FIG. 3B, the entire structure is turned over while the glass substrate 30 is attached so that the rear surface of the substrate 20 (see FIG. 3A) faces upward.

Subsequently, the rear surface of the substrate 20a is etched by a predetermined thickness h. For example, the back surface of the substrate 20a is etched about 400-600 μm to reduce the overall thickness of the substrate 20a. Preferably, a chemical mechanical polishing (CMP) process is performed until the substrate 20a remains by a thickness of 10 to 100 µm.

Subsequently, as shown in FIG. 3C, the wet etching process 31 is performed to form the acid B and the valley C on the rear surface of the substrate 29b. At this time, the reason that the back surface of the board | substrate 20b repeatedly has the sin B and the valley C is as follows.

In the wet etching process 31, a potassium hydroxide (KOH) solution is used. Usually, such potassium hydroxide solution is characterized in that a fast etching rate can be selectively obtained only for a specific crystal surface of a single crystal silicon wafer. In particular, the etching rate for the <100> plane is about 100 times faster than the etching speed for the <111> plane. Therefore, the hill B and the valley C are formed on the back surface of the substrate 20b. For example, a groove having a 'V' shape is formed.

Through this, the phenomenon in which light incident to the photodiode 25 from the outside is reflected as in the conventional may be minimized. Therefore, it is possible to suppress image loss of the image sensor, increase light transmittance, and remove noise.

The wet etching process 31 is performed until the final substrate 20b remains at a thickness of 2 to 20 µm.

Subsequently, as shown in FIG. 3D, the antireflection film 32 and the color filter 33 are sequentially formed along the step of the rear surface of the final substrate 20b having the acid B and the valley C.

Subsequently, an input / output pad 35 is formed through the glass substrate 30 and the adhesive layer 29 to be electrically connected to the contact plug 28. For example, the input / output pad 35 may be formed of an aluminum (Al) metal wiring or a bump made of copper (Cu).

Subsequently, after applying a well-known image sensor process technology to deposit a planarization film, such as an over coating layer (OCL) film to remove the step formed by the color filter 33, the micro lens to correspond to the color filter 33 To form.

When the light is irradiated as shown by the 'i' arrow, the light is incident on the rear surface of the substrate 20b through the micro lens, which is directly incident on the photodiode 25. That is, an image sensor capable of irradiating the rear surface may be formed.

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, a color filter is formed on the back surface of the substrate on which the process of forming the semiconductor structure layer including the photodiode and the plurality of metal wirings is completed and the backside illumination technology is applied to the back surface of the substrate. By irradiating light at, light incident from the outside may be directly incident on the photodiode.

Therefore, by directly irradiating the light on the back surface of the substrate on which the photodiode is formed, since the light does not pass through the semiconductor structure layer including the metal wiring, it is possible to suppress the reflection of light. In this way, image loss, light transmittance reduction and noise generation can be suppressed.

Claims (25)

A substrate having a photodiode formed therein; A semiconductor structure layer including a plurality of transistor gate electrodes, a plurality of metal interconnections, and a plurality of interlayer insulating layers formed on the substrate to insulate the metal interconnections; A protective layer formed to cover the semiconductor structure layer to protect the semiconductor structure layer; An adhesive layer formed on the protective layer; A glass substrate formed on the adhesive layer; And Color filter formed on the back of the substrate CMOS image sensor comprising a. The method of claim 1, The substrate is a CMOS image sensor formed so that the back side has a valley with the acid. The method of claim 2, The substrate is a CMOS image sensor formed so that the back surface has a vertex at the portion where the valley and the valley meet. The method of claim 3, wherein The color filter is a CMOS image sensor formed by applying along the acid and valley of the substrate. The method of claim 4, wherein The CMOS image sensor further comprises an anti-reflection film interposed between the color filter and the substrate. The method according to any one of claims 1 to 5, And a contact plug included in the semiconductor structure layer to connect the metal wires to each other. The method of claim 6, The contact plug is CMOS image sensor made of tungsten or copper. The method of claim 7, wherein Wherein the contact plug is made of copper, CMOS image sensor, characterized in that using any one selected from the group of Ta, TaN and WN as a diffusion barrier film or a laminated film laminated them. The method of claim 6, And an input / output pad connected to the contact plug through the adhesive layer and the glass substrate. The method of claim 9, The input and output pads CMOS image sensor made of aluminum wiring or copper bumps. The method of claim 10, The adhesive layer is CMOS image sensor made of any one polymer selected from the group of HSQ, MSQ and BCB. Forming a plurality of gate electrodes for the transistor on the substrate; Forming a photodiode locally in the substrate; Forming a semiconductor structure layer on the substrate, the semiconductor structure layer including a plurality of metal interconnections and a plurality of interlayer insulating layers for insulating between the metal interconnections; Forming a protective layer covering the semiconductor structure layer to protect the semiconductor structure layer; Forming an adhesive layer on the protective layer; Forming a glass substrate on the adhesive layer; And Forming a color filter on a rear surface of the substrate Method of manufacturing a CMOS image sensor comprising a. The method of claim 12, After forming the glass substrate, Planarizing a rear surface of the substrate; And Steps to perform a wet etching process Manufacturing method of the CMOS image sensor further comprises. The method of claim 13, The wet etching process is a method of manufacturing a CMOS image sensor using a potassium hydroxide solution so that the back of the substrate has acid and bone. The method of claim 14, The wet etching process is a method of manufacturing a CMOS image sensor is carried out so that the back surface of the substrate has a vertex at the portion where the acid and the bone meet. The method of claim 15, And the color filter is formed along the peaks and valleys of the substrate. The method of claim 16, Before forming the color filter, And forming an anti-reflection film along the peaks and valleys of the substrate. The method of claim 13, The planarization of the rear surface of the substrate may include And a CMP process until the substrate remains at a thickness of 10 to 100 µm. The method of claim 18, The wet etching process is a method of manufacturing a CMOS image sensor is carried out until the substrate remains in a thickness of 2 ~ 20㎛. The method according to any one of claims 12 to 19, And forming a contact plug in the semiconductor structure layer to connect the metal wires to each other when the semiconductor structure layer is formed. The method of claim 20, And the contact plug is formed using tungsten or copper. The method of claim 21, When the contact plug is formed of copper, a method for manufacturing a CMOS image sensor, characterized in that any one selected from the group of Ta, TaN, and WN is used as a diffusion barrier, or a laminated film in which the contact plugs are laminated. The method of claim 20, After the color filter is formed, And forming an input / output pad connected to the contact plug through the adhesive layer and the glass substrate. The method of claim 23, The input and output pad is a manufacturing method of the CMOS image sensor is formed of aluminum wiring or copper bumps. The method of claim 24, The adhesive layer is a method of manufacturing a CMOS image sensor is formed of any one polymer selected from the group of HSQ, MSQ and BCB.

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