KR100658924B1 - Image sensor using copper for metal line - Google Patents

Abstract

The present invention is to provide an image sensor that can increase the light efficiency by reducing the reflection component of the light due to the insulating barrier film used when copper is used as a metal line, to which the present invention comprises a photodiode And a microlens for focusing light at an upper portion overlapping the light receiving region and the light receiving region, and a metal line of a multilayer structure using copper disposed between the microlens and the light receiving region, wherein the metal line of the multilayer structure is an oxide film. And an insulating barrier film interposed between the metal film and the metal line to prevent mutual diffusion between the oxide film and the metal line positioned in another layer, wherein the insulating barrier film overlaps the light receiving region and the microlens. The image sensor is characterized in that the removed part .

The present invention also provides a metal line having a multilayer structure using a light receiving area including a photodiode and a microlens for focusing light at an upper portion overlapping the light receiving area, and copper disposed between the microlens and the light receiving area. The metal line of the multilayer structure is surrounded by an oxide film, and further comprises a conductive first barrier film disposed between the metal line and the metal line to prevent mutual diffusion between the oxide film and the metal line located in another layer, The conductive first barrier film provides an image sensor, wherein the light receiving area and the microlens are overlapped with each other.

Copper, metal line, image sensor, insulating barrier film, conductive barrier film, refractive index, image sensor.

Description

Image sensor using copper as metal line {IMAGE SENSOR USING COPPER FOR METAL LINE}             

1 is a cross-sectional view schematically showing an image sensor according to the prior art.

2 is a view showing a metal line structure of an image sensor using Cu according to the prior art.

3 is a cross-sectional view showing an image sensor according to an embodiment of the present invention.

4 is a sectional view showing an image sensor according to another embodiment of the present invention.

Explanation of symbols on the main parts of the drawings

300, 309: metal lines 301, 306, 308: conductive barrier film

302, 304: insulating barrier film 303, 305: oxide film

307: Via PD: Photodiode

ML: Micro Lens

The present invention relates to an image sensor, and more particularly to a CMOS image sensor having a copper wiring.

The image sensor is a semiconductor device that converts an optical image into an electrical signal. Among them, a charge coupled device (CCD) is a device in which charge carriers are stored and transported in a capacitor while individual MOS capacitors are located in close proximity to each other.

On the other hand, CMOS (Complementary MOS) image sensors use CMOS technology that uses a control circuit and a signal processing circuit as peripheral circuits to make MOS transistors as many as the number of pixels, and to use them. It is an element employing a switching method that detects the output of a pixel in turn.

In manufacturing such various image sensors, efforts are being made to increase the photo sensitivity of the image sensor, and one of them is a light collecting technology. For example, the CMOS image sensor is composed of a photodiode for detecting light and a portion of a CMOS logic circuit that processes and converts the detected light into an electrical signal.In order to increase the light sensitivity of the image sensor, the area of the photodiode in the overall image sensor area is increased. Efforts have been made to increase the ratio (commonly referred to as "fill factor"), but there is a limit to such efforts under a limited area since the logic circuit part cannot be removed essentially. Therefore, in order to increase the light sensitivity, other than photodiode A condensing technique that changes the path of light incident to the region of light and collects it into a photodiode has emerged. This technique is a microlens forming technique.

1 is a cross-sectional view schematically showing an image sensor according to the prior art.

Referring to FIG. 1, color filter arrays CFA such as blue, red, and green, which form unit pixels on the substrate 10 on which the photodiodes 11 and PD are formed; A color filter array 14 is disposed, an over-coating layer 15 is formed thereon, and a convex microlens is formed on an area overlapping the color filter array 14. (Microlens, 16) is formed.

A plurality of metal lines 13 are formed between the insulating layers 12, and the metal lines 13 are disposed in regions not overlapping with the photodiode 11 to serve as light blocking films.

In addition, a plurality of transistors 18 are formed on the substrate 10 adjacent to the photodiode 11, which includes a transfer transistor, a select transistor, a reset transistor, and a drive transistor in the case of a unit pixel having a 4Tr structure.

A protective film 17 is formed on the microlens 16 to protect the microlens 16 from scratches and the like.

The unit pixel of the CMOS image sensor illustrated in FIG. 1 includes a transistor 18 and one photodiode 11 for various purposes as described above. Firstly, light is transmitted through the photodiode 11 to excite holes (Hole) formed in the photodiode 11 to be converted into an electrical signal, and thirdly, the signal is transferred to the image.

Of these three processes, it is most ideal that the first incident light reaches 100% to the photodiode 11. As the image quality is required, the size of the unit pixel is gradually reduced, so that the area ratio occupied by the photodiode 11 per unit pixel is reduced to 30% or less. That is, since only 30% or less of light actually entering the photodiode 11 is used, a method of focusing 90% or more of light onto the photodiode by disposing the microlens 16 on each unit pixel.

On the other hand, since the metal lines 13 of various layers are formed on the photodiode 11 and the transistor 18, the photodiode 11 passes through the insulating layer 12 formed of various layers of light entering through the microlens 16. Will come in. On the other hand, the upper metal line 13 may vary depending on the technology node, but since it is formed in three or more layers, the distance from the microlens 16 into which the light is incident from the photodiode 11 increases. As a result, as shown by a dotted line in FIG. 1, the focus is disturbed, resulting in loss of light.

As a method of preventing such a loss, Cu is used instead of Al, which is used as a metal line 13.

When Cu is used as the metal line, the thickness of the metal line can be reduced because the resistance of the metal line can be reduced, thereby lowering the thickness of the insulating layer 12. In addition, the distance from the microlens 16 to the photodiode 11 is reduced, thereby improving the efficiency of incident light.

2 is a view showing a metal line structure of an image sensor using Cu according to the prior art.

Referring to FIG. 2, metal lines 200 and 209 of M1 and M2 are contacted through vias 207. The metal lines 200 and 209 are separated from the oxide-based insulating films 203 and 205 separating the layers, and the metal lines 200 and 209 and the vias 207 are formed using Cu. Since Cu has low resistance and excellent electromigration resistance as mentioned in the art, it has the advantage of being able to handle a high density current, but it is oxidized by interdiffusion when contacted with oxide series. (200, 209) and via 207 have conductive barrier films 201, 206, and 208 around them. The conductive barrier layers 201, 206, and 208 are for separation from the oxide layer existing between the same layers, while the metal lines 200 are formed due to different widths between the vias 207 and the metal lines 200 and 209. The insulating barrier films 202 and 204 are used to prevent contact between the insulating film 203 and the metal line 209 and the insulating film 203. SiN and SiC are used as the insulating barrier films 202 and 204.

On the other hand, the insulating barrier film is formed along the entire surface between the insulating films 203 and 205 and has a refractive index (n> 2) larger than the refractive index (n = 1.5) of the oxide film insulating films 203 and 205.

Some reflection occurs when light passes through materials with different refractive indices, and the larger the difference in refractive index, the greater the amount of reflection.

Since SiN has a refractive index of about 2.1 and SiC has a refractive index of about 2.4, the insulating barrier film 204 has such a refractive index between the insulating films 203 and 205 using the oxide film series having a refractive index of about 1.5. If present, the amount of light lost due to reflection increases in proportion to the number of metal lines.

Meanwhile, the reflectance generated when passing through two different refractive index materials is calculated using (n _i -n _{i + 1} ) / (n _i + n _{i + 1} ).

The present invention has been proposed to solve the above problems of the prior art, and provides an image sensor that can increase the light efficiency by reducing the reflection component of the light due to the insulating barrier film used when copper is used as the metal line. For that purpose.

In order to achieve the above object, the present invention provides a light-receiving area including a photodiode and a microlens for focusing light at an upper portion overlapping the light-receiving area, and a multilayer metal line disposed between the microlens and the light-receiving area. In the image sensor comprising a, each of the multi-layered metal line is formed of a damascene structure in the oxide film and further includes an insulating barrier film interposed between the oxide film located in the other layers of the upper and lower, to prevent mutual diffusion, The insulating barrier layer provides an image sensor, wherein a portion of the insulating barrier layer overlaps the light receiving region and the microlens is removed.

In addition, in order to achieve the above object, the present invention provides a microlens for focusing light in a light receiving area including a photodiode and an upper portion overlapping with the light receiving area, and a multi-layer disposed between the microlens and the light receiving area. In the image sensor including a metal line, each of the multi-layered metal line is formed of a damascene structure in the oxide film and interposed between the oxide film located in the other layer of the upper and lower, the conductive first barrier film to prevent mutual diffusion In addition, the conductive first barrier film provides an image sensor, characterized in that removed in the portion where the light receiving region and the microlens overlap.

The thickness of the metal line and the insulating layer can be reduced by using Cu, but if an insulating barrier layer such as SiN or SiC is used, the advantage of using Cu metal line in the image sensor is lost due to the loss of light.

Accordingly, the present invention selectively leaves an insulating barrier film only in a portion where the Cu and the oxide film are in contact with each other due to the different widths of the vias and the metal lines, and removes the insulating barrier film over the light receiving region where the photodiode is located. It suppresses the reflection of light due to the difference in refractive index between the oxide films and the decrease in light efficiency.

In addition, the barrier film itself may be used as a conductive material to increase adhesion between metal lines. The conductive barrier film may be selectively formed at a desired portion simply by an electroless plating method.

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. do.

3 is a cross-sectional view illustrating an image sensor according to an exemplary embodiment of the present invention.

Referring to FIG. 3, an image sensor according to an embodiment of the present invention may include a light receiving area including a photodiode PD, a microlens ML for focusing light at an upper portion overlapping the light receiving area, and a micro The metal lines 300 and 309 of the multilayer structure using copper disposed between the lens ML and the light receiving region are included, and the metal lines 300 and 309 of the multilayer structure are surrounded by the oxide films 303 and 305. Insulation between the metal lines 300 and 309 to prevent mutual diffusion between the oxide films 303 and 305 and the metal lines 300 and 309 which are positioned on different layers such as the metal line 300 and the oxide film 303. Barrier films 302 and 304 are provided, and the insulating barrier films 302 and 304 are removed at portions where the light receiving region and the microlens ML overlap.

Therefore, only the oxide films 303 and 305 having the same refractive index as above 1.5 are formed on the light receiving region where light is incident. As such, since there are no insulating barrier films 302 and 304 having different refractive indices between the oxide films 303 and 305, it is possible to prevent loss of light due to reflection.

Here, the metal lines 300 and 309 forming the multilayer structure are contacted to each other through the vias 307 filled with Cu, and correspond to the width difference between the vias 307 and the metal lines 300 and 309. The insulating barrier films 302 and 304 are provided only in the portion.

The insulating barrier films 302 and 304 are made of SiC or SiN. In addition, the metal lines 300 and 309 of the multi-layer structure may have a gap between the metal lines 300 and 309 and the vias 307 and the oxide films 303 and 305 to prevent coral diffusion from the oxide films 303 and 305 of the same layer. The conductive barrier films 301, 306, and 308 are disposed on the substrate.

In the image sensor of the present invention illustrated in FIG. 3, the metal lines 300 and 309 are formed through a single or dual damascene process having a single or dual structure as is well known.

4 is a cross-sectional view illustrating an image sensor according to another exemplary embodiment of the present invention.

Referring to FIG. 4, an image sensor of the present invention includes a light receiving area including a photodiode PD, a microlens ML for focusing light at an upper portion overlapping the light receiving area, a microlens ML, The metal lines 400 and 409 of the multilayer structure using copper disposed between the light receiving regions are included, and the metal lines 400 and 409 of the multilayer structure are surrounded by the oxide films 403 and 405.

Conductive between the metal lines 400 and 409 to prevent mutual diffusion between the oxide films 403 and 405 and the metal lines 400 and 409 positioned on other layers such as the metal line 400 and the oxide film 403. The first barrier films 402 and 404 are provided, and the conductive first barrier films 402 and 404 are removed at the portion where the light receiving region and the microlens ML overlap.

Therefore, only the oxide films 403 and 405 having the same refractive index as 1.5 above the light receiving region where light is incident. As such, since there is no conventional insulating barrier film having different refractive indices between the oxide films 403 and 405, it is possible to prevent loss of light due to reflection.

Here, the metal lines 400 and 409 forming a multilayer structure are contacted with each other through vias 407 filled with Cu, and correspond to the width difference between the vias 407 and the metal lines 400 and 409. The conductive first barrier films 402 and 404 are provided extending to portions and / or portions connected between the vias 407 and the metal lines 400 and 409.

The conductive barrier films 402 and 404 may also have an additional effect of increasing adhesion characteristics between the metal lines 400 and 409 and between the metal lines 400 and 409 and the multilayers, compared to an insulating barrier film made of SiC or SiN. .

The metal lines 400 and 409 of the multi-layer structure are electrically conductive between the metal lines 400 and 409 and the vias 407 and the oxide films 403 and 405 to prevent coral diffusion from the oxide films 403 and 405 of the same layer. Second barrier films 401, 406, and 408 are provided.

In the image sensor of the present invention shown in Figure 4, each metal line (400, 409) is formed through a single or dual structure damascene process as is well known.

Here, the conductive first barrier films 402 and 404 include at least one selected from the group consisting of NiMoP, CoMoP, CoWP, Ta, TaN, TaC, WN, TiN, TiW, TiSiN, WBN, and WC.

Here, the conductive first barrier films 402 and 404 are preferably limited to a thickness of 10 kPa to 500 kPa.

When the conductive first barrier films 402 and 404 are formed using Ta, TaN, TaC, WN, TiN, TiW, TiSiN, WBN, WC, etc., chemical vapor deposition (hereinafter, referred to as CVD) method Physical Vapor Deposition (hereinafter referred to as PVD) or Atomic Layer Deposition (hereinafter referred to as ALD) is used.

In the case where the conductive first barrier films 402 and 404 are used as NiMoP, CoMoP, CoWP, etc., they are formed by using an electroless plating method since they utilize the characteristic of selectively plating on Cu.

At this time, the concentration of Mo and P in Co (Mo, P) is limited to 0.1 to 5%, respectively, and the concentration of W and P in Co (W, P) is limited to 0.1 to 5%, respectively. The concentration of Mo and P in Ni (Mo, P) is preferably limited to 0.1 to 5%, respectively.

Cu is deposited by using a PVD or CVD method to form a seed layer having a low thickness of 50 to 1500 mW, and then using an electroless plating method, an electroplating method, a PVD or CVD method on the seed layer, and the like. After filling the damascene structure through the method, the heat treatment process, and then planarized through the CMP process to form the metal lines (400, 409).

The present invention made as described above, by implementing the metal line of the image sensor using copper, it is possible to lower the thickness of the metal line and the insulating film to increase the light efficiency and at the same time used to prevent the interdiffusion between copper and oxide film. By removing the insulating barrier film from the upper part of the light receiving area, only an oxide film having substantially the same refractive index exists in the light receiving area, thereby reducing light reflection due to the difference in refractive index between the insulating barrier film and the oxide film. I found out.

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.

The present invention as described above, while implementing the metal line using copper can increase the light efficiency by reducing the reflection due to the difference in refractive index, there is an effect of improving the performance of the image sensor.

Claims (10)

An image sensor comprising a light receiving area including a photodiode, a microlens for focusing light at an upper portion overlapping the light receiving area, and a plurality of metal lines disposed between the microlens and the light receiving area. Each of the multi-layered metal lines may further include an insulating barrier layer formed between the oxide layers positioned on the upper and lower layers and having a damascene structure in the oxide layer to prevent interdiffusion. And the microlens is removed from the overlapping part. The method of claim 1, The multilayer metal lines are in contact with each other through vias, and the insulating barrier layer is interposed between only the portions corresponding to the width differences between the vias and the metal lines. The method according to claim 1 or 2, The insulating barrier film is an image sensor, characterized in that consisting of SiC or SiN. The method of claim 1, Each of the multilayer metal lines formed of a damascene structure in the oxide film further includes a conductive barrier film interposed between the oxide films of the same layer and preventing mutual diffusion. An image sensor comprising a light receiving area including a photodiode, a microlens for focusing light at an upper portion overlapping the light receiving area, and a plurality of metal lines disposed between the microlens and the light receiving area. Each of the multi-layered metal lines further includes a conductive first barrier layer formed between the oxide layers positioned in the upper and lower layers and having a conductive first barrier layer formed therebetween to prevent mutual diffusion. And an area where the light receiving area and the microlens overlap each other. The method of claim 5, The multilayer metal lines are in contact with each other through vias, and the conductive first barrier layer is interposed only at a portion corresponding to a width difference between the vias and the metal lines. The method of claim 5, The multi-layered metal lines are in contact with each other through vias, and extend to a portion corresponding to a width difference between the vias and the metal lines and a portion connected between the vias and the metal lines. An image sensor, characterized in that the barrier film is interposed. The method according to any one of claims 5 to 7, The conductive first barrier layer includes at least one selected from the group consisting of NiMoP, CoMoP, CoWP, Ta, TaN, TaC, WN, TiN, TiW, TiSiN, WBN, and WC. The method according to any one of claims 5 to 7, The conductive first barrier film has an image sensor, characterized in that the thickness of 10 ~ 500Å The method according to any one of claims 5 to 7, Each of the multilayer metal lines formed of a damascene structure in the oxide film further includes a conductive second barrier film interposed between the oxide films of the same layer and preventing mutual diffusion.

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