KR20060114448A - Cmos image sensor method for fabricating the same - Google Patents

Abstract

A CMOS image sensor and a method for manufacturing the same are provided to improve the optical property without forming a SiC layer for interconnection on a photodiode. A photodiode(PD) is formed in a substrate. A first insulating layer is formed on the resultant structure. A second insulating layer is formed on the first insulating layer. The second interlayer dielectric is selectively etched to form an interconnection forming region. An interconnection is formed by filling a metal film in the interconnection forming region. A first SiC layer is formed on the resultant structure. The first SiC layer formed on the photodiode is selectively eliminated. A third insulating layer is then formed. A microlens is then formed on the third insulating layer to align the photodiode.

Description

CMOS image sensor and its manufacturing method {CMOS IMAGE SENSOR METHOD FOR FABRICATING THE SAME}

1 is a circuit diagram showing one unit pixel in a CMOS image sensor.

FIG. 2 is a process cross-sectional view of four MOS transistors forming a unit cycle shown in FIG.

3 is a process plan view of four MOS transistors shown in FIG.

Figure 4 is a schematic cross-sectional view of an image sensor according to the prior art.

Figure 5 is a cross-sectional view showing a problem of the image sensor according to the prior art.

6 is a cross-sectional view of the CMOS image sensor according to a preferred embodiment of the present invention.

7A to 7F are cross-sectional views illustrating a method of manufacturing a CMOS image sensor according to a preferred embodiment of the present invention.

Explanation of symbols on the main parts of the drawings

PD: Photodiode

Lens: Micro Lens

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a CMOS image sensor and a method of manufacturing the same, and more particularly, to a CMOS image sensor and a method of manufacturing the same, to allow more light to enter a photodiode.

In general, an image sensor of a semiconductor device is a semiconductor device that converts an optical image into an electrical signal. Representative image sensor devices include a charge coupled device (CCD) and a CMOS image sensor.

Among them, the charge-coupled device is a device in which charge carriers are stored and transported in the capacitor while individual metal-oxide-silicon (MOS) capacitors are located very close to each other. By using CMOS technology that uses a signal processing circuit as a peripheral circuit, a MOS transistor (typically four MOS transistors) corresponding to the number of pixels is made and sequentially output using the MOS transistor.

1 is a circuit diagram showing one unit pixel in a CMOS image sensor.

Referring to FIG. 1, one unit pixel includes one photodiode 10 and four an MOS transistors 11, 12, 13, and 14. As shown in FIG. Four NMOS transistors 11, 12, 13, and 14 are a transfer MOS transistor 11 for transporting the photocharge generated in the photodiode 10 to the charge sensing node N, and a charge for the next signal detection. The reset MOS transistor 12 for discharging the charge stored in the sensing node 11, the drive MOS transistor 13 serving as a source follower 13, and the switching role can be addressed. It is composed of a select MOS transistor 14 to enable.

Four MOS transistors 11, 12, 13, and 14 and one photodiode 10 form one unit pixel, and are provided in the pixel array of the CMOS image sensor according to the number of unit pixels included in the CMOS image sensor. The number of photodiodes 10 and the number of MOS transistors for unit pixels corresponding thereto are determined.

FIG. 2 is a process cross-sectional view of four MOS transistors constituting a unit circuit shown in FIG. 1, and four MOS transistors 11, 12, 13, and 14 respectively transmit signals Tx, Rx, Dx, and Sx to gates. The light transmitted to the photodiode PD is transmitted to the output terminal.

3 is a process plan view of four MOS transistors shown in FIG.

As shown in FIG. 3, gate patterns Tx of four MOS transistors 11, 12, 13, and 14 for transferring electrons collected by light transmitted from the photodiode 10 to an output terminal. , Rx, Dx, and Sx are disposed, and active regions 101 to 104 are disposed to the left and right of the gate patterns Tx, Rx, Dx, and Sx, respectively.

In this case, the active region 101 is a sensing node that receives electrons collected by the photodiode.

Referring to the operation of one unit device briefly, electrons collected by light transmitted to the photodiode 10 are transferred to the sensing node 101 through the transfer transistor 11.

Since the sensing node 101 is connected to the gate of the driving transistor 13, the driving transistor 13 adjusts the voltage level of the active region 103 bonded to one end in accordance with the voltage applied to the sensing node 101. Driving. Subsequently, the select transistor 104 is turned on to output a voltage applied to the active region 103 through an output terminal.

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

Referring to FIG. 4, a color filter array (CFA) such as blue, red, and green, which form unit pixels on the substrate 20 on which the photodiodes 10 and PD are formed, is formed. A color filter array 24 is disposed, and a flattening film called an overcoating layer (OCL) 25 is formed thereon, and an upper portion of the region overlapping with the color filter array 14; Convex microlenses 16 are formed.

Multi-layered wirings 23 are formed between the multi-layered insulating films 22, and the wirings 23 are disposed in regions not overlapping with the photodiode 10. The wirings formed of metal serve as a light blocking film. do.

In addition, a plurality of MOS transistors (region A) are formed on the substrate 20 adjacent to the photodiode 10, which is a transfer transistor, a select transistor, a reset transistor, and a drive as described above in the case of a 4Tr unit pixel. The transistor is placed.

A protective film 27 is formed on the microlens 26 to protect the microlens 26 from scratches and the like. Reference numeral 29 denotes a device isolation film.

Also, although not shown here, a macro lens is disposed on the upper portion of the micro lens to directly receive light incident from the outside and transmit the light to the micro lens.

As described above, the voltage applied to the gate of the driving transistor is controlled by electrons transferred from the photodiode to the floating node SD, and the source terminal of the driving transistor is driven in response to the regulated voltage.

5 is a cross-sectional view showing a problem of the image sensor according to the prior art.

Referring to FIG. 5, multilayer interlayer insulating films BPSG, TEOS, FSG, and SIN are disposed on the photodiode PD, and a microlens is disposed at the top thereof.

Metal wiring is disposed between the multilayer interlayer insulating films. In the past, metal wiring was made of aluminum, but copper has recently been used as wiring.

As the technology of CMOS image sensors is becoming more and more integrated, problems related to interconnect interconnects have become a major factor in the overall performance of a circuit. As a result, copper having low specific resistance is used as the wiring, but when copper is used as the wiring, diffusion and oxidation of copper become a problem.

Therefore, when using copper as a wiring, SiC is arrange | positioned so that a copper wiring may be enclosed.

In the CMOS image sensor, the performance of the photodiode, a light-receiving element, is essential.SiC used for the wiring is disposed between the photodiode and the microlens, so the light incident to the lens cannot be properly transmitted. It is happening.

The present invention has been proposed to solve the above-described problems, and an object of the present invention is to provide a CMOS image sensor and a method of manufacturing the same, which can prevent the optical characteristics from being degraded due to SiC.

The present invention comprises the steps of forming a photodiode on the substrate; Forming a first insulating film on the substrate on which the photodiode is formed; Forming a second insulating film on the first insulating film; Selectively removing the second insulating layer in a region where the photodiode is not formed to form a region where wiring is to be formed; Forming a wiring by embedding a metal in a region where the wiring is to be formed; forming a first silicon carbide film on an entire surface of the substrate on which the metal wiring is formed; Selectively removing the first silicon carbide film formed in a region where the photodiode is formed; Forming a third insulating film in a region where the first silicon carbide film is removed; And an alignment with the photodiode on the third insulating layer to form a micro lens.

The present invention is a photodiode; A multi-layered metal wiring disposed in an upper region of the photodiode without being aligned; Multilayer silicon carbide films disposed by bonding to the multilayer metal wirings, respectively; And a microlens aligned with the photodiode and disposed in an upper region of the photodiode, wherein the silicon carbide film provides a CMOS image sensor not disposed in a region between the photodiode and the microlens.

Hereinafter, the preferred 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. .

6 is a cross-sectional view of the CMOS image sensor according to a preferred embodiment of the present invention.

As shown in Fig. 6, the biggest feature of the CMOS image sensor according to the present embodiment is that the silicon carbide film (SiC), which is essentially used by the copper wiring, is removed between the photodiode and the microlens.

As a result, a single layer is formed between the photodiode and the microlens to reduce reflection of light and to transmit light to the silicon surface, that is, the region where the photodiode is formed, thereby improving optical characteristics.

7A to 7F are cross-sectional views illustrating a method of manufacturing a CMOS image sensor according to a preferred embodiment of the present invention.

As shown in FIG. 7A, the method for manufacturing the CMOS image sensor according to the present embodiment forms a photodiode PD in a state in which a device isolation film having an STI is formed.

Subsequently, a gate pattern is formed, and an insulating film made of TEOS + BPSG is formed. After the silicon carbide film (SiC) is formed, the SiC film formed on the upper portion of the region where the photodiode is formed is removed.

Then, as shown in Fig. 7B, an FSG film is formed, selectively removed, a copper wiring is formed where it is removed, and a silicon carbide film (SiC) film is formed on the provided wiring.

Also in this case, the silicon carbide film (SiC) is selectively removed from the region where the photodiode is formed.

Subsequently, as shown in Figs. 7C to 7D, copper wirings formed in multiple layers are formed, and silicon carbide films (SiC) are correspondingly formed on the respective copper wirings.

Also in this case, the silicon carbide film (SiC) is formed and selectively removed so that the silicon carbide film (SiC) is not formed on the region where the photodiode is formed.

Then, as shown in Fig. 7F, after the multilayer copper wiring is formed, a SiN + TEOS + SiN film is formed thereon.

Subsequently, a color filter, an OCL film, and a micro lens are formed thereon.

As described above, the present invention is not limited to the above-described embodiments and the accompanying drawings, and the present invention may be variously substituted, modified, and changed without departing from the spirit of the present invention. It will be apparent to those of ordinary skill in Esau.

Although copper wiring has been described above, it is possible to apply the present invention if a SiC film or the like is used in the case of using aluminum wiring.

The present invention does not form a SiC film, which is essentially used to prevent interconnection between copper wirings in the CMOS image sensor, in the upper region of the photodiode, so that light passing through the microlens is incident on the photodiode. Efficiency can be increased.

Claims (5)

Forming a photodiode on the substrate; Forming a first insulating film on the substrate on which the photodiode is formed; Forming a second insulating film on the first insulating film; Selectively removing the second insulating layer in a region where the photodiode is not formed to form a region where wiring is to be formed; Forming a wiring by embedding a metal in a region where the wiring is to be formed: Forming a first silicon carbide film on an entire surface of the substrate on which the metal wiring is formed; Selectively removing the first silicon carbide film formed in a region where the photodiode is formed; Forming a third insulating film in a region where the first silicon carbide film is removed; And Alignment with the photodiode on the third insulating layer to form a microlens CMOS image sensor comprising a. The method of claim 1, The metal is CMOS image sensor, characterized in that the copper or aluminum. The method of claim 2, The first to third insulating film is CMOS image sensor, characterized in that formed by the FSG film. Photodiode; A multi-layered metal wiring disposed in an upper region of the photodiode without being aligned; Multilayer silicon carbide films disposed by bonding to the multilayer metal wirings, respectively; And A micro lens aligned with the photodiode and disposed in an upper region of the photodiode And the silicon carbide film is not disposed in an area between the photodiode and the microlens. The method of claim 4, wherein The metal wiring image sensor, characterized in that the copper or aluminum wiring.

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