KR20060077110A - Cmos image sensor and method for fabricating the same - Google Patents

Abstract

The present invention provides a CMOS image sensor and a method of manufacturing the same so that the light passing through the micro lens can be focused on the photodiode provided at the bottom as much as possible to focus on the photodiode as much as possible. To this end, the present invention is a photodiode; A micro lens for refracting and transmitting the incident light to the photodiode; A multilayer insulating film provided between the photodiode and the micro lens; Multilayer wirings each insulated by the multilayer insulating film and not disposed on the photodiode; And a diffusion barrier layer disposed between at least one surface of the surface of the multilayer wiring and the insulating layer and not disposed above the photodiode.

CMOS image sensor, insulation film, photodiode.

Description

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

1 is a block diagram of a conventional CMOS image sensor.

2 is a circuit diagram showing the configuration of unit pixels of a conventional CMOS image sensor.

Figure 3 is a schematic cross-sectional view of an image sensor according to the prior art.

Figure 4 is a cross-sectional view showing a problem of the image sensor manufactured according to the prior art.

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

6A to 6H are cross-sectional views illustrating a manufacturing process of an image sensor according to a preferred embodiment of the present invention.

Explanation of symbols on the main parts of the drawings

20: substrate

21: photodiode

22a ~ 22d: interlayer insulation film

23a to 23d: wiring

28a ~ 28d: diffusion barrier                 

26: micro lens

24: color filter

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to CMOS image sensors, and more particularly to a CMOS image sensor and a method of manufacturing the same, wherein light transmitted through a microlens is focused more on 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, and the CMOS image sensor is a control circuit and a signal processing circuit. It is a device that adopts a switching method of making MOS transistors by the number of pixels by using CMOS technology using a signal processing circuit as a peripheral circuit and sequentially detecting the output using the MOS transistors.

Efforts have been made to increase the photo sensitivity of the CMOS image sensor, one of which is the light condensing technology. CMOS image sensor is composed of photodiode to detect light and CMOS logic circuit to process the detected light into electrical signal and make data.In order to increase the light sensitivity of image sensor, photodiode occupies the area of total image sensor area. Efforts have been made to increase the size (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.

Therefore, in order to increase the light sensitivity, a light condensing technology that changes the path of light incident to a region other than the photodiode and collects the photodiode has emerged. Such a technique is a microlens forming technology.

However, even if light is collected through the microlenses, the number of pixels accumulated is gradually increased, and the distance between the microlens and the photodiode disposed at the bottom thereof is gradually increased so that the light passing through the microlens cannot be focused. Effective delivery to photodiodes is becoming increasingly difficult.

1 is a block diagram of a conventional CMOS image sensor.

Referring to FIG. 1, a conventional CMOS image sensor includes a pixel array in which a plurality of unit pixels are arrayed, an ADC block for converting an analog signal output from the pixel array into a digital signal, and a digital value output from the ADC block. And a line buffer to store, a decoder / pixel driver for decoding the input address to select the unit pixel of the pixel array, and a control register and logic for controlling the decoder / pixel driver.

2 is a circuit diagram showing the configuration of unit pixels of a conventional CMOS image sensor.                         

FIG. 2 is a circuit diagram showing a unit pixel composed of one photodiode PD and four MOS transistors in a conventional CMOS image sensor, and includes a photodiode 100 for generating photocharges upon receiving light. A transfer transistor 101 for transporting the photocharges collected from the photodiode 100 to the floating diffusion region 102, and resets the floating diffusion region 102 by setting a potential of the floating diffusion region to a desired value and discharging electric charge. A reset transistor 103 for supplying voltage, a drive transistor 104 serving as a source follower buffer amplifier by applying a voltage of a floating diffusion region to a gate, and an addressing role as a switching role. It consists of a select transistor 105 that performs the following. Outside the unit pixel, a load transistor 106 for reading an output signal is formed.

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

Referring to FIG. 3, a color filter array (CFA) such as blue, red, and green, which form unit pixels on the substrate 10 on which the photodiodes 11 and PD are formed, is formed. A color filter array 14 is disposed, and a flattening film called an overcoating layer (OCL) 15 is formed thereon, and an upper portion of the region overlapping the color filter array 14 is formed. Convex microlenses 16 are formed.

Multi-layered wiring 13 is formed between the multi-layered insulating films 12, and the wiring 13 is disposed in an area not overlapping with the photodiode 11, and the wiring formed of metal serves as a light blocking film. do.                         

In addition, a plurality of MOS transistors 18 regions 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 4 Tr structure. do.

A protective film 17 is formed on the microlens 16 to protect the microlens 16 from scratches and the like. Reference numeral 9 denotes a device isolation film.

As described above, the CMOS image sensor collects an image of light incident through the microlens in the photodiode and converts the image into a voltage signal. At this time, a charge is generated in proportion to the intensity of light incident on the photodiode, and the generated charge is transferred to the internal circuit.

Therefore, as much light as possible must pass through the microlens and connected to the photodiode disposed at the bottom thereof to provide an image close to the real object.

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

As shown in FIG. 4, multilayer interlayer insulating films 22a to 22d are formed on the photodiode 11, and a color filter and a micro lens are provided thereon.

Further, wirings 13a to 13d are provided around the insulating film between the photodiode 11 and the microlens 16, that is, around the waveguide through which light propagates. The wiring also serves as the light blocking film as described above.

Previously, aluminum, which is easy to process in the manufacturing process, was used as the wiring material.

However, as the number of pixels integrated in the CMOS image sensor increases and faster operation is required, it is difficult to expect sufficient characteristics of aluminum conductivity. To solve this problem, copper with higher conductivity than aluminum was used as wiring.

When copper is used as the wiring, the thickness can be lowered than when aluminum is used in the related art, and thus the thickness of the insulating layer disposed between the microlens and the photodiode can be further reduced, thereby effectively condensing light onto the photodiode.

However, when copper is used as the wiring, the manufacturing process is more complicated than aluminum due to the characteristics of copper, and the diffusion barrier films 18a to 18d must be formed between the insulating films in contact with the copper formed as the wiring.

As the diffusion barrier, SiN or SiC is generally used, and these films have a refractive index (n> 2) larger than that of the conventional oxide film series (n ≒ 1.5).

Therefore, as shown in FIG. 4, the light incident through the microlens is not focused on the photodiode as a, but continues to be refracted while passing through the multilayer insulating film and the multilayer diffusion barrier like b, thereby leaving the photodiode. Discarded.

Therefore, the light is not concentrated to the photodiode, there is a problem that does not accurately implement the image corresponding to the real.

The present invention has been proposed to solve the above-described problems, so that the light passing through the micro lens can be focused on the photodiode as much as possible, so that the light passing through the micro lens can be focused on the photodiode provided at the bottom as possible. It is an object of the present invention to provide a CMOS image sensor and a method of manufacturing the same.

The present invention is a photodiode; A micro lens for refracting and transmitting the incident light to the photodiode; A multilayer insulating film provided between the photodiode and the micro lens; Multilayer wirings each insulated by the multilayer insulating film and not disposed on the photodiode; And a diffusion barrier layer disposed between at least one surface of the surface of the multilayer wiring and the insulating layer and not disposed above the photodiode.

The present invention comprises the steps of forming a photodiode on a substrate; Forming an insulating film on the photodiode; Forming a wiring in which a metal film / diffusion film is laminated on the first insulating film which does not overlap an upper surface of the photodiode; Forming a first insulating film on the wiring; Forming a color filter aligned with the photodiode on the first insulating layer; And forming a microlens on the color filter.

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.                     

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

Referring to FIG. 5, the biggest feature of the image sensor according to the present embodiment is the diffusion barrier layer disposed between the copper wiring and the adjacent insulating layers 22a to 22d while using the copper wirings 23b to 23d. 28a to 28d are removed between the photodiode 21 and the microlens 26. The lower end of the micro lens 26 is provided with a color filter 26.

Among the plurality of wirings, the wirings 23a represent via plugs and are formed of tungsten. The insulating film is usually formed of a silicon oxide film.

Therefore, the light passing through the micro lens can be focused directly to the photodiode 21 without passing through the diffusion barrier having a high refractive index while passing through the multilayer insulating film.

The diffusion barrier 28a is left because the light is more focused on the photodiode rather than being refracted by a further diffusion barrier.

6A to 6H are cross-sectional views illustrating a manufacturing process of an image sensor according to a preferred embodiment of the present invention.

As shown in FIG. 6A, the method for manufacturing the CMOS image sensor according to the present embodiment first forms a photodiode (see FIG. 5) on a substrate.

Subsequently, an interlayer insulating film 22c is formed on the photodiode, and the interlayer insulating film 22c in the region where the wiring is to be formed is selectively removed to form a hole X in which the wiring is to be formed.

Subsequently, as shown in Fig. 6B, the metal film 23c laminated with TaN / Ta / Cu is filled in the hole X. At this time, TaN / Ta is used as a barrier film to prevent copper from interacting with a neighboring insulating film, and most of the wiring is filled with Cu.

It is also possible to form the wiring using tungsten instead of copper.

Subsequently, as shown in FIG. 6C, the metal film 23c is removed through a chemical mechanical polishing process.

Subsequently, as shown in FIG. 6D, a portion of the upper surface of the copper is removed through a recess process. (Y) At this time, the portion to be removed is formed in the range of 300 to 1000 Å.

In this case, the recess process may be performed by wet etching in an acid-based chemical solution such as nitric acid or hydrochloric acid, or heat treatment in a nitrogen atmosphere after the chemical mechanical polishing process.

At this time, the wet etching process uses a chemical solution such as 10: 1 nitric acid or 10: 1 hydrochloric acid to perform a dip-out process within 30 seconds.

In addition, the chemical mechanical polishing process is a heat treatment process in N ₂ atmosphere at about 150 degrees 30 minutes.

Subsequently, it is buried in the recessed region using SiN or SiC as a diffusion barrier as shown in Fig. 6E.

In addition, a conductive material may be used as the diffusion barrier, and Ta, TaN, TaC, WN, TiN, TiW, TiSiW, or the like may be used.

6F, the diffusion barrier layer is removed so that the interlayer dielectric layer 22c is exposed through a chemical mechanical polishing process. Up to this point, the wiring process has been completed.

Subsequently, as shown in Fig. 6G, an interlayer insulating film 22d is formed again.

Then, as shown in Fig. 6H, a wiring process as shown in Figs. 6A to 6F is performed to form a new layer of wiring 23d. Here, the diffusion barrier film 28d is formed on the upper end surface of the wiring 23d.

As the diffusion barrier, SiN or SiC may be formed, or a conductive material may be used. Ta, TaN, TaC, WN, TiN, TiW, TiSiW, or the like may be used.

As described above, in the CMOS image sensor according to the present exemplary embodiment, the diffusion barrier layer is formed only on the upper surface of the surface on which the copper wiring is formed, and all remaining portions are removed.

Subsequently, the process of forming a color filter, a micro lens, etc. is performed.

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.

In the CMOS image sensor manufactured by the present invention, since the light passing through the microlens is transmitted to the photodiode, there is no diffusion preventing film having a high refractive index and only an interlayer insulating film. This photodiode can be focused.

In addition, since only an interlayer insulating film exists between the microlens and the photodiode, it is easy to adjust the focus of the microlens.

Claims (17)

Photodiode; A micro lens for refracting and transmitting the incident light to the photodiode; A multilayer insulating film provided between the photodiode and the micro lens; Multilayer wirings each insulated by the multilayer insulating film and not disposed on the photodiode; And A multilayer diffusion barrier layer disposed between at least one of the surfaces of the multilayer interconnection and the insulating layer and not disposed above the photodiode CMOS image sensor having a. The method of claim 1, And at least one diffusion barrier layer in the multilayer diffusion barrier layer is disposed between the photodiode and the microlens so that light passing through the microlens is refracted to the photodiode. The method of claim 1, The wiring image sensor, characterized in that the copper. The method of claim 3, wherein The diffusion barrier is A CMOS image sensor, characterized in that at least one of SiN or SiC is selected. The method of claim 3, wherein The diffusion barrier is A CMOS image sensor, characterized in that at least one selected from Ta, TaN, TaC, WN, TiN, TiW, or TiSiW. The method according to claim 4 or 5, The multilayer insulating film is a CMOS image sensor, characterized in that provided with a silicon oxide film. The method of claim 1, And a color filter aligning to the photodiode between the microlens and the multilayer insulating film. Forming a photodiode on the substrate; Forming an insulating film on the photodiode; Forming a wiring in which a metal film / diffusion film is laminated on the first insulating film which does not overlap an upper surface of the photodiode; Forming a first insulating film on the wiring; Forming a color filter aligned with the photodiode on the first insulating layer; And Forming a micro lens on the color filter Method for manufacturing a CMOS image sensor comprising a. The method of claim 8, Forming a wiring layer of a metal film / diffusion film on the first insulating film is formed Forming a second insulating film on the first insulating film; Selectively removing the second insulating film to form holes for forming wirings; Filling a metal into the hole to form a metal film; Recessing an upper portion of the buried metal film in a predetermined region; And And forming a diffusion barrier in the recessed region. The method of claim 9, Embedding the metal in the hole to form a metal film Filling a metal into the hole; And Method of manufacturing a CMOS image sensor comprising the step of leaving the metal only inside the hole through a chemical mechanical polishing process. The method of claim 9, The step of recessing A method for manufacturing a CMOS image sensor, characterized in that the wet etching process is carried out in an acid-based chemical solution. The method of claim 11, The wet etching process A method of manufacturing a CMOS image sensor, characterized in that the deep-out process is performed within 1 to 30 seconds using a chemical solution such as 10: 1 nitric acid or 10: 1 hydrochloric acid. The method of claim 9, The step of recessing Method of producing a CMOS image sensor, characterized in that the heat treatment in a nitrogen atmosphere after the chemical mechanical polishing process. The method according to claim 11 or 13, The recessed portion is a manufacturing method of the CMOS image sensor, characterized in that formed in the range of 300 ~ 1000Å. The method of claim 9, The metal film is a method of manufacturing a CMOS image sensor, characterized in that formed of copper. The method of claim 8, The diffusion barrier is A CMOS image sensor, characterized in that formed by selecting at least one of SiN or SiC. The method of claim 8, The diffusion barrier is A CMOS image sensor, characterized in that formed by selecting at least one of Ta, TaN, TaC, WN, TiN, TiW or TiSiW.

Images