KR20070105763A - Cmos image sensor and fabricating method therefore - Google Patents

Abstract

A CMOS image sensor and a manufacturing method of the same are provided to form a color filter in an inside of a groove formed in a metal layer by adjusting easily a thickness of the color filter. A light sensing element(33) is formed on one surface of a semiconductor substrate(31). A logic circuit layer(35) is formed on the semiconductor substrate. The logic circuit layer includes a plurality of layers of circuit patterns(37) and an insulating material formed between the circuit patterns. A metal layer(39) is formed on the insulating material as a top part and includes a plurality of grooves. Color filters(45) are formed in the grooves. A micro-lens(49) is formed on the color filters. A center of the groove corresponds to a center of the light sensing element. The center of the groove is positioned eccentrically to the center of the light sensing element.

Description

CMOS image sensor and its manufacturing method {CMOS IMAGE SENSOR AND FABRICATING METHOD THEREFORE}

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

2 is a cross-sectional view illustrating a state in which light is incident on the photosensitive device without passing through a color filter in a general CMOS image sensor.

3 is a cross-sectional view illustrating a state in which a photosensitive device and a logic circuit layer are formed on a semiconductor substrate in a method of manufacturing a CMOS image sensor according to an exemplary embodiment of the present invention.

4 is a cross-sectional view illustrating a state in which a groove is formed after stacking a metal layer on the passivation layer in FIG. 3.

FIG. 5 is a cross-sectional view illustrating a state in which a microlens is manufactured in a state where a color filter is formed in a groove illustrated in FIG. 4 and a planarization layer is interposed therebetween.

6A to 6C are cross-sectional views illustrating a microlens manufacturing process.

7 is a cross-sectional view showing a state in which light is incident on the CMOS image sensor according to an embodiment of the present invention.

<Description of Drawing>

31: semiconductor substrate 33: photosensitive device

35: logic circuit layer 37: circuit pattern

39: metal layer 41: groove

43: passivation layer 45: color filter

47: planarization layer 49: microlens

The present invention relates to a CMOS image sensor.

In general, an image sensor is a semiconductor device that converts an optical image into an electrical signal, and is generally referred to as a charge coupled device (CCD) and a complementary metal-oxide semiconductor (CMOS). It is divided into image sensors.

A CCD is a device in which charge carriers are stored and transported in a capacitor while each MOS (Metal-Oxide-Silicon) capacitor is located in close proximity to each other. The CMOS image sensor adopts a switching method that uses a 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 sequentially detects the output using the same. It is an element to make.

The most attracting attention with the conventional image sensor is the CCD is widely used in digital cameras, camera phones and the like. However, as the importance of the camera phone is highlighted, reducing the power consumption of the camera phone has emerged as an important problem, and accordingly, interest in the CMOS image sensor is increasing. The reason is that the CMOS image sensor is manufactured by a CMOS process for producing a general silicon semiconductor, which is small in size, inexpensive, and has low power consumption. CMOS sensors have excellent characteristics as portable sensors because of their high integration and low power consumption. However, various efforts have been made to improve them because they have a low photo sensitivity compared to conventional CCDs.

On the other hand, devices such as camera phones are increasingly pursuing miniaturization, and the optical system used in the image optical system constituting the camera phone is becoming more compact and higher quality. Therefore, the number of CMOS pixels used in camera phones, etc. increases to 300,000, 1 million, 1.3 million, 2 million, and 3 million pixels, and the pixel size of the sensor is gradually decreasing, and as the image module is compacted, The diagonal length of the image sensor is gradually decreasing. To this end, the backfocal length is decreasing, and as a result, the angle of incidence of light incident on the edge of the CMOS tends to increase. As a result, as the postfocal distance of the lens decreases, the light intensity ratio (hereinafter referred to as 'ambient light ratio') that enters the center portion and the edge portion of the CMOS gradually decreases. This is not limited to CCD, but also corresponds to CCD, which has recently emerged as one of the biggest problems with image sensors.

Referring to FIG. 1, a unit pixel composed of one photodiode PD and four MOS transistors in a typical CMOS image sensor is illustrated. The unit pixel includes a photodiode 10 for receiving light to generate photocharges, a transfer transistor 11 for transporting the photocharges collected from the photodiode 10 to the floating diffusion region 13, and a floating diffusion region at a desired value. A reset transistor 15 for resetting the floating diffusion region 13 by setting the potential of the transistor and discharging the electric charge, and a drive transistor acting as a source follower buffer amplifier by applying a voltage of the floating diffusion region to the gate. (17), it consists of a select transistor 19 which performs an addressing role as a switching role. A load transistor 21 is provided outside the unit pixel to read an output signal.

The CMOS image sensor is composed of a light-receiving portion for detecting light and a logic circuit portion for processing the detected light as an electrical signal and data. Efforts have been made to increase the size of the circuit, but this effort is limited in limited area conditions because the logic circuit part cannot be removed.

Therefore, in order to increase the light sensitivity, a condensing technology has been developed that changes the path of light incident to a region other than the light sensing portion and collects the light into the light sensing portion. The method of forming is used.

Referring to FIG. 2, light incident on the microlens 23 is condensed by the light sensing element 27 through the color filter 25 to reproduce an image. However, light passing through the color filters 25 is condensed by the light sensing element 27 without passing through the color filters 25, thereby causing a problem in which unwanted images are generated. In addition, since light passing between the microlenses 23 does not pass through the microlens 23, the light is condensed by the unwanted light sensing element 27 so that noise such as cross talk is generated. do.

The present invention provides a CMOS image sensor capable of generating accurate and clear images by removing noise such as crosstalk.

According to an embodiment of the present disclosure, a CMOS image sensor may include a semiconductor substrate having an optical sensing element formed on one surface thereof, a logic circuit layer formed on a semiconductor substrate, and an insulating material formed between a plurality of circuit patterns and a circuit pattern, and an insulating material on top. And a metal layer formed on and having a plurality of grooves, a color filter formed in the grooves, and a micro lens formed on the color filter.

Embodiments of the CMOS image sensor according to the present invention may have one or more of the following features. For example, the center of the groove may substantially coincide with the center of the photosensitive device, or the center of the groove may be eccentric at the center of the photosensitive device. The metal layer may be made of an antireflective coating metal, and the photosensitive device may be any one of a photodiode and a photogate.

The planarization layer may be further stacked on the color filter, and a microlens may be formed on the planarization layer.

According to an embodiment of the present disclosure, a method of manufacturing a CMOS image sensor may include forming a photosensitive device on a semiconductor substrate, and stacking a logic circuit layer made of an insulating material formed between a plurality of circuit patterns and a circuit pattern on the semiconductor substrate. Forming a plurality of grooves after forming a metal layer on the uppermost insulating material, forming a color filter inside the grooves, and forming a microlens on the color filter.

The method for manufacturing CMOS image sensor according to the present invention may include one or more of the following embodiments. For example, the center of the groove may be eccentrically constant or substantially coincident with the center of the light sensing element. And the metal layer may be made of an antireflective coating metal.

Hereinafter, an embodiment of a CMOS image sensor and a method of manufacturing the same according to the present invention will be described in detail with reference to the accompanying drawings. In the following description with reference to the accompanying drawings, the same or corresponding components are given the same reference numerals. Duplicate description thereof will be omitted.

Referring to FIG. 3, a state in which the process until the color filter is formed is performed. That is, in the process of fabricating the CMOS image sensor, the optical sensing element 33 is formed on the semiconductor substrate 31, and other CMOS devices (not shown), such as NMOS and PMOS transistors constituting the image sensor, are formed. The photosensitive device 33 may be any one of a general photo diode or a photo gate. In addition, when the photosensitive device 33 is a photodiode, a photodiode having a conventional p / n / p structure may be formed.

Although not shown, an isolation layer defining an active region and a field region is formed between the photosensitive elements 33. The device isolation layer may be manufactured by a LOCOS method using a thermal oxide film or a shallow trench isolation (STI) method.

On the other hand, the CMOS image sensor is composed of a light sensing portion for detecting light and a logic circuit portion for processing the detected light into an electrical signal to make data. A plurality of circuit patterns 37 are formed to form the logic circuit portion, which is surrounded by a plurality of oxide insulating materials 36 generated during the formation of the logic circuit portion. In addition, a passivation layer 43 is formed on the top of the insulating material 36 on the uppermost layer to protect the light sensing element 33 and the like from moisture and scratches.

Referring to FIG. 4, a metal layer 39 is stacked on the passivation layer 43, and a groove 41 is formed in the metal layer 39 corresponding to the light sensing element 33. The color filter 45 is formed in the groove 41 by a later process. As a result, light incident between the color filters 45 is blocked by the metal layer 39, thereby preventing unwanted image signals from being generated. .

The metal layer 39 is formed by laminating a copper or aluminum thin film on the passivation layer 43. Examples of the lamination method include an electrolytic or non-electrolytic plating method such as copper plating, but are not limited thereto. In addition, the metal layer 39 may be made of an anti-reflection coating metal. As such, the antireflective coating metal layer 39 does not reflect light absorbed by portions other than the microlens 49, thereby preventing interference of light. The thickness of the metal layer 39 may be adjusted in consideration of the thickness of the color filter 45 formed by a later process.

The grooves 41 formed on the metal layer 39 may be formed by a wet etching process or the like, and the grooves 41 penetrate the metal layer 39. Therefore, the top surface of the passivation layer 43 is exposed to the outside by the groove 41. The number of formations of the grooves 41 is the same as the number of the photosensitive elements 33. That is, each of the grooves 41 corresponding to one light sensing element 33 and the color filter 45 formed therein are provided. The groove 41 has a center, and the center of the groove 41 may be equal to or eccentric with the center of the light sensing element 33. 4 shows a state in which the center of the groove 41 is formed to coincide with the center of the light sensing element 33.

Referring to FIG. 5, the color filter 45 is formed in the groove 41, and the planarization layer 47 is stacked on the groove 41. On the planarization layer 47, a microlens 49 is formed corresponding to the position of the color filter 45.

The color filter 45 includes three colors of red (R), green (G), and blue (B), or three colors of yellow, magenta, and cyan. The light passing through the color filter 45 is separated into three types of red, green, and blue to realize a color image. The color filter 45 is manufactured by adding a dye to the photoresist PR, and its transmission characteristics may be determined by the amount of the dye added to the photoresist PR, but the thickness of the color filter that actually produces an optimal color. It is important to adjust the thickness of the color filter because the amount of dye addition is determined. The CMOS image sensor according to the present exemplary embodiment may easily adjust the thickness of the color filter 45 formed in the groove 41 formed in the metal layer 39 by adjusting the thickness of the metal layer 39. In addition, since the light incident between the color filters 45 is blocked by the metal layer 39 without proceeding to the inside, unwanted image signals may be prevented from occurring.

Since the top of the color filter 45 is rough, an over coating layer 47 is formed to remove the height difference generated by the color filter 45. The microlens 49 is formed on the planarization layer 47 in consideration of the positions of the light sensing element 33 and the color filter 45. The microlens 49 plays a role of concentrating light incident from the outside to the light sensing element 33 in order to improve light receiving efficiency.

As shown in FIG. 5, the microlens 49 includes a flat portion 51 parallel to the flattening layer 47 and a curved portion 53 extending from both ends of the flat portion 51.

The flat part 51 corresponds to a part which is not melted and flowed down by a reflow process after applying a resin for a microlens, and a method of manufacturing the flat part 51 will be described below. The flat part 51 increases the radius of curvature of the microlens 49, which is incident on the photosensitive element 33 without being refracted. Therefore, by forming the flat part 51, the image sensitivity of the image sensor is increased. In addition, since the area of the flat part 51 is formed to be the same as or slightly larger than that of the photosensitive device 33, the light incident in the direction of the photosensitive device 33 can be maximized.

The curved portion 53 is formed at both ends of the flat portion 51 to contact the flattening layer 47. The curved portion 53 corresponds to a portion melted and flowed down by a reflow process after coating the resin for a microlens.

Hereinafter, a method of manufacturing the microlens 49 of the CMOS image sensor according to an exemplary embodiment of the present invention will be described with reference to FIGS. 6A to 6C.

Referring to FIG. 6A, after preparing a semiconductor substrate on which a photodiode or the like is formed, a color filter 45 is formed, and a resist 55 for forming a micro lens on the planarization layer 47 is coated. Then, a portion of the resist 55 is partially exposed by selectively applying light (arrow mark) using a reticle 57.

As shown in Fig. 6B, the desired resist pattern 59 is formed by removing the exposed portions by development using an etching solution or the like, and as shown in Fig. 6C, the resist pattern is formed by baking. Slightly flows 59 to form curved portion 53. At this time, the area of the flat part 51 of the microlens 49 is preferably formed to be the same as or close to the area of the light sensing element 33.

Referring to FIG. 7 to describe the operation of the CMOS image sensor according to an exemplary embodiment of the present disclosure, all of the light incident through the microlens 49 may be collected by the photosensitive device 33. ), The refractive index and the radius of curvature are adjusted. In addition, since the light incident between the color pulp 45 is blocked by the metal layer 39 and cannot be collected by the light sensing element 33, light is incident in the direction of the adjacent light sensing element so that cross talk, etc. The same noise can be prevented from occurring.

Although the embodiments of the present invention have been described above, various changes and modifications of the present invention should also be construed as falling within the scope of the present invention as long as the technical idea of the present invention is realized.

The present invention can provide a CMOS image sensor capable of generating accurate and clear images by removing noise such as crosstalk.

The present invention can provide a CMOS image sensor that can easily adjust the thickness of the color filter because the color filter is formed in the groove formed in the metal layer.

Claims (10)

A semiconductor substrate having a photosensitive device formed on one surface thereof; A logic circuit layer formed on the semiconductor substrate and comprising a plurality of circuit patterns and an insulating material formed between the circuit patterns; A metal layer formed on an uppermost portion of the insulating material and having a plurality of grooves; The CMOS image sensor comprising a color filter formed in the groove and a micro lens formed on the color filter. The method of claim 1, And the center of the groove is substantially coincident with the center of the light sensing element. The method of claim 1, The center of the groove is a CMOS image sensor is eccentric from the center of the light sensing element. The method of claim 1, The metal layer is CMOS image sensor made of an anti-reflective coating metal. The method of claim 1, The photosensitive device is a CMOS image sensor of any one of a photodiode and a photogate. The method of claim 1, A planarization layer is further laminated on the color filter, The CMOS image sensor, wherein the microlens is formed on the planarization layer. Forming a photosensitive device on the semiconductor substrate; Stacking a logic circuit layer made of a plurality of circuit patterns and an insulating material formed between the circuit patterns on the semiconductor substrate; Forming a plurality of grooves after laminating a metal layer on the uppermost insulating material; Forming a color filter in the groove; The manufacturing method of the CMOS image sensor comprising the step of forming a micro lens on the color filter. The method of claim 7, wherein And a center of the groove substantially coincides with a center of the photosensitive device. The method of claim 7, wherein And a center of the groove is eccentrically spaced from the center of the photosensitive device. The method of claim 7, wherein The metal layer is anti-reflective coating metal CMOS image sensor manufacturing method.

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