KR20140008544A - Image sensor and method for fabricating the same - Google Patents

Abstract

The present invention relates to an image sensor and a manufacturing method thereof. A rear light emitting type image sensor according to the present invention includes a substrate having the front and the rear, a light receiving area formed on the front of the substrate, and a rear light emitting type sensor including a micro lens integrated with the substrate and formed on the rear of the substrate. The present invention can suppress image lag and crosstalk and improve optical sensitivity. [Reference numerals] (AA) A area; (BB) B area; (CC) C area

Description

Back-illuminated image sensor and manufacturing method thereof {IMAGE SENSOR AND METHOD FOR FABRICATING THE SAME}

The present invention relates to a manufacturing technology of a semiconductor device, and more particularly to a back-illuminated image sensor and a manufacturing method thereof.

In the manufacturing process of an image sensor such as a conventional CMOS image sensor, transistors are formed on a silicon substrate 21 on which photodiodes are formed for each pixel, and a plurality of layers of metal lines and interlayers are formed on the transistors. Insulation layers are formed. Then, color filters 29 and micro lenses are formed on the interlayer insulating film.

In the conventional image sensor having such a structure, the light must pass through many layers of interlayer insulating films until light reaches the photodiode from the microlens, and the light is reflected by a plurality of metal wires M1, M2, and M3. Blocked, the light condensation rate is reduced. As a result, the image quality may be darkened.

In order to solve this problem, a back-illuminated image sensor which receives light to the rear surface 200 has been proposed.

BRIEF DESCRIPTION OF THE DRAWINGS Fig. 1 is a view of a backside illuminated image sensor according to the prior art; Fig.

Referring to FIG. 1, metal interconnections M1, M2, and M3 and an interlayer insulating layer are disposed on the front surface 100 of a silicon substrate 11 having unit pixels including a photodiode 12. An anti-reflection film 13 is disposed on the backside 200 of the silicon substrate 11, and respective color filters 14 are disposed on the anti-reflection film 13. The color filter 14 may include a first color filter, a second color filter, and a third color filter. The first color filter may be, for example, a red color filter. The second color filter may be, for example, a green color filter. The third color filter may be, for example, a blue color filter. If the colors of the color filter are the same, among them, the wavelength of red light is the longest and the wavelength of blue light is the shortest.

Subsequently, the planarization layer 15 is positioned above the color filter 14. The microlens 16 is formed on the planarization layer 15 to correspond to each unit pixel.

However, such a structure requires an arbitrary thickness from the surface of the silicon substrate 11 to the upper portion of the microlens 16 regardless of the thickness of the silicon substrate 11. Accordingly, optical shading and optical crosstalk phenomenon are improved. Is limited, and shifted microlenses and color filters are inevitable to enhance shading characteristics.

Embodiments of the present invention provide a rear image sensor and a method of manufacturing the same that can improve optical shading and optical crosstalk.

Back-illuminated image sensor according to an embodiment of the present invention is a substrate having a front and back; A light receiving area formed on the entire surface of the substrate; And a micro lens formed on a rear surface of the substrate and integrally formed with the substrate.

In addition, forming a silicon substrate including a light receiving area; Etching a rear surface of the silicon substrate to form a microlens; And it may include a method of manufacturing a back-illuminated image sensor comprising the step of forming a color filter covering the micro lens.

This technology solves the problems of optical shading and optical crosstalk deterioration, thereby securing product competitiveness.

In addition, microlenses are formed by etching the back of the silicon substrate, and the microlenses and color filters are not shifted, which directly contributes to product cost reduction.

1 is a cross-sectional view showing a back-illuminated image sensor according to the prior art.
Figure 2 is a cross-sectional view showing a back-illuminated image sensor according to a first embodiment of the present invention.
Figure 3 is a cross-sectional view showing a back-illuminated image sensor according to a second embodiment of the present invention.
4A to 4F are cross-sectional views showing an example of a method of manufacturing a back-illuminated image sensor according to a first embodiment of the present invention.
5A to 5G are cross-sectional views illustrating a method of manufacturing a backside-illuminated image sensor according to a second embodiment of the present invention.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT Hereinafter, preferred embodiments of the present invention will be described in detail with reference to the accompanying drawings, in order to facilitate a person skilled in the art to easily carry out the technical idea of the present invention.

In the description of the embodiments, where described as being formed "on / over" of each layer, the on / over includes both being formed directly or through another layer. do.

2 is a cross-sectional view showing a back-illuminated image sensor according to a first embodiment of the present invention.

Referring to FIG. 2, the back-illuminated image sensor according to the present invention includes a metal formed on the front side 100 of the silicon substrate 21 including photodiodes for each unit pixel (region A, region B, region C). Wirings M1, M2, M3, and an interlayer insulating film, and a microlens 25 and a color filter 29 formed on the backside 200 of the silicon substrate 21 opposite to the front surface 100. .

In the silicon substrate 21, unit pixels (region A, region B, region C, hereinafter omitted) are defined, and a plurality of photodiodes 23 are formed in the unit pixel. An interlayer insulating film including metal wirings M1, M2, and M3 is formed on the front surface 100 of the silicon substrate 21. The silicon substrate 21 may be a silicon substrate 21 or a semiconductor epitaxial silicon substrate 21.

Subsequently, on the rear surface 200 of the silicon substrate 21, a hemispherical microlens 25 formed by etching the rear surface of the silicon substrate is formed.

The microlens 25 may be formed in a hemispherical shape by etching the back surface 200 of the silicon substrate 21 through a wet etching process so as to correspond to a unit pixel, and may condense light to the unit pixel. Each microlens 25 is formed to be spaced apart from the neighboring microlens 25.

An antireflection film 27 is formed on the microlens 25. The antireflection film 27 is formed according to the curvature of the microlens 25.

The color filter 29 is formed on the antireflection film 27. One color filter 29 is formed for each unit pixel to separate colors from incident light. Each of the color filters 29 represents a different color, and is composed of three colors of red, green, and blue, and adjacent color filters 29 may overlap each other slightly to have a step.

In this case, although not shown in the drawing, in order to protect the color filter 29, a planarization layer made of an oxide film or a nitride film may be formed on the color filter 29.

3 is a cross-sectional view showing a back-illuminated image sensor according to a second embodiment of the present invention. In the description of the second embodiment, the same components as those of the first embodiment described above will be denoted by the same reference numerals and the same names.

Referring to FIG. 3, the back-illuminated image sensor according to the present invention includes a wiring layer formed on the frontside 100 of the silicon substrate 21 and a rear surface of the silicon substrate 21 opposite to the front surface 100. and a micro lens 25 and a color filter 29 formed in the backside 200.

A plurality of photodiodes 23 are formed on the silicon substrate 21 having unit pixels (region A, region B, region C). An interlayer insulating film including metal wirings M1, M2, and M3 is formed on the front surface 100 of the silicon substrate 21. The silicon substrate 21 may be a silicon substrate 21 or a semiconductor epitaxial silicon substrate 21.

Subsequently, a hemispherical microlens 25 made of silicon is formed on the rear surface 200 of the silicon substrate 21.

The microlens 25 may be formed in a dome form by etching the back surface 200 of the silicon substrate 21 through a wet etching process so as to correspond to a unit pixel, and condensing light into the unit pixel. Each microlens 25 is formed to be spaced apart from the neighboring microlens 25.

An antireflection film 27 is formed on the microlens 25. The antireflection film 27 is formed according to the curvature of the microlens 25.

Subsequently, an oxide layer is deposited on the antireflection film 27 to form a planarization layer 28 to which CMP is applied.

A plurality of color filters 29 are formed on the planarization layer 28. One color filter 29 is formed for each unit pixel (region A, region B, region C) to separate colors from incident light.

Each of the color filters 29 represents a different color, and is composed of three colors of red, green, and blue, and adjacent color filters 29 may overlap each other slightly to have a step.

In this case, although not shown in the drawing, in order to protect the color filter 29, a planarization layer made of an oxide film or a nitride film may be formed on the color filter 29.

4A to 4G are cross-sectional views illustrating a method of manufacturing an image sensor according to a first embodiment of the present invention.

Referring to FIG. 4A, a unit pixel (region A, region B, region C) including a photodiode 43 and a CMOS circuit is formed on the silicon substrate 41.

In the silicon substrate 41, an isolation layer 42 defining an active region and a field region may be formed. The unit pixel formed in the active region includes a photodiode 43 for receiving light and generating photocharges, and a CMOS circuit connected to the photodiode 43 to convert the received photocharge into an electrical signal.

After the relevant elements including the unit pixels (regions A, B, and C) are formed, metal wirings M1, M2, and M3 and an interlayer insulating film are formed on the front surface 100 of the silicon substrate 41.

The interlayer insulating film may be formed of a plurality of layers. For example, the interlayer insulating film may be formed of a nitride film or an oxide film.

The metal wirings M1, M2, and M3 may be formed in plural through the interlayer insulating layer. The metal wires M1, M2, and M3 are intentionally laid out so as not to block light incident on the photodiode 43. The metal wires M1, M2, and M3 may be formed of a conductive material including a metal.

At this time, since the present invention implements the backside irradiation structure, the metal wirings M1, M2, and M3 of the multi-layered metal wirings M1, M2, and M3 are disposed on the pixel, preferably, the photodiode, so that the area of the pixel is increased. Widen.

Referring to Figure 4b, the present invention rotates up and down by implementing a back-illumination structure. In order to form the preliminary microlens pattern, a photoresist film is coated on the silicon substrate 41, and then the photoresist film is selectively patterned and wet-etched to correspond to the unit pixel, thereby forming a mask pattern for forming the preliminary microlens pattern.

Referring to FIG. 4C, a preliminary microlens pattern 45 is formed on the surface of the silicon substrate 41A by performing a diagonal etching through a wet etching process according to a mask pattern covering the rear surface 200 of the silicon substrate 41. . At this time, the silicon substrate 41A is inclinedly etched in the same manner as the inclined portion of the mask pattern due to the wet etching characteristic.

Referring to FIG. 4D, the wet microlens 46 is applied to the preliminary microlens pattern 45 to form the microlens 45A by etching the preliminary microlens pattern in a hemispherical shape according to curvature.

Here, by forming the rear surface 200 of the silicon substrate 41 as the microlens 45A through each process, which is a characteristic of the present technology, the deterioration of characteristics of the image sensor is improved by improving optical shading and optical crosstalk deterioration, which has been generated in the prior art. Removed the factor.

Referring to FIG. 4E, an antireflective coating (ARC) is formed on the microlens 45A along the curvature of the microlens 45A. By depositing the anti-reflection film 47 on the microlens 45A, the reflection of light can be reduced and the transmission can be increased. That is, most incident light is absorbed to reach the photodiode 43 region, which is a light receiving region, thereby increasing the light sensitivity. The antireflection film 47 may be, for example, a nitride film.

Referring to FIG. 4F, a color filter 48 is formed on the antireflection film 47.

The color filter 48 is formed along the curvature of the anti-reflection film 47 corresponding to each of the micro lenses 45A and the unit pixel.

The color filter 48 uses dyed photoresist, and one color filter 48 is formed for each unit pixel (region A, region B, region C) to separate colors from incident light.

Each of the color filters 48 represents a different color, and is composed of three colors of red, green, and blue, and adjacent color filters 48 may overlap each other slightly to have a step. .

In this case, although not shown in the drawing, in order to protect the color filter 48, an oxide film or a nitride film may be deposited on the color filter 48 to form a planarization layer by applying CMP.

5A to 5G are cross-sectional views illustrating a method of manufacturing a backside-illuminated image sensor according to a second embodiment of the present invention.

5A to 5E, the process sequence (FIGS. 4A to 4E) is the same as that of the first embodiment until the color filter is formed in the back-illuminated image sensor according to the second embodiment of the present invention. do.

Referring to FIG. 5F, the planarization layer 58 is formed on the antireflection film 57. The planarization layer 58 is formed by depositing a planarization material on the anti-reflection film 57 and planarization by applying CMP. In this case, the planarization material may be an oxide film or a nitride film-based material.

Referring to FIG. 5G, a color filter 59 is formed on the planarization layer 58. The color filter 59 is formed in alignment with each of the microlenses 54A and the unit pixels (region A, region B, region C). The color filter 59 uses dyed photoresist, and one color filter 59 is formed for each unit pixel to separate colors from incident light. Each of the color filters 59 represents a different color, and is composed of three colors of red, green, and blue, and may overlap with the adjacent color filters 59 little by little. have.

In this case, although not shown in the drawing, in order to protect the color filter 59, an oxide film or a nitride film may be deposited on the color filter 59 to form a planarization layer by applying CMP.

Although the technical spirit of the present invention has been described in detail according to a preferred embodiment, it should be noted that the embodiments are for the purpose of description and not of limitation. In addition, those skilled in the art will appreciate that various embodiments within the scope of the technical idea of the present invention are possible.

21, 41, 51: silicon substrate 41A, 51A: silicon substrate with microlens
22,42,52: device isolation layer 23,43,53: photodiode
44, 54: mask pattern 45, 55: spare microlens pattern
25.45A, 55A: Microlens 46,56: Wet cleaning
27,47,57: Antireflective coating 29,48,59: Color filter
28, 31, 49, 58: leveling layer 100: frontside
200: backside M1, M2, M3: metal wiring

Claims (11)

A substrate having a front side and a back side;
A light receiving area formed on the entire surface of the substrate; And
A microlens formed on a rear surface of the substrate and integrally formed with the substrate
Back-illuminated image sensor comprising a.
The method of claim 1,
And the substrate and the microlens are formed of silicon.
A substrate having a front side and a back side;
A light receiving area formed on the entire surface of the substrate;
A microlens formed on a rear surface of the substrate and integrally formed with the substrate; and
A color filter formed to cover the microlens
Back-illuminated image sensor comprising a.
The method of claim 3,
A back-illuminated image sensor further comprising an anti-reflection film formed on the microlens
The method of claim 3,
The microlens is a back-illuminated image sensor formed of silicon.
5. The method of claim 4,
A back-illuminated image sensor having a planarization layer formed on the anti-reflection film.
Forming a silicon substrate including a light receiving region;
Etching a rear surface of the silicon substrate to form a microlens; And
Forming a color filter covering the microlens
Back-illuminated image sensor manufacturing method comprising a.
The method of claim 7, wherein
And forming an anti-reflection film on the microlens.
The method of claim 7, wherein
Forming the micro lens,
Forming a mask pattern on a back surface of the silicon substrate;
Etching a rear surface of the silicon substrate using the mask pattern to form a preliminary microlens pattern; And
Performing a surface treatment process to have a curvature by applying wet cleaning to the preliminary microlens pattern
Back irradiation type image sensor manufacturing method having a.
9. The method of claim 8,
A method of manufacturing a backside-illuminated image sensor forming a planarization layer on the anti-reflection film.
The method of claim 10,
The planarization layer is formed by forming an interlayer insulating film on the antireflection film and then planarizing the interlayer insulating film.

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