KR20100079738A - Image sensor and method for manufacturing the sensor - Google Patents

Image sensor and method for manufacturing the sensor Download PDF

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Publication number
KR20100079738A
KR20100079738A KR1020080138293A KR20080138293A KR20100079738A KR 20100079738 A KR20100079738 A KR 20100079738A KR 1020080138293 A KR1020080138293 A KR 1020080138293A KR 20080138293 A KR20080138293 A KR 20080138293A KR 20100079738 A KR20100079738 A KR 20100079738A
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South Korea
Prior art keywords
optical waveguide
interlayer insulating
incident
angle
light
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KR1020080138293A
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Korean (ko)
Inventor
박승룡
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주식회사 동부하이텍
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Priority to KR1020080138293A priority Critical patent/KR20100079738A/en
Publication of KR20100079738A publication Critical patent/KR20100079738A/en

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    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01L—SEMICONDUCTOR DEVICES NOT COVERED BY CLASS H10
    • H01L27/00—Devices consisting of a plurality of semiconductor or other solid-state components formed in or on a common substrate
    • H01L27/14—Devices consisting of a plurality of semiconductor or other solid-state components formed in or on a common substrate including semiconductor components sensitive to infrared radiation, light, electromagnetic radiation of shorter wavelength or corpuscular radiation and specially adapted either for the conversion of the energy of such radiation into electrical energy or for the control of electrical energy by such radiation
    • H01L27/144—Devices controlled by radiation
    • H01L27/146—Imager structures
    • H01L27/14601—Structural or functional details thereof
    • H01L27/14625—Optical elements or arrangements associated with the device
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01L—SEMICONDUCTOR DEVICES NOT COVERED BY CLASS H10
    • H01L27/00—Devices consisting of a plurality of semiconductor or other solid-state components formed in or on a common substrate
    • H01L27/14—Devices consisting of a plurality of semiconductor or other solid-state components formed in or on a common substrate including semiconductor components sensitive to infrared radiation, light, electromagnetic radiation of shorter wavelength or corpuscular radiation and specially adapted either for the conversion of the energy of such radiation into electrical energy or for the control of electrical energy by such radiation
    • H01L27/144—Devices controlled by radiation
    • H01L27/146—Imager structures
    • H01L27/14601—Structural or functional details thereof
    • H01L27/14625—Optical elements or arrangements associated with the device
    • H01L27/14629—Reflectors
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01L—SEMICONDUCTOR DEVICES NOT COVERED BY CLASS H10
    • H01L27/00—Devices consisting of a plurality of semiconductor or other solid-state components formed in or on a common substrate
    • H01L27/14—Devices consisting of a plurality of semiconductor or other solid-state components formed in or on a common substrate including semiconductor components sensitive to infrared radiation, light, electromagnetic radiation of shorter wavelength or corpuscular radiation and specially adapted either for the conversion of the energy of such radiation into electrical energy or for the control of electrical energy by such radiation
    • H01L27/144—Devices controlled by radiation
    • H01L27/146—Imager structures
    • H01L27/14683—Processes or apparatus peculiar to the manufacture or treatment of these devices or parts thereof
    • H01L27/14685—Process for coatings or optical elements

Abstract

PURPOSE: An image sensor and a manufacturing method thereof are provided to improve the sensitivity of the image sensor by maximizing the amount of light which is inputted to a photo diode. CONSTITUTION: A photo diode(62) is formed on a semiconductor substrate. A first interlayer insulation layer(70) is formed on the upper side of the semiconductor substrate including the photo diode. An optical waveguide induces incident light to the photo diode and is formed on the first interlayer dielectric layer. A second interlayer insulation layer(80) includes the optical waveguide and is formed on the upper side of the first interlayer dielectric layer. The metal layers includes an incline to induce the incident to the optical waveguide by reflecting the incident light with a larger incident angle than a total reflection angle and is formed on the side of the upper side of the optical waveguide in the second interlayer dielectric layer.

Description

Image sensor and method for manufacturing the same

TECHNICAL FIELD The present invention relates to a semiconductor device and a method for manufacturing the same, and more particularly, to an image sensor and a method for manufacturing the same.

In recent years, CMOS image sensors (CIS) have been continuously reducing the size of unit pixels for high integration. In order to reduce the pixel size, in most cases, a method of reducing the size of a photodiode (PD), which is a light receiving area, is used. This reduces the effective area of light reception. In order to overcome this, sensitivity is improved by adding micro lenses in units of pixels. On the other hand, crosstalk arises from diffraction and scattering effects of light generated by additional structures such as metal layers present in the optical path from the micro lens to the PD. The presence of such crosstalk creates another problem besides sensitivity. To solve this problem, an optical waveguide structure is formed by filling a region from the microlens to the PD with a material having a high refractive index. In this case, the light converged by the microlenses reaches the PD well through total reflection in the optical waveguide.

1 shows a schematic cross-sectional view of a general image sensor employing the structure of an optical waveguide. Referring to FIG. 1, a PD (not shown) is formed on the semiconductor substrate 10, and an optical waveguide 14 is formed on the PD (not shown) in the interlayer insulating layer 12.

Referring to FIG. 1, light incident on a cell of a CIS has a different angle depending on its position. That is, light 20 incident to the center is incident vertically, while light 22 and 24 incident to the outer edge enter at an angle of up to 30 °. In this case, when the incident angles of the incident light 22 and 24 become more than the total reflection angle that can be accommodated in the optical waveguide 14, the light does not move along the optical waveguide 14 and is lost to the outside.

FIG. 2 illustrates a cross-sectional view of the image sensor illustrated in FIG. 1 in detail. Here, the photodiode 11 is formed on the semiconductor substrate 10, the metal layer 16 is formed on the other interlayer insulating film 17 formed on the interlayer insulating film 12, and the upper part of the interlayer insulating film 17. Another interlayer insulating film 18, the color filter array 30, and the microlens 32 are sequentially stacked.

As shown in FIG. 1, the angle of incidence of light reaching the cell region of a typical CIS varies according to its position, and as shown in FIG. 2, the structure of the optical waveguide 14 generally used in the CIS is vertical. It has a form. Therefore, the light 20 incident to the center and the light 21 and 23 in the vicinity thereof are not lost, but the light 22 and 24 incident to the outer side do not enter the waveguide 14 and are lost.

SUMMARY OF THE INVENTION The present invention has been made in an effort to provide an image sensor capable of maximizing the amount of light incident on a photodiode by inducing light incident at an angle into the optical waveguide and a method of manufacturing the same.

According to an aspect of the present invention, there is provided an image sensor comprising: a photodiode formed on a semiconductor substrate; a first interlayer insulating layer formed on the semiconductor substrate; An optical waveguide formed on the first interlayer insulating film, a second interlayer insulating film formed on the first interlayer insulating film including the optical waveguide, and an inclined surface to reflect the incident light having an incident angle greater than the total reflection angle to guide the optical waveguide And a metal layer formed on the side of the upper part of the optical waveguide in the second interlayer insulating film.

According to another aspect of the present invention, there is provided a method of manufacturing an image sensor, including: forming a photodiode on a semiconductor substrate, forming a first interlayer insulating layer on the semiconductor substrate, including the photodiode; Forming an optical waveguide for inducing incident light into the photodiode in the first interlayer insulating film, forming a second interlayer insulating film on top of the first interlayer insulating film including the optical waveguide, and an incident angle greater than a total reflection angle And forming a metal layer having an oblique inclined surface on the side of the upper part of the optical waveguide in the second interlayer insulating layer so as to reflect the incident light having the optical waveguide to guide the optical waveguide.

Since the image sensor and the manufacturing method thereof according to the present invention have the inclination of the metal layers, even if the incident angle of the incident light exceeds the total reflection angle, it is possible to reflect these incident lights at the sides of the metal layers and enter the optical waveguide. Since the limitations of the waveguide can be overcome, the amount of light incident on the photodiode via the optical waveguide can be maximized, thereby improving the sensitivity of the image sensor.

Prior to describing the present invention, a general property of light and a derivation process of the present invention will be described with reference to the accompanying drawings as follows.

3A and 3B are views for explaining total reflection of light.

In general, in order to improve the sensitivity of the CMOS image sensor (CIS), an optical waveguide 42 is formed inside the interlayer insulating film 40. The optical waveguide 42 utilizes total reflection that occurs between the medium 42 having a high refractive index n1 and the medium 40 having a low refractive index n2, and the light travels along the medium 42 having a high refractive index n1. It is derived. In this case, the propagation path of the light 50 and 52 is changed according to the angle of the light 50 and 52 incident to the optical waveguide 42. When the angle θ of the incident light 50 is small, as shown in FIG. 3A, the incident light 50 is effectively guided to the waveguide 42. However, when the angle θ of the incident light 52 is large, as shown in FIG. 3B, the incident light 52 is not effectively guided to the waveguide 42 and is lost.

The angle θ T of total reflection is determined by Equation 1 below by the difference between the refractive indices n1 and n2 of the two materials 40 and 42.

Figure 112008091038058-PAT00001

If the angle θ of the incident light 50 is less than the total reflection angle θ T as shown in FIG. 3A, the light 50 may travel along the optical waveguide 42 without loss. Therefore, in order to reduce the loss, the optical waveguide 42 should be generated obliquely in accordance with the path of the incident light or the path of the incident light should be close to the vertical. Thus, there is a need to make the path of the light incident on the optical waveguide 42 close to vertical but not vertical.

4 (a), 4 (b) and 4 (c) are photographs when incident to the image sensor while changing the incident angle of incident light. FIG. 4A shows a cross-sectional view of a general image sensor having a semiconductor element 10, a metal layer 16, a color filter 30 and a micro lens 32, and FIG. 4B shows an incidence angle of 5 ° of incident light. FIG. 4C shows a photograph in which the incident light path 34 is changed when the incident light is incident with an incident angle of 20 °.

In the structure of the image sensor shown in Fig. 4A, when the light is incident at an angle with inclinations of 5 ° and 20 ° as shown in Figs. 4B and 4C, respectively, the metal layer 16 It can be seen that the paths 33 and 34 are changed by being reflected from the plane of the plane. Therefore, it can be seen that if the metal layer 16 is formed to have a sufficient side surface area and the structure of the metal layer 16 is designed, the light paths 33 and 34 can be changed.

Hereinafter, an image sensor according to an embodiment of the present invention will be described with reference to the accompanying drawings.

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

Referring to FIG. 5, a photodiode 62 is formed on the semiconductor substrate 60. The first interlayer insulating film 70 is formed on the semiconductor substrate 60 including the photodiode 62. The optical waveguide 72 guides incident light 20 to 24 to the photodiode 62 and is formed on the first interlayer insulating film 70. The second interlayer insulating film 80 is formed on the first interlayer insulating film 70 including the optical waveguide 72. The metal layers 82 are formed in the second interlayer insulating layer 80 so as not to obstruct a path where light travels on the side of the optical waveguide 72.

According to the present invention, the appearance of the metal layers 82 is different from that of the general metal layers 16 shown in FIG. 2. That is, it can be seen that the metal layers 82 have an inclined surface to reflect the incident light 22 and 24 having the incident angle greater than the total reflection angle θ T to guide the optical waveguide 72. In addition, the metal layers 82 according to the present invention have a wider side surface than the metal layers 16 shown in FIG. To reflect at (82).

FIG. 6 is an enlarged view of the metal layer 82 shown in FIG. 5.

Referring to FIG. 6, it can be seen that the side surface of the metal layer 82 is formed to have an inclination angle θ k by an etching process as described below at the time of manufacturing the metal layer 82. By adjusting the inclination angle θ k , it can be seen that the angle at which the incident light 81 is reflected can be arbitrarily adjusted.

7 (a) to 7 (d) show various angles of the light 83 reflected from the metal layer 82 according to the angle of incident light 81.

As shown in FIGS. 7A and 7B, there is no reflection on the side of the metal layer 82 until the angle of the incident light 81 is 10 °. However, when the incident light 81 has an angle of 20 degrees, the light is reflected by the metal layer 82 and the light 83 proceeds vertically. In addition, when the incident light 81 has an angle of 30 °, the light is reflected by the metal layer 82 and the light 83 proceeds to −10 °. That is, when the reflection on the side of the metal layer 16 is not used, since the maximum angle of the light incident on the optical waveguide 14 is 30 ° as it is, the optical waveguide 14 is not entered and is lost. Since the side of the metal layer 82 is wide and inclined, the maximum angle is reduced to 10 ° even though the angle of the incident light 81 is 30 ° because the reflection of light from the side of the metal layer 82 is used. Can be.

Therefore, according to the present invention, the inclination angle θ k of the metal layers 82 may be 1/3 of the maximum incident angle of the incident light 22. Therefore, when the maximum incident angle of the light 81 is 30 degrees, it is preferable to set the angle θ k of the inclined surface of the side portion of the metal layer 82 to 10 degrees.

Parts other than the components of the image sensor described above are general matters, and thus, detailed descriptions thereof will be omitted and only outlined here. Therefore, the present invention can be variously applied without being limited by these components.

At least one third interlayer insulating film 90 is formed on the second interlayer insulating film 80 including the metal layers 82. The color filter array 100 is formed on the third interlayer insulating layer 90. The micro lens 102 is formed on the color filter array 100 and may be a graded index micro lens.

Hereinafter, a method of manufacturing an image sensor according to an embodiment of the present invention will be described with reference to the accompanying drawings.

8A to 8F show cross-sectional views of a method of manufacturing an image sensor according to an exemplary embodiment of the present invention.

In order to facilitate understanding of the present invention, only the manufacturing method of the portion 110 shown in FIG. 5 will be described. However, since the image sensor according to the present invention illustrated in FIG. 5 is a form in which the portion 110 is repeated, it is obvious that the portions not described are the same as the manufacturing process of the portion 110.

First, as shown in FIG. 8A, a photodiode 62 is formed on the semiconductor substrate 60. In the case of FIG. 8A, the photodiode 62 is illustrated as being formed under the semiconductor substrate 60. However, in some cases, the photodiode 62 may also be formed above the semiconductor substrate 60.

As shown in FIG. 8B, the first interlayer insulating layer 70 is formed on the semiconductor substrate 60 including the photodiode 62.

Subsequently, as illustrated in FIG. 8C, an optical waveguide 72 that guides incident light to the photodiode 62 is formed in the first interlayer insulating layer 70. For example, a photoresist mask (not shown) exposing a portion where the optical waveguide 72 is to be formed on the first interlayer insulating layer 70 is formed by a photolithography process. Thereafter, trenches (not shown) are formed in the first interlayer insulating layer 70 by an etching process using a photoresist mask. Subsequently, an optical waveguide 72 is formed by filling an insulating material having a refractive index higher than that of the first interlayer insulating layer 70 in the trench. After the optical waveguide 72 is formed, the photoresist mask is removed by an ashing process.

Thereafter, as shown in FIG. 8D, the second interlayer insulating layer 80 is formed on the first interlayer insulating layer 70 including the optical waveguide 72.

Subsequently, as illustrated in FIG. 8E, the metal layers 82 are formed on the side of the optical waveguide 72 in the second interlayer insulating layer 80. Here, the metal layers 82 are formed to have an inclined slope so as to reflect the incident light 22 having an angle of incidence greater than the total reflection angle θ T to guide the optical waveguide 72.

That is, in the method of manufacturing the image sensor according to the present invention, the angles of the side surfaces of the metal layers 82 may be inclined to optimize the angle of the light reflected by the optical waveguide 72. That is, the metal layers 82 may minimize the angle at which incident light is incident on the optical waveguide 72, thereby reducing the loss of light that is not incident on the optical waveguide 72. For example, the inclination angle of the sides of the metal layers 82 may be 1/3 of the maximum angle of incidence of the incident light 22.

For example, a photoresist mask (not shown) is formed on the second interlayer insulating layer 80 to expose a portion where the metal layers 82 are to be formed. Thereafter, the second interlayer insulating layer 80 is etched by an etching process using a photoresist mask to form a trench (not shown). Here, the side of the trench is etched to be inclined, and the etching process is performed such that the inclination angle is, for example, 1/3 of the maximum incident angle that the incident light 22 may have. The metal material is then embedded in the trench. Subsequently, a metal material is polished on the second interlayer insulating layer 82 by, for example, a chemical mechanical polishing (CMP) process until the second interlayer insulating layer 82 is exposed, and is shown in FIG. 8E. Complete the metal layers 82 of the type as shown.

In addition, since the manufacturing method of the image sensor is a general matter, only a brief description will be given here.

Subsequently, as shown in FIGS. 8E and 8F, a plurality of third interlayer insulating layers 83 and 90 are formed on the second interlayer insulating layer 80 including the metal layers 82.

Subsequently, as shown in FIG. 8F, the color filter array 100 is formed on the third interlayer insulating layer 90, and then the microlens 102 is formed on the color filter array 100.

The present invention described above is not limited to the above-described embodiment and the accompanying drawings, and it is common in the art that various substitutions, modifications, and changes can be made without departing from the technical spirit of the present invention. It will be evident to those who have knowledge of.

1 shows a schematic cross-sectional view of a general image sensor employing the structure of an optical waveguide.

FIG. 2 illustrates a cross-sectional view of the image sensor illustrated in FIG. 1 in detail.

3A and 3B are views for explaining total reflection of light.

4 (a), 4 (b) and 4 (c) are photographs when incident to the image sensor while changing the incident angle of incident light.

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

FIG. 6 is an enlarged view of the metal layer 82 shown in FIG. 5.

7 (a) to 7 (d) are views showing various angles of light reflected from the metal layer according to the angle of incident light.

8A to 8F show cross-sectional views of a method of manufacturing an image sensor according to an exemplary embodiment of the present invention.

DESCRIPTION OF THE REFERENCE NUMERALS

60 semiconductor substrate 62 photodiode

70, 80, 83, 90: interlayer insulating film 72: optical waveguide

82 metal layers 100 color filter array

102: Micro Lens

Claims (6)

A photodiode formed on the semiconductor substrate; A first interlayer insulating layer formed on the semiconductor substrate including the photodiode; An optical waveguide inducing incident light into the photodiode and formed in the first interlayer insulating film; A second interlayer insulating film formed over the first interlayer insulating film including the optical waveguide; And And an obliquely inclined surface to reflect the incident light having an incident angle greater than a total reflection angle to guide the optical waveguide, and having metal layers formed on the side of the optical waveguide in the second interlayer insulating film. The image sensor of claim 1, wherein the inclination angle of the sides of the metal layers is 1/3 of a maximum incident angle of the incident light. The image sensor of claim 1, wherein the image sensor A color filter array formed on the second interlayer insulating layer including the metal layers; And And a micro lens formed on the color filter array. Forming a photodiode on the semiconductor substrate; Forming a first interlayer insulating layer on the semiconductor substrate including the photodiode; Forming an optical waveguide for inducing incident light into the photodiode in the first interlayer insulating film; Forming a second insulating interlayer on top of the first insulating interlayer including the optical waveguide; And And forming metal layers having an oblique inclined surface on the side of the upper part of the optical waveguide in the second interlayer insulating layer to reflect the incident light having an incident angle greater than the total reflection angle to guide the optical waveguide. Method of preparation. The method of claim 4, wherein the inclination angle of the side portions of the metal layers is 1/3 of a maximum incident angle of the incident light. The method of claim 4, wherein the manufacturing method of the image sensor Forming a color filter array on top of the second interlayer insulating film including the metal layers; And And forming a micro lens on an upper portion of the color filter array.
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