KR100780544B1 - Method of manufacturing image sensor - Google Patents

Abstract

A method for manufacturing an image sensor is provided to improve resolution between micro lenses by using light transmission units having a concentric circle shape for patterning a photoresist film. First to third photo diodes(22,32,42) are formed. First to third color filters(74,76,78) corresponding to the first to third photo diodes are formed. A planarization layer covering the first to third color filters is formed. A photoresist film(80) including a photoresist material is formed on an upper surface of the planarization layer. Light transmission units(92) are formed from edge units of the first to third color filters toward the center of each of the first to third color filter. The light transmission units are formed in a concentric circle shape. The photoresist film is patterned by using the light transmission units. The exposed photoresist film is developed to form micro lenses.

Description

Manufacturing Method of Image Sensor {METHOD OF MANUFACTURING IMAGE SENSOR}

The present invention relates to a manufacturing method of an image sensor, and more particularly to a manufacturing method of an image sensor including a micro lens having more excellent light condensing characteristics.

In general, an image sensor is defined as a semiconductor device that converts an optical image into an electrical signal. Conventional image sensors are typically a charge coupled device (CCD), CMOS image sensor (CMOS image sensor) and the like.

The CMOS image sensor includes a plurality of pixels disposed in the pixel area and detecting a light amount, and a microlens corresponding to the pixel for condensing light into the pixel. Conventionally, the microlens of the CMOS image sensor includes a photoresist film. Patterning is performed to form a photoresist pattern, and the photoresist pattern is heated above the glass transition point (Tg) by a reflow process to form a microlens.

However, when forming a conventional microlens, the shape of the microlens is determined by the inclination of the sidewall of the photoresist pattern, and in order to prevent defects of the microlens, the side of the photoresist pattern is formed to have an inclined profile as much as possible. It is advantageous. However, when forming the inclined profile, on the contrary, it is difficult to maximize the margin of the photoresist pattern and minimize the gap.

Accordingly, the present invention has been made in view of such a conventional problem, and an object of the present invention is to improve the shape of a pattern mask for forming a microlens by patterning a photoresist film to manufacture an image sensor having a microlens having better quality. In providing a method.

In order to achieve one object of the present invention, a method of manufacturing an image sensor according to the present invention forms first to third photodiodes and first to third color filters corresponding to the first to third photodiodes. Forming a planarization film covering the first to third color filters to form a photodiode structure; Forming a photoresist film including a photosensitive material on an upper surface of the planarization film; The photoresist film may be firstly formed using a first pattern mask having a first light transmitting part having a first width formed corresponding to a boundary between the first and second color filters and a boundary between the second and third color filters. First exposure with exposure energy to form a first exposure portion; The photo by using a second pattern mask having a second light transmitting part having a second width larger than the first width corresponding to the boundary of the first and second color filters and the boundary of the second and third color filters. Secondarily exposing the resist film to a second exposure energy that is less than the first exposure energy to form a second exposure portion overlapping the first exposure portion; And developing the photoresist films on which the first and second exposure portions are formed to form micro lenses.

It has the advantage of forming a micro lens having better condensing properties.

Hereinafter, a method of manufacturing an image sensor according to embodiments of the present invention will be described in detail with reference to the accompanying drawings. However, the present invention is not limited to the following embodiments, and has ordinary skill in the art. It will be apparent to those skilled in the art that the present invention may be embodied in various other forms without departing from the spirit of the invention.

Manufacturing Method of Image Sensor

Example 1

1 is a cross-sectional view showing a photodiode structure, an insulating film structure and a color filter according to an embodiment of the present invention.

Referring to FIG. 1, to manufacture an image sensor, first, a photodiode structure 50 including first to third photodiode structures 20, 30, and 40 is formed on a semiconductor substrate 10. In this embodiment, the photodiode structure 30 includes three first to third photodiode structures 20, 30, and 40, but on the semiconductor substrate 10 a plurality of photodiode structures ( 50 may be arranged. The first to third photodiode structures 20, 30, and 40 respectively include the first to third photodiode 22, 32, and 42.

FIG. 2 is a plan view illustrating a first photodiode structure among the photodiode structures shown in FIG. 1.

Referring to FIG. 2, the first photodiode structure 20 includes a photodiode PD and a transistor structure TS that sense the amount of light.

The transistor structure TS includes a transfer transistor Tx, a reset transistor Rx, a select transistor Sx, and an access transistor Ax.

The transfer transistor Tx and the reset transistor Rx are connected in series to the photodiode PD. The source of the transfer transistor Tx is connected to the photodiode PD, and the drain of the transfer transistor Tx is connected to the source of the reset transistor Rx. A power supply voltage Vdd is applied to the drain of the reset transistor Rx.

The drain of the transfer transistor Tx serves as a floating diffusion (FD). The floating diffusion layer FD is connected to the gate of the select transistor Sx. The select transistor Sx and the access transistor Ax are connected in series. That is, the source of the select transistor Sx and the drain of the access transistor Ax are connected to each other. A power supply voltage Vdd is applied to the drain of the access transistor Ax and the source of the reset transistor Rx. The drain of the select transistor Sx corresponds to the output terminal Out, and the select signal Row is applied to the gate of the select transistor Sx.

An operation of the first photodiode structure 20 having the above-described structure will be briefly described. First, the reset transistor Rx is turned on to make the potential of the floating diffusion layer FD equal to the power voltage Vdd, and then the reset transistor Rx is turned off. This operation is defined as a reset operation.

When external light is incident on the photodiode PD, electron-hole pairs (EHP) are generated in the photodiode PD and signal charges are accumulated in the photodiode PD. Subsequently, as the transfer transistor Tx is turned on, the signal charges accumulated in the photodiode PD are output to the floating diffusion layer FD and stored in the floating diffusion layer FD.

Accordingly, the potential of the floating diffusion layer FD is changed in proportion to the amount of charges output from the photodiode PD, thereby changing the potential of the gate of the access transistor Ax. At this time, when the select transistor Sx is turned on by the selection signal Row, data is output to the output terminal Out.

After the data is output, the first photodiode structure 20 performs a reset operation again. Each photodiode structure 50 including the first grape diode structure 20 repeats these processes to convert light into an electrical signal and output the same.

After the photodiode structure 50 is formed on the semiconductor substrate 10, the insulating layer structure 60 is formed on the semiconductor substrate 10. The insulating layer structure 60 may include a wiring structure (not shown). In this embodiment, the insulating film structure 60 is included in the photodiode structure 50.

Color filters 72, 74, 76; 70 are formed on the insulating film structure 60. In this embodiment, the color filter 70 selectively selects the red color filter 72 which selectively passes the light of the red wavelength, the green color filter 74 which selectively passes the light of the green wavelength, and the light of the blue wavelength. Blue color filter 76 to pass through. In the present embodiment, the red, green, and blue color filters 72, 74, and 76 may have the same thickness or different thicknesses.

3 is a cross-sectional view of a photoresist film formed on the color filter illustrated in FIG. 1.

Referring to FIG. 3, after the color filter 70 is formed on the insulating layer structure 60, a photoresist film 80 including a photosensitive material is formed on the color filter 70.

In this embodiment, the photosensitive material may be a positive type photosensitive material whose cross link is reduced by light. Alternatively, the photosensitive material may be a negative type photosensitive material in which a cross link is formed by light.

4 is a cross-sectional view illustrating the primary exposure of the photoresist film shown in FIG. 3.

Referring to FIG. 4, after the photoresist film 80 is formed, the first pattern mask 90 is aligned on the photoresist film 80. The first pattern mask 90 has a first light transmitting part 92. In this embodiment, the first light transmitting portion 92 has a first width W1. The first light transmitting unit 92 is formed at the boundary between the first color filter 74 and the second color filter 76 and at the boundary between the second color filter 76 and the third color filter 78, respectively.

After the above-described first pattern mask 90 is aligned with the photoresist film 80, the photoresist film 80 is exposed by the light passing through the first light transmitting part 92 of the first pattern mask 90. As a result, the first exposure portion 82 is formed in the photoresist film 80. In the present embodiment, the light passing through the first light transmitting portion 92 has a first exposure energy and the first exposure portion 82 faces the top and top surfaces of the photoresist film 80 by the first exposure energy. It is formed to the bottom.

FIG. 5 is a cross-sectional view illustrating secondary exposure of the photoresist film shown in FIG. 4.

Referring to FIG. 5, after the first exposure part 82 is formed on the photoresist film 80, the second pattern mask 100 is aligned on the photoresist film 80.

The second pattern mask 100 has a second light transmitting part 102. In the present embodiment, the second light transmitting portion 102 has a second width W2 greater than the first width W1. The second light transmitting unit 102 is formed at the boundary between the first color filter 74 and the second color filter 76 and at the boundary between the second color filter 76 and the third color filter 78, respectively.

In the present embodiment, the light passing through the second light transmission portion 102 has a second exposure energy of 40% to 60% of the first exposure energy, preferably about 50%. The second exposure portion 84 is formed by the second exposure energy. The second exposure portion 84 overlaps the first exposure portion 82 and has a shallower thickness and a wider width than the first exposure portion 82.

FIG. 6 is a cross-sectional view of a microlens formed by developing the photoresist film illustrated in FIG. 5.

Referring to FIG. 6, after the second exposure portion 84 is formed, the photoresist film is developed by the developer, and as a result, the first and second exposure portions 82 and 84 are removed by the developer to form a respective angle. The micro lens 88 is formed on the color filters 70. Optionally, after the microlens 88 is formed, a reflow process may be performed on the microlens 88.

Example 2

FIG. 7 is a cross-sectional view illustrating aligning a pattern mask on a photoresist film according to a second embodiment of the present invention. FIG. In the method of manufacturing the image sensor according to the second embodiment of the present invention, the steps of forming the photoresist structure 50, the insulating layer structure 60, the color filter 70, and the photoresist film 80 are described in Embodiment 1 described above. Duplicate description as it is substantially the same as will be omitted. In addition, the same reference numerals and names will be given to the same components.

Referring to FIG. 7, the pattern mask 110 is aligned on the photoresist film 80 including the negative photosensitive material. The pattern mask 110 has a light transmitting part 112. In the present embodiment, the light transmitting unit 112 is formed at the boundary between the first color filter 74 and the second color filter 76 and at the boundary between the second color filter 76 and the third color filter 78, respectively. .

8 is a cross-sectional view illustrating an exposure profile of a photoresist film when the photoresist film is focused and exposed through the pattern mask shown in FIG. 7, and FIG. 9 is a cross-sectional view of the photoresist film through the pattern mask shown in FIG. 7. It is sectional drawing which shows the exposure profile of a photoresist film at the time of deforcused exposure.

7 to 9, after the pattern mask 110 is aligned on the photoresist film 80, the photoresist film 80 is primarily subjected to focus exposure at a first exposure energy. As the photoresist film 80 is subjected to focus exposure, the photoresist film 80 is first exposed to have a deep depth and a narrow width.

Thereafter, the photoresist film 80 is primarily subjected to focus exposure using the pattern mask 110, and then the photoresist film 80 is secondly decomposed at a second exposure energy using the same pattern mask 110. The focus is exposed. As the focus-exposed photoresist film 80 is defocused again, the photoresist film 80 is again exposed by light with a relatively wider width than the focus exposure.

In the present embodiment, it is preferable that the first exposure energy required when performing the focus exposure and the second exposure energy required when performing the defocus exposure are about half of the exposure energy for fully exposing the photoresist film 80. Do.

As described above, after the photoresist film 80 is defocused after the focus exposure, the microresist is formed by forming the photoresist film 80 by the developer. The microlenses formed in this way increase the resolution between the microlenses. Can be improved.

Example 3

FIG. 10 is a cross-sectional view illustrating aligning a pattern mask on a photoresist film according to a third embodiment of the present invention. In the method of manufacturing the image sensor according to the third embodiment of the present invention, the steps of forming the photoresist structure 50, the insulating film structure 60, the color filter 70, and the photoresist film 80 are described in Embodiment 1 described above. Duplicated descriptions will be omitted since they are substantially the same as. In addition, the same reference numerals and names will be given to the same components.

Referring to FIG. 10, the pattern mask 120 is aligned on the top surface of the photoresist film 80. In the present embodiment, the pattern mask 120 has a plurality of light transmitting parts 122. In the present exemplary embodiment, the plurality of light transmitting parts 122 may move the central portion of each of the first to third color filters 74, 76, and 78 from the edge of the first to third color filters 74, 76, and 78. A plurality is formed continuously in the direction. In the present embodiment, about 3 to about 5 light transmitting parts 122 are formed in one color filter, and the interval between the light transmitting parts 122 is preferably about 150 nm to about 200 nm. On the other hand, the width of each light transmitting portion 122 is continuously or intermittently widened from the edge portion of the color filter toward the center of the color filter.

FIG. 11 is a graph illustrating an exposure profile of a photoresist by light passing through the light transmitting portion of the pattern mask shown in FIG. 10.

Referring to FIG. 11, a plurality of light transmitting parts 122 are formed in an area corresponding to one color filter of the pattern mask 120, and the width of the light transmitting part 122 increases from the edge part of the color filter toward the center part. After the exposure, the photoresist pattern is exposed and developed using the light transmitting unit 122, thereby forming an excellent micro lens on the color filter.

Although the detailed description of the present invention has been described with reference to the embodiments of the present invention, those skilled in the art or those skilled in the art will have the spirit and scope of the present invention as set forth in the claims below. It will be understood that various modifications and variations can be made in the present invention without departing from the scope of the art.

1 is a cross-sectional view showing a photodiode structure, an insulating film structure and a color filter according to an embodiment of the present invention.

FIG. 2 is a plan view illustrating a first photodiode structure among the photodiode structures shown in FIG. 1.

FIG. 3 is a cross-sectional view illustrating primary exposure of the photoresist film shown in FIG. 2.

4 is a cross-sectional view illustrating secondary exposure of the photoresist film shown in FIG. 3.

FIG. 5 is a cross-sectional view illustrating a microlens formed by developing the photoresist film shown in FIG. 4.

6 is a cross-sectional view illustrating the alignment of the pattern mask on the photoresist film according to the second embodiment of the present invention.

FIG. 7 is a cross-sectional view illustrating an exposure profile of a photoresist film when the photoresist film is subjected to focus exposure through the pattern mask illustrated in FIG. 6.

FIG. 8 is a cross-sectional view illustrating an exposure profile of a photoresist film when the photoresist film is defocused through the pattern mask illustrated in FIG. 6.

9 is a cross-sectional view illustrating the alignment of the pattern mask on the photoresist film according to the third embodiment of the present invention.

FIG. 10 is a graph illustrating an exposure profile of a photoresist by light passing through the light transmitting portion of the pattern mask illustrated in FIG. 9.

FIG. 11 is a graph illustrating an exposure profile of a photoresist by light passing through the light transmitting portion of the pattern mask shown in FIG. 10.

Claims (4)

Forming first to third photodiodes and first to third color filters corresponding to the first to third photodiodes; Forming a planarization film covering the first to third color filters; Forming a photoresist film including a photosensitive material on an upper surface of the planarization film; Patterning the photoresist film using light transmitting parts formed in a plurality of concentric circles from an edge portion of each of the first to third color filters toward a center of the first to third color filters; And Developing the exposed photoresist film to form a micro lens. The method of claim 1, wherein the number of the light transmitting parts is three to five. The method of claim 1, wherein an interval between the light transmitting parts is 150 nm to 200 nm. The method of claim 1, wherein the width of each light transmitting portion is wider from the edge portion toward the center portion.

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