KR20050032867A - Complementary metal oxide semiconductor image sensor and method for fabricating thereof - Google Patents

Abstract

A CMOS(complementary metal oxide semiconductor) image sensor is provided to solve the problems caused by formation of an oxide layer on a lens part by embodying an image sensor having a micro lens from which a dead space is removed without using an oxide layer. A semiconductor substrate(106) is prepared which has a photocharge generating part and a predetermined pattern including a conductive interconnection. A color filter array(114) is formed on the pattern to filter the incident light from the outside. Lens parts concentrate the incident light from the outside on each color filter of the color filter array. A micro lens(122) from which a dead space between the lens parts is eliminated includes the semiconductor substrate, the color filter array and the lens parts. The lens parts are composed of a multilayer structure of at least two layers and each layer of the lens parts is made of the same material.

Description

IMAGE SENSOR AND MANUFACTURING METHOD THEREOF {COMPLEMENTARY METAL OXIDE SEMICONDUCTOR IMAGE SENSOR AND METHOD FOR FABRICATING THEREOF}

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an image sensor including a microlens and a method of manufacturing the same. More particularly, the present invention relates to an image sensor capable of removing dead space between lens sections of a microlens and a method of manufacturing the same. will be.

In general, an image sensor is a semiconductor device that converts an optical image into an electrical signal, and includes a Charged Coupled Device (CCD) image sensor and a Complementary Metal Oxide Semiconductor (CMOS) image sensor.

In the manufacture of the image sensor described above, efforts are being made to increase the photo sensitivity of the image sensor, one of which is a condensing technology.

For example, 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. Here, a photodiode is usually used for the light sensing portion.

In manufacturing the CMOS image sensor having such a configuration, in order to increase the light sensitivity, the ratio of the area of the light sensing portion to the total image sensor area (which is commonly referred to as "Fill Factor") must be increased.

However, since the light sensing portion can be formed only in portions except the logic circuit portion, there is a limit in increasing the area of the light sensing portion.

Therefore, many condensing techniques for changing the path of light incident to an area other than the light sensing portion and collecting the light into the light sensing portion have been studied. One of them is a technique of forming a microlens on the color filter of the image sensor.

This will be described with reference to FIGS. 1 and 2A to 2D.

FIG. 1 is a schematic cross-sectional view showing a configuration of an image sensor according to the prior art, and FIGS. 2A to 2D show process diagrams illustrating a method of manufacturing the image sensor according to the prior art.

The image sensor is provided on a semiconductor substrate 106 provided with photodetectors 104 including photodiodes 102 for generating and accumulating charges by receiving external light, and on top of the structure where the photodetectors 104 are formed. An oxide film 108, a nitride film 110, and a planarization layer 112 that are sequentially stacked. A color filter array 114, an over coating material (OCM) layer 116, and a micro lens 118 including a plurality of lens units 118 ′ are included.

The image sensor having such a configuration sequentially deposits the oxide film 108 and the nitride film 110 on the photodetectors 104 including the photodiode 102 and the semiconductor substrate 106 on which metal wires (not shown) are formed ( 2A), a planarization layer 112 is formed on the nitride film 110 to improve adhesion (see FIG. 2B). Here, the planarization layer 112 may be omitted.

Subsequently, the color filter array 114 is formed on the planarization layer 112 (see FIG. 2C). Here, the color filter array 114 is a red filter (R) formed by applying, exposing and developing a photoresist including a specific color, for example, red (R), green (G) and blue (B) pigments. ), A green filter (G) and a blue filter (B).

Subsequently, an OSC layer 116 is formed on top of the color filter array 114 for overcoming the step of the color filter array 114, for uniform production of the microlens 118, and for adjusting the focal length (see FIG. 2D). ). In this case, the OSM layer 116 may be formed of an insulating film based on a photoresist, an oxide film, or a nitride film.

Then, a photoresist is applied to the surface of the OSC layer 116, exposed to light, and developed to form a microlens 118 having a dead space 120 between the lens portions 118 ', as shown in FIG. After the microlens 118 is bleached, the photoresist is flowed by heat treatment to form a lens portion 118 'and then hardened.

Here, the reason for forming the dead space 120 is when the microlens 118 is formed without the dead space 120 between the lens portion 118 ', the lens portion 118' pattern in the lens forming process This is because the lens is combined with the adjacent lens portion pattern to be recessed, and thus the light sensitivity is lowered.

Therefore, when manufacturing the microlens 118 by a conventional lens manufacturing method, that is, the application, exposure and development of photoresist and heat treatment, the dead space 120 must be formed between the lens portion 118 ', There is a limit to increasing the light sensitivity of the lens 118.

Accordingly, in the related art, after the microlens 122 having the dead space 120 is formed in the state shown in FIG. 1 according to the aforementioned method, the lens portion of the microlens 122 is shown in FIG. 3. The microlens 122 was formed by removing the dead space 120 between the lens portions 122 'by forming a low temperature oxide film 122 "

The microlens 122 having such a configuration has an advantage of increasing optical sensitivity because the dead space between the lens portions 122 'is removed, but when applied to the product after the packaging process, a certain period of time has elapsed. If a crack occurs in the oxide film 122 ″ on the surface of the lens unit 122 ′, the lens performance is deteriorated. Also, a medium constituting the micro lens 122, that is, the lens unit 122 ′ is formed. Since the refractive index between the photoresist and the oxide film 122 "on the surface of the lens unit 122 'is different, there is a problem in that external light cannot be accurately focused on the photodiode.

SUMMARY OF THE INVENTION The present invention has been made to solve the above problems, and an object thereof is to eliminate dead spaces between the lens parts constituting the microlenses, and to prevent the occurrence of cracks and deterioration of the lens performance due to the formation of an oxide film, and an object thereof. It is to provide a manufacturing method.

The object of the present invention described above,

A semiconductor substrate having a predetermined pattern including a photocharge generating unit and conductive wirings;

A color filter array formed on top of the pattern to filter light incident from the outside;

A micro lens including condensing light incident from the outside to each color filter of the color filter array, wherein a dead space is removed between the lens parts;

The lens parts may be formed of a multilayer structure having two or more layers, and each layer of the lens parts may be achieved by an image sensor made of the same material, for example, a photoresist for a microlens.

An image sensor having such a configuration is a manufacturing method of an image sensor in which a microlens is formed on an upper layer of a color filter array provided on a semiconductor substrate.

A first material layer forming step of forming a first material layer for forming a micro lens;

A second material layer forming step of forming a second material layer for forming a micro lens on a surface of the first material layer;

A lens part primary forming step of patterning the second material layer to primarily form lens parts having a dead space between the lens parts;

A lens unit completing step of selectively removing the lens unit formed with the first material layer and completing the lens units from which dead spaces are removed;

It can be manufactured by a manufacturing method of an image sensor including a.

In manufacturing a microlens according to the above-described manufacturing method, the first material layer forming step is performed by applying a photoresist for forming a microlens, followed by bleaching and heat treatment to harden the second material layer forming step. Is performed by applying the same photoresist as the first material layer, and the primary forming of the lens unit is performed by patterning the second material layer, followed by bleaching and heat treatment to cure the same.

The second material layer may be formed thicker than the first material layer.

Hereinafter, preferred embodiments of the present invention will be described in detail with reference to the accompanying drawings.

4 is a cross-sectional view showing a schematic configuration of an image sensor according to an embodiment of the present invention, Figures 5a to 5c shows a process diagram showing a manufacturing method of an image sensor according to an embodiment of the present invention.

As shown in the drawing, the device region of the semiconductor substrate 10 is provided with photo detectors 14 including photodiodes 12 for generating and accumulating charges by receiving external light. The oxide film 16 and the nitride film 18 are sequentially provided on the structure where the holes are formed, and the planarization layer 20 for improving the adhesion is provided on the nitride film 18. Here, the planarization layer 20 may be removed in some cases, and the oxide film 16 and the nitride film 18 serve to protect the device from external moisture or scratches.

In addition, a color filter array 22 including color filters of red (R), green (G), and blue (B) is provided on the flattening layer 20, and on the upper part of the color filter array 22. An OSC layer 24 is provided. Here, the OSC layer 24 is to overcome the step of the color filter array 22, to uniformly manufacture the microlens 28, and to adjust the focal length, and is formed of a resist, an oxide film, or a nitride film-based insulating film.

In addition, a microlens 28 including a plurality of lens units 26 for condensing external light to each of the color filters R, G, and B is provided above the OSM layer 24.

Each of the lens units 26 has a multi-layer structure including a first material layer 26 ′ and a second material layer 26 ″, and a dead space between the lens parts 26 is removed. Has characteristics.

The micro lens 28 of such a structure can be manufactured by the manufacturing method mentioned later.

First, the optical sensing unit 14 including the photodiode 12, the conductive wiring, the oxide film 16 and the nitride film 18, and the planarization layer according to the same method as in FIGS. 20, the color filter array 22, and the semiconductor substrate 10 having the OSC layer 24 formed thereon, and the first material layer 26 for forming a microlens on the surface of the OSM layer 24. ') (See FIG. 5A).

Here, the first material layer 26 'is formed by applying a photoresist for forming a microlens, followed by bleaching and heat treatment to cure the same.

Subsequently, a second material layer 26 ″ for forming a microlens is formed on the surface of the first material layer 26 ′ (see FIG. 5B). In this case, the second material layer 26 ″ is formed as a first material. It is desirable to form thicker than layer 26 '. In addition, it is preferable to form the second material layer 26 "from the same material as the first material layer 26 ', which occurs due to the difference in refractive index when the lens portion 26 is made of different refractive index media. It is to eliminate the problem that becomes.

Subsequently, after exposing and developing the second material layer 26 " to pattern the lens parts having the dead spaces 30 between the lens parts, the lens parts are hardened by bleaching and heat treatment. (See FIG. 5C).

After hardening the lens portions formed of the second material layer 26 ″, the lens portions of the first material layer 26 ′ and the second material layer 26 ″ are selectively removed. As described above, the lens units 26 in which the dead space 30 is removed are completed. In this case, a known selective etching process may be used for the selective removal.

Although the preferred embodiments of the present invention have been described above, the present invention is not limited thereto, and various modifications and changes can be made within the scope of the claims and the detailed description of the invention and the accompanying drawings. Naturally, it belongs to the range of.

As described above, the present invention can implement an image sensor having a micro lens from which dead spacers are removed without using an oxide film.

Therefore, problems caused by the formation of an oxide film on the surface of the conventional lens unit (degradation of lens performance due to crack generation, deterioration in light collection efficiency due to refractive index difference, etc.) can be solved.

In addition, since the dead space is removed, the optical sensitivity can be increased, thereby achieving an ideal optical transmission rate.

1 is a cross-sectional view showing a schematic configuration of an image sensor according to the prior art,

2a to 2d is a process chart showing a manufacturing method of an image sensor according to the prior art,

3 is a cross-sectional view showing a schematic configuration of an image sensor according to another example of the prior art,

4 is a cross-sectional view illustrating a schematic configuration of an image sensor according to an embodiment of the present invention.

5A to 5C are flowcharts illustrating a method of manufacturing an image sensor according to an exemplary embodiment of the present invention.

Claims (11)

A semiconductor substrate having a predetermined pattern including a photocharge generating unit and conductive wirings; A color filter array formed on top of the pattern to filter light incident from the outside; A micro lens including condensing light incident from the outside to each color filter of the color filter array, wherein a dead space is removed between the lens parts; Includes, wherein the lens unit has a multi-layered structure of two or more layers, each layer of the lens unit is made of the same material. The image sensor according to claim 1, wherein each layer of the lens portions is made of photoresist for microlenses. The image sensor of claim 1, wherein the pattern formed on the semiconductor substrate includes an oxide film and a nitride film serving as a protective film. The image sensor of claim 3, wherein a planarization layer is provided between the nitride film and the color filter array to improve adhesion. The image sensor of claim 3, wherein an OCM layer is provided between the color filter and the micro lens. A method of manufacturing an image sensor in which a microlens is formed in an upper layer portion of a color filter array provided on a semiconductor substrate, A first material layer forming step of forming a first material layer for forming a micro lens; A second material layer forming step of forming a second material layer for forming a micro lens on a surface of the first material layer; A lens part primary forming step of patterning the second material layer to primarily form lens parts having a dead space between the lens parts; A lens unit completing step of selectively removing the lens unit formed with the first material layer and completing the lens units from which dead spaces are removed; Method of manufacturing an image sensor comprising a. The method of claim 6, wherein the forming of the first material layer is performed by applying a photoresist for forming a microlens, followed by bleaching and heat treatment. The method of claim 7, wherein the forming of the second material layer is performed by applying the same photoresist as the first material layer. The method of claim 8, wherein the second material layer is formed thicker than the first material layer. The method of claim 9, wherein the primary forming of the lens unit is performed by bleaching and heat treating the second material layer, followed by curing. The method of claim 10, wherein the patterning of the second material layer is performed by an exposure and development process.