KR20050103772A - Image sensor with double lense and the fabricating method thereof - Google Patents

Abstract

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an image sensor and a method of manufacturing the same, and more particularly, to an image sensor including a small microlens on an existing microlens and a method of manufacturing the same. In the present invention, by forming one more microlens with a relatively small size on the original microlens, it is possible to reduce the loss of received light. To this end, the present invention provides an image sensor having a microlens, comprising: a semiconductor substrate having a light receiving element; A passivation film formed on the semiconductor substrate; A color filter formed on the passivation film; A first micro lens formed on the color filter and having a dome shape; And a second microlens formed on the first microlens and having a dome shape.

Description

Image sensor with double lens and manufacturing method thereof {IMAGE SENSOR WITH DOUBLE LENSE AND THE FABRICATING METHOD THEREOF}

The present invention relates to an image sensor and a method of manufacturing the same, and more particularly, to an image sensor having a double microlens and a method of manufacturing the same. In the present invention, by stacking another microlens with a relatively small size on an existing microlens, the light condensing efficiency of incident light can be improved.

In general, an image sensor is a semiconductor device that converts an optical image into an electrical signal, and may be roughly divided into a CMOS image sensor and a charge coupled device.

Among them, a charge coupled device (CCD) is a device in which charge carriers are stored and transported in a capacitor while individual metal-oxide-silicon (MOS) capacitors are located very close to each other. It is a device that adopts the switching method that detects the output by using MOS transistor as many as pixel by using CMOS technology that uses control circuit and signal processing circuit as peripheral circuit. .

In addition, the image sensor is composed of a light sensing portion for detecting light and a logic circuit portion for processing the detected light as an electrical signal to make data. The ratio of the area of the light sensing portion in the entire image sensor element is increased to increase the light sensitivity. Efforts have been made to increase the fill factor, but these efforts are limited in a limited area because the logic circuit part cannot be removed.

Therefore, a condensing technology has emerged to change the path of light incident to an area other than the light sensing portion to raise the light sensitivity, and to collect the light sensing portion. For this purpose, the image sensor uses a microlens on the Cali filter. The method of forming is used.

1A to 1D are cross-sectional views illustrating a manufacturing process of a CMOS image sensor according to the prior art.

First, a field oxide film (not shown) defining an active region and a field region is formed on the semiconductor substrate 11. Here, the p-type substrate is mainly used as the semiconductor substrate. Next, the photodiode 12 is formed in a predetermined region on the active region.

Although not shown in detail in FIG. 1A, the photodiode 12 is typically composed of an n-type ion implantation region and a p-type ion implantation region, and it is common to form a p / n / p photodiode with a p-type substrate. . However, for convenience of description, only the photodiode is shown in FIG. 1A.

Next, although not shown in FIG. 1A, a gate patterning process of the transistor is performed. After the device isolation film and related devices including the photodiode 12 and the transistor are formed, various insulating films such as pre metal dielectric (PMD) and interlayer insulating film (IMD) are formed on the semiconductor substrate 11. In addition, a plurality of metal wirings are formed. However, in FIG. 1A, all of them are shown as one insulating film 14 for convenience of description.

In addition, the first metal wiring 13 and the final metal wiring 15 are shown in FIG. 1A, and a passivation film 16 is formed on the top of the final metal wiring 15 to protect the device from moisture and scratches. do.

Next, a color filter 17 is formed on the passivation film 16. The color filter is formed by applying a color filter forming material and patterning it using an appropriate mask. Dyeing photoresist is mainly used as a solvent.

Although not shown in FIG. 1A, a planarization film may be interposed between the passivation film 16 and the color filter 17, or the color filter 17 is formed directly on the passivation film 16 as shown in FIG. 1A. May be

As the color filter 17 described above, a dyed photoresist is typically used, and one color filter 17 is formed for each unit pixel to separate colors from incident light.

The color filter is typically composed of three colors of red, green, and blue, and adjacent color filters are formed to overlap each other slightly.

Since the adjacent color filters are formed to overlap each other slightly in this way, a step is generated due to this, and an overcoat layer (OCL) 18 is formed on the color filter 17 to compensate for this.

Microlenses for collecting light must be formed on the flattened surface, which eliminates the step caused by the color filter. Therefore, as described above, the overcoating layer 18 formed on the color filter 17 serves to eliminate the step, and the overcoating layer is also made of a photoresist-based film.

Next, as shown in FIGS. 1B-1C, a microlens 19 is formed on the overcoating layer 18 having the planarized surface. A method of forming the microlens 19 will be described below.

First, a photosensitive photoresist of a silicon oxide film series having high light transmittance is applied by using a spin-on-coater. Next, a patterning process using an appropriate mask is performed to form an angular microlens corresponding to each unit pixel.

Next, when a microlens having an angular shape is flowed by applying a thermal process, a dome-shaped microlens as shown in FIG. 1C may be obtained.

FIG. 1D illustrates an optical path of incident light in a CMOS image sensor completed according to the prior art, and incident light passes through the microlens 19 and enters the photodiode 12 through the color filter 17. It can be seen.

However, in the image sensor according to the related art, since the light incident through the microlenses does not enter all of the photodiodes and the amount of loss in the middle is not small, there is a disadvantage in that the light sensitivity characteristic is reduced.

That is, in the image sensor according to the prior art, the incident light is refracted by one microlens to focus the photodiode. However, the incident light is refracted and reflected by the metallization, the interlayer insulating film, etc. until the incident light reaches the photodiode. There was not much light reaching.

This was a problem that caused the degradation of color reproducibility and degradation of saturation characteristics.

The present invention has been made to solve the above-described problems, and an object of the present invention is to provide an image sensor and a method of manufacturing the same, which further include one microlens on the existing microlens to improve light condensation.

The present invention for achieving the above object, the image sensor provided with a microlens, the semiconductor substrate having a light receiving element; A passivation film formed on the semiconductor substrate; A color filter formed on the passivation film; A first micro lens formed on the color filter and having a dome shape; And a second microlens formed on the first microlens and having a dome shape.

In addition, the present invention provides a method of manufacturing an image sensor having a microlens, comprising: forming a light receiving element on a semiconductor substrate; Forming a passivation film on the semiconductor substrate; Forming a color filter on the passivation film; Patterning a pattern for a first microlens on the color filter; Patterning a second microlens pattern having a smaller size than the first microlens pattern on the first microlens pattern; And converting the first microlens pattern and the second microlens pattern into dome-shaped first microlenses and second microlenses, respectively.

In the present invention, by stacking a relatively small microlens on the existing microlens to improve the light condensation. That is, the present invention further comprises a first microlens made by the same process as in the prior art and a second microlens formed on the first microlens and having a relatively small size, thereby collecting incident light through the two microlenses. As a result, the amount of light collected by the photodiode can be increased, thereby improving color reproducibility and saturation characteristics.

Hereinafter, the most preferred embodiments of the present invention will be described with reference to the accompanying drawings so that those skilled in the art can easily implement the technical idea of the present invention.

2A through 2D are cross-sectional views illustrating a manufacturing process of a CMOS image sensor formed according to an exemplary embodiment of the present invention.

First, the process up to forming the planarization film 28 in FIG. 2A is the same as in the prior art. Referring to this point, first, a field oxide film (not shown) defining an active region and a field region is formed on the semiconductor substrate 21.

Here, the p-type substrate is mainly used as the semiconductor substrate. Next, the photodiode 22 is formed in a predetermined region on the active region.

Although not shown in detail in FIG. 2A, the photodiode 22 is typically composed of an n-type ion implantation region and a p-type ion implantation region, and it is common to form a p / n / p photodiode with a p-type substrate. . However, for convenience of description, only the photodiode is shown in FIG. 2A.

Next, although not shown in FIG. 2A, the gate patterning process of the transistor is performed. After the device isolation layer and related elements including the photodiode 22 and the transistor are formed, various insulating layers such as pre metal dielectric (PMD) and interlayer dielectric (IMD) are formed on the semiconductor substrate 211. In addition, a plurality of metal wirings are formed.

However, in FIG. 2A, all of them are illustrated as one insulating film 24 for convenience of description. In addition, the first metal wiring 23 and the final metal wiring 25 are shown in FIG. 2A, and a passivation film 26 is formed on the top of the final metal wiring 25 to protect the device from moisture or scratches. do.

Next, a color filter 27 is formed on the passivation film 26. The color filter is formed by applying a color filter forming material and patterning it using an appropriate mask. Dyeing photoresist is mainly used as a solvent.

Although not shown in FIG. 2A, a planarization film may be interposed between the passivation film 26 and the color filter 27, or the color filter 27 may be formed directly on the passivation film 26 as shown in FIG. 2A. It may be.

As the color filter 27 described above, a dyed photoresist is generally used, and one color filter 27 is formed for each unit pixel to separate colors from incident light. The color filter is typically composed of three colors of red, green, and blue, and adjacent color filters are formed to overlap each other slightly.

Since the adjacent color filters are formed to overlap each other slightly in this way, a step is generated due to this, and an over coating layer (OCL) 28 is formed on the color filter 27 to compensate for this.

Microlenses for collecting light must be formed on the flattened surface, which eliminates the step caused by the color filter. Therefore, as described above, the overcoating layer 18 formed on the color filter 17 serves to eliminate the step, and the overcoating layer is also made of a photoresist-based film.

Next, a microlens forming material is formed on the overcoating layer 28 having the planarized surface, and patterned using an appropriate mask to form the first microlens pattern 29.

In the following description of an embodiment of the present invention, a final dome shape through a flow process will be referred to as a 'microlens', and the patterned state in a rectangular shape before the flow process is referred to as 'micro'. The pattern for lenses will be referred to as'.

Next, as shown in FIG. 2B, a second microlens pattern 30 having a smaller size than the first microlens 29 is formed on the first microlens pattern 29.

As the material for forming the microlenses, a photosensitive photoresist based on a silicon oxide film having high light transmittance is mainly used, and is patterned using an appropriate mask after coating using a spin-on-coater. The process is performed to form the angle-shaped microlens patterns 29 and 30 corresponding to each unit pixel.

Next, when the bleaching process using light as shown in Figure 2c proceeds (bleaching), the connection in the photosensitive film for the microlens is broken, and after applying a high temperature hard bake process (hard bake) The photosensitive film for microlens with a broken link is formed of a microlens having a dome shape by the cohesive force at high temperature.

That is, as shown in FIG. 2C, a domed first microlens 31 is formed on the planarization film 28, and a relatively small second microlens (just above the first microlens 31) is formed. It can be seen that 32) is formed.

In this way, after the first microlens 31 and the second microlens 32 are completed, a microlens protective insulating film (not shown) for protecting the first and second microlenses may be applied.

FIG. 2D is a view illustrating a path of incident light to an image sensor according to an embodiment of the present invention. Referring to this, since light primarily refracted through a second microlens is refracted through the first microlens again, FIG. Finally, it can be seen that the amount of light incident to the photodiode is increasing than in the prior art.

In the image sensor according to the exemplary embodiment of the present invention, since the light primarily collected through the second microlens is focused once again through the first microlens, the light collecting efficiency may be increased without losing light as in the prior art.

The present invention having the features as described above is applicable to other image sensors (eg, charge coupling elements) using microlenses in addition to the CMOS image sensor.

As described above, the present invention is not limited to the above-described embodiments and the accompanying drawings, and the present invention may be variously substituted, modified, and changed without departing from the spirit of the present invention. It will be apparent to those of ordinary skill in Esau.

When the present invention is applied to an image sensor, the degree of integration of incident light can be further increased, and color reproducibility and saturation characteristics are improved.

1A to 1D are process cross-sectional views showing a conventional image sensor manufacturing process;

Figures 2a to 2d is a cross-sectional view showing a manufacturing process of the image sensor according to an embodiment of the present invention.

* Description of the symbols for the main parts of the drawings *

21 substrate 22 photodiode

23: first metal wiring 24: interlayer insulating film

25: final metal wiring 26: passivation film

27 color filter 28 planarization film

29: pattern for the first microlens 30: pattern for the second microlens

31: first microlens 32: second microlens

Claims (8)

In an image sensor having a micro lens, A semiconductor substrate on which a light receiving element is formed; A passivation film formed on the semiconductor substrate; A color filter formed on the passivation film; A first micro lens formed on the color filter and having a dome shape; And A second microlens formed on the first microlens and having a dome shape Image sensor made, including. The method of claim 1, An image sensor further comprising a planarization layer interposed between the color filter and the first microlens; The method of claim 1, An image sensor formed on the first microlens and the second microlens, further comprising a microlens protection insulating film for protecting the first and second microlenses. The method of claim 2, An image sensor formed on the first microlens and the second microlens, further comprising a microlens protective insulating film for protecting the first and second microlenses. In the manufacturing method of an image sensor having a micro lens, Forming a light receiving element on the semiconductor substrate; Forming a passivation film on the semiconductor substrate; Forming a color filter on the passivation film; Patterning a pattern for a first microlens on the color filter; Patterning a second microlens pattern having a smaller size than the first microlens pattern on the first microlens pattern; And Converting the first microlens pattern and the second microlens pattern into domed first microlenses and second microlenses, respectively Method of manufacturing an image sensor comprising a. The method of claim 5, The converting into the dome-shaped first microlens and the second microlens, Performing a bleaching process on the first microlens pattern and the second microlens pattern; Performing a hard bake process on the first microlens pattern and the second microlens pattern Manufacturing method of an image sensor, characterized in that it further comprises. The method of claim 5, And forming a microlens protective insulating film for protecting the first and second microlenses on the first microlens and the second microlens. The method of claim 6, And forming a microlens protective insulating film for protecting the first and second microlenses on the first microlens and the second microlens.