KR20030001059A - Method for fabricating Microlense - Google Patents

Abstract

PURPOSE: A method for forming a micro-lens improving a fill factor is provided to improve an optical condensing rate of the micro-lens of an image sensor by increasing the fill factor. CONSTITUTION: A plurality of neighboring color filters(21) are formed continuously. A planarization layer(22) is formed on the continuous color filters(21). A photoresist is formed on an upper portion of the planarization layer(22). The first dome-shaped micro-lenses(23a,23b) are formed on the planarization layer(22) by patterning the photoresist. The first micro-lenses(23a,23b) are formed on the color filter region corresponding to the first micro-lenses(23a,23b) formed on the planarization layer(22). A nitride layer(24) is deposited thereon. The second planarization layer(25) is formed on the nitride layer(24). The second micro-lenses(26a,26b) are formed on the second planarization layer(25). The second micro-lenses(26a,26b) are formed on color filter region corresponding to the second micro-lenses(26a,26b) formed on the second planarization layer(25). An oxide layer(27) of low temperature is formed thereon.

Description

Method for fabricating microlense with improved fill factor

The present invention relates to a method of manufacturing a microlens of an image sensor, and more particularly, to a method of manufacturing a microlens with an improved fill factor.

In general, an image sensor is a semiconductor device that converts an optical image into an electrical signal. A charge coupled device (CCD) is a charge carrier device in which individual metal-oxide-silicon (MOS) capacitors are in close proximity to each other. Is a device that stores and transfers a CMOS image sensor. The CMOS image sensor uses a CMOS technology that uses a control circuit and a signal processing circuit as peripheral circuits to make MOS transistors as many as the number of pixels, and employs a switching scheme that sequentially detects output using the same. to be

In manufacturing such various image sensors, efforts are being made to increase the photo sensitivity of the image sensor, and one of them is a light condensing technology. For example, the CMOS image sensor is composed of a light sensing portion for detecting light and a CMOS logic circuit portion for processing the detected light into an electrical signal to make data. In order to increase the light sensitivity, the area of the light sensing portion in the overall image sensor area is increased. Efforts have been made to increase the percentage of occupancy (commonly referred to as "Fill Factor"), but there is a limit to such efforts under a limited area since the logic circuit part cannot be removed. Therefore, a lot of researches have focused on condensing technology to change the path of light incident to the area other than the light sensing area to raise the light sensitivity.

A microlens is also one of such condensing techniques. A conventional method for manufacturing a conventional image sensor using the same will be described with reference to FIG. 1 as follows.

After forming a field oxide film 2 on the substrate 1 for electrical insulation between devices, a gate electrode is formed by successively applying and patterning a polysilicon and tungsten silicide film. (The gate electrode is not shown in Fig. 1). not.)

Afterwards, an appropriate ion implantation process is performed to form the photodiode 3, to perform ion implantation to form a source / drain and a sensing node of the transistor, and to form an interlayer insulating film 4, a metal connection window (not shown), and a metal wiring. Forming (5) and forming the passivation protective film 6 completes the general CMOS logic process.

Thereafter, three types of color filters 7 are formed to implement color images, and a planarization process using an over coating layer (OCL) layer 8 is performed to form a color filter array. The material of the color filter usually uses dyed photoresist.

The OCL 8 is a kind of photoresist and is used for the purpose of flattening to facilitate subsequent microlens mask patterning.

Then, in order to increase the light focusing rate, the organic photoresist patterning is performed, followed by a thermal process to form a microlens 9, and finally, the pad is opened.

When the organic photoresist is patterned to form the microlens 9, a certain interval must be maintained. Otherwise, a bridge phenomenon in which neighboring microlenses stick to each other may occur when the organic photoresist flows.

In this case, the microlenses made of only organic photoresist did not utilize 100% of the light sensing region because the microlenses composed of organic photoresist had to be spaced between adjacent microlenses in order to prevent them from sticking together.

In addition, since the size of the microlenses is also limited, as a result, the light focusing rate is lowered, and thus there is a limit in improving the light sensitivity of the image sensor.

An object of the present invention is to provide a method for manufacturing a microlens of an image sensor suitable for improving the light focusing ratio by utilizing a light sensing area 100% to solve the above problems.

1 is a view of an image sensor including a conventional microlens.

Figure 2a shows a prior art.

2b to 2c are views showing the technical idea of the present invention.

3 to 4 show one embodiment of the present invention.

5 to 9 show another embodiment of the present invention.

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

1: substrate 2: field oxide film

3: photodiode 4: interlayer dielectric film

5: metal wiring 6: passivation protective film

7: color filter 8: flattening film

9: microlens 21: color filter

22: planarization film 23a, 23b: first micro lens

24: nitride film 25: second planarization film

26a, 26b: myzm low lens 27: low temperature oxide film

31: oxide film 32: dry etching photoresist

33: oxide film 34: microlens patterned photoresist

In order to solve the above-mentioned problems, the present invention includes a first step of forming a first microlens corresponding to a first color filter on a substrate on which a predetermined process is completed; Forming a planarization film on the resultant of the first step; And a third step of forming a second microlens corresponding to the second color filter closest to the first color filter on the resultant of the second step.

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 to 2C are diagrams comparing the technical gist of the present invention with the prior art.

As shown in FIG. 2A, since the conventional microlenses are formed on the same layer, a distance d between the microlenses is required to prevent the bridge phenomenon.

In an embodiment of the present invention, as shown in FIG. 2B, neighboring microlenses are formed by dividing the layers so that they do not stick to each other during the flow process, and the light sensitivity of the image sensor may be increased by eliminating gaps between the microlenses.

In another embodiment according to the present invention, as shown in FIG. 2C, the base film of the microlens is formed with a step and the microlens is formed on the upper portion thereof, thereby eliminating gaps between neighboring microlenses.

3 and 4, an embodiment according to the present invention will be described.

The steps up to forming neighboring color filters are the same as in the conventional image sensor manufacturing method. After forming the color filters 21 adjacent to each other, the planarization film 22 is formed. The planarization film 22 is a planarization layer formed for the purpose of facilitating a mask pattern of a subsequently formed first microlens.

The photoresist is patterned and formed on the planarization layer 22 and then flown to form first dome-shaped first microlenses 23a and 23b. The first microlens is formed on the planarization layer, and the first microlens 23a and 23b is formed in the color filter area corresponding to the first microlens 23a and 23b.

Thereafter, a nitride film 24 having a high refractive index is deposited on the entire surface of the resultant product.

Next, as shown in FIG. 4, a second planarization film 25 including an organic photoresist film is formed on the nitride film 24. Similar to the planarization film 22, the second planarization film 25 is a planarization layer formed for the purpose of facilitating the mask pattern of subsequent microlenses.

Finally, second microlenses 26a and 26b are formed on the second planarization layer 25, and the second microlenses 26a and 26b are formed in corresponding color filter regions.

Forming a low-temperature oxide film 27, which is a kind of protective film on the resultant, ends the microlens manufacturing process of the embodiment according to the present invention.

In the above-described embodiment of the present invention, the distance between the second microlenses 26a and 26b and the photodiode is greater than the distance between the first microlenses 23a and 23b and the photodiode and thus the second microlenses 26a and 26b. In order to concentrate the light passing through the photodiode on the photodiode, a nitride film 24 having a high refractive index was deposited on the first microlenses 23a and 23b.

The thickness of the nitride film 24 and the thickness of the first micro lenses 23a and 23b are set in consideration of the distance from the photodiode. The nitride film 24 described above may not be formed in accordance with the specification or type of the device.

When the microlenses are formed in two layers in this manner, it can be seen that it is not necessary to maintain a predetermined distance between adjacent microlenses as shown in FIG. 4.

Another embodiment according to the present invention will be described with reference to Figs.

The steps up to forming neighboring color filters are the same as in the conventional image sensor manufacturing method, and as shown in FIG. 5, the neighboring color filters 21 are formed, and then the planarization film 22 is formed. An oxide film 31 is deposited on the planarization film 22 at a deposition temperature of 100 to 200 ° C. At this time, the thickness of the oxide film 31 is set in consideration of the width and thickness of the microlens and the step x of FIG.

In order to form a step in the oxide film 31, a photosensitive film pattern 32 is formed and the oxide film is partially etched. The degree of dry etching is such that a thin oxide film remains so that the flat layer 22, which is the underlying film, is not damaged when the photoresist 32 is removed.

The step x sets the step so that the width and thickness of the microlens are taken into consideration and the neighboring microlenses do not stick together during the microlens flow.

As shown in FIG. 6, when an oxide film 31 having a concave groove is formed on the planarization film 22, an organic photoresist 33 for forming a microlens is applied on the oxide film 32. As shown in FIG.

In consideration of the degree to which the microlenses flow, a photosensitive film pattern 34 for patterning an organic photoresist is formed. Subsequently, as shown in FIGS. 7 and 8, the organic photoresist 33 is etched and flowed, and then the photoresist pattern 34 is removed.

In this way, the microlenses are formed at positions corresponding to the respective color filters on the oxide film having the concave grooves, and the microlenses formed through the process shown in FIG. Since the distance between the microlens and the photodiode varies according to the step (x), the thickness of the microlens was formed in consideration of this point.

Finally, as shown in FIG. 9, an oxide film 34, which is a protective film, is deposited on the microlens at a deposition temperature of 100 to 200 ° C. to a thickness of 500 to 1000 μm to facilitate particle removal in a subsequent process.

When the microlenses are formed with a step in this manner, it can be seen that it is not necessary to maintain a predetermined interval between adjacent microlenses as shown in FIG. 8.

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 the art.

When the present invention is applied to a method of manufacturing a microlens of an image sensor, since neighboring microlenses have different layers, a bridge phenomenon can be prevented during a flow process, so that light sensitivity is improved and a gap between adjacent microlenses is eliminated. There is an effect that 100% of the light sensing area can be used.

Claims (7)

In the manufacturing method of a microlens of an image sensor having a plurality of color filters A first step of forming a first microlens corresponding to the first color filter on the substrate on which the predetermined process is completed; Forming a planarization film on the resultant of the first step; A third step of forming a second microlens corresponding to the second color filter closest to the first color filter on the resultant of the second step; Microlens formation method comprising a. The method of claim 1, And the first step further comprises forming a nitride film on the front surface of the substrate on which the first microlens is formed. The method according to claim 1 or 2, And the planarization film is an organic photoresist. In the microlens manufacturing method of an image sensor having a plurality of color filters Forming an oxide film on the substrate on which the predetermined process is completed; Etching a portion of the oxide film in a region corresponding to the first color filter; Applying an organic photoresist for microlenses to the entire surface of the resultant; Forming a pattern of the organic photoresist on a region corresponding to the first color filter and a region corresponding to a second color filter closest to the first color filter by a mask and an etching process; And Forming a first and a second microlens by flowing the pattern of the organic photoresist; Microlens formation method comprising a. In the image sensor, A first color filter and a second color filter neighboring each other; A first planarization film formed on the first and second color filters; A first micro lens formed on the planarization film in a region corresponding to the first color filter; A second planarization layer formed on the first microlens and on the second microlens; And A second microlens formed on the second planarization film in a region corresponding to the second color filter Image sensor made, including. The method of claim 5, And a nitride film formed at an interface between the first planarization layer and the second planarization film. In the image sensor, A first color filter and a second color filter neighboring each other; Planarization films formed on the first and second color filters; An oxide film formed on the planarization film and having a concave groove in a region corresponding to the first color filter; And A first microlens and a second microlens respectively formed on the oxide film in a region corresponding to the first color filter and a region corresponding to the second color filter Image sensor comprising a.