KR100760140B1 - Method of fabricating microlense in CMOS image sensor - Google Patents

Abstract

The present invention relates to a method for manufacturing a microlens with reduced light loss in a CMOS image sensor, and the present invention includes forming a color filter on a semiconductor substrate on which a light receiving element is formed; Forming a planarization film on the color filter; Forming a first low temperature oxide film on the planarization film; Forming a photoresist pattern corresponding to the light receiving element on the first low temperature oxide film; Forming microlenses on sidewalls of the photoresist pattern; And removing the photoresist pattern.

CMOS image sensor, microlens, optical loss

Description

Method of fabricating microlenses of CMOS image sensor {Method of fabricating microlense in CMOS image sensor}             

1 is a cross-sectional view showing a state of the conventional CMOS image sensor,

2 to 5 illustrate a manufacturing process of the CMOS image sensor according to the present invention.

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

1: substrate

2 photodiode

3: field oxide film

4: interlayer insulating film

5: color filter

6: planarization film

7: microlens

8: microlens protective oxide film

9: planarization film protection oxide film

10 photosensitive film                 

11: low temperature oxide film

The present invention relates to a method for manufacturing a microlens with reduced light loss in a CMOS image sensor.

In general, an image sensor is a semiconductor device that converts an optical image into an electrical signal. Among them, a charge coupled device (CCD) includes individual metal-oxide-silicon (MOS) capacitors. A device in which charge carriers are stored and transported in a capacitor while being in close proximity, and a CMOS (Complementary MOS) image sensor is a CMOS using a control circuit and a signal processing circuit as peripheral circuits. It is a device that adopts a switching method that makes MOS transistors by the number of pixels using technology and sequentially detects the output using them.

In manufacturing such various image sensors, efforts are being made to increase the photo sensitivity of the image sensor. 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. 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.

1 is a view showing a conventional image sensor including a microlens with reference to this will be described a conventional method of manufacturing a conventional image sensor.

After forming a field oxide film 3 on the substrate 1 for electrical insulation between devices, a gate electrode is formed by successively applying and patterning a polysilicon and a tungsten silicide film. (The gate electrode is not shown in FIG. 1). not.)

Thereafter, an appropriate ion implantation process is performed to form a light receiving region including the photodiode 2 and to perform ion implantation for forming a source / drain and a sensing node of the transistor. (Transistor not shown)

The interlayer insulating film 4 and the metal wiring (not shown) are sequentially formed on the resultant. In the case of using a plurality of metal wirings, an intermetallic insulating film is formed between the metal wirings and a passivation film is formed on the final metal wiring. The metal wirings and the passivation film are not shown in FIG.

After the passivation film is formed on the final metal wiring and the general CMOS logic process is completed, three types of color filters 5 are formed to implement color images. The color filters generally use dyed photoresist. Form.                         

When the color filter 5 is formed, as shown in FIG. 1, the flatness is poor due to the step, so that the microlenses 7 to be formed on the color filter 5 are formed differently in unit pixels. Uniformity is lowered.

In order to improve this point, the planarization film 6 is formed. The planarization layer 6 uses an overcoat layer (OCL), which is a kind of photoresist, and forms a microlens 7 to increase the light focusing ratio after such a planarization process. It forms using a resist.

After applying a photosensitive agent for forming a microlens, a pattern is formed through a mask process, and a dome-shaped microlens 7 is formed by flowing a rectangular microlens 7 through a thermal process.

In the case of the microlens of the image sensor formed by the above method, the light incident to the center portion passes through the microlens with a high refractive index, so that light transmittance is lowered and light loss occurs.

SUMMARY OF THE INVENTION The present invention has been made to solve the above problems, and an object thereof is to provide a method for manufacturing a microlens with reduced light loss in a CMOS image sensor.

The present invention for achieving the above object, forming a color filter on the semiconductor substrate on which the light receiving element is formed; Forming a planarization film on the color filter; Forming a first low temperature oxide film on the planarization film; Forming a photoresist pattern corresponding to the light receiving element on the first low temperature oxide film; Forming microlenses on sidewalls of the photoresist pattern; And removing the photoresist pattern.

In the present invention, when manufacturing the CMOS image sensor, the microlenses manufactured for light integration are manufactured in a spacer form to minimize light loss.

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.

2 to 5 are views illustrating a manufacturing process of the CMOS image sensor according to the present invention.

The process up to forming the planarization film on the color filter is similar to the prior art. That is, after forming the field oxide film 3 on the substrate 1 for electrical insulation between devices, the gate electrode is formed by successively applying and patterning polysilicon and tungsten silicide films. It is not done.)

Thereafter, an appropriate ion implantation process is performed to form a light receiving region including the photodiode 2 and to perform ion implantation for forming a source / drain and a sensing node of the transistor. (Transistor not shown)                     

The interlayer insulating film 4 and the metal wiring (not shown) are sequentially formed on the resultant. In the case where multiple metal wires are used, an intermetallic insulating film is formed between the metal wires and a passivation film is formed on the final metal wire. The metal wires and the passivation film are not shown in FIG.

After the passivation film is formed on the final metal wiring and the general CMOS logic process is completed, three types of color filters 5 are formed to implement color images. The color filters generally use dyed photoresist. Form.

When the color filter 5 is formed, the flatness becomes poor due to the step, and thus the microlens to be formed on the color filter is formed differently in unit pixels, thereby decreasing uniformity.

In order to improve this, a planarization process is performed. The planarization process is performed by using an over coating layer (OCL: 6), which is a kind of photoresist.

After the planarization film 6 is formed as described above, a low temperature oxide film 9 capable of being deposited at a low temperature is applied on the planarization film 6 to a thickness of several hundred microseconds. Preferably it has a thickness of 100-800 kPa.

The low temperature oxide film 9 serves to protect the planarization film so that the planarization film 6 is not damaged in a subsequent etching process, hereinafter referred to as the planarization film protection oxide film 9.

Next, as shown in FIG. 2, a photosensitive film 10 is coated on the planarization protective oxide film 9 and a pattern 10 is formed. The size of the pattern 10 is larger than that of the photodiode 2. Set it slightly smaller. The reason is that when the size of the pattern 10 is formed larger than the photodiode 2 due to the process change, light incident without refraction enters a region other than the photodiode 2 to act as a noise component. Because it becomes.

The photosensitive film 10 formed on the planarization film protective oxide film 9 uses an inexpensive general photoresist film instead of an expensive microlens formation photoresist film.

Next, as shown in FIG. 3, the low temperature oxide film 11 is deposited on a region including the planarization protective film 9 and the photosensitive film 10. The low temperature oxide film 11 is used to form a microlens in the form of a spacer. Will form. Therefore, the thickness of the low temperature oxide film 11 to be deposited is set in consideration of the size of the photoresist pattern 10 and the size of the spacer to be subsequently formed.

Next, the low-temperature oxide film 11 is etched without a mask to obtain the microlens 11 having the spacer shape shown in FIG. 4.

In the process of etching the low-temperature oxide film 11, the etching process is performed so that the photosensitive film pattern 10 is exposed. In this case, when the etching process is excessively excessive, the planarization film protective oxide 9 may be etched. The protective oxide film 9 is subjected to the low temperature oxide film 11 etching process so as not to be etched.

When etching of the low-temperature oxide film 11 is completed, a shape as shown in FIG. 4 may be obtained. A low-temperature oxide film 11 having a spacer shape may be formed on both sides of the photosensitive film pattern 10.

Next, the photoresist pattern 10 is etched without a mask to form a microlens 11 having a spacer shape formed of a low temperature oxide film as shown in FIG. 5. In the process of etching the photoresist pattern 10, the planarization protective film 9 serves to prevent the planarization film 8 from being damaged during the etching process.

As such, when the center portion is removed to form a spacer-type microlens, light loss can be reduced.

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 the manufacture of the image sensor, it is possible to condense as in the prior art, but it is possible to eliminate the optical energy loss of light incident to the center portion of the microlenses, thereby improving the light sensitivity of the entire image sensor.

Claims (4)

delete Forming a color filter on the semiconductor substrate on which the light receiving element is formed; Forming a planarization film on the color filter; Forming a first low temperature oxide film on the planarization film; Forming a photoresist pattern corresponding to the light receiving element on the first low temperature oxide film; Forming microlenses on sidewalls of the photoresist pattern; And Removing the photoresist pattern; Forming the micro lens Forming a second low temperature oxide film on the photoresist pattern; And Etching the entire surface of the second low temperature oxide layer to form a spacer on the sidewall of the photoresist pattern as the second low temperature oxide layer Microlens manufacturing method of the CMOS image sensor comprising a. The method of claim 2, The photosensitive film pattern is a microlens manufacturing method of the CMOS image sensor, characterized in that having a smaller size than the light receiving element. The method of claim 2, Etching the entire surface of the second low temperature oxide layer to form a spacer on the sidewall of the photoresist pattern with the second low temperature oxide layer The first low temperature oxide film is not etched, characterized in that the microlens manufacturing method of the CMOS image sensor.

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