KR100829360B1 - Image sensor and fabricating method thereof - Google Patents

Abstract

An image sensor and a manufacturing method thereof are provided to improve sensitivity of the image sensor by forming a microlens with a zero gap using an inorganic material. A first passivation microlens(13) is formed on an inorganic layer(11). An RIE(Reactive Ion Etching) is performed using a first etching condition on the first passivation microlens, such that a second passivation microlens is formed. A by-product(15) is attached to the second passivation microlens. An etched material is obtained while etching the first passivation microlens. The by-product is obtained after a reaction between the etched material and an etching gas. An RIE is performed using a second etching condition on the second passivation microlens and the by-product layer, such that the microlens is made of the inorganic layer.

Description

Image sensor and fabrication method

1 to 4 schematically show a method of manufacturing an image sensor according to an embodiment of the present invention.

<Explanation of symbols for main parts of the drawings>

11 ... Inorganic Layer

13 ... Sacrifice Micro Lens

15. Etch Byproducts

17 ... micro lens

The present invention relates to an image sensor and a method of manufacturing the same.

In general, an image sensor is a semiconductor device that converts an optical image into an electrical signal. In a dual charge coupled device (CCD), individual metal-oxide-silicon (MOS) capacitors are very different from each other. A device in which charge carriers are stored and transported in a capacitor while in close proximity. Moreover, CMOS image sensors use CMOS technology, which uses control circuits and signal processing circuits as peripheral circuits, to make MOS transistors as many as the number of pixels, It is a device that employs a switching method that detects an output in turn.

One of the most important processes that determine the performance of an image sensor is a color filter array (CFA) and a micro lens (ML) forming process.

The biggest influence on the performance of the image device in the ML formation process is the gap between the lenses formed between adjacent MLs. The smaller the gap is, the more the optical sensitivity of the device is improved by more than 10-15%. Proven in results and simulations.

This means that the smaller the gap between MLs (1), the more flux of light that is collected, the higher the optical efficiency of the light delivered to the lower end of the device's photodiode, etc., and (2) the metal wiring in the pixel area. This is because, in the case of a CMOS device disposed inside, the probability of uncondensed light passing through the metal wiring arranged to avoid the path of light passing from the upper layer to the lower portion is reduced.

Conventional ML forming processes use a lithography method to pattern organic materials in the form of photoresist (PR), which can be thermally reflowed by thermal energy, using a lithography method. After forming, the lens is manufactured by applying heat to reflow to form a spherical curved surface and cooling.

In the case of forming ML in this way, (1) the width of ML gap is determined by the gap of the pattern formed through photolithography before reflow, so the minimum gap line width is limited to ~ 50nm level due to the lithography resolution limit ( 2) The real refractive index n value and the imaginary refractive index k value of the lens material for forming ML are n ~ 1.4-1.7, k ~ 0 for light of visible wavelength. This makes it easy to form the lens shape and to ensure transparency for light of visible wavelength. (3) Generally, when the material satisfies these conditions is low in hardness, the chip may be removed at the final package stage. The disadvantage is that it is easy to be damaged by sawing particles generated by cutting.

In order to overcome these problems, there is a method of using an inorganic material such as an oxide thin film having a high hardness instead of an organic material of a low PR, but it has a disadvantage in that it is difficult to form a proper lens shape while reducing the gap effectively. In the case of using inorganic materials, it is difficult to form a zero-gap ML, and as an auxiliary lens for reinforcing the focusing function of the uppermost ML than the single-layer image sensor forming the ML on the uppermost layer of a conventional device. It is limitedly used as an auxiliary lens of an image sensor designed to have an auxiliary ML inserted into a dielectric layer of a back-end layer.

If there is a way to easily form the inorganic ML in the form of a zero-gap (zero-gap), it is possible to form a zero-gap inorganic material ML that solves the conventional process difficulties, and also utilized in the image sensor of a single lens structure This is possible.

In the case of inorganic ML, the easiest manufacturing method is to form the ML form with organic materials such as PR, and then transfer the ML form to the inorganic thin film using an anisotropic dry etching method. In this case, the organic seed pattern formed initially It is easy to form a seed pattern without a gap, so that the transferred ML can be easily formed as a zero-gap without a gap, so that an initial seed pattern is formed without a gap. It's the key.

The present invention provides an image sensor and a method of manufacturing the same that can improve the sensitivity of the device by forming a micro lens having a zero gap using an inorganic material.

Image sensor according to an embodiment of the present invention, the inorganic layer; A first micro lens formed of a photosensitive film on the inorganic layer; A second micro lens formed on the first micro lens and formed of an etch byproduct by etching the photosensitive film; It includes, the first micro lens and the second micro lens are stacked to form a micro lens.

In the image sensor according to the embodiment of the present invention, the inorganic layer is formed of a material having a real refractive index (n) of 1.4 to 1.7 and an imaginary refractive index (k) of zero at visible wavelengths.

In the image sensor according to the embodiment of the present invention, the inorganic layer is formed of a TEOS material.

The image sensor according to the embodiment of the present invention further includes a lower structure including a photodiode under the inorganic layer, and a color filter layer formed on the lower structure.

An image sensor manufacturing method according to an embodiment of the present invention, forming an inorganic layer; Forming a sacrificial micro lens on the inorganic layer; Performing RIE on the resultant with a first etching condition and allowing a by-product produced by etching the resultant to be attached to the sacrificial microlens; Performing a RIE on a second etching condition with respect to the resultant to form a microlens formed of the inorganic layer; It includes.

According to an image sensor manufacturing method according to an embodiment of the present invention, the inorganic layer is formed of a material having a real refractive index (n) of 1.4 to 1.7 and an imaginary refractive index (k) of zero at visible wavelengths.

According to the image sensor manufacturing method according to an embodiment of the present invention, the inorganic layer is formed of a TEOS material.

According to the image sensor manufacturing method according to an embodiment of the present invention, the sacrificial micro lens is formed of a photosensitive material.

According to the image sensor manufacturing method according to an embodiment of the present invention, the step of forming the sacrificial micro lens on the inorganic layer, forming a photosensitive film on the inorganic layer; Performing an exposure process on the photosensitive film and forming a patterned photosensitive film; Forming a sacrificial micro lens formed in a lens shape through heat treatment of the photosensitive film; It includes.

According to the image sensor manufacturing method according to an embodiment of the present invention, the micro lens is formed of a zero gap micro lens with no gap between neighboring lenses.

According to the image sensor manufacturing method according to an embodiment of the present invention, as the by-products are attached to the sacrificial micro lens, the gap between neighboring lenses forming the sacrificial micro lens is lost and a zero gap sacrificial micro lens is Is formed.

According to the image sensor manufacturing method according to an embodiment of the present invention, before the step of forming the inorganic layer, forming a substructure having a photodiode; Forming a color filter layer on the substructure; It further includes.

According to the image sensor and the manufacturing method according to the embodiment of the present invention, by forming a micro lens having a zero gap using an inorganic material, there is an advantage that can improve the sensitivity of the device.

In the description of embodiments according to the present invention, each layer (film), region, pattern or structure is described as being formed "on" or "under" a substrate, each layer (film), region, pad or pattern. In the case, the meaning may be interpreted as when each layer (film), region, pad, pattern or structures is formed in direct contact with the substrate, each layer (film), region, pad or patterns, and another layer. (Film), another region, another pad, another pattern, or another structure may be interpreted as a case where additional formation is made therebetween. Therefore, the meaning should be determined by the technical spirit of the invention.

Hereinafter, with reference to the accompanying drawings will be described an embodiment of the present invention;

1 to 4 are schematic views illustrating a method of manufacturing an image sensor according to an exemplary embodiment of the present invention.

In the method of manufacturing an image sensor according to an exemplary embodiment of the present invention, as shown in FIG. 1, an inorganic layer 11 is first formed to form a micro lens.

Herein, the inorganic layer 11 may be manufactured by using a material to be formed into a micro lens by a later process.

The inorganic layer 11 may be formed of a material having a real refractive index (n) of about 1.4 to 1.7 and an imaginary refractive index (k) of about 0 at visible wavelengths.

As an example, the inorganic layer 11 may be formed of a thin film of an oxide film such as TEOS.

And according to the image sensor manufacturing method according to an embodiment of the present invention, as shown in Figure 2, to form a sacrificial micro lens 13 on the inorganic layer (11).

The sacrificial micro lens 13 is formed to transfer the micro lens shape to the inorganic layer 11 through etching later.

The sacrificial micro lens 13 may be formed of a photosensitive material.

As one example, the sacrificial micro lens 13 may be formed through the following process.

First, a photosensitive film is formed on the inorganic layer 11.

The photosensitive film may be formed by, for example, a coating method.

Then, an exposure process is performed on the photosensitive film to form a patterned photosensitive film. In this case, the patterned photosensitive film may be formed in a hexahedral shape. Through the heat treatment of the patterned photosensitive film, it is possible to form a sacrificial micro lens 13 having a lens shape. The heat treatment may use a process such as thermal reflow.

Subsequently, according to the method of manufacturing an image sensor according to an exemplary embodiment of the present invention, as shown in FIG. 3, an etch by-product generated while performing RIE on the resultant as a first etching condition and etching the resultant product. 15 is attached to the sacrificial micro lens 13.

In this case, as the etch byproduct 15 is attached to the sacrificial micro lens 13, the distance between neighboring lenses forming the sacrificial micro lens 13 may be reduced.

In addition, as the etch by-product 15 is attached to the sacrificial microlens 13, a zero gap sacrificial microlens 13 in which a gap between neighboring lenses forming the sacrificial microlens 13 is lost. ) Can also be formed.

Here, the RIE process is performed such that a polymer by-product generated by etching the photosensitive material constituting the sacrificial microlens 13 adheres to the pattern of the sacrificial microlens 13. Through this RIE process, it is possible to easily form a zero gap shape according to the conditions.

According to the image sensor manufacturing method according to an embodiment of the present invention, the pattern shape consisting of the etching by-product 15 and the sacrificial micro lens 13 shown in Figure 3 depends on the shape of the resulting product generated by the dry etching later Therefore, this may be referred to as a kind of seed micro lens pattern.

Then, according to the manufacturing method of the image sensor according to an embodiment of the present invention, as shown in Figure 4, by performing the RIE on the second etching conditions with respect to the resultant, the microlens 17 made of the inorganic layer 11 It can be formed.

The microlens 17 may be formed as a zero gap microlens 17 having no gap between neighboring lenses.

Accordingly, according to the image sensor manufacturing method according to an embodiment of the present invention, it is possible to easily form a micro lens having a zero gap (gap). In addition, according to the embodiment of the present invention, it is possible to apply a micro lens having a zero gap, thereby improving the sensitivity of the device.

In addition, according to the image sensor manufacturing method according to an embodiment of the present invention, before forming the inorganic layer 11, forming a substructure having a photodiode, and forming a color filter layer on the substructure It may further comprise the step.

Meanwhile, as shown in FIG. 3, if the microlens pattern including the etching byproduct 15 and the sacrificial microlens 13 satisfies the refractive index condition described above, the microlens pattern may be applied as it is without a subsequent etching process. It may be.

In this case, the image sensor according to the embodiment of the present invention is formed of an inorganic layer, a first micro lens formed as a photosensitive film on the inorganic layer, and an etching by-product formed by etching the photosensitive film. And a second micro lens, wherein the first micro lens and the second micro lens are stacked to form a micro lens.

The microlens may be formed as a zero gap microlens without a gap between neighboring lenses.

On the other hand, in the embodiment of the present invention, the process using the etching by-product by the etching of the photosensitive film may be performed as an example as follows.

Such a process may be performed using a capacitive coupled plasma (CCP) device, and the process conditions are as follows.

First, a process of etching the photosensitive film may be performed, and a process for attaching the etching byproduct to the photosensitive film may be sequentially performed.

As described above, the etching by-products are formed on the surface of the photosensitive film. The plasma is formed by injecting a gas that is reactive with the photosensitive film into the chamber and applying RF power to the plasma in the electrostatically coupled plasma apparatus. It may be achieved by etching by radical. At this time, the reaction by-products generated during etching increase the probability that the reaction by-products are attached to the photoresist film, thereby increasing the probability that they are attached to the photoresist film. In fact, it is possible to increase the critical dimension of the photosensitive film after deposition of reaction by-products.

In an embodiment of the present invention, capacitive coupled plasma (CCP) equipment may be used, and the electrostatic coupled plasma equipment may use a dipole ring magnetron (DRM).

According to the image sensor and the manufacturing method according to the embodiment of the present invention, by forming a micro lens having a zero gap using an inorganic material, there is an advantage that can improve the sensitivity of the device.

Claims (12)

Forming an inorganic layer; Forming a first sacrificial micro lens on the inorganic layer; A material etched from the first sacrificial microlens formed by performing RIE on the first sacrificial microlens under a first etching condition to form a second sacrificial microlens , and etching the first sacrificial microlens. Allowing a by-product of the reaction product with the etching gas to adhere to the second sacrificial micro lens; Performing a RIE on the second sacrificial micro lens and the inorganic layer under a second etching condition to form a micro lens including the inorganic layer; Image sensor manufacturing method comprising a. The method of claim 1, And the inorganic layer is formed of a material having a real refractive index (n) of 1.4 to 1.7 and an imaginary refractive index (k) of zero at visible wavelengths. The method of claim 1, The inorganic layer is an image sensor manufacturing method, characterized in that formed of TEOS material. The method of claim 1, The first sacrificial microlens is formed of a photosensitive material. The method of claim 1, Forming the first sacrificial micro lens on the inorganic layer, Forming a photosensitive film on the inorganic layer; Performing an exposure process on the photosensitive film and forming a patterned photosensitive film; Forming a first sacrificial micro lens formed in a lens shape through heat treatment of the patterned photosensitive film; Image sensor manufacturing method comprising a. The method of claim 1, The micro lens is a method of manufacturing an image sensor, characterized in that formed as a zero gap micro lens with no gap between neighboring lenses. The method of claim 1, The reaction by-products manufacturing an image sensor, characterized in that the second as attached to the sacrificial microlens, said second no gap between adjacent lenses that make up the sacrificial microlens is formed with a zero gap (zero gap) sacrificial microlenses Way. The method of claim 1, Before forming the inorganic layer, Forming a substructure having a photodiode; Forming a color filter layer on the substructure; Image sensor manufacturing method comprising a further. Inorganic layer; A first micro lens formed of a photosensitive film on the inorganic layer; A second micro lens formed on the first micro lens, the second micro lens formed by a reaction by- product of an etching gas and a material etched from the photosensitive film, which is generated in an etching process for forming the first micro lens; Including; And the first micro lens and the second micro lens are stacked to form a micro lens. The method of claim 9, The inorganic layer is formed of a material having a real refractive index (n) of 1.4 to 1.7 and an imaginary refractive index (k) of zero at visible wavelengths. The method of claim 9, The inorganic layer is an image sensor, characterized in that formed of TEOS material. The method of claim 9, And a lower structure including a photodiode and a color filter layer formed on the lower structure under the inorganic layer.

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