Method for manufacturing image sensor

A method for manufacturing an image sensor according to an embodiment includes performing a plasma surface treatment on an oxide film microlens to mitigate high surface morphology. The image sensor can include a passivation layer on a substrate having a pad region and a pixel region and a color filter layer on the passivation layer. A first low temperature oxide can be formed over the substrate including the color filter layer; and an oxide film microlens can be formed on the first low temperature oxide layer. A portion of the first low temperature oxide layer can provide a seed microlens upon which a second low temperature oxide layer is formed to form the oxide film microlenses. The plasma surface treatment can then be applied with respect to the oxide film microlenses.

CROSS-REFERENCE TO RELATED APPLICATION

The present application claims the benefit under 35 U.S.C. §119 of Korean Patent Application No. 10-2007-0088256, filed Aug. 31, 2007, which is hereby incorporated by reference in its entirety.

BACKGROUND

In general, a microlens of an image sensor device is used to induce light incident from the outside into a photodiode. To this end, a typical microlens is generally manufactured through a photo process using organic-based materials.

However, the related art microlens introduces several sensitivities including contamination of the microlens due to particles generated in a wafer sawing process, and an attack of a pad layer when forming the microlens. These sensitivities degrade manufacturing yield.

Also, in many applications, a zero gap between microlenses is desired to reduce photon loss transferred to a pixel. However, the related art using the existing organic microlens has difficulties realizing a zero gap.

Further, the related art often uses a polymer-based planarization layer to remove a step difference generated upon forming a color filter. However, a vertical scale is increased by the addition of a planarization layer. The increased vertical scale can degrade image characteristics.

Thus, there exists a need in the art for an improved image sensor and method of manufacturing the same.

BRIEF SUMMARY

Embodiments of the present invention provide a method for manufacturing an image sensor adopting a microlens using an oxide film.

Embodiments of the present invention also provide a method for manufacturing an image sensor that does not need to include a polymer-based planarization layer.

Additionally, embodiments of the present invention can provide a method for manufacturing an image sensor capable of minimizing the gap between microlenses.

Further, an embodiment of the present invention provides a method for manufacturing an image sensor capable of mitigating the surface morphology of a microlens.

A method for manufacturing an image sensor according to an embodiment can include: forming a passivation layer on a substrate including a pad region and a pixel region; forming a color filter layer on the passivation in the pixel region; forming a first low temperature oxide over the substrate including the color filter layer; forming an oxide film microlens on the first low temperature oxide; and performing a plasma surface treatment on the oxide film microlens.

DETAILED DESCRIPTION

Hereinafter, a method for manufacturing an image sensor according to an embodiment will be described with reference to the accompanying drawings.

In the description of embodiments, it will be understood that when a layer (or film) is referred to as being ‘on’ another layer or substrate, it can be directly on another layer or substrate, or intervening layers may also be present. Further, it will be understood that when a layer is referred to as being ‘under’ another layer, it can be directly under another layer, or one or more intervening layers may also be present. In addition, it will also be understood that when a layer is referred to as being ‘between’ two layers, it can be the only layer between the two layers, or one or more intervening layers may also be present.

Referring toFIG. 1, a passivation layer130can be formed on a substrate110including a pad region120and a pixel region. In addition, although not illustrated in the figures, persons of ordinary skill in the art will appreciate that the substrate110can include structures such as metal interconnections, interlayer dielectric layers, transistors, diffusion regions, and so forth.

The passivation layer130can be formed of any suitable material known in the art.

In one embodiment, the passivation layer130can include an oxide film132and a nitride film134.

For example, the oxide film132can be formed of tetraethylorthosilicate (TEOS) and can have a thickness of about 1,000 Å to about 5,000 Å. In addition, the nitride film134can have a thickness of about 1,000 Å to about 10,000 Å.

Then, a color filter layer140can be formed on the passivation layer130. The color filter layer140can be formed by any suitable process known in the art. For example, a dyeable resist can be coated on the passivation layer130, and then subjected to exposure and development processes to form the color filter layer140. The color filter layer140can be red, green, and blue color filter layers filtering light according to wavelength band.

According to embodiments, a coating of a polymer-based planarization material for mitigating a step difference of a color filter layer140can be omitted. Instead, a first low temperature oxide (LTO)150can be directly formed on the color filter layer140.

In one embodiment, the first low temperature oxide150can be deposited at a temperature of between about 150° C. and about 300° C. For example, the first low temperature oxide150can be formed at a temperature of about 180° C. Of course, embodiments are not limited thereto.

The first low temperature oxide150can include any suitable material known in the art and can be formed by any suitable process known in the art. For example, the first low temperature oxide can be formed of silicon dioxide (SiO2). Additionally, the first low temperature oxide150can be formed by, for example, chemical vapor deposition (CVD), physical vapor deposition (PVD), or plasma enhanced chemical vapor deposition (PECVD).

In certain embodiments, there may be an irregularity (not shown) in the first low temperature oxide150. That is, a step difference may exist at a surface of the first low temperature oxide150due to the color filter layer140.

Accordingly, the first low temperature oxide150can be planarized.

According to an embodiment, one method for planarizing the first low temperature oxide150can include a chemical dry etching.

For example, a method for planarizing the first low temperature oxide150can be a chemical dry etching using CxFygas (where x and y are integers). In one embodiment, the chemical dry etching can be preformed using CF4gas. In a further embodiment, the chemical dry etching can include forming plasma at several mTorr using a microwave.

In another embodiment, a method for planarizing the first low temperature oxide150can include a plasma etching.

For example, the plasma etching can be an isotropic etch applying only a capacitively coupled plasma (ccp) type source power. For example, the plasma etching can utilize an enhanced isotropic characteristic by applying the source power of several tens to several hundreds of Watts. The plasma etching can also use CxFybased gas (where x and y are integers) while using pressure of several hundreds of mTorr.

Referring toFIG. 2, an organic microlens pattern260can be formed on the first low temperature oxide150.

The organic microlens pattern260can be formed using any suitable method known in the art. For example, an organic photosensitive film pattern (not shown) can be formed on the first low temperature oxide150. Then, the organic photosensitive pattern can be subjected to a reflowing process by a heat treatment at a temperature of 150° C. or more using, for example, a hot plate to form a semi-spherical shaped microlens pattern260.

Then, referring toFIG. 3, the first low temperature oxide150can be selectively etched using the organic microlens pattern260as an etch mask to form a seed microlens160ain the pixel region.

During the forming of the seed microlens160ain the pixel region by selectively etching the first low temperature oxide150, the selective etch of the first low temperature oxide150can be progressed in an atmosphere of about 40 sccm to about 120 sccm of CF4and about 2 sccm to about 20 sccm of O2.

In an embodiment, the seed microlens160acan be formed by etching the first low temperature oxide150by about 1,000 Å to about 19,000 Å by using an etching gas of CxHyFz(where x, y, and z are non-negative integers, i.e., 0, 1, 2, etc.) and atoms or molecules of O2or an inert gas such as Ar, He, and/or N2.

In certain embodiments, the etching selectivity (ratio) of the organic microlens pattern260and the first low temperature oxide film layer150can be between about 1:0.7 to about 1:1.3. For example, the etching selectivity of the first low temperature oxide layer150to the organic microlens pattern260can have a margin of about +/−30%.

In one embodiment, the seed microlens160acan have a height to between about 2,000 Å and about 6,000 Å.

Referring toFIG. 4, a second low temperature oxide160bcan be formed on the seed microlens160ain the pixel region to form the low temperature oxide film microlens160.

In an embodiment, the second low temperature oxide160bcan be formed to a thickness of about 500 Å to about 20,000 Å. According to embodiments, the second low temperature oxide160bcan be deposited to form a gapless microlens. The second low temperature oxide160bcan be used to reduce any gaps remaining between seed microlenses160a.

Next, referring toFIG. 5, the oxide film microlens160can be subjected to a plasma surface treatment (P).

Because the oxide film microlens160can be formed at a low temperature of 300° C. or less, the oxide film microlens160may have a high surface morphology. If the surface morphology of the microlens is high, photodiodes in adjacent pixels can be affected by a scattering of light by the high surface morphology of the microlens, and the transfer efficiency of the photodiodes can be degraded.

Therefore, by subjecting the oxide film microlens160to the surface treatment (P) as described in embodiments of the present invention, the surface morphology can be mitigated to reduce the scattering of light, making it possible to improve condensing efficiency of the microlens.

In one embodiment, the plasma surface treatment P can be performed by injecting an inert gas, such as Ar, He, and/or Xe, into a chamber for applying the plasma surface treatment, ionizing the injected gases to provide the plasma, and etching the surface of the oxide microlens160by about 5 Å to about 5,000 Å, making it possible to mitigate the surface morphology of the oxide film microlens160. The etching can be accomplished using the ionized gases.

In another embodiment, the plasma treatment P can be performed by injecting halogen gas, such as Cl, F, and/or Br, into a chamber for applying the plasma surface treatment, ionizing the injected gases to provide the plasma, and etching the surface of the oxide microlens160by about 5 Å to about 5,000 Å, making it possible to mitigate the surface morphology of the oxide film microlens160. The etching can be accomplished using the ionized gases.

In yet another embodiment, the plasma treatment P can be performed by injecting and ionizing inert gases and halogen gases to provide the plasma for the plasma surface treatment, and etching the surface of the oxide microlens160by about 5 Å to about 5,000 Å, making it possible to mitigate the surface morphology of the oxide film microlens160. The etching can be accomplished using the ionized gases.

Next, referring toFIG. 6, a pad mask pattern270can be formed to open the pad region120.

For example, a pad mask pattern270exposing the first low temperature oxide150above the pad can be formed.

Next, referring toFIG. 7, the exposed first low temperature oxide150can be selectively etched using the pad mask pattern270as an etch mask, making it possible to open the pad region120. For example, the etching condition for opening the pad region120can depend on the etching conditions of the seed microlens160a. That is, an etching gas of CxHyFz(where x, y, and z are non-negative integers, i.e., 0, 1, 2, etc.) and atoms or molecules of O2or an inert gas such as Ar, He, and/or N2can be used in certain embodiments.

The method for manufacturing the image sensor according to an embodiment can omit a polymer-based planarization layer.

Also, according to an embodiment, a gapless microlens can be formed by using the oxide film, making it possible to reduce photon loss.

In addition, a hard microlens can be provided by using oxide film, making it possible to inhibit defect occurrence caused by a package process or a bump process.

Further, a continuous type microlens can be formed, making it possible to provide the same focal length in all directions.

According to embodiments of the present invention, the surface morphology of the microlens can be mitigated by performing a plasma treatment on the oxide microlens to reduce the scattering of light, making it possible to improve the condensing efficiency of the oxide microlens.