KR100967482B1 - Method for fabricating image sensor - Google Patents

Abstract

Embodiments relate to a method of manufacturing an image sensor. In another embodiment, a method of manufacturing an image sensor includes: forming a microlens on a substrate including a photodiode and metal wires, forming a pad mask on the substrate to expose a portion of the metal wires; Removing the mask and silane-treating the entire surface of the substrate on which the microlens is formed. Embodiments can reduce the roughness of the lens surface of the hard mask and increase hydrophobicity to prevent adsorption of particles and to improve sensitivity.

Image Sensor, Micro Lens, Silane

Description

Manufacturing Method of Image Sensor {METHOD FOR FABRICATING IMAGE SENSOR}

Embodiments relate to a method of manufacturing an image sensor.

In general, an image sensor is a semiconductor device that converts an optical image into an electrical signal, and is mainly composed of a charge coupled device (CCD) and a CMOS (Complementary Metal Oxide Silicon) image. It is divided into a sensor (Image Sensor) (CIS).

On the other hand, the CCD has a complex driving method, a large power consumption, and requires a multi-stage photo process, so that the manufacturing process has a complex disadvantage. Recently, the CCD is used as a next-generation image sensor to overcome the disadvantage of the charge coupling device. Morse image sensor is attracting attention.

The CMOS image sensor implements an image by sequentially detecting an electrical signal of each unit pixel in a switching method of forming a photodiode and a MOS transistor in the unit pixel.

In manufacturing these 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 logic circuit portion for processing the sensed light as an electrical signal to make data. In order to increase the light sensitivity, the area of the light sensing portion occupies the entire image sensor area. Efforts have been made to increase the ratio (commonly referred to as "Fill Factor"), but this effort is limited under a limited area because the logic circuit portion cannot be removed in recent years. 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 representative example of the above condensing technique is to form a micro lens.

According to the related art, a method of forming a microlens during a manufacturing process of an image sensor generally forms a top metal wiring and passivation layer on a semiconductor substrate on which pixels are formed, and then performs a color filter and a microlens forming process.

The micro lens as described above forms a hemispherical shape by sequentially processing the photosensitive organic material in the order of exposure, development, and reflow. However, since the photosensitive organic material has a weak physical property, the microlens is easily damaged by cracks due to physical impact in a post process such as a package and bumps, and the photosensitive organic material has a relatively high viscosity, so that defects of the lens when particles are adsorbed. It is triggered.

In order to prevent this, a method of using a material such as an oxide film or a nitride film having a high hardness as a protective film is used, and efforts have been made to implement a hard micro lens using the inorganic material itself.

The surface of a micro lens made of a conventional oxide film is very rough. This is because the oxide film is made of a low temperature oxide film and the density of the film is very low. The reason why the microlens is formed of a low temperature oxide film is that the color filter under the microlens is an organic material, and thus, if the temperature is increased to increase the density at the time of forming the oxide film, the color filter organic material does not increase the temperature. For this reason, the low temperature oxide film is deposited, but the density of the film is low.

Therefore, due to the roughness of the conventional microlens surface, the light incident on the microlens surface is dispersed to a region other than the photodiode, so that loss such as incident or scattering on the surface occurs.

As a result, there is a problem that the sensitivity of the light of the image sensor is lowered and cross talk occurs.

The embodiment provides a method of manufacturing an image sensor that can improve the sensitivity by silane-treating the hard micro lens surface.

In another embodiment, a method of manufacturing an image sensor includes: forming a microlens on a substrate including a photodiode and metal wires, forming a pad mask on the substrate to expose a portion of the metal wires; Removing the mask and silane-treating the entire surface of the substrate on which the microlens is formed.

The embodiment has the effect of reducing the roughness of the lens surface of the hard mask and increasing the hydrophobicity to prevent the adsorption of particles and to improve the sensitivity.

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

In the description of the embodiment according to the invention, when described as being formed "on / over" of each layer, the on / over is directly or other layers. It includes all that are formed through (indirectly).

1 is a flowchart of a manufacturing method of an image sensor according to an exemplary embodiment.

Referring to FIG. 1, a microlens is formed on a semiconductor substrate on which a photodiode and a circuit region are formed (S100).

After forming the micro lens, the pad is opened (S110).

After the pad is opened, the surface of the substrate on which the microlens is formed is silane-treated (Silylation) (S120).

The silane treatment refers to the reaction of SiOH groups on the surface of the hydrophilicity substrate on which the microlenses are formed with organic silane to reduce hydrophilicity and increase hydrothermal stability.

The material used for the silane treatment may use at least one of chlorosilanes, alkoxysilanes, and silylamines. However, in the present invention, not only the material used for the silane treatment but also the organic silane may be used.

The micro lens is made of a low temperature oxide film, the surface roughness is so severe that small pores are formed on the surface.

After the silane treatment, the small pores on the surface of the microlens can be filled to decrease the surface area and increase hydrophobicity, thereby reducing the adsorption of water and polar organic molecules and increasing the adsorption of nonpolar organic molecules.

In addition, since the hydrophobicity of the surface of the substrate on which the microlens is formed is increased, it is possible to prevent damage caused by particles during wafer sawing (S130), thereby improving yield.

2 to 7 are cross-sectional views sequentially illustrating a method of manufacturing an image sensor according to an embodiment.

2, an optical sensing unit (not shown) including a photodiode (not shown) and a circuit area (not shown) is formed on the semiconductor substrate 10.

In detail, the light sensing unit including the photodiode is described. An isolation layer (not shown) defining an active region and a field region is formed on the semiconductor substrate 10, and light is received in each unit pixel. A photodiode for generating photocharges is formed, and a CMOS circuit (not shown) for converting an electric signal from the photocharges received by being connected to the photodiode is formed.

After the related devices including the device isolation layer and the photodiode are formed, an interlayer insulating film 20 is formed on the semiconductor substrate 10 and a plurality of metal wirings (not shown) are formed on the interlayer insulating film 20. . In addition, the interlayer insulating film 20 on which the metal wiring is formed may be formed of a plurality of layers.

The metal wiring is intentionally laid out so as not to block light incident on the photodiode.

Subsequently, a pad 21 may also be formed when the final metal wiring (not shown) is formed among the metal wires, and the passivation layer 30 may be formed on the interlayer insulating layer 20 including the pads 21.

The passivation layer 30 is to protect the device from moisture, scratches, or the like, and may form the passivation layer 30 on the pad 21.

The passivation layer 30 may be formed of any one of a silicon oxide film, a silicon nitride film, and a silicon oxynitride film, or may have a structure in which one or more layers are stacked.

Meanwhile, the color filter 40 may be formed in a subsequent process on the interlayer insulating film 20 in which the passivation layer 30 is not formed and the pad 21 is formed, which affects the overall height of the image sensor. It is also possible to provide a thin image sensor.

Additionally, a primary pad opening process may be performed to open the pad 21 on the passivation layer 30. In the first pad opening process, a photoresist pattern having a hole corresponding to the pad 21 area is formed on the passivation layer 30. The upper surface of the pad 21 may be opened by etching the passivation layer 30 using the photoresist pattern as a mask. After performing the first pad opening process, a microlens may be formed and the second pad opening process may be performed again. Here, the primary pad opening process may be omitted, and in the present embodiment, the primary pad opening process is omitted.

Next, the color filter 40 is formed on the passivation layer 30.

The color filter 40 is formed of three color filters 40 for realizing a color image. The material constituting the color filter 40 uses a dyed photoresist, one for each unit pixel. The color filter 40 is formed to separate colors from incident light. Each of the color filters 40 represents a different color, and is composed of three colors of red, green, and blue, and adjacent color filters 40 may overlap each other slightly to have a step. .

A flattening layer 50 is formed on the color filter 40 to compensate for this. The microlens to be formed in a subsequent process should be formed on the flattened surface, and for this purpose, the step due to the color filter 40 should be eliminated, and thus the planarization layer 50 may be formed on the color filter 40. Of course, the planarization layer 50 may not be formed.

Next, the first insulating layer 60 and the microlens mask 70 for forming the microlens are formed on the color filter 40.

The first insulating layer 60 may be formed of any one of an oxide film, a nitride film, and a nitride oxide film. In this case, the oxide film may be formed by CVD, PVD, PECVD, or the like.

The microlens mask 70 may form a dome-type microlens mask 70 by applying a photoresist film onto the first insulating layer 60 and then patterning and reflowing the film. Here, the microlens masks 70 are formed to be spaced apart from each other by a predetermined distance.

Referring to FIG. 3, the seed microlens 61 is formed by performing an etching process on the first insulating layer 60 using the microlens mask 70 as an etching mask.

The etching of the first insulating layer 60 may be performed at an etching ratio of 1: 0.7 to 1.3 with respect to the photoresist layer forming the microlens mask 70 and the oxide layer forming the first insulating layer 60. have.

Accordingly, etching of the first insulating layer 60 for forming the seed microlens 61 may be performed until all of the microlens masks 70 made of a photoresist material are etched.

The etching process of the first insulating layer 60 may be performed by using an etching gas of CxHyFz (x, y, z is 0 or natural number) and an inert gas such as Ar, He, O ₂ and N ₂ in the chamber. have.

Through the above process, as shown in FIG. 3, the dome-shaped seed microlens 61 made of a low temperature oxide film is formed on the color filter 40. In this case, the seed microlens 61 is formed to be spaced apart from the neighboring seed microlens 61 so that the merge of the microlenses is prevented so that the sensitivity of the image sensor is not lowered.

Referring to FIG. 4, a second insulating layer 70 is deposited on the semiconductor substrate 10 on which the seed microlens 61 is formed.

The second insulating layer 70 is deposited along the top surface of the seed microlens 61 so that the seed microlens 61 is in contact with a neighboring seed microlens.

Accordingly, the microlens 80 including the seed microlens 61 and the second insulating layer 70 may have a continuous dome shape to form a gapless microlens.

The second insulating layer 70 may be formed of the same material as the first insulating layer 60.

Accordingly, since the second insulating layer 70 is deposited to have a thin thickness on the seed microlens 61, the end portion of the microlens 80 is in continuous contact with the neighboring microlens. As a result, the gap between the microlenses 80 is reduced to a level of zero gab, thereby improving the image quality of the image sensor.

5 and 6, a pad mask 100 is formed on the semiconductor substrate 10 on which the microlens 80 is formed. The pad mask 100 may be a photoresist film and may selectively remove a portion to form a pad hole 110.

The pad mask 100 coats and patternes a photoresist on the second insulating layer 70. Then, the upper surface of the second insulating layer 70 of the portion corresponding to the pad 21 area is exposed by the pad hole 110 of the pad mask 100, and the remaining area is exposed by the pad mask 100. All are covered.

The pad open hole 23 is etched by etching the second insulating film 70, the first insulating film 60, and the passivation layer 30 on the pad 21 using the pad mask 100 as an etching mask. By forming it, the pad 21 can be exposed.

The pad 21 may be exposed by a dry etching process.

Referring to FIG. 7, the pad mask 100 is removed to expose the pad 21 formed on the semiconductor substrate 10.

Subsequently, the substrate exposed by the pad is reacted with organic silane to be silylated.

The above-described embodiments are not limited to the above-described embodiments and drawings, and it is common in the technical field to which the present embodiments belong that various changes, modifications, and changes can be made without departing from the technical spirit of the present embodiments. It will be apparent to those who have

1 is a flowchart of a manufacturing method of an image sensor according to an exemplary embodiment.

2 to 7 are cross-sectional views sequentially illustrating a method of manufacturing an image sensor according to an embodiment.

Claims (7)

Forming an interlayer insulating film including metal wiring on the semiconductor substrate on which the photodiode is formed; Forming a passivation layer on the interlayer insulating film; Forming a color filter and a planarization layer on a portion of the passivation layer; Forming a first hole in the passivation layer to expose a portion of the metal wiring first; Forming a first insulating film on the planarization layer; Forming a microlens mask on the first insulating film; Forming the first insulating layer as a seed micro lens using the microlens mask; Forming a microlens by forming a second insulating film on the seed microlens; Forming a pad mask on the substrate to form a second hole connected to the first hole in the first insulating film and the second insulating film to expose a part of the metal wires secondly; Removing the pad mask; And Silane-processing the entire surface of the substrate on which the microlens is formed. The method of claim 1, In the silane treatment step, And reacting the surface of the micro lens with organic silane. The method of claim 1, After the silane treatment step, And a cutting process of the substrate. delete The method of claim 1, The first insulating film and the second insulating film is a manufacturing method of the image sensor, characterized in that made of at least one of an oxide film, a nitride film and a nitride oxide film. The method of claim 1, The silane treatment uses an organic silane. The method of claim 6, The organic silane is at least one of chlorosilanes (chlorosilanes), alkoxysilanes (alkoxysilanes) and silylamines (silylamines).

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