KR100670536B1 - Image sensor having oxide layer over micro-lens - Google Patents

Abstract

The present invention is to provide an image sensor having a structure that is easy to remove the particles generated during the packaging process, easy backgrinding operation, and can implement the anti-reflective layer (ARC) to improve the light sensing characteristics, According to an aspect of the present invention, there is provided an image sensor including a microlens for condensing, the image sensor comprising: a nitride layer formed on the microlens with a predetermined thickness along a bend of the microlens; An oxynitride layer formed on the nitride layer to suppress reflection loss of incident light; And a planarization oxide layer formed on the oxynitride layer.

Image sensor. Microlens, planarization, nitride layer, oxynitride layer, oxide layer

Description

Image sensor having oxide layer over micro-lens}             

1 is a schematic cross-sectional view showing the structure of an image sensor according to the prior art.

Figure 2 is a schematic cross-sectional view showing the structure of the image sensor according to the present invention.

* Explanation of symbols for main parts of the drawings

201: photodiode 202: insulating layer

203: element protective film 204: color filter array

205: OCM layer 206: microlens

207: nitride layer 208: oxynitride layer

209: planarized oxide layer

The present invention relates to an image sensor and a method of manufacturing the same, and more particularly, to an image sensor and a method of manufacturing the same for minimizing damage to microlens.

The image sensor consists of a light sensing part that detects light and a logic circuit part that processes the detected light into an electrical signal to make data. Efforts have been made to increase the fill factor of the area of the photo-sensing part in the overall image sensor device to increase the light sensitivity. However, this effort is limited under a limited area because the logic circuit part cannot be removed. . Therefore, the microlens technology is a condensing technology that changes the path of light incident to a region other than the light sensing portion and collects the light sensing portion to increase the light sensitivity.

1 is a schematic cross-sectional view showing an image sensor structure according to the prior art.

Referring to FIG. 1, an insulating layer 102 is formed on a photodiode (PD) 101, a device passivation 103 is formed on the insulating layer 102, and a color filter array (CFA) is disposed thereon. 104 is formed. An over coating material (OCM) layer 105 is formed on the color filter array 104 and a microlens (ML) 106 is formed thereon.

However, the conventional image sensor having the above-described structure is packaged in the structure of FIG. 1, since the microlens is a material having a high viscosity as a photoresist component and susceptible to the external environment. Yield loss due to particles such as Al) cannot be avoided, and the removal method also has no suitable solution.

In addition, there is a disadvantage in that backgrinding cannot be performed due to the components of the microlenses and their topology.

In addition, in terms of light transmission characteristics, the reflection loss of incident light to the microlens having a refractive index of about 1.6 in air cannot be ignored, and it is difficult to implement an anti-reflective layer for compensation thereof.

It is an object of the present invention to provide an image sensor having a structure suitable for removing particles generated in a packaging process, easy backgrinding operation, and realization of an anti-reflective layer to improve light sensing characteristics.

An image sensor of the present invention for achieving the above object, the image sensor having a microlens for condensing, comprising: a nitride layer formed on the microlens with a predetermined thickness along the curvature of the microlens; An oxynitride layer formed on the nitride layer to suppress reflection loss of incident light; And a planarized oxide layer formed on the oxynitride layer.

DETAILED DESCRIPTION Hereinafter, exemplary embodiments of the present invention will be described with reference to the accompanying drawings so that those skilled in the art may easily implement the technical idea of the present invention. do.

2 schematically shows the structure of an image sensor according to a preferred embodiment of the present invention. The device structure under the protective film only shows a photodiode which is closely related to the present invention, and other devices such as transistors are not shown.

Referring to FIG. 2, an insulating layer 202 is formed on a photodiode (PD) 201, which is an optical sensing element, and a device passivation 203 is formed on the insulating layer 202, and a color is formed thereon. A filter array (CFA) 204 and an over coating material (OCM) layer 205 are formed.

The photodiode is a device generating photocharges by receiving light incident from the outside. The insulating layer 202 may be formed of a conventional multilayer oxide film such as an insulating layer formed before metal wiring, an insulating layer between metal wirings, and the device protective film 203 may be formed of an oxide film or an oxide film / nitride film.

The color filter array 204 is typically arranged in which red, blue, and green color filters correspond to unit pixels, and the color filter array has a step to flatten it and / or OCM layer is applied to improve light transmittance. The OCM layer typically uses photoresist.

Subsequently, a microlens 206 is formed on the OCM layer 205. At this time, unlike the conventional method, the CD (critical dimension) of the microlens is small. For example, in the case of a 0.5 μm CMOS image sensor, the CD is reduced by about 1 μm from about 7.6 μm to about 6.6 μm.

Subsequently, a nitride film 207 having a thickness of about 1 μm is formed on the microlens 206. Subsequently, an oxynitride (208) is formed as an anti-reflective layer (ARC) and a planarized oxide film 209 of about 5 μm or more is formed thereon. The planarization oxide film 209 may be set to a thickness corresponding to an allowable distance between the device and the sealing glass in consideration of the shading effect in the subsequent package. The method of forming the planarized oxide film is planarized by etching, etching back or chemical mechanical polishing after deposition of the oxide film.

The nitride film 207 is formed to be bent along the shape of the microlens 206 to function as a lens for focusing incident light. The oxynitride film 208 is used to prevent reflection loss of incident light due to the relatively large refractive index of the nitride layer 207. To minimize the reflection loss in the blue wavelength band, the thickness and refractive index of the oxynitride layer 208 is 0.45 μm. Design. This is taken into account because the light sensitivity of the image sensor is not good for the blue wavelength which is usually short wavelength.

 Since the uppermost layer of the device is an oxide film rather than a microlens, the image sensor having the above-described structure minimizes damage to the microlens in a subsequent process, facilitates the removal of particles generated during the packaging process, and the topmost layer of the device is Therefore, backgrinding is easy. In addition, it can not only contribute to the improvement of probe yield, but above all can prevent the typical yield loss due to white fail in the final test after package.

In addition, due to such a structure, the degradation of light transmission characteristics is formed into a nitride film to maintain the fill factor of the image sensor, and an anti-reflective layer is added to prevent reflection loss of incident light at the nitride film interface and to prevent air. The return loss of the incident light is reduced. That is, since the conventional microlens (photoresist) has a refractive index n = 1.6 while the oxide film has a refractive index n = 1.46, light loss is reduced as light enters a relatively low refractive index material.

Therefore, with the application of the present invention, the optical transmission characteristics of the image sensor are maintained or improved as compared to the conventional one, and a remarkable improvement in package yield can be expected, and furthermore, since the recessed part layer of the device is an oxide film instead of a microlens, Many applications are found, including those that can be applied to one-package processes.

Although the technical idea of the present invention has been described in detail according to the above preferred embodiment, it should be noted that the above-described embodiment is for the purpose of description and not of limitation. In addition, those skilled in the art will understand that various embodiments are possible within the scope of the technical idea of the present invention.

The present invention introduces a new device structure to the cause of yield degradation due to microlens damage and particles such as aluminum (Al) that occur during package assembly after probe testing. To prevent. In particular, it has the effect of remarkably improving the yield of a package final test in a package without degrading an optical characteristic.

Claims (2)

An image sensor having a microlens for condensing, A nitride layer formed on the microlens at a predetermined thickness along the curvature of the microlens and focusing incident light; An oxynitride layer formed on the nitride layer and formed to have a predetermined thickness along the curvature of the microlens to suppress reflection loss of incident light; And Planarization oxide layer formed on the oxynitride layer Image sensor made, including. The method of claim 1, The oxynitride layer is an image sensor, characterized in that the thickness and refractive index is designed to 0.45㎛ reference wavelength in order to improve the light sensitivity of the blue wavelength band.

Images