KR100683391B1 - Cmos image sensor and method for fabricating the same - Google Patents

Abstract

In the image sensor, even if the size of the light source incident from the outside is small, even the photodiode at the edge of the light incident from the light source is all properly transmitted image sensor that can represent the real image regardless of the size of the light source To provide a, for the present invention the photodiode; A micro lens disposed on the photodiode; And a light path area disposed in a space between the micro lens and the photodiode, and having a light path region that totally reflects the light passing through the micro lens to the edge to focus the photodiode.

CMOS image sensor, total reflection, optical path, point light source, refraction.

Description

CMOS image sensor and its manufacturing method {CMOS IMAGE SENSOR AND METHOD FOR FABRICATING THE SAME}

1 is a block diagram of a conventional CMOS image sensor.

2 is a circuit diagram showing the configuration of unit pixels of a conventional CMOS image sensor.

3 is a cross-sectional view of the CMOS image sensor according to the prior art.

4 is a view showing a problem of the CMOS image sensor according to the prior art.

5 is a view showing a description of the total reflection to show the principle of the present invention.

6 is a cross-sectional view showing a CMOS image sensor according to a preferred embodiment of the present invention.

7A to 7F are cross-sectional views illustrating a method of manufacturing a CMOS image sensor according to a preferred embodiment of the present invention.

8 is a sectional view showing a CMOS image sensor according to a second preferred embodiment of the present invention.

9A to 9G are cross-sectional views illustrating a method of manufacturing a CMOS image sensor according to a preferred embodiment of the present invention.

Explanation of symbols on the main parts of the drawings

21 substrate 22 photodiode

23,24,28: insulating film

26,27: insulating film for optical path 29: color filter

31: microlens 30: OCL

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a CMOS image sensor, and more particularly, to a CMOS image sensor and a method of manufacturing the same, which allow more light to pass through a microlens by a point light source to be collected at a lower photodiode.

In general, an image sensor of a semiconductor device is a semiconductor device that converts an optical image into an electrical signal. Representative image sensor devices include a charge coupled device (CCD) and a CMOS image sensor.

Among them, the charge-coupled device is a device in which charge carriers are stored and transported in the capacitor while individual metal-oxide-silicon (MOS) capacitors are located very close to each other, and the CMOS image sensor is a control circuit and a signal processing circuit. It is a device that adopts a switching method of making MOS transistors by the number of pixels by using CMOS processing using a signal processing circuit as a peripheral circuit and sequentially detecting the output using the MOS transistors.

1 is a block diagram of a conventional CMOS image sensor.

Referring to FIG. 1, a conventional CMOS image sensor includes a pixel array in which a plurality of unit pixels are arrayed, an ADC block for converting an analog signal output from the pixel array into a digital signal, and a digital value output from the ADC block. A line buffer to store, a decoder / pixel driver for decoding the input address to select a unit pixel of the pixel array, and a control register and logic for controlling the decoder / pixel driver.

2 is a circuit diagram showing the configuration of unit pixels of a conventional CMOS image sensor.

FIG. 2 is a circuit diagram showing a unit pixel composed of one photodiode PD and four MOS transistors in a conventional CMOS image sensor, and includes a photodiode 100 for generating photocharges upon receiving light. A transfer transistor 101 for transporting the photocharges collected from the photodiode 100 to the floating diffusion region 102, and resets the floating diffusion region 102 by setting a potential of the floating diffusion region to a desired value and discharging electric charge. A reset transistor 103 for supplying voltage, a drive transistor 104 serving as a source follower buffer amplifier by applying a voltage of a floating diffusion region to a gate, and an addressing role as a switching role. It consists of a select transistor 105 that performs the following. Outside the unit pixel, a load transistor 106 for reading an output signal is formed.

3 is a cross-sectional view of the CMOS image sensor according to the prior art.

As shown in FIG. 3, the light incident from the light source 16 passes through each microlens 15, and information corresponding to the light incident by the photodiode at the bottom is transmitted to the internal circuit of the image sensor.

In this case, when the size of the light source is large, since light is incident on all micro lenses of the image sensor in a straight line, it is possible to transmit light to all photodiodes provided corresponding to the micro lenses at the bottom thereof.

However, in an unusual case such as a point light source, light does not enter a single line to the microlens at the edge of the microlenses included in the image sensor.

As a result, light passing through the microlens at the edge cannot be transmitted to the photodiode at the bottom thereof.

4 is a view showing a problem of the CMOS image sensor according to the prior art.

As shown in FIG. 4, when light incident by a light source such as a point light source is incident on the microlens at the edge, the light is not transmitted to the photodiode at the bottom thereof, and is moved outward.

Therefore, when the image is formed in response to light incident from the outside, it is very difficult to express the outside part properly.

In the image sensor, even if the size of the light source incident from the outside is small, even the photodiode at the edge of the light incident from the light source is all properly transmitted image sensor that can represent the real image regardless of the size of the light source It is intended to provide.

According to the present invention, a photodiode formed in a substrate formed in a substrate and at least two insulating layers formed on the substrate with an etch stop layer interposed therebetween are patterned so that the etch stop layer is exposed. A groove formed to correspond to the photodiode, a first optical path layer formed of an insulating material having a first refractive index formed on a side of the groove, and a first refractive index of the first optical path layer in the groove; A CMOS image having a second optical path layer formed of an insulating material having a large second refractive index, a color filter formed on the second optical path layer to correspond to the photodiode, and a micro lens formed to correspond to the color filter Provide a sensor.

In another aspect, the present invention comprises the steps of forming a photodiode in the substrate; Forming a first insulating film on the substrate to cover the photodiode; Forming an etch stop film on the first insulating film; Forming a second insulating film on the etch stop film; Selectively removing the second insulating layer using the etch stop layer as an etch barrier to form a first hole corresponding to the photodiode; Depositing and patterning an insulating material having a first refractive index to fill the first hole to form a second hole, thereby forming a first light path layer having a constant thickness on a side of the first hole; Embedding an insulating material having a second refractive index having a larger refractive index than the second insulating layer in the second hole to form a second optical path layer; Forming a third insulating film on the second insulating film to cover the first and second optical path layers; And forming a microlens in a portion corresponding to the photodiode on the third insulating layer.

In another aspect, the present invention comprises the steps of forming a photodiode to be embedded in the substrate; Forming a first insulating film on the photodiode; Selectively removing the second insulating layer to form a first hole to expose the photodiode; Forming a second insulating film having a first refractive index in the first hole; Forming a second hole by selectively removing the second insulating film so that the second insulating film remains with a constant thickness only at an edge of the first hole; Filling a third insulating film having a refractive index greater than that of the second insulating film in the second hole; Forming a color filter on the third insulating layer to be aligned with the photodiode; And it provides a CMOS image sensor comprising the step of forming a micro lens on the color filter.

According to the present invention, when the light source coming from the outside of the module is unusual, such as a point light source, the light at the boundary of the CMOS image sensor is focused out of the photodiode. By using the principle of total reflection where all the light is reflected, the light path incident from the lens and the photodiode lens is formed by depositing two different media with different refractive indices in the part outside the photodiode. It is to maximize the light efficiency by being incident to the photodiode.

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

5 is a view showing a description of the total reflection to show the principle of the present invention.

Referring to Fig. 5, when the light is transmitted from the interface between the two media, the angle of refraction is θt, which is formed with a normal perpendicular to the interface, and the reflected angle is θr. This occurs.

n1 * sin θi = n2 * sin θt = n1 * sin θr (n1 and n2 are the refractive indices of each material)

This law is called Snell's law. If n1 is larger than n2, there is a critical angle θc where the refraction does not occur at the time when the light becomes refracted by θt being perpendicular to each other. Is established.

sin θc = n2 / n1

That is, the light incident on the medium having the small refractive index smaller than the critical angle θc among the light passing through the medium having the large refractive index is not refracted, but total reflection occurs. The present invention creates a light path between the microlens and the photodiode using the principle of total reflection so that all the light inside the light path is totally reflected so that all the incoming light is incident on the photodiode.

6 is a cross-sectional view illustrating a CMOS image sensor according to a preferred embodiment of the present invention.

Referring to FIG. 6, in the CMOS image sense, a color filter 29 and a micro lens 31 are disposed on a photodiode 21 disposed on a substrate 20, and two refractive indices are provided. In the optical path in which the light passing through the microlens 31 is focused to the photodiode, total reflection occurs using the material having the branched material.

Here, reference numeral 30 denotes an over coating layer, which is a planarization layer for forming a microlens on the color filter, and 24, 28, and 22 are insulating layers forming a body. 23 represents an etch stop film.

Subsequently, a method of manufacturing the CMOS image sensor according to the present embodiment will be described with reference to FIGS. 7A to 7F.

7A to 7F are cross-sectional views illustrating a method of manufacturing a CMOS image sensor according to a preferred embodiment of the present invention.

First, as shown in FIG. 7A, in the method of manufacturing the CMOS image sensor according to the present embodiment, a photodiode 21 is formed on a substrate 20, an insulating film 22 is formed on the substrate 20, and an etch stop layer is formed. (23) is formed. Subsequently, an insulating film 22 is formed on the etch stop film 23.

The insulating films 22 and 24 use SiO2 based films having good light transmittance, and the etch stop film 23 uses SiC having good etch stop characteristics and good light transmittance.

Subsequently, as shown in FIG. 7B, the insulating film 24 on which the photodiode 21 is disposed is selectively removed (the etch stop film 23 serves to stop the etching.) The insulating film 25 with a small refractive index is embedded.

Subsequently, after the photoresist pattern 26 is formed as shown in FIG. 7C, the insulating layer 25 is selectively removed to expose the etch stop layer 22 using the formed photoresist pattern 26 as an etching mask.

Subsequently, as shown in FIG. 7D, an insulating film 27 having a larger refractive index than the insulating film 25 is formed.

Subsequently, as shown in FIG. 7E, the insulating films 27 and 25 are removed and planarized to expose the insulating film 24. At this time, the planarization uses a chemical mechanical polishing process.

Then, as shown in Fig. 7F, the color filter 29, the OCL 30 are formed, and the microlens 31 is formed.

Here, the insulating films 25 and 27 may be any materials that have a refractive index capable of total reflection so that light is totally reflected when the light passing through the microlens is focused to the photodiode so as not to deviate from the optical path.

The completed CMOS image sensor is totally reflected in the optical path through which the light passing through the microlenses reaches the photodiode, thereby condensing the light onto the photodiode without loss.

8 is a cross-sectional view illustrating a CMOS image sensor according to a second exemplary embodiment of the present invention.

Referring to FIG. 8, the CMOS image sensor according to the second embodiment has the same idea of forming insulating films 34 and 36 having different refractive indices so that total reflection occurs on the optical path, but their insulating films and color filters 37 ) Is directly in contact with the photodiode (31a) is also configured to directly contact.

The photodiode 31a, the color filter 37, and the microlens 39 are disposed on the substrate 30a, and a plurality of insulating films 32, 34, and 36 form a body region therebetween. It is the same as CMOS image sensor.

Subsequently, a manufacturing method of the CMOS image sensor according to the second exemplary embodiment will be described with reference to FIGS. 9A to 9G.

9A to 9G are cross-sectional views illustrating a method of manufacturing a CMOS image sensor according to a preferred embodiment of the present invention.

First, as shown in FIG. 9A, in the method of manufacturing the CMOS image sensor according to the present embodiment, a photodiode 31a is formed on a substrate 30a and an insulating film 32 is formed thereon.

Next, as shown in FIG. 9B, the insulating film 32 on which the photodiode 21 is disposed is selectively removed using the photosensitive film pattern 33 to expose the photodiode 31a.

Subsequently, as shown in Fig. 9C, the insulating film 34 having a small refractive index is buried in the place where the insulating film 32 is removed.

Subsequently, as shown in FIG. 9D, after the photoresist pattern 35 is formed, the insulating layer 34 is selectively removed so that the photodiode 31a is exposed using the formed photoresist pattern 35 as an etch mask.

Next, as shown in Fig. 9E, an insulating film 27 having a larger refractive index than the insulating film 34 is formed.

9F, the insulating films 34 and 36 are removed and planarized so that the insulating film 32 is exposed. At this time, the planarization uses a chemical mechanical polishing process.

Then, as shown in Fig. 9G, the color filter 37, the OCL 38 are formed, and the microlens 39 is formed.

Herein, the insulating films 34 and 36 may be any materials that have a refractive index capable of total reflection so that the light is totally reflected when the light passing through the microlens is focused onto the photodiode.

The completed CMOS image sensor is totally reflected in the optical path through which the light passing through the microlenses reaches the photodiode, thereby condensing the light onto the photodiode without loss.

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 Esau.

According to the present invention, even when the light source coming from the outside of the module is unusual, such as a point light source, the light incident on the boundary of the sense is totally reflected inside the light path so that the sense boundary part does not receive light or is weakly received. This can eliminate the phenomenon of not expressing properly.

Claims (9)

A photodiode formed in the substrate; At least two insulating films formed on the substrate with an etch stop film interposed therebetween, wherein an insulating film formed on top of the at least two insulating films is patterned to expose the etch stop film so as to correspond to the photodiode; A first optical path layer formed of an insulating material having a first refractive index formed on a side of the groove; A second optical path layer formed of an insulating material having a second refractive index greater than the first refractive index of the first optical path layer in the groove; A color filter formed on the second optical path layer to correspond to the photodiode; Micro lens formed to correspond to the color filter CMOS image sensor having a. delete delete delete The method of claim 1, And a planarization layer formed to cover the first and second optical path layers on the insulating film formed on the upper part of the insulating film formed of at least two layers. The method of claim 1, The CMOS image sensor, characterized in that the etch stop film is formed of SiC. Forming a photodiode in the substrate; Forming a first insulating film on the substrate to cover the photodiode; Forming an etch stop film on the first insulating film; Forming a second insulating film on the etch stop film; Selectively removing the second insulating layer using the etch stop layer as an etch barrier to form a first hole corresponding to the photodiode; Depositing and patterning an insulating material having a first refractive index to fill the first hole to form a second hole, thereby forming a first light path layer having a constant thickness on a side of the first hole; Embedding an insulating material having a second refractive index having a larger refractive index than the second insulating layer in the second hole to form a second optical path layer; Forming a third insulating film on the second insulating film to cover the first and second optical path layers; And Forming a micro lens on a portion of the third insulating layer corresponding to the photodiode Method for manufacturing a CMOS image sensor comprising a. The method of claim 7, wherein Forming a color filter on a lower end of the micro lens formed on the third insulating film; And The method of claim 1, further comprising forming an OCL film on the color filter. delete

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