KR20110079340A - Image sensor and its manufacturing method - Google Patents

Abstract

The image sensor according to the embodiment includes a plurality of light receiving units formed for each unit pixel on a front side of the semiconductor substrate; A metal wiring layer including wiring formed on an entire surface of the semiconductor substrate; At least one first lens on the rear surface of the semiconductor substrate opposite to the front surface of the semiconductor substrate so that light is refracted by the light receiving unit; And a second lens disposed above the first lens on the rear surface of the semiconductor substrate, wherein the first lens is disposed between the second lens and the light receiving unit.

In another embodiment, a method of manufacturing an image sensor includes: forming a plurality of light receiving units for each unit pixel on a front side of a semiconductor substrate; Forming a metal wiring layer including wiring on a front surface of the semiconductor substrate; Forming at least one first lens on the rear surface of the semiconductor substrate opposite to the front surface of the semiconductor substrate to be refracted by the light receiving unit; And forming a second lens on the first lens on the rear side of the semiconductor substrate, wherein the first lens is disposed between the second lens and the light receiving unit.

Rear receiving image sensor

Description

Image sensor and manufacturing method thereof {IMAGE SENSOR AND METHOD FOR MANUFACTURING THE SAME}

Embodiments relate to an image sensor and a method of manufacturing the same.

An image sensor is a semiconductor device that converts an optical image into an electrical signal, and is classified into a charge coupled device (CCD) image sensor and a CMOS image sensor (CIS). .

In general, an image sensor forms a photodiode on a silicon substrate by ion implantation. As the size of the photodiode gradually decreases for the purpose of increasing the number of pixels without increasing the chip size, the image characteristic decreases due to the reduction of the area of the light receiver.

In addition, since the stack height is not reduced as much as the area of the light receiving unit is reduced, the number of photons incident on the light receiving unit also decreases due to a diffraction phenomenon of light called an airy disk.

As an alternative to overcome this problem, an attempt is made to receive light through the wafer back side to minimize the step difference of the light receiving unit, and to prevent light interference caused by metal routing (back light receiving image). Sensor).

In such a back-receiving image sensor, there is no device isolation region on the rear surface of the substrate, which is very vulnerable to optical cross talk.

The embodiment provides an image sensor and a method of manufacturing the same that can improve image characteristics.

The image sensor according to the embodiment includes a plurality of light receiving units formed for each unit pixel on a front side of the semiconductor substrate; A metal wiring layer including wiring formed on an entire surface of the semiconductor substrate; At least one first lens on the rear surface of the semiconductor substrate opposite to the front surface of the semiconductor substrate so that light is refracted by the light receiving unit; And a second lens disposed above the first lens on the rear surface of the semiconductor substrate, wherein the first lens is disposed between the second lens and the light receiving unit.

In another embodiment, a method of manufacturing an image sensor includes: forming a plurality of light receiving units for each unit pixel on a front side of a semiconductor substrate; Forming a metal wiring layer including wiring on a front surface of the semiconductor substrate; Forming at least one first lens on the rear surface of the semiconductor substrate opposite to the front surface of the semiconductor substrate to be refracted by the light receiving unit; And forming a second lens on the first lens on the rear side of the semiconductor substrate, wherein the first lens is disposed between the second lens and the light receiving unit.

The image sensor and the method of manufacturing the same according to the embodiment form a first lens in the form of a concave lens on the rear side of the semiconductor substrate, and form a microlens above the first lens.

The microlens may condense light in the form of a convex lens, and the first lens in the form of a concave lens may condense the light incident on the peripheral region of the microlens to the light receiving unit.

That is, although the light passes through the microlens, light incident on the peripheral region of the microlens is collected by the light receiving unit, thereby improving the light sensitivity of the image sensor.

This is because the first lens is disposed at the edge of the micro lens between the neighboring micro lenses, thereby changing the light path of the light passing through the edge of the micro lens, thereby increasing the light receiving efficiency of the image sensor.

In addition, since light passing through the microlens, but incident to the peripheral region of the microlens, is collected by the first lens to the light receiving unit, crosstalk to adjacent pixels can be prevented.

Accordingly, the image sensor can achieve high integration, and can also improve image characteristics.

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

In the description of the embodiments, where it is described as being formed "on / under" of each layer, it is understood that the phase is formed directly or indirectly through another layer. It includes everything.

6 is a cross-sectional view illustrating an image sensor according to an embodiment.

The image sensor according to the embodiment includes a semiconductor substrate 100, a light receiving unit 120, a metal wiring layer 140, a first lens 300, and a micro lens 200 which is a second lens.

On the front side of the semiconductor substrate 100, a plurality of light receiving parts 120 are formed for each unit pixel.

The metallization layer 140 is disposed on the front surface of the semiconductor substrate 100 and includes wiring.

The first lens 300 is formed such that light is refracted by the light receiving unit 120 on the rear surface of the semiconductor substrate 100 opposite to the front surface of the semiconductor substrate 100.

The microlens 200 is disposed on the first lens 300 on the rear surface of the semiconductor substrate 100.

The first lens 300 is formed to be bent toward the light receiving unit 120.

In this case, the photoresist pattern 10 is formed on the rear surface of the semiconductor substrate 100 in a region corresponding to the light receiving unit 120.

The first lens 300 is formed in a region corresponding to the light receiving units 120 different from each other.

The planarization layer 350 is disposed between the first lens 300 and the micro lens 200.

The planarization layer 350 may be formed using a photoresist.

Although not shown, another planarization layer may be formed on the color filter array 190 by using a photoresist.

The color filter array 190 may be formed one by one for each unit pixel using a dyed photoresist and separate colors from incident light.

For example, the color filter array 190 may include a first color filter 191 corresponding to a blue color, a second color filter 192 corresponding to a green color, and a third color filter 193 corresponding to a red color. It includes.

The first color filter 191 is formed to correspond to the first light receiver PD1, the second color filter 192 is formed to correspond to the second light receiver PD2, and the third color filter 193. ) May be formed to correspond to the third light receiver PD3.

That is, an area where the first color filter 191 and the second color filter 192 contact each other may be disposed at the center of the first lens 300, and the second color filter 192 and the third color filter may be disposed in the center of the first lens 300. An area where the 193 contacts may also be disposed at the center of the first lens 300.

The microlens 200 is formed in the form of a convex lens to condense light to the light receiving unit 120, and the first lens 300 condenses the light passing through the micro lens 200 to the light receiving unit 120 again. Let's do it.

The microlens 200 condenses the light in the form of a convex lens, and the first lens 300 in the concave lens form condenses the light incident to the peripheral region of the microlens 200 into the light receiving unit 120. have.

That is, although the light passes through the microlens 200, the light incident to the peripheral area of the microlens 200 is collected by the light receiver 120, thereby improving the light sensitivity of the image sensor.

This is because the first lens 300 is disposed at an edge of the micro lens 200 between the neighboring micro lenses 200, so that the light passes through the edge of the micro lens 200. By changing the furnace, the light receiving efficiency of the image sensor can be increased.

In addition, although the light passes through the microlens 200, the light incident on the peripheral area of the microlens 200 is collected by the first lens 300 to the light receiving unit 120, and thus crosstalk to adjacent pixels. (crosstalk) can be prevented.

Hereinafter, a method of manufacturing an image sensor according to an embodiment will be described with reference to FIGS. 1 to 6.

First, as shown in FIG. 1, the pixel isolation region is defined by forming the device isolation region 110 on the front side of the semiconductor substrate 100.

The semiconductor substrate 100 may be a high concentration p-type substrate (p ++). The front side of the semiconductor substrate 100 may include a low concentration p-type epi layer (p-epi) by performing an epitaxial process.

The device isolation region 110 may be formed on the front surface of the semiconductor substrate 100 by an STI process. Although not shown, an ion implantation region may be further formed to isolate the light receiver 120. The ion implantation region may be formed before or after the formation of the device isolation region 120.

Next, a unit pixel including the light receiving unit 120 and the readout circuit 130 is formed in the pixel region of the semiconductor substrate 100.

The light receiver 120 may be a photodiode.

The light receiver 120 may include a first light receiver PD1, a second light receiver PD2, and a third light receiver PD3.

For example, the first light receiver PD1 generates photocharges for the blue signal, the second light receiver PD2 generates photocharges for the green signal, and the third light receiver PD3 is light for the red signal. It can generate a charge.

The light receiver 120 may be formed in the semiconductor substrate 100 by pn junctions formed by an n-type ion implantation region and a p-type ion implantation region, but is not limited thereto.

By the p-type ion implantation region, excess electrons and the like can be prevented. In addition, the embodiment may form a PNP junction to obtain a charge dumping effect.

The readout circuit 130 for signal processing is formed on the semiconductor substrate 100 on which the light receiving unit 120 is formed.

For example, the readout circuit 130 may include a transfer transistor, a reset transistor, a drive transistor, and a select transistor, but is not limited thereto.

The embodiment may be a mirror type pixel (Mirror Type-2-Shared) structure in which two unit pixels share one floating diffusion region, but the present invention is not limited thereto, and each unit pixel may include one floating diffusion region. have.

Next, the metal wiring layer 140 including the wiring is formed on the front side of the semiconductor substrate 100. For example, the wiring may include a first metal M1 and a second metal M2.

Meanwhile, a carrier wafer (not shown) may be bonded onto the metal wiring layer 140 including the wiring. The carrier wafer may be a means for handling the semiconductor substrate 100.

Next, as shown in FIG. 2, a part of the back side opposite to the front side of the semiconductor substrate 100 is removed.

For example, the lower side is removed based on the ion implantation layer (not shown) formed in the lower region of the front surface of the semiconductor substrate 100.

That is, the heat treatment of the ion implantation layer (not shown) may be performed to remove hydrogen ions by cutting them with a blade or the like after porosizing the hydrogen ions.

Thereafter, a planarization process may be performed on the rear surface of the cut semiconductor substrate 100.

Alternatively, the opposite side of the front side of the semiconductor substrate 100 may be removed by a back graining process.

In this case, when the semiconductor substrate 100 is a silicon on insulator (SOI) wafer, an insulator may be removed by a backgrinding process.

3, the photoresist pattern 10 is formed on the rear surface of the semiconductor substrate 100 and a wet etching process is performed to bend the inside of the semiconductor substrate 100. The true first lens 300 is formed.

That is, since the wetness etching process is isotropic etching, isotropic etching is performed on the rear surface of the semiconductor substrate 100 exposed by the photoresist pattern 10.

Therefore, the first lens 300 is formed to be bent toward the light receiving unit 120.

In this case, the photoresist pattern 10 is formed on the rear surface of the semiconductor substrate 100 in a region corresponding to the light receiving unit 120.

The first lens 300 is formed in a region corresponding to the light receiving units 120 different from each other.

Subsequently, as shown in FIG. 4, the planarization layer 350 is formed on the back surface of the semiconductor substrate 100 on which the first lens 300 is formed, and the color filter array is formed on the planarization layer 350. 190 is formed.

The planarization layer 350 may be formed using a photoresist.

Although not shown in the drawing, another planarization layer may be formed on the color filter array 190 by using a photoresist.

The color filter array 190 may be formed one by one for each unit pixel using a dyed photoresist and separate colors from incident light.

For example, the color filter array 190 may include a first color filter 191 corresponding to a blue color, a second color filter 192 corresponding to a green color, and a third color filter 193 corresponding to a red color. It includes.

The first color filter 191 is formed to correspond to the first light receiver PD1, the second color filter 192 is formed to correspond to the second light receiver PD2, and the third color filter 193. ) May be formed to correspond to the third light receiver PD3.

That is, an area where the first color filter 191 and the second color filter 192 contact each other may be disposed at the center of the first lens 300, and the second color filter 192 and the third color filter may be disposed in the center of the first lens 300. An area where the 193 contacts may also be disposed at the center of the first lens 300.

As shown in FIG. 5, microlenses 200 are formed on the first, second and third color filters 191 and 192193, respectively.

The micro lens 200 may be formed in the form of a convex lens, and may condense light to a corresponding light receiving unit 120.

In this case, as shown in FIG. 6, the microlens 200 is formed in the form of a convex lens to condense light to the light receiving unit 120, and the first lens 300 passes through the microlens 200. The light is focused again to the light receiver 120.

The microlens 200 condenses light in the form of a convex lens, and the first lens 300 in the form of a concave lens condenses the light incident to the peripheral region of the microlens 200 to the light receiving unit 120. have.

That is, although the light passes through the microlens 200, the light incident to the peripheral area of the microlens 200 is collected by the light receiver 120, thereby improving the light sensitivity of the image sensor.

This is because the first lens 300 is disposed at an edge of the micro lens 200 between the neighboring micro lenses 200, so that the light passes through the edge of the micro lens 200. By changing the furnace, the light receiving efficiency of the image sensor can be increased.

In addition, although the light passes through the microlens 200, the light incident on the peripheral area of the microlens 200 is collected by the first lens 300 to the light receiving unit 120, and thus crosstalk to adjacent pixels. (crosstalk) can be prevented.

Accordingly, the image sensor can achieve high integration, and can also improve image characteristics.

The present invention is not limited to the described embodiments and drawings, and various other embodiments are possible within the scope of the claims.

1 to 6 are cross-sectional views illustrating a method of manufacturing an image sensor according to an embodiment.

Claims (15)

A plurality of light receiving units formed for each unit pixel on a front side of the semiconductor substrate; A metal wiring layer including wiring formed on an entire surface of the semiconductor substrate; At least one first lens on the rear surface of the semiconductor substrate opposite to the front surface of the semiconductor substrate so that light is refracted by the light receiving unit; And A second lens disposed on the first lens on the rear surface of the semiconductor substrate; And the first lens is disposed between the second lens and the light receiving unit. The method of claim 1, And the first lens is disposed in a region corresponding to the different first lenses. The method of claim 1, And the first lens is disposed in a region corresponding to the different light receiving units. The method of claim 1, The first lens is formed concave with respect to the back side of the semiconductor substrate, And the second lens is formed to be convex with respect to a back side of the semiconductor substrate. The method of claim 1, And the first lens is formed by partially removing a rear surface of the semiconductor substrate. The method of claim 1, And a planarization layer disposed between the first lens and the second lens. The method of claim 6, And the planarization layer is formed of photoresist. Forming a plurality of light receiving units for each unit pixel on a front side of the semiconductor substrate; Forming a metal wiring layer including wiring on a front surface of the semiconductor substrate; Forming at least one first lens on the rear surface of the semiconductor substrate opposite to the front surface of the semiconductor substrate to be refracted by the light receiving unit; And Forming a second lens on the first lens on the rear side of the semiconductor substrate; And the first lens is disposed between the second lens and the light receiving unit. The method of claim 8, And the first lens is disposed in a region corresponding to the second lenses different from each other. The method of claim 8, The first lens of claim 1, wherein the first lens is disposed in a region corresponding to the light receiving units different from each other. The method of claim 8, The first lens is formed concave with respect to the back side of the semiconductor substrate, And the second lens is formed to be convex with respect to the back side of the semiconductor substrate. The method of claim 8, And the first lens is formed by partially removing a rear surface of the semiconductor substrate. The method of claim 8, After forming the first lens, Forming a planarization layer on the first lens; And the planarization layer is formed between the first lens and the second lens. The method of claim 13, And the planarization layer is formed of photoresist. The method of claim 8, The first lens, Forming a photoresist pattern on a rear surface of the semiconductor substrate; And And performing a wet etch process on a rear surface of the semiconductor substrate on which the photoresist pattern is formed to form a curved first lens into the rear surface of the semiconductor substrate.

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