KR20090098003A - Image sensor and manufacturing method of image sensor - Google Patents

Abstract

An image sensor and a manufacturing method thereof are provided to minimize scattering of a light due to a metal structure on an insulation layer by regularly maintaining a focus position and a focus size according to a unit pixel of an image sensor. A plurality of photo diodes is formed on a semiconductor substrate(100). An insulation layer(200) is formed on the semiconductor substrate. A passivation layer(300) is formed on the insulation layer, and has a curved surface toward a top part. A plurality of micro lenses(700) is formed on the passivation layer corresponding to a photo diode region. A color filter layer(500) is formed on the passivation layer. A flattening passivation layer(600) is formed on the color filter layer.

Description

Image sensor and manufacturing method of image sensor

Embodiments disclose an image sensor and a method of manufacturing the image sensor.

An image sensor is a semiconductor device that converts an optical image into an electrical signal, and includes a charge coupled device (CCD) and a complementary metal oxide silicon (CMOS) image sensor. Separated by.

The CMOS image sensor uses CMOS technology using a control circuit, a signal processing circuit, and the like as peripheral circuits to form MOS transistors corresponding to the number of unit pixels on a semiconductor substrate, thereby outputting each unit pixel by MOS transistors. It is a device that employs a switching method that detects sequentially.

1 is a side cross-sectional view schematically illustrating a structure of an external lens module equipped with an image sensor, and FIG. 2 is a view schematically illustrating a case in which light is vertically incident on the image sensor mounted on the external lens module. FIG. 2 is a diagram schematically illustrating a case in which light is obliquely incident on an image sensor mounted on an external lens module.

As shown in FIG. 1, when an image sensor is used in a digital camera, a camera phone, or the like, the external lens 10 is coupled to the housing 20, and the image sensor 30 is mounted on a focal plane of the external lens 10. .

As the light incident angle to the external lens 10 is changed, the point where the focus is made on the image sensor 30 is different. In FIG. 1, the light path "A" is a light incident perpendicularly to the external lens 10. In this case, that is, the case has an incident angle of 0 degrees, and the optical paths "B", "C", and "D" have the incident angles of 7 degrees, 14 degrees, and 21 degrees, respectively.

FIG. 2 is an enlarged view of the unit pixel area of the image sensor 30 in focus in the case of the optical path "A", and FIG. 3 is a unit pixel area of the image sensor 30 in focus in the case of the optical path "D". It is shown to expand.

As shown in FIGS. 2 and 3, the microlenses 31 having the same spherical radius have the same focal length with respect to light incident in various squares through the external lens 10, and according to the unit pixel area of the image sensor. The size of the focus is different, there is a problem that the position of the focus is different according to the path of light.

Therefore, when a profile such as the thickness and spherical radius of the microlens is designed on the assumption of vertical incidence, such as the unit pixel positioned at the center of the image sensor, the unit pixel positioned outside the image sensor is positioned on the photodiode 36. It becomes difficult to focus precisely.

In this case, there is a problem that the image information sensed by the image sensor 30 is changed or the sensitivity of the photodiode 36 is lowered.

In addition, the light transmitted through the microlens 31 is incident on the photodiode 36 on the substrate 35 through the planarization protection layer 32, the color filter layer 33, and the insulating layer 34, as shown in FIG. 3. If the light is obliquely progressed, there is a risk of scattering due to metal wiring, contact holes, etc. formed on the insulating layer 34.

In other words, the risk of scattering due to metal wirings increases as the unit pixels formed on the outer side of the image sensor 30 become larger, and therefore, the metal wirings of the unit pixel region (FIG. 2) located in the center of the chip and the unit pixel region (FIG. The metal wires in 3) shall be designed in different locations.

However, in this case, it is not easy to find and arrange the optimum position of the metal wiring, and there are problems such as complicated process.

According to the embodiment, even if the light incident angle is different, the position where the focus is made and the size of the focus can be made constant according to the unit pixel of the image sensor, and the image sensor and the image sensor which can accurately focus on the photodiode for each pixel are manufactured. Provide a method.

In addition, the embodiment provides an image sensor and a method of manufacturing the image sensor that can minimize the risk of light scattered by the metal structure on the insulating layer even if various light paths are formed according to the light incident angle.

An image sensor according to an embodiment includes a semiconductor substrate on which a plurality of photodiodes are formed; An insulating layer formed on the semiconductor substrate; A protective layer formed on the insulating layer and curved upward; It includes a plurality of micro lenses formed on the protective layer corresponding to the photodiode region.

In another embodiment, a method of manufacturing an image sensor includes forming an insulating layer and a protective layer on a semiconductor substrate; Forming a resist layer having a curved surface upward on the protective layer; Performing an etch back process to remove the resist layer, and forming a protective layer to which the curved structure of the resist layer is transferred; And forming a plurality of micro lenses on the protective layer on which the curved structure is transferred.

According to the embodiment, the following effects are obtained.

First, when light incident angles are different, there is an effect that the size of the focusing position and the focus can be made constant according to the unit pixel of the image sensor.

Second, even if various light paths are formed according to the light incident angle, there is an effect of minimizing the risk of light scattering by the metal structure on the insulating layer.

Third, since accurate focusing can be achieved on the photodiodes for each unit pixel, the phenomenon that the image information sensed by the image sensor is changed or the sensitivity of the photodiode is reduced can be minimized.

Fourth, in order to minimize the light scattering phenomenon, it is not necessary to arrange the position of the metal structure on the insulating layer differently for each unit pixel, thus simplifying the process and improving the process efficiency.

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

4 is a side cross-sectional view illustrating an image sensor structure after a resist layer 400 is formed according to an embodiment, and FIG. 5 is a form of a photo mask F used to form the resist layer 400 according to an embodiment. Top view showing the.

Referring to FIG. 4, an insulating layer 200 is formed on the semiconductor substrate 100, and a passivation layer 300 is formed on the insulating layer 200.

For example, the protective layer 300 may be formed of silicon nitride and have a flat state.

When the protective layer 300 is formed, a resist material is applied thereon to a predetermined thickness to deposit a flat resist layer, and an exposure process is performed using the photo mask F shown in FIG. 5.

The flat resist layer may be made of a photosensitive material similar to the planarization protective layer (see FIG. 8; 600) to be formed later, and a negative type is used in the embodiment.

Thereafter, the development process is performed on the flat resist layer, thereby completing a convex resist layer 400 as shown in FIG. 4.

Before describing the process of forming the resist layer 400 in detail, the structure of the image sensor according to the embodiment shown in FIG. 4 will be briefly described as follows.

FIG. 6 is an enlarged side cross-sectional view of part “A” of FIG. 4.

The image sensor according to the embodiment of FIG. 6 is a state before the color filter layer (see FIG. 8; 500), the planarization protection layer 600, and the microlens (see FIG. 8; 700) is formed, and the semiconductor substrate 100 is formed. A plurality of photodiodes 110 are formed therein.

The color filter layer 500 and the microlens 700 are differentially formed so as to vertically correspond to the photodiode 110, and the photodiode 110 region of the semiconductor substrate 100 forms a unit pixel of the image sensor.

An insulating layer 200 having a plurality of stacked structures is formed on the semiconductor substrate 100, and the insulating layer 200 includes contact plugs, metal wires, and the like.

Referring to FIG. 6, the insulating layer may be formed of a first insulating layer 210, a second insulating layer 220, and a third insulating layer 230.

As described above, the photodiode 110 constitutes one pixel (Pixel, P) of the plurality of pixels constituting the image sensor, and controls the transfer and output of the charges stored in the photodiode 110, etc. Is connected to a transistor (not shown).

For example, the transistor may be formed in a region of the semiconductor substrate 100 between the photodiodes 110 through a semiconductor process, and may include a transfer transistor Tx, a reset transistor Rx, a select transistor Sx, and an access transistor Ax. ) And the like.

In addition, contact plugs, metal wires, etc. on the insulating layer 200 are formed in the insulating layer 200 corresponding to the region between the photodiodes 110, and thus are incident to the photodiode 110 from the upper side. Do not disturb the furnace.

Since the image sensor according to the embodiment deals with the technology related to the optical path of light, a detailed description of the semiconductor structure and operation will be omitted.

On the other hand, the photo mask F illustrated in FIG. 5 has a structure in which the transmittance gradually changes from the center portion toward the end portion. For example, the center portion of the photo mask F has a transmittance of 100% and toward the end portion. It may be gradually formed to be opaque so that the end portion may have a transmittance of 0%.

For example, the photo mask F may be manufactured in a manner similar to a filter having a color tone band structure of gray tones.

The rate of change of transmittance on the photo mask F area is adjusted in proportion to the curvature of the resist layer 400.

Since the resist material is a transparent negative type having a transmittance of 95% or more, the removal rate during development may be controlled according to the exposure energy.

Therefore, when the exposure process is performed using the photo mask F, the flat resist layer may gradually receive weaker exposure energy from the center toward the end. Thus, the flat resist layer has different resistance to the developer from the center to the end.

That is, according to the embodiment, the center portion of the flat resist layer is firmly fixed and is less likely to be lost by the developer, and the end portion is relatively soft and is lost most.

Accordingly, the flat resist layer may have a convex shape toward the top, as shown in FIG. 4 after the exposure and development processes.

7 is a side cross-sectional view showing the image sensor structure after the protective layer 300 according to the embodiment is completed.

Through this process, when the resist layer 400 is formed, the photo mask F is removed and an etch back process having anisotropic etching characteristics is performed.

The etch back process is performed to the predetermined depth of the protective layer 300 after the resist layer 400 is removed, the convex shape of the resist layer 400 is transferred to the protective layer 300.

Therefore, the protective layer 300 may have the same curved shape as the resist layer 400.

8 is a side cross-sectional view showing a form after the image sensor according to the embodiment is completed.

Thereafter, the color filter layer 500 is formed on the passivation layer 300, and the planarization protection layer 600 is formed thereon.

The color filter layer 500 may be formed of a plurality of color filters having different colors according to a unit pixel area, that is, the area of the photodiode 110.

In addition, the planarization protection layer 600 may be formed using a resist material.

Next, a plurality of micro lenses 700 are formed on the planarization protection layer 600 corresponding to the photodiode 110.

Therefore, the microlens 700 may be arranged to have a convex surface toward the end from the center of the chip of the image sensor as shown in FIG.

When the protective layer 300 is formed of nitride, the refractive index is about 2.0, and is larger than the refractive coefficients of the color filter layer 500, the planarization protective layer 600, and the microlens 700 forming the upper layer. For reference, the refractive index of the micro lens 700 is about 1.6.

As described above, according to the exemplary embodiment, by maximizing the arrangement characteristics and the interlayer refractive characteristics of the microlens 700, the light having different incidence angles is perpendicular to the photodiode 110 via the microlens 700. Will be able to maintain.

Accordingly, the position at which focus is achieved and the size of the focus may be constant according to the unit pixel of the image sensor regardless of the incident angle, and light may be prevented from being scattered by the metal structure on the insulating layer 200.

In addition, even when the microlenses are designed based on the center of the image sensor, the same focal plane may be formed at the end of the image sensor, thereby preventing the light from being distorted at the edge of the sensor chip.

The present invention has been described above with reference to the preferred embodiments, which are merely examples and are not intended to limit the present invention, and those skilled in the art to which the present invention pertains do not depart from the essential characteristics of the present invention. It will be appreciated that various modifications and applications are not possible that are not illustrated above. For example, each component specifically shown in the embodiment of the present invention can be modified. And differences relating to such modifications and applications will have to be construed as being included in the scope of the invention defined in the appended claims.

1 is a side cross-sectional view schematically showing the structure of an external lens module equipped with an image sensor.

2 is a view schematically illustrating a case in which light is vertically incident on an image sensor mounted to an external lens module.

3 is a view schematically illustrating a case in which light is obliquely incident on an image sensor mounted to an external lens module.

4 is a side cross-sectional view showing the image sensor structure after the resist layer is formed according to the embodiment.

Fig. 5 is a top view showing the form of a photo mask used to form a resist layer according to the embodiment.

FIG. 6 is an enlarged side cross-sectional view of portion “A” of FIG. 4; FIG.

7 is a side cross-sectional view showing the image sensor structure after the protective layer according to the embodiment is completed.

8 is a side sectional view showing a form after the image sensor according to the embodiment is completed;

Claims (12)

A semiconductor substrate on which a plurality of photodiodes are formed; An insulating layer formed on the semiconductor substrate; A protective layer formed on the insulating layer and curved upward; And a plurality of micro lenses formed on the protective layer corresponding to the photodiode region. The method of claim 1, A color filter layer formed on the protective layer; And a planarization protection layer formed on the color filter layer. The method of claim 1, wherein the protective layer Image sensor comprising a silicon nitride material. The method of claim 2, wherein the protective layer And a refractive index greater than that of the microlens, the color filter layer, and the planarization protective layer. Forming an insulating layer and a protective layer on the semiconductor substrate; Forming a resist layer having a curved surface upward on the protective layer; Performing an etch back process to remove the resist layer, and forming a protective layer to which the curved structure of the resist layer is transferred; And forming a plurality of micro lenses on the protective layer on which the curved structure is transferred. The method of claim 5, wherein the forming of the curved resist layer is performed. Forming a flat resist layer on the protective layer; Exposing the flat resist layer using a photomask with a gradually changing transmittance from the center to the end; Developing the exposed flat resist layer to form the curved resist layer; And removing the photo mask. The method of claim 6, The rate of change of the transmittance of the photo mask is adjusted in proportion to the curvature of the resist layer constituting the curved surface. The method of claim 6, The transmittance of the photo mask is gradually lowered from the center toward the end. The method of claim 5, wherein the protective layer A method of manufacturing an image sensor comprising a silicon nitride material. The method of claim 5, wherein the resist layer A method of manufacturing an image sensor comprising a negative type photosensitive material. The method of claim 5, wherein the forming of the plurality of micro lenses Forming a color filter layer on the protective layer on which the curved structure is transferred; Forming a planarization protective layer on the color filter layer; And the plurality of micro lenses are formed on the planarization protection layer. The method of claim 11, wherein the protective layer And a refractive index greater than that of the micro lens, the color filter layer, and the planarization protective layer.

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