Lens structure

A semiconductor device and a method for fabricating the semiconductor device are provided. In the method for fabricating the semiconductor device, at first, a dielectric layer is provided. Then, trenches are formed in the dielectric layer. Thereafter, the trenches are filled with spacer material to form a spacer structure in the dielectric layer for defining pixel regions. Then, lens structures are formed on the pixel regions. Each of the lens structures includes a first curved lens layer, a second curved lens layer and a curved color filter layer. The curved color filter layer is disposed on the second curved lens layer or between the first curved lens layer and the second curved lens layer.

BACKGROUND

In semiconductor technology, image sensors are used for sensing light emitted towards them to form an image. For converting various photo energy of the light into electrical signals, the image sensor includes pixels having photosensitive diodes, reset transistors, source follower transistors, pinned layer photodiodes, and/or transfer transistors. In general, the image sensor may be a complementary metal-oxide-semiconductor (CMOS) image sensor (CIS), an active-pixel sensor (APS), a passive-pixel sensor and a charged-coupled device (CCD) sensor. The above image sensor is widely used in various applications such as digital camera or mobile phone camera devices.

DETAILED DESCRIPTION

Terms used herein are only used to describe the specific embodiments, which are not used to limit the claims appended herewith. For example, unless limited otherwise, the term “one” or “the” of the single form may also represent the plural form. The terms such as “first” and “second” are used for describing various devices, areas and layers, etc., though such terms are only used for distinguishing one device, one area or one layer from another device, another area or another layer. Therefore, the first area can also be referred to as the second area without departing from the spirit of the claimed subject matter, and the others are deduced by analogy. In addition, the present disclosure may repeat reference numerals and/or letters in the various examples. This repetition is for the purpose of simplicity and clarity and does not in itself dictate a relationship between the various embodiments and/or configurations discussed. As used herein, the term “and/or” includes any and all combinations of one or more of the associated listed items.

Embodiments of the present disclosure are directed to a lens structure configured to enable light to be focused on a photodiode and a method for fabricating the lens structure. The lens structure includes a first curved lens layer, a second curved lens layer and a curved color filter layer. The light to be focused enters the first curved lens layer from an upper surface of the first curved lens layer and exit from a lower surface of the first curved lens layer. The second curved lens layer is disposed on the upper surface of the first curved lens layer. The curved color filter layer is disposed on the second curved lens layer or between the first curved lens layer and the second curved lens layer. Since the curved color filter layer is formed in the lens structure, the curved color filter layer can be designed to have a small thickness, and an image sensor using the lens structure may have increased quantum efficiency.

Referring toFIG. 1.FIG. 1is a schematic diagram showing a structure of a semiconductor device100in accordance with an embodiment of the present disclosure. The semiconductor device100includes a dielectric layer110, a spacer structure120and lens structures130. The spacer structure120is disposed in the dielectric layer110to define pixel regions PR in the dielectric layer110and the lens structures130are disposed on the pixel regions PR in a one-to-one manner. The spacer structure120is a grid to divide the dielectric layer110into the pixel regions PR. In this embodiment, each of the pixel regions PR is in a rectangular shape, and corresponds to one photodiode PD, but embodiments of the present disclosure are not limited thereto.

The lens structures130are configured to focus light on photodiodes PD, and thus the photodiodes PD convert photons of the light into electrons to generate a sensed image. The lens structures130includes a first curved lens layer132, a color filter layer134and a second curved lens layer136. The second curved lens layer136is disposed on the first curved lens layer132, and the curved color filter layer134is disposed between the first curved lens layer132and the second curved lens layer136. In this embodiment, the curved color filter layer134can be a red color filter, a blue color filter or a green color filter, but embodiments of the present disclosure are not limited thereto.

Since the curved color filter layer134and the second curved lens layer136are disposed on the first curved lens layer132, the curved color filter layer134and the second curved lens layer136conform to a surface of the first curved lens layer132. For example, the first curved lens layer132has a lower surface132aand an upper surface132b. The lower surface132acontacts the dielectric layer110, and the curved color filter layer134and the second curved lens layer136are disposed on the upper surface132bof the first curved lens layer132. In this embodiment, the first curved lens layer132is in a semi-circular shape, and thus the curved color filter layer134and the second curved lens layer136are in an arc shape. In some embodiments, the first curved lens layer132is in a triangle shape, and thus the curved color filter layer134and the second curved lens layer136have in an inverse V shape. However, embodiments of the present disclosure are not limited to the above embodiments. For example, the first curved lens layer132can be in a rectangular shape.

The first curved lens layer132, the curved color filter layer134and the second curved lens layer136are designed to have different refractive indexes to enable the light to be focused on the photodiode PD. The first curved lens layer132has a first refractive index(n1), the second curved lens layer136has a second refractive index(n2), and the curved color filter134has a third refractive index(n3), and n1>n3>n2. Therefore, when the light emitted to the lens structures130, the light is sequentially refracted by the second curved lens layer136, the curved color filter layer134and the first curved lens layer132, thereby enabling the light to be focused on the photodiode PD. For example, when the light is refracted to the first curved lens layer132by the curved color filter layer134and the second curved lens layer136, the light enters the first curved lens layer132from the upper surface132band exits from the lower surface136a, thereby being focused on the photodiode PD under the first curved lens layer132.

In this embodiment, the curved color filter layer134is included in the lens structure130and has thickness in a range from 0.01 to 0.5 micrometer (um), therefore quantum efficiency can be increased accordingly.

Referring toFIG. 2andFIG. 3toFIG. 6,FIG. 2is a flow chart showing a fabrication method200for fabricating the semiconductor device100in accordance with some embodiments of the present disclosure, andFIG. 3toFIG. 6are schematic structure diagrams of intermediate stages showing the fabrication method200of the semiconductor device100in accordance with some embodiments of the present disclosure.

In the method200, at first, operation210is performed to provide the dielectric layer110as show inFIG. 3. The dielectric layer110is a passivation layer such as silicon nitride or other suitable material, and can be formed by chemical vapor deposition (CVD), plasma enhanced CVD, sputter, and other methods known in the art. Then, operation220is performed to form trenches TR in the dielectric layer110, as shown inFIG. 4. The trenches TR are in a shape of grid and can be formed by etching the dielectric layer110. In this embodiment, the trenches TR divide the dielectric layer110into rectangular regions, but embodiments of the present disclosure are not limited thereto.

Thereafter, operation230is performed to fill the trenches TR with spacer material to form the spacer structure120in the dielectric layer110for defining the pixel regions PR in the dielectric layer110, as shown inFIG. 5. In this embodiment, the spacer material is metal, and the operation230can be performed by a deposition process including chemical vapor deposition (CVD), sputter deposition, or other techniques known and used in the art for depositing conductive materials. In some embodiments, the spacer material is Tungsten.

Then, operation240is performed form the lens structures130on the pixel regions PR in a one-to-one manner, as shown inFIG. 6. In this embodiments, the first curved lens layer132and the second curved lens layer136are made by silicon nitride or silicon oxide, but embodiments of the present disclosure are not limited thereto.

Referring toFIG. 7.FIG. 7is a schematic diagram showing a structure of a semiconductor device700in accordance with an embodiment of the present disclosure. The semiconductor device700includes the dielectric layer110, the spacer structure120and lens structures730. The spacer structure120is disposed in the dielectric layer110to define pixel regions PR in the dielectric layer110and the lens structures730are disposed on the pixel regions PR in a one-to-one manner. The spacer structure120is a grid to divide the dielectric layer110into the pixel regions PR. In this embodiment, each of the pixel regions PR is in a rectangular shape, and corresponds to one photodiode PD.

The lens structures730are similar to the lens structures130, but the difference is in that the second curved lens layer136is located between the first curved lens layer132and the curved color filter layer134, and thus the curved color filter layer134is located on the second curved lens layer136. Since the curved color filter layer134is located on the second curved lens layer136, a top surface of the curved color filter layer134is not covered by the second curved lens layer136and exposed to external environment. In this embodiment, the first curved lens layer132, the curved color filter layer134and the second curved lens layer136are designed to have different refractive indexes. The first curved lens layer132has a first refractive index(n1), the second curved lens layer136has a second refractive index(n2), and the curved color filter134has a third refractive index(n3), and n1>n2>n3.

In some embodiments, an additional protection layer can be formed on the curved color layer134to protect the curved color filter layer134, and thus the curved color filter layer134is located between the additional protection layer and the second curved lens layer136and well protected.

Referring toFIG. 8.FIG. 8is a schematic diagram showing a structure of a semiconductor device800in accordance with an embodiment of the present disclosure. The semiconductor device800includes the dielectric layer110, a spacer structure820and the lens structures130. The semiconductor device800is similar to the semiconductor device100, but the difference is in that the spacer structure820includes pinhole layers822.

The pinhole layers822are disposed in the pixel regions PR in a one-to-one manner. Each of the pinhole layers822has a pinhole PH configured to collimate the light emitted into the lens structure130. The pinhole PH is designed in accordance with the design of the lens structure130. For example, when the lens structure130is designed to enable most of the light emitted into the dielectric layer110along a main light path, the pinhole PH is designed to be located on the light path for a purpose of blocking light which is not in the main light path. Since only the light along a main light path is allowed to pass through the pinhole player822, the light emitted to the lens structure130is collimated. In this embodiment, the first curved lens layer132has a curvature radius in a range from 0.25 PS to 0.5 PS, and the pinhole PH has a size in a range from 0.1 PS to 0.9 PS, in which PS is a pixel size corresponding to each of the pixel regions PR.

To improve the performance of the collimating function of the pinhole layers822, additional layers can be formed on the pinhole layers822. In some embodiment, absorption layers can be formed on the pinhole players822to absorb the light which is not in the main light path. In some embodiments, reflection layers can be formed on the pinhole players822to reflect the light which is not in the main light path. In some embodiments, the pinhole layers822can be designed to have a curved shape. For example, each of the pinhole layers822are in an arc shape and a curvature radius thereof is in a range from 0.25 PS to 0.5 PS. It is noted that the curved e pinhole layers822are recessed towards the photodiodes under the pixel regions PR.

Further, in some embodiments, each of the pinhole layers822has two or more pinholes, since the lens structures130are designed to enable the light emitted to the lens structures130to have two or more main light paths.

Referring toFIG. 9andFIG. 10toFIG. 15,FIG. 9is a flow chart showing a fabrication method900for fabricating the semiconductor device800in accordance with some embodiments of the present disclosure, andFIG. 10toFIG. 15are schematic structure diagrams of intermediate stages showing the fabrication method900of the semiconductor device800in accordance with some embodiments of the present disclosure.

In the method900, at first, operation910is performed to provide the dielectric layer110as show inFIG. 10. The dielectric layer110is a passivation layer such as silicon nitride or other suitable material, and can be formed by chemical vapor deposition (CVD), plasma enhanced CVD, sputter, and other methods known in the art. Then, operation920is performed to form trenches TR in the dielectric layer110, as shown inFIG. 11. The trenches TR are in a shape of grid and can be formed by etching the dielectric layer110. In this embodiment, the trenches TR divide the dielectric layer110into rectangular regions, but embodiments of the present disclosure are not limited thereto.

Thereafter, operation930is performed to fill the trenches TR with spacer material1210to form a portion of the spacer structure820, as shown inFIG. 12. In the operation930, the spacer material is not only located in the trenches TR, but also located on a surface of the dielectric layer110. In this embodiment, the spacer material is metal, and the operation930can be performed by a deposition process including chemical vapor deposition (CVD), sputter deposition, or other techniques known and used in the art for depositing conductive materials. In some embodiments, the spacer material is Tungsten.

Then, operation940is performed to form openings OP in the spacer material1210to define the pixel regions PR, as shown inFIG. 13. Each of the openings OP has a wide portion and a narrow portion, and the narrow portion located under the wide portion is used as the pinhole PH. In this embodiment, the operation940is performed by etching the spacer material1210with masks.

Thereafter, operation950is performed to fill the openings OP with dielectric material, as shown inFIG. 14. The dielectric material can be such as silicon nitride or other suitable material, and formed by chemical vapor deposition (CVD), plasma enhanced CVD, sputter, and other methods known in the art.

Then, operation960is performed to form the lens structures130on the pixel regions PR in a one-to-one manner, as shown inFIG. 15. In this embodiments, the first curved lens layer132and the second curved lens layer136are made by silicon nitride or silicon oxide, but embodiments of the present disclosure are not limited thereto.

It can be understood that the pinhole PH of the pinhole layer822provides the collimating function to collimate the light emitted to the lens structure130. For example, the light emitted to the lens structure130may include light with wide incident angle, and the light with wide incident angle can be reduced by the collimating function provided by the pinhole PH of the pinhole layer822. Further, light crosstalk can be reduced by the spacer structure820.

Referring toFIG. 16.FIG. 16is a schematic diagram showing a structure of a semiconductor device1600in accordance with an embodiment of the present disclosure. The semiconductor device1600includes the dielectric layer110, a spacer structure1620and the lens structures130. The semiconductor device1600is similar to the semiconductor device100, but the difference is in that the spacer structure1620does not extend to a bottom surface of the dielectric layer110.

Referring toFIG. 17a.FIG. 17ais a schematic diagram showing a structure of a semiconductor device1700in accordance with an embodiment of the present disclosure. The semiconductor device1700includes the dielectric layer110, a spacer structure1720and lens structures1730. The spacer structure1720is disposed in the dielectric layer110to define pixel regions PR in the dielectric layer110and the lens structures1730are disposed on the pixel regions PR in a one-to-one manner. The spacer structure1720is a grid to divide the dielectric layer110into the pixel regions PR.

The lens structures1730are configured to focus light on photodiodes under the pixel regions PR, and thus the photodiodes convert photons of the light into electrons to generate a sensed image. The lens structures1730are similar to the lens structure730shown inFIG. 7, but the difference is in that the lens structures1730includes a curved color filter layer1734in an omega shape. Further, in this embodiment, intrusion portions of the spacer structure1720are disposed between the curved color filter layers1734of adjacent two lens structures1730to separate the curved color filter layers1734of the adjacent two lens structures1730.

Similarly, in this embodiment, the first curved lens layer132has a first refractive index(n1), the second curved lens layer136has a second refractive index(n2), and the curved color filter1734has a third refractive index(n3), and n1>n2>n3. Therefore, when the light emitted to the lens structures1730, the light is sequentially refracted by the curved color filter layer1734, the second curved lens layer136and the first curved lens layer132, thereby enabling the light to be focused on the photodiode. In some embodiments, an additional protection layer can be formed on the curved color filter layer1734to protect the curved color filter layer1734, and thus the curved color filter layer134is located between the additional protection layer and the second curved lens layer136and well protected.

In addition, in some embodiments, the curved color filter layer1734of the lens structure1730can be disposed between the first curved lens layer132and the second curved lens layer136, as shown inFIG. 17b. in this case, a relationship between the first refractive index n1of the first curved lens layer132, the second refractive index n2of the second curved lens layer136and the third refractive index n3of the curved color filter layer1734is n1>n3>n2.

Referring toFIG. 18.FIG. 18is a schematic diagram showing a structure of a semiconductor device1800in accordance with an embodiment of the present disclosure. The semiconductor device1800includes the dielectric layer110, a spacer structure1820and the lens structures1730. The spacer structure1820is similar to the spacer structure820of the semiconductor device800shown inFIG. 8. For example, the spacer structure1820includes pinhole layers1822.

The pinhole layers1822are disposed in the pixel regions PR in a one-to-one manner. Each of the pinhole layers1822has a pinhole PH configured to collimate the light emitted into the lens structure1730. The pinhole PH is designed in accordance with the design of the lens structure1730. For example, when the lens structure1730is designed to enable most of the light emitted into the dielectric layer110along a main light path, the pinhole PH is designed to be located on the light path for a purpose of blocking light which is not in the main light path. Since only the light along a main light path is allowed to pass through the pinhole player1822, the light emitted to the lens structure1730is collimated.

To improve the performance of the collimating function of the pinhole layers1822, additional layers can be formed on the pinhole layers1822. In some embodiment, absorption layers can be formed on the pinhole players1822to absorb the light which is not in the main light path. In some embodiments, reflection layers can be formed on the pinhole players1822to reflect the light which is not in the main light path. In some embodiments, the pinhole layers1822can be designed to have a curved shape. For example, each of the pinhole layers1822are in an arc shape and a curvature radius thereof is in a range from 0.25 PS to 0.5 PS. It is noted that the curved e pinhole layers1822are recessed towards the photodiodes under the pixel regions PR.

Further, in some embodiments, each of the pinhole layers1822has two or more pinholes, since the lens structures1730are designed to enable the light emitted to the lens structures1730to have two or more main light paths.

It can be understood that some embodiments of the present disclosure provide the lens structure having a curved color filter layer. Since the curved color filter layer is a portion of the lens structure and the curved color filter layer has a small thickness, quantum efficiency can be increased accordingly. Further, it can be understood that some embodiments of the present disclosure provide a spacer structure having pinhole layers. The pinhole layer provide light collimation function to collimate the light emitted to the lens structure, and thus light crosstalk and light with wide incident angle can be reduced.

It is noted that a geometry type of the lens structure and the pinhole layer is not limited to the above embodiments of present disclosure. The lens structure can be in a rectangle, triangle or other geometry type. Similarly, the pinhole layer can be in a rectangle, triangle or other geometry type.

In accordance with an embodiment of the present disclosure, the present disclosure discloses a lens structure configured to focus light on a photodiode. The semiconductor device includes a first curved lens layer, a second curved lens layer and a curved color filter layer. Regarding the first curved lens layer, the light enters the first curved lens layer from an upper surface of the first curved lens layer and exits from a lower surface of the first curved lens layer. The second curved lens layer is disposed on the upper surface of the first curved lens layer. The curved color filter layer is disposed on the second curved lens layer or between the first curved lens layer and the second curved lens layer.

In accordance with another embodiment of the present disclosure, the present disclosure discloses a semiconductor device configured to focus light on photodiodes. The semiconductor device includes a dielectric layer, a spacer structure and lens structures. The spacer structure is disposed in the dielectric layer to define pixel regions in the dielectric layer. The lens structures are disposed on the pixel regions in a one-to-one manner to focus light on the photodiodes. Each of the lens structure includes a first curved lens layer, a second curved lens layer and a curved color filter layer. Regarding the first curved lens layer, the light enters the first curved lens layer from an upper surface of the first curved lens layer and exits from a lower surface of the first curved lens layer. The second curved lens layer is disposed on the upper surface of the first curved lens layer. The curved color filter layer is disposed on the second curved lens layer or between the first curved lens layer and the second curved lens layer.

In accordance with another embodiment of the present disclosure, the present disclosure discloses a method for fabricating a semiconductor device. In the fabrication method, at first, a dielectric layer is provided. Then, trenches are formed in the dielectric layer. Thereafter, the trenches are filled with spacer material to form a spacer structure in the dielectric layer for defining pixel regions in the dielectric layer. Then, lens structures are formed on the pixel regions in a one-to-one manner. Each of the lens structures includes a first curved lens layer, a second curved lens layer and a curved color filter layer. Regarding the first curved lens layer, the light enters the first curved lens layer from an upper surface of the first curved lens layer and exits from a lower surface of the first curved lens layer. The second curved lens layer is disposed on the upper surface of the first curved lens layer. The curved color filter layer is disposed on the second curved lens layer or between the first curved lens layer and the second curved lens layer.