CN101211936A - Image sensor and manufacturing method thereof - Google Patents

Abstract

An image sensor and method for fabricating an image sensor are provided. The image sensor includes a substrate and a microlens array in a checkerboard pattern wherein the microlens array comprises a first set of microlenses and a second set of microlenses. In some embodiments, the first set of microlenses and the second set of microlenses involve alternating hydrophilic and hydrophobic microlenses. The image sensor is capable of inhibiting the generation of a lens bridge between neighboring pixels of a microlens and forming a microlens having a zero gap to improve the characteristics of a device.

Description

Image sensor and manufacturing method thereof

technical field

The present invention relates to sensors, and more particularly to image sensors and methods of manufacturing the same.

Background technique

Image sensors are semiconductor devices that convert optical images into electrical signals. The manufacturing process is very important in determining the performance of an image sensor. Two important processes are the formation process of color filter array (CFA) and microlens (ML).

In the microlens forming process, gaps are generally formed between adjacent microlenses. These gaps result in loss of sensor performance. Several studies and simulations have demonstrated that the light sensitivity of an image sensor can be increased by more than 15% when the gap is small.

A typical microlens formation process in the prior art uses an organic material in the form of a photoresist (PR), where thermal reflow using thermal energy is possible. Specifically, first, a pattern is formed at a position where a lens is to be provided by performing a photolithography method using a photoresist material. Next, thermal energy is applied to the above-mentioned material to reflow it, thereby forming a spherical curve; after that, it is cooled to complete the manufacture of the lens.

In a typical microlens forming process, the width of the gap between the microlenses is determined by a pattern formed by photolithography before reflowing the material. Therefore, due to current photolithographic resolution limitations, the minimum gap width is usually limited to about 50nm, and when the material is reflowed so that the gap between microlenses is narrower than 50nm, adjacent microlenses may bond during the reflow process. Together, the possibility of forming a lens bridge arises. Thus, current microlens formation processes cannot form microlenses with completely zero gaps.

Lens bridges arise due to mixing phenomena that exist when hydrophobic materials come into contact with each other, eg, when a hydrophobic photoresist and an adjacent hydrophobic lens come into contact with each other. This phenomenon is similar to what happens when two water droplets on a glass window come into contact with each other and join together. As shown in FIG. 1, because the photoresist for forming a lens has a predetermined level of viscosity in a fluid state, a gentle bend is generally formed between the photoresist 1 for forming a lens, by This creates a lens bridge.

Contents of the invention

The present invention provides an image sensor and a manufacturing method thereof capable of suppressing lens bridges from being generated between microlenses of adjacent pixels and forming microlenses with a zero gap, thereby improving device characteristics.

The image sensor of the present invention includes: a microlens array formed on a substrate and including a first group of microlenses and a second group of microlenses; wherein the first group of microlenses and the second group of microlenses are arranged in a checkerboard pattern.

The method for manufacturing an image sensor of the present invention comprises the following steps: forming a microlens array on a substrate, the microlens array comprising a first group of microlenses and a second group of microlenses; wherein the first group of microlenses and the second group of microlenses Arrange in a checkerboard pattern.

An image sensor according to an embodiment of the present invention of the above subject matter includes: a lower structure having a photodiode; a passivation layer formed over the lower structure; and a microlens array formed on the passivation layer and having a The first set of microlenses and the second set of microlenses made of hydrophobic material.

According to an embodiment of the present invention, a method for manufacturing an image sensor includes: forming a lower structure having a photodiode; forming a passivation layer on the lower structure; forming a planarization layer on the passivation layer; forming a patterned first layer on the planarization layer. A photosensitive film; forming sacrificial microlenses by heat treatment of the first photosensitive film; forming a first group of microlenses on the planarization layer through an etching process, wherein the shape of the sacrificial microlenses is transcribed to the first group of microlenses; A patterned second photosensitive film is formed in the gap between the microlenses of the first group of microlenses; and a microlens array consisting of the first group of microlenses and the second group of microlenses is formed, wherein the second group of microlenses is composed The second photosensitive film is formed by heat treatment.

An image sensor according to another embodiment of the present invention includes: a planarization layer formed to be patterned into first and second regions, and formed such that an upper surface of the second region protrudes more than an upper surface of the first region; The lens array has a first group of microlenses formed on the first area and a second group of lenses formed on the second area.

An image sensor according to still another embodiment of the present invention includes: a hydrophilic layer; a planarization layer formed to be patterned into first and second regions located on the hydrophilic layer, the first region being formed so that the hydrophilic layer is exposed, And the second region is formed such that the hydrophilic layer is not exposed; and a microlens array having a first group of microlenses formed on the first region and a second group of microlenses formed on the second region.

A method of manufacturing an image sensor according to an embodiment of the present invention includes: forming a planarization layer, dividing the planarization layer into a first region and a second region by patterning, and the upper surface of the second region is larger than the upper surface of the first region more prominent; and forming a microlens array having first and second sets of microlenses by forming a first set of microlenses on the first area and a second set of microlenses on the second area.

A method of manufacturing an image sensor according to another embodiment of the present invention includes: forming a hydrophilic layer; forming a planarization layer, and patterning the planarization layer by dividing the planarization layer into first and second regions on the hydrophilic layer, the first The region is formed so that the hydrophilic layer is exposed, and the second region is formed so that the hydrophilic layer is not exposed; and forming a microlens array having a first group of microlenses formed on the first region and A second group of microlenses formed on the second area.

The invention can suppress lens bridges between adjacent pixels in the microlens array, and form a microlens array with zero gap, thereby improving device characteristics.

Description of drawings

FIG. 1 shows a lens bridge produced by a manufacturing method of a prior art image sensor.

2 to 7 are diagrams illustrating a method of manufacturing an image sensor according to an embodiment of the present invention.

Fig. 8 shows an image sensor according to an embodiment of the present invention, showing adjacent microlenses without lens bridges in a magnified manner.

9 to 12 are diagrams illustrating a method of manufacturing an image sensor according to an embodiment of the present invention.

13 to 17 are diagrams illustrating a method of manufacturing an image sensor according to an embodiment of the present invention.

Detailed ways

In this specification, when referring to a layer, region, pattern or structure, when the term "on" or "over" is used, it should be understood that the layer, region, pattern or structure is directly located on another layer or structure, or is also There are intermediate layers, regions, patterns or structures. In this specification, when referring to a layer, region, pattern or structure, when the term "under" or "under" is used, it should be understood that the layer, region, pattern or structure is located directly under another layer or structure, or is also There are intermediate layers, regions, patterns or structures.

Refer to Figure 2. In an embodiment of the manufacturing method of the present invention, the lower layer 3 is formed before forming the microlens (ML) pattern. The lower layer 3 may be etched by a dry etching method such as reactive ion etching (RIE). In many embodiments, the lower layer 3 is formed from a hydrophilic material.

In a particular embodiment, the lower layer 3 serves as a planarization layer for the color filter array. In an embodiment, below the color filter array includes: a lower structure having photodiodes and a passivation layer formed on the lower structure. In embodiments where the image sensor is designed without the need for an upper color filter array, the lower layer 3 can be used as an additional layer.

In many embodiments, the material forming the planarization layer can transmit visible light well and thus has an imaginary reflective index (k˜0). In a typical image sensor, a color filter array is usually formed on an upper portion of the image sensor, and a planarization layer is formed of a hydrophobic material. However, in certain embodiments of the present invention, a hydrophobic material is formed below the microlens array.

For example, a low temperature oxide (LTO) such as tetraethyl orthosilicate (TEOS) can be used. In an embodiment using TEOS material, a low temperature oxidation (LTO) method capable of deposition at a temperature of about 220° C. is employed.

In embodiments incorporating TEOS, due to the conformal properties of TEOS, the step height difference of the color filter array is not completely eliminated after deposition. However, when deposited, TEOS has excellent coverage. Therefore, TEOS can play an important role in reducing the height variation at the step interface between adjacent pixels.

In embodiments where the image sensor is designed without an upper color filter array, a planarized passivation layer is formed below the microlens array, enabling chemical vapor deposition (CVD) to form the TEOS layer. A layer incorporating TEOS can additionally be used for a set of microlenses.

TEOS has a zero-valued virtual reflectance (RI) at visible light wavelengths, and meanwhile, it can be etched by a dry etching method. Therefore, TEOS can be used as the lower layer of the microlens array.

In many embodiments, the lower layer 3 used to form the microlens array is thicker than typical layers used to form microlenses. Since the photosensitive film is formed in the form of a microlens array by means of a dry etching method and transferred to the lower layer 3, the material thickness of the lower layer 3 should be considered. TEOS has a real reflective index (RI) value of about 1.4 at visible wavelengths. Therefore, assuming that the distance from the microlens array to the lower photodiode is approximately 3 to 4 microns, the thickness of the lower layer 3 may be about 500 nm.

As shown in FIG. 3 , in many embodiments, after forming the lower layer 3 just thicker than the thickness of the microlens, a photosensitive film 5 is formed and patterned by photolithography. Not all pixels are patterned, but every other pixel is patterned in a checkerboard fashion, ie, there is no pattern in adjacent pixels.

Referring to FIG. 4, after forming the pattern of the photosensitive film in the form of a checkerboard, the photosensitive film is formed again into sacrificial microlenses 5a by a thermal reflow method.

Referring to FIG. 5, after the sacrificial microlens 5a is completed, the material provided as the lower layer 3 is bulk etched by a dry etching method. In one embodiment, the etching is a reactive ion etching (RIE) process. A first group of microlenses 3b transcribing the shape of the sacrificial microlenses is thus formed. The first group of microlenses 3b are formed every other pixel on the lower layer 3a, arranged in a checkerboard shape. Accordingly, in many embodiments, the first set of microlenses 3b is formed of a hydrophilic material. For example, the material of the lower layer 3 is TEOS.

As shown in FIG. 6 , at the pixel area between the first group of microlenses 3 b formed of hydrophilic material, a photosensitive film 7 arranged in a checkerboard shape can be formed by photolithography. In an embodiment, the photosensitive film 7 can be formed of a photosensitive hydrophobic material. In the photolithography process, a photomask may be used by shifting at a pixel pitch vertically and horizontally.

Referring to FIG. 7, in many embodiments, the second group of microlenses 7a is formed by a heat treatment process such as thermal reflow. The second set of microlenses 7a can be formed from a hydrophobic material. Correspondingly, a microlens array including the first group of microlenses 3b and the second group of microlenses 7a can be formed.

As shown in FIG. 8, since the pixel microlenses are alternately formed of hydrophilic and hydrophobic materials respectively, no bridge is formed between the microlenses of one pixel and the microlenses of adjacent pixels.

The principle of not forming microlens bridges is similar to the principle that oil and water droplets do not mix and form a distinct interface when the oil drop is placed above water. Through the manufacturing method of the image sensor according to the embodiment of the present invention, the pattern size of the first group of microlenses 3b formed by hydrophilic materials and the second group of microlenses 7a formed by hydrophobic materials can be adjusted, so it is possible to achieve a completely zero-gap microlens array.

In many embodiments, the real reflectance (RI) values of the first set of microlenses 3b and the second set of microlenses 7a are different. Therefore, the thickness of the microlenses can be adjusted based on the materials of the first and second groups of microlenses. In certain embodiments, the focus distances of the first and second sets of microlenses may be the same.

In an embodiment of a complementary metal-oxide-semiconductor (CMOS) type image sensor, the distance from the microlens to the photodiode is about 3 to 4 microns, and TEOS with a real reflectance (RI) value of about 1.4 is used as the first The material of a set of microlenses, and the thickness of the first set of microlenses is about 450 nm. In an embodiment, the second set of microlenses is formed from a photosensitive film having a real reflectance (RI) value of 1.6 to 1.7 at visible light wavelengths, and the thickness of the second set of microlenses is about 350 nm.

The image sensor and manufacturing method according to the embodiments of the present invention have advantages of suppressing lens bridges from being generated between adjacent pixels of a microlens array and forming a microlens array with zero gap, thereby improving device characteristics.

9 to 12 are diagrams illustrating an image sensor manufacturing method according to another embodiment.

Referring to FIG. 9 , a planarization layer 11 may be formed.

The planarization layer 11 may be formed of a material capable of being patterned by a photolithography process, such as a photosensitive material. In one embodiment, the planarization layer 11 is formed on the color filter array. In alternative embodiments that do not include a color filter array, planarization layer 11 may be formed over the passivation layer.

The material forming the planarization layer 11 can transmit visible light well, so it has a virtual reflectance (k˜0). In an embodiment including a color filter array, a process in a mosaic scheme is used for the image sensor to form the planarization layer 11 . In alternative embodiments that do not include a color filter array, the planarization layer 11 may be formed directly on the passivation layer.

As shown in FIG. 10, in many embodiments, the passivation layer 11 is divided into a first region and a second region, and these regions are patterned so that the upper surface of the second region protrudes more than the upper surface of the first region. .

In many embodiments, the patterning of the planarization layer 11 is performed by photolithography.

In one embodiment, the patterned first and second regions are formed as squares with pixel pitch dimensions. These squares can be patterned into a checkerboard arrangement.

Referring to FIG. 11, a first photosensitive film 13 for forming a microlens array is formed on the first area of the patterned planarization layer 11a, and a first photosensitive film 13 for forming a microlens array is formed on a second area of the patterned planarization layer 11a. The second photosensitive film 15 of the lens array. In a particular embodiment, the first photosensitive film 13 and the second photosensitive film 15 are each formed of a hydrophobic material. In one embodiment, each of the first photosensitive film 13 and the second photosensitive film 15 is formed of a hydrophilic material. In an alternative embodiment, the first photosensitive film 13 is formed from a hydrophilic material and the second photosensitive film 15 is formed from a hydrophobic material.

As shown in FIG. 12, in many embodiments, the microlens array is formed by performing a heat treatment. In one embodiment, the heat treatment is thermal reflow.

In many embodiments, a first set of microlenses 13a is formed on the first region 13, and a second set of microlenses 15a is formed on the second region 15, thereby forming a lens having first and second sets of microlenses (13a, respectively). and 15a) microlens array.

In many embodiments, protrusions and depressions are formed on the lower layer between microlenses of adjacent pixels to suppress generation of lens bridges.

Repeated protrusions and depressions in each pixel can be formed using, for example, a planarization layer made of a photosensitive material on a layer below the microlenses, so that lens bridges can be effectively suppressed during thermal reflow processes.

In a particular embodiment, a lower structure having a photodiode is formed on a lower layer of the planarization layer. In one embodiment, a color filter array is formed on the lower structure.

13 to 17 are diagrams illustrating a method of manufacturing an image sensor according to another embodiment.

Referring to FIG. 13 , a hydrophilic layer 21 may be formed.

The hydrophilic layer 21 can be formed of a low temperature oxidation (LTO) material. For example, the hydrophilic layer 21 can be formed of TEOS material.

In one embodiment, a lower structure with photodiodes is formed under the hydrophilic layer 21 . In a further embodiment, a color filter array is formed on the lower structure below the hydrophilic layer 21 .

Referring to FIGS. 14 and 15 , a planarization layer 23 may be formed over the hydrophilic layer 21 and a patterning process may be performed on the planarization layer 23 .

In certain embodiments, the planarization layer 23 can be divided into a first region and a second region on the hydrophilic layer 21 . In one embodiment, the first region is formed to expose the hydrophilic layer 21 , and the second region is formed not to expose the hydrophilic layer 21 . The patterned planarization layer 23 is formed in a subsequent heat treatment process without reflow.

Referring to FIG. 16, a first photosensitive film 25 for forming a microlens array is formed on the first region where the hydrophilic layer 21 is exposed, and a film for forming a microlens is formed on a second region where the hydrophilic layer 21 is not exposed. The second photosensitive film 27 of the array. In one embodiment, each of the first photosensitive film 25 and the second photosensitive film 27 is formed of a hydrophobic material. In an alternative embodiment, the first photosensitive film 25 and the second photosensitive film 27 are each formed of a hydrophilic material. In other embodiments, the first photosensitive film 25 is formed of a hydrophilic material, and the second photosensitive film 27 is formed of a hydrophobic material.

As shown in FIG. 17, in certain embodiments, the microlens array is formed by performing a heat treatment. In one embodiment, the heat treatment is thermal reflow.

In a particular embodiment, a first set of microlenses 25a is formed on a first area and a second set of microlenses 27a is formed on a second area, thereby forming a lens having first and second sets of microlenses (25a and 27a, respectively). ) microlens array. In embodiments where the first and second sets of microlenses are formed from a hydrophobic material, the base width of each microlens in the first set of microlenses 25a is greater than that of each of the second set of microlenses 27a. The base width of the lens. For the case where the second photosensitive film 27 reflows faster than the first photosensitive film 25, this adjustment of the reference width can be performed.

In many embodiments, protrusions and depressions are formed on the lower layer between microlenses of adjacent pixels to suppress lens bridges during thermal reflow processes.

In one embodiment, the hydrophilic layer 21 is formed under the planarization layer 23 , so the concave portions of the protrusions and depressions have the hydrophilic property of the hydrophilic layer 21 , and the protruding portions thereof have the hydrophobic property of the planarization layer 23 . Therefore, when a hydrophilic surface and a hydrophobic surface are formed to form microlenses, the hydrophilic/hydrophobic surface is repeated every other pixel in a checkerboard arrangement. When thermally reflowing a photosensitive film of a hydrophobic material, the protrusions and depressions formed on the lower layer control the force of reflow, and the hydrophilic/hydrophobic surface controls the surface tension so that lens bridge generation can be suppressed.

Any reference in the specification to "one embodiment," "an embodiment," "exemplary embodiment," etc., means that a particular feature, structure, or characteristic described in connection with the embodiment is included in at least one aspect of the present invention. Examples. The occurrences of such phrases in various places in the specification are not necessarily all referring to the same embodiment. Furthermore, when a particular feature, structure, or characteristic is described in conjunction with any embodiment, it is considered within the scope of those skilled in the art to implement that feature, structure, or characteristic in combination with other embodiments.

Although the invention has been described in conjunction with a number of exemplary embodiments thereof, it should be understood that numerous other changes and embodiments can be devised by those skilled in the art that will fall within the spirit and scope of the principles of this disclosure. within. In particular, various variations and modifications may be made in the arrangement of components and/or accessories in combination arrangements within the scope of the description, drawings and appended claims. In addition to changes and modifications in components and/or arrangements, other alternative applications will be apparent to those skilled in the art.

Claims (19)

1. imageing sensor comprises:

Microlens array is formed on the substrate, and comprises first group of lenticule and second group of lenticule;

Wherein said first group of lenticule and described second group of lenticule are arranged in the draughtboard pattern.

2. imageing sensor as claimed in claim 1, wherein said first group of lenticule comprises water wetted material, and described second group of lenticule comprises hydrophobic material.

3. imageing sensor as claimed in claim 2 wherein is used to form described first group of described water wetted material of a lenticular part and is retained on the described substrate that is positioned at described first and second groups of lenticules below.

4. transducer as claimed in claim 1 also comprises:

The water wetted material layer comprises the groove that is arranged in the draughtboard pattern that forms on the described substrate;

Wherein said first group of lenticule is formed in the described groove of described water wetted material layer, and described second group of lenticule is formed on the top surface of described water wetted material layer.

5. imageing sensor as claimed in claim 4, wherein said first group of lenticule and described second group of lenticule all comprise hydrophobic material.

6. imageing sensor as claimed in claim 1 also comprises:

The water wetted material layer is formed on the described substrate; With

The hydrophobic material layer of patterning is formed on the described water wetted material layer, is the backgammon plate-like and arranges;

Wherein said first group of lenticule is formed on the described water wetted material layer, and described second group of lenticule is formed on the hydrophobic material layer of described patterning.

7. imageing sensor as claimed in claim 6, wherein said first group of lenticule and described second group of lenticule all comprise hydrophobic material.

8. the method for a shop drawings image-position sensor may further comprise the steps:

Form microlens array on substrate, this microlens array comprises first group of lenticule and second group of lenticule;

Wherein said first group of lenticule and described second group of lenticule are arranged in the draughtboard pattern.

9. method as claimed in claim 8, the step that wherein forms described microlens array comprises:

On described substrate, form planarization layer;

Form first photosensitive film of patterning on described planarization layer, first photosensitive film of described patterning is the backgammon plate-like and arranges;

Heat-treat by first photosensitive film, on described planarization layer, form and sacrifice lenticule described patterning;

By using the described planarization layer of described sacrifice lenticule etching to form described first group of lenticule;

Form second photosensitive film of patterning in the space between described first group of lenticular contiguous microlens; With

Heat-treat by second photosensitive film, form described second group of lenticule described patterning.

10. method as claimed in claim 9, wherein said planarization layer comprise and can come etched water wetted material by dry etching.

11. method as claimed in claim 10, wherein said planarization layer comprises low temperature oxide.

12. method as claimed in claim 9, wherein said first and second photosensitive films comprise hydrophobic material.

13. method as claimed in claim 8 is further comprising the steps of:

On described substrate, form planarization layer; With

The described planarization layer of patterning is arranged on groove in the draughtboard pattern with formation,

The step that wherein forms described microlens array comprises:

In the described groove of described planarization layer, form described first group of lenticule, and on the top surface of described planarization layer, form described second group of lenticule.

14. method as claimed in claim 13, wherein said planarization layer comprises water wetted material, and described first and second groups of lenticules comprise hydrophobic material.

15. method as claimed in claim 13 wherein forms described first group of lenticule and described second group of lenticular step comprises:

Deposition and patterning first photosensitive film on the described groove of described planarization layer;

Deposition and patterning second photosensitive film on the top surface of described planarization layer; With

Photosensitive film to first and second patternings carries out reflux technique.

16. method as claimed in claim 8 is further comprising the steps of:

On described substrate, form the water wetted material layer; With

Form the hydrophobic material layer of patterning on described water wetted material layer, the hydrophobic material layer of this patterning is the backgammon plate-like and arranges;

The step that wherein forms described microlens array comprises:

On the described water wetted material layer that exposes, form described first group of lenticule; With

On the hydrophobic material layer of described patterning, form described second group of lenticule.

17. method as claimed in claim 16, wherein said first group of lenticule and described second group of lenticule all comprise hydrophobic material.

18. method as claimed in claim 16 wherein forms described first group of lenticule and comprises with the described second group of lenticular step of formation:

Deposition and patterning first photosensitive film on the described water wetted material layer that exposes;

Deposition and patterning second photosensitive film on the hydrophobic material layer of described patterning; With

Photosensitive film to first and second patternings carries out reflux technique.

19. method as claimed in claim 18, the hydrophobic material layer of wherein said patterning have than the narrower width of described water wetted material layer that exposes.

Images