CN211957643U - Front-illuminated image sensor - Google Patents
Front-illuminated image sensor Download PDFInfo
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- CN211957643U CN211957643U CN202020225588.1U CN202020225588U CN211957643U CN 211957643 U CN211957643 U CN 211957643U CN 202020225588 U CN202020225588 U CN 202020225588U CN 211957643 U CN211957643 U CN 211957643U
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Abstract
The utility model discloses a front-illuminated image sensor, it includes: an optical path structure region; the optical path structure is limited by a plurality of metal layers, contact hole layers and polycrystalline silicon layers; at least one of the metal layers, the contact hole layer and the polysilicon layer is provided with a light blocking or light reflecting structure to form an annular optical path with at least contact hole layer metal. The utility model discloses a front-illuminated image sensor, through the injecing of a plurality of metal levels, contact hole layer, polycrystalline silicon layer among the optical path structure, carry out the integrated design of optical path structure trompil size, eliminate or reduce the crosstalk of the adjacent sensitization unit that light dispersed and lead to, improve the design tolerance of optical path structure trompil size, realize better sensitivity.
Description
Technical Field
The utility model relates to an image sensor field especially relates to front-lit image sensor.
Background
An image sensor is a semiconductor device that converts an optical signal into an electrical signal, and has a photoelectric conversion element, and generally, the photoelectric conversion element is formed below a surface of a substrate, a logic circuit is formed above the photoelectric conversion element, and light reaches the photoelectric conversion element after passing through the logic circuit, during which the light passes through a multilayer structure, causing light loss or crosstalk (crosstalk) to an adjacent photoelectric conversion element, affecting the photoresponse characteristic of each photoelectric conversion element.
The current fingerprint identification schemes include optical technology, silicon technology (capacitive/radio frequency type), ultrasonic technology, etc. Among them, the optical fingerprint recognition technology has been widely used in portable electronic devices.
The optical fingerprint identification technology adopts optical image capturing equipment according to the difference of reflected light of light at different positions of fingerprint valleys/ridges. Light from the screen strikes a fingerprint pressed on the outer surface of the glass, and reflected light passes through the glass and the screen to reach the photoelectric conversion element of the image sensor and is converted into an electrical signal, so that a fingerprint image is constructed. The intensity and direction of the reflected light depend mainly on the depth and width of the valleys/ridges of the fingerprint, and are also affected by the surface condition of the fingerprint, such as grease, moisture, etc. The basic photoelectric conversion element in the image sensor is designed to acquire reflected light information of a corresponding position, and therefore it is necessary to let reflected light of the corresponding position enter the photoelectric conversion element as much as possible while shielding reflected light of a non-corresponding position.
With the development of the optical fingerprint identification technology, more and more portable electronic devices adopt an optical fingerprint identification scheme under a screen, namely, a finger is illuminated by the screen, and then reflected light of the finger penetrates through the screen and is sensed by an image sensor below the screen, so that comparison and identification are performed.
At present, aiming at the optical fingerprint identification technology, some problems can occur in the process of the optical path stroke of the adopted front-illuminated image sensor.
In addition, the front-illuminated image sensor can also be applied to the field of TOF (time of flight), which constructs a three-dimensional image based on intensity and time information that light emitted by a pulsed light source reaches the surface of an illuminated object at different distances and is reflected back to the sensor. It is also necessary to obtain as much reflected light from the corresponding position of the photoelectric conversion element as possible by the photoelectric conversion element and to shield as much light from the non-corresponding position as possible.
Applications for TOF cameras include laser-based non-scanning lidar imaging systems, motion sensing and tracking, object detection for machine vision and autopilot, and topographical mapping, among others.
The prior art applied to the field of optical fingerprinting and TOF is illustrated by the following:
referring to fig. 1, fig. 1 is a schematic diagram illustrating a partial structure of a front-illuminated image sensor in the prior art, which can be applied in the field of optical fingerprint recognition or TOF sensor. Light is transmitted to the semiconductor metal interconnection layer 150 through the microlens 100 and the light-transmitting layer 120, and the light-absorbing layers 110 and 130 in a plurality of areas are optionally designed in the process of light path transmission; when light is transmitted to the metal interconnection layer 150, since the front-illuminated image sensor has several metal layers (shown as M3 layer 140, M2 layer 141, and M1 layer 142 in the prior art), light is diffracted at the opening of the optical path structure, and diffracted light reaches adjacent pixels to cause crosstalk, sacrificing light quantum efficiency and reducing resolution accuracy. In addition, non-corresponding light with a larger angle also enters the current photoelectric conversion element, so that the aliasing phenomenon is serious, and the resolution precision is further influenced.
In order to reduce the influence of a large angle under the existing design, the size of an opening of an optical path structure needs to be reduced, but the size of the opening is reduced, so that incident light is reduced and diffraction is enhanced, the light quantum efficiency of a target photoelectric conversion element is sharply reduced, and finally an image signal is weakened to influence the effect; when the aperture becomes small, the sensitivity of the optical system to the fluctuation of the luminous flux entering the photoelectric conversion element with the process (the size and shape of the lens, the thickness of each layer, the size of the aperture, and the alignment of each layer) increases, which is not favorable for realizing the batch stabilization of the device performance.
In order to reduce the influence of light diffraction and large-angle light on the adjacent photoelectric conversion elements, the prior art solution needs to add a buffer photoelectric conversion unit, which results in an increase of chip area, contrary to market orientation and product requirements.
The signal intensity is increased when the size of the opening is increased, but the occupation ratio of large-angle light (which is not corresponding to the current photoelectric conversion element) is greatly increased, the anti-aliasing effect is deteriorated, the signal-to-noise ratio is deteriorated, and the image definition is influenced. Therefore, how to solve the above problems in the field of optical fingerprint identification and TOF in front-illuminated image sensors is a focus of research in the industry.
SUMMERY OF THE UTILITY MODEL
In order to solve the above technical problem, the utility model provides a front-illuminated image sensor, front-illuminated image sensor includes: an optical path structure region; the optical path structure is limited by a plurality of metal layers, contact hole layers and polycrystalline silicon layers; at least one of the metal layers, the contact hole layer and the polysilicon layer is provided with a light blocking or light reflecting structure to form an annular optical path with at least contact hole layer metal.
Preferably, the light blocking or light reflecting structure is made of: any one or alloy of aluminum, copper, titanium nitride, tungsten, polysilicon, tantalum and tantalum nitride.
Preferably, the size of the top opening of the light path structure is greater than or equal to 0.4 micrometer.
Preferably, the front-illuminated image sensor is applied to an optical fingerprint recognition sensor or a TOF image sensor or other optical sensors based on three-dimensional information application.
The utility model discloses among front-illuminated image sensor's the light path structure, the formation has the annular optical path beneficial effect of contact hole layer metal as follows at least:
1) crosstalk to adjacent photosensitive units caused by light diffraction and divergence is eliminated or reduced, light limited by the annular passage enters the photosensitive units, the light quantum efficiency is improved, the target signal intensity and the contrast are improved, and meanwhile the design tolerance of the size of the opening of the light path structure is improved;
2) the combined design of the opening size of the optical path structure can be carried out through the limitation of a plurality of metal layers, contact hole layers and polycrystalline silicon layers in the optical path structure, so that large-angle light (not corresponding to the current photosensitive unit) is reflected and absorbed, the large-angle light is weakened, the anti-aliasing effect is increased, and higher detail resolution is realized;
3) an optical design window is added, so that crosstalk and aliasing can be effectively controlled on the basis of increasing the photosensitivity; but also a reduced sensitivity to process fluctuations (size, thickness, shape, alignment); a thinner optical system can be designed to reduce the thickness of the module;
4) the size of the pixel unit can be reduced, the effective filling factor can be improved, and the size of a chip with higher resolution or smaller size can be realized.
Drawings
FIG. 1 is a schematic diagram of a portion of a prior art front-illuminated image sensor;
fig. 2 is a schematic structural diagram of a front-illuminated image sensor according to a first embodiment of the present invention;
FIG. 3 is a top view of a portion of the structure in area A of FIG. 2;
FIG. 4 is a top view of a portion of the structure in the area B of FIG. 2;
FIG. 5 is a top view of a portion of the structure in area C of FIG. 2;
FIG. 6 is a top view of a portion of the structure in area D of FIG. 2;
fig. 7 is a schematic view of another preferred embodiment of a light blocking or light reflecting structure in a front-illuminated image sensor according to the present invention;
fig. 8 is a schematic structural diagram of a second embodiment of a front-illuminated image sensor according to the present invention;
fig. 9 is a schematic structural diagram of a third embodiment of a front-illuminated image sensor according to the present invention;
fig. 10 is a schematic structural diagram of a fourth embodiment of a front-illuminated image sensor according to the present invention;
fig. 11 is a schematic structural diagram of a fifth embodiment of a front-illuminated image sensor according to the present invention.
Detailed Description
In the following description, numerous specific details are set forth in order to provide a thorough understanding of the present invention. The present invention can be implemented in many different ways than those herein described and one skilled in the art can do so without departing from the spirit and scope of the present invention, which is not limited to the specific implementations disclosed below.
Secondly, the present invention is described in detail by using schematic diagrams, and when the embodiments of the present invention are described in detail, for convenience of illustration, the schematic diagrams are only examples, and the present invention should not be limited herein.
Referring to fig. 2, fig. 2 is a schematic structural diagram of a front-illuminated image sensor according to a first embodiment of the present invention. The light is transmitted to the metal interconnection layer 250 of the semiconductor through the microlens 200 and the transparent layer 220, the metal interconnection layer 250 has a plurality of metal layers, and in this embodiment, the order of the light path is: a third metal layer M3240, a second metal layer M2241, a first metal layer M1242; light shielding layers or light absorbing layers 210 and 230 in a plurality of areas can be designed optionally in the process of optical path transmission; when light is transmitted into the semiconductor metal interconnection layer 250, light blocking or light reflecting structures 280, 281, 282 and 283 are respectively formed between the adjacent third metal layer 240, second metal layer 241, first metal layer 242, semiconductor layer 260, contact hole layers 290, 291 and 292 and polysilicon layer 293, so that in this embodiment, a ring-shaped optical path having at least contact hole layer metal is formed to eliminate or reduce crosstalk to adjacent photosensitive cells caused by light diffraction and divergence. Wherein the optical circuit structure is defined by several metal layers 240, 241, 242, contact hole layers 290, 291, 292, and polysilicon layer 293 in turn, wherein the opening size (including the length, width, or diameter in the horizontal direction, and the height in the vertical direction) of each layer can be adjusted according to the process or design requirements. In the present embodiment, light blocking or light reflecting structures 280, 281, 282, 283 are formed between the metal layers 240, 241, 242, the contact hole layers 290, 291, 292, and the polysilicon layer 293 to realize a ring-shaped optical path.
Referring to fig. 2 to 6, fig. 3 is a top view of a portion of the structure in the area a of fig. 2; FIG. 4 is a top view of a portion of the structure in the area B of FIG. 2; FIG. 5 is a top view of a portion of the structure in area C of FIG. 2; fig. 6 is a top view of a portion of the structure in region D of fig. 2.
A light blocking or light reflecting structure 280 is formed in the contact hole layer 290 between the third metal layer 240 and the second metal layer 241 in fig. 2, 3, thereby realizing an enclosed annular optical via 270.
Light blocking or light reflecting structures 281 are formed in the contact hole layer 291 between the first metal layer 242 and the second metal layer 241 in fig. 2, 4, thereby realizing an enclosed annular optical via 270.
A light blocking or light reflecting structure 282 is formed in the layer of contact holes 292 between the first metal layer 242 and the polysilicon layer 293 in fig. 2, 5, thereby realizing an enclosed annular optical via 270.
A light blocking or light reflecting structure 283 is formed in the polysilicon layer 293 between the contact hole layer 292 and the semiconductor layer 260 in fig. 2, 6, thereby realizing an enclosed annular optical via 270.
With continuing reference to fig. 7, fig. 7 is a schematic diagram of another preferred embodiment of a light blocking or light reflecting structure 280, 281, 282, 283 in an image sensor according to the present invention, wherein the light blocking or light reflecting structure 280, 281, 282, 283 may be a structure with a partially open area, thereby forming an annular optical via 270 with an open area. Similarly, the metal layers 240, 241, 242 may be closed or have a partially open structure.
The light blocking or reflecting structures 280, 281, 282, 283 in the above illustrated embodiments are made of: any one or alloy of aluminum, copper, titanium nitride, tungsten, polysilicon, tantalum nitride; the top view of the annular optical passage 270 in the illustrated embodiment described above is circular or oval, and in other embodiments may be closed or have other shapes that are partially open, such as polygonal. Wherein, preferably, the size of the top opening of the optical path structure (taking the diameter of the circle D1 as an example) is greater than or equal to 0.4 micron; light shielding or light absorbing layers 210, 230 are formed around the top of the light path structure region.
Fig. 8-11 respectively show the second embodiment, the third embodiment, the fourth embodiment, and the fifth embodiment of the present invention, wherein the combination of the metal layers, the contact hole layers, and the polysilicon layers with different numbers, positions, and shapes can be used to implement the front-illuminated image sensor of the present invention, and the detailed description of the specific configuration is omitted. It will be appreciated by those skilled in the art that, in addition to the above preferred embodiments, the present invention can also select any other combination of metal layers, contact hole layers, and polysilicon layers in any number, position, and shape according to the design requirement to form the optical path structure of the front-illuminated image sensor, in which the annular optical path having at least the contact hole layer metal is formed, i.e. the present invention is within the protection scope of the present invention.
The utility model discloses among front-illuminated image sensor's the light path structure, the formation has the annular optical path beneficial effect of contact hole layer metal as follows at least:
crosstalk to adjacent photosensitive units caused by light diffraction and divergence is eliminated, light limited by an annular passage enters the photosensitive units, the light quantum efficiency is improved, the target signal intensity and the contrast are improved, and meanwhile the design tolerance of the size of an opening of a light path structure is improved;
the combined design of the opening size of the optical path structure can be carried out through the limitation of a plurality of metal layers, contact hole layers and polycrystalline silicon layers in the optical path structure, so that the large-angle light is reflected and absorbed, the large-angle light is weakened, the anti-aliasing effect is increased, and the higher detail resolution is realized;
an optical design window is added, so that crosstalk and aliasing can be effectively controlled on the basis of increasing the photosensitivity; but also a reduced sensitivity to process fluctuations (size, thickness, shape, alignment); a thinner optical system can be designed to reduce the thickness of the module;
the size of the pixel unit can be reduced, the effective filling factor can be improved, and the size of a chip with higher resolution or smaller size can be realized.
It should be noted that the front-illuminated image sensor of the present invention can be applied to an optical fingerprint sensor, a TOF image sensor, or other optical sensors based on reflected light information. Thus, the present invention is operational with numerous general purpose or special purpose computing system environments or configurations. For example: personal computers, server computers, hand-held or portable devices, tablet-type devices, multiprocessor systems, microprocessor-based systems, set top boxes, programmable consumer electronics, network PCs, minicomputers, mainframe computers, distributed computing environments that include any of the above systems or devices, and the like.
Although the present invention has been disclosed in the preferred embodiments, it is not intended to limit the present invention, and any person skilled in the art can use the above-mentioned method and technical contents to make possible changes and modifications to the technical solution of the present invention without departing from the spirit and scope of the present invention, therefore, any simple modification, equivalent changes and modifications made to the above embodiments by the technical substance of the present invention all belong to the protection scope of the technical solution of the present invention.
Claims (5)
1. A front-illuminated image sensor, comprising:
an optical path structure region;
the optical path structure is limited by a plurality of metal layers, contact hole layers and polycrystalline silicon layers;
at least one of the metal layers, the contact hole layer and the polysilicon layer is provided with a light blocking or light reflecting structure to form an annular optical path with at least contact hole layer metal.
2. The front-illuminated image sensor of claim 1, wherein the light blocking or light reflecting structure is made of: any one of aluminum, copper, titanium nitride, tungsten, polysilicon, tantalum, and tantalum nitride.
3. The front-illuminated image sensor according to claim 1, wherein a top opening size of the optical path structure is 0.4 μm or more.
4. Front-illuminated image sensor according to one of claims 1 to 3, characterized in that it is applied to optical sensors based on light reflection information.
5. Front-illuminated image sensor according to claim 4, characterized in that it is applied to an optical fingerprint recognition sensor or a TOF image sensor.
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CN202020225588.1U CN211957643U (en) | 2020-02-28 | 2020-02-28 | Front-illuminated image sensor |
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CN202020225588.1U CN211957643U (en) | 2020-02-28 | 2020-02-28 | Front-illuminated image sensor |
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| Publication Number | Publication Date |
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| CN211957643U true CN211957643U (en) | 2020-11-17 |
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| CN202020225588.1U Active CN211957643U (en) | 2020-02-28 | 2020-02-28 | Front-illuminated image sensor |
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