WO2020132912A1

WO2020132912A1 - Thin film semiconductor structure, image sensor, and handheld device

Info

Publication number: WO2020132912A1
Application number: PCT/CN2018/123742
Authority: WO
Inventors: 杨富强; 杨孟达
Original assignee: 深圳市汇顶科技股份有限公司
Priority date: 2018-12-26
Filing date: 2018-12-26
Publication date: 2020-07-02
Also published as: CN109844951A

Abstract

A thin film semiconductor structure (100), comprising: a substrate (102); a capacitor (108) comprising an upper board (108-1) and a lower board (108-3), the capacitor (108) being configured on the substrate (102); and a photodiode (112) configured above and coupled to the capacitor (108), such that the capacitor (108) is located between the substrate (102) and the photodiode (112). An image sensor (400) and a handheld device (500) which have the thin film semiconductor structure (100) implement a high filling factor of the image sensor (400) without affecting the stability during reading a sensing value of the photodiode (112).

Description

Thin film semiconductor structure, image sensor and handheld device

Technical field

The present application relates to semiconductor structures, in particular to a thin film semiconductor structure and related image sensors and handheld devices.

Background technique

The photodiode in the image sensor needs to be matched with the node capacitance. The larger the node capacitance, the more stable the image sensor will be when reading the sensing results of the photodiode. However, the node capacitance will occupy the area of the chip. The larger the area of the node capacitance, the larger the photodiode will be to increase the effective photosensitive area. That is, the fill factor of the image sensor will be reduced. To increase the effective photosensitive area of the image sensor Reducing the size of the node capacitance will increase the noise during reading due to the reduced stability.

Therefore, further improvements and innovations are needed to overcome the above problems.

Summary of the invention

One of the purposes of this application is to disclose a thin film semiconductor structure and related image sensors and handheld devices to solve the above problems.

An embodiment of the present application discloses a thin film semiconductor structure, including: a substrate; a capacitor, including an upper plate and a lower plate, the capacitor is arranged on the substrate; and a photodiode, arranged above the capacitor And it is coupled to the capacitor so that the capacitor is between the substrate and the photodiode.

An embodiment of the present application discloses an image sensor, including: the above-mentioned thin film semiconductor structure; and a microlens, disposed on the thin film semiconductor structure.

An embodiment of the present application discloses a handheld device for sensing a fingerprint of a specific object, including: a display screen assembly; and the image sensor described above, for obtaining fingerprint information of the specific object.

The thin film semiconductor structure and related image sensor and handheld device disclosed in this application can increase the effective sensing area without affecting the stability.

BRIEF DESCRIPTION

FIG. 1A is a cross-sectional view of a first embodiment of a thin film semiconductor structure of this application.

FIG. 1B is a cross-sectional view of the embodiment of the capacitor in FIG. 1A.

2A is a cross-sectional view of a second embodiment of a thin-film semiconductor structure of this application.

FIG. 2B is a schematic diagram of an embodiment in which a thin film transistor is used as a capacitor.

FIG. 2C is a schematic diagram of another embodiment where the thin film transistor is used as a capacitor.

3 is a cross-sectional view of a third embodiment of a thin-film semiconductor structure of this application.

4 is a cross-sectional view of an embodiment of an image sensor of this application.

5 is a schematic diagram of an embodiment of a handheld device of the present application.

6 is a cross-sectional view of an embodiment of a handheld device of the present application.

Among them, the reference signs are described as follows:

100, 200, 300 Thin film semiconductor structure

102 The substrates of the substrates

104, 204 TFT thin film transistors

106, 110, 114 Passivation layer

108 Capacitors Capacitors

112 photodiode photodiode

107, 109, 111, 207, 209, 211 metal layer

108_1 The upper plate of the metal plate

108_2

108_3 The lower plate of the metal

400 Image sensor Image sensor

402 Microlens microlens

404 Filters Filters

500, hand-held device, hand-held device

406 Display module for display panel

408 The display panel of the display panel

410 Protective cover plate

detailed description

The following disclosure provides various implementations or examples, which can be used to implement different features of the disclosure. Specific examples of components and configurations described below are used to simplify this disclosure. It is conceivable that these statements are only examples, and their intention is not to limit the disclosure. For example, in the following description, forming a first feature on or above a second feature may include certain embodiments in which the first and second features are in direct contact with each other; and may also include In some embodiments, additional components are formed between the first and second features, so that the first and second features may not have direct contact. In addition, the present disclosure may reuse component symbols and/or reference numerals in various embodiments. Such repeated use is based on the purpose of brevity and clarity, and does not itself represent the relationship between the different embodiments and/or configurations discussed.

Furthermore, the use of spatially relative terms here, such as "below", "below", "below", "above", "above", and similar ones, may be for the convenience of illustration The relationship between a component or feature shown relative to another component or feature. In addition to the orientation shown in the figures, the meaning of these spatially relative terms also covers many different orientations of the device in use or operation. The device may be placed in other orientations (eg, rotated 90 degrees or in other orientations), and these spatially relative description words should be interpreted accordingly.

Although the numerical ranges and parameters used to define the broader range of this application are approximate values, the relevant numerical values in the specific embodiments have been presented as accurately as possible. However, any numerical value inevitably contains standard deviations due to individual test methods. Here, "about" generally means that the actual value is within plus or minus 10%, 5%, 1%, or 0.5% of a specific value or range. Or, the term "about" means that the actual value falls within the acceptable standard error of the average value, depending on the consideration of those with ordinary knowledge in the technical field to which this application belongs. When understandable, in addition to the experimental examples, or unless otherwise clearly stated, all ranges, quantities, values and percentages used here (for example to describe the amount of materials, length of time, temperature, operating conditions, quantity ratio and other Similar) are modified by "about". Therefore, unless otherwise stated to the contrary, the numerical parameters disclosed in this specification and the accompanying patent application are approximate values, and can be changed as required. At least these numerical parameters should be understood as the indicated significant digits and the values obtained by applying the general rounding method. Here, the numerical range is expressed from one end point to another end point or between two end points; unless otherwise stated, the numerical range described herein includes the end points.

The thin-film semiconductor structure disclosed in this application utilizes the characteristics of the layer-by-layer manufacturing of active components in a thin-film transistor (TFT) process to place the capacitance required at the output point of the photodiode in a different layer from the photodiode to maximize The effective photosensitive area of the photodiode improves the fill factor of the image sensor without affecting the stability when reading the sensed value of the photodiode. The technical content of the thin film semiconductor structure of the present application and related image sensors and handheld devices will be described in detail below in conjunction with multiple embodiments and drawings.

First, please refer to FIG. 1A, which is a cross-sectional view of a first embodiment of a thin film semiconductor structure of the present application. It should be noted that the thin film semiconductor structure 100 in FIG. 1A only shows one photodiode 112, that is, one pixel unit, but in application, the thin film semiconductor structure 100 may include multiple pixel units, and the multiple pixel units It may extend along the X-axis direction and/or the Y-axis direction to form a pixel unit matrix. The application of the thin-film semiconductor structure 100 is not limited. In the embodiment of FIG. 4, the thin-film semiconductor structure 100 is used to form an image sensor 400 to perform the optical under-screen fingerprint sensing of the handheld device 500 of FIGS. 5 and 6.

Specifically, in this embodiment, the thin film semiconductor structure 100 is manufactured using a thin film transistor process. The thin film semiconductor structure 100 includes a substrate 102, a first thin film transistor 104, a capacitor 108, and a photodiode 112. The substrate 102 includes a glass substrate. In this embodiment, the first thin film transistor 104 is formed on the substrate 102. The first thin film transistor 104 may be an amorphous silicon thin film transistor or a polycrystalline silicon thin film transistor. The first thin film transistor 104 may include a gate, a source, and a drain (not (Shown in the figure), the first thin film transistor 104 constitutes a reading circuit of the photodiode 112. In this embodiment, the first thin film transistor 104 is a P-type bottom gate thin film transistor, but this application is not limited to this. In some embodiments, the first thin-film transistor 104 may also be a P-type top-gate thin-film transistor, an N-type bottom-gate thin-film transistor, or an N-type top-gate thin-film transistor, and the connection manner thereof also has corresponding changes.

The capacitor 108 includes an upper plate and a lower plate, wherein the contacts of the upper plate are located above the capacitor 108, that is, the side of the capacitor 108 facing the Z-axis direction, and the contacts of the lower plate are located below the capacitor 108, that is, the capacitor 108 faces The other side of the Z axis. The photodiode 112 is arranged above the capacitor 108 and is coupled to the contact of the upper plate of the capacitor 108 through the metal layer 111, so that the capacitor 108 is between the substrate 102 and the photodiode 112, and the contact of the lower plate of the capacitor 108 is transparent The metallization layer 107 is coupled to a reference voltage. The reference voltage may be any stable DC voltage. For example, when the value of the stable DC voltage is 0, the reference voltage is the ground voltage. In this embodiment, the photodiode 112 is further coupled to the upper plate of the first thin film transistor 104 and the capacitor 108 through the metal layer 109. In this way, the first thin film transistor 104 can affect the photodiode 112 through the metal layer 109 When the measured value is read out, the stability during reading can be increased by the capacitor 108, and the noise during reading can be reduced.

It should be particularly noted that the capacitor 108 is disposed between the first thin film transistor 104 and the photodiode 112, that is, the photodiode 112, the capacitor 108, and the first thin film transistor 104 are sequentially arranged on the substrate 102 from top to bottom , And the horizontal space occupied by each does not overlap each other. Specifically, the extension plane generated by the bottom plane of the photodiode 112 extending along the X-axis direction and the Y-axis direction is higher than the extension plane generated by the top plane of the capacitor 108 extending along the X-axis direction and the Y-axis direction. In this embodiment, the capacitor 108 is located below the photodiode 112, and from a top view, the capacitor 108 at least partially overlaps the photodiode 112. However, in some embodiments, although the capacitor 108 is located below the photodiode 112, from a top view, the capacitor 108 does not overlap the photodiode 112 at all.

In this embodiment, a first passivation layer 110 may be deposited between the photodiode 112 and the capacitor 108, and the first passivation layer 110 covers the capacitor 108; and the second passivation layer 114 and the second passivation layer 114 are deposited Cover the photodiode 112. In addition, a third passivation layer 106 may be deposited between the first thin film transistor 104 and the capacitor 108. The third passivation layer 106 covers the first thin film transistor 104. In some embodiments, the third passivation layer 106 extends to Between the first thin film transistor 104 and the substrate 102. The first passivation layer 110, the second passivation layer 114, and the third passivation layer 106 are insulating layers, and the metal layers 107, 109, and 111 are formed in the first passivation layer 110 and the third passivation layer 106 to provide photoelectricity. The electrical connection between the diode 112, the capacitor 108 and the first thin film transistor 104.

The implementation of the capacitor 108 may include the structure of FIG. 1B. The capacitor 108 of FIG. 1B includes a metal upper plate 108_1, an insulator 108_2, and a metal lower plate 108_3 stacked to form a metal-insulator-metal type capacitor.

2A is a cross-sectional view of a second embodiment of a thin-film semiconductor structure of this application. Similar to FIG. 1A, the thin film semiconductor structure 200 in FIG. 2A only shows one photodiode 112, that is, one pixel unit, but in application, the thin film semiconductor structure 200 may include multiple pixel units. The pixel unit may extend along the X-axis direction and/or the Y-axis direction to form a pixel unit matrix. The applications of the thin film semiconductor structure 200 are not limited. In the embodiment of FIG. 4, the thin film semiconductor structure 200 is used to form an image sensor 400 to perform the optical under-screen fingerprint sensing of the handheld device 500 of FIGS. 5 and 6.

Similar to the thin film semiconductor structure 100, in this embodiment, the thin film semiconductor structure 200 is also manufactured using a thin film transistor process. The thin film semiconductor structure 200 includes a substrate 102, a first thin film transistor 104, a second thin film transistor 204, and a photodiode 112. The first thin film transistor 104 and the second thin film transistor 204 may be amorphous silicon thin film transistors or polycrystalline silicon thin film transistors. In FIG. 2A, the first thin film transistor 104 and the second thin film transistor 204 are P-type bottom-gate thin film transistors, but this application is not limited thereto. In some embodiments, the first thin-film transistor 104 and/or the second thin-film transistor 204 may also be a P-type top-gate thin-film transistor, an N-type bottom-gate thin-film transistor, or an N-type top-gate thin-film transistor, and the connection method thereof There are also corresponding changes. The difference between the thin film semiconductor structure 200 and the thin film semiconductor structure 100 is that the thin film semiconductor structure 200 makes the second thin film transistor 204 have the function of a capacitor by setting the second thin film transistor 204, so that the capacitor 108 in FIG. 1A can be omitted to reduce The thickness of the overall thin film semiconductor structure 200. 2B is a schematic diagram of an embodiment in which the second thin film transistor 204 is used as a capacitor. In FIG. 2B, the second thin film transistor 204 is a P-type thin film transistor, and the source of the second thin film transistor 204 is coupled to the drain as a capacitor. The upper plate, and is coupled to the photodiode 112 through the metal layer 211, the gate of the second thin film transistor 204 serves as the lower plate of the capacitor, and is coupled to the reference voltage through the metal layer 207, the reference voltage can be any stable The DC voltage, for example, when the value of the stable DC voltage is 0, the reference voltage is the ground voltage. In this way, the first thin film transistor 104 can read the sensed value of the photodiode 112 through the metal layer 209, and the second thin film transistor 204 as a capacitor can increase the stability during reading and reduce the reading Time noise.

However, it should be understood that the conductivity types of all components can be exchanged. FIG. 2C is a schematic diagram of another embodiment in which the second thin film transistor 204 is used as a capacitor. In FIG. 2C, the second thin film transistor 204 is an N-type thin film transistor, and the first The source of the two thin film transistors 204 is coupled to the lower plate of the drain as a capacitor, and is coupled to a reference voltage through the metal layer 207. The reference voltage may be any stable DC voltage. For example, when the stable DC voltage When the value is 0, the reference voltage is the ground voltage, and the gate of the second thin film transistor 204 serves as the upper plate of the capacitor, and is coupled to the photodiode 112 through the metal layer 211.

FIG. 3 is a cross-sectional view of a third embodiment of a thin film semiconductor structure of the present application. The thin film semiconductor structure 300 substantially combines the thin film semiconductor structure of FIGS. 1A and 2A. In FIG. 3, only one photodiode 112, that is, one pixel unit is shown, but in application, the thin film semiconductor structure 300 may include a plurality of pixel units, and the plurality of pixel units may extend along the X-axis direction and/or Y The axis direction extends to form a matrix of pixel cells. The application of the thin-film semiconductor structure 300 is not limited. In the embodiment of FIG. 4, the thin-film semiconductor structure 300 is used to form an image sensor 400 to perform the optical under-screen fingerprint sensing of the handheld device 500 of FIGS. 5 and 6.

The thin-film semiconductor structure 300 uses both the capacitor 108 of the thin-film semiconductor structure 100 in FIG. 1A and the second thin-film transistor 204 as a capacitor in the thin-film semiconductor structure 200 in FIG. 2A, and is connected in parallel to increase the capacitance value, further improving the first The thin film transistor 104 reads the stability of the sensed value of the photodiode 112. Similar to FIG. 2A, in FIG. 3, the first thin film transistor 104 and the second thin film transistor 204 are P-type bottom-gate thin film transistors, but the present application is not limited thereto. In some embodiments, the first thin-film transistor 104 and/or the second thin-film transistor 204 may also be a P-type top-gate thin-film transistor, an N-type bottom-gate thin-film transistor, or an N-type top-gate thin-film transistor, and the connection method thereof There are also corresponding changes. Referring to FIG. 3, it can be seen that the lower plate of the capacitor 108 and the lower plate of the capacitor 204 (that is, the gate of the second thin film transistor 204) are coupled to the reference voltage through the metal layer 207. The reference voltage may be any stable DC voltage, for example In other words, when the value of the stable DC voltage is 0, the reference voltage is the ground voltage, and the upper plate of the capacitor 108 and the upper plate of the capacitor 204 are coupled to the photodiode 112 and the photodiode 112 through the metal layers 111, 109, and 211. The first thin film transistor 104 has a structure in which a capacitor 108 and a second thin film transistor 204 as a capacitor are connected in parallel.

4 is a cross-sectional view of an embodiment of an image sensor of the present application. The image sensor 400 includes a thin

film semiconductor structure

100, 200, or 300, a filter 404, and a micro lens 402. The thin film semiconductor structure 100/200/300 in the image sensor 400 may include a plurality of pixel units, and the filter 404 is disposed between the thin film semiconductor structure 100/200/300 and the micro lens 402. The filter 404 may be designed to have a specific A specific light wave of a wavelength passes through.

5 is a schematic diagram of an embodiment of a handheld device of the present application. The handheld device 500 includes a display screen assembly 406 and an image sensor 400. The handheld device 500 can be used for optical under-screen fingerprint sensing to sense the fingerprint of a specific object. The handheld device 500 may be any handheld electronic device such as a smart phone, personal digital assistant, handheld computer system, or tablet computer.

6 is a cross-sectional view of an embodiment of the handheld device of FIG. 5. According to FIG. 6, the display screen assembly 406 includes a display panel 408 and a protective cover 410. The protective cover 410 is disposed above the display panel 408, and the image sensor 400 is disposed below the display panel 408. In this embodiment, the display panel 408 It may be an organic electroluminescence display panel (OLED), but not limited to this.

As another alternative embodiment, the image sensor 400 may also be integrated into the display panel 408 to realize an in-screen optical fingerprint system; wherein, the

thin film transistor

104 or 204 may be specifically a thin film transistor inside the display panel 408, or may also be an image The thin film transistor of the sensor 400 itself.

Compared with the non-thin film semiconductor process using a silicon substrate, the thin film semiconductor process using a glass substrate can be fabricated by stacking layers of components. The above embodiment places the capacitance required for the output point of the photodiode in a different layer from the photodiode. To avoid affecting the effective photosensitive area of the photodiode in order to set the capacitor, when the photodiode is applied to the image sensor, the fill factor of the image sensor can be improved without affecting the stability when reading the sensed value of the photodiode.

The above description briefly proposes the features of certain embodiments of the present application, so that those with ordinary knowledge in the technical field to which the present application belongs can more fully understand the various aspects of the present disclosure. Those of ordinary skill in the technical field to which this application pertains should understand that they can easily use this disclosure as a basis to design or modify other processes and structures to achieve the same purposes and/or as the embodiments described herein Achieve the same advantages. Those of ordinary skill in the technical field to which this application belongs should understand that these equal implementations still fall within the spirit and scope of this disclosure, and that they can be subject to various changes, substitutions, and alterations without departing from the spirit of this disclosure With scope.

Claims

A thin-film semiconductor structure is characterized by comprising:

Substrate

A capacitor, including an upper plate and a lower plate, the capacitor being arranged on the substrate; and

The photodiode is arranged above the capacitor and is coupled to the capacitor so that the capacitor is between the substrate and the photodiode.
The thin film semiconductor structure according to claim 1, wherein the lower plate of the capacitor is coupled to a reference voltage.
The thin film semiconductor structure of claim 1, wherein the capacitor comprises a metal-insulator-metal type capacitor.
The thin film semiconductor structure of claim 1, wherein the substrate comprises a glass substrate.
The thin film semiconductor structure according to claims 1-4, further comprising a first thin film transistor between the substrate and the capacitor, and the first thin film transistor includes a gate, a source, and a drain.
The thin film semiconductor structure of claim 5, wherein the first thin film transistor is coupled to the photodiode and the upper plate of the capacitor.
The thin film semiconductor structure of claim 6, wherein the source of the first thin film transistor is coupled to the drain, and the first thin film transistor and the capacitor are arranged in parallel.
The thin film semiconductor structure of claim 7, wherein the first thin film transistor is a P-type thin film transistor, and the gate of the first thin film transistor is coupled to the reference voltage, and the first The source and drain of the thin film transistor are coupled to the upper plate of the capacitor.
The thin film semiconductor structure of claim 7, wherein the first thin film transistor is an N-type thin film transistor, and the source and drain of the first thin film transistor are coupled to the reference voltage, and the The gate of the first thin film transistor is coupled to the upper plate of the capacitor.
The thin film semiconductor structure of claim 1, wherein the capacitor includes a second thin film transistor.
The thin film semiconductor structure of claim 10, wherein the second thin film transistor is a P-type thin film transistor, and the gate of the second thin film transistor is coupled to a reference voltage, and the second thin film transistor Source and drain are coupled to the photodiode.
The thin film semiconductor structure of claim 10, wherein the second thin film transistor is an N-type thin film transistor, and the source and drain of the second thin film transistor are coupled to the reference voltage, and the The gate of the second thin film transistor is coupled to the photodiode.
The thin film semiconductor structure of claim 1, further comprising a first passivation layer disposed between the photodiode and the capacitor.
The thin film semiconductor structure of claim 1, further comprising a second passivation layer covering the photodiode.
The thin film semiconductor structure according to claim 5, further comprising a third passivation layer disposed between the first thin film transistor and the capacitor.
An image sensor, characterized in that it includes:

The thin film semiconductor structure according to any one of claims 1-15; and

The micro lens is arranged on the thin film semiconductor structure.
The image sensor according to claim 16, further comprising a filter, which is disposed between the thin-film semiconductor structure and the microlens.
A hand-held device for sensing a fingerprint of a specific object, which is characterized by including:

Display assembly; and

The image sensor according to any one of claims 16-17, for obtaining fingerprint information of the specific object.
The handheld device according to claim 18, wherein the display screen assembly includes a display panel and a protective cover.
The handheld device according to claim 18, wherein the display panel has a first side and a second side opposite to the first side, and the protective cover is disposed on the second side of the display panel And the image sensor is disposed on the first side of the display panel so that the display panel is located between the image sensor and the protective cover.