Patent Publication Number: US-2021175283-A1

Title: Flexible integrated array sensor and wafer-level manufacturing process thereof

Description:
CROSS REFERENCE TO RELATED APPLICATION 
     The present application claims the benefit of priority to Chinese Patent Application No. CN 2019112450562, entitled “Flexible Integrated Array Sensor and Wafer-Level Manufacturing Process Thereof”, filed with CNIPA on Dec. 6, 2019, the disclosure of which is incorporated herein by reference in its entirety. 
     FIELD OF TECHNOLOGY 
     The present disclosure generally relates to electronic devices, in particular to flexible sensors and their manufacturing processes. 
     BACKGROUND 
     Flexible sensors are widely used in the fields of human-computer interaction, robotic electronic skin, biomedicine, and health care. Flexible sensors&#39; sensor units can measure pressure and temperature, and sense air flow and different types of gas. They can also be classified as piezoresistive, capacitive, and piezoelectric, etc., according to their sensing mechanism. For example, a piezoelectric flexible sensor utilizes piezoelectric effect of certain sensitive material: when an external force acts on the sensitive material, the sensitive material deforms which causes positive and negative bound charges to gather on its surface, and thereby generates electronic signals in response to external pressure. 
     For many types of flexible sensors, regardless of sensing mechanisms and elements to be detected, the information gathered by a sensing unit needs to be processed by a readout circuit and sent to a back-end circuit system for analysis. In order for the sensor to receive external signals coming from a large area and to enable the back-end system to detect complex external information, the sensor usually adopts an array (or dot matrix) comprised of several sensing units, and each sensing unit is equipped with a corresponding readout circuit to respond to external signals acting on it. This means that the sensing unit and the readout circuit are needed in the sensor array, and they will increase in number with the increase of the size of the array, which is problematic in light of the current status of the field of flexible array sensors. 
     On the one hand, organic thin film transistors are widely used in the field of flexible electronics due to their flexibility, low cost, and simple process, and therefore most readout circuits in sensors are made of organic thin film transistors. However, the carrier mobility of organic materials is low, resulting in a low sampling frequency, which hinders high-frequency signal detection. On the other hand, in most of the flexible array sensors currently reported, their internal sensing unit and readout circuit are separated. Most sensing units are electrically connected with a readout circuit through leads. As the size of the array increases the number of leads required increases, resulting in a complex circuit structure, which will cause a lot of noise and crosstalk and is not conducive to improving the spatial resolution of the sensors. 
     Besides, in the manufacturing process of flexible sensors, the mainstream method is to directly print organic or amorphous materials on a flexible substrate, which can be easily scaled and reduces manufacturing cost. However, compared with traditional silicon-based materials, organic or amorphous materials have lower carrier mobility, which restricts the operating frequency and performance of the device. Moreover, although traditional silicon-based materials have high carrier mobility and offer better sampling frequency and operating speed, it is still difficult to use silicon-based materials to make a highly integrated, highly sensitive flexible array sensor that integrates a readout circuit and sensing units. It is because it is difficult to thin rigid and brittle silicon materials to required thickness and make them flexible while their shapes remain intact. Also, thinned silicon slices are prone to damaging other parts of a device, thereby greatly reducing the yield and increasing the manufacturing cost. 
     SUMMARY 
     In various embodiments, a flexible integrated array sensor is provided, which includes a readout circuit layer disposed on a silicon wafer suitable for a flexible application, and a sensing array layer stacked on the readout circuit layer. The readout circuit layer includes a plurality of readout circuit units. The sensing array layer includes a plurality of sensing units, each of which is connected with one of the plurality of readout circuit units through a conductive tungsten plug to form a function unit. The function units are distributed in an m*n array on the silicon wafer to form a function array. 
     More specifically, in one embodiment, the disclosed concepts provide a flexible integrated array sensor containing a polymer substrate layer. The polymer substrate layer may include a top polymer substrate covering the function array. Alternatively, the polymer substrate layer may also include a bottom polymer substrate covering the side of the silicon wafer away from the function array. 
     The present disclosure further provides a method for manufacturing a flexible integrated array sensor is provided, which includes: preparing a silicon wafer; fabricating a plurality of function arrays on a surface of the silicon wafer through a semiconductor process; etching one or more deep grooves on the surface of the silicon wafer in areas between the function arrays to separate the function arrays from each other; fabricating a top polymer substrate layer above each function array and patterning, fabricating a thinning support on the patterned top polymer substrate layer; thinning a bottom surface of the silicon wafer to a target thickness to separate the function arrays on the silicon wafer from each other; and removing the thinning support and releasing the flexible integrated array sensor. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a perspective view of a flexible integrated array sensor with a function array having a single-function according to certain embodiments. 
         FIG. 2  is a cross-sectional view of a function unit of a flexible integrated array sensor. 
         FIGS. 3.1 a -3.4 c    illustrate cross-sectional views of a flexible integrated array sensor with a function array having a single-function at various manufacturing operations according to certain embodiments. 
         FIG. 4  is a perspective view of a flexible integrated array sensor with a function array having multiple functions according to certain embodiments. 
         FIG. 5  is a cross-sectional view of a function unit of a flexible integrated array sensor. 
         FIGS. 6.1-6.4   c  illustrated cross-sectional views of a flexible integrated array sensor with a function array having multiple functions at various manufacturing operations according to certain embodiments. 
     
    
    
     DETAILED DESCRIPTION 
     One or more specific embodiments of the present disclosure will be described below. These described embodiments are only examples of the presently disclosed techniques, and are not intended to limit aspects of the presently disclosed invention. Additionally, in an effort to provide a concise description of these embodiments, all features of an actual implementation may not be described in the specification. It should be appreciated that in the development of any such actual implementation, numerous implementation-specific decisions must be made to achieve the developers&#39; specific goals, which may vary from one implementation to another. Moreover, it should be appreciated that such a development effort might be complex and time consuming, but would nevertheless be a routine undertaking of design, fabrication, and manufacture for those of ordinary skill having the benefit of this disclosure. 
     The disclosed sensor may be constructed based on a semiconductor fabrication process, which may be a multiple-step sequence of photographic and chemical-processing operations. During the fabrication process, different electronic components may gradually be created on a semiconductor wafer using various depositions and etching operations. The fabrication process may deposit a layer of material on top of other materials on, or etch/wash away material from, the semiconductor wafer. Throughout the disclosure, when a first layer of material (or “first layer”) is deposited “above” or “on” a second layer of material (or “second layer”), the first layer may either be directly on the top of the second layer, or there might be additional material in between the first and the second layers. In other words, after the second layer of material is fabricated, additional material may be deposited on the top of the second layer before the first layer of material being deposited. Further, the term “top”, “bottom”, “above”, “below”, “up”, or “down” may be relative to one surface of a horizontally-placed layer. Herein, a “groove”, which may also be referred to as a “trench”, may be a narrow or deep cut or depression on a surface of a layer. 
     The present disclosure generally relates to a flexible integrated array sensor. The flexible integrated array sensor functions without a complicated lead structure connecting its sensing units and readout circuit units. In one embodiment, there are micro-sensors functioning as sensing units of the array sensor, and the micro-sensors measure different objects by different mechanisms. One or more of the micro-sensors are manufactured by a semiconductor process. The sensing units&#39; responses to external change are converted into charge, current or voltage change, which are received and responded to by corresponding readout circuits, and resulted electrical signal is then adjusted and sent to a back-end system to detect external information contained in the resulted electrical signal. 
     The present disclosure provides a flexible integrated array sensor with a function array. A micro pressure sensor with a piezoelectric measurement mechanism as the sensing unit in the function array is taken as an example to illustrate the idea provided by the present disclosure. 
       FIG. 1  is a perspective view of a flexible integrated array sensor with a function array having a single-function according to one embodiment. As shown in  FIG. 1 , the present disclosure provides a flexible integrated array sensor, which includes, among other things, a readout circuit layer  210 , a piezoelectric sensing array layer  230 , a top polymer substrate layer  270 , and a bottom polymer substrate layer  280 . The readout circuit layer  210  is disposed on a silicon wafer  100  suitable for flexible applications, and includes a plurality of readout circuit units  211 . The piezoelectric sensing array layer  230  is disposed on the readout circuit layer  210  and includes a plurality of piezoelectric sensing units  231 . For illustrative purpose, only the piezoelectric sensing units  231  of the piezoelectric sensing array layer  230  are shown in  FIG. 1 . Each of the plurality of sensing units  231  is connected with one of the plurality of readout circuit units  211  to form a corresponding function unit  200   a.  Multiple function units  200   a  are distributed in an m*n array on the silicon wafer  100  to form a function array  200 . In one embodiment, as shown in  FIG. 1 , the function units  200   a  are distributed in a 3*2 array forming the function array  200 . 
     In some embodiments, the sensing units  200   a  in the function array  200  have a spatial resolution of less than 1 mm. 
     In some embodiments, the readout circuit units  211  in the readout circuit layer  210  are micro integrated circuits, such as CMOS circuits, bipolar circuits, and thin film transistor circuits. In one embodiment, the manufacturing process of the readout circuits units  211  includes deposition, etching, photolithography, and ion implantation on a silicon wafer. 
     In some embodiments, the readout circuit units  211  receive signals, and modify signals. In one embodiment, a readout circuit unit  211  may respond to a pressure signal from a piezoelectric sensing unit  231 , and convert the pressure signal into a voltage signal (or current signal), which is in turn recognized and received by a back-end system. 
     In some embodiments, silicon wafers suitable for flexible applications are thinner than 100 μm. 
     In operation, each of the plurality of readout circuit units  211  is connected with one of the plurality of piezoelectric sensing units  230  to form a corresponding function unit in the function array  200 . When one or several sensing units in the piezoelectric sensing array layer  230  detect pressure asserted on it, they generate positive and negative induced charges, which are measured by one or more of the plurality of readout circuit units  211 . Afterward, the plurality of readout circuit units  211  generate signals to be sent to a back-end system for processing. In some embodiments, each of the readout circuit units  211  and a corresponding sensing unit are integrated in one function unit, which can be prepared by semiconductor manufacturing techniques. In some embodiments, such integration reduces the number of leads, thereby reducing circuit complexity caused by traditional lead connection methods. In some embodiments, such integration also mitigates the problems of low sampling frequency and weak detection ability of high-frequency signals in traditional organic readout circuits, because the integration adopts silicon-based materials, which have high carrier mobility. 
     Turning to  FIG. 2 , a cross-sectional view of a function unit of a flexible integrated array sensor is shown. The flexible integrated array sensor includes, among other things, a silicon wafer  100 , a function array  200  including a plurality of function units  200   a,  a readout circuit layer  210  including a plurality of readout circuit units  211 , a dielectric layer  220 , conductive tungsten plugs  221 ,  222 , piezoelectric sensing unit  231 , a first connecting metal  240 , polymer  250 , a top polymer substrate layer  270 , a bottom polymer substrate layer, and a pad  290 . 
     Each of the plurality of readout circuit units  211  in the dielectric layer  220  is connected with two sets of conductive tungsten plugs  221 ,  222 . Each piezoelectric sensing unit  231  includes a top electrode layer  231   a,  a piezoelectric material layer  231   c,  and a bottom electrode layer  231   b,  with the piezoelectric material layer  231   c  located between the top electrode layer  231   a  and the bottom electrode layer  231   b.  The bottom electrode layer  231   b  of each sensing unit is directly connected with a first wiring part of one corresponding readout circuit unit  211  through a first set of conductive tungsten plugs  221 . The top electrode layer  231   a  of each sensing unit is indirectly connected with a second wiring part of the corresponding readout circuit unit  211  through a second set of conductive tungsten plugs  222  and first connecting metal  240 , as shown in  FIG. 2 . As a result, each piezoelectric sensing unit  231  is connected with one of the readout circuit units  211 , and the plurality of function units  200   a  further form the function array  200  as an m*n array on the silicon wafer  100 . 
     In some embodiments, the material of the top electrode layer  231   a  and the bottom electrode layer  231   b  is molybdenum, titanium, aluminum, copper, tantalum, or gold. In some embodiments, the top electrode layer  231   a  and the bottom electrode layer  231   b  are made of the same material. In some embodiments, the top electrode layer  231   a  and the bottom electrode layer  231   b  are made of different materials. 
     In some embodiments, the entire sensing array is made of the same material as the piezoelectric material layer  231   c.  In some embodiments, the piezoelectric material layer  231   c  is a piezoelectric thin film made of materials such as lead zirconate titanate, aluminum nitride, scandium-doped aluminum nitride, and zinc oxide. When an external pressure acts on the piezoelectric material layer  231   c,  positive and negative charges of equal amount are generated on the top electrode layer  231   a  and the bottom electrode layer  231   b  respectively. The positive and negative charges are measured by the corresponding readout circuit unit  211  through the conductive tungsten plugs  221 ,  222  connected with one of the readout circuit units  211 . 
     In some embodiments, a method for manufacturing the conductive tungsten plugs  221 ,  222  includes, but not limited to, fabricating a dielectric layer  220  on the readout circuit layer  210 , and disposing several conductive tungsten plugs  221 ,  222  connected with the readout circuit units  211  in the dielectric layer  220 . In some embodiments, the dielectric layer  220  is made of materials such as silicon dioxide, silicon nitride, and silicon oxynitride. 
     In some embodiments, the flexible integrated array sensor includes one or more polymer substrate layers, as shown in  FIG. 2 . In some embodiments, the flexible array sensor only includes a top polymer substrate layer  270  covering the function array  200 . In some embodiments, the flexible array sensor includes a bottom polymer substrate layer  280  covering a side of the silicon wafer away from the function array  200 . In some embodiments, the flexible array sensor includes both the top polymer substrate layer  270  and the bottom polymer substrate layer  280 . In some embodiments, the polymer substrate layers are disposed on corresponding layers through spin coating or deposition techniques. The polymer substrate layers are made of materials such as polyimide, polyester, polyurethane, ethylene-vinyl acetate copolymer, polyolefin, epoxy resin, polycarbonate, polyamide, acrylic resin, silicone resin, or parylene materials, or a combination of some of them. Some examples of the aforementioned parylene materials are Parylene C, Parylene D, Parylene F, Parylene N, and Parylene HT. 
       FIGS. 3.1 a -3.4 c    illustrate cross-sectional views of a flexible integrated array sensor with a function array having a single-function at various manufacturing stages according to one embodiment. Generally, the manufacturing process illustrated in  FIGS. 3.1 a -3.4 c    is as follows: 
     S 1 . Preparing a silicon wafer  100 , and fabricating a plurality of function arrays, each of which including m*n function units on a surface of the silicon wafer  100  through semiconductor manufacturing processes such as ion implantation, deposition, lithography, and etching. (referring to  FIGS. 3.1 a -3.1 f   ); for each function array  200 , S 1  further includes: 
     S 11 . Fabricating a readout circuit layer  210  including a plurality of readout circuit units  211  on the surface of the silicon wafer  100  (referring to  FIG. 3.1 a   ), and constructing conductive tungsten plugs  221 ,  222  connected with the readout circuit units  211  (referring to  FIG. 3.1 b   ); and 
     S 12 . Fabricating piezoelectric sensing units  231  on the readout circuit layer  210 , and forming a piezoelectric sensing array layer containing m*n piezoelectric sensing units  231  through lithography, and directly coupling each electrode of one of the readout circuit units to a corresponding readout circuit unit  211  or indirectly coupling each electrode of one of the readout circuit units with a corresponding readout circuit unit  211  through conductive tungsten plugs  221 ,  222  and a piece of connecting metal  240  to form a function array  200  (referring to  FIG. 3.1 c   - FIG. 3.1 f   ); 
     S 2 . Etching one or more deep grooves  110  on the surface of the silicon wafer  100  in areas between the function arrays  200  to separate the function arrays  200  from each other, with each of the one or more deep grooves  110  located between two of the function arrays  200 , with the etching depth equal to or greater than the thickness of the silicon wafer  100  when it is subsequently thinned at S 3  (referring to  FIG. 3.2 ); 
     S 3 . Fabricating a top polymer substrate layer  270  above each function array  200 , (referring to  FIG. 3.3 a   ), lithographing the top polymer substrate layer  270  (referring to  FIG. 3.3 b   ), fabricating a thinning support on the top polymer substrate layer  270  after lithographing (referring to  FIG. 3.3 c   ), and thinning a bottom surface of the silicon wafer  100  to a target thickness so that the function arrays  200  on the silicon wafer are separated from each other (referring to  FIG. 3.3 d   ), with the bottom surface of the silicon wafer  100  being a surface of the silicon wafer  100  away from the function array  200 ; and 
     S 4 . Spin-coating or depositing a bottom polymer substrate layer  280  on the bottom surface of the silicon wafer  100  after thinning (referring to  FIG. 3.4 a   ), lithographing the bottom polymer substrate layer  280  to make it match the top polymer substrate layer  270  (referring to  FIG. 3.4 b   ), and then removing the thinning support and releasing the flexible integrated array sensor (referring to  FIG. 3.4 c   ). 
     Further disclosure of operation S 1 : “constructing conductive tungsten plugs  221 ,  222  connected with the readout circuit units  211 ” at S 11  means that the dielectric layer  220  is fabricated on the readout circuit layer, and two sets of conductive tungsten plugs  221 ,  222  are connected with two wiring parts of the readout circuit units  211  on the dielectric layer  220  (referring to  FIG. 3.1 b   ). In some embodiments, S 12  includes: sequentially fabricating the bottom electrode layer  231   b,  the piezoelectric material layer  231   c,  and the top electrode layer  231   a  on the dielectric layer  220  (referring to  FIG. 3.1 c   ); lithographing the electrode layers to form the piezoelectric sensing array layer  230  including m*n separated piezoelectric sensing units  231 , directly connecting each bottom electrode layer  231   b  with the first wiring part of a corresponding readout circuit unit  211  through the conductive tungsten plug  221  (referring to  FIG. 3.1 d   ); and placing the first connecting metal  240  between the top electrode layer  231   a  and one of the conductive tungsten plugs  222  so that each top electrode layer  231   a  is connected with the second wiring part of one of the readout circuit units  211 , thereby forming a function array including m*n function units (referring to  FIG. 31 f   ). 
     As for fabricating the first connecting metal  240 , in some embodiments, a layer of polymer  250  is first deposited on the piezoelectric sensing array layer  230  (referring to  FIG. 3.1 e   ), where the polymer  250  has first contact holes  251  between each top electrode layer  231   a  of the piezoelectric sensing units  231  and the corresponding conductive tungsten plug  222  of the top electrode layer  231   a,  and then the first connecting metal  240  is placed where the first contact holes are, with the first connecting metal  240  connecting the top electrode layer  231   a  and the corresponding conductive tungsten plug  222 . 
     Further disclosure of operation S 2 : in some embodiments, the ion beam etching technique is used for etching the one or more deep grooves  110 ; in some embodiments, the reactive ion etching technique is used for etching the one or more deep grooves  110 . The plurality of function arrays  200  are simultaneously prepared on the silicon wafer  100  by semiconductor manufacturing techniques, and the deep groove etching of the silicon wafer  100  between the function arrays  200  causes the function arrays  200  to separate from each other (referring to  FIG. 3.2 ). 
     Further disclosure of operation S 3 : in some embodiments, the thinning support is fabricated on a surface of the top polymer substrate layer  270  by temporarily bonding another silicon wafer (hereinafter referred to as the support wafer  300 ) to the surface of the top polymer substrate layer  270  with bonding material  310  (referring to S 33  in  FIG. 3.3 c   ). The thinning support serves to facilitate the thinning process, which is conducted on the bottom surface of the silicon wafer  100 . Since the target thickness of the silicon wafer  100  is small, and the one or more deep grooves  110  are already etched and partially divide the arrays before the bottom surface is thinned, it is necessary to provide a rigid support for each array before thinning the bottom surface of the silicon wafer  100 . Techniques used for thinning the bottom surface of silicon wafers include grinding, chemical mechanical polishing, wet etching, plasma etching, and dry polishing. Besides, the aforementioned “thinning support” operation may be replaced by pasting a blue film to the silicon water  100  in some embodiments. When a temporary bonding method is used for the support wafer  300 , in some embodiments, the flexible integrated array sensor with a function array having a single-function is released by removing the thinned support after de-bonding. 
     Further disclosure of operations S 3  and S 4 : lithographing of the polymer substrate layer in operation S 3  and operation S 4  removes polymer substrate covering one or more deep grooves in areas between function arrays (referring to  FIG. 3.3 b    and  FIG. 3.3 c   ), so that the device can be smoothly released after thinning to obtain a flexible integrated array sensor with a function array having a single-function. The two lithographing processes occur where the deep groove etching occurs on the silicon wafer. It is worth noting that in some embodiments, the bottom polymer substrate layer  280  is omitted, and only the top polymer substrate layer  270  remains. In some embodiments, both the top polymer substrate layer  270  and the bottom polymer substrate layer  280  are fabricated, as shown in  FIGS. 3.1 a   - 3 . 4   c.  Besides, in some embodiments, when the top polymer substrate layer  270  is lithographed, a pad  290  for connecting the sensor and an external system is included (referring to  FIG. 3.3 c   ). 
     As mentioned above, in some embodiments, the plurality of function arrays  200 , each of which including m*n function units  200   a,  are fabricated on the silicon wafer  100  (take a piezoelectric micro pressure sensor as an example, each function unit  200   a  includes a piezoelectric sensing unit  231  and a corresponding readout circuit unit  211 ), and then one or more deep grooves with a thickness equal to or slightly larger than the target thickness are etched between the function arrays  200 . The advantages of one or more aspects of such operations in some embodiments are two-fold: first, the film stress generated in the thinning of the silicon wafer  100  is released by etching the one or more deep grooves, preventing the silicon wafer  100  from warping and cracking; second, there is no longer need to scribe the silicon wafer  100  after thinning, unlike traditional approaches, and therefore the silicon wafer  100  can be released without mechanical scribing, and damages caused by scribing are avoided. In some embodiments, the one or more deep grooves also help to isolate defects propagation during the thinning process. Techniques like this make silicon-based materials more promising as a candidate for flexible integrated sensing. In some embodiments, the target thickness of the thinned silicon wafer is less than 100 μm. Silicon wafers with a thickness less than 100 μm have higher flexibility, which increases the feasibility of preparing flexible integrated sensor arrays. 
     In some embodiments, the flexible array sensor with a function array having a single-function is manufactured by stacking a piezoelectric sensing unit  231  and a readout circuit unit  211  inside the device. Such arrangement not only improves the integration level, but also mitigates many problems caused by too many leads for researchers, such as complex circuit structures, noise, and interference, thereby making integrated piezoelectric array sensors possible. 
     Turning to  FIGS. 4-5 , the present disclosure also provides a flexible integrated array sensor with two different function arrays  200 ,  200 ′. One difference between the embodiments illustrated by  FIGS. 4-5  and the embodiments illustrated by  FIG. 1-3  is that the flexible integrated array sensors illustrated by  FIGS. 4-5  have at least two functions, which, in some embodiments, is achieved when the sensing array layers in the two function arrays consist of micro sensors with different sensing mechanisms and/or different performances. In some embodiments, as shown in  FIGS. 4-5 , the left function array  200  includes one or more function units  200   a,  the right function array  200 ′ includes one or more function units  200   a ′, and the two are made of different sensing units. Those skilled in the art should be enabled by the disclosure herein to make, without undue experimentation, a flexible array sensor with more than two different function arrays. 
       FIGS. 4-5  show a flexible integrated array sensor with two different function arrays  200 ,  200 ′. Another difference between the embodiments illustrated by  FIGS. 4-5  and the embodiments illustrated by  FIGS. 1, 2, 3.1   a - 3 . 4   c,  is that the flexible integrated array sensors illustrated by  FIGS. 4-5  have a polymer passivation layer  260  disposed between the top polymer substrate  270  and the function array  200 . The polymer passivation layer  260  includes several second contact holes  261  (referring to  FIG. 6.3 b   ), and two (or more than two) separate function arrays are electrically connected through the second contact holes  261  and a piece of second connecting metal  262 . Compared to the embodiments illustrated by  FIGS. 1, 2, 3.1   a - 3 . 4   c,  the embodiments illustrated by  FIGS. 4-5  adds a polymer passivation layer  260 , and uses the second contact holes  261  on the polymer passivation layer  260  to electrically connect two separate function arrays through the second connecting metal  262 . The polymer passivation layer  260  is made of materials such as polyimide, polyester, polyurethane, ethylene-vinyl acetate copolymer, polyolefin, epoxy resin, polycarbonate, polyamide, acrylic resin, silicone resin, parylene materials, and combinations thereof. 
     In terms of manufacturing processes, one difference between the embodiments illustrated by  FIGS. 1, 2, 3.1   a - 3 . 4   c  and the embodiments illustrated by  FIGS. 4-5  lies in the operation S 3 ′. Referring to  FIG. 6.3 a   - FIG. 6.3   g,  at S 3 ′, before fabricating the top polymer substrate layer  270 , the method includes: preparing a polymer passivation layer  260  on the function arrays  200  (referring to  FIG. 6.3 a   ), preparing the second contact holes  261  on the polymer passivation layer  260  (referring to  FIG. 6.3 b   ), electrically connecting the two separate function arrays  200  through the second connecting metal  262  by using the second contact holes  261  (referring to  FIG. 6.3 c   ); preparing a top polymer substrate layer  270  on the polymer passivation layer  260  (referring to  FIG. 6.3 d   ), and lithographing the polymer passivation layer  260  and the top polymer substrate layer  270  (referring to S 35 ′ in  FIG. 6.3 e   ). As illustrated by S 35 ′ in  FIG. 6.3   e,  when the polymer passivation layer  260  and the top polymer substrate layer  270  are lithographed, a pad  290  for connecting the sensor to an external system is also included. 
     One of the purposes of lithographing the polymer passivation layer  260  and the top polymer substrate layer  270  together is to remove the parts of the two layers covering the one or more deep grooves in order to smoothly release the device after thinning and obtain a flexible integrated array sensor with two different function arrays. Those skilled in the art should be able to decide on the specific lithographing position, according to the number and distribution of function arrays required during implementation.  FIGS. 4-5  of the present disclosure show schematic views of a flexible array sensor with two different function arrays  200 ,  200 ′ as an example. 
     Still referring to  FIGS. 6.3 a   - FIG. 6.3   g,  after the polymer passivation layer  260  and the top polymer substrate layer  270  are lithographed and the pad  290  is fabricated, subsequent processes regarding thinning support and thinning of the bottom surface of the wafer  100  are similar to those illustrated by  FIG. 3.3 c   - FIG. 3.3   d,  referring to S 36 ′ in  FIG. 6.3 f    and S 37 ′ in  FIG. 6.3   g,  and those skilled in the art should be able to implement S 36 ′, S 37 ′ without undue experimentation. 
     After the thinning at S 3 ′ is completed, the manufacturing processes, in some embodiments, further include S 4 ′: spin-coating or depositing a bottom polymer substrate layer  280  (referring to  FIG. 6.4 a   ) on the bottom surface of the silicon wafer  100 , and lithographing the bottom polymer substrate layer  280  to make the bottom polymer substrate layer  280  match the top polymer substrate layer  270  (referring to  FIG. 6.4 b   ), removing the thinning support fabricated at S 36 ′ (referring to  FIG. 6.4 c   ) and releasing the fabricated flexible integrated array sensor with function arrays having dual or multiple functions. 
     In some embodiments, the flexible array sensor has two or more different function arrays, and those skilled in the art should be able to modify the processes illustrated by S 1 ′ based on the present disclosure, to manufacture such flexible array sensor with two or more different function arrays. The present disclosure presents  FIGS. 4-6.4   c  only as examples. 
     The above description of illustrated implementations of the present disclosure is not intended to be exhaustive or to limit the invention to the precise forms disclosed. While specific implementations of, and examples for, the invention are described herein for illustrative purposes, various equivalent modifications are possible within the scope of the invention, as those skilled in the relevant art will recognize. 
     These modifications may be made to the invention in light of the above detailed description. The terms used in the following claims should not be construed to limit the invention to the specific implementations disclosed in the specification and the claims. Rather, the scope of the invention is to be determined entirely by the following claims, which are to be construed in accordance with established doctrines of claim interpretation. 
     LIST OF REFERENCE NUMERALS 
       100  Silicon wafer 
       110  Deep groove 
       200  Function array 
       200   a  Function unit 
       300  Support wafer 
       310  Bonding material 
       210  Readout circuit layer 
       211  Readout circuit unit 
       220  Dielectric layer 
       221 ,  222  Conductive tungsten plugs 
       230  Piezoelectric sensing array layer 
       231  Piezoelectric sensing unit 
       231   a  Top electrode layer 
       231   b  Bottom electrode layer 
       231   c  Piezoelectric material layer 
       240  First connecting metal 
       250  Polymer 
       251  First contact hole 
       260  Polymer passivation layer 
       261  Second contact hole 
       262  Second connecting metal 
       270  Top polymer substrate layer 
       280  Bottom polymer substrate layer 
       290  Pad