Patent Publication Number: US-10324054-B2

Title: Method of manufacturing sensor device

Description:
CROSS-REFERENCE TO RELATED APPLICATION 
     This application is a divisional application of and claims the priority benefit of U.S. patent application Ser. No. 14/961,906, filed on Dec. 8, 2015, now allowed. The prior application Ser. No. 14/961,906 claims the priority benefit of Taiwan application serial no. 104135766, filed on Oct. 30, 2015. The entirety of each of the above-mentioned patent applications is hereby incorporated by reference herein and made a part of this specification. 
    
    
     TECHNICAL FIELD 
     The disclosure relates a method of manufacturing a sensor device that senses gas, humidity and temperature. 
     BACKGROUND 
     The three important layers in the Internet of Things (IoT) are the perception layer, the internet layer and the application layer, and the most important component in the perception layer is the sensor. Therefore, as the technology IoT continues to develop, the demands for sensors increase correspondingly. Currently, sensors that are miniature, low in power consumption and highly sensitive are the most demanding in applications, especially for wearable or mobile phone devices. 
     Presently, the most fundamentally and customarily used sensors are gas, temperature, and humidity sensors, wherein in most gas sensors, a temperature sensor and a humidity sensor are integrated on an extra system board for performing calibrations under the different ambient conditions to provide a better accuracy. Alternatively speaking, most gas sensors are arranged with temperature and humidity sensors. However, for wearable or mobile phone devices, the space for accommodating sensors is very limited; hence, to miniaturize and integrate sensors of various functions in a same fabrication process has been actively pursued by the relevant industries. 
     SUMMARY 
     An exemplary embodiment of the disclosure relates to a method for manufacturing a sensor device. The method includes forming a plurality of sensing electrodes on a substrate, followed by forming a sensing material layer on the sensing electrodes and then etching the sensing material layer to form a first nanowire sensing region, a second nanowire sensing region and a third nanowire sensing region respectively between every two sensing electrodes. A dielectric layer is further formed to cover the first nanowire sensing region, the second nanowire sensing region and the third nanowire sensing region, and the first nanowire sensing region and the third nanowire sensing region are subsequently exposed. 
     Several exemplary embodiments accompanied with figures are described in detail below to further describe the disclosure in details. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The accompanying drawings are included to provide further understanding, and are incorporated in and constitute a part of this specification. The drawings illustrate exemplary embodiments and, together with the description, serve to explain the principles of the disclosure. 
         FIG. 1  is a stereoscopic schematic view exemplarily illustrating a sensor device according to a first embodiment of the disclosure. 
         FIG. 2  is a stereoscopic schematic view exemplarily illustrating a sensor device according to a second embodiment of the disclosure. 
         FIG. 3  is a circuit diagram of an exemplary sensor device according to a third embodiment of the disclosure. 
         FIGS. 4A, 4B-1, 4B-2, 4C, 4D-1, 4D-2 and 4E  are schematic views exemplarily illustrating respective steps of a method for manufacturing a sensor device according to a fourth embodiment of the disclosure. 
         FIGS. 5A-1, 5A-2, 5B-1, 5B-2, 5C-1, 5C-2, 5D-1 and 5D-2  are schematic views exemplarily illustrating variations of the fourth embodiment of the disclosure on the method for manufacturing a sensor device. 
         FIGS. 6A to 6E  are schematic views exemplarily illustrating variations of the fourth embodiment of the disclosure on the method for manufacturing a sensor device. 
     
    
    
     DETAILED DESCRIPTION OF DISCLOSED EMBODIMENTS 
     In the following detailed description, for purposes of explanation, numerous specific details are set forth in order to provide a thorough understanding of the disclosed embodiments. It will be apparent, however, that one or more embodiments may be practiced without these specific details. In other instances, well-known structures and devices are schematically shown in order to simplify the drawing. 
       FIG. 1  is a stereoscopic schematic view exemplarily illustrating a sensor device according to a first embodiment of the disclosure. 
     In the embodiment as shown in  FIG. 1 , a sensor device includes a substrate  100 , a plurality of sensing electrodes  102   a - 102   c , a humidity nanowire sensor  104 , a temperature nanowire sensor  106 , and a gas nanowire sensor  108 . The substrate  100  may be, for example, a silicon chip or other types of appropriate substrate. The sensing electrodes  102   a - 102   c  are formed on the substrate  100  and the size of each sensing electrode  102   a - 102   c  is 50 μm×50 μm or more to facilitate sensing. The material of the above sensing electrodes  102   a - 102   c  may be selected from, for example, at least one pure metal of or an alloy of platinum (Pt), titanium (Ti), tungsten (W), copper (Cu), aluminum (Al), but excluding pure copper. If the material of the sensing electrodes  102   a - 102   c  is, for example, an alloy, the material of the sensing electrodes  102   a - 102   c  may include CuAl, TiCu, TiW, TiCuAl, etc. The humidity nanowire sensor  104 , the temperature nanowire sensor  106 , and the gas nanowire sensor  108  are also configured on the substrate  100 . In the embodiment, the humidity nanowire sensor  104  includes an exposed first nanowire sensing region  110  and two sensing electrodes  102   a  that are respectively connected with two ends of the first nanowire sensing region  110 . The temperature nanowire sensor  106  includes a second nanowire sensing region  112 , two sensing electrodes  102   b  that are respectively connected with two ends of the second nanowire sensing region  112  and a dielectric layer  114  covering the second nanowire sensing region  112 . The gas nanowire sensor  108  includes an exposed third nanowire sensing region  116  and two sensing electrodes  102   c  that are respectively connected with two ends of the third nanowire sensing region  116 . 
     From the perspectives of reducing the manufacturing cost, the above first, second and third nanowire sensing regions  110 ,  112  and  116  are formed with a same sensing material layer; further, the size of the first nanowire sensing region  110  will have different sensitives for different humidity levels, the size of the second nanowire sensing region  112  will also affect its sensitivity on temperatures, and the different nanowire diameters of the third nanowire sensing region  116  will have different sensitivities for different gases. Therefore, the sizes (diameters) of the nanowires of the first, second and third nanowire sensing regions  110 ,  112  and  116  may vary based on the designs, for example, between 100 nm and 1000 nm; in another embodiment, the sizes (diameters) of the nanowires may be between 50 nm and 350 nm. Further, the nanowires of the first, second and third nanowire sensing regions  110 ,  112  and  116  may have the same or different diameters, but the disclosure is not limited thereto. The above first, second and third nanowire sensing regions  110 ,  112  and  116  may form with different sensing material layers. The material used in forming the sensing material layers for the above first, second and third nanowire sensing regions  110 ,  112  and  116  may include tin oxide (SnO 2 ), titanium oxide (TiO 2 ), zinc oxide (ZnO) or polysilicon (poly Si). In some embodiments, a hydrophilic material, such as titanium oxide, tin oxide, etc., is used. The dielectric layer  114  that covers the second nanowire sensing region  112  may also be covering other parts on the substrate  100  while exposing the sensing electrodes  102   a - 102   c . The material of the dielectric layer  114  may include silicon oxide (SiO 2 ), silicon nitride (SiN) or other appropriate materials. Although the second nanowire region  112  is covered by the dielectric layer  114  and a cross-section thereof is exposed in the Figures, one can easily realize that the second nanowire sensing region  112 , which is similar to the first nanowire sensing region  110  or the third nanowire sensing region  116 , is formed with a plurality of nanowires. The first and third nanowire sensing regions  110 ,  116  in  FIG. 1  are exemplified to have three nanowires, whereas the black dots in between signify that the number of the nanowires can be increased based on the designs. 
       FIG. 2  is a stereoscopic schematic view exemplarily illustrating a sensor device according to a second embodiment of the disclosure, wherein the same reference numbers are used to represent the same or similar structures as shown in  FIG. 1 . 
     Referring to  FIG. 2 , a difference between the first embodiment and the second embodiment lies in that the humidity nanowire sensor  200 , in addition to the first nanowire sensing region  110  and the sensing electrodes  102   a , also includes a hydrophilic material layer  202  covering the first nanowire sensing region  110 , wherein the hydrophilic material layer may be an ALD layer deposited by the atomic layer deposition (ALD) technique and a material of the hydrophilic material layer  202  may include, but is not limited to, aluminum oxide (Al 2 O 3 ), titanium oxide (TiO 2 ), tin oxide (SnO 2 ), Zinc chromate (ZnCr 2 O 4 ) or magnesium chromate (MgCr 2 O 4 ). Since the first nanowire sensing region  110  is covered by the hydrophilic material layer  202 , humidity adsorption is increased to thereby enhance the sensitivity of humidity sensing, even when the nanowire of the first nanowire sensing region  110  is not formed with a hydrophilic material. 
       FIG. 3  is a circuit diagram of an exemplary sensor device according to a third embodiment of the disclosure.  FIG. 3  illustrates a sensor device region  300  and a reading circuit  310 . The sensor device region  300  includes a humidity nanowire sensor  302 , a temperature nanowire sensor  304  and a gas nanowire sensor  306 , and the characteristics of these nanowire sensors can be referred to the first and second embodiments and will not reiterated herein. The reading circuit  310  in the third exemplary embodiment may concurrently read the humidity nanowire sensor  302 , the temperature nanowire sensor  304  and the gas nanowire sensor  306  and convert the readouts from these sensors  302 ,  304 ,  306  to digital signal outputs. Moreover, the sensor device region  300  may also include a plurality of calibration sensors  308   a - 308   c  for calibrating the ambient conditions. The plurality of calibration sensors  308   a - 308   c  which is connected respectively with the humidity nanowire sensor  302 , the temperature nanowire sensor  304  and the gas nanowire sensor  306  at one ends and is grounded at the other ends. The embodiment is exemplified by a half-bridge structure, wherein the lower half-bridge reference resistances of the humidity nanowire sensor  302  and the gas nanowire sensor  306  may directly use the resistances measured by an air-insulated temperature (nanowire) sensor, and the absolute temperature coefficient of the temperature nanowire sensor  304  is different from that of the lower half-bridge reference resistance to obtain the changes in temperature. The lower half-bridge reference resistance for the temperature nanowire sensor  304  is not attached by temperature. The voltage of the midpoint of the half-bridge is an analog voltage signal, and is converted as N bit digital data after being processed by an ADC (analog-to-digital converter) in the reading circuit  310  to facilitate the data comparison by, for example, a MCU (microcontroller) process unit. 
     Accordingly, when the sensors in the third exemplary embodiment start to detect, the program in the process unit of the reading circuit  310  determines which signal to select, and then switches MUX 3 to 1 (multiplexer) to obtain the midpoint voltage value of the humidity, temperature and gas nanowire sensors  302 ,  304  and  306  half-bridge structures. These values are respectively the responses of the humidity, temperature and gas nanowire sensors  302 ,  304  and  306  to the changes of humidity, temperature and gas. Then, the ADC in the reading circuit  310  converts respectively the three analog voltage values to digital values, and sends the ADC converted data to the process unit. The process unit first calculates a temperature value from the readout value of the temperature nanowire sensor  304 , and then a calibration value of humidity under this temperature is extracted from the calibration database  320 , for example, by implementing a look-up-table approach. After a calibrated humidity value is calculated by the process unit, a calibration value of the gas nanowire sensor  306  under the above temperature and humidity is read from the calibration database  320 . The process unit again calculates a gas response value under the above temperature and humidity. The disclosure is not limited thereto. The readout circuit  310  may not use the MUX for the switching; instead, three different ADCs are correspondingly used for the conversion of the humidity, temperature and gas nanowire sensors  302 ,  304  and  306 . Thereafter, data processing is performed by the process unit. 
       FIGS. 4A to 4E  are schematic views exemplarily illustrating respective steps of a method for manufacturing a sensor device according to a fourth embodiment of the disclosure, wherein  FIGS. 4A, 4B-1, 4C and 4D-1  are cross-sectional view, while  FIGS. 4B-2, 4D-2, and 4E  are perspective views. 
     Referring to  FIG. 4A , the substrate  400  includes an interconnection layer  402  thereon, and this interconnect layer  402  includes plural layers of metal conductive layers and dielectric layers (not shown), which may be connected with a transistor type of devices (not shown) disposed on the substrate  400 , wherein the interconnection layer  402  is exemplified by a topmost metal layer  404  in  FIG. 4A . Moreover, the insulation layer  406  formed on the interconnection layer  402  includes a plurality of contacts  408 . Thereafter, a conductive layer  410  is formed, but the disclosure is not limited thereto. The interconnection layer  402  and the contacts  408  thereon in  FIG. 4A  may be omitted, and the conductive layer  410  is formed directly on the substrate  400 . 
     Referring to  FIGS. 4B-1 and 4B-2 , the conductive layer  410  of  FIG. 4A  is etched to from a plurality of sensing electrodes  412 , and the material of the sensing electrodes  412  may be selected from at least a pure metal of or an alloy of platinum (Pt), titanium (Ti), tungsten (W), copper (Cu) and aluminum (Al), but excluding pure copper. If an alloy is used, the sensing electrodes  412  may be formed with CuAl, TiCu, TiW, TiCuAl, etc. Afterwards, an insulation layer  414  is deposited to cover the sensing electrodes  412  and fill the gaps between the sensing electrodes  412 , wherein the insulation layer  414  is, for example, an oxide layer. Thereafter, a CMP (chemical mechanical polishing) process, for example, is performed to expose the sensing electrodes  412  for facilitating the subsequent nanowire process and connection. 
     Continuing to  FIG. 4C , a sensing material layer  416  is formed on the sensing electrodes  412 . The material of the sensing material layer  416  is, for example, tin oxide (SnO 2 ), titanium oxide (TiO 2 ), Zinc oxide (ZnO) or polysilicon (Poly Si). The method used in forming the sensing material layer  416  includes, but is not limited to, PVD sputtering, furnace deposition, chemical bath deposition, etc. 
     Referring to  FIGS. 4D-1 and 4D-2 , the sensing material layer  416  is etched to form a first nanowire sensing region  418 , a second nanowire sensing region  420  and a third nanowire sensing region  422  respectively between every two sensing electrodes  412 . The dimensions (diameters) of the above first, second and third nanowire sensing regions  418 ,  420 ,  422  may vary according to the design requirements, for example, ranging from 10 nm to 1000 nm, and in some embodiments, they may range from 50 nm to 350 nm. Further, the first, second and third nanowire sensing regions  418 ,  420 ,  422  may have the same or different diameters. 
     Referring to  FIG. 4E , a dielectric layer  424  is formed to cover the first, second and third nanowire sensing regions  418 ,  420 ,  422 . The dielectric layer  424  may be formed with, for example, silicon oxide (SiO 2 ) or silicon nitride (SiN). Thereafter, the dielectric layer  424  on the first and third nanowire sensing regions  418 ,  422  is removed to expose the first and third nanowire sensing regions  418 ,  422 , which respectively serve as the humidity nanowire sensor and the gas nanowire sensor. The second nanowire sensing region  420  serving as the temperature nanowire sensor, however, is covered by the dielectric layer  424 . The first nanowire sensing region  418  serving as the humidity nanowire sensor is exposed directly to air; hence, the material used in forming thereof is a hydrophilic material, such as titanium oxide, tin oxide, etc. Further, in the present embodiment, when the dielectric layer  424  on the first and third nanowire sensing regions  418  and  422  is removed, the dielectric layer on the sensing electrodes  412  may also be removed concurrently to form a plurality of pad openings  426 . 
       FIGS. 5A-1 to 5D-2  are schematic views exemplarily illustrating variations of the fourth embodiment of the disclosure on the method for manufacturing a sensor device, wherein  FIGS. 5A-1, 5B-1, 5C-1 and 5D-1  are cross-sectional views and  FIGS. 5A-2, 5B-2, 5C-2 and 5D-2  are perspective views. 
     Referring to  FIGS. 5A-1 and 5A-2 , after the first, second and third nanowire sensing regions  418 ,  420 ,  422  are formed, continuing from  FIGS. 4D-1 and 4D-2 , a dielectric layer  500  is formed to cover the first, second and third nanowire sensing regions  418 ,  420 ,  422 , followed by exposing the first nanowire sensing region  418  and the third sensing region  422 . The above dielectric layer  500  may include silicon oxide (SiO 2 ) or silicon nitride (SiN), for example. 
     Thereafter, referring to  FIGS. 5B-1 and 5B-2 , a hydrophilic material layer  502  is coated on the substrate  400 , wherein the hydrophilic material layer  502  may include, for example, aluminum oxide (Al 2 O 3 ), titanium oxide (TiO 2 ), tin oxide (SnO 2 ), Zinc chromate (ZnCr 2 O 4 ) or magnesium chromate (MgCr 2 O 4 ). A photoresist  504  is further used to define the location where the hydrophilic material layer is to be retained and to facilitate the removable of the unwanted hydrophilic material. In these two Figures, the photoresist  504  is positioned above the first nanowire sensing region  418  and corresponds to the number of nanowires of the first nanowire sensing region  418 , but the disclosure is not limited thereto. The position, the size and the number of the photoresist  504  may vary according to the design requirements. 
     Then, continuing to  FIGS. 5C-1 and 5C-2 , using the photoresist  504  of  FIGS. 5B-1 and 5B-2  as a shield, the exposed hydrophilic material layer  502  is removed. The hydrophilic material layer  502   a  is formed on the first nanowire sensing region  418 , while the third nanowire sensing region  422 , which serves as a gas nanowire sensor, is exposed. Ultimately, the photoresist  504  is removed. 
     Now referring to  FIGS. 5D-1 and 5D-2 , the dielectric layer  500  on the sensing electrodes  412  is removed to form a plurality of pad openings  506 . The exposed sensing electrodes  412  may serve as bonding pads or probe pads. 
       FIGS. 6A to 6E  are schematic views exemplarily illustrating variations of the fourth embodiment of the disclosure on the method for manufacturing a sensor device. 
     Referring to  FIG. 6A , after forming the first, second and third nanowire sensing regions  418 ,  420 ,  422 , continuing from  FIGS. 4D-1 and 4D-2 , a dielectric layer  600  is formed to cover the first, second and third nanowire sensing regions  418 ,  420 ,  422 , followed by exposing the first nanowire sensing region  418 . The above dielectric layer  600  may be formed with silicon oxide or silicon nitride, for example. 
     Now referring to  FIG. 6B , a hydrophilic material layer  502  is coated on the substrate  400 , and a photoresist  504  is used to define the location where the hydrophilic material layer is to be retained. The material of the photoresist  504  and the hydrophilic material layer  502  are similar to those described above. 
     Referring to  FIG. 6C , using the photoresist  504  of  FIG. 6B  as a mask, the exposed hydrophilic material layer  502  is removed and a hydrophilic material layer  502   a  is formed on the first nanowire sensing region  418 . Since the third nanowire sensing region  422  which serves as a gas nanowire sensor has been covered by the dielectric layer  600 , it will not be affected by the fabrication process of the hydrophilic material layer  502   a . Further, no hydrophilic material residues will be remained on any part of the third nanowire sensing region  422 . Ultimately, the photoresist  504  is removed. 
     Thereafter, referring to  FIG. 6D , the dielectric layer  600  on the sensing electrodes  412  is removed to form a plurality of pad openings  506 . 
     Continuing to  FIG. 6E , the dielectric layer  600  on the third nanowire sensing region  422  is removed to expose the third nanowire sensing region  422  to serve as a gas nanowire sensor. 
     In view of the foregoing embodiments of the disclosure, the gas, temperature and humidity nanowire sensors may be concurrently fabricated to have the three sensors integrated on a same substrate. Accordingly, not only the characteristics of the nanowire sensor, such as high sensitivity, miniature, lower power consumption, etc., are provided, the overall volume can be greatly reduced to be applied to wearable devices of IoT. If a reading circuit with sufficient input range is further provided, it may read the sensors as described in the embodiments of the disclosure and then convert them into digital outputs. 
     It will be apparent to those skilled in the art that various modifications and variations can be made to the structure of the disclosed embodiments without departing from the scope or spirit of the disclosure. In view of the foregoing, it is intended that the disclosure cover modifications and variations of this disclosure provided they fall within the scope of the following claims and their equivalents.