Small-size temperature high-pressure integrated sensor via flip-chip method.pdf
Huang et al. Microsystems & Nanoengineering  (2024) 10:104  Microsystems & Nanoengineering https://doi.org/10.1038/s41378-024-00723-3 www.nature.com/micronano A R T I C L E O p e n A c c e s s Small-size temperature/high-pressure integrated sensor via ﬂip-chip method Mimi Huang1,2,3,4, Xiaoyu Wu4, Libo Zhao 1,2,3,5,6, Xiangguang Han1,2,3,5✉, Yong Xia1,2,3,5✉, Yi Gao1,2,3,4, Zeyu Cui1,2,3,5, Cheng Zhang1,2,3,4, Xiaokai Yang1,2,3,4, Zhixia Qiao1,2,3,4,7, Zhikang Li 1,2,3,5, Feng Han1,2,3,5, Ping Yang1,2,3,4,5 and Zhuangde Jiang1,2,3,4 Abstract Hydraulic technology with smaller sizes and higher reliability trends, including fault prediction and intelligent control, requires high-performance temperature and pressure-integrated sensors. Current designs rely on planar wafer- or chip-level integration, which is limited by pressure range, chip size, and low reliability. We propose a small-size temperature/high-pressure integrated sensor via the ﬂip-chip technique. The pressure and temperature units are arranged vertically, and the sensing signals of the two units are integrated into one plane through silicon vias and gold–gold bonding, reducing the lateral size and improving the efﬁciency of signal transmission. The ﬂip-chip technique ensures a reliable electrical connection. A square diaphragm with rounded corners is designed and optimised with simulation to sense high pressure based on the piezoresistive effect. The temperature sensing unit with a thin-ﬁlm platinum resistor measures temperature and provides back-end high-precision compensation, which will improve the precision of the pressure unit. The integrated chip is fabricated by MEMS technology and packaged to fabricate the extremely small integrated sensor. The integrated sensor is characterised, and the pressure sensor exhibits a sensitivity and sensitivity drift of 7.97 mV/MPa and −0.19% FS in the range of 0–20 MPa and −40 to 120 °C. The linearity, hysteresis, repeatability, accuracy, basic error, and zero-time drift are 0.16% FS, 0.04% FS, 0.06% FS, 0.18% FS, ±0.23% FS and 0.04% FS, respectively. The measurement error of the temperature sensor and temperature coefﬁcient of resistance is less than ±1 °C and 3142.997 ppm/°C, respectively. The integrated sensor has broad applicability in fault diagnosis and safety monitoring of high-end equipment such as automobile detection, industrial equipment, and oil drilling platforms. Introduction Hydraulic ﬂuid transmission is one of the most widely utilised transmission technologies in aerospace, engi- neering, robotics, and other industries. Hydraulic systems have evolved to be lighter in weight, smaller in size, with a higher pressure range, higher power density, and more intelligent, with the need for higher reliability and safety. The detection of hydraulic system faults is critical for avoiding system failure. As a typical hydraulic system, an electro-hydrostatic actuator (EHA) is an important growth path with advantages such as small size, high hydraulic output force, and ﬂexible control 1–4. However, owing to the lack of multi-parameter in-situ testing and the bulk and quality requirements of the testing parts, the ability to predict EHA faults is limited. The high-level integration of the EHA places additional demands on system safety. In a hydraulic system, the load size determines the operating pressure. It must operate within a speciﬁed pressure range to ensure the system operates safely and normally. Oil is utilised as the hydraulic transmission medium to achieve energy con- version. High oil temperatures cause a decrease in the ﬂuid viscosity, leakage, accelerated ageing of parts, and other difﬁculties that result in various hydraulic system © The Author(s) 2024 OpenAccessThisarticleislicensedunderaCreativeCommonsAttribution4.0InternationalLicense,whichpermitsuse,sharing,adaptation,distributionandreproduction in any medium or format, as long as you give appropriate credit to the original author(s) and the source, provide a link to the Creative Commons licence, and indicate if changes were made. The images or other third party material in this article are included in the article’s Creative Commons licence, unless indicated otherwise in a credit line to the material. If material is not included in the article’s Creative Commons licence and your intended use is not permitted by statutory regulation or exceeds the permitted use, you will need to obtain permission directly from the copyright holder. To view a copy of this licence, visit http://creativecommons.org/licenses/by/4.0/. Correspondence: Xiangguang Han (xiangguang@xjtu.edu.cn) or Yong Xia (yongxia@xjtu.edu.cn) 1State Key Laboratory for Manufacturing Systems Engineering, International Joint Laboratory for Micro/Nano Manufacturing and Measurement Technologies, Xi’an Jiaotong University, Xi’an 710049, China 2Xi’an Jiaotong University (Yantai) Research Institute for Intelligent Sensing Technology and System, Xi’an Jiaotong University, Xi’an 710049, China Full list of author information is available at the end of the article These authors contributed equally: Mimi Huang, Xiaoyu Wu 1234567890():,; 1234567890():,; 1234567890():,; 1234567890():,; failures5. Hence, temperature and pressure are two critical parameters related to hydraulic system safety with the miniaturisation and intelligent development of hydraulic systems. It is necessary to detect the temperature and pressure simultaneously to monitor system safety and avoid the occurrence of faults. Therefore, temperature and pressure-integrated sensors have broad application prospects and have garnered signiﬁcant attention. Inte- grated sensors can be divided into ﬂexible, ﬁbre-optic, and silicon-based sensors based on the sensing materials. Flexible sensors are mostly used in the ﬁelds of robot skin and biomedicine, and their pressure–temperature range is relatively small6–10. Although optical ﬁbre sensors have the advantages of anti-interference, electrical insulation, corrosion resistance, and long-distance signal transmis- sion, their signal processing requires special regulators, which increases the cost of post-processing11–15. How- ever, sensors made of ﬂexible and optical materials have problems such as a non-standard fabrication process and poor repeatability. Based on MEMS techniques, silicon-based temperature/ pressure integrated sensors have the features of small size, high repeatability, and a large linear measuring range and are widely utilised in industrial applications. Integrating sensors can be divided into two categories based on integration methods. The ﬁrst is chip-level stacking16. Although ﬂexible in integration, it greatly increases the cost and packaging size owing to its low efﬁciency and difﬁculty in small-die handling. The second is monolithic integration. According to the application requirements, multisensors are fabricated on the same silicon substrate using MEMS techniques. The pressure units in the integrated sensors designed by Lin17 and Chien18 were based on the capacitive effect, and the sensitivities in the ranges of 20–120 kPa and 20–100 kPa were 0.969 fF/kPa and 0.200 fF/kPa, respec- tively. Lin’s resistance temperature detector had a sensitivity of 0.26%/°C in the range of 25–85 °C. Chien used a diode temperature sensor, and the sensitivity was 0.82 mV/°C at 25–85 °C. Although capacitive pressure sensors have high temperatures and long-term stabilities, they are sensitive to the parasitic capacitance introduced by packaging structures, measurement mediums, and circuits. Cheng19 designed an integrated sensor with a resonant pressure unit and a Pt resistor temperature unit. Two parts with differential and static pressures were designed for the pressure sensing units. The sensitivity of the differential pressure part was 79.76 Hz/kPa in the range of 0–100 kPa, and the measurement accuracy of the static pressure component was 0.02% FS in the range of 110–200 kPa. The temperature unit was a Pt resistor with a sensitivity of 6.22 Ω/°C in the range of −20 to 60 °C. Although the resonant type is highly precise, the fabrication process is complicated, and the pressure range is narrow. The integrated sensor designed by Li20 used polysilicon for both pressure and temperature sensors. The pressure range was 0–450 kPa, and the full output was 45.9 mV, the linearity was ±0.84% FS. The temperature coefﬁcient of resistance (TCR) of the temperature sensor was −578 ppm/°C. The ﬁnal chip size was 2.5 × 2.5 × 0.84 mm3. Zhao21 designed an integrated sensor in which both pressure and temperature used the piezoresistors. The sensitivity of the pressure sensor was 0.020 mV/V/kPa with a non-linearity of 0.4% FS in the range of 0–200 kPa. The sensitivity of the temperature sensor was 5.617 Ω/°C with a non-linearity of 0.48% FS in the range of −30 to 150 °C. The ﬁnal chip size was 4 × 6 × 0.9 mm3. The existing monolithic integrated sensors are tiled, and all the sensing units are arranged in a plane. Conse- quently, the fabrication process should be compatible with every sensing unit, however, the performance of the sensing units may inevitably be lost. In addition, because the chips are packaged by wire-bonding, the size of the packaged sensor is large, and the reliability of the elec- tronic connection is poor in harsh environments, such as strong vibrations. Here, we propose a vertically integrated temperature/ pressure sensor based on leadless packaging techniques. The integrated sensor uses piezoresistors and platinum thin-ﬁlm resistors as the pressure and temperature- sensing elements, respectively. The pressure and tem- perature units are arranged vertically and closely bonded with through-silicon vias (TSV) and Au–Au thermo- compression bonding processes, ensuring electrical con- nections and saving planar space. A square diaphragm with rounded corners for pressure sensing is designed and optimised based to the numerical simulation results of the structure’s diaphragm stress and natural frequency. Finally, an integrated sensor is fabricated, and its perfor- mance is characterised. The results reveal that a sensor with a small size has high sensitivity, linearity, repeat- ability, and basic error. Material and methods Model and structure The designed integrated sensor is shown in Fig. 1a. There are two components: a pressure-sensing unit and a temperature-sensing unit. To reduce the lateral size of the chip and avoid mutual interference, two units are placed on Silicon Wafers I and II. Three types of elastic dia- phragms are used in the pressure sensors: circular, rec- tangular, and square. A circular diaphragm is not conducive to mass production. The maximum stress area of the rectangular diaphragm is located at the centre of the elastic diaphragm, and the maximum stress area of the square diaphragm is at the centre of the four sides of the elastic diaphragm. In the case of the same short side, the stress difference of the rectangular diaphragm is smaller Huang et al. Microsystems & Nanoengineering  (2024) 10:104  Page 2 of 10 Experimental test results An experimental platform was built to test the perfor- mance of the integrated sensor, as illustrated in Fig. 5a. The sensor was placed in a temperature chamber (FDW 701 P) with a control accuracy of ±0.5 °C to maintain the different temperatures. The piston pressure gauge (CW- 600T) with control accuracy of 0.02% provided different pressures in the range of 0–20 MPa utilising weights with a pressure interval of 4 MPa. During the tests, a source table (Keithley 2612B) provided a constant voltage of 5 V to the pressure unit of the integrated sensor. A multi- meter (Keithley DAQ6510) detected the changes in the output voltage of the pressure sensor, whereas another multimeter recorded the changes in the resistance of the temperature sensor. The performance of the pressure unit in the integrated sensor was tested at 25 °C with the built experimental platform. Two rounds of travel tests were conducted on the sensor at 0–20 MPa. The experimental data are pre- sented in Table 1, and the test curves are shown in Fig. 5b. Via the above data, the linearity of the pressure sensor at room temperature was 0.16% FS, the hysteresis was 0.04% FS, the repeatability was 0.06% FS, the basic error was ±0.23% FS, accuracy was 0.18% FS. The full-scale output and sensitivity were 159.42 mV and 7.97 mV/MPa, respectively. Compared with the theoretical data, the errors were within 3%. The zero output of the pressure unit was measured at room temperature. The sampling interval was 1 s, and the sampling time was 30 min. The output signal curve is shown in Fig. 5c. The zero-drift coefﬁcient was calculated to be 0.04% FS utilising Eq. 5. dz ¼ ðyd max  yd minÞ=yFS ´ 100% ð5Þ where ydmax is the maximum value in 30 min, and ydmin is the minimum value in 30 min. The piezoresistive coefﬁcient of silicon is a function of temperature, and the sensitivity of the pressure unit changes with temperature. Therefore, a different tem- perature environment was provided by a thermal chamber to test the sensitivity performance of the sensor at −40, 0, 40, 80, and 120 °C. The test was performed after holding for 30 min at each temperature to ensure temperature stability. The output values of the sensor at different temperatures are presented in Table 2, and Fig. 5d illus- trates the corresponding characteristic curves. The sen- sitivities of the pressure unit in the integrated sensor at different temperatures were calculated, as illustrated in Fig. 5e. The temperature sensitivity drift of the pressure unit was calculated to be −0.19% FS by Eq. 6, and the sensi- tivity of the sensor gradually decreased with increasing temperature. Subsequently, the sensitivity of the pressure sensor was compensated according to this law. β ¼ yFSðt2Þ  yFSðt1Þ yFSðt1Þðt2  t1Þ ´ 100% ð6Þ where t1 is the lowest temperature; t2 is the highest temperature; yFS(t1) is the full-scale output at the lowest Table 1 Calibration date at 25 °C Pressure (MPa) Voltage output (mV) 1st Round 2nd Round Upward Downward Upward Downward 0 87.42 87.47 87.47 87.47 4 119.00 118.96 119.03 118.97 8 150.78 150.72 150.83 150.74 12 182.68 182.63 182.73 182.72 16 214.72 214.69 214.76 214.74 20 246.84 246.84 246.82 246.82 Table 2 Calibration date at different temperatures Pressure (MPa) Voltage output (mV) −40 °C 0 °C 40 °C 80 °C 120 °C 0 84.98 77.54 73.70 69.63 68.90 4 122.22 110.87 103.66 97.50 94.57 8 159.83 144.43 133.77 125.83 120.60 12 197.56 178.14 164.51 153.83 146.71 16 235.47 211.98 194.98 181.90 172.80 20 273.38 245.96 225.47 210.20 199.12 Table 3 Resistance of temperature unit at different temperatures T/°C Test resistance/ kΩ Fitting resistance/ kΩ Resistance deviation/kΩ Temperature deviation/°C −40 1.395 1.394 −0.001 −0.275 0 1.595 1.594 −0.001 −0.196 40 1.791 1.794 0.003 0.683 80 1.993 1.995 0.002 0.363 120 2.197 2.195 −0.002 −0.355 Huang et al. Microsystems & Nanoengineering  (2024) 10:104  Page 8 of 10 temperature, and yFS(t2) is the full-scale output at the highest temperature. The resistance of the temperature sensor was also tested in the temperature range of −40 to 120 °C, and the least square method was employed to ﬁt it. The variations in platinum resistance at different temperatures are pre- sented in Table 3. The TCR obtained from Eq. 730 was 3142.997 ppm/°C. TCR ¼ Rt2  Rt1 Rt1ðt2  t1Þ ´ 106 ð7Þ where Rt2 is the resistance at t2; Rt1 is the resistance at t1; t1 is 0 °C, and t2 is the highest temperature of the test. The data were ﬁtted to a straight line, as illustrated in Fig. 5f, and the relationship between the platinum resistance and temperature is shown in Eq. 8. RT ¼ 0:00501T þ 1:594 ð8Þ The calculated temperature sensor sensitivity was 5.01 Ω/°C, the nonlinearity was 0.16% FS, accuracy was 0.32% FS, and the measurement error was less than ±1 °C. The outputs of the temperature sensor under different pressures are shown in Fig. 5g. It can be seen that the pressure does not affect the output of the temperature sensor. The indices of the temperature and pressure integrated sensors are listed in Table 4. Compared with the pub- lished literature, our integrated sensor chip had a small size, large pressure range, and high linearity and precision; however, there was still a gap compared with mature products. The temperature measurement unit also exhibited high sensitivity. Conclusion A leadless temperature and pressure integrated sensor based on TSV and Au–Au bonding processes is proposed. The pressure and temperature units are connected long- itudinally via the TSV and Au–Au bonding processes, which reduces the lateral dimension and avoids signal interference between the two units. The pressure unit adopts a simple and reliable ﬂat ﬁlm structure, and applies pressure to the back, effectively reducing the pressure medium requirements. The addition of the ﬁllet design increases the natural frequency. A platinum resistor with a stable chemical performance and high precision is selected as the temperature unit. Instead of conventional metal ball welding, a solder ball effectively improves the reliability of the electrical connection of the sensor. The chip is fabricated with a reasonable and reliable process and packaged as an integrated sensor. Finally, the sensi- tivity of the pressure unit in the integrated sensor is 7.97 mV/MPa in the range of 0–20 MPa, and the linearity is 0.16% FS. The hysteresis is 0.04% FS, the repeatability is 0.06% FS, the basic error is ±0.23%FS, the accuracy is 0.18% FS, the zero-time drift is 0.04% FS, and the thermal sensitivity drift is −0.20% FS at −40 to 120 °C. The TCR of the platinum resistor in the temperature unit is 3142.997 ppm/°C and the measurement error is less than ±1 °C. Acknowledgements This work was supported in part by the National Key Research & Development (R&D) Plan (2022YFB3205800), the National Natural Science Foundation of China (52305618). Author details 1State Key Laboratory for Manufacturing Systems Engineering, International Joint Laboratory for Micro/Nano Manufacturing and Measurement Technologies, Xi’an Jiaotong University, Xi’an 710049, China. 2Xi’an Jiaotong University (Yantai) Research Institute for Intelligent Sensing Technology and System, Xi’an Jiaotong University, Xi’an 710049, China. 3Shandong Laboratory of Yantai Advanced Materials and Green Manufacturing, Yantai 265503, China. 4School of Mechanical Engineering, Xi’an Jiaotong University, 710049 Xi’an, China. 5School of Instrument Science and Technology, Xi’an Jiaotong University, 710049 Xi’an, China. 6Chongqing Key Laboratory of Micro-Nano Systems and Intelligent Sensing, Chongqing Academician Workstation, Chongqing 2011 Collaborative Innovation Center of Micro/Nano Sensing and Intelligent Ecological Internet of Things, Chongqing Technology and Business University, Nan’an District, Chongqing 400067, China. 7Xi’an Aerospace Yuanzheng Fluid Control Co. Ltd., Xi’an 710049, China Author contributions Mimi Huang: Conceptualisation, Methodology, Validation, Formal analysis, Investigation, Writing—Original Draft; Xiaoyu Wu, Libo Zhao, Xiangguang Han, Yong Xia, Zhikang Li, Feng Han: Validation, Investigation, Resources, Data Curation, Writing—Review & Editing; Yi Gao, Zeyu Cui, Cheng Zhang, Xiaokai Yang, Zhixia Qiao: Data Curation, Resources, Writing—Review & Editing, Supervision; Ping Yang, Zhuangde Jiang: Project administration, Supervision, Funding acquisition. Conﬂict of interest The authors declare no competing interests. Table 4 Performance parameters comparison with published literature Source Chip size (mm) Pressure range Linearity Basic error Temperature range (°C) TCR Our work 1.8 × 1.8 × 0.75 0–20 MPa 0.16% FS ±0.23% FS −40 to 120 3142.997 ppm/°C Wang et al.20 2.5 × 2.5 × 0.84 0–450 kPa 0.84% FS / / −578 ppm/°C Xu et al.21 4.0 × 6.0 × 0.9 0–200 kPa 0.40% FS / −30 to 150 / Mansoor et al.31 3.8 × 3.8 0–75 kPa 0.25% FS / 20–300 / Huang et al. Microsystems & Nanoengineering  (2024) 10:104  Page 9 of 10 Received: 26 December 2023 Revised: 1 May 2024 Accepted: 22 May 2024 References 1. Cologni, A. L. et al. Modeling and identiﬁcation of an electro-hydrostatic actuator. Ifac Proc. Vol. https://doi.org/10.3182/20100913-3-US-2015.00020 (2010). 2. Alle, N. et al. Review on electro hydrostatic actuator for ﬂight control. Int. J. Fluid Power https://doi.org/10.1080/14399776.2016.1169743 (2016). 3. Hagen, D., Padovani, D. & Choux, M. A comparison study of a novel self- contained electro-hydraulic cylinder versus a conventional valve-controlled actuator-part 1: motion control. Actuators https://doi.org/10.3390/ACT8040079 (2019). 4. Hagen, D., Padovani, D. & Choux, M. A. A comparison study of a novel self- contained electro-hydraulic cylinder versus a conventional valve-controlled actuator—part 2: energy efﬁciency. Actuators https://doi.org/10.3390/ act8040078 (2019). 5. Junhui, Z. et al. Churning losses analysis on the thermal-hydraulic model of a high-speed electro-hydrostatic actuator pump. Int. J. Heat. Mass Transf. 127, 1023–30, https://doi.org/10.1016/j.ijheatmasstransfer.2018.06.133 (2018). 6. Zu, G. et al. Superhydrophobic ultraﬂexible triple-network graphene/poly- organosiloxane aerogels for high-performance multifunctional temperature/ strain/pressure sensing array. Chem. Mater. https://doi.org/10.1021/acs. chemmater.9b02437 (2019). 7. Han, S., Jiao, F., Khan, Z. U., Edberg, J., Fabiano, S. & Crispin, X. Thermoelectric polymer aerogels for pressure-temperature sensing applications. Adv. Funct. Mater. 27, 1703549, https://doi.org/10.1002/adfm.201703549 (2017). 8. Gui, Q., He, Y., Gao, N., Tao, X. & Wang, Y. A skin-inspired integrated sensor for synchronous monitoring of multiparameter signals. Adv. Funct. Mater. 27, 1702050, https://doi.org/10.1002/adfm.201702050 (2017). 9. Wang, Z., Zhang, L., Liu, J. & Li, C. A ﬂexible bimodal sensor based on an electrospun nanoﬁbrous structure for simultaneous pressure temperature detection. Nanoscale 11, 14242–9, https://doi.org/10.1039/C9NR03098K (2019). 10. Zhu, P., Wang, Y., Wang, Y., Mao, H., Zhang, Q. & Deng, Y. Flexible 3D archi- tectured piezo/thermoelectric bimodal tactile sensor array for E-skin applica- tion. Adv. Energy Mater. 10, 2001945, https://doi.org/10.1002/aenm.202001945 (2020). 11. Li, Z. et al. A high sensitivity temperature sensing probe based on microﬁber Fabry-Perot interference. Sensors 19, 1819, https://doi.org/10.3390/s19081819 (2019). 12. Hu, Jianyang. et al. Fiber Mach-Zehnder-interferometer-based liquid crystal biosensor for detecting enzymatic reactions of penicillinase. Appl. Opt. 58, 4806–11, https://doi.org/10.1364/AO.58.004806 (2019). 13. Liu, Y. et al. Fabrication of dual-parameter ﬁber-optic sensor by cascading FBG with FPI for simultaneous measurement of temperature and gas pressure. Opt. Commun. 443, 166–71, https://doi.org/10.1016/j.optcom.2019.03.034 (2019). 14. Dong, N. et al. Pressure and temperature sensor based on graphene dia- phragm and ﬁber Bragg gratings. IEEE Photonics Technol. Lett. https://doi.org/ 10.1109/LPT.2017.2786292 (2018). 15. Fu, D. et al. A simple, highly sensitive ﬁber sensor for simultaneous mea- surement of pressure and temperature. IEEE Photonics Technol. Lett. https://doi. org/10.1109/LPT.2020.2993836 (2020). 16. Tian, L. et al. Oil-ﬁlled high-temperature and high-pressure composite sensors of pressure and temperature. Micronanoelectron. Technol. 50, 776–778, https:// doi.org/10.3969/j.issn.1671-4776.2013.12.006 (2013). 17. Lin, Y. C. et al. Monolithic integration of pressure/humidity/temperature sen- sors for CMOS-mems environmental sensing hub with structure designs for performances enhancement. 2020 IEEE 33rd International Conference on Micro Electro Mechanical Systems (MEMS). (IEEE, 2020). https://doi.org/10.1109/ MEMS46641.2020.9056401. 18. Chien, T. L. et al. Fabrication and integration of SOC environment sensing hub with gas/pressure/temperature sensors. 2022 IEEE 35th International Conference on Micro Electro Mechanical Systems Conference (MEMS). (IEEE, 2022) 138–41. https://doi.org/10.1109/MEMS51670.2022.9699821. 19. Cheng, C. et al. A MEMS resonant differential pressure sensor with high accuracy by integrated temperature sensor and static pressure sensor. IEEE Electron Device Lett. 43, 2157–60, https://doi.org/10.1109/LED.2022.3211886 (2022). 20. Wang, Q. et al. On-chip integration of acceleration, pressure, and temperature composite sensor with a single-sided micromachining technique. J. Micro- electromech. Syst. 20, 42–52, https://doi.org/10.1109/JMEMS.2010.2100031 (2011). 21. Xu, J. et al. A monolithic silicon multi-sensor for measuring three-axis accel- eration, pressure and temperature. J. Mech. Sci. Technol. 22, 731–9, https://doi. org/10.1007/s12206-008-0105-6 (2008). 22. Bao, M.-H. Basic mechanics of beam and diaphragm structures. Handbook of Sensors and Actuators. (Elsevier, New York, NY, USA, 2000) pp. 23–88. https:// doi.org/10.1016/S1386-2766(00)80016-X. 23. Huang, M. et al. MEMS-based Pt ﬁlm temperature sensor chip on silicon substrate. Meas. Sci. Technol. 33, 125113, https://doi.org/10.1088/1361-6501/ ac90dd (2022). 24. Su, W. et al. Thermal compensation system for silicon piezoresistive pressure sensors based on surface ﬁtting and wild horse algorithm. IEEE Sens. J. https:// doi.org/10.1109/JSEN.2024.3365469. 25. Gao, C., Hua, X. & Zhang, D. Design and analysis of high-performance and small-size piezoresistive pressure sensors. IEEE Sens. J. 23, 6649–59, https://doi. org/10.1109/JSEN.2023.3248579 (2023). 26. Kim, N. H. et al. Electrical and thermal properties of platinum thin ﬁlms pre- pared by DC magnetron sputtering for micro-heater of microsensor appli- cations after CMP process. Solid State Phenomena https://doi.org/10.4028/ www.scientiﬁc.net/SSP.124-126.267 (2007). 27. Tiggelaar, R. M. et al. Stability of thin platinum ﬁlms implemented in high- temperature microdevices. Sens. Actuators A Phys. 152, 39–47, https://doi.org/ 10.1016/j.sna.2009.03.017 (2009). 28. Ekkels, P. et al. Evaluation of platinum as a structural thin ﬁlm material for RF- MEMS devices. J. Micromech. Microeng. 19, 065010, https://doi.org/10.1088/ 0960-1317/19/6/065010 (2009). 29. Boguhn, D. & Koepke, M. Typical, R(T90) characteristics of platinum thin- ﬁlm resistance thermometers in the temperature range from 50 °C to +660 °C. Int. J. Thermophys. 32, 2379–87, https://doi.org/10.1007/s10765- 011-1088-6 (2011). 30. Gao, C. & Zhang, D. Establishment and veriﬁcation of resistance temperature coefﬁcient model of P-type non-uniformly doped resistance. J. Micromech. Microeng. 32, 105006, https://doi.org/10.1088/1361-6439/ac8aa4 (2022). 31. Mansoor, M. et al. An SOI CMOS-based multi-sensor MEMS chip for ﬂuidic applications. Sensors 16, 1608, https://doi.org/10.3390/s16111608 (2016). Huang et al. Microsystems & Nanoengineering  (2024) 10:104  Page 10 of 10
Title: Small-size temperature/high-pressure integrated sensor via flip-chip method ​
Authors: Mimi Huang, Xiaoyu Wu, Libo Zhao, Yi Gao, Xiangguang Han, Yong Xia, Zeyu Cui, Cheng Zhang, Zhixia Qiao, Xiaokai Yang, Zhikang Li, Feng Han, Ping Yang, Zhuangde Jiang ​
Publisher: Microsystems & Nanoengineering, Nature Publishing Group ​
Date: 2024-07-23 00:00:00
Abstract: Hydraulic technology with smaller sizes and higher reliability trends, including fault prediction and intelligent control, requires high-performance temperature and pressure-integrated sensors. ​ Current designs rely on planar wafer- or chip-level integration, which is limited by pressure range, chip size, and low reliability. ​ We propose a small-size temperature/high-pressure integrated sensor via the flip-chip technique. ​ The pressure and temperature units are arranged vertically, and the sensing signals of the two units are integrated into one plane through silicon vias and gold–gold bonding, reducing the lateral size and improving the efficiency of signal transmission. ​ The flip-chip technique ensures a reliable electrical connection. ​ A square diaphragm with rounded corners is designed and optimised with simulation to sense high pressure based on the piezoresistive effect. ​ The temperature sensing unit with a thin-film platinum resistor measures temperature and provides back-end high-precision compensation, which will improve the precision of the pressure unit. ​ The integrated chip is fabricated by MEMS technology and packaged to fabricate the extremely small integrated sensor. ​ The integrated sensor is characterised, and the pressure sensor exhibits a sensitivity and sensitivity drift of 7.97 mV/MPa and −0.19% FS in the range of 0–20 MPa and −40 to 120 °C. ​ The linearity, hysteresis, repeatability, accuracy, basic error, and zero-time drift are 0.16% FS, 0.04% FS, 0.06% FS, 0.18% FS, ±0.23% FS and 0.04% FS, respectively. ​ The measurement error of the temperature sensor and temperature coefficient of resistance is less than ±1 °C and 3142.997 ppm/°C, respectively. ​ The integrated sensor has broad applicability in fault diagnosis and safety monitoring of high-end equipment such as automobile detection, industrial equipment, and oil drilling platforms. ​