Investigation of geometric parameters of silicon structures in device layer during manufacture of sensitive elements of micromechanical accelerometers

The technological processes of fabrication inertial elements of devices of microelectromechanical systems are investigated. The influence of etch square on critical parameters of the process of deep reactive ion etching, allowing to etch silicon structures with high aspect ratios for fabrication micromechanical accelerometers and gyroscopes, is studied. Inertial sensitive elements of micromechanical accelerometers were manufactured on a 150 mm wafer diameter within the framework of an advanced technological process with minimized square etch area on stage of formation of the device layer consisting of an inertial mass, an elastic suspension, control and measuring electrodes, and insulating frame. Values of geometric parameters of silicon structural layers of the device were obtained by analyzing the profiles of inertial visible elements on a scanning electron microscope. Elements of device layer were studied both in the radial and tangential directions of a substrate with a diameter of 150 mm to determine the spread of geometric parameters of inertial sensitive elements. The technological process of fabrication inertial sensitive elements to reduce square of etch area at the stage of device layer formation using an alternative opening the area of the contacts is shown. Based on measurements of the geometric parameters of the silicon structures of the device layer, it was found that the dimensions of the elements and their deviations change in the radial direction from the center of the substrate to the edge. The spread of the geometric parameters of the silicon structures of inertial sensitive elements manufactured according to the advanced technological process on a 150 mm diameter substrate was reduced to 0.4 μm, and the spread of their deviations was reduced to 0.2 μm. The proposed technological process can be used to increase the yield of devices goods during manufacture of inertial sensitive elements and to obtain more uniform characteristics of microelectromechanical systems, such as accelerometers and gyroscopes. The work results can be used in the design of technological processes for the manufacture of new inertial sensitive elements.

1. Barzegar M., Blanks S., Sainsbury B.-A., Timms W. MEMS technology and applications in geotechnical monitoring: a review. Measurement Science and Technology, 2022, vol. 33, no. 5, pp. 052001. https://doi.org/10.1088/1361-6501/ac4f00

2. Fitzgerald A.M. MEMS Inertial Sensors. Position, Navigation, and Timing Technologies in the 21st Century: Integrated Satellite Navigation, Sensor Systems, and Civil Applications. Wiley, 2021, pp. 1435–1446. https://doi.org/10.1002/9781119458555.ch45

3. Naumenko D., Tkachenko A., Lysenko I., Kovalev A. Development and research of the sensitive element of the MEMS gyroscope manufactured using SOI technology. Micromachines, 2023, vol. 14, no. 4, pp. 895. https://doi.org/10.3390/mi14040895

4. Torunbalci M., Alper S., Akin T. Advanced MEMS process for wafer level hermetic encapsulation of MEMS devices using SOI cap wafers with vertical feedthroughs. Journal of Microelectromechanical Systems, 2015, vol. 24, no. 3, pp. 556–564. https://doi.org/10.1109/JMEMS.2015.2406341

5. Zoschke K., Mackowiak P., Kröhnert K., Oppermann H., Jürgensen N., Wietstruck M., Göritz A., Wipf ST., Kaynak M., Lang K.D. Cap fabrication and transfer bonding technology for hermetic and quasi hermetic wafer level MEMS packaging. Proc. of the IEEE 70th Electronic Components and Technology Conference (ECTC), 2020, pp. 432–438. https://doi.org/10.1109/ECTC32862.2020.00076

6. Torunbalci M., Gavcar H., Yesil F., Alper S., Akin T. An all-silicon process platform for wafer-level vacuum packaged MEMS devices. IEEE Sensors Journal, 2021, vol. 21, no. 13, pp. 13958–13964. https://doi.org/10.1109/JSEN.2021.3073928

7. Evstifeev M.I. Design Methods for Micromechanical Gyroscope Structures. Study guide. St. Petersburg, ITMO, 2018. 182 p. (in Russian)

8. Timoshenkov S.P., Anchutin S.A., Zarjankin N.M., Kalugin V.V., Kochurina E.S., Timoshenkov A.S., Boev L.R. Research and Development of MEMS Accelerometer’s Sensor. Nanoand Microsystems Technology, 2021, vol. 23, no. 2, pp. 63–67. (in Russian). https://doi.org/10.17587/nmst.23.63-67

9. Xu J., Ren Z., Dong B., Wang C., Tian Y., Lee C. Evolution of Wafer Bonding Technology and Applications from Wafer-Level Packaging to Micro/Nanofluidics-Enhanced Sensing. Advanced MEMS/NEMS Fabrication and Sensors. Springer, 2022, pp. 187–215. https://doi.org/10.1007/978-3-030-79749-2_7

10. Oggioni L., Garavaglia M., Seghizzi L. Wafer-to-Wafer Bonding. Silicon Sensors and Actuators: The Feynman Roadmap. Springer, 2022, pp. 345–386. https://doi.org/10.1007/978-3-030-80135-9_11

11. Karanin N.S. Deep reactive ion etching of device layer during manufacture micromechanical accelerometer. Proc. of the Conference of Russian Young Researchers in Electrical and Electronic Engineering (ElConRus), 2022, pp. 962–965. https://doi.org/10.1109/ElConRus54750.2022.9755694

12. Li D., Shang Z., She Y., Wen Z. Investigation of Au/Si eutectic wafer bonding for MEMS accelerometers. Micromachines, 2017, vol. 8, no. 5, pp. 158. https://doi.org/10.3390/mi8050158

13. Kavitha S., Daniel R.J., Sumangala K. Design and analysis of MEMS comb drive capacitive accelerometer for SHM and seismic applications. Measurement, 2016, vol. 93, pp. 327–339. https://doi.org/10.1016/j.measurement.2016.07.029

14. Zhang Y., Wu Y., Sun Q., Shen L., Lan J., Guo L., Shen Z., Wang X., Xiao J., Xu J. Inductively coupled plasma dry etching of silicon deep trenches with extremely vertical smooth sidewalls used in microoptical gyroscopes. Micromachines, 2023, vol. 14, no. 4. pp. 846. https://doi.org/10.3390/mi14040846

15. Alnakhli Z., Liu Zh., AlQatari F., Cao H., Li X. UV-assisted nanoimprint lithography: the impact of the loading effect in silicon on nanoscale pattern of metalens. Nanoscale Advances, 2024, vol. 6, no. 11, pp. 2954–2967. https://doi.org/10.1039/D4NA00120F

16. Wang X., Bleiker S.J., Edinger P., Errando-Herranz C., Roxhed N., Stemme G., Gylfason B., Niklaus F. Wafer-level vacuum sealing by transfer bonding of silicon caps for small footprint and ultra-thin MEMS packages. Journal of Microelectromechanical Systems, 2019, vol. 28, no. 3, pp. 460–471. https://doi.org/10.1109/JMEMS.2019.2910985

17. Liu J., Xia S., Peng C., Wu Z., Chu Z., Zhang Z., Lei H., Zheng F., Zhang W. Wafer-level vacuum-packaged electric field microsensor: structure design, theoretical model, microfabrication, and characterization. Micromachines, 2022, vol. 13, no. 6, pp. 928. https://doi.org/10.3390/mi13060928

18. Belyaev Y.V., Belogurov A.A., Bocharov A.N., Kostygov D.V., Lemko I.V., Mihteeva A.A. Design of a micromechanical accelerometer. Proc. of the 25th International Conference on Integrated Navigation Systems (ICINS), 2018, pp. 1–7. https://doi.org/10.23919/ICINS.2018.8405921

19. Xu Y., Liu S., He C., Wu H., Cheng L., Yan G., Huang Q. Reliability of MEMS inertial devices in mechanical and thermal environments: a review. Heliyon, 2024, vol. 10, no. 5, pp. e27481. https://doi.org/10.1016/j.heliyon.2024.e27481

20. Peng T., You Z. Reliability of MEMS in shock environments: 2000– 2020. Micromachines, 2021, vol. 12, no. 11, pp. 1275. https://doi.org/10.3390/mi12111275

21. Wenk B., Collet J., Gaff V. Technology platform for high performance Mems inertial & vibration sensors. Proc. of the IEEE International Symposium on Inertial Sensors and Systems (INERTIAL), 2024, pp. 1–4. https://doi.org/10.1109/INERTIAL60399.2024.10502059