(Invited) Hafnia Ferroelectric Device for Semiconductor, Sensor, and Display Applications
Authors: Jeon Sanghun 
Published: December 2020

For the ferroelectric material with the conventional perovskite crystal structure and the chemical formula of ABO3, the charge neutral level is located close to the conduction band edge, and when forming a device, it causes a high leakage current due to low Schottky barrier height. Therefore, a relatively thick ferroelectric thin film was required, which was not suitable for the existing CMOS technology that is evolving through miniaturization. Meanwhile, ferroelectric properties were discovered in hafnia in 2011, and the ferroelectric properties of hafnia is observed in an orthorhombic crystal structure. Due to its simple structure and excellent CMOS process compatibility, it has received much attention for ferroelectric hafnia thin films and various application technologies using them. In this report, we will look at various application technologies using hafnia ferroelectrics, and we will examine the characteristics of hafnia ferroelectrics suitable for each device.

Ferroelectrics are one of the most crucial inorganic materials due to their fantastic functionalities and their remarkable properties in response to electrical and mechanical stimuli [1-4]. As a representative ferroelectric material, the perovskite-type ferroelectrics materials have received intense attention. However, the electrical properties of perovskite materials become deteriorating with the scaling of area and thickness, which doesn't allow to make use it for a scaled device [1-2]. In particular, the process incompatibility between Si technology and the perovskite material has not been overcome and their applications are limited. Thus, the exploration for ferroelectric materials having outstanding process compatibility with Si technology has been highly required [3-4].

In 2011, hafnia-based ferroelectric material was reported and the most surprising feature of this material is its simple chemical composition and thermodynamic stability [5-6], which has outstanding process compatibility with Si-based semiconductor technology [1]. Hafnia-based materials are actually being utilized as alternative gate dielectric layers in MOSFET because of their high-k value. The ferroelectric field effect transistor (FeFET) is being considered as the DRAM cell in next generation [7-8]. Multi-level FeFETs are reported not only for NAND flash but also for processing-in-memory architecture [9]. In addition, recent intensive studies have revealed new ferroelectric applications including sensor, logic and energy devices. In this presentation, we will review various device applications of hafnia ferroelectric thin films.

In our research, we have developed hafnia-based ferroelectric materials, processes and devices. The different characteristics of the hafnia ferroelectric materials are required for NAND Flash, processing-in-memory, DRAM, sensor, and thin-film transistors for display. We are making it the best fit for each application by the hafnia ferroelectric process development, gate stack and device design. In this presentation, we will examine the issues and requirements of each of these devices, see how we are solving these issues, summarize the remaining issues to date, and discuss the possibility to further improve speed, reliability and the memory window.

References

[1] T. Böscke, J. Müller, D. Bräuhaus, U. Schröder, and U. Böttger, "Ferroelectricity in hafnium oxide thin films," Applied Physics Letters, vol. 99, p. 102903, 2011.

[2] M. H. Park, Y. H. Lee, H. J. Kim, Y. J. Kim, T. Moon, K. D. Kim, et al., "Ferroelectricity and antiferroelectricity of doped thin HfO2‐based films," Advanced Materials, vol. 27, pp. 1811-1831, 2015.

[3] M. H. Park, Y. H. Lee, T. Mikolajick, U. Schroeder, and C. S. Hwang, "Review and perspective on ferroelectric HfO 2-based thin films for memory applications," MRS Communications, vol. 8, pp. 795-808, 2018.

[4] Z. Fan, J. Chen, and J. Wang, "Ferroelectric HfO2-based materials for next-generation ferroelectric memories," Journal of Advanced Dielectrics, vol. 6, p. 1630003, 2016.

[5] J. Müller, E. Yurchuk, T. Schlösser, J. Paul, R. Hoffmann, S. Müller, et al., "Ferroelectricity in HfO 2 enables nonvolatile data storage in 28 nm HKMG," in 2012 Symposium on VLSI Technology (VLSIT), 2012, pp. 25-26.

[6] T. Mikolajick, U. Schroeder, and S. Slesazeck, "Hafnium oxide based ferroelectric devices for memories and beyond," in 2018 International Symposium on VLSI Technology, Systems and Application (VLSI-TSA), 2018, pp. 1-2.

[7] M. Hoffmann, U. Schroeder, T. Schenk, T. Shimizu, H. Funakubo, O. Sakata, et al., "Stabilizing the ferroelectric phase in doped hafnium oxide," Journal of Applied Physics, vol. 118, p. 072006, 2015.

[8] M. Hyuk Park, H. Joon Kim, Y. Jin Kim, W. Lee, H. Kyeom Kim, and C. Seong Hwang, "Effect of forming gas annealing on the ferroelectric properties of Hf0. 5Zr0. 5O2 thin films with and without Pt electrodes," Applied Physics Letters, vol. 102, p. 112914, 2013.