Oxygen Scavenging in HfZrO_x‐Based n/p‐FeFETs for Switching Voltage Scaling and Endurance/Retention Improvement

Abstract

the internet of things, big-data analysis, and machine learning are required. As one method to solve the issues, logic-inmemory (LiM) devices that combine the memory unit and the logic unit have been proposed, and the HfZrO x (HZO)-based ferroelectric field-effect transistor (FeFET) is one of the promising candidates for LiM devices because of its sufficient remanent polarization (P r ), low power, high speed, high scalability, and good compatibility with complementary metal-oxide-semiconductor technology. [1,2] However, when the HZO film is directly stacked on the Si substrate, an unintentional interfacial layer (IL) of SiO x is formed, resulting in a metal/ferroelectric film/insulator/semiconductor (MFIS) structure. The presence of IL causes several critical problems in ferroelectric behavior, inducing a significant amount of charge trapping, [3,4] causing a huge gate voltage (V g ) drop due to a lower dielectric constant (≈3.9), [5] and forming a strong depolarization field. [5,6] In particular, the interfacial charge trap density of ≈10 12 cm −2 is involved in breakdown and fatigue induced by charge trapping, [3,4] which causes issues of low endurance and read delay in FeFETs. [3,4,7] On the other hand, beneficial effects such as charge-assisted polarization [8] and leakage reduction [9] by IL are also exerted. Therefore, IL engineering to reduce thickness and unnecessary charge trapping is a promising direction in improving FeFET performances such as switching voltage (V sw ), memory window (MW), endurance, and retention properties.As attempts for IL engineering, methods such as the insertion of the additional IL, the modification by plasma treatment, and the inhibition of the IL formation have been reported. For the additional IL, Al 2 O 3 layers that can reduce leakage and improve endurance properties were explored, however, V sw increased due to an additional V g drop across the additional IL. [9] Alternatively, the insertion of ZrO 2 , which can improve the crystalline quality of the ferroelectric orthorhombic phase of HZO, improved P r and endurance property, but did not improve V sw . [10,11] Forming SiON by replacing SiO x was beneficial for endurance and retention properties, but a high-temperature process of 850 °C was required. [12] Treatment of IL with N 2 plasma improved endurance property only and had no effect on V sw . [13] In order to inhibit IL growth, microwave annealing, [14,15] The authors demonstrate improved switching voltage, retention, and endurance properties in HfZrO x (HZO)-based n/p-ferroelectric field-effect transistors (FeFETs) via oxygen scavenging. Oxygen scavenging using titanium (Ti) in the gate stack successfully reduce the thickness of interfacial oxide between HZO and Si and the oxygen vacancy at the bottom interface of the HZO film. The n/p-FeFETs with scavenging exhibit an immediate read-afterwrite with stable retention property and improved endurance property. In particular, n-FeFET with scavenging exhibits excellent endurance property that does not show breakdown up t...

Role of oxygen vacancies in ferroelectric or resistive switching hafnium oxide

“…Moreover, a high concentration is not conducive to achieving high operation speeds, because it would decelerate the propagation of domain walls resulting from the attraction between defects. The frequently reported read-after-write latency [ 220 , 221 ] is also strongly correlated to charge trapping/de-trapping, which is generally significantly slower than the polarization switching dominated by the domain wall propagation [ 222 – 225 ]. Furthermore, a high V o concentration decreases the average grain size in oxide thin films.…”

Evidence for reversible oxygen ion movement during electrical pulsing: enabler of emerging ferroelectricity in binary oxides

“…Research into ferroelectric HfO 2 -based devices has been extensive, covering a wide range of applications. This includes next-generation memory devices and various logic devices such as ferroelectric random-access memory [22,23], ferroelectric tunnel junctions [24,25], ferroelectric field-effect transistors [26][27][28][29][30], and negative capacitance fieldeffect transistors [31][32][33]. Each of these applications opens new possibilities in the semiconductor domain.…”