Abstract
In this paper, SiO2 capping layers were introduced to improve the ferroelectric properties of Hf0.5Zr0.5O2 (HZO) thin films. HZO thin films with the SiO2 capping layers exhibit excellent ferroelectric characteristics. The largest remnant polarization (2Pr) was about 35.6 µC/cm2 for the HZO film with the SiO2 capping layer. The remnant polarization was larger than that for the film with the W capping layer after annealing at 550 °C and 600 °C and there was more oxygen content in the film with the SiO2 capping layer.
Highlights
HZO films with a Hf:Zr ratio of 0.5:0.5 were deposited using a 1:1 HfO2:ZrO2 atomic layer deposition (ALD) cycle ratio, and the growth per cycle of HZO was about 0.15 nm/cycle. 50-nm-thick SiO2 capping layers were deposited by plasma enhanced chemical vapor deposition (PECVD) at 300 ○C, and N2O and SiH4/He were used as the reaction gases at 900 mTor chamber pressure
In order to measure the electric characteristic of the HZO films, the SiO2 capping layers were etched by a buffered oxide etch (BOE) after rapid thermal annealing, and 50-nm-thick W top electrodes with 50-μm-diameter were deposited by the sputtering system and released by a lift-off process
The atomic concentration of oxygen in the HZO film of the method A sample is higher than that in the method B sample, which means that oxygen is diffused into the HZO film during SiO2 deposition, which may contribute to a lower concentration oxygen vacancy (Vo) in the HZO film
Summary
The samples with 50-nm-thick SiO2 capping layers were annealed at 500 ○C, 550 ○C, and 600 ○C for 30 s in an N2 atmosphere using rapid thermal annealing. In order to measure the electric characteristic of the HZO films, the SiO2 capping layers were etched by a buffered oxide etch (BOE) after rapid thermal annealing, and 50-nm-thick W top electrodes with 50-μm-diameter were deposited by the sputtering system (method A) and released by a lift-off process.
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