| Summary: | 碩士 === 國立清華大學 === 工程與系統科學系 === 100 === This study investigates the ion-implantation doping behavior of phase change memory materials. First, we discuss the phase-change characteristics of the Ge2Sb2Te5 films subjected to N+ or O+-implantation. Secondly, we study the phase-change characteristics of the ultra thin Sb films enclosed by different capping layers and then compare with those of Ge2Sb2Te5 films. Finally, we study the phase-change characteristics Si+-implanted ultra thin Sb films enclose by different capping layers.
The first part studies the improvement of phase-change characteristics of Ge2Sb2Te5 films by N+ or O+ implantation, respectively. The implantation doses are 8×1015 and 3.2×1016 ions/cm2. When implantation dose is 8×1015 ions/cm2, the crystallization temperature(Tx) increases from 158 to 170 ℃, the activation energy of crystallization(Ea) increases from 2.73 to 3.33 eV, and the temperature of 10-year data retention(T10y) also increases from 81 to 100 ℃, respectively. When implantation dose is 3.2×1016 ions/cm2, the Tx, the Ea, and the T10y are 176 ℃, 3.12 eV, 102 ℃, respectively. The doping effect of N+-implanted films is better than that of O+-implanted films.
The second part of study is to investigate the phase-change behaviors of the ultra thin Sb films subjected to Si+ implantation. The Tx of the 5 nm thick Sb film capped with Si3N4 is 191 ℃, the Ea is 4.70 eV, and the T10y is 135 ℃. The T10y of the 5 nm thick Sb film is 54 ℃ higher than Ge2Sb2Te5 film. By using Zacharias’s equation, the Tx of 1.7 nm thick Sb film is equal to its melting temperature. The suppression of crystallization by Si3N4 capping layer is better than those by SiC and Al2O3 capping layers. The thermal stability of the Al2O3 capping layer degraded due to the formation of oxidative compound in Sb film. Si3N4 is the only capping layer that may increase the thermal stability of Sb film subjected to Si+ implantation. Since it may resist the degradation caused by the ion-implantation.
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