텔루륨 기반 칼코게나이드계 물질의 임계 스위칭 특성

Abstract

본 논문에서는 텔루 라이드 물질에 기반한 임계 스위칭 특성 분석을 수행 하였다. 임계 스위칭의 기원은 두 가지 다른 구조적 접근 방법을 시도하여 연구되었으며 임계 전압 및 오프 전류 레벨의 변화가 삽입 층에 의해 관찰되었다. 먼저 아연과 텔루륨 층을 가진 멀티 스택 유형의 셀렉터와 아연 텔 루라이드 선택기를 제작하여 물질 자체의 계면 특성이나 구조적 특성이 임계 스위칭 파라미터에 지배적으로 작용하는지 여부를 분석 하였다. 아연 및 텔루 라이드 멀티스택 셀렉터는 각 레이어를 1nms 씩 증착함으로써 만들어졌다. 이원계 물질 유형은 텔루 라이드 아연 타겟으로 준비되었다. 둘째, 문턱 스위칭을 조작할 때 음의 바이어스에서 불안정한 특성을 해결하기 위해 어닐링 프로세스가 수행되었다. 기판을 200 ℃에서 1 시간 동안 열처리함으로써 전류 전압 특성의 안정된 곡선을 얻을 수 있었다. 셋째, 오버 슈트 문제를 해결하기 위한 추가적인 처리가 이루어졌다. 추가 처리전에는 오버 슛으로 히스테리시스 창이 보였다. 그러나 추가 처리에 의해 오버 슈트가 방지되고 결과적으로 히스테리시스 윈도우 없이 안정된 특성을 보였다. 마지막으로, 고저항 유전체층이 임계 전압 및 오프 전류 레벨을 제어하기 위해 삽입되었다. 층을 삽입 한 후에 변화가 관찰되었고 기판을 어닐링 한 후에 그에 따른 추가적인 변화가 얻어졌다. |This dissertation describes an experimental study on characteristic of threshold switching in selector device based on tellurium based chalcogenide materials. Various control of parameters including Vth , Ioff, device stability was obtained.

At first, analysis based on multi stacked selector and binary alloy material based selector was done in order to investigate whether the interface issue affects the threshold switching characteristics dominantly or the structural nature of material itself does. The multi stacked type was fabricated with zinc and tellurium layered by layered with full stack of 10nm. Binary alloy material type was prepared with one target type of 25nm deposited zinc telluride. Second, annealing process was done to achieve negative biased threshold switching. Negative biased threshold switching was instable before annealing process. By annealing, density of the switching layer was improved. Therefore, asymmetry of conductive path caused from electrode asymmetry was improved. Third, we tried additional treatment in order to prevent overshoot issue which causes hysteresis window. Characterizations were done by changing the degree of additional treatment. As the treatment increases, the hysteresis window becomes narrower and the number of cycles increased. Consequently, it was able to confirm that by preventing overshoot issue, device stability is able to obtain. We plotted the variation of hysteresis window and device stability in accordance with the treatment level. Finally, high resistive dielectric layer was inserted to selector device. By inserting various kinds of layers, control of Vth¬ and Ioff was achieved. Change of Vth and Ioff varied after annealing treatment according to the material of insertion layer.; This dissertation describes an experimental study on characteristic of threshold switching in selector device based on tellurium based chalcogenide materials. Various control of parameters including Vth , Ioff, device stability was obtained.

At first, analysis based on multi stacked selector and binary alloy material based selector was done in order to investigate whether the interface issue affects the threshold switching characteristics dominantly or the structural nature of material itself does. The multi stacked type was fabricated with zinc and tellurium layered by layered with full stack of 10nm. Binary alloy material type was prepared with one target type of 25nm deposited zinc telluride. Second, annealing process was done to achieve negative biased threshold switching. Negative biased threshold switching was instable before annealing process. By annealing, density of the switching layer was improved. Therefore, asymmetry of conductive path caused from electrode asymmetry was improved. Third, we tried additional treatment in order to prevent overshoot issue which causes hysteresis window. Characterizations were done by changing the degree of additional treatment. As the treatment increases, the hysteresis window becomes narrower and the number of cycles increased. Consequently, it was able to confirm that by preventing overshoot issue, device stability is able to obtain. We plotted the variation of hysteresis window and device stability in accordance with the treatment level. Finally, high resistive dielectric layer was inserted to selector device. By inserting various kinds of layers, control of Vth¬ and Ioff was achieved. Change of Vth and Ioff varied after annealing treatment according to the material of insertion layer.