在本研究中，我們使用HfSnO2 作為 RRAM 的絕緣層。首先，為了比較 HfSnO2 絕緣層的 OxRAM 或 CBRAM 的阻值轉換特性，我們製作了 Al/HfSnO¬2/Pt 和 Ag/HfSnO2/Pt 的RRAM 樣本。測量結果顯示出HfSnO2 CBRAM 在 Vset、電阻和電壓均勻性和耐連續切換次數方面具有更好的性能。
接下來，我們研究了 HfSnO2 厚度、濺鍍壓力和 O2 比例對 Ag 上電極的 CBRAM 特性的影響。通過改變 HfSnO2 厚度和限流大小，我們知道了 3 個現象： (1) Vset 隨著 HfSnO2 厚度的增加而增加。 (2) 在相同的 RRAM 樣本中，連續切換次數會隨著限流的增加而降低。 (3)當絕緣層足夠厚時，維持電阻的能力會很差。這三種現象告訴我們銀燈絲是如何在電場的作用下形成和斷裂。當 HfSnO2 厚度調整為 40nm，元件的 Vset 為 0.4V，其連續切換次數可超過 1000 次。如果 HfSnO2 厚度降低到 20 nm，其 Vset 將為 0.35V，但它的連續切換次數只剩 306 次。
然後，我們嘗試通過改變濺鍍壓力來降低 Vset，同時保持超過 1000 次的連續切換次數。當濺鍍壓力為 5 mTorr 時，元件的 Vset 為 0.369 V，其連續切換次數可超過 1000 次。如果濺鍍壓力增加到 10mTorr，則 Vset 降低到 0.352V，但其連續切換次數僅為 637 次。
為了降低 Vset 的同時保持超過 1000 次連續切換次數，我們試圖改變HfSnO2濺鍍過程中的 Ar/O2 比率。通過將 O2 比率提高到 30%，該元件的 Vset 為 0.33V，並且連續切換次數可以超過 1000 次。如果 O2 比例增加到 40%，Vset 可以降低到 0.3V，但它的連續切換次數只有 200 次。通過改變 HfSnO2 的沉積條件，我們得到了最小 Vset 為 0.33V 的元件，同時保持了 1000 次以上的連續切換次數。
最後，通過堆疊絕緣層，同時降低了 Vset 和增加連續切換次數。其機制是增加電場集中度，因此可以降低 Vset。結果顯示，2層HfSnO2元件其Vset可以降至0.259V，且其連續切換次數可超過1000次。

In this study, HfSnO2 ¬was used for the insulating layer of RRAM. First, in order to find out the switching properties of OxRAM or CBRAM of HfSnO2 insulating layer is better, we fabricated Al/HfSnO2/Pt and Ag/HfSnO2/Pt RRAM sample. The measurement result showed that HfSnO2 CBRAM had better performances in terms of Vset, resistance and voltage uniformity and endurance.
Next, we investigated the effect of HfSnO2 thickness, sputtering pressure and O2 ratio on the switching properties of CBRAM with Ag TE. By changing HfSnO2 thickness and compliance current, we knew 3 phenomena: (1) Vset increases as HfSnO2 thickness increases. (2) In the same RRAM sample, endurance decreases as compliance current increases. (3) When the insulator layer is thick enough, retention will be poor. These 3 phenomena told us how Ag filament was formed and ruptured by external electric field. By adjusting the HfSnO2 thickness to 40nm, the sample had a V¬set of 0.4V and its endurance could exceed 1000 cycles. If the HfSnO2 thickness was decreased to 20 nm, its Vset would be 0.35V. But its endurance was only 306 cycles.
Then, we tried to reduce Vset while keeping endurance over 1000 cycles by changing sputtering pressure. When the sputtering pressure was 5 mTorr, the device had a Vset of 0.369 V and its endurance could exceed 1000 cycles. If the sputtering pressure was increased to 10mTorr, the Vset was reduced to 0.352V but its endurance was only 637 cycles.
With the same goal of reducing Vset while keeping endurance over 1000 cycles, we tried to change the Ar/O2 ratio in the sputtering process. By increasing the O2 ratio to 30%, the device had a V¬set of 0.33V and the endurance could exceed 1000 cycles. If the O2 ratio was increased to 40%, Vset could be reduced to 0.3V, but its endurance was only 200 cycles. Through changing the deposition condition of HfSnO2, we got the device with smallest Vset of 0.33V while keeping its endurance over 1000 cycles.
Finally, we improved the V¬set and endurance at the same time by stacking the insulating layers. Its mechanism was to increase the electric field concentration and thus Vset could be reduced. The result demonstrated that the device with 2-layer HfSnO¬2 had a Vset of 0.259V and its endurance could exceed 1000 cycles.

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