金屬(鋁)/鐵電薄膜(鐵酸鉍)/絕緣層(氧化釔)/矽 結構電容與場效電晶體在非揮發性記憶體的應用

The Study of Metal (Al)/ Ferroelectric (BiFeO3)/ Insulator (Y2O3)/ Silicon (p-type) MFIS Capacitors and Field Effect Transistors for Nonvolatile Memory Applications

林志銘(Chih-Ming Lin)

指導教授 ： 李雅明

國立清華大學/電機資訊學院/電子工程研究所/碩士(2008年)

摘要

在本次研究中，我們製作出鋁(Al)/鐵酸鉍(BFO)/氧化釔(Y2O3)/半導體結構的電容器與場效電晶體。在電容器方面，為了探討BFO薄膜在不同溫度下退火的效果，我們分別施以500 ℃和600 ℃的退火處理並對其作比較。結果顯示，500 ℃的退火溫度在電性上的結果優於600 ℃，退火溫度500 ℃的最大記憶窗約0.91 V，而漏電流在5 V下約2 x 10-7 A/cm2。
　　另外，我們也使用表面處理的方法試圖改善絕緣層與半導體間的介面特性，進而降低漏電流。在沉積絕緣層前先將晶圓浸泡H2O2，並且在沉積絕緣層後再以稀釋的鹽酸溶液沖洗晶圓。在表面處理後，漏電流從原先的2 x 10-7 A/cm2 降低到 4 x 10-9 A/cm2。
　　在電晶體方面，我們得到不錯的IDS-VDS與IDS-VGS特性，從量測到的資料來分析，次臨界斜率約155 mV/dec，最大電荷遷移率155 cm2/V-s，IDS-VGS的開關電流比值在4個數量級左右。而記憶體特性量測上，IDS-VGS記憶窗最大值約0.93 V左右，至於電荷保持時間在經過10000秒之後仍然保有3個數量級的IDS電流比值。
　　從以上的結果我們可以歸納出，鋁(Al)/鐵酸鉍(BFO)/氧化釔(Y2O3)/半導體結構的電容器與場效應電晶體在非揮發性記憶體的應用上，是很適合的選擇。

關鍵字

非揮發性記憶體 ； 鐵電記憶體 ； 鐵酸鉍 ； 氧化釔 ； 鐵電薄膜 ； HASH(0x1d83f8e0)

並列摘要

Al/ BiFeO3 (BFO)/ Y2O3/ p-Si metal ferroelectric insulator semiconductor (MFIS) capacitors and transistors were fabricated. To compare the effect of different annealing temperature, the BFO thin films were annealed at 500 ℃ and 600 ℃. The BFO films annealed at 500 ℃ show better electrical properties than those at 600 ℃. The maximum C-V memory window was 0.91 V at the annealing temperature of 500 ℃. The corresponding leakage current density was 2 x 10-7 A/cm2 at a bias voltage of 5 V.
In addition, a surface treatment method was also used to passivate the Y2O3/Si interface and to reduce the leakage current. The wafers were given a H2O2 pre-treatment before Y2O3 deposition and a HCl post-treatment after deposition. The leakage current density at a bias voltage of 5 V was reduced from 2 x 10-7 A/cm2 to 4 x 10-9 A/cm2.
The fabricated MFIS transistors (MFIS-FET) show good transistor characteristics. The subthreshold swing (St) was about 155 mV/dec. The IDS-VGS on-off ratio was approximately 4 orders of magnitude. The maximum electron mobility was 155 cm2/V-s. To measure the memory properties, the shift of IDS-VGS curves was observed. The maximum IDS-VGS memory window was 0.93 V. The drain current on/off ratio was more than 3 orders of magnitude after applying poling voltages of ± 7 V with duration of 10 μs. The IDS maintains an on/off ratio of more than 3 orders after an elapsed time of 104 sec.
These results show that the Al/BFO/Y2O3/p-Si structure has great potential for nonvolatile memory applications.

並列關鍵字

nonvolatile memories ； FeFET ； MFIS ； BiFeO3 ； Y2O3 ； retention

參考文獻

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