| 摘要: | 隨著科技的進步，5G建設、人工智慧（AI）、車用電子、物聯網 (Internet of Things , IoT)等領域發展迅速且滲透至生活各個層面中。越快速的資料傳輸和更龐大的系統對記憶體的效能與需求日益增加。如何設計出能夠符合現今強調寬廣頻寬與低延遲的要求，且能夠廣泛應用於各種層面的記憶體晶片將會是未來記憶體發展的一大趨勢。
在本論文中，提出了創新的1T-1T的embedded DRAM架構，其中1T作為控制電晶體另一個1T則為儲存電荷的儲存電晶體，此設計所採用的編程機制為碰撞游離效應 (impact ionization)，利用impact ionization機制產生的電子電洞對中的電子大量在nMOSFET的通道內累積，再搭配儲存電晶體的閘極浮節來達到儲存電荷的目的。藉由使用16 nm FinFET製程製作的embedded DRAM可以有效縮減傳統DRAM 1T-1C的電容所帶來的龐大面積，也同時降低了晶片的操作電壓來達到低功耗的效果。
本研究設計容量為4kb的embedded DRAM矩陣單位面積僅有0.07 μm2，晶片面積為0.214 μm2，且單元記憶胞 (unit cell) 的良率超過99 %，具有小面積、高良率與低成本的優勢。記憶體矩陣與其周邊電路具有很快的編程與讀取速度 (7 ns)，同時具有很低的操作電壓 (0.8 V)、良好的資料保存性 (120 µsec) 與優秀的抗干擾性，在連續進行超過1013操作後仍然可以正常運作且可以在75 ℃的高溫下操作展現出良好的可靠度與耐久性。在進行讀取時，僅需要使用-0.2 V的電壓來對儲存電晶體進行讀取便可以有超過30倍的0/1讀取窗口，且僅有36 nW的讀取消耗功率。在上述的特性中顯示本設計之1T-1T的embedded DRAM在許多層面皆有相當好的表現，在未來將會有很好的整合性，也會有更多且靈活的應用層面，也可以幫助embedded DRAM隨著FinFET製程繼續微縮到5~3 nm，在未來將可有效突破目前電晶體製程與嵌入式記憶體整合應用之瓶頸。
;With advancement of science and technology, the 5th generation mobile networks (5G), artificial intelligence (AI), automotive electronics, internet of things (IoT) have developed rapidly and could be active in all aspects. Owing to faster data transfers and bigger systems, demands on memory performance and needs are also increasing. How to design a memory chip that can meet requirements of today′s emphasis on wide bandwidth and low latency widely used in various levels will be a development tendency of memory in the future.
In this thesis, an innovative 1T-1T embedded DRAM architecture is proposed, in which 1T is used as a control transistor and the other 1T is a storage transistor that stores charges. Programming mechanism used in this design is impact ionization, many electrons in the electron-hole pair generated by the impact ionization mechanism are accumulated in the channel of the nMOSFET, and with the storage transistor gate floating the charges will be stored. The embedded DRAM fabricated by using the 16 nm FinFET process can effectively reduce huge area caused by capacitance of the traditional 1T-1C DRAM and at the same time reduce the operating voltage to achieve low-power consumption.
In design of this test chip, the 1T-1T embedded DRAM 4kb array unit cell has area of only 0.07 μm2 and the chip area of 0.214 mm2, and yield of the unit cell exceeds 99%, which has advantages of small area, high-yield and low cost. The memory array and its peripheral circuits have fast programming and reading speeds, low operating voltage, high data retention and excellent anti-interference performance. This memory can be operated at a high temperature of 75 °C and after more than 1013 continuous operations. These shows good reliability and durability. During reading the unit cell, just a voltage of -0.2 V applied to the storage transistor can have more than 30 times of 0/1 reading window with only 36 nW of reading power consumption. The 1T-1T embedded DRAM of this design has magnificent performance in many aspects. In the future, this embeddded DRAM technology can be extensively deployed in mobile and portable electronic devices with good cost-efficiecny and ultra-low power-consumption and can also shrink to 5~3 nm FinFET process to effectively break through the bottleneck of integrated application of transistor process and embedded memory. |
