基于常规CMOS工艺的单层多晶硅EEPROM单元设计

A single-poly EEPROM cell based on standard CMOS process

设计了一种由两个MOS电容器和一个读取NMOS管构成的单层多晶硅EEPROM存储单元。该EEPROM单元可采用常规CMOS工艺实现,通过在两个MOS电容器端施加一定电压产生n阱和浮栅间电荷的富勒-诺德海姆隧穿效应,从而实现写入和擦除。该结构可以更为方便地实现对特定位单元进行位粒度的写入和擦除操作。通过常规0.35μm CMOS工艺制作了测试芯片,并搭建测试系统对其进行了测试,对EEPROM单元的写入、擦除、读取以及可靠性等特性进行了详细研究。测试结果表明,存储单元可以在16 V电压下,在小于1 ms时间内被写入,在小于10 ms时间内被擦除;并且在阈值电压窗口保持大于2.5 V的条件下至少循环7000次。

A single-poly EEPROM memory cell composed of two MOS capacitors and a reading NMOS was presented.The EEPROM cell can be fabricated with standard CMOS process,and the programming and erasing operations were conducted by applying a certain high voltage between the two MOS capacitor terminals,which generates the Fowler-Nordheim tunneling effect between the n-well and the floating gate.The program and erase bit granularity can be easily realized for the particular bit cell through its unique structure.A test-chip was fabricated with a standard 0.35μm CMOS process and a test system it was established.A detailed study was conducted on the program,erase,read and reliability characteristics of the proposed EEPROM cell.The test results show that the memory cell can be programmed in less than 1 ms with V_(P)=16 V,and erased in less than 10 ms with V_(E)=16 V.The proposed EEPROM cell can endure at least 7000 operation cycles with the threshold voltage window greater than 2.5 V.