发明公开
EP0774788A1 A PMOS flash memory cell capable of multi-level threshold voltage storage 失效
PMOS-Flash-Speicherzelle mit mehrstufiger Schwellspannung

A PMOS flash memory cell capable of multi-level threshold voltage storage
摘要:
A P-channel flash EEPROM cell (40) has P+ source (50) and P+ drain (52) regions, and a channel (51) extending therebetween, formed in an N-type well (42). A thin layer of tunnel oxide (62) is provided over the channel (51). A poly-silicon floating gate (56) and poly-silicon control gate (58), separated by a dielectric layer (57), overlie the tunnel oxide (62). Programming is accomplished via hot electron injection while erasing is realized by electron tunneling. The threshold voltage of the cell may be precisely controlled by the magnitude of voltage coupled to the floating gate (56) during programming. Since the injection of hot electrons into the floating gate (56) is independent of variations in the thickness of the tunnel oxide layer (62) and the coupling ratio between the floating gate (56) and the control gate (58), programming operations and data retention are not affected by process variations. In addition, PMOS devices conduct a gate current via hot electron injection over a narrow range of gate voltages, thereby allowing for precise control over the gate current and thus over the charging of the floating gate. This control over the gate current, as well as the independence of the cell's threshold voltage of process parameters, advantageously allows the threshold voltage of the cell to be more accurately controlled, thereby resulting in a more reliable cell capable of storing a greater number of bits of data.
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IPC分类:
H 电学
H01 基本电气元件
H01L 半导体器件;其他类目中不包括的电固体器件(使用半导体器件的测量入G01;一般电阻器入H01C;磁体、电感器、变压器入H01F;一般电容器入H01G;电解型器件入H01G9/00;电池组、蓄电池入H01M;波导管、谐振器或波导型线路入H01P;线路连接器、汇流器入H01R;受激发射器件入H01S;机电谐振器入H03H;扬声器、送话器、留声机拾音器或类似的声机电传感器入H04R;一般电光源入H05B;印刷电路、混合电路、电设备的外壳或结构零部件、电气元件的组件的制造入H05K;在具有特殊应用的电路中使用的半导体器件见应用相关的小类)
H01L29/00 专门适用于整流、放大、振荡或切换,并具有至少一个电位跃变势垒或表面势垒的半导体器件;具有至少一个电位跃变势垒或表面势垒,例如PN结耗尽层或载流子集结层的电容器或电阻器;半导体本体或其电极的零部件(H01L31/00至H01L47/00,H01L51/05优先;除半导体或其电极之外的零部件入H01L23/00;由在一个共用衬底内或其上形成的多个固态组件组成的器件入H01L27/00)
H01L29/66 .按半导体器件的类型区分的
H01L29/68 ..只能通过对一个不通有待整流、放大或切换的电流的电极供给电流或施加电位方可进行控制的(H01L29/96优先)
H01L29/76 ...单极器件
H01L29/772 ....场效应晶体管
H01L29/78 .....由绝缘栅产生场效应的
H01L29/788 ......带有浮栅的
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