Invention Publication
EP0774788A1 A PMOS flash memory cell capable of multi-level threshold voltage storage
失效
PMOS-Flash-Speicherzelle mit mehrstufiger Schwellspannung
- Patent Title: A PMOS flash memory cell capable of multi-level threshold voltage storage
- Patent Title (中): PMOS-Flash-Speicherzelle mit mehrstufiger Schwellspannung
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Application No.: EP96307875.3Application Date: 1996-10-30
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Publication No.: EP0774788A1Publication Date: 1997-05-21
- Inventor: Chang, Shang-De T.
- Applicant: Programmable Microelectronics Corporation
- Applicant Address: 1350 Ridder Park Drive San Jose, California 95131 US
- Assignee: Programmable Microelectronics Corporation
- Current Assignee: Programmable Microelectronics Corporation
- Current Assignee Address: 1350 Ridder Park Drive San Jose, California 95131 US
- Agency: Atkinson, Ralph
- Priority: US577514 19951114
- Main IPC: H01L29/788
- IPC: H01L29/788 ; H01L27/115 ; G11C16/04
Abstract:
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.
Public/Granted literature
- EP0774788B1 A PMOS flash memory cell capable of multi-level threshold voltage storage Public/Granted day:2001-08-01
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