Patent FR-2816751-A1 (FR)
Title: Flash memory erasable by page and method for data storaage, comprising array with counter and sectors, and circuits for reading page address and incrementing counter
Inventor: CAVALERI PAOLA
IPC: G11C16/16
Filed: 2000-11-15
Abstract: The page-erasable flash memory (MEM1) comprises a flash memory array (FMA) containing floating-gate transistors whose gates are connected to the word lines, where the transistors connected to the same word line form a page, a row decoder (XDEC1) connected to the word lines, and control circuits which apply a positive erase voltage (Ver+) for a page erasing to the source of the drainn electrodes of all transistors of one of the sectors (S1,S2,...S8) comprisingn the page. The row deecodere contains voltage adapters for applying, during the page erassing, a negative erase voltage (Ver-) to the gates of transistors of the page to be erased, and a positive inhibition voltage (Vinhib) to the gates of transistors of at least one of the other pages.  The inhibition voltage is below the positive erase voltage. In the process of the page erasing, a polarization voltage (Vpol) is equal to the negative erase voltage (Ver-) and a row polarization voltage (Vpex) is equa to the inhibition voltage (Vinhib); in the process of word reaading the polarization voltage is equal to the ground potential and the row polarization voltage is equal to a read voltage (Vread). The polarization voltages are delivered by a polarization module (PMP) by the intermediary of a switching element to the voltage adapters receiving the page selection signals and contained in the row deecoder (XDEC1). Each voltage adapter contains an output inverter staage and a control stage with an exclusive-OR gate receiving the selection signal and the erase signal. The circuits for the control of the voltage threshold of transistors and for reprogramming when the voltage threshold is below a set value include a counter (CMPT) formed by at least one row of transistors, the address counter read circuits including a shift register (SREG), a conversion circuit (CONVC) and a zero-detector (DETZ), and the counter increment circuits including the shift register and a register with latches (LT). The page addrses read circuits comprise the counter word-to-word read circuits including a counter decoder (CDEC), a sense amplifier (SA), the zero-detector and a column address counter (CAC), the page address high-value bit circuits including the conversion circuit and a multiplexer (MUX1), and the page address low-value bit circuits including the conversion circuit and a multiplexer (MUX1), and the page address low-value bit circuits including the column address counter and a multiplexer (MUX2). The page control includes the reading of a word of the page by applying the first read voltage (Vread), the reading of the same word of the page by applying the second read, that is verify, voltage (Vvrfy), the comparison of the two readings, and the reprogramming if the two readings are different. The positive erase voltage (Ver+) is applied to the source or the drain electrodes of transistors by the intermediary of a material forming the channel of transistors.