Jean Devin

Addressing of redundant columns and rows of an integrated circuit memory

A method for the addressing of redundant elements of an integrated circuit memory is disclosed. This memory comprises an array of row memory elements and column memory elements, respectively addressable by row addresses and column addresses, at least one battery of fuses to store the address of a faulty element of the memory. The method consists: for one battery, in associating said battery with a row/column address pair; in memorizing, through the blowing of certain fuses in the battery after the testing of a memory element, the address either of a column element if the faulty element is a column element or that of a row element if the faulty element is a row element; and in enabling only the row addresses when the stored address is that of a row element or only the column addresses when the stored address is that of a column element, to address either a row redundant element or a column redundant element.

Fowler-Nordheim erasing time prediction in flash memory

Programming of a flash memory cell used two different mechanisms: a fast channel hot electrons injection in programming mode (with programming time of about mus) and a slow Fowler-Nordheim injection in erasing mode (with erasing time of about ms). In order to pre-evaluate the necessary time needed to write a flash cell memory (programming or erasing), we use a simplified expression for the Fowler-Nordheim injecting current during the erase mode which is the longer one. This allows us to find a relationship between the applied voltages and the resulting threshold voltage. We show in this study that the absolute value of the derivative of the threshold voltage is equal to the positive signal slope applied on the control gate. We validate this assumption by measurements on samples provided by STMicroelectronics with different slope and with samples with different coupling ratios. In order to reduce this erasing time, we need a better modeling of the Fowler-Nordheim injecting current, especially during the establishment of the current