Recently, multilevel Flash memory attracted many developers' attentions. P-channel Flash memory has been found as a promising candidate due to the low-voltage and low-power programming and the ease of scaling-down. Two programming mechanisms: (a) Channel Hot Hole Induced Hot Electron (CHHIHE), and (b) Band-To-Band Tunneling Induced Hot Electron (BTBTIHE) can be used as a rather high efficient programming manner in P-channel than in Nchannel Flash memory. Based upon CHHIHE and BTBTIHE programming, the multilevel applications and analysis of P-channel Flash memory are presented. Different engineering guidelines are given for these two programming techniques.

We propose a novel operation scheme for multilevel p-channel flash memory cell with a self-convergent programming process. By utilizing the simultaneous Fowler-Nordheim electron tunneling out of floating gate and channel hot electron injection into floating gate, the threshold voltage of memory cell can be converged to a specific value. The gate pulse level can be varied to result in different converged threshold voltages such that multilevel can be achieved. Owing to the nature of self-convergence, the possibility of eliminating or reducing the verification operation in multilevel applications increases considerably by using the proposed scheme. In this study the reliability considerations of this programming technique for long-term operations are also addressed.