FLASH GATE AIR GAP

摘要

Flash memory cells and methods of formation are described for flash memory cells having air gaps through which electrons may pass to alter the charge state of the floating gate. A dummy gate is initially deposited and a polysilicon gate is deposited on the dummy gate. A silicon oxide film is then deposited on the sides of the active area, the dummy gate and the polysilicon. The silicon oxide film holds the polysilicon in place while the dummy gate is selectively etched away. The dummy gate may be doped to increase etch rate. Formerly, silicon oxide was used as a dielectric barrier through which electrons were passed to charge and discharge the floating gate (polysilicon). Eliminating material in the dielectric barrier reduces the tendency to accumulate trapped charges during use and increase the lifespan of flash memory devices.

主权项

1. A method of forming a flash memory cell on a substrate, the method comprising:
forming dummy silicon oxide over active area silicon on the substrate; forming polysilicon over the dummy silicon oxide; patterning the polysilicon and the dummy silicon oxide into a stack having vertical walls; forming conformal silicon oxide on the vertical walls of the stack, wherein the conformal silicon oxide borders walls of the polysilicon, the dummy silicon oxide and the active area silicon; selectively removing the dummy silicon oxide to leave behind a void, wherein the conformal silicon oxide, the polysilicon and the active area silicon all remain in place following the selective removal of the dummy silicon oxide; and depositing non-conformal dielectric to trap the void in the flash memory cell.