Split gate NAND flash memory structure and array, method of programming, erasing and reading thereof, and method of manufacturing
View Patent ↗A split gate NAND flash memory structure is formed on a semiconductor substrate of a first conductivity type. The NAND structure comprises a first region of a second conductivity type in the substrate with a second region of the second conductivity type in the substrate, spaced apart from the first region. A continuous first channel region is defined between the first region and the second region. A plurality of floating gates are spaced apart from one another with each positioned over a separate portion of the channel region. A plurality of control gates are provided with each associated with and adjacent to a floating gate. Each control gate has two portions: a first portion over a portion of the channel region and a second portion over the associated floating gate and capacitively coupled thereto.
1. A method of erasing a plurality of flash memory cells in a flash memory structure formed in a semiconductor substrate of a first conductivity type wherein said structure has a first region of a second conductivity type in said substrate; a second region of the second conductivity type in said substrate, spaced apart from said first region, thereby defining a continuous first channel region therebetween; a plurality of floating gates, spaced apart from one another, each of the plurality of floating gates is positioned over and controlling a conductivity of a separate portion of the channel region, wherein each floating gate defines a flash memory cell; a plurality of control gates, each of the plurality of control gates is associated with and adjacent to one of the floating gates, each control gate having two portions: a first portion over and controlling a conductivity of a portion of the channel region with no portion of the floating gate disposed between the control gate first portion and the substrate, and a second portion over and capacitively coupled to the associated floating gate; wherein said method comprising:
applying a positive voltage to said substrate;
applying a voltage to each of said control gates, where said voltage applied to said control gates is less than said positive voltage; thereby
causing tunneling of electrons from said floating gates to said substrate.
2. The method of claim 1 wherein said voltage applied to said control gates is a negative voltage.
3. The method of claim 1 wherein said voltage applied to said control gates is at ground.