Ping Ca Guo

US Patent:

20020000605, Jan 3, 2002

Filed:

Apr 3, 2001

Appl. No.:

09/827056

Inventors:

Chun-Mai Liu - San Jose CA, US
Albert Kordesch - San Jose CA, US
Ping Guo - San Jose CA, US

International Classification:

H01L029/788

US Classification:

257/316000, 438/266000

Abstract:

A method of fabricating a flash memory device including an array of split gate cells, comprising the steps of: providing a silicon substrate having a top surface; implanting ions into a predefined area of the substrate to form a common source region of the substrate; forming at least one floating gate over the substrate, each floating gate being associated with one of the cells and having a portion which overlies a portion of the common source region, the overlying portion of each floating gate providing for a high coupling ratio for the associated flash cell; forming a select gate over at least a portion of each floating gate; and forming a drain region associated with each cell. The high coupling ratio flash cell device of the present invention overcomes limitations associated with conventionally formed split gate flash cells by forming the common source region first and then forming the floating gates over the common source region in order to provide a high coupling ratio for the cells.

US Patent:

63011514, Oct 9, 2001

Filed:

Aug 9, 2000

Appl. No.:

9/634180

Inventors:

Lawrence D. Engh - Redwood City CA
Albert V. Kordesch - San Jose CA
Ping Guo - Campbell CA
Chun-Mai Liu - San Jose CA

Assignee:

Information Storage Devices, Inc. - San Jose CA

International Classification:

G11C 700

US Classification:

36518503

Abstract:

Adaptive programming method and apparatus for flash memory analog storage. The present invention method is to adjust the voltage of the programming pulse each time based on the result of the previous pulse. The expected change in the programmed value is compared to the measured change, and the difference used to improve the model of that cell after each programming pulse. The algorithm is "adaptive" because the voltage of each pulse is adapted to whatever the cell needs. If the cell is programming too slowly, the voltage is increased dramatically to make it faster. Conversely if the results show that a particular cell is programming too fast, the next voltage pulse is increased by only a small amount (or even decreased if necessary). Because the response of the cell is non-linear, a special analog circuit is used to calculate the optimum voltage for each pulse. As one alternative, a digital calculation may also be used to program the cells.