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United States Patent 5,959,896
Forbes Sept. 28, 1999

Multi-state flash memory cell and method for programming single electron differences


A flash memory cell. The cell includes a transistor with a floating gate that is formed from a number of crystals of semiconductor material. The crystals are disposed in the gate oxide of the transistor. The size of the crystals and their distance from a surface of a semiconductor layer of the transistor are chosen such that the crystals can trap a single electron by hot electron injection. Each trapped electron causes a measurable change in the drain current of the transistor. Thus, multiple data bits can be stored and retrieved by counting the changes in the drain current.

Inventors: Forbes; Leonard (Corvallis, OR).
Assignee: Micron Technology Inc. (Boise, ID).
Appl. No.: 31,930
Filed: Feb. 27, 1998

Related U.S. Application Data
Continuation of (including streamline cont.) Ser. No. 790,903, Jan. 29, 1997, Pat. No. 5,740,104.
Intl. Cl. : G11C 13/00
Current U.S. Cl.: 365/185.33; 365/185.01; 365/185.1
Field of Search: 365/185.01, 185.1, 185.33, 189.01, 218

References Cited | [Referenced By]

U.S. Patent Documents
4,507,673Mar., 1985Aoyama et al. 357/23.R
5,021,999Jun., 1991Kohda et al. 365/168
5,027,171Jun., 1991Reedy et al. 357/23.5
5,055,890Oct., 1991Dawson et al. 365/218
5,111,430May, 1992Morie 365/185
5,253,196Oct., 1993Shimabukuro 365/45
5,293,560Mar., 1994Harari 365/185
5,317,535May, 1994Talreja et al. 365/185
5,357,134Oct., 1994Shimoji 257/325
5,388,069Feb., 1995Kokubo 365/185
5,418,743May, 1995Tomioka et al. 365/189.01
5,424,993Jun., 1995Lee et al. 365/218
5,430,670Jul., 1995Rosenthal 365/45
5,434,815Jul., 1995Smarandoiu et al. 365/189.01
5,438,544Aug., 1995Makino 365/185
5,449,941Sept., 1995Yamazaki et al. 257/411
5,467,306Nov., 1995Kaya et al. 365/185.2
5,477,485Dec., 1995Bergemont et al. 365/185.24
5,485,422Jan., 1996Bauer et al. 365/168
5,493,140Feb., 1996Iguchi 257/316
5,508,543Apr., 1996Hartstein et al. 257/314
5,627,781May, 1997Hayashi et al. 365/185.2
5,670,790Sept., 1997Katoh et al. 257/14
5,714,766Feb., 1998Chen et al. 257/20
5,754,477May, 1998Forbes

Foreign Patent Documents
0139185May, 1985EP
0448118Sept., 1991EP
0750353Dec., 1996EP
Other References

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Primary Examiner: Fears; Terrell W.
Attorney, Agent or Firm: Schwegman, Lundberg, Woessner & Kluth P.A.
13 Claims, 3 Drawing Figures

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