Waferscale Integration, Inc.

American Microsystems, Inc.

Rustom F Irani

Boaz Eitan

Reza Kazerounian

Mark Michael Nelson

Larry Willis Petersen

An electrically programmable read-only memory (EPROM) array having self-aligned thick oxide isolation units, and a method for manufacturing the EPROM array are disclosed. The EPROM array is formed of EPROM areas having EPROM cells and control areas, two per EPROM area. Each control area includes at least one row and each row includes a first polysilicon strip, a second polysilicon strip lying on top of and perpendicular to the first polysilicon strip, and alternating thick and thin oxide elements under the first polysilicon strip. The thick and thin oxide elements are self-aligned to the first polysilicon strip. The thin oxide and the first and second polysilicon strips form a select transistor. The thick oxide and the first and second polysilicon strips form a novel self-aligned thick oxide isolation unit.

Scalable EPROM array

A read only memory (ROM) array is disclosed which includes a) a voltage supply providing an operating voltage level, b) a plurality of word-lines, c) a multiplicity of ROM transistors, and d) a word-line clamper. The ROM transistors are divided into turned on and turned off transistors. Each ROM transistor has a gate connected to one of the word-lines, a gate oxide beneath the gate, whose thickness is less than 250 .ANG., and a channel beneath the gate oxide. The turned off transistors additionally have a ROM implant in their channel whose dosage is no larger than the amount which generates a predetermined desired minimal band-to-band tunneling current The ROM implant and gate oxide thickness define a threshold voltage for the tamed off tranistors, the threshold voltage being less than the operating voltage level. The word-line damper provides a word-line voltage to each of the word-lines, the word-line voltage being clamped to a voltage level no higher than the threshold voltage of the turned off transistor.

Operating method for ROM array which minimizes band-to-band tunneling

A method of manufacturing a ROM array to minimize band-to-band tunneling is described. The method includes the steps of: a) implanting bit lines into the core area of a substrate as per a later-removed bit line mask, b) providing a ROM oxide layer over the entirety of the substrate, c) etching the ROM oxide layer only from the periphery area as per a later-removed core protect mask, d) providing a gate oxide layer over the entirety of the ROM array, e) laying down polysilicon rows in the core area as per a polysilicon mask and f) implanting a ROM implant into selected areas of the core area, thereby to produce turned off core transistors. The thickness of the gate oxide layer and the ROM oxide layer are independent of each other.

Manufacturing method for ROM array with minimal band-to-band tunneling

Scalable EPROM array with thick and thin non-field oxide gate insulators

An electrically programmable read only memory contains alternating metal bit lines and diffused bit lines. Each diffused bit line is broken into a plurality of segments. Each of the segments of the diffused bit line comprises a virtual source. A multiplicity of floating gate transistors are arranged in rows and columns. The floating gate transistors in each column are divided into M groups of N floating gate transistors each. The floating gate transistors in the n.sup.th and the (n+1).sup.th columns, where n is an odd integer given by 1.ltoreq.n.ltoreq.N and (N+1) is the maximum number of columns in the array are connected to the segments of one diffused bit line placed between the n.sup.th and the (n+1).sup.th columns. At least one first transfer transistor is arranged to connect one segment comprising a virtual source to a first metal bit line. The first metal bit line functions as the source for the N floating gate transistors in the (n+1).sup.th column connected to said one segment. At least one second transfer transistor connects the same one segment comprising a virtual source to a second metal bit line. The second metal bit line functions as a source for the N floating gate transistors in the n.sup.th column connected to said one segment. The removal of each select transistor from the cell where it previously resided in series with its corresponding floating gate transistor, and the combining of a plurality of select transistors into one select transistor substantially reduces the area taken by each memory cell in the array.

Growing community of inventors

Santa Clara, CA, United States of America

Rustom F Irani