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THE CONTINUED NEED for higher density, higher performance erasable proms (EPROMs) has been established by the evolution of faster, more dense microprocessors; and their dependence on convenient program storage memories. This need was first served by the 2Kb FAMOS P-channel floating gate EPROM"2, implemented by a two-transistor cell. The second generation 1C-channel microprocessors were served by the 8Kb and 16Kb314, N-channel MOS stacked gate EPROMs which used a one transistor cell.With the arrival of another generation of microprocessors*, the need for yet higher density and higher performance EPROMs has again become critical. In response to this need; a third-generation 64K EPROM has been developed featuring a scaled stacked cell (cell area = 0.25mi12), tarCe,, <200ns, fully static operation and single 2OV pulse programming. Advances in both technology and circuitry were utilized in realizing these characteristics.The cell, illustrated in Figure 1, is a self-aligned structure fabricated by a dual-layer polysilicon gate process. The first layer of poly (POLY 1) forms the floating gate and the second layer of poly (POLY 2) forms the top select gate.through the use of a scaled EPROM technology. Channel lengths of -3.5pm are obtained in the array and periphery with better Critical Dimension (CD) control and less undercutting. Increased coupling for lower programming voltages and smaller programming times is available by scaling down the first and second gate oxide thickness to approximately 7 0 0 8 and 800A respectively. Additional geometry changes in the cell and periphery are the result of scaling, optimized to account for special EPROM requirements. As demonstrated in Figure 2, the chip size for a 32K density changes from 200mi12 on a standard EPROM technology to 145miI2 on a scaled EPROM technology. injected through the oxide to the floating gate3. The charge retention characteristics have not changed and are similar to the A cell size of 159pm2 ( O.25mil2) is achieved The memory cell is programmed by means of hot electrons *SO86