1971: Reusable semiconductor ROM introduced

User-erasable, programmable ROMs support microprocessor system design

 

 

 

Early integrated circuit ROMs offered a non-volatile form of semiconductor memory (NVM) but required a custom mask for each design. In 1970, Radiation Inc. introduced a 512-bit bipolar TTL user-programmable ROM (PROM) that allowed designers to input the code themselves by “burning” metal fuse links with an external programming unit but could be used once only. Monolithic Memories, Motorola, and Signetics developed 1K through 16K-bit nickel-chromium fuse PROMs. AMD, Intel, and TI used alternative fuse materials to achieve higher speed.

Dawon Kahng and Simon Sze of Bell Labs described in 1967 how the floating gate of an MOS semiconductor device could be used for the cell of a reprogrammable ROM. In the early 1970s, General Instruments, Hicksville, NY adapted a metal nitride oxide semiconductor (MNOS) process to build small electrically-alterable EAROMs for TV tuners. 1971 Intel announced the 1702, a 2048-bit user-erasable, PROM (EPROM) designed by Dov Frohman that could be reused multiple times by erasing the pattern with ultra-violet light. Generations of UV EPROMs with multi-million bits of storage from Intel and others found wide application for storing and modifying program codes as firmware in microprocessor-based system designs.

Working at Hughes Microelectronics, Newport Beach, CA, from 1976-1978, Eli Harari demonstrated a thin oxide floating-gate, electrically erasable PROM (EEPROM) cell that eliminated the need for external UV erasure. George Perlegos employed the thin oxide technique for Intel’s first EEPROM in 1978. At Toshiba in 1980, Fujio Masuoka modified the EEPROM architecture to increase the speed of programming, appropriately naming it "flash." He followed that in 1987 with a lower-cost NAND structure that led to the Solid State Disk (SSD) and the ubiquitous USB flash memory “stick”. Toshiba introduced commercial flash products in 1987 followed by Intel in 1988. Concurrent with these developments, flash memory has found widespread use in such personal device applications as mobile phones, cameras and GPS navigation systems.