A new I2L memory cell - Double diffused base structure

A new structure of I²L static memory cell is proposed to improve the electrical characteristics. The cell was fabricated by the double diffused base technology. An additional p-type dopant was introduced to the base region of the bit transistor before the usual base diffusion. The downward current gain of the bit transistor has been successfully reduced by increasing the base width without influencing the upward current gain of the flip-flop transistor. As a result, a minimum write pulse width of 40 ns was obtained compared with 100-200 ns in the conventional structure. A static 1K bits I²L RAM, which was developed by introducing the new structure cell, operated at an address access time of 20 ns and a write pulse width of 40 ns with a power dissipation of 350 mW.