In order to develop silicon ICs operating up to above 450, Integrated Injection Logic (IIL) was chosen. A new structure for IIL was designed through experimental and theoretical studies of pn junctions, transistors, and IIL at high temperatures. A 5-µm design rule was used. The new IIL was fabricated by a specially developed combined process of ion implantation and low temperature epitaxy. The IIL was fully operational from room temperature to 454, and the output amplitude of a nine-stage ring oscillator was about 30 mV at 454. The minimum delay time of the IIL was 22 nsec at 454. The minimum power-delay product was 11 pJ and was one-third of that for IILs fabricated by 10-µm rule at 50.