Analysis of temperature distribution in stacked IC with a thermal simulation and a specially designed test structure

Temperature distributions in three dimensional (3D) ICs were analyzed with a thermal simulation and compared with measured results of test 3D ICs, in which sensor p-n diode arrays and on chip heaters were embedded. The 3D IC consists of a top tier test chip and a 410 um thick bottom dummy chip. Both top tier chips and bottom dummy chips were fabricated by a standard 0.18 um CMOS process. The top tier chips had four kinds of the thickness of 50 through 410 um. The temperature distributions of the top tier test chip under the constant heater power were analyzed by both measurements and thermal simulations. The thinner top tier structures showed the higher temperature and affected the temperature distributions. Effect of various boundary conditions such as substrate size and peripheral bonding pads were examined with thermal simulation. The test structure and the simulation modeling can provide an effective way for analysis of thermal conduction in 3D ICs.