Three-dimensional IC trends

Silicon on insulator (SOI) process technology, the basic technology for fabricating three-dimensional (3D) structures, is described. 3D integration is expected to provide such advantages as parallel processing, high-speed operation, high packing density, and multifunctional operation. Basic technologies of 3D ICs are to fabricate SOI layers and stack them monolithically. Crystallinity of the recrystallized layer in SOI has been steadily improving, and laser recrystallization technology has recently permitted crystal-axis-controlled, defect-free, single-crystal areas to be obtained on the level of chip size. Some basic functional models showing the concept or image of a future 3D IC have been fabricated in two or three stacked active layers. Proposols of subsystems applying 3D structures, technical issues for realizing practical 3D ICs, crosstalk of the signals between the stacked layers, total power consumption, and cooling of the chip are discussed.