Ultimate Layer Stacking Technology for High Density Sequential 3D Integration

A review of wafer-level stacking technology providing a ultra thin and uniform single-crystalline silicon film onto a device wafer is reported in this paper. Smart Cut™ technology has been adapted at low temperatures for the transfer of a thin Si layer - ready for device fabrication. The surface micro-roughness is below 0.2nm and film thickness uniformity of 0.4nm within wafer and wafer-to-wafer measurements. Combining with low temperature device processing, the sequential manufacturing of 3D devices is demonstrated. Although the maximum temperature of the sequential 3D process does not exceed 500°C, the transistor characteristics are preserved. In this paper we report for the first time demonstration of Smart Cut layer stacking below 400°C.