Mechanical Stress Effects on MOS Capacitors including FeRAM

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1. MOSn-MOS and p-MOS capacitances were measured at 1MHz, and at room temperature under tension and compression. Capacitance change can be explained by the change of depletion layer width through energy gap change and density of state effective mass change of hole bands. The slope of C-V curve doesn't displace in parallel. The C-V curve does not stretch-out.Dielectric constant, fixed oxide charge and interface trap density don't change. Geometric deformation does not affect the capacitance. The stress dependence of intrinsic carrier density was explained.2. FeRAMPt lower electrode was deposited on MOS structure. PZT thin film was deposited on the electrode by sol-gel method and annealed at 550 C. The thickness of the film is 220 nm. Pt circular electrode with 220 μm diameter was deposited on it. Hysteresis loops were observed by Saujer-Tower circuit at 100 kHz under tension and compression. The stress coefficients of residual polarization, coercive field and spcCapacitance vs voltage characteristics with tensile stress and without stress were measured. Capacitance decrease slightly with tensile stress.