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A high-robustness and low-capacitance clamp for on-chip electrostatic discharge (ESD) protection is developed. The low capacitance is obtained by mitigating the capacitance associated with the lightly doped n-well/p-well junction. In addition to minimizing the capacitance, the high ESD robustness is achieved by optimizing independently within the same structure a silicon-controlled rectifier and a diode for the forward and reverse conduction processes, respectively. The new clamp with an area of 50 × 10 μm 2 is able to handle an ESD current in excess of 1.5 A, whereas the capacitance at zero bias is kept at 94 fF.Index Terms-Electrostatic discharge (ESD), parasitic capacitance, silicon-controlled rectifier (SCR).

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The stability of high sidewalls of large-span underground powerhouses will be a major issue when the cavern axis forms a small angle to the steeply inclined rock strata. A synthetic test scheme composed of four experiments was performed on two rocks with clear bedding features, aiming at better understanding the otherwise confusing deformation behavior and failure patterns of bedded rocks. Bedding orientations with respect to stress direction impose significant effect on the mechanical behavior of bedded rocks. Excessive tensile strain is observed in the direction perpendicular to bedding or across material interface in uniaxial test. Under low confinement in true triaxial test, the r 2 angle mainly influences the deformation and fracture propagation but not strength. Deformation dependence of bedded rocks on two stress paths is thoroughly investigated. Confining pressure unloading leads to pronounced volumetric dilation accompanied by moduli drop. Samples with large bedding angle exhibit more obvious lateral dilation. Post-peak degradation of deformation parameters is confirmed by cyclic test. Fractures entirely or partly along bedding occurred under different stress states depend not only on the bonding strength between beds but on the anisotropic deformation field. Based on these observations, it is deduced that the possible reasons for the failure of steeply dipping rock mass after excavation are a combination of (1) the pervasive bedding planes, (2) the more pronounced deformation normal to bedding, and (3) the excavationinduced unloading of confinement. Keywords Bedded rock Á Anisotropy Á Weak plane Á Tensile strain Á Confining pressure unloading test Á Cyclic test Á True triaxial test Á Wudongde underground caverns Á Bedding plane List of symbols CTC Conventional triaxial compression TTC True triaxial compression r 1 Maximum principle stress in TTC test or axial stress in CTC test r 2 Intermediate principle stress r 3 Minimum principle stress in TTC test or confining pressure in CTC test e 1 Strain parallel to the direction of r 1 in TTC test or axial strain in CTC test e 2 Strain parallel to the direction of r 2 in TTC test e 3 Strain parallel to the direction of r 3 in TTC test or circumferential strain in CTC test e vVolumetric strain in CTC test le 10 -6 strain, or microstrain bBedding angle, the angle between the normal vector of bedding and r 1 direction (0°-90°) E

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