| Summary: | 碩士 === 亞洲大學 === 資訊工程學系碩士班 === 100 === Lateral PNP bipolar junction transistors (BJTs) fabricated using a bulk 0.25 µm CMOS technology are presented. This lateral PNP device has good ESD protection as we demonstrated that in this work. It is found that a lateral PNP device can exhibit snapback behavior similar to that characteristics associated with NPN based ESD clamps. The advantages of this lateral PNP is provide local ESD protection that is robust against transient latch up.
The structure also has an avalanche diode connected with lateral PNP to reduce the Ron. Breakdown voltage roll-off occurs in multi-finger PNP BJT devices with different base width from 1.6 to 2.2 um. The results of this research presents the results of investigations using a process and device simulation tools, and clearly concluded that the breakdown roll-off caused by punch-trough on devices with a narrow base width. The physical mechanism of breakdown roll off, punch through and second breakdown of the device in lateral PNP transistor are investigated. The ESD (triggering and holding voltage) and forward IV curve behavior and mechanism is also investigated in this work.
The use of BF2 as an implant to form a shallow junction because of its amorphous behavior plays an important role to minimize the channeling effect, but implantation above the STI oxide, with the goal of optimization the vertical diode width as the perimeter of the collector needs to consider the mechanism of boron enhanced diffusivity through the oxide, especially for the devices with a narrow base width. The boron transient enhanced diffusion (TED) and channeling effect of boron can demonstrate by Monte Carlo simulation. It is shown that with the optimized parameters for boron and fluorine, BF2 implantation can be accurately predicated without further calibration with binary collision approximation (BCA) based Monte Carlo (Alpha Tauri) model. The physical mechanism of boron and fluorine has been presented in this work with the help of Monte Carlo table implantation of BF2.
Mesh strategy holds a key in Medici 2D simulations, which has to be taken extra care and needs special type of mesh designing in order to avoid any convergence issues thereafter. This mesh design not only includes eliminating convergence issues, which also emphasize on achieving good doping profile with smooth curves comparatively a better device simulation. Extra care has been taken in emitter, collector and base region. Optimized mesh also helps in eliminating unnecessary nodes and overall reduction in number of nodes and results in faster simulation without losing accuracy; this has been presented in this thesis.
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