The lateral gate-all-around (GAA) field effect transistor is considered to be the most promising candidate for the next generation of logic devices at the 3nm technology node and beyond. SiGe plays an important role as a sacrificial layer in the GAA device, which requires isotropic etching, and the quality of the etching has a critical impact on the device performance. However, there is no definite scheme in the industry for the choice of etching method. In this paper, we choose two etching methods: CP(Inductively coupled Plasma) and RPS (Remote Plasma Source) etching according to the presence or absence of particle incidence. The profile and etching effect of the two etching methods are analyzed by PEGASUS simulation software. The presence or absence of particle incidence has different effects on the damage of the structure, the inconsistency of etching amount and the reflection of the particles on the Si surface. Compared with ICP etching, the optimization of RPS etching on etching damage and etch amount consistency is verified by TEM and roughness characterization . And through the extraction of MOSCAP capacitance, it is found that the density of interface states(Dit) after ICP etching is 3.5 times higher than that of RPS etching.
To achieve efficient optical communication and optical interconnection, it is necessary to develop and prepare detectors with high gain, low noise, high bandwidth and strong anti-electromagnetic interference. Because III-V materials cannot be integrated with CMOS process line, therefore, avalanche photodiodes (APDs) based on germanium silicon substrates are considered as detectors with large scale integration. Waveguide integrated structure can solve the contradiction between response and bandwidth in surface illuminated structure. Moreover, with germanium as the absorption region, a SACM (separate absorption charge multiplication) structure with silicon as a multiplication region has become a widely used device structure. In this work, a new vertical structure waveguide integrated structure of silicon-based germanium APD is designed with the charge layer on both sides of the germanium absorption layer, and the influence of the thickness of the multiplication layer on the dark current is simulated and tested. It shows that when the width of the multiplication layer increases, the breakdown voltage of the device increases, indicating that the electric field level of the multiplication region is similar to that of different devices at the breakdown voltage, furthermore, the simulation and experimental results are basically consistent. Under the input power of -16.8 dBm for 1310 nm incident light, the bandwidth of the designed vertical structure SACM silicon-based germanium APD can reach 25.7 GHz at 15.7 V bias. The primary responsivity of the device is up to 0.68 A/Wand the gain bandwidth product is up to 247 GHz, showing the great potential of the present Ge/Si APD for the application in future high-speed data transmission systems.
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