Complete Process Modeling for VLSI Multilayer Structures

Abstract

A new one‐dimensional process simulator, ASPREM or advanced SUPREM, has been developed. ASPREM features the capability for multilayer structures and the incorporation of many up‐to‐date models. In this paper, general features of ASPREM are first described. Then details of many up‐to‐date models, such as oxidation‐enhanced diffusion with or without polysilicon, impurity diffusion in polysilicon and SiO2 , and stress effects to phosphorus diffusion after high dose ion implantation are reported with experimental results. Finally, applications to base‐emitter self‐aligned technology (BEST) transistors are described, followed by brief concluding remarks.

Anomalous B diffusion profiles in nanocrystalline Si

“…This type of shoulder observed in dopant diffusion profiles measured in monocrystalline Si is usually explained by a diffusion coefficient varying with dopant concentration (C B in our case) due to the variation of the Si Fermi level with dopant concentration (change in charge carrier and point defect concentrations) [14]. However, to the best of our knowledge, this type of profile has not yet been reported in the case of dopant diffusion in poly-Si [15,16]. It should be noted that the experiments reported in the literature on dopant diffusion in poly-Si were usually performed using poly-Si layers with stabilized grains (no or reduced GB motion) exhibiting large grain sizes [15,16].…”

“…However, to the best of our knowledge, this type of profile has not yet been reported in the case of dopant diffusion in poly-Si [15,16]. It should be noted that the experiments reported in the literature on dopant diffusion in poly-Si were usually performed using poly-Si layers with stabilized grains (no or reduced GB motion) exhibiting large grain sizes [15,16]. Since B is a usual p-type dopant (acceptor) for Si, its diffusion in monocrystalline Si has been extensively studied [14].…”

“…Usually, dopants are not activated in GBs [17]. At point defect equilibrium, GB diffusion coefficients (D gb ) were found to be constant at given temperature, and for B diffusion in Si GBs D gb = 0.8 exp(À2.6 eV/k B T) cm 2 s À1 [15]. Figure 2 shows the results of two-dimensional (2-D) finite-element simulations of B diffusion in the nc-Si layer considering the Fisher geometry [18] with a grain width of 50 nm and a GB size of 0.5 nm [8,9,19,20], as well as considering the B diffusion coefficients D B and D gb and the electrical effects in grains given in the literature and described above (Eqs.…”

“…In this model, the B atoms are considered to be incorporated in the Si grain after the lateral migration of the GB. From the literature, D gb was set to 2.74 Â 10 À15 cm 2 s À1 in GBs at 700°C [15] (experiments support that GB diffusion is identical in immobile and mobile GBs [21]) and D g was adjusted according to the simulation results [8,9,19,20]. In order to fit the experimental profiles, we set D g = 4.33 Â 10 À19 cm 2 s À1 (Eq.…”

Boron Redistribution During Crystallization of Phosphorus-Doped Amorphous Silicon

“…Dopant redistribution in silicon is of great importance in microelectronics. While boron diffusion has been extensively studied in crystalline silicon (c-Si), fewer studies exist concerning boron redistribution in poly-crystalline silicon [1][2][3][4] as well as in amorphous silicon [5][6][7][8]. In this work, we investigate the boron redistribution in a thin silicon film during a typical non volatile memory (NVM) process flow.…”