Phosphorus and boron diffusion paths in polycrystalline silicon gate of a trench-type three-dimensional metal-oxide-semiconductor field effect transistor investigated by atom probe tomography
- The Oarai Center, Institute for Materials Research, Tohoku University, 2145-2 Narita, Oarai, Ibaraki 311-1313 (Japan)
- Department of Electrical Engineering, Faculty of Engineering, Tokyo City University, 1-28-1 Tamazutsumi, Setagaya-ku, Tokyo 158-8557 (Japan)
- Renesas Semiconductor Manufacturing Co., Ltd., 1120 Shimokuzawa, Sagamihara, Kanagawa 252-5298 (Japan)
- Renesas Electronics Corporation, 751 Horiguchi, Hitachinaka, Ibaraki 312-8504 (Japan)
The dopant (P and B) diffusion path in n- and p-types polycrystalline-Si gates of trench-type three-dimensional (3D) metal-oxide-semiconductor field-effect transistors (MOSFETs) were investigated using atom probe tomography, based on the annealing time dependence of the dopant distribution at 900 °C. Remarkable differences were observed between P and B diffusion behavior. In the initial stage of diffusion, P atoms diffuse into deeper regions from the implanted region along grain boundaries in the n-type polycrystalline-Si gate. With longer annealing times, segregation of P on the grain boundaries was observed; however, few P atoms were observed within the large grains or on the gate/gate oxide interface distant from grain boundaries. These results indicate that P atoms diffuse along grain boundaries much faster than through the bulk or along the gate/gate oxide interface. On the other hand, in the p-type polycrystalline-Si gate, segregation of B was observed only at the initial stage of diffusion. After further annealing, the B atoms became uniformly distributed, and no clear segregation of B was observed. Therefore, B atoms diffuse not only along the grain boundary but also through the bulk. Furthermore, B atoms diffused deeper than P atoms along the grain boundaries under the same annealing conditions. This information on the diffusion behavior of P and B is essential for optimizing annealing conditions in order to control the P and B distributions in the polycrystalline-Si gates of trench-type 3D MOSFETs.
- OSTI ID:
- 22483204
- Journal Information:
- Applied Physics Letters, Vol. 107, Issue 2; Other Information: (c) 2015 AIP Publishing LLC; Country of input: International Atomic Energy Agency (IAEA); ISSN 0003-6951
- Country of Publication:
- United States
- Language:
- English
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