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

Bin Han, Hisashi Takamizawa, Yasuo Shimizu, Koji Inoue, Yasuyoshi Nagai, Fumiko Yano, Yorinobu Kunimune, Masao Inoue, Akio Nishida

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21 Citations (Scopus)

Abstract

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.

Original languageEnglish
Article number023506
JournalApplied Physics Letters
Volume107
Issue number2
DOIs
Publication statusPublished - 2015 Jul 13

ASJC Scopus subject areas

  • Physics and Astronomy (miscellaneous)

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