Enhanced SnO2 FETs via selective area fluorine doping

초록

In this study, a selective fluorine (F) doping process was developed to enhance the performance of field-effect transistors (FETs) with SnO2 channels deposited by thermal atomic layer deposition. The fluorination process was applied selectively to the source (S) and drain (D) regions of the SnO2 FETs. Fluorination of the S/D regions before the annealing step of the SnO2 channel resulted in a significant improvement in specific contact resistivity (rho(c)), reducing it from 1.1 x 10(-2) to 3.1 x 10(-3) Omega cm(2) - more than a threefold enhancement compared to SnO2 FETs without S/D fluorination. However, in this case, the SnO2 channel could not be modulated, likely due to the diffusion of F ions into the channel during the annealing process. When fluorination was applied to the annealed SnO2 channel, an on/off ratio of 2.4 x 10(8) was achieved. However, rho(c) was 9.1 x 10(-3) Omega cm(2), showing only a 15 % improvement compared to untreated SnO2 FETs. To address this limitation, a two-step approach was developed for SnO2 FETs, in which F-doped S/D regions were formed prior to depositing the SnO2 channel. This approach yielded stable channel modulation with an on/off ratio > 10(8), along with a significant enhancement in field-effect mobility, increasing from 10.4 to 25.3 cm(2)/V<middle dot>s. Furthermore, the entire process was conducted at 400 degrees C or below, demonstrating its potential for enabling high-performance oxide transistors compatible with low temperature processes.

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