Characterization of 22 nm FDSOI nMOSFETs With Different Backplane Doping at Cryogenic Temperature

In this work, the electrostatic and radio frequency performances of 22 nm FDSOI nMOSFETs with p-type or n-type doped backplane (BP, highly doped layer of silicon below thin buried oxide) at cryogenic temperatures have been investigated. Greater enhancement of drain current <inline-formula> <...

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Autores principales: Tiantian Xie, Qing Wang, Hao Ge, Yinghuan Lv, Zhipeng Ren, Jing Chen
Formato: article
Lenguaje:EN
Publicado: IEEE 2021
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Acceso en línea:https://doaj.org/article/1626b04f45ec4e618814bae339bfac75
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Sumario:In this work, the electrostatic and radio frequency performances of 22 nm FDSOI nMOSFETs with p-type or n-type doped backplane (BP, highly doped layer of silicon below thin buried oxide) at cryogenic temperatures have been investigated. Greater enhancement of drain current <inline-formula> <tex-math notation="LaTeX">$\text{I}_{\mathrm{ d}}$ </tex-math></inline-formula>, maximum transconductance <inline-formula> <tex-math notation="LaTeX">$\text{g}_{\mathrm{ m,max}}$ </tex-math></inline-formula> and threshold voltage <inline-formula> <tex-math notation="LaTeX">$\text{V}_{\mathrm{ TH}}$ </tex-math></inline-formula> values have been demonstrated at liquid nitrogen temperatures. Furthermore, FDSOI nMOSFETs with n-type BP achieve the maximum transconductance at lower bias voltage and smaller <inline-formula> <tex-math notation="LaTeX">$\text{V}_{\mathrm{ ZTC}}$ </tex-math></inline-formula>, which is mainly due to its small threshold voltage. The variation of threshold voltage of BP-p devices is greater with the decrease of temperature. About 40&#x0025; improvement of <inline-formula> <tex-math notation="LaTeX">$\text{f}_{\mathrm{ T}}$ </tex-math></inline-formula> and 30&#x0025; improvement of <inline-formula> <tex-math notation="LaTeX">$\text{f}_{\mathrm{ max}}$ </tex-math></inline-formula> depended on the <inline-formula> <tex-math notation="LaTeX">$\text{W}_{\mathrm{ f}}$ </tex-math></inline-formula> of devices have been shown. Relevant small-signal parameters (e.g., transconductance <inline-formula> <tex-math notation="LaTeX">$\text{g}_{\mathrm{ m}}$ </tex-math></inline-formula>, gate capacitance <inline-formula> <tex-math notation="LaTeX">$\text{C}_{\mathrm{ gg}}$ </tex-math></inline-formula>, gate resistance <inline-formula> <tex-math notation="LaTeX">$\text{R}_{\mathrm{ g}}$ </tex-math></inline-formula> and output conductance <inline-formula> <tex-math notation="LaTeX">$\text{g}_{\mathrm{ ds}}$ </tex-math></inline-formula>) are also extracted for comparison and analysis. This study presents both 22 nm FDSOI nMOSFETs with p-type or n-type backplane as good candidates for cryogenic applications down to 77 K, and especially, BP-n FDSOI are more suitable for low power operation applications because of their lower threshold voltage. Similar <inline-formula> <tex-math notation="LaTeX">$\text{g}_{\mathrm{ m.max}}$ </tex-math></inline-formula> and the peak values of RF FOMs can be obtained at lower bias voltage compared with BP-p devices.