Novel High voltage silicon-on-insulator Device with Composite dielectric buried Layer
A novel silicon-on-insulator (SOI) high voltage device with a composite dielectric buried layer (CD SOI) is proposed in this paper. In the proposed structure, the composite dielectric buried layer consists of Si 3 N 4 dielectric and low-k (relative permittivity) dielectric. The electric field strength in the buried layer is enhanced by the low-k dielectric. The Si 3 N 4 dielectric in the buried layer not only modulates the electric field distribution in the drift region, but also provides a heat conduction path for the SOI layer and alleviates the self-heating effect (SHE). The breakdown voltage (BV) = 362 V for CD SOI is obtained by simulation on a 1 μm SOI layer over 2 μm buried layer, which is enhanced by 26% compared with that of conventional SOI.
Field Enhancement for Dielectric Layer of High-Voltage Devices on Silicon on Insulator
Based on the continuity theorem of electric displacement including interface charges, the enhanced dielectric layer field (ENDIF) for silicon-on-insulator (SOI) high-voltage devices is proposed. The following three approaches for enhancing the dielectric layer electric field EI to increase the vertical breakdown voltage of a device VB,V are presented: 1) using a thin silicon layer with a high critical electric field ES,C ; 2) introducing a low-permittivity dielectric buried layer; and 3) implementing interface charges between the silicon and the dielectric layer. Considering the threshold energy of silicon epsivT, the formula of ES,C on silicon layer thickness tS is first obtained, which increases sharply with a decrease of tS, and reaches up to 141 V/mum at tS = 0.1 mum. Expressions for EI and VByV are given, which agree well with simulative and experimental results. Based on the ENDIF, the new device structures are given, and an EI value of 300 V/mum has been experimentally obtained for double-sided trench SOI. Moreover, several conventional SOI devices are explained well by ENDIF.
New Low-Profile Applicators for Local Heating of Tissues
A new type of low-profile applicator is described giving efficient power transfer to tissue with low leakage. It consists of a resonant element spaced from a ground plane by low-loss material having high relative permittivity and some relative permeability. This combination is covered by similar material which can be placed in direct contact with the tissue to be heated, or separated from it by a water bolus as required. Laboratory measurements using phantom materials show that these applicators are well matched and produce well defined and relatively uniform heating profiles. Applicators having maximum dimensions of 3-15 cm covering the frequency range 1000-100 MHz, respectively, are described. Penetration depths of at least 4 cm at 100-200 MHz are achieved. Tests on anesthetised pigs and some clinical assessment have confirmed the usefulness of this compact low-frequency type of applicator and have shown that performance compares favorably with that of other recently reported types. The design can be optimized for treatment of specific sites, and suitable choice of dimensions and electrical characteristics of the layer material allow the low-profile concept to be extended over a wide range of operating frequencies.