RADIATION-DAMAGE-COMPENSATION-CIRCUIT AND SOI-MOSFET
|発明の名称 （英語）||RADIATION-DAMAGE-COMPENSATION-CIRCUIT AND SOI-MOSFET|
|発明の概要（英語）||The present invention provides a radiation-damage-compensation-circuit and a SOI-MOSFET that has high radiation resistance. The SOI-MOSFET has the radiation-damage-compensation-circuit to recover the characteristics of the SOI-MOSFET after X-ray irradiation.|
CROSS-REFERENCE TO RELATED APPLICATIONS
This application is based on and claims the benefit of priority of JP Application Serial No. 2015/199200, filed on October 7, 2015 and U.S. Patent Application Serial No. 62/312,804, filed on March 24, 2016, the entire contents of which are incorporated herein by reference.
“SOI” is the same as “silicon-on-insulator”. “MOSFET” is the same as “metal-oxide-semiconductor-field-effect-transistor”. The conventional MOSFET has a structure in which a MOSFET is fabricated on a silicon-substrate, as shown in Fig. 1. The MOSFET comprises a source, gate and drain on the silicon-substrate (1). The gate (1a) consists of a channel, SiO2-layer on the channel and gate-electrode (3) on the SiO2-layer. An assembly of the source, channel and drain is called a silicon-membrane (2). An assembly of the source, gate and drain is called a transistor (1b). “SOI-MOSFET” means a MOSFET fabricated with the SOI. The conventional SOI-MOSFET has a structure in which a MOSFET is fabricated with the SOI, as shown in Fig. 2. “Depletion” means a state in which carriers such as electrons or positive holes are absent in the gate. “Partial depletion” means a state in which depletion is partial. “Complete depletion” means a state in which depletion is complete.
Positive charge is generated in the BOX when exposed with X-ray radiation. The SOI-MOSFET is less radiation-resistant against appreciable amounts of X-ray irradiation because radiation-induced positive charge in the BOX has ill effects on the transistor characteristics.
In order to solve the above problems, several methods which apply negative voltage to a bottom of the silicon-substrate, a back-gate, have been presented (Patent Literatures 1-3).
The Patent Literature 1 discloses a method for setting voltage applied to the back-gate as a function of radiation-exposition times. As shown in Fig. 2, the conventional SOI-MOSFET has a thick BOX (4) buried in a very thick silicon-substrate (1). For example, the silicon-substrate (1) is μm thick and the BOX (4) is sub-μm thick. This causes secondary problems: a very large voltage for long periods of time is required for canceling the positive charge in the BOX; discontinuous or non-constant radiation makes the performance of the SOI-transistor instable, due to overhigh or overlow voltage. The conventional SOI-MOSFET may be destroyed due to such a large voltage for long periods of time. However, the method disclosed by the Patent Literature 1 cannot resolve the above problems. The positive charge in the BOX cannot be removed with ease by applying voltage to the back-gate.
The Patent Literature 2 discloses a SOI-MOSFET that is capable of inhibiting leak-current independently with the gate-control. However, the SOI-MOSFET is essentially less resistant against radiation-exposure due to no method to cancel radiation-induced positive charge.
The Patent Literature 3 discloses the SOI-MOSFET that is capable of increasing or decreasing a threshold voltage by using high bias-substrate-coefficient on stand-by or line.
The present invention differs from the Patent Literatures 1-3 in respect to the structure and function with each other, as follows.
1) The SOI-MOSFET disclosed in the Patent Literature 1 has no system to detect the radiation-induced positive charge. Contrary, the present invention has a structure that detects a voltage threshold shift due to the radiation-induced positive charge followed by application of voltage to cancel the radiation-induced positive charge.
2) The SOI-MOSFET disclosed in the Patent Literature 2 has a well-in-well including a p-well and a n-well. Contrary, the present invention has any one of p-well or n-well but does not have the both.
3) The SOI-MOSFET disclosed in the Patent Literature 2 installs a circuit connecting the well-in-well and the back-gate in order to inhibit leak-current in the gate of the MOSFET. Contrary, the present invention mounts a circuit connecting a gate, a voltage-source and a via that penetrates the BOX to lead a buried p-well, wherein a voltage of the voltage-source is applied to the buried p-well, negative electron of the buried p-well generates, electron-tunneling to the BOX takes place, and positive charge in the BOX is canceled with the negative electron.
4) The SOI-MOSFET disclosed in the Patent-Literature 3 is able to increase a threshold voltage but is not able to detect a voltage threshold shift. Contrary, the present invention has a structure that detects a voltage threshold shift due to the radiation-induced positive charge followed by application of voltage to cancel the radiation-induced positive charge.
National States: AE AG AL AM AO AT AU AZ BA BB BG BH BN BR BW BY BZ CA CH CL CN CO CR CU CZ DE DJ DK DM DO DZ EC EE EG ES FI GB GD GE GH GM GT HN HR HU ID IL IN IR IS JP KE KG KN KP KR KW KZ LA LC LK LR LS LU LY MA MD ME MG MK MN MW MX MY MZ NA NG NI NO NZ OM PA PE PG PH PL PT QA RO RS RU RW SA SC SD SE SG SK SL SM ST SV SY TH TJ TM TN TR TT TZ UA UG US UZ VC VN ZA ZM ZW
ARIPO: BW GH GM KE LR LS MW MZ NA RW SD SL SZ TZ UG ZM ZW
EAPO: AM AZ BY KG KZ RU TJ TM
EPO: AL AT BE BG CH CY CZ DE DK EE ES FI FR GB GR HR HU IE IS IT LT LU LV MC MK MT NL NO PL PT RO RS SE SI SK SM TR
OAPI: BF BJ CF CG CI CM GA GN GQ GW KM ML MR NE SN ST TD TG
『 RADIATION-DAMAGE-COMPENSATION-CIRCUIT AND SOI-MOSFET 』に関するお問合せ
- 大学共同利用機関法人 高エネルギー加速器研究機構（KEK) 研究協力部研究協力課産学公連携・知財係
- URL: http://www.kek.jp/
- Address: 〒305-0801 茨城県つくば市大穂1-1
- TEL: 029-864-5125
- FAX: 029-864-4602