• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2010.06a
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• pp.199-199
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• 2010

A back-gated MOSFET on silicon-on-insulator (SOI) substrate for pH sensor was investigated. We used concentrations of pH solution from 6 to 9. The fabricated back-gated MOSFET has current difference and threshold voltage shift by pH concentrations. Therefore, It can be used to simplification of conventional pH sensor.

• JSTS:Journal of Semiconductor Technology and Science
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• v.4 no.1
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• pp.18-26
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• 2004

Back-gated silicon-on-insulator MOSFET -a threshold-voltage adjustable device-employs a constant back-gate potential to terminate source-drain electric fields and to provide carrier confinement in the channel. This suppresses shortchannel effects of nano-scale and of high drain biases, while allowing a means to threshold voltage control. We report here a theoretical analysis of this geometry to identify its natural length scales, and correlate the theoretical results with experimental device measurements. We also analyze experimental electrical characteristics for misaligned back-gate geometries to evaluate the influence on transport behavior from the device electrostatics due to the structure and position of the back-gate. The backgate structure also operates as a floating-gate nonvolatile memory (NVRAM) when the back-gate is floating. We summarize experimental and theoretical results that show the nano-scale scaling advantages of this structure over the traditional front floating-gate NVRAM.

• Proceedings of the Korean Vacuum Society Conference
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• 2010.08a
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• pp.242-242
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• 2010

SiO2박막을 이온 감지막으로 이용한 pH농도센서를 제작하였다. 현재 많은 연구중인 pH센서, pH-ISFET(pH-Ion Sensitive Field Effect Transistor)는 용액과 기준전극간의 전기화학적 변위차를 이용하여 pH를 센싱한다. pH-ISFET는 기존 CMOS공정을 그대로 이용할 수 있고, 이온감지막의 변화만으로 다양한 센서를 제작할 수 있어 최근 많은 연구가 진행 중이다. 하지만 FET를 제작하기 위한 공정의 복잡성과 용액의 전위를 정해주고 FET에 바이어스를 인가해줄 기준전극이 반드시 필요하다는 제한성이 있다. 따라서 본 연구에서는 SOI 기판을 이용하여 간단한 구조의 pH센서를 제작하였다. 센서는 (100)결정면을 가지는 p-타입 SOI(Silicon On Insulator)기판을 사용하였으며 포토리소그래피 공정을 이용하여 back-gated MOSFET구조로 제작하였다. 이온감지막으로 사용할 SiO2박막은 RF 스퍼터링을 이용하여 $100{\AA}$ 증착하였다. 바이어스는 기존 pH-ISFET와는 다르게 기준전극 대신 기판을 backgate로 사용하여 FET에 바이어스를 인가해 주었다. pH 용액 주입을 위해 PDMS재질의 챔버를 제작하고 실리콘글루를 이용하여 센서에 부착하였다. pH12부터 pH4까지 단계적으로 누적시키며 챔버에 주입하였고, pH에 따른 드레인전류의 변화를 관찰하였다. pH용액을 챔버에 주입시, pH농도에 따라 제작된 센서의 문턱전압이 오른쪽으로 이동하는 결과를 관찰할 수 있었다. 결과적으로, 구조가 간단한 pseudo MOSFET을 이용하여 pH센서의 적용가능성을 확인하였으며 SiO2박막 역시 본 pH센서의 이온감지막의 역할과 센서의 안정성을 향상시킬 수 있다는 점을 확인하였다.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2009.11a
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• pp.35-35
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• 2009

Capacitorless one transistor dynamic random access memory (1T-DRAM) cells were fabricated on the fully depleted strained-silicon-on-insulator (FD sSOI) and the effects of silicon back interface state on buried oxide (BOX) layer on the memory properties were evaluated. As a result, the fabricated 1T-DRAM cells showed superior electrical characteristics and a large sensing current margin (${\Delta}I_s$) between "1" state and "0" state. The back interface of SOI based capacitorless 1T-DRAM memory cell plays an important role on the memory performance. As the back interface properties were degraded by increase rapid thermal annealing (RTA) process, the performance of 1T-DRAM was also degraded. On the other hand, the properties of back interface and the performance of 1T-DRAM were considerably improved by post RTA annealing process at $450^{\circ}C$ for 30 min in a 2% $H_2/N_2$ ambient.

• Journal of the Korean Vacuum Society
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• v.17 no.3
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• pp.199-203
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• 2008

The effects of surface treatment by $O_2$ plasma on the Bio-FETs were investigated by using the pseudo-MOSFETs on the SOI substrates. After a surface treatment by $O_2$ plasma with different RF powers, the current-voltage and field effect mobility of pseudo-MOSFETs were measured by applying back gate bias. The subthreshold characteristics of pseudo-MOSFETs were significantly degraded with increase of RF power. Additionally, a forming gas anneal process in 2 % diluted $H_2/N_2$ ambient was developed to recover the plasma process induced surface damages. A considerable improvement of the subthreshold characteristics was achieved by the forming gas anneal. Therefore, it is concluded that the pseudo-MOSFETs are a powerful tool for monitoring the surface treatment of Bio-FETs and the forming gas anneal process is effective for improving the electrical characteristics of Bio-FETs.