DEVELOPMENT AND CHARACTERIZATION OF A HIGH ASPECT … · DEVELOPMENT AND CHARACTERIZATION OF A HIGH...
1
DEVELOPMENT AND CHARACTERIZATION OF A HIGH ASPECT RATIO VERTICAL FET SENSOR FOR MOTION DETECTION DEVELOPMENT AND CHARACTERIZATION OF A HIGH ASPECT RATIO VERTICAL FET SENSOR FOR MOTION DETECTION Flexure Vertical Transistor Vertical Transistor Seismic Mass Comb Electrodes d A gs V ds V i Sour ce B u lk D ra in Gate S. Heinz 1 , S. Buschnakowski 1 , A. Bertz 2 , W. Bräuer 2 , R. Schuberth 2 , G. Ebest 1 , T. Gessner 2, 3 1 Chemnitz University of Technology, Chair Electronic Devices 2 Chemnitz University of Technology, Centre of Microtechnologies 3 Fraunhofer Institute of Reliability and Microintegration, Department of Micro Devices and Equipment Nowadays, inertial sensors for car dynamics stabilisation, acceleration detection and human body motion monitoring are popular MEMS applications. Additionally, motion/position detection is often required for actuators too (xy stages, switches, etc.). At present, these systems are usually based on piezoelectric or capacitive sensors. While especially the latter principle is already used for mass production of inertial sensors an increase of the signal/area consumption ratio is desired. That’s why alternative approaches have been presented looking for a direct integration of mechanical and electrical principles. The detection principle of the FET sensor for motion sensing is the electrical field effect. A schematic of the structure is shown in figure 1. The system consists of a laterally moving spring-mass- system (figure 2 and figure 3). There are two arms at the seismic mass. Transistor regions are located at the end of the arms (figure 4). INTRODUCTION PROCESS FLOW Contact Author: Steffen Heinz Chemnitz University of Technology, Chair Electronic Devices 09107 Chemnitz Phone +49 371/ 531 3090 Fax: +49 371/ 531 4715 e-mail: [email protected] Figure 1: Schematic view of the vertical FET The moving mass (single crystalline silicon) is acting as a in plane gate electrode. The air gap between the channel and the gate electrode decreases / increases due to the deflection of the mass caused for example by the moment of inertia. A displacement of the mass changes the air gap of the vertical FET influencing the capacitance of the gate insulator. Figure 2: Layout of the transistor Figure 3: SEM view of the vertical FET Figure 4: . Light-optical microscope view of the transistor FET SENSOR The main advantages of the vertical FET with respect to capacitive sensor systems are: SUMMARY •higher signal-to-chip size ratio •simplifications of the signal conditioning circuitry •low impedance sensing technique •the sensing element is an “active sensor” •mechanical movement and output sensor signal are in phase. The measurements were carried out on wafer level and on single vertical FET’s. A HP 4062 UX process control system with a HP 4142B modular DC source / monitor was used to bias the gate, drain, source and substrate of the vertical FET. Figure 5 shows the measure arrangement and figure 6 and 7 the results. Figure 6: I-U-characteristic depending on deflection voltage Figure 7: Transfer characteristic at V DS = 0,4 V and V GS = 5 V EXPERIMENTAL RESULTS Figure 5:Measure arrangement
Transcript of DEVELOPMENT AND CHARACTERIZATION OF A HIGH ASPECT … · DEVELOPMENT AND CHARACTERIZATION OF A HIGH...
DEVELOPMENT AND CHARACTERIZATION OF A HIGH ASPECT RATIO
VERTICAL FET SENSOR FOR MOTION DETECTION
DEVELOPMENT AND CHARACTERIZATION OF A HIGH ASPECT RATIO
VERTICAL FET SENSOR FOR MOTION DETECTION
FlexureVertical Transistor
Vertical Transistor
Seismic Mass
Comb Electrodesd
A
gsV
dsV
i
SourceBulk
Drain
Gate
S. Heinz1, S. Buschnakowski1, A. Bertz2, W. Bräuer2, R. Schuberth2, G. Ebest1, T. Gessner2, 3
1Chemnitz University of Technology, Chair Electronic Devices2Chemnitz University of Technology, Centre of Microtechnologies
3Fraunhofer Institute of Reliability and Microintegration, Department of Micro Devices and Equipment
Nowadays, inertial sensors for car dynamics stabilisation, acceleration detection and human body motion monitoring are popularMEMS applications. Additionally, motion/position detection is often required for actuators too (xy stages, switches, etc.). At present,these systems are usually based on piezoelectric or capacitive sensors. While especially the latter principle is already used formass production of inertial sensors an increase of the signal/area consumption ratio is desired. That’s why alternative approacheshave been presented looking for a direct integration of mechanical and electrical principles.
The detection principle of theFET sensor for motionsensing is the electrical fieldeffect. A schematic of thestructure is shown in figure 1.The system consists of alaterally moving spring-mass-system (figure 2 and figure 3).There are two arms at theseismic mass. Transistorregions are located at the endof the arms (figure 4).
INTRODUCTION
PROCESS FLOW
Contact Author: Steffen HeinzChemnitz University of Technology, Chair Electronic Devices09107 ChemnitzPhone +49 371/ 531 3090 Fax: +49 371/ 531 4715e-mail: [email protected]
Figure 1: Schematic view of the vertical FET
The moving mass (single crystalline silicon) is acting as a in plane gate electrode. The air gapbetween the channel and the gate electrode decreases / increases due to the deflection of the masscaused for example by the moment of inertia. A displacement of the mass changes the air gap of thevertical FET influencing the capacitance of the gate insulator.
Figure 2: Layout of the transistor
Figure 3: SEM view of the vertical FET
Figure 4: . Light-optical microscope viewof the transistor
FET SENSOR
The main advantages of the vertical FET with respect to capacitive sensorsystems are:
SUMMARY
•higher signal-to-chip size ratio
•simplifications of the signal conditioning circuitry
•low impedance sensing technique
•the sensing element is an “active sensor”
•mechanical movement and output sensor signal are in phase.
The measurements were carried out on wafer level and onsingle vertical FET’s. A HP 4062 UX process controlsystem with a HP 4142B modular DC source / monitor wasused to bias the gate, drain, source and substrate of thevertical FET. Figure 5 shows the measure arrangementand figure 6 and 7 the results.
Figure 6: I-U-characteristic depending ondeflection voltage
Figure 7: Transfer characteristic at VDS= 0,4 Vand VGS= 5 V
EXPERIMENTAL RESULTS
Figure 5:Measure arrangement
