Improvement in Strain Sensor Stability by Adapting the Metal Contact Layer

Research on stretchable strain sensors is actively conducted due to increasing interest in wearable devices. However, typical studies have focused on improving the elasticity of the electrode. Therefore, methods of directly connecting wire or attaching conductive tape to materials to detect deformation have been used to evaluate the performance of strain sensors. Polyaniline (PANI), a p-type semiconductive polymer, has been widely used for stretchable electrodes. However, conventional procedures have limitations in determining an appropriate metal for ohmic contact with PANI. Materials that are generally used for connection with PANI form an undesirable metal-semiconductor junction and have significant contact resistance. Hence, they degrade sensor performance. This study secured ohmic contact by adapting Au thin film as the metal contact layer (the MCL), with lower contact resistance and a larger work function than PANI. Additionally, we presented a buffer layer using hard polydimethylsiloxane (PDMS) and structured it into a dumbbell shape to protect the metal from deformation. As a result, we enhanced steadiness and repeatability up to 50% strain by comparing the gauge factors and the relative resistance changes. Consequently, adapting structural methods (the MCL and the dumbbell shape) to a device can result in strain sensors with promising stability, as well as high stretchability.

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Microstructural Characterization of Au-Ge-Ni based ohmic contacts to GaAs/AlGaAs modfet device

Proceedings, annual meeting, Electron Microscopy Society of America ◽

10.1017/s0424820100126433 ◽

1987 ◽

Vol 45 ◽

pp. 326-327

Author(s):

A.K. Rai ◽

A.K. Petford-Long ◽

A. Ezis ◽

D.W. Langer

Keyword(s):

Contact Resistance ◽

Ohmic Contact ◽

Ohmic Contacts ◽

Microstructural Characterization ◽

Almost Everywhere ◽

Spacer Layer ◽

Good Contact ◽

The Relationship ◽

Lower Contact

Considerable amount of work has been done in studying the relationship between the contact resistance and the microstructure of the Au-Ge-Ni based ohmic contacts to n-GaAs. It has been found that the lower contact resistivity is due to the presence of Ge rich and Au free regions (good contact area) in contact with GaAs. Thus in order to obtain an ohmic contact with lower contact resistance one should obtain a uniformly alloyed region of good contact areas almost everywhere. This can possibly be accomplished by utilizing various alloying schemes. In this work microstructural characterization, employing TEM techniques, of the sequentially deposited Au-Ge-Ni based ohmic contact to the MODFET device is presented.The substrate used in the present work consists of 1 μm thick buffer layer of GaAs grown on a semi-insulating GaAs substrate followed by a 25 Å spacer layer of undoped AlGaAs.

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Study of Ohmic Contacts on P-Type ZnSe and ZnSe Epitaxial Layers Grown by Molecular Beam Epitaxy

MRS Proceedings ◽

10.1557/proc-281-727 ◽

1992 ◽

Vol 281 ◽

Author(s):

C. Piskoti ◽

B. Mykolajenko ◽

M. Vaziri

Keyword(s):

Molecular Beam Epitaxy ◽

Ohmic Contact ◽

Ohmic Contacts ◽

Molecular Beam ◽

Metal Contact ◽

Epitaxial Layers ◽

Preliminary Results ◽

Current Voltage ◽

Current Voltage Characteristics ◽

P Type

ABSTRACTTo study the formation of ohmic contacts, several metals have been deposited on p-types ZnTe and ZnSe epitaxial layers. The metals were deposited on the layers either by simple evaporation or by electroplating. The current-voltage characteristics associated with each metal contact were measured. The preliminary results of these measurements indicate that electroplating is a better technique for making ohmic contact to these layers.

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Laser annealed ohmic contact to n+-GaAs

Canadian Journal of Physics ◽

10.1139/p83-154 ◽

1983 ◽

Vol 61 (8) ◽

pp. 1218-1221 ◽

Cited By ~ 5

Author(s):

P. Sircar

Keyword(s):

Surface Morphology ◽

Contact Resistance ◽

Excimer Laser ◽

Ohmic Contact ◽

Ohmic Contacts ◽

Laser Annealing ◽

Furnace Annealing ◽

Gaas Substrates ◽

Thin Nickel ◽

Lower Contact

Ohmic contacts were made on n+-GaAs substrates by evaporating a gold–germanium eutectic film with or without a thin nickel overlayer and then alloying these samples either in a furnace or by means of an excimer laser. It is found that laser annealing gives a better surface morphology and a lower contact resistance than furnace annealing.

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Improved Low Resistance Contacts of Ni/Au and Pd/Au to P-Type GaN Using a Cryogenic Treatment

MRS Proceedings ◽

10.1557/proc-595-f99w11.77 ◽

1999 ◽

Vol 595 ◽

Author(s):

Mi-Ran Park ◽

Wayne A. Anderson ◽

Seong-Ju Park

Keyword(s):

Contact Resistance ◽

Ohmic Contact ◽

Cryogenic Treatment ◽

Microstructural Analysis ◽

Chemical Vapor ◽

Specific Contact Resistance ◽

Mixed Gas ◽

Low Resistance ◽

Specific Contact ◽

P Type

AbstractA low resistance Ohmic contact to p-type GaN is essential for reliable operation of electronic and optoelectronic devices. Such contacts have been made using Ni/Au and Pd / Au contacts to p-type Mg-doped GaN (1.41×1017 cm−3) grown by metalorganic chemical vapor deposition ( MOCVD ) on ( 0001 ) sapphire substrates. Thermal evaporation was used for the deposition of those metals followed by annealing at temperatures of 400 ∼ 700 °C in an oxygen and nitrogen mixed gas ambient, then subsequently cooled in liquid nitrogen which reduced the specific contact resistance from the range of 9.46∼2.80×10−2 ωcm2 to 9.84∼2.65×10−4 ωcm2 for Ni/Au and from the range of 8.35∼5.01×10−4 ωcm2 to 3.34∼1.80×10−4 ωcm2 for Pd/Au. The electrical characteristics for the contacts were examined by the current versus voltage curves and the specific contact resistance was determined by use of the circular transmission line method (c-TLM). The effects of the cryogenic process on improving Ohmic behavior (I-V linearity) and reducing the specific contact resistance will be discussed from a microstructural analysis which reveals the metallurgy of Ohmic contact formation.

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Improved Low Resistance Contacts of Ni/Au and Pd/Au to p-Type GaN Using a Cryogenic Treatment

MRS Internet Journal of Nitride Semiconductor Research ◽

10.1557/s109257830000524x ◽

2000 ◽

Vol 5 (S1) ◽

pp. 901-907

Author(s):

Mi-Ran Park ◽

Wayne A. Anderson ◽

Seong-Ju Park

Keyword(s):

Contact Resistance ◽

Ohmic Contact ◽

Cryogenic Treatment ◽

Microstructural Analysis ◽

Chemical Vapor ◽

Specific Contact Resistance ◽

Mixed Gas ◽

Low Resistance ◽

Specific Contact ◽

P Type

A low resistance Ohmic contact to p-type GaN is essential for reliable operation of electronic and optoelectronic devices. Such contacts have been made using Ni/Au and Pd / Au contacts to p-type Mg-doped GaN (1.41×1017 cm−3) grown by metalorganic chemical vapor deposition ( MOCVD ) on ( 0001 ) sapphire substrates. Thermal evaporation was used for the deposition of those metals followed by annealing at temperatures of 400 ∼ 700 °C in an oxygen and nitrogen mixed gas ambient, then subsequently cooled in liquid nitrogen which reduced the specific contact resistance from the range of 9.46∼2.80×10−2 Ωcm2 to 9.84∼2.65×10−4 Ωcm2 for Ni/Au and from the range of 8.35∼5.01×10−4 Ωcm2 to 3.34∼1.80×10−4 Ωcm2 for Pd/Au. The electrical characteristics for the contacts were examined by the current versus voltage curves and the specific contact resistance was determined by use of the circular transmission line method (c-TLM). The effects of the cryogenic process on improving Ohmic behavior (I-V linearity) and reducing the specific contact resistance will be discussed from a microstructural analysis which reveals the metallurgy of Ohmic contact formation.

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Formation of Ni/Pt/Au Ohmic Contacts to p-GaN

MRS Proceedings ◽

10.1557/proc-482-1053 ◽

1997 ◽

Vol 482 ◽

Cited By ~ 7

Author(s):

Ja-Soon Jang ◽

Hyo-Gun Kim ◽

Kyung-Hyun Park ◽

Chang-Sub Um ◽

Il-Ki Han ◽

...

Keyword(s):

Contact Resistance ◽

Ohmic Contact ◽

Ohmic Contacts ◽

Chemical Vapor ◽

Electron Beam Evaporation ◽

Specific Contact Resistance ◽

Metal Thin Films ◽

Linear Behavior ◽

Specific Contact ◽

P Type

AbstractWe report a new Ni/Pt/Au (20/30/80 nm) metallization scheme to achieve a low ohmic contacts to p-type GaN with a carrier concentration of 9.4 × 1016 cm-3. A Mg-doped GaN layer (0.5 μm) was grown on (0001) sapphire substrate by metalorganic chemical vapor deposition (MOCVD). All metal thin films were deposited on the p-GaN layer in an electron-beam evaporation system. Samples were annealed by a rapid thermal annealing (RTA) process at a range of temperatures from 300 °C to 850 °C under a flowing Ar atmosphere. A circulartransmission line model (c-TLM) was employed to calculate the specific contact resistance, and current-voltage (I-V) data were measured with HP4155A. The Ni/Pt/Au contacts without the annealing process showed nearly rectifying characteristics. The ohmic contacts were formed on the samples annealed at 500 °C for 30 sec and the I-V data showed a linear behavior. The specific contact resistance was 2.1 × 10-2 Ωcm2. However with increasing the annealing temperature above 600 °C, ohmic contacts were again degraded. Auger electron spectroscopy (AES) depth profiles were used to investigate the interfacial reactions between the trilayer and GaN. AES results suggested that Pt plays a significant role in forming ohmic contact as an acceptor at the interface. Atomic force microscope (AFM) also showed that the samples with good ohmic contact have very smooth surface.

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Investigation of Al-Ti Ohmic Contact to N-Type 4H-SiC

Materials Science Forum ◽

10.4028/www.scientific.net/msf.711.184 ◽

2012 ◽

Vol 711 ◽

pp. 184-187 ◽

Cited By ~ 3

Author(s):

Alexia Drevin-Bazin ◽

Jean Francois Barbot ◽

Thierry Cabioch ◽

Marie France Beaufort

Keyword(s):

Contact Resistance ◽

Barrier Height ◽

Ohmic Contact ◽

Ohmic Contacts ◽

Wide Band ◽

Interfacial Structure ◽

Max Phase ◽

Specific Contact Resistance ◽

Formation Mechanisms ◽

P Type

Metal/semiconductor contacts have a great impact on device performances. Contact properties to wide band gap semiconductors, in particular, are more difficult to control due to the large potential barrier which arises when the metal is deposited on the semiconductor’s surface. Moreover, intrinsic interface states also lead to deviation of the Schottky-Mott limit and the barrier height is no more dependent of the work function of the metal. The contact property has also become very important with the race for miniaturisation toward the nanoscale. Contacts must also be adherent, able to resist to the temperatures for which SiC based-devices are intended, and also they should be compatible with conventional device processing techniques (die attachment). Ohmic contacts to SiC have thus been investigated for decades. The difficulties of controlling the interface properties between the metal and SiC to obtain low resistive ohmic contact have not been overcome yet; the specific contact resistance being proportional to the exponential of the barrier height for a given doping concentration. For example, nickel has been studied for the ohmic contacts on n and p-type, however the presence of voids at the interface has been reported leading to the degradation of the contact properties [1]. More recently low ohmic contact resistance has been reported of Au/Ti/Al/n-type-4H-SiC contact [2]. The formation of TiSi, TiSi2and Ti3SiC2has been reported according to x-ray diffraction experiments after annealing. The formation of Ti3SiC2(or MAX phase) has also been reported in TiAl-based contacts to both n-and p-type [3-6]. This ternary carbide layer is supposed to reduce the barrier height at the contact and thus leads to low contact resistances. The addition of Ge also leads to the formation of Ti3SiC2at lower temperature of annealing [7]. However, other compounds are frequently observed at the interface showing that the control of the interfacial structure must be optimized. The objective of our work is to obtain uniform epitaxial Ti3SiC2thin film on n-type 4H-SiC to form ohmic contact with low resistance by studying the influence of different parameters such as the role of Aluminium on the formation mechanisms, the polarity and doping dependence. The temperature and the annealing time are also parameters to be optimized for the improvement of the ohmic contact.

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Cobalt Silicidation on Sub 100nm Hole Patterned Vertical Diode Formed by Silicon Epitaxial Growth and Its Electrical Properties

MRS Proceedings ◽

10.1557/proc-1079-n08-06 ◽

2008 ◽

Vol 1079 ◽

Author(s):

Min Yong Lee ◽

K. B. Lee ◽

H. S. Lee ◽

S. J. Chae ◽

I. K. Han ◽

...

Keyword(s):

Electrical Properties ◽

Epitaxial Growth ◽

Ohmic Contact ◽

Consumption Rate ◽

Void Formation ◽

Contact Layer ◽

Electrical Performance ◽

Hole Dimension ◽

Hole Dimensions ◽

P Type

ABSTRACTSelf-aligned Cobalt silicide as ohmic contact layer on sub 100 nm hole patterned Si vertical diode formed by silicon epitaxial growth (SEG) is investigated and silicon epitaxial growth of higher than 4000 Å thickness and good crystalinity for PN diode has been successfully developed. Also, electrical isolation of 100 nm pitch size between diode and diode, and removal of unreacted Co/Ti/TiN layer have been realized by dip-out process without CMP simultaneously. Through the mechanism of void formation due to the variation of Si consumption rate during silicidation at limited hole pattern dimension, critical Co and Capping Ti thickness are investigated as various hole dimensions (80∼120 nm), and then with p+ type dopant species (49BF2, 11B). The ratio of Co thickness to hole dimension demonstrates void free cobalt silcidation on various pattern sizes of silicon epitaxial growth. Silicon epitaxial growing PN diodes including void free CoSi2 show excellent electrical performance, especially lower than 10 pA reverse off leakage current.

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