HEMT test structure technology for fast on-wafer characterization of epitaxial GaN-on-Si material

Schuster, M.; Wachowiak, Andre; Szabó, N.; Jahn, Α.; Merkel, U.; Ruf, A.; Mikolajick, Thomas; Murad, S. K.; Hu, Cheng Chao; Groh, Lars; Lutgen, S.

doi:10.1109/iscdg.2013.6656315

Cited by 6 publications

(5 citation statements)

References 2 publications

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“…Similar observations with degraded contacts in case of an AlN spacer layer have been also reported for Au-free Ti/Al based contacts annealed at high temperature (>800 • C) [26]. It is worth mentioning, that our Ti/Al/Ni/Au-contacts fabricated as reported in [27] and annealed at 800 • C show only a minor increase in ohmic contact resistance of about 20% with additional AlN spacer. In the latter case, the contact is most likely formed by metal protrusions through the AlGaN barrier directly to the 2DEG [3,7,28,29].…”

Section: Aln Spacer Layer Influencesupporting

confidence: 88%

Material investigations for improving stability of Au free Ta/Al-based ohmic contacts annealed at low temperature for AlGaN/GaN heterostructures

Calzolaro

Hentschel

Edokam

et al. 2020

Semicond. Sci. Technol.

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Gold-free Ta/Al-based ohmic contacts fabricated by sputtering on AlGaN/GaN heterostructures and annealed at low temperature were investigated. The presence of a thin AlN spacer layer at the AlGaN/GaN heterojunction is demonstrated to prevent the ohmic contact formation as shown by rectifying behavior after annealing. Ta as an additional capping layer on Al leads to a severe morphology degradation and subsequent deterioration of the metal stack after annealing at 600 • C due to strong Ta-Al alloying verified by transmission electron microscopy. Using the compound metal TiN as capping layer circumvents the alloy formation, thereby making the contacts much more stable under annealing. A low contact resistance of 0.8 Ω mm was obtained using Ta/Al/TiN metal layers annealed at only 500 • C. The nature of the current transport was investigated by analyzing the temperature dependence of the specific contact resistance, which points towards a current path through the AlGaN barrier by thermionic field emission.

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Section: Aln Spacer Layer Influencesupporting

confidence: 88%

Material investigations for improving stability of Au free Ta/Al-based ohmic contacts annealed at low temperature for AlGaN/GaN heterostructures

Calzolaro

Hentschel

Edokam

et al. 2020

Semicond. Sci. Technol.

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“…Micro‐fabrication of reference test structures is based on contact lithography, details on processing and test structure characterization are reported elsewhere . In brief, isolation process, if performed, uses dry etching with BCl 3 /Cl 2 chemistry for mesa structuring, followed by ohmic contact formation with rapid annealing and gate structuring by means of lift‐off technology.…”

Section: Methodsmentioning

confidence: 99%

Using vertical capacitance–voltage measurements for fast on‐wafer characterization of epitaxial GaN‐on‐Si material

Schuster

Wachowiak

Groh

et al. 2015

Physica Status Solidi (a)

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We propose and demonstrate an efficient approach to extract key parameters of GaN‐based 2DEG heterostructures grown on conducting Silicon substrates. The methodology enables an electrical feedback on different epitaxial design or MOCVD growth conditions in a very short‐time frame by means of vertical capacitance–voltage (C–V) measurement on simple gate‐metal top‐electrodes, which are evaporated through a shadow mask. Key parameters such as sheet charge carrier density of the 2DEG‐channel, (AlGaN) barrier thickness between 2DEG and top‐electrode and threshold voltage of 2DEG depletion can be extracted with minimum effort. All respective parameters can be logged across the entire wafer without the need for a sophisticated device process and reveal the lateral (in‐) homogeneity of the wafer material. In addition, this method can be used to mimic the gate‐module of metal–insulator–semiconductor (MIS)‐HEMTs and, therefore, to study different charge‐related properties of the dielectric‐GaN interface or the dielectric layer itself.

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“…MISHEMT device micro‐fabrication comprised a basic 4‐layer contact lithography HEMT process sequence with micrometre scale minimum feature size and rectangular gate cross section without field plate structures . After the mesa isolation structuring by a BCl 3 /Cl 2 dry etching process and ohmic contact formation by rapid thermal annealing, the wafer surface was wet‐chemically cleaned with 1:10 HCl:DI‐H 2 O for 30 s. Al 2 O 3 and HfO 2 were grown by thermal ALD.…”

Section: Methodsmentioning

confidence: 99%

Analysis of threshold voltage instability in AlGaN/GaN MISHEMTs by forward gate voltage stress pulses

Winzer

Schuster

Hentschel

et al. 2016

Physica Status Solidi (a)

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We report on the investigation of the V th drift behaviour of AlGaN/GaN MISHEMTs upon forward gate voltage stress in dependence of stress bias and stress time. The pulsed measurements allow for the evaluation of the operational regime for optimum device efficiency. We compared the effect of two different high-k gate dielectric materials with similar equivalent oxide thickness e 0 e r /t high-k on the V th instability in order to separate the influence of the heterojunction design and the high-k/GaN-cap interface from the bulk high-k. The matched gate capacitance coupling of the studied Al 2 O 3 and HfO 2 gate dielectric results in an nearly identical critical forward gate voltage, where the AlGaN barrier potential is lowered and severe threshold voltage shift (DV th ) into the positive voltage direction is induced. Beyond this critical forward voltage, detailed time-dependent stress pulse measurements from 1 ms to 1000 s revealed an immediate electron injection and trapping at the oxide/GaN interface for stress pulses with t stress ! 1 ms. The presented results of V th drift analysis demonstrate the limits of the maximum tolerable forward gate voltage of the investigated Al 2 O 3 and HfO 2 MISHEMTs, although the excellent low-leakage currents of the insulated gate would imply a potentially higher gateoverdrive.

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HEMT test structure technology for fast on-wafer characterization of epitaxial GaN-on-Si material

Cited by 6 publications

References 2 publications

Material investigations for improving stability of Au free Ta/Al-based ohmic contacts annealed at low temperature for AlGaN/GaN heterostructures

Material investigations for improving stability of Au free Ta/Al-based ohmic contacts annealed at low temperature for AlGaN/GaN heterostructures

Using vertical capacitance–voltage measurements for fast on‐wafer characterization of epitaxial GaN‐on‐Si material

Analysis of threshold voltage instability in AlGaN/GaN MISHEMTs by forward gate voltage stress pulses

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