Preliminary Studies of Al‐Ge‐Ni Ohmic Contacts to p‐ and n‐type GaAs

Graham, R. J.; Erkaya, H. H.; Roedel, R. J.

doi:10.1149/1.2095577

Cited by 9 publications

(1 citation statement)

References 0 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…I'2 Based on previous data, the etching morphology and etch rate were known to vary considerably with etching conditions and the kind of etching solutions mainly because of the complex nature of the various reactions involved in the etching. [3][4][5][6] Chemical species that are formed on the wafer surface during the etching reaction usually have a strong influence on the characteristics and mechanism of the silicon etching. Amorphous silicon, 7'8 silicon hydride, 9 silicon dioxide, silicon monoxide or suboxide, mixtures of silicon oxides, I~ and adsorbed mixed-valence complexes ~'14~5 have been proposed as compositions to account for the surface species.…”

Section: Introductionmentioning

confidence: 99%

Ohmic Contacts to p‐ and n‐type GaAs Made with Al‐Sn‐Ni

Roedel

Davito

West

et al. 1993

J. Electrochem. Soc.

View full text Add to dashboard Cite

We report the results of preliminary investigations into the suitability of the metallization system, aluminum-tinnickel, as an ohmic contact to both p-type and n-type GaAs. We have found that the A1-Sn-Ni contact is similar to A1-Ge-Ni in that it makes an adequate ohmic contact to both types of GaAs (with specific contact resistances as low as 1.0 • 10 4 ~_cm2), but the A1-Sn-Ni metallization has more uniform surface morphology after annealing. This metallization scheme is most appropriate for test structures in which rapid turnaround and low processing costs are essentiM.After thirty years of fabrication of GaAs devices and integrated circuits, it has been established that the best ohmic c~ontacts are made from gold alloys, and different alloys are needed for n-type and p-type contacts. 1 This complicates GaAs processing, requiring separate deposition steps, separate masking or etching procedures, and so on. An additional problem in the extensive use of goldbased contacts is the high cost of the base material. Consequently, there has been a steady search for a low cost metal system that can be used for both n-and p-type contacts. One promising alternative is the A1-Ge-Ni system, first employed by Zuteeg et al. 2 who demonstrated that this metallization can produce ohmic contacts to n-type GaAs with high radiation hardness and specific contact resistance competitive with Au-Ge-Ni. Additional work by Graham et al. 3 revealed that this metallization made an excellent contact to p-type material and maintained an atomically fiat interface with the GaAs after alloying, ~ without the spiking so prevalent with Au-Ge-Ni. Unfortunately, the A1-Ge-Ni contact shows a tendency to produce unusual surface features after alloying, Ge-rich, raised protrusions, which could interfere with later processing steps like wirebonding? An investigation for an alternative to germanium has been carried out, and it has been discovered that tin appears to be a suitable choice. As the results in this paper detail, the A1-Sn-Ni metallization can produce a contact ohmic to both n-type and p-type GaAs, and it has morphological characteristics superior to the A1-Ge-Ni contact. It is especially easy to pattern A1-Sn-Ni with the ]ift-off process and the surface remains remarkably smooth and planar after alloying. Experimental and Measurement DetailsIn the search for an alternative to germanium in the aluminum based contact, the various column IV elements, silicon, tin, and lead, were tested for suitability with a simple procedure. In separate experiments, metallizations consisting of 300 A column IV element, 300 ,~ Ni, and 1000 .~ A1 were evaporated onto n-type GaAs substrates (No = 1 • 1018 cm-3), fashioned into large circular patterns (100 ~m diam) by lift-off photolithography, and tested electrically for ohmic character before and after alloying steps. Curt-* Electrochemical Society Active Member.ously enough, the AI-Si-Ni contact always demonstrated rectifying characteristics, regardless of alloying time, temperature, or ambient. This is con...

show abstract

Section: Introductionmentioning

confidence: 99%