TiB2 and ZrB2 diffusion barriers in GaAs Ohmic contact technology

Abstract

The transition metal diboride compounds, ZrB 2 and TiB 2 , interposed between Ni/Ge/ Au Ohmic contact metallization on n-type GaAs wafers and an overlying thick Au contact layer, have been investigated to evaluate their effectiveness in stabilizing the Ohmic contact by limiting the indiffusion of Au. All of the metal layers were e-beam deposited except the ZrB 2 which was rf-diode sputtered. The barrier layer thicknesses were 50 and 100 nm for the TiB 2 and the ZrB 2 , respectively. Postdeposition alloying of the contacts was performed at 400, 425, or 450 ·c. Auger electron spectroscopy depth profiling of the resultant Ohmic contacts demonstrates that the barrier layers effectively preclude penetration of Au to the Ohmic contact structure. Specific contact resistivities for such contacts are in the low 10-7 fl cm 2 range; although some degradation of the contact resistivity is observed after long term annealing, the values of resistivities do not exceed 1.5 X 10-6 n cm 2 after 92 h at 350 ·c.

Nanostructure and bonding of zirconium diboride thin films studied by X-ray spectroscopy

“…[5,7] Combined with remarkable high temperature stability, these properties make ZrB 2 an attractive material for thin film based electronic devices that must withstand harsh, high temperature environments. [7,8] For several decades is has been known that agglomeration limits the morphological stability of metallic thin films at elevated temperatures, [9,10] where the dewetting process is driven by atomic 10 diffusion that minimizes the total surface and interfacial energy of the system. [11] Some success has been achieved in avoiding agglomeration in Pt films by using adhesion layers and combining Pt with nanostructured oxide phases.…”

A convenient solid-state reaction route to nanocrystalline TiB2

“…Titanium diboride (TiB 2 ), like borides of Zr, Cr and other transition metals, is well known for its high melting point, outstanding hardness, low specific weight, high modulus, high chemical stability, good wear resistance and so forth [1][2][3]. Due to these attractive properties, TiB 2 has extensive applications in many areas.…”

Improved Schottky Contacts on n-Type 4H-SiC Using ZrB2 Deposited at High Temperatures

“…23,24 The refractory nature of the borides offers a very attractive advantage as contact metallization for high-temperature device applications. While refractory borides have been investigated for contact and diffusion barrier metallizations on Si and GaAs, [25][26][27][28][29] there is very little reporting on the investigation of their suitability for Schottky contacts on SiC. Boltovets et al investigated Schottky contacts on n-type 6H-SiC using TiB 2 and found them to have very stable electrical properties under thermal stressing at 1,000°C for 2 min, where the barrier height remained around 0.7 eV and the ideality at 1.5.…”