International Business Machines Corporation

Robert G Schad

Edward M Engler

Yaffa Tomkiewicz

John D Kuptsis

Naftali Eliahu Lustig

Aaron J Fleischman

This invention describes a low resistance contact structure to n-type GaAs and a method for making such a contact structure. The contact structure is formed by depositing successive layers of Ni, Au, Ge, and Ni. A fifth layer is then deposited on the first four layers. The fifth layer is a metallic tungsten oxide. The metallic tungsten oxide is formed by sputtering tungsten onto the 4 layer stack in a low pressure argon plus oxygen atmosphere. The resulting 5 layer stack is then annealed in a rapid thermal anneal (RTA) process. The RTA process heats the stack for 5 seconds at 600 degrees. The resulting structure consists of an intermetallic NiGe compound having a small amount of a AuGa compound dispersed within it and being covered by a metallic tungsten oxide film. The oxygen from the metallic tungsten oxide film acts as a gettering mechanism to create gallium vacancies in the GaAs lattice structure during the RTA process. The oxygen forms a compound with gallium which is sandwiched between the metallic tungsten layer and the NiGe metallurgy. The sheet resistance of the contact metallurgy is low because the metallic tungsten oxide film is substantially thicker than that required to provide oxygen for the gettering process. The contact resistance to the n-type GaAs is low because the oxygen acts in a similar fashion to gold and creates more gallium vacancies in the GaAs. These vacancies are filled with an n-type dopant (Ge), supplied by the contact metallurgy, to create a better ohmic contact. The contact structure is reliable because there is a low gold content in the contact and because the nickel stabilizes the germanium which is not used for filling the gallium vacancies in the GaAs lattice.

Oxygen assisted ohmic contact formation to n-type gallium arsenide

Oxygen assisted ohmic contact formation to N-type gallium arsenide

Novel E-beam resists and process for their use are described. These resists are conducting organic charge transfer salts. Films of these materials can be deposited by solvent casting or by sublimation. The deposited film can be made to produce a positive or negative resist image depending on the E-beam energy and exposure time. Exposure of this material to an E-beam produces patterns having differential electrical, optical and solvation properties.

Class of E-beam resists based on conducting organic charge transfer salts

Growing community of inventors

Yorktown Heights, NY, United States of America

Robert G Schad