Low TCR Kanthal Resistive Films For Hybrid IC's

Secondary Author(s)

Sharma, G; Parikh, Nalin


Investigations were carried out regarding the feasibility of Kanthal resistive films in hybrid integrated circuits. The technique for deposition was conventional evaporation from a multistrand tungsten filament onto substrates at 325 °C, in vacua better than 1'10'5 Torr. The filament source life was found to be long because of the absence of nickel in the alloy. The adhesion of films to glass and ceramic substrates and the compatibility with Al, Au thin films and thick-film Ag compositions used for conductors, were found to be good. Better substrate cleaning procedures and faster deposition rates resulted in lower TCR-value films. Fast evaporation of fresh charge invariably resulted in low TCR-value films. On the other hand the evaporation of the portion of the charge still remaining on the filament after the first evaporation resulted in high TCR-value films. To get low TCR-value films of given sheet resistances using fast evaporation and without the evaporation of the entire charge it was necessary to optimize the Kanthal charge on the filament. Low TCR films (~10 ppm) were obtained in the range of sheet resistance 20 /sq'250 /sq. Because of simple evaporation technique, excellent adhesion to substrates, compatibility with conductor films, and low TCR values in a wide range of resistivities, Kanthal has been recommended for hybrid IC's.

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