A study of dielectrics generated by electro-less electrochemical method

for semiconductor devices

K. Umamakeshvaria,*, S. C. Vella Duraib

^aAssistant Professor, Department of Physics, Christopher Arts and Science

College (Women), Nanguneri, Tirunelveli-627108, Tamilnadu, India

^bAssociate Professor, Department of Physics, JP College of Arts and Science,

Agarakattu, Tenkasi-627852, Tamilnadu, India

The aim of this work is to the basic concepts of the varies chemical and electrochemical procedures used m the fabrication of semiconductor devices seems to be useful to provide a suitable background for the present work, a brief review of the same as also the results obtained by earlier workers has been undertaken at the outset. A careful scrutiny of the results obtained by different workers reveals that although the aforesaid methods have a few limitations, they may be satisfice borily used as an alternative to sputter and evaporation techniques for device fabrication. The author carried out experimental investigations on the formation and properties of ohmic contact to silicon using two electroless plating baths - one operated at room temperature and the other at 95°C. In particular, the variation of contact resistance of ohmic contacts formed by electroless Ni-P process on silicon was studied as a function of sintering temperatures with operating point temperatures and pH of the baths as parameters. ^rom these studies it has been shown that both the baths yielded an adherent and dense deposit of nickel-phosphorous alloy on n-Si, which when sintered at very high temperatures give a less value of contact resistance due to the formation of metal-n -n contact. The phosphorous component of the Ni-P deposit diffuses into n-Si during heat treatment and forms the metal-n+ --n contact which behaves as an ohmic contact. As expected, the value of contact resistance was found to decrease with the increase of phosphorous materials in the deposit. The most favourable temperature range of heat treatment was found to be between 600°-700°C. Heats studying above 700°C slightly less increase the contact resistance probably due to the out diffusion of phosphorous from the Ni-P deposit. The barrier height and ideality factor are two important parameters for m-s contacts. The values of these two parameters of electrochemically fabricated Schottky diodes as obtained from the capacitance and current voltage characteristics were found to be in fairly close agreement with those of vacuum- evaporated diodes. It is therefore, concluded that the electrochemical method of metal deposition is a valid and convenient technique for the fabrication and study of metal- semiconductor contacts.