Study Of Ni-P Metallization Coating On The Semiconductor Silicon Surface

Electroless plating, under the catalytic form the surface of the substrate,Ni2+ in the bath provided electronic by a reducing agent, deposition to the substrate,is a redox reaction.Alkaline plating, can operate at low temperature and get low phosphorus coating.Silicon, as the main material of solar cells, microelectronics devices and integrated circuits,in their surface modification, is almost pretreated with the mixture of hydrofluoric acid and nitric acid, and the operating environment has been greatly affected.This study is,under the low temperature, after a simple pretreatment solution without fluoride,the Ni-P alloy coating with good electrical conductivity and adhesion,is obtained on the silicon surface through the alkaline electroless nickel plating,.Choosing complex system of the electroless plating bath.For the choice of complexing agent, the paper has tested citric acid, sodium pyrophosphate, auxiliary complexing agent, borax and other reagents.Or alone, for example, citric acid as a complexing agent,is used alone to study the minimum amount; or in combination, for example, complex system composed of citric acid+auxiliary complexing agent, citric acid+borax, citric acid+sodium pyrophosphate,is used for the associated experiment.The complex system is determined according to the bath stability, deposition rate and the quality of the coating, and ultimately the complex system composed of citric acid+auxiliary complexing agent, is more suitable for alkali chemical bath.Through a series of experiment to study the influence of the temperature on stability of the plating bath, plating rate and quality of coating, the ratio of citric acid and auxiliary complexing agent, and related operating conditions will be adjusted to obtain the appropriate complex system under 30-90℃.Research on low-temperature electroless plating.At low temperature around 40℃, according to GB/T 17359-98, GB/T 13913 standard, by EDX and ICP method, mass content of phosphorus in the coating is studied in a qualitative and quantitative analysis.This paper has studied the affection of the concentration of citric acid, auxiliary complexing agent, sodium hypophosphite in the bath,and temperature, pH of the bath on the phosphorus content of the coating,to get a list of related curves, and then the bath composition and operating conditions will be adjusted to attain low phosphorus coating.Considering the plating rate, bath stability and phosphorus content of the coating, the paper has found a new low phosphorus electroless nickel alkaline solution and proved that low-phosphorus coating is easy to obtain under the conditions of low temperature and high pH. For the low-temperature alkaline electroless nickel plating onto the P111, N111, N100 silicon,the paper studied the affection of the citric acid, auxiliary complexing agent, and temperature, pH on the plating rate and adhesion of the coating.After adjusting the parameters of the plating, the binding becomes better, and the contact resistance between the coating and the silicon surface reduces because the binding force of the coating has a direct impact, the contact resistanceIn addition, in an alkaline electroless nickel plating solution, the anionic surfactant is conducive to attain uniform Ni coating on the substrate surface, making the combination between the coating and the substrate better.Therefore, in the alkaline electroless nickel solution, sodium dodecyl sulfate is added to study the affection of it on the coating adhesion and get the best concentration.Finally, this paper obtained a new alkaline electroless nickel plating solution,that is used for variety type silicon and gets good adhesion coating.