Gas Chemistry Dependence of Si Surface Reactions in a Fluorocarbon Plasma during Contact Hole Etching

Abstract

Gas chemistry dependence of Si surface reactions in a high C/F ratio fluorocarbon plasma during contact hole etching was investigated. CO and C4F8 were selected as additional gases for CF4/CHF3/Ar chemistry. CO addition increased the neutral carbon density in the plasma, C4F8 addition increased not only the fluorocarbon radicals but also the fluorocarbon ion flux. Although both gases enhanced the deposition rate of the fluorocarbon film on the Si surface, there is a difference in the mechanism of the film deposition. CO addition increased the radical sticking site in the fluorocarbon film deposited on the Si surface due to an abundant carbon density in the plasma. C4F8 addition increased the precursor radical density in the plasma due to the electron impact dissociation of C4F8. Since damage formation depends on the fluorocarbon ion flux, increasing of the fluorocarbon ion flux by C4F8 addition enhanced the damage formation.

Adsorption Behavior of Various Fluorocarbon Gases on Silicon Wafer Surface

“…Up to now, many researchers have been studying this subject. 3,[8][9][10][11][12][13] In RIE, the etching reaction is promoted by high-energy ions irradiating to low-molecular-weight fluorocarbon gases (fluorocarbon radicals generated by dissociation of fluorocarbon gas) adsorbed on the substrate surface. 1,2,14,15) Therefore, one factor that determines the etching characteristics is the adsorption behavior of low-molecular-weight fluorocarbon gases on the substrate surface.…”