In this paper we report on the role of reaction products in F- production i
n low-pressure, high-density CF4 plasmas. The spatial distributions and tem
poral variations of F- density (n(-)), and plasma parameters in the dischar
ge phase and afterglow of helicon-wave CF4 plasmas which had an electron de
nsity (n(e)) of 10(11)-10(13) cm(-3) were measured by the laser-photodetach
ment technique combined with a heated Langmuir probe. The relationship betw
een the n(-)/n(e) ratio and the degree of ionization was investigated in th
e discharge phase. The n(-)/n(e) ratios in the plasma column of highly ioni
zed plasmas were much higher than those expected from dissociative electron
attachment to CF4, and n(-)/n(e) ratios were larger by several orders of m
agnitude in the outer region. The efficient increase in n(-) was observed i
n the afterglow and n(-)/n(e) was enhanced by increasing the discharge dura
tion. It is concluded that the attachment to the reaction products contribu
tes greatly to F- production in low-pressure, high-density plasmas.