RF plasma etching of a polyimide film with oxygen mixed with nitrogen trifluoride - Polyimides and Other High Temperature Polymers - page 406

analyzed the PI surface etched with oxygen mixed with NF 3 , the composition of
outgas during etching and constructed a chemical reaction model of the PI etch-
ing. In this paper, we report on the reason why the etching rate is increased by the
addition of fluorine gases such as CF 4 , SF 6 , NF 3 , and furthermore why NF 3 is the
most effective gas for increasing the etching rate.

2. EXPERIMENTAL

Kapton-V (0.05 mm thick; Toray-DuPont, Inc.) was used as the PI substrate. Ta-
ble 1 shows the experimental conditions for plasma etching. Figure 1 shows the
etching chamber which is equipped with a pair of parallel electrodes, 13.56 MHz
RF generator and quadruple mass spectrometer (QMS).

Table 1.
Etching conditions

Gas 100% O 2 30% NF 3 / 70% O 2 80% NF 3 / 20% O 2

Flow rate (cc/min) 20.0 6.0/14.0 16.0/4.0

Pressure (Pa) 60 60 60

RF power (W) 200 200 200

Etching time (min) 5-20 5-20 5-20

Figure 1. RF plasma system used to etch PI films.