Appeal 2007-1097
Application 10/230,593
1 Gupta indicates that the source of the oxygen plasma is preferably
2 molecular oxygen, O2, and reference to “O2 plasma” is directed to this
3 embodiment. Gupta 7:24-27.
4 Nevertheless, Gupta discloses that alternative sources of oxygen such
5 as CO2, NO, and N2O may be suitably employed as a source of oxygen
6 plasma in the process of the present invention. Gupta 9:17-21.
7 To minimize the effect of atomic oxygen near the reaction site,
8 scavenger atoms are provided in the Gupta process. The scavenger atoms
9 comprise free radicals which are capable of sweeping and/or capturing
10 atomic oxygen. Gupta 7:50-54.
11 Preferably, the scavenger atoms are provided by including a nitrogen
12 plasma in the plasma etchant. Preferably, the nitrogen plasma is provided by
13 N2. Gupta 7:64-67.
14 Additionally, a significant amount of helium is added to the mixture
15 of nitrogen and oxygen. Gupta 8:12-13.
16 Helium is said to minimize thermal degradation of the photoresist
17 layer. Gupta 8:14-17.
18 Without helium or other inert gases, melting of the photoresist layer is
19 said to be a concern, and in some cases, the etching process must be
20 periodically stopped to allow for cooling. Gupta 8:17-19.
21 In Example 2, a mixture of oxygen and nitrogen without helium is
22 said to have provided an increased etch rate. Gupta 11:26-47.
23 Adding helium in Example 2 is said to have reduced the residence
24 time of active oxygen species. Gupta 11:48-53.
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