Process parameters, sensitivity, resolution, edge quality and dimensional stability are exemplarily shown for AR-N 4340.
Investigations were performed on 150mm-wafers with Si-surface. Prior to coating, HMDS was applied from the gas phase as adhesion promoter. The film thickness was adjusted to 1.3 µm, and the bake was carried out at 110 °C, 3 minutes on a hot plate. I-line stepper Nikon NSR-2205i14 was used for exposure. To determine optimum parameters and resolution, only AR 300-44 was employed as developer which is compatible with other 0.26 n metal ion-free developers.
A high resist adhesion was obtained – no removal of resist structures or even smallest spots was observed which also means that structures possess no undercut. Determined was in these experiments the resolution of lines, line grids and of spots. With AR-N 4340T, a maximum resolution of 0.6µm could be achieved for line grids. Edge quality and structural stability were also very high.
Optimum parameters (110 °C soft bake):
Soft bake: 110°C, 180s, hot plate
Film thickness: 1.3 µm
Exposure: 40mJ/cm 2 Nikon NSR-2205i14
PEB 95°C, 60s, hot plate
Development time: 60-90s, immersion development
Fig. 1: 0.6 µm line (top view)
Fig. 2: 0.6 µm line
Fig. 3: 0.5 µm line
If applied light dose or post-exposure bake temperatures are too high, scattering events will cause a pattern-specific broadening of resist structures which cannot be removed during development.