04. lift-off - high TH/high AR
h. Application Examples
04. lift-off - high thickness & high aspect ratio
lift-off - high thickness & high aspect ratio
During dry chemical etching, for example in the structuring of silicon nitride, AR-P 6200 (CSAR 62) combines the best of two worlds: It not only allows the use as a high resolution positive resist similar to PMMA, but also offers a stability which is comparable to novolacs.
This facilitates the production of pattern with sharp edges that provide the required etch stability without the disturbing faceting at the edges which otherwise occurs frequently. CSAR 62 is normally used for films with thickness values between 50 and 300 nm. Intense plasma etching for the fabrication of deep etch structures however requires significantly thicker resist layers and places special demands on resolution and contrast. Resist AR-P 6200.18 was thus designed for high layer thicknesses of 0.6-1.6 μm and is particularly well suited for the realisation of high metal structures with lift-off, deep plasma etching processes or nanowires.
Fig. 5 Lift-off structures with large undercut at a film thickness of 800 nm
It is nonetheless possible to produce trenches with a width of < 100 nm at a film thickness of 800 nm. The high contrast is made possible through the use of our developer AR 600-546. By increasing the irradiation dose, the degree of the generated undercut can be adjusted specifically (Fig. 5 + 6). Each user can thus select the most favourable profile for his specific lift-off process.
Fig. 6 AR-P 6200.13, 823 nm layer, dose: 1440 pC/cm
If circles are irradiated and developed in such thick layers, columns (nanowires) can be produced due to a high metal deposition (evaporation, sputtering or electroplating)
(👉see vertical edges in Fig. 7).
Fig. 7 Vertical structures at an area dose of 120 μC/cm² for nanowires