11. How high is the solvent resistance of e-beam resist films?

With respect to the source materials used, e-beam resists fall into two different categories:

• PMMA resists (AR-P 6000)

• Novolak resists (AR-N/P 7000)

The general rule is that with increasing bake- or process temperatures, the solubility of resist films decreases, which results in gradually increasing removal problems. After a bake step above a temperature of 200 °C, resists are inert in the presence of most solvents. Only remover AR 300-70 (NMP) and AR 300-73 (TMAH, aqueous-alkaline) still cause film swelling and are in some cases able to remove layers.

PMMA-Resists:

Easily soluble in: acetone, MEK, PMA (PGMEA), NMP, chlorbenzene, ethylbenzene, anisol, MIBK, ethyl lactate

Not soluble in: water, strong bases, isopropanol, ethanol, nonan, and the like.

Novolak resists:

Easily soluble in: acetone, MEK, PMA (PGMEA), NMP, anisol, MIBK, isopropanol, butyl acetate, ethyl lactate, strong acids

Not soluble in: water, chlorbenzene, ethylbenzene, nonan, and the like.

Abbreviations of solvents and raw materials used: MEK: methyl ethyl ketone; PMA (= PGMEA): 1- methoxy-2-propyl acetate, NMP: N-methyl-2-pyrrolidone, MIBK: methyl isobutyl ketone, TMAH: tetramethylammonium hydroxide, KOH: caustic potash solution, HF: hydrofluoric acid