5. How are e-beam resists exposed? How can the optimum exposure dose be determined?

By using very short-wavelength electrons for the exposure of the resists, an excellent resolution of up to 2 nm can be achieved (spot beam). Exposure is carried out by conventional e-beam equipment following the principle of direct writing or shaped beam procedure.

4.What is the optimal pre-treatment of substrates for photoresists?

If new and clean substrates (wafers) are used, a bake at approximately 200 °C for several minutes is sufficient for drying, but the substrates have to be processed quickly afterwards.

6. Which developers are optimal for e-beam resists, and how do factors like developer concentration and temperature influence the result?

During development, a positive tone resist film is patterned by a removal of exposed areas, while unexposed areas are removed when negative resists are used. To achieve reproducible results,

5. What are the adhesion features of photoresists on different wafers?

Adhesion between coating and substrates is a very sensitive feature. Smallest changes of the cleaning procedures or the process parameters can have a fatal impact on the adhesive strength.

7. How can e-beam resist films be removed again?

For the removal of all e-beam resist coatings baked at lower temperatures (softbake), polar solvents may be used such as e.g. the recommended thinner AR 300-12 or AR 600-01, 600-07,

6. What are the optimum coating parameters for photoresists in order to achieve good film images?

Prior to the coating procedure, resists have to be adjusted to the temperature of the (preferably air-conditioned) working area. If the resist is too cold, air moisture may precipitate on the resist.

8. Which resolutions do e-beam resists achieve?

With respect to the achievable resolution, purely academic resolution values and industrially utilisable values represent two quite different aspects. Theoretically, resolutions of 2 nm are possible (single electron spot)

7. Why may air bubbles develop in photoresist films, and how can they be avoided?

Bubbles after spin deposition are in most cases air bubbles, e.g. if the resist bottle was agitated or moved around, or if the resist was diluted prior to the coating step. Coating procedures performed immediately after bottle opening,

9. How high is the plasma etch resistance of e-beam resists?

Electron beam resists of the AR 6000 and AR 7000 production line display quite different etch resistance features in dry etch processes such as e.g. argon sputter and CF 4 . Novolak-

8. What is the function of the softbake of photoresist films after the coating?

Just recently coated resist films still contain a substantial amount of residual solvent, depending on the respective film thickness. The subsequent bake step at 90 – 100 °C is performed in order to dry the resist films,