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.

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.

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,

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,

9. How are photo resists exposed, and how can the optimum exposure dose be determined? How long can coated and exposed substrates be stored prior to exposure?

The exposure is performed using masks in suitable exposure systems such as e.g. steppers (i-, g-line), mask aligners or contact exposure systems in the appropriate spectral working range.

10. Which developers are optimal for photoresist, and how do factors like developer concentration and temperature influence the result?

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

11. How can resist coatings be removed again?

For the removal of softbaked coatings, polar solvents such as e.g. the respective resist thinner AR 300-12 (methoxy propyl acetate = PGMEA) and the remover AR 600-70 (acetone-based)

12. What is the application range of protective coatings?

Protective coatings are available for a large variety of applications, e.g. for the protection of wafer-backsides: or mechanical protection during transport

13. How do image reversal resists work?

With image reversal resists such as AR-U 4000, positive or negative tone images can be generated of the optical transmitted pattern depending on the manufacturing process. If the resist is processed according to the general protocol for positive resists without any additional steps,

14. How can undercut patterns (lift-off structures) be produced in one- or two layer systems?

A variety of one- or two layer systems are available which generate undercut patterns. For example, AR-P 5350 is a one layer system suitable for the production of metallic vapour phase structures.