Specific Process Knowledge/Lithography/Development: Difference between revisions
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Several aspects of the outcome of SU-8 processing are affected by the development process. The lithographic resolution is affected by the time between PEB (post-exposure bake) and development, as the cross-linking process continues in the interface between exposed and unexposed regions even at room temperature. Cracks in the structures is affected by two things; the development time, and how much has previously been developed in the developer bath. Cracking is worse with longer development time, and worst in a new developer bath. The effect of the developer use quickly saturates (5-10 wafers). Finally, the stability of fine structures (high aspect ratio) is affected by the rinse after development, as the lower surface tension of IPA compared to PGMEA reduces pattern collapse during drying. | Several aspects of the outcome of SU-8 processing are affected by the development process. The lithographic resolution is affected by the time between PEB (post-exposure bake) and development, as the cross-linking process continues in the interface between exposed and unexposed regions even at room temperature. Cracks in the structures is affected by two things; the development time, and how much has previously been developed in the developer bath. Cracking is worse with longer development time, and worst in a new developer bath. The effect of the developer use quickly saturates (5-10 wafers). Finally, the stability of fine structures (high aspect ratio) is affected by the rinse after development, as the lower surface tension of IPA compared to PGMEA reduces pattern collapse during drying. | ||
Development time is strongly dependent on the SU-8 thickness. | Development time is strongly dependent on the SU-8 thickness. | ||
*Minimum development time: 1 min per 20µm in FIRST | |||
Suggestions: | |||
*2-5µm: 2 min. in FIRST; 2 min. in FINAL | *2-5µm: 2 min. in FIRST; 2 min. in FINAL | ||
*40µm: 5 min. in FIRST; 5 min. in FINAL (however, 3 min. in FIRST and 2 min. in FINAL is sufficient) | *40µm: 5 min. in FIRST; 5 min. in FINAL (however, 3 min. in FIRST and 2 min. in FINAL is sufficient) | ||