thick_resist_processing (1063654), страница 2

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The document Rehydration ofPhotoresists gives more details on this0,1110100rehydration time @ 52%/22°C (min)topic.Photoresists, wafers, plating solutions, etchants and solvents ...Phone: +49 731 977343 0www.microchemicals.eusales@microchemicals.eu-3-MicroChemicals GmbH - Thick Resist ProcessingBubbling and Cracks in the Resist Film after ExposureDisclaimer of WarrantyAll information, process guides, recipes etc. given in this brochurehave been added to the best of our knowledge. However, we cannotissue any guarantee concerning the accuracy of the information.We assume no liability for any hazard for staff and equipment whichmight stem from the information given in this brochure.Generally speaking, it is in the responsibility of every staff memberto inform herself/himself about the processes to be performed inthe appropriate (technical) literature, in order to minimize any riskto man or machine.Too much remaining solvent due to a softbake too short/too cool causesbubbles especially near the substrate (top, right-hand).

Resist films softbaked very long/hot tend to embrittle causing cracks by the expanding nitrogen (bottom: onsight view left-hand, cross-section right-hand).Resist FilmDuring exposure of DNQ-based resists (such as the AZ® 4562 or 9260 series - but NOT theAZ® 40 XT), the photo active compound diazonaphtoquinone (DNQ) is converted into indenecarboxylic acid with a nitrogen molecule (N2) as a side product. Completely exposed photoresist releases a N2-volume significantly exceeding the resist volume which, thermally activated, diffuses to the resist surface and dissipates.Especially thick resists generate a comparable high N2-volume with respect to the resist surface.

As a consequence, during or after exposure, bubbles or cracks may appear in the resistfilm. In some cases even a milky, styrofoam-like appearance becomes visible (pictures seeoverleaf). Possible reasons are:„ A softbake too cool/too short (details see Softbake of Photoresists)„ Inferior resist adhesion by insufficient substrate pretreatment (see document SubstrateCleaning and Adhesion Promotion), or a substrate surface modified by previous processsteps„ An exposure intensity too high, with a N2 generation rate too high as a consequence. Inthis case, try multiple exposure with delays in between.„ An exposure dose too high. It is generally recommended to evaluate the optimum exposure dose for each process.„ A photoresist not suitable (photo active compound concentrationtoo high, N2 permeability too low) for the required resist filmthickness.

For recommended thick resists, please consult thefirst section of this document.SubstrateAZ and the AZ logo are registered trademarks of AZ Electronic Materials (Germany) GmbH.Photoresists, wafers, plating solutions, etchants and solvents ...Phone: +49 731 977343 0www.microchemicals.eusales@microchemicals.eu-4-.

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