DMSO is used as a solvent in selected photoresist-removal systems. Its role is to help dissolve or remove the organic resist material after the relevant patterning operation. Successful stripping also requires the exposed device materials to remain acceptable after cleaning, rinsing and drying.
In this article
Identify the resist and the process step
A developed resist, a thick packaging resist and a residue modified by plasma processing are different cleaning targets. Specify the resist chemistry, thickness and prior thermal or plasma history before choosing the solvent system.
WO2000041037A1 describes DMSO removal of photoresist over specified low-dielectric-constant materials. Later stripper patents describe DMSO in blends containing amines, quaternary ammonium hydroxide, water and corrosion inhibitors. These are examples of different cleaning systems, not one universally interchangeable solvent wash.
Bulk resist stripping and post-etch residue cleaning should also be distinguished. A process that removes the organic film may still leave inorganic or mixed residues requiring a separately qualified treatment.
Judge removal and material compatibility together
Follow remaining film, particles and redeposited material with methods appropriate to the feature size and residue. Visual cleanliness alone may miss a thin residual layer.
Evaluate the exposed metals, dielectric films and other sensitive materials using the complete formulation. Corrosion, film loss and surface change can depend on water, additives, contact time and temperature. Compatibility reported for one substrate stack does not qualify another.
Test the proposed bath lifetime as well as freshly prepared solution. Resist loading and carried-in material change the working composition, so a successful initial coupon test may not establish end-of-bath performance.
Include rinsing and incoming contamination controls
DMSO’s low volatility means that removal of the cleaning liquid needs a defined rinse and dry sequence. Demonstrate that the chosen rinse removes dissolved resist and formulation components without precipitation, staining or retained residue.
Set incoming DMSO limits for the contamination pathways relevant to the process. Individual metals, ionic species, particles, water and residue may need different tests and reporting limits. An electronic-grade label or a bulk assay value does not establish these requirements.
Sampling containers and delivery packaging belong in the assessment where they can affect contamination. Select skin and splash protection for the entire cleaning mixture, including dissolved residue and reactive additives, rather than DMSO alone.
For sourcing review, provide YUJI with the DMSO analytical limits, methods and packaging requirements established for the formulation.