UV Photolithography

Substrate preparation & cleaning

The substrate is cleaned using solvent and/or oxygen plasma to remove organic contamination and ensure strong resist adhesion. An HMDS adhesion promoter layer may be applied depending on substrate type and resist system.

Photoresist coating

Photoresist is spin-coated onto the substrate at controlled speed and acceleration to achieve the target film thickness (0.5 µm to >100 µm). Thickness is tuned by resist viscosity and spin parameters. A soft bake removes residual solvent and stabilizes the film.

Mask alignment & UV exposure

The photomask is aligned to existing features on the substrate (for multi-layer processes) using our mask aligner with ±0.5–1 µm overlay accuracy. The substrate is then exposed to i-line (365 nm) UV radiation for a calibrated dose, selectively crosslinking or scissioning the resist in the exposed regions.

Post-exposure bake (PEB)

For chemically amplified resists and certain deep-UV systems, a post-exposure bake drives the acid-catalyzed deprotection reaction. PEB conditions (temperature and time) are critical to resolution and CD control, and are optimized for each resist system.

Development

The exposed substrate is immersed in or puddle-developed with an aqueous alkaline developer (e.g. TMAH) for positive resists, or a solvent-based developer for negative resists. Development time and agitation are tightly controlled to achieve target critical dimensions with sharp sidewall profiles.

Inspection & hard bake (optional)

Pattern quality is inspected optically for CD uniformity, defects, and alignment. For processes requiring etch or ion implantation mask, a hard bake hardens the resist to improve etch resistance and thermal stability.

Downstream processing & resist strip

The patterned substrate proceeds to etching, deposition, doping, or lift-off as required. After the downstream process, photoresist is stripped using solvent or oxygen plasma, leaving the completed pattern on the substrate surface.