Photomasks

Photomasks are crucial templates in photolithographic processes, serving as precise stencils for producing integrated circuits, high-performance electronic components, semiconductor devices, displays, and more. Despite continual advances in transistor miniaturization, photomask-based UV lithography remains the leading technology for microfabrication.

Typically, photomasks are made from a soda-lime or quartz substrate with a thin metal layer—most often chrome—to absorb light across specific wavelengths, such as i-, g-, and h-lines. The transparent sections on the photomask define the circuit pattern, which is transferred to a photosensitive layer using a mask aligner or stepper. In semiconductor and display manufacturing, several photomasks are needed to complete the intricate layers of a device. To avoid contamination, semiconductor photomasks are protected by a pellicle foil.

The patterns on photomasks are generated through high-resolution laser lithography or electron-beam lithography, depending on the required precision. As master templates, photomasks must meet rigorous specifications, including uniform linewidths, exact pattern positioning, minimal edge roughness, and very small feature sizes. These tight tolerances are essential for enabling a broad process window, ensuring reliability in high-volume manufacturing.

Heidelberg Instruments’ VPG⁺ systems are high-volume pattern generators with direct-write capability, producing small to large-area photomasks with excellent image fidelity and high throughput. Additionally, the ULTRA, a certified laser mask writer for semiconductor photomask production, achieves exceptional precision, creating structures down to 500 nm. This makes it ideal for manufacturers requiring exacting standards for advanced semiconductor and display applications.