Standard Photolithography Process Flow

Photolithography transfers a geometric pattern from a mask onto a photoresist-coated substrate.

Steps

1. Wafer cleaning: Remove particles, organic contamination and moisture from the substrate.
2. Dehydration/bake: Heat the wafer to remove residual moisture.
3. Photoresist coating: Spin-coat a uniform layer of photoresist.
4. Soft bake: Remove solvent and stabilize the resist film.
5. Mask alignment: Align the photomask with existing wafer features.
6. UV exposure: Expose selected resist regions through the mask.
7. Development: Developer removes the soluble portion of the resist. In a positive resist the exposed area is removed; in a negative resist the exposed area remains.
8. Rinse and dry: Remove developer residues.
9. Hard bake: Improve adhesion and mechanical stability where required.
10. Etching/deposition: Transfer the resist pattern into the underlying material or use it as a mask for subsequent fabrication.
11. Resist stripping: Remove the remaining resist after pattern transfer.

Simplified flow

Clean wafer → Coat resist → Soft bake → Align mask → UV exposure → Develop → Rinse → Etch/deposit → Strip resist

Photolithography provides precise pattern definition and is fundamental to MEMS and microelectronic fabrication.