A microfabrication process that uses light to transfer geometric patterns from a photomask to a light-sensitive chemical photoresist on a substrate.

Photolithography

Photolithography (also called optical lithography) is a fundamental process in modern semiconductor manufacturing that enables the creation of intricate microscopic patterns essential for integrated circuits and microelectronics.

Core Process

The photolithographic process consists of several key steps:

Substrate Preparation
- A silicon wafer is cleaned and prepared
- A layer of photoresist is applied through spin coating
Mask Alignment
- A photomask containing the desired pattern is precisely aligned
- Modern systems use sophisticated optical alignment systems
Exposure
- ultraviolet light passes through the photomask
- Creates a chemical change in exposed photoresist areas
- Utilizes complex optical systems and precision engineering
Development
- Exposed areas become either soluble (positive resist) or insoluble (negative resist)
- Chemical developers remove unwanted photoresist

Advanced Technologies

Deep UV Lithography

Modern photolithography employs deep ultraviolet light sources, including:

Resolution Enhancement

Various techniques improve pattern resolution:

Industrial Applications

The primary applications include:

Limitations and Future Developments

Current challenges include:

Physical diffraction limits
Cost of advanced equipment
Complex process control requirements

Future developments focus on:

Economic Impact

Photolithography equipment represents one of the largest capital investments in semiconductor fabs, with advanced machines costing upwards of $100 million. This technology has enabled the continuation of Moore's Law and drives the global electronics industry.

Environmental Considerations

The process requires:

Careful handling of chemical waste
Significant clean room infrastructure
High energy consumption
Water purification systems