what is lithography semiconductor ? | JUNR Technology

I. Introduction

Lithography is one of the most critical and technically sophisticated processes in semiconductor manufacturing. It is the technique used to define intricate patterns on silicon wafers that ultimately become the transistors, interconnects, and circuit elements inside microchips. Without lithography, the creation of modern integrated circuits (ICs) would not be possible.

Often compared to a highly precise form of printing, lithography enables the transfer of detailed patterns from a photomask onto a wafer coated with a light-sensitive material known as photoresist. These patterns determine the layout and functionality of each chip layer, down to the nanometer scale.

As semiconductor devices have become increasingly complex and compact, the demand for more advanced lithography techniques has grown. Lithography is not just a step in the process — it is the foundation for innovation in chip scaling and performance.

II. The Role of Lithography in Semiconductor Fabrication

Lithography plays a central role in the semiconductor manufacturing process, particularly in defining the geometry of features on a chip. As semiconductor fabrication involves building multiple layers of circuitry on a silicon wafer, lithography is repeated dozens of times — once for each patterned layer.

Each step in the lithography process contributes to:

• Patterning transistors for logic and memory functions

• Creating interconnects that link components on the chip

• Defining alignment marks for precision across layers

• Controlling critical dimensions (CDs) that affect performance and yield

Without accurate and repeatable lithography, it would be impossible to fabricate devices with billions of transistors, such as modern CPUs and DRAM chips.

III. Basic Principles of Lithography

At its core, lithography is a pattern transfer process that uses light to print nanoscale designs onto a silicon wafer. This involves the use of three main components:

1. Photomask (Reticle) – Contains the desired pattern to be transferred

2. Photoresist – A light-sensitive coating applied to the wafer

3. Exposure System – Projects light through the mask to expose the photoresist

When the photoresist is exposed to light (typically ultraviolet), chemical changes occur that make parts of it soluble (positive resist) or insoluble (negative resist) during the development step. This reveals the pattern which is then transferred to the wafer substrate through an etching process.

IV. Lithography Process: Step-by-Step

Lithography is a multi-step process, requiring precision and cleanliness at every stage. Below is a simplified view of the main steps involved:

1. Wafer Preparation

• The silicon wafer is first cleaned to remove any particles or residues that might interfere with resist adhesion or imaging.

2. Photoresist Coating

• A thin, uniform layer of photoresist is applied using spin coating. Thickness may vary depending on the application and resolution needs.

3. Soft Bake (Prebake)

• The coated wafer is baked to remove solvent from the photoresist and improve adhesion.

4. Mask Alignment

• The wafer is aligned with the photomask to ensure accurate placement of the pattern. Precision at this stage is critical for multi-layer devices.

5. Exposure

• Ultraviolet (or EUV) light is shone through the photomask. The light interacts with the photoresist, changing its solubility.

6. Post-Exposure Bake

• A second baking step helps to stabilize the chemical changes in the photoresist before development.

7. Development

• The wafer is immersed in a developer solution, which removes either the exposed or unexposed regions of the resist, depending on the resist type.

8. Etching

• The remaining resist serves as a mask during plasma or wet etching, transferring the pattern into the underlying material (e.g., silicon dioxide or polysilicon).

9. Photoresist Removal

• After etching, the residual photoresist is stripped, leaving only the final pattern etched into the wafer.

V. Key Components and Materials

The effectiveness and precision of the lithography process depend heavily on the performance of several core components and materials. Each plays a specific role in ensuring high-resolution, high-yield patterning.

1. Photomask (Reticle)

A photomask is a high-precision glass plate that contains the circuit design to be transferred onto the wafer. It is created with chrome or other opaque materials to block light where patterns should not be transferred.

• Used in projection lithography systems

• One photomask per layer of the IC

• Requires extreme cleanliness and defect-free surfaces

2. Photoresist

Photoresists are light-sensitive polymers that change their chemical structure upon exposure to light. There are two main types:

Positive resists offer better resolution and are commonly used in advanced manufacturing nodes.

3. Exposure Tools (Steppers and Scanners)

Modern lithography systems include:

• Steppers: Project the entire mask image onto small areas (dies) sequentially

• Scanners: Use slit-shaped projection, moving mask and wafer simultaneously for higher throughput

Both systems include high-precision optics and are capable of nanometer-scale accuracy.

4. Light Sources

The light source determines the resolution limit of the pattern. The most common types include:

Shorter wavelengths enable the creation of finer features but introduce greater cost and complexity.

VI. Common Lithography Techniques

There are several types of lithography processes, each with its own use cases, advantages, and limitations.

1. Contact and Proximity Lithography

• Contact Lithography: The photomask touches the wafer directly. High resolution but high defect risk.

• Proximity Lithography: Mask is kept close to the wafer (few microns), reducing damage but also resolution.

These methods are mostly outdated but still used in LED and MEMS industries.

2. Projection Lithography (Mainstream Technology)

This technique uses high-resolution lenses to project and reduce the pattern from a mask onto the wafer surface. It dominates modern semiconductor manufacturing due to:

• Non-contact exposure (no risk of mask damage)

• High precision and repeatability

• Compatibility with automated wafer steppers and scanners

3. Advanced Techniques

Some emerging or specialty techniques include:

• Extreme Ultraviolet (EUV) Lithography: Used in advanced nodes (5nm, 3nm), using 13.5nm wavelength

• Nanoimprint Lithography (NIL): Mechanical pressing of patterns into resist; suitable for low-cost, high-volume production

• Maskless Lithography: Uses digital light modulation, bypassing photomasks; still under research for high-volume applications

VII. Lithography Equipment in the Industry

The global semiconductor industry relies on a small group of advanced manufacturers for lithography tools. Below is a brief overview of the major equipment providers:

These systems require extensive support — including maintenance, upgrades, spare parts, and installation expertise — to operate reliably in fabrication environments.

JUNR’s Role in the Lithography Supply Chain

Wuxi Junr Technology Co., Ltd. (JUNR) contributes to the lithography ecosystem by:

• Supplying refurbished lithography tools

• Providing replacement parts and consumables for exposure systems

• Offering professional services, including disassembly, installation, calibration, and maintenance

• Integrating international resources from suppliers in the US, Japan, Korea, and Taiwan

This helps semiconductor manufacturers maintain high uptime and reduce operational costs without compromising quality.

VIII. Conclusion

Lithography is the cornerstone of semiconductor manufacturing. It defines the critical features of integrated circuits and directly affects performance, power consumption, and cost. From i-line lithography to today’s EUV systems, the evolution of lithography reflects the ongoing advancement of Moore’s Law.

Understanding lithography is essential for anyone working in or partnering with the semiconductor industry. It’s not just about printing patterns — it’s about enabling innovation at the atomic scale.

At JUNR, we are proud to support our customers with high-quality lithography equipment, accessories, and technical services. Whether you're expanding a production line or maintaining legacy tools, we are committed to delivering timely, cost-effective solutions tailored to your needs.