Nikon NSR SF 155 i-Line Stepper: Complete Engineering Guide
In semiconductor manufacturing, photolithography is one of the most critical and technically demanding processes. The ability to transfer circuit patterns onto wafers with precision directly determines device performance, yield, and production efficiency.
Among the many lithography systems developed over the years, the Nikon NSR SF 155 i-Line stepper remains a reliable and widely used platform for mature-node semiconductor production. Even today, it continues to play an important role in analog ICs, power devices, MEMS, and specialty semiconductor manufacturing.
This guide provides a comprehensive, engineering-level analysis of the NSR SF 155, covering its working principles, specifications, applications, and key considerations for users and buyers.
What is the Nikon NSR SF 155 i-Line Stepper?
The Nikon NSR SF 155 is a reduction projection stepper designed for semiconductor photolithography using i-line ultraviolet light (365 nm).
Unlike contact or proximity lithography systems, a stepper projects a reduced image of a photomask onto the wafer using high-precision optics. The wafer is exposed field by field through a step-and-repeat process.
Key characteristics:
- ● i-line (365 nm) exposure system
- ● Reduction projection optics (typically 5× reduction)
- ● High overlay accuracy for mature nodes
- ● Designed for 150 mm and 200 mm wafers (depending on configuration)
This architecture allows the NSR SF 155 to deliver consistent patterning performance across a wide range of semiconductor processes.
Working Principle of an i-Line Stepper
The Nikon NSR SF 155 operates based on optical projection lithography.
Process overview:
- ● A photomask containing circuit patterns is illuminated by an i-line UV light source
- ● Projection optics reduce the mask image (e.g., 5:1 reduction)
- ● The reduced image is projected onto photoresist-coated wafers
- ● The wafer stage moves step-by-step to expose multiple fields
Why i-line (365 nm)?
- ● Stable and mature light source technology
- ● Cost-effective compared to DUV systems
- ● Suitable for feature sizes typically in the 0.35 µm – 0.8 µm range
- ● Widely used in power, analog, and MEMS processes
Core Technical Specifications
While configurations may vary, typical specifications of the NSR SF 155 include:
Wafer Compatibility
- ● 150 mm (6-inch) wafers
- ● 200 mm (8-inch) wafers (depending on setup)
Exposure System
- ● Light source: Mercury lamp (i-line, 365 nm)
- ● Stable illumination for consistent CD control
Resolution Capability
- ● Typically suited for ≥0.5 µm nodes
- ● Actual resolution depends on resist process and optics condition
Reduction Optics
- ● 5× reduction projection lens (common configuration)
- ● High optical stability with long-term alignment consistency
Overlay Accuracy
- ● Designed for mature-node overlay requirements
- ● Performance depends on stage calibration and system condition
Stage System
- ● Precision XY wafer stage
- ● Closed-loop positioning control
- ● High repeatability step-and-repeat motion
Alignment System
- ● Optical alignment with wafer mark detection
- ● Global and field alignment capabilities
Key Advantages of the Nikon NSR SF 155
1. Proven Stability in Production
The NSR SF 155 has been widely used in semiconductor fabs for many years, offering stable and repeatable performance under production conditions.
2. Cost-Effective Lithography Solution
Compared to advanced DUV or EUV systems, i-line steppers offer significantly lower acquisition and operating costs.
3. Suitable for Mature Nodes
Many semiconductor applications do not require sub-100 nm resolution. For these processes, the NSR SF 155 provides more than sufficient capability.
4. Durable Optical System
Nikon optics are known for long-term stability, provided proper maintenance and contamination control are maintained.
Typical Applications
The Nikon NSR SF 155 remains highly relevant in several semiconductor sectors:
Power Semiconductor Manufacturing
- ● IGBT
- ● MOSFET
- ● SiC device processing (non-critical layers)
Analog & Mixed-Signal ICs
- ● Operational amplifiers
- ● Power management ICs
- ● Sensor interface chips
MEMS Fabrication
- ● Micro-sensors
- ● Actuators
- ● Microfluidic devices
Discrete Devices
- ● Diodes
- ● Transistors
- ● RF components
Research & Development
- ● University labs
- ● Process development lines
- ● Pilot production
Engineering Considerations Before Using or Buying
When evaluating a Nikon NSR SF 155 system—especially a used unit—several technical aspects must be carefully reviewed.
1. Optical System Condition
- ● Lens contamination or haze
- ● Transmission stability
- ● Focus performance
- ● CD uniformity across field
2. Illumination System
- ● Lamp lifetime and stability
- ● Power supply condition
- ● Illumination uniformity
3. Stage Accuracy
- ● Step accuracy and repeatability
- ● Backlash or drift
- ● Interferometer calibration
4. Alignment System
- ● Mark recognition accuracy
- ● Camera clarity
- ● Alignment repeatability
5. Software & Control System
- ● Version compatibility
- ● Error logs and history
- ● Integration with factory MES
6. Spare Parts Availability
- ● Lamps
- ● power modules
- ● control boards
- ● motion components
A well-maintained system can still deliver excellent performance, but poor condition can significantly affect yield.
Cost Considerations
The cost of a Nikon NSR SF 155 system depends on:
- ● Manufacturing year
- ● Usage hours
- ● Optical condition
- ● Refurbishment level
- ● Included spare parts
Additional cost factors:
- ● Installation and cleanroom preparation
- ● Power and cooling requirements
- ● Maintenance and calibration
- ● Spare parts inventory
Compared to modern lithography tools, the total cost of ownership is relatively low, making it attractive for many fabs.
FAQ – Nikon NSR SF 155 i-Line Stepper
What process nodes can the NSR SF 155 support?
The system is typically suitable for 0.5 µm and above process nodes, depending on resist processes and exposure conditions.
Is the NSR SF 155 still used in production?
Yes. It is widely used in mature-node semiconductor fabs, especially for power devices, analog ICs, and MEMS manufacturing.
What is the biggest risk when buying a used stepper?
The most critical risks include:
- ● optical lens condition
- ● stage accuracy
- ● alignment performance
These directly affect overlay and yield.
How long can an i-line stepper remain operational?
With proper maintenance and spare parts support, i-line steppers can operate reliably for many years or even decades.
Is i-line technology still relevant today?
Yes. While advanced nodes require DUV or EUV, i-line remains essential for mature-node and specialty semiconductor production.
Conclusion
The Nikon NSR SF 155 i-Line stepper represents a mature, reliable, and cost-effective lithography solution for a wide range of semiconductor applications. Its stable optical system, proven mechanical platform, and suitability for mature nodes make it a practical choice for many production environments.
While newer lithography technologies dominate advanced nodes, systems like the NSR SF 155 continue to deliver strong value in power semiconductor manufacturing, analog IC production, and research applications.
For companies evaluating such equipment, a detailed technical assessment—covering optics, stage accuracy, and system condition—is essential to ensure long-term performance and yield stability.
As a professional service provider in semiconductor equipment, we focus on technically verified systems, responsible refurbishment, and long-term support. Our approach emphasizes engineering reliability and lifecycle performance, helping customers maintain stable and efficient lithography operations over time.
