Enhancing Laser Metrology with Diffractive Optics: Precise Solutions for Semiconductor Manufacturing

Introduction to laser Metrology applications

Laser metrology, an important  technique in semiconductor manufacturing, relies on precise optical measurements to ensure product quality and yield. Laser metrology refers to a wide array of techniques that utilize lasers to measure physical dimensions of parts or sub-parts (such as microstructures on a wafer). Diffractive optics, with their unique properties, offer significant advantages in enhancing the performance and efficiency of laser metrology systems. A variety of industries utilize laser optical metrology due to the undeniable advantages it offers, as detailed in the below table:

	Industry	Application	Some key advantages per industry
1	Semiconductors	In fabrication, it is used for characterizing micro-structures and complex geometries e.g. optical critical dimension (OCD).	High Precision and throughput, non-destructive
2	Aerospace & Automotive	Laser metrology is used to measure critical components with High precision	Traceability that meets the highest standards
3	Medical	Enhancing manufacturing of medical devices by measuring physical dimensions	Measures quickly and accurately

Table 1: Laser metrology key benefits per Industry segment

Laser Metrology usage in the Semiconductor Industry

Laser metrology equipment, such as laser interferometers, is used to passively scan and characterize substrates, making this non-destructive optical method superior to others. Furthermore, laser scanning metrology offers high sensitivity, precision, and accuracy, which is why it is widely adopted by leading semiconductor industry players. The quality of each device is governed by the performance of the fabrication machinery and its tight process control. Semiconductor fabrication facilities prioritize yield and throughput, driving the integration of wafer inspection tools into production lines. These tools provide real-time 3D data for process optimization, enabling the characterization of nanometric features, roughness, wafer bow, film thickness, and defect inspection. The result of high-precision machinery is high-quality device and consequently, a high-quality consumer product.  

Challenges in Laser Metrology

Accurate laser metrology requires state-of-the-art components to minimize noise and ensure precision. High-resolution measurements, especially for features created using extreme ultraviolet lithography, demand advanced optical solutions. Laser metrology scanning may be used to measure small  features created by extreme ultraviolet lithography ,  a cutting-edge lithography technique used to create extremely small features in semiconductor devices. Such laser metrology can employ elongated focus DOEs to improve resolution and increase the detection range. An illustration of elongated focus produced by Holo/Or’s diffractive optics can be seen below:  

Diffractive Optics: A High Precision Solution for laser metrology

Holo/Or’s Diffractive Optical Elements (DOEs) offer a range of benefits to laser metrology applications:

• High Precision: Tight tolerances and near-absolute angular accuracy ensure precise measurements.
•  Customization: Tailored field of illumination, from lean-line to uniform top-hat, meets specific requirements
•  Design Support:   Holo/Or offers simulations of our DOEs performance in  with customer supplied optical systems
• Durability: Our DOEs are etched, monolithic fused silica or Zinc selenide window with laser grade AR coating. They have high LDT, high stability and no polymers or other soft materials.

Holo/Or specializes in beam shaping and splitting solutions, including collimated beam shaping elements, diffractive prism arrays, diffractive lens arrays and diffractive beam splitter elements. These elements can be combined into a single component incorporating multiple optical functions in a single surface and reducing interference due to back reflections. An illustrated flat top line generated from Gaussian beam using Holo/Or’s Diffractive Optics  

Conclusion

Diffractive optics, integrated into laser metrology systems, can boost system performance and speed in semiconductor manufacturing. By offering precision, durability  and customization, these elements enhance defect inspection, metrology, and lithography processes. Holo/Or’s expertise in diffractive optics provides tailored solutions that meet the demanding requirements of the semiconductor industry, including a full support envelope with simulations of our components in the customers optical setup. Check out our custom solutions, and feel free to contact us for more details