Filter Frames CNC Machining for Optical Semiconductor Systems

Aluminum filters designed to automate systems utilize less energy due to the excellent strength and weight profile of aluminum 6061 and 7075, which reduces the moving mass by 40 to 60 percent. The thermal conductivity of aluminum also assists in passive temperature stabilization, while the machinability allows for complex kinematic features to be incorporated. Aesthetically, black anodizing provides a non-reflective surface which reduces stray light to less than 5 percent. Excellent machinability and corrosion resistance of stainless steel 303, 304, and 316L allow for non-biased electromagnetic systems to incorporate stainless steel in moving components, all while maintaining a vacuum with a minimalist outgassing rate. Invar 36 serves its purpose in systems where thermal stability is paramount, maintaining an optical alignment of ±0.5 microns over 50°C. These parameters make thermal expansion coefficients ideal for interferometry and precision metrology applications. The combination of biocompatibility and the strength-to-weight ratio of titanium grade 5 offers the ideal corrosion resistance required. PEEK and Ultem both have low outgassing rates below 10-10 torr.Ls.cm-2, UHV compatibility, and in addition have excellent insulating and chemical resistant properties.

CNC (Computer Numerical Control) milling is responsible for creating filter mounting cavities, achieving tolerances of ±0.012 mm, and controlling pocket depth to ±0.025 mm. This results in proper filter retention without stress. The performance of 5-axis and multi-axis CNC milling demonstrates the construction of kinematic mounting interfaces featuring 3-point contact geometry, repeatability of ±1 microns, and performance of surface grinding. This serves the purpose of maintaining a reference surface and achieving flatness of 2 microns per 25mm with parallelism of 5 arc-seconds. Furthermore, maintaining surface reference optics and preserving wavefront necessitated the use of wire EDM and the construction of retention springs with a slot width tolerance of ±0.010 mm. This required precision for the spring to perform its intended purpose. The rest of the described CNC operations serve the purpose of contouring and creating surfaces to serve as a reference for optics.

We achieve optical mounting surface flatness of 2 microns per 25mm, which prevents wavefront distortion of less than λ/10 at the 632.8nm wavelength. We attain parallelism between opposing surfaces of less than 5 arc seconds while maintaining the filter wedge angle distortion of less than 30 arc seconds. We achieve dimensional tolerances of ±0.012mm for the filter cavity sizing to ensure clearance for stress-induced birefringence to prevent distortion. We uphold concentricity of 0.010mm for cylindrical filter mounts to maintain beam centering and achieve the angle positioning accuracy of ±0.05 degrees for the dichroic mirrors and polarizers. We achieve the mounting hole position accuracy of ±0.012mm for kinematic assembly and below 1.6 Ra microns surface finish on contact surfaces of filter frames which support optical systems with clear apertures of 6mm to 150mm, filter thickness of 1 to 10mm, and λ/4 to λ/10 wavefront preservation optical quality with transmission efficiency in the pass band of 95 percent, stray light rejection of more than 10⁻⁴, and which hold position with ±0.5 microns over 24 hours of thermal cycles.

Yes, we provide rapid prototyping to verify fit and test assembly, with same-day CAD-to-part capability available for critical projects. For custom automation cells and research platforms, we perform low-volume production of 20 to 500 brackets. For standardized robot models, we perform high-volume production of thousands to tens of thousands of brackets annually, incorporating complete dimensional inspection, flatness verification, and material certifications.

All components are built and managed according to ISO 9001 standards, including the management of quality materials traceable to vacuum out gassing certification per ASTM E595, and documents for mechanical properties for adherence to optical design specifications, dimensional verification, interferometric flatness testing, and optical design specifications dimensional verification, and other controls for pe particulate contamination meeting Class 1 cleanroom standards with particle generation of 100 particles > 0.1µm per minute. Components are also certified compliant with semiconductor equipment standards SEMI E10 for cleanroom set up, SEMI S2 and S8 for safety guidelines, vacuum materials SEMI F57, MIL-PRF-13830 for optical components, ISO 10110 for optical drawing standards, environmental RoHS and REACH compliance, and mechanical reliability for stable optical performance through 20,000 to 50,000 hours of continuous operation for over 10 to 15 years during semiconductor fabrication.

We provide comprehensive finishing solutions tailored to aerospace requirements:
Anodizing (Type II and Type III)
Passivation for corrosion resistance
Precision polishing for aerodynamic surfaces
Custom protective coatings and thermal barriers

For standard filter frames based on semiconductor equipment designs, it usually takes 14-20 business days. This duration covers the machining, surface grinding, finishing, interferometric tuning, cleanroom packing, and the final validation steps. On the other hand, more intricate, tailored assemblies that include kinematic mounts and motorized positioning systems take 6-8 weeks to complete. If available, we can provide prototype filter frames for optical testing in 10-14 days, depending on the desired surface finish and available materials.

Filter frames are designed for specific optics and process conditions. For DUV and EUV systems with wavelengths from 13.5 to 365nm whose photolithography requires vacuum compatibility to 10⁻⁸ torr, thermal stability is maintained at ±0.1°C to shift the wavelength by 0.1nm. Filters for wafer inspection systems are designed with motorized turrets integrated with 6 to 12 position indexing assemblies for 0.5 micron repeatability, which is essential for defect determination at sub-100nm resolution. For plasma etching equipment with quartz filters and UV-resistant mounts, the filters withstand operating temperatures of 150°C and highly corrosive fluorine with quartz filters. For optical profilometry systems, the designs for white light interferometers with filter holders require a flatness specification of less than 0.5 microns to maintain a coherence length of over 50 microns. For metrology microscopes with infinity corrected optics, the designed filter cubes maintain a parfocality of ±10 microns through 8-10 filter positions. For spectroscopic ellipsometry systems, designed polarizer-analyzer pairs achieve dust and moisture sealed, and angular accuracy of ±0.02 degrees with extinction ratios over 10,000:1. Specialized features designed include a kinematic coupling of three point contact and spring preload for a repeatability of ±0.3 microns, piezoelectric tip-tilt adjustment of ±2 degrees with 0.001 degree resolution, integrated temperature sensors with ±0.1°C thermistor accuracy, and liquid cooling integration for temperature stability of ±0.5°C for high power lasers. Filters designed for laser applications also include RFID for automated identification and tracking. Other features include hermetic sealing with optical windows for maintaining pressure differential and modular design for standardized mounting interfaces that accept 12.5, 25, 50, and 100mm diameter filters.

The performance of CNC machining in enhancing filter frame performance is immeasurable. The optical mounting surface of CNC filters is flat to within 2 microns per 25mm, giving filter surfaces parallel to within 5 arc seconds. This parallelism prevents beam deviation greater than 10 arc seconds and preserves wavefront quality better than λ/10 at 632.8nm, which is critical in interferometry and high-resolution imaging. Excellent filters are made possible due to precisely balancing dimensions to ±0.012mm, which eliminates stress-induced birefringence block loss in extinction ratios, which is critical for polarization-sensitive measurements. The filter's failsafe points of contact are finished to a surface roughness of less than 1.6 Ra microns, which means the filters will produce less than 100 particulates greater than 0.1 microns per minute, thus certified to meet Class 1 Cleanroom standards. The retention features of CNC-machined filters are optimally designed to provide even spring pressure of 0.5 - 2.0 N/mm around the edge of the filter to eliminate localized stress points that cause optical distortion. The materials used have matched coefficients of thermal expansion of 1.6 to 23 µm/m·°C with filter substrates to minimize thermally induced stress to maintain alignment to ±0.5 microns within 50°C of a 50° span. The kinematic holding mounts with ground contact points provide positional repeatability of ±1 micron and allow optical filters to be exchanged without realignment, which reduces setup time 7by 0-90%.
Using black anodized surfaces reduces unwanted stray light reflections and decreases background noise by 30 to 50 percent. This increases the signal-to-noise ratio on the most sensitive spectroscopy measurements to over 1000:1. For vacuum-compatible materials, I ensure that the outgassing rate and base pressure remain at 10¯⁷ torr and 10¯⁷ torr in process chambers, respectively. This is possible through precision manufacturing which ensures reliable operation of the photolithography stepper for the semiconductors’ optical system with 5 to 50nm resolution, ±2nm overlay accuracy, and wafer inspection tools with extensive throughput of over 100 wafers per hour, detecting defects greater than 20nm, laser annealing with ±2 percent beam uniformity, and optical metrology for thickness measurement of ±0.1nm, thickness and refractive index of ±0.001, spectroscopic systems of wavelength accuracy ±0.5nm and resolution of 1nm FWHM and ellipsometry for film thickness of 1nm and 10 microns with repeatability of ±0.05nm. The system shows stable and confident optical performance for over 10 to 15 years, demonstrating respect for modern optical systems. This is shown by precise wavelength selection, stable polarization control, minimal optical loss, and consistent performance for complex systems equipped with integrated circuits and MEMS devices for modern advanced packaging, research labs, and semiconductor fabs.