Lens Mounts CNC Machining for Semiconductor Inspection Systems

Aluminum 6061-T6 has great machinability, which allows for the construction of complicated forms, precision threads, and internal bores. It can also make multiple mounting interfaces with tolerances of ±0.0005 inches. It has a yield strength of 276 MPa, which is enough for lens-retaining 10 to 100 Newton forces, preventing optical displacement under 2 to 10 g of vibration. It also has a low density of 2.70 g/cm³,³ which is important for the weight of the lens mounts for scanning inspection systems and robotic wafer handling systems, as it minimizes the mass of moving parts. It also has a thermal conductivity of 167 W/m· K, which is important for the lens mount to dissipate the heat of high-power sources of illumination (50 to 500 watts), which can reach thermal lensing and degrade the image with a resolution of 0.5 to 2.0 micrometers. It also prevents thermal lensing, which degrades the image resolution. Finally, it is also compatible with black anodizing, which allows the mount to absorb 95 to 98 percent of surface radiation in the wavelengths of 200 to 2500 nanometers, eliminating internal reflections that cause a contrast reduction of the image about 15 to 40 percent.
Aluminum 7075-T6 has a weight-strength ratio of 1:6 with a yield strength of 503 MPa and can have lengths of rigid lens mounts with a maximum of 1 micrometer deflection with operational loads. This rigid lens mount is stable to within 0.5 micrometers over high magnification objectives. Over a 5+ year service life, it has stress-relief aging and maintains dimensions of ± 2 micrometers over 5+ years. It also has stress-relief aging. It also has excellent vibration damping. For inspection systems, fab floors with ambient vibrations of 1 to 5 micrometers pk to pk, vibrations of 20 to 40 percent are reduced by a micrometer of peak to peak. Titanium Grade 5 (Ti-6Al-4V) has a low thermal expansion coefficient of 8.6×10⁻⁶ per °C which is a 60 percent improvement over aluminum with thermal stability, maintaining a focus position of ± 5 micrometers over a 3 °C temperature swing and ± 3 °C over a 3 °C, and has exceptional STW and a yield strength of 880 MPa and a density of 4.43 g/cm³ to have constrain lightweight rigid designs, corrosion resistance, and has surface integrity over 1,000 clean room cycles using dilute hydro- chlorinate clean, isopropyl alcohol, and peroxide and non-magnetic properties which do not interfere with electron beams inspection systems of magnetic strength of 0.5 mq.

CNC turning operations use horizontal and vertical lathes with spindle speeds of 2000 to 6000 RPM to produce lens mount bodies, achieving size tolerances of ±0.0005 inches on 20 to 100 millimeter outer diameters, ±0.0003 inches on internal bore diameters for lens element seating, and surface finishes of Ra 0.2 to 0.8 microns on optical surfaces. This is accomplished with polycrystalline diamond or carbide inserts at 150 to 400 meters per minute cutting speeds. Precision boring operations accomplish internal diameters concentric with the external mounting datum to within 0.001 millimeter, thereby achieving optical axis alignment to within 5 to 10 micrometers, and cylindricity to 2 micrometers over bore lengths of 10 to 80 millimeters. CNC thread cutting with single-point tools performs the optical threads M25X0.5 to M52X0.75 with pitch accuracy of ±0.005 millimeters, ±15 arc-minutes thread angle tolerance, and mounting face perpendicularity within 0.002 millimeters per 25 millimeters diameter for proper lens element seating. Face grooving operations complete axial positioning.
When grinding surfaces and mounting faces, flatness within 0.001 inches (25 micrometers) and perpendicularity within 0.0005 inches per inch (12.7 microradians) relative to the internal bore centerline is achieved. For more complex designs, 5-axis CNC milling is used to create mounting features, wrench flats, and cable routing channels within ±0.0005 inches of specified dimensions. On ultra-precision lathes, < 0.5 to 0.5 micrometers of form accuracy is achieved during diamond turning for critical imaging applications, along with producing optical reference surfaces that capture images and critically finish the surfaces to micrometers 10 to 50 nanometers Ra (average roughness) during polishing.

Mounting diameter optical bore concentricity achieved within 10 micrometers 0.0004 inches, maintained vignetting 5 to 15 micrometers for 10-50 mm sensor areas, resolution uniformity 10-15 micrometers, lens seating surface flatness 5 micrometers 0.0002 inches, stomps uniformly 63nan0m 0.1 wavefront distortion, imaging, thread pitch accuracy 0.0002 inches 5 micrometers per canceled plane positioning parfocal within 10 micrometers for our automatic change. Optical bore and mounting face perpendicularity within 0.0002 inches, tilting image plane 50 microradians.2-10 micrometers, runout external mounting surfaces 0. 7.6 micrometers TIR, lens assemblies precision cleaning, repeat alignment. Parfocal height critical dimension 5 micrometers 0.0002 inches to combine focus plane ole g 10 micrometers during wafer inspection seamless.

Yes, Zintilon offers rapid prototyping and will deliver 5 to 25 functional prototypes for optical testing validation in 2 to 4 weeks, which include interferometric testing of lens element tilt to within 50 microradians, verification of centration within 10 micrometers using coordinate measuring machines, and positioning accuracy measurement of the parfocal plane at ±10 micrometers, along with low volume production of 50 to 500 lens mounts for specialized inspection tools and research optical systems with full dimensional inspection certificates that include reports on runout measurement, verification of thread quality, and other dimensional inspection criteria, and high volume production of more than 5,000 lens mounts each year for commercial wafer inspection equipment and automated optical metrology systems with documented control of production processes.
No production step is complete without inspections like CMMs that achieve 10 nanometers of repeatability, Optical Interferometers for form and flatness checks that achieve 32 nanometers for the lens seating surfaces (32 nanometers is λ/20), runout measurements with dial indicators that capture TIR within 10 micrometers, thread checking according to ISO 1502 for the pitch diameter, flank angle, and thread form, and thermal stability testing measuring contractions of under 10 micrometers within 20 to 26°C, and Dimensional checks of lens mounts against ISO 10110 optical standards, SEMI E148 optical module specifications, and ISO 9001 quality with traceable materials.

For every manufacturing process, the ISO 9001:2015 quality management systems are followed, which include material certifications, handling processes, and cleanroom handling protocols for semiconductor fabrication compatibility, which is lens mounts. For the lens mounts, we implement the ISO 10110 standards, which cover optical component drawing standards, surface quality, dimensional tolerances, and centration requirements. Moreover, we cover the SEMI E148 optical module mounting interface standards for wafer inspection equipment, the ISO 8038 and 9022 standards for environmental testing of optical instruments, and the SEMI F57 vacuum materials specifications regarding outgassing rates for e-beam inspection tools. As for dimensional validation, we perform interferometric testing, coordinate measuring per ISO 10360, and optical centration measurement for alignment validation, which is done to achieve stated standards and accuracy. For cleanroom compatibility, the SEMI F21 standard is followed, and outgassing and surface testing for vacuum applications.
There are certifications for the materials, which include checking the alloy composition as per ASTM standards, checking anodized coating thickness of 10 to 25 microns per MIL-A-8625, as well as certificates of conformance of RoHS and REACH compliance.

Surface finishing options include black anodizing Type II for aluminum producing an anodized oxide layer of 10 to 25 microns with a surface absorption of 95 to 98 percent at 200 to 2500 nanometers for reducing stray light and internal reflections 3 to 10 dB on defect detection signal-to-noise ratio, as-machined finish on optical bearing surfaces achieving Ra 0.4 to 0.8 microns with either carbide or PCD tooling is good for non-critical lens retention interfaces while precision diamond-turned optical surfaces with Ra 10 to 50 nanometers and form accuracy of 0.1 to 0.5 micrometers serve for critical lens seating interfaces that require sub-micron positioning accuracy, followed by diamond tuning to optical quality surface for wear resistance and dimensional restoration, and then electroless nickel plating of 10 to 25 microns on aluminum substrate, and finally passivation for stainless steel components per ASTM A967.
We also provide special treatments which include stress-relief heat treatments for 120 to 150°C for 2 to 4 hours which reduce residual machining stresses, which helps prevent dimensional drifts of 2 micrometers or more during the 5-plus years service life, ultrasonic cleaning with cleanroom-grade DI water or isopropyl alcohol which helps in reaching the particle cleanliness of fewer than 50 particles per 0.1 square meter for 5 microns per SEMI F21, vacuum baking at 100 to 120°C for 12 to 24 hours which decreases the outgassing rates to less than 1×10⁻⁸ Torr·L/s for e-beam inspection systems, and optical-quality thread cutting to achieve fine surface finishes of Ra 0.8 to 1.6 microns which helps in preventing particulate generation during the installation or removal of objectives in cleanroom environments.

When it comes to basic lens holder sizes ranging from M25 to M42 or from 1-inch to 2-inch RMS using 6061-T6 aluminum with black anodizing and basic optics, the timeline is about 3 to 5 weeks. This is inclusive of the time taken to order materials, do precision CNC turning, threading, anodizing, and finishing, where the dimensions and run-out must be checked. For complex custom lens mounts that have ultra-precision surfaces that are diamond-turned, built-in focus mechanisms, or are made of titanium and constructed with precision machining needing thermal stability testing, the time taken is 6 to 10 weeks. This is because it involves multi-axis machining, diamond turning, and the final optical testing. For rapid optical system development or inspection tool troubleshooting, basic functional lens mounts are available in 1 to 3 weeks, with the CNC turning and surface finishing process accelerated. For the mass production of over 2,000 lens mounts, the first production setup for volume semiconductor inspection equipment manufacturing takes 8 to 14 weeks. This includes turning fixture optimization, thread cutting tool preparation, and the first article inspection, which includes full optical testing.

Sure, we make ultra-high numerical aperture objective mounts for NA 0.7 to 0.95 lenses with centering precision of 5 micrometers, tilt less than 50 microradians, and feature 20 to 50 nanometers advanced defect inspection, all in parfocal multi-objective turret assemblies. These mount 3 to 6 positions, allowing a seamless focus plane within ±5 micrometers for magnification changes of 5 to 150×, which are done during wafer scanning. We also make motorized focus mounts with piezo actuators for a travel range of 10 to 50 millimeters and a resolution of 0.1 to 0.5 micrometers, with closed-loop capacitive sensing for automation in focus within metrology systems. For telecentric lens mounts, we make them with a magnification consistency of 0.05 percent for critical dimension measurement, with uncertainty below ±2 nanometers. Our specialty designs include deep UV lens mounts using fused silica optics with a purged enclosure for 193 to 266 nanometers wavelengths, for UV absorption and ozone formation prevention. We also make vacuum-compatible e-beam objective mounts for inspection systems with outgassing below 1×10⁻⁹ Torr·L/s and operating ranges of 1×10⁻⁸ to 1×10⁻¹⁰ Torr, with e-beam objectives and electropolished to Ra 0.1 microns. For overlay metrology, we athermalized designs using titanium-Invar composites for focus within ±2 micrometers over temperature ranges of 18 to 25°C, with measurement uncertainty below ±0.5 nanometers. We integrated with liquid immersion objective mounts and fluid delivery systems for a refractive index fluid of 0.1 to 0.5 millimeters and layers for numerical apertures of 1.0 and greater. We also have integrated illumination lens assemblies that combine imaging objectives with Köhler illumination optics. These have been designed to reduce system lengths by 30 to 50 percent.

Machining improves optics by keeping the internal bore concentric to the external mounting diameter within 0.0004 inches. This also ensures that the optical axis is kept aligned within 5 to 15 micrometers, which is necessary to avoid asymmetry in the image field and focus shift between 2 and 10 micrometers on the sensor, which can resultin unsatisfactory resolution in the range of 0.5 to 1.5 micrometers, which can lead to loss of sensitivity in defect detection, which is 30 to 80 nanometers. Flatness of the lens seating surface within 0.0002 inches contributes to the formation of even compression of the optical element which aids in the uniform application of optical contact pressure and prevention of localized stress points which can lead to concentration birefringence of 5 to 20 nanometers retardance and distorted wavefront of λ/10 to λ/5 which can shift the image quality metrics to the worse side including MTF from 0.7 to 0.4 at 500 line pairs per millimeter. Accuracy of the thread pitch within ±0.0002 inches per revolution assists in maintaining the position of the parfocal plane within ±10 micrometers. This is important in multi-objective inspection systems to change magnifications from 10× to 100× without refocusing. It also helps to reduce the measurement cycle time from 15 to 3 seconds per site.
Ensuring perpendicularity between the mounting face and the bore to within 0.0002 inches (5 microradians) keeps the image plane from tilting and varying the focus across the field-of-view by 5 to 25 micrometers. This would degrade resolution at the corners from 0.5 to 2.0 micrometers, which is unacceptable for full-wafer defect mapping that requires uniform sensitivity. Controlling runout to within 0.0003 inches (7.6 micrometers) TIR on the mounting surfaces ensures repositioning repeatability ±5 micrometers, which is crucial when cleaning the objectives, then reattaching them while keeping the optical system calibrated across 500+ cleaning cycles. In contrast, mounts with runout greater than 25 micrometers only last 50 cycles. This imaging reliability supports the 8 to 12 year design life on wafer defect scanners that inspect 300 millimeter wafers at 100 to 300 wafers per hour, with defect detection sensitivity between 20 to 100 nanometers, photomask inspection tools, and optical critical dimension metrology systems. The latter measures linewidths from 10 to 500 nanometers with an uncertainty of ±0.5 to ±2.0 nanometers, while film thickness measurement equipment operates in Class 1 to Class 100 cleanrooms at 20 to 24°C ±1°C and measures stack thickness of 1 to 10,000 nanometers with ±0.1 to ±1.0 nanometers accuracy.