Laser Housing's CNC Machining for Lithography Equipment

Aluminum 6061-T6 has great machinability, allowing for the creation of complex features, including adjustable screw threads, spring retention pockets, and mounting interfaces with a tolerance of ±0.0005 inches. It has a yield strength of 276 MPa, which means aluminum 6061-T6 has enough structural rigidity for mirror clamp loads of 5 to 50 newtons and a deflection of less than 1 micrometer. Furthermore, the aluminum 6061-T6 has a low density of 2.70 g/cm³,³ meaning that the mirror assembly mounts of scanning systems and robotic optical inspections, for example, will not be too heavy. It has a thermal conductivity of 167 W/m, K, which helps to get rid of excess heat and helps to control the temperature. With a thermal gradient of less than 5 microradians per °C, uneven temperature distribution, and thermal lensing-induced angular drift are reduced. The aluminum 6061-T6 also has a thermal black anodized finish, which means that 95 to 98 percent of the radiation from 400 to 2500 nanometers will be absorbed to help eliminate stray light that reflects off the mirror and contrast the optical image by 10 to 30 percent.
Invar 36 (64Fe-36Ni alloy) has an extremely low thermal expansion coefficient of 1.2 to 1.5 × 10-6 per °C over the temperature range -50 to +200 °C, giving it dimensional stability 20 times better than aluminum. It maintains mirror angular alignment within 1 micro radian over temperature variations of ±10 °C. It has excellent long-term dimensional stability with aging effects below 0.5 micrometers per year, which is beneficial for metrology applications with long-term which have calibration intervals of 12 to 24 months. It is also compatible with precision grinding to achieve a surface flatness of λ/20 (32 nanometers) and perpendicularity within 5 microradians for reference datum surfaces. Titanium Grade 5 (Ti-6Al-4V) has a high yield strength of 880 MPa, a low density of 4.43 g/cm³, and a high strength-to-weight ratio, which enables lightweight designs for dynamic scanning applications where system inertia can be reduced by 40 to 60 percent. It also has corrosion resistance, which maintains surface integrity in marine and chemical environments without protective coatings that outgas in vacuum systems, has a thermal expansion coefficient of 8.6 × 10-6 per °C, which is between aluminum and Invar, which is good for moderate-stability applications, and is biocompatible and can pass the autoclave for sterilization. Thus, it can be used for medical optical imaging equipment, which is a requirement for it to be sterilized.

Complex mirror holder bodies, which also include adjustment mechanisms, spring pockets, and mounting features, are produced using 5-axis CNC machining centers, which are capable of achieving spindle speeds of 15,000 to 30,000 RPM, with a reasonable dimensional tolerance of 0.0005 inches on component dimensions of 20 to 150 millimeters. This is accomplished using solid-carbide end mills with diameters ranging from 1 to 20 millimeters and cutting at a feed rate of 500 to 3000 millimeters per minute. The precision surface grinding of optical reference surfaces is accomplished by achieving a flatness of 0.0002 inches (5 micrometers) over 25 to 100 millimeters and with the perpendicularity of 0.0001 inches (2.5 micrometers) by using resin-bonded or vitrified aluminum oxide wheels at surface speeds ranging from 1800 to 2500 meters per minute. The mirror contact surfaces are subjected to diamond turning on ultra-precision lathes to achieve a flatness of λ/10 (63 nanometers at 632.8 nanometers) and a surface finish of Ra 5 to 20 nanometers with single-crystal diamond tools having a nose radius of 0.5 to 2.0 millimeters at cutting speeds of 100 to 500 meters per minute. CNC thread milling produces adjustment screw threads of M3 to M6 size with a pitch tolerance of ±0.005 millimeters and perpendicularity of 0.01 millimeters, which assures smooth angular adjustment with a backlash of no more than 10 microradians.
Wire EDM cutting can create precision slots and kinematic contact features with dimensional tolerance ±0.003 millimeters. The surface finish can be adjusted between Ra 0.8 to 1.6 microns. With regards to cylindrical grinding operations, the surface finish of the mounting pins and kinematic contact spheres can be adjusted between Ra 0.1 to 0.4 microns, achieving a diameter tolerance of ±0.001 millimeters, and a roundness within 0.5 micrometers. This creates repeatable kinematic location accuracy of ±1 microradian.

We achieve optical reference surface flatness of 5 microns across 25 to 100 mm, encompassing the entire mirror when the substrate is in contact, to prevent contact-induced wavefront distortion of 63 nm (λ/10). Wave distortion is primarily induced by mounting stress. Kinematic contact sphere position accuracy of ± 0.005 in (±12.7 micrometers) within 3-point contact geometry. The repeatability of the mounting geometry of ± 1 microradian is guaranteed while mirrors are reinstalled for cleaning or replacement. This avoids mirror angle repositioning. Perpendicularity of the mounting surface to the optical axis is within 2.5 microradians (0.0001 in per in) to avoid angular misalignment, causing 25 micrometer deflection of laser beams at a 10 m distance. Adjustment screw thread pitch accuracy is ± 5 micrometers (±0.0002 in) per revolution to maintain screw resolution of 10 to 50 microradians movement per turn. This is for 80 to 100 TPI screws. Positioning of mounting holes within 7.6 micrometers (±0.0003 in) is within 25 to 150 mm patterns to allow proper alignment with optical breadboard or instrument frame mounting grids. For thermal stability, critical dimensions prescribe uniformity of wall thickness within ± 0.001 in to achieve a uniform temperature distribution of ± 0.5 °C. This aids in ensuring thermal drift of 5 microradians per °C change of temperature.

Certainly, Zintilon offers rapid prototyping, and for optical components, we provide 5 to 20 functional prototypes within 2 to 4 weeks for optical alignment testing. These include interferometric flatness measurements within λ/20, drift stability validation within 10 microradians over temperature cycles of -10 to +50°C, and kinematic repeatability testing within ±1 to 5 microradians of repositioning accuracy. For mirror holders and custom metrology instruments with research optics, we carry low-volume production runs of 50 to 500 and fully dimensioned inspection and surface quality certified reports. Exceeding 5,000 holders is done annually for commercial laser systems and optical inspection equipment using automated CMM inspection. Each production phase involves CMM inspection to 0.5 micrometer repeatability, optical interferometry of reference surface flatness within λ/20 (32 nanometers), infringing surface quality to scratch-dig 60-40 per MIL-PRF-13830, and confirming Ra 0.05 to 0.8 microns surface roughness on optical contact surfaces. Verifying surfaces for thermal stability testing to an angular drift of 10 microns per °C is done along with angular measurement using autocollimators and ensuring holders are dimensionally compliant to ISO 10110 optical standards and ISO 9001 quality standards, along with material traceability.

Yes, for every step taken, we also have proof of quality as stated ISO 9001:2015 quality standards system. We do mirror holders according to ISO 10110 standards for best optics, ISO 9211 for coated optics, SEMI E57 for integrated optics, and numerous other standards. We also developed proprietary standards to control important optical and mechanical features according to dimensions and tolerances. We use interferometric methods for flat surfaces checking to λ/20, an autocollimation system for angular checking to 5 microradians, and a CMM to measure the optical standards and mechanical features to ±0.5 micrometers according to ISO 10360. We also automated the servo control for the expected angular positioning to 10 microradians for the stability testing per temperature cycle. We drill to the standards of ISO 10929 for substrate material to control thermal stability and provide the drill annotated with the thermal expansion and the drilled anodizing per MIL-A-8625 for the surface absorption standards.

The finishes include black anodizing Type II for aluminum of 10 to 25 microns with an absorption surface of 95 to 98 percent and an anodized layer forming oxide aluminum surface 10 to 25 microns between the wavelengths 400 to 2500 nanometers, which eliminates stray light reflections. These reflections reduce the contrast of the optical system. These surface finishes reflect optical reference surfaces achieving Ra 0.4 to 0.8 microns with carbide tooling which is fitted for non-critical mounting applications, precision diamond turning surfaces achieving Ra 5 to 20 nanometers and flatness λ/10 to λ/20 for critical contact interfaces of the mirror which requires sub-wavelength accuracy, electroless nickel plating 10 to 25 microns on Invar for diamond turning to final optical quality which is performed for the quality optical surface to provide improved machinability and corrosion protection, and chemical conversion coating per MIL-DTL-5541 which is for temporary corrosion protection during assembly.
Some of the extra services we offer involve heat treatment to relieve stress, which is done at a temperature of 150 to 200°C for 2 to 4 hours, lowering machining stress to 20 MPa, seamlessly preventing a micrometer dimensional drift over 5 years. Ultrasonic cleaning in de-ionized water or isopropanol cleaning removes residue and contaminants to levels of particulates dropping to less than 100 over 0.1 square meters for particulates over 5 microns. Then, we do vacuum baking to reduce outgassing for periods of 12 to 24 hours at a temperature of 120 to 150°C, which brings the outgassing rate to below 1×10⁻⁸ Torr·L/s. This helps in vacuum optical systems, which function at a range of 1×10⁻⁶ to 1×10⁻⁹ Torr.

Typically, Kinematic mirror holders of standard sizes (between 25.4 to 50.8 millimeters, or 1 to 2 inches in diameter) made of aluminum 6061 T6, finished with basic adjustments, black anodization, and simple black anodization, take 3 to 5 weeks. This includes the entire time of acquiring the materials, the precision CNC machining, grinding the surface, anodizing, and throughout the dimensional inspections, and interferometric flatness verification. The lead time is about 6 to 10 weeks for more complicated custom mirror holders because optical testing, ultra-precision machining, and heat treatment for material stabilization will be needed. Functional mirror holders for Optical system development, or alignment troubleshooting, basic surface finishing, and expedited machining can be provided in 1 to 3 weeks. Once the initial setup for large production orders over 2,000 units is complete, for example, Pmirror holders for commercial laser systems or optical metrology equipment, it will take 8 to 14 weeks for the rest of the setup including development of fixtures for multi-part nesting, diamond turning program for optical surfaces, and first article inspection with interferometric and thermal stability validation per the ISO 10110 standards is completed. Then, they will ship in batches of 200 to 1,000 each month.

Definitely! We do create ultra-stable metrology mirror mounts for laser interferometers and coordinate measuring machines requiring calibration stability of about 12 to 24 months, piezo-actuated tip-tilt platforms for closed loop capacitive sensing with an adaptive optics and laser beam steering systems of DC to 1 kHz, vacuum-compatible mirror holders electropolished to Ra 0.1 to 0.2 microns for XUV lithography and electron microscopy systems operating 1×10⁻⁸ to 1×10⁻¹¹ Torr with outgassing rates below 1×10⁻⁹ Torr·L/s, cryogenic optical mounts for infrared astronomy and quantum optics with alignment of 5 microradians during cooldown from 300 to 4 Kelvin using OFHC copper or aluminum 6061, specialty configurations including motorized gimbal mounts providing remote angular adjustment via RS-232 or Ethernet with encoder resolution of 1 microradian, and for large mirror mounts for substrates of 150 to 300 millimeter diameter with kinematic support of 3 to 6 points for masses of 1 to 10 kilograms. Athermalized designs using titanium-Invar composite construction for alignment of 2 microradians over -40 to +85°C, optical systems for aerospace and defense, and active optical stabilization systems integrated alignment sensors with capacitive or inductive position measurement providing feedback of ±0.1 micrometers.

Precision machining optimizes optical alignment by maintaining reference surface flatness within 0.0002 inches (5 micrometers) across mounting interfaces 25 to 100 millimeters, ensuring uniform mirror substrate contact with stress-induced wavefront distortion below λ/20 (32 nanometers), preventing image quality degradation that reduces MTF (modulation transfer function) from 0.8 to 0.4 at 50 line pairs per millimeter spatial frequency. Kinematic contact sphere positioning accuracy within ±0.0005 inches (±12.7 micrometers) maintains three-point support geometry, providing mounting repeatability ±1 microradian when mirrors are removed for cleaning and reinstalled, enabling optical system realignment within 5 minutes versus 2 hours for non-kinematic designs. Perpendicularity between mounting datum and optical axis within 0.0001 inches per inch (2.5 microradians) prevents beam pointing errors that deflect laser beams 25 micrometers at 10 10-meter propagation distance, causing measurement uncertainty increases from ±0.1 to ±5.0 micrometers in interferometric metrology. Thread pitch accuracy within ±0.0002 inches per revolution ensures angular adjustment resolution uniformity within ±10 percent, enabling consistent fine-tuning 10 to 50 microradians per turn of 80 to 100 TPI adjustment screws critical for laser cavity alignment requiring angular precision 5 to 20 microradians. Thermal mass distribution uniformity through wall thickness control within ±0.001 inches minimizes thermal gradients below 0.5°C across holder body reducing thermal drift from 20 to below 5 microradians per °C temperature change maintaining laser beam pointing stability within 10 microradians over ambient variations ±5°C, achieving optical stability validating 10 to 15 year design life in laser interferometers measuring displacements 0.1 nanometer to 1 meter with uncertainty ±10 nanometers, optical coordinate measuring machines achieving 3D position accuracy ±0.5 micrometers over volumes 500×500×500 millimeters, spectroscopy systems resolving wavelengths 200 to 2500 nanometers with resolution 0.1 to 1.0 nanometers, and photonics research systems aligning optical components with angular precision 1 to 10 microradians and position accuracy 0.5 to 5.0 micrometers for fiber coupling efficiency exceeding 80 percent and maintaining alignment over temperature cycling -20 to +70°C.