Tutorial Course Descriptions

Detailed Syllabus

C-326 Manufacture of Precision Evaporated Coatings (half-day)

 This tutorial provides detailed information on how to establish and improve evaporative coating processes for precision optical coatings.  Design considerations for coating chambers, such as source placement, substrate fixturing, control of film thickness uniformity, and thickness monitors will be discussed.  Trade-offs in the selection of source materials, means of controlling film structure, and the influence on the performance of the coated component will be considered.  Process details will be approached with a focus on practicality; film properties must be measurable and system designs must be practical and cost-effective.  These process concepts are readily implemented in standard evaporation systems, providing significant improvements in existing coating facilities.

Topical Outline:
    Chamber components for an evaporation system
    Deposition monitoring and control
         - Optical monitoring
         - Advanced methods for quartz crystal monitoring
    Thin-film uniformity concepts and calculations
         - Source placement
         - Substrate rotation and fixturing
         - Analysis and selection of system gearing
         - Design of uniformity masks to correct film thickness variations
    Stress in optical coatings
         - Theoretical basis for film stress
         - Measurements of stress in thin films
         - Process design to minimize stresses in optical coatings 
Course Details:

1. Chamber Components
a) Pumping

  1. Types of pumps and gauges
  2. Cleanliness
  3. Mean-free path

b) Heating

• Influence on film struxxcture

• Types of heaters and output spectra

• Risks in heating/cooling profiles (breakage)

c) Gas Control

• Pressure control

• Flow control

d) Evaporant Sources
• Electron-beam guns (sweeps, material form, comparisons of different configurations
• Resistance sources (boats, filaments, material form)

2. Thin-film Monitoring

a) Optical monitoring
• Single-wavelength (reflection, transmission, addressing limitations of each)
• Broad-spectrum (data fitting, understanding of complexity in implementation)

b) Quartz crystal monitoring

• Stability and control with a single monitor
• Multi-point monitoring
• Crystal changing due to dynamic calibration changes

• Understanding of vapor plume through multiple crystal monitors

3. Thin-film Uniformity

a) Simple rotation

• Uniformity calculations

• Optimal source placement

• Mask design for improved film distribution

b) Domed, or pyramidal, rotation

• Improved system capacity

• Uniformity and source determination

• Masking

c) Planetary Rotation

• Influence of gearing on achieved film uniformity, and optimal selection of gears

• Optimal source placement

• Characterization of uniformity using laser photometry (single wavelength)

• Calculation of film distribution in a uniformity model

• Design and modeling of a corrective mask

• Advanced planetary motion (tilted planets, domed planets)

d) Impact of errors

• Changes in substrate height

• Influence of tilt in a planet

4. Thin-film stress

a) Theoretical basis of stress

• Calculation of stress from Stoney’s equation

• Thermal stresses

• Intrinsic stresses

• Structure zone models (Movchan & Demchishin, Thorton)

b) Measurements of optics for determination of film stress

• Choice of substrate

• Influence of interferometer wavelength and coating phase

• Impact of humidity on thin-film stress

• Aging of film stress

c) Modifications to film stress by process changes

• Thermal

• Pressure

• Substrate material

• Coating material
• Densification (ion sources, plasma sources)

Instructor: Jim Oliver, Vacuum Innovations, LLC and Univ. of Rochester LLE
Jim Oliver

is founder and owner of Vacuum Innovations, LLC and is a research engineer at the University of Rochester's Laboratory for Laser Energetics.  A graduate of the University of Rochester’s Institute of Optics, his work has focused on process design and modeling for precision evaporated coatings.  Thin-film uniformity control is of particular interest, having developed advanced distribution models and planetary rotation systems.  He also teaches optical coating design at the Institute of Optics as well as at the Institute’s annual thin film summer school program. 

This course is currently available via:
On Location Education Program

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