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| Enhanced Ion Assisted Deposition |
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| Quality Thin Films began an Ion Assisted Deposition R&D effort in 1996. The result has been development of a proprietary IAD process, which features a number of custom deposition and process innovations. With these innovations the IAD process achieves films exhibiting desirable characteristics of both Ion Beam Sputtering (IBS) and traditional Electron Beam (EB) evaporation deposition, at an affordable cost. |
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| QTF’s Enhanced IAD (IAD) process provides films of remarkably high density, uniformity and stability. The QTF IAD process employs proprietary source materials, which give much tighter control over the evaporation process, providing superb rate control, and vapor distribution which result in films that are both repeatable and highly homogeneous. These source materials can be used because QTF has developed custom deposition equipment, which allows the IAD process to be conducted with deposition parameters not commonly employed in conventional IAD. |
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IAD Characteristics
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Index: 3 - 5% higher than those of similar EB process films.
Thickness: Excellent physical thickness control.
Density: Typical design using EB exhibits a post-process shift of ~1% of bandwidth; the same design deposited by IAD shows a shift of <0.2% of bandwidth.
Stoichiometry: QTF has developed innovative source materials and allows sensitive control over film stoichiometry. This also contributes to index uniformity, as well as low absorption and coating stability.
Microscopic homogeneity (structure): eIAD’s rate control and proprietary source materials result in films of exceptional homogeneity on a microscopic level. The chamber geometry and source evaporation characteristics eliminate the ejection of macro particles of evaporant, resulting in coatings with very low scatter loss. Scatter loss has been characterized as reduced by a factor of five when the design was converted to eIAD.
Macroscopic homogeneity (distribution): The combination of deposition geometry, rate control, and monitoring technique allows QTF to achieve a uniform vapor deposition profile. Realizing this goal allows for the coating of large parts, or of large numbers of parts, even when coatings with very tight spectral specifications are involved.
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| Additional IAD Benefits |
Fewer Layers: High performance designs are produced which would take as many as 30-35% more layers in comparable EB designs.
High Order Control: This is important because many designs require precision control over second and higher orders of the design bandwidth.
Economic Benefits
Yields: The large uniformity zone and precise control available using eIAD reduces the number of test runs required for parametrically sensitive designs, reduces the number of failed runs, and yields parts in tolerance over a large area of the deposition region. This all translates into improved yields.
Throughput: The deposition zone allows relatively large lot sizes (or large parts) and the deposition rates are characteristically four to five times as fast as IBS.
Cost: Although the deposition system is more complex and run times slightly longer, eIAD is somewhat more costly than conventional EB systems, but far less than IBS coatings. |
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