Specific Process Knowledge/Lithography/Aligners/Aligner: Maskless 02 processing: Difference between revisions
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=Process Parameters= | =Process Parameters= | ||
The lithographic result of exposure on Aligner: Maskless 02 depends on a lot of factors, including the dose and defocus parameters, and the exposure mode used. The optimal dose and defocus | The lithographic result of exposure on Aligner: Maskless 02 depends on a lot of factors, including the dose and defocus parameters, and the exposure mode used. The optimal dose and defocus depends on the type and thickness of the resist, as well as the optical properties of the substrate (e.g. reflective/absorbing/transparent). All of these factors influence the obtainable resolution, as well as the writing speed. | ||
The correct way to determine the best dose-defocus settings is to generate a so-called Bossung plot (known from projection lithography), which plots the printed linewidth as a function of dose and defocus. From this, the most stable region of parameter space is chosen, i.e. the region where the linewidth changes the least when dose and defocus changes. Any deviation from the design linewidth may be corrected using the CD bias parameter. This typically involves SEM imaging of resist cross-sections, and quickly becomes time consuming. However, in most cases, inspection of a dose-defocus matrix (easily generated using the series exposure function) in an optical microscope will get you most of the way. | The correct way to determine the best dose-defocus settings is to generate a so-called Bossung plot (known from projection lithography), which plots the printed linewidth as a function of dose and defocus. From this, the most stable region of parameter space is chosen, i.e. the region where the linewidth changes the least when dose and defocus changes. Any deviation from the design linewidth may be corrected using the CD bias parameter. This typically involves SEM imaging of resist cross-sections, and quickly becomes time-consuming. However, in most cases, inspection of a dose-defocus matrix (easily generated using the series exposure function) in an optical microscope will get you most of the way. | ||
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==Defocus== | ==Defocus== | ||
Aligner: Maskless 02 offers two autofocus modes; optical or pneumatic | Aligner: Maskless 02 offers two autofocus modes; optical or pneumatic. The autofocus mode is selected via the substrate template. The defocus process parameter is used to compensate for offsets between the autofocus mechanism and the focal point of the exposure light, and simultaneously optimize print quality in different resists and varying thicknesses. | ||
'''Optical:''' | '''Optical:''' Works for substrates down to 3x3 mm. | ||
'''Pneumatic:''' | '''Pneumatic:''' Substrates must be at least 5x5 mm to be successfully loaded. The pneumatic AF freezes at a distance of 3 mm form the substrate edge, which means that in order to have any ''dynamic'' focusing, using the pneumatic AF, the substrate must be larger than 6x6 mm. | ||
==Exposure mode== | ==Exposure mode== | ||
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Aligner: Maskless 02 offers two exposure modes. The exposure mode is selected during design conversion. | Aligner: Maskless 02 offers two exposure modes. The exposure mode is selected during design conversion. | ||
'''High quality | '''High quality''' mode is used for minimum stitching effects.<br> | ||
In the high quality mode, an area of the pattern is exposed by 5 stripes, each 500µm wide and exposing a fifth of the dose. At the same time, sub-pixel interpolation is applied, giving an address grid size of 100 nm. | |||
'''Fast''' mode is used for maximum exposure speed.<br> | |||
In the fast mode, each area of the pattern is exposed by 2 stripes only. This effectively cuts the exposure time by 2.5 times, but also increases the size of the address grid in the X-direction by 2.5. Due to less averaging of non-uniformities, stitching effects will be more prominent in this mode. | |||
'''Fast''' mode is used for maximum exposure speed. | |||
In the fast mode, each area of the pattern is exposed by 2 stripes only. This effectively cuts the exposure time | |||
==Writing speed== | ==Writing speed== | ||
According to specs, the writing speed of Aligner: Maskless 02 is | According to specs, the writing speed of Aligner: Maskless 02 is 1200 mm<sup>2</sup>/min in fast mode. Using the high quality exposure mode cuts this speed by 2.5, to approximately 480 mm<sup>2</sup>/min. The writing speed for a 100x100 mm<sup>2</sup> area measured after being modified to write mode 2 tool (2023-03-21) of the machine was ~1200 mm<sup>2</sup>/min. | ||
[[Image:MLA150_speedVSarea.JPG|400x400px|thumb|The writing speed of Aligner: Maskless 02 (fast mode, 375nm) as a function of the exposure area]] | [[Image:MLA150_speedVSarea.JPG|400x400px|thumb|The writing speed of Aligner: Maskless 02 (fast mode, 375nm) as a function of the exposure area]] | ||
'''Speed vs. area:''' | '''Speed vs. area:''' | ||