Specific Process Knowledge/Lithography/Aligners/Aligner: Maskless 03 processing: Difference between revisions
No edit summary |
|||
| (10 intermediate revisions by 2 users not shown) | |||
| Line 5: | Line 5: | ||
[[Category: Equipment|Lithography]] | [[Category: Equipment|Lithography]] | ||
[[Category: Lithography]] | [[Category: Lithography]] | ||
__TOC__ | __TOC__ | ||
| Line 12: | Line 10: | ||
=Exposure technology= | =Exposure technology= | ||
Aligner: Maskless 03 is ''not'' a direct writer. In the maskless aligner, the exposure light is passed through a spatial light modulator, much like in a video projector, and projected onto the substrate, exposing a small area of the design at a time. The substrate is fully exposed by scanning the exposure field across the substrate in a succession of exposure stripes. | Aligner: Maskless 03 is ''not'' a direct laser writer. In the maskless aligner, the exposure light is passed through a spatial light modulator, much like in a video projector, and projected onto the substrate, exposing a small area of the design at a time. The substrate is fully exposed by scanning the exposure field across the substrate in a succession of exposure stripes. | ||
The light source is a laser diode (array) with a wavelength of 405 nm (8 W). The spatial light modulator is a digital micro-mirror device. The individual mirrors of the DMD are switched on and off in order to represent the design, and the laser is flashed on and off, in order to give the desired exposure dose. The exposure image is projected onto the substrate through a lens-system. The projected image has a pixel size of 500x500 nm on the substrate surface. The image is scanned across the substrate in stripes in order to expose the entire design. Each stripe is overlapping 2 or 5 times, depending on the chosen [[Specific_Process_Knowledge/Lithography/Aligners/Aligner:_Maskless_03_processing#Exposure_mode|exposure mode]]), in order to reduce light-source non-uniformity effects and stitching errors. The address grid size is 250 nm or 100 nm for Fast and High Quality exposure mode, respectively. | The light source is a laser diode (array) with a wavelength of 405 nm (8 W). The spatial light modulator is a digital micro-mirror device. The individual mirrors of the DMD are switched on and off in order to represent the design, and the laser is flashed on and off, in order to give the desired exposure dose. The exposure image is projected onto the substrate through a lens-system. The projected image has a pixel size of 500x500 nm on the substrate surface. The image is scanned across the substrate in stripes in order to expose the entire design. Each stripe is overlapping 2 or 5 times, depending on the chosen [[Specific_Process_Knowledge/Lithography/Aligners/Aligner:_Maskless_03_processing#Exposure_mode|exposure mode]]), in order to reduce light-source non-uniformity effects and stitching errors. The address grid size is 250 nm or 100 nm for Fast and High Quality exposure mode, respectively. | ||
| Line 24: | Line 22: | ||
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. | ||
<br clear="all" /> | <br clear="all" /> | ||
==Exposure dose and defocus== | |||
[[Specific Process Knowledge/Lithography/Resist#Aligner:_Maskless_03|Information on UV exposure dose]] | |||
==Exposure mode== | ==Exposure mode== | ||
| Line 174: | Line 176: | ||
=Alignment= | =Alignment= | ||
In order to get good alignment, it is advised to use four alignment marks for alignment, and to activate scaling (possibly also shearing) before starting the exposure. It is recommended to use the "High Res" camera for the final alignment of each mark in order to achieve the best overlay accuracy. Exposure using the fast mode decreases the overlay accuracy, since the address grid size is increased to 250 nm. | |||
In order to get good alignment, it is advised to use four alignment marks for alignment, and to activate scaling (possibly also shearing) before starting the exposure. It is recommended to use the "High Res" camera for the final alignment of each mark in order to achieve the best overlay accuracy. Exposure using the fast mode decreases the overlay accuracy, since the address grid size is increased to | |||
==Top Side Alignment== | ==Top Side Alignment== | ||
'''Overlay accuracy (spec):''' 0. | '''Overlay accuracy (spec):''' 0.5 µm | ||
'''Camera field of view (W x H):''' <br> | '''Camera field of view (W x H):''' <br> | ||
| Line 192: | Line 192: | ||
To be sure the Overview camera can be used to locate the first alignment mark, it is advised to use a mark in the bottom left portion (3<sup>rd</sup> quadrant) of the design as mark 1. <br> | To be sure the Overview camera can be used to locate the first alignment mark, it is advised to use a mark in the bottom left portion (3<sup>rd</sup> quadrant) of the design as mark 1. <br> | ||
{| cellpadding="2" style="border: 2px solid darkgray;" align=" | {| cellpadding="2" style="border: 2px solid darkgray;" align="center" | ||
! width="320" | | ! width="320" | | ||
! width="320" | | ! width="320" | | ||
| Line 198: | Line 198: | ||
|+'''Camera views during alignment on Aligner: Maskless 03. Screenshots by Thomas Anhøj @ DTU Nanolab, 2019.''' | |+'''Camera views during alignment on Aligner: Maskless 03. Screenshots by Thomas Anhøj @ DTU Nanolab, 2019.''' | ||
|- border="0" align="center" | |- border="0"; align="center" | ||
|[[Image:MLA150 TSA Overview.JPG|300px]] | |[[Image:MLA150 TSA Overview.JPG|300px]] | ||
|[[Image:MLA150_BSA_Backside.JPG|300px]] | |[[Image:MLA150_BSA_Backside.JPG|300px]] | ||
| Line 204: | Line 204: | ||
|- align="center" | |- align="center" | ||
| Overview camera image of a TSA alignment mark during alignment.<br/> The circle is | | Overview camera image of a TSA alignment mark during alignment.<br/> The circle is 3 mm in diameter, the alignment mark is 300 µm. The blue cross-hair is ~400 µm. || Low Res camera image of a TSA alignment mark during alignment.<br/> The mark is 300 µm wide. The blue cross-hair is ~18 µm. || High Res camera image of a TSA alignment mark during alignment.<br/> The lines of the cross are 20 µm wide. The blue cross-hair is ~7 µm. | ||
|} | |} | ||
| Line 212: | Line 212: | ||
==Back Side Alignment== | ==Back Side Alignment== | ||
'''Overlay accuracy (spec):''' 1.0 µm | |||
''' | '''BSA windows:''' along the X and Y axes, 10 mm x 46 mm, starting 14.5 mm from the center. | ||
''' | '''Camera field of view (W x H):''' 640 µm x 480 µm | ||
[[Image:MLA150_BSA_Backside.JPG|center|300px|thumb|Image of a BSA alignment mark during alignment. The mark is 300 µm wide. The blue cross-hair is ~18 µm. Screenshot by Thomas Anhøj @ DTU Nanolab, 2019.]] | |||
The alignment marks must be placed within the BSA windows. The Overview camera only shows the top side of the substrate, and cannot be used to locate the BSA marks. | The alignment marks must be placed within the BSA windows. The Overview camera only shows the top side of the substrate, and cannot be used to locate the BSA marks. | ||
{| cellpadding="2" style="border: 2px solid darkgray;" align=" | {| cellpadding="2" style="border: 2px solid darkgray;" align="center" | ||
! width="320" | | ! width="320" | | ||
! width="320" | | ! width="320" | | ||
! width="320" | | ! width="320" | | ||
|+'''Substrate view during backside alignment. Screenshots by Thomas Anhøj @ DTU Nanolab, 2019.''' | |+'''Substrate view during backside alignment. Screenshots by Thomas Anhøj @ DTU Nanolab, 2019.''' | ||
| Line 234: | Line 236: | ||
|- align="center" | |- align="center" | ||
| BSA marks positioned at x = | | BSA marks positioned at x = ±20 mm on a 2" wafer || BSA marks positioned at x = ±40 mm on a 100 mm wafer || BSA marks positioned at x = ±50 mm on a 150 mm wafer | ||
|} | |} | ||
| Line 242: | Line 244: | ||
==Advanced Field alignment (TSA)== | ==Advanced Field alignment (TSA)== | ||
'''Overlay accuracy (spec):''' 0. | '''Overlay accuracy (spec):''' 0.25 µm (5x5 mm<sup>2</sup> area) | ||
Shift, rotation, scaling, and shearing is determined and set by global alignment marks. The shift is corrected by automatic alignment to one mark in each field (chip). | Shift, rotation, scaling, and shearing is determined and set by global alignment marks. The shift is corrected by automatic alignment to one mark in each field (chip). | ||
| Line 264: | Line 266: | ||
(Jehem Feb 2020) | (Jehem Feb 2020) | ||
|'''X''' | |'''X''' | ||
| | | 100 ±55 | ||
| | | 106 ±55 | ||
|- | |- | ||
|-style="background:WhiteSmoke; color:black" | |-style="background:WhiteSmoke; color:black" | ||
|'''Y''' | |'''Y''' | ||
| | | 100 ±56 | ||
| | | 104 ±56 | ||
|} | |} | ||
<br clear="all" /> | <br clear="all" /> | ||