Patterning Tasks - Spring 2025

This page documents the current work being done on patterning systems and the goals of that work. If you want to start a new project or research related to patterning, add it here so we can keep track of what's being done!

Task	Metrics	Timeline	Task Lead
Backlash Improvements	<2µm backlash	Before February	Carson Swoveland (@_salix)
Absolute Positioning	<5µm accuracy+precision	End of semester	Carson Swoveland (@_salix)
Cost Reductions	Stepper price <$2000	End of semester	Joel Gonzalez Sky Bailey

Backlash Improvements

The current design for stepper v2 involves having the micrometer-motor couplers slide along the shaft of the motor. This leads to wear in the 3D print and prevents the use of a rigid connection, leading to the coupler eventually becoming loose. This can cause ~30º of backlash in the rotation, which corresponds to about 15 microns.

Mounting the motors on the stage that they move, rather than on a (relatively) fixed stage allows for using a rigid coupling without significant modification to other parts of the design. These fixes should be applicable to any fab with an existing v2 stage. This is a major enabler for Absolute Positioning.

This may require redesigning the stage to be mounted upright, or the stage to be turned sideways.

The WIP CAD files are available on Onshape and more information can be found on Discord.

Absolute Positioning

In order to enable many features like automated or computer-assisted patterning, it must be possible to consistently refer to positions on a die. This requires being able to determine the absolute position of the stage.

There has been some experimentation with using inductive sensors for determining the stage position, though calibrating and mounting the sensors is difficult. The accuracy for a properly calibrated and mounted sensor may be sufficient, though. (TODO: Link inductive sensor notes once those get merged)

Currently, a design using simple limit switches is being developed (though blocked on Backlash Improvements).

Cost Reductions

The current optics system is not physically capable of handling the projector's resolution, i.e. some amount of detail is wasted in the optics system. This means that we can use a lower resolution (read: cheaper) projector.

There are two main items that we are looking at replacing to reduce our cost. The first is the projector itself, as we are using an expensive 4K projector that does not appear to yield much benefit in patterning resolution. We are considering going from the DLPDLCR471TPEVM ($999) to the DLPDLCR230NPEVM ($299).

The second item that we are looking at is our camera. We are currently using a high-resolution FLIR camera ($700) which, again, is excessive for our application. We believe that we can find a similar C-mount camera for less than $200.

Lastly, there are other components in the optics system itself that we believe can be modified/replaced to further reduce the cost. The ThorLabs components cost at least $700, but many of those parts such as tubes and flanges could be replaced by 3D-printed parts. We will have to test to see if heat generated by the stepper becomes an issue, but this would provide a significant reduction in cost.

Altogether, we believe that we can bring the cost of the stepper below $2000 - perhaps even $1500.