The fabrication of a photomask requires several steps. We will describe each one of them in the following section.
The pattern information is created by the researcher in a drawing package, often in AutoCAD or other suitable software packages such as L-Edit. The data is sent to the manufacturer by a variety of methods, such as email or ftp. This data is then processed into internal CAD format (Gerber) and transferred to a lithography tool which then exposes the design onto the photomask substrate. We use the same equipment and exposure process for both glass & film photomasks.
Once the manufacturing process is finished, the mask is cleaned and inspected, ready to be shipped to the laboratory for fabrication of your microfluidic mold.
Mask data preparation (MDP) is the step that translates an intended set of designs and layers into a form that can be physically written by the photomask writer. Usually this involves processing complex polygons into a data format such as Gerber. Typically a design is delivered to photomask data preparation in DXF or GDSii format, and quite often the design needs re-formatting to fix drawing errors that have been created when constructing the design.
Data preparation is a crucial step in making a photomask – and incorrectly formatted designs are the number one factor for delays in manufacturing. Once the design has been formatted, a PDF checkplot is sent to the customer for approval before moving on to the next stage.
The imager is a flat bed, granite based system able to expose both glass and film substrates. It has a photohead, mounted onto a Y stage of the coordinate table.
The coordinate table transports the photohead to those areas of the mask where the relevant images are to be placed. A Z-axis controls the photohead depth, thus allowing for different material thicknesses to be used. A laser exposes short, high energy flashes of light, which are directed onto a modulating digital micromirror (DMD).
This matrix consists in a bank of tiny square mirrors that can be tilted electronically into one of two orientations. With the mirrors tilted in one orientation, the light from the mirror goes through the optical system to image the mask, in the other orientation the light is absorbed.
This matrix is then projected through a series of lenses and optically reduced onto the pre-sensitized material, giving a pixel size of 0.8µm. This configuration works like a darkroom enlarger where the matrix replaces the slide and the laser replaces the projection lamp.
The film or chrome plate acts like the photographic film. Each projected picture represents a small area of the whole mask. To get a complete image you have to add as many pictures (frames) as the photomask requires. The Y-motor moves the photohead continuously along the Y-axis of the plotter while a linear encoder tracks the position and triggers the next flash at the correct point.
The encoders then move the head one step over in the X direction, and the imaging process re-starts. Every frames are stitched together to give the overall photomask image.
The film is fed into the processor after imaging via a series of rollers, and undergoes some chemical changes through the development of the image. Development changes the exposed silver halide crystals into ‘black’ particles in the emulsion layer of the photomask.
The development times and temperatures are critical for maintaining the correct CD of the photomask, and the transportation of the film from one step to another needs to be finely tuned. Fresh chemicals are added to the tanks in pre-defined rates according to the mask size, and the chemistry is pumped and re-circulated through the tank to ensure correct dilution.
Fixation is the next chemical process of the photomask fabrication and is necessary to stop the development reactions and obtain a stable image. At this stage, the unexposed silver halide is washed out of the film photomask and the base dyes are cleared. Just like during development, the fixer is consumed during the process, and materials washed out of the film build up in the fixer tank. Fixer replenishment helps to counteract these processes.
Following adequate fixation, it is important to wash the film to remove residual processing chemicals and byproducts. Again, careful replenishment rates are set to ensure that the wash stage is clean and free of contaminates (which are washed to drain). The chemical and wash phases are complete and all that remains is to dry the film.
At this stage the most important factors are adequate drying of the film while maintaining good dimensional stability.
A turnkey offer to fabricate your su-8 mold and pdms chips
The photomasks go through a robust cleaning process before they are sent to final inspection. The benefit of using a glass based photomask is that they are much easier to clean – the glass and chrome surface can be treated with a variety of chemicals, with no detriment of the image or surface quality, whereas film photomasks are much more delicate and have to be treated with care.
Once the photomask has been processed and cleaned, we then have to inspect it for accuracy / quality / defects and flaws that can sometimes affect the final product. The inspection process includes a visual inspection, the measurement of an image coupon or similar, and a surface inspection.
Once an order is finalized, we package the photomask carefully and arrange dispatch directly to the customer. We ship by registered methods throughout the world, and you will be emailed your tracking number on dispatch of the photomask.
Email* I hereby agree than Elveflow uses my personal data
Do you want tips on how to best set up your microfluidic experiment? Do you need inspiration or a different angle to take on your specific problem? Well, we probably have an application note just for you, feel free to check them out!
Microfabrication techniques for a circular channel
In soft lithography, the fabrication of a mold, often made in SU-8, is required for replicating PDMS microfluidic structures.
Replicating PDMS-based structures first requires the fabrication of a SU-8 master mold that will serve as a patterned template for PDMS casting
How do you perform a successful SU-8 exposure? Here you will find the tips and tricks to do it.
How do you perform a successful photoresist baking? Here you will find the tips and tricks to do it.
How do you perform a successful spin coating? Here you will find the tips and tricks to do it.
The final PDMS layer thickness mainly depends of spin-coating speed and duration.
Here you can find a complete overview of a SU-8 mold fabrication process.
Here you can find a complete overview of a PDMS chip replication.
Unlike photolithography, soft lithography can process a wide range of elastomeric materials, i.e. mechanically soft materials.
A UV Lamp to expose your SU-8 photoresist. You will find here the relevant points to think about.
A plasma cleaner to bond your PDMS chip, you will find here the relevant points to think about.
A spin coater creates a thin layer of photoresist or PDMS, you will find here the relevant information about how to choose one.
You have the choice between glass or plastic photolithography mask, but how do you choose? here is some information to help you with the decision
A hot plate to bake your SU-8 photoresist, you will find here the relevant points to think about.
Get a quote
Name*
Email*
Message
Newsletter subscription
We will answer within 24 hours
By filling in your info you accept that we use your data.
Collaborations
Need customer support?
Serial Number of your product
Support Type AdviceHardware SupportSoftware Support
Subject*
I hereby agree that Elveflow uses my personal data Newsletter subscription
How can we help you?
Message I hereby agree that Elveflow uses my personal data Newsletter subscription