Pellicle beamsplitters are very thin, lightweight polymer membranes stretched and bonded over a flat aluminum frame. Due to the thinness of the membrane, images from secondary reflections are eliminated. In addition to this feature, pellicles technology is resistant to mechanical shock and climate variations, and also has multiple wavelength versatility. These are features that systems requiring beamsplitters may want to take advantage of, so to make it easier, pellicle beamsplitters include mounting holes underneath the frame for easier integration.
High quality pellicles can be either uncoated or coated to produce a range of reflections necessary for various applications. Uncoated, high quality pellicles have a reflectivity of approximately 8 percent, and work well for applications, such as beam sampling. As opposed to uncoated pellicles technology, coated high quality pellicles produce equal reflectivity and transmission over a wide percentage of reflections.
While high quality pellicles do offer a lot of benefits for semiconductor manufacturing processes, they are a delicate technology that does come with some downfalls. The following are a couple of things that should be taken into consideration in regards to integration of pellicle beamsplitters:
- Vibrations. While the thinness of pellicle beams offers many benefits for semiconductor processes, it can also cause a negative effect on the membrane. Thin pellicle beams can easily vibrate during any number of processes, causing the membrane to ring. To avoid any vibration issues, you should use posts or blocks to mount pellicles to an optical table.
- Interference. The thinness of the membranes can cause monochromatic interference between the surfaces, which produces fringes in the beam. The thinness also leads to sinusoidal oscillation in the splitting ratio based on the wavelength, which can change quickly creating significant effects.
- Delicate. The polymer membranes are stretched over the aluminum frame, producing a very delicate surface. For this reason, pellicle beamsplitters cannot be touched as the optic can easily be destroyed.
As long as you are aware of the constraints of pellicle beamsplitters, such as those listed above, and work carefully within those constraints, you can receive the benefits of using high quality pellicles in your semiconductor manufacturing processes.
If you are interested in using pellicles in your semiconductor operations, Shin-Etsu MicroSi offers quality pellicles that can be used for processes, such as photomasking. With our technological expertise developed through the manufacturing of electronic materials, we have developed pellicles of various grades for a variety of applications. For more information on our products, please call Shin-Etsu MicroSi at (480) 893-8898 or contact us online.