Research :: ECE :: UD



Chemical Imprint Lithography

Dennis Prather

Chemical imprint lithography is similar to the well-established nano-imprint lithography. However, there is an important difference. In chemical lithography, before the physical structure is obtained in the resist, latent image is first formed. This property makes the chemical lithography process similar to photolithography where imagewise exposure to ultraviolet radiation results in forming latent image in the resist, which is subsequently developed to obtain the physical structure. This distinction, while it introduces an extra step as compared to the nano-imprint lithography, makes the proposed method more flexible and also relaxes some of the requirements placed on the template. For example, for nano-imprint to reproduce pattern with high fidelity, it is necessary that the resist penetrate all the crevices of the template, which is accomplished by either increasing the temperature above the glass transition of the resist and applying pressure or by using a photo-curable resin in a step-and-flash procedure. In the case of chemical imprint, only the contact of the resist with the top-most surface of the template is required. This allows more flexibility in the choice of material for the template and the substrate since neither has to be transparent to UV as opposed to the case of step-and-flash method, nor do the substrate and the template necessarily have to have matched thermal expansion coefficients as is necessary for the method relying on raising the temperature to bring the resist above the resist glass transition. Yet, chemical lithography has all the advantages of nano-imprint including the possibility of patterning curved surfaces. Indeed, it appears that whatever material/structure is possible in nano-imprint lithography, it should be possible in chemical imprint lithography (but not vice versa). Also, the template developed for nano-imprint can be used for chemical imprint.

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