The demolding process in nanoimprint lithography is studied using molecular dynamics simulations. The difference in the mold separation behaviors between molecular dynamics and continuous mechanics simulations is shown, and the effect that the molecular size of the polymer resist has upon the demolding force is explained from the perspective of the molecular behavior. Depending upon the correlation between the type of resist molecule and the mold cavity size, the demolding force originates from the molecular flow, molecular stretching, or the friction between the resist and mold sidewall. When the molecular size is comparable to the cavity size, the resist is deformed by molecular stretching and the demolding force is at its largest.

Template release in nanoimprint lithography was computationally studied. The impact of resist shrinkage on template release load is described. The resist shrinkage affects the state of the boundary status between resist and template, and is a factor that influences whether the resist adheres to or separates from the template. When the resist fully adheres to the template, the release load increases due to residual stress as the residual layer becomes thinner. This is because compressive stress at the residual layer is induced by resist shrinkage in the pattern cavity. In addition, the release load increases when the resist partially adheres to the template, a consequence of the decrease in interfacial area. This is because the decrement of interface area due to concentration of stress.

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A template release force is one of the important factors for a low-defect template release process in nanoimprint lithography. In this work, the origin of the template release force is investigated by computational study of side wall quality characteristics such as the critical separation forces between the template and the resist interface, and the slope angle of the side wall. The critical separation forces in the normal and shear directions, which are related to adhesion and friction characteristics are experimentally evaluated for the computational study. The computational results show that the shear separation force, which is related to the static friction between the template surface and the resist, strongly affects the release force characteristics. On the other hand, the side wall slope angle also affects the template release force above the critical side wall slope angle. The computational results show good agreement with experimental results.

In earlier works, the authors observed that the template stiffness played a role in the success of the demolding step in nanoimprint lithography. They established that the release force increases with the template stiffness whereas the induced stress in the resist follows an opposite trend, decreasing with an increase in the template stiffness. However, the results obtained were quantitatively inconsistent with the experimental results; therefore, the authors set up a new simulation model in order to obtain realistic values. They successfully demonstrated that the bending of the template, depending on its stiffness, is a key factor to be optimized in order to reduce the defect formation during the process.