| With the expanding in the field of microstructure technology application, there is more kinds of semiconductor preparation process in the silicon technology times. Patterning transfer is the key of micro-nano manufacturing. Nanoimprint lithography avoids the restrictions which is the diffraction of exposure wavelength on the application in small size, and has simple process, high resolution, low cost and high yield, etc. Since it was proposed, nanoimprint lithography drew the attention and got vigorous development, and has been recommended to be one of semiconductor patterning transfer support technology for years by ITRS. Now it has been applied to various fields of micro- nano manufacturing.There are many kinds of classification according to the use of different mask, fluid medium and pressure in Nanoimprint lithography. Metal direct nanoimprint doesn’t need etching, lift-off and metal deposition process again, and shows obvious advantages in metal micro-nano structure manufacturing. Currently, metal direct nanoimprint can be divided into three main types, which each has advantages and disadvantages according to the demand for different transfer patterning. Nanoimprint lithography where pseudoplastic metal nanoparticle fluid(PMNF) is used as the medium is a novel process with short imprinting time, high filling degree for mask cavity, and no bubble patterning.Demolding is a critical step in nanoimprint lithography, the fluids in the top of patterning may slump during demolding, because the shear thinning nature of PMNF. And the inference is confirmed through software simulation. Slumping of microstructure that will seriously affect the fidelity even the resolution of transfer patterning has a great harm. Through the force analysis of microstructure at the end of demolding, the critical viscosity of non-slumping is obtained. And microstructure will slump when its viscosity is smaller than the critical viscosity. The parameters that affect the critical viscosity are consistency coefficient and rheological index and surface tension coefficient of PMNF. The critical viscosity increases with the increase of consistency coefficient or rheological index, decrease s with the increase of surface tension coefficient. The viscosity of PMNF is from large to small during demolding, the smaller the critical viscosity the microstructure is not easy to slump. In addition, the bigger demolding speed, the bigger degree of viscosity decrease of the slumping body. In a word, the process should take the PMNF with small consistency coefficient, small rheological index and big surface tension coefficient, and also decrease the demolding speed in order to avoid the microstructure slumping.In addition to the medium fluid, mask is another key factor which affect the morphology of transfer patterning in nanoimprint. But there are some mask topology microstructure, such as trapezoidal, inverted trapezoidal and zigzag cavity structure of mask, because of the structure characteristic of mask material and preparation process limitation. Through the analysis o f the initial pressure, imprinting speed and filling degree of mask cavity in nanoimprint lithography, the conclusions proved the initial pressure is proportional to sidewall tilt angle α and the ratio of circumference and area of mask cavity at the bottom, the imprinting speed increases with the increase of α, decreases with the increase of aspect ratio, the filling height of mask cavity is related to gas pressure of the environment where the mask is aligned on the substrate and the size of mask cavity volume.The filling process of topological mask cavity with pseudoplastic fluid is simulated by software. And the result is compared with ideal mask cavity, learned that the pseudoplastic fluid viscosity change gradient with trapezoidal cavity mask is the best for the filling to mask cavity. The patterning is easier to transform to be ideal micro- nano structure. On the contrary, the imprinting effect with inverted trapezoidal mask is the worst. |
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