纳米压印脱模坍塌及掩模板拓扑结构图形转移影响研究

发布时间：2019-05-15 04:09

【摘要】：随着微电子技术应用领域的不断扩展,硅技术时代的半导体制备工艺种类越来越多。图形转移是微纳制造的最主要核心,纳米压印工艺相比传统光刻工艺避免了在小尺寸应用上的曝光波长衍射的限制,并具有工艺简单、分辨率高、低成本和高产率等优点,自被提出以来而备受关注并得到蓬勃发展,成为国际半导体技术蓝图多年来一直推荐的半导体图形转移支撑技术之一,目前已应用于各个领域的微纳结构图形制造。纳米压印工艺根据使用的掩模板、介质流体、施压方式等不同有很多分类方式。金属直接压印不需要刻蚀溶脱和金属再淀积的繁琐工艺,用于金属微纳图形的制备具有显著的优势。目前金属直接压印技术主要可分为三种,对于不同工艺需求各有优缺点。金属纳米粒子假塑性流体纳米压印是一种新发展工艺,具有压印时间短、掩模板图案间隙填充度高、压印图形线条无气泡等优点。脱模工艺是纳米压印流程中关键的一步,由于金属纳米粒子假塑性流体具有剪切变稀的性质,脱模过程中压印微结构图形顶部存在坍塌的可能,并通过软件仿真证实了这一推论。微结构体坍塌将严重影响转移图形的保真度甚至分辨率,具有极大的危害。通过脱模完成瞬间微结构图形受力分析,得出微结构体不坍塌的临界粘度,当微结构体粘度小于临界粘度时微结构体将坍塌。而影响临界粘度的参数有金属纳米粒子假塑性流体的稠度系数、流变指数和表面张力系数,临界粘度随稠度系数、流变指数的增加而增加,随表面张力系数的增加而减小。由于金属纳米粒子假塑性流体的粘度在脱模过程中是由大变小,临界粘度越小微结构体越不容易坍塌。另外脱模速度越大,坍塌体粘度变小的程度越大。因此为使微结构体不坍塌应采用小稠度系数、小流变指数和大表面张力系数的金属纳米粒子假塑性流体,并降低脱模速度。除了介质流体,掩模板是纳米压印工艺中影响转移图形形貌的另一关键因素。但由于制备掩模板材质的结构特性和工艺局限,出现一些掩模板拓扑结构,如梯形、倒梯形、锯齿形间隙结构。通过分析纳米压印工艺的初始压强、压印速度及掩模板图案间隙填充度,得知初始压强与掩模板侧壁倾斜角度α和掩模板底部间隙的周长面积比成正比;而压印速度随α的增大而增大,随掩模板的深宽比的增大而减小;掩模板图案间隙填充高度与掩模板对准时所处环境的气体压强及掩模板图案间隙体积大小相关。通过软件仿真假塑性流体对拓扑掩模板结构间隙的填充过程,并与理想掩模板作对比得知梯形掩模板结构下的假塑性流体粘度变化梯度最利于掩模板图案间隙的填充而较易实现理想微纳结构图形的转化,而倒梯形掩模板结构压印的图形效果最差。
[Abstract]:With the continuous expansion of the application field of microelectronics technology, there are more and more kinds of semiconductor preparation processes in the era of silicon technology. Graphic transfer is the most important core of micro-nano manufacturing. Compared with the traditional lithography process, nano-imprinting process avoids the limitation of exposure wavelength diffraction in small size applications, and has the advantages of simple process, high resolution, low cost and high yield. Since it was put forward, it has attracted much attention and has been vigorously developed, and has become one of the semiconductor graphics transfer support technologies recommended by the international semiconductor technology blueprint for many years. It has been used in micro-nano structure graphics manufacturing in various fields. There are many classification methods according to the mask, medium fluid, pressure mode and so on. Metal direct imprinting does not need the tedious process of etch dissolution and metal re-deposition, so it has remarkable advantages in the preparation of metal micro-nano graphics. At present, metal direct imprinting technology can be divided into three kinds, which have their own advantages and disadvantages for different process requirements. Metal nanoparticles pseudo-plastic fluid nano-imprinting is a new development technology, which has the advantages of short imprinting time, high filling degree of mask pattern gap, no bubbles in imprint graphic lines and so on. Demoulding process is a key step in the process of nano-imprinting. Because the pseudoplastic fluid of metal nanoparticles has the property of shear thinning, it is possible that the top of imprint microstructure may collapse in the process of demoulding. This inference is confirmed by software simulation. The collapse of microstructure will seriously affect the fidelity and even resolution of the transfer pattern, which is of great harm. Through the stress analysis of the instantaneous microstructure figure, it is concluded that the critical viscosity of the microstructure does not collapse, and when the viscosity of the microstructure is less than the critical viscosity, the microstructure will collapse. The parameters affecting the critical viscosity are the consistency coefficient, the flow index and the surface tension coefficient of the pseudoplastic fluid of metal nanoparticles. The critical viscosity increases with the increase of the consistency coefficient and the flow index, and decreases with the increase of the surface tension coefficient. Because the viscosity of metal nanoparticles pseudo-plastic fluid changes from large to small in the process of demoulding, the smaller the critical viscosity is, the less likely the microstructure is to collapse. In addition, the higher the demoulding speed, the greater the viscosity of the collapse becomes smaller. Therefore, in order to make the microstructure not collapse, the pseudo-plastic fluid of metal nanoparticles with small consistency coefficient, small flow index and large surface tension coefficient should be used, and the demoulding speed should be reduced. In addition to dielectric fluid, mask is another key factor affecting the morphology of transfer pattern in nano-imprint process. However, due to the structural characteristics and process limitations of mask materials, there are some mask topologies, such as ladder, inverted ladder and sawtooth gap structure. By analyzing the initial pressure, imprint speed and filling degree of mask pattern gap, it is found that the initial pressure is proportional to the inclination angle 伪 of the side wall of the mask and the perimeter area ratio of the gap at the bottom of the mask. However, the imprinting speed increases with the increase of 伪 and decreases with the increase of the aspect ratio of the mask, and the filling height of the mask pattern gap is related to the gas pressure of the mask to the punctual environment and the volume of the mask pattern gap. The filling process of topological mask structure gap by pseudo-plastic fluid is simulated by software. Compared with the ideal mask, it is found that the variation gradient of pseudoplastic fluid viscosity under the ladder mask structure is most beneficial to the filling of the pattern gap of the mask, and it is easier to realize the transformation of the ideal micro-nano structure figure. However, the graphic effect of inverted ladder mask structure imprint is the worst.
【学位授予单位】：郑州大学
【学位级别】：硕士
【学位授予年份】：2015
【分类号】：TN305

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