Nanoimprint Lithography (NIL) is a new and breakthrough micro-nano processing technology. It replicates the micro-nano structure patterns on the die onto the substrate coated with polymer materials through physical imprinting. Its core idea is similar to the ancient seal printing technique, but it achieves high-precision pattern replication at the nanoscale.

In the 1990s, the semiconductor industry accelerated the miniaturization process of chip manufacturing. Traditional optical lithography technology was limited by the diffraction limit of light, and the minimum feature size was difficult to break through the resolution limit. Although electron beam lithography could achieve a precision of less than 100 nanometers, its scanning processing efficiency was extremely low, and the equipment and process costs were high, which could not meet the requirements of large-scale mass production. At this critical juncture in technological development, nanoimprint technology emerged. Its core advantage is: by using die replication instead of beam scanning, nanoscale patterns can be imprinted onto the substrate in one go. This not only significantly reduces production costs but also achieves a resolution of less than 5nm.  

The essence of nanoimprint is graphic replication: By using a die with nanoscale patterns, precise pressure is applied to a substrate coated with photoresist to shape the photoresist layer according to the die's contour. After curing, the die is peeled off, leaving a complementary nanostructure on the substrate. According to different curing methods, it is mainly divided into types such as thermal nanoimprint (heating and softening the adhesive layer), UV nanoimprint (UV light curing the adhesive layer), and micro-contact printing (soft etching). The core process of nanoimprinting includes key links such as die preparation, imprinting adhesive coating, imprinting forming, demolding and post-treatment.

First of all, a die with the required nano-pattern (commonly known as a "seal" or "mold") should be made. The die material needs to be hard and durable (such as silicon or quartz, etc.), and its surface pattern is processed through high-precision techniques such as electron beam lithography or focused ion beam etching. Before using the prepared die for imprinting, the die and the substrate need to be aligned at the sub-nanometer level. Traditional mechanical positioning systems are limited by mechanical gaps and thermal drift, which may be difficult to meet the requirements.

The production of nanoimprint technology uses physical contact for graphic transfer. The die is pressed into the imprint adhesive (polymer layer) under certain pressure to fill the concave structures on the die. This can achieve a very high resolution, with the minimum resolution being less than 5 nanometers. For instance, in hot embossing, the contact pressure between the die and the base needs to be evenly distributed; otherwise, it may lead to uneven thickness of the adhesive layer, and the pattern may appear uneven.

After the polymer gets solid, carefully separate the die from the substrate. At this point, a nanostructure pattern complementary to the template is formed on the polymer layer. During demolding, the adhesion force between the template and the solid adhesive layer can easily cause the nanostructure to tear, which requires precise control. For example, the demolding speed and displacement accuracy can be dynamically adjusted at the micrometer level.