A continuing goal of integrated circuit fabrication is to decrease the dimensions thereof. Integrated circuit dimensions can be decreased by reducing the dimensions and spacing of the constituent features or structures. For example, by decreasing the dimensions and spacing of semiconductor features (e.g., storage capacitors, access transistors, access lines) of a memory device, the overall dimensions of the memory device may be decreased while maintaining or increasing the storage capacity of the memory device.
As the dimensions and spacing of semiconductor device features become smaller, conventional lithographic processes become increasingly more difficult and expensive to conduct. Therefore, significant challenges are encountered in the fabrication of nanostructures, particularly structures having a feature dimension (e.g., critical dimension) less than a resolution limit of conventional photolithography techniques (currently about 50 nm). It is possible to fabricate semiconductor structures of such feature dimensions using a conventional lithographic process, such as shadow mask lithography and e-beam lithography. However, use of such processes is limited because the exposure tools are extremely expensive or extremely slow and, further, may not be amenable to formation of structures having dimensions of less than 50 nm.
The development of new processes, as well as materials useful in such processes, is of increasing importance to make the fabrication of small-scale devices easier, less expensive, and more versatile. One example of a method of fabricating small-scale devices that addresses some of the drawbacks of conventional lithographic techniques is self-assembled block copolymer lithography.
Although self-assembled block copolymer lithography is useful for fabrication of semiconductor structures having dimensions of less than 50 nm, there are still problems that must be addressed. Self-assembled block copolymer materials may not provide nanostructures exhibiting sufficiently low defect levels.
Self-assembled nucleic acids have been researched for forming semiconductor devices. The specificity of complementary base pairing in nucleic acids provides self-assembled nucleic acids that may be used for self-assembled nucleic acid lithography processes.