Block Copolymer Nanolithography

• Author / Creator

  Jin,Cong

• The development of photolithography has been the main driving force of the semiconductor industry to keep pace with Moore’s Law for over five decades. The theoretical resolution limit of state-of-the-art 193 nm photolithography is about 36 nm (half pitch). By integrating multiple patterning technologies, the semiconductor industry has now successfully extended the resolution of photolithography to 14 nm half-pitch. Innovative and cost-effective patterning technologies need to be developed for sub-14 nm patterning. Directed self-assembly, referred to as DSA, of block copolymers is a patterning technology that is able to form 5 - 200 nm patterns spontaneously, at low cost. It is one of two potential solutions for low cost sub- 20 nm half-pitch lines and spaces patterning, in 2017, and one of four potential solutions for sub-14 nm half-pitch patterns by 2019, according to the International Technology Roadmap for Semiconductors, 2015 edition. Moreover, directed self- assembly of block copolymers has already been demonstrated on 300 mm wafers, and a fully automatic lithography system for finFET, bit patterned media, and contact hole applications. This thesis is divided into two parts. The first part deals with understanding the annealing process of block copolymer self-assembly, the critical step in which the actual nanoscale phase segregation takes place. First, the mechanism of microwave annealing of block copolymers on silicon was studied and elucidated. In this work, it was discovered that the semiconductor itself is the source of heating and not the polymer, contrary to the reports in the literature. In the next phase of this part of thesis, a new solvent flow annealing system with in situ laser reflectometry and an optical microscope was developed. By integrating a feedback loop, this system is able to control the swelling/deswelling rate, degree of swelling, and annealing time to accurately control the annealing conditions to eliminate the formation of dewetting or double layers, leading to much improved reproducibility. Multi-step swelling and deswelling in an individual process run have also been demonstrated. In the second part of the thesis, the concept of density multiplication was examined. Density doubled and tripled dot patterns are studied, as a means of creating more complex patterns that could be attained with single step annealing. The quality of the resulting dot patterns was analyzed and a theoretical model was developed to predict the quality of density doubled and tripled patterns using only two parameters obtained from single layer patterns. As an intriguing extension of this work, the orientational relationship between sequentially deposited BCP dot patterns with different pitches was investigated. From large scale helium-ion microscope images, it was found that preferential orientations, or Moiré patterns, are formed, which is determined by the pitch ratio and dot size.

• Subjects / Keywords

  • Lithography
  • Block copolymers
  • Self-Assembly

• Graduation date

  Fall 2017

• Type of Item

  Thesis

• Degree

  Doctor of Philosophy

• DOI

  https://doi.org/10.7939/R35Q4S104

• License

  This thesis is made available by the University of Alberta Libraries with permission of the copyright owner solely for non-commercial purposes. This thesis, or any portion thereof, may not otherwise be copied or reproduced without the written consent of the copyright owner, except to the extent permitted by Canadian copyright law.