| Research Abstract |
In recent years, micro-and nanofabrication techniques have become important in realizing electronic microdevices and in fabricating quantum devices. In the lithography process, in particular, the resist is regarded as an important mask material for both dry and wet etching processes. As the important problems that needs to be solved, various properties such as pattern collapse, line edge roughness, pattern defect and nanoscale bubbles have been recognized. Understanding these fundamental properties is of crucial importance for development not only microelectronic devices but devices in nanometer scale. In this study, as the resist processing, resist pattern adhesion, Young's modulus estimation, surface hardened layer analysis by tip indentation, manipulation of polymer aggregate and nanobubble analysis for immersion lithography are discussed by using the AFM.
(1) By the tip indentation technique, the condensation property of resist pattern surface can be analyzed quantitatively. The fun
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damental property of tip indentation depending on measurement position is investigated. The pattern edge affects strongly on indenting property of a micro tip. The indenting position should be set apart from the pattern edge at least 80nm. As the representative value of surface condensation, the indentation slope value of micro tip is employed. In the indenting curve, it is clearly indicated that a certain hardened thin layer is formed on the resist surface after pattern development. These results are enhanced by the various hardening processes such as electron beam (EB) irradiation and thermal curing. One can safely state that the surface cohesion property of resist pattern can be analyzed by the tip indentation method.
(2) Condensation properties of polymer aggregate are characterized by the typical AFM techniques, collapse, separation, indentation and manipulation. The association of polymer aggregate of approximately 50nm size is clearly observed in the resist surface. By the separation technique, the cohesive property of associated polymer aggregate is analyzed. It is clearly indicated that two associated polymer aggregates are separated into 13 pieces of aggregates. The interaction force among polymer aggregates can be analyzed based on Derjaguin approximation. By the tip indentation, the condensation of polymer aggregate accompanying a certain vacancy can be analyzed. The polymer aggregate of 20tun size can be manipulated and rearranged in linear position. One can safely state that polymer aggregate is regarded as a granular solid material which has a certain cohesive strength. The condensation model of polymer aggregate accompanying with vacancy resist is introduced.
(3) By using atomic force microscope (AFM), a nanoscale bubble (NB) formed on a film surface of-ArF excimer resist can be imaged clearly in deionized water. The diameter and height of NBs observed are approximately 40-100nm and 3-8nm, respectively. By approaching the AFM tip onto the NBs, the repulsive force can be detected but the attractive force on the resist surface. The interaction analysis between the AFM tip and the ArF excimer resist surface is effective in order to identify the NBs and to distinguish from solid particles. These phenomena can be discussed on the basis of Lifshitz theory. The separation procedure of the NB is accomplished with the AFM tip. The analysis of NB nature is discussed on the point of the immersion lithography.
As the resist processing in nanometer scale, various serious problems are discussed by using the AFM. One can safely state that the AFM has a meaningful potential for analyzing the resist processing. This technique will prove useful in other fields, for example, for the condensation control of microparticles and the structural design of micromachines and so on. Less
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