Koichi Wago

Integration of nanoimprint lithography with block copolymer directed self-assembly for fabrication of a sub-20 nm template for bit-patterned media

We propose a novel strategy to integrate the nanoimprint lithography (NIL) technique with directed self-assembly (DSA) of block copolymer (BCP) for providing a robust, high-yield, and low-defect-density path to sub-20 nm dense patterning. Through this new NIL-DSA method, UV nanoimprint resist is used as the DSA copolymer pre-pattern to expedite the DSA process. This method was successfully used to fabricate a 1.0 Td in(-2) servo-integrated nanoimprint template for bit-patterned media (BPM) application. The fabricated template was used for UV-cure NIL on a 2.5-inch disk. The imprint resist patterns were further transferred into the underlying CoCrPt magnetic layer through a carbon hard mask using ion beam etching. The successful integration of the NIL technique with the DSA process provides us with a new route to BPM nanofabrication, which includes the following three major advantages: (1) a simpler and faster way to implement DSA for high-density BPM patterning; (2) a novel method for fabricating a high-quality dot pattern template through an iterative imprint-DSA-template procedure; and (3) an uncomplicated integration scheme for implementing non-periodic servo features with BCP patterns, thus accelerating the transition of moving the DSA technique from laboratory research to the BPM manufacturing environment.

Servo-Integrated Patterned Media by Hybrid Directed Self-Assembly

A hybrid directed self-assembly approach is developed to fabricate unprecedented servo-integrated bit-patterned media templates, by combining sphere-forming block copolymers with 5 teradot/in.(2) resolution capability, nanoimprint and optical lithography with overlay control. Nanoimprint generates prepatterns with different dimensions in the data field and servo field, respectively, and optical lithography controls the selective self-assembly process in either field. Two distinct directed self-assembly techniques, low-topography graphoepitaxy and high-topography graphoepitaxy, are elegantly integrated to create bit-patterned templates with flexible embedded servo information. Spinstand magnetic test at 1 teradot/in.(2) shows a low bit error rate of 10(-2.43), indicating fully functioning bit-patterned media and great potential of this approach for fabricating future ultra-high-density magnetic storage media.

Magnetic Damage and Performance Recovery in Discrete Track Media

Discrete track media (DTM) has been widely studied recently as a solution to achieve high track density for hard disk drives. In DTM, nano-patterning process is used to isolate magnetic tracks. During the fabrication process, magnetic damage occurs in the resist striping process using O2 plasma. The on-track SNR of DTM degrades by ~ 2-3 dB. We used Ar IBE cleaning process to remove the oxide layer. The removal process induces unexpected magnetic property change. Nevertheless, this process can still improve the SNR significantly. However, the cleaning step also causes track corner rounding, and results in a faster SNR roll-off at high linear densities. Several methods for further improving DTM performance are discussed in this paper, including using a protective cap layer and media magnetic design reoptimization.

P1–15: Patterning of high density magnetic nanodot arrays by imprint lithography with hole tone template

Nanoimprint Lithography presents unique opportunities for high density patterning due to its advantages of sub-10nm resolution capability and high throughput. Imprint and pattern transfer with Pillar tone template were widely studies recently. However, there are several critical issues that still remain very challenging, including fabrication of pillar templates and pattern reverse from imprint holes to nano dots array at high density. In this Paper, we will demostrated the feasibility of imprint with hole tone template and its application in high-density nanodot array patterning. The authors have successfully demonstrated hole-tone template fabrication process and pattern transfer results with imprint pillar. The profile of imprint resist pillar was analyzed with cross-section scanning electron microscope(SEM). Pattern was transferred to underneath Co alloy thin films by ion beam milling into aligned dots with pitch of 50nm. Magnetic dots array were investigated with SEM and M-H loop measurement. Strong perpendicular anisotropy was induced by the patterning process. Magnetic measurement reveals through ion milling process, magnetization reversal was changed from domain wall pinning dominated to Stoner-Wohlfarth coherent rotation dominated. Coercivity and Remanence change during Ion beam etching were discussed. Extendibility to ultra-high density patterning is also investigated.

SEM CD metrology on nanoimprint template: an analytical SEM approach

Critical dimension metrology is the most needed feedback in nanofabrication and automatic CDSEM-based methods are by far the industrial standard for its well-established methodology and ease of programming and flexibility in measurement setup and operation. The dimensional measurements from SEMs consist of two steps, the first being the pixel based electron emission signal intensity profile generation and the second being the algorithm treatment on the generated intensity profile for the dimension determination. However, SEM metrology involves uncertainty of the measurement in the signal processing step, because the SEM signal formation is an extremely complex process depending on the pattern geometry, materials, detector setup, and beam voltage. Analytical SEMs are even less optimized for the task of quantitative metrology, especially at the CD ranging below 100 nm. In this work, we used an analytical SEM for CD metrology applications on quartz nanoimprint template from the perspective that only analytical SEM is accessible. The machine was tuned and beam characterization was done first to find the best reasonable condition for consistent manual operation using BEAMETR beam measurement pattern and software. The optimized beam condition set was then used for image collection on pitch pattern quartz template and the measurements were done using regular imaging processing and physical model based processing tool myCD. In order to discuss the spot size on the scan signal and the resulting influence on CD measurements, we used CHARIOT simulation software for simulated intensity profile as demonstration. The quartz template was then measured through a mask CDSEM for final data comparison. Selected sites were cross sectioned to reveal profile information as metrology comparison reference. Through our exercise, the metrology capability and fundamental limitation of analytical SEM operation with regular imaging processing was identified and the improvement using the physical modeling imaging process was verified.