Fabrication of Discrete Track Media with Patterned Servo-areas and Tracks on Disk Substrate
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1032-I05-07
Fabrication of Discrete Track Media with Patterned Servo-areas and Tracks on Disk Substrate Yuko Tsuchiya, Kenichi Ito, Chiseki Haginoya, and Yoshiyuki Hirayama Magnetic Drive Technology Research Department, Hitachi, Ltd., Central Research Laboratory, 1-280, Higashi-Koigakubo, Kokubunji, 1858601, Japan ABSTRACT Discrete track media (DTM) with patterned servo-areas and recording tracks were fabricated on disk substrates in a two-step RIE process, creating a fine pattern transfer from an imprinted resist mask to a substrate surface without variations in groove depth. The fabricated DTM with perpendicular magnetic recording layers flew stably during read out signal detection. INTRODUCTION Patterned media recording is now regarded as next-generation technology [1] and is currently being used with perpendicular magnetic recording (PMR) to achieve higher magnetic recording densities. In the broad sense, there are two types of patterned media: bit-patterned media (BPM) [2, 3] and discrete track media (DTM) [4~6]. One of the more important processes in patterned media fabrication is transferring nano-patterns from a resist layer to a substrate or a metal film by etching or milling. The resist patterns are fabricated by photolithography, EB lithography, and nano-imprinting lithography (NIL). In the mass-production patterned media stage, efficient and stable resist pattern transfer is required even though there are inhomogeneous properties in resist thickness. The purposes of this study are to fabricate DTM using inhomogeneous resist patterns as etching masks and to resolve the issue of nano-pattern transfer. We investigated a two-step reactive ion etching (RIE) process that transfers inhomogeneous imprinted resist patterns to a SiN layer on a glass disk. After the pattern was transferred to the SiN layer, we fabricated DTM with perpendicular magnetic recording layers on the SiN layer and tested its flyability using a spin-stand. EXPERIMENT Resist patterns obtained by NIL contained servo and track patterns of about 240 nm in track pitch were imprinted on a 100-nm-thick SiN layer on a 2.5-inch glass disk. A dry etching equipment (an RIE-10NR from SAMCO) was used to transfer resist patterns to the SiN layer. O2 and CHF3 were used as etching gas. We used an RIE-10NR (SAMCO) as our dry etching equipment and CHF3 and O2 as our etching gases. A scanning electron microscope (an S-4200 from HITACHI) was used to observe cross-sectional views of substrates fabricated by several DTM fabrication processes. A spin-stand with an acoustic emission-sensing element was used to test for flyability and to obtain DTM read out signals.
DISCUSSION Figure 1 is a schematic of a DTM fabricated using imprinted pattern transfer in a twostep RIE process. After the NIL process, a base layer (BL) remains at the bottom of the imprinted resist patterns on the substrate, as shown in Figure 1(a). The variation in BL thickness caused no uniformity in the etch depth on the SiN layer. In the first RIE step, we removed the BL using a reactive ion e
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