Effect of target processing on CoCrPtTa thin-film media

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M. Bartholomeusz and M. Tsai Heraeus MTD, Chandler, Arizona 85226 (Received 6 January 2000; accepted 13 September 2000)

The ensuing paper summarizes an investigation on the effect of target microstructural morphology on resultant sputter deposited media magnetic performance. Significant differences in media magnetic coercivity were obtained from Co–Cr–Pt–Ta targets possessing the same chemistry, sputtered under identical conditions, but possessing different microstructural phase and crystallographic texture characteristics. This result was most likely caused by the difference in sputter yields for the Ta-containing phases in the two distinct target microstructures. Results support enhanced chromium segregation yielding a decrease in the intergranuler exchange energy field for the deposited thin films.

I. INTRODUCTION

Magnetron sputter processing has long been the dominant technique for recording media production based in terms of film quality and cost effectiveness. In pursuit of improved recording performance, scientists have sought to understand the role of process environment on typical magnetic thin film structures. While many reports have revealed important effects of vacuum level and microcontamination,1,2 the role of sputter target microstructure has been largely ignored. Over the past several years, empirical observations by the authors have revealed that the microstructure and processing of target materials can noticeably impact the properties of resultant thin-film media. The multitude of interrelated factors involved in the physical vapor deposition (PVD) formation of media storage devices renders decoupling the target/media property and process effects rather complex. These factors include the following: (i) the dependence of atomic ejection on target material phase(s) packing density and crystallography; (ii) the relatively small mean free path of ejected atoms compared with the deposition distance at current operative pressures; (iii) the prevalence of complex shaped target erosion grooves; (iv) the relative geometries of the magnetron, target, and media system. The manifestation and magnitude of the target/media effects can vary considerably on the basis of the application, sputter process tool, and alloy set utilized. CoCrPt(Ta,B,Nb,W,X) alloys are thermodynamically constrained to exhibit complex multiphasic microstructures depending on the specific composition. In bulk a) b)

Present address: Seagate RMO, Fremont, CA 94538. Present address: Hambrecht & Quist, San Francisco, CA 94107. J. Mater. Res., Vol. 15, No. 12, Dec 2000

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form, the Co matrix is allotropic and exhibits both FCC and HCP crystallographies. Other phases formed via the addition of elements such as Ta, B, Nb, and W are more complex with significantly reduced packing densities. Crystallite grain sizes of the various phases can vary from submicron to several hundred microns. Depending on the target material-processing route selected, a variety of crystallographic textures, diff

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