AVS1997 Session MI+MR+AS+MS-WeA: Magnetic Recording Technology: Processing Issues

Wednesday, October 22, 1997 2:00 PM in Room J3

Wednesday Afternoon

Start	Invited?	Item
2:00 PM	Invited	MI+MR+AS+MS-WeA-1 Sigma's and Cpk's - Process Challenges in Thin-Film Disk Technology I.L. Sanders, K.E. Johnson, T.W. Wu (Hyundai Electronics America) Storage densities in magnetic disk drives are projected to reach 8-10 gigabits/in2 by the year 2000. If current trends prevail, the data storage capacity of a single 95mm disk platter will approach 10 Gbytes, while a two-disk 65mm drive could achieve a capacity of over 12 Gbytes. These density improvements represent an increase of roughly one order of magnitude over today's technology. Although it is generally accepted that the rigid disk industry can provide the necessary technology enhancements through an evolutionary approach to disk design, these requirements present a significant technological challenge for engineers, if manufacturing yields and throughputs are to be maintained at current levels. For example, the magnetic film thickness of the storage medium itself is likely to be reduced to the 100Å range, while the protective overcoat layer will be approximately 50Å; the surface roughness of the disk substrate will need to be better than 2Å. Stringent tolerances on these parameters will force the development of more robust material systems and improved processing techniques. In addition, a more sophisticated approach to process monitoring and process controls will almost certainly be needed to meet the quality and reliability requirements for adequate performance in the disk drive. We will consider these challenges in the context of manufacturing constraints for high volume, thin-film disk production and provide an outlook for the future of film disk technology.
2:40 PM		MI+MR+AS+MS-WeA-3 Interfacial Interactions of Perfluoropolyether Lubricants with Amorphous Carbon Surfaces G.W. Tyndall (IBM Almaden Research Center); R.J. Waltman, J. Castaneda (IBM Storage Systems Division) The interactions of thin films (2 - 40 A) of various perfluoropolyether lubricants with amorphous carbon were studied. The surface energy of these films were determined as a function of polymer backbone and end-group structure, molecular weight, and applied lubricant thickness. The dispersive component of the surface energy is shown to be a measure of the coverage of the carbon surface by the PFPE. The efficacy of the PFPE in covering the high energy carbon surface is strongly dependenct on whether the polymer chain is terminated with polar functionalities. Non-functionalized chains adopt a random orientation on the carbon surface. Functionalization of the polymer ends with polar moieties, e.g.carboxyl, hydroxyl, etc., results in the formation of a more highly ordered film structure. In the case of the di-hydroxy terminated PFPE ZDOL, interaction of the hydroxy end-groups with the surface active sites leads to a structure in which the polymer backbone is oriented parallel to the carbon surface. The polar component of the surface energy provides information on the interaction strength between the lubricant and the carbon surface that is difficult to obtain by other methods.
3:00 PM	Invited	MI+MR+AS+MS-WeA-4 Processing Issues in Magnetic Recording Technology T. Yamashita (Komag)
4:00 PM		MI+MR+AS+MS-WeA-7 Development of ECR and ICP High Density Plasma Etching for Patterning of NiFe and NiFeCo K.B. Jung, J.R. Childress, S.J. Pearton (University of Florida, Gainesville); M. Jenson, A.T. Hurst, Jr. (Honeywell, Inc.) Next generation MRAM devices require sub-micron track width with extremely smooth feature sidewalls. Currently employed ion milling processes would be improved if a chemical component to the etching were developed. We studied high ion density plasma etching of NiFeCo and Ni_0.8Fe_0.2 and also oxidation and contact barrier materials such as TaN, CrSi using Electron Cyclotron Resonance and Inductively Coupled Plasma Cl₂/Ar discharges. Etch rates, surface morphology and near surface stoichiometry after etching in these two tools were investigated. For ECR etching, etch rates were typically 3000Å/min for all materials at source powers of 1000W and rf chuck powers of 150W, corresponding to ion energies of ~100eV, while those in the ICP tool were somewhat lower for the same plasma conditions. SiO₂-based mask materials were found to be a better choice than photoresists in order to obtain anisotropic sidewalls which are necessary in magnetic devices. Chlorine residues were found on the surface of both Ni_0.8Fe_0.2 and NiFeCo after etching in both reactors using Auger Electron Spectroscopy. We developed several approaches to in-situ cleaning after plasma etching to remove these residues. Most effective was a H₂ plasma (10mTorr, 10minutes, 25W rf, 500W source power) treatment to volatilize the Cl residues. Extremely clean anisotropic features at the micron dimension were produced by combination of Cl₂/Ar etching and post-etch in-situ cleaning.
4:20 PM		MI+MR+AS+MS-WeA-8 Reactive Plasma Etching of Magnetic Head Materials C. Doughty, D.C. Knick (PlasmaQuest, Inc.) Magnetic disk drive read/write heads are generally made on an Al₂O₃/TiC ceramic and require an air bearing or slider structure on the face in contact with the disk in order to maintain proper disk to head spacing. Critical requirements for this structure include good surface roughness, well-controlled depth and sidewall angle. The air bearing must be made after the devices in the head are fabricated. As the industry switches to giant magnetoresistive read heads, thin film interdiffusion and interface roughening will become increasingly important, and maintaining low temperature during air bearing patterning will become a priority. Plasma etching offers several advantages over competing techniques such as ion milling, and is currently a subject of intense development, although little has been published for proprietary reasons. We describe a high-density plasma etching system and F and Cl based processes resulting in etch rates >1500 Å/min over 300 mm diam. process areas. AlTiC is difficult to etch due to both the strength of the Al-O bond, and surface roughness which develops due to differences between the etch rates of the Al₂O₃ and TiC grains. Both plasma chemistry and ion bombardment play a central role in the process and will be discussed. By controlling the chemical and physical etch processes a smooth surface can be maintained. In addition, the chemical nature of the etch allows for processing at lower thermal input to the substrate relative to purely physical processes such as ion milling. Hence high rates can be retained at the lower temperatures required for next-generation devices.
4:40 PM		MI+MR+AS+MS-WeA-9 Macromagnetic Properties of CoPt12Cr13 Thin Films W.Y. Lee, T. Nguyen (IBM Almaden Research Center); J.S. Li (IBM Storage System Division) The effects of Ar sputtering gas pres sure, deposition rate, underlayer (Ge, Ru, and CrV), film thickness and controlled O₂ doping on the macromagnetic properties o f Co-12Pt-13Cr thin films sputter-deposited on glass substrates at ambient temperature are reported. Higher coercivity (H_c) is observed for the films deposited in higher sputtering gas pressure. For example, an extremely high H_c of 5110 Oe was obtained f or a130 Å film (M_r.t = 0.5 memu/cm²) deposited on 1200 Å Ru underlayer in 24 mTorr Ar. High H_c (2598 Oe) fi lms can also be deposited under similar conditions for a 75 Å film on 20 Å thick Ge underlayer. For the films sputter-deposited in the same Ar pressure, H_c tends to be higher at lower deposition rates. Concomitant with the higher H_c is the higher e lectrical resistivity for the films deposited in higher pressure and at lower deposition rates, suggesting a higher degree of reactio n with the residual water in the vacuum system under these deposition conditions. This is confirmed by the strong dependence of the H_c on the O₂ concentration doped into the Ar sputtering gas. For these films, H_c increases rapidly with increasin g O₂ concentration, reaches a maximum value at 0.4 % O₂, and decreases at higher concentration. Through this controlled O₂ doping, excellent magnetic properties (H_c = 2440 Oe, M_r .t = 0.8 memu/cm², S^*= 0.82) have been achieved for 150 Å Co-12Pt-13Cr/400 Å CrV films deposited on glass substrates without the use of high temperature and high pres sure deposition processes.
5:00 PM		MI+MR+AS+MS-WeA-10 Thin-Film, Extreme-High Vacuum System A. Komura, J. Ishibe, Y. Maeda (Hitachi Zosen Corporation, Japan); M. Takahashi, S. Sohji, M. Tsunoda, T. Shimazu (Tohoku University, Japan); O. Okaniwa (Hitachi Zosen Corporation, Japan) According to the miniaturization of magnetic devices such as thin film magnetic recording media and heads, the thickness of the magnetic metal film on the devices have been very thin (< 100Å). It is important to control the microstructure of such ultra thin metallic films, in order to induce excellent magnetic properties. However, the film fabrication under the normally used sputtering process is not sufficiently enough to control fine structure of ultra thin films, therefore, the fundamental concept change to control initial film growth should be indispensable. Since the impurities in the sputtering atmosphere is easily thought to affect strongly on the initial film growth, the highly purified atmosphere will be required to establish a fabrication technology of ultra thin metallic films. In the present study, we developed a specialized multi-sputtering system, which enable to realize 10^-12 Torr vacuum condition and is appreciated with the followings: 1) The system is comprised of a transfer chamber which incorporates handling robots and the other chambers in several kinds of use, such as loading, precleaning, sputtering and analysing materials; 2) The chambers and the related components are made up from aluminum alloys all so as to decrease gas emissions from the inner surfaces; 3) The exhaust systems is based on oil-free devices of high quality, constituted by magnetic floating types of TMP and some kinds of scroll pumps; 4) The loading robots are in the extremely high-vacuum conditions of 10 ^-11 Torr during no-operation, or 10 ^-10 Torr even during operation, due to magnetic couplings for the drive transmission of the robots and ball bearings with highly low gas emissions; 5) Gas and particle discharges are maintained at very small because of adapting the all metal gate valves and uses a differential exhaust system; 6) The beam shutters are composed of high-speed shutters (max 1.0 m/s) and low-speed shutters, being possible to control the film thickness precisely. The all shutters are produced by metals and small gas emission materials.