We investigated a new class of coupled granular/continuous (CGC) perpendicular media consisting of CoCrPt-SiO 2 granular layer with magnetically decoupled small grains. By changing the number of Co/Pd bi-layers in the continuous layer, the degree of exchange coupling can be systematically controlled. The introduction of Co/Pd multilayer improved the nucleation field (H n ) from -570 to -1670 Oe and K u V/k B T values from 67 to 97. Compared to the base granular media, the CGC media had 1 dB gain in signal-to-noise ratio (SNR) as well as 14 dB gain in write-ability (OW). Moreover, the output decay was reduced from -0.11 to -0.035 dB per decade. In CGC approach, a more appropriate strength of exchange coupling can be introduced that yields the significant improvement in both SNR and thermal stability
The role of substrate bias during the sputter deposition of various layers of double-layered CoCrPt−SiO2 perpendicular recording media has been investigated in order to understand the physical mechanisms behind the various effects observed. Perpendicular recording media with dual Ru intermediate layers were investigated using several magnetic and microstructural characterization techniques. It was observed that, in general, the application of a bias voltage during the deposition of the seedlayer (Ta) and the first intermediate layer (Ru) is helpful in reducing the c-axis dispersion of the recording layer. For the other layers, application of bias voltage leads to deterioration in the magnetic properties. It was also observed that the application of a bias voltage during the deposition of the first intermediate layer (especially Ru) may not enhance the preferred growth of Ru hexagonal-close-packed (00.2) planes parallel to the disk surface, as predicted before. However, the bias voltage on the Ru layer still reduces the c-axis dispersion of the magnetic layer. From the omega-offset x-ray diffraction investigations, it is estimated that the lattice parameter “a” of the Ru layer is reduced slightly with bias voltage, which could probably lead to a reduction in the lattice mismatch between the Ru layer and Co-alloy layer. Bias conditions also could lead to improved interface condition. Such an improvement in the lattice matching or interface conditions could probably be the cause of the reduction of c-axis dispersion of the recording layer.
Critical dimensions (CD) measured in resist are key to understanding the CD distribution on photomasks. Vital to this understanding is the separation of spatially random and systematic contributions to the CD distribution. Random contributions will not appear in post etch CD measurements (final) whereas systematic contributions will strongly impact final CDs. Resist CD signatures and their variations drive final CD distributions, thus an understanding of the mechanisms influencing the resist CD signature and its variation play a pivotal role in CD distribution improvements. Current technological demands require strict control of reticle critical dimension uniformity (CDU) and the Advanced Mask Technology Center (AMTC) has found significant reductions in reticle CDU are enabled through the statistical analysis of large data sets. To this end, we employ Principle Component Analysis (PCA) - a methodology well established at the AMTC1- to show how different portions of the lithographic process contribute to CD variations. These portions include photomask blank preparation as well as a correction parameter in the front end process. CD variations were markedly changed by modulating these two lithographic portions, leading to improved final CDU on test reticles in two different chemically amplified resist (CAR) processes.
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