DEVELOPMENT OF HIGH SENSITIVE THIN-FILM MAGNETIC SENSORS BY APPLYING THE IMPURITY REDULATED SPUTTERING PROCESS

金属多层材料中的巨磁阻效应已被积极研究用于磁传感器。获得敏感磁流变响应的关键技术因素是：1)多层的平面界面以保持较大的磁流变比；2)Co、Co- fe等铁磁层的软磁特性。这两个因素是通过控制加工过程中的杂质来实现的。在沉积过程中在溅射气氛中引入氧气是改善Co/Cu多层膜界面平整度的有效方法，本文作者已经证明了这一点。氮和硼是众所周知的用于Co-Fe薄膜磁软化的添加剂。在本研究中，为了更精确地阐明氧对GMR的作用，在不同的溅射气氛下制备了Co/Cu多层膜，其中加工氩气体中的杂质氧含量从0.1 ppm急剧变化到0.1%。研究了磁流变比与多层膜微观结构，特别是界面粗糙度之间的关系，并将其作为溅射腔中氧气分压的函数。当杂质氧含量从20 ppm略微增加到80 ppm时，MR比从不足20%急剧增加到54%，当杂质氧含量超过200 ppm时，MR比几乎消失。在MR比急剧增加的前一区域，随着氧含量的增加，多层膜的均方根粗糙度从6.5 Å下降到4.5 Å，同时晶粒尺寸减小。多层膜的部分氧化是解释多层膜中界面变平的最可能的机制。

The giant magnetoresistance(GMR)effect in metallic multilayer has been actively investigated to be applied to magnetic sensors. Key technical factors to obtain sensitive MR response are 1)flat interfaces of multilayers to retain large MR ratio and 2)soft magnetic properties of ferromagnetic layers, such as Co iud Co-Fe. These two factors are realized with controlling impurities in fabrication process. Introducing oxygen into the sputtering atmosphere during the deposition is an effective way to improve the interfacial flatness, which has been demonstrated for Co/Cu multilayers by the present authors. Nitrogen and boron are well-know additives to make magnetic softering of Co-Fe films. In the present study, in order to clarify the role of oxygen on GMR more precisely, Co/Cu multilayers were fabricated under different sputtering atmospheres in which the impurity oxygen content was changed dramatically from 0.1 ppm to 0.1 % within processing Ar gas. The correlation between the MR ratio and microstructure of the multilayers, especially the interfacial roughess, was investigated as a function of the partial pressure of oxygen introduced into the sputtering chamber. The MR ratio drastically increased from less than 20 % to 54 % when the content of impurity oxygen was slightly increased from 20 ppm to 80 ppm, then nearly varished when the content become more than 200 ppm. In the former region where the MR ratio steeply increased, the root mean square rougtness of the multilayers decreased from 6.5 Å to 4.5 Å accompanied by a reduction of in grain size as the oxygen content was increased. The partial oxidation of the multilayers is the most probable mechanism by which the flattening of the interfaces in the multilayer can be explained.