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

金属多层膜中的巨磁电阻(GMR)效应已被积极研究并应用于磁性传感器。获得灵敏的MR响应的关键技术因素是1)多层膜的平坦界面以保持较大的MR比，2)铁磁层的软磁性质，如Co IUD Co-Fe。这两个因素是通过在制造过程中控制杂质来实现的。在沉积过程中向溅射气氛中引入氧气是改善界面平坦度的一种有效方法，作者在Co/Cu多层膜中证明了这一点。氮和硼是众所周知的软化Co-Fe薄膜的添加剂。在本研究中，为了更准确地阐明氧在巨磁电阻中的作用，在不同的溅射气氛下制备了Co/Cu多层膜，在不同的溅射气氛中，杂质氧含量在处理Ar气体中从0.1ppm急剧变化到0.1%。研究了磁阻比与多层膜的微观结构，特别是界面粗糙度之间的关系，作为引入溅射室的氧分压的函数。当杂质氧含量从20ppm增加到80ppm时，磁流变率从不到20%急剧增加到54%，当杂质氧含量超过200ppm时，磁流变率几乎消失。在磁阻比急剧增加的区域，随着氧含量的增加，多层膜的均方根粗糙度从6.5Å下降到4.5Å，并伴随着晶粒尺寸的减小。多层膜的部分氧化是解释多层膜界面扁平化的最可能机制。

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.