CoFeB應用在磁紀錄媒體上普遍使用MgO作為電子絕緣穿隧層，經由後退火處理後會發生B堆積在MgO/CoFeB介面的現象，這會使電子同調穿隧效應變差，故阻止B往MgO擴散是個值得探討的問題。利用覆蓋層去吸附B是阻止B往MgO擴散的其中一個方法，直到目前為止，還沒有人在相同的製程條件下證實Zr覆蓋層是否比Ta更適合作為B的吸附劑，故本實驗探討在相同的CoFeB厚度、相同退火溫度，藉由改變退火時間、覆蓋層厚度、覆蓋層元素去影響 B擴散的行為。
X光反射率顯示退火500℃，1小時的條件下，會明顯降低薄膜整體厚度和CoFeB介面粗糙度，增加CoFeB(CoFe)和覆蓋層的密度，特別是增加覆蓋層厚度到6.5 nm時，磁光科爾效應顯示CoFeB的矯頑力提升較多。X光光電子能譜顯示Fe、Co、Zr、Ta被還原的程度也最大。XRD顯示CoFe (002)的結晶化程度最強。推測是因退火使B從CoFeB分離至覆蓋層被氧化，導致CoFeB結晶化成緻密的CoFe B2 結構的多晶相。反映出退火0.5 ~ 1小時B擴散到覆蓋層的效率最高。退火1.5小時後，藉由縱深分析可證明Zr吸附B能力比Ta強，因ZrBx的形成焓比TaBx還要小，導致B擴散至Zr的表面濃度大約是擴散到Ta的2倍。可能的擴散機制是樣品在破真空前，退火使B藉由格隙擴散到Zr(Ta)層形成ZrBX(TaBx)，但樣品破真空後有部分ZrBX被氧化形成BOx，TaBx則幾乎氧化。最後，利用極化中子反射率分析B在CoFe/MgO介面的分佈不會超過3 nm厚，代表CoFeB薄膜沉積越厚，離覆蓋層越遠的B越難被吸附。此外，CoFeB結晶化後的CoFe相也提升了磁性薄膜的磁化量。

CoFeB is commonly used in magnetic recording media. MgO is commonly used as an electronic insulating tunneling layer. After post-annealing, B will accumulate on the MgO/CoFeB interface, which will make the electron coherent tunneling effect worse. Until now, no one has confirmed whether the Zr capping layer is more suitable than Ta as an adsorbent for preventing the diffusion of B to MgO. Therefore, this experiment explores the influence of B diffusion behavior by changing the annealing time, capping layer thickness, and capping layer elements. Under the condition of annealing for 1 h. The X-ray reflectivity shows that the overall thickness of the film and the roughness of the Ta(Zr)/CoFeB interface is significantly reduced, and the density of CoFeB (CoFe) and density of the capping layer are increased. Mangneto-optic Kerr effect measurement shows that thicker Ta(Zr) capping layer can increase coercivity of CoFeB. X-ray photoelectron spectroscopy shows that Fe, Co, Zr, and Ta are reduced to the great extent. XRD shows that CoFe (002) has the strongest degree of crystallization. It is presumed that the annealing caused B to be separated from CoFeB to the coating layer and oxidized, which resulted in the crystallization of CoFeB into a dense polycrystalline phase of CoFe B2 structure. Reflects that the efficiency of B diffusion to the cappinofg layer is the highest when annealing for 0.5~1 h. After annealing for 1.5 h, the depth analysis shows that Zr has a stronger ability to adsorb B than Ta. Because the enthalpy of formation of ZrBx is smaller than that of TaBx, the surface concentration of B diffused to Zr is about twice than that of Ta. Finally, by using polarized neutron reflectivity we confirmed the distribution of B on the CoFe/MgO interface is less than 3 nm. In addition, the thicker the CoFeB film is deposited, the more difficult for the B to be diffused into the capping layer. Furthermore, after annealing, the CoFe phase growth from the crystallization of CoFeB thin film gives rise to a higher magnetization.

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