Synthesis of High Performance Thin Film Magnet on Semiconductor Substrate for the Micromagnetic Devices

采用射频溅射和后退火技术，成功地在Si（111）单晶衬底上合成了矫顽力约为15 kOe的Nd-Fe-B稀土磁体薄膜。在半导体衬底上制备薄膜磁体对MEMS器件的实际应用具有很大的优势。我们在衬底和Nd-Fe-B层之间插入了厚度约为2微米的MoSi_2缓冲层。我们认为缓冲层有一个轧辊来降低热应变。为了防止Nd-Fe-B层氧化，在表层涂覆了Ti层。沉积膜为非晶相。经650℃真空红外辐射退火后，Nd_2Fe_14B相在薄膜中结晶良好。XRD谱图显示出（00l）衍射和强（410）峰。磁滞现象在平行和垂直于薄膜平面的磁场中表现为各向同性。这个结果来自于c轴的随机方向。XRD分析结果与c轴取向不足一致。而薄膜的矫顽力较大，约为15 μ k。对薄膜的SEM和MFM观察表明，薄膜实现了直径200 ~ 350 nm的单磁畴结构。虽然薄膜的c轴优先取向的实现仍然是一个有待克服的问题，但薄膜的高矫顽力对微电机或微执行器在MEMS器件中的具体应用具有良好的性能。

We successfully synthesized thin films of Nd-Fe-B rare earth magnets with coercive force of about 15 kOe on Si(111) single crystal substrate by RF sputtering and post annealing technique. Preparation of thin film magnet on semiconductor substrate has great advantage for the practical application of MEMS devices. We inserted the buffer layer of MoSi_2 between the substrate and Nd-Fe-B layer with approximately 2 micron thickness. We consider that the buffer layer has a roll to depress the thermal strain. The Ti top layer was coated for the protect from oxidation of the Nd-Fe-B layer. The as-deposited films shows the amorphous phase. After annealing at 650 degreeC by infrared radiation in vacuum atmosphere, the Nd_2Fe_14B phase was well crystallized in the film. The XRD pattern showed (00l) diffraction and the strong (410) peak was also observed. The magnetic hysteresis showed the isotropic in the magnetic field parallel and perpendicular to the film plane. This result come from the random orientation of c-axis. The XRD analysis is agreement with the insufficient c-axis orientations. However, the coercive force of the film shoed the large value of aboout 15 kOe. The SEM and MFM observation of the film suggested the single magnetic domain structure with 200-350 nm diameter was realized. Although the realization of the c-axis preferential orientation of the film remains a subject matter to overcome, the high coercivity of the film is good property for the concrete application of the micromotor or microactuator in the MEMS devices.