PLD-Made Nd-Fe-B Thick Film Magnets Deposited on Si Substrates and Their Micromachining

Abstract

Several researchers have reported Nd-Fe-B thick films on Si substrates with a metal buffer layer prepared by a sputtering method [1] [2], and the thickness of each film was less than 100 $\mu \mathrm{m}$ . Recently, we demonstrated PLD (Pulsed Laser Deposition)-fabricated Nd-Fe-B films with the thickness up to approximately 160 $\mu \mathrm{m}$ on Si substrates without a buffer layer [3]. In the study, the effect of the boundary between a Si substrate and a Nd-Fe-B film on various properties was investigated. This contribution reports the mechanical together with magnetic properties of the samples deposited on Si substrates with a thermal or a natural oxide film. Furthermore, a wet etching process of a Nd-Fe-B film was carried out. Each rotated target with the composition of Nd x Fe 14 B (x=2.0, 2.6, 3.0, 3.5) was ablated by an Nd-YAG laser. All the as-deposited Nd-Fe-B thick films on SiO 2 (a thermal or a natural oxide film) /Si(100) substrates(5 mm $\times 5$ mm: square) without a buffer layer had amorphous structure, therefore they were crystallized by a pulse annealing (PA) method in the vacuum atmosphere. Although the magnetic properties of films deposited on the both oxide films were almost the same, a peeling phenomenon occurred in a Nd-Fe-B film thicker than 20 $\mu \mathrm{m}$ from a Si substrate with a natural oxide film. The result was different phenomenon of a Nd-Fe-B film deposited on a Si substrate with a thermal oxide film [3]. Namely, in the previous experiment, even if a Nd-Fe-B film deposited on a Si with a thermal oxide film was broken, the sample was destroyed from the inside of the substrate. The result suggests that the thermal oxide film is indispensable to obtain a strong adhesion between a Nd-Fe-B film and a Si substrate. In addition, we confirmed no deterioration of magnetic properties after a chemical etching in a Nd-Fe-B film prepared on a thermal SiO 2 /Si substrate.