Shin-Etsu Chemical Co., Ltd. (Head office: Tokyo, President: Chihiro Kanagawa) has succeeded in developing a large-size magnetic circuit which will be the world’s largest-class permanent magnet-type magnetic circuit. Its total weight is about 10 tons, and it will be used mainly in manufacturing-process applications, such as for the making of next-generation MRAM* semiconductors and MR (Magneto Resistive) sensors.

For the manufacturing of MRAMs, heat treatment in a magnetic field is essential, and in that process, generation of a very large magnetic field of more than 1 tesla is required. So far, electromagnets and superconducting magnets have been used for this purpose. However, recently many semiconductor manufacturers are adopting permanent magnet-type magnetic circuits because of their good magnetic-field performance and magnetic-field stability, as well as the fact that these permanent magnet-type magnetic circuits have the advantage of being power-saving and maintenance-free. At the same time, with the trend in recent years toward larger-diameter silicon wafers, the need for these types of larger magnetic circuits has been increasing.

Shin-Etsu Chemical has been manufacturing various large-size magnetic circuits using its rare earth magnets. With its total weight of about 10 tons, cylindrical shape of 1.4-meter diameter and height of 1-meter, the new type of magnetic circuit that Shin-Etsu has now developed is the world’s largest-class permanent magnet-type magnetic circuit that generates a strong magnetic field. This magnetic circuit is being introduced ahead of other companies worldwide for application in the processing of 300mm wafers.

To generate a strong magnetic field in a permanent magnet-type magnetic circuit, a complex magnet alignment is required, and accordingly, the production of such magnetic circuits has been difficult to achieve. Until now, the production of small-size magnetic circuits with an inner diameter of about 100mm was the limit. Based on its own analytical method, Shin-Etsu Chemical re-examined how to achieve optimization of magnet shapes as well as the manufacturing process related to the configuration of the magnets. As a result of these R&D efforts, the company realized this new very large-size permanent magnet-type magnetic circuit.

In addition to the semiconductor-related field, this large-size magnetic circuit is expected to be used in application fields where a stable, strong magnetic generation source is required, such as for high-end HDD drive heads, medical devices and for basic research uses. After the completion of the development of this new type of magnetic circuit at the end of last year, product samples were delivered to those device makers, and presently they are now conducting various evaluation assessment experiments.

Shin-Etsu Chemical, in addition to manufacturing of rare earth magnets, is carrying out analysis, design and manufacturing of various magnetic circuits for use in such areas as MRI (magnetic resonance imaging) machines and electrical generators, and the company will continue to focus on product development that will meet users’ requirements that are expected to become more diversified in future.

*MRAM: Magnetoresistive Random Access Memory
A MRAM is a next-generation memory device. Unlike conventional memory chip technologies, in a MRAM device, data is stored by magnetic storage elements. This technology will achieve both higher speed and higher integration