The Metrology Institute of Japan (MIJ) of the National Institute of Advanced Industrial Science and Technology (AIST), an independent administrative institution, has developed a large aperture Fizeau flatness interferometer (Photo.1) for assessing flatness of an object, in collaboration with Fuji Photo Optical Co., Ltd. (FPOC), and implemented flatness measurement with best precision in the world. The instrument covers a measurement area of 300 mm diameter and achieved measurement uncertainty of 10 nm (1nm = 1/1,000,000,000m).

The AIST is in charge of providing testing and measurement services, as a public research organization, and is going to start flatness measurement service (supply of flatness standards) from April 2004 by using the Fizeau-type interferometer developed in this work.

No flatness standard has been available in Japan, hence objective assessment of flatness was impossible

The flatness is an index for how flat surface of an object is. For achieving large capacity of semiconductor devices and hard disks and upgrading process yield, the flatness of silicon wafers and hard disk substrates is of crucial importance. For this reason, the objective assessment of flatness by a public authority has been sought for. But none of such measurement services based on a national standard were provided.

A large aperture Fizeau interferometer of world's best precision developed

The MIJ-AIST has developed a large aperture Fizeau flatness interferometer of smallest uncertainty in the world in collaboration with FPOC. The instrument can assess the flatness of an object at 10nm uncertainty for a measurement area of about 300mm diameter. This is the best accuracy in the world, which is equivalent to detecting 3mm roughness in the Kanto Plain, an area of around 17,000 square kilometers.

Flatness calibration service provided with world's best accuracy

The MIJ-AIST, as a public metrology institute, offers testing and measuring services for a number of quantities, such as length, geometrical quantities, mass, force, torque and so on, and issues a certificate on the basis of test results. The MIJ-AIST is going to start calibration service for flatness measurement from April 2004, by using the Fizeau interferometer developed in this work.

Contributing to improving capacity of IC/hard disk and process yield

Supplying flatness standards through the Fizeau-type interferometer makes it possible to objectively evaluate the flatness of silicon wafers and hard disk substrates. It is expected that the instrument will contribute to improvement of capacity of integrated circuits and hard disk, as well as process yield.

Photo. A large aperture Fizeau-type flatness interferometer

Fig.1. An example of flatness measurement results