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Matsushita surface measurement unit called Blu-ray disk system enabler

Posted: 15 Apr 2002 ?? ?Print Version ?Bookmark and Share

Keywords:ua3p 4? ua3p 5? ua3p 6? profilometer? blu ray dvd?

Matsushita Electric Industrial Co. Ltd has developed a 3D profilometer that it says is a crucial tool for making the lens for the next-generation Blu-Ray DVD systems. Using a diamond stylus as an atomic-force probe, the instrument measures an area as large as 400-by-400-by-90mm with 10nm accuracy, even in grooves and trenches, the company said.

Matsushita intends to position its 3D profilometer as the standard for the DVD sector, which it expects to represent roughly a $1 billion market in 2010.

The Blu-Ray Disc system, which aims to realize a capacity of 25GB to 27GB per one recording layer on a DVD, needs an aspheric lens with a numeric aperture of 0.85. To make a metal mold for the aspheric lens, a precise process deeper than 100 nm is necessary even in the periphery, where lens performance is determined.

Matsushita's existing profilometer uses a ruby stylus with a 0.5mm radius ?too large for the Blu-Ray job.

"At present, the lens for the Blu-Ray Disc systems can be made only by this [10nm] profilometer," said Masashi Makino, director of Matsushita's corporate production engineering division. "There is no competing system which can scan as large an area as this system can do with this high a level of accuracy." Matsushita is now the sole supplier of the lens to disk-system developers.

Submicron accuracy

Atomic-force microscopes and scanning-electron microscopes can measure more accurately at an angstrom order, but their measurement range is limited at the micron order. 3D measurement systems that can measure >15m do not have a nanometer-level accuracy.

"Only Matsushita's profilometer can measure an area as large as 400-by-400mm with submicron accuracy," said Keiichi Yoshizumi, GM of the 3D profilometer project.

Aside from DVD usage, Matsushita also intends to promote the system to optical-device and semiconductor manufacturers by touting the advantages of a large measurement area combined with nanolevel accuracy.

The main target will be lens manufacturers, but "this profilometer can measure both wafers and chucks at nanometer accuracy," Yoshizumi said. "If a wafer becomes warped, the system can measure the warpage as well. It takes less than 10 minutes to measure the whole surface of an 8-inch wafer."

Matsushita attributed the performance to the development of a diamond stylus and a probe-control mechanism that works by means of a precise position-detection method.

The probe is kept at a nanometer-level distance from an object so as to engender atomic repulsion between the probe and the object. Keeping the repulsion at a constant level, the probe scans the object's surface, moving according to its shape.

The movement is detected by a semiconductor laser and its position read out as displacement, using a stabilized helium-neon laser as the graduation. The subtle movement of the probe is immediately fed back to the control circuitry of the linear motor that drives the probe head to follow the shape of the object surface.

"We developed the diamond stylus to scan larger areas. Probing styluses of existing atomic-force microscopes easily abrade. Diamond is rigid and does not abrade," said Yoshizumi.

Matsushita will offer three models in the Ultra Accurate 3D Profilometer series. The UA3P-4 measures 100-by-100-by-35mm, with the scanning speed changeable from 0.01mm/s to 10mm/s. The UA3P-5 covers an area twice as large200-by-200-by-45mmat the same scanning speed. And the UA3P-6 measures 400-by-400-by-90mm at a speed adjustable from 0.02mm/s to 20mm/s.

Matsushita says it will begin taking orders for the system next month, charging in the range of $390,000 to $770,000 per unit, depending on the model and options. Matsushita expects to sell 30 to 50 units in the first year.

Yoshiko Hara

EE Times

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