Matsushita Electric Industrial Co. Ltd. has developed a 3-D profilometer that it says is a crucial tool for making the lens for the next-generation Blu-ray digital video disk systems. Using a diamond stylus as an atomic-force probe, the instrument measures an area as large as 400 x 400 x 90 mm with 10-nanometer accuracy, even in grooves and trenches, the company said.
Matsushita intends to position its 3-D profilometer as the standard for the digital video disk 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 25 to 27 Gbytes 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 0.5-mm (500-micron) radius — too large for the Blu-ray job.
"At present, the lens for the Blu-ray Disc systems can be made only by this [10-nm] 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.
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. Three-dimensional measurement systems that can measure over 1 micron do not have a nanometer-level accuracy. "Only Matsushita's profilometer can measure an area as large as 400 x 400 mm with submicron accuracy," said Keiichi Yoshizumi, general manager of the 3-D 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 3-D Profilometer series. The UA3P-4 measures 100 x 100 mm x 35 mm high, with the scanning speed changeable from 0.01 to 10 mm per second. The UA3P-5 covers an area twice as large — 200 x 200 x 45 mm — at the same scanning speed. And the UA3P-6 measures 400 x 400 x 90 mm at a speed adjustable from 0.02 to 20 mm/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.