Achieving 17-Picometer Resolution
Sony Laserscale Products for the Next Generation of Innovative Manufacturing

Laserscale is an ultra-precision measuring technology indispensable for modern innovative manufacturing. Sony Manufacturing Systems Corporation develops and manufactures the Laserscale products, which use laser beams to achieve picometer level measurement (one picometer is one trillionth of a meter). The Laserscale products are indispensable in leading-edge technology manufacturing where ultra-precision measurement is required. Applications range from next generation semiconductor manufacturing to Blu-ray discs and lenses for digital cameras.
This issue of CX-News introduces Sony’s Laserscale technology.

Interferometers and scales are used in ultraprecision machining equipment and semiconductor manufacturing equipment.
While interferometers have the major advantages that they can be used in line and that they have good linearity, they have the disadvantage that when used in air, the laser wavelength used as the reference for measurement can change with air disturbances and changes in air pressure.
In contrast, scales are difficult to use in line, and their linearity is inferior to that of inter-ferometers due to bending of the scale itself and errors when recording readings. However, since the measurement reference consists of a solid state scale, they are resistant to environment influences and provide a superlative stability appropriate to their resolution.
Therefore, although interferometers were used previously, by the early 1990s, when primary signal pitches in scales became finer than the signal pitches in interferometers, scales became the instrument of choice. Recently, since mechanical hardnesses have increased and error compensation has become easier, currently almost all equipment is controlled with these mechanical scales.
Figure 1 shows Dr. Norio Taniguchi’s predictions for progress in mechanical accuracy and the corresponding changes in scale accuracy.
Despite mechanical accuracy already having reached the atomic level, there are strong demands for increased accuracy from semiconductor manufacturing equipment development divisions, where line widths are narrowing rapidly, magnetic disks, in which the recording density increases steadily, and optical disc write equipment, in which new recording methods compete fiercely. To respond to these demands, Sony has combined their Laserscale technology with a new interpolator that can interpolate to 1/8000 and has achieved a resolution of about 17 pm.