Canon Immersion Scanner Uses Twin-Stage Pipeline Scheme
Kenji Tsuda, Asia Contributing Editor -- Semiconductor International, 12/17/2007 8:45:00 AM
At SEMICON Japan 2007, Canon Inc. (Tokyo) disclosed more detailed information on its new immersion scanner, the FPA-7000AS7, designed for 45 nm devices and beyond.
The ArF scanner has a numerical aperture (NA) of 1.35 and a published throughput of 124 300 mm wph using two stages. Canon officials said the stage design differs from its competitors.
In most scanners, the first stage measures the lens distortion caused by heat in the beam exposure. Next, the wafer is adjusted with off-axis alignment, and alignment marks on the wafer are detected and aligned at the second stage. The wafer is then sent back to the first stage for exposure.
Canon claims that it has a more efficient operation, handling the lens distortion correction at beam exposure and the alignment operation/correction in the same stage. While the foregoing wafer is being exposed in the scanner’s second stage, the first stage is used to measure and correct heat distortion on the target wafer and align with the alignment marks. Canon’s pipeline scheme simultaneously operates the measurement and exposure stages.
By simultaneously performing thermal distortion correction and alignment correction, it is possible to simulate the thermal expansion of the lens. However, Canon officials said the company does not plan to disclose the simulation scheme.
The Canon scanner uses automatic calibration for lens astigmatism correction, which the company said is also a different approach from conventional techniques.
At first glance, the Canon performance appears to be similar to that of the Nikon Corp.’s NSR-S610C scanner, announced in July 2006. The throughput of the Canon AS7 is rated at 124 wph, compared with the Nikon S610C’s claimed throughput of 130 wph. The NA of the AS7 is 1.35, while the NA of the S610C lens is 1.30. The field size is the same: 26 × 33 mm.
Both companies claim to have shipped their most advanced scanners to specific customers to evaluate the machines. In October, Nikon announced that Toshiba Corp. will use the S610C for NAND flash production at 43 nm design rules.
While Canon officials have said the AS7 was shipped to customers in November, it has not identified them.
