Apparatus for and a method of transverse position measurement in

Details Apparatus for and a method of transverse position measurement in Apparatus for and a method of transverse position measurement in

1991-10-08

1993-02-16

Nelms, David C.

Radiant energy

Photocells; circuits and apparatus

Photocell controls its own optical systems

356401, G01N 2186

Patent

active

051873729

ABSTRACT:
Apparatus for transverse position measurement in a proximity lithographic system including a prism (10) having a glass plate (14) index matched beneath the prism on which a T.I.R. hologram (13) is pre-recorded. A laser source (12) provides a replay beam. A silicon wafer (16) is situated below the hologram and parallel therewith. A second laser source (17) produces through optics (18) a beam with gaussian intensity profile to generate a collimated strip of light (19) at the hologram plane. Elemental grating structures (20) are provided at different locations over the surface of the wafer. Detectors (22,24) collect parts of the lightfield resulting from the interaction of the laser beam with the grating structures. A piezo device (26) operated from a micro-processor (28) moves the silicon wafer in small increments in a direction substantially parallel to the hologram following measurements made by the two detectors which are processed by the micro-processor to produce an alignment signal for the piezo device.

REFERENCES:
patent: 4311389 (1982-01-01), Fay et al.
patent: 4496241 (1985-01-01), Mayer
patent: 4779001 (1988-10-01), Makosch
patent: 4814626 (1989-03-01), Doemens et al.
patent: 4948983 (1990-08-01), Maruyama et al.
patent: 5004348 (1991-04-01), Magome

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