International Business Machines Corporation

John M Warlaumont

Michael John Brady

James L Speidell

Bernard S Meyerson

Juan R Maldonado

Warren D Grobman

Vincent Di Milia

Vincent DiMilia

David A Nelson, Jr

An X-ray mask structure for X-ray lithography which can be adjusted by applied force to provide variable magnification of a pattern on the mask membrane. The applied force is provided by the heat expansion of a deformable member and the resultant stress on a support ring. A circular patterned mask membrane is supported in a ring composed, for example, of silicon or silicon-pyrex. The support ring contains a concentric aluminum ring having an embedded circular heating element. The heating element causes expansion of the aluminum ring which causes mechanical stress in the support and expansion of the mask membrane. Expansion of the mask membrane results in a corresponding magnification of the pattern thereon.

Variable magnification mask for X-ray lithography

A pinchuck is formed in accordance with this invention by using lithographic techniques to define and to etch a pattern of pins from an extremely flat etchable surface. Since the pins are formed from a surface which is already flat, it is not necessary to level or polish the pins after they are formed. Since lithographic techniques are used, the pin head dimensions, the number of pins, the arrangement of pins, and the density of pins all may be freely chosen without affecting the fabrication cost. By surrounding the region of etched pins with an unetched band, a raised peripheral ring will be formed which can act as a vacuum sealing ring when the pinchuck is used as a vacuum pinchuck. By fabricating the pins from an electrically conductive material (such as doped silicon) and then covering the pins with a dielectric film (such as silicon dioxide), the pinchuck can be used as an electrostatic pinchuck. By doing both, the same pinchuck can be used as an electrostatic pinchuck or as a vacuum pinchuck or as both simultaneously.

Electrostatic or vacuum pinchuck formed with microcircuit lithography

An improved X-ray lithography mask has been fabricated by forming an X-ray absorbing lithography pattern on a supporting foil of hydrogenated amorphous carbon. The substrate foil is formed by depositing a carbon film in the presence of hydrogen onto a surface having a temperature below 375.degree. C. The hydrogen concentration is maintained sufficiently high that the resulting film has at least one atom percent of hydrogen. A film having about 20 atom percent of hydrogen is preferred. While impurities are permitted, impurities must be maintained at a level such that the optical bandgap of the resulting film is at least one electron volt. A film with an optical bandgap of about 2 electron volts is preferred.

X-Ray mask

Fine alignment of mask and wafer, using Fresnel zone plates is achieved. Light is focused on the wafer by a zone plate in the mask. Light diffracted from a zone plate on the wafer is received by a sensor. The received light is coded (analog or digital) to indicate alignment. For analog coding the wafer zone plate diffracts light to the sensor from an area of the wafer zone plate which is indicative of alignment. For digital coding, the wafer zone plate is digitally encoded as a function of alignment to similarly code the diffracted light. To eliminate ambiguity, the mask zone plate is formed from a plurality of 'elements', each of which is itself a Fresnel zone plate. The focal length of the elemental Fresnel zone plate can be related to the mask/wafer separation distance, whereas the focal length of the macro zone plate (made up of a plurality of the elemental zone plates) is related to the distance between mask and light sensor.

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Ridgewood, NJ, United States of America

John M Warlaumont