Device for detecting the levelling of the surface of an object

• US 4,902,900 A
• Filed: 12/15/1988
• Issued: 02/20/1990
• Est. Priority Date: 12/21/1987
• Status: Expired due to Fees

• Current Assignee: Nikon Corporation
• Original Assignee: Nikon Corporation
• Inventors: Kamiya, Saburo, Mizutani, Hideo
• Primary Examiner(s): Nelms, David C.
• Assistant Examiner(s): Oen, William L.
• Application Number:
  US07/284,659
• Time in Patent Office: 432 Days
• Field of Search: 250/548, 250/557, 250/561, 250/231 SE, 356/400, 356/401
• US Class Current: 250/548
• CPC Class Codes: G01B 11/26 for measuring angles or tapers; for testing the alignment of axes
• CPC Class Codes: G03F 7/70066 Size and form of the illuminated area in the mask plane, e.g. reticle masking blades or blinds
• CPC Class Codes: G03F 9/7023 Aligning or positioning in direction perpendicular to substrate surface

Abstract

A device for detecting the levelling of an object disposed on a plane substantially perpendicular to the optic axis of main objective optical means and worked by a radiation beam from the main objective optical means comprises levelling detecting optical means including an irradiating optical system for supplying a collimated light beam to a particular area of the surface of the object from an oblique direction, and a condensing optical system having light receiving means and for condensing the light beam reflected by the particular area on the light receiving means, and field stop means providing a plurality of stop openings differing in shape from one another, the field stop means being disposed in the levelling detecting optical means, one stop opening corresponding to the shape of the particular area being selected from among the plurality of stop openings.

Claims

1. A device for detecting the levelling of an object disposed on a plane substantially perpendicular to the optic axis of main objective optical means and worked by a radiation beam from said main objective optical means, comprising:

levelling detecting optical means including an irradiating optical system for supplying a collimated light beam to a particular area of the surface of said object from an oblique direction, and a condensing optical system having light receiving means and for condensing the light beam reflected by said particular area on said light receiving means; and

field stop means providing a plurality of stop openings differing in shape from one another, said field stop means being disposed in said levelling detecting optical means, one stop opening corresponding to the shape of said particular area being selected from among said plurality of stop openings.

2. A device according to claim 1, wherein said irradiating optical system includes a supply source of said light beam, and said field stop means is disposed at a position optically equivalent to said particular area between said supply source and said light receiving means.

3. A device according to claim 2, wherein said field stop means is provided in said irradiating optical system.

4. A device according to claim 1, wherein said field stop means includes a stop member in which said plurality of stop openings are formed, and means for selecting one of said plurality of stop openings and disposing it in said levelling detecting optical means.

5. A device according to claim 1, further comprising moving means for moving said object relative to said main objective optical means and determining said particular area and wherein said field stop means includes means responsive to said moving means to select one of said plurality of stop openings which has a shape corresponding to said determined particular area.

6. A device according to claim 1, further comprising means responsive to said light receiving means to determine the levelling of said particular area.

7. A device for detecting the levelling of an object disposed on a plane substantially perpendicular to the optic axis of main objective optical means, comprising:

a first levelling detection system having a first irradiating optical system for supplying a collimated first light beam to a particular area of the surface said object from a direction oblique relative to the optic axis of said main objective optical means, and a first condensing optical system for condensing on first light receiving means the first light beam supplied from said first irradiating optical system and reflected by said particular area, the optic axis of said first irradiating optical system and the optic axis of said first condensing optical system being disposed symmetrically with respect to the optic axis of said main objective optical means, said first levelling detection system detecting the inclination of said particular area relative to a reference plane with respect to a first direction on said reference plane;

a second levelling detection system having a second irradiating optical system for supplying a collimated second light beam to said particular area from a direction oblique relative to the optic axis of said main objective optical means, and a second condensing optical system for condensing on second light receiving means the second light beam supplied from said second irradiating optical system and reflected by said particular area, the optic axis of said second irradiating optical system and the optic axis of said second condensing optical system being disposed symmetrically with respect to the optic axis of said main objective optical means, said second levelling detection system detecting the inclination of said particular area relative to said reference plane with respect to a second direction on said reference plane differing from said first direction; and

means for determining the levelling of said reference plane on the basis of the inclination of said first direction and the inclination of said second direction.