초록 ▼

A device is provided for determining the height and/or tilt of local features on the surface of a sample. The device includes a laser projecting a collimated beam at an oblique angle at a reflection point on the sample surface and a converging lens having an optical axis extending at an angle of ref

A device is provided for determining the height and/or tilt of local features on the surface of a sample. The device includes a laser projecting a collimated beam at an oblique angle at a reflection point on the sample surface and a converging lens having an optical axis extending at an angle of reflection equal to the angle of incidence from the reflection point. The focusing characteristics of the lens are used to separate the deflection of the reflected collimated beam due to tilt of the surface from such deflection due to linear displacement of the surface.

대표청구항 ▼

[ What is claimed is:] [1.] Apparatus for measuring linear displacement of a sample surface from a nominal level in a direction perpendicular to said sample surface at a nominal inclination, wherein said apparatus comprises:projection means for projecting an energy beam at said sample surface to str

[ What is claimed is:] [1.] Apparatus for measuring linear displacement of a sample surface from a nominal level in a direction perpendicular to said sample surface at a nominal inclination, wherein said apparatus comprises:projection means for projecting an energy beam at said sample surface to strike said sample surface at said nominal level at a reflection point and at an oblique angle of incidence relative to said sample surface at said nominal inclination;a converging lens with a first focal point, displaced in a first direction from said converging lens, at said reflection point, with an optical axis extending at an angle of reflection relative to said sample surface at said nominal inclination equal to said oblique angle of incidence, and with a second focal point displaced opposite said first direction from said converging lens;a first photodetector producing a signal in response to a position at which said first photodetector is struck by said energy beam; andfirst imaging means for directing a portion of said energy beam, having been reflected at said sample surface and refracted through said converging lens, to said first photodetector, wherein said first imaging means directs a ray traveling coincident with said optical axis from said converging lens opposite said first direction to strike said first photodetector at a first central point, wherein said first imaging means directs a ray traveling from said converging lens through said second focal point to fall on said first photodetector at a first displacement distance from said first central point, with said first displacement distance increasing with an angle between said ray and said optical axis at said second focal point, wherein said first imaging means directs a ray traveling parallel to said optical axis from said converging lens opposite said first direction to strike said first photodetector at said first central point, wherein said imaging means includes a reflector extending through said second focal point in a flat plane perpendicular to said optical axis, reflecting said energy beam, having been reflected at said sample surface and refracted through said converging lens, to be transmitted through said converging lens in said first direction and to be reflected again at said sample surface, forming a return beam, and a first beamsplitter directing a portion of said return beam to said first photodetector.