Nikon Corporation

Nikon Precision Incorporated

Other

Nikon Research Corporation of America

John H McCoy

Kyoichi Suwa

Michael R Sogard

Martin E Lee

Arun Ananth Aiyer

Henry K Chau

W Thomas Novak

Alan D Brodie

Daniel L Cavan

N William Parker

Kyochi Suwa

An inspection system and method are disclosed. The inspection system is configured to inspect a projection unit having multiple optical subsystems. The optical subsystems are configured to project an image during a lithography step. The inspection system provides self calibration by measuring both a test mask and the aerial image of the test mask with the same detector assembly. The inspection system is also capable of measuring multiple fields simultaneously using multiple detectors and 6 axis interferometry to accurately determine the position of each detector. Additionally, the inspection system is capable of measuring the distance between the test mask and the detector assembly with an indirect path around the projection unit which normally blocks the direct path.

Inspection tool for testing and adjusting a projection unit of a lithography system

A projection exposure apparatus for exposing a semiconductor wafer to a pattern, formed on a reticle, using a projection lens system. An alignment optical system is disposed at a backside of the wafer which is remote from the projection lens system. The alignment optical system detects an alignment mark provided on the frontside of the wafer from the backside of the wafer. Thus the wafer alignment mark is detected without being adversely affected by integrated circuit layers, e.g. photoresist, metallization, etc. applied to the principal surface (frontside) of the wafer, and the reticle and wafer can be aligned accurately. Any tilting or wedging of the wafer, i.e. non-normality to the incident light beam, is detected and corrected for.

Semiconductor wafer alignment using backside illumination

A proximity effect correction method for electron beam lithography suitable for use in a raster scan system. The exposure pattern consists of shapes; these shapes are subdivided into edge pixels and interior pixels; the pattern is then modified by uniformly removing a fraction of the interior pixels. The method reduces the backscattered electron background dose, improving the contrast for shapes with fine features, particularly when they are in close proximity to large or densely packed shapes.

Proximity effect correction method through uniform removal of fraction of interior pixels

An electron beam lithography system having a beamlet shaping section that includes a first multi-aperture array having m rows and n columns of apertures having a first shape and a second multi-aperture array with m rows and n columns of apertures having a second shape. Electron beamlets formed by the first multi-aperture array are deflected by a deflector unit before passing through the second multi-aperture array. The superposition of the electron beamlets on the second multi-aperture produces electron beamlets having a selected shape. Deflection logic on an active beam aperture array blank selected electron beamlets. The deflection logic can be updated with the next logic pattern as the current logic pattern is being executed. The unblanked electron beamlets are directed onto a surface to be exposed. The deflection logic on the active beam aperture array, and the multi-aperture arrays, are shielded from electrons and x-rays generated by the electrons striking surfaces within the electron beam lithography system. Sensitive deflection logic is radiation hardened to prevent degradation.

High throughput electron beam lithography system

A method and apparatus for detecting the presence of a thin film such as a photoresist film on a semiconductor wafer or other substrate. Only when a film is present does the surface reflectance (reflective power) of light incident on the wafer surface vary sinusoidally when the incidence angle of the light is varied. This sinusoidal variation in the reflected optical power is due to interference occurring between the film surface and wafer surface reflections. This method and apparatus allows determining whether an undeveloped photoresist layer is present on a wafer; this is not possible using merely visual inspection especially when an underlying pattern is present. The present method and apparatus may also be used to determine the thickness of a particular thin film.

Thin film detection method and apparatus

A mask alignment system for integrated circuit lithography achieves reticle to wafer referencing. A detection system located below the main projection lens detects the image of reticle alignment marks while also detecting wafer alignment marks. The reticle marks are imaged in light at the exposure wavelength. A first detection method images the fluorescence produced in the photoresist by the reticle mark images. A microscope located below the main projection lens produces the image and also images the wafer marks with broadband non-actinic illumination. The second method images the reticle marks in exposure light using a microscope which images and detects the exposure wavelength while maintaining the illumination and detection of the wafer marks. The third method collects directly both the exposure light and fluorescent light that is scattered and reflected from the wafer surface; the presence of wafer alignment marks changes this light collection. Scanning the wafer relative to the reticle produces a signal indicating the relative position of reticle and wafer alignment marks. All three methods provide information for complete field-by-field alignment including offsets, reticle-to-wafer magnification, rotation, and skew for both step-and-repeat and scanning exposure systems.

Direct reticle to wafer alignment using fluorescence for integrated

Defects in a processed or partly processed semiconductor wafer, or other similar three-dimensional periodic pattern formed on a substrate surface, are detected by light diffraction. Incident monochromatic light is provided from an elongated and extended source to illuminate the entire wafer surface. By use of automated image processing techniques, wafer macro inspection is thereby automated. The elongated and extended light source allows light at different angles to be incident upon each point of the wafer surface, thereby allowing defect detection for an entire wafer surface in a single field of view and reducing inspection time. The particular wavelength of the incident monochromatic light is predetermined to allow optimum detection of defects in the periodic pattern on the wafer, depending on the width and pitch of the features of the periodic pattern.

Wafer inspection method and apparatus using diffracted light

Accurate measurement of the sidewalls of photoresist features formed on a semiconductor substrate is achieved by a double mask exposure process. This allows probing the sidewalls of closely spaced photoresist features with the probe tip of an atomic force microscope, in spite of the small (submicron) physical dimensions involved. First a conventional line/space pattern is exposed onto the photoresist using the desired mask. Then a second exposure is made using a second mask which has a special space pattern to effectively remove the already exposed photoresist features along at least one side of one of the previously exposed features. Hence, at least that one side of that one feature is clear of any adjoining photoresist features when the photoresist is then developed after the two exposures. This allows easy access to the sidewall of that one photoresist feature by tilting the probe tip of the atomic force microscope. This allows the measurement of the photoresist feature sidewall characteristics, including for instance angle, curvature and any artifacts present.

Atomic force microscope measurement process for dense photoresist

A prealignment and global alignment system in a semiconductor wafer lithography system includes reflected light microscopes which form images of a wafer near a wafer loading position. The reflected light microscopes are mounted on the perimeter of a main projection lens assembly and have large object areas, typically about 5 mm wide so that features of the wafer are in the object areas even when the wafer is loaded with a very coarse alignment of about .+-.2.5 mm. The prealignment system identifies points on the wafer's edge to align the wafer for a first projection. For second and subsequent projections, the alignment system identifies alignment marks on the wafer to globally align the wafer. Magnification of the microscopes may be increased during global alignment to provide greater accuracy and precision. Prealignment and global alignment are performed while the wafer is at or near the loading position, can be performed in parallel with projection of a pattern on a second wafer, and can be performed quickly with only small movements of the wafer.

Alignment system with large area search for wafer edge and global marks

An improved method for stitching together reticle patterns on a substrate is described. One or more reticles, whose reticle border patterns are to be blended together on the substrate, are provided on an X-Y movable stage in a scanning type exposure system. Each of the reticles has a border pattern which is identical to the border pattern of at least one of the other reticles so that, when the images of these reticles border patterns overlap on the substrate, the overlapping border patterns effectively form a single image on the substrate. To prevent the double exposure of the overlapping border patterns from overexposing the photoresist and to reduce any detrimental effects resulting from misalignment between the overlapping patterns, either a triangular end portion of the scanning source, a filter, or a movable blind is used to partially shade the overlapping border pattern as the UV source is scanned over the border pattern. The graded exposures of the photoresist by the overlapping border patterns combine to fully expose the overlapping border patterns on the substrate. This procedure is continued so as to provide repeated reticle patterns in two dimensions which blend together.

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San Carlos, CA, United States of America

John H McCoy