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US 5793052
Added 9/23/2026, 12:54:39 PM
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Patent summary
Title, assignee, inventors, filing/issue dates, abstract, and a plain-language overview of the claims.
Patent Overview — US 5,793,052 A
Title: Dual stage following method and apparatus
Assignee / Inventor: Original assignee and current assignee listed as Nikon Corp; inventor Ryoichi Kawaguchi. A related JP priority filing JP10066401A (published as JPH10261587A) is dated 1998-03-17.
Dates (as listed): Filing/priority date 1997-03-18; granted and published 1998-08-11; anticipated expiration 2017-03-18; legal status "Expired – Lifetime."
Purpose: To minimize relative position error between two stages driven by a single input signal. The stages must move in perfect synchronization; deviation arises from mechanical/environmental and electrical/electronic disturbances. One exemplary application is synchronizing reticle and wafer X-Y stages in a scanning exposure device for semiconductor lithography, where a reticle is imaged through a reduction-projection lens onto a wafer. Scanning permits projection of reticle patterns larger than the projection lens image field.
Plain-language scope: Rather than driving two stages (plants) in parallel from input x0 to produce outputs y1 and y2 (the prior-art FIG. 1 arrangement), the invention couples the stages serially for control purposes: the first stage is driven by input positioning signal x0, and its output position signal y1 drives the second stage, which thus follows the first. This avoids the added mechanical complexity, cost, and reliability penalty of adding a Fine Motion Mechanism (FMM) plus actuator and sensor onto a primary stage. The specification states the relative position error is guaranteed to be no larger than the smaller of the absolute position errors of either stage alone, and does not require a direct mechanical linkage. Which stage is driver and which is follower depends on individual stage characteristics; FIGS. 5a/5b show either reticle-follows-wafer or wafer-follows-reticle, with an illustrative ×4 or ×0.25 scaling factor for reticle-to-wafer motion. Position signals may come from interferometers, capacitive or magnetic sensors, or linear encoders. Application extends to high-precision stage synchronization generally, including a laser-printer paper-advance stage versus line-exposure stage, with an appropriate scale factor.
What the excerpt does not establish: It provides no claims text, no claim construction, no complete equations, no full figure content, and no prosecution history. It does not establish validity, enforceability, ownership transfers, litigation, or prior-art effect; no such matters were researched. Accuracy of the listed assignee/status is expressly disclaimed by the source.
Generated 10/1/2026, 9:53:24 PM
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