US 5,308,222 A · Noncentering specimen prealigner

Abstract

A prealigner (10) employs an X-Y stage (20) and a rotary stage (26) to position and orient a specimen (12) without centering it on the prealigner. In a preferred embodiment, the rotary stage is mounted on the X-Y stage and receives a semiconductor (12) in a substantially arbitrary position and orientation. The prealigner employs the rotary stage and translation in only an X-axis direction to scan the peripheral edge (76) of the wafer across an optical scanning assembly (36) to form a polar coordinate map of the wafer. A microprocessor (162) determines the location and orientation of the wafer from the map and cooperates with a motor drive controller (122) to generate control signals for positioning and orienting the wafer in the preselected alignment without changing the location at which the wafer is held.

Claims22

Dependent claims

A specimen prealigner for positioning in a preselected alignment a specimen having a peripheral edge with plural contours having contour transitions between them, the preselected alignment including a selected position and a selected orientation, comprising:

holding means for releasibly holding the specimen at a first specimen location;
edge detecting means for detecting the peripheral edge of the specimen and forming a map of the specimen, the edge detecting means including first and second light emitters that direct light beams toward the peripheral edge of the specimen and first and second light detectors that receive the light beams after they strike the specimen, the first light emitter and first light detector cooperating to detect the peripheral edge of the specimen and the second light emitter and the second light detector cooperating to detect the contour transitions before they are scanned by the first light emitter and first light detector, thereby to allow the contours and contour transitions to be scanned at respective first and second scan rates;
and
positioning means coupled to the specimen holding means and responsive to the map formed by the edge detecting means for positioning the specimen in the preselected alignment without changing the first specimen location at which the holding means releasibly holds the specimen.

1 more element

A specimen prealigner for positioning in a preselected alignment a specimen having a peripheral edge that includes adjacent edge segments of first and second contours with a contour transition between them, comprising:

edge detecting means for detecting the peripheral edge of the specimen, the edge detecting means including a first light emitter that directs a light beam toward the peripheral edge of the specimen and a corresponding light detector that receives the light beam after it strikes the specimen;
scanning means for scanning the first and second contours of the peripheral edge past the edge detecting means at a first scan rate and for scanning the contour transition past the edge detecting means at a second scan rate;
and
contour predicting means for predicting whether the edge detecting means will scan the contour transition and for generating a corresponding contour prediction signal, the scanning means including a second light emitter that directs a light beam toward the peripheral edge of the specimen and a corresponding light detector that receives the light beam after it strikes the specimen, and the scanning means being responsive to the contour prediction signal to scan the peripheral edge with the edge detecting means along the contour transition at the second scan rate.

1 more element

Dependencies are inferred from the claim text.

Noncentering specimen prealigner

Life of this patent

Noncentering specimen prealigner

Life of this patent

Abstract

Claims22