Electric heating – Metal heating – By arc
Reexamination Certificate
1999-03-30
2001-05-29
Evans, Geoffrey S. (Department: 1725)
Electric heating
Metal heating
By arc
C219S121700, C219S121810, C700S166000
Reexamination Certificate
active
06239406
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a laser beam machining apparatus and in particular, to a laser beam machining apparatus having an improved throughput and an improved machining accuracy.
2. Description of the Related Art
Conventionally, there is a known laser beam machining apparatus called “laser repair” for cutting a fuse for switching an LSI internal wiring or a defective circuit to a redundant circuit, for example, in a DRAM. This laser beam machining apparatus applies a beam focus spot of about 2 micrometers to scan a wafer surface with accuracy in the order of sub-micrometer at a high speed, thus cutting a predetermined position.
Such a laser beam machining apparatus comprises a laser oscillator for emitting a laser beam, and a stage movable in two-dimensional directions of XY with an object such as a wafer mounted thereon. A laser beam emitted from the laser oscillator is focused on the object to be machined (hereinafter, referred to as a workpiece).
The laser beam machining apparatus further comprises a central processing unit (CPU) for performing various controls according to a program, so as to apply a laser beam from the laser oscillator onto a plurality of machining points pre-specified on the workpiece mounted on the stage. In general, positioning of the stage is controlled so that the laser beam is applied to a predetermined machining point on the workpiece.
Conventionally, there has also been an attempt to improve the throughput by accelerating the stage for an interval between machining points.
However, with the rapid technical progress, more and more fine machining is required with an increasing number of machining points.
The laser beam machining apparatus also needs to further increase its machining accuracy and further improve the throughput.
SUMMARY OF THE INVENTION
It is therefore an object of the present invention to provide a laser beam machining apparatus and method enabling to obtain an improved throughput, machining accuracy including a machining position accuracy.
The laser beam machining apparatus according to the present invention comprises: a laser oscillator; a stage for moving a workpiece in XY directions; and a central processing unit (CPU) for controlling laser emission of the laser oscillator and movement of the stage, wherein the CPU causes the laser beam machining apparatus to: group machining points on the workpiece into a plurality of segments, each segment being a set of machining points aligned parallel to one of the X axis and Y axis; create a shortest route through the plurality of segments; drive the stage along the shortest route; and apply a laser beam on the machining points on the shortest route.
In the aforementioned configuration, laser beam machining is performed according to data for the shortest route connecting the machining points. This enables significant improvement of the throughput.
According to another aspect of the present invention, each of the segments is a set of machining points having an identical coordinate value on one of the X and Y axes and being within a predetermined distance from an adjacent machining point on the other axis.
In this configuration, a plurality of machining points having an identical feed direction are grouped into a segment. This eliminates useless movement of the stage, thus increasing the throughput.
According to still another aspect of the present invention, the CPU adds one or more head and tail points to precede and follow each of the segments according to a stage acceleration/deceleration time.
In this configuration, laser beam machining is performed at a constant linear velocity. This enables attainment of laser beam machining with a high accuracy.
According to yet another aspect of the present invention, the CPU further adds one or more head and tail points to precede and follow each of the segments according to a ball bearing screw torque stabilizing time.
In this configuration, the laser beam machining can be performed with a ball bearing screw torque in a stable state. This increases the laser beam machining accuracy.
According to still yet another aspect of the present invention, the CPU further adds one or more head and tail points to precede and follow each of the segments according to a laser output stabilizing time after the laser oscillator is turned on.
In this configuration, the laser beam machining is performed with a laser output power in a stable state. This enhances the laser beam machining accuracy.
According to yet still another aspect of the present invention, the CPU further adds one or more head and tail points to precede and follow each of the segments according to a stage acceleration/deceleration time required until the stage reaches a constant linear velocity and a time required for stabilizing a laser output after the laser oscillator is turned on.
In this configuration, the laser emission timing can be obtained with a predetermined frequency to apply a stable laser beam power. This increases the laser beam machining accuracy.
According to yet another aspect of the present invention, the CPU further adds one or more empty points to precede and follow each of the segments where the laser oscillator emits a laser beam but the laser beam is shaded by a shutter so that the laser beam is not applied onto the workpiece.
In this configuration, the stage is moved (fed) with the least necessary load. This also increases the laser beam machining accuracy.
REFERENCES:
patent: 5293025 (1994-03-01), Wang
patent: 60-180687 (1985-09-01), None
patent: 2-99285 (1990-04-01), None
patent: 8-206867 (1996-08-01), None
patent: 9-5385 (1997-01-01), None
Edahiro Masato
Onoma Yoshimi
Evans Geoffrey S.
NEC Corporation
Sughrue Mion Zinn Macpeak & Seas, PLLC
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