Alignment method and apparatus for aligning cutting blade

• US 6,494,122 B2
• Filed: 07/05/2001
• Issued: 12/17/2002
• Est. Priority Date: 07/14/2000
• Status: Active Grant

• Current Assignee: Disco Corporation
• Original Assignee: Disco Corporation
• Inventors: Kamigaki, Masakado
• Primary Examiner(s): Rachuba, M.
• Application Number:
  US09/898,009
• Publication Number:
  US 20020025616A1
• Time in Patent Office: 530 Days
• Field of Search: 83/13, 838/80, 838/81, 838/82, 838/83, 838/84, 838/86, 83/27, 83/34, 83/761, 83/766, 83/767, 83/768, 839/291, 125/13.01, 125/20, 125/23.01
• US Class Current: 83/13
• CPC Class Codes: B23D 59/001 Measuring or control devices, e.g. for automatic control of work feed pressure on band saw blade measuring in general G01; controlling in general G05
• CPC Class Codes: B28D 5/0088 the supporting or holding device being angularly adjustable
• CPC Class Codes: B28D 5/023 with a cutting blade mounted on a carriage
• CPC Class Codes: H01L 21/3043 Making grooves, e.g. cutting
• CPC Class Codes: Y10T 83/0348 Active means to control depth of score
• CPC Class Codes: Y10T 83/04 Processes
• CPC Class Codes: Y10T 83/173 Arithmetically determined program
• CPC Class Codes: Y10T 83/175 With condition sensor

Abstract

Alignment method and apparatus for aligning a cutting blade with a selected street on a semiconductor wafer. It has square chip areas defined by crossing streets and alignment spots formed on its surface. Two street lines with at least one street intervening therebetween are selected, and linear functions ƒ(x) and g(x) are determined on the basis of the coordinates of their alignment spots according to the least squares method. The linear functions ƒ(x) and g(x) run among the alignment spots at the closest distances thereto to represent the two selected streets. Another linear functions ƒ′(x) and g′(x) are determined by putting the linear functions f(x) and g(x) into parallelism with the X-axis. The angular difference and the distance between the two selected streets from the linear functions ƒ′(x) and g′(x), and the angular difference and inter-distance are divided by the number of street-to-street spaces between the two selected streets to provide the angle of correction and the indexing amount per street. Beginning with the street adjacent to one of the two selected streets the cutting blade is aligned sequentially with the subsequent intervening streets.

Claims

1. In dicing a workpiece having a plurality of chip areas defined by a plurality of streets running and crossing in a first and a second directions and a plurality of alignment spots formed on a surface of the workpiece, the workpiece being diced by a dicing machine including at least a chuck table for fixedly holding the workpiece, the chuck table being rotatable, and being adapted to be put in a controlled angular position;

a cutting means having a cutting blade;

a feeding means for moving the chuck table and/or the cutting means relative to each other in directions in which required cutting may be effected on the workpiece; and

indexing means for moving the chuck table and/or the cutting means a street-to-street distance,

an alignment method for aligning a selected street and the cutting blade with each other comprising;

a first step of;

imaging the surface of the workpiece to detect alignment spots which permit recognition of selected first and second streets running in same direction with at least one street intervening therebetween, determining and storing X- and Y-coordinates of the first and second streets, provided that X-axis is corresponding to a feeding-and-cutting direction whereas Y-axis is corresponding to a feeding-and-indexing direction;

a second step of;

determining an angular difference between an inclination of the first street and that of the second street based on the coordinates of the detected alignment spots, obtaining an angle of correction for each street by dividing the angular difference by number of street-to-street spaces existing between the first and second streets, and storing the angle of correction;

a third step of;

putting the first and second streets in parallelism with the X-axis to determine the Y-coordinates of intercept of so oriented first and second streets and a distance between the so oriented first and second streets, determining an indexing amount by dividing so determined distance by number of the street-to-street spaces existing between the first and second streets, and storing so determined indexing amount; and

a fourth step of;

moving the cutting blade and/or the workpiece in the Y-axial direction based on both of the so determined angle of correction and the indexing amount so that the cutting blade may be put exactly in alignment with a selected street to be cut.

2. An alignment method according to claim 1, wherein

in the first step: at least three alignment spots are detected for recognizing the first street and the second street respectively, and the coordinates of the so detected alignment spots are stored;

in the second step;

a first linear function representing the first street is determined from the coordinates of the alignment spots for recognizing the first street according to the least squares method;

a second linear function representing the second street is determined from the coordinates of the alignment spots for recognizing the second street according to the least squares method; and

the angular difference between the inclination of the first street and that of the second street is determined relative to the X-axis from the first and second linear functions; and

in the third step;

the first linear function is rotated until the first street has been put in parallelism relative to the X-axis, thereby reducing the angle of inclination to zero and determining the Y-coordinate of the first street to be the intercept of the so rotated first linear function; and

the second linear function is rotated until the second street has been put in parallelism relative to the X-axis, thereby reducing the angle of inclination to zero and determining the Y-coordinate of the second street to be the intercept of the so rotated second linear function.

3. An alignment method according to claim 1, wherein the first and second streets are the opposite outermost streets formed in the workpiece.

4. An alignment method according to claim 1, wherein the workpiece is a CSP substrate.

7. An alignment method according to claim 2, wherein the workpiece is a CSP substrate.

8. An alignment method according to claim 3, wherein the workpiece is a CSP substrate.

5. An alignment apparatus to be built in a dicing machine including at least a chuck table for fixedly holding a workpiece, the chuck table being rotatable, and being adapted to be put in a controlled angular position;

a cutting means having a cutting blade;

a feeding means for moving the chuck table and/or the cutting means relative to each other in directions in which required cutting may be effected on the workpiece; and

an indexing means for moving the chuck table and/or the cutting means a street-to-street distance;

the workpiece having a plurality of chip areas defined by a plurality of streets running and crossing in first and second directions and a plurality of alignment spots formed on a surface of the workpiece, characterized in that the alignment apparatus for aligning a selected street and the cutting blade with each other comprises;

an imaging means for taking a picture of the surface of the workpiece, which is fixedly held by the chuck table;

a coordinates detecting-and-storing means for detecting alignment spots which permit recognition of selected first and second streets running in same direction with at least one street intervening therebetween and for determining and storing X- and Y-coordinates of the first and second streets, provided that X-axis is corresponding to a feeding-and-cutting direction whereas Y-axis is corresponding to a feeding-and-indexing direction;

a linear function determining means for determining first and second linear functions ƒ

(x) and g(x) representing the first and second streets on the basis of the X- and Y-coordinates of the first and second streets memorized in the coordinates detecting-and-storing means;

a correction angle setting means for determining and storing an angular difference between the first and second linear functions ƒ

(x) and g(x) to divide the so determined angular difference by number of the street-to-street spaces between the first and second streets, thereby determining and storing an angle of correction for each street;

an indexing means for determining the intercepts of the first and second linear functions ƒ

(x) and g(x) which have been rotated to be parallel to the X-axis, determining a distance between the first and second linear functions ƒ

(x) and g(x), and dividing so determined distance by number of the street-to-street spaces between the first and second streets, thereby determining and storing the indexing amount;

a positioning control means for indexing the cutting blade in Y-axial direction and aligning a selected street with the X-axis on the basis of the angle of correction and the indexing amount; and

an alignment data storage means connected to the coordinates detecting-and-storing means, the linear function determining means, the correction angle setting means, the indexing means and the positioning means for storing pieces of alignment information pertaining to the workpiece for permitting random access.

6. An alignment apparatus according to claim 5, wherein

in the coordinates detecting-and-storing means, at least three alignment spots are detected for recognizing the first street and the second street respectively, and the coordinates of the so detected alignment spots are stored;

in the linear function determining means, a first linear function representing the first street is determined from the coordinates of the alignment spots for recognizing the first street according to the least squares method; and

a second linear function representing the second street is determined from the coordinates of the alignment spots for recognizing the second street according to the least squares method.