The present invention relates to a laser processing apparatus that performs desired processing on a workpiece held on a chuck table.
A wafer having a plurality of devices such as integrated circuits (ICs) or large scale integrations (LSIs) formed on a top surface thereof so as to be demarcated by a plurality of intersecting planned dividing lines is divided into individual device chips by a dicing apparatus or a laser processing apparatus. The divided device chips are used in electric apparatuses such as mobile telephones, or personal computers.
The laser processing apparatus roughly includes: a chuck table that holds the wafer; an imaging unit that images the wafer held on the chuck table and detects a region to be processed; a laser beam irradiating unit that irradiates the wafer held on the chuck table with a pulsed laser beam; a processing feed mechanism that processing-feeds the chuck table and the laser beam irradiating unit relative to each other. The laser processing apparatus can process the wafer with high accuracy (see Japanese Patent Laid-Open No. 2015-085347, for example).
In a case where the laser processing apparatus described in the above Japanese Patent Laid-Open No. 2015-085347 is used to form a groove having a desired depth by irradiating the wafer with the pulsed laser beam of a wavelength absorbable by the wafer, there is a problem in that, even when, for example, the condensing point of the pulsed laser beam is positioned at a planned dividing line, the number of passes in which the pulsed laser beam is to be applied is set, and the pulsed laser beam is applied repeatedly, desired processing cannot be performed due to a constraint of a limit to a processing depth for a spot size.
Accordingly, the present applicant has considered calculating the number of spots to be positioned in the width direction of the planned dividing line and the number of passes in which the pulsed laser beam is to be applied in consideration of a limit value of the processing depth for the spot diameter of the pulsed laser beam and the thickness of the wafer to be divided, inputting processing information necessary for the laser processing apparatus, and forming grooves having a desired depth.
However, a problem is found in that a worker has to perform the calculation described above each time a wafer having a different thickness is to be processed, which is too troublesome. Further, a problem occurs in that proper laser processing is unable to be performed and the wafer is damaged due to an error in the calculation. Such problems are not limited to a case where the planned dividing lines of the wafer having the plurality of devices formed on the top surface thereof so as to be demarcated by the plurality of intersecting planned dividing lines are processed, but can occur also in a case where a plate-shaped object is cut and processed into a desired shape.
It is accordingly an object of the present invention to provide a laser processing apparatus that can solve the problem in that a worker has to calculate the number of spots to be positioned in a width direction and the number of passes in which a pulsed laser beam is to be applied each time a workpiece having a different thickness is to be processed, which is too troublesome, in a case of forming grooves having a desired depth by irradiating a workpiece with the pulsed laser beam.
In accordance with an aspect of the present invention, there is provided a laser processing apparatus including a chuck table having a holding surface defined by an X-axis direction and a Y-axis direction and configured to hold a workpiece, a laser beam irradiating unit configured to irradiate the workpiece held on the chuck table with a pulsed laser beam, and a controller. The laser beam irradiating unit includes a laser oscillator configured to emit the pulsed laser beam, and a condenser configured to condense the pulsed laser beam emitted by the laser oscillator onto the workpiece held on the chuck table. The controller includes a processing trajectory storage section configured to store X-coordinates and Y-coordinates of processing trajectories to be formed on the workpiece held on the chuck table, a thickness storage section configured to store a thickness of the workpiece, a limit processing depth storage section configured to store a spot diameter of the pulsed laser beam and a limit value of a processing depth, a pass number storage section configured to store the number of passes of the pulsed laser beam reaching the limit value of the processing depth, an overlap rate storage section configured to store an overlap rate of spots, a selecting section configured to select a product region and a non-product region, a processing width calculating section configured to calculate a processing width by multiplying, by the spot diameter, a value obtained by dividing the thickness stored in the thickness storage section by the limit value stored in the limit processing depth storage section, and a pass number calculating section configured to calculate the number of passes of the pulsed laser beam to be applied to a section in the processing width by multiplying the value obtained by dividing the thickness stored in the thickness storage section by the limit value stored in the limit processing depth storage section by the number of passes stored in the pass number storage section, and multiplying a result of the multiplication by the number of spots determined from the spot diameter of the pulsed laser beam, the overlap rate of the spots, the overlap rate being stored in the overlap rate storage section, and the processing width calculated by the processing width calculating section. The controller performs control to perform desired processing on the workpiece held on the chuck table by irradiating the processing width calculated by the processing width calculating section in the non-product region selected by the selecting section on a basis of the X-coordinates and the Y-coordinates stored in the processing trajectory storage section with the pulsed laser beam in the number of passes calculated by the pass number calculating section.
Preferably, the laser processing apparatus described above further includes an X-axis feed mechanism configured to processing-feed the chuck table and the laser beam irradiating unit relative to each other in the X-axis direction, and a Y-axis feed mechanism configured to processing-feed the chuck table and the laser beam irradiating unit relative to each other in the Y-axis direction. The controller performs the processing by controlling the laser oscillator and controlling the X-axis feed mechanism and the Y-axis feed mechanism. The laser beam irradiating unit further includes an X-axis optical scanner configured to guide the pulsed laser beam in the X-axis direction, and a Y-axis optical scanner configured to guide the pulsed laser beam in the Y-axis direction. The condenser includes an fθ lens.
According to the laser processing apparatus in accordance with the present invention, the controller computes and calculates the number of spots to be positioned in the width direction of desired processing trajectories and the number of passes in which the pulsed laser beam is to be applied in consideration of the limit value of the processing depth for the spot diameter of the pulsed laser beam and the thickness of the workpiece to be divided. The number of spots to be positioned in the width direction of the desired processing trajectories and the number of passes in which the pulsed laser beam is to be applied are reflected in the laser processing performed by the control of the controller. This obviates a need for a worker to calculate the parameters described above one by one, input the parameters to the laser processing apparatus, and thereby set the parameters so as to form grooves having a desired depth, and solves a problem in that the complex calculation described above needs to be performed each time a workpiece having a different thickness is to be processed, which is too troublesome. In addition, a problem of damaging the workpiece due to an error in the calculation is also solved.
The above and other objects, features and advantages of the present invention and the manner of realizing them will become more apparent, and the invention itself will best be understood from a study of the following description and appended claims with reference to the attached drawings showing a preferred embodiment of the invention.
A laser processing apparatus according to an embodiment of the present invention will hereinafter be described in detail with reference to the accompanying drawings.
In addition, the laser processing apparatus 1 includes: a moving mechanism 4 including an X-axis feed mechanism 41 that moves the chuck table 35 in an X-axis direction and a Y-axis feed mechanism 42 that moves the chuck table 35 in a Y-axis direction; a frame body 5 including a vertical wall portion 5a erected on the base 2 and on a side of the moving mechanism 4 and a horizontal wall portion 5b extending in a horizontal direction from an upper end portion of the vertical wall portion 5a; and an imaging unit 7 that images the wafer held on the chuck table 35 to perform alignment. An input unit 8 and a display unit not depicted are connected to the controller 100. Incidentally, the display unit can also be used as the input unit 8 when the display unit is configured as a touch panel that allows touch input.
As depicted in
The X-axis feed mechanism 41 converts rotary motion of a motor 43 into rectilinear motion via a ball screw 44, and transmits the rectilinear motion to the X-axis direction movable plate 31. The X-axis feed mechanism 41 thereby moves the X-axis direction movable plate 31 in the X-axis direction along a pair of guide rails 2a and 2a arranged along the X-axis direction on the base 2. The Y-axis feed mechanism 42 converts rotary motion of a motor 45 into rectilinear motion via a ball screw 46, and transmits the rectilinear motion to the Y-axis direction movable plate 32. The Y-axis feed mechanism 42 thereby moves the Y-axis direction movable plate 32 in the Y-axis direction along a pair of guide rails 31a and 31a arranged along the Y-axis direction on the X-axis direction movable plate 31.
An optical system constituting the laser beam irradiating unit 6 described above and the imaging unit 7 are housed inside the horizontal wall portion 5b of the frame body 5. A lower surface side of a distal end portion of the horizontal wall portion 5b is provided with a condenser 61 that constitutes part of the laser beam irradiating unit 6 and irradiates the wafer 10 with a pulsed laser beam LB. The imaging unit 7 is imaging means for imaging the wafer 10 held on the chuck table 35 and detecting the position and orientation of the wafer 10, a position to be irradiated with the pulsed laser beam, and the like. The imaging unit 7 is disposed at a position adjacent to the condenser 61 described above in the X-axis direction indicated by an arrow X in the figure.
Incidentally, the laser beam irradiating unit according to the present embodiment is not limited to the laser beam irradiating unit 6 depicted in
Configurations of the wafer 10 as a workpiece of the laser processing apparatus 1 according to the present embodiment and the controller 100 will next be described below. Incidentally, in the embodiment to be described below, description will be made supposing that the laser beam irradiating unit 6 is arranged in the laser processing apparatus 1 depicted in
The workpiece to be processed by the laser processing apparatus 1 according to the present embodiment is, for example, a silicon (Si) wafer 10 depicted in
The controller 100 is constituted by a computer. The controller 100 includes: a central processing unit (CPU) that performs arithmetic processing according to a control program; a read-only memory (ROM) that stores the control program and the like; a readable and writable random access memory (RAM) for temporarily storing an arithmetic result and the like; an input interface; and an output interface. The controller 100 is connected with the imaging unit 7, the input unit 8, the laser oscillator 62, the X-axis feed mechanism 41, the Y-axis feed mechanism 42, and the like.
The laser processing apparatus 1 according to the present embodiment generally has the configuration as described above. Functions and actions of the laser processing apparatus 1 will specifically be described below.
Laser processing of the laser processing apparatus 1 according to the present embodiment on the wafer 10 is performed by the controller 100.
Referring to
The controller 100 further includes: a processing width calculating section 105 that calculates a processing width V by multiplying, by the spot diameter S, a value obtained by dividing the thickness H stored in the thickness storage section 101 by the limit value R stored in the limit processing depth storage section 102; a pass number calculating section 106 that calculates the number of passes Pt of the pulsed laser beam LB to be applied to a section in the processing width V by multiplying the value obtained by dividing the thickness H stored in the thickness storage section 101 by the limit value R of the processing depth which limit value is stored in the limit processing depth storage section 102 by the number of passes P stored in the pass number storage section 103 and multiplying a result of the multiplication by the number of spots St determined from the overlap rate W of the spots which overlap rate is stored in the overlap rate storage section 104 and the processing width V calculated by the processing width calculating section 105. Moreover, the controller 100 includes: a processing trajectory storage section 107 that stores coordinate information I regarding the X-coordinates and the Y-coordinates of processing trajectories to be formed on the wafer 10 held on the chuck table 35; and a selecting section 108 that selects a product region A and a non-product region B. On the basis of information aggregated from the processing width calculating section 105, the pass number calculating section 106, the processing trajectory storage section 107, and the selecting section 108 described above, a processing executing section 109 that performs the laser processing controls the laser oscillator 62, the X-axis feed mechanism 41, and the Y-axis feed mechanism 42 described above to realize the desired laser processing.
Each functional section of the foregoing controller 100 will be described in further detail. The thickness H of the wafer 10 which thickness is to be stored in the thickness storage section 101 is, for example, stored after being obtained through input by a worker operating the input unit 8 or by reading bar code information formed on the wafer 10. The thickness H of the wafer 10 according to the present embodiment is 300 μm, for example. The thickness storage section 101 stores the thickness H=300 μm of the wafer 10.
The limit processing depth storage section 102 stores the limit value R of the processing depth on the basis of the spot diameter S of the pulsed laser beam LB applied by the laser beam irradiating unit 6. This will be described with reference to
The pass number storage section 103 stores the number of passes P for reaching the actually measured limit value R of the processing depth in the limit processing depth storage section 102 described above. In the present embodiment, the pass number storage section 103 stores the number of passes P=8 as an actually measured value. In addition, as depicted in
The processing width calculating section 105 calculates the processing width V necessary to form the dividing groove 18 having such a depth as to completely divide the wafer 10. Specifically, the processing width V is calculated as follows by multiplying, by the spot diameter S (10 μm), a value obtained by dividing the thickness H (300 μm) stored in the thickness storage section 101 by the limit value R (100 μm) stored in the limit processing depth storage section 102.
Processing Width V=(H/R)·S=(300/100)·10=30 [μm]
A processing width V=30 μm is thereby calculated and stored.
The pass number calculating section 106 calculates the number of passes Pt of the pulsed laser beam LB to be applied to a section in the processing width V described above. The number of passes Pt is the number of passes of the pulsed laser beam LB which number of passes is necessary to form the dividing groove 18 that completely divides the wafer 10 along a planned dividing line 14 of the wafer 10. The number of passes Pt is calculated by multiplying a value obtained by dividing the thickness H (300 μm) stored in the thickness storage section 101 by the limit value R (100 μm) stored in the limit processing depth storage section 102 by the number of passes P (eight times) stored in the pass number storage section 103, and multiplying a result of the multiplication by the number of spots St determined from the overlap rate W (50%) of spots which overlap rate is stored in the overlap rate storage section 104 and the processing width V (30 μm) calculated by the processing width calculating section 105.
Here, letting x be the number of pulsed laser beams LB applied so as to be overlapped in a width direction following a first spot, the number of spots St of the pulsed laser beam LB applied in the processing width V is expressed by “St=1+x.” From a relational equation (Spot Diameter S)·{1+(100%−Overlap Rate W)·x}=Processing Width V, this x is obtained by solving 10·{1+(1−0.5)·x}=30 with respect to x (x=4). Thus, the number of spots St applied for the processing width V=30 μm is “5” (see also
Then, the number of passes Pt of the pulsed laser beam LB to be applied to a section in the processing width V is calculated as follows.
Pt=(H/R)·P·St=(300/100)·8.5=120
As is understood by referring to
As described above, the controller 100 includes the processing trajectory storage section 107 that stores the coordinate information I regarding the X-coordinates and the Y-coordinates of processing trajectories to be formed in the wafer 10 held on the chuck table 35. The coordinate information I stored in the present embodiment, that is, the coordinate information I regarding the X-coordinates and the Y-coordinates identifying central lines 16 along planned dividing lines 14 of the wafer 10 depicted on an enlarged scale in
Further, the controller 100 includes the selecting section 108 that selects a product region A and a non-product region B, as described above. The product region A in the present embodiment means a region that includes a device 12 described above or the device 12 and outer edges thereof and in which laser processing is not allowed. The non-product region B means a region in which the above-described laser processing is allowed. That is, making description with reference to
After the controller 100 obtains the processing width V, the number of passes Pt of the pulsed laser beam LB to be applied to a section in the processing width V, and the coordinate information I regarding the X-coordinates and the Y-coordinates of processing trajectories to be formed and the product region A and the non-product region B are selected, as described above, laser processing on the wafer 10 is performed on the basis of the processing executing section 109 of the controller 100.
Incidentally, the laser processing conditions in the present embodiment are set as follows, for example.
The wafer 10 transported to the laser processing apparatus 1 described with reference to
On the basis of information detected by the alignment described above, as depicted in
Next, while a spot is positioned at the bottom of the recessed groove by lowering the position of the condensing point in a Z-axis direction indicated by an arrow Z in
According to the embodiment described above, the controller 100 calculates the number of spots St to be positioned in the width direction of the planned dividing line 14 and the number of passes Pt in which the pulsed laser beam LB is to be applied in consideration of the limit value R of the processing depth for the spot diameter S of the pulsed laser beam LB and the thickness H of the wafer 10 to be divided. The number of spots St and the number of passes Pt are reflected in the laser processing performed by the controller 100. This obviates a need for the worker to calculate the parameters described earlier one by one, input the parameters to the laser processing apparatus 1, and thereby set the parameters so as to form dividing grooves 18 having a desired depth, and solves a problem in that the worker has to perform the complex calculation described above each time another wafer having a different thickness is to be processed, which is too troublesome. In addition, a problem of damaging the wafer due to an error in the calculation is also solved.
In the embodiment described above, description has been made of an example in which the laser processing apparatus 1 forms grooves having a desired depth by processing the wafer 10 having the plurality of devices 12 formed on the top surface 10a so as to be demarcated by the plurality of intersecting planned dividing lines 14. However, the present invention is not limited to this. For example, in a case where a silicon plate having a circular shape is to be processed as a workpiece and a product having a desired shape, for example, a silicon plate having a quadrangular shape identified by the X-coordinates and the Y-coordinates of processing trajectories to be formed, the X-coordinates and the Y-coordinates being stored in the processing trajectory storage section 107, is to be obtained from the silicon plate having the circular shape, the silicon plate having the desired quadrangular shape can be obtained as a product by selecting a region having the desired quadrangular shape as a product region A in the selecting section 108 described above, selecting a region surrounding the product region A as a non-product region B in the selecting section 108 described above, performing the laser processing described above on the non-product region B along the outer edges of the product region A, and thereby forming dividing grooves 18.
The present invention is not limited to the details of the above described preferred embodiment. The scope of the invention is defined by the appended claims and all changes and modifications as fall within the equivalence of the scope of the claims are therefore to be embraced by the invention.
Number | Date | Country | Kind |
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2022-094574 | Jun 2022 | JP | national |