Laser processing apparatus and correction method for focus point position

Abstract

The present application provides a laser processing device and a method for correcting a focal point position, and provides a new laser processing device, in which, in view of the influence of thermal expansion accompanying heat generation of a moving mechanism, the shift of the focal point position due to the influence of thermal expansion is corrected to achieve improvement in processing quality. The laser processing device includes: a laser beam irradiation mechanism that causes a focal point to converge on a workpiece held by a holding mechanism to irradiate a laser beam; and a temperature detector that detects the temperature of the holding mechanism or the temperature of a drive section that moves the holding mechanism in a processing feed direction. The laser beam irradiation mechanism has a focal point position adjustment unit. A controller controls the focal point position adjustment unit to set the focal point position of the laser beam in the thickness direction of the workpiece based on the temperature detected by the temperature detector, and controls the drive section to set the position of the focal point in the index feed direction of the workpiece, thereby correcting the focal point position of the laser beam.

Description

TECHNICAL FIELD

[0001] The present application relates to a laser processing apparatus, and more particularly to a technique for eliminating a reduction in processing quality that accompanies a shift in the position of a focal point of a laser beam. BACKGROUND

[0002] In a manufacturing process of a semiconductor device, a semiconductor wafer on which a plurality of devices are formed on a front surface is divided, thereby forming a plurality of semiconductor device chips.

[0003] In the division of the semiconductor wafer, in addition to a cutting apparatus having a cutting tool that has been widely used conventionally, a laser processing apparatus has been widely used in recent years, and the laser processing apparatus can increase a processing feed rate at a high speed and can reduce a cutting allowance as compared with the cutting apparatus. In the laser processing apparatus, a laser beam emitted from a laser oscillator is irradiated to the semiconductor wafer.

[0004] In the case of the cutting apparatus that performs cutting processing by a rotating cutting tool, although depending on the kind of the wafer, a holding stage that holds the semiconductor wafer performs processing feed at a feed rate of about 80 mm / s to 100 mm / s.

[0005] In contrast to this, in the laser processing apparatus, the holding stage that holds the semiconductor wafer performs processing feed at a feed rate of about 100 mm / s to 600 mm / s. In recent years, the feed rate is further increased at a high speed, and sometimes processing feed is performed at a speed of 600 mm / s to 1000 mm / s or more.

[0006] With respect to the laser processing apparatus that performs processing feed at a high speed like this, in Patent Literature 1, a laser processing apparatus that performs laser ablation processing is disclosed, and in Patent Literature 2, a laser processing apparatus that performs so-called stealth dicing processing that forms a modified layer by converging a focal point inside a wafer is disclosed.

[0007] Patent Literature 1: Japanese Patent Application Laid-Open No. 2003-320466

[0008] Patent Literature 2: Japanese Patent No. 3408805

[0009] When processing feed is performed at a high speed, heat is generated in a moving mechanism that moves the holding stage at a high speed. Specifically, a motor that constitutes a drive section of the moving mechanism generates heat, and a portion that is affected by the heat expands thermally.

[0010] When the position of a workpiece held by the holding stage is changed due to the thermal expansion, the focal point cannot be positioned at a desired position, and desired processing cannot be performed, which reduces processing quality.

[0011] Therefore, for example, countermeasures such as temporarily stopping the processing at a prescribed timing in the processing, detecting the laser processed mark formed and correcting the position of the focal point, detecting the height of the upper surface of the workpiece and the position of the processing intended line in advance before the processing and correcting them, and the like are considered.

[0012] However, in these countermeasures, the time for detection is spent and the processing time can become long. In addition, in the case where the influence of the thermal expansion is large as described above, the correction based on these countermeasures can not cope with the shift of the position of the focal point due to the influence of the thermal expansion. SUMMARY

[0013] Therefore, the object of the present application is to provide a laser processing apparatus which corrects the shift of the position of the focal point due to the influence of the thermal expansion of the moving mechanism due to the heat generation and achieves the improvement of the processing quality.

[0014] The object of the present application described above is explained next for the means for solving the object.

[0015] According to one embodiment of the present application, a laser processing apparatus is provided, wherein the laser processing apparatus has: a holding mechanism which holds a workpiece; a laser beam irradiation mechanism which irradiates a laser beam with a focal point converged on the workpiece held by the holding mechanism; a moving mechanism which moves the holding mechanism in a processing feed direction and an indexing feed direction; a controller which controls at least the laser beam irradiation mechanism and the moving mechanism; and a temperature detector which detects the temperature of the holding mechanism or the temperature of a driving section which moves the holding mechanism in the processing feed direction, the laser beam irradiation mechanism has a focal point position adjustment unit for adjusting the position of the focal point of the laser beam in the thickness direction of the workpiece, the controller controls the focal point position adjustment unit to set the position of the focal point of the laser beam in the thickness direction of the workpiece in accordance with the change of the temperature detected by the temperature detector, and controls the driving section to set the position of the focal point in the indexing feed direction of the workpiece, whereby the position of the focal point of the laser beam is corrected.

[0016] It is preferable that a correlation map which is stored in advance defining the correlation between the change of the temperature of the holding mechanism or the driving section and the change of the position of the focal point is stored in the controller, the controller acquires the change of the position of the focal point corresponding to the temperature detected by the temperature detector by referring to the correlation map, and the controller corrects the position of the focal point of the laser beam using a correction value corresponding to the change of the position of the focal point.

[0017] Preferably, the drive unit that moves the holding mechanism in the machining feed direction in the moving mechanism is a linear motor with an electromagnetic coil, and the temperature detector detects the temperature of the electromagnetic coil.

[0018] According to another aspect of the present invention, a method for correcting the focal point position of a laser processing apparatus is provided. The laser processing apparatus includes: a holding mechanism for holding a workpiece; a laser beam irradiation mechanism for focusing a focal point onto the workpiece held by the holding mechanism to irradiate a laser beam; a moving mechanism for moving the holding mechanism in a processing feed direction and an indexing feed direction; a controller for controlling at least the laser beam irradiation mechanism and the moving mechanism; and a temperature detector for detecting the temperature of the holding mechanism or the temperature of the drive unit that moves the holding mechanism in the processing feed direction. The laser beam irradiation mechanism includes a focal point position adjustment unit, wherein the focal point position... The adjustment unit is used to adjust the focusing point position of the laser beam in the thickness direction of the workpiece. The focusing point position correction method includes the following steps: a temperature detection step, in which the temperature is detected by the temperature detector; a correction value calculation step, in which a correction value for shifting the focusing point position of the laser beam is calculated based on the detected temperature; and a focusing point position correction step, in which the focusing point position adjustment unit is controlled to set the focusing point position of the laser beam in the thickness direction of the workpiece based on the correction value, and the driving unit is controlled to set the position of the focusing point in the indexing feed direction of the workpiece, thereby correcting the focusing point position of the laser beam.

[0019] Preferably, the controller stores a correlation graph, which is pre-stored and defines the correlation between the temperature change of the holding mechanism or the drive unit and the change of the focal point position. In the correction value calculation step, the controller obtains the change of the focal point position corresponding to the temperature detected by the temperature detector by referring to the correlation graph, and calculates the correction value corresponding to the change of the focal point position.

[0020] Preferably, the drive unit that moves the holding mechanism in the machining feed direction in the moving mechanism is a linear motor with an electromagnetic coil, and the temperature detector detects the temperature of the electromagnetic coil.

[0021] According to the present invention, the offset of the focal point position of the laser beam within the workpiece can be corrected, and the offset of the focal point position within the workpiece caused by the thermal expansion of the holding mechanism can be prevented.

[0022] In addition, by directly detecting the temperature of the drive unit that enables the holding mechanism to perform high-speed machining feed, temperature changes can be identified early, and position correction with higher accuracy can be performed. Attached Figure Description

[0023] Figure 1 Fig. 1 is a perspective view showing a laser processing apparatus according to one embodiment of the present application.

[0024] Figure 2 Fig. 2 is a view showing an optical system and the like of a laser beam irradiation mechanism.

[0025] Figure 3 Fig. 3 is a block diagram showing a controller that controls the laser processing apparatus and its control objects.

[0026] Figure 4 (A) of Fig. 6 is a correlation diagram of a temperature of a driving section and an offset amount of a focal point in the -Y axis direction within a workpiece, Figure 4 (B) of Fig. 6 is a correlation diagram of the temperature of the driving section and an offset amount of the focal point in the -Z axis direction within the workpiece.

[0027] Figure 5 (A) of Fig. 7 is a schematic view that explains a focal point position at a reference temperature, Figure 5 (B) of Fig. 7 is a schematic view that explains an offset of the focal point position in the Y axis direction at the time of temperature rise, Figure 5 (C) of Fig. 7 is a schematic view that explains a corrected focal point position.

[0028] Figure 6 (A) of Fig. 8 is a schematic view that explains a focal point position at a reference temperature, Figure 6 (B) of Fig. 8 is a schematic view that explains an offset of the focal point position in the Z axis direction at the time of temperature rise, Figure 6 (C) of Fig. 8 is a schematic view that explains a corrected focal point position.

[0029] Figure 7 Fig. 9 is a flowchart of a control method that performs correction of a focal point position.

[0030] Explanation of Reference Numerals

[0031] 10: laser processing apparatus; 12: laser beam irradiation mechanism; 13: holding stage; 14: moving mechanism; 20: indexing feed mechanism; 21: processing feed mechanism; 24: Y axis direction moving base; 32: X axis direction moving base; 33: driving section; 35: magnet plate; 36: temperature detector; 40: processing head; 41: laser oscillator; 42: mirror; 43: condensing lens; 44: focal point position adjustment unit; 46: laser beam; 100: controller; 102: control section; 104: storage section; Ml: correlation diagram; M2: correlation diagram; P: focal point; Tl: reference temperature; T2: temperature; W: workpiece; Ay: correction value; Az: correction value. DETAILED DESCRIPTION

[0032] Figure 1 is a perspective view showing a laser processing apparatus of one embodiment of the present application. The laser processing apparatus 10 is configured to relatively move a laser beam irradiation mechanism 12 that irradiates a laser beam and a holding table 13 that holds a work W on an upper surface to process the work W.

[0033] The work W is a round plate-shaped semiconductor wafer such as a silicon wafer, and is divided into a plurality of regions by division predetermined lines arranged in a lattice shape. A device such as an IC, LSI, or the like is formed in each region divided by the division predetermined lines. In addition, as the work W, in addition to a work in which silicon or the like is used as a material, a work formed of another material such as ceramic, glass, sapphire, or the like can be used.

[0034] The work W is attached to a tape T, and is fixed to a ring-shaped frame F by the tape T. In this way, a work unit U is configured, and the work unit U is handled as a unit.

[0035] The laser processing apparatus 10 has a rectangular parallelepiped-shaped base 11. A movement mechanism 14 that processes a work W in a processing feed direction (X-axis direction) and indexes in a Y-axis direction is provided on an upper surface of the base 11. A standing wall portion 16 is provided upright at a rear of the movement mechanism 14. An arm portion 17 protrudes from a front surface of the standing wall portion 16, and the laser beam irradiation mechanism 12 is supported on the arm portion 17 in a manner facing the work W.

[0036] The movement mechanism 14 has an indexing mechanism 20 that relatively moves the work W and the laser beam irradiation mechanism 12 in the indexing direction (Y-axis direction), and a processing feed mechanism 21 that relatively moves the work W and the laser beam irradiation mechanism 12 in the processing feed direction (X-axis direction).

[0037] The indexing mechanism 20 is configured to have a pair of guide rails 23 arranged on the upper surface of the base 11 in parallel with the Y-axis direction, and a drive motor 26 that moves a Y-axis direction moving base 24 provided in a slidable manner on the pair of guide rails 23 in the indexing direction (Y-axis direction). In the movement in the indexing direction (Y-axis direction), after laser processing of a certain division predetermined line, an indexing feed for laser processing of a parallel adjacent division predetermined line is performed.

[0038] A nut portion not shown is formed on the lower surface side of the Y-axis direction moving base 24, and a ball screw 25 is screwed into the nut portion. Further, the Y-axis direction moving base 24, the machining feed mechanism 21, and the holding table 13 disposed on the Y-axis direction moving base 24 are moved in the Y-axis direction along the guide rail 23 by rotational driving of a driving motor 26 coupled to one end portion of the ball screw 25. In addition, the indexing feed mechanism 20 can be configured to be moved by a linear motor, similarly to the machining feed mechanism 21 described later.

[0039] The machining feed mechanism 21 is configured to have a pair of guide rails 30 disposed on the upper surface of the Y-axis direction moving base 24 in parallel with the X-axis direction, and a driving portion 33 for moving an X-axis direction moving base 32 movably placed on the guide rail 30 in the machining feed direction (X-axis direction).

[0040] The driving portion 33 is configured by a linear motor provided at the lower portion of the X-axis direction moving base 32, and is configured to have an electromagnetic coil (not shown) at a position opposed to a magnet plate 35 disposed in the X-axis direction between the guide rails 30. The electromagnetic coil is energized in three phases in sequence with the phases being offset, for example, to form a moving magnetic field that moves the driving portion 33 itself and the X-axis direction moving base 32 in the reciprocating direction as the X-axis direction.

[0041] A temperature detector 36 for detecting the temperature of the electromagnetic coil that constitutes the linear motor is provided in the driving portion 33, and the temperature of the driving portion 33 is detected by the temperature detector 36. The X-axis direction moving base 32 (holding table 13) is moved at high speed by the driving portion 33, and thus the amount of heat generated by the electromagnetic coil increases, which causes thermal expansion of the surrounding components.

[0042] The temperature detector 36 measures the temperature of the electromagnetic coil assembled in the driving portion 33, and in addition, can be disposed in the X-axis direction moving base 32 as a structure independent of the driving portion 33. In addition, the temperature of the holding mechanism 37 (X-axis direction moving base 32, holding table 13) that holds the workpiece can be detected by the temperature detector 36, and a temperature change caused by the heat generation of the driving portion 33 can be detected based on the detected temperature.

[0043] The holding table 13 is provided on the upper surface side of the X-axis direction moving base 32. The holding table 13 is configured to be rotatable (θ-direction rotation) by a vertical rotation shaft. An adsorption surface is formed of a porous ceramic material on the upper surface of the holding table 13. Four clamping portions 39 are provided around the holding table 13. The four clamping portions 39 are driven by air actuators (not shown), and thus clamp and fix the annular frame F of the workpiece unit U from four sides.

[0044] A holding mechanism 37 that holds the workpiece is constituted by moving the base 32 and the holding table 13 in the X-axis direction. The holding mechanism 37 as a whole moves in the machining feed direction and the indexing feed direction.

[0045] The laser beam irradiation mechanism 12 has a machining head 40 provided at the front end of the arm portion 17. An optical system and the like of the laser beam irradiation mechanism 12 are provided in the arm portion 17 and the machining head 40.

[0046] Figure 2 Fig. 8 is a view showing the optical system and the like of the laser beam irradiation mechanism 12. The laser beam irradiation mechanism 12 is constituted by a laser oscillator 41 that emits a laser beam 46, a mirror 42 that reflects the laser beam 46 emitted from the laser oscillator, a condensing lens 43 that condenses the laser beam 46 reflected by the mirror 42 to irradiate the workpiece W, and a condensing point position adjustment unit 44 that moves the condensing lens 43 in the Z-axis direction to adjust the condensing point position (focal point) of the laser beam 46.

[0047] The laser beam 46 emitted from the laser oscillator 41 is, for example, a YAG laser beam or a YVO laser beam. As a kind of laser machining, there are an ablation machining that constitutes a laser machined groove on the front surface by irradiating the workpiece W with a laser beam having an absorbable wavelength and a so-called stealth dicing machining that forms a modified layer inside by irradiating the workpiece W with a laser beam having a transmittable wavelength.

[0048] Next, a structure for correcting the position of the condensing point of the laser beam will be described.

[0049] Figure 3 Fig. 9 is a view showing a controller 100 that controls the laser machining device and its control objects. The controller 100 has a control section 102 that controls the actions of various mechanisms and a storage section 104 that stores various data.

[0050] The control section 102 controls the movement of the holding table by controlling the movement mechanism 14. Specifically, by controlling the action of the indexing feed mechanism 20 (driving motor 26), the movement control of the indexing feed direction (Y-axis direction) of the holding table 13 (13a) is performed. In addition, by controlling the action of the machining feed mechanism 21 (driving section 33), the movement control of the machining feed direction (X-axis direction) of the holding table 13 (13a) is performed. Figure 1 ) of the holding table 13 (13a) is performed. In addition, by controlling the action of the machining feed mechanism 21 (driving section 33), the movement control of the machining feed direction (X-axis direction) of the holding table 13 (13a) is performed. Figure 1 The control section 102 controls the movement of the holding table by controlling the movement mechanism 14. Specifically, by controlling the action of the indexing feed mechanism 20 (driving motor 26), the movement control of the indexing feed direction (Y-axis direction) of the holding table 13 (13a) is performed. In addition, by controlling the action of the machining feed mechanism 21 (driving section 33), the movement control of the machining feed direction (X-axis direction) of the holding table 13 (13a) is performed.

[0051] Figure 2 The control section 102 controls the movement of the holding table by controlling the movement mechanism 14. Specifically, by controlling the action of the indexing feed mechanism 20 (driving motor 26), the movement control of the indexing feed direction (Y-axis direction) of the holding table 13 (13a) is performed. In addition, by controlling the action of the machining feed mechanism 21 (driving section 33), the movement control of the machining feed direction (X-axis direction) of the holding table 13 (13a) is performed.

[0052] ​Temperature detector 36 is connected to controller 100, and the temperature detected by temperature detector 36 is input to control unit 102.

[0053] The storage unit 104 stores Figure 4 (A) Figure 4 The related diagrams M1 and M2 are shown in (B).

[0054] Figure 4 In the related diagram M1 shown in (A), the horizontal axis represents the drive unit 33. Figure 1 The temperature (°C) of the light source is used as the ordinate, and the offset (μm) of the focal point within the workpiece along the Y-axis is used as the ordinate. The correlation diagram M1 is based on the temperature detector 36 (…). Figure 1 The result is obtained by measuring the temperature and the Y-axis coordinate of the focusing point at each temperature.

[0055] In the relevant figure M1, it is shown that with the drive unit 33 ( Figure 1 As the temperature increases from the reference temperature T1, the focusing point shifts towards the -Y axis. In this embodiment, in Figure 1 In the structure shown, the X-axis moving base 32, affected by the temperature rise of the drive unit 33, undergoes thermal expansion, causing the holding stage 13 to shift from its reference position in the +Y-axis direction. In this case, the relative position of the holding stage 13 with respect to the laser beam irradiation mechanism 12 shifts in the +Y-axis direction, and simultaneously, the focusing point shifts in the -Y-axis direction within the workpiece W. Furthermore, at the reference temperature T1, the Y-axis offset of the focusing point within the workpiece is zero, and the focusing point is positioned at the designed location.

[0056] More specifically, for example Figure 5 As shown in (A), at the reference temperature T1, while maintaining the Y-axis coordinate of the center C of the worktable 13 as Ya and the focusing point P positioned at a predetermined location within the workpiece W, under the following conditions... Figure 5 As shown in (B), when the temperature rises to T2, the center C of the worktable 13 is moved Δy in the +Y axis direction, and the Y axis coordinate becomes Yb. On the other hand, the focus point P is shifted within the workpiece W to a position Py that has been moved Δy in the -Y axis direction.

[0057] When the worktable 13 is shifted in the +Y axis direction as shown, the focus point P shifts in the -Y axis direction within the workpiece W. This is because the laser beam irradiation mechanism 12 does not move in the Y axis direction; only the worktable 13 is moved in the Y axis direction due to thermal expansion.

[0058] Similarly, Figure 4 In the related diagram M2 shown in (B), the horizontal axis represents the drive unit 33. Figure 1The temperature (°C) of the light source is used as the ordinate, and the offset (μm) of the focal point within the workpiece along the Z-axis is used as the vertical axis. The correlation between these two parameters is defined in the correlation graph M2, which is based on the temperature detector 36 (…). Figure 1 The result is obtained by measuring the temperature and the Z-axis coordinate of the focusing point at each temperature.

[0059] In the relevant diagram M2, it is shown that with the drive unit 33 ( Figure 1 As the temperature increases from the reference temperature T1, the focusing point shifts towards the -Z axis. In this embodiment, in Figure 1 In the structure shown, the X-axis moving base 32, affected by the temperature rise of the drive unit 33, undergoes thermal expansion, causing the holding stage 13 to shift from its reference position in the +Z-axis direction. In this case, the relative position of the holding stage 13 with respect to the laser beam irradiation mechanism 12 shifts in the +Z-axis direction, and simultaneously, the focusing point shifts in the workpiece W in the -Z-axis direction. Furthermore, at the reference temperature T1, the Z-axis offset of the focusing point within the workpiece is zero, and the focusing point is positioned at the designed location.

[0060] More specifically, for example Figure 6 As shown in (A), at a certain reference temperature T1, while maintaining the Z-axis coordinate of the center C of the worktable 13 as Za and the focusing point P positioned at a specified position within the workpiece W, under the following conditions... Figure 6 As shown in (B), when the temperature rises to T2, the center C of the worktable 13 is moved Δz in the +Z axis direction, and the Z axis coordinate becomes Zb. On the other hand, the focusing point P is shifted within the workpiece W to a position Pz that has been moved Δz in the -Z axis direction.

[0061] When the worktable 13 is kept offset in the +Z axis direction as shown, the focus point P is offset in the -Z axis direction within the workpiece W. This is because the laser beam irradiation mechanism 12 (focusing lens 43) does not move in the Z axis direction, and only the worktable 13 is kept moving in the Z axis direction due to thermal expansion.

[0062] Furthermore, the data used to create the aforementioned correlation diagrams M1 and M2 vary depending on the individual differences of the laser processing apparatus and the environment in which the laser processing apparatus is installed. Regarding the creation of correlation diagrams M1 and M2, they can be created in advance during the manufacturing process before the laser processing apparatus leaves the factory, through experimental processing to acquire data, and then stored in the storage unit 104. Alternatively, they can be created after the laser processing apparatus is installed, through experimental processing to acquire data, and then stored in the storage unit 104.

[0063] Next, the control method for correcting the position of the focusing point in the above structure will be explained. Figure 7 This is a flowchart illustrating the control method.

[0064] Figure 7 The control shown is performed at the time of laser processing. The laser processing is the ablation processing or the stealth dicing processing described above.

[0065] Specifically, as shown in Figure 1 , mutually perpendicular division predetermined lines are provided in a lattice shape on a workpiece W that is a processing target. The holding stage 13 that holds the workpiece W is moved in a processing feed direction (X-axis direction), whereby laser processing is performed on a certain division predetermined line, and then the holding stage 13 is moved (index feed) in an index feed direction (Y-axis direction), whereby laser processing is performed on an adjacent next division predetermined line. After laser processing has been performed on all of the division predetermined lines extending in a first direction, the holding stage 13 is rotated by 90 degrees, and laser processing is performed on division predetermined lines in a second direction that is perpendicular to the first direction. At the time of this laser processing, the following control is performed.

[0066] <TEMPERATURE DETECTION STEP>

[0067] This step detects the temperature of the holding mechanism 37 or the temperature of the drive section 33 by the temperature detector 36. The temperature detection by the temperature detector 36 can be performed in real time throughout the laser processing, or the temperature detection can be performed at a certain timing and stored in advance in the storage section 104.

[0068] <CORRECTION VALUE CALCULATION STEP>

[0069] This step refers to a correlation diagram that defines a correlation of the temperature with the shift amount of the focal point position, and calculates a correction value for eliminating the shift amount of the focal point position corresponding to the temperature detected by the temperature detector 36.

[0070] Specifically, for example, in the case of the temperature T2, the correlation diagram Ml of (A) is referred to, whereby the shift amount Ay is found. In this case, as shown in (B) of Figure 4 , the focal point is moved in the -Y-axis direction by the shift amount Ay within the workpiece W. Figure 5

[0071] Further, the correction value is defined as a value for eliminating this shift amount Ay. In addition, the correction value can be another value calculated from the shift amount Ay, in addition to being the same as the shift amount Ay.

[0072] In addition, the shift in the Z-axis direction shown in (B) of Figure 4 , (B) of Figure 6 , is also defined as a correction value from the shift amount Az.

[0073] <FOCAL POINT POSITION CORRECTION STEP>

[0074] ​This step corrects the position of the focal point in the workpiece using the calculated correction value. The correction can be performed at all times during laser processing in real time, or can be performed at certain timings. For example, the correction can not be performed during movement of the holding stage in the processing feed direction (X-axis direction), but can be performed when the holding stage is moved in the indexing feed direction (Y-axis direction) after laser processing for a certain division intended line (indexing feed).

[0075] Specifically, as shown in the example of (C) of Figure 5 , the holding stage 13 is moved in the -Y-axis direction by the correction value Ay (offset Ay), thereby making the position of the focal point in the Y-axis direction in the workpiece W coincide with the position at the reference temperature Tl.

[0076] Similarly, as shown in the example of (C) of Figure 6 , the focal point position adjusting unit 44 is driven to change the Z-axis position of the condensing lens 43 Figure 2 , thereby moving the position of the focal point in the +Z-axis direction by the correction value Az, and making the position of the focal point in the Z-axis direction in the workpiece W coincide with the position at the reference temperature Tl.

[0077] As described above, by implementing the focal point position correction step, the position of the focal point in the workpiece W can be made to coincide with the position at the reference temperature Tl, thereby making it possible to prevent the focal point from shifting in the workpiece W due to thermal expansion of the holding mechanism 37.

[0078] In addition, in the correction value calculation step, the correction value is calculated with reference to the relevant drawings, but in addition thereto, the correction value per unit temperature change can be calculated in advance, and the correction can be performed using this correction value.

[0079] Specifically, for example, regarding an apparatus in which it is confirmed that the position of the focal point in the workpiece shifts -20 μm in the Z-axis direction and +3 μm in the Y-axis direction when the temperature of the driving section 33 Figure 1 increases by 5°C, the correction is performed in such a manner that the position shifts +4 μm in the Z-axis direction and -0.6 μm in the Y-axis direction per unit temperature change (temperature increase of 1°C).

Claims

1. A laser processing apparatus, wherein the laser processing apparatus has: a holding mechanism that holds a workpiece; a laser beam irradiation mechanism that irradiates a laser beam with a focal point converged on the workpiece held by the holding mechanism; a moving mechanism that moves the holding mechanism in a processing feed direction and an indexing feed direction; a controller that controls at least the laser beam irradiation mechanism and the moving mechanism; and a temperature detector that detects a temperature of the holding mechanism or a temperature of a drive section that moves the holding mechanism in the processing feed direction, the laser beam irradiation mechanism has a focal point position adjustment unit for adjusting a focal point position of the laser beam in a thickness direction of the workpiece, the controller controls the focal point position adjustment unit to set the focal point position of the laser beam in the thickness direction of the workpiece and controls the drive section to set a position of the focal point in the indexing feed direction of the workpiece in accordance with a change in the temperature detected by the temperature detector, thereby correcting the focal point position of the laser beam in laser processing.

2. The laser processing apparatus according to claim 1, wherein a correlation map that defines a correlation between a change in the temperature of the holding mechanism or the drive section and a change in the focal point position is stored in the controller in advance, the controller acquires the change in the focal point position corresponding to the temperature detected by the temperature detector by referring to the correlation map, the controller corrects the focal point position of the laser beam using a correction value corresponding to the change in the focal point position.

3. The laser processing apparatus according to claim 1 or 2, wherein the drive section that moves the holding mechanism in the processing feed direction in the moving mechanism is a linear motor having an electromagnetic coil, the temperature detector detects a temperature of the electromagnetic coil.

4. A method of correcting a focal point position of a laser processing apparatus, the laser processing apparatus has: a holding mechanism that holds a workpiece; a laser beam irradiation mechanism that irradiates a laser beam with a focal point converged on the workpiece held by the holding mechanism; a moving mechanism that moves the holding mechanism in a processing feed direction and an indexing feed direction; a controller that controls at least the laser beam irradiation mechanism and the moving mechanism; and a temperature detector for detecting a temperature of the holding mechanism or a temperature of a drive section that moves the holding mechanism in the processing feed direction, wherein the laser beam irradiation mechanism has a focal point position adjustment unit for adjusting a focal point position of the laser beam in a thickness direction of the workpiece, the method of correcting the focal point position has the steps of: a temperature detecting step of detecting a temperature by the temperature detector; a correction value calculating step of calculating a correction value for shifting the focal point position of the laser beam in accordance with the detected temperature; and a correcting step of correcting the focal point position of the laser beam using the correction value. A light condensing point position correction step in which, based on the correction value, the light condensing point position adjustment unit is controlled to set the light condensing point position of the laser beam in the thickness direction of the workpiece, and the drive unit is controlled to set the position of the light condensing point in the indexing feed direction of the workpiece, thereby correcting the light condensing point position of the laser beam in laser processing.

5. The method of correcting the light condensing point position of a laser processing apparatus according to claim 4, wherein a correlation map defining a correlation between a temperature change of the holding mechanism or the drive unit and a change in the light condensing point position is stored in the controller in advance, in the correction value calculation step, the controller acquires the change in the light condensing point position corresponding to the temperature detected by the temperature detector by referring to the correlation map, and calculates the correction value corresponding to the change in the light condensing point position.

6. The method of correcting the light condensing point position of a laser processing apparatus according to claim 4 or 5, wherein the drive unit that moves the holding mechanism in the processing feed direction in the moving mechanism is a linear motor having an electromagnetic coil, the temperature detector detects the temperature of the electromagnetic coil.

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