Source: https://patents.google.com/patent/US10293433B2/en
Timestamp: 2019-12-14 12:52:12
Document Index: 495175862

Matched Legal Cases: ['art 4', 'art 4', 'art 4', 'art 4', 'art 4', 'art 45', 'art 45', 'art 45', 'art 45', 'art 45', 'art 45', 'art 45', 'art 45', 'art 45', 'art.\n2']

US10293433B2 - Laser processing method and device - Google Patents
US10293433B2
US10293433B2 US15/255,926 US201615255926A US10293433B2 US 10293433 B2 US10293433 B2 US 10293433B2 US 201615255926 A US201615255926 A US 201615255926A US 10293433 B2 US10293433 B2 US 10293433B2
US15/255,926
US20160368085A1 (en
2008-05-07 Priority to US58534308A priority
2013-12-06 Priority to US14/099,236 priority patent/US9511449B2/en
2016-09-02 Assigned to HAMAMATSU PHOTONICS K.K. reassignment HAMAMATSU PHOTONICS K.K. ASSIGNMENT OF ASSIGNORS INTEREST (SEE DOCUMENT FOR DETAILS). Assignors: ATSUMI, KAZUHIRO, FUKUMITSU, KENSHI, FUKUYO, FUMITSUGU, KUSUNOKI, MASAYOSHI, SUZUKI, TATSUYA, KUNO, KOJI
2016-09-02 Priority to US15/255,926 priority patent/US10293433B2/en
2016-09-02 Application filed by Hamamatsu Photonics KK filed Critical Hamamatsu Photonics KK
2016-12-22 Publication of US20160368085A1 publication Critical patent/US20160368085A1/en
2018-09-07 First worldwide family litigation filed litigation Critical https://patents.darts-ip.com/?family=34747111&utm_source=google_patent&utm_medium=platform_link&utm_campaign=public_patent_search&patent=US10293433(B2) "Global patent litigation dataset” by Darts-ip is licensed under a Creative Commons Attribution 4.0 International License.
2019-05-21 Publication of US10293433B2 publication Critical patent/US10293433B2/en
This is a divisional application of copending application Ser. No. 14/099,236 filed on Dec. 6, 2013, which is a continuation application of application Ser. No. 10/585,343 filed on May 7, 2008 (now U.S. Pat. No. 8,624,153), which is a national stage application of PCT Application No. PCT/JP2004/018594 filed on Dec. 13, 2004, designating the U.S.A. The entire contents of each of these applications are incorporated by reference herein in their entirety.
Patent Document 1: Japanese Patent Application Laid-Open No 2002-219591
As the silicon wafer 800 shifts in the direction of arrow A in FIG. 10(A), the optical axis of the first laser beam 806 and second laser beam 808 reaches a position where it intersects the silicon wafer 800. The piezoelectric actuator 804 c causes the lens holder 804 b to advance/retract with respect to the silicon wafer 800 such that an astigmatism signal detected from reflected light of the second laser beam 808 becomes a predetermined value. Therefore, the piezoelectric actuator 804 c retracts from the state of FIG. 10(B), so as to raise the lens holder 804 b and condenser lens 804 a. However, since the silicon wafer 800 keeps shifting in the direction of arrow A in FIG. 10(A), a time lag occurs until the lens holder 804 b and condenser lens 804 a rise to a predetermined position so that the converging point of the first laser beam 806 is positioned at the line to cut 800 a. Also, the astigmatism signal may vary so much, that the converging point of the first laser beam 806 fluctuates.
Therefore, as shown in FIG. 10(C) a part other than the line to cut 800 a is processed with the laser in an area B until the first laser beam 806 is in focus with the line to cut 800 a so as to attain a stable state. For example, assuming that the silicon wafer 800 has a thickness of 100 μm, and that a time delay of 15 mS occurs, the length of the area B is theoretically 1.5 mm when the processing speed is 100 mm/S.
It will be preferred in the laser processing method of the present invention if, in the second processing step, the first laser beam and a second laser beam for measuring a displacement of the main surface are converged by the lens onto the object on the same axis, and the lens is released from being held after the quantity of reflected light of the second laser beam reflected by the main surface exceeds a predetermined threshold. Since the first and second laser beams are converged by the lens so as to be emitted on the same axis, the converging point of the first laser beam can be prevented from deviating from a predetermined position within the object because of a vibration of a stage mounting the object, for example. The quantity of reflected light varies depending on the distance from the reflecting surface. Therefore, when a predetermined threshold is set to a value corresponding to the height of the main surface, and a location where the quantity of reflected light becomes the predetermined threshold is assumed to correspond to an outer edge of the main surface, of the object to be processed, the lens can be released from being held.
Since the modified region is formed in one end part of the line to cut while the lens is held at the initial position, the laser processing apparatus of the present invention can form the modified region while excluding the influence of fluctuations in the shape of end parts in the object as much as possible. After the modified region is formed at one end part of the line to cut, the lens is released from being held, and the modified, region is formed in the remaining part while adjusting the lens position, whereby the modified region can be formed at a predetermined position within the object.
It will also be preferred in the laser processing apparatus of the present invention if, after forming the modified region in the one end part of the line to cut, the control means controls the holding means so as to release the lens from being held at the initial position and hold the lens while adjusting a gap between the lens and the main surface and controls the moving means so as to move the lens and the object relative to each other along the main surface, thereby forming the modified region; and the control means controls the holding means so as to hold the lens such that the lens is kept from being driven toward the main surface and move the lens and the object relative to each other along the main surface. Since the lens is held so as not to be driven toward the main surface after forming the modified region, a smooth transition is possible when shifting to the processing of the next line to cut, for example.
The laser head unit 3 is detachably attached to an upper end part of the optical system main part 4. The laser head unit 3 includes an L-shaped cooling jacket 11. Embedded in a vertical, wall 11 a of the cooling jacket 11 is a cooling pipe 12 in a winding state, through which cooling water circulates. Attached to the front face of the vertical wall 11 a are a laser head 13 which emits the processing laser beam L1 downward, and a shutter unit 14 for selectively opening and closing an optical path of the processing laser beam L1 emitted from the laser head 13. This can prevent the laser head 13 and shutter unit 14 from overheating. For example, the laser head 13 uses an Nd:YAG laser and emits a pulsed laser beam having a pulse width of 1 μs or shorter as the processing laser beam L1.
In the laser head unit 3, an adjuster 15 for adjusting the inclination of the cooling jacket 11 and the like is attached to the lower face of a bottom wall 11 b of the cooling jacket 11. The adjuster 15 is used for aligning an optical axis α of the processing laser beam L1 emitted from the laser head 13 with an axis β which is set in the optical system main part 4 and objective lens unit 5 such as to extend vertically. Namely, the laser head unit 3 is attached to the optical system main part 4 by way of the adjuster 15. When the inclination of the cooling jacket. 11 or the like is adjusted by the adjuster 15 thereafter, the inclination of the laser head 13 or the like is adjusted in conformity to the movement of the cooling jacket 11. As a consequence, the processing laser beam L1 advances into the optical system main part 4 while in a state where its optical axis α coincides with the axis β. The bottom wall 11 b of the cooling jacket 11, the adjuster 15, and a housing 21 of the optical system main part 4 are formed with through holes through which the processing laser beam L1 passes.
An outline of a laser processing method carried out by thus configured laser processing apparatus 1 will now be explained. First, the object S is mounted on the stage 2, and the stage 2 is moved such that the converging point P of the processing laser beam L1 is positioned within the object S. The initial position of the stage 2 is determined by the thickness and refractive index of the object S the numerical aperture of the processing objective lens 42, etc.
The laser emission controller 701 of the control unit 7 outputs a control signal to the laser diode 44 so as to make the latter emit the rangefinding laser beam L2 (step S05), in response to the output of this control signal, the laser diode 44 emits the rangefinding laser beam L2, whereas its reflected light beam reflected by the surface S1 of the object S is received by the four-divided position detecting device in the light-receiving part 45. In response to the light received, signals are outputted to the converging point calculator 704 and the end part determiner 705.
The rangefinding laser beam L2 is reflected less by the dicing film 2 a so that the total quantity of light reflected thereby is smaller, whereas the total quantity of reflected light increases in the object S. Namely, the total quantity of reflected light beam of the rangefinding laser beam L2 detected by the four-divided position detecting device in the light-receiving part 45 (see FIG. 1) increases, whereby it can be determined that the processing objective lens 42 is located at the position intersecting the line to cut C1 in the object S when the total quantity of reflected light beam exceeds a predetermined threshold. Therefore, when the total light quantity detected by the four-divided position detecting device in the light-receiving part 45 (see FIG. 1) is greater than the predetermined threshold, the processing objective lens 42 is assumed to be located at one end of the line to cut C1 (in the state corresponding to FIG. 6(A)), the expansion amount of the actuator 43 at this time is released from being held, and the expansion amount control of the actuator 43 is started such that the astigmatism signal becomes the reference value held at step S06 at predetermined intervals (e.g., at individual sampling points). Hence, when the processing objective lens moves in the direction of arrow E in FIG. 6(A), the state shown in FIG. 6(B) is attained. As shown in FIG. 6(B), a modified region R is formed by a predetermined processing height in area F (one end part). After the modified region R is formed by a predetermined processing height in this area F, the processing objective lens 42 moves along the line to cut and forms the modified region R with the processing laser beam L1. During this period, the actuator 43 is adjusted such that the astigmatism signal obtained from the reflected light beam of the rangefinding laser beam L2 becomes the above-mentioned reference value.
When the processing objective lens 42 further moves in the direction of arrow E in FIG. 6(A) from the state shown in FIG. 6(B), the processing objective lens 42 is located at the other end of the line to cut C1 as shown in FIG. 6(C). When the processing objective lens 42 reaches a position outside of the object S, a state opposite to that explained with reference to FIG. 6(A) is attained, whereby the total quantity of the reflected light beam of the rangefinding laser beam L2 detected by the four-divided position detecting device in the light receiving part 45 (see FIG. 1) decreases. Therefore, when the total quantity of light detected by the four-divided position detecting device in the light-receiving part 45 (see FIG. 1) becomes smaller than a predetermined threshold, the processing objective lens 42 is assumed to be located at a position corresponding to one end of the line to cut C1 (in the state corresponding to FIG. 6(C)), and the amount of expansion of the actuator at this time is held. While keeping the amount of expansion of the actuator 43, the stage 2 is moved such that the processing objective lens 42 reaches the position of X2 in FIG. 6(C), so as to be ready for the processing of the next line to cut C2 (transition step).
From the graph of FIG. 7(A), at predetermined intervals (e.g., at individual sampling points), the amount of change in difference obtained by subtracting the previous total light quantity value from the current total light quantity value is calculated, Thus obtained values are plotted in FIG. 7(B) whose ordinate and abscissa indicate the amount of change and time, respectively. In this case, a part exhibiting a positive peak seems to be a point where the change in the total light quantity is the largest, i.e., a part corresponding to the vicinity of the center of an edge (outer edge) of the object S. Therefore, the tracking of the actuator 43 can be started after the differential peak shown in FIG. 7(B) stops changing after the total light quantity shown in FIG. 7(A) becomes the threshold T1.
Though the processing objective lens 42 having reached a position corresponding to the other end of the line to cut C1 (FIG. 6(C)) is detected according to the fact that: the total light quantity detected by the four-divided position detecting device in the light-receiving part 45 (see FIG. 1) becomes smaller than a predetermined threshold in the foregoing explanation, this is not restrictive, whereby other criteria may also be employed. An example of such criteria will be explained with reference to FIGS. 8(A) and 8(B). FIG. 8(A), whose ordinate and abscissa indicate the total light quantity detected by the four-divided position detecting device of the light-receiving part 45 (see FIG. 1) and time, respectively, is a chart recording the change in the total light quantity detected by the four-divided position detecting device of the light-receiving part 45 (see FIG. 1) in the states of FIGS. 6(B) and 6(C). In this case, as mentioned above, it is determined that the processing objective lens 42 is located at a position corresponding to one end of the line to cut C1 at the time when the light quantity becomes smaller than a predetermined threshold T2.
According to the signal outputted from the light-receiving part 45, the end part determiner 705 determines whether the processing objective lens 42 is located at the other end part of the object S or not (step S15). When it is determined that the processing objective lens 42 is located at the end part of the object S, the end part determiner 705 outputs an instruction s al to the actuator controller 703 so as to make the latter stop the expansion/contraction of the actuator 43. In response to the output of this instruction signal, the actuator controller 703 outputs a control signal to the actuator 43 so as to make the latter stop expanding/contracting and attain a held state (step S16). In response to the output of this control signal, the actuator 43 stops expanding/contracting. When the processing Objective lens 42 is located at the point X2 on an extension of the line to cut C1, the stage movement controller 702 outputs a control signal to the stage 2 so as to make the latter stop moving (step S17). Thereafter, an average value of the amounts of expansion/contraction of the actuator 43 stored in the 20, first 5 channels of the circular memory 706 among the amounts of expansion/contraction of the actuator 43 stored in the circular memory 706 is calculated, and the amount of expansion/contraction of the actuator 43 is fixed so as to become this average value (step S18).
Since this embodiment starts laser processing by emitting the processing laser be at L1 while holding the processing objective lens 42 at the initial position, the influence of fluctuations in the shape of end parts in the object S can be excluded as much as possible.
1. A laser processing apparatus for irradiating an object to be processed with a first laser beam while converging the first laser beam, and forming a modified region within the object along a horizontal cutting line in the object, the apparatus comprising:
a lens for converging the first laser beam while the first laser beam is irradiating the object such that a converging point is positioned within the object;
a holder for holding the lens such that the lens is capable of freely expanding and retracting in a vertical direction with respect to the main surface; and
control means for controlling respective behaviors of the moving means and the holder;
wherein the control means causes the holder to hold the lens at an initial position with resect to the main surface of the object in the vertical direction, the initial position being set so that the converging point is located at a predetermined position within the object;
wherein, while the first laser beam is irradiating the object, the control means prohibits movement of the lens from the initial position in the vertical direction by outputting an auto-focus off instruction signal prohibiting expansion/contraction of an actuator of the tens, and the control means controls the moving means so as to move the object and the lens relative to each other along the main surface, thereby forming an initial portion of the modified region in one end part of the cutting line; and
wherein, while the first laser beam is irradiating the object, and after forming the initial part of the modified region in the one end part of the cutting line, the control means controls the holder so as to release the lens from being prohibited from moving from the initial position in the vertical direction by outputting an auto-focus on instruction signal initiating allowance of expansion/contraction of an actuator of the lens, and moves the lens and the object relative to each other along the main surface of the object while at the same time adjusting a distance of a gap between the lens and the main surface of the object, thereby forming a remainder portion of the modified region in a part of the cutting line that is different than the one end part.
2. The laser processing apparatus according to claim 1, wherein the first laser beam and a second laser beam for measuring a displacement of the main surface are converged by the lens into the object on the same axis; and wherein the control means controls the holder so as to release the lens from being prohibited from moving from the initial position in the vertical direction when the quantity of detected light of the second laser beam reflected by the main surface exceeds a predetermined threshold.
3. The laser processing apparatus according to claim 1, wherein the first laser beam and a second laser beam for measuring a displacement of the main surface are converged by the lens into the object on the same axis; and wherein the control means controls the holder so as to release the lens from being prohibited from moving from the initial position in the vertical direction when an amount of change in the quantity of detected light of the second laser beam reflected by the main surface becomes a maximum value.
4. The laser processing apparatus according to claim 1, wherein, after forming the initial portion of the modified region in the one end part of the cutting line, the control means controls the holder so as to release the lens from being prohibited from moving from the initial position in the vertical direction and moves the lens and the object relative to each other along the main surface while at the same time adjusting a distance of a gap between the lens and the main surface of the object, thereby forming a remainder portion of the modified region in part of the cutting line that is different than the one end part; and wherein, during the forming of the initial portion of the modified region in the one end part of the cutting line, the control means controls the holder so as to hold the lens such that the lens is kept from being driven toward the main surface while at the same time moving the lens and the object relative to each other along the main surface.
5. The laser processing apparatus according to claim 4, wherein the first laser beam and a second laser beam for measuring a displacement of the main surface are converged by the lens into the object on the same axis; and wherein, during the forming of the initial portion of the modified region in the one end part of the cutting line, the control means controls the holder so as to hold the lens such that the lens is kept from being driven toward the main surface when the quantity of detected light of the second laser beam reflected by the main surface becomes smaller than a predetermined threshold.
6. The laser processing apparatus according to claim 4, wherein the first laser beam and a second laser beam for measuring a displacement of the main surface are converged by the lens into the object on the same axis; and wherein the control means controls the holder so as to hold the lens such that the lens is kept from being driven toward the main surface when the quantity of detected light of the second laser beam reflected by the main surface becomes a minimum value.
7. The laser processing apparatus according to claim 4, wherein the cutting line includes first and second cutting lines;
wherein the apparatus further comprises displacement storage memory for successively storing respective displacements of the main surface in unit time zones; and
wherein the control means sets a position based on the displacement stored in the unit time zone earlier by a predetermined number than the unit time zone where the lens is held so as to be kept from being driven in the first cutting line as the initial position in the second cutting line.
US15/255,926 2004-01-09 2016-09-02 Laser processing method and device Active 2026-02-18 US10293433B2 (en)
US58534308A true 2008-05-07 2008-05-07
US14/099,236 US9511449B2 (en) 2004-01-09 2013-12-06 Laser processing method and device
US15/255,926 US10293433B2 (en) 2004-01-09 2016-09-02 Laser processing method and device
US16/380,660 US20190232422A1 (en) 2004-01-09 2019-04-10 Laser processing method and device
US14/099,236 Division US9511449B2 (en) 2004-01-09 2013-12-06 Laser processing method and device
US16/380,660 Continuation US20190232422A1 (en) 2004-01-09 2019-04-10 Laser processing method and device
US20160368085A1 US20160368085A1 (en) 2016-12-22
US10293433B2 true US10293433B2 (en) 2019-05-21
JP6294378B2 (en) 2016-03-30 2018-03-14 ファナック株式会社 Laser processing apparatus and laser processing method provided with pre-processing control unit
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Free format text: ASSIGNMENT OF ASSIGNORS INTEREST;ASSIGNORS:ATSUMI, KAZUHIRO;KUNO, KOJI;KUSUNOKI, MASAYOSHI;AND OTHERS;SIGNING DATES FROM 20060712 TO 20060714;REEL/FRAME:039624/0228