Laser irradiation method and apparatus

Abstract

A laser irradiation method sets scan lines in an x direction in parallel, and in a y direction to be separate by an inter-scan-line distance Py corresponding to laser irradiation areas of a processing target object, orients a length direction of a linear laser spot with length Wy and width Wx in the y direction, and irradiates target object with the laser spot in each of irradiation positions arranged at width direction intervals while moving the laser spot relative to the target object along the scan lines. The method includes determining the inter-scan-line distance Py, the width direction interval , and a position shift quantity x (where, 0<x<) so that the irradiation positions on adjacent scan lines are shifted in the x direction by the position shift quantity x and a cumulative value of the applied laser intensity is substantially equalized.

Claims

1. A laser irradiation method that sets a plurality of scan lines extending in an x direction in parallel to one another and arranged in a y direction so as to be separate from one another by an inter-scan-line distance Py in correspondence with laser irradiation areas of a processing target object, orients a length direction of a linear laser spot having a length Wy and a width Wx in the y direction, and irradiates the processing target object with the laser spot in each of irradiation positions arranged at a width direction interval while moving the laser generating the laser spot relative to the processing target object along the x direction such that the laser spot moves relative to the processing target object along the scan lines, the laser irradiation method comprising: determining the inter-scan-line distance Py, the width direction interval , and a position shift quantity x (where 0<x<) such that the irradiation positions on adjacent scan lines are shifted from each other in the x direction by the position shift quantity x and a cumulative value of the applied laser intensity is substantially equalized, in accordance with a profile of the laser spot.

2. The laser irradiation method according to claim 1, wherein in a case where an angle between the length direction of the linear laser spot and the y direction is not negligible, the position shift quantity x is corrected in accordance with the angle .

3. The laser irradiation method according to claim 1, wherein in a case where the laser spot moves in relatively opposite directions along scan lines adjacent to each other and a delay period that elapses from a timing when a laser oscillation instruction signal is issued until laser beam emission actually starts is not negligible, the position shift quantity x is corrected in accordance with the delay period .

Description

BRIEF DESCRIPTION OF DRAWINGS

(1) FIG. 1 is a configuration descriptive diagram showing a laser delamination apparatus according to Example 1.

(2) FIG. 2 describes scan lines.

(3) FIG. 3 describes a linear laser spot and the profile thereof.

(4) FIG. 4 is a descriptive diagram showing a laser irradiation method according to Example 1.

(5) FIG. 5 describes an angle between the length direction of the linear laser spot and the y direction.

(6) FIG. 6 is a descriptive diagram showing a correction method according to the angle between the length direction of the linear laser spot and the y direction.

(7) FIG. 7 describes a delay period that elapses from the timing when an irradiation trigger signal is issued until irradiation is performed.

(8) FIG. 8 is a descriptive diagram showing a correction method according to the delay period that elapses from the timing when the irradiation trigger signal is issued until irradiation is performed.

(9) FIG. 9 is a descriptive diagram showing an actual shape of a laser spot.

(10) FIG. 10 is a flowchart showing the process of determining an inter-scan-line distance Py, a width direction interval , and a position shift amount x.

(11) FIG. 11 is a descriptive diagram showing a laser irradiation method according to Comparative Example 1.

(12) FIG. 12 is a descriptive diagram showing a laser irradiation method according to Comparative Example 2.

DESCRIPTION OF EMBODIMENTS

(13) The present invention will be described below in more detail with reference to embodiments shown in the drawings. It is not intended that the embodiments limit the scope of the present invention.

(14) FIG. 1 is a configuration descriptive diagram showing a laser delamination apparatus according to Example 1.

(15) FIG. 2 describes scan lines.

(16) FIG. 3 describes a linear laser spot and the profile thereof.

(17) FIG. 4 is a descriptive diagram showing a laser irradiation method according to Example 1.

(18) FIG. 5 describes an angle between the length direction of the linear laser spot and the y direction.

(19) FIG. 6 is a descriptive diagram showing a correction method according to the angle between the length direction of the linear laser spot and the y direction.

(20) FIG. 7 describes a delay period that elapses from the timing when an irradiation trigger signal is issued until irradiation is performed.

(21) FIG. 8 is a descriptive diagram showing a correction method according to the delay period that elapses from the timing when the irradiation trigger signal is issued until irradiation is performed.

(22) FIG. 9 is a descriptive diagram showing an actual shape of a laser spot.

(23) FIG. 10 is a flowchart showing the process of determining an inter-scan-line distance Py, a width direction interval , and a position shift amount x.

(24) FIG. 11 is a descriptive diagram showing a laser irradiation method according to Comparative Example 1.

(25) FIG. 12 is a descriptive diagram showing a laser irradiation method according to Comparative Example 2.

EXAMPLES

Example 1

(26) FIG. 1 is a configuration descriptive diagram showing a laser delamination apparatus 100 according to Example 1.

(27) The laser delamination apparatus 100 includes a laser irradiation unit 1, which outputs a laser beam having an ultraviolet wavelength in the form of pulses, an attenuator 2, a mirror 3, a beam shaper 4, which shapes the laser beam into a linear laser spot W, a lens system 5, a stage 6, on which a processing target object B is placed and which moves the processing target object B in the x direction and the y direction, an x-direction movement motor 7, a y-direction movement motor 8, an x-direction movement driver 9, a y-direction movement driver 10, and a system controller 11, which controls the laser irradiation unit 1, controls the x-direction movement motor 7, controls the y-direction movement motor 8, and performs other types of control.

(28) The processing target object B is, for example, a glass carrier which has a thickness ranging from 500 m to 1000 m and on which a plastic substrate (polyimide film substrate, for example) having a thickness of several tens of micrometers is laminated. The plastic substrate has, for example, an organic EL element and terminals formed therein.

(29) The processing target object B is placed on the stage 6 with the glass carrier facing the laser irradiation side.

(30) The processing target object B is irradiated with the laser spot via the glass carrier to be locally heated, whereby the plastic substrate is delaminated from the glass carrier.

(31) The laser irradiation unit 1 is, for example, an LD-pumped laser made of Nd:YAG as the lasing medium.

(32) The output intensity of the laser irradiation unit 1 is, for example, 50 W, and the attenuator 2 is adjusted so that the processing target object B is irradiated with a laser spot having, for example, 10 W.

(33) The wavelength of the laser beam is, for example, 355 nm that is a result of wavelength conversion of 1064 nm.

(34) A cycle T1 at which the laser beam is outputted in the form of pulses is, for example, 1/6000 seconds.

(35) The length direction of the linear laser spot W is oriented in the y direction, and the stage 6 moves the processing target object B in the x direction at a speed V to scan the processing target object B in the +x direction along the scan line L1, as shown in FIG. 2. The speed V is, for example, 180 mm/second.

(36) The stage 6 then moves the processing target object B in the y direction by the inter-scan-line distance Py.

(37) The stage 6 then moves the processing target object B in the +x direction at the speed V to scan the processing target object B with the laser spot W in the x direction along the scan line L2.

(38) The stage 6 then moves the processing target object B in the y direction by the inter-scan-line distance Py.

(39) The stage 6 then moves the processing target object B in the x direction at the speed V to scan the processing target object B with the laser spot W in the +x direction along the scan line L3.

(40) The stage 6 then moves the processing target object B in the y direction by the inter-scan-line distance Py.

(41) The stage 6 then moves the processing target object B in the +x direction at the speed V to scan the processing target object B with the laser spot W in the x direction along the scan line L4.

(42) The stage 6 then moves the processing target object B in the y direction by the inter-scan-line distance Py.

(43) The stage 6 then moves the processing target object B in the x direction at the speed V to scan the processing target object B with the laser spot W in the +x direction along the scan line L5.

(44) When the processing target object B is scanned with the laser spot W along the scan line L3, laser irradiation in which the processing target object B is irradiated with the laser spot W in the form of pulses is repeated.

(45) Even in the period other than the laser irradiation performed on the processing target object B, the laser irradiation unit 1 repeats emission of the laser beam in the form of pulses to maintain the intensity of the laser beam constant.

(46) Let Wy be the length of the laser spot W and Wx be the width thereof, as shown in FIG. 3(a). Wy is, for example, 8 mm, and Wx is, for example, 0.06 mm. FIG. 3 is drawn in an exaggerated manner in the width direction for ease of illustration.

(47) Let Cy be the major axis of the laser spot W and Cx be the minor axis thereof. Further, the axis extending in the y direction and separate from the major axis Cy by Wx/4 in the x direction is called the intermediate axis My.

(48) As shown in FIG. 3(b), along the major axis Cy, the laser spot W has the profile Iyc, which has the flat portion Fyc, where the laser intensity can be considered to be uniform, and the peripheral portions Syc, where the laser intensity gradually decreases.

(49) As shown in FIG. 3(c), along the minor axis Cx, the laser spot W has the profile Ixc, which has a roughly Gaussian distribution.

(50) As shown in FIG. 3(d), along the intermediate axis My, the laser spot W has the profile Iym, which has the flat portion Fym, where the laser intensity can be considered to be uniform, and the peripheral portions Sym, where the laser intensity gradually decreases.

(51) The profile Iym along the intermediate axis My differs from the profile Iyc along the major axis Cy in that the laser intensity is halved and the length in the y direction is shortened.

(52) To scan the processing target object B with the laser spot W in the +x direction along the scan line L1, the processing target object B is irradiated with the laser spot W in the form of pulses in irradiation positions arranged at width direction intervals =Wx/2, as shown in FIG. 4(a). When Wx=0.06 mm, =0.03 mm. is also equal to VT1. That is, when V=180 mm/second and T1= 1/6000 seconds, =180 mm/6000=0.03 mm. The system controller 11 stores the irradiation positions where the processing target object B has been irradiated with the laser spot W along the scan line L1.

(53) Thereafter, to scan the processing target object B with the laser spot W in the x direction along the scan line L2, the processing target object B is also irradiated with the laser spot W in the form of pulses in irradiation positions arranged at the width direction intervals =Wx/2. The system controller 11, however, shifts the stored irradiation positions along the scan line L1 by a position shift quantity x=Wx/4 in the x direction and sets the shifted positions as the irradiation positions along the scan line L2.

(54) That is, the major axis Cy (L1) in each of the irradiation positions on the scan line L1 and the major axis Cy (L2) in the corresponding irradiation position on the scan line L2 are shifted from each other by x=Wx/4. As a result, the major axis Cy (L1) in each of the irradiation positions on the line L1 coincides with the intermediate axis My (L2) in the corresponding irradiation positions on the line L2. Further, the intermediate axis My (L1) in each of the irradiation positions on the line L1 coincides with the major axis Cy (L2) in the corresponding irradiation position on the line L2.

(55) To scan the processing target object B with the laser spot W in the +x direction along odd-numbered scan lines (L3, L5), the scanning is performed in the same manner in which the processing target object B is scanned with the laser spot W in the +x direction along the scan line L1.

(56) To scan the processing target object B with the laser spot W in the +x direction along an even-numbered scan line (L4), the scanning is performed in the same manner in which the processing target object B is scanned with the laser spot W in the +x direction along the scan line L2.

(57) Since the laser irradiation unit 1 repeats emission of the laser beam in the form of pulses in the cycle T1, the system controller 11 controls the timing of movement of the stage 6 on the basis of the laser beam emission timing to control the irradiation positions.

(58) The inter-scan-line distance Py is adjusted so that the peripheral portion Syc (L1) of the profile Iyc (L1) along the major axis Cy (L1) in each of the irradiation positions on the scan line L1 half overlaps with the peripheral portion Sym (L2) of the profile Iym (L2) along the intermediate axis My (L2) in the corresponding irradiation position on the scan line L2, as shown in FIG. 4(b). For example, fine adjustment only needs to be made on the inter-scan-line distance Py with reference to Py=Wy(Syc+Sym)/2. It is noted that since the laser intensities in two irradiation positions adjacent to each other in the x direction are combined with each other on the intermediate axis My, the actual laser intensity is doubled or 2.Math.Iym(L2).

(59) The combined profile Iyc(L1)+2.Math.Iym(L2) on the major axis Cy (L1) and the intermediate axis My (L2) therefore has a roughly flat shape, as shown in FIG. 4(c).

(60) With the inter-scan-line distance Py adjusted as shown in FIG. 4(b), the peripheral portion Sym (L1) of the profile Iym (L1) along the intermediate axis My (L1) in each of the irradiation position on the scan line L1 half overlaps with the peripheral portion Syc (L2) of the profile Iyc (L2) along the major axis Cy (L2) in the corresponding irradiation position on the scan line L2, as shown in FIG. 4(d). Since the laser intensities in two irradiation positions adjacent to each other in the x direction are combined with each other on the intermediate axis My, the actual laser intensity is doubled or 2.Math.Iym(L1).

(61) The combined profile 2.Math.Iym(L1)+Iyc(L2) on the intermediate axis My (L1) and the major axis Cy (L2) therefore also has a roughly flat shape, as shown in FIG. 4(e).

(62) The positional relationship between the irradiation positions on odd-numbered scan lines and the irradiation positions on even-numbered scan lines is the same as the positional relationship between the irradiation positions on the first scan line L1 and the irradiation positions on the second scan line L2.

(63) According to the laser delamination apparatus 100 of Example 1, since the inter-scan-line distance Py, the width direction interval , and the position shift quantity x are determined so that the cumulative value of the applied laser intensity is substantially equalized, the processing target object B can be irradiated with the linear laser spot W to be locally heated with no insufficient intensity portion or excessive intensity portion. The plastic substrate can therefore be preferably delaminated from the glass carrier with no damage of the plastic substrate or parts attached thereto.

Example 2

(64) It is assumed that the length direction of the laser spot W and the y direction forms an angle , and that the angle is not negligible, as shown in FIG. 5.

(65) The system controller 11 corrects the position shift quantity x in accordance with the angle , as shown in FIG. 6. Let x be the position shift quantity in a case where the angle can be considered to be zero and D1 be the amount of correction, and a corrected position shift quantity x for the adjacent scan line is x+D1.

(66) In a case where the conditions are the same as those in Example 1 except that the angle cannot be considered to be zero, x=Wx/4 and D1=Wy.Math.sin .

(67) The angle depends on adjustment of the mirror 3 and the beam shaper 4 and is fixed after the mirror 3 and the beam shaper 4 are adjusted.

(68) According to the laser delamination apparatus of Example 2, even when the angle is not negligible, the major axis Cy in each of the irradiation positions on an odd-numbered scan line coincides with the intermediate axis My in the corresponding irradiation position on an even-numbered scan line, and the intermediate axis My in each of the irradiation positions on an odd-numbered scan line coincides with the major axis Cy in the corresponding irradiation position on an even-numbered scan line.

Example 3

(69) It is assumed that after the system controller 11 issues a laser oscillation instruction signal to the laser irradiation unit 1, there is a delay period until the laser irradiation unit 1 actually starts emitting the laser beam, as shown in FIG. 7, and the delay period is not negligible.

(70) The system controller 11 corrects the position shift quantity x in accordance with the delay period , as shown in FIG. 8. Let x be the position shift quantity in a case where the delay period can be considered to be zero and D2 be the amount of correction, and a corrected position shift quantity x for the adjacent scan line is x+D2.

(71) In a case where the conditions are the same as those in Example 1 except that the delay period cannot be considered to be zero, x=Wx/4 and D2=2.Math.V.Math..

(72) According to the laser delamination apparatus of Example 3, even when the delay period is not negligible, the major axis Cy in each of the irradiation positions on an odd-numbered scan line coincides with the intermediate axis My in the corresponding irradiation position on an even-numbered scan line, and the intermediate axis My in each of the irradiation positions on an odd-numbered scan line coincides with the major axis Cy in the corresponding irradiation position on an even-numbered scan line.

Example 4

(73) In a case where both of the angle and the delay period is not negligible, the system controller 11 corrects the position shift quantity x in accordance with the angle and the delay period . Let x be the position shift quantity in a case where the angle and the delay period can each be considered to be zero, D1 be the amount of correction according to the angle , and D2 be the amount of correction according to the delay period , and a corrected position shift quantity x for the adjacent scan line is x+D1+D2.

(74) In a case where the conditions are the same as those in Example 1 except that the angle and the delay period cannot each be considered to be zero, x=Wx/4, D1=Wy.Math.sin , and D2=2.Math.V.Math..

(75) According to the laser delamination apparatus of Example 4, even when both of the angle and the delay period is not negligible, the major axis Cy in each of the irradiation positions on an odd-numbered scan line coincides with the intermediate axis My in the corresponding irradiation position on an even-numbered scan line, and the intermediate axis My in each of the irradiation position on an odd-numbered scan line coincides with the major axis Cy in the corresponding irradiation position on an even-numbered scan line.

Example 5

(76) An actual shape of the laser spot W is a deformed shape in many cases, such as that in FIG. 9, as compared with the shape in FIG. 3. In view of the fact described above, the inter-scan-line distance Py, the width direction interval , and the position shift quantity x are in practice determined by a cut-and-try approach in each laser delamination apparatus.

(77) FIG. 10 is a flowchart showing the process of setting the inter-scan-line distance Py, the width direction interval , and the position shift quantity x.

(78) In step S1, the processing target object B is placed in the laser delamination apparatus and irradiated along a single scan line at certain width direction intervals repeatedly with the width direction interval changed to search for a width direction interval that allows most uniform irradiation in the x direction, and the resultant width direction interval is set. In step S2, the processing target object B is irradiated along two scan lines adjacent to each other and separate from each other by a certain inter-scan-line distance Py and a position shift quantity x repeatedly with the inter-scan-line distance Py and the position shift quantity x changed to search for an inter-scan-line distance Py and a position shift quantity x that allow most uniform irradiation in the y direction, and the resultant inter-scan-line distance Py and position shift quantity x are set.

(79) The process is then terminated.

(80) According to Example 5, an optimum inter-scan-line distance Py, width direction interval , and position shift quantity x can be set in each laser delamination apparatus.

INDUSTRIAL APPLICABILITY

(81) The laser irradiation method and apparatus according to the present invention can be used, for example, to carry out the process of delaminating a plastic substrate formed on a glass carrier.

REFERENCE SIGNS LIST

(82) 1 Laser irradiation unit 2 Attenuator 3 Mirror 4 Beam shaper 5 Lens system 6 Stage 7 X-direction movement motor 8 Y-direction movement motor 9 X-direction movement driver 10 Y-direction movement driver 11 System controller 100 Laser delamination apparatus B Processing target object W Laser spot