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Timestamp: 2017-11-19 14:05:21
Document Index: 562338864

Matched Legal Cases: ['art 2011', 'art; 21', 'art 16', 'art 16', 'art 16', 'art 71', 'art 71', 'art 16', 'art 16', 'art 71', 'art 71', 'art 16', 'art 16', 'art 71', 'art 71', 'art 72', 'art 72', 'art 73', 'art 71', 'art 71', 'art 71', 'art 71', 'art 16', 'art 16', 'art 16', 'art 16', 'art 16', 'art 16', 'art 16', 'art 16', 'art 16', 'art 16', 'art 16', 'art 16', 'art 16', 'art 16', 'art 16', 'art 16', 'art 16', 'art 16', 'art 16', 'art 71', 'art 71', 'art 72', 'art 72', 'art 73']

Laser processing method for cutting substrate and laminate part bonded to the substrate - Hamamatsu Photonics K.K.
United States Patent 8946055
Sakamoto, Takeshi (Hamamatsu, JP)
Fukumitsu, Kenshi (Hamamatsu, JP)
10/594907
257/618, 438/458, 438/459, 438/460, 438/464
H01L21/00; B23K26/00; B23K26/04; B23K26/40; B28D5/00; H01L21/301; H01L29/06
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1. A laser processing method of irradiating a substrate having a front face formed with a laminate part including a plurality of functional devices with laser light while locating a light-converging point of the laser light within the substrate so as to form a modified region which functions as a start point for cutting within the substrate along a cutting line of the substrate, the method comprising: a first forming step of forming a plurality of rows of first modified regions along the cutting line; a second forming step of forming at least one row of a second modified region along the cutting line at a position between the first modified region closest to a rear face of the substrate and the rear face to form a fracture extending along the cutting line from the second modified region to the rear face such that the fracture does not reach the front face of the substrate; expanding an expandable film bonded to the rear face of the substrate in a direction that is parallel to the rear face of the substrate to expand the fracture at the rear face to cut the substrate and the laminate part along the cutting line by advancing the fracture from the substrate to the laminate part by way of the first modified regions.
2. A laser processing method according to claim 1, wherein the substrate is a semiconductor substrate, and wherein the first and second modified regions include a molten processed region.
7. A laser processing method according to claim 6, wherein the energy of the laser light for forming the first modified regions is 1.6 to 3.0 times as large as the energy of the laser light for forming the second modified region.
9. A laser processing method according to claim 1, wherein the light-converging point of the laser light is located at a position distanced by 50 μm to [(the substrate thickness)×0.9] μm from the rear face when forming the first modified regions.
12. A laser processing method according to claim 11, wherein, when forming a plurality of rows of second modified regions, while the energy of the laser light for forming the second modified region closest to the rear face of the substrate is set to 1, the energy of the laser light for forming the second modified region farthest from the rear face of the substrate is set to 1.3 to 3.3.
13. A laser processing method according to claim 11, wherein, when forming a plurality of rows of second modified regions, while the energy of the laser light for forming the second modified region closest to the rear face of the substrate is set to 1, the energy of the laser light for forming the first modified regions is set to 1.3 to 3.3.
14. A. laser processing method according to claim 1, wherein, when forming a plurality of rows of second modified regions, a position where the light-converging point of the laser light is located when forming the second modified region closest to the rear face of the substrate is distanced from the rear face by 20 μm to 110 μm, and a position where the light-converging point of the laser light is located when forming the second modified region second closest to the rear face of the substrate is distanced from the rear face by 140 μm or less.
Preferably, in the above-mentioned laser processing method, the light-converging point of the laser light is located at a position distanced by 50 μm to [(the substrate thickness)×0.9] μm from the rear face when forming the first modified regions. This is because the substrate and laminate part can be cut easily even when the substrate is thick if the first modified regions are formed under such a condition.
Preferably, in the above-mentioned semiconductor chip, the first modified regions have a total width of 40 μm to [(the substrate thickness)×0.9] μm in the thickness direction of the substrate. When the first modified regions are formed under such a condition, fractures starting from the first modified regions tend to occur along the line to cut with a high precision at the time of cutting the substrate and laminate part, whereby the side face of the semiconductor chip becomes a highly accurate cut section. When the total width of the first modified regions is less than 40 μm, fractures starting from the first modified regions are harder to occur at the time of cutting the substrate and laminate part, whereby the side face of the substrate of the semiconductor chip is harder to become a highly accurate cut section. When the total width of the first modified regions exceeds [(the substrate thickness)×0.9] μm, on the other hand, fractures starting from the first modified regions are likely to deviate from the line to cut at the time of cutting the substrate and laminate part, whereby the side face of the substrate of the semiconductor chip is harder to become a highly accurate cut section.
FIG. 19 is a partly sectional view of the object taken along the line XIX-XIX of FIG. 16(b);
1 . . . object to be processed; 3 . . . front face; 4 . . . substrate; 4a . . . cut section (side face); 5 . . . line to cut; 7 . . . modified region; 8 . . . starting point region for cutting; 13 . . . molten processed region; 15 . . . functional device; 16 . . . laminate part; 21 . . . rear face; 24 . . . fracture; 25 . . . semiconductor chip; 71 . . . quality modified region; 72 . . . segmented modified region (first modified region); 73 . . . HC modified region (second modified region); L . . . laser light; P . . . light-converging point.
An object to be processed (e.g., glass or a piezoelectric material made of LiTaO3) is irradiated with laser light while locating a light-converging point therewithin under a condition with a field intensity of at least 1×108 (W/cm2) at the light-converging point and a pulse width of 1 μs or less. This magnitude of pulse width is a condition under which a crack region can be formed only within the object while generating multiphoton absorption without causing unnecessary damages on the front face of the object. This generates a phenomenon of optical damage by multiphoton absorption within the object. This optical damage induces a thermal distortion within the object, thereby forming a crack region therewithin. The upper limit of field intensity is 1×1012 (W/cm2), for example. The pulse width is preferably 1 ns to 200 ns, for example. The forming of a crack region by multiphoton absorption is disclosed, for example, in “Internal Marking of Glass Substrate with Solid-state Laser”, Proceedings of the 45th Laser Materials Processing Conference (December, 1998), pp. 23-28.
An object to be processed (e.g., glass) is irradiated with laser light while locating a light-converging point within the object under a condition with a field intensity of at least 1×108 (W/cm2) at the light-converging point and a pulse width of 1 ns or less. When multiphoton absorption is generated within the object with a very short pulse width, the energy caused by multiphoton absorption is not converted into thermal energy, whereby an eternal structure change such as ion valence change, crystallization, or orientation polarization is induced within the object, thus forming a refractive index change region. The upper limit of field intensity is 1×1012 (W/cm2), for example. The pulse width is preferably 1 ns or less, for example, more preferably 1 ps or less. The forming of a refractive index change region by multiphoton absorption is disclosed, for example, in “Forming of Photoinduced Structure within Glass by Femtosecond Laser Irradiation”, Proceedings of the 42nd Laser Materials Processing Conference (November, 1997), pp. 105-111.
As shown in FIGS. 14 and 15, an object to be processed 1 comprises a substrate 4 made of silicon having a thickness of 290 μm; and a laminate part 16, formed on the front face 3 of the substrate 4, including a plurality of functional devices 15. Each functional device 15 comprises an interlayer insulating film 17a laminated on the front face 3 of the substrate 4, a wiring layer 19a disposed on the interlayer insulating film 17a, an interlayer insulating film 17b laminated on the interlayer insulating film 17a so as to cover the wiring layer 19a, and a wiring layer 19b disposed on the interlayer insulating film 17b. The wiring layer 19a and the substrate 4 are electrically connected to each other by a conductive plug 20a penetrating through the interlayer insulating film 17a, whereas the wiring layers 19a and 19b are electrically connected to each other by a conductive plug 20b penetrating through the interlayer insulating film 17b.
A number of functional devices 15 are formed like a matrix in directions parallel and perpendicular to an orientation flat 6 of the substrate 4, whereas the interlayer insulating films 17a, 17b are formed between neighboring functional devices 15, 15 so as to cover the front face 3 of the substrate 4 as a whole.
Thus configured object 1 is cut into the functional devices 15 as follows. First, as shown in FIG. 16(a), a protective tape 22 is bonded to the object 1 so as to cover the laminate part 16. Subsequently, as shown in FIG. 16(b), the object 1 is fixed onto a mount table (not depicted) of a laser processing apparatus such that the rear face 21 of the substrate 4 faces up. Here, the protective tape 22 prevents the laminate part 16 from coming into direct contact with the mount table, whereby each functional device 15 can be protected.
When forming the quality modified region 71, one row of the quality modified region 71 is formed at a position where the distance between the front face 3 of the substrate 4 and the end part 71a on the front face side of the quality modified region 71 is 5 μm to 15 μm or at a position where the distance between the front face 3 of the substrate 4 and the end part 71b on the rear face side of the quality modified region 71 is [(the thickness of substrate 4)×0.1] μm to [20+(the thickness of substrate 4)×0.1] μm. When forming the segmented modified regions 72, three rows of segmented modified regions 72 are formed in series in the thickness direction of the substrate 4. Further, when forming the HC modified regions 73, two rows of HC modified regions 73 are formed as shown in FIG. 16(b), so as to generate fractures 24 from the HC modified regions 73 to the rear face 21 of the substrate 4. Depending on forming conditions, a fracture 24 may also occur between the neighboring segmented modified region 72 and HC modified region 73.
After forming the modified regions 71, 72, 73, an expandable tape 23 is bonded to the rear face 21 of the substrate 4 of the object 1 as shown in FIG. 17(a). Subsequently, the protective tape 22 is irradiated with UV rays as shown in FIG. 17(b), so as to lower its adhesive force, whereby the protective tape 22 is peeled off from the laminate part 16 of the object 1 as shown in FIG. 18(a).
After peeling the protective tape 22 off, the expandable tape 23 is expanded as shown in FIG. 18(b), so as to start fractures from the modified regions 71, 72, 73, thereby cutting the substrate 4 and laminate part 16 along the lines to cut 5, and separating the semiconductor chips 25 obtained by the cutting from each other.
In the above-mentioned laser processing method, the quality modified region 71 is formed at a position where the distance between the front face 3 of the substrate 4 and the end part 71a of the quality modified region 71 on the front face side is 5 μm to 15 μm, or at a position where the front face 3 of the substrate 4 and the end part 71b on the rear face side of the quality modified region 71 is [(the thickness of substrate 4)×0.1] μm to [20+(the thickness of substrate 4)×0.1] μm. When the quality modified region 71 is formed at such a position, the laminate part 16 (constituted by the interlayer insulating films 17a, 17b here) formed on the front face 3 of the substrate 4 can also be cut along the lines to cut 5 with a high precision.
In each of the semiconductor chips 25 cut by using the foregoing laser processing method, the cut section (side face) 4a of the substrate 4 formed with the modified regions 71, 72, 73 and the cut section (side face) 16a of the laminate part 16 become highly accurate cut sections whose irregularities are suppressed as shown in FIG. 18(b).
FIG. 20 is a photograph showing the cut section 4a of the substrate 4 cut by using the above-mentioned laser processing method. As mentioned above, the substrate 4 is made of silicon and has a thickness of 300 μm. Forming conditions of the modified regions 71, 72, 73 are listed in the following Table 1. In Table 1, the light-converging position refers to the distance from the rear face 21 to a position where the light-converging point P of laser light L is located, whereas the energy refers to the energy of laser light L at the time of forming the modified regions 71, 72, 73. The pulse width at the time of forming the modified regions 71, 72, 73 is 180 ns, whereas the interval (which will hereinafter be referred to as laser light irradiation position interval) between positions where respective pulses of laser light L are located when irradiating the laser light L along the lines to cut 5 (positions locating the light-converging point P) is 4 μm.
CONVERGING ENERGY
POSITION (μm) (μJ)
QUALITY MODIFIED REGION 267 15
SEGMENTED MODIFIED 196 20
SEGMENTED MODIFIED 160 20
SEGMENTED MODIFIED 125 20
HC MODIFIED REGION 73 71 10
HC MODIFIED REGION 73 39 10
Here, in the thickness direction of the substrate 4, the quality modified region 71 had a width of about 20 μm, each segmented modified region 72 had a width of about 37 μm, and each HC modified region 73 had a width of about 20 μm. The distance between the front face 3 and the end part 71a of the quality modified region 71 on the front face side was about 7 μm, the distance between the end part 71b of the quality modified region 71 on the rear face side and the end part 72a of the segmented modified region 72 on the front face side opposing each other was about 59 μm, and the distance between the end part 72b of the segmented modified region 72 on the rear face side and the end part 73a of the HC modified region 73 on the front face side was about 24 μm. The segmented modified regions 72 were formed in series in the thickness direction of the substrate 4.
The width of the quality modified region 71 refers to the distance between the end part 71a of the quality modified region 71 on the front face side and the end part 71b thereof on the rear face side (see FIG. 19). The end part 71a of the quality modified region 71 on the front face side refers to an “average position in the thickness direction of the substrate 4” of the end part on the front face 3 side of the quality modified region 71 formed along the lines to cut 5, whereas the end part 71b of the quality modified region 71 on the rear face side refers to an “average position in the thickness direction of the substrate 4” of the end part on the rear face 21 side of the quality modified region 71 formed along the lines to cut 5. The same holds in the segmented modified regions 72 and HC modified regions 73.
(1) Energy of Laser Light L when Forming the HC Modified Region 73
As can be seen from data of the following Table 2, the energy of laser light L at the time of forming the HC modified region 73 is preferably 1 μJ to 20 μJ. More specifically, the energy is preferably 1 μJ to 10 μJ when the transmittance of laser light in the substrate 4 is 30% or higher, and 2 μJ to 20 μJ when the transmittance is 15% or less. The transmittance decreases remarkably when the substrate 4 is thick and includes a large content of impurities.
0.5 1.0 2.0 2.5 5.0 10 15 20 25
TRANSMITTANCE ≧ 30% Δ ◯ ◯ ◯ ◯ ◯ X X X
TRANSMITTANCE ≦ 15% X Δ ◯ ◯ ◯ ◯ ◯ ◯ X
“Δ” on the lower energy side: respective parts where fractures 24 reach the rear face 21 of the substrate 4 and not coexist
“X” on the lower energy side: fractures 24 hardly reach the rear face 21 of the substrate 4
“X” on the higher energy side: damages such as melting occur in the rear face 21 of the substrate 4
(2) Energy of Laser Light L when Forming the Segmented Modified Regions 72
As can be seen from data of the following Table 3, the energy of laser light at the time of forming the segmented modified regions 72 is preferably 1.6 to 3.0 when the energy of laser light L at the time of forming the HC modified region 73 is taken as 1. More specifically, the energy is preferably 1.6 to 3.0 when the transmittance of laser light L in the substrate 4 is 30% or higher, and 2.3 to 3.0 when the transmittance of laser light L in the substrate 4 is 15% or less.
1.0 1.1 1.3 1.4 1.5 1.6 1.7 1.8
TRANSMITTANCE ≧ 30% X X X X Δ ◯ ◯ ◯
TRANSMITTANCE ≦ 15% X X X X X X X X
1.9 2.0 2.1 2.2 2.3 3.0 3.1 3.2
TRANSMITTANCE ≧ 30% ◯ ◯ ◯ ◯ ◯ ◯ Δ X
TRANSMITTANCE ≦ 15% X X Δ Δ ◯ ◯ Δ X
“Δ” on the lower energy side: favorable and unfavorable cutting quality parts coexist
“X” on the lower energy side: fractures do not occur unless an excessive stress is applied, whereby cutting quality is unfavorable
“Δ” on the higher energy side: favorable and unfavorable cutting quality parts coexist
“X” on the higher energy side: cutting quality is low, e.g., chipping occurs in cut sections
1.0 2.0 3.0 5.0 10 15 20
TRANSMITTANCE ≧ 30% X ◯ ◯ ◯ ◯ ◯ Δ
TRANSMITTANCE ≦ 15% X Δ ◯ ◯ ◯ ◯ ◯
TRANSMITTANCE ≧ 30% X X X X X X X
TRANSMITTANCE ≦ 15% ◯ ◯ ◯ ◯ ◯ Δ X
(3) Energy of Laser Light when Forming the Quality Modified Region 71
As can be seen from data of the following Table 5, in the case where the energy of laser light L at the time of forming the HC modified regions 73 is taken as 1, the energy of laser light L at the time of forming the quality modified region 71 is preferably 1.4 to 1.9 when the transmittance of laser light L in the substrate 4 is 30% or higher, and 2.3 to 3.0 when the transmittance of laser light L in the substrate 4 is 15% or less.
TRANSMITTANCE ≧ 30% X X Δ ◯ ◯ ◯ ◯ ◯
TRANSMITTANCE ≧ 30% ◯ Δ X X X X X X
“Δ” on the higher energy side: damages such as melting partly occur in the laminate part 16
“X” on the higher energy side: damages such as melting occur in the laminate part 16
(4) Forming Position of Segmented Modified Regions 72
The distance between respective positions at which the light-converging point P of laser light is located when forming neighboring segmented modified regions 72 is preferably 24 μm to 70 μm. More specifically, the distance is preferably 30 μm to 70 μm when the transmittance of laser light L in the substrate 4 is 30% or higher, and 24 μm to 50 μm when the transmittance is 15% or less. When the segmented modified regions 72 are formed under such a condition, neighboring modified regions 72 tend to become in series in the thickness direction of the substrate 4, whereby the substrate 4 and laminate part 16 can easily be cut even if the substrate 4 is thick.
Preferably, the position at which the light-converging point P of laser light L is located when forming the segmented modified regions 72 is distanced from the rear face 21 by 50 μm to [(the thickness of substrate 4)×0.9 (preferably 0.7)] μm. When the segmented modified regions 72 are formed under such a condition, the substrate 4 and laminate part 16 can easily be cut even if the substrate 4 is thick.
(5) Forming Position of HC Modified Regions 73
Preferably, the position at which the light-converging point P of laser light L is located when forming the HC modified region 73 is distanced from the rear face 21 by 20 μm to 110 μm. When the HC modified region is formed under such a condition, fractures 24 starting from the HC modified region 73 tend to reach the rear face 21 of the substrate 4 reliably. When the distance from the rear face 21 is less than 20 μm, damages 30 such as melting are likely to occur in the rear face 21 of the substrate 4 as shown in FIG. 22. FIG. 22 is a view showing a photograph of the rear face 21 of the substrate 4 in the case where the position at which the light-converging point P of laser light is located when forming the HC modified region 73 is distanced from the rear face 21 by 15 μm while the energy of laser light L is 10 μJ. When the distance from the rear face 21 exceeds 110 μm, on the other hand, fractures 24 starting from the HC modified region 73 are harder to reach the rear face 21 of the substrate 4. Here, the distance between the rear face 21 of the substrate 4 and the end part of the HC modified region 73 on the rear face side becomes 10 μm to 100 μm.
The distance between the end part of the segmented modified region 72 on the rear face side and the end part of the HC modified region 73 on the front face side opposing each other is preferably 15 μm to 60 μm, more preferably 15 μm to 35 μm. When the segmented modified region 72 and HC modified region 73 are formed under such a condition, fractures starting from the modified regions 72, 73 tend to occur along the lines to cut 5 with a high precision, whereby the cut section 4a of the substrate 4 in each semiconductor chip 25 becomes a highly accurate cut section. When the distance is less than 15 μm, fractures starting from the modified regions 72, 73 are likely to deviate from the lines to cut 5 at the time of cutting the substrate 4 and laminate part 16, whereby the cut section 4a of the substrate 4 in the semiconductor chip 25 is harder to become a highly accurate cut section. When the distance exceeds 60 μm, on the other hand, the interaction between the modified region 72 and HC modified region 73 becomes smaller at the time of cutting the substrate 4 and laminate part 16, whereby the cut section 4a of the substrate 4 in the semiconductor chip 25 is harder to become a highly accurate cut section.
The distance between the end part of the quality modified region 71 on the rear face side and the end part of the segmented modified region 72 on the front face side opposing each other is preferably 0 μm to [(the thickness of substrate 4)−(the thickness of substrate 4)×0.6] μm. When the quality modified region 71 and segmented modified region 72 are formed under such a condition, fractures starting from the modified regions 71, 72 tend to occur along the lines to cut 5 with a high precision at the time of cutting the substrate 4 and laminate part 16, whereby the cut section 4a of the substrate 4 and the cut section 16a of the laminate part 16 in each semiconductor chip 25 become highly accurate cut sections. When the distance exceeds [(the thickness of substrate 4)−(the thickness of substrate 4)×0.6] μm, the cut section 4a of the substrate 4 of the semiconductor chip 25 is harder to become a highly accurate cut section between the quality modified region 71 and segmented modified region 72 at the time of cutting the substrate 4 and laminate part 16. The distance is set to 0 μm when completely cutting the substrate 4 by irradiation with the laser light L alone.
(8) Forming Position of the Quality Modified Region 71
Preferably, the quality modified region 71 is formed at a position where the distance between the front face 3 of the substrate 4 and the end part of the quality modified region 71 on the front face side is 5 μm to 15 μm, or at a position where the distance between the front face 3 of the substrate 4 and the end part of the quality modified region 71 on the rear face side is [(the thickness of substrate 4)×0.1] μm to [20+(the thickness of substrate 4)×0.1] μm. When the quality modified region 71 is formed under such a condition, the skirt width S can be suppressed to 3 μm or less as shown in FIG. 23, whereby the laminate part 16 formed on the front face 3 of the substrate 4 can be cut along the lines to cut 5 with a high precision.
When the quality modified region 71 is formed at a position where the distance between the front face 3 of the substrate 4 and the end part of the quality modified region 71 on the front face side is 5 μm to 15 μm, the skirt width S can be suppressed to 1 μm or less as shown in FIG. 23, whereby the end part of the substrate 4 on the front face 3 side and the laminate part 16 can be cut along the lines to cut 5 with a higher precision. In terms of the distance between the front face 3 of the substrate 4 and the end part of the quality modified region 71 on the rear face side, the quality modified region 71 is preferably formed at a position where the distance is [5+(the thickness of substrate 4)×0.1] μm to [20+(the thickness of substrate 4)×0.1] μm, more preferably at a position where the distance is [5+(the thickness of substrate 4)×0.1] μm to [10+(the thickness of substrate 4)×0.1] μm. When the quality modified region is formed under such a condition, the end part of the substrate 4 on the front face 3 side and the laminate part 16 can be cut along the lines to cut 5 with a higher precision.
(9) Widths of Modified Regions 71, 72, 73
The width of the HC modified region 73 (the total of widths of HC modified regions 73 if they are formed in a plurality of rows) in the thickness direction of the substrate 4 is preferably 110 μm or less. When the HC modified region 73 is formed under such a condition, fractures 24 reaching the rear face 21 of the substrate 4 from the HC modified region 73 tend to be formed along the lines to cut 5 with a high precision. When the width of the HC modified region 73 exceeds 110 μm, fractures 24 reaching the rear face 21 of the substrate 4 from the HC modified region 73 are likely to deviate from the lines to cut 5.
The total of widths of the segmented modified regions 72 in the thickness direction of the substrate 4 is preferably 40 μm to [(the thickness of substrate 4)×0.9] μm. When the segmented modified regions 72 are formed under such a condition, fractures starting from the segmented modified regions 72 tend to occur along the lines to cut 5 with a high precision at the time of cutting the substrate 4 and laminate part 16, whereby the cut section 4a of the substrate 4 in each semiconductor chip 25 becomes a highly accurate cut section. When the total of widths of the segmented modified regions 72 is less than 40 μm, fractures starting from the segmented modified regions 72 are harder to occur at the time of cutting the substrate 4 and laminate part 16, whereby the cut section 4a of the substrate 4 in the semiconductor chip 25 is less likely to become a highly accurate cut section. When the total of widths of the segmented modified regions 72 exceeds [(the thickness of substrate 4)×0.9] μm, fractures starting from the segmented modified regions 72 are likely to deviate from the lines to cut 5 when cutting the substrate 4 and laminate part 16, whereby the cut section 4a of the substrate 4 in the semiconductor chip 25 is harder to become a highly accurate cut section.
Preferably, the width of the quality modified region 71 in the thickness direction of the substrate 4 is not greater than [(the thickness of substrate 4)×0.1] μm. When the quality modified region 71 is formed under such a condition, fractures starting from the quality modified region 71 tend to reach the laminate part 16 along the lines to cut 5 with a high precision at the time of cutting the substrate 4 and laminate part 16. When the width of the quality modified region 71 exceeds [(the thickness of substrate 4)×0.1] μm, fractures starting from the quality modified region 71 are likely to reach the laminate part 16 while deviating from the lines to cut 5 at the time of cutting the substrate 4 and laminate part 16.
FIG. 25 is a view showing a photograph of a cut section 4a of a substrate 4 cut by using the above-mentioned laser processing method. As mentioned above, the substrate 4 is made of silicon and has a thickness of 290 μm. Forming conditions of the modified regions 71, 72, 73 are listed in the following Table 7. In Table 7, the light-converging position refers to the distance from the rear face 21 to a position where the light-converging point P of laser light L is located, whereas the energy refers to the energy of laser light L at the time of forming the modified regions 71, 72, 73. The pulse width at the time of forming the modified regions 71, 72, 73 is 150 ns, whereas the interval (which will hereinafter be referred to as laser light irradiation position interval) between positions where respective pulses of laser light L are located when irradiating the laser light L along the lines to cut 5 (positions locating the light-converging point P) is 3.75 μm.
QUALITY MODIFIED REGION 275 7
SEGMENTED MODIFIED 228 14
SEGMENTED MODIFIED 194 14
SEGMENTED MODIFIED 165 14
HC MODIFIED REGION 73 104 14
HC MODIFIED REGION 73 57 9
Here, in the thickness direction of the substrate 4, the quality modified region 71 had a width of about 22 μm, each segmented modified region 72 had a width of about 33 μm, the HC modified region 73 on the front face 3 side had a width of about 28 μm, and the HC modified region 73 on the rear face 21 side had a width of about 20 μm. The distance between the front face 3 and the end part 71a of the quality modified region 71 on the front face side was about 8 μm, the distance between the end part 71b of the quality modified region 71 on the rear face side and the end part 72a of the segmented modified region 72 on the front face side opposing each other was about 25 μm, and the distance between the end part 72b of the segmented modified region 72 on the rear face side and the end part 73a of the quality modified region 73 on the front face side was about 25 μm. The segmented modified regions 72 were formed in series in the thickness direction of the substrate 4.
(10) Relationship Between the Energy of Laser Light L for Forming Segmented Modified Regions 72 and that for Forming HC Modified Regions 73
As can be seen from data of the following Table 8, when forming a plurality of rows of HC modified regions 73, the energy of laser light at the time of forming the segmented modified regions 72 is preferably 1.3 to 3.3 in the case where the energy of laser light L at the time of forming the HC modified region 73 closest to the rear face 21 of the substrate 4 is taken as 1. More specifically, the energy is preferably 1.3 to 3.0 when the transmittance of laser light L in the substrate 4 is 30% or higher, and 1.5 to 3.3 when the transmittance is 15% or less.
TRANSMITTANCE ≧ 30% X X ◯ ◯ ◯ ◯ ◯ ◯
TRANSMITTANCE ≦ 15% X X X Δ ◯ ◯ ◯ ◯
TRANSMITTANCE ≧ 30% ◯ ◯ ◯ ◯ ◯ ◯ X X
TRANSMITTANCE ≦ 15% ◯ ◯ ◯ ◯ ◯ ◯ ◯ ◯
TRANSMITTANCE ≧ 30% X X X X
TRANSMITTANCE ≦ 15% ◯ Δ X X
(11) Energy of Laser Light L when Forming the Quality Modified Region 71
As can be seen from data of the following Table 9, in the case where the energy of laser light L at the time of forming the HC modified region 73 on the rear face 21 side is taken as 1, the energy of laser light L at the time of forming the quality modified region 71 is preferably 0.6 to 1.9 when the transmittance of laser light L in the substrate 4 is 30% or higher, and 0.6 to 3.0 when the transmittance is 15% or less.
TRANSMITTANCE ≧ 30% X X Δ ◯ ◯ ◯ ◯
TRANSMITTANCE ≦ 15% X X Δ ◯ ◯ ◯ ◯
TRANSMITTANCE ≧ 30% ◯ ◯ ◯ ◯ ◯ ◯ ◯ ◯
TRANSMITTANCE ≦ 15% ◯ ◯ ◯ ◯ ◯ ◯ Δ X
Forming Positions of HC Modified Regions 73 when Forming a Plurality of Rows of HC Modified Regions 73
When forming a plurality of rows of HC modified regions 73, it will be preferred if the position at which the light-converging point P of laser light L is located when forming the HC modified region 73 closest to the rear face 21 of the substrate 4 is distanced from the rear face 21 by 20 μm to 110 μm, and the position at which the light-converging point P of laser light L is located when forming the HC modified region 73 second closest to the rear face 21 of the substrate 4 is distanced from the rear face 21 by 140 μm or less.
When the above-mentioned various forming conditions for the segmented modified regions 72 are not satisfied in the forming of the segmented modified regions 72, a part not cut into semiconductor chips 25 occurs in the object 1 as shown in FIG. 26(a). When the above-mentioned various forming conditions for the segmented modified regions 72 are satisfied, on the other hand, the whole object 1 is reliably cut into the semiconductor chips 25 as shown in FIG. 26(b).
QUALITY MODIFIED REGION 167 15
SEGMENTED MODIFIED 121 20
SEGMENTED MODIFIED 71 20
QUALITY MODIFIED REGION 256 15
SEGMENTED MODIFIED 153 20
QUALITY MODIFIED REGION 71 644 15
SEGMENTED MODIFIED REGION 72 641 20
SEGMENTED MODIFIED REGION 72 612 20
SEGMENTED MODIFIED REGION 72 584 20
SEGMENTED MODIFIED REGION 72 555 20
SEGMENTED MODIFIED REGION 72 527 20
SEGMENTED MODIFIED REGION 72 498 20
SEGMENTED MODIFIED REGION 72 470 20
SEGMENTED MODIFIED REGION 72 441 20
SEGMENTED MODIFIED REGION 72 413 20
SEGMENTED MODIFIED REGION 72 384 20
SEGMENTED MODIFIED REGION 72 356 20
SEGMENTED MODIFIED REGION 72 328 20
SEGMENTED MODIFIED REGION 72 299 20
SEGMENTED MODIFIED REGION 72 271 20
SEGMENTED MODIFIED REGION 72 242 20
SEGMENTED MODIFIED REGION 72 214 20
SEGMENTED MODIFIED REGION 72 185 20
SEGMENTED MODIFIED REGION 72 157 20
SEGMENTED MODIFIED REGION 72 121 20
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