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DESCRIPTION JP2011023503

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DESCRIPTION JP2011023503
An object of the present invention is to cause multiphoton absorption by aligning a focusing
point of laser light inside a semiconductor device and form a modified region inside the
semiconductor device, and then forming a crack along a planned dividing line starting from the
modified region Reduce the processing time in the dicing step of growing the semiconductor
device and dividing the semiconductor device. SOLUTION: A plurality of modified regions (7a, 7b)
are formed inside a semiconductor substrate (7) by forming a light transmitting film (refractive
layer 4) on the surface of a semiconductor substrate (7) in a dicing region. 7b) can be
simultaneously formed to shorten the processing time. [Selected figure] Figure 3
Semiconductor device and method of manufacturing the same
[0001]
The present invention relates to a structure of a semiconductor device suitable for laser
processing for dividing into individual semiconductor devices.
[0002]
Conventionally, blade dicing has been most commonly used as a method for dicing
semiconductor devices.
In this blade dicing, an annular dicing saw in which particles of diamond or CBN (Cubic Boron
Nitride) are held by a bonding material is rotated at high speed, and dicing lanes as an area
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necessary for division (actual dicing width by dicing saw) Crush and process the wafer.
[0003]
In the dicing technology using dicing saws, improvement in processing quality is achieved
through improvement and optimization of equipment conditions such as particle size and density
of diamond particles, dicing saw specifications for bonding materials, etc., rotation speed, feed
speed, and cutting depth. Has been addressed.
[0004]
However, for processing with a dicing saw, water such as MEMS (Micro Electro Mechanical
Systems) is used because water is used during processing, such as cooling for suppressing heat
generation due to crushing processing and washing for discharging cutting chips. It can not be
used for devices that dislike it.
[0005]
In recent years, processing by laser light has attracted attention as a method for solving the
above problems.
For example, Patent Document 1 describes a technique for forming a modified region in an object
by multiphoton absorption.
Multiphoton absorption is a phenomenon in which absorption occurs in a material when the light
intensity is very large, even when the energy of photons is smaller than the absorption band gap
of the material, that is, optically transmitted.
[0006]
In this method, multiphoton absorption is caused by aligning the focusing point of the laser light
inside the semiconductor device, and after the reformed region is formed inside the
semiconductor device, the reformed region is taken as a starting point along the planned dividing
line Cracks are grown to divide the semiconductor device. This makes it possible to dice the
semiconductor device without generating unnecessary cracks or chipping out of the planned
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dividing line.
[0007]
Therefore, the conventional method can suppress the reduction in chipping strength due to
chipping and the generation of dust. Moreover, unlike the crushing process, the dicing width can
be extremely narrowed because the physical cutting width is not provided in the planar direction,
unlike the dicing process.
[0008]
Furthermore, since it does not generate heat due to generation of cuttings or processing and
does not require water, it is also suitable for processing of devices that dislike water.
[0009]
Further, when the thickness of the semiconductor device is thick, as described in Patent
Document 2, a plurality of reformed regions are formed at different depth positions of the
semiconductor device by changing the depth of the focusing point, and It is possible to divide by
connecting the cracks generated from the reformed area.
[0010]
At this time, the thicker the semiconductor device, the more the number of reformed regions is
required, which causes a problem that processing takes time.
In addition, when the distance between the modified regions is increased in order to reduce the
number of modified regions, or when the distance from the modified region to the surface of the
semiconductor device is long, reliable division is not performed and it becomes undivided. Parts
may occur.
Even when the division is performed, the straightness of the crack is impaired, and as a result,
the straightness on the semiconductor surface is deteriorated.
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[0011]
For example, Patent Document 3 describes a method of advancing a crack in a small reformed
region and reliably dividing a semiconductor device. In Patent Document 3, after the reformed
region is formed, the semiconductor device is cooled and a stress due to thermal stress is applied
to propagate a crack in the reformed region.
[0012]
Further, for example, Patent Document 4 describes a method for improving the straightness of a
crack. In the method described in Patent Document 4, a rectilinear recess is formed on the
surface of the semiconductor device, and a crack from the modified region is guided to the recess
to enable division with rectilinearity.
[0013]
JP-A-2002-192370 JP-A-2002-205180 JP-A-2003-88980 JP-A-2005-268752
[0014]
However, the methods disclosed in the above-mentioned patent documents have the following
problems.
[0015]
First, as described in Patent Document 2, when a plurality of reformed regions are formed and
connected, the thicker the semiconductor device, the more the number of the reformed regions is
required, so it takes time for processing. There is a problem.
[0016]
Further, in the method disclosed in Patent Document 3, after the formation of the modified
region, the number of steps of applying thermal stress to grow a crack is increased, and
equipment for controlling heat is required.
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In addition, when the distance from the modified region to the surface of the semiconductor
device is long, there is a problem that straightness on the surface of the semiconductor device is
deteriorated.
[0017]
In the method shown in Patent Document 4, although it is possible to control the direction of the
crack, when the number of modified regions is suppressed, as shown in Patent Document 3, a
special process for dividing and Equipment is required.
[0018]
An object of the present invention is to provide a semiconductor device capable of suppressing
an increase in the number of reformed regions even if the thickness of the semiconductor device
is large, and more preferably shortening the processing time.
[0019]
The present invention does not have to solve all the problems listed above, and it is preferable
that at least one problem be solved, and it is preferable that there are many problems that can be
solved.
[0020]
In order to solve the above problems, in the method of manufacturing a semiconductor device
according to the present invention, a transparent film transmitting light between the step (a) of
forming a plurality of element regions on a wafer and the plurality of element regions And (c)
forming a dicing line by forming a plurality of modified regions inside the wafer by irradiating
light between the plurality of element regions. It has a step (d) of dividing the wafer along the
line, and the transparent film formed in the step (b) is characterized by being formed at least at a
position where light is incident. .
[0021]
In addition, it is preferable to form the permeable film formed in step (b) on both sides of the
dicing line.
[0022]
Further, the plurality of element regions have a first element region and a second element region
located next to the first element region, and the transmissive film formed in the step (b) is a
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dicing line And the first element region, and not between the dicing line and the second element
region.
[0023]
Further, it is preferable to form the permeable film formed in the step (b) so as to be thinner
from the element region toward the dicing line.
[0024]
In addition, after the transparent film is formed in the step (b), it is preferable to remove the
transparent film by etching in a portion to be a dicing line on the wafer surface.
[0025]
Further, the permeable membrane is preferably a laminated structure composed of a plurality of
membranes.
[0026]
In addition, the permeable film is preferably formed of any of SiN, SiO2, BPSG, PSG, NSG, PS, and
Si, or a laminated film thereof.
[0027]
Further, the element region preferably includes an interlayer insulating film and a wiring formed
on the wafer.
[0028]
Further, the element region preferably includes a MEMS element having a vibrating film formed
on a through hole penetrating the wafer.
[0029]
A semiconductor device according to the present invention has a substrate, an element region
formed on the substrate, and an external region other than the element region on the substrate,
and a transparent film transmitting light is formed on the substrate in the external region. It is
characterized in that it is formed.
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[0030]
A MEMS device according to the present invention penetrates from a substrate having a first
surface and a second surface opposite to the first surface, and from the first surface to the
second surface of the substrate. A through hole and a film formed on the first surface of the
substrate so as to cover the through hole, and in an external region located outside the element
region having the through hole and the film, on the substrate Is a MEMS device characterized in
that a light transmitting film is formed.
[0031]
Preferably, the permeable membrane is formed to surround the element region.
[0032]
Further, it is preferable to have a portion formed to be thinner toward the outside of the element
region.
[0033]
Further, it is preferable that the permeable membrane has a laminated structure composed of a
plurality of membranes.
[0034]
The permeable film is preferably a film of SiN, SiO2, BPSG, PSG, NSG, PS, or Si, or a laminated film
thereof.
[0035]
According to the semiconductor device and the method of manufacturing the same of the present
invention, since there are a plurality of focal points where laser light is absorbed by multiple
photons by refraction, the number of times of laser light scanning is one time. It is possible to
generate a plurality of quality layers.
[0036]
In addition, even when the semiconductor device is thick, it is possible to reduce the number of
times of scanning with the laser light, and the processing time can be shortened.
[0037]
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A plan view showing a semiconductor device according to a first embodiment of the present
invention, and a partial schematic view a structural schematic view of the A-A cross section of
FIG. 1 A dicing process using a laser beam in the first embodiment of the present invention is
described. Figure showing the principle of simultaneous formation of multiple reformed regions
Figure showing a schematic structure of a MEMS device according to a second embodiment of
the present invention (b) explaining a dicing process using laser light The figure explaining the
composition of the semiconductor device concerning a 3rd embodiment of the present invention,
and the dicing process using a laser beam The composition of the semiconductor device
concerning a 4th embodiment of the present invention and the dicing process using a laser beam
The figure to explain
[0038]
Each embodiment of the semiconductor device of the present invention will be described below
with reference to the drawings.
[0039]
Further, the materials and numerical values used in the present invention only exemplify
preferable examples, and the present invention is not limited to this form.
Moreover, changes can be made as appropriate without departing from the scope of the concept
of the present invention.
Furthermore, combinations with other embodiments are also possible.
[0040]
First Embodiment <Basic Configuration> As shown in FIGS. 1 and 2, in the semiconductor wafer 1
of the present embodiment, a plurality of dividing lines 3 are set from the upper surface to the
lower surface. A plurality of chip areas (semiconductor devices 2) partitioned by the planned
dividing lines 3 are provided.
[0041]
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The semiconductor device 2 has an element region 5 and a dicing region 6 on a semiconductor
substrate 7.
For example, as shown in FIG. 2, the element region 5 is a logic circuit in which a plurality of
pads 51, vias 52, wirings 53, plugs 54 and the like are formed via an interlayer insulating film
50. It is
[0042]
Around the element region 5, a refractive layer 4 which is a permeable film having a refractive
index higher than that of the air layer is formed so as to surround the element region 5.
The refractive layer 4 may be a layer used for various purposes such as an element formation
layer and an etching stop in the semiconductor wafer 1.
Although in FIG. 2 the refractive layer 4 and the passivation film 55 are described separately to
clarify the configuration of the refractive layer 4, it is preferable that both be formed of the same
layer.
Thereby, the refractive layer 4 can be formed without newly adding a manufacturing process or
manufacturing equipment.
[0043]
Further, the refractive layer 4 may be formed of a single film or a laminated structure of a
plurality of films, but it is preferable that the degree of transparency to laser light used for dicing
be high.
Materials which can be suitably used for the refractive layer 4 include SiN, SiO 2, BPSG
(Borophospho Silicate Glass), PSG (Phosphorus Sillicon Glass), NSG (None-doped Silicate Glass),
PS (Poly Sillicon), Si (Silicon) And the like.
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[0044]
However, the film is not limited to the above.
Divided lines 3 are set in an external area where the refractive layers 4 of each element area 5
are adjacent to each other, and a dicing area 6 is formed.
<Dicing Process> FIG. 3 is a cross-sectional view showing a process of dicing the semiconductor
device 2 of the present embodiment using the laser light 8.
The width of the refractive layer 4 is preferably about 1.5 when the distance from the dividing
line 3 to the refractive layer 4 is 1.
The wavelength range of the laser light used for dicing is, for example, preferably a near infrared
wavelength (0.7 to 2.5 μm) which is transparent to Si, and particularly preferably around 1.0
μm.
[0045]
As shown in FIG. 3, when the laser light 8 is incident from the element region 5 side, multiphoton
absorption is caused at the focusing point of the laser light 8, and the modified regions 7 a and 7
b are formed inside the semiconductor substrate 7.
[0046]
Here, since the condensing point of the laser beam 8 passing through the refractive layer 4 and
the condensing point of the laser beam 8 not passing through the refractive layer 4 are at
different positions, the two modified regions 7a and 7b can be simultaneously It can be formed.
Then, the semiconductor wafer 1 can be divided into the individual semiconductor devices 2 by
propagating the cracks 7 c starting from the modified regions 7 a and 7 b.
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[0047]
Assuming that the amount of positional deviation of the two reforming regions 7a and 7b is d
and the height of the reforming region is x, the relationship between d and x is
[0048]
It is preferable that
In the case of 0.5x> d, the distance between the two modified regions is too close to ensure
sufficient straight-line stability of the crack 7c, and it is too close to obtain the effect of the
present invention. difficult.
In the case of d> 3x, on the contrary, the distance between the two modified regions is too long,
and the straight stability of the crack 7c is not sufficient.
[0049]
The height x of the modified region changes depending on the specifications of the laser light
output device, but according to our verification, it is about 10 to 30 μm.
The positional deviation amount d of the reforming regions 7a and 7b will be described in detail
next.
[0050]
Through the dicing process, the semiconductor device 2 divided and formed into chips is
completed.
Since the semiconductor substrate 7 is divided along the planned dividing line 3 sandwiched
between the refractive layers 4, the semiconductor device 2 after division has a state in which the
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refractive layer 4 is formed along the outer periphery of the semiconductor substrate 7. Become.
<Principle of forming a plurality of modified regions> Here, with reference to FIG. 4, the principle
of forming a plurality of modified regions simultaneously by providing the refractive layer 4 will
be described.
[0051]
As shown in FIG. 4, it is assumed that light is incident in order of medium α (refractive index:
na), medium β (refractive index: nb, thickness t), and medium γ (refractive index: nc).
Let A be an incident point from medium α to medium β, B be an incident point from medium β
to medium γ, and D be a point at which incident light reach planned dividing line 3 be an
incident angle of light at medium α θa, medium The refraction angle of light at β is θb, and
the refraction angle of light at medium γ is θc.
[0052]
On the other hand, assuming that light does not exist in the medium β and light is directly
incident on the medium γ from the medium α, the incident point of the medium α to the
medium γ in this case reaches C and the incident light reaches the dividing line 3 Let E be a
point.
[0053]
Assuming that the distance AC = Qa, the distance AB = Qb, the distance BD = Qc, the distance CE
= Qd, and the distance DE = d, the following equation holds from the geometrical constraint
condition.
[0054]
[0055]
[0056]
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Also, the following equation holds from the boundary condition (Snell's law).
[0057]
[0058]
Assuming that the medium α is an air layer, na 1 1 may be satisfied.
If we eliminate Qa to Qd, θb, and θc from (Equation 2) to (Equation 6)
[0059]
When the medium α is an air layer, the medium β is a refractive layer 4 and the medium γ is a
semiconductor substrate 7, the positional displacement amount d of the modified region is the
thickness t of the refractive layer 4, the refractive layer It is a function of the refractive index nb
of 4, the refractive index nc of the semiconductor substrate 7, and the laser light incident angle
θa.
[0060]
As understood from (Equation 7), the positional displacement amount d of the modified region is
proportional to the thickness t of the refractive layer 4.
Therefore, by providing the region in which the refractive layer 4 is formed and the region in
which the refractive layer 4 is not formed in the dicing region as shown in FIG. It is also possible
to form positional deviation of the modified region (by forming a step in the refractive layer 4) by
providing a difference in thickness of the refractive layer 4 in the dicing region.
Furthermore, it is also possible to increase the number of reformed regions simultaneously
formed by increasing the number of steps provided in the refractive layer 4.
[0061]
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Under the conditions verified by the present inventors, sin θa ≒ 0.72, and the refractive index
of the semiconductor substrate 7 (SiC) was nc ≒ 3.6.
Substituting these into (Equation 7),
[0062]
となる。
The focusing point of the light passing through the refracting layer 4 and the focusing point of
the light not passing through the refracting layer 4 cause positional deviation of d given by
(Equation 8). A quality zone is formed at the same time.
[0063]
If d is eliminated from (Equation 1) and (Equation 8), the following equation is derived as a
preferable range of the thickness t of the refractive layer 4.
[0064]
The height x of the modified region changes depending on the specifications of the laser light
output device, but according to our verification, it is about 10 to 30 μm.
Further, the refractive index nb of SiN, SiO2, BPSG, PSG, NSG, PS, Si or the like suitable as the
material of the refractive layer 4 is about 1.5 to 2.
Therefore, the preferable range (unit: μm) of the thickness t in the case where these materials
are used for the refractive layer 4 according to equation (9) is as shown in the following table.
[0065]
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As described above, if dicing with laser light is performed using the semiconductor wafer 1 of the
present embodiment, two modified regions 7 a and 7 b in the depth direction can be formed
simultaneously.
Therefore, even if the semiconductor wafer 1 is thick, it can be divided into the individual
semiconductor devices 2 in a processing time shorter than the conventional one.
[0066]
In addition, it can also be used in the manufacture of semiconductor devices that dislike water by
using laser light, and the occurrence of chipping can be suppressed, and the width of the planned
dividing line (scribe line) 3 can be made smaller compared to the method using a dicing saw. Can.
[0067]
Second Embodiment <Basic Configuration> FIG. 5 is a cross-sectional view showing a
semiconductor device according to a second embodiment of the present invention.
This figure shows the MEMS element 9 formed in the element region 5 shown in FIG.
In FIG. 5A, the MEMS element 9 is one in which a MEMS microphone element is formed on a
semiconductor substrate 7 and is produced by MEMS (micro-electro-mechanical system)
technology of semiconductor processing.
[0068]
A through hole 72 is formed in the semiconductor substrate 7 by a through etching process, and
a pedestal portion 71 is formed by the remaining portion of the semiconductor substrate 7.
A vibrating film 93 formed of conductive polysilicon, an insulator, a dielectric film 99 formed on
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the vibrating film 93 to be electretized, and insulation such as BPSG on the pedestal portion 71
via an insulator. A fixed film 94 is formed to face the vibrating film 93 via the material 96.
[0069]
The dielectric film 99 is formed by laminating a silicon nitride film and a silicon oxide film, and
the fixed film 94 is formed by laminating conductive polysilicon and a silicon oxide film or a
silicon nitride film. , And a plurality of fixed membrane sound holes 94a.
[0070]
The vibrating film 93 may be a laminated film of an insulating film and conductive polysilicon, or
may be a conductive polysilicon single layer.
Moreover, as long as it is a conductor film which functions as a vibrating electrode, conductor
films other than conductive polysilicon may be used.
[0071]
The fixing film 94 may be a laminated film of an insulating film and conductive polysilicon, or
may be a conductive polysilicon single layer.
Moreover, as long as it is a conductor film which functions as a fixed electrode, conductor films
other than electroconductive polysilicon may be sufficient.
[0072]
In addition, since the vibrating membrane 93 and the fixed film 94 face each other through the
gap 95 to function as a pair of capacitors, the vibrating membrane 93 may be formed on the
fixed film 94 with the gap 95 interposed therebetween.
[0073]
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In the present embodiment, the insulating material 96 formed of BPSG or the like has the
function of the refractive layer 4 in the first embodiment.
Element Forming Step In the step of forming the MEMS element 9, first, the vibrating film 93 is
formed on the semiconductor substrate 7, the dielectric film 99 is formed on the vibrating film
93, and the sacrificial film is formed thereon.
Thereafter, the fixed film 94 is formed on the sacrificial film, and the fixed film sound holes 94 a
are formed in the fixed film 94.
Thereafter, a through etching process is performed on the semiconductor substrate 7 to form the
through hole 72 and the pedestal portion 71.
Thereafter, the sacrificial film is etched through the fixed film sound holes 94 a to form a gap 95
between the vibrating film 93 and the fixed film 94, and the remaining portion of the sacrificial
film becomes the insulating material 96.
[0074]
At this time, by forming the insulating material 96 so as to extend in the vicinity of the planned
dividing line 3, the insulating material 96 can have the function of the refractive layer 4.
Thereafter, the dielectric film 99 is electretized, and dicing of the semiconductor substrate 7 is
performed.
Note that electretization may be performed after the dicing step.
[0075]
In the second embodiment, the MEMS element having the electretized dielectric film 99 is
described, but the electretized dielectric film 99 may be omitted.
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In addition, in the case where the electretized dielectric film 99 is present, it may be formed
between the vibrating electrode and the fixed electrode. <Dicing Process> FIG. 5B is a crosssectional view showing a process of dicing the semiconductor substrate 7 on which the MEMS
element 9 is formed using the laser light 8. In the present embodiment, the insulating material
96 has a role of the refractive layer 4, but the other points are the same as those of the first
embodiment.
[0076]
That is, according to the principle described in the first embodiment, when the laser beam 8 is
incident, it passes through the condensing point of the laser beam 8 passing through the
insulating material 96 (refractive layer 4) and the insulating material 96 (refractive layer 4).
Since the position is different from that of the focused point of the laser light 8, two modified
regions 7 a and 7 b can be formed simultaneously. Then, the semiconductor wafer 1 can be
divided into the individual MEMS elements 9 by advancing the cracks 7 c starting from the
modified regions 7 a and 7 b.
[0077]
Third Embodiment As shown in FIG. 6, in the semiconductor device 2 of this embodiment, a
refractive layer 4 is formed on one side centering on the planned dividing line 3 on the upper
surface of the semiconductor device, and on the other side Is different from the first embodiment
in that the refractive layer 4 is not formed and the semiconductor substrate 7 is formed to be
exposed. At this time, it is desirable that the width of the refractive layer 4 and the exposed width
of the semiconductor substrate 7 be 1: 1. The other points are the same as in the first
embodiment.
[0078]
As in the first embodiment, the semiconductor device 2 is divided by simultaneously forming the
modified regions 7a and 7b by aligning the focusing point of the laser light with the planned
dividing line 3 using the semiconductor device 2 of the present embodiment. can do. For this
reason, the semiconductor device 2 can be divided in less processing time than conventional.
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[0079]
Furthermore, it is possible to simultaneously form the modified regions 7a and 7b at arbitrary
positions by swinging the condensing point of the laser light up and down. For this reason, when
the thickness of the semiconductor device 2 is thick, the processing time can be halved by
simultaneously forming the two reformed regions even if the focusing point of the laser light is
shaken up and down.
[0080]
Fourth Embodiment FIG. 7 is a cross-sectional view showing a semiconductor device according to
a fourth embodiment of the present invention. The semiconductor device 2 of the present
embodiment differs from the first embodiment in that the thickness of the refractive layer 4
gradually decreases toward the outside of the element region 5. The other points are the same as
in the first embodiment.
[0081]
As in the first embodiment, the semiconductor device 2 is divided by simultaneously forming the
modified regions 7a and 7b by aligning the focusing point of the laser light with the planned
dividing line 3 using the semiconductor device 2 of the present embodiment. can do. For this
reason, the semiconductor device 2 can be divided in less processing time than conventional.
[0082]
In the first to fourth embodiments, it is possible to simultaneously form the modified regions 7a
and 7b at arbitrary positions by swinging the condensing point of the laser light up and down.
For this reason, when the thickness of the semiconductor device 2 is thick, the processing time
can be halved by simultaneously forming the two reformed regions even if the focusing point of
the laser light is shaken up and down.
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[0083]
The material of the semiconductor substrate 7 is not limited to Si, and may be a compound
semiconductor such as SiGe or GaAs.
[0084]
According to the semiconductor device of the present invention, since there are a plurality of
focal points where laser light is absorbed by multiphoton by refraction, a plurality of reformed
layers formed inside the semiconductor device are performed only once by scanning the laser
light. It is possible to generate.
Therefore, the processing time can be shortened, and it can be used for all semiconductor devices
divided by laser processing and electronic devices using the same.
[0085]
DESCRIPTION OF SYMBOLS 1 semiconductor wafer 2 semiconductor device 3 division intended
line 4 refractive layer 5 element area 50 interlayer insulation film 51 pad 52 via 53 wiring 54
plug 55 passivation film 6 dicing area 7 semiconductor substrate 7 a first modified area 7 b
second modified Region 7 c Crack 71 pedestal 72 through hole 8 laser light 9 MEMS element 93
vibrating film 94 fixed film 94 a fixed film sound hole 95 gap 96 insulating material 99 dielectric
film
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