JP2006110593A - Laser machining method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To suppress resticking of produced vaporized dust to the surface of a member in laser machining where the prescribed position of the member is removed using pulsed laser light. <P>SOLUTION: In the laser machining where the surface of a member 7 is irradiated with pulsed laser light L to remove the part 6b to be irradiated, the pulse width of the pulsed laser light is selected to ≤10 picoseconds. Further, the density of the energy applied to the member 7 by the irradiation of the pulse laser light L is selected to ≤0.1 J/cm<SP>2</SP>per pulse. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a laser processing method for irradiating a member surface with pulsed laser light to remove an irradiated portion and processing the member surface into a predetermined shape.

  2. Description of the Related Art Conventionally, in the manufacture of semiconductor devices and the manufacture of video devices such as liquid crystal displays and organic electroluminescence (EL) displays, the shape of a photomask used for manufacturing, and thin film transistors (Thin Film Transistors) constituting the devices. TFT) Pattern formation such as wiring on the substrate, or fine processing for correcting the pattern shape, for example, a pattern that should be originally separated in the fine pattern is not separated but is short-circuited (hereinafter referred to as a short-circuit portion). In some cases, separation processing of the short-circuit portion is required. In recent years, members such as wirings constituting semiconductor devices and video devices have been rapidly miniaturized and complicated, so that the importance of microfabrication is increasing.

  As this fine processing means, a laser processing technique for removing a predetermined position of a target member by irradiation with pulsed laser light can be exemplified. In this laser processing technology, the temperature of the irradiated portion is raised by irradiation with a pulse laser, and only the member material of the irradiated portion is selectively removed by melting and vaporizing, so that the member has a desired shape. Has been done.

However, in the conventional laser processing technique, the melted member material is scattered around the irradiated portion, and thus the scattered member material is reattached to the peripheral portion and a molten dust is formed.
In addition, the pulse width of the laser beam used for conventional laser processing is sufficiently long to allow processing even if the maximum value of energy per pulse is relatively small, for example, on the order of nanoseconds. In the meantime, most of the energy is spent on melting around the irradiated part, and the inconvenience such as the formed hole and the peripheral part of the recess deform and rise.

  On the other hand, the temperature of the irradiated part is adjusted by irradiating the member with a short pulse width laser beam having a pulse width smaller than that of the conventionally used nanosecond order pulse laser light and a pulse width of picosecond order. A processing method has been proposed in which desired holes and recesses are formed by raising the boiling point or more and removing it by evaporation or evaporation.

Although processing with this short pulse width laser suppressed the generation of molten dust, the vaporized dust removed from the irradiated area was cooled in the atmosphere or diffused by colliding with gas molecules in the atmosphere. As a result of this, a new problem has arisen in that it liquefies or solidifies and reattaches to the periphery.
On the other hand, a laser processing apparatus having a configuration in which pulsed laser light irradiation is performed while blowing a gas for evaporation on an irradiated portion of a target member, and a laser processing apparatus having a configuration in which pulsed laser light irradiation is performed in a vacuum have been proposed ( For example, see Patent Document 1).
Japanese Patent Laid-Open No. 2001-207267

However, it may not always be possible to sufficiently reduce the reattachment of dust generated around the irradiated portion only by reducing the atmospheric pressure for performing laser processing with pulsed laser light.
That is, by reducing the tendency of the generated vaporized dust to stay in the vicinity of the irradiated part due to the decrease in the atmospheric pressure, the generated gas dust can be separated from the vicinity of the irradiated part. It does not necessarily move away from the surface, and vaporized dust moves to the vicinity of the surface of the member other than the irradiated portion and is cooled, thereby causing problems such as reattachment to the surface of the member.

  The occurrence of reattachment of vaporized dust not only affects the reliability of processing, but particularly when reattachment occurs at a position away from the irradiated portion of laser light, re-lasing is not possible. Since complicated work is also required for confirmation and identification of the reattachment position that has become necessary, the mass productivity of the semiconductor device and the video device described above also decreases, which is a serious problem.

  The present invention is intended to solve the above-described problems in a laser processing method in which a member surface is irradiated with pulsed laser light to remove an irradiated portion and the member surface is processed into a predetermined shape.

  A laser processing method according to the present invention is a laser processing method for processing a surface of a member into a predetermined shape by irradiating the surface of the member with a pulse laser beam and removing an irradiated portion on the surface of the member. The pulse width of the laser beam is selected to be 10 picoseconds or less.

Moreover, the present invention is characterized in that, in the laser processing method, the energy density given to the member by irradiation with the pulse laser beam is 0.1 J / cm ² or less per pulse.
Moreover, the present invention is characterized in that, in the laser processing method, the atmospheric pressure of the member irradiated with the pulse laser beam is selected to be 1000 Pa or less.
Further, the present invention is characterized in that, in the laser processing method, the atmosphere of at least the irradiated portion of the member irradiated with the pulsed laser light is reduced by local exhaust. In the laser processing method, the member includes a first material layer and a second material layer that can be removed by irradiation with pulsed laser light having a smaller energy density than the first material layer. Only the second material layer is removed by irradiation with the pulsed laser light.
Moreover, the present invention is characterized in that in the laser processing method, the second material layer constitutes a wiring member.
In the laser processing method according to the present invention, the second material layer includes any one of a single metal, an alloy containing the single metal, and a multilayer film containing the single metal. It is characterized by.
In the laser processing method according to the present invention, the second material layer includes at least one of aluminum (Al), molybdenum (Mo), and titanium (Ti).

  According to the laser processing method of the present invention, the pulse width of the pulsed laser beam is selected to be 10 picoseconds or less in the laser processing for irradiating the member surface with the pulsed laser beam and removing the irradiated portion on the member surface. In addition, even for a conventional member that has been difficult to be finely processed by, for example, nanosecond order pulse laser light, fine processing by laser processing is possible, and the rise of the peripheral edge of the processed portion can be reduced. Therefore, high-precision fine processing is possible.

Further, according to the present invention, since the density of energy given to the member by pulse laser light irradiation is set to 0.1 J / cm ² or less per pulse, it can be simply separated from the irradiated portion after generation of vaporized dust. However, as will be described later, it is possible to perform pulsed laser irradiation that can suppress the reattachment of vaporized dust, and the reattachment of dust is suppressed.

  Further, according to the present invention, in the laser processing method, since the atmospheric pressure of the member irradiated with the pulsed laser light is selected to be 1000 Pa or less, the reattachment of vaporized dust can be further suppressed. According to the present invention, it is possible to bring about important and many effects, such as mass production of finally obtained semiconductor devices and video devices.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings. However, the present invention is not limited to these embodiments.

1A and 1B are a schematic configuration diagram showing a configuration of an example of a laser processing apparatus suitable for carrying out the laser processing method according to the present invention, and a schematic bottom surface of a local exhaust device that constitutes the laser processing apparatus, respectively. FIG.
In this embodiment, the laser processing apparatus 1 includes at least a pulse laser light source 2, a local exhaust device 3, and a support base 4. At least the local exhaust device 3 and the support base 4 are disposed, for example, in a common chamber (not shown).

  In this embodiment, as shown in FIG. 1A, the local exhaust device 3 has, for example, a transmission hole 39 for the laser beam L at the center thereof, and around the center thereof, compressed nitrogen is supported around the support base 4. Compressed gas supply means 31 that statically levitates the local exhaust device 3 by injecting it toward the air, exhaust means 32 that exhausts the compressed gas injected toward the support base 4 from the ring-shaped suction groove 36 together with outside air, A purge gas supply means 33 for supplying a purge gas to a local exhaust part 37 close to a part to be irradiated with pulsed laser light, which will be described later, a local exhaust means 34 for exhausting in order to stably maintain the reduced pressure state of the local exhaust part 37, It has a compressed gas supply path from the compressed gas supply means 31, a ring-shaped compressed gas supply path 31a constituting a ventilation hole, and a porous ventilation means 35 disposed in the opening thereof.

A transparent window 38 that is hermetically sealed and transmits the laser light L is disposed at a required depth position in the transmission hole 39 that forms the optical path of the laser light L of the local exhaust device 3.
With this configuration, the local exhaust part 37 is formed in the space part between the transparent window 38 and the arrangement part of the member 7 in the region surrounded by the suction groove 36.

  A member 7 having first and second material layers 5 and 6 is disposed on the upper surface of the support 4 so as to face the local exhaust device 3. In this embodiment, the first material layer 5 of the member 7 is a TFT substrate, and the second material layer 6 is removed by irradiation with pulsed laser light having a smaller energy density than the first material layer 5. This is a patterned wiring member in which correction processing is performed on the short-circuit portion 6a of the incomplete pattern of the wiring member.

Examples of the material for forming the first material layer 5 include glass made of SiO ₂ . On the other hand, the material forming the second material layer 6 preferably includes at least one of metals such as aluminum (Al), molybdenum (Mo), and titanium (Ti). In addition to the single metal described above, an alloy or a multilayer film containing at least one of these metals can be used.

  In this embodiment, first, the member 7 to be irradiated with the short pulse width laser light L is placed on the support 4 and then moved below the local exhaust device 3. At this time, the compressed gas supply means 31 injects, for example, 0.2 MPa of compressed nitrogen through the compressed gas supply path 31a and the porous ventilation means 35, and starts the exhaust from the exhaust means 32, and the local exhaust device. It is preferable to avoid the collision with the moving member 7 by sufficiently stably raising the pressure 3 and to set the atmosphere of the arrangement portion of the member 7 to 1000 Pa or less as will be described later.

Next, while introducing 50 ccm of argon gas from the purge gas supply means 33, the atmosphere at a predetermined position of the member 7 to be irradiated in the laser light L irradiation finally performed by the local exhaust means 34, that is, the local exhaust part 37 is set. While sufficiently reducing the pressure, the rigidity between the local exhaust device 3 and the member 7 is ensured.
In this embodiment, the atmosphere at a predetermined position of the member 7, that is, the local exhaust part 37 has a height from the transparent window 38 in the local exhaust device 3 to the member 7 placed on the support base 4, and It is considered that a substantially cylindrical space is formed inside the concentric ring formed by the suction groove 36.

  Here, the rigidity is an adsorption force between the local exhaust device 3 and the member 5 constituting the member 7, for example, and if the rigidity is not sufficient, the height of the local exhaust device 3 relative to the substrate 5, that is, a gap. However, it is desirable to ensure this rigidity sufficiently, because problems such as insufficient stability of the engine or insufficient mechanical or mechanical stability of the local exhaust device 3 occur.

  Next, while observing the laser irradiation part through the transparent window 38 of the local exhaust device 3, the support base 4 is moved so that the short-circuit part 6 a formed on the member 7 is finally irradiated with the short pulse width laser light L. It moves to a desired position so that it may become the part 6b. Thereafter, a short pulse width laser beam L is emitted from the pulsed laser light source 2 while continuing local pumping of the local pumping unit 37 by the local pumping unit 34. The short pulse laser light L is selected by the mirror 21, is condensed by the lens 22, and is irradiated to the short-circuit portion 6 a through the transparent window 38 of the local exhaust device 3.

FIG. 1C is a schematic diagram showing a state of an example of a member whose surface shape has been processed by the laser processing method according to the present invention.
As shown in FIG. 1C, the short-circuit portion 6 a on the member 7 can be removed by the short pulse laser light emitted from the pulse laser light source 2.

  In the case of pulsed laser light, energy is concentrated in a shorter time as the pulse width is smaller, so the maximum value of energy per pulse is improved. When irradiating with laser light with a smaller pulse width, Thus, it is possible to perform processing in a short time even with an energy density smaller than that of the conventional case. Further, according to this processing method, since the laser irradiation time per pulse is short, the laser light irradiation time per pulse is shortened, so that the heat generated in the irradiated portion by the laser light is transferred to the peripheral portion. Is also suppressed.

Therefore, the pulse width of the short pulse width laser light L can avoid generation of heat in the material in at least one of the first and second material layers 5 and 6 constituting the member 7 in 10 picoseconds or less. Therefore, it is preferable to select 10 picoseconds or less.
In addition, when the predetermined position of only the second material layer 6 is selectively removed without removing the first material layer 5, the wear of the pulse laser light source 2, the mirror 21, the lens 22, and the like, that is, the shortening of the service life is achieved. For example, when it is necessary to suppress the maximum value of energy per pulse, the pulse width L of the laser light L is selected to be, for example, 2 picoseconds or more without extremely reducing the pulse width L. It is preferable to do.

  When laser processing is performed on the member 7 by the laser processing apparatus described above, the purge gas can be supplied from the purge gas supply means 33 during irradiation as well as before irradiation with the short pulse laser beam. In laser processing by a processing method, it is not always necessary to supply a purge gas during irradiation with a short pulse laser beam.

  That is, conventionally, the surface of the transparent window 38 on the side of the local exhaust part 37 is likely to be contaminated due to adhesion of vaporized dust generated during laser irradiation. In order to reduce the labor required for maintenance, when the vaporized dust is generated when the laser beam is irradiated, purge gas is supplied toward the transparent window 38, for example, as indicated by an arrow in FIG. In the case of the laser processing method according to the present invention, the surface of the transparent window 38 is not affected by the supply of the purge gas during irradiation. Since it was confirmed that vaporized dust does not easily adhere to the surface, it is possible to perform maintenance without supplying purge gas during laser beam irradiation. That reduction of labor and burden can be reduced.

2A and 2B are enlarged cross-sectional views of a member to be processed for explaining a laser processing method according to the present invention, respectively.
According to the laser processing method of the present invention, for example, power setting is performed by adjusting an attenuator (not shown) connected to the pulse laser light source 2 for a short pulse width laser beam having a wavelength of 390 nm and a pulse width of 3 picoseconds. The recess can be formed by performing selective removal by irradiating the short-circuit portion 6a a plurality of times.

The attenuator is configured such that, for example, a polarizing plate (not shown) is provided on the optical path of the pulse laser light L, the pulse laser light L is, for example, linearly polarized light, and the angle of the polarizing plate with respect to the polarization direction of the pulse laser light L is adjusted. Thus, the amount of light incident on the polarizing plate can be transmitted through the polarizing plate, and the power of the pulse laser beam L is set.
In the laser processing method according to the present invention, the wavelength and other conditions can be appropriately selected without being limited to the power setting. The processing size of the processing portion 6c indicated by X in FIG. 2B is also 20 μm ^{2 in} this embodiment, but is not limited to this.

While the embodiment of the present invention has been described above, the laser processing method according to the present invention is not limited to this embodiment.
For example, in this embodiment, the case where only the second material layer 6 of the member 7 composed of the first and second material layers 5 and 6 is partially removed has been described as an example. The laser processing method according to the present invention is not limited to this, and can be applied to the case where the member 7 is a single layer or three or more layers. Various changes and modifications can be made, such as removal of the holes to form holes.

Next, examples of the present invention will be described.
Using the laser processing apparatus 1 shown in FIG. 1, a short-circuit portion 6 a of a member 7 having a first material layer 5 made of a glass TFT substrate and a second material layer 6 made of aluminum having a thickness of about 500 μm. Laser processing was performed by irradiating with a short pulse width laser beam having a processing size of 20 μm ² and a pulse width of 3 picoseconds. In this embodiment, the local exhaust part 37 has a height from the transparent window 38 in the local exhaust apparatus 3 to the member 7 placed on the support base 4, and a concentric ring formed by the suction groove 36. It is a substantially cylindrical space having a radius of about 2 mm, which is formed on the inside.

First, the results of studying the relationship between the laser energy density and the number of dusts around the processed part will be described.
FIG. 3A shows an optical micrograph of the surface of a member subjected to laser processing at an atmospheric pressure of 1000 Pa and a laser energy density of 0.63 J / cm ² .
It can be confirmed that a large amount of dust is scattered around the processed portion. As a result of observation with an optical microscope, the number of dusts was 97.

FIG. 3B shows an optical micrograph of the surface of a member subjected to laser processing at an atmospheric pressure of 1000 Pa and a laser energy density of 0.10 J / cm ² .
It can be confirmed that the amount of dust around the processed portion is greatly reduced. As a result of observation with an optical microscope, the number of dusts was 46.

FIG. 3C shows an optical micrograph of the surface of a member subjected to laser processing at an atmospheric pressure of 1000 Pa and a laser energy density of 0.07 J / cm ² .
Although it was confirmed that the amount of dust around the processed part was further reduced as compared with the laser energy density of 0.10 J / cm ² , the number of dusts was 29 as a result of observation with an optical microscope. there were.

FIG. 4 is a schematic diagram showing a measurement result by the above-described optical microscope. In this measurement result, compared with the dust decreasing from a laser energy density of 0.63J / cm ² over the laser energy density 0.10J / cm ^2, the laser energy density 0.07J from the laser energy density 0.10J / cm ² Since it can be confirmed that the tendency of dust reduction toward / cm ² is moderate, reattachment of vaporized dust around the processed part by selecting the laser energy density to be 0.1 J / cm ² or less per pulse. Is considered to be significantly suppressed.

Next, the result of studying the relationship between the atmospheric pressure in the local exhaust part and the number of dusts around the processed part will be described.
FIG. 5A shows an optical micrograph of the surface of a member subjected to laser processing with the atmospheric pressure equal to atmospheric pressure and laser energy of 0.07 J / cm ² . It can be confirmed that a large amount of dust is scattered and reattached around the processed part.

FIG. 5B shows an optical micrograph of the surface of a member subjected to laser processing with an atmospheric pressure of 2700 Pa and laser energy of 0.07 J / cm ² . Although the amount is considerably reduced around the processed part, it can be confirmed that a lot of dust is reattached and remains.

FIG. 5C shows an optical micrograph of the surface of a member subjected to laser processing with an atmospheric pressure of 1000 Pa and laser energy of 0.07 J / cm ² . It can be confirmed that almost no dust is observed around the processed portion, and reattachment is greatly suppressed.

The result of examining the atmospheric pressure in more detail will be described.
6A and 6B are electron micrographs of members processed at an atmospheric pressure of 1000 Pa and 100 Pa, respectively, by the laser processing method according to the present invention.
When the atmospheric pressure was made lower than 1000 Pa, for example, even if the pressure was lowered to 100 Pa, there was no significant difference in dust reattachment.

  From the above examination results, it is considered that the reattachment of vaporized dust around the processed portion is significantly suppressed by selecting the atmospheric pressure to be 1000 Pa or less.

FIG. 7 is a schematic view showing the measurement result of the height of the peripheral edge of the processed part by the energy per pulse of the short pulse width laser light in the laser processing method according to the present invention.
In the processing with a short pulse width laser beam according to the present invention, it is possible to suppress the rising of the peripheral edge of the processed portion, which has occurred as much as 500 nm in the conventional pulse laser of the nanosecond order, and in particular, the laser energy density is set to 0. 0 per pulse. When it is selected to be 1 J / cm ² or less, the rising height can be suppressed to about 20 nm.

1A to 1C are each a schematic configuration diagram showing a configuration of an example of a laser processing apparatus suitable for carrying out a laser processing method according to the present invention, and a schematic plan view of a local exhaust device constituting the laser processing apparatus. It is a schematic diagram which shows the state of the member which processed the surface shape with the laser processing method by this invention. 2A and 2B are enlarged cross-sectional views of a member to be processed for explaining a laser processing method according to the present invention, respectively. 3A to 3C are optical micrographs for each energy per pulse of the short pulse width laser light of the member processed by the laser processing method according to the present invention. It is a schematic diagram which shows the measurement result of the number of dust by the energy per pulse of the short pulse width laser beam in the laser processing method by this invention. 5A to 5C are optical micrographs of members processed by the laser processing method according to the present invention for each processing atmosphere pressure. 6A and 6B are electron micrographs of members processed by the laser processing method according to the present invention for each processing atmosphere pressure. It is a schematic diagram which shows the measurement result of the rising height of the process part periphery by the energy per pulse of the short pulse width laser beam in the laser processing method by this invention.

Explanation of symbols

  DESCRIPTION OF SYMBOLS 1 ... Laser processing apparatus, 2 ... Pulse laser light source, 3 ... Local exhaust apparatus, 4 ... Support stand, 5 ... 1st material layer, 6 ... 2nd material layer , 6a ... short-circuit portion, 6b ... irradiated portion, 6c ... processed portion, 7 ... member, 21 ... mirror, 22 ... lens, 31 ... compressed gas supply means, 31a ... compressed gas supply path, 32 ... exhaust means, 33 ... purge gas supply means, 34 ... local exhaust means, 35 ... porous ventilation means, 36 ... suction groove, 37 ..Local exhaust section, 38 ... transparent window, 39 ... transmission hole

Claims (8)

A laser processing method for processing the surface of the member into a predetermined shape by irradiating the surface of the member with a pulse laser beam and removing the irradiated portion on the surface of the member,
A laser processing method, wherein the pulse width of the pulse laser beam is selected to be 10 picoseconds or less. ^2. The laser processing method according to claim 1, wherein a density of energy given to the member by irradiation with the pulse laser beam is set to 0.1 J / cm ² or less per pulse.   The laser processing method according to claim 1, wherein an atmospheric pressure of the member irradiated with the pulsed laser light is selected to be 1000 Pa or less.   2. The laser processing method according to claim 1, wherein at least an atmosphere of an irradiated portion of the member irradiated with the pulsed laser light is decompressed by local exhaust. The member includes a first material layer, and a second material layer that is removed by irradiation with pulsed laser light having a lower energy density than the first material layer,
2. The laser processing method according to claim 1, wherein only the second material layer is removed by irradiation with the pulsed laser light.   The laser processing method according to claim 5, wherein the second material layer constitutes a wiring member.   6. The laser processing according to claim 5, wherein the second material layer has any one of a single metal, an alloy containing the single metal, and a multilayer film containing the single metal. Method.   The laser processing method according to claim 5, wherein the second material layer includes at least one of aluminum (Al), molybdenum (Mo), and titanium (Ti).