The present invention relates to a laser processing method used for cutting an object to be processed such as semiconductor material substrate, piezoelectric material substrate, or glass substrate.
An example of literatures disclosing a conventional technique of this kind is International Publication Pamphlet No. 02/22301. The specification of this literature discloses a technique of irradiating an object to be processed with laser light, so as to form a modified region within the object along a line along which the object is intended to be cut, and cutting the object from the modified region acting as a start point.
Since the technique disclosed in the above-mentioned literature is a quite effective technique which can accurately cut the object along a line along which the object is intended to be cut, there has been a demand for a technique which can cut the object from the modified region more accurately.
In view of such circumstances, it is an object of the present invention to provide a laser processing method which can accurately cut the object from the line along which the object is intended to be cut.
In order to achieve the above-mentioned object, in one aspect, the present invention provides a laser processing method comprising a first step of irradiating a wafer-like object to be processed with laser light while locating a light-converging point within the object, so as to form a modified region due to multiphoton absorption within the object, and causing the modified region to form a cutting start region inside of a laser light entrance surface of the object by a predetermined distance along a line along which the object is intended to be cut in the object; and a second step of irradiating the modified region with laser light transmittable through an unmodified region of the object and more absorbable by the modified region than by the unmodified region after the first step, so as to generate a stress at a portion where the object is cut along the line along which the object is intended to be cut.
This laser processing method forms a modified region within an object to be processed by irradiating the object with laser light while locating a light-converging point within the object and utilizing a phenomenon of multiphoton absorption in the first step. When a start point exists at a portion where the object is to be cut, the object can be cleaved with a relatively small force, so as to be cut. This laser processing method irradiates the object with laser light transmittable through an unmodified region of the object and more absorbable by the modified region than by the unmodified region along a line along which the object is intended to be cut in the second step, so that the object is heated along the modified region, whereby a stress such as thermal stress due to a temperature difference occurs. This stress grows a crack in the thickness direction of the object from the modified region acting as a start point, thereby making it possible to cleave and cut the object. Thus, the object can be cut by a relatively small force such as a stress typified by a thermal stress due to a temperature difference, whereby the object can be cut with a high accuracy without generating unnecessary fractures deviating from the line along which the object is intended to be cut on a surface of the object.
This laser processing method forms the modified region by locally generating multiphoton absorption within the object in the first step. In the second step, laser light transmittable through the unmodified region is emitted. Therefore, the laser light is hardly absorbed at the surface of the object, so that the surface of the object is hardly molten in both steps. The unmodified region refers to a region not formed with a modified region after the first step. The light-converging point refers to a portion where the laser light is converged. The line along which the object is intended to be cut may be a line actually drawn on the surface of the object or therewithin, or a virtual line.
In another aspect, the present invention provides a laser processing method comprising a first step of irradiating a wafer-like object to be processed with laser light while locating a light-converging point within the object under a condition with a peak power density of at least 1×108 (W/cm2) at the light-converging point and a pulse width of 1 μs or less, so as to form a modified region including a crack region within the object, and causing the modified region to form a cutting start region inside of a laser light entrance surface of the object by a predetermined distance along a line along which the object is intended to be cut in the object; and a second step of irradiating the modified region with laser light transmittable through an unmodified region of the object and more absorbable by the modified region than by the unmodified region after the first step, so as to generate a stress at a portion where the object is cut along the line along which the object is intended to be cut.
This laser processing method irradiates the object with laser light while locating a light-converging point within the object under a condition with a peak power density of at least 1×108 (W/cm2) at the light-converging point and a pulse width of 1 μs or less in the first step. Consequently, a phenomenon of optical damage due to multiphoton absorption occurs within the object. This optical damage induces a thermal distortion within the object, thereby forming a crack region therewithin. Since this crack region is an example of the above-mentioned modified region while the second step is equivalent to that mentioned above, this laser processing method enables laser processing without melting the surface of the object or generating unnecessary fractures thereon deviating from the line along which the object is intended to be cut. An example of the object to be processed in this laser processing method is a member including glass. The peak power density refers to the electric field intensity at the light-converging point of pulsed laser light.
In still another aspect, the present invention provides a laser processing method comprising a first step of irradiating a wafer-like object to be processed with laser light while locating a light-converging point within the object under a condition with a peak power density of at least 1×108 (W/cm2) at the light-converging point and a pulse width of 1 μs or less, so as to form a modified region including a molten processed region within the object, and causing the modified region to form a cutting start region inside of a laser light entrance surface of the object by a predetermined distance along a line along which the object is intended to be cut in the object; and a second step of irradiating the modified region with laser light transmittable through an unmodified region of the object and more absorbable by the modified region than by the unmodified region after the first step, so as to generate a stress at a portion where the object is cut along the line along which the object is intended to be cut.
This laser processing method irradiates the object with laser light while locating a light-converging point within the object under a condition with a peak power density of at least 1×108 (W/cm2) at the light-converging point and a pulse width of 1 μs or less in the first step. Consequently, the inside of the object is locally heated by multiphoton absorption. The heating forms a molten processed region within the object. Since this molten processed region is an example of the above-mentioned modified region while the second step is equivalent to that mentioned above, this laser processing method enables laser processing without melting the surface of the object or generating unnecessary fractures thereon deviating from the line along which the object is intended to be cut. An example of the object to be processed in this laser processing method is a member including a semiconductor material.
In still another aspect, the present invention provides a laser processing method comprising a first step of irradiating a wafer-like object to be processed with laser light while locating a light-converging point within the object under a condition with a peak power density of at least 1×108 (W/cm2) at the light-converging point and a pulse width of 1 ns or less, so as to form a modified region including a refractive index change region as a region with a changed refractive index within the object, and causing the modified region to form a cutting start region inside of a laser light entrance surface of the object by a predetermined distance along a line along which the object is intended to be cut in the object; and a second step of irradiating the modified region with laser light transmittable through an unmodified region of the object and more absorbable by the modified region than by the unmodified region after the first step, so as to generate a stress at a portion where the object is cut along the line along which the object is intended to be cut.
This laser processing method irradiates the object with laser light while locating a light-converging point within the object under a condition with a peak power density 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 thus generated within the object with a very short pulse width, the energy due to the multiphoton absorption is not converted into thermal energy, whereas an eternal structural change such as ionic valence change, crystallization, or polarization orientation is induced within the object, whereby a refractive index change region is formed. Since the refractive index change region is an example of the above-mentioned modified region while the second step is equivalent to that mentioned above, this laser processing method enables laser processing without melting the surface of the object or generating unnecessary fractures thereon deviating from the line along which the object is intended to be cut. An example of the object to be processed in this laser processing method is a member including glass.
Preferably, the second step performs the same laser light irradiation as with the first step while locating a light-converging point at the modified region. Even when the second step performs the same laser light irradiation as with the first step, the laser light absorption due to scattering by the modified region, changes in physical properties of the modified region, etc. or the occurrence of multiphoton absorption in the modified region can heat the object along the modified region without melting the front face of the object, thereby generating a stress such as thermal stress due to a temperature difference.
In still another aspect, the present invention provides a laser processing method comprising the steps of irradiating a wafer-like object to be processed secured to a surface of an expandable holding member with laser light while locating a light-converging point within the object, so as to form a modified region within the object, and causing the modified region to form a cutting start region inside of a laser light entrance surface of the object by a predetermined distance along a line along which the object is intended to be cut in the object; irradiating the modified region with laser light transmittable through an unmodified region of the object after the step of forming the cutting start region, so as to cut the object along the line along which the object is intended to be cut; and expanding the holding member after the step of cutting the object, so as to separate cut portions of the object from each other.
In this laser processing method, the modified region formed by multiphoton absorption can form a cutting start region within the object along a desirable line along which the object is intended to be cut the object. Then, irradiating the object with laser light transmittable through the unmodified region (the part of the object other than the modified region) along the line along which the object is intended to be cut can generate fractures from the cutting start region acting as a start point, whereby the object can be cut accurately along the line along which the object is intended to be cut. Expanding the holding member having the object secured thereto separates portions of the object from each other, whereby the reliability in cutting the object along the line along which the object is intended to be cut can further be improved.
In still another aspect, the present invention provides a laser processing method comprising the steps of irradiating a wafer-like object to be processed secured to a surface of an expandable holding member with laser light while locating a light-converging point within the object, so as to form a modified region within the object, and causing the modified region to form a cutting start region inside of a laser light entrance surface of the object by a predetermined distance along a line along which the object is intended to be cut in the object; irradiating the modified region with laser light transmittable through an unmodified region of the object after the step of forming the cutting start region; and expanding the holding member after the step of irradiating the object, so as to cut the object and separate cut portions of the object from each other.
This laser processing method can form a cutting start region within the object along a line along which the object is intended to be cut as with the laser processing methods mentioned above. Then, irradiating the object with laser light transmittable through the unmodified region along a line along which the object is intended to be cut allows fractures started from the cutting start region to reach the front and rear faces of the object with a smaller force than that in the case without such irradiation. Therefore, the holding member having the object secured thereto can be expanded with a smaller force, so that the object can be cut accurately. Expanding the holding member separates portions of the object from each other, so that the reliability in cutting the object along the line along which the object is intended to be cut can further be improved.
The cutting start region refers to a region to become a start point for cutting when cutting the object. Therefore, the cutting start region is a part to cut where cutting is to be done in the object. The cutting start region may be made by a modified region formed continuously or modified regions formed intermittently. The object may be formed from a semiconductor material, in which the modified region is a molten processed region.
In the following, a preferred embodiment of the present invention will be explained in detail with reference to the drawings. The laser processing method in accordance with this embodiment forms a modified region by utilizing multiphoton absorption. The multiphoton absorption is a phenomenon occurring when the intensity of laser light is very high. Therefore, the multiphoton absorption will be explained first in brief.
A material becomes transparent when its absorption bandgap EG is greater than photon energy hν. Hence, a condition under which absorption occurs in the material is hν>EG. However, even when optically transparent, the material generates absorption under a condition of nhν>EG (where n=2, 3, 4, . . . ) if the intensity of laser light becomes very high. This phenomenon is known as multiphoton absorption. In the case of pulsed waves, the intensity of laser light is determined by the peak power density (W/cm2) of laser light at a light-converging point. The multiphoton absorption occurs under a condition where the peak power density is 1×108 (W/cm2) or greater, for example. The peak power density is determined by (energy of laser light at the light-converging point per pulse)/(beam spot cross-sectional area of laser light×pulse width). In the case of continuous waves, the intensity of laser light is determined by the field intensity (W/cm2) of laser light at the light-converging point.
The principle of the laser processing method in accordance with the embodiment using such multiphoton absorption will be explained with reference to
As shown in
The laser light L is relatively moved along the line 5 along which the object is intended to be cut (i.e., in the direction of arrow A), so as to shift the light-converging point P along the line 5 along which the object is intended to be cut. Consequently, as shown in
When a start point exists in a portion to cut at the time of cutting the object 1, the object 1 fractures from the start point, whereby the object 1 can be cut with a relatively small force as shown in
There seem to be the following two ways of cutting an object to be processed from the modified region acting as the start point. The first case is where an artificial force is applied to the object after forming the modified region, so that the object fractures from the modified region, whereby the object is cut. This is the cutting in the case where the object has a large thickness, for example. Applying an artificial force refers to exerting a bending stress or shear stress to the object along the cutting start region, or generating a thermal stress by applying a temperature difference to the object, for example. The other case is where the forming of the modified region causes the object to fracture naturally in its cross-sectional direction (thickness direction) from the modified region acting as a start point, thereby cutting the object. This becomes possible, for example, if one modified region is formed when the object 1 has a small thickness, or if a plurality of modified regions are formed in the thickness direction when the object has a large thickness. Even in this naturally fracturing case, fractures do not extend onto the front face at a portion corresponding to an area not formed with the modified region, so that only the portion corresponding to the area formed with the modified region can be cleaved, whereby cleavage can be controlled well. Such a cleaving method with a favorable controllability is quite effective, since the object such as silicon wafer has recently been apt to decrease its thickness.
The modified region formed by multiphoton absorption in this embodiment encompasses the following cases (1) to (3):
(1) Case where the Modified Region is a Crack Region Including One Crack or a Plurality of Cracks
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 to 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 Harmonics”, Proceedings of the 45th Laser Materials Processing Conference (December, 1998), pp. 23-28.
The inventors determined the relationship between field intensity and crack size by an experiment. The following are conditions of the experiment.
(A) Object to be processed: Pyrex (registered trademark) glass (with a thickness of 700 μm and an outer diameter of 4 inches)
(B) Laser
(C) Condenser lens
(D) Moving rate of the mounting table mounting the object: 100 mm/sec
The laser light quality of TEM00 means that the light-converging characteristic is so high that convergence to about the wavelength of laser light is possible.
A mechanism by which the objet to be processed is cut by forming a crack region will now be explained with reference to
(2) Case where the Modified Region is a Molten Processed Region
An object to be processed (e.g., semiconductor material such as silicon) 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 μs or less. As a consequence, the inside of the object is locally heated by multiphoton absorption. This heating forms a molten processed region within the object. The molten processed region encompasses regions once molten and then re-solidified, regions just in a molten state, and regions in the process of being re-solidified from the molten state, and can also be referred to as a region whose phase has changed or a region whose crystal structure has changed. The molten processed region may also be referred to as a region in which a certain structure has changed to another structure among monocrystal, amorphous, and polycrystal structures. For example, it means a region having changed from the monocrystal structure to the amorphous structure, a region having changed from the monocrystal structure to the polycrystal structure, or a region having changed from the monocrystal structure to a structure containing amorphous and polycrystal structures. When the object to be processed is of a silicon monocrystal structure, the molten processed region is an amorphous silicon structure, for example. 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.
By an experiment, the inventors verified that a molten processed region was formed within a silicon wafer. The following are conditions of the experiment.
(A) Object to be processed: silicon wafer (with a thickness of 350 μm and an outer diameter of 4 inches)
(B) Laser
(C) Condenser lens
(D) Moving rate of the mounting table mounting the object: 100 mm/sec
The fact that the molten processed region 13 is formed by multiphoton absorption will now be explained.
For example, at the Nd:YAG laser wavelength of 1064 nm, the laser light appears to be transmitted through the silicon substrate by at least 80% when the silicon substrate has a thickness of 500 μm or less. Since the silicon wafer 11 shown in
A fracture is generated in a silicon wafer from a cutting start region formed by a molten processed region, acting as a start point, toward a cross section, and reaches the front and rear faces of the silicon wafer, whereby the silicon wafer is cut. The fracture reaching the front and rear faces of the silicon wafer may grow naturally or as a force is applied to the object. The fracture naturally growing from the cutting start region to the front and rear faces of the wafer encompasses a case where the fracture grows from a state where the molten processed region forming the cutting start region is molten and a case where the fracture grows when the molten processed region forming the cutting start region is re-solidified from the molten state. In either case, the molten processed region is formed only within the wafer, and thus is present only within the cross section after cutting as shown in
(3) Case where the Modified Region is a Refractive Index Change Region
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.
In the above, cases (1) to (3) are explained as a modified region formed due to multiphoton absorption within the object, but when under the consideration of crystal structure and cleave of a wafer type object to be processed, cutting start region is formed as stated below, it is possible to cut a object to be processed with smaller power and higher accuracy by using the cutting start region as a start point of the object.
That is, in the case that the object to be processed is a substrate made of a single crystal semiconductor having a diamond structure such as a silicon, it is preferable to form a cutting start region in a direction along (1, 1, 1) (the first cleavage plane) or (1, 1, 0) plane (the second cleavage plane) of the object in the object. Further, in the case that the object to be processed is a substrate made of III-V group compound semiconductor having a blende type crystal structure such as a GaAs, it is preferable to form a cutting start region in a direction along (1, 1, 0) plane of the object in the object. More further, in the case that the object to be processed is a substrate having a hexagonal type crystal structure such as Safire (Al2O3), it is preferable to form a cutting start region in a direction along (1, 1, 2, 0) plane (A plane) or (1, 1, 0, 0) plane (M plane) of the object in the object when a main surface of the object is (0, 0, 0, 1) plane (C plane).
Besides, when an orientation flat is formed in the substrate along the above stated direction along which the above explained cutting start region should be formed in the object, for example a direction along (1, 1, 1) plane in the single crystal silicon substrate) or along a direction perpendicular to the direction along which the above explained cutting start region should be formed in the object, it is possible to form the cutting start region along the direction along which the cutting start region should be formed in the object in the object with easy and high accuracy by using the orientation flat as a reference.
The invention will be explained concretely, referring embodiments hereinbelow.
Example 1 of the present invention will now be explained. The laser processing method in accordance with Example 1 comprises a modified region forming step (first step) of forming a modified region due to multiphoton absorption within an object to be processed, and a stress step (second step) of generating a stress in a portion to cut the object. In Example 1, the modified region forming step and stress step perform the same laser light irradiation. Therefore, a laser processing apparatus which will be explained later emits laser light twice under the same condition in the modified region forming step and stress step.
The laser processing apparatus in accordance with Example 1 will now be explained.
The Z axis is orthogonal to the front face 3 of the object 1, and thus is the direction of focal depth of the laser light incident on the object 1. Therefore, the light-converging point P of the laser light L can be positioned within the object 1 by moving the Z-axis stage 113 along the Z axis. The movement of the light-converging point P along the X (Y) axis is performed by moving the object 1 along the X (Y) axis by the X (Y)-axis stage 109 (111).
The laser light source 101 is Nd:YAG laser generating pulsed laser light. Other examples of the laser employable in the laser light source 101 include Nd:YVO4 laser and Nd:YLF laser. The above-mentioned laser light sources are preferably used for forming a crack region or a molten processed region, whereas a titanium sapphire laser is preferably used for forming a refractive index change region. Though Example 1 uses pulsed laser light for processing the object 1, continuous wave laser light may also be used if it can cause multiphoton absorption.
The laser processing apparatus 100 further comprises an observation light source 117 for generating visible rays for illuminating the object 1 mounted on the mount table 107, and a visible ray beam splitter 119 disposed on the same optical axis as with the dichroic mirror 103 and condenser lens 105. The dichroic mirror 103 is disposed between the beam splitter 119 and condenser lens 105. The beam splitter 119 functions to reflect about a half of the visible rays and transmit the remaining half therethrough, and is disposed so as to change the orientation of the optical axis of visible rays by 90°. About a half of the visible rays generated from the observation light source 117 are reflected by the beam splitter 119. Thus reflected visible rays pass through the dichroic mirror 103 and condenser lens 105, thereby illuminating the front face 3 of the object 1 including the line 5 along which the object is intended to be cut and the like.
The laser processing apparatus 100 further comprises an image pickup device 121 and an imaging lens 123 which are disposed on the same optical axis as with the beam splitter 119, dichroic mirror 103, and condenser lens 105. An example of the image pickup device 121 is a CCD (charge-coupled device) camera. The reflected light of visible rays having illuminated the front face 3 including the line 5 along which the object is intended to be cut and the like passes through the condenser lens 105, dichroic mirror 103, and beam splitter 119, so as to be focused by the imaging lens 123 and captured by the image pickup device 121, thus yielding imaging data.
The laser processing apparatus 100 further comprises an imaging data processor 125 for inputting the imaging data outputted from the image pickup device 121, an overall controller 127 for controlling the laser processing apparatus 100 as a whole, and a monitor 129. Based on the imaging data, the imaging data processor 125 calculates focal data for positioning the focal point of visible rays generated by the observation light source 117 onto the front face 3. According to the focal data, the stage controller 115 regulates the movement of the Z-axis stage 113, so as to position the focal point of visible rays at the front face 3. Thus, the imaging data processor 125 functions as an autofocus unit. The focal point of visible light coincides with the light-converging point of laser light L. On the basis of imaging data, the imaging data processor 125 calculates image data such as enlarged images of the front face 3. The image data are sent to the overall controller 127, so as to be subjected to various processing operations, and thus processed data are transmitted to the monitor 129. As a consequence, enlarged images and the like are displayed on the monitor 129.
The data from the stage controller 115, the image data from the imaging data processor 125, etc. are fed into the overall controller 127, whereas the laser light source controller 102, observation light source 117, and stage controller 115 are regulated according to these data as well, whereby the laser processing apparatus 100 as a whole is controlled. Hence, the overall controller 127 functions as a computer unit.
With reference to
First, the light absorption characteristic of the object 1 is measured by a spectrophotometer or the like which is not depicted. According to the result of measurement, a laser light source 101 which generates laser light L having a wavelength to which the object 1 is transparent or less absorptive is chosen (S101). Subsequently, the thickness of the object 1 is measured. According to the result of measurement of thickness and the refractive index of the object 1, the amount of movement of the object 1 along the Z axis in the laser processing apparatus 100 is determined (S103). This is an amount of movement of the object 1 along the Z axis with reference to the light-converging point P of laser light L positioned at the front face 3 of the object 1 for locating the light-converging point P of laser light L within the object 1. This amount of movement is fed into the overall controller 127 in the laser processing apparatus 100 used in the modified region forming step.
The object 1 is mounted on the mount table 107 of the laser processing apparatus 100. Then, visible rays are generated from the observation light source 117, so as to illuminate the object 1 (S105). The front face 3 of the object 1 including the illuminated line 5 along which the object is intended to be cut is captured by the image pickup device 121. The imaging data captured by the image pickup device 121 is sent to the imaging data processor 125. According to the imaging data, the imaging data processor 125 calculates such focal data as to position the focal point of visible rays from the observation light source 117 onto the front face 3 (S107).
The focal data is sent to the stage controller 115. According to the focal data, the stage controller 115 moves the Z-axis stage 113 along the Z axis (S109). As a consequence, the focal point of the visible rays from the observation light source 117 is positioned at the front face 3. According to the imaging data, the imaging data processor 125 calculates enlarged image data of the front face 3 of the object 1 including the line 5 along which the object is intended to be cut. The enlarged image data is sent to the monitor 129 by way of the total controller 127, whereby an enlarged image of the line 5 along which the object is intended to be cut and its vicinity is displayed on the monitor 129.
The movement amount data determined by step S103 has been fed into the total controller 127 beforehand, and is sent to the stage controller 115. According to the movement amount data, the stage controller 115 causes the Z-axis stage 113 to move the object 1 along the Z axis to such a position that the light-converging point P of laser light L is located within the object 1 (S111).
Subsequently, laser light L is generated from the laser light source 101, so as to illuminate the line 5 along which the object is intended to be cut in the front face 3 of the object 1.
After the modified region is formed, the crack region 9 is irradiated with the laser light L along the line 5 along which the object is intended to be cut in the front face 3 of the object 1 again under the same condition (i.e., while the light-converging point P is located at the crack region 9 that is a modified region). As a consequence, the absorption of laser light L due to scattering and the like by the crack region 9 or the occurrence of multiphoton absorption in the crack region heats the object 1 along the crack region 9, thereby causing a stress such as thermal stress due to a temperature difference (S114).
Though the stress step performs the same laser light irradiation as with the modified region in Example 1, it will be sufficient if laser light transmittable through the unmodified region that is the region not formed with the crack region in the object and more absorbable by the crack region than by the unmodified region is emitted. This is because the laser light is hardly absorbed at the front face of the object in this case as well, so that the object is heated along the crack region, whereby a stress such as thermal stress due to a temperature difference occurs.
Though Example 1 relates to a case where a crack region is formed as a modified region, the same holds in cases where the above-mentioned molten processed region and refractive index change region are formed. That is, irradiation with absorbable laser light can cause a stress, so as to generate and grow cracks from the molten processed region or refractive index change region acting as a start point, thereby cutting the object to be processed.
Even when cracks grown from the modified region acting as a start point by the stress step fail to reach the front and rear faces of the object in the case where the object has a large thickness, etc., the object can be fractured and cut by applying an artificial force such as bending stress or shear stress thereto. This artificial force can be kept smaller, whereby unnecessary fractures deviating from the line to cut can be prevented from occurring in the front face of the object.
Effects of Example 1 will now be explained. In this case, the line 5 along which the object is intended to be cut is irradiated with pulsed laser light L while locating a light-converging point P within the object 1 under a condition generating multiphoton absorption in the modified region forming step. Then, the X-axis stage 109 and Y-axis stage 111 are moved, so as to shift the light-converging point P along the line 5 along which the object is intended to be cut. This forms a modified region (e.g., crack region, molten processed region, or refractive index change region) within the object 1 along the line 5 along which the object is intended to be cut. When a start point exists in a portion to cut the object, the object can be fractured and cut with a relatively small force. In Example 1, the stress step performs the same laser irradiation as with the modified region forming step, thereby causing a stress such as thermal stress due to a temperature difference. As a consequence, a relatively small force typified by a stress such as thermal stress due to a temperature difference can cut the object 1. This can cut the object 1 without generating unnecessary fractures deviating from the line 5 along which the object is intended to be cut in the front face 3 of the object 1.
In the modified region forming step in Example 1, since the object 1 is irradiated with pulsed laser light L while locating the light-converging point P within the object 1 under a condition generating multiphoton absorption in the object 1, the pulsed laser light L is transmitted through the object 1, whereby the pulsed laser light is hardly absorbed by the front face 3 of the object 1. The stress step performs the same laser light irradiation as with the modified region forming step. Therefore, the front face 3 does not incur damages such as melting because of irradiation with laser light.
As explained in the foregoing, Example 1 can cut the object 1 without generating unnecessary fractures deviating from the line 5 along which the object is intended to be cut in the front face 3 of the object 1 or melting the same. Therefore, when the object 1 is a semiconductor wafer, for example, semiconductor chips can be cut out from the semiconductor wafer without generating unnecessary fractures deviating from a line to cut in the semiconductor chips or melting the same. The same holds in objects to be processed having a front face formed with electronic devices such as objects to be processed having a front face formed with electrode patterns, piezoelectric device wafers, and glass substrates formed with display devices such as liquid crystals. Hence, Example 1 can improve the yield of products (e.g., semiconductor chips, piezoelectric device chips, and display devices such as liquid crystals) made by cutting objects to be processed.
In Example 1, since the line 5 along which the object is intended to be cut in the front face 3 of the object 1 does not melt, the width of the line 5 along which the object is intended to be cut (which is the gap between respective regions to become semiconductor chips in the case of a semiconductor wafer, for example) can be made smaller. This increases the number of products formed from a single sheet of object to be processed 1, and can improve the productivity of products.
Example 1 uses laser light for cutting and processing the object 1, and thus enables processing more complicated than that in dicing with diamond cutters. For example, cutting and processing is possible even when lines 5 along which the object is intended to be cut have complicated forms as shown in
Example 2 of the present invention will now be explained.
As shown in
A unit U thus constructed by the object 1, expandable film 19, and film securing frame 20 is mounted on the mount table 107 of the above-mentioned laser processing apparatus 100, for example, such that the front face 3 of the object 1 opposes the condenser lens 105. Then, a holder 107a secures the film securing frame 20 onto the mount table 107, while the expandable film 19 is attracted to the mount table 107 in a vacuum.
Subsequently, as shown in
Then, as shown in
Subsequently, as shown in
A main cause of such fractures 24 is that the object 1 is heated along the lines 5 along which the object is intended to be cut upon irradiation with the laser light L2, whereby a thermal stress occurs in the object 1. For example, upon irradiation with the laser light L2, a boundary between modified and unmodified regions yields continuous irregularities as shown in
After the object 1 is cut into a plurality of chips 25, the unit U is transferred to a film expander 200. As shown in
In the foregoing laser processing method in accordance with Example 2, the modified region 7 formed by multiphoton absorption can form the cutting start region 8 within the object 1 along the lines 5 along which the object is intended to be cut. Irradiating the object 1 with laser light L2 transmittable through the unmodified region of the object 1 (preferably more absorbable by the modified region 7 than by the unmodified region) along the lines 5 along which the object is intended to be cut can generate fractures 24 in the object 1 from the cutting start region 8 acting as a start point, whereby the object 1 can be cut accurately along the lines 5 along which the object is intended to be cut. Expanding the expandable film 19 having the object 1 secured thereto separates the chips 25 from each other, which can further improve the reliability in cutting the object 1 along the line 5 along which the object is intended to be cut.
Example 3 of the present invention will now be explained. Example 3 differs from Example 2 in that fractures 24 do not reach the front face 3 and rear face 21 of the object 1. In the following, the differences from Example 2 will mainly be explained.
As in Example 2, a unit U constituted by the object 1, an expandable film 19, and a film securing frame 20 is prepared, a modified region 7 is formed within the object 1 by using the above-mentioned laser processing apparatus 100, and a cutting start region 8 is formed by the modified region 7 inside of the front face 3 of the object 1 by a predetermined distance along lines 5 along which the object is intended to be cut. The object 1 is a silicon wafer having a thickness of 300 μm.
Subsequently, as shown in
Next, as in Example 2, the unit U is transferred to the film expander 200. In the film expander 200, the pressing member 203 is pressed against the rear face 19b of the expandable film 19, and is raised. This expands contact portions of the individual chips 25 in the expandable film 19 outward. As the expandable film 19 expands, leading ends of the fractures 24 within the object 1 reach the front face 3 and rear face 21 of the object 1, so that the object 1 is divided into a plurality of chips 25, whereby the chips 25 are separated from each other.
Depending on the irradiation condition of laser light L2, the fractures 24 may not occur upon irradiation with the laser light L2. Even in such a case, expanding the expandable film 19 can cut the object 1 along the lines 5 along which the object is intended to be cut more easily with a higher accuracy than in the case without irradiation with laser light L2.
The foregoing laser processing method in accordance with Example 3 can form the cutting start region 8 within the object 1 along the lines 5 along which the object is intended to be cut as with the above-mentioned laser processing method in accordance with Example 2. Then, irradiating the object 1 with laser light L2 transmittable through the unmodified region of the object 1 (preferably more absorbable by the modified region 7 than by the unmodified region) along the lines 5 along which the object is intended to be cut can cause the fractures 24 started from the cutting start region 8 to reach the front face 3 and rear face 21 of the object 1 with a force smaller than that in the case without such irradiation. Therefore, the expandable film 19 having the object 1 secured thereto can be expanded with a smaller force, and the object 1 can be cut accurately along the lines 5 along which the object is intended to be cut. Expanding the expandable film 19 separates the chips 25 from each other, whereby the reliability in cutting the object 1 along the lines 5 along which the object is intended to be cut can further be improved.
The present invention is not restricted to Examples 1 to 3 mentioned above.
The following are preferred examples of the material of the object 1 and species of laser light L2 transmittable through the unmodified region of the object 1 and more absorbable by the modified region 7 than by the unmodified region. Namely, when the object 1 is a silicon wafer or GaAs-based wafer, laser light having a wavelength of 900 nm to 1100 nm is preferably used as the laser light L2. A specific example is YAG laser (with a wavelength of 1064 nm).
The fractures 24 generated upon irradiation with the laser light L2 may reach one of the front face 3 and rear face 21 of the object 1. Such control is possible when the modified region 7 is formed at a position shifted from the center position in the thickness direction of the object 1 toward the front face 3 or rear face 21. In particular, when the fractures 24 are caused to reach the surface of the object 1 on the expandable film 19 side upon irradiation with the laser light L2, the accuracy in cleaving the object 1 by expanding the expandable film 19 can further be improved.
Here, “the modified region 7 is formed at a position shifted from the center position in the thickness direction of the object 1 toward the front face 3” means that the modified region 7 constituting the cutting start region 8 is formed so as to shift from the half thickness position of the object 1 in the thickness direction toward the front face 3. Namely, it refers to a case where the center position of the width of the modified region in the thickness direction of the object 1 is shifted from the center position of the object 1 in the thickness direction toward the front face 3, without being restricted to the case where the whole modified region 7 is shifted from the center position of the object 1 in the thickness direction toward the front face 3. The same holds in the case where the modified region 7 is formed so as to shift toward the rear face 21 of the object 1.
Though the above-mentioned light-converging point P2 of the laser light L2 is positioned within the modified region 7 of the object 1, it may be positioned in the vicinity of the modified region 7 as long as the modified region 7 is irradiated with the laser light L2.
As explained in the foregoing, the laser processing method in accordance with the present invention can cut the object to be processed accurately along lines along which the object is intended to be cut.
Filing Document | Filing Date | Country | Kind | 371c Date |
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PCT/JP03/02943 | 3/12/2003 | WO | 00 | 7/10/2006 |
Publishing Document | Publishing Date | Country | Kind |
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WO2004/080642 | 9/23/2004 | WO | A |
Number | Name | Date | Kind |
---|---|---|---|
3448510 | Johnson, Jr et al. | Jun 1969 | A |
3543979 | Grove et al. | Dec 1970 | A |
3610871 | Lumley | Oct 1971 | A |
3613974 | Chatelain et al. | Oct 1971 | A |
3626141 | Daly | Dec 1971 | A |
3629545 | Graham et al. | Dec 1971 | A |
3790051 | Moore | Feb 1974 | A |
3790744 | Bowen | Feb 1974 | A |
3824678 | Harris et al. | Jul 1974 | A |
3970819 | Gates et al. | Jul 1976 | A |
4092518 | Merard | May 1978 | A |
4242152 | Stone | Dec 1980 | A |
4306351 | Ohsaka et al. | Dec 1981 | A |
4336439 | Sasnett et al. | Jun 1982 | A |
4475027 | Pressley | Oct 1984 | A |
4531060 | Suwa et al. | Jul 1985 | A |
4546231 | Gresser et al. | Oct 1985 | A |
4562333 | Taub et al. | Dec 1985 | A |
4650619 | Watanabe | Mar 1987 | A |
4682003 | Minakawa et al. | Jul 1987 | A |
4734550 | Imamura et al. | Mar 1988 | A |
4769310 | Gugger et al. | Sep 1988 | A |
4814575 | Petitbon | Mar 1989 | A |
4899126 | Yamada | Feb 1990 | A |
4914815 | Takada et al. | Apr 1990 | A |
4981525 | Kiyama et al. | Jan 1991 | A |
5096449 | Matsuzaki | Mar 1992 | A |
5132505 | Zonneveld et al. | Jul 1992 | A |
5211805 | Srinivasan | May 1993 | A |
5230184 | Bkhman | Jul 1993 | A |
5251003 | Vigouroux et al. | Oct 1993 | A |
5254149 | Hashemi et al. | Oct 1993 | A |
5254833 | Okiyama | Oct 1993 | A |
5304357 | Sato et al. | Apr 1994 | A |
5376793 | Lesniak | Dec 1994 | A |
5382770 | Black et al. | Jan 1995 | A |
5534102 | Kadono et al. | Jul 1996 | A |
5543365 | Wills et al. | Aug 1996 | A |
5575936 | Goldfarb | Nov 1996 | A |
5580473 | Shinohara et al. | Dec 1996 | A |
5609284 | Kondratenko | Mar 1997 | A |
5622540 | Stevens | Apr 1997 | A |
5637244 | Erokhin | Jun 1997 | A |
5641416 | Chadha | Jun 1997 | A |
5656186 | Mourou et al. | Aug 1997 | A |
5767483 | Cameron et al. | Jun 1998 | A |
5776220 | Allaire et al. | Jul 1998 | A |
5786560 | Tatah et al. | Jul 1998 | A |
5795795 | Kousai et al. | Aug 1998 | A |
5814532 | Ichihara | Sep 1998 | A |
5826772 | Ariglio et al. | Oct 1998 | A |
5841543 | Guldi et al. | Nov 1998 | A |
5882956 | Umehara et al. | Mar 1999 | A |
5886319 | Preston et al. | Mar 1999 | A |
5900582 | Tomita et al. | May 1999 | A |
5925271 | Pollack et al. | Jul 1999 | A |
5968382 | Matsumoto et al. | Oct 1999 | A |
5976392 | Chen | Nov 1999 | A |
5998238 | Kosaki | Dec 1999 | A |
6031201 | Amako et al. | Feb 2000 | A |
6055829 | Witzmann et al. | May 2000 | A |
6057525 | Chang et al. | May 2000 | A |
6121118 | Jin et al. | Sep 2000 | A |
6127005 | Lehman et al. | Oct 2000 | A |
6156030 | Neev | Dec 2000 | A |
6172329 | Shoemaker et al. | Jan 2001 | B1 |
6175096 | Nielsen | Jan 2001 | B1 |
6181728 | Cordingley et al. | Jan 2001 | B1 |
6187088 | Okumura | Feb 2001 | B1 |
6211488 | Hoekstra et al. | Apr 2001 | B1 |
6229114 | Andrews et al. | May 2001 | B1 |
6252197 | Hoekstra et al. | Jun 2001 | B1 |
6257224 | Yoshino et al. | Jul 2001 | B1 |
6259058 | Hockstra | Jul 2001 | B1 |
6285002 | Ngoi et al. | Sep 2001 | B1 |
6294439 | Sasaki et al. | Sep 2001 | B1 |
6322958 | Hayashi | Nov 2001 | B1 |
6325855 | Silmon et al. | Dec 2001 | B1 |
6333486 | Troitski | Dec 2001 | B1 |
6344402 | Sekiya | Feb 2002 | B1 |
6376797 | Piwczyk et al. | Apr 2002 | B1 |
6402004 | Yoshikuni et al. | Jun 2002 | B1 |
6407363 | Dunsky et al. | Jun 2002 | B2 |
6420678 | Hockstra | Jul 2002 | B1 |
6438996 | Cuvelier | Aug 2002 | B1 |
6489588 | Hockstra et al. | Dec 2002 | B1 |
6562698 | Manor | May 2003 | B2 |
6566683 | Ogawa et al. | May 2003 | B1 |
6653210 | Choo et al. | Nov 2003 | B2 |
6726631 | Hatangadi et al. | Apr 2004 | B2 |
6744009 | Xuan et al. | Jun 2004 | B1 |
6770544 | Sawada | Aug 2004 | B2 |
6787732 | Xuan et al. | Sep 2004 | B1 |
6908784 | Farnworth et al. | Jun 2005 | B1 |
6951799 | Roche | Oct 2005 | B2 |
6992026 | Fukuyo et al. | Jan 2006 | B2 |
7174620 | Chiba et al. | Feb 2007 | B2 |
7396742 | Fukuyo et al. | Jul 2008 | B2 |
7489454 | Fukuyo et al. | Feb 2009 | B2 |
7547613 | Fukuyo et al. | Jun 2009 | B2 |
7566635 | Fujii et al. | Jul 2009 | B2 |
7592237 | Sakamoto et al. | Sep 2009 | B2 |
7592238 | Fukuyo et al. | Sep 2009 | B2 |
7605344 | Fukumitsu | Oct 2009 | B2 |
7608214 | Kuno et al. | Oct 2009 | B2 |
7615721 | Fukuyo et al. | Nov 2009 | B2 |
7626137 | Fukuyo et al. | Dec 2009 | B2 |
7709767 | Sakamoto | May 2010 | B2 |
7718510 | Sakamoto et al. | May 2010 | B2 |
7719017 | Tanaka | May 2010 | B2 |
7732730 | Fukuyo et al. | Jun 2010 | B2 |
7749867 | Fukuyo et al. | Jul 2010 | B2 |
7754583 | Sakamoto | Jul 2010 | B2 |
7825350 | Fukuyo et al. | Nov 2010 | B2 |
7897487 | Sugiura et al. | Mar 2011 | B2 |
7902636 | Sugiura et al. | Mar 2011 | B2 |
7939430 | Sakamoto et al. | May 2011 | B2 |
7947574 | Sakamoto et al. | May 2011 | B2 |
20010029673 | Brown et al. | Oct 2001 | A1 |
20010035401 | Manor | Nov 2001 | A1 |
20010046112 | Herchen | Nov 2001 | A1 |
20020006765 | Michel et al. | Jan 2002 | A1 |
20020025432 | Noguchi et al. | Feb 2002 | A1 |
20020096994 | Iwafuchi et al. | Jul 2002 | A1 |
20020115235 | Sawada | Aug 2002 | A1 |
20020158288 | Yamazaki et al. | Oct 2002 | A1 |
20020170896 | Choo et al. | Nov 2002 | A1 |
20020177288 | Brown et al. | Nov 2002 | A1 |
20030010275 | Radojevic et al. | Jan 2003 | A1 |
20030024909 | Hoekstra et al. | Feb 2003 | A1 |
20030141570 | Chen et al. | Jul 2003 | A1 |
20040002199 | Fukuyo et al. | Jan 2004 | A1 |
20040245659 | Glenn et al. | Dec 2004 | A1 |
20050173387 | Fukuyo et al. | Aug 2005 | A1 |
20050181581 | Fukuyo et al. | Aug 2005 | A1 |
20050184037 | Fukuyo et al. | Aug 2005 | A1 |
20050189330 | Fukuyo et al. | Sep 2005 | A1 |
20050194364 | Fukuyo et al. | Sep 2005 | A1 |
20050202596 | Fukuyo et al. | Sep 2005 | A1 |
20050272223 | Fujii et al. | Dec 2005 | A1 |
20060011593 | Fukuyo et al. | Jan 2006 | A1 |
20060040473 | Fukuyo et al. | Feb 2006 | A1 |
20060121697 | Fujii et al. | Jun 2006 | A1 |
20060144828 | Fukumitsu et al. | Jul 2006 | A1 |
20060148212 | Fukuyo et al. | Jul 2006 | A1 |
20060160331 | Fukuyo et al. | Jul 2006 | A1 |
20070085099 | Fukumitsu et al. | Apr 2007 | A1 |
20070125757 | Fukuyo et al. | Jun 2007 | A1 |
20070158314 | Fukumitsu et al. | Jul 2007 | A1 |
20070252154 | Uchiyama et al. | Nov 2007 | A1 |
20080035611 | Kuno et al. | Feb 2008 | A1 |
20080037003 | Atsumi et al. | Feb 2008 | A1 |
20080090382 | Fujii et al. | Apr 2008 | A1 |
20080218735 | Atsumi et al. | Sep 2008 | A1 |
20080251506 | Atsumi et al. | Oct 2008 | A1 |
20090008373 | Muramatsu et al. | Jan 2009 | A1 |
20090032509 | Kuno et al. | Feb 2009 | A1 |
20090098713 | Sakamoto | Apr 2009 | A1 |
20090107967 | Sakamoto et al. | Apr 2009 | A1 |
20090117712 | Sakamoto et al. | May 2009 | A1 |
20090166342 | Kuno et al. | Jul 2009 | A1 |
20090166808 | Sakamoto et al. | Jul 2009 | A1 |
20090250446 | Sakamoto | Oct 2009 | A1 |
20090261083 | Osajima et al. | Oct 2009 | A1 |
20090302428 | Sakamoto et al. | Dec 2009 | A1 |
20100006548 | Atsumi et al. | Jan 2010 | A1 |
20100009547 | Sakamoto | Jan 2010 | A1 |
20100012632 | Sakamoto | Jan 2010 | A1 |
20100012633 | Atsumi et al. | Jan 2010 | A1 |
20100015783 | Fukuyo et al. | Jan 2010 | A1 |
20100025386 | Kuno et al. | Feb 2010 | A1 |
20100032418 | Kuno et al. | Feb 2010 | A1 |
20100055876 | Fukuyo et al. | Mar 2010 | A1 |
20100151202 | Fukumitsu | Jun 2010 | A1 |
20100176100 | Fukuyo et al. | Jul 2010 | A1 |
20100184271 | Sugiura et al. | Jul 2010 | A1 |
20100200550 | Kumagai | Aug 2010 | A1 |
20100203678 | Fukumitsu et al. | Aug 2010 | A1 |
20100203707 | Fujii et al. | Aug 2010 | A1 |
20100227453 | Sakamoto | Sep 2010 | A1 |
20100240159 | Kumagai et al. | Sep 2010 | A1 |
20100258539 | Sakamoto | Oct 2010 | A1 |
20100301521 | Uchiyama | Dec 2010 | A1 |
20100311313 | Uchiyama | Dec 2010 | A1 |
20100327416 | Fukumitsu | Dec 2010 | A1 |
20110000897 | Nakano et al. | Jan 2011 | A1 |
20110001220 | Sugiura et al. | Jan 2011 | A1 |
20110021004 | Fukuyo et al. | Jan 2011 | A1 |
20110027971 | Fukuyo et al. | Feb 2011 | A1 |
20110027972 | Fukuyo et al. | Feb 2011 | A1 |
20110037149 | Fukuyo et al. | Feb 2011 | A1 |
20110274128 | Fukumitsu et al. | Nov 2011 | A1 |
Number | Date | Country |
---|---|---|
1160228 | Sep 1997 | CN |
196 46 332 | May 1998 | DE |
0345752 | Dec 1989 | EP |
0 863 231 | Sep 1998 | EP |
1 026 735 | Aug 2000 | EP |
1 138 516 | Oct 2001 | EP |
1 498 216 | Jan 2005 | EP |
1 580 800 | Sep 2005 | EP |
46-24989 | Jul 1971 | JP |
48-12599 | Feb 1973 | JP |
53-33050 | Mar 1978 | JP |
53-141573 | Dec 1978 | JP |
56-076522 | Jun 1981 | JP |
56-028630 | Jul 1981 | JP |
56-128691 | Oct 1981 | JP |
58-36939 | Mar 1983 | JP |
58-057767 | Apr 1983 | JP |
58-171783 | Oct 1983 | JP |
58-181492 | Oct 1983 | JP |
59-76687 | May 1984 | JP |
59-130438 | Jul 1984 | JP |
59-141233 | Aug 1984 | JP |
59-150691 | Aug 1984 | JP |
60-55640 | Mar 1985 | JP |
60-144985 | Jul 1985 | JP |
60-167351 | Aug 1985 | JP |
61-096439 | May 1986 | JP |
61-112345 | May 1986 | JP |
61-121453 | Jun 1986 | JP |
61-220339 | Sep 1986 | JP |
62-004341 | Jan 1987 | JP |
62-098684 | May 1987 | JP |
63-215390 | Sep 1988 | JP |
63-278692 | Nov 1988 | JP |
64-038209 | Feb 1989 | JP |
1-112130 | Apr 1989 | JP |
H1-225509 | Sep 1989 | JP |
H1-225510 | Sep 1989 | JP |
03-124486 | May 1991 | JP |
03-234043 | Oct 1991 | JP |
3-276662 | Dec 1991 | JP |
3-281073 | Dec 1991 | JP |
04-029352 | Jan 1992 | JP |
04-111800 | Apr 1992 | JP |
04-167985 | Jun 1992 | JP |
04-188847 | Jul 1992 | JP |
4-300084 | Oct 1992 | JP |
04-339586 | Nov 1992 | JP |
04-356942 | Dec 1992 | JP |
05-335726 | Dec 1993 | JP |
406039572 | Feb 1994 | JP |
06-188310 | Jul 1994 | JP |
6-198475 | Jul 1994 | JP |
07-029855 | Jan 1995 | JP |
07-037840 | Feb 1995 | JP |
07-040336 | Feb 1995 | JP |
07-075955 | Mar 1995 | JP |
7-76167 | Mar 1995 | JP |
7-32281 | Apr 1995 | JP |
07-263382 | Oct 1995 | JP |
7-308791 | Nov 1995 | JP |
8-148692 | Jun 1996 | JP |
8-197271 | Aug 1996 | JP |
08-264488 | Oct 1996 | JP |
08-264491 | Oct 1996 | JP |
09-017756 | Jan 1997 | JP |
09-017831 | Jan 1997 | JP |
9-150286 | Jun 1997 | JP |
09-216085 | Aug 1997 | JP |
9-260310 | Oct 1997 | JP |
09-263734 | Oct 1997 | JP |
10-034359 | Feb 1998 | JP |
10-071483 | Mar 1998 | JP |
10-163780 | Jun 1998 | JP |
10-214997 | Aug 1998 | JP |
10-233373 | Sep 1998 | JP |
10-305420 | Nov 1998 | JP |
10-321908 | Dec 1998 | JP |
11-028586 | Feb 1999 | JP |
11-121517 | Apr 1999 | JP |
11-138896 | May 1999 | JP |
11-156564 | Jun 1999 | JP |
11-160667 | Jun 1999 | JP |
11-162889 | Jun 1999 | JP |
11-163097 | Jun 1999 | JP |
11-163403 | Jun 1999 | JP |
11-177137 | Jul 1999 | JP |
11-177176 | Jul 1999 | JP |
11-207479 | Aug 1999 | JP |
11-221684 | Aug 1999 | JP |
11-224866 | Aug 1999 | JP |
11-267861 | Oct 1999 | JP |
11-071124 | Nov 1999 | JP |
2000-009991 | Jan 2000 | JP |
2000-015467 | Jan 2000 | JP |
2000-042764 | Feb 2000 | JP |
2000-61677 | Feb 2000 | JP |
2000-104040 | Apr 2000 | JP |
2000-124537 | Apr 2000 | JP |
2000-158156 | Jun 2000 | JP |
2000-195828 | Jul 2000 | JP |
2000-210785 | Aug 2000 | JP |
2000-216114 | Aug 2000 | JP |
2000-219528 | Aug 2000 | JP |
2000-237885 | Sep 2000 | JP |
2000-237886 | Sep 2000 | JP |
2000-247671 | Sep 2000 | JP |
02000249859 | Sep 2000 | JP |
2000-323441 | Nov 2000 | JP |
2001-47264 | Feb 2001 | JP |
2001-064029 | Mar 2001 | JP |
2001-085736 | Mar 2001 | JP |
2001-127015 | May 2001 | JP |
2001-135654 | May 2001 | JP |
2001-196282 | Jul 2001 | JP |
2001-250798 | Sep 2001 | JP |
2001-326194 | Nov 2001 | JP |
2001-345252 | Dec 2001 | JP |
2002-026443 | Jan 2002 | JP |
2002-47025 | Feb 2002 | JP |
2002-050589 | Feb 2002 | JP |
2002-158276 | May 2002 | JP |
2002-192367 | Jul 2002 | JP |
2002-192368 | Jul 2002 | JP |
2002-192369 | Jul 2002 | JP |
2002-192370 | Jul 2002 | JP |
2002-192371 | Jul 2002 | JP |
2002-205180 | Jul 2002 | JP |
2002-205181 | Jul 2002 | JP |
2002205181 | Jul 2002 | JP |
2002-224878 | Aug 2002 | JP |
2002-226796 | Aug 2002 | JP |
2003-001458 | Jan 2003 | JP |
2003-017790 | Jan 2003 | JP |
2003-039184 | Feb 2003 | JP |
2003-046177 | Feb 2003 | JP |
2003-154517 | May 2003 | JP |
2003-334812 | Nov 2003 | JP |
2003-338467 | Nov 2003 | JP |
2003-338468 | Nov 2003 | JP |
2003-338636 | Nov 2003 | JP |
2005-001001 | Jan 2005 | JP |
2005-047290 | Feb 2005 | JP |
2005-159378 | Jun 2005 | JP |
2005-159379 | Jun 2005 | JP |
2005-313237 | Nov 2005 | JP |
2006-128723 | May 2006 | JP |
2006-135355 | May 2006 | JP |
2001-017690 | Aug 1999 | KR |
165354 | Aug 1991 | TW |
192484 | Oct 1992 | TW |
219906 | Feb 1994 | TW |
404871 | Sep 2000 | TW |
415036 | Dec 2000 | TW |
428295 | Apr 2001 | TW |
440551 | Jun 2001 | TW |
443581 | Jun 2001 | TW |
512451 | Dec 2002 | TW |
521310 | Feb 2003 | TW |
WO 0190709 | Nov 2001 | WO |
WO 0207927 | Jan 2002 | WO |
WO 0222301 | Mar 2002 | WO |
WO 03076118 | Sep 2003 | WO |
WO 2004082006 | Sep 2004 | WO |
Number | Date | Country | |
---|---|---|---|
20060255024 A1 | Nov 2006 | US |