Patent Description:
In the related art, a laser machining device is known which irradiates a workpiece with a laser beam so as to carry out predetermined machining work including drilling, annealing, or welding work.

PTL <NUM> discloses a configuration of a laser welding device as follows. A temperature of a welding location is detected by an infrared detector so as to detect a defect in the welding work. PTL <NUM> (describing the features and steps of the preamble of claims <NUM> and <NUM>) discloses a laser annealing apparatus that performs processing on a workpiece and that simultaneously confirms the normality of annealing in a deep region. PTL <NUM> discloses a processing method using a pulsed laser beam, a processing apparatus using a pulsed laser beam which carries out this method, a crystallization method using a pulsed laser beam, a laser crystallization apparatus which carries out this method, and a display device.

A laser machining device uses a laser beam source, an optical system, and a workpiece so as to form a machined product corresponding to a machining content in a machining location. That is, in a case of a laser drilling device, a hole portion is generated. In a case of a laser annealing device, a transformation portion is generated by heating. In a case of a laser welding device, a welding portion is generated.

According to a technique disclosed in PTL <NUM>, a defect in the welding portion, that is, a portion generated through machining work, is detected based on a temperature detected by an infrared detector. However, PTL <NUM> does not disclose a technical idea of inspecting or controlling an object used in laser machining work, for example, such as a laser beam source, an optical system or a workpiece, based on the temperature detected by the infrared detector.

It is desirable to provide a laser machining device which can realize easy and proper inspection for an object used in laser machining work.

According to a first aspect of the present invention, there is provided a laser machining device as defined in claim <NUM>, including a scanning unit that changes an irradiation position of a workpiece irradiated with a laser beam, a heat radiation measurement unit that measures intensity of heat radiation of the workpiece irradiated with the laser beam, and a control unit that includes a determination unit and a display unit and controls the scanning unit, in which the control unit is configured to achieve the following: in a first abnormality determination process, comparing a measurement value of the heat radiation at each scanning position with one or both of an upper limit threshold and a lower limit threshold for identifying an abnormality and then determining the scanning position having the measurement value beyond the upper limit threshold or the scanning position having the measurement value below the lower limit threshold, as an abnormal location, in a second abnormality determination process, comparing the measurement value obtained at a first position of the workpiece with the measurement value obtained at a position in a vicinity of the
first position, in a third abnormality determination process, two-dimensionally arranging a series of data items of the measurement values of the heat radiation in accordance with the scanning positions and comparing the measurement value obtained at each scanning position with the measurement value obtained at the position in the vicinity thereof, based on the data of the measurement value of the heat radiation which is associated with the position in an X-Y coordinate, and in a fourth abnormality determination process, analyzing a distribution of the measurement values on the X-Y coordinate, based on the data of the measurement values of the heat radiation which are developed on the X-Y coordinate and then analyzing whether or not a distribution of a measurement value has a predetermined characteristic and determining a pattern of a warpage of the workpiece, a position of the warpage, or a size of the warpage, based on a result of the analysis, and outputting the abnormality when existing, or when no abnormality exists, completing a machining process.

Further embodiments of the laser machining device are defined in the dependent claims <NUM> to <NUM>.

According to a second aspect of the present invention, there is provided a process of laser machining as defined in claim <NUM>.

According to an embodiment of the present invention, an advantageous effect is achieved in that easy and proper inspection can be realized for an object used in laser machining work.

Hereinafter, respective embodiments will be described in detail with reference to the drawings.

In the related art, a laser machining device is known which carries out machining work for a workpiece by using a laser beam. The laser machining device includes a laser annealing device that uses a wafer of a semiconductor element material as a workpiece, and that performs heat treatment on a surface portion of the workpiece by scanning the surface portion of the workpiece with a laser beam. As a technique relating to Embodiment <NUM>, PTL <NUM> (<CIT>) discloses a configuration in which the laser welding device detects a welding defect by causing an infrared detector to detect a temperature of a welding location.

In some cases, the workpiece may include an abnormality such as a crack, foreign substance contamination, or severe warpage. However, in the related art, when machining work is carried out for the workpiece by using the laser machining device, it is not possible to detect the abnormality included in the workpiece. The technique disclosed in PTL <NUM> is used in order to detect whether there is a defect in a machined portion, and is not used in order to detect the abnormality included in the workpiece.

The invention according to Embodiment <NUM> aims to provide a laser machining device capable of detecting an abnormal location included in the workpiece during a machining process.

Subsequently, a laser machining device <NUM> according to Embodiment <NUM> will be described. <FIG> is a configuration diagram illustrating the laser machining device according to Embodiment <NUM> of the present invention. In the drawings, an optical axis of a laser beam is illustrated using a solid line, heat radiation is illustrated using a thick broken line, and a control line and an output line of a measurement result are illustrated using a thin broken line.

The laser machining device <NUM> according to Embodiment <NUM> is a laser annealing device which performs annealing treatment on a workpiece <NUM> by defining a wafer of a semiconductor element material as the workpiece <NUM>. The annealing treatment is a process of heating a surface portion of the workpiece <NUM> to a high temperature by scanning an entire two-dimensional region set on the surface portion of the workpiece <NUM> with the laser beam.

The laser machining device <NUM> includes a control unit <NUM>, a laser beam source <NUM>, a scanning optical system <NUM>, a dichroic mirror <NUM>, lenses <NUM> and <NUM>, a heat radiation measurement unit <NUM>, and a stage <NUM>. The scanning optical system <NUM> corresponds to an example of a scanning unit according to an embodiment of the present invention.

For example, the laser beam source <NUM> is a solid laser such as a YAG laser or a gas laser such as a CO<NUM> laser, and outputs the laser beam with which the workpiece <NUM> is irradiated so as to heat a machining target position P100 of the workpiece <NUM> to a high temperature. The laser beam source <NUM> may be called a laser oscillator.

For example, the scanning optical system <NUM> includes a galvano mirror, and can change the irradiation position of the laser beam, that is, the machining target position P100, in two directions along an upper surface of the stage <NUM>, for example.

The dichroic mirror <NUM> reflects light of an output wavelength of the laser beam source <NUM>, and transmits light of an infrared region including the heat radiation.

For example, the lens <NUM> is an Fθ lens, and converges the laser beam to the machining target position. Also, the lens <NUM> collects the heat radiation from the machining target position P100 of the workpiece.

The lens <NUM> converges the heat radiation collected by the lens <NUM> and transmitted through the dichroic mirror <NUM> to the heat radiation measurement unit <NUM>.

For example, the heat radiation measurement unit <NUM> measures intensity of the heat radiation input to a light receiving unit serving as an infrared sensor.

The stage <NUM> holds the workpiece <NUM>. The stage <NUM> may be configured to be movable in two directions intersecting the optical axis of the laser beam.

The control unit <NUM> is a computer having a storage device for storing a program, a central processing unit (CPU) for executing the program, a working memory, and an I/O for inputting and outputting a control signal and a detection signal. The control unit <NUM> performs drive control of the laser beam source <NUM> and drive control of the scanning optical system <NUM>, and inputs a measurement result of the heat radiation measurement unit <NUM>. The control unit <NUM> further includes a display unit <NUM> and a determination unit <NUM> serving as a functional module for causing the CPU to execute a program.

The determination unit <NUM> determines an abnormal location included in the workpiece <NUM>, based on data of the intensity of the heat radiation incorporated into the control unit <NUM>.

The display unit <NUM> is a display capable of displaying warning light or an image. In a case where it is determined that the workpiece <NUM> has the abnormal location, the display unit <NUM> displays a notification of the abnormality. The display unit <NUM> further displays and outputs the data (refer to <FIG>) of the intensity data of the heat radiation, which is processed into a two-dimensional image after being incorporated into the control unit <NUM>.

<FIG> is a flow chart illustrating a procedure of a machining process performed by the control unit.

The machining process in <FIG> is a process of detecting whether or not the workpiece <NUM> is abnormal and whether there is the abnormal location, while the annealing treatment is performed on the workpiece <NUM>. The machining process starts in a state where the workpiece <NUM> is located on the stage <NUM>.

When the machining process starts, the control unit <NUM> starts a scanning process of scanning the entire surface portion of the workpiece <NUM> with the laser beam by driving the laser beam source <NUM> and (Step S101). Here, the laser beam output from the laser beam source <NUM> passes through the scanning optical system <NUM>, the dichroic mirror <NUM>, and the lens <NUM>, and the machining target position P100 of the workpiece <NUM> is irradiated with the laser beam so as to heat the machining target position P100 to a high temperature. Furthermore, the heat radiation is discharged from the machining target position P100 heated to a high temperature, and passes through the lens <NUM>, the dichroic mirror <NUM>, and the lens <NUM>, thereby causing the heat radiation to be collected by the light receiving unit of the heat radiation measurement unit <NUM>. The heat radiation measurement unit <NUM> outputs a measurement result (for example, a voltage) corresponding to the intensity of the received heat radiation.

If the scanning starts, the control unit <NUM> proceeds to the loop processing in Steps S102 to S105. In the loop processing, first, the control unit <NUM> continuously outputs the laser beam, and controls the scanning optical system <NUM> so that the irradiation position of the laser beam is changed to a subsequent position along a preset route (Step S102). In this manner, the subsequent position in the scanning route is set as the machining target position P100, and the subsequent position is irradiated with the laser beam, thereby discharging the heat radiation from the position. Then, the heat radiation measurement unit <NUM> measures the intensity of the heat radiation, and the control unit <NUM> inputs a measurement value (Step S103). Next, the control unit <NUM> stores the input measurement value of the heat radiation and the scanning position in association with each other (Step S104). Subsequently, the control unit <NUM> determines whether a preset region is completely scanned (Step S105). If the scanning is not completed, the process returns to Step S102. However, if the scanning is completed, the control unit <NUM> finishes the loop processing, and proceeds to the next step.

The loop processing in Steps S102 to S105 above is repeatedly performed. In this manner, the preset two-dimensional region is sequentially irradiated with the laser beam, and the annealing treatment is completely performed on the set region of the workpiece <NUM>. In addition, the measurement value of the intensity of the heat radiation obtained when at each scanning position of the workpiece <NUM> is irradiated with the laser beam is incorporated into the control unit <NUM>.

If the loop processing is finished, the control unit <NUM> determines whether or not the workpiece <NUM> is abnormal, based on the incorporated measurement value of the intensity of the heat radiation. Subsequently, an example will be described which adopts four abnormality determination processes.

In a first abnormality determination process (Step S106), the control unit <NUM> compares the measurement value of the heat radiation at each scanning position with one or both of an upper limit threshold and a lower limit threshold for identifying the abnormality. Then, the control unit <NUM> determines the scanning position having the measurement value beyond the upper limit threshold or the scanning position having the measurement value below the lower limit threshold, as the abnormal location. In the workpiece <NUM> such as the wafer, if there is the crack or the foreign substance contamination, high-temperature heat generated by the irradiation of the laser beam is transferred to the location of the crack or the foreign substance in an unusual manner. Accordingly, the measurement value of the heat radiation increases or decreases around the location of the crack or the foreign substance. Therefore, the abnormal locations can be determined by performing the first abnormality determination process.

<FIG> are graphs illustrating an example of data of the heat radiation which is acquired by performing the loop processing in Steps S102 to S105 in <FIG>.

In a second abnormality determination process (Step S107), as illustrated by a graph in <FIG>, the control unit <NUM> compares the measurement value obtained at each scanning position with the measurement value obtained at a front stage position and the measurement value obtained at a rear stage position, along the incorporated order of the data of the measurement value of the heat radiation. Here, the "measurement value obtained at each scanning position" corresponds to the "intensity of the heat radiation obtained when the first position is irradiated with the laser beam" according to the present invention. The "measurement value obtained at the front position and the measurement value obtained at the rear position" correspond to the "intensity of the heat radiation obtained when the vicinity of the first position is irradiated with the laser beam" according to the present invention. When the comparison is performed, the control unit <NUM> may calculate movement averages of the measurement values obtained at the respective scanning positions, and may perform the comparison using statistically processed values of the measurement values, as in a case where the movement average values are compared with each other. Then, the control unit <NUM> determines that the scanning positions (for example, locations D101 and D102 in <FIG>) having a rapid change in the measurement value are abnormal locations. As described above, in a case where the workpiece <NUM> such as the wafer has the crack or the foreign substance contamination, the high-temperature heat generated by the irradiation of the laser beam is transferred to the location of the crack or the foreign substance in an unusual manner. Therefore, a rapid change is likely to appear in the measurement value of the heat radiation around the location of the crack or the foreign substance. If there is no abnormality, as illustrated in <FIG>, the rapid change does not appear in the measurement value. Therefore, the abnormal locations can be determined by the second abnormality determination process.

<FIG> illustrate an example of data of heat radiation two-dimensionally arranged through Step S108 in <FIG>. <FIG> illustrate data obtained when the intensity of the heat radiation is measured at each scanning position by performing the scanning with the laser beam in an X-axis direction and performing the scanning multiple times while shifting the position in a Y-axis direction. In <FIG>, the intensity of the heat radiation is illustrated using color shades.

In a third abnormality determination process (Steps S108 and S109), first, the control unit <NUM> two-dimensionally arranges a series of data items of the measurement values of the heat radiation in accordance with the scanning positions (Step S108). In this manner, as illustrated in <FIG>, a series of the measurement values of the heat radiation incorporated in time series are illustrated in association with positions on an X-Y coordinate on which the surface portion of the workpiece <NUM> is projected.

Next, the control unit <NUM> compares the measurement value obtained at each scanning position with the measurement value obtained at the position in the vicinity thereof, based on the data of the measurement value of the heat radiation which is associated with the position in the X-Y coordinate (Step S109). When the comparison is performed, the control unit <NUM> may calculate movement averages of the measurement values obtained at the respective scanning positions, and may perform the comparison using statistically processed values of the measurement values, as in a case where the movement average values are compared with each other. In Step S109, the control unit <NUM> determines whether or not there is a location where the intensity of the heat radiation is rapidly changed not only in a scanning direction (X-axis direction) of the laser beam but also in an intersecting direction thereof (Y-axis direction). Then, the control unit <NUM> determines that the scanning position (for example, locations D103 and D104 in <FIG>) having a rapid change in the measurement value is the abnormal location on the two-dimensional X-Y coordinate. As described above, in a case where the workpiece <NUM> such as the wafer has the crack or the foreign substance contamination, the measurement value of the heat radiation is likely to be rapidly changed around this location. For example, the location D103 is a location where the wafer has a flaw, and the location D104 is a location where the foreign substance is present. If there is no abnormality, as illustrated in <FIG>, there is no location where the measurement value of the heat radiation is rapidly changed. The abnormal location can be determined by performing the third abnormality determination process, in a case where the abnormal location present is in the middle of the scanning route of the laser beam or between the scanning routes adjacent to each other.

In a fourth abnormality determination process (Step S110), first, the control unit <NUM> analyzes the distribution of the measurement values on the X-Y coordinate, based on the data of the measurement values of the heat radiation which are developed on the X-Y coordinate. Then, the control unit <NUM> analyzes whether or not the distribution of the measurement values has a predetermined characteristic, and determines a pattern of a warpage of the workpiece, a position of the warpage, or a size of the warpage, based on a result of the analysis. In the analysis process, the control unit <NUM> may store distribution data of the measurement values of the heat radiation for the plurality of the workpieces having the warpage with several patterns, as reference data, and may analyze the distribution by calculating these reference data and The distribution may be analyzed by calculating a common degree between the reference data and the distribution of the measurement values of the heat radiation. If the wafer has the warpage, the irradiation position of the laser beam is changed in a height direction in accordance with the pattern of the warpage. Accordingly, the pattern of the warpage appears in the distribution pattern of the measurement values of the heat radiation. Therefore, the abnormality relating to the warpage of the workpiece <NUM> can be determined by performing the fourth abnormality determination process.

If the abnormality determination process is completely performed, the control unit <NUM> determines whether or not the determination result is abnormal. If the determination result is abnormal, for example, the control unit <NUM> outputs a type of the abnormality and the abnormal location by using a data output, a display output, or a print output (Step S112). When the data is output, the abnormal location may be indicated using an image.

In a case where the workpiece <NUM> is the wafer provided with a pattern, the intensity of the heat radiation may be rapidly changed at a pattern boundary, even if the pattern boundary is a normal location. In this case, the abnormal location indicated using the image. In this manner, an operator can distinguish the originally abnormal location and the normal location such as the pattern boundary from each other by comparing the image with the pattern of the wafer. Alternatively, although there is no abnormality as in the pattern boundary, in a case where the position where the intensity of the heat radiation is rapidly changed is known in advance, the information may be stored in the control unit <NUM>. Then, based on the information, the control unit <NUM> may be configured so that the location where the intensity of the heat radiation is rapidly changed rapidly although there is no abnormality is excluded from abnormality determination locations.

If the control unit <NUM> outputs the abnormality in Step S112 or determines that there is no abnormality in Step Sill, the control unit <NUM> completes the machining process in <FIG>.

As described above, according to the laser machining device <NUM> of Embodiment <NUM>, the laser machining device <NUM> not only can perform the machining process by scanning the workpiece <NUM> with the laser beam, but also can determine whether or not the workpiece <NUM> has the abnormal location during the machining process. Therefore, it is not necessary to spend time only for the inspection. Simultaneously with the machining process, the abnormal location of the workpiece <NUM> can be detected. In this manner, a yield rate of final products can be improved by removing the abnormal workpiece from the manufacturing process.

In addition, according to the second abnormality determination process (Step S107) and the third abnormality determination process (Step S108), the abnormal location is determined by comparing the measurement value of the heat radiation obtained at each scanning position with the measurement value of the heat radiation obtained in the vicinity thereof. Therefore, if the measurement value of the heat radiation generally increases or decreases due to a type or a thickness of the workpiece, even in a case where a threshold of the measurement value which enables the abnormality to be identified is not determined, the abnormal location of the workpiece can be determined.

Hitherto, Embodiment <NUM> according to the present invention has been described. However, the present invention is not limited to Embodiment <NUM> described above. For example, in Embodiment <NUM>, a configuration for determining the abnormal location of the workpiece <NUM> simultaneously with the annealing treatment has been described as an example. However, if the machining process is performed by scanning the surface portion of the workpiece <NUM> with the laser beam, a process for determining the abnormal location may be performed simultaneously with a process other than the annealing treatment. In addition, in Embodiment <NUM>, as the scanning unit according to the present invention, the scanning optical system <NUM> has been described which changes the irradiation position of the laser beam. However, the scanning unit according to the present invention may be configured so that a position of the workpiece <NUM> irradiated with the laser beam is changed by moving the workpiece <NUM>. In addition, in Embodiment <NUM>, the wafer of the semiconductor element material has been described as the workpiece, and the crack, the foreign substance contamination, or the warpage of the wafer has been described as the abnormality. However, various configurations such as an electronic board can be adopted as the workpiece. In addition, as the abnormality to be detected, for example, various abnormalities such as a foreign substance adhering to the surface of the workpiece may be adopted. In addition, details described in Embodiment <NUM> can be appropriately modified within the scope of the present invention as defined in the appended claims.

According to these preferred embodiments of the invention, during the machining process, the abnormal location included in the workpiece can be detected.

As the laser machining device, a laser annealing device is known which performs annealing treatment on the workpiece by defining the wafer of the semiconductor element material as the workpiece. In addition, as the laser machining device, a laser drilling device is known which drills a hole in the workpiece by using the laser beam and setting a substrate having a resin layer and a metal layer as the workpiece, and a laser welding device is known which welds the workpiece. This laser machining device generally has a power measurement unit that measures output power of a laser beam source (for example, refer to PTL <NUM>: <CIT>). Then, before the machining process, the power measurement unit measures the power of the laser beam, and adjusts the output of the laser beam source by performing feedback control. In addition, as a technique relating to Embodiment <NUM>, not covered by the present invention, PTL <NUM> (<CIT>) discloses a technique of monitoring a temperature of a target surface by using an infrared sensor in a laser sintering device using a radiant heater.

In the laser machining device, it is preferable that the power of the laser beam used in irradiating the workpiece is adjusted in accordance with the settings. Through investigations, the present inventors have found out the followings. The power of the laser beam used in irradiating the workpiece is changed due to an output error of the laser beam source, an error factor of an optical system such as dirt or misalignment of a lens or a mirror, and a measurement error of the power measurement unit. Out of these, the output error of the laser beam source can be adjusted within an allowable range, if the measurement of the power measurement unit is correctly performed. In addition, the error factor of the optical system can be found by inspecting a beam shape of the laser beam. On the other hand, the laser machining device in the related art has no means for detecting the measurement error of the power measurement unit. If a relatively big measurement error occurs in the power measurement unit, there is a problem in that the power error increases in the laser beam used in irradiating the machining target position. As an example, the measurement error of the power measurement unit occurs due to a change in an ambient temperature.

Embodiment <NUM>, not covered by the present invention, aims to provide a laser machining device which can detect a measurement error in a case where the measurement error exceeds an allowable range in a power measurement unit.

Subsequently, a laser machining device <NUM> according to Embodiment <NUM>, not covered by the present invention, will be described. <FIG> is a configuration diagram illustrating the laser machining device according to Embodiment <NUM>, not covered by the present invention.

In <FIG>, the optical axis of the laser beam is illustrated using a solid line or a two-dot chain line, the heat radiation is illustrated using a thick broken line, and the control line and the output line of the measurement result are illustrated using a thin broken line.

The laser machining device <NUM> according to Embodiment <NUM> is a laser annealing device which performs annealing treatment by defining the wafer of the semiconductor element material as a workpiece <NUM> and irradiating the workpiece <NUM> with the laser beam. The laser machining device <NUM> includes a control unit <NUM>, a laser beam source <NUM>, a scanning optical system <NUM>, a dichroic mirror <NUM>, lenses <NUM> and <NUM>, a heat radiation measurement unit <NUM>, a stage <NUM>, an image sensor <NUM>, a total reflection mirror <NUM>, a power measurement unit <NUM>, and a workpiece for inspection <NUM>.

For example, the laser beam source <NUM> is a solid laser such as a YAG laser, a gas laser such as a CO<NUM> laser, or a semiconductor laser such as a laser diode (LD), and outputs the laser beam with which the workpiece <NUM> is irradiated so as to heat a machining target position P200 of the workpiece <NUM> to a high temperature. The laser beam source <NUM> may be called a laser oscillator.

For example, the scanning optical system <NUM> includes a galvano mirror, and can change the irradiation position of the laser beam, that is, the machining target position P200, in two directions along an upper surface of the stage <NUM>, for example. The scanning optical system <NUM> may be omitted, and the stage <NUM> holding the workpiece <NUM> may be moved. In this manner, a configuration may be adopted so that the irradiation position of the laser beam and the workpiece <NUM> are moved relative to each other.

The dichroic mirror <NUM> reflects the light having the output wavelength of the laser beam source <NUM>, and transmits the light in the infrared region including the heat radiation.

For example, the lens <NUM> is an Fθ lens, and converges the laser beam to the machining target position. In addition, the lens <NUM> collects the heat radiation from the machining target position P200 of the workpiece.

For example, the heat radiation measurement unit <NUM> measures the intensity of the heat radiation input to the light receiving unit which is the infrared sensor.

The stage <NUM> holds the workpiece <NUM>, and is configured to be movable in two directions intersecting the optical axis of the laser beam. The stage <NUM> holds the image sensor <NUM> and the total reflection mirror <NUM> at a location different from the region holding the workpiece <NUM>. In addition, the stage <NUM> holds the workpiece for inspection <NUM> at the same height as the workpiece <NUM>.

For example, the image sensor <NUM> is a charge coupled device (CCD) camera, and can be moved to the irradiation position of the laser beam (optical axis position of the laser beam emitted from the lens <NUM> for irradiation) by driving the stage <NUM>. The image sensor <NUM> images a beam shape of the laser beam at the irradiation position of the laser beam. The beam shape means the intensity distribution inside a beam spot of the laser beam, and also called a beam profile. In <FIG>, the optical axis of the laser beam when the image sensor <NUM> is moved to the irradiation position of the laser beam is illustrated by a two-dot chain line.

The total reflection mirror <NUM> can be moved to the irradiation position of the laser beam (optical axis position of the laser beam emitted from the lens <NUM> for irradiation) by driving the stage <NUM>. The total reflection mirror <NUM> reflects the laser beam, and transmits the reflected laser beam to the power measurement unit <NUM> at the irradiation position of the laser beam. In <FIG>, the optical axis of the laser beam when the total reflection mirror <NUM> is moved to the irradiation position of the laser beam is illustrated by a two-dot chain line.

<FIG> is a graph illustrating an example of an output of the power measurement unit.

The power measurement unit <NUM> is also called a power meter, and receives the laser beam so as to measure power of the laser beam. The power means energy per unit time of the laser beam. For example, as the power measurement unit <NUM>, it is possible to adopt a thermal sensor which has a light receiving surface for converting the laser beam into heat so as to measure the power of the laser beam from the temperature of the light receiving surface. As illustrated in <FIG>, if a short time elapses after the power measurement unit <NUM> receives the laser beam, the output is stabilized. In a stabilized state, the power measurement unit <NUM> outputs a measurement result indicating the power of the laser beam. In the power measurement unit <NUM>, an error occurs due to the ambient temperature. For example, even if the laser beams have the same power, as illustrated in <FIG>, the power measurement unit <NUM> outputs different measurement results in a case where the ambient temperature is <NUM> and in a case where the ambient temperature is <NUM>. The laser machining device <NUM> is normally operated in an environment controlled to maintain a set ambient temperature. Accordingly, in many cases, the measurement error does not increase due to the ambient temperature of the power measurement unit <NUM>. However, when the abnormality occurs, the measurement error of the power measurement unit <NUM> may increase due to the ambient temperature or other factors, in some cases.

The workpiece for inspection <NUM> can be moved to the machining target position P200 irradiated with the laser beam, by driving the stage <NUM>. The workpiece for inspection <NUM> is a pseudo-workpiece, and is used when inspecting whether there is a big measurement error in the power measurement unit <NUM>. When the power measurement unit <NUM> is inspected, the same workpiece <NUM> is used every time. However, the workpiece for inspection <NUM> may be replaced with a new one periodically or at any desired time. The workpiece for inspection <NUM> may have the thickness, the width, and the depth which are different from those of the actual workpiece <NUM>. The work is not actually carried out for the workpiece for inspection <NUM>. However, the workpiece for inspection <NUM> is irradiated with the laser beam in the same manner as the workpiece <NUM>. Accordingly, herein, the workpiece for inspection <NUM> is called the workpiece. If the workpiece for inspection adopts the same material as the actual workpiece <NUM>, inspection accuracy can be improved. However, if the workpiece for inspection adopts a material whose temperature is raised similarly to that of the actual workpiece <NUM> by irradiating the material with the laser beam, it is not necessary to adopt the same material as workpiece <NUM>.

The control unit <NUM> is a computer having a storage device for storing a program, a central processing unit (CPU) for executing the program, a working memory, and an I/O for inputting and outputting the control signal and the detection signal. The control unit <NUM> performs drive control of the laser beam source <NUM>, drive control of the stage <NUM>, and drive control of the scanning optical system <NUM>. Furthermore, the control unit <NUM> inputs the measurement value of the heat radiation measurement unit <NUM>, the imaging result of the image sensor <NUM>, the measurement result of the power measurement unit <NUM>, and the measurement result of the heat radiation measurement unit <NUM>. The control unit <NUM> performs an adjustment process including power adjustment of the laser beam source <NUM> at a proper timing before the machining process is performed on the workpiece <NUM>.

The control unit <NUM> further includes a storage unit <NUM>, a display unit <NUM>, and a determination unit <NUM> and a data processing unit <NUM> as functional modules which cause the CPU to execute the program. The display unit <NUM> is a display capable of displaying warning light or an image. In a case where it is determined that the adjustment process is abnormal, the display unit <NUM> displays a warning. Each function of the determination unit <NUM>, the data processing unit <NUM>, and the storage unit <NUM> will be described later.

<FIG> is a flowchart illustrating a procedure of a reference data acquisition process performed by the control unit.

The reference data acquisition process is a process of acquiring required reference data in advance in order to determine whether the measurement error of the power measurement unit <NUM> falls within an allowable range. The reference data acquisition process is performed in the following state. An error factor such as dust, dirt, or misalignment is removed from the optical system of the laser machining device <NUM>, and it is guaranteed that an environmental parameter such as the ambient temperature satisfies a preset condition. If this state is ready, a user inputs a start command of the reference data acquisition process to the control unit <NUM>. In this manner, the control unit <NUM> starts the reference data acquisition process in <FIG>.

If the reference data acquisition process starts, the control unit <NUM> first performs a process of measuring the heat radiation by irradiating the workpiece for inspection <NUM> with the laser beam (Step S201). Specifically, the control unit <NUM> first moves the workpiece for inspection <NUM> to the irradiation position of the laser beam by driving the stage <NUM>. Next, the control unit <NUM> emits the laser beam by driving the laser beam source <NUM>. Then, the workpiece <NUM> is irradiated with the laser beam passing through the scanning optical system <NUM>, the dichroic mirror <NUM>, and the lens <NUM> so as to heat the machining target position P200 of the workpiece <NUM>. If the machining target position is heated, the heat radiation corresponding to the heating amount is generated from the machining target position. The heat radiation is incident on the heat radiation measurement unit <NUM> after passing through the lenses <NUM>, the dichroic mirror <NUM>, and the lenses <NUM>. The heat radiation measurement unit <NUM> measures the intensity of the heat radiation, and the control unit <NUM> incorporates the measurement result. The measurement value of the heat radiation acquired by performing the measurement process in Step S201 is indicated by "P201".

In the measurement process in Step S201, in some cases, the intensity of the heat radiation of the workpiece <NUM> may be changed depending on a continued irradiation time of the laser beam and a measurement timing of the heat radiation. In this case, the control unit <NUM> may perform the measurement process of the heat radiation by defining the continued irradiation time of the laser beam and the measurement timing of the heat radiation as a preset value. Alternatively, the control unit <NUM> may set the continued irradiation time of the laser beam to be constant, and may incorporate statistics such as the maximum value or the average value of the heat radiation during the measurement period, as the measurement result.

Next, the control unit <NUM> performs the measurement process on the power of the laser beam (Step S202). Specifically, the control unit <NUM> first moves the total reflection mirror <NUM> to the irradiation position of the laser beam by driving the stage <NUM>. Next, the control unit <NUM> drives the laser beam source <NUM> with the same power setting as that in Step S201. Then, the laser beam is incident on the power measurement unit <NUM> after passing through the scanning optical system <NUM>, the dichroic mirror <NUM>, the lens <NUM>, and the total reflection mirror <NUM>. The power measurement unit <NUM> measures the power of the laser beam, and outputs the measurement result so that the control unit <NUM> inputs the measurement result. For example, the control unit <NUM> may continuously output the laser beam for a predetermined time, and may incorporate a value acquired when the output of the power measurement unit <NUM> is stabilized, as the measurement result. The measurement value of the power acquired by performing the measurement process in Step S202 is indicated by "P202".

Subsequently, the control unit <NUM> stores a combination between the measurement value P201 of the intensity of the heat radiation incorporated in Step S201 and the measurement value P202 of the power of the laser beam incorporated in Step S202, as a set of reference data Di = (P201 and P202) (Step S203).

The control unit <NUM> further performs the determination process in Step S204. In this manner, the control unit <NUM> repeatedly performs the loop processing in Steps S201 to S203 multiple times by changing the power of the laser beam source <NUM>, for example. A plurality of reference data items D201, D202, D203, D204, and so forth are acquired by performing the loop processing multiple time in this way.

<FIG> is a view illustrating an example of a normal range of the measurement value stored in the storage unit.

If the reference data is acquired, next, in the control unit <NUM>, the data processing unit <NUM> adds an allowable error to reference data items D201, D202, D203, D204, and so forth, and determines the normal range of the measurement value (Step S205). For example, as illustrated in <FIG>, a case is assumed where the four reference data items D201 to D204 are acquired. In this case, the data processing unit <NUM> calculates a regression line L201 indicating a correlation between the intensity of the heat radiation and the power of the laser beam, based on the plurality of reference data items D201 to D204, and determines a normal range W201 by adding the allowable error to the regression line L201.

In the above-described example, a case has been described where the data processing unit <NUM> determines the normal range W201, based on the plurality of reference data items D201, D202, D203, D204, and so forth. However, the data processing unit <NUM> may determine the normal range, based on only one reference data item D201. In this case, for example, the data processing unit <NUM> can determine the normal range, for example, such as "(P201/P202)+<NUM>%" by adding the allowable error to a ratio "P201/P202" between the measurement value P201 of the intensity of the heat radiation and the measurement value P202 of the power measurement unit <NUM>.

If the data processing unit <NUM> determines the normal range of the measurement value, the data processing unit <NUM> causes the storage unit <NUM> to store the data indicating the normal range (Step S206). Then, the control unit <NUM> completes the reference data acquisition process.

<FIG> is a flowchart illustrating a flow of the adjustment process of the laser machining device which is performed by the control unit.

The adjustment process is a process performed before the machining process in order to confirm whether the workpiece <NUM> is irradiated with the laser beam by using the set beam shape and the set power. The adjustment process is performed at a proper timing, for example, periodically or before batch processing is performed on the plurality of workpieces <NUM>. If a user inputs a command to start the adjustment process to the control unit <NUM> at the proper timing, the control unit <NUM> starts the adjustment process in <FIG>.

If the adjustment process starts, the control unit <NUM> first performs a power adjustment process of the laser beam (Step S211). Specifically, the control unit <NUM> first moves the total reflection mirror <NUM> to the irradiation position of the laser beam by driving the stage <NUM>. Next, the control unit <NUM> drives the laser beam source <NUM> by using the set power, and inputs the measurement result of the power measurement unit <NUM>. Then, in a case where the measurement result deviates from the set power, the control unit <NUM> adjusts the set power of the laser beam source <NUM> so that the measurement value of the power measurement unit <NUM> is equal to the set value.

Subsequently, the control unit <NUM> performs a process of confirming the beam shape of the laser beam (Step S212). Specifically, the control unit <NUM> first moves the image sensor <NUM> to the irradiation position of the laser beam by driving the stage <NUM>. Next, the control unit <NUM> drives the laser beam source <NUM> so as to irradiate the workpiece with the laser beam, and inputs an imaging result of the image sensor <NUM>. Then, the control unit <NUM> compares the beam shape set in advance with the imaging result. As a result of the comparison, if a difference falls within the allowable range, the control unit <NUM> determines the result as normal. If the difference exceeds the allowable range, the control unit <NUM> determines the result as abnormal.

If the beam shape is confirmed, the control unit <NUM> determines the result (Step S213). If the result is abnormal, the control unit <NUM> causes the display unit <NUM> to display the determination result of the abnormality and the warning (Step S217), and proceeds to error processing. The warning display enables the user to inspect contamination or misalignment of the optical system, and to correct the abnormality of the beam shape.

On the other hand, if the confirmation result of the beam shape is normal, the control unit <NUM> proceeds to the inspection process of the power measurement unit <NUM> (Steps S214 to S216). That is, the control unit <NUM> first irradiates the workpiece for inspection <NUM> with the laser beam so as to perform the measurement process of the heat radiation (Step S214). The measurement value incorporated at this time is indicated by "P201". The process in Step S214 is the same as the process in Step S201 described above.

Next, the control unit <NUM> performs the measurement process of the power of the laser beam (Step S215). The measurement value incorporated at this time is indicated by "P202". The process in Step S215 is the same as the process in Step S202 described above. The set power of the laser beam source <NUM> driven in Step S215 is set to be the same as the set power of the laser beam source <NUM> driven in Step S214.

If the measurement value is incorporated, subsequently, the control unit <NUM> compares data D = (P201 and P202) incorporated by the determination unit <NUM> with the data (refer to <FIG>) indicating the normal range W201 stored in the storage unit <NUM>. Then, the determination unit <NUM> determines whether or not the data D is included in the normal range W201 (Step S216).

As a result of the determination in Step S216, if the data D is included in the normal range W201, the control unit <NUM> completes the adjustment process without displaying the warning of the abnormality. In this case, the user can determine that the laser machining device <NUM> is normally adjusted, and can proceed to the machining process of the workpiece <NUM>.

On the other hand, as a result of the determination of the determination unit <NUM> in Step S216, if the data D is not included in the normal range W201, the control unit <NUM> causes the display unit <NUM> to display the warning of the abnormality (Step S217), and proceeds to the error processing. In this case, the warning display enables the user to determine that the adjustment of the laser machining device <NUM> is not normal. For example, the user can stop the laser machining device <NUM>, and can investigate which is a cause of the abnormality. In this way, the user can avoid a possibility that the machining process of the workpiece may be performed in an abnormal state and a yield rate may be lowered.

As described above, according to the laser machining device <NUM>, in the adjustment process, it is determined whether or not the data D = (P201 and P202) of the combination between the measurement value "P201" of the power of the laser beam and the measurement value "P202" of the heat radiation falls within the normal range. In this manner, in a case where the measurement error exceeding the allowable range occurs in the power measurement unit <NUM>, the measurement error can be detected.

In addition, according to the laser machining device <NUM>, the pseudo-workpiece for inspection <NUM> is provided. The inspection process of the power measurement unit <NUM> is performed using the same workpiece <NUM> every time in the inspection processes performed multiple times. Therefore, due to the influence of an individual difference in the workpieces <NUM>, a difference may occur in the measurement values "P202" of the heat radiation. Accordingly, it is possible to avoid a possibility that the power measurement unit <NUM> may erroneously determine the difference as abnormal.

In addition, according to the laser machining device the data processing unit <NUM> calculates the normal range of the combination data D, based on the reference data items D201, D202, D203, D204, and so forth which are acquired in the reference data acquisition process in <FIG>, and causes the storage unit <NUM> to store the data indicating the normal range. Therefore, even in a case where a use environment or a use condition of the laser machining device <NUM> is changed, the correct inspection of the power measurement unit <NUM> can be performed by acquiring the reference data again and updating the data of the normal range.

Hitherto, Embodiment <NUM>, not covered by the present invention, has been described. However, the description is not limited to Embodiment <NUM> described above. For example, in Embodiment <NUM>, not covered by the present invention, described above, a case applied to the laser annealing device has been described as an example. However, the description is similarly applicable to various laser machining devices such as a laser drilling device and a laser welding device. In addition, in Embodiment <NUM> described above, a configuration has been described as follow. The wafer of the semiconductor element material is set as the workpiece. The workpiece for inspection has a pseudo-configuration formed of the same material as that of the actual workpiece. However, the workpiece for inspection may not be formed of the same material as that of the actual workpiece, and may be the workpiece manufactured exclusively for inspection. In this case, the workpiece may be called a laser irradiation workpiece for inspection. In addition, as described above, an example has been described where the power of the laser beam of the machining target position P200 is adjusted by adjusting the power of the laser beam source <NUM>. However, instead of adjusting the power of the laser beam source <NUM>, a configuration may be adopted in which the power of the laser beam of the machining target position P200 is adjusted by adjusting an attenuation factor of the laser beam in the optical system through which the laser beam passes. Alternatively, detailed portion described in Embodiment <NUM>, not covered by the present invention, can be appropriately modified.

According to these embodiments, during the machining process, it is possible to provide the laser machining device which can detect the measurement error in a case where the measurement error exceeds the allowable range in the power measurement unit.

In the related art, a laser machining device is known which carries out machining work for a workpiece by irradiating and heating a machining target position with a laser beam. The laser machining device includes a laser annealing device that performs annealing treatment on a surface portion of the workpiece by defining a wafer of a semiconductor element material as the workpiece and using the laser beam. PTL <NUM> (<CIT>) discloses a laser annealing device that includes a sensor for measuring energy of the laser beam and an attenuator capable of changing transmittance of the laser beam, and that controls the attenuator, based on a measurement value of the energy of the laser beam. PTL <NUM> (<CIT>) discloses a laser annealing device that includes a sensor for measuring a beam shape of the laser beam and an attenuator capable of changing the transmittance of the laser beam, and that controls the attenuator, based on intensity per unit area of the laser beam.

In the laser machining device that carries out machining work by irradiating and heating the machining target position with the laser beam, it is preferable to properly control the temperature of the machining target position when the machining target position is irradiated with the laser beam. According to the techniques respectively disclosed in PTL <NUM> and PTL <NUM>, the intensity of the laser beam is controlled to be constant. In this manner, the techniques aim to improve machining quality or machining safety of the machining target position.

However, through investigations, one has clearly found out the followings. Even in a case where the workpiece is irradiated with the laser beam having constant intensity, the temperature of the machining target position may not be uniform. For example, in a case of the laser annealing device that performs the annealing treatment on the workpiece by scanning the entire surface of the workpiece with the laser beam, even if the laser beam having the constant intensity is used for the scanning, the temperature in an edge portion of the workpiece having a folded scanning route is higher than the temperature of other portions. In addition, in a case where the beam shape of the laser beam is right-left asymmetry, when the scanning is performed leftward with the laser beam and when the scanning is performed rightward with the laser beam, a difference may occur in uneven temperature of the machining target position. In addition, in general, even if the workpiece is irradiated with the laser beam having the constant intensity, due to a state of the surface portion of the workpiece, the difference may occur in the temperature heated by the laser beam.

Embodiment <NUM>, not covered by the present invention, aims to provide a laser machining device which can properly control the heating temperature of the machining target position.

Subsequently, a laser machining device <NUM> according to Embodiment <NUM>, not covered by the present invention, will be described. <FIG> is a configuration diagram illustrating such laser machining device. In <FIG>, the optical axis of the laser beam is illustrated using a solid line or a two-dot chain line, the heat radiation is illustrated using a thick broken line, and the control line and the signal line of the measurement result are illustrated using a thin broken line.

This laser machining device <NUM> is a laser annealing device that performs the annealing treatment by defining the wafer of the semiconductor element material as a workpiece <NUM> and irradiating the workpiece <NUM> with the laser beam. The laser machining device <NUM> includes a control unit <NUM>, a laser beam source <NUM>, an attenuator <NUM> serving as a transmittance change unit, a scanning optical system <NUM> serving as a scanning unit, a dichroic mirror <NUM>, lenses <NUM> and <NUM>, a heat radiation measurement unit <NUM>, a stage <NUM>, a total reflection mirror <NUM>, and a power meter <NUM>.

For example, the laser beam source <NUM> is a solid laser such as a YAG laser or a gas laser such as a CO<NUM> laser, and outputs the laser beam with which the surface portion of the workpiece <NUM> is irradiated to a high temperature. The laser beam source <NUM> outputs a near infrared beam whose wavelength is at an upper limit of a visible light wavelength range, for example, such as the wavelength of <NUM>. The laser beam source <NUM> may be called a laser oscillator.

The attenuator <NUM> is a module which can change the light transmitting amount of the laser beam. The attenuator <NUM> changes reflectance or absorptivity of the laser beam, based on a control signal. In this manner, the attenuator <NUM> can continuously change the light transmitting amount of the laser beam.

For example, the scanning optical system <NUM> includes a galvano mirror, and can change the irradiation position of the laser beam, that is, a machining target position P300, in two directions along an upper surface of the stage <NUM>, for example.

The dichroic mirror <NUM> reflects the light having the output wavelength of the laser beam source <NUM>, and transmits the light in the infrared region including the heat radiation. A wavelength of the infrared region to be transmitted is <NUM> to <NUM>, for example. In the infrared region, a wavelength which is less absorbed by the workpiece <NUM> (for example, a single crystal wafer) is set.

For example, the lens <NUM> is an Fθ lens, and converges the laser beam to the machining target position. In addition, the lens <NUM> collects the heat radiation from the machining target position P300 of the workpiece.

The stage <NUM> holds the workpiece <NUM>, and is configured to be movable in two directions intersecting the optical axis of the laser beam. The stage <NUM> holds the total reflection mirror <NUM> at a location different from a region for holding the workpiece <NUM>.

The total reflection mirror <NUM> can be moved to the irradiation position of the laser beam (optical axis position of the laser beam emitted from the lens <NUM> for irradiation) by driving the stage <NUM>. The total reflection mirror <NUM> reflects the laser beam, and transmits the reflected laser beam to the power meter <NUM> at the irradiation position of the laser beam. In <FIG>, the optical axis of the laser beam when the total reflection mirror <NUM> is moved to the irradiation position of the laser beam is illustrated by a two-dot chain line.

The power meter <NUM> receives the laser beam so as to measure the power of the laser beam. The power means the energy per unit time of the laser beam.

The control unit <NUM> is a computer having a storage device for storing a program, a central processing unit (CPU) for executing the program, a working memory, an I/O for inputting and outputting the control signal and the detection signal, and various functional circuits. The control unit <NUM> performs drive control of the laser beam source <NUM>, drive control of the scanning optical system <NUM>, and drive control of the attenuator <NUM>. Furthermore, the control unit <NUM> inputs the measurement value of the heat radiation measurement unit <NUM> and the measurement value of the power meter <NUM>. The control unit <NUM> corresponds to an example of the determination unit , and determines a state of the attenuator <NUM>, based on the measurement value of the heat radiation measurement unit <NUM> and the measurement value of the power meter <NUM>.

<FIG> is a block diagram illustrating a partial internal configuration of the control unit.

The control unit <NUM> further has a target value setting unit <NUM> and a feedback control unit <NUM>.

The target value setting unit <NUM> calculates a target value of the heat radiation to be discharged from the workpiece during the machining process. For example, the target value of the heat radiation is set to a constant value corresponding to an ideal heating temperature of the workpiece. Alternatively, in a case where the ideal heating temperature differs depending on the scanning position, the target value of the heat radiation may be set to a value which is changed in accordance with the scanning position. The ideal heating temperature may be included in the machining data input from the user to the control unit <NUM>. The target value setting unit <NUM> may calculate the ideal heating temperature, based on various parameters included in the machining data. The machining data is data for defining a place and a method of irradiating the workpiece with the laser beam, and is prepared by the user. The target value setting unit <NUM> outputs the target value to the feedback control unit <NUM> in a scanning period in which the workpiece is irradiated with the laser beam.

The feedback control unit <NUM> inputs the target value set by the target value setting unit <NUM> and the measurement value of the heat radiation measurement unit <NUM>. The feedback control unit <NUM> performs a feedback process so as to reduce a difference between the input target value and the measurement value, based on the difference, and generates an attenuator control signal. The attenuator control signal is transmitted to the attenuator <NUM> so as to control the amount of the laser beam transmitted through the attenuator <NUM>. The feedback control unit <NUM> may be configured to generate the attenuator control signal by performing proportional-integral-differential (PID) control.

According to the laser machining device <NUM> configured as described above, first, the output adjustment of the laser beam source <NUM> is performed in a front stage of the annealing treatment of the workpiece <NUM>. When the output adjustment is performed, the stage <NUM> moves so that the total reflection mirror <NUM> is located at the irradiation position of the laser beam, and the attenuator <NUM> is controlled to have predetermined transmittance (for example, <NUM>%). Then, the control unit <NUM> emits the laser beam from the laser beam source <NUM>, and inputs the measurement value of the power meter <NUM>. In this manner, the output of the laser beam source <NUM> is adjusted so that the power of the laser beam has a set value.

Subsequently, the annealing treatment of the workpiece <NUM> starts in a state where the workpiece <NUM> held by the stage <NUM> is located at the irradiation position of the laser beam. In the annealing treatment, the laser beam is emitted from the laser beam source <NUM> under the control of the control unit <NUM>. Then, the machining target position P300 of the workpiece <NUM> is irradiated with the laser beam passing through the attenuator <NUM>, the scanning optical system <NUM>, the dichroic mirror <NUM>, and the lens <NUM>. When the machining target position P300 is irradiated with the laser beam, the machining target position P300 of the workpiece <NUM> is heated, and the heat radiation is discharged from the machining target position P300. The heat radiation is transferred to the heat radiation measurement unit <NUM> by way of the lens <NUM>, the dichroic mirror <NUM>, and the lens <NUM>, and the heat radiation measurement unit <NUM> measures the amount of the heat radiation. The control unit <NUM> controls the scanning optical system <NUM> while continuously driving the laser beam source <NUM>, and changes the irradiation position of the laser beam along the scanning route set in the machining data.

While the laser beam source <NUM> is continuously driven, the feedback control unit <NUM> inputs the measurement value of the heat radiation measurement unit <NUM> and the target value set by the target value setting unit <NUM>, and generates the attenuator control signal so as to reduce a difference therebetween. Then, the transmission amount of the laser beam passing through the attenuator <NUM> is controlled using the attenuator control signal. In this manner, the power of the laser beam used in irradiating the machining target position P300 is adjusted, and the heating temperature of the machining target position P300 is controlled to be close to the ideal temperature set in advance.

Here, description will be made on the amount of the heat radiation discharged from the workpiece <NUM> in a case where the annealing treatment is performed without performing the control in this way.

<FIG> illustrate an example of the temperature distribution measured when the surface portion of the wafer is scanned with the laser beam having the constant intensity. <FIG> is a view illustrating the overall wafer, and <FIG> is an enlarged view illustrating a range C. <FIG> illustrate a high temperature and a low temperature by using gray shades. The darker one represents the low temperature. An example illustrated in <FIG> shows the following case. A scanning route L301 extends in an X-direction, a plurality of the scanning routes L301 are juxtaposed with each other in a Y-direction, and the scanning using the laser beam is performed along the scanning routes L301. The irradiation position of the laser beam is folded back in an edge portion of the respective scanning routes L301, and moves to the adjacent scanning route L301 so that a scanning direction is reversed in the two adjacent scanning routes L301.

In this scanning pattern, even if the intensity of the laser beam is constant, as illustrated in <FIG>, the edge portion of the workpiece <NUM> has a higher temperature than the central portion. The reason is as follows. As illustrated in <FIG>, in the edge portion of the workpiece <NUM>, the scanning using the laser beam is performed from the center toward the end. Thereafter, while the heat remains in a periphery thereof, the scanning using the laser beam is performed from the end toward the center along the adjacent scanning route L301. That is, the reason is considered that the heat of the laser beam is added to the residual heat.

<FIG> illustrates a graph of the measurement values of the heat radiation corresponding to three scanning patterns. Out of the three scanning patterns in <FIG>, <FIG> is a view for describing the scanning pattern of "Plus", <FIG> is a view for describing the scanning pattern of "Minus", and <FIG> is a view for describing the scanning pattern of "Raster". In each graph in <FIG>, a vertical axis represents a sensor voltage of the heat radiation measurement unit <NUM>, and a horizontal axis represents a measurement number. The measurement number is a serial number added to each measurement value in time series. Three graph lines in <FIG> represent the measurement values measured using the scanning patterns in <FIG>.

The example in <FIG> described above corresponds to the example when the scanning pattern in <FIG> is applied. If the measurement values of the heat radiation in this case are juxtaposed with each other in time series, the graph of "Raster" in <FIG> is obtained. Dropped locations n301 to n303 in <FIG> indicate times at which one linear scanning route L301 is switched to an adjacent linear scanning route L301. From the graph of "Raster" in <FIG>, it can be understood that the heat radiation becomes higher immediately after the scanning route L301 is folded back.

In addition, as illustrated in <FIG>, even in a case of the scanning pattern in one direction ("Plus") or the scanning pattern in the reverse direction ("Minus"), if the intensity of the laser beam is constant, the amount of the heat radiation is not uniform as illustrated in <FIG>. Furthermore, from the graph in <FIG>, it can be understood that there is a difference in appearance forms of the heat radiation between the scanning in one direction and the scanning in the reverse direction. The reason is considered as follows. The beam shapes of the laser beams are not perfectly symmetrical between one side and the other side along the scanning direction. Depending on the scanning direction of the laser beam, a difference occurs in temporal change patterns of the intensity of the laser beams used in irradiating the same point. The beam shape means the intensity distribution inside the spot of the laser beam, and is also called a beam profile.

In this way, in a case where the annealing treatment is performed using the laser beam having constant power, the heating temperature of the surface portion of the workpiece is not uniform depending on the scanning pattern or the scanning direction.

On the other hand, according to the laser machining device <NUM> of Embodiment <NUM>, the light quantity of the laser beam used in irradiating the machining target position P300 is controlled under the feedback control based on the measurement value of the heat radiation so that the measurement value of the heat radiation is close to the target value. In this manner, the non-uniform heating temperatures of the surface portion of the workpiece as illustrated in <FIG> and <FIG> are reduced. For example, a proper heating process can be realized so that the heating temperatures of the respective portions can be approximately uniform.

As described above, according to the laser machining device <NUM>, the heating process can be performed on the machining target position P300 of the workpiece <NUM> to have the proper temperature under the control of the attenuator <NUM>, based on the measurement value of the heat radiation. In this manner, the annealing treatment can be performed at the proper heating temperature, for example, so that the respective portions of the surface portion of the workpiece <NUM> can have the uniform heating temperature.

In addition, according to the laser machining device <NUM>, the feedback control unit <NUM> controls the attenuator <NUM>, based on the difference between the target value and the measurement value of the heat radiation. Accordingly, the heating temperature can be easily set and changed by defining the target value.

Hitherto, Embodiment <NUM>, not covered by the present invention, has been described. However, the description is not limited to the aspects described above. For example, in Embodiment <NUM>, not covered by the present invention, described above, a configuration in which the description is applied to the laser annealing device has been described as an example. However, the description is similarly applicable to a laser welding device or a laser soldering device which performs welding or soldering by irradiating the workpiece with the laser beam. Furthermore, the description is also applicable to a laser drilling device which forms a hole in a substrate by irradiating the substrate with the laser beam. For example, the laser drilling device forms the hole by irradiating one location multiple times with a pulse of the laser beam. However, based on the amount of heat radiation measured when the pulse of the first laser beam is output, it is possible to control the transmission amount of the second and subsequent laser beams. In a case where the heating amount obtained by the laser beam deviates from a proper value depending on the position of the substrate for forming the hole, the heating amount obtained by the second and subsequent laser beams can have the proper value under this control. In this manner, the respective holes can be formed to have uniform quality.

In addition, in Embodiment <NUM>, not covered by the present invention, described above, the scanning optical system <NUM> which changes the irradiation position of the laser beam has been described as the scanning unit. However, the scanning unit may be configured to change the position irradiated with the laser beam by moving the workpiece <NUM>. Alternatively, detailed portions described in the embodiments can be appropriately modified.

According to the features disclosed in Embodiment <NUM>, not covered by the present invention, an advantageous effect is achieved in that the heating temperature of the machining target position can be properly controlled.

Claim 1:
A laser machining device (<NUM>, <NUM>, <NUM>) comprising:
a scanning unit (<NUM>, <NUM>, <NUM>) that changes an irradiation position of a workpiece irradiated with a laser beam;
a heat radiation measurement unit (<NUM>, <NUM>, <NUM>) that measures intensity of heat radiation of the workpiece irradiated with the laser beam; and
a control unit (<NUM>, <NUM>, <NUM>) that includes a determination unit (<NUM>, <NUM>) and a display unit (<NUM>) and controls the scanning unit (<NUM>, <NUM>, <NUM>),
characterized in that the control unit (<NUM>, <NUM>, <NUM>) is configured to achieve the following:
in a first abnormality determination process, comparing a measurement value of the heat radiation at each scanning position with one or both of an upper limit threshold and a lower limit threshold for identifying an abnormality and then determining the scanning position having the measurement value beyond the upper limit threshold or the scanning position having the measurement value below the lower limit threshold, as an abnormal location,
in a second abnormality determination process, comparing the measurement value obtained at a first position of the workpiece with the measurement value obtained at a position in a vicinity of the first position,
in a third abnormality determination process, two-dimensionally arranging a series of data items of the measurement values of the heat radiation in accordance with the scanning positions and comparing the measurement value obtained at each scanning position with the measurement value obtained at the position in the vicinity thereof, based on the data of the measurement value of the heat radiation which is associated with the position in an X-Y coordinate, and
in a fourth abnormality determination process, analyzing a distribution of the measurement values on the X-Y coordinate, based on the data of the measurement values of the heat radiation which are developed on the X-Y coordinate and then analyzing whether or not a distribution of a measurement value has a predetermined characteristic and determining a pattern of a warpage of the workpiece, a position of the warpage, or a size of the warpage, based on a result of the analysis, and outputting the abnormality when existing, or when no abnormality exists, completing a machining process.