JP2024075632A - Laser beam irradiation device that can adjust processing depth with incident angle - Google Patents

Abstract

To provide a laser beam irradiation device for semiconductor processing which includes: a laser beam output unit that outputs, onto the surface of a semiconductor, a laser beam with an incident angle that is set with respect to a processing direction by depth of penetration into a semiconductor substrate; and a focusing lens that forms an image of a laser spot moving in the processing direction and vibrating in the vibration direction on the semiconductor, and in which the depth of penetration into the semiconductor substrate varies depending on the incident angle of the laser beam with respect to the processing direction.SELECTED DRAWING: Figure 1

Description

The technical idea of this disclosure relates to a laser beam irradiation device and its operating method for completely cutting semiconductors, and more specifically, to a laser beam irradiation device and its operating method for preventing optical damage to semiconductor elements.

Due to rapid developments in the electronics industry and user demands, electronic devices are becoming smaller, more highly integrated, and larger in area. As a result, the size of the semiconductor elements contained in electronic devices is now approaching the nanometer range.

Semiconductor processing methods related to this disclosure include a dicing process, which is a type of cutting process that cuts and separates a large-area wafer into multiple chips, a grinding process that reduces the thickness of the wafer, and a grooving process that creates grooves for forming conductive wiring.

In relation to the dicing process, blade dicing is used, which is a method of cutting a substrate using a thin cutting blade made of fine diamond. However, in the process of cutting a substrate using a cutting blade, chipping occurs on the front and back surfaces of the substrate, and this chipping can reduce the performance of the separated chips.

Stealth dicing, another dicing process, focuses laser light on a localized area to create internal cracks for cutting. However, because the laser light used in stealth dicing has an extremely high peak power, the process of creating internal cracks can also cause cracks on the semiconductor surface, which can lead to a decrease in chip performance.

The problem that the technical idea of the present disclosure aims to solve is to provide a laser beam irradiation device for semiconductor processing and an operating method thereof that can improve chip performance by oscillating the laser beam to reduce the accumulation of thermal energy due to laser focusing.

In order to achieve the above-mentioned object, a laser beam irradiation device for semiconductor processing according to one aspect of the technical idea of the present disclosure may include a laser beam output unit that advances a laser beam in a processing direction to perform semiconductor processing, and oscillates the laser beam to have a constant amplitude in a vibration direction different from the processing direction, and a focusing lens that images the laser spot that advances in the processing direction and oscillates in the vibration direction on the semiconductor.

The laser beam output unit can output a first laser to the semiconductor along the processing direction in one processing run, and output a second laser having an incident angle different from that of the first laser along the processing direction.

The laser beam output unit may include a first laser beam output unit that outputs the first laser and a second laser beam output unit that outputs the second laser that forms a cut surface on the semiconductor in order to perform pre-processing for cutting the semiconductor with good processing quality.

Meanwhile, the laser beam output unit may further include a laser oscillator that oscillates and outputs a laser beam, and a vibration unit that physically vibrates an optical element so as to vibrate the laser beam irradiated from the laser oscillator in the vibration direction.

In addition, the laser oscillator and the focusing lens are fixed without vibration, and the optical element can be rotated in simple harmonic motion by the driving force of the motor of the vibration unit.

The optical element may also include a horizontal mirror, and the motor may be at least one of an ultrasonic motor and a resonant motor.

The device may also include an input unit that receives operation commands for semiconductor processing, and a control unit that controls the vibration unit to apply a sine wave input to the motor in a first mode and apply a triangular wave or square wave to the motor in a second mode based on the operation commands.

The first mode may be a user mode selected by a user who assigns a priority to the vibration speed of the laser beam, and the second mode may be a user mode selected by a user who assigns a priority to the vibration amplitude of the laser beam.

On the other hand, the optical element includes a pair of polygon mirrors, each of which has a number of reflective surfaces, and each of the pair of polygon mirrors can rotate in different directions.

The semiconductor includes a semiconductor substrate, and the focusing lens can output the laser beam so that the laser beam has a predetermined angle of incidence perpendicular to the plane of the semiconductor.

The incident angle is substantially a right angle, and the laser beam output unit can vibrate the laser beam by an amplitude in the vibration direction corresponding to a distance determined by the line width of the semiconductor substrate.

In accordance with an exemplary embodiment of the present disclosure, unlike stealth dicing, the thermal energy is dispersed by oscillating the laser beam rather than accumulating in a small localized area, thereby preventing damage and deformation of the semiconductor material.

According to an exemplary embodiment of the present disclosure, the quality of the irradiated object and the mass-produced product using the same can be ensured through pre-processing using a leading laser, and mass-produced quality can be achieved through complete cutting using a trailing laser.

According to an exemplary embodiment of the present disclosure, semiconductor processing can be performed precisely by easily determining processing parameters (e.g., line width) using the diameter of the laser spot adjusted by the lens, thereby reducing the defect rate and increasing the yield.

According to an exemplary embodiment of the present disclosure, a vibrating laser beam can be used to pump out ejections (e.g., dust, particles, and debris) that are generated during the semiconductor processing process, thereby increasing process yield.

According to an exemplary embodiment of the present disclosure, the angle of incidence of the oscillating laser beam can be adjusted to be acute, right or obtuse to obtain a customized result that meets the producer's needs.

FIG. 1 is a conceptual diagram for explaining a laser beam irradiation device according to an exemplary embodiment of the present disclosure. 1 is a diagram for explaining a processing method using a laser beam irradiation device 10 according to an exemplary embodiment of the present disclosure. 1 is a diagram for explaining a processing method using a laser beam irradiation device 10 according to an exemplary embodiment of the present disclosure. This is to illustrate conventional blade dicing and stealth dicing. 1 is a diagram illustrating a method of vibrating a laser beam according to an exemplary embodiment of the present disclosure. 1 is a diagram illustrating a vibration method, a focusing lens, and a processing method of a laser beam irradiation device according to an exemplary embodiment of the present disclosure. 1 is a diagram for explaining mirror vibration among vibration methods according to an exemplary embodiment of the present disclosure. 1 is a diagram for explaining polygon vibration among vibration methods according to an exemplary embodiment of the present disclosure. 1 is a diagram illustrating a light source vibration method according to an exemplary embodiment of the present disclosure. 1 is a diagram illustrating a focusing lens according to an exemplary embodiment of the present disclosure; 10 is a diagram for explaining a vibration direction and a processing direction determined by a processing method according to an exemplary embodiment of the present disclosure. 1 is for illustrating the processing direction and incidence angle according to an exemplary embodiment of the present disclosure. 1 is an electron microscope image for explaining the quality of a semiconductor processing result according to an exemplary embodiment of the present disclosure together with a comparative example. 1 is an electron microscope image for explaining the quality of a semiconductor processing result according to an exemplary embodiment of the present disclosure together with a comparative example.

The following describes in detail an embodiment of the present invention with reference to the attached drawings.

Figure 1 is a conceptual diagram illustrating a laser beam irradiation device 10 according to an exemplary embodiment of the present disclosure.

Referring to FIG. 1, the laser beam irradiation device 10 may include an input unit 100, a control unit 200, a laser beam output unit 300, and a focusing lens 400. The laser beam output unit 300 may further include a laser oscillation unit 310, a vibration unit 320, and an optical element 330.

The laser beam irradiation device 10 can image a laser spot LS on the irradiated object ST by outputting a laser beam.

The irradiated object ST may include a semiconductor substrate and a wafer. For ease of explanation, the irradiated object ST may hereinafter be explained together with a semiconductor, a semiconductor substrate, or a semiconductor wafer. In this case, the substrate may be processed in various ways by the thermal energy of the laser beam, and the various methods may include a dicing process in which the laser beam irradiation device 10 cuts and separates a large-area wafer into a plurality of chips, a grinding process in which the thickness of the wafer is reduced, and a grooving process in which a groove is made for forming a conductive wiring.

The irradiated object ST may also include a semiconductor film (e.g., an oxide film). For example, the laser beam irradiation device 10 may anneal the semiconductor film.

In the following, "processing" may refer to a process in which the laser beam of the laser beam irradiation device 10 causes physical deformation in the irradiated object ST, and the technical idea of the present disclosure is not limited to the examples described above.

According to an exemplary embodiment of the present disclosure, the laser beam application device 10 can oscillate the laser beam to reduce the accumulation of thermal energy focused by the laser spot LS.

Specifically, the laser beam irradiation device 10 can advance the laser beam in the processing direction to process the irradiated object ST. At the same time, the laser beam irradiation device 10 can vibrate the laser beam to have a certain amplitude (processing amplitude) in a vibration direction different from the processing direction. This makes it possible to reduce the defect rate of the irradiated object ST by vibrating with the second laser spot LS2 before the irradiated object ST is deformed due to excessive accumulation of thermal energy in the first laser spot LS1.

Meanwhile, as described later in FIG. 3, the laser beam irradiating device 10 can vibrate the laser beam with a constant amplitude in the same vibration direction as the processing direction. By using a laser beam with the same vibration direction as the processing direction, the laser beam irradiating device 10 can pump or clean up ejections (e.g., dust, particles, debris) generated during the processing of the irradiated object ST out of the processing area based on the vibrating laser. This makes it possible to prevent a decrease in yield due to the ejections.

The input unit 100 can receive an operation command from a user. As an example, the operation command can include an instruction for the user to determine the line width to be engraved into the irradiated object ST, and as another example, the operation command can include an instruction to control the speed at which the irradiated object ST is processed.

The input unit 100 allows a user to select one of a first mode and a second mode. The first mode may be a user mode in which a priority is assigned to the vibration speed of the laser beam, and the second mode may be a user mode in which a priority is assigned to the vibration amplitude of the laser beam. The processing methods in the first mode and the second mode will be described later together with the control unit 200.

Meanwhile, the input unit 100 may be implemented as a device (e.g., a keyboard) or software (input user interface) that can receive a user's operation command and transmit it to the control unit 200. Alternatively, the input unit 100 may be an input interface of an operating system (O/S). Without being limited thereto, the input unit 100 may include various types of hardware, software or firmware type input means.

The control unit 200 can output an oscillation signal SO to control the laser oscillation unit 310.

The laser oscillator 310 may include any type of oscillator capable of processing the irradiated object ST, which may be a semiconductor device or semiconductor component, or may be a component included therein. For example, the laser oscillator 310 may include a laser with an output ranging from several hundred watts to several hundred kilowatts. The oscillation signal SO may control the overall operation of the laser oscillator 310.

The control unit 200 can output a vibration signal SV to control the vibration unit 320. The vibration signal SV can include information about a vibration amplitude, a vibration speed, and an input waveform. For example, the vibration unit 320 can include a resonance motor. Hereinafter, a resonance motor can refer to a driving device in which an oscillator resonates and vibrates, and can have a higher vibration frequency than a galvo motor.

The control unit 200 can apply different input waveforms to the vibration unit 320 based on a plurality of user modes including a first mode and a second mode. Here, the input waveform can include the waveform of an electrical signal applied to drive a motor.

The control unit 200 can output a vibration signal SV that applies a sine wave input to the motor of the vibration unit 320 in the first mode based on an operation command. The motor to which the sine wave input is applied can maximize the vibration speed of the laser beam. That is, the accuracy of the vibration amplitude is lower than in the second mode, but the maximum vibration speed (frequency) at which the laser beam can vibrate can be further increased.

In addition, the control unit 200 can output a vibration signal SV to apply a triangular wave or a square wave to the motor of the vibration unit 320 in the second mode based on the operation command. A motor to which a triangular wave or square wave input is applied can precisely determine the vibration amplitude. That is, the vibration speed is lower than in the first mode, but the laser beam can vibrate at a amplitude closer to the target vibration amplitude.

The laser beam output unit 300 may include a laser oscillation unit 310 that oscillates and outputs a laser beam. The laser oscillation unit 310 outputs the oscillated laser to the optical element 330 to process the irradiated object ST. The vibration unit 320 can vibrate the optical element 330 so as to vibrate the laser beam irradiated from the laser oscillation unit 310 in the vibration direction. This is to vibrate the laser beam input to the focusing lens 400.

As an example, the irradiated laser beam may be a single ray, and as another example, the laser beam irradiating device 10 may output multiple laser beams. When multiple laser beams are output, the laser oscillator 310 may include multiple oscillation modules for outputting multiple laser beams.

In the process of vibrating the laser beam, only a portion of the components of the laser beam output unit 300 can vibrate. In other words, the laser oscillation unit 310 and the focusing lens 400 are fixed without vibration, and the optical element 330 can vibrate in simple harmonic motion due to the driving force of the motor of the vibration unit 320. Compared to vibrating the laser oscillation unit 310 and the focusing lens 400, the processing of the irradiated object ST can be performed more precisely and heat accumulation can be prevented.

The vibration unit 320 can determine the vibration amplitude and vibration speed of the optical element 330. For example, the motor of the vibration unit 320 can be mechanically connected directly or indirectly to the optical element 330. The optical element 330 outputs the laser beam output from the laser oscillation unit 310 to the focusing lens 400, so the vibration unit 320 can determine the vibration amplitude and vibration speed of the laser beam by controlling the optical element 330.

The optical element 330 may include a mirror. That is, the optical element 330 may reflect the laser beam output from the laser oscillation unit 310 and output it to the focusing lens 400. The vibration unit 320 may be at least one of an ultrasonic motor and a resonance motor. This is because a general motor using electromagnetic force cannot achieve the technical idea of the present disclosure to prevent excessive accumulation of thermal energy applied to the irradiated object ST.

The focusing lens 400 can output the laser beam so that the laser beam has a predetermined angle of incidence in a direction perpendicular to the plane of the irradiated object ST. The predetermined angle of incidence can be 0 degrees or more and 90 degrees or less.

The focusing lens 400 may be an objective lens, a short focal length lens, or an F-theta lens. The focusing lens 400 may be selected from among an objective lens, a short focal length lens, and an F-theta lens depending on the processing method and the user's requirements. This will be described later.

The laser beam irradiation device 10 according to the exemplary embodiment of the present disclosure can improve processing quality and speed by vibrating quickly in a vibration direction different from the processing direction. In comparison, conventional technology has the disadvantage of reducing processing quality and speed.

Figures 2a and 2b are intended to explain a processing method using a laser beam irradiation device 10 according to an exemplary embodiment of the present disclosure.

Referring to FIG. 2a and FIG. 2b, the laser beam irradiation device 10 may include a first laser beam output unit 300a and a second laser beam output unit 300b, each of which may correspond to the laser beam output unit 300 described above in FIG. 1. Meanwhile, the laser beam irradiation device 10 may include a first focusing lens 400a and a second focusing lens 400b, each of which may correspond to the focusing lens 400 described above in FIG. 1.

According to an exemplary embodiment of the present disclosure, the laser beam irradiation device 10 can output a first laser to the workpiece ST along the processing direction in one processing run, and output a second laser having an incident angle different from that of the first laser along the processing direction.

According to an exemplary embodiment of the present disclosure, the second laser beam output unit 300b can output a second laser for cutting the irradiated object ST. For example, the second laser can form a cutting surface on the irradiated object ST. The first laser beam output unit 300a can output a first laser for performing pre-processing for cutting the irradiated object ST with mass production quality. Here, the mass production quality may refer to the target quality that the processing entity aims to achieve, and may include, for example, cross-sectional uniformity, cutting speed, cutting size, line width, etc. Also, for example, when the irradiated object ST is a wafer, the first laser beam output unit 300a can output a first laser for the purpose of removing compounds on the semiconductor surface.

According to an exemplary embodiment of the present disclosure, the second laser beam output unit 300b can output a second laser along the path along which the first laser beam output unit 300a performed pre-processing. That is, the second laser beam output unit 300b can process (e.g., cut) the irradiated object ST in the area prepared for processing by the first laser beam output unit 300a. In this sense, the first laser can be referred to as a leading laser, and the second laser can be referred to as a trailing laser.

According to an exemplary embodiment of the present disclosure, the first laser beam output unit 300a can output a laser having a lower wavelength than the second laser beam output unit 300b. Experiments have shown that when the first laser beam output unit 300a outputs a first laser beam having a wavelength of 515 nm to 532 nm or a wavelength of 266 nm to 355 nm, the surface of the irradiated object ST can be modified without protrusions. This is because materials on the semiconductor wafer surface, such as metals, ceramics, and compounds, are materials that easily absorb the first laser beam of the aforementioned wavelengths.

According to an exemplary embodiment of the present disclosure, the first laser beam output unit 300a may have a higher intensity but a lower average power than the second laser beam output unit 300b. Experiments have shown that if the average power of the leading laser output from the first laser beam output unit 300a is high, the irradiated object ST may be processed to an excessive depth. This is because it may be an obstacle to ensuring processing quality when the second laser beam output unit 300b actually performs processing (e.g., cutting). Therefore, the first laser (i.e., the leading laser) may have a higher intensity but a lower average power than the second laser (i.e., the trailing laser).

Referring to FIG. 2a, the first laser beam output unit 300a can output a first laser to the irradiated object ST in a vertical direction of the irradiated object ST, and the second laser beam output unit 300b can output a second laser to have a first angle with respect to the processing direction. Here, the first angle θa can be greater than 90 degrees and less than 180 degrees.

In addition, the first laser beam output unit 300a can output a first laser in the vertical direction of the irradiated object ST along the processing direction without any vibration motion, and the second laser beam output unit 300b can output a second laser that vibrates in the processing direction.

Referring to FIG. 2b, the first laser beam output unit 300a can output the first laser to have a second angle θb with respect to the processing direction. Here, the second angle θb can be greater than 0 degrees and less than 90 degrees. In the case of an irradiated object ST that is sensitive and fragile to the laser beam, the quality of processing the irradiated object ST by the second laser beam output unit 300b can be further improved by outputting the first laser at an acute incidence angle. In addition, compared to the first laser having a vertical incidence angle, the first laser having an acute incidence angle can obtain target processing quality even if it is output to the irradiated object ST with a higher output. Therefore, surface removal and depth processing can be more easily performed at once with more energy.

Also, unlike what has been described above in FIG. 2a, the first laser beam output unit 300a can output a first laser that has a vibration motion, i.e., vibrates along the processing direction. For example, when a vibration is applied to the first laser, more effective and rapid processing (e.g., cutting) can be performed in that cutting processing is performed using both the first and second lasers when processing an irradiated object ST made of a thick material. However, without being limited thereto, the first laser beam output unit 300a can output a first laser that does not vibrate while having the second angle θb.

2a and 2b, full cutting of the irradiated object ST (e.g., a semiconductor wafer) can be achieved through the continuous cutting operation of the leading laser (i.e., the first laser) and the trailing laser (i.e., the second laser). In other words, in the past, when attempting to completely cut the irradiated object with a single laser, mass production quality could not be achieved due to excessive laser beam output (e.g., FIG. 12(a) and FIG. 13(a)). However, according to an exemplary embodiment of the present disclosure, the quality of the irradiated object ST and the mass production result using the same can be ensured through pre-processing by the leading laser, and mass production quality can be achieved by full cutting by the trailing laser. In addition, by using the leading laser and the trailing laser, the output of each laser can be reduced, thereby preventing heat accumulation in the irradiated object ST and preventing material deformation of the irradiated object ST.

Figure 3 is intended to explain conventional blade dicing and stealth dicing.

Referring to FIG. 3(a), the blade dicing device rapidly rotates a thin cutting blade made of fine diamond. In other words, the blade dicing device cuts the target object using a saw blade formed on the cutting blade.

During this process, the cutting blade may peel off the cut surface of the front or back surface of the substrate where the blade is located while cutting the target object (e.g., substrate). Also, chipping may occur in the substrate while the target object is being peeled off. This can be a major factor in reducing the performance of the chips that are separated after dicing is completed.

However, the laser beam irradiation method does not cause the above-mentioned performance degradation factors because it irradiates a high-output laser beam to a localized area.

On the other hand, referring to FIG. 3(b), a stealth dicing device can focus a laser beam on a localized area of an object to form internal cracks for cutting. The object can be separated along the cracks formed in a certain pattern. During the separation process, the cut surface of the area adjacent to the cracks can be irregular. In addition, because the stealth dicing laser beam has an extremely high peak power, undesirable cracks can be generated on the semiconductor surface, which can lead to a decrease in chip performance.

However, according to an exemplary embodiment of the present disclosure, the irradiated object ST is entirely cut using a laser beam, and therefore, unlike stealth dicing, a separate peeling process is not required, and thus factors that degrade performance can be eliminated. In addition, even if a high peak power is used like stealth dicing, the time that the laser remains in a specific area can be dramatically reduced by vibration compared to stealth dicing, and deformation of the irradiated object ST due to accumulation of thermal energy can be prevented.

Figure 4 is intended to explain a method of vibrating a laser beam according to an exemplary embodiment of the present disclosure. Below, the method will be explained in chronological order in the order of (a) to (c) in Figure 4.

Referring to (a) to (c) of FIG. 4, the laser beam irradiation device 10 can output the laser beam LB3 at different positions of the focusing lens 400 by vibrating the laser beam LB3. For convenience of explanation, different reference symbols are given to the laser beams LB31 to LB33 in the first, second, and third phases, but they may be one laser beam output from the same laser oscillator 310. However, without being limited thereto, the laser beams LB31 to LB33 may be laser beams generated by different oscillators.

In chronological order, the laser beam irradiation device 10 first outputs a laser beam LB31 to the edge region of the focusing lens 400. Then, due to vibration, the laser beam irradiation device 10 outputs a laser beam LB32 to the central region of the focusing lens 400. Then, due to vibration, the laser beam irradiation device 10 outputs a laser beam LB33 to the edge region opposite the edge region at the first phase.

The laser beam irradiation device 10 can form a laser spot LS on each of the different regions a1 to a3 of the irradiated object ST. The laser beam irradiation device 10 can process each of the regions a1 to a3 that are not far apart in the x-axis direction, but are spaced apart by a vibration distance (processing width, line width) in the y-axis direction. Here, the vibration distance can correspond to the line width of the conductor. In other words, the laser beam irradiation device 10 can vibrate by the line width in the y-axis direction.

According to an exemplary embodiment of the present disclosure, the laser beam application device 10 can oscillate the laser beam LB3 so that the laser spot LS remains in a localized area (e.g., a1) only for a period of time during which no material deformation occurs according to a preset quality standard.

As an example, the control unit 200 may transmit the vibration signal SV so that the vibration unit 320 has at least one of a vibration speed greater than 0 and less than or equal to 20 kHz. In this case, when the control unit 200 outputs a vibration signal SV having a vibration speed equal to or greater than 1 kHz, the vibration unit 320 may be embodied as one of an ultrasonic motor and a resonant motor.

As another example, the control unit 200 can transmit the vibration signal SV so that the vibration unit 320 has at least one vibration speed greater than 0 and less than or equal to 10 MHz.

According to one embodiment, the laser beam irradiation device 10 receives an input through the input unit 100 that the irradiated object ST is a wafer made of a first material, and the control unit 200 transmits a vibration signal SV including a first frequency, thereby controlling the laser spot LS to remain in a localized area (e.g., a1) for a time corresponding to the first frequency.

Figure 5 is intended to explain the vibration method, focusing lens, and processing method of a laser beam irradiation device according to an exemplary embodiment of the present disclosure.

According to one embodiment of the present disclosure, the laser beam irradiation device 10 can form a cutting surface having a width equal to the vibration distance in the y-axis direction by using the oscillating laser beam LB4 that passes through the focusing lens 400. In other words, the laser beam irradiation device 10 can perform a dicing process.

According to another embodiment of the present disclosure, the laser beam irradiation device 10 can form a groove having a width equal to the vibration distance in the y-axis direction. That is, the laser beam irradiation device 10 can perform a grooving process.

According to yet another embodiment of the present disclosure, the laser beam irradiation device 10 can perform the grinding process by vibrating the laser beam LB4 significantly in the y-axis direction.

Below, the vibration method of the laser beam irradiation device 10 will be explained with reference to Figures 6 to 8, and the mirror vibration, polygon vibration, and light source vibration will be explained.

The focusing lens 400 will be explained with reference to FIG. 9, and the cases of an objective lens, a short focal length lens, and an F-theta lens will be described.

Figure 6 is intended to explain mirror vibration, one of the vibration methods according to an exemplary embodiment of the present disclosure.

Referring to FIG. 6, the vibration unit 320 may include a motor 321, which may be at least one of an ultrasonic motor and a resonant motor. In addition, the optical element 330 may include a horizontal mirror 331.

According to an exemplary embodiment of the present disclosure, the horizontal mirror 331 is mechanically connected to the motor 321, and the driving force of the motor 321 is transmitted to the mirror, so that the horizontal mirror 331 can vibrate in a simple harmonic motion. At this time, the frequency of the simple harmonic motion can be substantially the same as the vibration speed at which the laser beam irradiation device 10 vibrates in a vibration direction different from the processing direction.

According to an exemplary embodiment of the present disclosure, the optical element 330 can vibrate in a direction parallel to the focusing lens 400. Accordingly, the laser beam can vibrate back and forth between points that are symmetrical with respect to the origin, with the center point of the focusing lens 400 as the reference point.

According to an exemplary embodiment of the present disclosure, the optical element 330 may vibrate in a direction in which the laser output from the laser oscillator 310 is incident on the optical element 330. In this case, the optical element 330 may be a plane mirror that reflects the laser output from the laser oscillator 310 to the focusing lens 400.

According to an exemplary embodiment of the present disclosure, the motor 321 may be a vibration motor, such as an ultrasonic motor or a resonant motor. The vibration motor may generate high frequency vibrations inside the motor 321 to generate a driving force. The high frequency driving force may be transmitted to the horizontal mirror 331, which is structurally directly or indirectly coupled to the motor 321, through a transmission part of the motor 321.

Preferably, the motor 321 can generate a vibration frequency equal to or greater than 1 kHz and equal to or less than 20 kHz. That is, at least one of the ultrasonic motor and the resonant motor vibrates the laser beam at a frequency equal to or greater than 1 kHz and equal to or less than 20 kHz, so that the vibrating laser beam can pump out the ejection material (e.g., dust, particles, debris) generated during the semiconductor processing process, thereby increasing the process yield. A commonly used linear actuator motor cannot achieve the effect of the exemplary embodiment of the present disclosure due to a low vibration frequency of less than 1 kHz, but it has been confirmed through numerous experiments that the laser beam can pump out the ejection material at a frequency equal to or greater than 1 kHz and equal to or less than 20 kHz, while drastically reducing the thermal deformation of the irradiated object ST.

Referring to FIG. 6(a), in the first phase, the horizontal mirror 331 can be located at point b1. Referring to FIG. 6(b), in the second phase, the horizontal mirror 331 can be located at point b3 via point b2 due to the driving force (vibration) of the motor 321. Thereafter, the horizontal mirror 331 can reciprocate from point b3 to point b1 due to the driving force (vibration) of the motor 321.

In other words, the laser beam irradiation device 10 according to the exemplary embodiment of the present disclosure can output a laser beam that vibrates in a vibration direction to the irradiated object ST by utilizing the driving force of the motor 321 and the vibration of the horizontal mirror 331 based on the driving force.

Figure 7 is intended to explain polygon vibration, one of the vibration methods according to an exemplary embodiment of the present disclosure.

Referring to FIG. 7, the optical element 330 includes a pair of polygon mirrors 332, which may include a first polygon mirror 332a and a second polygon mirror 332b having multiple reflective surfaces.

According to an exemplary embodiment of the present disclosure, the laser oscillator 310 may include a plurality of oscillator modules. For example, the laser oscillator 310 may output a plurality of laser beams including a first laser beam i_a and a second laser beam i_b. The laser oscillator 310 may output the first laser beam i_a to the first polygon mirror 332a and may output the second laser beam i_b to the second polygon mirror 332b.

The first polygon mirror 332a can rotate in a first direction d1_a, and the second polygon mirror 332b can rotate in a second direction d1_b that is opposite to the first direction d1_a. As an example, the vibration unit 320 can be embodied as a rotary motor, and can rotate the first polygon mirror 332a and the second polygon mirror 332b in different directions. As another example, the vibration unit 320 can be embodied as a vibration motor, and can output a driving force (vibration) to the multiple polygon mirrors so that the first polygon mirror 332a and the second polygon mirror 332b vibrate in opposite phases to each other.

According to an exemplary embodiment of the present disclosure, when the optical element 330 includes a pair of polygon mirrors 332, the reflected output laser beams o_a and o_b can be output to the object ST. At this time, the reflected output laser beams o_a and o_b can vibrate in different directions from each other.

The reflected output laser beams o_a and o_b can each vibrate in a single direction. As an example, the first output laser beam o_a can vibrate in the order of the first point p1_a, the second point p2_a, the third point p3_a, the first point p1_a, the second point p2_a, and so on of the irradiated object ST. The second output laser beam o_b can vibrate in the order of the fourth point p1_b, the fifth point p2_b, the sixth point p3_b, the fourth point p1_b, the fifth point p2_b, and so on. That is, when the output laser beams o_a and o_b reach the third point p3_a and the sixth point p3_b, respectively, they return to the first point p1_a and the fourth point p1_b. This is due to the shape of the polygon mirror.

That is, according to an exemplary embodiment of the present disclosure, when the optical element 330 includes a pair of polygon mirrors 332, the laser beam irradiation device 10 can process the irradiated object ST by outputting output laser beams o_a and o_b that vibrate in simple vibration in different directions to the irradiated object ST. At this time, the direction of the simple vibration can be different from the direction in which the processing of the irradiated object ST proceeds.

On the other hand, the output laser beams o_a and o_b can be output to the irradiated object ST through the focusing lens 400.

Figure 8 is intended to explain light source vibration, one of the vibration methods according to an exemplary embodiment of the present disclosure.

Referring to (a) and (b) of FIG. 8, the optical element 330 can include a fixed horizontal mirror 333.

According to an exemplary embodiment of the present disclosure, the laser oscillator 310 can be mechanically connected directly or indirectly to the vibrating unit 320 to transmit a driving force (vibration). Unlike FIG. 5, the fixed horizontal mirror 333 and the focusing lens 400 can be fixed without vibration, and the laser oscillator 310 can be vibrated by the vibrating unit 320. As an example, the laser oscillator 310 can perform simple harmonic motion by moving from point d1 to point d3 and then back and forth from point d3 to point d1.

According to an exemplary embodiment of the present disclosure, the irradiated object ST can be processed in the vibration direction from point a1 to point a3 by the vibration of the laser oscillation unit 310.

Figure 9 illustrates a focusing lens according to an exemplary embodiment of the present disclosure.

Referring to FIG. 9(a), the focusing lens 400 can be realized as an f-theta lens 401, and FIG. 9(b) is for explaining an achromatic lens 402. Unlike the achromatic lens 402, the f-theta lens 401 may not have a top curvature phenomenon.

The laser beam irradiation device 10 according to an exemplary embodiment of the present disclosure can be used for semiconductor processing on a nanoscale basis. When a top surface curvature phenomenon occurs, as with the achromatic lens 402, it may be difficult to achieve the effect of the invention according to the technical idea of the present disclosure in that the vibration width cannot be finely adjusted. Accordingly, the laser beam irradiation device 10 can precisely adjust the vibration width by using the f-theta lens 401.

In addition, the focusing lens 400 according to the exemplary embodiment of the present disclosure may include a short focal length lens, a singlet lens, and a bi-convex lens.

Meanwhile, the focusing lens 400 according to an exemplary embodiment of the present disclosure may include an objective lens. In this case, the objective lens may have a magnification of 5x or more and 100x or less. The objective lens is optimized to form a finer laser spot LS than the above-mentioned f-theta lens 401. According to an experiment, when the objective lens among the above-mentioned lenses is embodied as the focusing lens 400, the diameter of the laser spot LS can be formed to be the smallest and clearest. In this regard, a description will be given with reference to FIG. 9.

Figure 10 is intended to explain the vibration direction and machining direction determined by the machining method according to an exemplary embodiment of the present disclosure.

Referring to FIG. 10(a), the laser beam irradiation device 10 can output a laser beam along the processing direction while vibrating widely in the lateral direction.

Accordingly, when the irradiated object ST is embodied as a wafer, the laser beam irradiation device 10 can perform at least one of the following processes: grooving, scribing, removing, and grinding.

Referring to FIG. 10(b), the laser beam irradiation device 10 can output a laser beam along the horizontal direction while vibrating narrowly and deeply in the vertical direction (vertical direction).

Accordingly, the laser beam irradiation device 10 can perform dicing processing when the irradiated object ST is embodied as a wafer.

Figure 11 is intended to explain the processing direction and incidence angle for an exemplary embodiment of the present disclosure.

Referring to (a), (b) and (c) of FIG. 11, respectively, the laser beam irradiation device 10 can perform forward processing, right-angle (vertical) processing and reverse processing depending on the angle of incidence. In the case of forward processing, the laser beam irradiation device 10 can output a laser beam to the irradiated object ST at an acute angle θ1 to the processing direction. In the case of right-angle (vertical) processing, the laser beam irradiation device 10 can output a laser beam to the irradiated object ST at a right angle θ2 to the processing direction. In the case of reverse processing, the laser beam irradiation device 10 can output a laser beam to the irradiated object ST at an obtuse angle θ3 to the processing direction. The uses and utility of each processing method have been described above and will not be discussed here.

According to an exemplary embodiment of the present disclosure, the laser beam irradiation device 10 may have different penetration depths into the irradiated object ST depending on the incident angle of the laser beam. For example, when etching is to be performed to a first depth, the laser beam irradiation device 10 may perform right-angle processing, and when etching is to be performed to a second depth shallower than the first depth, the laser beam irradiation device 10 may perform forward processing or reverse processing.

Figures 12 and 13 are electron microscope images to explain the quality of the semiconductor processing results according to an exemplary embodiment of the present disclosure, along with a comparative example.

Figure 12(a) is a cross-sectional view of an irradiated object ST diced according to a comparative example, and Figure 12(b) is a cross-sectional view of an irradiated object ST diced according to an exemplary embodiment of the present disclosure.

The comparative example shows that non-homogeneous areas occur on both the surface and cross section, resulting in a deterioration in processing quality.

However, according to the exemplary embodiment of the present disclosure, a smooth cross section can be confirmed, and the surface does not experience any laser-induced cracking, confirming excellent processing quality.

Figures 13(a) and (b) are images taken vertically of a semiconductor in which only the line width has been processed using a comparative example and an exemplary embodiment of the present disclosure, respectively.

In the comparative example, it was confirmed that by irradiating a strong laser beam in the processing direction without vibration, the strong heat of the laser caused damage to the irradiated object even in areas that were not the target area.

However, according to an exemplary embodiment of the present disclosure, a laser beam of appropriate intensity is irradiated in the processing direction while vibrating in the vibration direction, so that no damage caused by the laser can be found in areas other than the target area.

As above, exemplary embodiments have been disclosed in the drawings and specification. Although specific terms have been used in the present specification to describe the embodiments, these terms are used only for the purpose of describing the technical ideas of the present disclosure, and are not used to limit the meaning or the scope of the present disclosure described in the claims. Therefore, a person having ordinary skill in the art would understand that various modifications and equivalent other embodiments are possible. Therefore, the true technical scope of protection of the present disclosure should be determined by the technical ideas of the appended claims.

Claims (1)

In a laser beam irradiation device for semiconductor processing,
a laser beam output unit that outputs a laser beam having an incident angle with respect to a processing direction that is set according to a penetration depth into a semiconductor substrate onto a surface of the semiconductor substrate; and a focusing lens that images a laser spot that advances in the processing direction and vibrates in a vibration direction on the semiconductor substrate,
13. A laser beam irradiation device, comprising: a laser beam irradiation unit for irradiating a semiconductor substrate with a laser beam having a depth that varies depending on an incident angle of the laser beam with respect to the processing direction.

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