Abstract:
A non-metallic material is separated using a single laser beam that is converted into a scribe beam and a break beam. A system includes a single laser source for generating a laser beam and a beam separator for converting the laser beam into a scribe beam having a first average power and a break beam having second average power. The beam separator directs the scribe beam to a scribe line on a substrate and the break beam to the substrate at a location that is spaced apart from the scribe beam. The scribe beam rapidly heats the substrate along the scribe line. A quenching subsystem applies a stream of cooling fluid to the substrate to propagate a microcrack along the scribe line. The break beam rapidly reheats the substrate quenched by the stream of cooling fluid to separate the substrate along the microcrack.

Description:
TECHNICAL FIELD 
       [0001]    This disclosure relates to separating non-metallic materials into a plurality of smaller pieces. In particular, this disclosure is directed to using a single laser source to generate a scribe beam and a break beam for use with a cooling source to separate glass, silicon, ceramic, or other non-metallic materials. 
       BACKGROUND 
       [0002]    High-power lasers (e.g., 500 W CO 2  lasers) may cut through non-metallic substrates such as glass, silicon, or ceramic by melting, evaporation, and ejection of material, which leads to poor surface integrity, wide tolerances, and degraded strength. Other methods for separating a non-metallic material use a non-melting (or non-evaporation) thermal process followed by a strain process. For the thermal process, any brittle material exceeds its critical thermal shock temperature when its temperature is elevated to a desired level and then rapidly cooled or quenched to break its molecular bonds. This forms a “vent” or “blind crack” in the material. Certain thermal processes use a first laser source to generate a first laser beam that heats the material along a scribe line. The first laser beam may be closely followed by a cooling stream of fluid (e.g., Helium and/or water) for quenching. 
         [0003]    The strain process may then be used to completely separate the material by breaking the material along the blind crack using either traditional mechanical methods or a second laser process. Mechanical strain may include, for example, using a “guillotine” breaker to apply sufficient physical force to a thin substrate (e.g., less than about 0.5 mm) so as to completely break the substrate along the scribe line. For thicker material, however, the residual tensile forces resulting from the laser scribing operation may not be sufficient to cleanly separate the material using mechanical force. Thus, a second laser source may be used to generate a second laser beam to rapidly reheat the substrate along the scribe line, following the quenching step, to fully separate the material. Using two lasers, however, increases system complexity and maintenance. 
       SUMMARY 
       [0004]    A non-metallic material is separated using a single laser beam that is converted into a scribe beam and a break beam. A system includes a single laser source for generating a laser beam and a beam separator for converting the laser beam into a scribe beam having a first average power and a break beam having second average power. The beam separator directs the scribe beam along a first path to a scribe line on a non-metallic substrate and the break beam along a second path to the non-metallic substrate at a location that is spaced apart from the scribe beam. The scribe beam rapidly heats the non-metallic substrate along the scribe line. A quenching subsystem applies a stream of cooling fluid to the non-metallic substrate to propagate a microcrack along the scribe line heated by the scribe beam. The break beam rapidly reheats the non-metallic substrate quenched by the stream of cooling fluid to separate the non-metallic substrate along the microcrack. 
         [0005]    Additional aspects and advantages will be apparent from the following detailed description of preferred embodiments, which proceeds with reference to the accompanying drawings. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0006]      FIG. 1  is a block diagram of a laser processing system for separating a non-metallic material according to one embodiment. 
           [0007]      FIGS. 2A ,  2 B, and  2 C graphically illustrate how the power of a CW laser beam is distributed with respect to time between a scribe beam and a break beam according to an example embodiment. 
           [0008]      FIG. 3  is a schematic diagram of a top view of the material shown in  FIG. 1  illustrating relative locations of laser beam spots and a quenching location along a scribe line according to one embodiment. 
           [0009]      FIG. 4  is a schematic diagram of a top view of the material shown in  FIG. 1  illustrating dual laser beam spots corresponding to the break beam according to one embodiment. 
           [0010]      FIG. 5A  is a block diagram of a laser processing system for separating the non-metallic material according to one embodiment. 
           [0011]      FIG. 5B  is a block diagram of a laser processing system for separating the non-metallic material according to another embodiment. 
           [0012]      FIG. 6  is a block diagram of a dual-path laser processing system for separating the non-metallic material according to another embodiment. 
           [0013]      FIGS. 7A and 7B  graphically illustrate how an AOM distributes and modulates the power of the CW laser beam between the scribe beam and the break beam according to an example embodiment. 
       
    
    
     DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS 
       [0014]    Systems and methods separate a non-metallic material by converting a laser beam from a single laser source into a scribe beam and a break beam. By way of example, and not by limitation, the non-metallic material may include glass, silicon, ceramic, or other material. The average power of the scribe beam is selected so as to propagate, in cooperation with a cooling stream, a microcrack along a desired scribe line in the non-metallic material, without substantially ablating (e.g., melting, evaporating, and/or ejecting) the material. The average power of the break beam is selected to produce a tensile force along the scribe line so as to break the material into separate pieces. 
         [0015]    In one embodiment, a continuous wave (CW) laser beam is “time-shared” between the scribe beam and the break beam using, for example, a fast steering mirror (FSM), a mirror galvanometer beam deflector (referred to herein as a “galvo” or “galvo mirror”), an acousto-optic deflector (AOD), an electro-optic deflector (EOD), other optical deflection devices, or a combination of the foregoing. In such embodiments, the CW beam is deflected along a scribing beam path during certain time periods and along a breaking beam path during other time periods. As discussed below, the average powers of the respective beams may be controlled by selecting duty cycles for the scribe beam and the break beam. 
         [0016]    In addition, or in other embodiments, the respective average powers may be controlled by selectively modulating the scribe beam and the break beam. For example, as discussed in detail below, an acousto-optic modulator (AOM) may receive the CW beam and output both (e.g., as a 0th order beam and a 1st order beam) a modulated scribe beam and a modulated break beam. 
         [0017]    The average power of the scribe beam is selected to heat the material with little or no ablation, and to keep the surface temperature of the material (e.g., glass) below the “transition” temperature to avoid damaging the integrity of the material. Once a quenching jet is applied, the surface of the glass contracts while the center is still under expansion, which results in large surface tensile stress. When such tensile stress exceeds the critical breaking point of glass, a vent is created which follows the path defined by the scribe beam and the cooling nozzle. Depending on the material, a cooling liquid jet, a mix of liquid and gas, or even gas alone may be used for quenching. For certain materials, such as those with low thermal expansion coefficients, a high gradient may be required to exceed the critical breaking stress. In such embodiments, a gas/water mixture may be used for effective quenching. In other words, latent heat released from the evaporation of the liquid is combined with convective and conductive heat transfer and serves to quench the material in a more efficient manner, thereby providing fast temperature quenching and creating a large thermal gradient for high tensile stress. 
         [0018]    In certain embodiments, an initial defect, e.g., a notch on the edge or a small crack, may be required to propagate a microcrack through a material. Many materials already have defects positioned along their edges as result of previous manufacturing processes. It has been found more desirable, however, to introduce an initiation defect in a controlled manner at a given location rather than to rely on residual defects. 
         [0019]    Reference is now made to the figures in which like reference numerals refer to like elements. For clarity, the first digit of a reference numeral indicates the figure number in which the corresponding element is first used. In the following description, numerous specific details are provided for a thorough understanding of the embodiments disclosed herein. However, those skilled in the art will recognize that the embodiments can be practiced without one or more of the specific details, or with other methods, components, or materials. Further, in some cases, well-known structures, materials, or operations are not shown or described in detail in order to avoid obscuring aspects of the invention. Furthermore, the described features, structures, or characteristics may be combined in any suitable manner in one or more embodiments. 
         [0020]    Embodiments may include various steps, which may be embodied in machine-executable instructions to be executed by a general-purpose or special-purpose computer (or other electronic device). Alternatively, the steps may be performed by hardware components that include specific logic for performing the steps or by a combination of hardware, software, and/or firmware. 
         [0021]    Embodiments may also be provided as a computer program product including a non-transitory, machine-readable medium having stored thereon instructions that may be used to program a computer (or other electronic device) to perform the processes described herein. The machine-readable medium may include, but is not limited to, hard drives, floppy diskettes, optical disks, CD-ROMs, DVD-ROMs, ROMs, RAMs, EPROMs, EEPROMs, magnetic or optical cards, solid-state memory devices, or other types of media/computer-readable medium suitable for storing electronic instructions. 
         [0022]      FIG. 1  is a block diagram of a laser processing system  100  for separating a non-metallic material  110  according to one embodiment. The system  100  includes a single CW laser source  112 , a steerable deflector  114 , a focus lens  116 , a quenching subsystem  118 , and a motion stage  120 . The CW laser source  112  is configured to output a CW laser beam  122  at a predetermined wavelength and average power selected to process a particular type of material  110 . By way of example only, and not by limitation, the CW laser source  112  may comprise a carbon dioxide (CO 2 ) laser configured to output the laser beam  122  having a wavelength in a range between about 9 μm and about 11 μm. In certain examples discussed herein, the CW laser beam  122  has an average power in a range between about 700 W and about 750 W. However, skilled persons will recognize from the disclosure herein that these values are provided as one example, and that any wavelength or average power may be used based on material or laser process. Further, in other embodiments, the CW laser source  112  may be replaced with a pulsed laser wherein different pulses are directed along respective scribing and breaking paths. 
         [0023]    As shown in  FIG. 1 , the steerable deflector  114  may include an FSM, galvo, or other deflector that may be controlled to receive the laser beam  122  from the CW laser source  112  and to selectively deflect the laser beam  122  along either a first path corresponding to a scribe beam  124  or a second path corresponding to a break beam  126 . In certain embodiments, the steerable deflector  114  may selectively operate over a range of frequencies to provide desired heating of the material. For example, glass may dissipate heat on the order of milliseconds. By deflecting the laser beam  122  between the scribe beam  124  and the break beam  126  at a high frequency (e.g., greater than or equal to 1 kHz), the pulses in each beam  124 ,  126  (see  FIGS. 2B  and  2 C) are separated by 1 millisecond or less. Thus, at such a switching frequency, both the scribe beam  124  and the break beam  126  provide continuous heating to a glass material. 
         [0024]    For illustrative purposes, the scribe beam  124  is shown with a solid line and the break beam  126  is shown with a dashed line. In this embodiment, the steerable deflector  114  time-shares the laser beam  122  between the two paths. By way of example, time-sharing may result in the 750 W laser beam  122  being divided such that the scribe beam  124  has an average power of about 250 W and the break beam  126  has an average power of about 500 W. Skilled persons will recognize, however, that the power of the laser beam  122  may be distributed in any way between the scribe beam  124  and the break beam  126 , depending on the particular material being separated and the particular laser processing application, including distributing more power to the scribe beam  124  than to the break beam  126 . In certain embodiments, parameters (e.g., spot size or shape) of the scribe beam  124  and the break beam  126  may be selectively and separately controlled by additional optical elements (not shown) in the respective scribing and breaking beam paths. 
         [0025]      FIGS. 2A ,  2 B, and  2 C graphically illustrate how the power of the CW laser beam  122  is distributed with respect to time between the scribe beam  124  and the break beam  126  according to an example embodiment. For illustrative purposes, both power and time are shown in arbitrary units (a.u.).  FIG. 2A  shows the power with respect to time for the CW laser beam  122  output by the laser source.  FIG. 2B  shows the power with respect to time for the scribe beam  124 .  FIG. 2C  shows the power with respect to time for the break beam  126 . In this example, the steerable deflector  114  directs 100% of the laser power along the path corresponding to the scribe beam  124  during time periods between 0 to about 1 a.u., between about 4 a.u. to about 5 a.u., and between about 8 a.u. to about 9 a.u. along the time axis. During the scribe beam&#39;s off times, the steerable deflector  114  directs 100% of the laser power along the path corresponding to the break beam  126  (e.g., from about 1 a.u. and about 4 a.u., and from about 5 a.u. and about 8 a.u. along the time axis). Thus, in this example, about 25% of the power is distributed to the scribe beam  124  and about 75% of the power is distributed to the break beam  126 . 
         [0026]    Returning to  FIG. 1 , the motion stage  120  provides relative motion between the laser beams  124 ,  126  and the material  110  along the scribe line. In this example, the motion stage  120  moves the material  110  to the right, as indicated by arrow  128  such that the scribe beam  124  is followed by a cooling stream (not shown) output by the quenching subsystem  118 , which in turn is followed by the break beam  126 . 
         [0027]    For example,  FIG. 3  is a schematic diagram of a top view of the material  110  shown in  FIG. 1  illustrating relative locations of laser beam spots  310 ,  312  and a quenching location  314  along a scribe line  316  according to one embodiment. The laser spots  310 ,  312  in  FIG. 3  are elliptical, with each having its longer axis aligned with the scribe line  316 . Skilled persons will recognize from the disclosure herein, however, that circular or other spatially shaped (e.g., rectangular or tapered) beam spots may also be used. Further, the respective distances between the laser beam spots  310 ,  312  and the quenching location depend on the type of material  110  being processed, heat dissipation within the material  110 , laser parameters used (e.g., wavelength, power, and other parameters), and the rate at which the quenching cools the material  110 . In this example, the steerable deflector  114  shown in  FIG. 1  deflects the portion of the laser beam  122  corresponding to the scribe beam  124  to the laser spot  310  and the portion corresponding to the break beam  126  to the beam spot  312  as the motion stage  120  moves the material in the direction shown by the arrow  128 . 
         [0028]    In other embodiments, the steerable deflector  114  is configured to deflect in two directions (e.g., in both an X-axis direction and a Y-axis direction). For example, the steerable deflector  114  may include a first FSM to deflect in the X-axis and a second FSM to deflect in the Y-axis. Other configurations are also possible such as an FSM to deflect in a first direction and a galvo to deflect in a second direction. Thus, the steerable deflector  114  may deflect one or both of the beams  124 ,  126  in a direction that is perpendicular to the scribe line  316 . 
         [0029]    For example,  FIG. 4  is a schematic diagram of a top view of the material  110  shown in  FIG. 1  illustrating dual laser beam spots  410 ,  412  corresponding to the break beam  126  according to one embodiment. In this embodiment, the steerable deflector  114  further divides (e.g., time-shares) the break beam  126  into two break beams that are deflected both in the X-direction (horizontal or in the direction shown by the arrow  128 ) and in the Y-direction (vertical or in a direction that is perpendicular to the arrow  128 ). This may be accomplished, for example, by cascading a first deflector (e.g., for the X-axis) followed by a second deflector (e.g., for the Y-axis). As shown in  FIG. 4  the laser spots  410 ,  412  corresponding to the dual break beams may be located on either side of the scribe line  316  to increase the tensile force on the microcrack created by the scribe beam  124  and the quenching subsystem  118 . 
         [0030]      FIG. 5A  is a block diagram of a laser processing system  500  for separating the non-metallic material  110  according to one embodiment. The system  500  includes the single CW laser source  112 , focus lens  116 , quenching subsystem  118 , and motion stage  120  discussed above with respect to  FIG. 1 . In this embodiment, however, the system  500  includes an AOD  510  to selectively deflect the laser beam  122  along either a first path corresponding to the scribe beam  124  or a second path corresponding to the break beam  126 . An EOD may be used instead of, or with, the AOD  510 . Again, for illustrative purposes, the scribe beam  124  is shown with a solid line and the break beam  126  is shown with a dashed line. In this embodiment, the AOD  510  time-shares the laser beam  122  between the two paths. 
         [0031]    The system  500  also includes a relay lens  512  and a deflector  514  for directing the scribe and break beams  124 ,  126  along their respective paths to the material  110 . In one embodiment, the deflector  514  comprises a fixed mirror. In other embodiments, the deflector  514  is a steerable deflector and may include, for example, one or more FSM and/or one or more galvo. In addition, or in other embodiments, the AOD may include a plurality of AODs and/or EODs for selectively deflecting at least one of the scribe beam  124  and the break beam  126  in at least two directions (e.g., in the X-axis direction and the Y-axis direction), as discussed above. 
         [0032]      FIG. 5B  is a block diagram of a laser processing system  520  for separating the non-metallic material  110  according to another embodiment. The system  520  includes the single CW laser source  112 , focus lens  116 , quenching subsystem  118 , and motion stage  120  discussed above with respect to  FIG. 1 . The system  520  also includes the relay lens  512  and deflector  514  discussed above with respect to  FIG. 5A . In this embodiment, however, the system  520  includes an AOM  522  to separate the laser beam  122  into the scribe beam  124  and the break beam  126 , and to selectively modulate the scribe beam  124  and the break beam  126  to further control the respective average powers. In one embodiment, the AOM  522  simultaneously outputs a 0th order beam and a 1st order beam as the scribe beam  124  and the break beam  126 . In other embodiments, the AOM  522  may be configured to output two separately controlled 1st order beams as the scribe beam  124  and the break beam  126  (e.g., with the 0th order beam being sent to a beam dump). In addition, or in other embodiments, the AOM  522  includes AOD functionality. In one embodiment, the deflector  514  comprises a fixed mirror. In other embodiments, the deflector  514  is a steerable deflector and may include, for example, one or more FSM and/or one or more galvo. 
         [0033]      FIG. 6  is a block diagram of a dual-path laser processing system  600  for separating the non-metallic material  110  according to another embodiment. The system  600  includes the single CW laser source  112 , focus lens  116 , quenching subsystem  118 , and motion stage  120  discussed above with respect to  FIG. 1 . In this embodiment, however, the system  600  includes a beam splitter  610  configured to direct a portion of the laser beam (e.g., the scribe beam  124 ) down a first optical path including a first deflector  514 ( a ), first optic elements  612 ( a ), if any, and a beam combiner  614 . The beam splitter  610  also directs a portion of the laser beam (e.g., the break beam  126 ) down a second optical path including a second deflector  514 ( b ), second optic elements  612 ( b ), if any, and the beam combiner  614 . The beam splitter  610  may include bulk optics such as polarizing beam splitter cubes or partially reflecting mirrors. AODs, EODs, and switchable liquid crystal display (LCD) polarizers may also be configured and driven to perform beam splitting. Alternatively, fiber optic couplers may serve as a beam splitter in fiber-optic implementations. 
         [0034]    In certain embodiments, parameters of the scribe beam  124  and the break beam  126  may be selectively and separately controlled. For example, the optic elements  612 ( a ),  612 ( b ) in each path, which are optional, may be included to shape or change the optical properties of the beams and may include, for example, polarizers, polarization modifiers, faraday isolators, spatial beam profile modifiers, temporal beam profile modifiers, frequency shifters, frequency-multiplying optics, attenuators, pulse amplifiers, mode-selecting optics, beam expanders, lenses, and relay lenses. Additional optic elements may also include delay elements that include an extra optical path distance, folded optical paths, and fiber-optic delay lines. 
         [0035]      FIGS. 7A and 7B  graphically illustrate how the AOM  522  distributes and modulates the power of the CW laser beam  122  between the scribe beam  124  and the break beam  126  according to an example embodiment. For illustrative purposes, both power and time are shown in arbitrary units (a.u.). As discussed above,  FIG. 2A  shows the power with respect to time for the CW laser beam  122  output by the laser source.  FIG. 7A  shows the power with respect to time for the scribe beam  124 .  FIG. 7B  shows the power with respect to time for the break beam  126 . The example shown in  FIG. 7A  is similar to the example shown in  FIG. 2B , except that the AOM  522  further modulates the power of the scribe beam  124  shown in  FIG. 7A  between 0% and 80%. Thus, during the on periods of the scribe beam  124  (e.g., 0 to about 1 a.u., from about 4 a.u. to about 5 a.u., and from about 8 a.u. to about 9 a.u. along the time axis), the AOM  522  continues to distribute 20% of the power to the break beam  126 , as shown in  FIG. 7B . In other words, rather than turning the power completely off for the break beam  126 , the AOM  522  maintains at least 20% of the maximum power in the break beam  126  at all times. 
         [0036]    It will be understood by those having skill in the art that many changes may be made to the details of the above-described embodiments without departing from the underlying principles of the invention. The scope of the present invention should, therefore, be determined only by the following claims.