KR20120038268A - Ultrathin wafer micro-machining method and system by laser rail-roading technique - Google Patents

Abstract

PURPOSE: A method and apparatus for minutely processing a wafer by a laser rail-roading process are provided to improve productivity and quality by controlling the polarization of laser at a right angle to a laser radiation direction. CONSTITUTION: A light irradiating unit(110) irradiates an object(500) with multiple laser. The object is loaded on the upper side of a stage(120). A moving unit(130) moves the light irradiating unit and the stage. A nozzle(140) removes foreign materials from the surface of the object and removes byproducts.

Description

Wafer micro-machining method and system by laser multi-line process {Ultrathin wafer micro-machining method and system by laser rail-roading technique}

The present invention relates to a method and apparatus for fine wafer processing by laser multi-line process.

The method used to pattern or cut a pattern on a thin wafer or thin film (where lamination is commonly referred to as deposition, printing, etc.) is largely liquid or vapor phase. Chemical etching methods, mechanical processes such as diamond sawing, and ablation methods caused by direct irradiation of conventional laser energy.

In case of chemical etching, the precision of the process is very high, but there are several disadvantages as follows. First, in order to form a pattern, a mask corresponding to a pattern shape must be manufactured, which requires a very complicated process step. In addition, there is a problem that the applicable materials are limited, and the application of the large-area process is limited. In addition, there is a problem that the adverse effects on the environment is large when considering the toxicity of the etching material, the use thereof tends to be gradually limited, there is a limit to its application in the future.

In the mechanical process method, there is a problem in that the thin film or the wafer to be applied may be damaged due to mechanical shock, and thus there is a limitation in its application. In addition, the physical size of the saw blade or needle-shaped structure used in the process should be reduced to approximately 50μ or less, which is very difficult. In addition, if the physical-mechanical properties of the thin film have brittle properties, chipping during the process cannot be overcome, resulting in greatly reduced process precision and debris on the surface. There is a problem, and above all, there is a big problem that the delamination of the thin film cannot be overcome when the adhesion between the laminated thin film and the lower wafer is small compared to the torque added in the mechanical process.

For the reasons as described above, the cutting or pattern forming method using a laser has been actively developed and expanded in recent years. Currently, the direct cutting or pattern forming method using a laser is largely made of the following two cases. One is to use nanosecond ultraviolet or visible light, near-infrared and infrared laser to cut or pattern by thermal energy. However, this method has a problem that a decrease in process precision and a decrease in mechanical strength of a process product cannot be avoided due to a change in material properties due to thermal deformation. The other is a process using an ultrafast laser. In this case, the process precision and the mechanical strength of the workpiece are very superior to that of other lasers. However, the high speed laser process is not suitable for large area processing, which causes a problem in that the process productivity is lowered.

In addition, the main technical limitation in pattern formation by the conventional laser process is that the surface inside the pattern after the process cannot be deformed during processing or contamination by process by-products such as debris can be avoided. . Such deformation or contamination may cause various problems such as poor electrical or optical contact when laminating new materials on a pattern, separation of layers or poor stacking in a future lamination process. do.

In addition, in the case of a pulsed laser that is commonly applied, the degree of ablation or mechanism of overlap between the pulse and the other part of the pulse is generated, and thus an ideally uniform pattern can be obtained. In the case of having a laser shape of the Gaussian type, there is a problem that the process surface exhibits a roughly bead shape, and the quality of the component material after the process is degraded.

Therefore, the present invention has been made to solve the problems of the prior art as described above, an object of the present invention is to form or cut a pattern by irradiating multiple light to the object to be formed of a wafer or a wafer laminated thin film The present invention provides a method and apparatus for fine wafer processing by a laser multi-line process, which maximizes process precision and process quality. More specifically, the present invention directly or indirectly irradiates two or more laser beams on top of a thin wafer or a thin film stacked on the wafer, thereby minimizing deformation of the object to be processed and at the same time accompanied by a shock wave generated by the laser itself. The present invention provides a method and apparatus for fine wafer processing by a laser multi-line process for cutting or patterning an object to be processed.

In order to achieve the object as described above, the method for fine wafer processing by the laser multi-line process of the present invention includes a pattern on a workpiece 500 formed of a wafer 510 or a wafer 510 in which a thin film 520 is stacked. In the micro-machining method for forming a cutting or cutting, a plurality of laser light spaced apart from each other at a predetermined interval (D) determined according to the characteristics of the laser and the object 500 on the surface of the object 500. Irradiated to correspond to the pattern shape to form a multi-line, and the inner portion of the formed multi-line is spontaneously removed by the shockwave energy generated during the pattern formation process to form a pattern or cut the multi-line part This is characterized in that to be performed.

At this time, the predetermined interval (D) is characterized in that determined according to the following equation.

D ≤ 2x ₀

From here,

The laser light is double-irradiated, the center point of the line segment connecting each position irradiated on the surface of the object 500 to be processed is 0, and any position on the line segment is x, and the line segment Given the coordinates of each endpoint of -x ₀ and x ₀ ,

1) When the object to be processed 500 is a wafer 510 in which a thin film 520 is stacked,

F _shock is the combined force of the shock waves generated by the double light laser irradiation, F _{c, film} is the cohesion of the thin _film , F _{a, film} is the adhesion between the thin film and the wafer, x ₀ is determined by the following conditions,

F _shock (x = x ₀ , -x ₀ )> F _{c, film} (x = x ₀ , -x ₀ )

F _shock (-x ₀ <x <x ₀ )> F _{a, film} (-x ₀ <x <x ₀ )

2) When the object to be processed 500 is made of only the wafer 510,

F _shock is the combined force of the shock waves generated by the double light laser irradiation, F _{c, wafer} is the cohesive force of the wafer, x ₀ is determined by the following conditions,

F _shock (-x ₀ ≤ x ≤ x ₀ )> F _{c, wafer} (-x ₀ ≤ x ≤ x ₀ )

3) When mechanical force is applied from the outside or laser light is additionally applied between the double lights, and the object 500 is the wafer 510 in which the thin film 520 is stacked,

F _shock is the combined force of the shock waves generated by the double light laser irradiation, F _add is the force applied mechanically from the outside or additionally applied by the additionally irradiated laser light, F _sum is F _shock + F _add , F _{c, film} is the cohesion of the thin _film , F _{a, film} is the adhesion between the thin film and the wafer, x ₀ is determined by the following conditions,

F _sum (x = x ₀ , -x ₀ )> F _{c, film} (x = x ₀ , -x ₀ )

F _sum (-x ₀ <x <x ₀ )> F _{a, film} (-x ₀ <x <x ₀ )

4) When a mechanical force is applied from the outside or additionally laser light is radiated between the double light and the object 500 is made of only the wafer 510,

F _shock is the combined force of the shock waves generated by the double light laser irradiation, F _add is the force applied mechanically from the outside or additionally applied by the additionally irradiated laser light, F _sum is F _shock + F _add , F _{When c and wafer} are the cohesion force of a wafer, x ₀ is determined by the following conditions.

F _sum (-x ₀ ≤ x ≤ x ₀ )> F _{c, wafer} (-x ₀ ≤ x ≤ x ₀ )

In addition, the micro-processing method is characterized in that the processing using a laser light having a wavelength of less than the ultraviolet region wavelength.

In addition, the fine processing method is characterized in that the pulse width is performed using a laser light of any one selected from femtoseconds, picoseconds, nanoseconds.

In addition, the micro-machining method is that when a plurality of laser light is simultaneously linearly irradiated on the surface of the object 500 to form a multi-line, compressed gas is injected to the surface of the object 500 to supersonic adiabatic expansion Through the surface of the processing object 500 is directly cooled through, it is characterized in that the foreign matter and processing by-products of the surface of the processing object 500 is removed.

In addition, the micro-processing method is characterized in that the laser polarization is perpendicular to the traveling direction of the laser light so that the polarized laser is irradiated on the surface of the object 500.

In addition, the fine processing method is characterized in that the processing is performed using double light.

In addition, in the wafer micromachining apparatus according to the laser multi-line process according to the present invention, the wafer 510 or the thin film 520 is a pattern formed on the object 500 formed of the wafer 510 is laminated or cut is performed In the micro-machining apparatus 100, the micro-machining apparatus 100 is a laser and a plurality of laser light spaced apart from each other at a predetermined interval (D) determined according to the characteristics of the processing object 500 to the processing object. (500) a light irradiation unit 110 for irradiating onto a surface to perform processing, a stage 120 on which the object to be processed 500 is disposed, and a relative position of the light irradiation unit 110 and the stage 120 It comprises a moving means for moving the 130, the multiple light irradiated from the light irradiation unit 110 is irradiated to correspond to the pattern shape on the surface of the processing object 500 to form a multi-line, Formed The inside part is spontaneously removed by the shock wave (shockwave) energy generated in the pattern formation process, the pattern of the track is formed or cut a part of the multi-track is characterized in that the cutting is performed.

At this time, the predetermined interval (D) is characterized in that determined according to the following equation.

D ≤ 2x ₀

From here,

The laser light is double-irradiated, the center point of the line segment connecting each position irradiated on the surface of the object 500 to be processed is 0, and any position on the line segment is x, and the line segment Given the coordinates of each endpoint of -x ₀ and x ₀ ,

1) When the object to be processed 500 is a wafer 510 in which a thin film 520 is stacked,

F _shock is the combined force of the shock waves generated by the double light laser irradiation, F _{c, film} is the cohesion of the thin _film , F _{a, film} is the adhesion between the thin film and the wafer, x ₀ is determined by the following conditions,

F _shock (x = x ₀ , -x ₀ )> F _{c, film} (x = x ₀ , -x ₀ )

F _shock (-x ₀ <x <x ₀ )> F _{a, film} (-x ₀ <x <x ₀ )

2) When the object to be processed 500 is made of only the wafer 510,

F _shock is the combined force of the shock waves generated by the double light laser irradiation, F _{c, wafer} is the cohesive force of the wafer, x ₀ is determined by the following conditions,

F _shock (-x ₀ ≤ x ≤ x ₀ )> F _{c, wafer} (-x ₀ ≤ x ≤ x ₀ )

3) When mechanical force is applied from the outside or laser light is additionally applied between the double lights, and the object 500 is the wafer 510 in which the thin film 520 is stacked,

F _shock is the combined force of the shock waves generated by the double light laser irradiation, F _add is the force applied mechanically from the outside or additionally applied by the additionally irradiated laser light, F _sum is F _shock + F _add , F _{c, film} is the cohesion of the thin _film , F _{a, film} is the adhesion between the thin film and the wafer, x ₀ is determined by the following conditions,

F _sum (x = x ₀ , -x ₀ )> F _{c, film} (x = x ₀ , -x ₀ )

F _sum (-x ₀ <x <x ₀ )> F _{a, film} (-x ₀ <x <x ₀ )

4) When a mechanical force is applied from the outside or additionally laser light is radiated between the double light and the object 500 is made of only the wafer 510,

F _shock is the combined force of the shock waves generated by the double light laser irradiation, F _add is the force applied mechanically from the outside or additionally applied by the additionally irradiated laser light, F _sum is F _shock + F _add , F _{When c and wafer} are the cohesion force of a wafer, x ₀ is determined by the following conditions.

F _sum (-x ₀ ≤ x ≤ x ₀ )> F _{c, wafer} (-x ₀ ≤ x ≤ x ₀ )

In addition, the light irradiation unit 110 includes a laser light source 111; A second harmonic generator (112) for generating at least a second or higher order harmonic light by passing the laser fundamental light emitted from the laser light source 111 through a non-linear optical crystal; A beam splitter 113 for splitting the light passing through the SHG 112 into a fundamental light and a multi-order harmonic light; An optical system 114 for controlling the optical paths of the basic light and the multiple harmonic wave light emitted through the optical separator 113 to be spaced apart by a predetermined interval; A beam combiner 115 for combining the fundamental light and the multi-order harmonic light emitted through the optical system 114; An optical concentrator 116 for irradiating and focusing the primary light and the multi-order harmonic light spaced apart from each other by passing through the optical coupler 115 on the surface of the object to be processed 500; And a control unit.

In addition, the light irradiation unit 110 is characterized in that for generating laser light having a wavelength less than the ultraviolet region wavelength.

In addition, the light irradiation unit 110 is characterized in that the pulse width generates laser light of any one selected from femtoseconds, picoseconds, nanoseconds.

In addition, the microfabrication apparatus 100 includes a nozzle 140 that directly cools the wafer surface by supersonic adiabatic expansion by spraying compressed gas, and removes foreign substances and processing byproducts from the surface of the object 500; Characterized in that further comprises.

In addition, the light irradiation unit 110 is characterized in that the polarized laser is irradiated on the surface of the object to be processed 500 so that the laser polarization is perpendicular to the traveling direction of the laser light.

In addition, the light irradiation unit 110 is characterized in that the irradiation by generating a double light.

In addition, the optical splitter 113 is characterized by consisting of a dichroic beam splitter.

In addition, the optical coupler 115 is characterized by consisting of a dichroic beam splitter.

According to the present invention, a change in adhesion force of a wafer or coated thin film to be processed on a lower substrate or support by thermal deformation caused by linear or nonlinear absorption of laser energy upon local damage or removal of a material by a laser. By minimizing the process quality, the process quality is excellent, and the quality of the cut part or the pattern is maximized while two or more laser beams are well controlled in time and space. That is, according to the present invention, there is a great effect of minimizing quality damage due to damage to the substrate portion remaining after the processing by-products are removed or chipping of the cut surface itself.

In addition, according to the present invention, the cutting width or the pattern line width can be freely adjusted by controlling the laser light spacing, and the productivity and quality of the process are further improved by controlling the polarization of the laser at right angles to the laser irradiation direction. There is.

In addition, according to the present invention, by injecting a compressed gas to the processing site to cause adiabatic expansion by direct cooling can be spontaneous removal of the processing by-products more smoothly, and in this case, the cohesive force of the material constituting the wafer Alternatively, by controlling the degree of adiabatic expansion of the outside air injection gas according to the degree of adhesion of the thin film, ultimately, the process quality of the substrate may be controlled to optimize the process quality.

1 is a fine processing apparatus of the present invention.
2 is a block diagram of a light irradiation part in the microfabrication apparatus of the present invention.
3 is an embodiment of an optical system in the microfabrication apparatus of the present invention.
4 to 7 are principles of the microfabrication method of the present invention.
8 is a result processed by the fine processing method of the present invention.
9 is a comparison of the results processed by the conventional laser processing method of the present invention.

Hereinafter, a method and an apparatus for fine wafer processing by a laser multi-line process according to the present invention having the configuration as described above will be described in detail with reference to the accompanying drawings.

In order to briefly explain a method for finely processing a wafer by the laser multi-line process of the present invention, a pattern is formed or a cutting is performed on the object 500 formed of the wafer 510 on which the wafer 510 or the thin film 520 is stacked. In the fine machining method, a plurality of laser light spaced apart from each other at a predetermined interval (D) determined according to the characteristics of the laser and the object 500 to correspond to the pattern shape on the surface of the object 500. Irradiated to form a multi-line, the inner portion of the formed multi-line is spontaneously removed by the shock wave (shockwave) energy generated during the pattern forming process to form a pattern or cut the multi-line part to be cut.

In addition, at this time, when a plurality of laser light is simultaneously linearly irradiated on the surface of the object 500 to form a multi-line, a compressed gas is injected to the surface of the object 500 to the supersonic adiabatic expansion The surface of the object 500 is directly cooled, and foreign matter and processing by-products of the surface of the object 500 are removed.

In addition, in the micro-processing method of the present invention, the micro-processing method is such that the laser polarization is perpendicular to the traveling direction of the laser light so that the polarized laser is irradiated on the surface of the object 500, femtosecond laser light It is preferable to allow the processing to be carried out using. In addition, in the concrete implementation of the present invention, the multi-line process is performed by the double light, it is possible to cause the pattern formation by removing the inner portion of the double line.

The micromachining apparatus 100 for implementing the micromachining method of the present invention as described above is briefly illustrated in FIGS. 1 and 2. In order to perform the microfabrication method of the present invention on the object to be processed 500 as described above, the microfabrication apparatus 100 of the present invention, as shown in Figure 1, the microfabrication apparatus 100 is a laser And a light irradiation part 110 for performing processing by irradiating a plurality of laser lights spaced apart from each other at a predetermined interval D determined according to the characteristics of the object 500 to be processed. The object 500 may include a stage 120 disposed thereon, and a moving unit 130 for moving the light irradiation unit 110 and the relative position of the stage 120.

Multiple light irradiated from the light irradiation unit 110 is irradiated to correspond to the pattern shape on the surface of the processing object 500 to form a multi-line, the shock wave generated in the inner portion of the formed multi-line pattern forming process ( The spontaneous removal by the energy of the shockwave forms a pattern, or the cutting of multiple track sites is performed.

In the stage 120, the object to be processed 500 is placed, and at this time, the light irradiation unit 110 and the stage 120 are moved relative to each other by the moving unit 130. The light emitting unit 110 and the movement means 130 may be configured to move only the light irradiation unit 110, only the stage 120, or both. As long as the relative position between the stage 120 can be moved, it may be configured in any form.

In addition, the microfabrication apparatus 100 further includes a nozzle 140 that directly cools the wafer surface through supersonic adiabatic expansion by spraying compressed gas and removes foreign substances and processing byproducts from the surface of the object 500. Can be done. The nozzle 140 is shown in close contact with the light irradiation unit 110 in FIG. 1, but of course, this is just one example, and thus the present invention is not limited thereto. The position or shape of the nozzle 140 can be freely determined.

At this time, a detailed configuration of the light irradiation unit 110 will be described in more detail with reference to FIG. 2. The light irradiator 110 includes a laser light source 111, a second harmonic generator (SHG) 112, a light splitter 113, an optical system 114, a light combiner 115, and an optical concentrator 116. ) Will be made.

The laser light source 111 is literally a device for generating a laser beam. As will be described in detail later, it is preferable to generate a femtosecond laser in the laser light source 111.

The SHG 112 passes through the laser fundamental light emitted from the laser light source 111 to a non-linear optical crystal to generate at least a second order or higher harmonic wave light, and the optical separator 113 receives the SHG 112. The light passing through is separated into fundamental light and multi-order harmonic light.

The optical system 114 adjusts optical paths of the basic light and the multi-order harmonic light emitted through the optical separator 113 to space the predetermined intervals. An embodiment of the SHG 112, the optical separator 113, and the optical system 114 is shown in FIG. 3. As shown in FIG. 3, the optical path of the fundamental light and the multi-order harmonic light is controlled by the optical system 114, and accordingly, the distance D between the lights can be adjusted. Of course, what is shown in FIG. 3 is one embodiment, and the present invention is not limited to FIG. 3, and the optical system 114 may be formed in any form if the optical path and interval of the fundamental light and the multi-order harmonic light can be adjusted. It may be.

The optical coupler 115 combines the fundamental light and the multi-order harmonic light emitted through the optical system 114, and finally, the optical concentrator 116 is predetermined to each other through the optical combiner 115. Radiation-focused fundamental light and multi-order harmonic light are focused on the surface of the object 500 to be irradiated.

Hereinafter will be described in more detail with respect to the principle of the unit techniques applied to the method and apparatus of the present invention or the technical effects by the unit techniques.

A) Patterning principle by multiple rail-roading

Basically referring to Figure 4, the principle of patterning by the multi-line process of the present invention will be described in more detail.

When irradiating a laser onto a workpiece, linear or nonlinear laser absorption occurs initially in the region to which the laser is directly irradiated. The energy thus absorbed generates free electrons or holes of constant density in the material. When the density of free electrons or holes generated is more than a certain degree, a substantial ablation of the material occurs. This phenomenon occurs simultaneously in two different laser beam lines, causing microscopic separation from other areas of the thin film. do.

On the other hand, when the laser as described above is focused on a very small area, the actual abrasion caused by the object being absorbed by the laser, and the acoustic-shock caused by the laser occur simultaneously. The shock-pressure generated at this time is initially isotropic in the material, but especially when the process object is formed by laminating a thin film on the wafer in a layer form, the shock-wave pressure is Very fast along the thin film and wafer interface. (SAW, surface-acoustic wave)

In the present invention, the SAW caused by the laser is generated simultaneously on the multiple lines. At this time, assuming that there is no change in the adhesive force in the ablated cross section due to the thermal change occurring during or after the laser process, the lower wafer having the total area of the thin film in which the SAW force is applied to the thin film is located inside the multi-line. When the adhesion force of the film is greater than, the thin film inside the multi-line is naturally lifted very effectively and can be lifted off (hereinafter referred to as 'lift-off').

FIG. 4 shows a case in which double light is used, and the relationship between the forces generated when the patterning is formed by the multi-line process of the present invention in the wafer on which the CIGS thin film is stacked is shown. As shown in FIG. 4, the force of the force transmitted to the inner side of the double line is changed according to the predetermined distance D from which the double light is spaced from each other. Therefore, if the predetermined distance D between the double lights is too far apart, Since lift-off cannot occur properly, it is important to determine the interval D at which the lift-off phenomenon can occur effectively.

In addition, similar principles apply to general wafers, not thin wafers. When ablation is performed by a laser, a crack generating force is propagated at the end of the ablation portion, and these forces are combined with each other at the inner side of the multiple line. If this force is greater than the cohesive force of the materials constituting the wafer, cracks will be generated and propagated at the deep end position of the abraded portion of the inner side of the multi-line, so that the inner side of the multi-line will fall off and lift-off too. It becomes possible. Of course, even in this case, the interval D at which the lift-off phenomenon can occur effectively must be determined.

4 to 7, the theoretical background and principle of determining the interval D for various cases will be described in more detail as follows.

First, the embodiment of FIG. 4 is formed by forming a back electrode on a ceramic substrate (mol) with molybdenum (Mo) and lifting the double object by irradiating double light on a workpiece having a CIGS (Cu (InGa) Se ₂ ) thin film deposited thereon. -The principle of turning off is explained. In Figure 4, F _{a, CISG} is the adhesion between CIGS and Mo, F _{a, Mo} is the adhesion between Mo and the substrate, F _{c, CISG} is the cohesion of CIGS, F _{c, Mo} is the cohesion of Mo, F _shock Indicates the force due to the shock wave generated by laser irradiation, respectively.

As shown in FIG. 4, when two different laser beams are irradiated simultaneously at the positions of x ₀ and -x ₀ , the shock wave F _shock (x) at the predetermined position x = x is the shock wave F _shock caused by the two different laser beams. _It can be expressed as the sum of _{, 1} (x ₀ , x) and F _{shock, 2} (-x ₀ , x) and can be expressed as follows.

F _shock (x) = F _{shock, 1} (x ₀ , x) + F _{shock, 2} (-x ₀ , x)

The _shock F (x) is a laser to cut the CIGS cohesion of F _c, greater than the _CIGS CIGS thin film in the irradiation position that is x ₀ and -x ₀ position, and also within the x ₀ -x ₀ interval CIGS CIGS can be separated from Mo only if it is greater than the adhesion force between Mo _{and CIGS} . That is, in order to enable the pattern formation by the multi-line process, the following equation must be satisfied.

F _shock (x = x ₀ , -x ₀ )> F _{c, CIGS} (x = x ₀ , -x ₀ )

F _shock (x ₀ >x> -x ₀ )> F _{a, CIGS} (x ₀ >x> -x ₀ )

Summarizing the above equations, the predetermined interval D can be expressed as the following equation.

D ≤ x ₀ -(-x ₀ ) = 2x ₀

It is a figure explaining the determination principle of the said predetermined space | interval D with respect to the more general process object. In FIG. 5A, the processing object 500 is formed by stacking a thin film 520 on the wafer 510. In FIG. 5B, the processing object 500 is merely a wafer 510. Each figure is shown. The example of FIG. 5A may be regarded as the same as the embodiment shown in FIG. 4. (Strictly, the wafer in FIG. 5A may correspond to the ceramic glass in FIG. 4, but the entire object formed by stacking Mo on the ceramic substrate in FIG. 4 is regarded as the wafer 510. The example of 5 (A) and the example of FIG. 4 become the same.)

In FIG. 5A, the force F _shock by the shock wave must be greater than the cohesive force of the thin film 520 at the x ₀ and -x ₀ positions, and between the thin film 520 and the wafer (x ₀ and -x ₀ ). 510 should be greater than the adhesion force between. Therefore, in this case, the condition of D can be expressed as follows.

D ≤ 2x ₀

Here, F _shock is the combined force of the shock waves generated by the double light laser irradiation, F _{c, film} is the cohesion of the thin _film , F _{a, film} is the adhesion between the thin film and the wafer, x ₀ is Is determined.

F _shock (x = x ₀ , -x ₀ )> F _{c, film} (x = x ₀ , -x ₀ )

F _shock (-x ₀ <x <x ₀ )> F _{a, film} (-x ₀ <x <x ₀ )

In the case of FIG. 5B, a crack occurs inside the wafer 510 at the inner side of the double light due to the force of the shock wave, and a lift-off phenomenon occurs due to the crack. Therefore, in this case, the force F _shock due to the shock wave must be greater than the cohesive force of the wafer 510 at both the x ₀ and -x ₀ positions and between x ₀ and -x ₀ . Therefore, in this case, the condition of D can be expressed as follows.

D ≤ 2x ₀

Here, F _shock is the sum of the shock waves generated by the double light laser irradiation, and F _{c, wafer} is the cohesion force of the wafer, and x ₀ is determined by the following conditions.

F _shock (-x ₀ ≤ x ≤ x ₀ )> F _{c, wafer} (-x ₀ ≤ x ≤ x ₀ )

On the other hand, Figure 6 describes a Winra that can maximize the effect of the above invention by applying an additional force (F _add ) using a third laser beam or a mechanical method other than double light. That is, when the force (F _shock ) applied by the double line is less than the cohesion and adhesion of the target material, the force (F _sum ) that is the sum of the above additional forces (F _add ) is greater than the cohesion and the adhesion. Desired patterning may be possible.

7 shows a diagram in which this is generalized. In FIG. 7A, a thin film 520 is stacked on the wafer 510 (as shown in FIG. 5A), and in FIG. 7B (also FIG. 5 (A)). As shown in B), each of the processing objects 500 is merely a wafer 510.

In FIG. 7 (A), the _sum of the force F _shock and the force F _sum of the additional force F _add , a force caused by other laser light, or a mechanical force applied externally, is x ₀ and −x _{The zero} position should be greater than the cohesive force of the thin film 520, and between x ₀ and -x ₀ should be greater than the adhesion between the thin film 520 and the wafer 510. Therefore, in this case, the condition of D can be expressed as follows.

D ≤ 2x ₀

Here, F _shock is the combined force of the shock waves generated by the double light laser irradiation, F _add is the additional force applied, F _sum is F _shock + F _add , F _{c, film} is the cohesion of the thin _film , F _{a, film} is In terms of adhesion between the thin film and the wafer, x ₀ is determined by the following conditions.

F _sum (x = x ₀ , -x ₀ )> F _{c, film} (x = x ₀ , -x ₀ )

F _sum (-x ₀ <x <x ₀ )> F _{a, film} (-x ₀ <x <x ₀ )

For FIG. 7B, the _sum F _sum must be greater than the cohesion force of the wafer 510 at both the x ₀ and -x ₀ positions and between x ₀ and -x ₀ . Therefore, in this case, the condition of D can be expressed as follows.

D ≤ 2x ₀

Here, F _shock is the combined force of the shock waves generated by the double light laser irradiation, F _add is the additional force applied, F _sum is F _shock + F _add , F _{c, wafer} is the cohesion of the wafer, x ₀ Is determined by the following conditions.

F _sum (-x ₀ ≤ x ≤ x ₀ )> F _{c, wafer} (-x ₀ ≤ x ≤ x ₀ )

B) Laser light source: UV laser process and ultrafast laser process for removing adverse effects caused by heat change in conventional laser process

On the other hand, in the conventional laser processing method, that is, the laser processing method of directly irradiating a material having a pulse width of a conventional nanosecond or longer depending on linear absorption, a considerable level excluding the energy required for vaporization of the material among the administered energy. Laser is rapidly diffused outside the focusing region to partially melt the thin film. At this time, after the laser process, the backside decreases very rapidly and is bonded to the lower wafer again in a significantly different state from before the process. (It can be understood that a kind of high-temperature curing occurs very locally.) Therefore, the adhesive force of the thin film of the laser irradiated part is completely different from other parts, so that the lift caused by the laser-induced shock wave The quality deterioration of the off is caused. Increasing the laser fluence to generate SAW that can overcome the change in adhesion caused by the laser-induced melting causes a force on the thin film other than between the two lines. It is true that control to prevent delamination or chipping is very difficult.

In the present invention, by using a laser such as a laser in the ultraviolet region, ultrafast laser, it is possible to minimize the laser induced thermal energy generated during the laser process. This laser process technology has the great advantage of minimizing the change in the process cross section. Specifically, in order to satisfy such conditions in the present invention, it is preferable to use a femtosecond laser.

More detailed description is as follows. In order to implement the technique of the present invention as described above, in the case where thermal deformation occurs by the laser in the areas x ₀ and -x ₀ to which the laser light is applied to increase the cohesion force and the adhesion force, the conditions described in a) Additional impact energy is required to satisfy these requirements. Therefore, it is desirable to use a laser light that can minimize the increase in adhesion and cohesion due to thermal deformation that may occur during laser processing. In the embodiment of the present invention it was confirmed that this condition is satisfied by performing the processing using the femtosecond laser light, even in the case of other laser micromachining method, that is, nanosecond or picosecond laser when using the wavelength of the ultraviolet region target material It was experimentally confirmed that the thermal deformation of the system was minimized and the conditions described in (a) were satisfied. Therefore, it is preferable that the laser used by the microfabrication method of this invention has a wavelength below the ultraviolet range wavelength.

In other words, the laser used in the multi-line process of the present invention should be able to minimize the change in physical properties of the target material, and also be able to generate local lines and shock waves. In order to satisfy these conditions, the laser used in the present invention may be an ultrafast laser having a pulse width of femtosecond or picosecond, or a laser having a wavelength below the ultraviolet range even in the case of a laser having a pulse width of picosecond or nanosecond. From a practical point of view, in the actual implementation of the method and apparatus of the present invention, of course, it is best to use an ultrafast laser such as a femtosecond laser as in the embodiment of the present invention, but when the present invention is commercialized, the equipment cost is relatively high. By using this inexpensive nanosecond laser, but having a wavelength below the ultraviolet region, it is possible to satisfy the conditions as described above (minimizing changes in the physical properties of the object, local lines and shock waves can be generated).

In addition, as described above, according to the present invention, since the change in the cross section of the process is minimized, the quality of the process may be greatly increased in the cutting process as well as the pattern forming process. In the pattern formation process, ablation by laser irradiation may be performed as much as the thickness of the thin film in the case of the wafer in which the thin film is laminated and by the desired depth in the case of the general wafer. This is done by irradiating a laser with energy as much as possible.

3) Nozzle: Supersonic gas injection effect

As described above, in the present invention, an ultrafast laser such as a femtosecond laser is used to form a multi-line (rail-roading), so that a lift-off phenomenon occurs at the inner side of the multi-line, thereby spontaneously parting the thin film or wafer surface. The pattern is formed by removing. (Or abrasion occurs by the thickness of the object to be cut, and cutting is performed.) At this time, the following effects can be obtained by injecting a compressed gas to a portion where a pattern is formed or cut is performed.

The pulse repetition rate (PRR) of recent microfabrication lasers is set very high from tens of kHz to 1 MHz, because of the tendency to increase the total laser power and increase the process productivity. More detailed description is as follows. The temperature change due to the increase in the thermal energy of the focusing area by each single pulse is relatively less affected by material change, but accumulated when the pulsed heat is administered very quickly compared to the thermal relaxation time constant. Due to the thermal effect, the laser-induced temperature change in the irradiated region is ultimately too high to be ignored. This effect not only reduces the breaking strength by causing mechanical damage of the material of interest, but also results in local deformation of the adhesion force attached to the lower wafer at the cross-section of the thin film process, as discussed above. There is a possibility to interrupt the process.

In the present invention, in order to overcome such problems, that is, to effectively diffuse the laser-induced thermal energy (diffusion), by focusing the compressed gas lowered to the processing site by adiabatic expansion, the effective relaxation of the accumulated heat To cause. Of course, the lift-off can thus also occur more effectively.

In addition, as the compressed gas is injected to the processing site in this manner, the laser-induced SAW may be spatially limited to more effectively lift-off the thin film. That is, as the high pressure compressed gas is locally focused, the shock wave at the portion where the laser is focused is very effectively limited to propagating upwards, i.e., in the air, of the object to be processed, and ultimately the shock wave is more effectively in the thin film direction. To propagate To solve this problem, by compressing the compressed gas to the outside of the multiple lines, the shock wave diffused to the outside of the multiple lines to offset by the pressure generated by the compressed gas to effectively prevent the separation or crack propagation to the outside of the multiple lines. Thus, the lift-off at the inside of the multiple lines can be performed more effectively.

The compressed gas is a compressed gas that has a large heat capacity and does not affect the electrical, physical, or optical properties of the material, and is a temperature of a process target material that is increased by accumulated thermal energy due to overlap of laser pulses in a process. It can be cooled to be lower than the heat distortion temperature such as the melting point of the target material. Specific types and characteristics of the compressed gas satisfying such conditions are described in detail in Korean Patent Application No. 2010-0085412 filed by the present applicant ("wafer processing and its apparatus", et al.). Omit the description.

D) Optical system: polarization effect

In general, shock wave generation due to the polarization of the laser occurs in an isotropic form. On the other hand, the micro-crack already made has a different LIEF (Light Intensity Enhancement Factor) in the case of orthogonal to the surface, the polarization parallel to the crack direction and vice versa. It has been shown theoretically that the maximum of LIEF in the depths of the cracks is achieved in the latter, which is about 3.9 / 2.7 larger than in the former case (FY Genin, A. Salleo, TV Pistor, and LL). Chase, "Role of light intensification by cracks in optical breakdown on surfaces" Vol. 18, No. 10 / October 2001 / J. Opt. Soc.Am.A 2607-2617). In the case of selecting the laser optical system having the polarized light, the LIFE is localized at the interface between the thin film and the lower wafer more effectively in the depth of ablation cross section by the laser processing line made previously. ing) so that shock-pressure can be generated where desired.

In the present invention, based on the theoretical experimental results as described above, by further providing an optical system for making the laser polarization perpendicular to the direction in which the laser proceeds, the polarization direction control by causing the shock wave pressure more effectively in the same laser fluence It can achieve technical progress by

E) Multi-line process: increase productivity by causing lift of large area by limited area survey

In general, when a portion of a material of a specific area is to be removed by laser ablation, the laser should be projected to all of the desired areas. In particular, since the area to be processed is relatively large and the energy per unit pulse of the laser is low, the focused cross-sectional area may be smaller than the ablation critical fluence value when irradiated over a large area. It is also possible to fail to achieve the desired depth of cut using a given laser power. In a laser process, a laser is scanned one or more times to perform a given process in order to ablate the desired area to a desired depth, thereby resulting in relatively low productivity.

In the present invention, the laser beam is irradiated only on a very small area, i.e., a line, without irradiating the laser to the entire desired pattern area so that only a depth corresponding to the thickness of the thin film is cut by ablation, as described in a). By using the SAW generated during ablation, the inner side of the multiple lines can be removed, so that a desired large area thin film can be removed from the lower wafer with a relatively low laser power. Therefore, the method proposed in the present invention is able to exhibit much higher productivity than the conventional laser process.

F) Optical system: Increased productivity by maximizing the use of laser energy by adopting SHG combined optical system

As described above, in the present invention, the multi-line, at least the double-line should be formed, and the laser beam must be divided into two or more to focus. On the other hand, in consideration of the required high process precision, the laser beam should be spaced at a distance smaller than the general laser beam size and then focused using an objective lens having a relatively high magnification. For example, when using a telecentric lens, the distance between laser beams corresponding to the process precision should be spaced apart. To this end, generally, a beam obtained from a laser is divided into two beams using a beam splitter, and then a combination is performed using another optical splitter. In this case, two laser beams having different polarizations may be polarized using a polarization beam splitter, and the two beams may be matched again at a desired interval without relatively losing energy. However, the above method has a problem in that the distance between laser beams having a desired degree can be separated from the laser beam without loss of laser power while having the same wavelength and the same polarization.

In order to overcome this problem, the present invention generates a second harmonic generation by passing a fundamental output beam of a laser through a nonlinear optical crystal so that the laser beam can be separated without loss of output. . That is, as shown in FIG. 2, when the laser first penetrates the SHG 111, a laser beam having a wavelength corresponding to the fundamental wavelength of the laser and its second harmonic wave is simultaneously present. The light splitter 112 separates the beam corresponding to the fundamental wavelength. At this time, the optical splitter 112 is preferably a dichroic beam splitter. The second harmonic laser beam separated by the optical splitter 112 is diverted to another path through the optical system 114, thereby allowing two beams to be generated without losing the total laser energy. The light combiner 115 is then used to combine the fundamental wavelength laser beam and the second harmonic laser beam through a constant light path. In this case, the optical coupler 115 is also preferably a dichroic beam splitter.

By configuring the device in this way, two or more laser beams can be obtained without losing energy, and the distance between the laser beams can be adjusted as desired. The multi-line process can be performed by concentrating the multiple light thus obtained to the thin wafer or the thin film laminated on the wafer through the light converging unit 115. This makes it possible to obtain a productivity increase effect by maximizing the use of laser energy compared to the conventional method. The light focusing unit 115 may be simply formed of a single objective lens, or may be formed of an optical system including two or more lenses according to a user's design or purpose.

G) Lower support structure when cutting thin wafer dicing

In the case of cutting or dicing a thin wafer by using the multi-line process devised in the present invention, it is possible to maximize productivity and quality when the following supporting structure is provided.

When the energy of the irradiated laser absorbs the support structure very effectively as compared with the material to be cut or diced, and the absorption-induced shock wave is generated with a very high efficiency, the lift-off phenomenon is increased in the inner region between the laser beam irradiation lines. The support structure is also designed so that the desired chip area is two lasers, if the adhesion force with the material to be cut or diced is comparable to the force due to the acoustic shock pressure generated by a single laser pulse. If it is larger than the area between the beams, the chip can be cut or diced very effectively without peeling the chip. As shown in FIG. 8, this technical review is found to be particularly effective in the patterning of deposition type solar cells in which a metal such as molybdenum is used as the lower electrode. Can be.

8 is an optical photograph (A), an electron microscope (SEM) photograph (B), and an atomic force microscope (AFM) photograph (C) of the results of performing essential P3 patterning in the CIGS-type solar cell process fabricated by the present invention, respectively. Is showing.

FIG. 9 is a pattern result (A) formed by patterning a thin film deposited on a wafer using a conventionally-used laser as shown, and a diamond needle contacting and scratching a diamond needle on top of a brittle CIGS thin film. The pattern result (B) which is conventionally obtained by the conventional method is compared with the pattern result (C) formed by the process of the present invention. As shown in FIG. 9, in the case of the conventional patterning using a laser, the pattern line forms a beads shape (FIG. 9 (A)), and when the mechanical method is used, the damage around the pattern is very much broken. (B) results in poor results, whereas the pattern formed by the method and apparatus of the present invention yields very good results with high process precision as shown in FIG. 9C. can confirm.

The present invention is not limited to the above-described embodiments, and the scope of application of the present invention is not limited to those of ordinary skill in the art to which the present invention pertains without departing from the gist of the present invention as claimed in the claims. Of course, various modifications can be made.

100: fine processing apparatus (of the present invention)
110: light irradiation unit
111: laser light source 112: second harmonic generator (SHG)
113: beam splitter 114: optical system
115: beam combiner 116: light combiner
120: stage 130: moving means
140: nozzle
500: object to be processed
510: wafer 520: thin film

Claims (17)

In the microfabrication method of forming a pattern or cutting in the object to be processed 500 formed of the wafer 510 in which the wafer 510 or the thin film 520 is stacked,
Multiple laser lights spaced apart from each other at predetermined intervals D determined according to the characteristics of the laser and the object 500 are irradiated to correspond to the pattern shape on the surface of the object 500 to form multiple lines In the laser multi-line process, the inner part of the formed multi-line is spontaneously removed by the shockwave energy generated in the pattern forming process so that the pattern is formed or the multi-line part is cut to perform the cutting. Wafer fine processing method.
The method of claim 1, wherein the predetermined interval (D) is
Wafer fine processing method by a laser multi-line process characterized in that determined according to the following equation.
D ≤ 2x ₀
From here,
The laser light is double-irradiated, the center point of the line segment connecting each position irradiated on the surface of the object 500 to be processed is 0, and any position on the line segment is x, and the line segment Given the coordinates of each endpoint of -x ₀ and x ₀ ,
1) When the object to be processed 500 is a wafer 510 in which a thin film 520 is stacked,
F _shock is the combined force of the shock waves generated by the double light laser irradiation, F _{c, film} is the cohesion of the thin _film , F _{a, film} is the adhesion between the thin film and the wafer, x ₀ is determined by the following conditions,
F _shock (x = x ₀ , -x ₀ )> F _{c, film} (x = x ₀ , -x ₀ )
F _shock (-x ₀ <x <x ₀ )> F _{a, film} (-x ₀ <x <x ₀ )
2) When the object to be processed 500 is made of only the wafer 510,
F _shock is the combined force of the shock waves generated by the double light laser irradiation, F _{c, wafer} is the cohesive force of the wafer, x ₀ is determined by the following conditions,
F _shock (-x ₀ ≤ x ≤ x ₀ )> F _{c, wafer} (-x ₀ ≤ x ≤ x ₀ )
3) When mechanical force is applied from the outside or laser light is additionally applied between the double lights, and the object 500 is the wafer 510 in which the thin film 520 is stacked,
F _shock is the combined force of the shock waves generated by the double light laser irradiation, F _add is the force applied mechanically from the outside or additionally applied by the additionally irradiated laser light, F _sum is F _shock + F _add , F _{c, film} is the cohesion of the thin _film , F _{a, film} is the adhesion between the thin film and the wafer, x ₀ is determined by the following conditions,
F _sum (x = x ₀ , -x ₀ )> F _{c, film} (x = x ₀ , -x ₀ )
F _sum (-x ₀ <x <x ₀ )> F _{a, film} (-x ₀ <x <x ₀ )
4) When a mechanical force is applied from the outside or additionally laser light is radiated between the double light and the object 500 is made of only the wafer 510,
F _shock is the combined force of the shock waves generated by the double light laser irradiation, F _add is the force applied mechanically from the outside or additionally applied by the additionally irradiated laser light, F _sum is F _shock + F _add , F _{When c and wafer} are the cohesion force of a wafer, x ₀ is determined by the following conditions.
F _sum (-x ₀ ≤ x ≤ x ₀ )> F _{c, wafer} (-x ₀ ≤ x ≤ x ₀ )
The method of claim 1, wherein the fine processing method
A wafer fine processing method by a laser multi-line process, characterized in that the processing is performed using a laser light having a wavelength below the ultraviolet region wavelength.
The method of claim 1, wherein the fine processing method
A wafer fine processing method using a laser multi-line process, characterized in that the processing using a laser light having a pulse width of any one selected from femtoseconds, picoseconds, nanoseconds.
The method of claim 1, wherein the fine processing method
When multiple laser lights are simultaneously linearly irradiated on the surface of the object 500 to form multiple lines,
Compressed gas is sprayed on the surface of the object 500 to directly cool the surface of the object 500 through supersonic adiabatic expansion, and removes foreign substances and by-products from the surface of the object 500. Wafer microfabrication method by laser multi-line process.
The method of claim 1, wherein the fine processing method
Laser polarization is perpendicular to the advancing direction of the laser light so that the polarized laser is irradiated to the surface of the object to be processed (500), characterized in that the fine wafer processing method by the laser multi-line process.
The method of claim 1, wherein the fine processing method
Process for fine wafer processing by laser multi-line process, characterized in that the processing is performed using a double light.
In the micro-processing apparatus 100 for forming a pattern or cutting a processing object 500 formed of the wafer 510 or the wafer 510 on which the thin film 520 is stacked,
The microfabrication apparatus 100 is irradiated with a plurality of laser light spaced apart from each other at a predetermined interval (D) determined according to the characteristics of the laser and the object to be processed on the surface of the object 500. A light irradiation unit 110 to perform, a stage 120 on which the object to be processed 500 is disposed, and moving means 130 for moving the relative positions of the light irradiation unit 110 and the stage 120. By the way,
Multiple light irradiated from the light irradiation unit 110 is irradiated to correspond to the pattern shape on the surface of the processing object 500 to form a multi-line, the shock wave generated in the inner portion of the formed multi-line pattern forming process ( Shockwave) Wafer microfabrication apparatus using a laser multi-line process characterized in that the spontaneous removal by energy to form a pattern or the multi-line part is cut and the cutting is performed.
The method of claim 8, wherein the predetermined interval (D) is
Wafer fine processing method by a laser multi-line process characterized in that determined according to the following equation.
D ≤ 2x ₀
From here,
The laser light is double-irradiated, the center point of the line segment connecting each position irradiated on the surface of the object 500 to be processed is 0, and any position on the line segment is x, and the line segment Given the coordinates of each endpoint of -x ₀ and x ₀ ,
1) When the object to be processed 500 is a wafer 510 in which a thin film 520 is stacked,
F _shock is the combined force of the shock waves generated by the double light laser irradiation, F _{c, film} is the cohesion of the thin _film , F _{a, film} is the adhesion between the thin film and the wafer, x ₀ is determined by the following conditions,
F _shock (x = x ₀ , -x ₀ )> F _{c, film} (x = x ₀ , -x ₀ )
F _shock (-x ₀ <x <x ₀ )> F _{a, film} (-x ₀ <x <x ₀ )
2) When the object to be processed 500 is made of only the wafer 510,
F _shock is the combined force of the shock waves generated by the double light laser irradiation, F _{c, wafer} is the cohesive force of the wafer, x ₀ is determined by the following conditions,
F _shock (-x ₀ ≤ x ≤ x ₀ )> F _{c, wafer} (-x ₀ ≤ x ≤ x ₀ )
3) When mechanical force is applied from the outside or laser light is additionally applied between the double lights, and the object 500 is the wafer 510 in which the thin film 520 is stacked,
F _shock is the combined force of the shock waves generated by the double light laser irradiation, F _add is the force applied mechanically from the outside or additionally applied by the additionally irradiated laser light, F _sum is F _shock + F _add , F _{c, film} is the cohesion of the thin _film , F _{a, film} is the adhesion between the thin film and the wafer, x ₀ is determined by the following conditions,
F _sum (x = x ₀ , -x ₀ )> F _{c, film} (x = x ₀ , -x ₀ )
F _sum (-x ₀ <x <x ₀ )> F _{a, film} (-x ₀ <x <x ₀ )
4) When a mechanical force is applied from the outside or additionally laser light is radiated between the double light and the object 500 is made of only the wafer 510,
F _shock is the combined force of the shock waves generated by the double light laser irradiation, F _add is the force applied mechanically from the outside or additionally applied by the additionally irradiated laser light, F _sum is F _shock + F _add , F _{When c and wafer} are the cohesion force of a wafer, x ₀ is determined by the following conditions.
F _sum (-x ₀ ≤ x ≤ x ₀ )> F _{c, wafer} (-x ₀ ≤ x ≤ x ₀ )
The method of claim 8, wherein the light irradiation unit 110
Laser light source 111;
A second harmonic generator (112) for generating at least a second or higher order harmonic light by passing the laser fundamental light emitted from the laser light source 111 through a non-linear optical crystal;
A beam splitter 113 for splitting the light passing through the SHG 112 into a fundamental light and a multi-order harmonic light;
An optical system 114 for controlling the optical paths of the basic light and the multiple harmonic wave light emitted through the optical separator 113 to be spaced apart by a predetermined interval;
A beam combiner 115 for combining the fundamental light and the multi-order harmonic light emitted through the optical system 114;
An optical concentrator 116 for irradiating and focusing the primary light and the multi-order harmonic light spaced apart from each other by passing through the optical coupler 115 on the surface of the object to be processed 500;
Wafer fine processing apparatus by a laser multi-line process comprising a.
The method of claim 8, wherein the light irradiation unit 110
A laser microfabrication apparatus according to a laser multi-line process, characterized by generating laser light having a wavelength below the ultraviolet region wavelength.
The method of claim 8, wherein the light irradiation unit 110
A wafer microfabrication apparatus using a laser multi-line process, wherein the pulse width generates laser light having any one selected from femtoseconds, picoseconds, and nanoseconds.
The method of claim 8, wherein the fine processing apparatus 100
A nozzle 140 for directly cooling the wafer surface by supersonic adiabatic expansion by spraying compressed gas, and removing foreign substances and processing by-products from the surface of the object 500;
Wafer fine processing apparatus by a laser multi-line process characterized in that it further comprises.
The method of claim 8, wherein the light irradiation unit 110
The apparatus for fine wafer processing by the laser multi-line process, characterized in that the polarized laser is irradiated on the surface of the processing object (500) so that the laser polarization is perpendicular to the traveling direction of the laser light.
The method of claim 8, wherein the light irradiation unit 110
Wafer microfabrication apparatus by laser multi-line process characterized by generating and irradiating double light.
The method of claim 10, wherein the optical separator 113
A wafer microfabrication apparatus using a laser multi-line process, comprising a dichroic beam splitter.
The method of claim 10, wherein the optical coupler 115 is
A wafer microfabrication apparatus using a laser multi-line process, comprising a dichroic beam splitter.

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