CN213969513U

CN213969513U - System for applying nanosecond pulse laser to strip epitaxial chip

Info

Publication number: CN213969513U
Application number: CN202022333183.2U
Authority: CN
Inventors: 蔡明聪; 洪瑜亨; 游家豪; 黄俊杰
Original assignee: Xuzhen Technology Co ltd
Current assignee: Xuzhen Technology Co ltd
Priority date: 2020-10-19
Filing date: 2020-10-19
Publication date: 2021-08-17
Anticipated expiration: 2030-10-19

Abstract

A system for peeling an epitaxial chip by applying nanosecond pulse laser comprises a nanosecond pulse laser optical machine, a processing carrying platform, a beam expander set, a diffraction optical element, a galvanometer scanning module, a visual identification module and a control unit. The nanosecond pulse laser optical machine provides a laser pulse light beam as a laser processing light source for stripping the epitaxial chip; the beam expanding lens group, the diffraction optical element and the galvanometer scanning module are all positioned on a transmission path of laser pulse beams; the visual identification module is used for inspecting the state of the laser pulse light beam projected on the position to be processed; the control unit is electrically connected and enables the processing platform deck, the galvanometer scanning module, the visual identification module and the nanosecond pulse laser optical machine to synchronously cooperate, and is matched with a specific laser processing path and a properly designed diffraction optical element to overcome the problem of laser heat effect when the nanosecond pulse laser is used for precision processing, so that the nanosecond pulse laser optical machine is used for carrying out laser ablation stripping operation on the epitaxial chip.

Description

System for applying nanosecond pulse laser to strip epitaxial chip

Technical Field

The present invention relates to a system for peeling off an epitaxial chip, and more particularly, to a system for peeling off an epitaxial chip using nanosecond pulse laser, which employs a nanosecond pulse laser optical machine in combination with a specific laser processing path and a diffractive optical element to overcome a thermal effect of the laser.

Background

Conventionally, a gallium nitride (GaN) -based light emitting chip is manufactured by using Sapphire (Sapphire) or a similar transparent material as a substrate, stacking a light emitting layer on the substrate to form a nitride semiconductor layer, and forming an epitaxial wafer by a plurality of semiconductor layers to form a nitride semiconductor light emitting diode chip; that is, the epitaxial wafer stacked on the sapphire substrate is used to be divided into a plurality of chips, but the sapphire substrate has high hardness, which makes the dividing operation difficult.

Secondly, a manufacturing method called "Lift-off" has been widely used in the field of epitaxial wafer dicing operations; specifically, a chip layer including an n-type semiconductor layer and a p-type semiconductor layer is formed on a surface of an epitaxial substrate through a buffer layer, and laser light having a wavelength that can penetrate the epitaxial substrate and be absorbed by the buffer layer is irradiated from a back surface side of the epitaxial substrate to break the buffer layer, and the epitaxial substrate is peeled off from the chip layer, and the chip layer is further transferred to a transfer circuit substrate made of Au or Sn (gold or tin) as a main material.

However, in the method of irradiating the buffer layer with the laser beam, the buffer layer may not be sufficiently broken, and the epitaxial substrate may not be smoothly peeled from the chip layer. Or, when the laser beam is used for irradiation, because the pulse length of the nanosecond pulse laser is long, and the energy distribution of the traditional laser focusing light spot is too concentrated or uneven, a serious thermal effect is easily generated, so that the periphery of the epitaxial chip generates thermal damage, and even more, the epitaxial chip is damaged, further the brightness of the crystal grain is greatly attenuated, and the reject ratio of the light emitting diode chip is improved.

Therefore, how to further improve the yield and reduce the processing cost, on the premise of not using picosecond and femtosecond pulse lasers with relatively high manufacturing cost, the nanosecond pulse laser is used to solve the defects that the epitaxial substrate cannot be smoothly stripped from the chip layer at present, and the high-power laser light source is used for processing in the stripping operation, which causes the attenuation of the brightness of the crystal grains, the improvement of the fraction defective of the product, and the like, is a topic that the present inventors have eagerly wanted to research and improve.

SUMMERY OF THE UTILITY MODEL

The main purpose of this creation is to apply the nanosecond pulse laser source, match the specific laser processing path, and properly designed diffractive optical element to overcome the problem of laser thermal effect, and then realize the operating system that uses the nanosecond pulse laser source to carry out laser ablation on the epitaxial chip.

To achieve the above object, the technical means adopted by the present invention comprises: a frame body; the laser light source comprises a nanosecond pulse laser optical machine and a beam deflector which are respectively arranged on the frame body and can provide a laser pulse beam which is used as a laser processing light source for stripping the epitaxial chip; a processing carrier arranged on the frame body and positioned at the opposite side of the laser light source, wherein the processing carrier is provided with a working platform and a displacement mechanism, so that the epitaxial wafer to be processed placed on the working platform can carry out X, Y, Z displacement in three axial directions; the beam expanding lens group is arranged on the frame body, is positioned on the adjacent side of the laser light source and the transmission path of the laser pulse light beam, and is provided with a lens element for changing the diameter and the divergence angle of the laser pulse light beam and enabling the laser pulse light beam to form a parallel light beam; and the diffraction optical element is arranged on the frame body, is positioned on the adjacent side of the beam expanding lens group and on a transmission path of the laser pulse light beam and is used for adjusting the intensity of the laser pulse light beam so as to achieve the effects of shaping and redistributing the energy of the laser facula.

A galvanometer scanning module, which is arranged above the working platform and is positioned on a transmission path of the laser pulse light beam, is provided with an X-Y optical scanning lens and an optical reflection lens, and realizes the focusing of laser faculae and the generation of corresponding angle shift through the reflection of the optical reflection lens and the focusing of the X-Y optical scanning lens, so that the laser pulse light beam is deflected and focused on a desired processing point of the epitaxial wafer to ablate an epitaxial chip; and the visual identification module is arranged on the frame body, can provide a visual area for visual identification and is used for inspecting the state of the laser pulse light beam projected on the position to be processed.

The control unit is arranged on the frame body, is electrically connected with the processing carrying platform, the galvanometer scanning module, the visual identification module and the nanosecond pulse laser optical machine to synchronously cooperate, is matched with a specific laser processing path and a properly designed diffraction optical element, and overcomes the laser heat effect when the nanosecond pulse laser is used for precision processing, thereby realizing the laser ablation operation of the nanosecond pulse laser optical machine on the epitaxial chip.

According to the features disclosed above, the beam expander set in the present invention includes an optical element composed of a concave lens and a convex lens, so as to change the size and the divergence characteristics of the laser pulse beam.

According to the above disclosed features, the vision module in the present invention includes a lens and a charge-coupled device (CCD) for inspecting the state of the laser pulse beam projected on the desired position.

With the help of the technical characteristics that publish above, this creation "use nanosecond pulse laser in order to peel off epitaxial chip's system next generation", the benefit that has is:

(1) the present creation applies a diffractive optical element to solve the problem of excessive Ablation caused by the laser spot irradiating a specific area of an epitaxial wafer, or the problem of an unmanageable state caused by the energy of the laser spot not reaching an Ablation threshold (Ablation threshold); generally, the energy of a common laser spot is Gaussian distribution (Gaussian distribution), and in order to achieve a line width required by processing, the laser energy is usually adjusted to an intensity greater than an ablation threshold of a material of a processed workpiece, so that the processed workpiece is excessively ablated at the center of the laser spot; the laser spot shaping device redistributes the energy of the laser spot through the diffraction optical element, so as to achieve the effect of shaping the laser spot, and the laser spot is uniformly irradiated on the workpiece, thereby reducing and reducing the damage of the processed workpiece.

(2) The creation applies a galvanometer scanning module to enable laser pulse light beams to accurately carry out laser ablation on a buffer layer of an epitaxial chip according to a planned specific laser processing path; in particular, the laser processing path is determined according to the shape of the workpiece to be processed and the distribution of the target to be processed, and the workpiece is generally processed one by one from the outside to the inside in a concentric or spiral manner from the outermost periphery of the workpiece to be processed; meanwhile, the laser processing path of the galvanometer scanning module can improve the exhaust efficiency of waste gas generated during laser processing and reduce the thermal stress applied to a processing workpiece during gas exhaust.

Drawings

FIG. 1: is a schematic diagram of a system for laser lift-off of an epitaxial chip.

FIG. 2: is the front view of the system combination of the laser stripping epitaxial chip.

FIG. 3: the laser beam irradiation and the processing path are schematic.

FIG. 4: is a comparative graph of the laser spot shaping effect of the creation.

FIG. 5: is a laser spot processing line width comparison graph of the creation.

List of reference numerals: 10-a frame body; 20-a laser light source; 21-nanosecond pulse laser optical machine; 22-a beam deflector; 30-processing a carrier; 31-a working platform; 32-a displacement mechanism; 40-galvanometer scanning module; a 41-X-Y optical scanning lens; 42-an optical mirror plate; 50-a visual recognition module; 52-lens; 53-Charge Coupled Devices (CCD); 60-a beam expander set; 61-concave lens; 62-convex lens; 70-a diffractive optical element; 80-a control unit; e1-energy before shaping value; e2-ablation threshold; e3-energy value after shaping; l1 — laser pulse beam; m-processing the workpiece; W1-Pre-reshaped linewidth; w2-line width after reshaping; w3-full line width; w4-unsaturated linewidth; w5-oversaturated linewidth.

Detailed Description

First, the present creation "system for peeling off an epitaxial chip by applying nanosecond pulse laser" is shown in fig. 1 to 2, and includes: a frame 10 for assembling the related system components of the present creation; a laser light source 20, including a nanosecond pulse laser machine 21 and a beam deflector 22, respectively disposed on the frame 10, wherein the nanosecond pulse laser machine 21 can provide a laser pulse beam L1 as a laser processing light source for peeling off an epitaxial chip, and the beam deflector 22 is disposed on a transmission path of the laser pulse beam L1 projected by the nanosecond pulse laser machine 21, for adjusting a reflection direction of the laser pulse beam L1 thereof, and reducing an occupied space of the laser light source 20; in the embodiment, the beam deflector 22 is configured with 2 stages, so that the laser pulse beam L1 is reflected for 2 times and then projected in the horizontal direction, which makes the laser light source 20 occupy the least space and makes the adjustment of the laser pulse beam L1 more flexible and convenient; a processing carrier 30, which is disposed on the frame 10 and located on the opposite side of the nanosecond pulse laser optical machine 21, and has a working platform 31 for placing an epitaxial wafer (referred to as "processing workpiece M"), and a displacement mechanism 32 capable of performing X, Y, Z three axial displacements, wherein the X, Y two axial displacements can move the processing workpiece M to a desired laser processing position, and the Z-axis displacement can make the working platform 31 match the projection focal length of the laser pulse beam L1 to raise or lower the height thereof; since the axial displacement function of the displacement mechanism 32 is the application of the existing technology, the principle and the mode of the displacement mechanism are not repeated; a beam expander set 60 disposed on the frame 10, located on the adjacent side of the laser light source 20 and the transmission path of the laser pulse light beam L1, and having a lens element, wherein the lens element in the present invention may include a concave lens 61 and a convex lens 62, but not limited thereto, such as two convex lenses 62, and may be implemented in combination with other lenses, so as to change the diameter and divergence angle of the laser pulse light beam L1 and make it form a parallel light beam; a diffractive optical element 70 disposed on the frame 10 and located adjacent to the beam expander set 60 and on the transmission path of the laser pulse beam L1, for adjusting the intensity of the laser pulse beam L1, so as to achieve the effects of laser spot shaping and energy redistribution.

A galvanometer scanning module 40, disposed above the working platform 31 and on the transmission path of the laser pulse beam L1, having an X-Y optical scanning lens 41 and an optical reflection lens 42, and reflecting the laser beam by the optical reflection lens 42 and focusing the laser beam by the X-Y optical scanning lens 41 to focus the laser spot and generate a corresponding angle shift, so as to deflect and focus the laser pulse beam L1 on the desired processing point of the processing workpiece M for laser ablation of the epitaxial chip; a vision module 50 disposed on the frame 10 and above the processing stage 30, wherein the vision module 50 includes a lens 52 and a charge-coupled device (CCD)53, which can provide a visual area for visual identification to inspect the state of the laser pulse beam L1 projected on the processing workpiece M to be processed; in this embodiment, an automatic optical inspection device (AOI analysis) can be further connected to improve the accuracy of the visual inspection; and a control unit 70, which is disposed on the frame body 10, and is electrically connected to the processing stage 30, the galvanometer scanning module 40, and the visual recognition module 50, and makes them cooperate with the nanosecond pulse laser optical machine 21 synchronously, and matches with a specific laser processing path and a properly designed diffractive optical element, so as to overcome the thermal effect of deriving laser when the nanosecond pulse laser is used for precision processing, and further realize the peeling operation of laser ablation on the epitaxial chip by the nanosecond pulse laser light source.

Therefore, the laser ablation operation mode of the epitaxial chip is as follows: a workpiece M to be processed is placed on the working platform 31, and the laser optical machine 21 sends out a laser pulse beam L1, which is turned to the horizontal direction by the beam deflector 22 and then is refracted by the optical reflection lens 42, so that the laser pulse beam L1 in the horizontal direction is turned to the working platform 31 below; step 1, the control unit 70 drives the displacement mechanism 32 of the machining carrier 30 to zero, and performs displacement of the working platform 31 to move the machining workpiece M to a desired machining position; step 2, the control unit 70 controls the vision identification module 50 to identify and judge the current position of the processing workpiece M, and meanwhile, the control unit 70 cooperates with the fine adjustment displacement mechanism 32 of the processing carrier 30 to adjust the processing workpiece M to a more accurate laser processing position; step 3, the control unit 70 cooperates with the vision recognition module 50 synchronously to control the galvanometer scanning module 40 according to the position to be processed, so as to move the laser pulse beam L1 to the position to be processed; step 4, the control unit 70 cooperates with the visual recognition module 50 synchronously to control the galvanometer scanning module 40 to adjust the energy of the laser pulse beam L1; step 5, repeating the

steps

3 and 4 until all positions of the machining workpiece M to be machined are machined by the laser; step 6, repeating the

steps

1 and 2, and replacing a newly machined workpiece M; and 7, repeating the

steps

3 and 4 until all positions of the newly processed workpiece M to be processed are processed by the laser.

In order to improve the efficiency of exhausting the waste gas generated during the laser processing and reduce the thermal stress applied to the workpiece M during the gas exhausting, the laser processing path and direction are shown in fig. 3; in the drawing, the processing path of the laser pulse beam L1 transferred by the galvanometer scanning module 40 is processed one by one from the outside to the inside in a concentric or spiral manner starting from the outermost periphery of the workpiece M to be processed; meanwhile, the path of the laser pulse beam L1 depends on the shape of the workpiece M and the distribution of the target to be processed.

In the creation, in order to prevent the situation that a specific area of a workpiece M irradiated by a laser spot is excessively ablated or the energy of the laser spot does not reach the ablation threshold of the material of the workpiece M during laser processing, so that the workpiece M cannot be processed; in the present creation, for the material characteristics and processing requirements of different processing workpieces M, a corresponding and properly designed diffractive optical element 70 is added to the front section of the path for transmitting the laser pulse beam L1, so as to achieve the effects of shaping the laser spot and redistributing the energy, thereby reducing the above-mentioned processing doubt; fig. 4 is a graph showing the laser spot shaping effect comparison of the present invention, wherein the left graph is a laser spot not shaped by the diffractive optical element, the line width W1 before shaping of the laser beam is smaller, and the energy value E1 before shaping is greater than the Ablation threshold (Ablation threshold) E2, so that the machined workpiece M will generate the excessive Ablation phenomenon; on the contrary, the right graph shows that the laser spot is shaped, the line width W2 of the shaped laser beam is large, and the energy value E3 is close to the ablation threshold E2, so that the workpiece M is not excessively ablated and damaged. Generally, the energy of a common laser spot is Gaussian distribution (Gaussian distribution), and in order to achieve a line width required by processing, the laser energy is usually adjusted to an intensity greater than an ablation threshold of a workpiece material to be processed; however, due to the gaussian distribution of the laser spot, the machined workpiece M is easily over-ablated at the center of the laser spot; therefore, the diffractive optical element 70 of the present invention not only achieves the effect of shaping the laser spot, but also easily redistributes the energy of the laser spot to uniformly irradiate the workpiece M, thereby reducing and reducing the damage to the workpiece M.

Please further refer to fig. 5, which is a comparison of different processing line widths of the laser spots; wherein the figure in the upper figure is the laser processing using the diffractive optical element 70, and the processing of the full line width W3 can be obtained; the graph of the middle graph is laser processing of a common Gaussian distribution light spot, which may cause processing of an unsaturated line width W4 due to insufficient overlapping rate; the graph of the lower graph is laser processing of a general Gaussian distribution light spot, which may cause processing of a supersaturated linewidth W5 due to an excessively high overlap ratio; obviously, the diffractive optical element 70 with a proper design is adopted in the present creation to perform laser processing, so as to achieve the effects of shaping the laser spot and redistributing the energy, and further avoid the doubts that the processing workpiece M cannot be processed or the processing workpiece M is excessively ablated.

It should be understood, however, that the drawings and detailed description thereto are merely exemplary of the preferred embodiments of the present invention, and that various modifications and equivalent arrangements which are within the spirit and scope of the present invention will be suggested to those skilled in the art.

Claims

1. A system for applying nanosecond pulsed laser to lift off an epitaxial chip, comprising:

a frame body;

the laser light source comprises a nanosecond pulse laser optical machine and a beam deflector which are respectively arranged on the frame body, can provide a laser pulse beam and is used as a laser processing light source for stripping the epitaxial chip;

the processing carrier is arranged on the frame body and positioned on the opposite side of the laser light source, and is provided with a working platform and a displacement mechanism, so that the epitaxial wafer placed on the working platform can carry out X, Y, Z displacement in three axial directions;

the beam expanding lens group is arranged on the frame body, is positioned on the adjacent side of the laser light source and the transmission path of the laser pulse light beam, and is provided with a lens element so as to change the diameter and the divergence angle of the laser pulse light beam and enable the laser pulse light beam to form a parallel light beam;

a diffraction optical element arranged on the frame body and positioned on the adjacent side of the beam expanding lens group and the transmission path of the laser pulse light beam so as to adjust the intensity of the laser pulse light beam and further achieve the reshaping of laser spots and the redistribution of energy;

a galvanometer scanning module, which is arranged above the working platform and is positioned on a transmission path of the laser pulse light beam, is provided with an X-Y optical scanning lens and an optical reflection lens, and realizes the focusing of laser spots and the generation of corresponding angle shift through the reflection of the optical reflection lens and the focusing of the X-Y optical scanning lens, so that the laser pulse light beam is deflected and focused on a desired processing point of the epitaxial wafer to ablate an epitaxial chip;

the visual identification module is arranged on the frame body and positioned above the processing carrying platform, and can provide a visual area for visual identification so as to inspect the state of the laser pulse light beam projected to a position to be processed;

the control unit is arranged on the frame body, is electrically connected with the processing carrying platform, the galvanometer scanning module, the visual identification module and the nanosecond pulse laser optical machine to synchronously cooperate, is matched with a designed specific laser processing path, and is matched with a properly designed diffraction optical element, so that the problem of laser heat effect when the nanosecond pulse laser is used for precision processing is solved, and the laser ablation operation of the nanosecond pulse laser optical machine on an epitaxial chip is realized.

2. The system for peeling off an epitaxial chip using nanosecond pulsed laser according to claim 1, wherein the beam expander set comprises an optical element consisting of a concave lens and a convex lens,

thereby changing the size of the laser pulse beam and its divergence characteristics.

3. The system of claim 1, wherein the vision recognition module comprises a lens and a charge-coupled device (CCD) for inspecting the state of the pulsed laser beam projected onto the desired position.