Wafer continuous peeling apparatus and wafer continuous peeling method

Abstract

The application discloses a wafer continuous peeling device and a wafer continuous peeling method, and comprises the following steps: forming a plurality of peeling layers in a crystal ingot by using an ultrashort pulse laser, and the distance between adjacent peeling layers is the thickness of a wafer; placing the crystal ingot on a lifting platform, adjusting the height of the lifting platform, making the uppermost peeling layer of the crystal ingot flush with the upper surface of a clamping jaw, and then clamping the crystal ingot by the clamping jaw; applying ultrasonic waves to the upper surface of the crystal ingot by using an ultrasonic component, and the peeling layer cracks under the action of the ultrasonic waves, so that the wafer is peeled from the crystal ingot; the wafer is moved out of the crystal ingot by using a vacuum adsorption component, and subsequent processing is carried out; the clamping jaw is loosened, the height of the lifting platform is adjusted, and the wafer is prepared by using the same method. The wafer can be continuously prepared by using the method, and the preparation efficiency of the wafer is effectively improved.

Description

TECHNICAL FIELD

[0001] The present application belongs to the technical field of semiconductor element processing method and wafer stripping device, and particularly relates to a wafer continuous stripping device and a wafer continuous stripping method. BACKGROUND

[0002] The statements herein merely provide background technology related to the present application, and do not necessarily constitute prior art.

[0003] At present, traditional silicon-based semiconductors cannot meet the demand of people for high power and low energy consumption. Silicon carbide (SiC) has the advantages of high chemical stability, high hardness, high power density and low heat loss, and becomes an ideal substrate material for high-power radio frequency devices and high-voltage power devices, and has a wide application prospect in electric vehicles, communication base stations, high-voltage power transmission and other industries. However, the most important factor restricting its development and promotion at present is the high cost of substrate material. At present, SiC single crystal substrate accounts for a large proportion of the cost of finished devices, about 50%.

[0004] At present, the processing method of SiC wafer is mainly diamond wire saw cutting, which needs to go through cutting, grinding and polishing processes. The processing process is complex, and there is a lot of material loss in the cutting process and the grinding of the front and back surfaces of the cut wafer. At the same time, chemical reagents are needed in the process of grinding and polishing, which causes serious environmental pollution. In addition, due to the high hardness of SiC crystal ingot, it is difficult to cut off by using a wire cutting machine, so the cutting process is time-consuming, low in efficiency and low in production efficiency, which increases the production cost of SiC wafer.

[0005] Although some people have studied in the prior art to form a stripping layer in the crystal ingot at a depth corresponding to the thickness of the wafer from the surface of the crystal ingot along the C face, adhere the first surface of the crystal ingot to the solid substrate through the adhesive layer, take the crystal ingot as the interface, and strip a part of the crystal ingot to generate a wafer, and then perform subsequent operations. Although this method can improve the preparation efficiency of single wafer to a certain extent, it cannot realize the continuous preparation of wafer, and the preparation efficiency of wafer is still low. SUMMARY

[0006] In view of the deficiencies in the prior art, the purpose of the present application is to provide a wafer continuous stripping device and a wafer continuous stripping method, which can reduce material loss and production cost, and improve the production efficiency of the laser stripping wafer processing method.

[0007] In order to achieve the above-mentioned purpose, the present application is realized by the following technical scheme:

[0008] In the first aspect, the present application provides a wafer continuous stripping device, which comprises a working base, a clamping jaw, an ultrasonic component and a vacuum adsorption component.

[0009] The working base includes a lifting platform, which is rotatable and vertically movable relative to the working base;

[0010] The clamping jaw is arranged outside the lifting platform in a sleeve manner, and forms a hollow cylinder when closed; the laser is scanned according to a set route, and the ingot with multiple stripping layers is fixed on the lifting platform by the clamping jaw;

[0011] The clamping jaw is rotatable with the lifting platform;

[0012] The ultrasonic component is arranged above the clamping jaw;

[0013] The vacuum adsorption component is arranged above the clamping jaw and used for moving the formed wafer out.

[0014] In some embodiments, the clamping jaw is a hollow cylindrical electrically driven locking clamp, and the opening and closing of the clamping jaw are controlled by electromagnetic driving.

[0015] In some embodiments, the clamping surface of the clamping jaw is serrated, and the surface is coated with an anti-skid layer.

[0016] In some embodiments, the vacuum adsorption component and the ultrasonic component are integrally arranged above the clamping jaw. The ultrasonic vibration is realized by the ultrasonic component, the head of the ultrasonic component is connected with an ultrasonic generator through a connecting frame, and the connecting frame is used for delivering the output ultrasonic wave of the ultrasonic generator to the surface of the ingot and adjusting the position of the ultrasonic component.

[0017] The vacuum adsorption function requires that the ultrasonic component is closely attached to the surface of the ingot, and the negative pressure is generated through small pores on the surface of the ultrasonic component. The head of the ultrasonic component is hollow, the hollow ultrasonic component is connected with a vacuumizing device through an internal channel, and the vacuum adsorption is realized. The two functions can be integrated in the mechanical interior, and the functions are realized by controlling the position of the ultrasonic component and selecting which function to start.

[0018] In some embodiments, a water gun is arranged on one side above the clamping jaw, and the water gun is used for spraying a water column with a set pressure on the upper surface of the ingot and / or the stripping layer.

[0019] The ultrasonic vibration applied to the upper surface of the ingot makes the wafer to be stripped separated from the ingot, the water flow at the position can play a buffering role for the ultrasonic wave, avoids the direct action of the ultrasonic wave on the upper surface, the upper surface of the ingot receives the maximum intensity of the ultrasonic wave, and unnecessary damage is caused to the wafer, and meanwhile, the cleaning effect is provided.

[0020] In a second aspect, the application provides a wafer continuous stripping method, which includes the following steps:

[0021] A plurality of stripping layers are formed in the ingot by using an ultrashort pulse laser, and the distance between adjacent stripping layers is the thickness of the wafer.

[0022] Put the ingot on the lifting platform, adjust the height of the lifting platform so that the uppermost exfoliation layer of the ingot is flush with the upper surface of the clamping jaw, and then the clamping jaw clamps the ingot;

[0023] An ultrasonic component is used to apply ultrasonic waves to the upper surface of the ingot, and a water jet is sprayed onto the upper surface of the ingot at the same time. The exfoliation layer cracks under the action of ultrasonic waves, and the wafer is separated from the ingot. A vacuum suction component is used to remove the wafer from the ingot for subsequent processing;

[0024] Loosen the clamping jaw, adjust the height of the lifting platform, and use the same method to prepare subsequent wafers.

[0025] In some embodiments, during the process of absorbing and removing the wafer by the vacuum suction component, the lifting platform rotates the ingot, and a water gun sprays a water column with a set water pressure in the direction of the exfoliation layer to break the remaining connection between the wafer and the ingot, so that the wafer is successfully separated from the ingot.

[0026] Preferably, the spraying direction of the water column is parallel to the exfoliation layer.

[0027] In some embodiments, it further includes the step of grinding and polishing the surface of the separated wafer.

[0028] The beneficial effects achieved by one or more embodiments of the above-mentioned application are as follows:

[0029] By means of an ultrashort pulse laser with a penetrating wavelength, a plurality of exfoliation layers along the C face are formed by vertically focusing at a certain depth from the first surface and moving along a certain path. The end of the ingot away from the first surface is fixed in a positioning frame, and ultrasonic waves are applied to the highest surface of the ingot to cause the ingot on both sides of the exfoliation layer to vibrate relatively, thereby separating the part close to the first surface of the ingot to generate a wafer. The generated wafer is separated from the remaining ingot by vacuum suction and rotation of the lifting platform. By adjusting the height of the ingot, a group of wafers can be obtained without repeatedly moving the horizontal position of the ingot. This method is simple and easy to operate, can reduce material loss and production cost, and improve production efficiency. BRIEF DESCRIPTION OF DRAWINGS

[0030] The drawings accompanying the specification of this application form a part thereof, serve to provide further understanding of the application, and together with the description of the exemplary embodiments of the application, serve to explain the application, and do not constitute an improper limitation on the application.

[0031] Figure 1 A flowchart of the method for continuously separating wafers from an ingot according to an embodiment of the application is shown in the figure;

[0032] Figure 2A schematic diagram of the structure of a SiC crystal ingot in an embodiment of the present application;

[0033] Figure 3 A schematic diagram of the process of forming a separation surface by focusing a pulse laser with an ultra-short pulse width vertically inside a crystal ingot and scanning along parallel lines to a preset depth in an embodiment of the present application;

[0034] Figure 4 A schematic diagram of the structure of a crack formed at a separation surface inside a crystal ingot after laser scanning in an embodiment of the present application;

[0035] Figure 5 A schematic diagram of the structure of a crystal ingot fixed by a positioning frame in an embodiment of the present application;

[0036] Figure 6 In the figure, (A) is a schematic diagram of the front view of the positioning frame; (B) is a schematic diagram of the top view of the positioning frame;

[0037] Figure 7 A schematic diagram of the top view of a working base;

[0038] Figure 8 A schematic diagram of the process of separating a crystal ingot into a remaining crystal ingot and a wafer along a separation surface by ultrasonic action and water flow in an embodiment of the present application;

[0039] Figure 9 A schematic diagram of the process of separating a remaining crystal ingot and a wafer by vacuum suction and rotation of a positioning frame in an embodiment of the present application;

[0040] Figure 10 A schematic diagram of the structure of a polished wafer in an embodiment of the present application;

[0041] Figure 11 A schematic diagram of the process of changing the focusing depth of a pulse laser with an ultra-short pulse width to obtain different depth preset separation surfaces inside a crystal ingot in an embodiment of the present application;

[0042] Figure 12 A schematic diagram of the process of changing the height of a positioning frame to be parallel to different depth separation surfaces in an embodiment of the present application.

[0043] In the figure: 110-crystal ingot; 111-wafer; 120-first surface; 121-first separation surface; 122-second separation surface; 123-third separation surface; 124-fourth separation surface; 125-fifth separation surface; 130-vertical line on the first surface of the crystal ingot; 140-c-axis; 150-C-face; 161-parallel line scanning path; 170-crack; 210-positioning frame; 211-claw; 212-claw contact surface; 220-working base; 221-lifting platform; 310-fixed crossbeam; 320-water gun; 330-ultrasonic component. DETAILED DESCRIPTION

[0044] It should be noted that the following detailed description is illustrative only, and is intended to further explain the present application. All technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this application belongs unless otherwise specifically defined.

[0045] The present application is further described below in conjunction with embodiments.

[0046] Referring to Figure 1 , a processing method for continuously peeling wafers from a crystal ingot using a positioning frame 210 is described. The present application provides a processing method for continuously peeling wafers from a crystal ingot using a positioning frame 210, which includes steps S100, S200, S300, and S400.

[0047] S100: Focus the focus point of the ultra-short pulse laser with a transmission wavelength at a distance of an integer multiple (nd) of the thickness d of the target wafer from the first surface 120 of the crystal ingot, and scan along a predetermined path, which includes but is not limited to a parallel line scanning route. Re-position the laser focus point at a distance of (n-1)d from the first surface 120, and scan along the predetermined path. In this way, the positioning height of the laser focus point is constantly changed until the depth from the first surface 120 of the crystal ingot is d, and finally a plurality of peeling layers 121-125 are generated in the crystal ingot 110.

[0048] wherein the pulse width of the ultra-short pulse laser is femtosecond or picosecond level, and the pulsed laser emitted by the laser moves along the preset scanning path, forming extended cracks 170 in the radial direction of the preset peeling surface in the crystal ingot, and the cracks are connected to each other to form the peeling layers 121-125.

[0049] Figure 2 The structure of the SiC crystal ingot 110 to be processed in the present embodiment is shown in the structural schematic diagram, which is an SiC crystal ingot 110 having a c-axis 140 and a C-face 150 perpendicular to the c-axis.

[0050] As Figure 3 and Figure 4 shown, the present application forms a peeling surface 125 by vertically focusing the pulse laser with an ultra-short pulse width inside the crystal ingot 110 and scanning along the parallel line 161 at a preset depth, and further forms cracks 170 extending along the radial direction of the preset peeling surface inside the crystal ingot, and the cracks are connected to each other to form the peeling layer 125. The modification layer and the peeling layer refer to the same plane, and the laser acts on the inside of the crystal to form a modification layer, and peeling is performed along the modification layer.

[0051] It can be understood that, as Figure 3As shown, the "radial direction along the preset peeling surface" refers to the X-axis direction in the figure, and the "axial direction along the preset peeling surface" refers to the Y-axis direction in the figure. The pulsed laser is incident along the axial direction of the preset peeling surface.

[0052] Of course, the setting mode of this step S100 is not limited to this, for example, in another embodiment of the present application, as shown in Figure 9 As shown, the step S110 changes the focus depth of the pulsed laser with different short pulse widths to obtain different depths of the preset peeling surface 121-125 inside the crystal ingot.

[0053] S200, fix one end of the crystal ingot 110 away from the first surface 120 in a hollow cylindrical electric locking positioning frame 210, and realize the positioning of the highest point of the positioning frame and the highest peeling layer by lifting the corresponding size base 221 at the bottom of the crystal ingot to make them level.

[0054] As shown in Figure 5 and Figure 6 As shown, the crystal ingot 110 is fixed in a hollow cylindrical electric locking positioning frame 210. After the positioning frame clamping jaw 211 is controlled to open to a certain angle by the control circuit, the crystal ingot 110 to be peeled is fixed on the base 220, and the positioning frame clamping jaw 211 is controlled to close to each other again, so that the clamping jaw 211 finally covers the target crystal ingot 110.

[0055] Among them, the fixed frame 210 can play a role in positioning and protecting the crystal ingot 110, avoiding the crystal ingot 110 from shaking under the action of ultrasound. Specifically, the distance from one of the surfaces 120 of the crystal ingot 110 to the highest preset peeling surface 121 is less than the distance from the other surface of the crystal ingot 110 to the preset peeling surface 121, that is, the thicker side of the crystal ingot is preferably fixed in the positioning frame 210 for fixation and protection.

[0056] Specifically, as shown in Figure 6 The positioning frame 210 is a hollow cylindrical electric locking clamp, which can control the opening and closing of the positioning frame clamping jaw 211 through electromagnetic drive. The contact part of the two clamping jaws 211, that is, the clamping surface 212 is serrated, and the contact part 212 is coated with an anti-skid layer.

[0057] As shown in Figure 7 As shown, there is a rotatable and partially liftable concentric circular base 220 below the crystal ingot 110. By lifting the part of the base 221 corresponding in size to the bottom surface of the crystal ingot, the highest peeling layer 125 of the crystal ingot is made to correspond to the highest point of the positioning frame, and the base is moved while the clamping jaw 211 is slightly opened to a certain angle to facilitate the movement of the crystal ingot 110. After positioning is completed, the locking clamping jaw 211 is locked.

[0058] S300, as shown in Figure 8As shown, an ultrasonic wave 330 is applied at a distance of a certain water layer thickness (about 1 cm) from the highest plane 120 of the crystal ingot. The vibration is transmitted through the water layer and the part of the crystal ingot 111 near the first surface 120 of the crystal ingot with the release layer as the interface to the release layer 121. The release layer 121 cracks under the ultrasonic force, thereby realizing the generation of the wafer 111.

[0059] Specifically, the end face of the ultrasonic device 330 is parallel to the first surface 120 of the crystal ingot, and it has both ultrasonic output and vacuum suction functions. The ultrasonic generating unit and the water flow generating unit are mounted on the fixed crossbeam 310 of the working platform, and the Z-axis direction is adjustable.

[0060] Furthermore, the water gun 320 is adjusted to be level with the first surface 120 of the crystal ingot (this process involves applying ultrasonic vibration to the first surface of the crystal ingot to separate the wafer to be peeled from the crystal ingot; the water flow at this point can buffer the ultrasonic waves and also provide a cleaning effect), with the water flow direction parallel to the first surface 120 of the crystal ingot, and the water flow is released until the ultrasonic process ends.

[0061] S400: Vacuum is drawn onto the highest surface 120 of the crystal ingot, and the water gun 320 corresponding to the height of the stripping layer, i.e., the highest point of the positioning frame, is activated. While the water flows, the crystal ingot 110 and the positioning frame 210 are slowly rotated, thereby separating the remaining crystal ingot from the stripped wafer 111. After the topmost stripped wafer is successfully stripped, the wafer is lifted to a certain height using a vacuum device, and then the wafer is grasped and collected by a robotic arm.

[0062] like Figure 9 As shown, a vacuum is drawn onto the highest surface 120 of the crystal ingot, and a water gun 320 corresponding to the height of the stripping layer, i.e., the highest point of the positioning frame, is activated. While the water flows, the crystal ingot 110 and the positioning frame 210 are slowly rotated, thereby separating the remaining crystal ingot from the stripped wafer 111. After the topmost stripped wafer is successfully stripped, the wafer is lifted to a certain height using a vacuum device, and then gripped and collected by a robotic arm.

[0063] Specifically, in the X and Y directions, the rotation of the positioning frame 210 achieves the stretching of the remaining ingot thicker than the peeling surface 121 and the wafer 111 thinner than the peeling surface in opposite directions; in the Z direction, vacuum attraction achieves the stretching of the remaining ingot thicker than the peeling surface and the wafer 111 thinner than the peeling surface in opposite directions, thereby achieving the peeling of the wafer 111.

[0064] In one embodiment of the present application, step S400 "suck the vacuum on the highest surface 120 of the ingot, and turn on the water gun 320 corresponding to the peeling layer height, i.e. the highest point of the positioning frame, while slowly rotating the ingot 110 and the positioning frame 210 under the action of water flow, so as to realize the separation of the remaining ingot and the peeled wafer 111. After the uppermost peeling wafer is successfully peeled off, the wafer is lifted to a certain height by the vacuum device, and then the wafer is grabbed and collected by the mechanical hand." Then step S410 can be included.

[0065] Step S410, grinding and polishing the first split surface formed after the first workpiece unit (ingot) 110 is split along the preset peeling surface 121.

[0066] In step S410, by grinding and polishing the first split surface, a smooth surface can be obtained.

[0067] Of course, the setting mode of this step S410 is not limited to this, for example, in another embodiment of the present application, step S420, grinding and polishing the second split surface and / or the third split surface formed after the second workpiece unit (wafer) 111 is split along the preset peeling surface.

[0068] In step S420, by grinding and polishing the second split surface and / or the third split surface, a smooth surface can be obtained.

[0069] Of course, in still another embodiment of the present application, step S430 can also include: grinding and polishing the first split surface formed after the first workpiece unit (ingot) 110 is split along the preset peeling surface, and grinding and polishing the second split surface and / or the third split surface formed after the second workpiece unit (wafer) 111 is split along the preset peeling surface.

[0070] Repeat the above steps until a group of wafers is obtained.

[0071] Among them, the remaining ingot after grinding and polishing can be reused, and the peeling layer is not limited to the five-layer peeling layer 121-125, and can be increased or decreased according to the needs.

[0072] The above only describes the preferred embodiments of the present application and is not intended to limit the present application. For those skilled in the art, the present application can have various modifications and changes. Any modification, equivalent replacement, improvement, etc. made within the spirit and principles of the present application shall be included in the protection scope of the present application.

Claims

1. A continuous wafer stripping apparatus, characterized in that: Includes a working platform, grippers, ultrasonic components, and vacuum adsorption components; The working platform includes a lifting platform, which is rotatable and movable up and down relative to the working platform. The grippers are fitted on the outside of the lifting platform, and when the grippers are closed, they form a hollow cylinder; the ingot, which is scanned by the laser along a set route and has formed multiple peeling layers, is fixed on the lifting platform by the grippers. The grippers can rotate together with the lifting platform. By adjusting the height of the ingot, a set of wafers can be obtained without repeatedly moving the horizontal position of the ingot. The ultrasonic component is positioned above the gripper; The vacuum adsorption component is positioned above the grippers and is used to remove the formed wafer. The vacuum adsorption component and the ultrasonic component are integrated and installed on the top of the gripper, which has the functions of both outputting ultrasonic waves and vacuum suction.

2. The wafer continuous stripping apparatus according to claim 1, characterized in that: The gripper is a hollow cylindrical electric locking clamp, and the opening and closing of the gripper is controlled by electromagnetic drive.

3. The wafer continuous stripping apparatus according to claim 2, characterized in that: The clamping surfaces of the grippers are serrated and coated with an anti-slip layer.

4. The wafer continuous stripping apparatus according to claim 1, characterized in that: A water gun is provided on one side above the gripper. The water gun is used to spray a water jet of set pressure onto the stripping layer of the crystal ingot, so as to separate the wafer from the crystal ingot.

5. A method for continuous wafer stripping, characterized in that: Includes the following steps: Multiple release layers are formed in the ingot using an ultrashort pulse laser, with the distance between adjacent release layers being the thickness of the wafer; Place the crystal ingot on the lifting platform, adjust the height of the lifting platform so that the topmost peeling layer of the crystal ingot is flush with the upper surface of the jaws, and then clamp the crystal ingot with the jaws. An ultrasonic component is used to apply ultrasound to the upper surface of the crystal ingot. The release layer cracks under the action of ultrasound, and the wafer is peeled off from the crystal ingot. A vacuum adsorption component is used to remove the wafer from the crystal ingot for subsequent processing. The vacuum adsorption component and the ultrasonic component are integrated and installed above the gripper, which has both the functions of outputting ultrasonic waves and vacuum suction. During the process of adsorbing and removing the wafer using a vacuum adsorption component, the lifting platform drives the ingot to rotate, while a water gun sprays a water jet of set pressure towards the stripping layer to disconnect the remaining connection between the wafer and the ingot, so that the wafer can be successfully stripped from the ingot. Release the grippers, adjust the height of the lifting platform, and use the same method to prepare subsequent wafers, obtaining a set of wafers without repeatedly moving the horizontal position of the ingot.

6. The wafer sequential stripping method according to claim 5, characterized in that: An ultrasonic component is used to apply ultrasound to the upper surface of the crystal ingot while simultaneously spraying water onto the upper surface of the crystal ingot.

7. The wafer continuous stripping method according to claim 5, characterized in that: The water jet is sprayed in a direction parallel to the stripping layer.

8. The wafer sequential stripping method according to claim 5, characterized in that: It also includes the step of grinding and polishing the surface of the separated wafer.

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