Wafer tensile lift-off apparatus and method

Abstract

The application provides a wafer tensile stripping device and method, and relates to the technical field of semiconductor processing. The device comprises oppositely arranged first and second tensile stripping devices. The first and second tensile stripping devices each comprise an adhesive disc workpiece and a tension arm. The adhesive disc workpiece is used to realize wafer tensile stripping, and the tension arm is used to adjust the relative distance between the first and second tensile stripping devices. The adhesive disc workpiece comprises a constant-temperature hot plate and a transition plate. The constant-temperature hot plate is provided with a temperature rising and falling device. The transition plate is arranged on the outer side of the constant-temperature hot plate and is used to contact a silicon carbide crystal ingot. The difference between the thermal expansion coefficients of the transition plate and the silicon carbide is smaller than the difference between the thermal expansion coefficients of the constant-temperature hot plate and the silicon carbide. The silicon carbide crystal ingot has a modified layer at a first distance from a first end face of the silicon carbide crystal ingot. The application can improve the yield of wafer slicing.

Description

Technical Field

[0001] This invention relates to the field of semiconductor processing technology, and more specifically to a wafer stretching and peeling apparatus and method. Background Technology

[0002] Third-generation semiconductor materials such as silicon carbide possess excellent electro-optical-acoustic-thermal properties, making them crucial for applications in aerospace, weaponry, and high-energy physics. However, silicon carbide is a typical hard and brittle material, and traditional machining methods suffer from slow cutting speeds, easy edge chipping, and high material loss, significantly reducing material utilization. Ultrafast laser precision machining technology is a strong-field manufacturing technique that induces multiphoton nonlinear absorption and phase transitions in materials by tightly focusing laser light in both the temporal and spatial domains. It enables three-dimensional and penetrating machining, regardless of the type of material being processed. Compared to conventional mechanical wire cutting, ultrafast laser wafer stripping technology for silicon carbide avoids sawing edge damage in principle, and the lower internal stress of the wafer greatly reduces material loss during silicon carbide processing. It also offers advantages such as high speed, high efficiency, and no edge chipping, making it a new and highly efficient alternative in the field of silicon carbide substrate processing.

[0003] The ultrafast laser wafer stripping technology for silicon carbide wafers, as commonly seen in existing technologies such as Chinese invention patents CN115555736A and CN 106463374 B, mainly consists of two steps: laser radiation modification and wafer stripping. First, a high-repetition-rate ultrashort pulse laser is focused at a predetermined depth inside the SiC ingot through a high numerical aperture objective lens. Simultaneously, the ingot moves relative to the focusing objective lens along a specific path, enabling point-by-point scanning processing of the pulse laser within a specific depth plane inside the SiC ingot, thereby forming a modified layer plane inside the SiC ingot. Second, a layer of solid paraffin wax is uniformly coated on the upper and lower surfaces of the SiC ingot. The SiC ingot is then clamped between two circular heated copper disks. These copper disks are heated by an electric current and then cooled naturally to melt and solidify the paraffin wax, achieving a tight bond between the SiC ingot and the copper disks. Finally, a tensioning device on the outside of the copper disks applies tension to separate the SiC ingot from the internal modified layer, completing the wafer stripping process.

[0004] However, during the peeling process after cooling, this method has a high probability of causing edge chipping and breakage of the wafer material (on the order of hundreds of μm thick) at the interface of the modified layer, resulting in a low production yield. Summary of the Invention

[0005] To address the shortcomings of existing technologies, the present invention aims to provide a wafer stretching and peeling apparatus and method to reduce the incidence of edge chipping and breakage during peeling and improve the yield of wafers.

[0006] To achieve the above objectives, a first aspect of the present invention provides a wafer stretching and peeling apparatus, comprising a first stretching and peeling apparatus and a second stretching and peeling apparatus disposed opposite to each other. Both the first stretching and peeling apparatus and the second stretching and peeling apparatus include an adhesive disc workpiece and a tension arm. The adhesive disc workpiece is used to perform wafer stretching and peeling, and the tension arm is used to adjust the relative distance between the first stretching and peeling apparatus and the second stretching and peeling apparatus.

[0007] The bonding disc workpiece includes a constant temperature heating plate and a transition plate. The constant temperature heating plate is equipped with a heating and cooling device. The transition plate is located outside the constant temperature heating plate and is used to contact the silicon carbide ingot to be peeled off. The difference in the coefficient of thermal expansion between the transition plate and silicon carbide is less than the difference in the coefficient of thermal expansion between the constant temperature heating plate and silicon carbide. The silicon carbide ingot has a modified layer at a first distance from the first end face of the silicon carbide ingot.

[0008] Preferably, the transition plate is a quartz transition plate.

[0009] Preferably, the constant temperature heating plate is provided with a water channel to realize the temperature rise and fall of the surface of the constant temperature heating plate.

[0010] Preferably, it also includes an adhesive for applying to the surface of the transition plate to bond the transition plate to the silicon carbide ingot.

[0011] Preferably, the system also includes a first constant temperature water tank and a second constant temperature water tank. The water temperature in the first constant temperature water tank is higher than the melting temperature of the adhesive, and the water temperature in the second constant temperature water tank is lower than the solidification temperature of the adhesive. Both the first constant temperature water tank and the second constant temperature water tank are connected to a water channel.

[0012] Preferably, it further includes an ultrasonic module, with the transition plate of the first tensile peeling device facing the first end face of the silicon carbide ingot. The ultrasonic module is disposed on the first tensile peeling device and is used to generate ultrasonic waves to propagate to the silicon carbide ingot, inducing the cracks in the modified layer to further expand and connect.

[0013] Preferably, there are multiple ultrasonic modules, which are evenly arranged on the outer surface of the first stretching and peeling device.

[0014] Preferably, a first tension arm is provided at the center position of the first stretching and peeling device on the side away from the second stretching and peeling device, and / or a second tension arm is provided at the center position of the second stretching and peeling device on the side away from the first stretching and peeling device.

[0015] A second aspect of the present invention, based on the wafer stretching and peeling apparatus provided in the first aspect, further provides a wafer stretching and peeling method, comprising:

[0016] Apply adhesive evenly to the transition plate between the first and second stretching and peeling devices.

[0017] Place the silicon carbide ingot with the modified layer between the two transition plates, and adjust the first stretching and peeling device and the second stretching and peeling device to clamp the silicon carbide ingot.

[0018] The constant temperature heating plate is heated first and then cooled down, so that the adhesive melts and then recrystallizes, thus bonding the silicon carbide ingot to the transition plate.

[0019] The ultrasonic module generates ultrasonic waves, which are used to induce further propagation and connection of cracks in the modified layer of silicon carbide ingots.

[0020] Pulling apart the first and second stretching and peeling devices separates the wafer above the modified layer of the silicon carbide ingot from the silicon carbide ingot.

[0021] Preferably, the silicon carbide ingot is processed by ultrafast laser irradiation, so that a modified layer is formed on the silicon carbide ingot at a first distance from the first segment surface.

[0022] Compared with the prior art, the beneficial effects of the present invention are:

[0023] This invention provides a wafer stretching and peeling device and method. Considering that the surface of the constant-temperature heating plate is typically made of copper, which has a significantly different coefficient of thermal expansion from that of silicon carbide ingots, direct contact can lead to wafer chipping and breakage during the stretching and peeling process due to the difference in deformation stress. Therefore, a quartz transition plate with a coefficient of thermal expansion similar to that of the silicon carbide ingot is additionally installed on the stretching and peeling device, allowing direct contact between the silicon carbide ingot and the quartz. This greatly avoids the wafer chipping and breakage problems that occur when copper and silicon carbide ingots are directly contacted during peeling, significantly improving the yield of the wafers. An ultrasonic device is integrated into the stretching and peeling device, enabling simultaneous ultrasonic-induced crack propagation and the peeling process. On the one hand, ultrasonic-induced crack propagation reduces the external force required for peeling, lowering the probability of wafer damage. On the other hand, the integrated design eliminates the need for additional devices, reducing costs and improving peeling efficiency. The use of a dual-channel water system allows for both heating and cooling, solving the problem of long natural cooling time for the constant-temperature heating plate and further improving peeling efficiency.

[0024] Advantages of additional aspects of the invention will be set forth in part in the description which follows, and in part will be obvious from the description, or may be learned by practice of the invention. Attached Figure Description

[0025] The accompanying drawings, which form part of this invention, are used to provide a further understanding of the invention. The illustrative embodiments of the invention and their descriptions are used to explain the invention and do not constitute an improper limitation of the invention.

[0026] Figure 1 This is a schematic diagram of a wafer stretching and peeling device provided in an embodiment of the present invention;

[0027] Figure 2 This is a structural diagram of the double-channel water tank;

[0028] Figure 3 This is a schematic diagram of the structure of a silicon carbide ingot;

[0029] Figure 4 This is a flowchart of the method.

[0030] Among them, 1. First stretching and peeling device; 111. Constant temperature heating plate; 112. Transition plate; 113. Double-pass water tank; 1131. First water channel interface; 1132. Second water channel interface; 1133. Sensor interface; 121. First ultrasonic module; 122. Second ultrasonic module; 123. Third ultrasonic module; 13. Pull arm; 2. Second stretching and peeling device; 3. Silicon carbide ingot; 31. First end face; 32. Modified layer; 33. First distance; 34. Second end face. Detailed Implementation

[0031] The present invention will be further described below with reference to the accompanying drawings and embodiments.

[0032] Example 1

[0033] like Figures 1-3 As shown, this embodiment provides a wafer stretching and peeling device, including a first stretching and peeling device 1 and a second stretching and peeling device 2 arranged opposite to each other. Both the first stretching and peeling device 1 and the second stretching and peeling device 2 include an adhesive disc workpiece and a tension arm 13. The adhesive disc workpiece is used to achieve wafer stretching and peeling, and the tension arm 13 is used to adjust the relative distance between the first stretching and peeling device and the second stretching and peeling device.

[0034] The first stretching and peeling device 1 and the second stretching and peeling device 2 are vertically arranged and can move up and down in the vertical direction. Taking the first stretching and peeling device 1 as an example, the first stretching and peeling device 1 includes a bonding disc workpiece and a tension arm 13. The bonding disc workpiece includes a constant temperature heating plate 111 and a transition plate 112. The constant temperature heating plate 111 is equipped with a heating and cooling device. The transition plate 112 is located outside the constant temperature heating plate and at the bottom of the first stretching and peeling device 1. It is used to contact the silicon carbide ingot 3 to be peeled, avoiding direct contact between the constant temperature heating plate and the silicon carbide ingot. The difference in the coefficient of thermal expansion between the transition plate 112 and silicon carbide is less than the difference in the coefficient of thermal expansion between the constant temperature heating plate 111 and silicon carbide. The silicon carbide ingot 3 has a modified layer 32 at a first distance 33 from the first end face 31 of the silicon carbide ingot.

[0035] Traditional wafer peeling methods using mechanical stretching require heating and cooling to allow the paraffin wax to act as an adhesive. Copper, a stable material with good thermal conductivity, is typically used for heating. However, during the heating and cooling process, the coefficient of thermal expansion of copper differs significantly from that of SiC. This leads to a high probability of edge chipping and breakage of the wafer material (on the order of hundreds of μm thick) at the modified layer interface during peeling after cooling, greatly reducing production yield. To address this, this embodiment designs a transition plate, preferably a quartz transition plate, as its coefficient of thermal expansion is closer to that of silicon carbide. By placing the quartz transition plate at the contact point between the copper and silicon carbide, the wafer chipping and breakage problems that occur during peeling from direct contact between the copper block and the silicon carbide ingot can be largely avoided, significantly improving the wafer yield.

[0036] Furthermore, during the cooling process, even with copper materials possessing high thermal conductivity, natural cooling still takes a considerable amount of time. Therefore, to further improve the stripping efficiency, this embodiment designs the constant-temperature heating plate as having controllable heating and cooling. Specifically, the heating and cooling device within the constant-temperature heating plate 111 is a double-channel water tank 113. The double-channel water tank 113 has water passages inside, used to achieve heating and cooling of the surface of the constant-temperature heating plate, thereby melting and re-solidifying the adhesive applied to the surface of the transition plate, achieving bonding and fixing of the silicon carbide ingot. Paraffin wax is preferably used as the adhesive, as it is solid at room temperature and can be applied to the quartz transition plate connected to the constant-temperature heating plate. The water passages within the double-channel water tank 113 can be designed as a spiral structure to maximize the heat exchange area. The dual-channel water tank 113 has a first water channel interface 1131, a second water channel interface 1132, and a sensor interface 1133. The first water channel interface 1131 and the second water channel interface 1132 are respectively connected to both ends of the water channel for injecting heating and cooling water into the water channel. The sensor interface 1133 is used to install a temperature sensor to monitor the temperature of the dual-channel water tank in real time.

[0037] The heating and cooling processes share a single water channel. Switching between hot and cold water can be achieved via an external three-way valve. The first water channel interface 1131 and the second water channel interface 1132 are connected to a first constant-temperature water tank (heating water tank) and a second constant-temperature water tank (cooling water tank) respectively via the three-way valve. The water temperature in the first constant-temperature water tank is higher than the melting temperature of the adhesive (paraffin wax), and the water temperature in the second constant-temperature water tank is lower than the solidification temperature of the adhesive (paraffin wax). In one embodiment, the water temperature in the first constant-temperature water tank is set to be higher than 70°C, and the water temperature in the second constant-temperature water tank is set to be lower than 20°C.

[0038] An ultrasonic module is also provided on the first tensile peeling device near the modified layer of the silicon carbide ingot. The modified layer is located at a first distance from the first end face of the silicon carbide ingot. The transition plate of the first tensile peeling device faces the first end face of the silicon carbide ingot. The ultrasonic module is used to generate ultrasonic waves to propagate to the silicon carbide ingot, inducing further propagation and connection of cracks in the modified layer.

[0039] For methods involving mechanically peeling wafers using external tensile force, an extremely uniform and sufficient modified layer needs to be generated inside the SiC ingot. This places high demands on the laser radiation modification process, significantly increasing its difficulty and requiring greater precision in the laser processing system design and advanced laser processing technology. Furthermore, it increases the risk of wafer damage. Therefore, an ultrasonic module is incorporated to generate ultrasonic waves that propagate to the silicon carbide ingot, inducing further crack propagation.

[0040] The ultrasonic module uses an ultrasonic transducer, and there are multiple ultrasonic modules, which are evenly arranged on the outer surface of the first tensile peeling device. Figure 1 Taking three modules as an example, including a first ultrasonic module 121, a second ultrasonic module 122, and a third ultrasonic module 123, the three ultrasonic modules are evenly distributed on the upper surface of the first tensile peeling device with the probes pointing downwards to emit ultrasonic waves to the silicon carbide ingot, inducing further crack propagation in the modified layer. Integrating the ingot peeling and slicing with the ultrasonic modules can simultaneously realize the ultrasonic-induced crack propagation and peeling and slicing processes without the need for additional devices, thus reducing costs.

[0041] The first and second stretching and peeling devices are moved by a tension arm, which is located on the outer side of the first and second stretching and peeling devices, away from each other. Specifically, the first tension arm is located at the center of the side of the first stretching and peeling device away from the second stretching and peeling device, and the second tension arm is located at the center of the side of the second stretching and peeling device away from the first stretching and peeling device. The tension arm applies a counter-directional pulling force to the stretching and peeling devices to peel and separate the silicon carbide ingots into sheets.

[0042] Example 2

[0043] Based on the wafer stretching and peeling apparatus provided in Embodiment 1, this embodiment further provides a wafer stretching and peeling method, such as... Figure 4 As shown, it includes:

[0044] An adhesive (paraffin wax) is evenly applied to the transition plate between the first and second stretching and peeling devices; the paraffin wax is solid at room temperature.

[0045] A silicon carbide ingot with a modified layer is placed between two transition plates, and the first and second stretching and peeling devices are adjusted to clamp the silicon carbide ingot. The silicon carbide ingot to be peeled has a first end face 31 and a second end face 34 with opposite sides. After being processed by ultrafast laser irradiation at a position 33 deep from the first end face 31, a modified layer 32 is formed. The quartz transition plates of the first and second stretching and peeling devices are in close contact with the first end face and the second end face of the silicon carbide ingot, respectively.

[0046] The constant temperature heating plate is heated first and then cooled down, so that the adhesive melts and then recrystallizes, thus bonding the silicon carbide crystal ingot to the transition plate. The constant temperature heating plate is designed with a double-pass water tank inside, and two constant temperature water tanks with water pumps are connected to the double-pass water tank outside (one temperature is greater than 70°C and the other temperature is less than 20°C). The constant temperature heating plate is heated and cooled by water circuit heating and water cooling respectively, so that the paraffin on the inside of the quartz transition plate is melted and recrystallized through heat transfer, and the crystal ingot is firmly bonded between the upper and lower quartz transition plates.

[0047] The ultrasonic module generates ultrasonic waves, which are used to induce further propagation and connection of cracks in the modified layer of silicon carbide ingots.

[0048] By applying a reverse pulling force through the pull arm, the first and second stretching and peeling devices are pulled apart, separating the wafer above the modified layer of the silicon carbide ingot from the silicon carbide ingot, thus achieving wafer stripping.

[0049] The above description is merely a preferred embodiment of the present invention and is not intended to limit the invention. Various modifications and variations can be made to the present invention by those skilled in the art. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the scope of protection of the present invention.

Claims

1. A wafer stretching and peeling device, characterized in that, The device includes a first stretching and peeling device and a second stretching and peeling device arranged opposite to each other. Both the first stretching and peeling device and the second stretching and peeling device include an adhesive disc workpiece and a tension arm. The adhesive disc workpiece is used to achieve wafer stretching and peeling, and the tension arm is used to adjust the relative distance between the first stretching and peeling device and the second stretching and peeling device. The bonding disc workpiece includes a constant temperature heating plate and a transition plate. The constant temperature heating plate is equipped with a heating and cooling device. The transition plate is a quartz transition plate, which is set on the outside of the constant temperature heating plate and is used to contact the silicon carbide ingot to be peeled off. The difference in the coefficient of thermal expansion between the transition plate and silicon carbide is less than the difference in the coefficient of thermal expansion between the constant temperature heating plate and silicon carbide. The silicon carbide ingot has a modified layer at a first distance from the first end face of the silicon carbide ingot; It also includes an ultrasonic module, with the transition plate of the first tensile peeling device facing the first end face of the silicon carbide ingot. The ultrasonic module is disposed on the first tensile peeling device and is used to generate ultrasonic waves to propagate to the silicon carbide ingot, inducing the cracks in the modified layer to further expand and connect.

2. The wafer stretching and peeling apparatus as described in claim 1, characterized in that, The constant temperature heating plate is equipped with a water channel to achieve temperature rise and fall of the surface of the constant temperature heating plate.

3. The wafer stretching and peeling apparatus as described in claim 2, characterized in that, It also includes an adhesive for applying to the surface of the transition plate to bond the transition plate to the silicon carbide ingot.

4. The wafer stretching and peeling apparatus as described in claim 3, characterized in that, It also includes a first constant temperature water tank and a second constant temperature water tank. The water temperature in the first constant temperature water tank is higher than the melting temperature of the adhesive, and the water temperature in the second constant temperature water tank is lower than the solidification temperature of the adhesive. Both the first constant temperature water tank and the second constant temperature water tank are connected to the water channel.

5. The wafer stretching and peeling apparatus as described in claim 1, characterized in that, The number of ultrasonic modules is multiple, and the multiple ultrasonic modules are evenly arranged on the outer surface of the first stretching and peeling device.

6. The wafer stretching and peeling apparatus as described in claim 1, characterized in that, A first tension arm is provided at the center position of the first stretching and peeling device on the side away from the second stretching and peeling device, and / or a second tension arm is provided at the center position of the second stretching and peeling device on the side away from the first stretching and peeling device.

7. A wafer stretching and peeling method, characterized in that, A wafer stretching and peeling apparatus according to any one of claims 1-6, comprising: Apply adhesive evenly to the transition plate between the first and second stretching and peeling devices. Place the silicon carbide ingot with the modified layer between the two transition plates, and adjust the first stretching and peeling device and the second stretching and peeling device to clamp the silicon carbide ingot. The constant temperature heating plate is heated first and then cooled down, so that the adhesive melts and then recrystallizes, thus bonding the silicon carbide ingot to the transition plate. The ultrasonic module generates ultrasonic waves, which are used to induce further propagation and connection of cracks in the modified layer of silicon carbide ingots. Pulling apart the first and second stretching and peeling devices separates the wafer above the modified layer of the silicon carbide ingot from the silicon carbide ingot.

8. The wafer stretching and peeling method as described in claim 7, characterized in that, By processing silicon carbide ingots with ultrafast laser irradiation, a modified layer is formed on the silicon carbide ingot at a first distance from the first segment surface.

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