Wafer stretching and stripping device and method

Abstract

The invention provides a wafer stretching and stripping device and method, and relates to the technical field of semiconductor processing, the device comprises a first stretching and stripping device and a second stretching and stripping device which are oppositely arranged, and each of the first stretching and stripping device and the second stretching and stripping device comprises a bonding disc workpiece and a tension arm, the bonding disc workpiece is used for stretching and stripping a wafer, and the tension arm is used for adjusting the relative distance between the first stretching and stripping device and the second stretching and stripping device; the bonding disc workpiece comprises a constant-temperature heating plate and a transition plate, a heating and cooling device is arranged in the constant-temperature heating plate, the transition plate is arranged on the outer side of the constant-temperature heating plate and used for making contact with a silicon carbide crystal ingot, and the difference value of the thermal expansion coefficient of the transition plate and the thermal expansion coefficient of silicon carbide is smaller than the difference value of the thermal expansion coefficient of the constant-temperature heating plate and the thermal expansion coefficient of 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. According to the invention, the yield of fragmentation can be improved.

Description

Technical Field

[0001] The present invention relates to the technical field of semiconductor processing, and in particular to a wafer stretching and peeling device and method. Background Art

[0002] Third-generation semiconductor materials such as silicon carbide have excellent electro-optical, acoustic and thermal properties and have important applications in aerospace, weapons and equipment, and high-energy physics. However, silicon carbide is a typical hard and brittle material. In traditional mechanical processing, there are many problems such as slow cutting, easy edge collapse, and high loss, which greatly reduce the utilization rate of the material. Ultrafast laser precision processing technology is a strong field manufacturing technology that induces multi-photon nonlinear absorption and phase change of materials by focusing the laser tightly in the time and space domains. It can achieve three-dimensional processing and penetration processing and is not limited by the type of processing materials. Compared with conventional mechanical wire cutting processing methods, ultrafast laser stripping technology for silicon carbide wafers avoids saw cut loss in principle, and the internal stress of the wafer is small, which greatly reduces the material loss in the silicon carbide processing process. It also has the advantages of fast speed, high efficiency, and no edge collapse, becoming an emerging and efficient alternative in the field of silicon carbide substrate processing.

[0003] Ultrafast laser stripping technology for silicon carbide wafers, common processes in the prior art such as Chinese invention patents CN115555736A and CN 106463374 B are mainly divided into two steps: laser radiation modification and wafer stripping. First, a high-repetition-rate ultrashort pulse laser is focused at a set depth inside the SiC ingot through a high numerical aperture objective lens. At the same time, the ingot is moved relative to the focusing objective lens in a certain path to achieve point-by-point scanning processing of the pulsed laser within a specific depth plane inside the SiC ingot, thereby forming a modified layer plane inside the SiC ingot. Secondly, a layer of solid paraffin wax is evenly applied to the upper and lower end surfaces of the SiC ingot, and then the SiC ingot is clamped between two circular heating copper disks. The copper disk can melt and recondense the paraffin wax by applying electric current heating and natural cooling to achieve a close bonding effect between the SiC ingot and the copper disk. Finally, a tensile force is applied by the stretching device on the outside of the copper disk to achieve material separation of the SiC ingot with the internal modified layer as the boundary, completing the wafer stripping process.

[0004] However, during the stripping process after the cooling is completed, there is a high probability that the upper wafer material (hundreds of μm thick) at the interface of the modified layer will suffer from edge collapse, fragmentation, and other problems, resulting in a low production yield. Summary of the invention

[0005] In order to solve the deficiencies of the prior art, the purpose of the present invention is to provide a wafer stretching and peeling device and method to reduce the incidence of edge collapse and cracking problems during peeling and improve the yield rate of wafer separation.

[0006] In order to achieve the above-mentioned object, the first aspect of the present invention provides a wafer stretching and peeling device, comprising a first stretching and peeling device and a second stretching and peeling device arranged opposite to each other, wherein the first stretching and peeling device and the second stretching and peeling device both comprise a bonding disc workpiece and a tension arm, wherein the bonding 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;

[0007] The bonding disc workpiece includes a constant temperature heating plate and a transition plate, wherein a heating and cooling device is arranged inside the constant temperature heating plate, and the transition plate is arranged outside the constant temperature heating plate for contacting with the silicon carbide ingot to be peeled off, and the difference between the thermal expansion coefficients of the transition plate and silicon carbide is smaller than the difference between the thermal expansion coefficients of 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, a water channel is provided in the constant temperature heating plate to achieve temperature rise and fall on the surface of the constant temperature heating plate.

[0010] Preferably, an adhesive is also included, and the adhesive is used to be applied on the surface of the transition plate to bond the transition plate and the silicon carbide ingot.

[0011] Preferably, 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 greater 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, and the first constant temperature water tank and the second constant temperature water tank are both connected to the water channel.

[0012] Preferably, an ultrasonic module is also included, wherein the transition plate of the first stretching and stripping device faces the first end face of the silicon carbide ingot, and the ultrasonic module is arranged on the first stretching and stripping device to generate ultrasonic waves to propagate to the silicon carbide ingot, thereby inducing the cracks in the modified layer to further expand and connect.

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

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

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

[0016] Evenly apply adhesive on the transition plate of the first stretching and peeling device and the second stretching and peeling device;

[0017] Placing the silicon carbide ingot with the modified layer between the two transition plates, and adjusting the first stretching and peeling device and the second stretching and peeling device to clamp the silicon carbide ingot;

[0018] Controlling the constant temperature heating plate to heat first and then cool down, so that the adhesive is melted and then re-solidified, and the silicon carbide ingot is bonded to the transition plate;

[0019] The ultrasonic module generates ultrasonic waves, and utilizes ultrasonic vibration to induce the cracks in the modified layer of the silicon carbide ingot to further expand and connect;

[0020] The first stretching and stripping device and the second stretching and stripping device are pulled apart to separate the wafer above the modified layer of the silicon carbide crystal ingot from the silicon carbide crystal ingot.

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

[0022] Compared with the prior art, the present invention has the following beneficial effects:

[0023] The present invention provides a wafer stretching and stripping device and method. Considering that the surface of the constant temperature heating plate is usually made of copper, which has a large difference in thermal expansion coefficient with the silicon carbide ingot, direct contact will cause the wafer to break and crack during the stretching and stripping process due to different deformation stresses. A quartz transition plate with a thermal expansion coefficient similar to that of the silicon carbide ingot is additionally provided on the stretching and stripping device, so that the silicon carbide ingot is in direct contact with the quartz, which can greatly avoid the wafer breaking and cracking problems that exist when the copper and silicon carbide ingot materials are directly contacted and stripped, and greatly improve the yield rate of the slicing. An ultrasonic device is integrated on the stretching and stripping device, which can simultaneously realize the ultrasonic induced crack expansion and the stripping and slicing process. On the one hand, through the ultrasonic induced crack expansion, the external force required for stripping can be reduced, and the probability of wafer damage can be reduced. On the other hand, the integrated design does not require the use of additional devices, which reduces costs and improves the stripping efficiency. By adopting a double-pass water channel design, the water channel can be heated and cooled, which solves the problem of long time-consuming natural cooling of the constant temperature heating plate and improves the stripping efficiency.

[0024] Advantages of additional aspects of the present invention will be given in part in the following description, and in part will become obvious from the following description, or will be learned through practice of the present invention. BRIEF DESCRIPTION OF THE DRAWINGS

[0025] The accompanying drawings in the specification, which constitute a part of the present invention, are used to provide a further understanding of the present invention. The exemplary embodiments of the present invention and their descriptions are used to explain the present invention and do not constitute improper limitations on the present invention.

[0026] Figure 1 A schematic structural diagram of a wafer stretching and peeling device provided by an embodiment of the present invention;

[0027] Figure 2 It is a structural schematic diagram of a double-pass water tank;

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

[0029] Figure 4 The figure is a flow chart of the method.

[0030] Among them, 1. a first stretching and stripping device; 111. a constant temperature heating plate; 112. a transition plate; 113. a double-pass water trough; 1131. a first water channel interface; 1132. a second water channel interface; 1133. a sensor interface; 121. a first ultrasonic module; 122. a second ultrasonic module; 123. a third ultrasonic module; 13. a pulling arm; 2. a second stretching and stripping device; 3. a silicon carbide ingot; 31. a first end face; 32. a modified layer; 33. a first distance; 34. a second end face. DETAILED DESCRIPTION

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

[0032] Embodiment 1

[0033] like Figure 1-Figure 3 As shown, this embodiment provides a wafer stretching and peeling device, comprising a first stretching and peeling device 1 and a second stretching and peeling device 2 arranged opposite to each other. The first stretching and peeling device 1 and the second stretching and peeling device 2 both comprise a bonding disc workpiece and a tension arm 13, the bonding 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 arranged vertically 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, and the bonding disc workpiece includes a constant temperature heating plate 111 and a transition plate 112. A heating and cooling device is arranged in the constant temperature heating plate 111. The transition plate 112 is arranged on the outside of the constant temperature heating plate and is located at the bottom of the first stretching and peeling device 1, and is used to contact the silicon carbide ingot 3 to be sliced ​​and peeled, so as to avoid direct contact between the constant temperature heating plate and the silicon carbide ingot. The difference in thermal expansion coefficient between the transition plate 112 and silicon carbide is less than the difference in thermal expansion coefficient 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] In the traditional solution of wafer peeling by mechanical stretching, it is necessary to increase or decrease the temperature so that the paraffin wax can play a bonding role. The heating material is usually copper material with stable properties and good thermal conductivity. However, during the temperature increase or decrease process, the thermal expansion coefficient of copper is quite different from that of SiC, which will cause the wafer material (hundreds of μm thick) on the upper part of the modified layer interface to collapse and break during the peeling process after the temperature decrease is completed. This greatly reduces the production yield. For this reason, the present embodiment designs a transition plate, which preferably uses a quartz transition plate. The thermal expansion coefficient of the quartz transition plate is closer to that of the silicon carbide material. The quartz transition plate is designed at the contact position between the copper material and the silicon carbide material, which can greatly avoid the wafer collapse and cracking problems that exist when the copper block and the silicon carbide ingot material are directly in contact and peeled, greatly improving the yield of the slice.

[0036] In addition, during the cooling process, if natural cooling is used, even for copper materials with high thermal conductivity, it still takes a long time. Therefore, in order to further improve the stripping efficiency, the constant temperature heating plate is designed in this embodiment to be controllable in heating and cooling. Specifically, the heating and cooling device provided in the constant temperature heating plate 111 is a double-pass water tank 113. The double-pass water tank 113 has a water channel inside, which is used to achieve heating and cooling of the surface of the constant temperature heating plate, so that the adhesive applied on the surface of the transition plate is melted and recondensed to achieve bonding and fixation of the silicon carbide ingot. The adhesive preferably uses paraffin wax, which is solid at room temperature and can be applied to the quartz transition plate connected to the constant temperature heating plate. The water channel in the double-pass water tank 113 can be designed as a spiral structure to maximize the heat exchange area. The double-pass water tank 113 has a first water channel interface 1131, a second water channel interface 1132 and a sensor interface 1133, wherein the first water channel interface 1131 and the second water channel interface 1132 are respectively connected to the two ends of the water channel, and are used to inject heating and cooling water into the water channel. The sensor interface 1133 is used to set a temperature sensor to monitor the temperature of the double-pass water tank in real time.

[0037] The heating and cooling processes share a water channel. The switching of hot and cold water can be achieved through an external three-way valve. The first water channel interface 1131 and the second water channel interface 1132 are respectively connected to the first constant temperature water tank (heating water tank) and the second constant temperature water tank (cooling water tank) through a three-way valve. The water temperature in the first constant temperature water tank is greater than the melting temperature of the adhesive (paraffin), and the water temperature in the second constant temperature water tank is lower than the solidification temperature of the adhesive (paraffin). In one embodiment, the water temperature in the first constant temperature water tank is set to be greater 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 stretching and stripping device of the modified layer near the silicon carbide ingot. The modified layer is located at a first distance from the silicon carbide ingot to the first end face thereof. The transition plate of the first stretching and stripping 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 the cracks of the modified layer to further expand and connect.

[0039] For the method of mechanically peeling the wafer by external pulling force, it is necessary to generate an extremely uniform and sufficient modified layer inside the SiC ingot, which has high requirements for the laser radiation modification process, greatly increases the difficulty of the laser radiation modification process, and puts forward higher requirements for the precision of the laser processing system design and the advancement of the laser processing technology, and is prone to wafer damage. To this end, an ultrasonic module is provided to generate ultrasonic waves to propagate to the silicon carbide ingot to induce further crack expansion.

[0040] The ultrasonic module is an ultrasonic transducer, and there are multiple ultrasonic modules, which are evenly arranged on the outer surface of the first stretching and peeling device. Figure 1 Taking three 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 stretching and stripping device, and the probes are downward to emit ultrasonic waves to the silicon carbide ingot to induce the cracks in the modified layer to further expand. Integrating the ingot stripping and slicing with the ultrasonic module can simultaneously realize the ultrasonic induced crack expansion and stripping and slicing processes without the need for additional devices, thereby reducing costs.

[0041] The first stretching and stripping device and the second stretching and stripping device are moved by a tension arm, and the tension arm is arranged outside the first stretching and stripping device and the second stretching and stripping device in a direction away from each other. Specifically, the first stretching and stripping device is provided with a first tension arm at the center of a side away from the second stretching and stripping device, and the second stretching and stripping device is provided with a second tension arm at the center of a side away from the first stretching and stripping device. The tension arm realizes the stripping and slicing of the silicon carbide ingot by applying a tension force in the opposite direction to the stretching and stripping device.

[0042] Embodiment 2

[0043] Based on the wafer stretching and peeling device provided in the first embodiment, this embodiment further provides a wafer stretching and peeling method, such as Figure 4 As shown, including:

[0044] Evenly apply adhesive (paraffin wax) on the transition plate of the first stretching and peeling device and the second stretching and peeling device; the paraffin wax is solid at room temperature;

[0045] The silicon carbide ingot with the modified layer is placed between two transition plates, and the first stretching and stripping device and the second stretching and stripping device are adjusted to clamp the silicon carbide ingot; the silicon carbide ingot to be stripped has a first end face 31 and a second end face 34 opposite to each other, and a modified layer 32 is formed after ultrafast laser irradiation processing at a position a first distance 33 from the first end face 31; the quartz transition plates of the first stretching and stripping device and the second stretching and stripping device 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 controlled to heat first and then cool down, so that the adhesive is melted and then recondensed, and the silicon carbide ingot is bonded to the transition plate; a double-pass water tank is designed inside the constant temperature heating plate, and the double-pass water tank is externally connected to two constant temperature water cylinders with water pumps (one with a temperature greater than 70°C and the other with a temperature less than 20°C), and the constant temperature heating plate is heated and cooled by water heating and water cooling respectively, so that the paraffin on the inner side of the quartz transition plate is melted and recondensed by heat transfer, and the ingot is firmly bonded between the upper and lower quartz transition plates;

[0047] The ultrasonic module generates ultrasonic waves, and utilizes ultrasonic vibration to induce the cracks in the modified layer of the silicon carbide ingot to further expand and connect;

[0048] A reverse pulling force is applied by the pulling arm to pull apart the first pulling and stripping device and the second pulling and stripping device, so that the wafer above the modified layer of the silicon carbide ingot is separated from the silicon carbide ingot, thereby achieving wafer stripping.

[0049] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. For those skilled in the art, the present invention may have various modifications and variations. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present invention shall be included in the protection scope of the present invention.

Claims

1. A wafer stretching and peeling device, characterized in that: It comprises a first stretching and peeling device and a second stretching and peeling device which are arranged opposite to each other, wherein the first stretching and peeling device and the second stretching and peeling device both comprise a bonding disc workpiece and a tension arm, wherein the bonding disc workpiece is used to realize 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, wherein a heating and cooling device is arranged inside the constant temperature heating plate, and the transition plate is arranged outside the constant temperature heating plate for contacting with the silicon carbide ingot to be peeled off, and the difference between the thermal expansion coefficients of the transition plate and silicon carbide is smaller than the difference between the thermal expansion coefficients of 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.

2. A wafer stretching and peeling device as claimed in claim 1, characterized in that: The transition plate is a quartz transition plate.

3. A wafer stretching and peeling device as claimed in claim 1, characterized in that: The constant temperature heating plate is provided with a water channel for achieving temperature rise and fall on the surface of the constant temperature heating plate.

4. A wafer stretching and peeling device as claimed in claim 3, characterized in that: It also includes an adhesive, which is used to be applied on the surface of the transition plate to bond the transition plate and the silicon carbide ingot.

5. A wafer stretching and peeling device as claimed in claim 4, 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 greater 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, and the first constant temperature water tank and the second constant temperature water tank are both connected to the water channel.

6. A wafer stretching and peeling device as claimed in claim 1, characterized in that: It also includes an ultrasonic module. The transition plate of the first stretching and stripping device faces the first end face of the silicon carbide ingot. The ultrasonic module is arranged on the first stretching and stripping device and is used to generate ultrasonic waves to propagate to the silicon carbide ingot to induce the cracks in the modified layer to further expand and connect.

7. A wafer stretching and peeling device as claimed in claim 6, characterized in that: There are multiple ultrasonic modules, and the multiple ultrasonic modules are evenly arranged on the outer surface of the first stretching and peeling device.

8. The wafer stretching and peeling device according to claim 1, characterized in that: A first tension arm is provided at a center position of the first stretching and peeling device away from the second stretching and peeling device, and / or a second tension arm is provided at a center position of the second stretching and peeling device away from the first stretching and peeling device.

9. A wafer stretching and peeling method, characterized in that: A wafer stretching and peeling device according to any one of claims 1 to 8, comprising: Evenly apply adhesive on the transition plate of the first stretching and peeling device and the second stretching and peeling device; Placing the silicon carbide ingot with the modified layer between the two transition plates, and adjusting the first stretching and peeling device and the second stretching and peeling device to clamp the silicon carbide ingot; Controlling the constant temperature heating plate to heat first and then cool down, so that the adhesive is melted and then re-solidified, and the silicon carbide ingot is bonded to the transition plate; The ultrasonic module generates ultrasonic waves, and utilizes ultrasonic vibration to induce the cracks in the modified layer of the silicon carbide ingot to further expand and connect; The first stretching and stripping device and the second stretching and stripping device are pulled apart to separate the wafer above the modified layer of the silicon carbide crystal ingot from the silicon carbide crystal ingot.

10. A wafer stretching and peeling method according to claim 9, characterized in that: 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 section surface.

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