wafer processing equipment

Abstract

This invention discloses a wafer processing apparatus, belonging to the field of semiconductor technology. The wafer processing apparatus includes a stage, a laser lens assembly, and an ultrasonic device. The stage is used to hold a crystal ingot; the laser lens assembly is disposed above the stage and is used to pulse-scan the crystal ingot and generate cracks; the ultrasonic device is disposed above the stage and is capable of generating transverse vibration waves, which are used to vibrate along the crystal ingot and cause the cracks to propagate laterally. This invention enables the cracks formed by the laser pulses on the crystal ingot to grow and connect laterally, avoiding longitudinal crack growth. This not only improves the production efficiency of the modified layer but also eliminates the need for dense laser pulse emission, shortening the wafer processing cycle.

Description

Technical Field

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

[0002] SiC semiconductors possess wide bandgap, high breakdown voltage, and high thermal conductivity, maintaining high efficiency in high-power, high-frequency environments, leading to a significant increase in demand for high-power microwave RF devices and high-voltage power electronic devices. However, SiC also exhibits extremely high hardness, with a Mohs hardness exceeding 9, making it second only to diamond in hardness, posing greater challenges to its processing.

[0003] SiC is formed into ingots with a thickness of 20mm after crystal growth, rounding, and truncation (the technology is developing towards thicker thicknesses, such as 40mm). The ingots need to be separated into 350μm standard wafers for subsequent thin film growth and other processes.

[0004] Existing mature technologies use wire EDM (Digital Separation and Cutting) methods such as diamond wire or slurry wire. Because wire EDM requires wire machining, SiC material with a diameter similar to the cutting wire is ground into chips approximately 100μm wide. Simultaneously, the wire sawing process creates rough undulations and structural damage of about 80μm on each side of the cutting wire, which must be removed by polishing, resulting in a total material loss exceeding 43%. Furthermore, due to the extremely high hardness of SiC, processing a single wafer takes over an hour.

[0005] Current laser cutting solutions can effectively reduce the loss layer, but in order for the cracks formed by the laser pulses to connect with each other, very dense pulse firing is required, with each pulse interval only about 0.5-1μm. Typically, it takes more than 30 minutes to complete the modification process for a 6-inch wafer. Adding the subsequent peeling and grinding time, the total time is more than 40 minutes, so the advantage over wire cutting is not obvious.

[0006] Therefore, there is an urgent need to provide a wafer processing apparatus to solve the above problems. Summary of the Invention

[0007] The purpose of this invention is to provide a wafer processing apparatus that enables cracks formed by laser pulses on a crystal ingot to grow and connect laterally, avoiding longitudinal crack growth. This not only improves the production efficiency of the modified layer, but also eliminates the need for dense laser pulse emission, thus shortening the wafer processing cycle.

[0008] To achieve the above objectives, the following technical solution is provided:

[0009] A wafer processing apparatus, comprising:

[0010] A stage, used to hold crystal ingots;

[0011] A laser lens assembly is disposed above the stage and is used to pulse scan the ingot and generate cracks;

[0012] An ultrasonic device is disposed above the stage, the ultrasonic device being capable of generating transverse vibration waves, the transverse vibration waves being used to vibrate along the ingot and cause the crack to propagate transversely.

[0013] As an alternative to a wafer processing apparatus, the ultrasonic device includes an ultrasonic generator and a vibration transmission medium arranged sequentially along the height direction, the vibration transmission medium being used to contact the surface of the ingot.

[0014] As an alternative to wafer processing equipment, the vibration transmission medium is a semi-liquid substance.

[0015] As an alternative to wafer processing equipment, the semi-liquid substance includes a gel.

[0016] As an alternative to the wafer processing apparatus, the semi-liquid material includes a water-containing flexible physical absorbent, which includes at least one of water-containing cotton, paper, sponge, and hair bundles.

[0017] As an optional solution for the wafer processing apparatus, the ultrasonic device also includes a water distributor, which has a plurality of water leakage holes uniformly arranged inside, the water leakage holes being used to drip liquid into the vibration transmission medium.

[0018] As an alternative to the wafer processing apparatus, the ultrasonic generator includes a housing with a shock-absorbing ring and a piezoelectric ceramic. One end of the shock-absorbing ring, away from the housing, is connected to the water distributor. The fixed section of the piezoelectric ceramic is located inside the housing and connected to the water distributor, while the movable section of the piezoelectric ceramic passes through the receiving cavity of the water distributor and is connected to the vibration transmission medium.

[0019] As an optional solution for the wafer processing apparatus, the wafer processing apparatus further includes a lifting assembly, and the ultrasonic device further includes an adapter connector. One end of the adapter connector is connected to the ultrasonic generator, and the other end of the adapter connector is connected to the movable end of the lifting assembly. The lifting assembly is used to adjust the height of the ultrasonic device.

[0020] As an optional embodiment of the wafer processing apparatus, the wafer processing apparatus further includes a base with a gantry, on which several sets of the laser lens assemblies and several sets of the ultrasonic devices are mounted.

[0021] As an optional embodiment of the wafer processing apparatus, the base is provided with a first-direction moving module, the first-direction moving module is provided with a second-direction moving module, and the stage is rotatably mounted on the second-direction moving module; and / or

[0022] The platform is provided with several vacuum adsorption holes.

[0023] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0024] The wafer processing apparatus provided by this invention places a wafer ingot to be laser-cut onto a stage. A laser lens assembly located above the ingot generates pulses to create cracks at a predetermined thickness within the ingot. One pulse creates one crack, and multiple cracks form a modified layer. For the areas of the ingot that have already been laser-scanned, an ultrasonic device is used to assist crack propagation, ensuring that all modified cracks grow laterally and connect, preventing longitudinal crack growth. By adding an ultrasonic device, the pulse interval generated by the laser lens assembly can be increased, which helps to accelerate the modification processing speed of the entire wafer. The ultrasonic-assisted crack propagation reduces the need for a large peeling force in the peeling unit, lowering the structural complexity of the peeling unit and allowing for a smaller size. Attached Figure Description

[0025] To more clearly illustrate the technical solutions in the embodiments of the present invention, the accompanying drawings used in the description of the embodiments of the present invention will be briefly introduced below. Obviously, the accompanying drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on the content of the embodiments of the present invention and these drawings without creative effort.

[0026] Figure 1 This is an assembly diagram of the wafer processing apparatus in an embodiment of the present invention;

[0027] Figure 2 This is an isometric view of the laser lens assembly and ultrasonic device used to process the crystal ingot in an embodiment of the present invention;

[0028] Figure 3 This is a side view of the laser lens assembly and ultrasonic device processing the crystal ingot in an embodiment of the present invention;

[0029] Figure 4 This is a cross-sectional view of the ultrasonic device in an embodiment of the present invention;

[0030] Figure 5 This is a schematic diagram of the water equalizer in an embodiment of the present invention;

[0031] Figure 6 This is an exploded view of the ingot and the stage in an embodiment of the present invention.

[0032] Figure label:

[0033] 100. Crystal ingot; 101. Modified layer;

[0034] 1. Stage; 2. Laser lens assembly; 3. Ultrasonic device; 4. Base; 41. Gantry; 42. First direction moving module; 43. Second direction moving module; 5. Ingot positioning device; 6. Ingot height measuring device;

[0035] 11. Vacuum adsorption pores;

[0036] 31. Ultrasonic generator; 311. Housing; 312. Piezoelectric ceramic; 313. Shock-absorbing ring component; 32. Vibration transmission medium; 33. Water distributor; 331. Annular cavity; 332. Leakage hole; 333. Water inlet; 334. Receiving cavity; 34. Water inlet pipe; 35. Lifting assembly; 36. Adapter connector; 37. Fastener. Detailed Implementation

[0037] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. The components of the embodiments of the present invention described and shown in the accompanying drawings can generally be arranged and designed in various different configurations.

[0038] In the description of this invention, it should be noted that the terms "upper," "lower," "left," "right," "vertical," "horizontal," "inner," and "outer," etc., indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings, or the orientation or positional relationship commonly used when the product of this invention is in use. They are used only for the convenience of describing the invention and for simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation. Therefore, they should not be construed as limitations on the invention. Furthermore, the terms "first," "second," and "third," etc., are used only to distinguish descriptions and should not be construed as indicating or implying relative importance. In the description of this invention, unless otherwise stated, "a plurality of" means two or more.

[0039] In the description of this invention, it should also be noted that, unless otherwise explicitly specified and limited, the terms "set" and "connection" should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral connection; they can refer to a mechanical connection or an electrical connection. Those skilled in the art can understand the specific meaning of the above terms in this invention based on the specific circumstances.

[0040] Embodiments of the present invention are described in detail below. Examples of these embodiments are shown in the accompanying drawings, wherein the same or similar reference numerals denote the same or similar elements or elements having the same or similar functions throughout. The embodiments described below with reference to the accompanying drawings are exemplary and are only used to explain the present invention, and should not be construed as limiting the present invention.

[0041] In the existing laser wafer dicing technology CN115302108A - laser processing apparatus, the SiC ingot structure is hexagonal single-crystal SiC, where the C-plane forms an angle α with the upper surface of the ingot. Different crystal forms have different angles, such as 0°, 3°, 4°, or 6°. The C-axis is perpendicular to the C-plane and forms an angle α with the ingot's central axis along the A direction. When the laser pulse reaches a depth equal to the thickness of the formed SiC wafer, a modification layer forms along the C-plane, which expands to form cracks. Pulses are emitted along the laser scanning path, connecting the cracks and ultimately forming a peel surface. This technology suffers from insufficient crack development and a tendency for longitudinal cracks, increasing the difficulty of peeling and leading to a larger loss layer due to longitudinal cracks.

[0042] To enable the cracks formed by laser pulses on the ingot to grow and connect laterally, avoiding longitudinal crack growth and improving the production efficiency of the modified layer, this embodiment provides a wafer processing apparatus that eliminates the need for dense laser pulse emission and shortens the wafer processing cycle. The following is a detailed description... Figures 1 to 6 The specific content of this embodiment will be described in detail.

[0043] like Figures 1 to 3 As shown, the wafer processing apparatus in this embodiment includes a stage 1, a laser lens assembly 2, and an ultrasonic device 3. The stage 1 is used to hold a wafer ingot 100. The laser lens assembly 2 is disposed above the stage 1 and is used to pulse scan the wafer ingot 100 and generate cracks. The ultrasonic device 3 is disposed above the stage 1 and is capable of generating transverse vibration waves. The transverse vibration waves generated by the ultrasonic device 3 are used to vibrate along the wafer ingot 100 and cause the cracks to propagate laterally.

[0044] In summary, the wafer processing apparatus provided in this embodiment places the wafer ingot 100 to be laser-cut onto the stage 1. The laser lens assembly 2, located above the wafer ingot 100, generates pulses to form cracks at a predetermined thickness inside the wafer 100. One pulse forms one crack, and multiple cracks form a modified layer 101. For the areas of the wafer 100 that have already been laser-scanned, an ultrasonic device 3 assists in crack propagation, ensuring that all modified cracks grow laterally and connect, preventing longitudinal crack growth. By adding the ultrasonic device 3, the pulse interval emitted by the laser lens assembly 2 can be increased, which helps to accelerate the modification processing speed of the entire wafer. The ultrasonic device 3 assists in crack propagation, reducing the need for a large peeling force in the peeling unit, lowering the structural complexity of the peeling unit, and allowing for a smaller peeling unit size.

[0045] In this embodiment, the laser lens assembly 2 emits pulses while simultaneously using ultrasonic vibration to assist in the transverse growth and connection of modified cracks, thereby increasing the pulse interval to 2.5 μm. This allows the modification process to be completed within 10 minutes, with the total processing time for a single piece controlled within 15 minutes.

[0046] Furthermore, such as Figures 2 to 5 As shown, the ultrasonic device 3 includes an ultrasonic generator 31 and a vibration transmission medium 32 arranged sequentially along the height direction. The vibration transmission medium 32 is used to contact the surface of the crystal ingot 100. When the crystal ingot 100 on the stage 1 moves directly below the ultrasonic device 3, the ultrasonic generator 31 transmits transverse ultrasonic waves to the crystal ingot 100 through the vibration transmission medium 32 to assist crack growth in the transverse direction. The ultrasonic transducer is an energy conversion device that converts electrical energy into the mechanical vibration energy of ultrasonic waves. The ultrasonic transducer is an important component of the ultrasonic generator 31, mainly used to generate and emit ultrasonic waves. The ultrasonic transducer typically consists of a piezoelectric ceramic 312, a housing 311, and wires. The piezoelectric ceramic 312 is the core part of the transducer; it utilizes the piezoelectric effect to convert electrical energy into mechanical vibration energy. When an alternating voltage is applied to the piezoelectric ceramic 312 through the wires, it deforms and generates mechanical vibrations, which in turn generate ultrasonic waves that propagate into the surrounding medium.

[0047] For example, the vibration transmission medium 32 in this embodiment can be fixed to the lower end of the piezoelectric ceramic 312 by fasteners 37 such as bolts or screws.

[0048] For example, the vibration transmission medium 32 in this embodiment is a semi-liquid material. Semi-liquid materials have a large ultrasonic energy load, good directionality, and high utilization rate of unit ultrasonic energy. Semi-liquid materials have the following technical effects: (1) High ultrasonic energy transmission efficiency. The transmission of ultrasound by semi-liquid materials and the transmission of ultrasound by water flow are analogous to copper wire and iron wire. Copper wire has a lower resistance than iron wire, so copper wire has better conductivity than iron wire. Transmitting ultrasound by semi-liquid materials can reduce or avoid the vibration and splashing effect of ultrasound on water, so that a large amount of ultrasonic energy is transmitted to the wafer with little attenuation. In the traditional method, ultrasound is transmitted by water flow. The ultrasonic energy has a peak value, that is, the ultrasonic energy cannot be too high (higher than the adsorption force between water molecules). If it is too high, the water flow will splash into water droplets, which will not achieve a good transmission effect. Similarly, the ultrasonic frequency cannot be too low. If the ultrasonic energy is too low, it will not achieve a good crack propagation effect. However, by transmitting ultrasound by semi-liquid materials, higher energy ultrasonic transmission can be achieved. The reason is that the adsorption force of semi-liquid materials on water is greater than the adsorption force between water molecules. Water on semi-liquid materials is not easy to disperse or splash. (2) Good directionality: In traditional methods of transmitting ultrasound using water flow, the water flow is non-directional, making the direction of ultrasound transmission unstable and difficult to operate; while semi-liquid materials have certain solid properties, which can transmit ultrasound in a good direction, making it easier to perform precise directional crack propagation operations. (3) High utilization rate of unit ultrasound energy: In traditional methods of transmitting ultrasound using water flow, there are two parts of energy consumption: 1) water flow dispersion and sputtering consume ultrasound energy, 2) a large amount of water flow gathers on the wafer, absorbing ultrasound energy. However, the transmission of ultrasound using semi-liquid materials does not produce a large amount of water splashes or water accumulation, and with the support of the directional transmission performance of semi-liquid materials, most of the ultrasound energy is directionally concentrated and transmitted to a point on the wafer surface, which can greatly improve the utilization rate of ultrasound energy.

[0049] For example, the semi-liquid substance includes a gel, and the gel includes a hydrogel. The hydrogel is fixed to the lower surface of the water distributor 33. The hydrogel is a highly absorbent material that does not impede the transmission of ultrasonic waves through water (it can also be other absorbent materials or other liquids). The hydrogel contacts the upper surface of the ingot 100, and the ultrasonic generator 31 (which can be a piezoelectric ceramic 312 or other vibration generating device) is activated to transmit ultrasonic waves through the hydrogel to the ingot 100. The internal cracks of the ingot 100 grow and connect with each other under the influence of the ultrasonic waves.

[0050] For example, the semi-liquid substance includes a water-containing flexible physical absorbent, which includes at least one of water-containing cotton, paper, sponge, and hair bundles (similar to a paintbrush). The water-containing flexible physical absorbent has a physical cavity water-absorbing structure (similar to a molecular sieve), and its adsorption capacity depends on the average radius of the cavity. The adsorption capacity is positively correlated with the specific surface area; however, it cannot effectively retain water after absorption, and its water absorption is limited.

[0051] Furthermore, the ultrasonic device 3 also includes a water distributor 33, which has multiple drainage holes 332 evenly distributed within it. These drainage holes 332 are used to drip liquid into the vibration transmission medium 32. By adding the water distributor 33, the vibration transmission medium 32 is kept moist. Understandably, as the hydrogel moves on the wafer, water will be lost; only a small amount needs to be replenished.

[0052] Furthermore, the water distributor 33 is also provided with a receiving cavity 334 and an annular cavity 331. The ultrasonic generator 31 includes a housing 311 with a shock-absorbing annular component 313 and a piezoelectric ceramic 312. The end of the shock-absorbing annular component 313 away from the housing 311 is connected to the water distributor 33. The fixed section of the piezoelectric ceramic 312 is located inside the housing 311 and connected to the water distributor 33. The movable section of the piezoelectric ceramic 312 passes through the receiving cavity 334 of the water distributor 33 and is connected to the vibration transmission medium 32. Understandably, the receiving cavity 334 is used to pass through the lower end of the piezoelectric ceramic 312. The water inlet 333 and a plurality of drainage holes 332 arranged at intervals along the circumferential direction of the water distributor 33 are all connected to the annular cavity 331. A water inlet 333 on the side wall of the water distributor 33 is connected to a water inlet pipe 34, through which liquid can be replenished into the water distributor 33 in a timely manner.

[0053] Furthermore, the wafer processing apparatus also includes a lifting assembly 35, and the ultrasonic device 3 includes a connecting member 36. One end of the connecting member 36 is connected to the ultrasonic generator 31, and the other end of the connecting member 36 is connected to the movable end of the lifting assembly 35. The lifting assembly 35 is used to adjust the height of the ultrasonic device 3. After the ingot 100 on the stage 1 completes laser scanning, the ultrasonic device 3 moves freely in the vertical direction and stops under the drive of the lifting assembly 35. Since the shock-absorbing ring 313 is disposed between the housing 311 and the water distributor 33, the vibration generated by the ultrasonic generator 31 can be transmitted downward only through the vibration transmission medium 32, avoiding the vibration generated by the ultrasonic generator 31 from being transmitted upward to the lifting assembly 35, which would reduce the moving accuracy of the lifting assembly 35.

[0054] For example, the lifting assembly 35 includes a lead screw slide module or a telescopic cylinder. The ultrasonic device 3 is mounted on the slide of the lead screw slide module or the piston rod of the telescopic cylinder. When the ingot 100 is directly below the ultrasonic device 3, the height of the ultrasonic device 3 can be adjusted by the lead screw slide module or the telescopic cylinder.

[0055] Furthermore, such as Figure 1As shown, the wafer processing apparatus also includes a base 4 with a gantry 41, on which several sets of laser lens assemblies 2 and several sets of ultrasonic devices 3 are mounted. The number of laser lens assemblies 2 and ultrasonic devices 3 added to the gantry 41 according to actual usage requirements helps to further improve wafer processing efficiency. The distance between the laser lens assemblies 2 and the ultrasonic devices 3 is constant. The upper ends of the ultrasonic devices 3 and the laser lens assemblies 2 can be integrated or separate.

[0056] Furthermore, a first-direction moving module 42 is provided on the base 4, and a second-direction moving module 43 is provided on the first-direction moving module 42. The stage 1 is rotatably mounted on the second-direction moving module 43. By adding the first-direction moving module 42 and the second-direction moving module 43, it is convenient to move the stage 1 to the target position, with the first and second directions being perpendicular to each other. In this embodiment, the laser lens assembly 2 can scan the ingot 100 along a straight path along the first or second direction using either the first-direction moving module 42 or the second-direction moving module 43, or it can scan the ingot 100 along an arc path by rotating the stage 1.

[0057] Optionally, such as Figure 6 As shown, the stage 1 is provided with a number of vacuum adsorption holes 11. The crystal ingot 100 is firmly adsorbed and fixed on the stage 1 through the vacuum adsorption holes 11, so that when the ultrasonic device 3 transmits vibration to the crystal ingot 100 on the stage 1, the crystal ingot 100 is prevented from shifting.

[0058] The working principle of the wafer processing apparatus in this embodiment is as follows: the ingot 100 is placed on the stage 1, and the stage 1 is moved to the processing position by the first direction moving module 42 and the second direction moving module 43. The ingot is positioned by the ingot positioning device 5, and the ingot height measuring device 6 measures the height of the ingot 100. Then the ingot 100 begins pulse scanning along the set laser scanning path. For the positions that have been laser-scanned, the ultrasonic device 3 is used to cause the modified cracks to grow and connect laterally. Laser modification and ultrasonic-assisted crack propagation continue until the entire surface is processed. Then it enters the peeling unit, where the ingot 100 and the wafer are separated by mechanical pulling force. Then it enters the grinding unit, where the peeled surface is ground to achieve the roughness required for laser incidence.

[0059] Note that the above description is merely a preferred embodiment of the present invention and the technical principles employed. Those skilled in the art will understand that the present invention is not limited to the specific embodiments described herein, and various obvious changes, readjustments, and substitutions can be made without departing from the scope of protection of the present invention. Therefore, although the present invention has been described in detail through the above embodiments, the present invention is not limited to the above embodiments, and may include many other equivalent embodiments without departing from the concept of the present invention, the scope of which is determined by the scope of the appended claims.

Claims

1. Wafer processing apparatus, characterized in that The application relates to a wafer processing device. The wafer processing device comprises a carrier (1) for placing a crystal ingot (100); a laser lens assembly (2) arranged above the carrier (1) for pulsed scanning of the crystal ingot (100) and generating cracks; and an ultrasonic device (3) arranged above the carrier (1), wherein the ultrasonic device (3) can generate transverse vibration waves for vibrating the crystal ingot (100) and making the cracks expand in the transverse direction. The ultrasonic device (3) comprises an ultrasonic wave generator (31) and a vibration transmission medium (32) arranged in sequence in the height direction, wherein the vibration transmission medium (32) is used for contacting the surface of the crystal ingot (100). The vibration transmission medium (32) is a semi-liquid substance. The semi-liquid substance comprises a gel. Alternatively, the semi-liquid substance comprises a water-containing flexible physical water-absorbing substance, which comprises at least one of water-containing cotton, paper, sponge and hair bundle. The ultrasonic device (3) further comprises a water distributor (33) uniformly provided with a plurality of water leakage holes (332) for dripping liquid into the vibration transmission medium (32). The ultrasonic wave generator (31) comprises a shell (311) provided with a damping ring (313) and a piezoelectric ceramic (312), wherein one end of the damping ring (313) away from the shell (311) is connected with the water distributor (33), the fixed section of the piezoelectric ceramic (312) is located in the shell (311) and connected with the water distributor (33), and the movable section of the piezoelectric ceramic (312) penetrates through the accommodating cavity (334) of the water distributor (33) and is connected with the vibration transmission medium (32).

2. The wafer processing apparatus of claim 1, wherein The wafer processing device further comprises a lifting assembly (35), and the ultrasonic device (3) further comprises an adapter connector (36), one end of the adapter connector (36) is connected with the ultrasonic wave generator (31), and the other end of the adapter connector (36) is connected with the movable end of the lifting assembly (35), so that the lifting assembly (35) is used for adjusting the height of the ultrasonic device (3).

3. The wafer processing apparatus of claim 2, wherein The wafer processing device further comprises a base (4) provided with a gantry (41), and a plurality of groups of the laser lens assemblies (2) and a plurality of groups of the ultrasonic devices (3) are arranged on the gantry (41).

4. The wafer processing apparatus of claim 3, wherein The base (4) is provided with a first direction moving module (42), the first direction moving module (42) is provided with a second direction moving module (43), and the carrier (1) is rotationally arranged on the second direction moving module (43); and / or 5. The wafer processing apparatus of claim 1, wherein The carrier (1) is provided with a plurality of vacuum adsorption holes (11).

6. The wafer processing apparatus of claim 5, wherein ​ ​

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