A pre-treatment device and method for laser delaminating a surface

Abstract

The application discloses a surface pretreatment method and device for laser stripping wafers, and aims to solve the problem of fast abrasion of a grinding wheel caused by directly grinding a laser stripping rough surface; the method comprises the following steps: providing wafers and / or ingots with rough surfaces after laser stripping; and placing the two rough surfaces opposite to each other and applying pressure to drive relative grinding of the two rough surfaces, so as to remove hard and sharp protrusions which are easy to damage subsequent grinding tools, and simultaneously remove surface debris. The application also provides a device for realizing the method. The method adds a simple and low-cost pretreatment process before grinding and thinning, and targets and eliminates surface defect structures which are most likely to damage expensive diamond grinding wheels, so that the abrasion of the grinding wheel in the subsequent grinding process is reduced, the overall machining efficiency is improved, and experiments show that, after the application is adopted, the subsequent grinding time can be shortened by about 17-33%, and the abrasion of the grinding wheel can be reduced by about 25-52%.

Description

Technical Field

[0001] This invention relates to the field of semiconductor and crystal material processing technology, and specifically to a pretreatment apparatus and method for laser-lifted surfaces. Background Technology

[0002] Laser lift-off technology is an advanced processing method in the semiconductor manufacturing field, primarily used to prepare single-crystal wafers (i.e., substrate wafers) from bulk single crystals. This technology uses a laser beam to form a modified layer at a specific depth within the material to be processed (such as hard and brittle semiconductor materials like silicon carbide, diamond, and sapphire). An external load is then applied to cause the crystal to fracture at the modified layer, thereby achieving the separation of the target wafer from the parent ingot. This method can efficiently obtain high-quality single-crystal substrate materials.

[0003] However, the fracture surface (or peeling surface) after laser ablation, i.e., the new surface of the wafer and the corresponding ingot after peeling, retains a rough layer with significant undulations or even sharp microstructures formed by laser ablation and brittle fracture. Currently, the mainstream method in the industry for removing this rough layer after peeling to obtain a smooth surface is to use a thinning machine for grinding, usually by directly grinding the wafer peeling surface with a bonded diamond wheel. However, this method has significant drawbacks when dealing with such special surfaces: Severe tool wear: The significant undulations or sharp microstructures on the peeled surface cause severe wear on the grinding wheel. Furthermore, the main processing targets of laser peeling, such as silicon carbide, are high-hardness materials, leading to rapid wear of the grinding wheel during the grinding process, significantly shortening the grinding wheel life and increasing production costs.

[0004] Low processing efficiency: During the grinding process using a thinning machine, the spindle stroke is the sum of the workpiece removal amount and the grinding wheel wear. On the one hand, the rough layer on the peeled surface has significant undulations and needs to be removed through machining; on the other hand, the rough surface causes significant grinding wheel wear. The combined effect of these two factors results in a long thinning time for each surface, low material removal efficiency, and limited production capacity.

[0005] Therefore, there is a lack of existing technologies that can perform efficient and low-tool-wear preliminary homogenization treatment on the rough surface of wafers and / or ingots after laser ablation, thereby creating favorable conditions for subsequent precision grinding and thinning. Summary of the Invention

[0006] This invention aims to specifically address the core problem of excessive wear and low processing efficiency caused by the hard, brittle, and sharp protrusions on the surface of laser-exfoliated rough surfaces during direct grinding. It provides a pretreatment device and method for laser-exfoliated surfaces. The purpose of this invention is not to provide a general surface smoothing method, but rather to insert a rapid, low-cost pretreatment process before the grinding and thinning steps. This process fully utilizes the hard and brittle characteristics of laser-exfoliated objects such as silicon carbide to remove hard, sharp protrusions on the surface that cause significant damage to subsequent grinding tools (such as diamond wheels), thereby significantly reducing the tool wear ratio and processing costs of subsequent processes and improving overall processing efficiency.

[0007] To solve the above-mentioned technical problems, the technical solution adopted by the present invention is as follows: a pretreatment device for laser ablation of surfaces, including a liquid container, a second carrier installed on the inner side of the bottom of the liquid container, a second rotating mechanism provided at the bottom of the second carrier, and a first carrier, a pressure control mechanism and a driving mechanism arranged sequentially from bottom to top above the second carrier. Both the first carrier and the second carrier are provided with a rotating shaft inside, and the rotating shaft can be driven by the rotating mechanism to achieve rotation.

[0008] As a further limitation of the technical solution of the present invention, the liquid container contains a liquid medium.

[0009] Preferably, the liquid medium is water, a water-based solution, or an atomized coolant.

[0010] As a further limitation of the technical solution of the present invention, the pressure control mechanism is an active pressure controller such as a motor, cylinder, or piezoelectric element, and may include flexible buffer components such as mechanical springs, pneumatic or hydraulic bladders, rubber or polyurethane elastic pads, and may also include force sensors to form a closed-loop pressure adaptive control system.

[0011] As a further limitation of the technical solution of the present invention, both the first carrier and the second carrier are vacuum suction cups, or planar structures that use adhesives to fix the workpiece and the carrier.

[0012] In addition, the present invention provides a stripping and slicing device for laser ablation processes, comprising the pretreatment device as described above, wherein the stripping and slicing device is provided with a clamping mechanism for separating a first carrier and a second carrier. The clamping mechanism fixes the workpiece and causes it to move relative to the first carrier. The stripping and slicing process is ultrasonic vibration stripping or mechanical tensile stripping.

[0013] A pretreatment method for laser-abraded surfaces, using the aforementioned pretreatment apparatus, includes the following steps: S1 Prepare workpiece pair Take a pair of workpieces after laser ablation, namely the first workpiece and the second workpiece. The first workpiece and the second workpiece are respectively the target wafer separated from the parent body and the remaining ingot after being ablated from the parent body, or both the first workpiece and the second workpiece are target wafers separated from the parent body; or both the first workpiece and the second workpiece are remaining ingots after being ablated from the parent body. The separation surfaces of the target wafer and the ingot have rough surfaces with sharp protrusions formed by laser ablation. The material of the target wafer is silicon carbide, diamond or sapphire.

[0014] S2 workpiece clamping The first workpiece and the second workpiece are placed in the pretreatment device, and the two are fixed by the first carrier and the second carrier respectively, and the rough surfaces of the two are placed opposite each other, and the overlapping length of the two in the diameter direction is greater than or equal to their radius. S3 relative grinding pretreatment The first and / or second rotating mechanisms drive the target wafer and / or the ingot to rotate. If the workpieces have the same diameter and completely overlap, one of the first and second rotating mechanisms is omitted, and only one workpiece rotates while the other remains stationary. This causes the two rough surfaces to undergo relative grinding under contact and pressure, removing hard, sharp protrusions that could cause significant damage to subsequent grinding tools, thereby simultaneously removing the sharp protrusions and loose modified layers from both surfaces. S4 Separation and Cleaning The target workpiece pair processed in step S3 is separated to obtain wafers and / or ingots with homogenized surface conditions suitable for subsequent grinding and thinning. The pre-treated target wafers are then cleaned to remove residual grinding debris.

[0015] As a further limitation of the above method, step S3, relative to the grinding pretreatment, is carried out in a liquid medium.

[0016] Compared with the prior art, the present invention has the following beneficial effects: Low cost and ingenious implementation: This invention creatively utilizes the rough surfaces that appear after laser ablation, making them each other "abrasives," achieving effective pretreatment at extremely low cost without the need for additional expensive consumables.

[0017] Significantly reduced tool wear: This invention removes the sharp protrusions that are most likely to damage diamond abrasive grains, allowing subsequent grinding and thinning to proceed under stable conditions, thus greatly reducing the processing wear of the grinding wheel and extending the service life of expensive tools.

[0018] Improve overall processing efficiency: The pretreatment step quickly removes the thickness of the protrusions that need to be ground off on both peeling surfaces at the same time, while reducing the wear of the grinding wheel during the processing. Therefore, under the same conditions, the spindle feed rate during grinding and thinning is reduced, the single-piece processing time of the grinding and thinning process is shortened, thereby improving the overall production cycle time.

[0019] Protecting the workpiece and reducing microcracks: Through optimized methods such as flexible pressurization and grinding in a liquid medium environment, mechanical impact is effectively buffered and debris detached from the workpiece during grinding is removed in a timely manner, reducing the risk of wafer breakage or internal microcracks during pretreatment.

[0020] Easy to integrate and highly flexible: The pretreatment step can directly utilize the existing clamping mechanism of the existing stripping device for separating wafers and ingots. Only a simple relative rotational motion component needs to be added to achieve in-situ processing after stripping. This integration is not a simple superposition of functions, but rather makes full use of the inherent links in the process chain (paired rough surfaces and clamping states), achieving a significant simplification of the process and a synergistic effect of "1+1>2". In addition, this device can also stand alone as a processing equipment for unified pretreatment after stripping different ingots and wafers. The device proposed in this invention can exist in different forms to meet different production needs, offering high flexibility. Attached Figure Description

[0021] Figure 1 This is a schematic diagram of the pretreatment device for laser-abraded surfaces according to the present invention.

[0022] The markings in the image are as follows: 100-Liquid container, 101-Liquid medium, 102-First rotating mechanism, 103-Pressure control mechanism, 104-First carrier, 105-Second carrier, 106-Second rotating mechanism, W1-First workpiece, W2-Second workpiece. Detailed Implementation

[0023] The present invention will be further described below with reference to specific embodiments. Example 1

[0024] like Figure 1 As shown, a pretreatment device for laser-abraded surfaces includes a liquid container 100 for holding liquid media such as pure water. A second carrier 105 is installed on the inner bottom of the liquid container 100. A second rotating mechanism 106 is provided at the bottom of the second carrier 105. A first carrier 104, a pressure control mechanism 103, and a first rotating mechanism 102 are arranged sequentially from bottom to top above the second carrier 105. A rotating shaft is provided inside both the first carrier 104 and the second carrier 105. The rotating shaft is respectively powered by the first rotating mechanism 102 and the second rotating mechanism 106, enabling the two to generate relative rotational motion.

[0025] Furthermore, the liquid container 100 contains a liquid medium 101.

[0026] Furthermore, the liquid medium 101 is water, a water-based solution, or an atomized coolant; it provides a buffer and cleaning environment for the pre-processing process, can remove the debris that falls off the workpiece during grinding in a timely manner, improve the surface quality of the pre-processed sample, and avoid scratches or microcracks.

[0027] Furthermore, the pressure control mechanism 103 is connected to at least one carrier, such as the first carrier 104, for precisely controlling and applying the contact pressure between the rough surfaces of two workpieces. The pressure control mechanism 103 can preferably employ a flexible pressurization system with buffering and adaptive adjustment capabilities. This flexible pressurization system can be implemented by introducing an elastomer into the force transmission path, such as, but not limited to, mechanical springs, pneumatic or hydraulic bladders, rubber or polyurethane elastic pads, and closed-loop pressure adaptive control systems composed of drive devices such as motors / cylinders / piezoelectric devices and force sensors. These methods all enable more flexible and controllable applied pressure, avoiding microcracks or breakage of the wafer due to impact from the rough surfaces.

[0028] Furthermore, both the first carrier 104 and the second carrier 105 are vacuum suction cups, or adhesives are used to fix the workpiece to the planar structure of the carrier; to ensure stable clamping and to prevent the introduction of additional stress. The clamping surfaces of the two carriers are arranged opposite each other. Example 2

[0029] A pretreatment method for laser-abraded surfaces, using the aforementioned pretreatment apparatus, includes the following steps: S1 Prepare workpiece pair Provides a workpiece after laser lift-off processing. Specifically, a target silicon carbide wafer is separated from a silicon carbide single crystal ingot using laser lift-off technology. At this point, both the lift-off surface of the target wafer (as the first workpiece W1) and the lift-off surface of the remaining ingot (as the second workpiece W2) are rough surfaces. These rough surfaces are covered with high-hardness, sharp protrusions and a loose modified layer.

[0030] S2 workpiece clamping The first workpiece W1 (target wafer) and the second workpiece W2 (ingot) are placed into the working area of ​​a pre-processing device. They are fixed in place by a first carrier 104 and a second carrier 105, both composed of vacuum chucks, and their positions are adjusted so that the rough surfaces of the two workpieces are opposite each other and parallel. It is necessary to ensure that the overlap area of ​​the two workpieces is large, and that the grinding area covers the entire surface during relative movement and / or rotation.

[0031] S3 relative grinding pretreatment One workpiece (such as the first carrier 104) is driven to rotate, while another workpiece (such as the second carrier 105) is driven to rotate in the same or opposite direction, maintaining a large speed difference between the two. During this process, the two rough surfaces are brought into contact under a set pressure by the pressure control mechanism 103. The two rough surfaces rub and grind against each other under relative motion, and the sharp rough parts on their surfaces break off, fall off, and are scraped off. The core purpose of this process is to "remove sharp points" and "clean" to create a relatively smooth machined surface for subsequent grinding, rather than pursuing extremely low surface roughness. The grinding time, pressure, and speed can be optimized according to the initial surface condition and are usually completed within a few seconds to a few minutes.

[0032] S4 Separation and Cleaning The two workpieces, after mutual grinding pretreatment, are separated. At this point, macroscopic undulations on both surfaces may still exist, but the sharp protrusions that most easily damage the grinding wheel have been largely removed. The pretreated target wafer is then cleaned to remove residual grinding debris.

[0033] S4 subsequent precision grinding The pre-treated first workpiece W1 and second workpiece W2 are transferred to a thinning machine for conventional grinding using diamond wheels. Since there are no longer numerous hard and brittle protrusions impacting the surface, the grinding wheel can contact the workpiece surface more smoothly and evenly, resulting in a stable grinding process and significantly reduced wheel wear. Simultaneously, the thickness to be removed from each workpiece and the wear of the grinding wheel are greatly reduced, thus shortening the overall grinding time required for a single wafer / ingot and lowering the cost of grinding wheels. Example 3

[0034] Relative grinding pretreatment in functional media As a further optimization of this method, the relative grinding pretreatment process described in step S3 of Example 2 can be performed in an environment where a functional medium is provided to the grinding interface. The medium serves to buffer mechanical impact and promptly remove at least one of the grinding debris.

[0035] Buffer protection: The medium (such as deionized water, water-based solution or atomized coolant) can effectively buffer the mechanical impact of the two rough surfaces coming into contact, greatly reducing the risk of the wafer cracking or developing deep internal microcracks during the pre-processing stage.

[0036] Cleaning and cooling: The flowing medium can promptly wash away the debris and abrasive grains detached from the grinding process, preventing them from rubbing between the two workpieces and causing scratches or wafer breakage. At the same time, the medium also plays a cooling role, preventing localized overheating.

[0037] This medium environment can be achieved through methods such as immersion or spraying. Example 4

[0038] Pretreatment method integrated into laser ablation device The relative grinding pretreatment step described in step S3 of Example 2 can be performed continuously in the same device as the peeling and slicing process, realizing the integration and functional expansion of the existing peeling and slicing device. The key insight of this invention lies in recognizing that the naturally occurring paired, matching rough surfaces after laser peeling, and the dual-workpiece clamping mechanism necessary for the separation action, are themselves the ideal basis for realizing the pretreatment scheme of this invention.

[0039] For various slitting and separating devices (such as ultrasonic vibration slitting devices or mechanical stretching slitting devices) equipped with clamping mechanisms that respectively fix the target wafer and the ingot, it is only necessary to add a component (such as a rotary motor) to the clamping mechanism to drive its relative rotational movement, and to utilize or add a component to control the contact pressure between the two. After the wafer separation is completed, the relative grinding pretreatment step can be performed in situ without transferring the workpiece. This integrated solution maximizes the use of existing process steps and hardware, seamlessly embedding the pretreatment process, which originally required separate processing, into the existing workflow. This not only saves equipment costs and floor space, but also reduces the risks of contamination, breakage, and alignment errors caused by workpiece transfer, achieving a high degree of synergy and simplification.

[0040] In ultrasonic vibration stripping devices, the existing liquid environment can be used as a functional medium to drive the fixed wafers and ingots to rotate relative to each other and apply pressure for pretreatment after separation.

[0041] In a mechanical stretching and peeling device, the two fixed parts can be directly driven to rotate relative to each other after separation, and a media spraying or immersion mechanism can be selectively added. Example 5

[0042] The relative grinding pretreatment step described in step S3 of Example 2 can also be performed in a separate device, wherein the upper and lower workpieces can both be wafers, both be ingots, or one ingot and one wafer. Depending on the production line organization mode, the ingots and wafers generated in the laser lift-off process can be arbitrarily combined and batch-processed in a separate pretreatment device. After removing significant surface undulations or sharp microstructures, they are then batch-sent to the grinding and thinning process for subsequent processing. Example 6

[0043] Comparison of specific process parameters and effects This embodiment provides a set of specific process parameters and comparative test data to quantify the beneficial effects of the present invention.

[0044] Preprocessing parameters: Relative motion mode: The target wafer, as the first workpiece W1, rotates at a fixed speed and maintains constant pressure under the drive of the first rotating mechanism 102 and the pressure control mechanism 103. The ingot, as the second workpiece W2, is fixed on the second carrier 105 and remains stationary.

[0045] Rotation speed: First vehicle 104 rotates at 60 rpm.

[0046] Apply pressure: 10N.

[0047] Grinding time: 60s.

[0048] Processing environment: The workpiece is completely immersed in pure water.

[0049] Comparative Test: Comparative processing was performed on silicon carbide wafers from the same batch after laser stripping.

[0050] Test Group A (Traditional Process): After peeling, grinding was performed directly using a thinning grinding wheel to the target thickness. Results: Total grinding time 23 min; wear of the grinding wheel used in the rough grinding process 60 μm.

[0051] Test Group B (process of this invention): After peeling, relative grinding pretreatment was performed according to the above parameters, and then the same grinding process parameters as Group A were used to process to the same target thickness. The results were: pretreatment time 60s; total subsequent grinding time 16min; wear of the grinding wheel used in the rough grinding process 37μm.

[0052] Effect Analysis: After pretreatment using the method of this invention, the subsequent grinding time was shortened by approximately 30%, and the wear of the rough grinding wheel in a single machining operation was reduced by approximately 38%. This fully demonstrates that the present invention can effectively remove surface defects that damage the grinding wheel, significantly improve machining efficiency, and reduce tool wear.

[0053] The above embodiments illustrate specific implementations of the present invention in detail. It should be understood that the present invention is not limited to the specific details described above. Within the scope of the inventive concept, those skilled in the art can make various simple modifications, all of which are considered to fall within the protection scope of the present invention.

Claims

1. A pretreatment device for laser delaminating a surface, characterized in that The device includes a liquid container (100), a second carrier (105) is installed on the inner side of the bottom of the liquid container (100), a second rotating mechanism (106) is provided at the bottom of the second carrier (105), and a first carrier (104), a pressure control mechanism (103) and a first rotating mechanism (102) are arranged sequentially from bottom to top on the second carrier (105). The first carrier (104) and the second carrier (105) are both provided with rotating shafts, which are driven to rotate by the first rotating mechanism (102) and the second rotating mechanism (106) respectively.

2. The pretreatment apparatus for laser-abraded surfaces according to claim 1, characterized in that, The liquid container (100) contains a liquid medium (101).

3. The pretreatment apparatus for laser-abraded surfaces according to claim 1, characterized in that, The liquid medium (101) is water, a water-based solution, or an atomized coolant.

4. The pretreatment apparatus for laser-abraded surfaces according to claim 1, characterized in that, The pressure control mechanism (103) is an active pressure controller consisting of a motor, cylinder, and piezoelectric element, and includes a mechanical spring, a pneumatic or hydraulic bladder, a rubber or polyurethane elastic pad, and a flexible buffer component. It may also include a force sensor to form a closed-loop pressure adaptive control system.

5. The pretreatment apparatus for laser-abraded surfaces according to claim 1, characterized in that, Both the first carrier (104) and the second carrier (105) are vacuum suction cups, or planar structures that use adhesives to fix the workpiece to the carrier.

6. A stripping and slitting device for laser ablation processes, characterized in that, The laser stripping device includes a pretreatment apparatus as described in any one of claims 1-5, and is provided with a clamping mechanism for separating the first carrier (104) and the second carrier (105).

7. A pretreatment method for laser-abraded surfaces, comprising using the pretreatment apparatus as described in any one of claims 1-5, characterized in that, Includes the following steps: S1 Prepare workpiece pair Take a pair of workpieces after laser ablation, namely the first workpiece (W1) and the second workpiece (W2). The first workpiece (W1) and the second workpiece (W2) are respectively the target wafer separated from the parent body and the remaining ingot on the parent body after ablation; or the first workpiece (W1) and the second workpiece (W2) are both target wafers separated from the parent body; or the first workpiece (W1) and the second workpiece (W2) are both remaining ingots on the parent body after ablation; the separation surfaces of the target wafer and the ingot have rough surfaces with sharp protrusions formed by laser ablation. S2 workpiece clamping The first workpiece (W1) and the second workpiece (W2) are placed in the pretreatment device and fixed by the first carrier (104) and the second carrier (105) respectively, and the separation rough surfaces of the two are placed opposite each other, and the overlapping length of the two in the diameter direction is greater than or equal to their radius. S3 relative grinding pretreatment The first rotating mechanism (102) and / or the second rotating mechanism (106) drive the target wafer and / or the ingot to rotate. If the workpieces have the same diameter and are completely overlapping, one of the first rotating mechanism (102) and the second rotating mechanism (106) is omitted, and only one workpiece rotates while the other remains stationary. The two rough surfaces are subjected to relative grinding under the condition of mutual contact and pressure to remove the hard and sharp protrusions that cause significant damage to subsequent grinding tools, thereby simultaneously removing the sharp protrusions and loose modified layers on the two surfaces. S4 Separation and Cleaning The target workpiece pair processed in step S3 is separated to obtain wafers and / or ingots with homogenized surface conditions suitable for subsequent grinding and thinning. The pre-treated target wafers are then cleaned to remove residual grinding debris.

8. The pretreatment method for laser-abraded surfaces according to claim 7, characterized in that, Step S3, relative grinding pretreatment, is carried out in liquid medium (101).

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