Hidden cutting blocking and double-blade four-cutting cutting method

Abstract

The invention belongs to the technical field of semiconductor manufacturing, and discloses a cutting method for implicit cutting blocking and double-blade four-cutting, which comprises the following steps: pre-thinning the back of an incoming product, removing an anti-oxidation coating on the back of a Wafer, reducing energy reflection during implicit cutting, enabling the laser energy reflection of a silicon surface to be stable, and carrying out annular cutting on a step on the periphery of the edge of the product by using an annular cutting function of implicit cutting equipment. The purpose of preventing the crack from extending towards the inside of the wafer is achieved; according to the invention, a product which is easy to chip is matched with a FOW process scribing double-blade four-cutting cutting method, traditional step cut double-blade double-cutting is changed into step cut double-blade four-cutting through scribing, the overall packaging yield and reliability of the product are improved, the packaging yield of the product is improved on the basis of further satisfying the ultra-thin and small-size core stacking process of the product and reducing the integration space of a terminal product, and the production cost is reduced. Therefore, unnecessary cost waste caused by packaging defects is reduced.

Description

Technical Field

[0001] This invention belongs to the field of semiconductor manufacturing technology, specifically a method for hidden-cut blocking and double-blade quad-cutting. Background Technology

[0002] Chips are the core of modern technology, with wide-ranging applications covering computers, communications, automobiles, industry, medical devices, home appliances, and the Internet of Things (IoT). Reducing chip size brings significant advantages in performance, power consumption, speed, integration, production costs, and portability, making it a crucial trend in modern electronics development. Minimizing the integration space of end products necessitates processes such as ultra-thinning and wafer stacking; however, conventional processes for thinning ultra-thin products can lead to edge step collapse, causing micro-cracks to extend to the wafer center, resulting in product yield losses and impacting production efficiency, especially when significant height differences exist around the wafer edge.

[0003] Currently, stacked chip products have become the main form of 3D electronic packaging. To adapt to high-density solutions, stacked chips generally consist of two or more functional chips stacked in the same package. There are two basic stacking methods. However, the conventional step-cut mode is prone to chipping, which affects product performance. Due to the thick adhesive layer of the FOW film, the cross-sectional area between the DAFs on the chip side is large, causing the adhesive layer to stick back. The film expansion effect is poor when the chip size is smaller than 2*2mm. These two points combined lead to chip bridging, resulting in serious product yield loss and low operation efficiency.

[0004] Several invention patents have been developed to address the aforementioned issues.

[0005] For example, CN115172540A discloses a method for improving the yield of back-plated LED chips through stealth dicing. This method involves steps such as growing an adhesion layer, applying a film, stealth dicing, back-filming, back plating, flipping, and wafer splitting. It employs a two-blade dicing technique to improve the yield of splitting the wafer into an independent LED chip, and the back-filming improves the yield of wafer back plating. However, when growing the adhesion layer on the back of the wafer, the adhesion force is still insufficient, which can easily lead to the detachment of the metal reflective layer in subsequent processes.

[0006] CN110265346A discloses a novel wafer fabrication method. This method involves attaching a support film to the back of a thinned ultrathin wafer, thereby fusing the support film with the ultrathin wafer and redistributing the internal stress of the ultrathin wafer to reduce the risk of breakage. However, the material of the support film in this method still needs improvement in its support effect on the ultrathin wafer and its ability to distribute internal stress. Summary of the Invention

[0007] This invention provides a hidden cutting and double-blade four-cut cutting method, which solves the problem that in conventional thinning processes, there is a large height difference around the edge of the wafer, which can easily cause the edge steps to collapse, leading to micro-cracks extending to the center of the wafer, resulting in product yield loss and affecting production efficiency.

[0008] To achieve the above objectives, the present invention provides the following technical solution: A method for concealed cutting and double-blade four-cutting includes: Apply a protective film to the front of the product; Use thinning equipment to pre-thin the back of the product; Using a hidden cutting device, laser internally breaks the edge around the back of the product, ensuring that the edge remains inseparable from the product. The back side of the wafer is thinned again using a thinning device to the required thickness for the product. The product is cut using a double-blade, four-cut method.

[0009] Preferably, the step of pre-thinning the back side of the product using a thinning device specifically includes: Attach the front of the product to the thinning worktable; The back of the product is pre-thinned using a thinning device.

[0010] Preferably, the pre-thinning thickness of the product is 50 μm.

[0011] Preferably, the step of using a hidden cutting device to laser-cut the inner edge of the back of the product specifically involves: Place the product on the worktable of the concealed cutting equipment; Activate the circumferential cutting function of the hidden cutting device; Laser internal breakage is performed around the edge of the product.

[0012] Preferably, the step of further thinning the back side of the wafer to the required thickness using a thinning device specifically involves: Reattach the product to the worktable of the thinning equipment, ensuring the back of the product is facing up; Set the thinning parameters to control the thinning equipment to thin the product until it reaches the required thickness, and separate the waste silicon around the edge from the product.

[0013] Preferably, the steps for cutting the product using a double-blade, four-cut method are as follows: Place the product on the cutting table; Install two cutting blades, Z1 and Z2, with the width of cutting blade Z1 being greater than the width of cutting blade Z2; Start the cutting equipment and execute the first stage of Z1 cutting; The Z1 first-stage cutting surface cutting quality is checked. If the quality is not up to standard, the parameters are adjusted and optimized. If the tool mark deviation is ≥3um, the equipment alarms and stops the operation. Personnel need to confirm and correct the tool mark. If the tool mark deviation is <3um, the equipment will automatically correct it. If the quality meets the standard, the Z1 second-stage cutting is executed. The Z2 cut is confirmed by short-cut detection. If the Z2 cut does not deviate and there are no quality abnormalities, cutting continues. Repeat the above process until the cutting is complete.

[0014] Preferably, the first stage of Z1 cutting involves grooving the front of the product, with a grooving depth of 30~50um into the product surface.

[0015] Preferably, in the second stage of Z1, the cutting is performed according to the slotting position of the first stage of Z1, cutting into more than 2 / 3 of the product but not completely cutting it off, and then the cutting stops.

[0016] Preferably, the second stage of cutting involves cutting the product into individual pieces.

[0017] Preferably, in the second stage, Z2 cuts 5µm into the substrate to remove residual adhesive between the bottom DAF layers of a single chip.

[0018] Compared with existing technologies, the present invention has the following beneficial effects: The present invention provides a method for hidden cut blocking and double-blade quad-cutting. By pre-thinning the back side of the incoming product and removing the anti-oxidation coating on the back side of the wafer, energy reflection during hidden cut is reduced, and the laser energy reflection on the silicon surface is stabilized. The circumferential cutting function of the hidden cutting equipment is used to perform circumferential cutting around the edge of the product, thereby preventing cracks from extending into the wafer. For products prone to chipping, the FOW process dicing double-blade quad-cutting method is used. The dicing changes the traditional step cut double-blade double-cutting to step cut double-blade quad-cutting, improving the overall packaging yield and reliability of the product. While further meeting the requirements of ultra-thin and small-size stacked core processes and reducing the integration space of the end product, the packaging yield of the product is improved at the same time, thereby reducing unnecessary cost waste caused by packaging defects.

[0019] Furthermore, the first stage shallow cut of blade Z1 can effectively improve front chipping, and the second stage of blade Z1 takes on the main cutting amount to reserve a thinner thickness for Z2. The cutting of Z2 will minimize the chipping value of the back and side. The second stage of blade Z2 acts to clean the DAF adhesive layer, so that there is no residual adhesive between the bottom DAF of a single chip and the gap is obvious, which can effectively prevent the DAF back-sticking problem. Attached Figure Description

[0020] Figure 1 These are schematic diagrams of the front and back of the wafer in an embodiment of the present invention; Figure 2 A schematic diagram of the front protective film being applied in an embodiment of the present invention; Figure 3 This is a schematic diagram of the pre-thinning process according to an embodiment of the present invention; Figure 4 This is a schematic diagram of a circumferential cut according to an embodiment of the present invention; Figure 5 This is a schematic diagram of the secondary thinning method in an embodiment of the present invention; Figure 6 This is a schematic diagram of the cutting process according to an embodiment of the present invention; Figure 7 This is a schematic diagram of the cut finished product according to an embodiment of the present invention; Figure 8 This is a flowchart of a cutting method for hidden cutting and double-blade four-cutting according to the present invention; In the diagram, 1-Wafer back silicon layer, 2-Wafer front circuit layer and plating, 3-BG film substrate layer, 4-BG film adhesive layer, 5-Laying stage, 6-Laying roller, 7-Roller movement direction, 8-Roller downward force, 9-BG film can compensate for step height but cannot completely cover, 10-Grinding wheel, 11-Grinding stage, 12-Laser beam, 13-Internal cutting, 14-Internal cracks not reaching the top and bottom surfaces, 15-Laser beam circumferentially cutting the product edge, 16-Stop grinding (internal crack splitting) (edge) 17-Target thickness (bottom silicon layer + front circuit layer, plating), 18-DAF layer (50um+), 19-Substrate layer, 20-Cutting table, 21-Z1 first stage cutting amount (grooving function), 22-Z1 second stage cutting amount (bearing the main cutting amount), 23-Z2 first stage cutting amount, 24-Z2 second stage cutting amount (DAF cleaning), 25-Step formed by Z1 and Z2 cutting, 26-Z1 total cutting amount, 27-Z2 total cutting amount, 28-Processed product. Detailed Implementation

[0021] 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.

[0022] Therefore, the following detailed description of the embodiments of the invention provided in the accompanying drawings is not intended to limit the scope of the claimed invention, but merely to illustrate selected embodiments of the invention. All other embodiments obtained by those skilled in the art based on the embodiments of the invention without inventive effort are within the scope of protection of the invention.

[0023] It should be noted that similar labels and letters in the following figures indicate similar items. Therefore, once an item is defined in one figure, it does not need to be further defined and explained in subsequent figures.

[0024] To enable those skilled in the art to better understand the technical solution of the present invention, the present invention will be further described in detail below with reference to the accompanying drawings.

[0025] like Figure 8 As shown, the present invention provides a method for concealed cutting and double-blade four-cutting, comprising: S1: Apply a protective film to the front of the product; S2: Use a thinning device to pre-thin the back of the product; S3: Use a hidden cutting device to laser internally break the edge around the back of the product, so that the edge does not separate from the product. S4: Use thinning equipment to thin the back side of the wafer again to the required thickness for the product; S5: The product is cut using a double-blade, four-cut method.

[0026] The specific steps are as follows: S1: As Figure 2 The product has a front protective film (BG film). S2 (Pre-thinning): such as Figure 3 The back of the product is pre-thinned by 50µm using a thinning device (to facilitate IR identification by the hidden cutting device).

[0027] S3 (circumferential cutting): as shown in the example Figure 4 Using the ring cutting function of the hidden cutting equipment, the inner edge of the product is laser-cut around the edge (the edge is not separated from the product, and there are no traces of operation on the front and back).

[0028] S4 (Thinning): such as Figure 5 The product is thinned again using the thinning equipment until it reaches the internal breakage stage. A ring of waste silicon around the edge separates from the product. During the thinning process, the tiny cracks generated at the edge of the wafer stop extending inward at the breakage point.

[0029] S5 (cutting): such as Figure 6The process employs a dual-blade, four-cut method in step-cut mode to cut a complete wafer into individual chips. The first stage, Z1, cuts a shallow depth to create grooves and effectively mitigates chipping caused by metal pads and long metal strips within the cutting path. The second stage, Z1, handles the majority of the cutting, leaving only the thinner bottom silicon layer for Z2, effectively improving chipping on the back and sides. The first stage, Z2, normally cuts the product into individual chips. The second stage, Z2, cuts 5µm into the dicing film substrate to remove residual adhesive between the bottom DAF layers of each chip, becoming a crucial factor in resolving DAF re-adhesion in small-sized FOW processes. The finished product... Figure 7 As shown.

[0030] Another embodiment of the present invention provides a method for concealed cutting and double-blade four-cutting, comprising: S1: Apply a protective film to the front of the product; Attach the product to the film application worktable and use a vacuum pen to blow clean the front and back of the product to remove surface impurities. S2: Use a thinning device to pre-thin the back of the product; The back of the product was pre-thinned using a thinning device, Z1 (grinding wheel mesh number #320, grinding speed 4μm / s, grinding wheel speed 3200rpm), with a total pre-thinning cutting amount of 50um.

[0031] S3: Use a hidden cutting device to laser internally break the edge around the back of the product, so that the edge does not separate from the product. Place the pre-thinned product on the worktable of the invisible cutting equipment, ensuring that the front of the product is facing up; Start the ring cutting function of the hidden cutting equipment, and adjust the laser parameters to a frequency of 120kHz, a power of 3W, and an angular velocity of 90° / s. Laser cuts are made around the edge of the product, with the cut width being the width of the wafer edge step.

[0032] S4: Use thinning equipment to thin the back side of the wafer again to the required thickness for the product; Reattach the product to the worktable of the thinning equipment, ensuring the back of the product is facing up; Set the thinning parameters as follows: Z1 (grinding wheel mesh size #320, grinding stage speed 4 / 3 / 2μm / s, grinding wheel speed 3200rpm), Z2 (grinding wheel mesh size #6000, grinding stage speed 0.4 / 0.3 / 0.2μm / s), Z3 (polishing pressure 150 / 200 / 200N, polishing amount 2um); The thinning equipment is controlled to thin the product until it reaches the internal break-off stage, at which point a ring of waste silicon around the edge separates from the product.

[0033] S5: The product is cut using a double-blade, four-cut method.

[0034] Place the product on the cutting table, ensuring the front side is facing up; Install two cutting blades, Z1 and Z2; Start the cutting equipment and execute the first stage of Z1 cutting. The cutting speed of Z1 cutter is 30mm / s, and the spindle speed is 50000rpm to perform grooving with a grooving depth of 30μm. If the quality does not meet the standard, the parameters will be adjusted and optimized. If the tool mark deviation is ≥3μm, the equipment will alarm and stop the operation. Personnel need to confirm and correct the tool mark. If the tool mark deviation is <3μm, the equipment will automatically correct it. If the quality meets the standard, execute the second stage of Z1 cutting. After the second stage of Z1 cutting is completed, Z2 jumps to the step before Z1 and makes a shallow cut on the edge of the wafer, with a cutting depth of 30~50um and a cutting length of 8~20um. If the Z2 cut does not deviate and the quality is normal, the cutting continues to execute the first stage of Z2 cutting. The cutting speed of Z2 cutter is 30mm / s and the spindle speed is 35000rpm. During the cutting process, the equipment has an automatic blade mark detection function (10~25 cuts / time). If the cutting quality meets the standard, the equipment will automatically start to continue cutting. If it exceeds the equipment's calibration range, the equipment will alarm and personnel will need to confirm the cutting quality until the cutting is completed.

[0035] Another embodiment of the present invention provides a hidden cutting blocking technique and a double-blade four-cutting method, the specific steps of which are as follows: Step 1: Apply film and pre-thin the back of the incoming product: Step 101: Attach the product to the film application worktable and use a lint-free cloth soaked in isopropyl alcohol solution to wipe the front and back of the product to remove surface contaminants. Step 102: Use a thinning device to pre-thin the back of the product. Use a diamond grinding wheel with a grit size of 2500#, a grinding wheel pressure of 0.4MPa, and a grinding speed of 0.7μm / s to thin it to 50μm.

[0036] Step 2: Perform a circumferential cutting treatment on the stepped area around the edge of the product: Step 201: Place the pre-thinned product on the worktable of the invisible cutting equipment, ensuring that the front of the product is facing up; Step 202: Activate the ring cutting function of the hidden cutting device, and adjust the laser parameters to a wavelength of 532nm and a power of 250W; Step 203: Laser cut along the edge of the product, with a cut width of 60μm.

[0037] Step 3: Thinning the product: Step 301: Re-secure the product onto the worktable of the thinning equipment, ensuring the back of the product is facing up; Step 302: Set the thinning parameters, using a 15μm thick polytetrafluoroethylene (PTFE) film as a protective layer, a grinding wheel pressure of 0.4MPa, a grinding speed of 0.8μm / s, and a circular arc grinding path; Step 303: Control the thinning equipment to thin the product until it reaches the internal break stage, and the waste silicon around the edge separates from the product. Step 304: Use a high-precision micrometer to check the thickness of the thinned product. If the thickness is not within the range of 80-120μm, return to step 302 to adjust the thinning parameters. If it is within the range of 80-120μm, proceed to step 4.

[0038] Step 4: Cut the product using a double-blade, four-cut method: Step 401: Place the product on the cutting table, ensuring the front side is facing up; Step 402: Install the two cutting blades, Z1 and Z2; Step 403: Start the cutting equipment and perform the first stage of Z1 cutting. The feed speed of the Z1 cutter is 0.8μm / s to perform grooving with a grooving depth of 50μm. Step 404: After the second stage of Z1 cutting is completed, Z2 jumps to the step before Z1 and makes a shallow cut on the edge of the wafer, with a cutting depth of 30~50um and a cutting length of 8~20um. If the Z2 cut does not deviate and the quality is normal, continue cutting and execute the first stage of Z2 cutting. The feed speed of the Z2 cutter is 1.0μm / s. Step 405: Use a high-precision automatic optical inspection system to inspect the cutting quality of the first stage of Z2. If the cutting surface is flat and smooth, then perform the second stage of Z2 cutting. During the cutting process, the equipment has an automatic blade mark detection function (10~25 cuts / time). If the cutting quality meets the standard, the equipment will automatically start to continue cutting. If it exceeds the equipment's calibration range, the equipment will alarm and personnel will need to confirm the cutting quality until the cutting is completed.

[0039] Although embodiments of the present invention have been described above in conjunction with the accompanying drawings, the present invention is not limited to the specific embodiments and application fields described above. The specific embodiments described above are merely illustrative and instructive, and not restrictive. Those skilled in the art, guided by the specification, can make many other modifications without departing from the scope of the claims of the present invention, and all of these modifications are within the scope of protection of the present invention.

Claims

1. A method for concealed cutting and double-blade four-cutting, characterized in that, include: Apply a protective film to the front of the product; Use thinning equipment to pre-thin the back of the product; Using a hidden cutting device, laser internally breaks the edge around the back of the product, ensuring that the edge remains inseparable from the product. The back side of the wafer is thinned again using a thinning device to the required thickness for the product. The product is cut using a double-blade, four-cut method.

2. The cutting method for concealed cutting and double-blade four-cutting according to claim 1, characterized in that, The specific steps for pre-thinning the back of the product using a thinning device are as follows: Attach the front of the product to the thinning worktable; The back of the product is pre-thinned using a thinning device.

3. The cutting method for concealed cutting and double-blade four-cutting according to claim 2, characterized in that, The pre-thinning thickness of the product is 50μm.

4. The method for concealed cutting and double-blade four-cutting according to claim 1, characterized in that, The specific steps for using a hidden cutting device to laser-cut the inner edge of the back of the product are as follows: Place the product on the worktable of the concealed cutting equipment; Activate the circumferential cutting function of the hidden cutting device; Laser internal breakage is performed around the edge of the product.

5. The cutting method for concealed cutting and double-blade four-cutting according to claim 1, characterized in that, The specific steps for further thinning the back side of the wafer to the required thickness using thinning equipment are as follows: Reattach the product to the worktable of the thinning equipment, ensuring the back of the product is facing up; Set the thinning parameters to control the thinning equipment to thin the product until it reaches the required thickness, and separate the waste silicon around the edge from the product.

6. The cutting method for concealed cutting and double-blade four-cutting according to claim 1, characterized in that, The specific steps for cutting the product using the double-blade, four-cut method are as follows: Place the product on the cutting table; Install two cutting blades, Z1 and Z2, with the width of cutting blade Z1 being greater than the width of cutting blade Z2; Start the cutting equipment and execute the first stage of Z1 cutting; The Z1 first-stage cutting surface cutting quality is checked. If the quality is not up to standard, the parameters are adjusted and optimized. If the tool mark deviation is ≥3um, the equipment alarms and stops the operation. Personnel need to confirm and correct the tool mark. If the tool mark deviation is <3um, the equipment will automatically correct it. If the quality meets the standard, the Z1 second-stage cutting is executed. The Z2 cut is confirmed by short-cut detection. If the Z2 cut does not deviate and there are no quality abnormalities, cutting continues. Repeat the above process until the cutting is complete.

7. The cutting method for concealed cutting and double-blade four-cutting according to claim 6, characterized in that, The first stage of Z1 cutting involves grooving the front of the product, with a grooving depth of 30~50μm into the product surface.

8. The method for concealed cutting and double-blade four-cutting according to claim 7, characterized in that, The second stage of Z1 involves cutting based on the slotting position of the first stage of Z1, cutting into more than 2 / 3 of the product but not completely cutting it off, and then stopping the cutting.

9. The cutting method for concealed cutting and double-blade four-cutting according to claim 6, characterized in that, The second stage of cutting involves cutting the product into individual pieces.

10. The method for concealed cutting and double-blade four-cutting according to claim 6, characterized in that, The second stage of Z2 cuts into the substrate to 5um, removing residual adhesive between the bottom DAFs of a single chip.

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