Scribing and splitting method for SiC-based device and SiC-based device manufactured by scribing and splitting method

Abstract

The invention discloses a SiC-based device scribing and splitting method and a SiC-based device manufactured by the same, and belongs to the technical field of semiconductor processing. The method is used for dividing a wafer structure comprising a SiC substrate, a front process layer and a front metal pattern layer into a plurality of Die. Comprising the following steps: S1, pasting a film on the back surface of a wafer, and slotting the front surface of the wafer according to a preset cutting line; s2, pasting a film on the front surface of the wafer, and scribing the back surface of the wafer according to a preset cutting line; s3, pasting a film on the back surface of the wafer and carrying out front surface splitting operation; and S4, carrying out wafer film expansion operation. According to the invention, through the process of firstly grooving the front surface and then scribing the back surface, the front surface and the back surface of the wafer are enabled to form the cutting channels, thereby facilitating the splitting operation, avoiding the situation that the front surface is not provided with the cutting channels during the splitting, and causing the crushing of fragments, and improving the yield. Moreover, the cutting channels on the front surface and the back surface of the wafer do not need to be processed too deep, so that the overheating and abrasion consumption of the cutter wheel can be effectively relieved, and the scribing and splitting efficiency is improved.

Description

Technical Field

[0001] The invention belongs to the technical field of semiconductor processing, and in particular relates to a SiC-based device scribing and splitting method and a SiC-based device prepared by the same. Background Art

[0002] At present, with the rise of SiC materials, many silicon-based semiconductor devices are gradually being replaced by SiC devices. For example, traditional silicon-based IGBTs dominate high-voltage and high-current scenarios, but silicon-based IGBTs cannot withstand high-frequency conditions and have high power consumption. SiC has the characteristics of high voltage and high temperature resistance, which allows it to cover the voltage resistance level of silicon-based IGBTs with only simpler MOSFET devices, while avoiding the shortcomings of high energy consumption of silicon-based IGBTs. Under the same environment, SiC-based MOSFETs reduce energy losses by 66% compared to silicon-based IGBTs of the same specifications, mainly due to a significant reduction in switching losses. In addition, in industries such as new energy vehicles, SiC-based devices can be used to drive and control motor inverters, on-board chargers, and fast charging piles; in photovoltaic power generation, photovoltaic inverter manufacturers have currently widely adopted SiC-based power devices to replace silicon-based devices.

[0003] However, silicon carbide has a high hardness and is difficult to process. For example, in the process of manufacturing SiC-based MOS or IGBT devices, see Figure 1 , the traditional process is as follows:

[0004] (1) Perform wafer front side processing;

[0005] (2) performing a thinning operation;

[0006] (3) performing wafer front side processing;

[0007] (4) Conduct CP & reliability testing;

[0008] (5) Wafer film is attached and a one-time dicing operation is performed.

[0009] In the above-mentioned traditional process, a one-time scribing operation is adopted when dividing the wafer into multiple Dies (single semiconductor chips). Due to the extremely high hardness of the SIC material, the scribing cost is very high. For example, the size of the Die distributed on a 6-inch wafer is 2030um*2030um. The tool needs to be changed after scribing 10 complete pieces, and the production capacity is 1H / pcs.

[0010] At present, a new process of scribing + cracking + film expansion has been developed for the scribing of SiC-based devices. Figure 2 , the specific process is as follows:

[0011] (1) Perform wafer front side processing;

[0012] (2) performing a thinning operation;

[0013] (3) performing wafer front side processing;

[0014] (4) Conduct CP & reliability testing;

[0015] (5) Film is applied to the front side of the wafer and scribing is performed on the back side;

[0016] (6) Laminating the back side of the wafer with film and performing back side splitting operation;

[0017] (7) Perform wafer expansion operation.

[0018] In the above-mentioned existing technology, the dicing depth is only 2-5um, and after optimization, a single-knife dicing can achieve 180pcs. In addition, the dicing capacity is 5-6 times that of the traditional process; in addition, the cutting path can be reduced from the original 80um to 40um, thereby improving the utilization rate of the wafer.

[0019] However, the new process of scribing + cracking + film expansion is to scribing on the back of the wafer, and then cracking + film expansion. However, due to the metal layer process, there will be some patterns on the front of the wafer, and the metal patterns will be metal-connected and sticky during the cracking process, resulting in a reduction in yield. Summary of the invention

[0020] The purpose of the present invention is to provide a SiC-based device slicing and splitting method and a SiC-based device manufactured therefrom, aiming to improve the slicing and splitting efficiency and yield rate. The present invention is achieved by the following scheme:

[0021] A first aspect of the present invention provides a SiC-based device dicing and splitting method for dividing a wafer structure including a SiC substrate, a front process layer and a front metal pattern layer into a plurality of dies; comprising:

[0022] S1, film is applied to the back of the wafer, and a slot is made on the front of the wafer according to the preset cutting line;

[0023] S2, film is applied to the front side of the wafer, and the back side of the wafer is diced according to the preset cutting line;

[0024] S3, film is attached to the back of the wafer and the front side is split;

[0025] S4. Perform wafer expansion operation.

[0026] The SiC-based device scribing and splitting method provided by the above technical solution forms cut streets on both the front and back sides of the wafer through the process of first grooving the front side and then scribing on the back side, which is more convenient for the splitting operation and avoids the situation where fragments are squeezed due to the lack of cut streets on the front side during splitting, thereby improving the yield rate; moreover, the cut streets on the front and back sides of the wafer do not need to be processed too deep, which can effectively reduce the overheating and wear of the cutter wheel, thereby improving the scribing and splitting efficiency.

[0027] As a preferred technical solution, in step S1, a groove operation is performed on the front side of the wafer, specifically including:

[0028] S1a, machining a first groove with a depth of d1 on the metal pattern layer by a cutter wheel, d1+d2=d0, d0 is the thickness of the metal pattern layer, d2 is the thickness of the metal layer temporarily remaining at the bottom of the first groove;

[0029] S1b, using a laser to continue to process downward along the bottom of the first groove to form a second groove with a depth of d5. The second groove should pass through the front process layer and be opened on the SiC substrate.

[0030] As a preferred technical solution, d2 = 0.2 ~ 0.3um.

[0031] As a preferred technical solution, d5=d2+d3=0.4~0.6um, d3=0.2~0.3um, d3 is the depth of the second groove on the front process layer and the SiC substrate, d3>d4, d4 is the thickness of the front process layer.

[0032] As a preferred technical solution, d5=d2+d3=0.4-0.6um, d3 is the depth of the second groove on the front process layer and the SiC substrate, d3>d4, d4 is the thickness of the front process layer.

[0033] As a preferred technical solution, in step S1b, when the second slot is processed by laser, the laser wavelength is controlled to be 355±50nm, the slot energy is controlled to be 1.0-4.0w, and the slot width is controlled to be 5-10um.

[0034] In the above preferred solution, the first groove is first processed on the metal graphic layer by the cutter wheel without cutting the metal graphic layer. On the one hand, the metal graphic layer can be roughly cut by utilizing the characteristic of the guide wheel that is convenient for processing metal, and the cutting efficiency is high; on the other hand, it can avoid the defects of too wide cutting path and broken edges caused by the guide wheel cutting the front process layer and SiC substrate. In addition, by laser processing the second groove, on the one hand, the metal layer temporarily left at the bottom of the first groove can be completely cut, which can reduce energy consumption compared with laser cutting the entire metal graphic layer; on the other hand, the front process layer and substrate can be cut by laser, which can make the cutting path thinner and less prone to broken edges; furthermore, d3>d4 is set, that is, the second groove must pass through the front process layer and be opened on the SiC substrate, which is better for the subsequent splitting and prevents the occurrence of twin crystals during splitting.

[0035] As a preferred technical solution, step S2 specifically includes: tearing off the back film of the wafer and sticking the front film on it, placing the wafer with the back side facing up on the dicing equipment, controlling the dicing force for dicing the back side of the wafer to 2-8N, the dicing groove depth to 2-10um, and the dicing groove width to 12-20um.

[0036] In the above preferred solution, since the width of the scribe groove is wider than the second slot width, when the front side is split, the back side has more room for deformation, thus avoiding the back side from being squeezed and damaged.

[0037] As a preferred technical solution, when scribing is performed in step S2, a lower camera is used to capture the area of ​​the second groove formed on the front side of the wafer, and the boundary of the scribing groove is determined according to the area of ​​the second groove and scribing is started from the middle.

[0038] In the above preferred solution, the second groove area on the front side of the wafer is captured by the lower camera, which can provide an accurate positioning reference for the upper dicing and ensure the alignment accuracy of the dicing equipment.

[0039] As a preferred technical solution, step S3 specifically includes: sticking a protective film with a thickness of 0.02-0.2mm on the back of the wafer and a protective film with a thickness of 0.02-0.05mm on the front; then placing the wafer with the front side facing up on the splitting device, performing front splitting, and controlling the splitting pressure to be 50-150um.

[0040] In the above preferred solution, since the width of the second groove on the front side is small, the splitting accuracy can be improved, and the wafer utilization rate can be improved, that is, more effective dies can be made on a single wafer, thereby reducing the cost.

[0041] As a preferred technical solution, step S4 specifically includes: tearing off the protective films on the front and back sides of the split wafer, and sticking a new film on the back side of the wafer; then placing the wafer with the front side facing up on a film expander and expanding the film from the back side of the wafer, and the upward movement distance of the top cylinder of the film expander is controlled to be 10-50mm, so that each split die is fully separated, and the spacing is 100-150um.

[0042] In the above preferred solution, by setting a suitable upward distance of the top cylinder, the Dies are completely separated after expansion while the spacing is 100-150um, avoiding the film layer on the back of the wafer from breaking when the spacing is too large, and facilitating the concentrated transportation of multiple Dies on the film layer.

[0043] A second aspect of the present invention provides a SiC-based device, which is manufactured by the SiC-based device scribing and splitting method described above. BRIEF DESCRIPTION OF THE DRAWINGS

[0044] Figure 1This is a process flow chart for processing a wafer into multiple dies using traditional technology.

[0045] Figure 2 The figure is a process flow chart of processing a wafer into multiple dies in the prior art.

[0046] Figure 3 FIG. 4 is a process flow chart of processing a wafer into multiple dies according to an embodiment of the present invention.

[0047] Figure 4 It is a schematic diagram of forming a first groove on the front side of the wafer structure in an embodiment of the present invention.

[0048] Figure 5 It is a schematic diagram of forming a first groove on the front side of the wafer structure and then processing to form a second groove in an embodiment of the present invention.

[0049] Figure 6 Schematic diagram of forming scribe lines on the back side of a wafer structure according to an embodiment of the present invention.

[0050] Figure 7 This is a diagram showing the effect of forming a scribe line on the back side of a wafer in an embodiment of the present invention.

[0051] Figure 8 It is a schematic diagram of a wafer structure undergoing a front-side slicing operation after front-side grooving and back-side dicing in an embodiment of the present invention.

[0052] Fig. 9 It is a schematic diagram of the wafer structure undergoing a film expansion operation after completing a front-side splitting operation in an embodiment of the present invention. DETAILED DESCRIPTION

[0053] The technical solutions of the embodiments of the present invention are explained and described below in conjunction with the drawings of the embodiments of the present invention, but the following embodiments are only preferred embodiments of the present invention, not all of them. In the description of the present invention, the terms "first" and "second" are only used for the purpose of distinction in the description, and cannot be understood as indicating or implying relative importance or implicitly indicating the number of technical features indicated. Therefore, the features defined as "first" and "second" may explicitly or implicitly include one or more of the features. In the description of the present invention, unless otherwise specified, "multiple" means two or more, unless otherwise clearly defined.

[0054] The specific implementation modes of the present invention are described in detail below with reference to the accompanying drawings. Under the premise that there is no conflict between them, the technical features of each specific implementation mode can be inherited and used interchangeably.

[0055] The SiC-based device dicing and splitting method provided in this embodiment is used to divide a wafer structure into multiple Dies (single semiconductor chips, such as SiC-based MOS chips). The wafer structure in this embodiment includes a front process layer and a SiC substrate 10, and also includes a metal pattern layer 20 on the front process layer and the SiC substrate 10, such as Figure 4 shown.

[0056] Combination Figure 3 As shown, the SiC-based device scribing and splitting method provided in this embodiment includes:

[0057] S1, film is applied to the back of the wafer, and a slot is made on the front of the wafer according to the preset cutting line;

[0058] S2, film is applied to the front side of the wafer, and the back side of the wafer is diced according to the preset cutting line;

[0059] S3, film is attached to the back of the wafer and the front side is split;

[0060] S4. Perform wafer expansion operation.

[0061] Of course, the SiC-based device slicing and splitting method provided in this embodiment will also perform conventional operations such as wafer front side processing, thinning operation, wafer front side processing, CP & reliability testing before executing the above steps S1-S4.

[0062] The SiC-based device scribing and splitting method provided in the above embodiment is a process of first grooving the front side and then scribing on the back side, so that cut lines are formed on both the front and back sides of the wafer, which is more convenient for the splitting operation and avoids the situation in the prior art where there is no cut line on the front side resulting in extrusion of fragments, thereby improving the yield rate; moreover, under the method of this embodiment, the cut lines on the front and back sides of the wafer do not need to be processed too deep, which can effectively reduce the overheating and wear of the cutter wheel, thereby improving the scribing and splitting efficiency and reducing costs.

[0063] The following is a detailed description of steps S1-S4 in conjunction with the accompanying drawings:

[0064] First, for step S1 of the above-mentioned SiC-based device scribing and splitting method, how to make the operation of grooving the front side of the wafer efficient and safe, this embodiment makes the following analysis and considerations: if a simple cutter wheel is used to groove the substrate, it will cause large edge collapse of the substrate; and if only laser grooving is used, for thick metal film layers, such as the metal graphic layer on the front side of the SIC device, the thickness is generally 4 to 6 um, which requires a large laser grooving energy and produces a large amount of metal melt, which will splash onto the effective area of ​​the wafer and cause device failure.

[0065] Therefore, step S1 of this embodiment adopts a combination of a cutter wheel and laser slotting, which specifically includes the following steps:

[0066] S1a, machining a first groove with a depth of d1 on the metal pattern layer by a cutter wheel, d1+d2=d0, d0 is the thickness of the metal pattern layer, d2 is the thickness of the metal layer temporarily left at the bottom of the first groove, combined with Figure 4 As shown;

[0067] S1b, using laser to continue to process downward along the bottom of the first groove to form a second groove with a depth of d5, the second groove should pass through the front process layer and be opened on the SiC substrate, combined with Figure 5 shown.

[0068] Step S1a is specifically as follows: on the cutter wheel scribing device, the front side of the wafer is facing upward, and the metal pattern layer 20 on the front side of the wafer is grooved, and the groove depth is the metal film layer depth -0.2 to 0.3um, that is, d1+d2=d0, d2=0.2 to 0.3um, d0 can be 4 to 6um, but there is no limit. This ensures that a metal layer of d2 thickness is left at the bottom of the first groove, avoiding the cutter wheel from scratching the SIC substrate, and will not cause the substrate to collapse and damage the effective Die.

[0069] Step S1b is specifically as follows: on the laser grooving equipment, the front side of the wafer is placed upward, the laser wavelength is 355nm, the grooving energy is 1.0-4.0w, the grooving width is 5-10um, and the depth d5 ​​of the second grooving is 0.4-0.6um; among them, 0.2-0.3um in d5 is the thickness of the remaining metal layer, and the other 0.2-0.3um is d3, which passes through the front process layer and is opened on the SiC substrate; in addition, assuming that the thickness of the front process layer is d4, d3>d4, the thickness d4 of the front process layer is very small, which is not shown in the figure.

[0070] In addition, when laser grooving is performed in step S1b, an upper camera is used to capture the area of ​​the first groove formed on the front side of the wafer, and the boundary is determined based on the area of ​​the first groove and the second groove is processed from the middle, so that the alignment accuracy of the second groove and the first groove can be ensured.

[0071] As can be seen from the above, the above step S1 adopts a combination of a cutter wheel and laser grooving. The first groove is first processed on the metal graphic layer by the cutter wheel without cutting the metal graphic layer. On the one hand, the guide wheel can be used to facilitate the processing of metals and roughly cut the metal graphic layer, with high cutting efficiency. On the other hand, it can avoid the guide wheel cutting the front process layer and the SiC substrate, resulting in excessive cutting width and edge collapse defects. In addition, by laser processing the second groove, on the one hand, the metal layer temporarily retained at the bottom of the first groove can be completely cut, which can reduce energy consumption compared to laser cutting the entire metal graphic layer; on the other hand, using laser to cut the front process layer and substrate can make the cutting path thinner and less prone to edge collapse; furthermore, the setting d3>d4, that is, the second groove must pass through the front process layer and be opened on the SiC substrate, which is better for the subsequent splitting and prevents the occurrence of twinning during splitting (twinning refers to the fact that the die is not completely separated, causing adjacent dies to stick together); in addition, when using laser to groove a thinner layer of metal with a thickness of d2, the melt is limited, and with the barrier of the first groove above, even if there is splashing, it will only spread in part of the groove area and will not splash into the effective area of ​​the wafer.

[0072] Combination Figure 6 As shown, step S2 of the above-mentioned SiC-based device slicing and splitting method specifically includes: tearing off the film on the back side of the wafer and pasting a front film, such as a D-485H film, and this patent is not limited to the D-485H film; then placing the wafer on the slicing equipment with the back side facing up, and controlling the slicing force for slicing the back side of the wafer to be 2-8N, the slicing groove depth to be 2-10um, and the slicing groove width to be 12-20um. Since the width of the slicing wheel determines that the width of the slicing groove is wider than the second slot width (5-10um), when the front side of the wafer is subsequently split, the back side of the wafer has more room for deformation to avoid back side extrusion and damage.

[0073] In step S2, when dicing, a lower camera is used to capture the second grooved area formed on the front side of the wafer, and the boundary of the dicing groove is determined according to the second grooved area, and dicing starts from the middle. This can provide an accurate positioning reference for the upper dicing, and ensure the alignment accuracy of the dicing equipment. Figure 7 The figure shows the back side of the wafer after the scribe line 121 is formed on the back side.

[0074] Combination Figure 8As shown, step S3 of the above-mentioned SiC-based device slicing and splitting method specifically includes: attaching a V8 protective film with a thickness of 0.02-0.2mm to the back of the wafer, and attaching a PET protective film with a thickness of 0.02-0.05mm to the front, and the front and back films are not limited to V8 film and PET film; then placing the wafer with the front side facing up on the splitting device, and performing front splitting, and the splitting pressure is controlled to be 50-150um. At this time, since the width of the second groove on the front side is small, the splitting accuracy can be improved, and at the same time, the wafer utilization rate can be improved, that is, more effective dies can be made on a single wafer, thereby reducing costs.

[0075] Combination Fig. 9 As shown, step S4 of the above-mentioned SiC-based device slicing and splitting method specifically includes: tearing off the protective films on the front and back sides of the split wafer, and sticking a new film, such as D-485H film, on the back side of the wafer; then placing the wafer with the front side facing up on the film expander and expanding the film from the back side of the wafer, and the upward movement distance of the top cylinder of the film expander is controlled to be 10-50mm, so that each diced Die is fully separated, and the spacing is 100-150um. Among them, the main function of sticking a new film is to ensure the adhesion of the new film to each Die while preventing it from breaking during film expansion; in addition, by setting a suitable upward movement distance of the top cylinder, the Die is completely separated after expansion, and the spacing is 100-150um, so as to avoid the film layer on the back side of the wafer from breaking when the spacing is too large, so as to facilitate the centralized transportation of multiple Dies on the film layer.

[0076] The above disclosure is only the preferred embodiment of the present application, which certainly cannot be used to limit the scope of rights of the present application. Therefore, equivalent changes made according to the claims of the present application are still within the scope covered by the present application.

Claims

1. A SiC-based device dicing and splitting method, used to divide a wafer structure including a SiC substrate, a front process layer and a front metal pattern layer into a plurality of dies; characterized in that: include: S1, film is applied to the back of the wafer, and a slot is made on the front of the wafer according to the preset cutting line; S2, film is applied to the front side of the wafer, and the back side of the wafer is diced according to the preset cutting line; S3, film is attached to the back of the wafer and the front side is split; S4. Perform wafer expansion operation.

2. The SiC-based device scribing and splitting method according to claim 1, characterized in that: In step S1, a groove operation is performed on the front side of the wafer, specifically including: S1a, machining a first groove with a depth of d1 on the metal pattern layer by a cutter wheel, d1+d2=d0, d0 is the thickness of the metal pattern layer, d2 is the thickness of the metal layer temporarily remaining at the bottom of the first groove; S1b, using a laser to continue processing a second groove with a depth of d5 downward along the bottom of the first groove, the second groove passes through the front process layer and is opened on the SiC substrate.

3. The SiC-based device scribing and splitting method according to claim 2, characterized in that: d2=0.2~0.3um.

4. The SiC-based device scribing and splitting method according to claim 2, characterized in that: d5=d2+d3=0.4-0.6um, d3=0.2-0.3um, d3 is the depth of the second groove on the front process layer and the SiC substrate, d3>d4, d4 is the thickness of the front process layer.

5. The SiC-based device scribing and splitting method according to claim 2, characterized in that: In step S1b, when the second slot is processed by laser, the laser wavelength is controlled to be 355±50nm, the slot energy is controlled to be 1.0-4.0w, and the slot width is controlled to be 5-10um.

6. The SiC-based device scribing and splitting method according to claim 2, characterized in that: Step S2 specifically includes: tearing off the back film of the wafer and sticking the front film, placing the wafer with the back side facing up on the dicing equipment, controlling the dicing force for dicing the back side of the wafer to 2-8N, the dicing groove depth to 2-10um, and the dicing groove width to 12-20um.

7. The SiC-based device scribing and splitting method according to any one of claims 2 to 6, characterized in that: When scribing is performed in step S2, a lower camera is used to capture the area of ​​the second groove formed on the front side of the wafer, and the boundary of the scribing groove is determined according to the area of ​​the second groove, and scribing starts from the middle.

8. The SiC-based device scribing and splitting method according to claim 2, characterized in that: Step S3 specifically includes: attaching a protective film with a thickness of 0.02-0.2mm to the back of the wafer and attaching a protective film with a thickness of 0.02-0.05mm to the front; then placing the wafer with the front side facing up on a slicing device, and slicing the front side, with the slicing pressure controlled to be 50-150um.

9. The SiC-based device scribing and splitting method according to claim 2, characterized in that: Step S4 specifically includes: tearing off the protective films on the front and back sides of the split wafer, and sticking a new film on the back side of the wafer; then placing the wafer with the front side facing up on a film expander and expanding the film from the back side of the wafer. The upward movement distance of the top cylinder of the film expander is controlled to be 10-50mm, so that each split die is fully separated, and the spacing is 100-150um.

10. A SiC-based device, characterized in that: The SiC-based device is manufactured by the SiC-based device scribing and splitting method according to any one of claims 1 to 9.

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