Wafer processing method, wafer processing equipment and crystal grain

Abstract

The present application relates to the field of semiconductor manufacturing technology, and in particular to a wafer processing method, wafer processing equipment, and crystal grains. The processing method includes the following steps: using a first laser to implicitly cut the wafer to form a modified layer inside the wafer; using a splitter to split the wafer from the front side of the wafer to divide the wafer into several single crystal grains, and a V-shaped groove is generated on the surface of the back metal layer facing away from the substrate layer; performing film expansion treatment on the wafer to separate the several single crystal grains from each other. During the splitting process, a V-shaped groove is generated on the surface of the back metal layer facing away from the substrate layer, so that during the film expansion treatment, the back metal layer will split along the V-shaped groove, thereby separating the several single crystal grains from each other without generating twin crystals, thereby improving the efficiency of wafer slicing and the product yield. In addition, compared with the existing wafer dicing method, the processing method of the present application can reduce the four steps of wafer front film lamination, back grooving, UV debonding, and film tearing, so as to streamline equipment and reduce processing costs.

Description

Technical Field

[0001] The present application relates to the field of semiconductor manufacturing technology, and in particular to a wafer processing method, wafer processing equipment, and crystal grains. Background Art

[0002] At present, the laser stealth cutting technology is usually used for dicing silicon carbide-based wafers. The laser stealth cutting technology uses laser to perform modification processing inside the silicon carbide-based wafer that has completed the device process to form a modified layer, and then splits and expands the crystal to divide the silicon carbide-based wafer into several single grains. However, since the back metal layer of the wafer has strong ductility, after laser cutting, the wafer part may be separated into core grains after splitting, while the back metal layer is not separated, resulting in problems such as twin crystals, affecting the slicing efficiency and yield. To this end, one solution is to etch the metal on the back of the silicon carbide-based wafer to form a cutting path, but this method has complicated steps, increases the difficulty of process control and material costs, takes a long time, and is prone to problems such as yield loss in the middle. Summary of the Invention

[0003] The present application discloses a wafer processing method, wafer processing equipment and crystal grains, so as to solve the problem of twin crystals easily generated in laser stealth cutting technology without etching and grooving the metal layer on the back of the wafer.

[0004] To achieve the above objectives, this application provides the following technical solutions:

[0005] In the first aspect, the present application provides a method for processing a wafer, wherein the wafer includes a stacked substrate layer and a back metal layer, and the wafer processing method includes the following steps: using a first laser to implicitly cut the wafer to form a modified layer inside the wafer; using a splitter to split the wafer from the front side of the wafer to divide the wafer into several single grains, and a V-groove is generated on the surface of the back metal layer away from the substrate layer, and the opening of the V-groove is away from the substrate layer; performing film expansion processing on the wafer to separate the several single grains from each other.

[0006] Among them, the first laser is used to implicitly cut the wafer to form a modified layer inside the wafer, thereby forming microcracks near the modified layer, and then when the front of the wafer is split by a splitting knife, the wafer will split along the microcracks to divide the wafer into several single grains. At the same time, during the splitting process, a V-shaped groove is generated on the surface of the back metal layer away from the substrate layer, and the opening of the V-shaped groove is away from the substrate layer, so that during the film expansion process, the back metal layer will split along the V-shaped groove, thereby separating several single grains from each other and not producing twin crystals, thereby improving the efficiency of wafer slicing and product yield. In addition, compared with the existing wafer dicing method, the processing method in this application can reduce the four processes of wafer front film lamination, back grooving, UV degumming and film tearing, effectively streamlining equipment and reducing processing costs.

[0007] In a possible implementation, before the first laser stealth cutting of the wafer is performed, the method further includes: attaching a cutting film to a surface of the back metal layer that is away from the substrate layer.

[0008] In a possible implementation, the pressing depth of the cleaver is positively correlated with the thickness of the back metal layer.

[0009] In a possible implementation, the pressing depth of the cleaver is greater than or equal to the sum of the thicknesses of the wafer and the dicing film.

[0010] In one possible implementation, after the first laser is used to implicitly cut the wafer, before the wafer is split from the front side of the wafer using a splitter, the process includes: setting the two carriers of the splitting machine at intervals, and along the first direction, the size of the gap between the two carriers is 1-1.2 times the size of a single grain; placing the wafer on the two carriers, and making the direction of the line between the two carriers parallel to the first direction; wherein a first cleavage path and a second cleavage path are provided on the wafer, the first direction is the extension direction of the first cleavage path, the extension direction of the second cleavage path is the second direction, and the first direction and the second direction are perpendicular to each other.

[0011] In a possible implementation, using a cleaver to cleave the wafer from the front side of the wafer includes: cleaving the wafer along the second direction with the cleaver; and rotating the wafer 90° and then cleaving the wafer along the first direction with the cleaver.

[0012] In the second aspect, the present application provides a wafer processing equipment adopting the processing method of the first aspect, the wafer processing equipment includes a laser stealth cutting machine, a splitting machine and a film expanding machine, wherein the laser stealth cutting machine is used to laser stealth cut the wafer to form a modified layer inside the wafer; the splitting machine is used to split the wafer from the front side of the wafer to divide the wafer into several single grains, and a V-shaped groove is generated on the surface of the back metal layer facing the cutting film, and the opening of the V-shaped groove is away from the substrate layer; the film expanding machine is used to perform film expansion processing on the wafer; the splitting machine includes a splitting knife and two spaced-apart supporting platforms, and the supporting platforms are used to support the wafer; the wafer processing equipment also includes a first shooting unit, the first shooting unit is located on the side of the supporting platform facing the splitting knife, and the first shooting unit is used to obtain an image of the front side of the wafer.

[0013] In one possible implementation, the wafer processing equipment also includes a second shooting unit, which is located on the side of the carrier platform away from the splitting knife, and the orthographic projections of the second shooting unit and the two spaced-apart carrier platforms on the wafer do not overlap, and the second shooting unit is used to obtain an image of the back side of the wafer.

[0014] In a possible implementation, the first shooting unit is a CCD camera; and / or the second shooting unit is a CCD camera.

[0015] In a third aspect, the present application provides a grain produced by the processing method of the first aspect, wherein the grain includes a stacked substrate layer and a back metal layer, the edge of the back metal layer has a continuous serrated structure, and the surface of the substrate layer facing the back metal layer is flat. BRIEF DESCRIPTION OF THE DRAWINGS

[0016] Figure 1 A schematic diagram of a conventional wafer processing method;

[0017] Figure 2 A schematic flow chart of a wafer processing method according to an embodiment of the present application;

[0018] Figure 3 This is a schematic diagram of the structure of a wafer splitting machine according to an embodiment of the present application;

[0019] Figure 4 This is a schematic structural diagram of a crystal grain according to an embodiment of the present application;

[0020] Figure 5 A schematic diagram of the structure of a conventional wafer splitting machine;

[0021] Figure 6 This is a magnified microscope image of the grains of Example 1 of the present application;

[0022] Figure 7 This is a magnified microscope image of the grains of Comparative Example 1 of the present application.

[0023] Reference numerals: 100 - splitter; 110 - splitter; 120 - carrier; 200 - first imaging unit; 300 - second imaging unit; 400 - wafer; 410 - substrate layer; 420 - back metal layer; 421 - sawtooth structure; 430 - cutting film;

[0024] 01-V-groove; 02-depression. DETAILED DESCRIPTION

[0025] To make the objectives, technical solutions, and advantages of this application more clear, this application will be further described in detail below with reference to the accompanying drawings. Obviously, the embodiments described are only some of the embodiments of this application, not all of them. Based on the embodiments in this application, all other embodiments obtained by ordinary technicians in this field without making any creative efforts are within the scope of protection of this application.

[0026] The application scenarios described in the embodiments of this application are intended to more clearly illustrate the technical solutions of the embodiments of this application and do not constitute a limitation on the technical solutions provided by the embodiments of this application. Persons skilled in the art will appreciate that, as new application scenarios emerge, the technical solutions provided by the embodiments of this application are equally applicable to similar technical problems. In the description of this application, unless otherwise specified, "multiple" means two or more.

[0027] The existing wafer dicing method usually uses laser stealth cutting technology. Since the back metal layer of the wafer has strong ductility, after laser cutting, the wafer part may be separated into core particles after cleaving, while the back metal layer is not separated, resulting in problems such as twin crystals. In order to solve the above problems, the back metal layer needs to be scribed and grooved before laser stealth cutting of the wafer. Figure 1 This is a flow chart of the existing wafer processing method, refer to Figure 1 , the existing wafer processing method includes the following steps: front film lamination, back grooving, UV debonding, film tearing, back film lamination, laser hidden cutting, back splitting and film expansion. Correspondingly, the existing wafer processing equipment needs to include an additional film lamination machine, a film tearing machine, a UV machine and a laser grooving machine. Each wafer requires an extra film, and materials such as laser grooving liquid are also required. The laser grooving liquid is not environmentally friendly and requires sewage treatment. Therefore, the existing wafer processing method is not only complicated in steps and has high preparation costs, but also, the film lamination on the front of the wafer may cause the device to have residual glue risk, and there is a risk of breakage when the thin wafer is inverted.

[0028] In view of this, an embodiment of the present application provides a wafer processing method to improve the success rate of wafer dicing and product yield.

[0029] Figure 2 This is a flow chart of a wafer processing method according to an embodiment of the present application. The wafer includes a stacked substrate layer and a back metal layer. Figure 2 , the wafer processing method includes the following steps:

[0030] Using a first laser to implicitly cut the wafer to form a modified layer inside the wafer;

[0031] A cleaver is used to split the wafer from the front side of the wafer so that the wafer is divided into a number of individual grains, and a V-shaped groove is formed on the surface of the back metal layer facing away from the substrate layer, with the opening of the V-shaped groove facing away from the substrate layer;

[0032] The wafer is expanded to separate several individual dies from each other.

[0033] The wafer processing method disclosed in this application can create a V-shaped groove on the surface of the back metal layer facing away from the substrate layer during the splitting process. This allows the back metal layer to split along the V-shaped groove during the film expansion process, thereby separating several individual grains from each other and preventing the formation of twin crystals. This improves the efficiency of wafer slicing and product yield. In addition, compared to existing wafer dicing methods, the processing method disclosed in this application can reduce the four steps of wafer front film lamination, back grooving, UV debonding, and film tearing, effectively streamlining equipment and reducing processing costs.

[0034] In some embodiments of the present application, before the first laser stealth cutting of the wafer is performed, the method further includes: attaching a cutting film to the surface of the back metal layer facing away from the substrate layer.

[0035] Among them, the function of the cutting film is to protect the individual grains from scattering after the wafer is split.

[0036] In some embodiments of the present application, the pressing depth of the cleaver is positively correlated with the thickness of the back metal layer.

[0037] Under the action of the cleaver, a V-shaped groove is formed on the back metal layer along the orthographic projection of the cleaver on the back metal layer, allowing the back metal layer to be cracked along the V-shaped groove during the subsequent film expansion process. It is understood that the thicker the back metal layer, the deeper the cleaver needs to press down to ensure that the V-shaped groove is formed on the back metal layer under the action of the cleaver.

[0038] In some embodiments of the present application, the depth of the cleaver's downward pressure is greater than or equal to the sum of the thicknesses of the wafer and the dicing film. This ensures that after the cleaver is pressed down on the wafer, the wafer is divided into a plurality of individual grains, and a V-groove is formed on the surface of the back metal layer facing away from the substrate layer, with the opening of the V-groove facing away from the substrate layer.

[0039] In some embodiments of the present application, after irradiating the front side of the wafer with a first laser and before cleaving the wafer from the front side of the wafer with a cleaver, the process includes:

[0040] The two supporting platforms of the splitting machine are spaced apart, and along the first direction, the size of the gap between the two supporting platforms is 1-1.2 times the size of a single grain;

[0041] The wafer is placed on two carriers, and the direction of the connection line between the two carriers is parallel to the first direction.

[0042] It is understandable that after the wafer is laser cut, microcracks are formed near the modified layer. When the splitter splits the front of the wafer, the splitter will press down on the wafer, and the wafer will transfer the pressure to the carrier. The carrier will give the wafer a reaction force. The reaction force is opposite to the direction of the pressure of the splitter on the wafer. Under the joint action of the two, the wafer will split along the microcracks.

[0043] Along the first direction, the size of the gap between the two supporting platforms is 1-1.2 times the size of a single die, so that the wafer is divided into a plurality of single dies.

[0044] A first cleavage street and a second cleavage street are provided on the wafer, the first direction is the extension direction of the first cleavage street, the extension direction of the second cleavage street is the second direction, and the first direction and the second direction are perpendicular to each other.

[0045] Optionally, the position where the wrecking knife presses down on the wafer may be located in an area corresponding to the orthographic projection of the gap between the two carriers on the wafer. Further, the position where the wrecking knife presses down on the wafer may be located in the middle of the orthographic projection of the gap on the wafer.

[0046] In some embodiments of the present application, cleaving the wafer from the front side of the wafer using a cleaver includes:

[0047] The cleaver cleaves the wafer along the second direction so as to divide the wafer into a plurality of long strips;

[0048] After the wafer is rotated 90 degrees, the wafer is split by a splitter along a first direction, and the long strip portion is further divided into a plurality of individual crystal grains.

[0049] It is understood that by splitting the wafer along the first and second directions, the wafer is precisely divided into a plurality of dies of a predetermined size, each of which can be packaged and used independently. This splitting method helps maximize the efficiency of wafer utilization and ensures that each die can be effectively separated from the wafer.

[0050] Based on the same technical concept, the embodiment of the present application also provides a wafer processing device that adopts the processing method in various possible embodiments of the present application, and the wafer processing device includes a laser hidden cutting machine, a splitting machine and a film expanding machine. Among them, the laser hidden cutting machine is used to perform laser hidden cutting on the wafer to form a modified layer inside the wafer. The splitting machine is used to split the wafer from the front side of the wafer to divide the wafer into several single grains, and a V-groove is generated on the surface of the back metal layer facing the cutting film, and the opening of the V-groove is away from the substrate layer. The film expanding machine is used to perform film expansion processing on the wafer.

[0051] Figure 3 This is a schematic diagram of the structure of a wafer splitting machine according to an embodiment of the present application, referring to Figure 3 The wafer splitter 100 includes a splitter 110 and two spaced-apart platforms 120 for supporting a wafer 400. The wafer includes a stacked substrate layer 410, a back metal layer 420, and a dicing film 430. When the wafer 400 is placed on the dicing film 430, the dicing film 430 adheres to the dicing film 430.

[0052] It can be understood that when the splitting knife 110 presses down the wafer 400, the two supporting platforms 120 will respectively apply a reaction force to the back metal layer 420, which are named as the first force F1 and the second force F2 respectively. Since there is a gap between the two supporting platforms 120, the splitting knife 110 acts on the area of ​​the back metal layer 420 facing the above gap, and the first force F1 and the second force F2 act on the areas on both sides of the orthographic projection of the above gap on the back metal layer 420. Therefore, under the combined action of the pressure of the splitting knife 110, the first force F1 and the second force F2, the back metal layer 420 can form a V-shaped groove 01 along the orthographic projection of the splitting knife 110 on the back metal layer 420.

[0053] You can continue to refer to Figure 3 The wafer 400 processing equipment also includes a first shooting unit 200, which is located on the side of the carrier 120 facing the splitting knife 110. The first shooting unit 200 is used to obtain an image of the front side of the wafer 400 to facilitate observation of the splitting condition of the wafer 400 by the splitting knife 110.

[0054] The first shooting unit 200 is a charge-coupled device (CCD) camera.

[0055] In some embodiments of the present application, the wafer 400 processing equipment also includes a second shooting unit 300, which is located on the side of the carrier 120 away from the splitting knife 110, and the second shooting unit 300 and the two spaced-apart carriers 120 have no overlapping orthographic projections on the wafer 400. The second shooting unit 300 is used to obtain an image of the back side of the wafer 400, so as to facilitate observation of the splitting effect of the splitting knife 110 on the back metal layer 420 of the wafer 400.

[0056] The second shooting unit 300 is a CCD camera.

[0057] In some embodiments of the present application, the wafer 400 processing equipment further includes a driving unit, which is configured to drive the cleaver 110 to move closer to or away from the carrier 120 to control the pressing depth of the cleaver 110 .

[0058] In some embodiments of the present application, the wafer 400 processing equipment further includes a control module, which is signal-connected to the drive unit, the first camera unit 200, and the second camera unit 300. The first camera unit 200 and the second camera unit 300 can transmit the acquired image information to the control module, which analyzes the cleavage condition of the wafer 400 to control the start and stop of the drive unit.

[0059] Based on the same technical concept, the embodiment of the present application further provides a grain produced by the processing method in various possible embodiments of the present application. Figure 4 This is a schematic diagram of the structure of a grain according to an embodiment of the present application, referring to Figure 4 The crystal grain includes a stacked substrate layer 410, a back metal layer 420 and a cutting film 430. The edge of the back metal layer 420 (the wafer splitting point) has a continuous sawtooth structure 421, and the surface of the substrate layer 410 facing the back metal layer 420 is flat.

[0060] Figure 5 This is a schematic diagram of the structure of the existing wafer splitting machine, refer to Figure 5 After the back metal layer of the existing wafer is grooved and laser ablated, an obvious ablation layer can be seen at the edge of the back metal layer 420. Moreover, after laser ablation, the surface of the substrate layer facing the back metal layer has a depression 02 with a depth greater than 3μm.

[0061] Compared with the existing processing technology, the processing method in this application can not only simplify the production process and reduce costs, but also the processing method will not affect the substrate layer 410 when splitting the back metal layer 420. The entire surface of the substrate layer 410 facing the back metal layer 420 is flat and has no pits. Therefore, the processing method of this application can improve the product quality of the grains.

[0062] The wafer processing method and wafer processing equipment in this application will be described below with reference to specific embodiments and comparative examples. Example

[0063] Example 1 provides a wafer processing method, referring to Figure 2 , the wafer processing method comprises the following steps:

[0064] A cutting film is attached to the surface of the back metal layer facing away from the substrate layer;

[0065] Using a first laser to implicitly cut the wafer to form a modified layer inside the wafer;

[0066] A cleaver is used to split the wafer from the front side of the wafer so that the wafer is divided into a number of individual grains, and a V-shaped groove is formed on the surface of the back metal layer facing away from the substrate layer, with the opening of the V-shaped groove facing away from the substrate layer;

[0067] The wafer is expanded to separate several individual dies from each other.

[0068] Figure 6 This is a microscope magnified view of the grains of Example 1 of the present application, refer to Figure 6 After the wafer in Example 1 is subjected to front-side cleavage and film expansion processing, the wafer is divided into several individual grains. Under a microscope with a magnification of 500 times or more, it can be seen that the edges of the cracks in the back metal layer have a continuous serrated structure.

[0069] Comparative Example 1

[0070] Comparative Example 1: Existing wafer processing method, referring to Figure 1 , the wafer processing method includes the following steps:

[0071] Front film lamination, back grooving, UV debonding, film tearing, back film lamination, laser invisible cutting, back splitting and film expansion.

[0072] Figure 7 This is a microscope magnified view of the crystal grains of Comparative Example 1 of the present application, refer to Figure 7 After the back metal layer of the wafer in Comparative Example 1 is grooved and laser ablated, an obvious ablation layer can be seen.

[0073] Compared with Comparative Example 1, the wafer processing method in Example 1 is simple to operate and reduces four steps of wafer front-side film lamination, back-side grooving, UV debonding and film tearing, which not only streamlines equipment but also reduces processing costs.

[0074] The above are only specific embodiments of the present application, but the scope of protection of this application is not limited thereto. Any changes or substitutions that can be easily conceived by a person skilled in the art within the technical scope disclosed in this application should be included in the scope of protection of this application. Therefore, the scope of protection of this application should be based on the scope of protection of the claims.

Claims

1. A method for processing a wafer, wherein the wafer comprises a substrate layer and a back metal layer stacked together, wherein: The processing method comprises the following steps: Using a first laser to implicitly cut the wafer to form a modified layer inside the wafer; Placing the wafer on two carriers with a gap between the two carriers, and splitting the wafer from the front side of the wafer using a cleaver to divide the wafer into a plurality of individual grains, wherein the cleaver acts on a region of the back metal layer facing the gap, and the two carriers respectively apply a reaction force to the back metal layer. Under the combined action of the pressure of the cleaver and the two reaction forces, a V-shaped groove is generated on the surface of the back metal layer facing away from the substrate layer, with the opening of the V-shaped groove facing away from the substrate layer; The wafer is subjected to a film expansion process, and the back metal layer is split along the V-shaped grooves to separate the individual grains from each other.

2. The processing method according to claim 1, characterized in that: Before the first laser is used to implicitly cut the front side of the wafer, the method further includes: A dicing film is attached to the surface of the back metal layer facing away from the substrate layer.

3. The processing method according to claim 2, characterized in that: The pressing depth of the cleaver is positively correlated with the thickness of the back metal layer.

4. The processing method according to claim 2, characterized in that: The pressing depth of the cleaver is greater than or equal to the sum of the thickness of the wafer and the cutting film.

5. The processing method according to claim 1, characterized in that: After the wafer is cut by the first laser, and before the wafer is split from the front side of the wafer by the cleaver, the method includes: The two supporting platforms of the splitting machine are spaced apart, and along the first direction, the size of the gap between the two supporting platforms is 1-1.2 times the size of the single grain; Placing the wafer on the two carriers, and making the direction of the line connecting the two carriers parallel to the first direction; The wafer is provided with a first cleave street and a second cleave street, the first direction is an extension direction of the first cleave street, the extension direction of the second cleave street is a second direction, and the first direction and the second direction are perpendicular to each other.

6. The processing method according to claim 5, characterized in that: The step of splitting the wafer from the front side of the wafer by using a cleaver comprises: The cleaver cleaves the wafer along the second direction; After the wafer is rotated 90 degrees, the cleaver cleaves the wafer along the first direction.

7. A grain obtained by the processing method according to any one of claims 1 to 6, characterized in that: The crystal grain comprises a substrate layer and a back metal layer which are stacked. The edge of the back metal layer has a continuous sawtooth structure, and the surface of the substrate layer facing the back metal layer is a plane.

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