Wafer splitting direction control method and photoetching mask

Abstract

The invention provides a wafer splitting direction control method and a photoetching mask, and belongs to the technical field of wafer splitting. The control method comprises the following steps: determining a specific crystal orientation according to the cleavage plane direction of a wafer; providing a photoetching mask with a photoresist pattern in a target direction; calculating a rotation angle of the wafer based on the specific crystal orientation and the target splitting direction; with the flat edge of the wafer as a reference, setting an angle alignment mark to form an angle scale; rotating the wafer to the calculated rotation angle by using an angle scale, executing a photoetching process, and forming photoresist lines arranged along the vertical direction of the crystal orientation on the wafer; and carrying out splitting operation to obtain a fracture surface of which the light resistance line direction is vertical to the crystal orientation. An angle scale is designed in a photoetching mask to assist a wafer in rotating. By accurately controlling the direction of the photoresist pattern relative to the crystal orientation, the photoresist lines are arranged along the vertical direction of the crystal orientation. The wafer is effectively guided to generate cracks in the specific crystal orientation, the wafer cracking process is controllable and stable, and the wafer cracking structure is more complete and neat.

Description

Technical Field

[0001] This application relates to the field of wafer dicing technology, and in particular to a method for controlling the direction of wafer dicing and a photomask. Background Technology

[0002] In the fields of semiconductor processing and micro / nano manufacturing, wafer dicing is a crucial step in process verification and structural analysis. After processes such as photolithography, etching, and thin film deposition are completed, wafer dicing is used to obtain the cross-sectional morphology of the wafer in order to evaluate process parameters such as the verticality of the microstructure, sidewall angles, and interface states. In particular, obtaining a clean cross-sectional structure of the target pattern is quite difficult for wafers that are not horizontal or perpendicular to the crystal orientation.

[0003] In actual testing, the cleaving crystal orientation of special crystal orientation substrates (such as non-traditional <100> Si substrates, Y-cut / Z-cut lithium niobate, sapphire, etc.) deviates from the horizontal / vertical orientation, making it difficult to control the cleaving direction. During the cleaving process, it may not be possible to cleave along the cross-sectional direction of the photoresist structure, resulting in observation angle deviation and affecting the accurate assessment of structural perpendicularity, sidewall angle, interface state, etc.

[0004] However, in the current wafer dicing process, the control of the dicing direction mainly relies on two methods: one is the physical scribing guidance method, which uses a diamond scribing pen or laser scribing equipment to scribe shallow grooves on the edge or back of the wafer as a guide path for crack propagation. During operation, the dicing direction of the target structure must be determined in advance, and scribing is applied along that direction. The crack propagates along the scribing under stress, achieving dicing. This method relies on high-precision equipment (such as laser cutting machines), is complex and costly, and if the scribing direction deviates from the crystal orientation, the crack is prone to chipping, affecting the cross-sectional quality. The other method is the mask-assisted structure method, which designs auxiliary structures (such as straight lines, narrow grooves, cross alignment marks, etc.) in the photolithography mask, forming visible marks on the wafer surface through photolithography as a dicing reference. During operation, the precise angular relationship between the wafer's crystal orientation and the flat edge must be known in advance, and the marks are matched with the crystal orientation by rotating the mask. However, this method is not applicable to wafers with unknown crystal orientations, and relies on the operator's subjective experience to adjust the alignment angle, posing a risk of dicing direction deviation. Summary of the Invention

[0005] This application provides a wafer cleaving direction control method and a photomask. An angle scale is designed in the photomask to assist wafer rotation. By precisely controlling the orientation of the photoresist pattern on the photomask relative to the crystal orientation, the photoresist lines after photolithography are aligned perpendicular to the crystal orientation. This effectively guides the wafer to generate cracks along a specific crystal orientation, making the cleaving process controllable and stable.

[0006] To achieve the above objectives, this application provides the following technical solution:

[0007] The first aspect of this application provides a method for controlling the direction of wafer cleaving, the method comprising:

[0008] The specific crystal orientation of the wafer is determined based on the cleavage plane orientation.

[0009] Provide a photomask and determine the target orientation and cleavage orientation of the photoresist pattern on the photomask based on the required cleavage orientation;

[0010] The rotation angle of the wafer is calculated based on the specific crystal orientation and the target direction of the photoresist pattern.

[0011] Using the flat edge of the wafer as an alignment reference mark, angle alignment marks are set on the photomask to form an angle scale for wafer rotation alignment;

[0012] Using an angle scale, the wafer is rotated to the calculated rotation angle, and a photolithography process is performed to form target photoresist lines arranged perpendicular to the crystal orientation on the wafer;

[0013] A dicing operation is performed on the photolithographically etched wafer to obtain a fracture surface in which the direction of the target photoresist line is perpendicular to the crystal orientation.

[0014] The wafer cleaving direction control method provided in the first aspect of this application includes: determining a specific crystal orientation of the wafer based on the cleavage plane orientation; providing a photomask and determining the target orientation and cleaving direction of the photoresist pattern on the photomask based on the required cleaving direction; calculating the wafer rotation angle based on the specific crystal orientation and the target orientation of the photoresist pattern; setting angle alignment marks on the photomask using the wafer's flat edge as an alignment reference mark to form an angle scale for wafer rotation alignment; rotating the wafer to the calculated rotation angle using the angle scale and performing a photolithography process to form photoresist lines arranged perpendicular to the crystal orientation on the wafer; and performing a cleaving operation on the photolithographically ... It effectively guides the wafer to generate cracks along a specific crystal orientation, making the cleaving process controllable and stable.

[0015] Based on the above technical solution, the following improvements can be made to this application.

[0016] In one possible implementation, a specific crystal orientation of the wafer is determined based on the cleavage plane orientation, including:

[0017] Scratches are applied to the edge of the wafer to create initial cracks. These initial cracks spontaneously fracture along the cleavage plane to determine the specific crystal orientation of the wafer.

[0018] In one possible implementation, the wafer rotation angle is calculated based on a specific crystal orientation and the target orientation of the photoresist pattern, including:

[0019] The rotation angle of the wafer satisfies the following formula:

[0020]

[0021] θ is the rotation angle of the wafer, α is the angle between the specific crystal orientation and the direction of the wafer's flat edge, and β is the angle between the direction of the target photoresist pattern and the direction of the wafer's flat edge.

[0022] In one possible implementation, using the flat edge of the wafer as an alignment reference mark, angular alignment marks are set on the photomask to form an angular scale for wafer rotation alignment, including:

[0023] Using the center of the photomask as the axis, the wafer is rotated multiple times at the same angle. Several angle alignment marks are set on the photomask at different angle intervals. The angle alignment marks are matched with the flat edge of the wafer to achieve rotational alignment of the wafer at a specific angle.

[0024] In one possible implementation, using the flat edge of the wafer as an alignment reference mark, angle alignment marks are set on the photomask to form an angle scale for wafer rotation alignment, and the implementation also includes:

[0025] Set the angle alignment marks on both sides of the photomask in the direction of the wafer's flat edge;

[0026] Angle alignment marks intersect with the wafer's flat edge projection at different rotation angles. Angle alignment marks at different angles are arranged by sharing a portion of the angle alignment marks to form an angle scale.

[0027] In one possible implementation, after rotating the wafer to a calculated rotation angle using an angle scale, the photolithography process is performed, and the process further includes:

[0028] In the photolithography process, the relative positions of the wafer's flat edge and the angle scale are observed through a microscope to precisely align the wafer's flat edge and the angle scale.

[0029] In one possible implementation, before cleaving the photolithographically etched wafer, the following is also included:

[0030] After the photolithography process is completed, the relative position of the wafer's flat edge and the angle scale is observed again under a microscope to determine whether the wafer's rotation angle error meets the cleaving conditions.

[0031] A second aspect of this application provides a photomask for wafer dicing alignment, comprising:

[0032] The substrate has a photoresist pattern in the target direction;

[0033] An angle scale, which includes several spaced angle alignment marks, is used to match the flat edge of the wafer to achieve rotational angle alignment of the wafer before the photolithography process.

[0034] The second aspect of this application provides a photomask for wafer dicing alignment, comprising a substrate and an angle scale. The substrate has a photoresist pattern in any orientation. The angle scale includes several spaced-apart angle alignment marks, each used to mate with the flat edge of the wafer to achieve rotational angle alignment of the wafer before the photolithography process. Thus, the photomask provided in this application, by setting the angle scale to assist wafer rotation, avoids the problem of uncontrollable dicing direction for wafers with unknown crystal orientation angles, allowing dicing to proceed precisely along a preset direction and ensuring dicing accuracy.

[0035] In one possible implementation, the wafer is rotated multiple times at the same angle, with each angle alignment mark coinciding with the projection of the two endpoints of the wafer's flat edge at the corresponding rotation angle.

[0036] In one possible implementation, at least some of the angle alignment marks at different angles intersect to reduce at least some of the angle alignment marks, forming an angle scale.

[0037] In addition to the technical problems solved by this application, the technical features constituting the technical solutions, and the beneficial effects brought about by the technical features of these technical solutions described above, other technical problems that can be solved by the wafer cleaving direction control method and photomask provided by this application, other technical features contained in the technical solutions, and the beneficial effects brought about by these technical features will be further explained in detail in the specific embodiments. Attached Figure Description

[0038] To more clearly illustrate the technical solutions in the embodiments of this application or the prior art, the drawings used in the description of the embodiments of this application or the prior art will be briefly introduced below. Obviously, the drawings described below are only a part of the embodiments of this application. These drawings and text descriptions are not intended to limit the scope of the concept of this application in any way, but to illustrate the concept of this application to those skilled in the art by referring to specific embodiments. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0039] Figure 1 This is a schematic flowchart of a wafer cleaving direction control method provided in an embodiment of this application;

[0040] Figure 2 This is a schematic diagram of the wafer cleavage plane orientation in a wafer cleavage direction control method provided in an embodiment of this application.

[0041] Figure 3 This is a schematic diagram of the structure of the photoresist pattern under different angle rotations in a wafer cleaving direction control method provided in an embodiment of this application;

[0042] Figure 4 This is a schematic diagram of the angle alignment mark in a wafer cleaving direction control method provided in an embodiment of this application;

[0043] Figure 5 This is a schematic diagram of the angle alignment mark at different angles in a wafer cleaving direction control method provided in an embodiment of this application;

[0044] Figure 6 This is a schematic diagram of the rotating distribution of angle alignment marks in a wafer cleaving direction control method provided in an embodiment of this application.

[0045] Figure 7 This is a schematic diagram of the structure when the angle alignment marks intersect in a wafer cleaving direction control method provided in an embodiment of this application;

[0046] Figure 8 This is a schematic diagram of the angle scale in a wafer cleaving direction control method provided in an embodiment of this application;

[0047] Figure 9 This is a schematic diagram of the structure of a photomask and a wafer provided in an embodiment of this application.

[0048] Explanation of reference numerals in the attached figures:

[0049] 100 - Photomask;

[0050] 200 - Substrate; 210 - Photoresist pattern;

[0051] 300 - Angle scale; 310 - Angle alignment mark;

[0052] 400 - wafer; 410 - wafer flat edge. Detailed Implementation

[0053] The technical solutions of the embodiments of this application will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only a part of the embodiments of this application, and not all of the embodiments. Based on the embodiments of this application, all other embodiments obtained by those of ordinary skill in the art without creative effort are within the scope of protection of this application.

[0054] As described in the background section, current wafer dicing processes primarily rely on two methods to control the dicing direction: one is the physical scribing guidance method, which uses a diamond scribing pen or laser scribing equipment to scribe shallow grooves on the wafer edge or back side as a guide path for crack propagation. During operation, the target structure dicing direction must be predetermined, and scribing is applied along that direction. The crack propagates along the scribing under stress, achieving dicing. This method relies on high-precision equipment (such as laser cutters), has a complex process, and is costly. Furthermore, if the scribing direction deviates from the crystal orientation, the crack is prone to chipping, affecting the cross-sectional quality. The other method is the mask-assisted structure method, which designs auxiliary structures (such as straight lines, narrow grooves, cross alignment marks, etc.) in the photolithography mask. Visible marks are formed on the wafer surface through photolithography, serving as a dicing reference. During operation, the precise angular relationship between the wafer's crystal orientation and the flat edge must be known beforehand, and the marks must be matched with the crystal orientation by rotating the mask for alignment. However, this method is not applicable to wafers with unknown crystal orientation, and it relies on the operator's subjective experience to adjust the alignment angle, which carries the risk of cleavage direction deviation.

[0055] To address the aforementioned technical problems, the first aspect of this application provides a wafer cleaving direction control method. This method includes: determining a specific crystal orientation of the wafer based on the cleavage plane orientation; providing a photomask and determining the target orientation and cleaving direction of the photoresist pattern on the photomask; calculating the wafer rotation angle based on the specific crystal orientation and the target orientation of the photoresist pattern; setting angle alignment marks on the photomask using the wafer's flat edge as an alignment reference mark to form an angle scale for wafer rotation alignment; rotating the wafer to the calculated rotation angle using the angle scale, performing a photolithography process to form photoresist lines arranged perpendicular to the crystal orientation on the wafer; and performing a cleaving operation on the photolithographically ... It effectively guides the wafer to generate cracks along a specific crystal orientation, making the cleaving process controllable and stable.

[0056] A second aspect of this application provides a photomask for wafer dicing alignment. The photomask includes a substrate and an angle scale. The substrate has a photoresist pattern with a target orientation. The angle scale includes several spaced-apart angle alignment marks, each of which mates with the flat edge of the wafer to achieve rotational angle alignment of the wafer before the photolithography process. Thus, the photomask provided in this application, by setting the angle scale to assist wafer rotation, avoids the problem of uncontrollable dicing direction for wafers with unknown crystal orientation angles, allowing dicing to proceed precisely along a preset direction and ensuring dicing accuracy.

[0057] To make the above-mentioned objectives, features, and advantages of the embodiments of this application more apparent and understandable, the technical solutions of the embodiments of this application will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only a part of the embodiments of this application, and not all of them. All other embodiments obtained by those skilled in the art based on the embodiments of this application without creative effort are within the scope of protection of this application.

[0058] This application provides a wafer cleaving direction control method and a photomask. An angle scale is designed in the photomask to assist wafer rotation. By precisely controlling the orientation of the photoresist pattern on the photomask relative to the crystal orientation, the photoresist lines after photolithography are aligned perpendicular to the crystal orientation. This effectively guides the wafer to generate cracks along a specific crystal orientation, making the cleaving process controllable and stable. The specific structure of the photomask and the wafer cleaving direction control method provided in this application are described below with reference to the accompanying drawings.

[0059] refer to Figure 1 The first aspect of this application provides a method for controlling the cleaving direction of a wafer 400. This control method may include: determining a specific crystal orientation of the wafer 400 based on the cleavage plane orientation; providing a photomask 100; determining the target orientation and cleaving direction of a photoresist pattern 210 on the photomask 100 based on the desired cleaving direction; calculating a rotation angle of the wafer 400 based on the specific crystal orientation and the target orientation of the photoresist pattern 210; setting an angle alignment mark 310 on the photomask 100 using the wafer's flat edge 410 as an alignment reference mark to form an angle scale 300 for rotating and aligning the wafer 400; rotating the wafer 400 to the calculated rotation angle using the angle scale 300; performing a photolithography process to form photoresist lines arranged perpendicular to the crystal orientation on the wafer 400; and performing a cleaving operation on the photolithographically etched wafer 400 to obtain a fracture surface where the photoresist lines are perpendicular to the crystal orientation.

[0060] In the embodiments of this application, it is understood that the wafer 400 cleaving direction control method provided in the embodiments of this application can be applied to photoresist cleaving in the photolithography process, and can also be used to observe the morphology of the cleaved wafer after etching. The embodiments of this application are not limited here.

[0061] Figure 1 A schematic flowchart illustrating a wafer 400 cleavage orientation control method provided in this application embodiment is shown below. Figure 1 As shown in the embodiment of this application, a method for controlling the cleavage direction of a 400-mesh wafer includes:

[0062] S101. Determine the specific crystal orientation of wafer 400 based on the cleavage plane orientation of wafer 400.

[0063] In the embodiments of this application, it is understood that wafer 400 exhibits significant anisotropy in terms of mechanics and fracture energy, and wafer 400 possesses cleavage planes with low fracture surface energy. During the propagation of a crack in wafer 400, it spontaneously chooses to advance along the path of the cleavage plane with the lowest energy. Specific crystal orientations at the edges of wafer 400 create favorable geometric conditions for crack contact and propagation along the cleavage planes, ultimately causing wafer 400 to neatly fracture along a predetermined, crystallographically determined crystal orientation. Thus, the specific crystal orientation of wafer 400 can be determined based on the orientation of its cleavage planes.

[0064] In one possible implementation, such as Figure 2 As shown, determining the specific crystal orientation of wafer 400 based on its cleavage plane orientation can include applying scratches to the edge of wafer 400 to create an initial crack. This initial crack spontaneously fractures along the cleavage plane direction, thus determining the specific crystal orientation of wafer 400. Alternatively, pressure can be applied to the edge of wafer 400 using a mechanical device, generating extremely high local stress at the contact point between the device and the wafer 400. This local stress can then induce a tiny initial crack on the surface of wafer 400. During its propagation, this initial crack can spontaneously fracture along the cleavage plane direction, thereby determining the specific crystal orientation of wafer 400 and causing it to crack along that specific crystal orientation.

[0065] For example, the mechanical device may include a diamond pen, but this application is not limited thereto.

[0066] S102. Provide a photomask 100 and determine the target orientation and cleaving orientation of the photoresist pattern 210 on the photomask 100 based on the required cleaving orientation.

[0067] In the embodiments of this application, such as Figure 3 As shown, a photomask 100 can be provided. The layout of the photomask 100 may include a specially designed photoresist pattern 210. In one possible implementation, the target orientation of the photoresist pattern 210 can be determined based on any desired wafer cleaving direction. Thus, the photomask 100 provided in this embodiment can have a photoresist pattern 210 with a target orientation. It is understood that the target orientation of the photoresist pattern 210 is consistent with the desired cleaving direction.

[0068] Specifically, the photoresist pattern 210 can be a photoresist line in any direction, and this embodiment of the application is not limited thereto. Exemplarily, the photoresist pattern 210 can be a linear structure. In one possible implementation, the number of linear structures can be several. In some embodiments, several linear structures are arranged parallel to each other and at equal intervals on the photomask 100, and each linear structure can be a light-blocking or light-transmitting area. It is understood that the extending direction of the linear structure is the target direction of the photoresist pattern 210.

[0069] S103. Based on the specific crystal orientation and the target direction of the photoresist pattern 210, calculate the rotation angle of the wafer 400.

[0070] In the embodiments of this application, such as Figure 2 and Figure 3 As shown, the rotation angle of the wafer 400 can be calculated based on the direction of a specific crystal orientation and the direction of the photoresist pattern 210 on the photomask 100.

[0071] In one possible implementation, the rotation angle of wafer 400 can satisfy the following formula:

[0072]

[0073] Wherein, with the direction of the wafer flat edge 410 parallel to the horizontal direction as the reference, θ is the rotation angle of the wafer 400, α is the angle between the specific crystal orientation and the direction of the wafer flat edge 410, and β is the angle between the direction of the target photoresist pattern 210 and the direction of the wafer flat edge 410.

[0074] It is understandable that, such as Figure 3 As shown, when the rotation angle of wafer 400 is positive, wafer 400 rotates counterclockwise. Correspondingly, when the rotation angle of wafer 400 is negative, wafer 400 rotates clockwise.

[0075] S104. Using the wafer flat edge 410 as an alignment reference mark, an angle alignment mark 310 is set on the photomask 100 to form an angle scale 300 for rotating alignment of the wafer 400.

[0076] In the embodiments of this application, such as Figure 4 as well as Figure 5 As shown, the wafer flat edge 410 can be used as an alignment reference mark, and an angle alignment mark 310 can be set on the photomask 100 to form an angle scale 300. The angle scale 300 can be used to perform wafer 400 rotation alignment.

[0077] In one possible implementation, using the wafer flat edge 410 as an alignment reference mark, angle alignment marks 310 are set on the photomask 100 to form an angle scale 300 for rotating alignment of the wafer 400. This may include rotating the wafer 400 multiple times at the same angle with the center of the photomask 100 as the axis, and setting a number of angle alignment marks 310 at different angle intervals on the photomask 100. The angle alignment marks 310 cooperate with the wafer flat edge 410 to achieve rotational alignment of the wafer 400 at a specific angle.

[0078] For example, such as Figure 6 As shown, with the wafer flat edge 410 where the angle alignment mark 310 is located as the reference mark 0°, the wafer 400 is rotated at an angle of 10° each time with the center of the photomask 100 as the axis, and the angle alignment mark 310 is set at the position where the photomask 100 and the wafer flat edge 410 coincide. Finally, several angle alignment marks 310 with different angle intervals are set on the photomask 100 to form an angle scale 300.

[0079] In one possible implementation, such as Figure 7 As shown, with the wafer flat edge 410 as the alignment reference mark, an angle alignment mark 310 is set on the photomask 100 to form an angle scale 300 for rotating alignment of the wafer 400. It can also be further included to set the angle alignment mark 310 on both sides of the photomask 100 in the direction of the wafer flat edge 410. The angle alignment mark 310 intersects with the projection of the wafer flat edge 410 at different rotation angles. The angle alignment marks 310 at different angles are arranged by sharing a portion of the angle alignment mark 310 to form the angle scale 300.

[0080] It is understandable that, such as Figure 8 As shown, taking the rotation of wafer 400 at an angle of 10° each time as an example, there are two corresponding angle alignment marks 310 for each rotation of wafer 400. The origin is defined as the position extending from the center of photomask 100 perpendicular to the wafer's flat edge 410. The two angle alignment marks 310 are respectively positioned on either side of the origin at locations where the photomask 100 and the wafer's flat edge 410 coincide. This allows the angle alignment marks 310 to intersect with the projections of the wafer's flat edge 410 at different rotation angles, enabling the angle alignment marks 310 at different angles to be arranged by sharing a portion of the angle alignment marks 310, thus forming an angle scale 300.

[0081] For example, such as Figure 5As shown, the intersection of the 0° wafer flat edge 410 and the 10° wafer flat edge 410 is b1, the intersection of the 0° wafer flat edge 410 and the 20° wafer flat edge 410 is b2, and so on; correspondingly, the intersection of the 0° wafer flat edge 410 and the -10° wafer flat edge 410 is a1, the intersection of the 0° wafer flat edge 410 and the -20° wafer flat edge 410 is a2, and so on. When the angle alignment mark 310 is placed left and right with a1 as the center, it intersects with the angle alignment mark 310 placed left and right with b1 as the center, thus making part of the angle alignment mark 310 shared, forming a fixed scale. Correspondingly, when the angle alignment mark 310 is placed left and right with a2 as the center, it intersects with the angle alignment mark 310 placed left and right with b2 as the center, so that part of the angle alignment mark 310 is shared, forming a fixed scale...; at this time, the intersection point of the angle alignment marks 310 forms the angle scale 300, thereby reducing the angle alignment mark 310 by half.

[0082] In this way, because the interval range of each rotation of the wafer 400 is small, the alignment marks 310 at different angles are close together, which can easily cause interference and overlap, making it difficult to quickly find the alignment marks 310 for alignment. However, by sharing some of the alignment marks 310, interference can be reduced, making it easier to align quickly.

[0083] In one possible implementation, the angle alignment mark 310 can be a sector-shaped reference mark. The angle range of the angle alignment mark 310 can be +5° to -5°, with an accuracy of 1°; however, this embodiment does not impose any limitations on this.

[0084] S105. Using the angle scale 300, rotate the wafer 400 to the calculated rotation angle, and perform photolithography to form photoresist lines arranged perpendicular to the crystal direction on the wafer 400.

[0085] In this embodiment, after the angle scale 300 is set, the wafer 400 can be aligned using the angle scale 300 on the photomask 100. By adjusting the angular orientation of the wafer 400, the flat edge 410 of the wafer is aligned with the angle scale 300. After alignment, a photolithography process is performed using a photolithography machine, including exposure and development steps, thereby forming photoresist lines arranged perpendicular to a specific crystal orientation on the surface of the wafer 400.

[0086] In one possible implementation, after rotating the wafer 400 to the calculated rotation angle using the angle scale 300, the photolithography process is performed. This may further include: during the photolithography process, observing the relative position of the wafer flat edge 410 and the angle scale 300 under a microscope to precisely align the wafer flat edge with the angle scale. It is understood that during the photolithography process, after calculating the rotation angle of the wafer 400, the wafer flat edge 410 is placed near the rotation angle on the angle scale 300, and then the angle scale 300 is observed under a microscope to adjust and rotate the wafer flat edge 410 to be parallel to the angle scale 300, thereby improving alignment accuracy.

[0087] In one possible implementation, before performing the dicing operation on the wafer 400 after photolithography, the process may include: performing an inspection after the photolithography process is completed, and observing the relative position of the wafer flat edge 410 and the angle scale 300 again through a microscope to determine whether the rotation angle error of the wafer 400 meets the dicing conditions.

[0088] Understandably, after photolithography and development, the position of the wafer flat edge 410 on the angle scale 300 of the photolithography mask 100 can be directly observed under a microscope, thereby obtaining the alignment rotation angle error, and then judging whether the wafer 400 rotation angle meets the requirements for dicing along a specific crystal orientation.

[0089] S106. Perform a dicing operation on the photolithographically etched wafer 400 to obtain a fracture surface in which the photoresist lines are perpendicular to the crystal orientation.

[0090] In this embodiment, after the photolithography process is completed, the photoresist pattern 210 on the photomask 100 can be transferred to the surface of the wafer 400, thereby forming photoresist lines on the wafer 400 arranged perpendicular to a specific crystal orientation. Then, the photolithographically completed wafer 400 is cleaved to obtain a fracture surface where the photoresist lines are perpendicular to the crystal orientation.

[0091] In this way, during the cleavage process, when the crack propagates along the low-energy cleavage plane, it can effectively ensure that the fracture surface passes through the vertical optical resist lines, thereby obtaining a smooth, flat, high-quality fracture surface.

[0092] In one possible implementation, taking a 6-inch lithium niobate bulk wafer 400 as an example, the fracture crystal orientation is determined. First, a diamond pen is used to apply pressure across the edge of the wafer 400, generating extremely high local stress below the contact point. After the crack propagates, it fractures along the crystal orientation. After fracture, the angle α1 between the crack fracture direction and the wafer's flat edge 410 is measured using a protractor, with the angle ranging from 60° to 70°.

[0093] Next, the photomask 100 is designed, and a photoresist pattern 210 with a target orientation is drawn according to process requirements. The angle between the photoresist pattern 210 and the wafer flat edge 410 is β1, β2, β3, etc. Angle scales 300 of +90° to -90° are added to the edge of the photomask 100. The angle scales 300 include several angle alignment marks 310, which are composed of intersecting (-5° to +5°) fan-shaped lines with a line width ranging from 20 to 100 μm. The overall size of the angle alignment marks 310 does not exceed 2.2 mm * 2.2 mm. Additionally, the length of the lithium niobate wafer flat edge 410 is L1 mm, and the diameter is D mm. After the wafer 400 is rotated by ±10°, the positional distance L2 between the origin and a1, b1 is... This makes it easier to align the wafer at a 400° rotation angle.

[0094] Furthermore, in the spin coating and exposure alignment stages, according to the target process, a layer of adhesion promoter is applied to the surface of wafer 400 through staged temperature rise and fall, and then spin coating is performed on the surface of wafer 400 through staged temperature rise and fall. For example, 1μm MIR701 photoresist can be used. After spin coating, wafer 400 is loaded onto the lithography machine, and wafer 400 can be manually rotated to the vicinity of the α+β-π / 2 position. During alignment, the microscope is moved to the position of the α+β-π / 2 alignment angle scale 300, and then the position of wafer 400 is moved so that the angle scale 300 is perfectly matched with the direction of the wafer's flat edge 410. After matching, exposure is performed so that the target direction of the photoresist pattern 210 is consistent with the perpendicular direction of the specific crystal orientation.

[0095] Subsequently, photolithography steps such as pre-baking, exposure, development, and post-baking are performed according to predetermined process conditions. The target orientation of the photoresist pattern 210 is examined using a microscope to confirm that the target orientation is consistent with the specific crystal orientation. After the photolithography process is completed, the photoresist pattern 210 on the photomask 100 can be transferred to the surface of the wafer 400, thereby forming photoresist lines on the wafer 400 that are arranged perpendicular to the specific crystal orientation.

[0096] Next, the developed wafer 400 is placed on a flat surface, and scratches are applied to the edge of the wafer 400 along a direction perpendicular to the photoresist lines. A slight bending force is applied along the scratch direction, causing the wafer 400 to develop cracks along a predetermined crystal orientation. Understandably, the cracked surface of the wafer 400 is perpendicular to the photoresist lines, resulting in a complete and flat cross-section.

[0097] Finally, the morphology of the photoresist port was observed again using a microscope to check for phenomena such as edge chipping and debris, and the cross-section of the fragment was observed using a scanning electron microscope. It is understandable that the cross-section can be used to measure process parameters such as photoresist thickness, morphological accuracy, and etching depth.

[0098] Based on the aforementioned wafer 400 cleaving direction control method, a second aspect of this application provides a photomask 100 for wafer 400 cleaving alignment, referring to... Figure 9 The photomask 100 may include a substrate 200 and an angle scale 300. In this embodiment, the substrate 200 may have a photoresist pattern 210 with a target direction. The angle scale 300 may include angle alignment marks 310. In one possible implementation, the number of angle alignment marks 310 may be several, and this embodiment is not limited thereto. Several angle alignment marks 310 may be spaced apart on the photomask 100, and each angle alignment mark 310 can be used to cooperate with the wafer flat edge 410, thereby realizing the rotation angle alignment of the wafer 400 before the photolithography process.

[0099] Thus, the photomask 100 provided in this embodiment of the application, by setting an angle scale 300, assists in the rotation of the wafer 400, avoiding the situation where the wafer 400 with unknown crystal orientation angle is cleaved along the photoresist structure in any direction, thus ensuring the accuracy of cleaving.

[0100] Continue to refer to Figure 9 In the specific implementation of this application embodiment, the wafer 400 can be rotated multiple times at the same angle. In one possible implementation, for each rotation of the wafer 400, there are two corresponding angle alignment marks 310. The two angle alignment marks 310 can be symmetrically arranged, and the angle alignment marks 310 are located at any position between the origin and the endpoint of the wafer flat edge 410. Exemplarily, each angle alignment mark 310 can coincide with the projection of the two endpoints of the wafer flat edge 410 at the corresponding rotation angle. This application embodiment is not limited in its scope.

[0101] Continue to refer to Figure 9 Based on the above embodiments, in one possible implementation, at least a portion of several angle alignment marks 310 at different angles intersect, thereby making a portion of the angle alignment marks 310 shared, thus reducing the number of angle alignment marks 310 and forming an angle scale 300. In this way, after the portion of the angle alignment marks 310 is shared, the overlap and interference of the angle alignment marks 310 can be reduced, facilitating rapid alignment.

[0102] In this embodiment, the wafer cleaving direction control method provided in this application uses an angle scale 300 designed in the photomask 100 to assist the rotation of the wafer 400. By precisely controlling the direction of the photoresist pattern 210 on the photomask 100 relative to the crystal orientation, the photoresist lines after photolithography can be aligned along the direction perpendicular to the crystal orientation. This effectively guides the wafer 400 to generate cracks along a specific crystal orientation, making the cleaving process controllable and stable.

[0103] In this embodiment, the wafer 400 dicing direction control method provided does not require laser processing, dicing machines, dicing machines, or other equipment; dicing can be performed using a common diamond pen, thus reducing costs. Furthermore, dicing along the wafer 400 crystal orientation yields a cross-section perpendicular to the photoresist lines, reducing the likelihood of chipping and facilitating observation of the photoresist morphology.

[0104] It is also understandable that for any photoresist line with a specific crystal orientation, the angle between the specific crystal orientation and the wafer's flat edge 410 can be calculated. During exposure alignment, the alignment angle between the angle scale 300 and the wafer's flat edge 410 can be adjusted to ensure that the photoresist line is placed perpendicular to the crystal orientation, thereby obtaining a complete and clean photoresist cross-section after dicing. Furthermore, after photolithography, the wafer's 400 rotation angle can be read to determine whether the crystal orientation is perpendicular to the photoresist line direction, thus determining whether dicing can proceed and reducing the dicing failure rate.

[0105] The various embodiments or implementation methods described in this specification are presented in a progressive manner. Each embodiment focuses on the differences from other embodiments, and the same or similar parts between the embodiments can be referred to each other.

[0106] It should be noted that phrases such as "in specific implementations," "in some embodiments," "in this embodiment," and "exemplarily" in the specification indicate that the described embodiments may include specific features, structures, or characteristics, but not every embodiment necessarily includes that specific feature, structure, or characteristic. Furthermore, such phrases do not necessarily refer to the same embodiment. Moreover, when a specific feature, structure, or characteristic is described in connection with an embodiment, implementing such a feature, structure, or characteristic in conjunction with other embodiments, whether explicitly described or not, is within the knowledge scope of those skilled in the art.

[0107] Generally speaking, terms should be understood at least in part by their use in context. For example, at least in part by context, the term "one or more" as used in the text can be used to describe any feature, structure, or characteristic of the singular meaning, or a combination of features, structures, or characteristics of the plural meaning. Similarly, at least in part by context, terms such as "a" or "the" can also be understood to convey either singular or plural usage.

[0108] It should be readily understood that “on,” “above,” and “on top of” in this disclosure should be interpreted in the broadest manner, such that “on” means not only “directly on something” but also “on something” with an intermediate feature or layer therebetween, and that “above” or “on top of” means not only “on something” but also “on something” without an intermediate feature or layer therebetween (i.e., directly on something).

[0109] Furthermore, for ease of explanation, spatially relative terms such as "below," "below," "under," "above," and "above" may be used to describe the relationship of one element or feature relative to other elements or features as shown in the figures. Spatially relative terms are intended to encompass different orientations of the device in use or operation other than those shown in the figures. The device may have other orientations (rotated 90 degrees or in other orientations), and the spatially relative descriptive terms used herein may be interpreted accordingly.

[0110] Finally, it should be noted that other embodiments of this application will readily conceive of by those skilled in the art upon consideration of the specification and practice of the application disclosed herein. This application is intended to cover any variations, uses, or adaptations of this application that follow the general principles of this application and include common knowledge or customary techniques in the art not disclosed herein, and is not limited to the precise structures described above and shown in the accompanying drawings, and various modifications and alterations may be made without departing from its scope. The scope of this application is limited only by the appended claims.

Claims

1. A method for controlling the direction of wafer cleaving, characterized in that, The control method includes: The specific crystal orientation of wafer (400) is determined based on the cleavage plane orientation of wafer (400); Provide a photomask (100) and determine the target orientation and cleavage orientation of the photoresist pattern (210) on the photomask (100); Based on the specific crystal orientation and the target orientation of the photoresist pattern (210), the rotation angle of the wafer (400) is calculated; Using the wafer flat edge (410) as an alignment reference mark, an angle alignment mark (310) is set on the photomask (100) to form an angle scale (300) for rotating alignment of the wafer (400). Using the angle scale (300), the wafer (400) is rotated to the calculated rotation angle, and a photolithography process is performed to form photoresist lines arranged perpendicular to the crystal direction on the wafer (400); A dicing operation is performed on the photolithographically etched wafer (400) to obtain a fracture surface in which the photoresist lines are perpendicular to the crystal orientation.

2. The wafer cleaving direction control method according to claim 1, characterized in that, Determining the specific crystal orientation of wafer (400) based on the cleavage plane orientation includes: Scratches are applied to the edge of the wafer (400) to create initial cracks in the wafer (400), which spontaneously break along the cleavage plane to determine a specific crystal orientation of the wafer (400).

3. The wafer cleaving direction control method according to claim 2, characterized in that, The calculation of the rotation angle of the wafer (400) based on the specific crystal orientation and the target orientation of the photoresist pattern (210) includes: The rotation angle of the wafer (400) satisfies the following formula: θ is the rotation angle of the wafer (400), α is the angle between the specific crystal orientation and the direction of the wafer flat edge (410), and β is the angle between the direction of the target photoresist pattern (210) and the direction of the wafer flat edge (410).

4. The wafer cleaving direction control method according to claim 3, characterized in that, The method of setting an angle alignment mark (310) on the photomask (100) using the wafer flat edge (410) as an alignment reference mark to form an angle scale (300) for wafer (400) rotation alignment includes: With the center of the photomask (100) as the axis, the wafer (400) is rotated multiple times at the same angle. Several angle alignment marks (310) are set on the photomask (100) at different angle intervals. The angle alignment marks (310) cooperate with the flat edge (410) of the wafer to achieve rotational alignment of the wafer (400) at a specific angle.

5. The wafer cleaving direction control method according to claim 4, characterized in that, The method of setting an angle alignment mark (310) on the photomask (100) using the wafer flat edge (410) as an alignment reference mark to form an angle scale (300) for wafer (400) rotation alignment also includes: The angle alignment mark (310) is set on both sides of the photomask (100) in the direction of the wafer flat edge (410); The angle alignment mark (310) intersects with the projection of the wafer flat edge (410) at different rotation angles. The angle alignment marks (310) at different angles are arranged by sharing a portion of the angle alignment mark (310) to form the angle scale (300).

6. The wafer cleaving direction control method according to claim 5, characterized in that, The step of rotating the wafer (400) to the calculated rotation angle using the angle scale (300) and then performing the photolithography process further includes: In the photolithography process, the relative position of the wafer flat edge (410) and the angle scale (300) is observed by microscopy, and the wafer flat edge (410) and the angle scale (300) are precisely aligned.

7. The wafer cleaving direction control method according to claim 6, characterized in that, Before performing the dicing operation on the photolithographically etched wafer (400), the process also includes: After the photolithography process is completed, the relative position of the wafer flat edge (410) and the angle scale (300) is observed again under a microscope to determine whether the rotation angle error of the wafer (400) meets the cleaving condition.

8. A photomask for aligning wafer dicing, characterized in that, include: A substrate (200) having a photoresist pattern (210) in a target direction; An angle scale (300) includes a plurality of spaced angle alignment marks (310), each of the angle alignment marks (310) being used to cooperate with the wafer flat edge (410) to achieve rotational angle alignment of the wafer (400) before the photolithography process.

9. The photomask according to claim 8, characterized in that, The wafer (400) is rotated multiple times at the same angle, and the angle alignment mark (310) of each angle coincides with the projection of the two endpoints of the flat edge (410) of the wafer at the corresponding rotation angle.

10. The photomask according to claim 9, characterized in that, At least a portion of the angle alignment marks (310) at different angles intersect to reduce at least a portion of the angle alignment marks (310) to form the angle scale (300).

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