CN117604646A - Method of manufacturing sapphire cover window and sapphire cover window manufactured thereby - Google Patents

Abstract

A method of manufacturing a sapphire overlay window and a sapphire overlay window manufactured thereby are presented, the method comprising: preparing a sapphire wafer; forming a unit edge processing portion on the sapphire wafer with a laser beam; forming an etching portion on the sapphire wafer by selectively performing wet etching on the cell edge processing portion; and separating the cells from the sapphire wafer by pressing the sapphire wafer having the etched portions formed thereon.

Description

Method of manufacturing sapphire cover window and sapphire cover window manufactured thereby

Cross Reference to Related Applications

The present application claims priority from korean patent application No. 10-2022-0104573 filed on month 22 of 2022 and korean patent application No. 10-2022-018298 filed on month 9 of 2022, the entire contents of which are incorporated herein by reference for all purposes.

Technical Field

The present disclosure relates to a method of manufacturing a cover window and a cover window manufactured thereby. More particularly, the present disclosure relates to a method of manufacturing a sapphire cover window in which a process is performed at a wafer level and to the sapphire cover window manufactured thereby.

Background

The cover window is typically attached to the front surface of the display or camera module to protect the display panel, camera module, etc.

The cover window needs to be highly transparent, durable and scratch resistant in nature, and thus glass-based cover windows using tempered glass have been widely used.

As expensive mobile phones are equipped with high performance camera modules, the demand for better durability and scratch resistance is growing. For this purpose, a cover window using sapphire has been studied.

Sapphire has a higher surface hardness than tempered glass and is known to be physically and chemically stable, so that it can be effectively applied to a cover window for a camera module.

Such sapphire undergoes a cutting process using a diamond wheel or with a laser beam to be processed into a predetermined shape due to the characteristic of high surface hardness.

In the existing process of manufacturing the cover window, a unit process of cutting the sapphire wafer into unit cells and then performing a subsequent process (a process of forming a printed layer or the like) at a unit cell level is performed.

FIGS. 1A, 1B, 1C, 1D, 1E, 1F, 1G, and 1H illustrate schematic diagrams of existing unit processes for manufacturing camera overlay windows, wherein the process comprises: firstly, preparing a sapphire wafer (fig. 1A), cutting the sapphire wafer into unit cells (fig. 1B), performing a primary cleaning process (fig. 1C) by replacing the cells in the cleaning jig, performing a printing process (fig. 1D) by replacing the cells in the printing jig, performing a secondary cleaning process (fig. 1E) by replacing the cells in the cleaning jig again, and performing an anti-reflection (AR) coating process and an anti-fingerprint (AF) coating process by replacing the cells in the AR coating jig (fig. 1F) and the anti-fingerprint (AF) coating jig (fig. 1G) on the opposite surface, respectively; and finally separating the final unit (fig. 1H).

In other words, in the existing unit process, the unit cell is formed by: the wafer is completely cut along the edge of the cell using a diamond grinding wheel or with a laser beam, virtual parts (dummy) are removed, and then the subsequent process is performed.

In the case of manufacturing the camera cover window, as shown in fig. 1A, 1B, 1C, 1D, 1E, 1F, 1G, and 1H, due to the characteristics of each process, it is necessary to continuously use different types of jigs while changing the direction of the unit.

For example, it is necessary to clean both surfaces of the unit during a cleaning process, form a printing layer on the rear surface (back surface) of the unit during a printing process, and form an AR coating layer on the rear surface (back surface) or both surfaces of the unit during an AR coating process. In this case, the jig needs to be designed to have such a structure: so that the unit is not detached by its own weight because the unit is attached to the top of the vacuum evaporator. Further, since an AF coating layer needs to be formed on the front surface of the unit during an AF coating process, jigs for each process are incompatible.

When the jigs are not compatible, as described above, processing is frequently required to insert and remove the unit into and from the jigs every time each process starts and ends, resulting in extremely low efficiency.

Further, even during the unit cell-level process in which the printing process, the AR coating process, and the AF coating process are performed, there is a high possibility that quality variation between cells or a process defect rate increases.

In particular, in the case of a small unit having a size smaller than 30mm or less, unit handling is not easy as compared with the case of a unit having a large size. Therefore, the above-described jig is necessary for use. For this purpose, the process of loading the units onto the jigs and unloading them from the jigs must be repeated one by one.

The above problems become more pronounced in such small cells. In addition, the yield decreases and the defect rate further increases, so that the production cost increases rapidly.

Disclosure of Invention

The present disclosure is derived from the above-mentioned needs. An object of the present disclosure is to provide a method of manufacturing a sapphire overlay window in which a cell manufacturing process using a sapphire wafer is performed at a wafer level, and a sapphire overlay window wafer manufactured thereby.

To achieve the objects of the disclosure, the present disclosure relates to a method of manufacturing a sapphire overlay window and a sapphire overlay window manufactured thereby, the method of manufacturing a sapphire overlay window comprising: preparing a sapphire wafer; forming a unit edge processing portion on the sapphire wafer with a laser beam; forming an etching portion on the sapphire wafer by selectively performing wet etching on the cell edge processing portion; and separating the cells from the sapphire wafer by pressing the sapphire wafer having the etched portions formed thereon.

In addition, when forming the cell edge processing portion, a picosecond laser or a femtosecond laser is preferably used.

Further, the cell edge processing section preferably includes a finishing section formed along the cell edge by vertically transferring energy from the laser to the sapphire wafer.

Further, the finishing portion is preferably formed in a direction perpendicular to the sapphire wafer along the cell edge and includes a plurality of through holes spaced apart from each other by a distance in the range of 1 μm to 5 μm.

Further, the modified portion preferably includes a crack formed around the through hole due to impact diffusion at the time of forming the through hole.

In addition, in forming the etching portion, an aqueous NaOH solution, an aqueous KOH solution, or a mixture of both is used as an etchant.

Further, when an aqueous NaOH solution is used as the etchant, wet etching is preferably performed under the following conditions: the concentration of the aqueous NaOH solution is in the range of 50% to 95%, the temperature is in the range of 130 ℃ to 220 ℃, and the etching time is in the range of 1 hour to 48 hours.

Further, when an aqueous KOH solution is used as the etchant, wet etching is preferably performed under the following conditions: the concentration of the KOH aqueous solution is in the range of 40% to 90%, the temperature is in the range of 130 ℃ to 220 ℃, and the etching time is in the range of 10 minutes to 20 hours.

Further, the etching portion preferably includes a gap formed along the edge of the cell between the cells or between the cells and the dummy portion.

Further, the gap preferably includes a chamfer having a predetermined depth from the surface of the cell and a predetermined width from the side surface of the cell. The chamfer preferably has a depth of 10% to 50% of the thickness of the sapphire wafer and a width in the range of 1 μm to 50 μm.

Further, in forming the cell edge processing portion, the cell edge processing portion is preferably formed such that the cell size L and the cell pitch S, which is a cell-to-cell pitch, satisfy 0.ltoreq.s.ltoreq.l.

Further, after forming the etched portion, any one or two or more of a Black Matrix (BM) print layer, an anti-reflection (AR) coating layer, and an anti-fingerprint (AF) coating layer are preferably formed on the sapphire wafer.

In addition, the unit dimension L and the thickness T of the sapphire wafer preferably satisfy 10 T.ltoreq.L.ltoreq.250T.

In the present disclosure, as described above, after the entire process is performed at the sapphire wafer level, unit cells are separated from the sapphire wafer, which is useful in providing a sapphire cover window manufactured by the above-described method with a size of 30mm or less.

The present disclosure provides a method of manufacturing a sapphire cover window in which the entire process can be performed at a wafer level when the cover window is manufactured using a sapphire wafer, and the sapphire cover window manufactured thereby.

In the present disclosure, a cell edge treatment portion is formed on a sapphire wafer with a laser beam, and then an etching portion is formed by selectively performing etching on the cell edge treatment portion through a wet etching process. Thus, the entire process can be completed at the wafer level and the units can be separated, thereby greatly improving performance and yield.

In other words, in the present disclosure, wet etching is selectively performed around the cell edge processing portion, that is, the modified portion (through hole and crack) weakened or deformed by absorbing energy from the laser. Thus, by optimizing the process conditions of the laser processing and wet etching, a wafer-level process (WLP) that keeps the cells from separating during the subsequent process and allows the wafer shape to be maintained can be performed.

Furthermore, the wafer level process does not require a jig. Since the wafer itself functions as a jig, there is no need for a process of loading or unloading the unit onto or from the jig between the respective processes. Thus, the whole process is simplified.

Further, according to the present disclosure, the manufacturing process of the sapphire cover window using the sapphire wafer has such advantages that: compared to existing manufacturing processes of glass-based cover windows, no strengthening process, masking process, etc. are required, thereby further simplifying the overall process.

The sapphire cover window thus fabricated includes etched portions formed along the edges of the cells and chamfers formed particularly at corners to minimize chipping or cracking that occurs during cell separation. In addition, a sapphire cover window may be used as the cover window with improved durability and scratch resistance.

In particular, when small products having a size of 30mm or less (e.g., a cover window for a camera or a smart watch) are manufactured, productivity can be greatly improved by the wafer level process according to the present disclosure, thereby providing high quality products.

Drawings

FIGS. 1A, 1B, 1C, 1D, 1E, 1F, 1G and 1H show schematic diagrams for explaining a conventional unit process;

fig. 2A, 2B, 2C, 2D, 2E, 2F, 2G, and 2H show schematic diagrams for illustrating a Wafer Level Process (WLP) according to an embodiment of the disclosure;

fig. 3 shows a schematic view of a cell edge (cell line) formed on a sapphire wafer according to one embodiment of the present disclosure;

Fig. 4A and 4B show schematic diagrams for explaining a forming process of a cell edge processing section (fig. 4A) and a forming process of an etching section (fig. 4B) according to an embodiment of the present disclosure;

FIG. 5 illustrates a schematic view of a side surface of a sapphire cover window manufactured in accordance with one embodiment of the present disclosure;

fig. 6A and 6B show diagrams for explaining a relationship of friction between a unit and a virtual part based on a weight of the unit according to one embodiment of the present disclosure;

7A, 7B, 7C and 7D show electron micrographs of the front surface of a sapphire wafer formed after laser treatment designed according to one embodiment of this disclosure;

fig. 8A, 8B, and 8C show electron micrographs of the front surface of a sapphire wafer formed after wet etching designed according to one embodiment of this disclosure;

9A, 9B, 9C and 9D show optical micrographs of the front and side surfaces of a cell according to various embodiments of the present disclosure;

FIGS. 10A and 10B show images of a sapphire overlay window made in accordance with the present disclosure;

FIG. 11 shows an electron micrograph of the front surface of a cell according to a prior art cell process;

FIGS. 12A and 12B show images of cell edges magnified with an optical microscope when a wet etching process is performed poorly during a wafer level process;

13A, 13B and 13C show electron micrographs of the front surface of a cell according to one embodiment of the present disclosure;

fig. 14 shows an electron micrograph of a side surface (upper portion) of a cell according to various embodiments of the present disclosure;

15A, 15B, 15C, 15D, and 15E show actual images of the wafer and product after each process is completed according to one embodiment of the present disclosure; and

fig. 16 shows images of virtual parts remaining after the completion of the cell separation according to fig. 15A, 15B, 15C, 15D, and 15E.

Detailed Description

The present disclosure relates to a method of manufacturing a cover window and a cover window manufactured thereby. More particularly, the present disclosure relates to a method of manufacturing a sapphire cover window in which the entire process is performed at a sapphire wafer level, and a sapphire cover window manufactured thereby.

In the present disclosure, a cell edge treatment portion is formed on a sapphire wafer with a laser beam, and then an etching portion is formed by selectively performing etching on the cell edge treatment portion through a wet etching process. Thus, the entire process can be completed at the wafer level and the units can be separated, thus greatly improving performance and yield.

The sapphire cover window thus fabricated includes etched portions formed along the edges of the cells and chamfers formed particularly at corners to minimize chipping or cracking that occurs during cell separation. In addition, a sapphire cover window may be used as the cover window with improved durability and scratch resistance.

Hereinafter, the present disclosure will be described in detail with reference to the accompanying drawings. Fig. 2A, 2B, 2C, 2D, 2E, 2F, 2G, and 2H show schematic diagrams for illustrating a Wafer Level Process (WLP) according to an embodiment of the disclosure. Fig. 3 shows a schematic view of a cell edge (cell line) formed on a sapphire wafer according to one embodiment of the present disclosure. Fig. 4A and 4B show schematic diagrams for explaining a forming process of a cell edge processing portion (fig. 4A) and a forming process of an etching portion (fig. 4B) according to one embodiment of the present disclosure. Fig. 5 shows a schematic view of a side surface of a sapphire cover window manufactured in accordance with one embodiment of the present disclosure. Fig. 6A and 6B show diagrams for explaining a relationship of friction between a unit and a virtual part based on a weight of the unit according to one embodiment of the present disclosure. Fig. 7A, 7B, 7C, and 7D show electron micrographs of the front surface of a sapphire wafer formed after laser treatment designed according to one embodiment of this disclosure. Fig. 8A, 8B, and 8C show electron micrographs of the front surface of a sapphire wafer formed after wet etching designed according to one embodiment of this disclosure. Fig. 9A, 9B, 9C, and 9D show optical micrographs of the front and side surfaces of a cell according to various embodiments of the present disclosure. Fig. 10A and 10B show images of a sapphire overlay window made in accordance with the present disclosure. Fig. 11 shows an electron micrograph of the front surface of a cell according to the prior art cell process. Fig. 12A and 12B show images of cell edges magnified with an optical microscope when a wet etching process is performed poorly during a wafer level process. Fig. 13A, 13B, and 13C show electron micrographs of the front surface of a cell according to one embodiment of the present disclosure. Fig. 14 shows an electron micrograph of a side surface (upper portion) of a cell according to various embodiments of the present disclosure. 15A, 15B, 15C, 15D, and 15E show actual images of the wafer and product after each process is completed according to one embodiment of the present disclosure. Fig. 16 shows images of virtual parts remaining after the completion of the cell separation according to fig. 15A, 15B, 15C, 15D, and 15E.

As shown in fig. 2A, 2B, 2C, 2D, 2E, 2F, 2G, and 2H, a method of manufacturing a sapphire overlay window, according to the present disclosure, includes: preparing a sapphire wafer; forming a unit edge processing portion on the sapphire wafer with a laser beam; forming an etching portion on the sapphire wafer by selectively performing wet etching on the cell edge processing portion; and separating the cells from the sapphire wafer by pressing the sapphire wafer having the etched portions formed thereon.

According to the present disclosure, a sapphire wafer is used by: the ingot is cut into flat wafers having a desired thickness using a diamond saw, and then polished. While wafers having a size of about 4 inches are most commonly used, wafers having a size up to 12 inches may be used in the present disclosure.

According to one embodiment of the present disclosure, the camera cover window has a small thickness in the range of about 0.3mm to 1.0 mm. When an ingot having an excessively large diameter is formed into a wafer, the processing yield is low, and thus the size of the ingot is preferably about 4 inches. Therefore, depending on the thickness or size of the cover window, a wafer having an appropriate size may be used in consideration of the processing yield.

As shown in fig. 2 and 3, the sapphire wafer 100 has a 4 inch (100 mm) circular shape and is used to form a 10mm circular unit 200 according to one embodiment of the present disclosure. The cell pitch S (which is a cell-to-cell pitch) may be appropriately set to maintain the wafer shape in view of productivity. In general, the cell pitch is described as a virtual portion, and its value may vary according to the shapes of the wafer and the cells. However, depending on the process conditions or product specifications, zero cell spacing may exist.

When cells are formed in a circular shape according to one embodiment of the present disclosure, the cell pitch S means a pitch between edges of two cells adjacent to each other on a line connecting centers of the adjacent cells.

In the sapphire wafer 100 according to one embodiment in fig. 3, a flat portion having a size of about 30mm is formed on one surface to indicate a direction. Further, the size of the cell pitch is about 2.0mm, and the diameter of the cell 200 is about 10mm, so that about 51 cells per sapphire wafer are manufactured.

The line shown in the shape of cell 200 in fig. 3 is a cell edge 210 or cell line, and in this disclosure means the boundary of a cell (cell boundary on a surface or cell perimeter on a side surface).

Such units may have many different shapes, such as circular, square and oval, depending on the product specifications.

When the sapphire wafer is prepared as described above (fig. 2A), the cell edge processing section 300 is formed on the sapphire wafer 100 with a laser beam (fig. 2B). That is, the cell edge processing section 300 is formed along the cell edge 210 as shown in the shape of the cell in fig. 2 and 3.

After aligning the sapphire wafer, the laser system is designed to irradiate the sapphire wafer with a laser beam along the cell edge. For example, laser energy, spot to spot (spot to spot), spot size, speed, pulse train, etc. are designed, and the laser system is designed to illuminate a sapphire wafer along the cell edge with an optical system.

According to the present disclosure, a method of manufacturing a sapphire overlay window is implemented as a "Wafer Level Process (WLP)" in which a subsequent process is performed at a wafer level. Therefore, the cell edge processing section 300 is formed so that the wafer shape can be well maintained and the cell separation process is performed without difficulty.

In one embodiment of the present disclosure, ultra-high speed lasers, such as picosecond lasers or femtosecond lasers, may be used to achieve unit processing of sapphire wafers.

The cell edge processing section 300 in the present disclosure may include any variation that occurs in the sapphire wafer 100 when energy from laser light is transferred to the sapphire wafer 100. When energy from the laser is vertically transferred, the cell edge processing part 300 may be a finishing part formed along the cell edge.

The modified portion means any change in the sapphire wafer caused by energy from laser light, and may include, for example, a through-hole, a crack, a change in structure or crystalline phase, etc., and any secondary or tertiary change caused thereby.

In one embodiment of the present disclosure, according to the cell edge processing part 300, the finishing part may include a plurality of through holes vertically formed on the sapphire wafer along the cell edge. Further, the modified portion may include a crack, which is a deformation caused around the periphery of the through hole due to impact propagation when such a through hole is formed.

According to the present disclosure, cracks appear around the periphery of the through hole, generally in random shapes and random directions.

For example, in accordance with the present disclosure, a crack may include any one or two or more of the following: the first crack formed around the periphery of the through hole, the second crack originating from the first through hole and reaching the adjacent second through hole, and the third crack originating from each of the adjacent first and second through holes bonded together, but is not limited thereto. In addition, the cracks may have different patterns due to energy transferred when forming the through holes.

That is, according to the present disclosure, the cell edge processing part 300 is formed as a finishing part that deforms the sapphire wafer by receiving energy from the laser. The modification portion may be formed as a first modification portion caused by directly receiving energy from the laser light and other modification portions including a second modification portion and a third modification portion caused by indirect energy transferred during formation of the first modification portion. The through hole may correspond to the first modified portion, and the crack may correspond to the second modified portion or the third modified portion.

The magnitude or extent of such deformation of the modified portion (e.g., the diameter or spacing of the vias and the extent of cracking) may be adjusted depending on the design of the laser system. This is to complete the wafer level process and is determined by considering thickness, dimensions, etc. according to product specifications.

In one embodiment of the present disclosure, the through holes are formed at intervals ranging from 1 μm to 5 μm in a direction perpendicular to the sapphire cover window. That is, after the etching portion and the functional layer (BM print layer, AR coating layer, AF coating layer, etc.) are formed according to the subsequent process, the through holes are formed at appropriate intervals so that cell separation can be finally performed in the wafer-level process. When the interval is smaller than the above range, the cells may be randomly separated during a subsequent process, making it difficult to control the yield according to the wafer-level process. In contrast, when the interval is greater than the above range, there may be a concern that the cells are affected or damaged during cell separation. The spacing may be adjusted according to the thickness or size of the cells.

Fig. 4A and 4B show schematic diagrams for explaining a forming process of a cell edge processing portion (fig. 4A) and a forming process of an etching portion (fig. 4B) according to one embodiment of the present disclosure. Fig. 5 shows a schematic view of a side surface of a sapphire cover window manufactured in accordance with one embodiment of the present disclosure.

Fig. 4A shows through holes 310 and cracks 320 formed at uniform intervals on the cell edge processing part 300, and fig. 4B shows an etched part 400 formed around the cell edge processing part 300 by performing wet etching, in which chamfers 410 are formed around the cell edge processing part 300 on the surface of the sapphire wafer.

Fig. 5 shows a schematic view of the side surface of a cell 200 (sapphire-covered window) having a thickness T, which depicts a chamfer 410 (etched portion 400) and a cell edge treatment portion 300 (modified portion, via, crack, etc.). In fact, wet etching of the manufactured sapphire cap window is performed by the cell edge processing portion 300, and thus the etched portion 400 is mainly observed from the side surface. However, the degree to which the etching portion and the cell edge processing portion are mixed may vary depending on etching conditions or product specifications. Further, fig. 5 shows a via and an etched portion 400 formed along a crack around the periphery of the via.

Further, the cell edge processing portion is formed such that the cell size L (diameter in the case of a circular cell and diagonal length in the case of a rectangular cell) and the cell pitch S (which is a cell-to-cell pitch) satisfy 0.ltoreq.s.ltoreq.l (see fig. 3). In other words, according to the product specification, cells may be formed without dummy portions, or adjacent cells may be formed between cell steps in consideration of the product yield. In terms of reducing the defect rate and stably maintaining the wafer shape, 0.05 L.ltoreq.S.ltoreq.L is more preferable.

Further, the cell edge processing section 300 is formed such that the cell size L and the sapphire wafer thickness T satisfy 10 t+.l+.250t. In other words, when the thickness is too large or too small compared to the cell size, the wafer-level process may be performed poorly. For example, in the case of L >250×t, the cell size is excessively large compared to the sapphire wafer thickness, making it difficult to maintain the wafer shape. In the case of L <10×t, the cell size is too small compared to the sapphire wafer thickness, and thus the cell separation process may be performed poorly or damage may be caused to the side surface during cell separation.

In addition, in forming the unit edge processing portion with the laser beam, the alignment mark may be formed using the laser for the convenience of the subsequent process. The alignment marks may include optical marks or mechanical marks.

As described above, in the present disclosure, the cell edge processing portion is formed on the sapphire wafer with the laser beam, and thus the cell is held between the dummy portions without detachment. In addition, the wafer shape is maintained so that the cells can be smoothly separated in the final process.

Further, when the cell edge processing portion 300 is formed, wet etching is performed on the sapphire wafer 100 such that the cell edge processing portion 300 is selectively wet etched, thereby forming an etching portion 400 on the sapphire wafer 100 (fig. 2B). In other words, the cell edge processing portion 300 is wet etched while the etchant penetrates the cell edge processing portion 300 that has been weakened or deformed by absorbing energy from the laser. Accordingly, the etching portion 400 is formed around the cell edge processing portion 300.

In general, wet etching is difficult to perform on the surface of a sapphire wafer, especially with an etchant according to one embodiment of the present disclosure. Further, the etching ratio between the surface of the sapphire wafer and the unit edge treatment portion is in the range of about 1:several 10 to several hundred. Thus, wet etching is intensively (selectively) performed on the cell edge processing portion to form an etched portion.

The etching part 400 may be formed around the cell edge treating part in different patterns due to penetration of the etchant. When the modified portion is a through hole, the size (diameter) of the through hole becomes large or wide, and thus adjacent through holes are partially joined together. Alternatively, when the modified portion is a crack (first crack, second crack, and third crack), the crack becomes more serious and thus propagates along the cell edge, or the crack widens and thus forms a gap. Thus, the crack and the etched portion 400 are bonded together.

Etched portions having different patterns may be formed on a portion of all cell edge processing portions, and may result in gaps formed between cells or between cells and dummy portions along cell edges.

The gap is formed with protrusions or surface roughness due to etching of the cell edge treated portions (modified portions, through holes, cracks, etc.) around the through holes and the irregularly formed cracks. In other words, a gap may be formed between the cells or between the cells and the dummy portion by connecting the through holes, or may be formed by etching the surface of the crack.

In particular, etching is further actively performed around the cell edge processing portion, and thus the gap may include a chamfer having a predetermined depth (described as "b" in fig. 5) from the front surface (surface) of the cell and a predetermined width (described as "a" in fig. 5) from the side surface of the cell. The chamfer may have a depth of 10% to 50% of the thickness of the sapphire cover window, and a width (interval between side surfaces of adjacent cells around the cell edge processing portion) in the range of 1 μm to 50 μm.

The chamfer serves to further smooth the outer corners of the cell and reduce microcracks that occur during processing of the cell with the laser beam. Further, the chamfer has a shape in which the sharp corner is softened, thereby preventing breakage during assembly and reducing damage from external impact during use. When the chamfer is too large, the cells are easily separated in the middle of the process, making it difficult to perform the process at the wafer level. Conversely, when the chamfer is too small, chipping or cracking may occur during cell separation.

As described above, by adjusting the surface roughness of the cell edge processing portion, it is possible to form the etched portion as a smooth surface, as a chamfer having a predetermined depth and width on the surface along the cell line, as a gap formed by a crack widening due to penetration of the etchant, or the like. The etched portion is formed by adjusting the etching degree in consideration of the implementation of the wafer level process and the cell separation.

That is, due to the cell edge processing portion and the etching portion, a portion connected to an adjacent cell and a portion not connected to an adjacent cell coexist between cells or between a cell and a dummy portion. Further, even when connected, these portions are connected with gaps having protrusions or surface roughness. Therefore, even after the cell edge processing section is formed and etching is completed, the cells remain undivided and the wafer shape is maintained.

As described above, wet etching of a sapphire wafer is difficult to implement. In the present disclosure, wet etching is performed around a cell edge processing portion, that is, a modified portion (through hole, crack, etc.) weakened or deformed by absorbing energy from laser. To implement a wafer level process according to the present disclosure, cell processing and etching work organically with each other.

As the etchant for wet etching of the sapphire wafer used herein, naOH aqueous solution, KOH aqueous solution, or a mixture of both may be used. In the case of using an aqueous NaOH solution as an etchant, wet etching was performed under the following conditions: the concentration of the aqueous NaOH solution (weight concentration) is in the range of 50% to 95%, the temperature is in the range of 130 ℃ to 220 ℃, and the etching time is in the range of 1 hour to 48 hours. In the case of using an aqueous KOH solution as an etchant, wet etching is performed under the following conditions: the concentration of the KOH aqueous solution (weight concentration) is in the range of 40% to 90%, the temperature is in the range of 130 ℃ to 220 ℃, and the etching time is in the range of 15 minutes to 20 hours.

As described above, in performing the wafer-level process, wet etching process conditions are adjusted in consideration of the thickness and size of the cells so that the cells remain not randomly detached (separated). When the degree of wet etching is less than the above range, the etched portion is formed insufficiently for cell separation according to the wet etching process conditions. In contrast, when the degree of wet etching exceeds the above range, cells may be randomly separated due to overetching, thereby reducing the yield of the wafer-level process.

Further, depending on the surface conditions, a process of polishing the surface of the sapphire wafer may also be performed after the etching portion is formed. In other words, when the surface roughness and scratches generated on the surface become severe after wet etching, a polishing process may be further performed to remove the scratches and improve the surface roughness. As for the polishing process, diamond mechanical polishing (diamond mechanical polishing, DMP), chemical mechanical polishing (chemical mechanical polishing, CMP), or a combination thereof may be performed according to the scratch depth and the surface roughness.

On the other hand, according to one embodiment of the present disclosure, after the etching portion 400 is formed, a cleaning process is performed at a wafer level (fig. 2C). When the wet etching process is completed, the wafer is transferred to a wafer-level cleaning tank, and then subjected to a cleaning process, such as ultrasonic cleaning. In the existing unit process, a process of transferring a single unit to a jig is necessary. However, in the present disclosure, the wafer itself acts as a jig, and thus only needs to be transferred for the subsequent process. If desired, a jig capable of placing a plurality of wafers may be designed to improve productivity.

When the cleaning process is completed, different functional layers may be formed on the sapphire wafer (fig. 2D). The functional layer may be formed on one surface or both surfaces of the sapphire wafer according to product specifications. Further, the functional layer may be formed of any one layer or two or more layers of a deposited layer, a coating layer, a printed layer, and an etched layer, or may be formed of a mixture thereof to form a multilayer structure.

For example, in the case where the camera covers a window, the functional layer may be a printed layer, a coating layer, a deposited layer, or the like formed on a peripheral portion other than the region through which the central portion is transmitted.

Specifically, as shown in fig. 2A, 2B, 2C, 2D, 2E, 2F, 2G, and 2H, a Black Matrix (BM) print layer 510 may be formed on the boundary of the rear surface of the cell (fig. 2D), an anti-reflection (AR) coating layer 520 may be formed on the entire area or the central area on the rear surface or both surfaces of the cell (in one embodiment of the present disclosure, an AR coating layer is formed on the entire area of the rear surface) (fig. 2F), or an anti-fingerprint (AF) coating layer 530 may be formed on the entire area of the front surface of the cell (fig. 2G). Alternatively, if necessary, an etching layer having an etching pattern may be formed.

A cleaning process may be included between the above processes (fig. 2E), as desired. One embodiment of the present disclosure shows that a cleaning process (fig. 2E) is performed between the process of forming the BM print layer (fig. 2D) and the process of forming the AR coating layer (fig. 2F).

The process of forming such functional layers and the cleaning process are performed as wafer-level processes, which greatly simplify the process compared to the existing unit processes, and greatly improve the product yield and unit cost.

As described above, in the present disclosure, the cell edge processing section and the etching section are formed by optimizing the process conditions of the laser processing and the wet etching in consideration of the product specifications, so that the wafer-level process can be performed. Thus, the cells remain unseparated during subsequent processes, thereby enabling Wafer Level Processing (WLP).

As described above, the wafer level process does not require a jig, and the wafer itself functions as a jig, compared to the existing unit process. Thus, the overall process becomes significantly simplified without the unnecessary process of loading and unloading units from the jigs between the individual processes. Further, since the thickness of the dummy portion is the same as that of the unit, both surfaces (front surface and rear surface) of the unit are exposed, so that processes during printing (on the rear surface), cleaning (on both surfaces), AR coating (on the rear surface or both surfaces), and AF coating (on the front surface) are performed without difficulty.

Finally, when the entire wafer level process is completed, the sapphire wafer having the etched portions and functional layers formed thereon is pressed to separate the cells from the sapphire wafer, thereby providing a sapphire cover window (fig. 2H).

Fig. 2H shows a sapphire cover window in a unit cell finally separated from a sapphire wafer, in which a BM print layer 510 and an AR coating layer 520 are formed on the rear surface of the cell 200 and an AF coating layer 530 is formed on the front surface of the cell 200.

As described above, between the cells or between the cells and the dummy portion are connected by a frictional force generated along the edges of the cells through the gaps due to the cell edge processing portion and the etched portion. Therefore, the cells are separated from the sapphire wafer by vertically applying a physical load having a predetermined size to the sapphire wafer.

Fig. 6A and 6B illustrate a relationship between the frictional force F between the unit 200 and the dummy 500 based on the unit weight W according to one embodiment of the present disclosure. After the wet etching, an etched portion, such as a gap with protrusions on the surface, is formed between the cell 200 and the dummy portion 500. The frictional force F between the unit 200 and the dummy portion 500 is greater than the weight W of the unit 200, so the unit 200 remains free from the dummy portion 500 (fig. 6A). Further, when a load Fs greater than the friction force F is vertically applied, the unit 200 is separated from between the dummy portions 500 (fig. 6B).

In this case, the cells are easily separated by etching portions formed along the cell lines without chipping or cracking occurring on the side surfaces of the cells.

As described above, when small products (e.g., cover windows for cameras or smart watches) having a size of 30mm or less are manufactured through a wafer-level process in which unit cells are separated from a wafer after the entire process is performed at a sapphire wafer level, the present disclosure can significantly improve productivity and provide high-quality products.

Hereinafter, different embodiments and comparative examples of the present disclosure will be described in detail. A sapphire wafer having a diameter of 100mm and a thickness of 0.33mm was prepared.

Example 1

1) Forming cell edge treatment portions with laser beams

-using a femtosecond laser

Bessel beam optics using a Fresnel lens-based

-500 femtosecond laser pulses

-1040nm wavelength

-point-to-point: 2.5 μm

Dot size: diameter of 1.0 μm

-speed: 80 mm/sec

-pulse train: 4

2) Forming etched portions by wet etching

Aqueous NaOH (60% at 170 °)

-6 hours or less: conditions under which separation of the units is unlikely (damage occurs during separation of the units)

-in the range of 7 hours to 19 hours: conditions for good separation of units

-20 hours or more: conditions for detachment of units during formation of functional layer

Aqueous KOH solution (60% at 170 ℃)

-2 hours or less: conditions under which the unit is unlikely to separate (damage occurs during unit separation) -in the range of 3 hours to 9 hours: conditions for good separation of the units-10 hours or longer: conditions for detachment of units during formation of functional layer

Example 2

1) Forming cell edge treatment portions with laser beams

-using picosecond laser

Bessel beam optics based on Fresnel lenses-8 picosecond laser pulses

-1040nm wavelength

-point-to-point: 2.5 μm

Dot size: diameter of 1.0 μm

-speed: 70 mm/sec

-pulse train: 2

2) Forming etched portions by wet etching

Aqueous NaOH (60% at 170 °)

-14 hours or less: conditions under which the unit is unlikely to separate (damage occurs during unit separation) -in the range of 15 hours to 47 hours: conditions for good separation of the units-48 hours or more: conditions for detachment of units during formation of functional layer

Aqueous KOH solution (60% at 170 ℃)

-7 hours or less: conditions under which the unit is unlikely to separate (damage occurs during unit separation) -in the range of 8 hours to 19 hours: conditions for good separation of the units-20 hours or longer: conditions for cell separation during the formation process of functional layers

Example 3

1) Forming cell edge treatment portions with laser beams

-using a femtosecond laser

-using a Bessel beam optics system based on Fresnel lenses-350 femtosecond laser pulses

-1040nm wavelength

-point-to-point: 3 μm

Dot size: diameter of 1.5 μm

-speed: 50 mm/sec

-pulse train: 2

2) Forming etched portions by wet etching

Aqueous NaOH (80% at 190 ℃)

-1 hour or less: conditions under which the unit is unlikely to separate (damage occurs during unit separation) -in the range of 2 hours to 6 hours: conditions for good separation of the units-7 hours or more: conditions for detachment of units during formation of functional layer

Aqueous KOH (80% at 190 ℃)

-15 minutes or less: conditions under which the unit is unlikely to separate (damage occurs during unit separation) -in the range of 0.5 hours to 1 hour: conditions for good separation of units-2 hours or longer: conditions for cell separation during the formation process of functional layers

Example 4

1) Forming cell edge treated portions with laser

-using picosecond laser

Bessel beam optics based on Fresnel lenses-10 picosecond laser pulses

-1040nm wavelength

-point-to-point: 3 μm

Dot size: diameter of 1.5 μm

-speed: 50 mm/sec

-pulse train: 2

2) Forming etched portions by wet etching

Aqueous NaOH (80% at 200 ℃)

-2 hours or less: conditions under which the unit is unlikely to separate (damage occurs during unit separation) -in the range of 3 hours to 12 hours: conditions for good separation of units

-13 hours or longer: conditions for cell separation during the formation process of functional layers

Aqueous KOH solution (80% at 200 ℃)

-1 hour or less: conditions under which separation of the units is unlikely (damage occurs during separation of the units)

-in the range of 1.5 hours to 3 hours: conditions for good separation of units

-4 hours or longer: conditions for detachment of units during formation of functional layer

Depending on the type of etchant (NaOH aqueous solution or KOH aqueous solution), concentration and temperature given as described above, the optimum etching amount is adjusted for each etching time so that cell separation proceeds smoothly while maintaining the wafer shape well up to the final process.

According to the above embodiment, when the etching amount is excessively small, damage of the cell or dummy portion occurs during cell separation. When the etching amount is appropriate, the subsequent process may be performed while maintaining the wafer shape in the post-etching process. Further, during the separation of the cells, damage of the cells or the dummy portion does not occur, and the cells are easily separated by a predetermined pressure. In contrast, when the etching amount is excessively large, the cells may be detached from the wafer during the post-etching process, making a wafer-level process impossible.

The above embodiments aim to find the optimal process conditions for wafer level processes by adjusting the etching time within specific concentration and temperature ranges of aqueous NaOH and aqueous KOH solutions. When changing the concentration and temperature ranges, a suitable etching time can be found experimentally. When a gap having appropriate protrusions and surface roughness is formed between the cell and the dummy portion by adjusting temperature and time according to the etchant, the cell separation condition can be found while maintaining the wafer-level process condition.

Fig. 7A, 7B, 7C, and 7D show electron micrographs of the front surface of a sapphire wafer formed after laser treatment designed according to one embodiment of the present disclosure when NaOH aqueous solution (concentration 80%, temperature 190 ℃, and etching time 4 hours) was used in example 3. In this case, the cell edge processing portion 300 (the through-hole 310, the finishing portion around the periphery of the through-hole, the crack 320 formed around the periphery of the through-hole, the crack 320 connected between the through-holes, etc.) is formed with a laser beam.

Fig. 8A, 8B, and 8C show electron micrographs of the front surface of a sapphire wafer formed after wet etching designed according to one embodiment of the present disclosure when aqueous NaOH (concentration 80%, temperature 190 ℃, and etching time 4 hours) was used in example 3. In this case, the etching portion 400 is formed by wet etching along the cell edge processing portion (the through hole and the crack). As shown in fig. 8A, 8B and 8C, the through holes are completely connected on the surface, thereby forming a gap having protrusions or surface roughness. Further, a chamfer having a predetermined depth and width from the surface is formed.

Even when the cell edge processing portion and the etching portion are formed, the wafer shape is maintained due to the different patterns of the etching portion.

Fig. 9 shows optical micrographs of the front and side surfaces of a cell according to various embodiments of the present disclosure when aqueous NaOH (80% concentration, 190 ℃ temperature, and etching times of 2 hours, 4 hours, 6 hours, and 8 hours) was used in example 3. In this case, the wet etching times in fig. 9A, 9B, 9C, and 9D were set to 2 hours, 4 hours, 6 hours, and 8 hours, respectively.

As shown in fig. 9A, 9B, 9C, and 9D, as the wet etching time increases, it was confirmed that the gap on the front surface gradually widened (the width and depth of the chamfer increased), and etching proceeded from the surface when viewed from the side surfaces 1 and 2 (at high magnification). Existing sapphire wafers are not easily wet etched. However, in the present disclosure, wet etching is achieved by cell deformation caused by the cell edge processing section.

In the case where the wet etching time is set to 2 hours in fig. 9A, cell separation may be performed under a load of about 5 kg. In the case where the wet etching time is set to 4 hours in fig. 9B, cell separation can be performed under a load of about 2kg, so that cells can be smoothly separated at a medium level. In the case where the wet etching time is set to 6 hours in fig. 9C, cell separation can be performed under a load of about 1kg, so that cells can be smoothly separated at a medium level. In contrast, in the case where the wet etching time is set to 8 hours in fig. 9D, cell separation occurs spontaneously, making a wafer level process impossible. In other words, the unit may be detached while the subsequent process is performed.

Fig. 10A and 10B show images of a sapphire overlay window fabricated according to one embodiment of the present disclosure when NaOH aqueous solution (80% strength, 190 ℃ temperature, and 4 hours etching time) was used and a functional layer was formed in example 3. In this case, the sapphire cover window is formed as a circular unit having a diameter of 10 mm. The portions protruding in red in fig. 10A (front surface) and 10B (side surface) are photographed with an electron microscope.

Fig. 11 shows an electron micrograph of the front surface of a cell according to the existing cell process (when the cell is manufactured by completely separating the cell with a laser beam and forming a functional layer in example 3).

Fig. 11 shows an image of the front surface according to the existing unit process. In this case, negative factors such as chipping and cracking on the surface, rough and sharp corner surfaces, and the like are observed. In other words, in the existing cell process, the laser process is the last process performed on the side of the cell. Therefore, it was confirmed that the corners were easily damaged, and a large amount of chipping occurred.

Fig. 12A and 12B show enlarged images of the cell edges enlarged with an optical microscope when the wet etching process was performed poorly during the wafer level process (when the wet etching was performed for 1 hour or less in example 3). In this case, the sapphire wafer is subjected to poor wet etching, thereby insufficiently forming a chamfer. Thus, it was determined that chipping occurred on the edge.

Fig. 13A, 13B, and 13C show electron micrographs of the front surface of a cell according to one embodiment of the present disclosure when an aqueous NaOH solution (concentration 80%, temperature 190 ℃, and etching time 4 hours) was used in example 3 and a functional layer was formed.

Fig. 13A, 13B, and 13C illustrate the front surface by varying magnification according to one embodiment of the present disclosure. In this case, wet etched portions were observed on the surface, and chamfers were well formed at corners of the cells without chipping or the like. Thus, it was confirmed that the surface (boundary) was formed smoother than that of the existing unit process.

Fig. 14 shows an electron micrograph of a side surface (upper portion) of a cell according to various embodiments of the present disclosure when an aqueous NaOH solution (concentration 80%, temperature 190 ℃, and etching time 2 hours, 4 hours, and 6 hours) was used in example 3 and a functional layer was formed.

As shown in fig. 14, an etched portion formed by wet etching can be observed. Further, as the etching time increases, the area of the etched portion increases, confirming that the interval between the gaps increases.

Fig. 15A, 15B, 15C, 15D, and 15E show actual images of a wafer and a product after each process is completed according to one embodiment of the present disclosure, in which fig. 15A shows a sapphire wafer, fig. 15B shows a cell edge treatment portion formed on the sapphire wafer with a laser beam according to one embodiment of the present disclosure, fig. 15C shows an etching portion formed around the cell edge treatment portion by wet etching the sapphire wafer having the cell edge treatment portion formed thereon according to one embodiment of the present disclosure, fig. 15D shows a printed layer formed on each cell while maintaining the shape of the sapphire wafer, and fig. 15E shows each cell separated from the sapphire wafer.

Fig. 16 shows images of virtual parts remaining after the completion of cell separation according to fig. 15A, 15B, 15C, 15D, and 15E. In this case, only the cells are cleanly separated, and the wafer shape remains good even when the cell separation is completed.

As described above, the present disclosure provides a method of manufacturing a sapphire cover window in which the entire process can be performed at a wafer level when using a sapphire wafer manufacturing unit, and a cover window manufactured thereby, which significantly improves mass productivity and productivity.

In particular, in the present disclosure, wet etching is selectively performed around the cell edge processing portion, that is, the modified portion (through hole and crack) weakened or deformed by absorbing energy from the laser. Accordingly, it is possible to solve the problem of difficulty occurring when wet etching is performed on the existing sapphire wafer, thereby realizing a Wafer Level Process (WLP) using the sapphire wafer.

The sapphire cover window thus fabricated includes etched portions formed along the edges of the cells and chamfers formed particularly at corners to minimize chipping or cracking that occurs during cell separation. In addition, the sapphire cover window may be used as a sapphire cover window having improved durability and scratch resistance.

In particular, when small products having a size of 30mm or less (e.g., a cover window for a camera or a smart watch) are manufactured, productivity can be greatly improved by the wafer level process according to the present disclosure, thereby providing high quality products.

Claims (16)

1. A method of manufacturing a sapphire overlay window, the method comprising:

preparing a sapphire wafer;

forming a unit edge processing portion on the sapphire wafer with a laser beam;

forming an etching portion on the sapphire wafer by selectively performing wet etching on the cell edge processing portion; and

the units are separated from the sapphire wafer by pressing the sapphire wafer on which the etching portions are formed.

2. The method of claim 1, wherein a picosecond laser or a femtosecond laser is used in forming the cell edge treatment portion.

3. The method of claim 2, wherein the cell edge processing portion comprises a modified portion formed along a cell edge by vertically transferring energy from the laser to the sapphire wafer.

4. The method of claim 3, wherein the modified portion is formed along the cell edge in a direction perpendicular to the sapphire wafer and includes a plurality of through holes spaced apart from each other by a distance in a range of 1 μm to 5 μm.

5. The method of claim 4, wherein the modified portion comprises a crack formed around the through hole due to impact propagation when the through hole is formed.

6. The method of claim 1, wherein an aqueous NaOH solution, an aqueous KOH solution, or a mixture of both is used as an etchant in forming the etched portion.

7. The method of claim 6, wherein when using the aqueous NaOH solution as the etchant, the wet etching is performed under the following conditions: the concentration of the aqueous NaOH solution is in the range of 50% to 95%, the temperature is in the range of 130 ℃ to 220 ℃, and the etching time is in the range of 1 hour to 48 hours.

8. The method of claim 6, wherein when using the aqueous KOH solution as the etchant, the wet etching is performed under the following conditions: the concentration of the KOH aqueous solution is in the range of 40% to 90%, the temperature is in the range of 130 ℃ to 220 ℃, and the etching time is in the range of 10 minutes to 20 hours.

9. The method of claim 1, wherein the etched portion comprises a gap formed along a cell edge between cells or between the cells and a dummy portion.

10. The method of claim 9, wherein the gap comprises a chamfer having a predetermined depth from a surface of the cell and a predetermined width from a side surface of the cell.

11. The method of claim 10, wherein the chamfer has a depth of 10% to 50% of the thickness of the sapphire wafer, and

the chamfer has a width in the range of 1 μm to 50 μm.

12. The method of claim 1, wherein in forming the cell edge processing portion, the cell edge processing portion is formed such that a cell size L and a cell spacing S, which is a cell-to-cell spacing, satisfy 0+.s+.l.

13. The method of claim 1, wherein after forming the etched portion, any one or two or more of a Black Matrix (BM) print layer, an anti-reflection (AR) coating, and an anti-fingerprint (AF) coating are formed on the sapphire wafer.

14. The method of claim 1, wherein the sapphire wafer has a cell size L and a thickness T that satisfy 10 t+.l+.250t.

15. The method of claim 1, wherein after the entire process is performed at a sapphire wafer level, unit cells are separated from the sapphire wafer.

16. The method of claim 15, wherein the cover window thus manufactured has a size of 30mm or less.