System and method for controlling wafer breakage during ingot slicing.

Abstract

A system for slicing wafers from a single-crystal semiconductor ingot includes a wire saw, a bond beam, a single-crystal semiconductor ingot, and two sacrificial disks. The wire saw includes a wire web and a wire guide that is operable to drive the wire web during the slicing operation. The bond beam is connected to the wire saw. The wire saw is operable to move the bond beam toward the wire web during the slicing operation to slice wafers from the ingot. The ingot includes longitudinal end faces and circumferential end faces extending between the longitudinal end faces. The ingot is attached to the bond beam along its periphery. Sacrificial disks are positioned adjacent to each of the longitudinal end faces of the ingot, one on each side.

Description

Cross - reference to related applications

[0001] This application claims priority to U.S. Patent Application No. 18 / 356,362, filed on July 21, 2023, and U.S. Patent Application No. 18 / 356,371, filed on July 21, 2023, the entire disclosures of which are incorporated herein by reference.

Technical Field

[0002] The present disclosure generally relates to a wire saw process used to slice a single - crystal semiconductor ingot into wafers, and more particularly, to a system and method for controlling breakage of wafers sliced from an ingot during a wire saw process.

Background Art

[0003] Single - crystal silicon is the starting material for most processes to manufacture many electronic components such as semiconductor devices and solar cells, and is generally manufactured by the batch - type Czochralski (CZ) method or the continuous - type Czochralski (CCZ) method. In these methods, a polycrystalline raw material such as polycrystalline silicon ( "polysilicon") is put into a quartz crucible in the form of a solid raw material and melted, a single seed crystal is brought into contact with the molten silicon or melt, and a single - crystal (or monocrystalline) silicon ingot is grown by slowly extracting it.

[0004] Single - crystal silicon wafers can be sliced from a single - crystal silicon ingot using a wire saw machine. The ingot is connected to the wire saw structure by a bond beam and an ingot holder. The ingot is adhered to the bond beam with an adhesive along its periphery. The bond beam is adhered to the ingot holder with an adhesive. The ingot holder is connected to the wire saw structure by any suitable fixing system. The ingot is suspended or "hung" from the bond beam and the ingot holder within the wire saw such that the longitudinal end face of the ingot extends perpendicular to the bond beam.

[0005] During slicing, the periphery of the ingot comes into contact with the web of the moving or translating wires of the wire saw that slices the ingot into a silicon wafer. Silicon wafers sliced ​​near the longitudinal end face of the ingot may be inadvertently damaged during the wire sawing operation, or the wafer may break uncontrollably. Wafer breakage during wire sawing reduces the number of wafers produced from the ingot, creates manufacturing inefficiencies, increases costs, and lowers wafer yield. Therefore, there is a need for practical and cost-effective systems and methods that facilitate the reduction or elimination of wafer damage or breakage during wire sawing.

[0006] This section is intended to introduce to the reader various aspects of the technology that may relate to various aspects of the present disclosure, which are described and / or claimed below. This discussion is intended to help the reader provide background information to better understand various aspects of the invention. Accordingly, these descriptions should be read in this regard and do not constitute an admission of prior art. [Overview of the Initiative]

[0007] One embodiment is a system for slicing wafers from a single-crystal semiconductor ingot. The system includes a wire saw that includes a wire web and an operable wire guide for driving the wire web during the slicing operation. The system also includes a bond beam connected to the wire saw. The wire saw is operable to move the bond beam toward the wire web during the slicing operation to slice wafers from the ingot. The system also includes a single-crystal semiconductor ingot. The ingot includes a longitudinal end face and a circumferential end face extending between the longitudinal end faces. The ingot is attached to the bond beam along its periphery. The system also includes two sacrificial disks. The sacrificial disks are positioned adjacent to each of the longitudinal end faces of the ingot to prevent uncontrolled wafer breakage during the slicing operation.

[0008] Another embodiment is a method for slicing wafers from a single-crystal semiconductor ingot. This method involves attaching the periphery of the ingot to a bond beam and placing sacrificial disks adjacent to the longitudinal end faces of the ingot. One sacrificial disk is placed adjacent to each longitudinal end face. This method also includes performing a slicing operation on the ingot by connecting the bond beam to a wire saw containing a wire web, operating the wire saw to drive the wire web, and moving the bond beam and ingot toward the wire web in the direction of movement, thereby slicing wafers from the ingot. The sacrificial disks act to suppress uncontrolled breakage of the wafer during the slicing operation.

[0009] Various improvements exist to the features described in relation to the embodiments described above. Further features can also be incorporated into the embodiments described above. These improvements and additional features may exist individually or in any combination. For example, various features described later in relation to any of the illustrated embodiments can be incorporated into any of the embodiments described above, either individually or in any combination. [Brief explanation of the drawing]

[0010] [Figure 1] Figure 1 is a perspective view of a wafer slicing system including an ingot and a wire saw. [Figure 2] Figure 2 is a front view of an ingot attached to a wire saw. [Figure 3] Figure 3 is a perspective view of the ingot. [Figure 4] Figure 4 is a perspective view showing the position of the cleavage plane of the ingot when it is attached to the bond beam of the system in Figures 1 and 2. [Figure 5] Figure 5 is an exploded perspective view showing the ingot and sacrificial disk that suppress uncontrolled wafer breakage during slicing. [Figure 6]Figure 6 is a perspective view of an ingot attached to a bond beam and a sacrificial disc positioned adjacent to the longitudinal end face of the ingot. [Figure 7] Figure 7 is a perspective view of the ingot and sacrificial disk, where the cleavage plane of the disk is offset from the cleavage plane of the ingot. [Figure 8] Figure 8 is a graph showing the correlation between the diameter and thickness of the sacrificial disk and the number of wafers that fracture prematurely during the slicing operation.

[0011] Corresponding reference numerals indicate the corresponding parts across multiple drawings in the drawing. [Modes for carrying out the invention]

[0012] The systems and methods of this disclosure facilitate the suppression (e.g., control, limit, or prevention) of uncontrolled wafer breakage during slicing operations performed on single-crystal semiconductor ingots using a wire saw. The systems and methods increase the number of wafers produced by the slicing operation that are suitable for subsequent processing and device manufacturing, thereby reducing manufacturing inefficiencies, costs, and yield losses. Without being bound by any particular theory, wafers sliced ​​from an ingot may experience stress along relatively weak crystal planes (also called cleavage planes) during the slicing operation. Stresses generated in wafers sliced ​​near the longitudinal ends of the ingot ("longitudinal end wafers") can cause these wafers to break along the cleavage planes. Longitudinal end wafers have less support to compensate for or offset stresses compared to wafers sliced ​​near the central bulk region of the ingot.

[0013] The examples of the systems and methods described include, for each, a sacrificial disk positioned adjacent to one of the longitudinal ends of the ingot during the slicing operation. The sacrificial disk longitudinally supports the longitudinal end wafers and compensates for and / or offsets the stresses generated in these wafers during the slicing operation. Thus, the sacrificial disk suppresses uncontrolled breakage of the longitudinal end wafers during the slicing operation. Furthermore, the sacrificial disk can preferably be made of a semiconductor material (e.g., single-crystal silicon) that gives the disk higher rigidity and better supports the longitudinal end wafers. The semiconductor material preferably conforms to the slurry used during the slicing operation and does not substantially affect the quality of the slurry, thereby allowing the slurry to be recycled for subsequent slicing operations. Single-crystal semiconductor material (e.g., single-crystal silicon) can preferably be used for the sacrificial disk to reduce impurities that may be introduced into the single-crystal ingot by adjacent disks.

[0014] Referring here to the drawings, Figure 1 is a schematic diagram of a wafer slicing system 100 for slicing wafers from an ingot 102, which may also be called a single-crystal semiconductor ingot or a “single-crystal” silicon ingot. Figure 2 is a front view of the system 100. The system includes an ingot 102 and a wire saw 104 that can be operated to slice the ingot 102 into a single-crystal semiconductor wafer. Various components of the wire saw 104 are omitted from the system 100 shown in Figures 1 and 2 for the sake of illustration and explanation. The wire saw 104 may include additional, fewer, or other components other than those illustrated and described.

[0015] The single-crystal semiconductor ingot 102 used in system 100 can be made from any suitable semiconductor material. In the exemplary system 100, the single-crystal semiconductor ingot 102 is a single-crystal silicon ingot. In this specification, the single-crystal semiconductor ingot 102 may also be referred to as single-crystal silicon ingot 102 or single-crystal silicon ingot 102. The single-crystal semiconductor ingot 102 is not limited to being made of single-crystal silicon, but may be made of, for example, single-crystal silicon, single-crystal germanium, single-crystal gallium arsenide, etc. The single-crystal semiconductor ingot 102 can be manufactured using any suitable technique for growing a single-crystal ingot. For example, the single-crystal semiconductor ingot 102 can be grown by the batch Czochralski method, the continuous Czochralski method, or the float-zone method.

[0016] Referring further to Figure 3, a schematic diagram of a single-crystal semiconductor ingot 102, the ingot 102 is substantially cylindrical and defines a longitudinal axis A1. The ingot 102 includes longitudinal end faces 106 and 108 at its opposing longitudinal ends. The ingot 102 also includes a periphery 110 extending substantially parallel to the longitudinal axis A1 between the longitudinal end faces 106 and 108. Since the illustrated ingot 102 is cylindrical, the wafer sliced ​​from the ingot is circular. The shape of the ingot 102 is not limited to the cylindrical shape of the illustrated example. The ingot 102 may have any suitable shape to produce the desired shape of the wafer sliced ​​from the ingot. For example, the shape of the ingot 102 may be rectangular.

[0017] The ingot 102 has an ingot outer diameter D1 defined by its peripheral edge 110 and longitudinal end faces 106 and 108. The ingot outer diameter D1 may be any suitable diameter and may vary depending on the desired diameter of the wafer sliced ​​from the ingot 102. For example, the ingot outer diameter D1 may be at least about 100 millimeters (mm), at least about 200 mm, at least about 300 mm, at least about 400 mm, or at least about 450 mm (in other words, equal to or greater than). The outer diameter D1 of ingot 102 can be approximately 100 mm or more and approximately 450 mm or less, for example, approximately 100 mm or more and approximately 400 mm or less, approximately 100 mm or more and approximately 300 mm or less, approximately 100 mm or more and approximately 200 mm or less, approximately 150 mm or more and approximately 450 mm or less, approximately 150 mm or more and approximately 400 mm or less, approximately 150 mm or more and approximately 300 mm or less, approximately 150 mm or more and approximately 200 mm or less, approximately 200 mm or more and approximately 450 mm or less, approximately 200 mm or more and approximately 300 mm or less, or approximately 300 mm or more and approximately 450 mm or less.

[0018] The ingot 102 extends longitudinally for a length L1 between its longitudinal end faces 106 and 108. Length L1 can be any suitable length and may vary depending on the desired number of wafers to be sliced ​​from the ingot 102. For example, length L1 can be at least about 25 cm, at least about 50 cm, at least about 75 cm, at least about 100 cm, at least about 150 cm, or at least about 200 cm (in other words, equal to or greater than these lengths). The length L1 of the ingot 102 can be between about 25 cm and about 300 cm.

[0019] Ingot 102 and wafers sliced ​​from ingot 102 may have one of the following crystal orientations: (100), (110), or (111). The exemplary ingot 102 has a (100) crystal orientation and has (100) crystal planes on the longitudinal end faces 106 and 108. A wafer sliced ​​from an ingot with a (100) crystal orientation similarly has a (100) crystal orientation. Figure 4 depicts the (100) crystal plane of ingot 102 at end face 108. The exemplary ingot 102 with a (100) crystal orientation has mutually perpendicular (110) crystal planes (shown in Figure 4) intersecting along the longitudinal axis A1. In other embodiments, the crystal orientation of ingot 102 may vary depending on the desired crystal orientation of the wafer sliced ​​from ingot 102, which may vary depending on the desired end use of the wafer. The crystal orientation of ingot 102 is not limited.

[0020] The ingot 102 can undergo various operations to produce the cylindrical shape of the ingot 102 shown in Figure 3, or any other desired shape of the ingot 102, before the slicing operation performed using the wire saw 104. For example, a single-crystal silicon ingot grown by the Czochralski method typically includes seed cones and tail cones at opposing longitudinal ends of the ingot, and a roughly cylindrical body portion between the seed cones and end cones. The seed end and tail cones are removed from the ingot (e.g., by cropping, lapping, and / or grinding operations), and the remaining body portion forms an ingot 102 (or more ingots 102) with the desired shape. Alternatively, the ingot 102 may be trimmed to form an orientation flat or notch (not shown) on the periphery 110 and / or longitudinal end faces 106 and / or 108, which is used to determine the crystal orientation of the ingot 102. The ingot 102 may also be subjected to grinding (e.g., via a grind wheel) to produce a desired ingot outer diameter D1 and / or a desired length L1 of the ingot 102. Polishing may be performed on the entire single-crystal silicon ingot, for example, before cropping, lapping, and / or trimming operations. Notches or planes may be carved using other grinding wheels or appropriate tools to define the proper orientation of the future wafer relative to a specific crystal axis.

[0021] Referring again to FIGS. 1 and 2, wire saw 104 includes a continuous wire web 112 (also referred to as wire 112). Wire 112 is used to slice (alternatively, cut or saw) ingot 102 into wafers. In this embodiment, wire web 112 includes a plurality of wires. In other examples, wire web 112 can include a single continuous wire that forms the web. Wire 112 can be of any type suitable for slicing ingot 102, such as, for example, a diamond wire. The number of wires 112 included in wire saw 104 is significantly reduced in FIGS. 1 and 2 for purposes of illustration and description. The spacing between adjacent wires 112 is also exaggerated in FIGS. 1 and 2. The number of wires 112 in wire saw 104 and the spacing between adjacent wires 112 can be selected to slice ingot 102 into wafers having a desired thickness. For example, wafers sliced from ingot 102 using wire saw 104 can have a thickness of at least about 200 micrometers (μm), at least about 300 μm, at least about 400 μm, at least about 500 μm, at least about 600 μm, at least about 700 μm, at least about 800 μm, at least about 900 μm, or at least about 1000 μm. Wafers sliced from ingot 102 using wire saw 104 can have a thickness of about 250 μm or more and about 1500 μm or less, such as, for example, about 300 μm or more and about 1000 μm or less, or about 500 μm or more and about 1000 μm or less. Wafers sliced from ingot 102 can have the same desired thickness (in which case the spacing between adjacent wires 112 is the same throughout the web), or wafers sliced from ingot 102 can have different desired thicknesses (in which case the spacing between adjacent wires 112 varies).

[0022] Wire 112 is supported by wire guide 114. The wire 112 extends substantially parallel between each pair of adjacent wire guides 114. In the exemplary wire saw 104, three wire guides 114 are included and are arranged in an inverted triangular shape. Any suitable number of wire guides 114 can be included in any suitable arrangement. For example, the wire saw 104 can include four wire guides 114 arranged in a square or rectangular shape.

[0023] Each wire guide 114 has opposing ends 116, 118 connected to the frame 120 of the wire saw 104 (only a part of which is shown in FIG. 2) by bearings 122. The bearings 122 can be any suitable type of bearing, such as ball bearings, roller bearings, etc. The cooling fluid can be in thermal communication with the bearings 122 that support each wire guide 114 and can be structured to contact at least a part of the bearing or the bearing in sequence. The coolant is circulated in contact with the bearings 122 to control the temperature of the bearings 122 (e.g., to cool the bearings during operation of the wire saw 104).

[0024] One or more of the wire guides 114 can be connected to a drive source (not shown), such as a motor, to rotate the guide. The wire guide 114 rotates to drive the wire web 112 that circulates around the wire guide 114 when slicing the ingot 102. Each wire guide 114 can be a drive guide that is actively rotated by a drive source. Alternatively, while one or more of the wire guides 114 are drive guides, one or more of the wire guides 114 can be follower guides that are rotated by the movement of the wire 112 driven by the drive guide. The wire guide 114 can rotate in one direction during the slicing operation, or can rotate in reverse to change the direction in which the wire 112 moves around the wire guide 114 during the slicing operation.

[0025] System 100 also includes a bond beam 124 that facilitates connecting the ingot 102 to the wire saw 104. The bond beam 124 has a first surface 126 that is attached to the ingot holder 128 and a second surface 130 that is attached to the periphery 110 of the ingot 102. Surfaces 126 and 130 of the bond beam 124 can be attached to the ingot holder 128 and the ingot 102, respectively, using an adhesive (e.g., glue). Figure 6 shows an adhesive layer 152 used to bond the ingot 102 to the second surface 130 of the bond beam 124. The second surface 130 of the bond beam 124 may have a contour suitable for bonding to the ingot 102 with adhesive and forming a sufficient adhesive bond between them. For example, the second surface 130 may have a concave contour extending in the longitudinal direction of the beam 124 to complement the periphery 110 of the ingot 102. The first surface 126 of the bond beam 124 may be substantially flat in order to complement the lower surface of the ingot holder 128 to which the first surface is attached.

[0026] During slicing, to ensure that the ingot is completely sliced ​​into the wafer, the wires 112 of the saw 104 may come into contact with the bond beam 124 after the ingot 102 has been sliced ​​into the wafer. The bond beam 124 can be formed from a material that is easily sawed or sliced ​​by the wire saw 104 when slicing the ingot 102 into the wafer without damaging the saw wires 112. Examples of such materials include epoxy, glass, and other resins.

[0027] The ingot holder 128 and the bond beam 124 attached to the ingot holder are connected to the structure 132 of the wire saw 104 by any suitable means. For example, the ingot holder 128 may be connected to the structure 132 by a clamp rail (not shown) received by the ingot holder, which allows the ingot holder to slide in and out of the structure 132 along the rail. Thus, other components of the system 100 connected to the ingot holder 128 (e.g., the bond beam 124 and the ingot 102) can also slide in and out of the structure 132. In other embodiments, any suitable fastening system (e.g., mechanical fasteners) can be used to connect the ingot holder 128 to the structure 132.

[0028] The wire saw 104 is operable to move the structure 132 along the movement axis A2 relative to the wire web 112. The movement of the structure 132 can be facilitated by any suitable means, such as a linear actuator, motor, hydraulic cylinder, or pneumatic cylinder. By moving the structure 132 along axis A2, the bond beam 124 and the ingot 102 can be moved toward the wire web 112 to slice the ingot 102 into a wafer. In the illustrated system 100, the structure 132 is moved downward along axis A2 during the slicing operation. In other embodiments, the structure 132 can be moved in any direction toward the wire 112, and the relative positions of the wire web 112, the structure 132, and the movement axis A2 are not limited to the illustrated embodiment. For example, in some embodiments, the structure 132 can be moved upward along the movement axis A2 during the slicing operation to move the bond beam 124 and the ingot 102 toward the wire 112.

[0029] System 100 may also include one or more slurry sprayers (not shown) capable of supplying slurry onto the ingot 102 and / or wire 112 during the slicing operation. The slurry may be a liquid formulation containing abrasive particles or a liquid without abrasive particles (e.g., water). This slurry allows the wire 112 to work against the single-crystal semiconductor material of the ingot 102, enabling slicing of wafers from the ingot. Additionally and / or alternatively, the slurry can be used to control the temperature of the ingot 102 during the slicing operation. When slicing a single-crystal ingot, friction between the ingot 102 and the wire 112 generates heat, causing the temperature of the ingot to rise. By spraying slurry onto the ingot 102 and wire web 112, the heat can be dissipated.

[0030] In the operation of the wire saw 104, the ingot 102 is attached to the bond beam 124 along its periphery 110, and the bond beam 124 is further attached to the ingot holder 128. The ingot holder 128 is connected to the movable structure 132 of the wire saw 104. The ingot 102 "hangs" from the structure 132, and the wire saw 104 operates to move the structure 132 and the hanging ingot 102 toward the wire web 112. At this stage, the wire web 112 is driven by the wire guide 114 and moves around the guide for slicing the ingot 102. The structure 132 is moved along the moving axis A2, bringing the periphery 110 of the ingot 102 into contact with the wire 112. The wire 112 acts on the periphery 110 of the ingot 102 until the ingot continues to move along axis A2 and a wafer is sliced ​​from the ingot 102. The slurry may be sprayed onto the ingot 102 and / or wire 112 as the wire acts against the ingot. The wire 112 may at least partially cut into the bond beam 124 to ensure complete separation of the wafer.

[0031] During the slicing operation, wafers sliced ​​from near the longitudinal end faces 106 and 108 of ingot 102 ("longitudinal end wafers") may fracture along relatively weaker planes or cleavage planes due to the stress exerted by the wire 112. Referring to Figure 4, an example of the crystal orientation of ingot 102 is shown to illustrate this effect. The crystal orientation of ingot 102 is shown in Figure 4 in relation to the position of ingot 102 when it is attached to the bond beam 124 and placed on the movable structure 132. The exemplary ingot 102 has a (100) crystal orientation, with (100) crystal planes on the longitudinal end faces 106 and 108. The (100) crystal plane is shown on longitudinal end face 108 in Figure 4. Ingot 102 has mutually perpendicular (110) crystal planes intersecting along the longitudinal axis A1. The crystal planes are relatively weak cleavage planes, and if sufficient stress is applied along these planes, the wafer sliced ​​from the ingot 102 may fracture. The ingot 102 may be arranged such that one (110) crystal plane extends substantially perpendicular to the movement axis A2 and substantially parallel to the wire 112, and the other (110) crystal plane extends substantially parallel to the movement axis and substantially perpendicular to the wire.

[0032] As the wire 112 moves through the ingot 102 along the movement axis A2, the area of ​​the (110) crystal planes decreases. The stress exerted by the wire 112 concentrates along the reduced (110) crystal planes, and the longitudinal end wafers may break (e.g., fracture) along these cleavage planes. The wafers sliced ​​from the ingot 102 at both longitudinal ends ("center wafers") are supported on both longitudinal sides by the mass of the wafers sliced ​​from the ingot toward both longitudinal ends. The longitudinal support provided to the center wafer can compensate and / or offset the stress, preventing the stress from concentrating along the cleavage planes, thereby reducing the tendency for the center wafer to break during the slicing operation. However, the longitudinal end wafers sliced ​​from the ingot 102 lack this longitudinal support and are therefore more prone to cracking during the slicing operation. This negative result can occur at any stage of the ingot 102's crystal orientation and / or slicing operation, but the longitudinal edge wafer is particularly susceptible to breakage during the slicing operation when the cleavage planes are positioned as shown in Figure 4.

[0033] Referring again to Figures 1 and 2, system 100 includes sacrificial disks 134 and 136 that provide longitudinal support to wafers sliced ​​from ingot 102 adjacent to the longitudinal end faces 106 and 108, i.e., the longitudinal end wafers, and suppress uncontrollable breakage. One of the sacrificial disks 134 and 136 is positioned adjacent to each of the longitudinal end faces 106 and 108 of ingot 102 when the ingot is attached to the bond beam 124. Sacrificial disk 134 is positioned adjacent to longitudinal end face 106, and sacrificial disk 136 is positioned adjacent to longitudinal end face 108. In the exemplary system 100, two sacrificial disks 134 and 136 are included. Any appropriate number of sacrificial disks can be included so that the disks function as described above. For example, multiple sacrificial disks 134 can be stacked longitudinally from their longitudinal end faces 106, and / or multiple sacrificial disks 136 can be stacked longitudinally from their longitudinal end faces 106.

[0034] Sacrificial disks 134 and 136 can be made from any suitable material, including semiconductor materials such as silicon. For example, each sacrificial disk 134, 136 may be made from a single-crystal semiconductor material such as single-crystal silicon. Using a single-crystal semiconductor material for disks 134, 136 is cost-effective and can provide the disks with sufficient rigidity to support the longitudinal end faces 106, 108 of the ingot 102 during wafer slicing. Other semiconductor materials include, for example, sintered or amorphous semiconductor materials (e.g., sintered or amorphous silicon). Single-crystal semiconductor materials provide more rigidity to disks 134 and 136 than other semiconductor materials, allowing disks 134 and 136 to better support the longitudinal end wafer during the slicing operation. The single-crystal semiconductor material forming disks 134 and 136 may be similar to or different from the single-crystal semiconductor material of ingot 102.

[0035] In the exemplary system 100, the ingot 102 and disks 134, 136 are preferably made of single-crystal silicon or single-crystal silicon. By using similar single-crystal semiconductor material (e.g., single-crystal silicon) for disks 134, 136 and ingot 102, it may be easier to reduce impurities that may be introduced into the longitudinal edge wafer of ingot 102 by adjacent disks 134, 136. Furthermore, single-crystal semiconductor material (e.g., single-crystal silicon) is suitably compatible with the slurry used during the slicing operation, which may allow the slurry to be recycled for subsequent slicing operations where recycling is desired.

[0036] Figures 5 and 6 show the ingot 102 and sacrificial discs 134 and 136 in more detail. Figure 5 is an exploded view of the ingot 102, the sacrificial discs 134 and 136 at the opposing longitudinal ends of the ingot, and the adhesive layer 138 which may be used to bond the discs 134 and 136 to the longitudinal end faces 106 and 108, respectively. Figure 6 shows the ingot 102 mounted on a bond beam 124 with the sacrificial discs 134 and 136 positioned adjacent to the longitudinal end faces 106 and 108, respectively.

[0037] An exemplary sacrificial disc 134 includes two main faces 140 and 142 and a periphery 144 extending between faces 140 and 142. The first main face 140 of the sacrificial disc 134 is positioned adjacent to the longitudinal end face 106 of the ingot 102, and the second main face 142 is oriented away from the ingot 102. Preferably, when the sacrificial disc 134 is positioned adjacent to the longitudinal end face 106 of the ingot 102, the first main face 140 is in surface contact with the longitudinal end face 106, with little or no gap between them. The sacrificial disc 134 has an outer disc diameter D2 defined by faces 140 and 142 and the periphery 144. The sacrificial disc 134 also has a thickness L2, which is measured as the distance the periphery 144 extends between faces 140 and 142.

[0038] Similarly, an exemplary sacrificial disc 136 includes two main faces 146 and 148 and a periphery 150 extending between faces 146 and 148. The first main face 146 of the sacrificial disc 136 is positioned adjacent to the longitudinal end face 108 of the ingot 102, and the second main face 148 is oriented away from the ingot 102. Preferably, when the sacrificial disc 136 is positioned adjacent to the longitudinal end face 108 of the ingot 102, the first main face 146 is in surface contact with the longitudinal end face 108, with little or no gap between them. The sacrificial disc 136 has an outer disc diameter D3 defined by faces 140 and 142 and a periphery 144. The sacrificial disc 136 also has a thickness L3, which is measured as the distance the periphery 150 extends between faces 146 and 148.

[0039] The shapes of the sacrificial discs 134 and 136 may vary depending on the shape of the ingot 102. In the exemplary system 100, the discs 134 and 136 are preferably circular in shape to complement the circular shape of the longitudinal end faces 106 and 108 of the cylindrical ingot 102. In other examples, the discs 134 and 136 may have other shapes to complement the shape of the ingot 102. For example, the discs 134 and 136 may be rectangular or square in shape.

[0040] Sacrificial discs 134 and 136 can be attached to adjacent longitudinal end faces 106 and 108, respectively, of the ingot 102. In the exemplary system 100, the first main face 140 of sacrificial disc 134 is bonded to the longitudinal end face 106 with an adhesive layer 138, and the first main face 146 of sacrificial disc 136 is bonded to the longitudinal end face 108 with an adhesive layer 138. The adhesive layer 138 can include any suitable adhesive material for bonding materials, such as an adhesive. To facilitate the reduction of the tendency for adhesion failure due to heat generated during the slicing operation by friction between the ingot 102 and the wire 112, the adhesive layer 138 can preferably include a heat-resistant adhesive that can withstand temperatures of 80°C or higher.

[0041] Any suitable method can be used to attach disks 134 and 136 to the longitudinal end faces 106 and 108, respectively. For example, disks 134 and 136 may be bonded to the longitudinal end faces 106 and 108 by thermal bonding, adhesive bonding, pressure bonding, or any combination thereof. In some examples, disks 134 and 136 can be attached to the longitudinal end faces 106 and 108 without any significant additional processing (e.g., heating, bonding, pressure bonding). For example, if disks 134 and 136 and ingot 102 are each made of single-crystal silicon, disks 134 and 136 can be positioned adjacent to the respective longitudinal end faces 106 and 108 of the ingot and held there by attractive forces (e.g., van der Waals bonds) present between silicon atoms on the main surface of the disk and the longitudinal end faces of the ingot.

[0042] Sacrificial discs 134 and 136 can be additionally and / or alternatively attached (e.g., with adhesive) to the second surface 130 of the bond beam 124 adjacent to the respective longitudinal end faces 106 and 108 of the ingot 102. For example, as shown in Figure 6, the adhesive layer 152 (e.g., adhesive) used to bond the periphery 110 of the ingot 102 to the second surface 130 of the bond beam 124 can also be used to bond the peripheries 144 and 150 of discs 134 and 136 to the second surface 130 of the bond beam 124, respectively. Alternatively, separate adhesive layers can be used to attach discs 134 and 136 to the bond beam 124.

[0043] In the exemplary system 100, the outer disk diameters D2 and D3 are each smaller than the outer ingot diameter D1. Smaller outer disk diameters D2 and D3 offer several advantages. For example, smaller diameter disks 134 and 136 can further reduce wafer breakage compared to larger diameter disks 134 and 136. Referring to Figure 8, the correlation between the diameters of sacrificial disks 134 and 136 and the number of wafers that broke during the experimental ingot slicing operation is shown. As shown in Figure 8, when 8-inch (or approximately 200 mm in diameter) sacrificial disks 134 and 136 were used, fewer wafers were broken than when 12-inch (or approximately 300 mm in diameter) sacrificial disks 134 and 136 were used. Therefore, using smaller diameter disks 134 and 136 can easily reduce the number of longitudinal edge wafers that break during slicing.

[0044] Using smaller diameter disks 134 and 136 reduces material loss caused by using sacrificial disks during the slicing operation. Furthermore, smaller outer disk diameters D2 and D3 allow for greater rigidity of the sacrificial disks 134 and 136. For example, single-crystal semiconductor disks 134 and 136 are more rigid with smaller diameters and are inherently less prone to breakage during the slicing operation and / or when positioned adjacent to the respective longitudinal end faces 106 and 108 of the ingot. In this respect, using smaller diameter disks 134 and 136 may allow for repeated use of sacrificial disks between multiple slicing operations. In addition, using smaller diameter disks 134 and 136 may make inspection easier to ensure that disks 134 and 136 are properly positioned adjacent to their respective longitudinal end faces 106 and 108, and that disks 134 and 136 are properly aligned (e.g., having the desired crystal plane positioning). In other examples, one or both of the outer disk diameters D2 and D3 can be the same as the outer ingot diameter D1.

[0045] The outer disc diameters D2 and D3 can be any suitable diameter to allow discs 134 and 136 to function as described. For example, the outer disc diameters D2 and D3 can be at least about 100 mm, at least about 200 mm, at least about 300 mm, at least about 400 mm, or at least about 450 mm (in other words, equal to or greater than). The outer disk diameters D2 and D3 can be between approximately 100 mm and approximately 450 mm, for example, between approximately 100 mm and approximately 400 mm, between approximately 100 mm and approximately 300 mm, between approximately 100 mm and approximately 200 mm, between approximately 150 mm and approximately 450 mm, between approximately 150 mm and approximately 400 mm, between approximately 150 mm and approximately 300 mm, between approximately 150 mm and approximately 200 mm, between approximately 200 mm and approximately 450 mm, between approximately 200 mm and approximately 400 mm, between approximately 200 mm and approximately 300 mm, or between approximately 300 mm and approximately 450 mm. The outer disk diameters D2 and D3 can be selected from these ranges, with the caveat that one or both of the outer disk diameters D2 and D3 are smaller than the outer ingot diameter D1. In some examples, the outer disk diameters D2 and D3 are between approximately 150 mm and 300 mm, for example, approximately 150 mm, 200 mm, 250 mm, or 300 mm, and the outer ingot diameter D1 is larger than each of the outer disk diameters D2 and D3, for example, between approximately 300 mm and 450 mm, for example, approximately 300 mm, 400 mm, or 450 mm. The outer disk diameters D2 and D3 may be the same or different.

[0046] In examples where the sacrificial disks 134 and 136 have outer diameters D2 and D3 smaller than the outer ingot diameter D1, the sacrificial disks 134 and 136 may be axially offset from the longitudinal axis A1 (Figure 3) when positioned adjacent to the longitudinal end faces 106 and 108. Preferably, the smaller diameter disks 134 and 136 are axially offset from axis A1 and positioned adjacent to the bond beam 124 (as shown in Figure 5). In this position, the smaller diameter disks 134 and 136 support the wafers at the longitudinal ends of the ingot 102 longitudinally along the region where these wafers are most likely to break during the slicing operation. Returning to Figure 4, as described above, the area of ​​the (110) crystal plane decreases as the wire 112 gradually slices the ingot 102 toward the bond beam 124, and the longitudinal end wafers may be particularly prone to fracture as the wire 112 approaches the bond beam. The small-diameter disks 134 and 136 are preferably positioned adjacent to the bond beam 124, providing longitudinal support to the longitudinal end wafer at this stage. The disks 134 and 136 may have relatively small outer diameters D2 and D3, which reduces the likelihood of wafer breakage during the initial stages of slicing when the wire 112 penetrates the ingot 102 and begins working, thus suppressing uncontrolled wafer breakage.

[0047] The thicknesses L2 and L3 of the sacrificial disks 134 and 136 can be any suitable thickness to allow the disks to function as described. For example, thicknesses L2 and L3 are at least about 300 μm, at least about 400 μm, at least about 500 μm, at least about 600 μm, at least about 700 μm, at least about 800 μm, at least about 900 μm, or at least about 1000 μm (in other words, equal to or greater than). Thicknesses L2 and L3 can be approximately 100 μm or more and approximately 5000 μm or less, for example, approximately 500 μm or more and approximately 5000 μm or less, approximately 500 μm or more and approximately 4000 μm or less, approximately 500 μm or more and approximately 3000 μm or less, approximately 500 μm or more and approximately 2000 μm or less, approximately 500 μm or more and approximately 1600 μm or less, and approximately 500 μm or more and approximately 1000 μm or less. The thickness ranges from approximately μm to about 5000 μm, from about 1000 μm to about 4000 μm, from about 1000 μm to about 3000 μm, from about 1000 μm to about 2000 μm, from about 1000 μm to about 1600 μm, from about 1400 μm to about 2000 μm, from about 1400 μm to about 1800 μm, or from about 1500 μm to about 1700 μm. In various examples, thicknesses L2 and L3 are each about 800 μm to about 1600 μm, for example, from about 800 μm to about 1000 μm. In some examples, thicknesses L2 and L3 are about 800 μm, about 850 μm, about 900 μm, about 950 μm, or about 1000 μm, respectively. The thicknesses L2 and L3 of the sacrificial disks 134 and 136 may be the same or different. The thicknesses L2 and L3 of the sacrificial disks 134 and 136 may be for a single disk, or the thickness may be constructed, for example, by stacking multiple disks 134 and / or multiple disks 136 longitudinally.

[0048] Using relatively large thicknesses L2 and L3, for example, at least about 500 μm, or at least about 800 μm, for example, between about 500 μm and about 2000 μm, or between about 800 μm and about 1600 μm, can further reduce wafer breakage compared to sacrificial disks with smaller thicknesses. Referring again to Figure 8, the correlation between the thickness of sacrificial disks 134 and 136 and the number of wafers broken during experimental ingot slicing operations is shown. As shown in Figure 8, for both 8-inch (or about 200 mm in diameter) sacrificial disks 134 and 136 and 12-inch (or about 300 mm in diameter) sacrificial disks, the number of wafers broken during slicing decreased as the disk thickness increased. Therefore, using thicker diameter disks 134 and 136 can easily reduce the number of longitudinal edge wafers broken during slicing.

[0049] As described above, sacrificial disks 134 and 136 can be made from the same single-crystal semiconductor material as ingot 102 and the wafer sliced ​​from the ingot. In the exemplary system 100, ingot 102 and disks 134 and 136 are each made of single-crystal silicon. Disks 134 and 136 may also have the same crystal orientation as ingot 102 and the wafer. For example, sacrificial disks 134 and 136, ingot 102, and the wafer sliced ​​from ingot 102 may have one of the crystal orientations (100), (110), or (111). In the exemplary system 100, ingot 102, the wafer sliced ​​from the ingot, and sacrificial disks 134 and 136 have the (100) crystal orientation. In other examples, sacrificial disks 134 and 136 may have different crystal orientations from ingot 102 and the wafer sliced ​​from the ingot.

[0050] Sacrificial disks 134 and 136, which have a crystal orientation, also have a cleavage (110) crystal plane. In some examples, sacrificial disks 134 and 136 may be positioned with their cleavage planes offset from the cleavage planes of ingot 102. As described above with reference to Figure 4, the cleavage planes of ingot 102 can be positioned perpendicular and parallel to the movement axis A2, respectively. The cleavage planes of sacrificial disks 134 and 136 can be positioned at an oblique angle to the cleavage planes of ingot 102 and the movement axis A2. This provides a more advantageous orientation of sacrificial disks 134 and 136 during the slicing operation, making it easier to reduce the tendency for the disks to break and detach from ingot 102 and / or bond beam 124.

[0051] Figure 7 shows an example where the cleavage (110) crystal planes of disks 134 and 136 (only disk 136 is shown in Figure 7) are offset at an oblique angle θ from the cleavage plane of ingot 102 and the movement axis A2. The oblique angle θ can be any appropriate offset angle to allow the sacrificial disks 134 and 136 to function as described and / or to reduce the tendency for the disks to break during the slicing operation. For example, the cleavage planes of the sacrificial disks may be positioned at an angle θ of about 10° to about 80°, about 20° to about 70°, about 30° to about 60°, or about 40° to about 50° relative to the cleavage plane of ingot 102 and the movement axis A2. The angle θ can be, for example, about 10°, 15°, 20°, 25°, 30°, 35°, 40°, 45°, 50°, 55°, 60°, 65°, 70°, 75°, or 80° with respect to the cleavage plane and moving axis A2 of the ingot 102. The cleavage plane of the sacrificial disk 134 may be positioned at the same offset angle θ as the cleavage plane of the sacrificial disk 136, or the cleavage plane of the sacrificial disk 134 may be positioned at a different offset angle than the cleavage plane of the sacrificial disk 136.

[0052] Advantageously, the examples described herein include sacrificial disks that reduce the tendency for wafers to break and detach prematurely from the ingot during wire saw slicing operations. Wafer breakage during the wire sawing process reduces the number of wafers that can be manufactured from the ingot, resulting in manufacturing inefficiencies, increased costs, and other unacceptable yield reductions. The described systems and methods, including sacrificial disks positioned adjacent to each longitudinal end of the ingot, facilitate increasing the number of wafers produced from the slicing operation that are suitable for subsequent processing and device manufacturing, reduce manufacturing inefficiencies and costs, and improve yield. Furthermore, the sacrificial disks may preferably be made of a semiconductor material (e.g., silicon) that gives the disk higher rigidity and better support to the longitudinal end wafers. The semiconductor material may preferably be compatible with the slurry used during the slicing operation, allowing the slurry to be reused in subsequent slicing operations. Single-crystal semiconductor materials (e.g., single-crystal silicon) can preferably be used for the sacrificial disks to reduce impurities that may be present in the single-crystal ingot.

[0053] When used with ranges of dimensions, concentrations, temperatures, or other physical or chemical properties or characteristics, the terms “about,” “substantially,” “essentially,” and “approximately” mean to encompass any variations that may exist at the upper and / or lower limits of the range of the property or characteristic, including variations resulting from, for example, rounding, measurement methods, or other statistical variability.

[0054] When describing elements or embodiments of this disclosure, the articles “a,” “an,” “the,” and “said” are intended to indicate that there are one or more elements. The terms “comprising,” “including,” “containing,” and “having” are intended to indicate comprehensiveness and mean that there may be additional elements other than those listed. The use of terms indicating a particular direction (e.g., “up,” “down,” “side,” “horizontal,” “vertical,” “lateral,” etc.) is for explanatory convenience and does not require a specific direction for the item being described.

[0055] Because various modifications are possible in the above configuration and method without departing from the scope of this disclosure, all matters included in the above description and shown in the accompanying drawings are to be conspicuous and not limited in meaning.

Claims

1. A system for slicing wafers from single-crystal semiconductor ingots, A wire saw including a wire web and an operable wire guide for driving the wire web during slicing, A bond beam connected to the wire saw, wherein the wire saw moves the bond beam toward the wire web in the direction of movement during slicing, and operates to slice the wafer from the ingot. The single-crystal semiconductor ingot has a longitudinal end face and a peripheral portion extending between the longitudinal end faces, and is attached to the bond beam along the peripheral portion, and The invention includes two sacrificial disks, each of which is positioned adjacent to each of the longitudinal end faces of the ingot. system.

2. The ingot has an outer ingot diameter, and the sacrificial disks each have an outer disk diameter smaller than the outer ingot diameter. The system according to claim 1.

3. Each sacrificial disc is axially offset from the adjacent longitudinal end face. The system according to claim 2.

4. The ingot has an outer ingot diameter, and the sacrificial disks each have an outer disk diameter equal to the outer ingot diameter. The system according to claim 1.

5. The sacrificial disk is made of semiconductor material. The system according to any one of claims 1 to 4.

6. The sacrificial disk is made of a single-crystal semiconductor material. The system according to claim 5.

7. The sacrificial disk is made of an amorphous semiconductor material. The system according to claim 5.

8. The sacrificial disk is made of a sintered semiconductor material. The system according to claim 5.

9. Each sacrificial disc is bonded to an adjacent longitudinal end face with adhesive. The system according to any one of claims 1 to 8.

10. Each sacrificial disc is glued to the bond beam. The system according to any one of claims 1 to 9.

11. The single-crystal semiconductor ingot is a single-crystal silicon ingot. The system according to any one of claims 1 to 10.

12. The single-crystal silicon ingot has (110) crystal planes arranged perpendicular to the direction of movement. The system according to claim 11.

13. A wafer sliced ​​from the aforementioned single-crystal silicon ingot is (100) a single-crystal silicon wafer. The system according to claim 11 or claim 12.

14. The sacrificial disk is made of single-crystal silicon. The system according to any one of claims 1 to 6 or 9 to 13.

15. At least one of the sacrificial disks has a (110) crystal plane that is positioned obliquely to the direction of movement. The system according to claim 14.

16. At least one of the sacrificial disks has a (110) crystal plane positioned at an angle of 30° to 60° with respect to the direction of movement. The system according to claim 15.

17. At least one of the sacrificial disks has a (110) crystal plane positioned at an angle of 45° with respect to the direction of movement. The system according to claim 15.

18. Each of the sacrificial disks has a (110) crystal plane arranged at an oblique angle with respect to the direction of movement. The system according to any one of claims 14 to 17.

19. Each of the sacrificial disks has a (110) crystal plane arranged at an angle of 30° to 60° with respect to the direction of movement. The system according to claim 18.

20. Each of the sacrificial disks has a (110) crystal plane positioned at a 45° angle with respect to the direction of movement. The system according to claim 18.

21. Each of the sacrificial disks has a thickness of more than 500 μm. The system according to any one of claims 1 to 20.

22. Each of the sacrificial disks has a thickness exceeding 800 μm. The system according to claim 21.

23. Each of the sacrificial disks has a thickness of 500 μm or more and 2000 μm or less. The system according to any one of claims 1 to 20.

24. Each of the sacrificial disks has a thickness of 800 μm or more and 1600 μm or less. The system according to any one of claims 1 to 20.

25. The sacrificial disk operates to suppress uncontrolled wafer damage during slicing operations. The system according to any one of claims 1 to 24.

26. A method for slicing wafers from a single-crystal semiconductor ingot, Attaching the periphery of the ingot to the bond beam, The sacrificial discs are placed adjacent to the longitudinal end faces of the ingot, and one sacrificial disc is placed adjacent to each of the longitudinal end faces. Connecting the bond beam to the wire saw including the wire web, This includes performing a slicing operation, which involves operating a wire saw to drive a wire web and moving the bond beam and ingot toward the wire web to slice a wafer from the ingot. method.

27. Positioning the sacrificial discs adjacent to their longitudinal end faces includes bonding each sacrificial disc to the adjacent longitudinal end face with adhesive. The method according to claim 26.

28. Positioning the sacrificial disc adjacent to the longitudinal end face includes bonding the sacrificial disc to the bond beam with adhesive. The method according to claim 26 or claim 27.

29. The ingot has an outer ingot diameter, and the sacrificial disks each have an outer disk diameter smaller than the outer ingot diameter. The method according to any one of claims 26 to 28.

30. Each sacrificial disc is offset axially from the adjacent longitudinal end face. The method according to claim 29.

31. The ingot has an outer ingot diameter, and the sacrificial disks each have an outer disk diameter equal to the outer ingot diameter. The method according to any one of claims 26 to 28.

32. The sacrificial disk is made of semiconductor material. The method according to any one of claims 26 to 31.

33. The sacrificial disk is made of single-crystal semiconductor material. The method according to claim 32.

34. The sacrificial disk is made of amorphous semiconductor material. The method according to claim 32.

35. The sacrificial disk is made of sintered semiconductor material. The method according to claim 32.

36. A single-crystal semiconductor ingot is a single-crystal silicon ingot. The method according to any one of claims 26 to 35.

37. Attaching the periphery of the ingot to the bond beam includes positioning the (110) crystal plane of the single-crystal silicon ingot perpendicular to the direction of movement. The method according to claim 36.

38. A wafer sliced ​​from an ingot is a (100) single-crystal silicon wafer. The method according to claim 36 or claim 37.

39. The sacrificial disk is made of single-crystal silicon. The method according to any one of claims 26 to 33 or 36 to 38.

40. Positioning the sacrificial disk adjacent to the longitudinal end face of the ingot includes positioning at least one (110) crystal plane of the sacrificial disk at an oblique angle with respect to the direction of movement. The method according to claim 39.

41. At least one (110) crystal plane of the sacrificial disk is positioned at an angle between 30° and 60° with respect to the direction of movement. The method according to claim 40.

42. At least one (110) crystal plane of the sacrificial disk is positioned at an angle of 45° with respect to the direction of movement. The method according to claim 40.

43. Positioning the sacrificial disk adjacent to the longitudinal end face of the ingot includes positioning each (110) crystal plane of the sacrificial disk at an oblique angle with respect to the direction of movement. The method according to any one of claims 39 to 42.

44. Each (110) crystal plane of the sacrificial disk is positioned at an angle of 30° to 60° with respect to the direction of movement. The method according to claim 43.

45. Each (110) crystal plane of the sacrificial disk is positioned at an angle of 45° with respect to the direction of movement. The method according to claim 43.

46. Each sacrificial disk has a thickness exceeding 500 μm. The method according to any one of claims 26 to 45.

47. Each sacrificial disk has a thickness exceeding 800 μm. The method according to claim 46.

48. Each sacrificial disk has a thickness of 500 μm or more and 2000 μm or less. The method according to any one of claims 26 to 45.

49. Each sacrificial disk has a thickness of 800 μm or more and 1600 μm or less. The method according to any one of claims 26 to 45.

50. The sacrificial disk operates to prevent uncontrolled wafer damage during slicing operations. The method according to any one of claims 26 to 49.

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