Wire cutting unit, device, silicon wafer and manufacturing method thereof

Abstract

Embodiments of the present invention disclose a wire cutting unit, a device, a silicon wafer and a manufacturing method thereof, a cutting wire; at least two spools arranged spaced apart and parallel to each other, and a plurality of guiding grooves parallel and spaced apart from each other are provided on each spool, and the cutting wire is wound around each guiding groove of each spool in sequence to form an array composed of a plurality of cutting segments spanning across the at least two spools and parallel to each other, and the array is used to cut a silicon rod into a plurality of silicon wafers at one time by moving along the extending direction of the cutting wire; wherein, the distance between adjacent guiding grooves among the plurality of guiding grooves is set according to a set rule along the arrangement direction of the plurality of cutting segments according to the deformation of the cutting wire, so that the plurality of cut silicon wafers have a consistent thickness.

Description

Technical Field

[0001] Embodiments of the present invention relate to the technical field of wafer processing, and particularly to a wire cutting unit, a device, a silicon wafer, and a manufacturing method thereof. Background Art

[0002] As a carrier for semiconductor circuit manufacturing processes, the quality of silicon wafers has a decisive impact on the formation of integrated circuits. Currently, the main processes in the preliminary forming process of silicon wafers include: silicon rod cutting, physical and chemical grinding, chemical etching, physical and chemical polishing, etc. Silicon rod cutting is one of the core processes in the silicon wafer forming process, which mainly includes multi-wire slurry (SiC) cutting and inner circle cutting. Taking the forming of 12-inch wafers as an example, the current mainstream process is multi-wire cutting, because compared with inner circle cutting, multi-wire cutting has advantages such as high efficiency, good quality, and high wafer yield.

[0003] Multi-wire cutting is an advanced slicing processing technology at present. Its principle is to wind the cutting wire around a set of wire spools to form an array of cutting wire segments, and use the high-speed reciprocating motion of the cutting wire to bring the abrasive into the processing area of the material to be cut (such as a silicon rod) for grinding. The workpiece to be cut realizes vertical feeding through the lifting of the workbench, so as to cut the workpiece into several thin slices (such as wafers) of the required size and shape at the same time. Usually, the abrasive used in the multi-wire cutting process is preferably slurry, which can not only help with grinding but also play a cooling role during multi-wire cutting.

[0004] Currently, the cutting wires used in the multi-wire cutting process include ordinary steel wires and structured wires. The difference between ordinary steel wires and structured wires is that ordinary steel wires are composed of a cylindrical steel wire plus a copper-zinc alloy, while structured wires are based on ordinary steel wires and have twisted parts added in the axial and radial directions to make the cutting wire carry the cutting fluid more stably during the cutting process, and at the same time, the cutting ability is enhanced. However, as the cutting operation progresses, the cutting wire will deform due to stress and / or wear, and the deformation of the cutting wire will result in poor consistency of the thickness of the cut silicon wafers, especially the consistency of the thickness of multiple silicon wafers cut from the same silicon rod at one time. Therefore, in the wire cutting process, how to improve the thickness consistency of different silicon wafers has become an urgent problem to be solved in this field. Summary of the Invention

[0005] In view of this, embodiments of the present invention are expected to provide a wire cutting unit, a device, a silicon wafer, and a manufacturing method thereof; which can improve the problems of poor flatness and thickness difference of silicon wafers caused by factors such as temperature changes when the silicon rod is cut, changes in the diameter of particles in the cutting fluid, and wear and deformation of the cutting wire, and improve the yield of silicon wafers.

[0006] The technical solution of the embodiments of the present invention is implemented as follows:

[0007] In a first aspect, an embodiment of the present invention provides a wire cutting unit, which includes:

[0008] A cutting wire;

[0009] At least two wire spools arranged parallel to each other with a space therebetween, and a plurality of guiding grooves parallel to each other and spaced apart are provided on each wire spool. The cutting wire is wound around each guiding groove of each wire spool in sequence to form an array composed of a plurality of cutting line segments spanning across the at least two wire spools and parallel to each other. The array is used to cut a silicon rod into a plurality of silicon wafers at one time by moving along the extending direction of the cutting wire;

[0010] Wherein, the distance between adjacent guiding grooves among the plurality of guiding grooves is set according to a set rule along the arrangement direction of the plurality of cutting line segments according to the deformation of the cutting wire, so that the plurality of cut silicon wafers have a consistent thickness.

[0011] In a second aspect, an embodiment of the present invention provides a wire cutting device, which includes:

[0012] The wire cutting unit according to the first aspect;

[0013] A carrying unit for loading and fixing a silicon rod to be processed;

[0014] A movement control unit for controlling the movement of the wire cutting unit and / or the carrying unit, so that the wire cutting unit and the carrying unit move towards each other to cut the silicon rod.

[0015] In a third aspect, an embodiment of the present invention provides a method for manufacturing a silicon wafer, the method including:

[0016] Manufacturing a silicon wafer by using the wire cutting device according to the third aspect, including the following steps:

[0017] Loading and fixing a silicon rod through the carrying unit;

[0018] Controlling the wire cutting unit and the carrying unit loaded with and fixed with the silicon rod to move towards each other through the movement control unit to cut the silicon rod;

[0019] Cleaning and detecting the silicon wafers obtained after cutting the silicon rod.

[0020] In a fourth aspect, an embodiment of the present invention provides a silicon wafer obtained by using the wire cutting device according to the second aspect.

[0021] Embodiments of the present invention provide a wire cutting unit, a device, a silicon wafer and a manufacturing method thereof; according to the technical solution provided by the embodiments of the present invention, a plurality of guiding grooves for guiding a cutting wire are provided on a wire spool of the wire cutting unit. Since the distance between adjacent guiding grooves is set according to a set rule along the arrangement direction of the plurality of cutting wire segments according to the deformation of the cutting wire, the thickness difference between a plurality of silicon wafers obtained by cutting can be compensated due to the deformation of the cutting wire, thereby improving the thickness consistency of different silicon wafers. Description of the Drawings

[0022] Figure 1 is a schematic diagram of a conventional wire cutting device;

[0023] Figure 2 is a schematic diagram of another conventional wire cutting device;

[0024] Figure 3 is a schematic structural diagram of a conventional wire cutting unit;

[0025] Figure 4 is a schematic structural diagram of a wire cutting unit provided by an embodiment of the present invention;

[0026] Figure 5 is a partial schematic diagram of a cutting unit provided by an embodiment of the present invention;

[0027] Figure 6 is a partial schematic diagram of a cutting unit provided by another embodiment of the present invention;

[0028] Figure 7 is a partial schematic diagram of a cutting unit provided by still another embodiment of the present invention;

[0029] Figure 8 is a schematic structural diagram of a wire cutting device provided by an embodiment of the present invention;

[0030] Figure 9 is a flowchart of a method for manufacturing a silicon wafer provided by an embodiment of the present invention. Detailed Embodiments

[0031] Next, the technical solutions in the embodiments of the present invention will be clearly and completely described in conjunction with the accompanying drawings in the embodiments of the present invention.

[0032] Referring to Figure 1 , which shows a schematic diagram of a conventional wire cutting device 1. It can be understood that Figure 1 the shown structure is only for illustrative purposes of the principle, and does not mean that those skilled in the art will not add or subtract components based on the specific implementation state on the Figure 1 shown composition structure. The embodiments of the present invention do not make specific limitations on this. Figure 1As shown, the wire cutting device 1 may include a wire cutting unit 11 and a carrying unit 12; in some examples, the wire cutting unit 11 may be placed vertically below the carrying unit 12 as shown in Figure 1 , or may be placed vertically above the carrying unit 12 in some examples as shown in Figure 2 . Specifically, the wire cutting unit 11 may include a plurality of wire spools 111 and a cutting wire 112, and the cutting wire 112 is wound around the wire spools 111 to form an array composed of mutually parallel cutting line segments; in Figure 1 , the number of wire spools 111 is taken as an example of 2 for illustration, and the reciprocating movement directions of the wire spools 111 and the cutting wire 112 towards and away from the carrying unit 12 are as shown by the solid arrows in Figure 1 , and the reciprocating movement speed may exemplarily be 10 m / s to 15 m / s. The carrying unit 12 is used to load and fix the silicon rod 2 to be processed. In the example shown in Figure 1 , the carrying unit 12 may include a base 121 and a holding arm 122 mounted on the base 121. The holding arm 122 may clamp both ends of the silicon rod 2 to be processed along the axis direction of the silicon rod 2 to be processed to fix the silicon rod 2 to be processed. Of course, for those skilled in the art, it can be envisioned that the silicon rod 2 to be processed can also be fixed to the holding arm in other ways. For example, the silicon rod to be processed can be directly bonded to the lower surface of the holding arm through its outer peripheral surface to be fixed to the holding arm. In the example shown in Figure 2 , in addition to the base 121 and the holding arm 122 described in the foregoing example, the carrying unit 12 may further include a base 123 for carrying the silicon rod 2 to be processed.

[0033] For Figure 1 , 2 the wire cutting device 1 shown, the wire cutting unit 11 or the carrying unit 12 can be moved to enable the cutting wire 112 and the silicon rod 2 to be processed to move towards each other in the vertical direction. After the cutting wire 112 and the silicon rod 2 to be processed come into contact with each other, the cutting of the silicon rod 2 to be processed is realized by the movement of the cutting wire 112 along its extending direction. In the example shown in Figure 1 , the wire cutting unit 11 can be moved in the direction shown by the black arrow, or the carrying unit 12 can be moved in the direction of the dotted white arrow to realize the movement of the cutting wire 112 and the silicon rod 2 to be processed towards each other in the vertical direction. In the example shown in Figure 2In the illustrated example, the carrier unit 12 can be moved in the direction indicated by the black arrow, or the wire cutting unit 11 can be moved in the direction of the dotted white arrow, so as to achieve the relative movement in the vertical direction between the cutting wire 112 and the silicon rod 2 to be processed. It should be noted that in the embodiment of the present invention, a lifting device (not shown in the figure) is added to realize the movement of the wire cutting unit 11 or the carrier unit 12. It can be understood that those skilled in the art can also realize the movement of the wire cutting unit 11 or the carrier unit 12 in other ways according to actual needs and implementation scenarios, and the embodiment of the present invention will not elaborate on this.

[0034] In the conventional solution, a plurality of guiding grooves for guiding the cutting wire 112 are provided on the wire spool 111, and the guiding grooves are spaced apart from each other at uniform intervals, that is to say, the distance between adjacent guiding grooves is the same. The cutting wire 112 is wound around each guiding groove of each wire spool 111 in turn so that the cutting wire 112 forms an array composed of a plurality of cutting line segments. In this array, the cutting line segments are parallel to each other in order to cut the silicon rod into a plurality of silicon wafers at one time. However, in fact, during the process of cutting with the cutting wire carrying the cutting fluid, whether it is for ordinary steel wires or for structural wires, the cutting wire will at least bear the frictional force with the silicon rod and the tension force of the wire spool on it, and the cutting wire will also be worn during the cutting operation. These factors will cause the cutting wire to deform. For example, during the cutting process, if the cutting wire is fed generally in a single direction and other cutting conditions such as the state of the cutting fluid, temperature, etc. are the same, the cutting wire segment near its head will have a greater degree of deformation than the cutting wire segment near its tail because it participates in more cutting operations, and finally the cutting wire will gradually become thicker from the head to the tail along the feeding direction as a whole. For a cutting wire with deformation, if it is still wound around the wire spool at equal intervals, it will lead to poor consistency in the thickness of the cut silicon wafers. For example, referring to Figure 3 , in a conventional wire cutting unit, the length of the ingot is L, the number of slots required for the wire spool is N, the thickness of the silicon wafer is T, the distance between adjacent guiding grooves is a fixed value D, and the diameter of the cutting wire is d. If the diameter d of the cutting wire changes, for example, d1 > d2 > d3 > d4, then the thickness T of the silicon wafer also changes: T1 < T2 < T3 < T4. It should be noted that the cross-sectional shape of the guiding groove includes but is not limited to a rectangle, a triangle, etc.

[0035] Based on the above situation, the embodiment of the present invention expects to provide a solution for wire cutting a silicon rod, which can compensate for the thickness difference between the multiple silicon wafers obtained by cutting caused by the deformation of the cutting wire, so as to improve the thickness consistency of different silicon wafers.

[0036] Based on this, referring to Figure 4 , which shows a wire cutting unit 11 provided by the embodiment of the present invention. The wire cutting unit 11 includes:

[0037] Cutting line 112;

[0038] At least two spools 111 arranged spaced apart from each other and in parallel, with a plurality of guiding grooves 113 arranged parallel to and spaced apart from each other on each spool 111. The cutting line 112 is wound around each guiding groove 113 of each spool 111 in sequence to form an array AR composed of a plurality of cutting segments SE that span across the at least two spools 111 and are parallel to each other. The array AR is used to cut a silicon rod 2 into a plurality of silicon wafers at one time by moving along the extending direction of the cutting line 112;

[0039] Wherein, the spacing between adjacent guiding grooves among the plurality of guiding grooves 113 is set according to a set rule along the arrangement direction Y of the plurality of cutting segments SE according to the deformation of the cutting line 112, so that the plurality of cut silicon wafers have a consistent thickness.

[0040] The following takes Figures 4 to 6 as an example for illustration. The arrangement direction Y of the cutting segments SE refers to the direction from the first end 111A to the second end 111B of the spool 111. The spacings between two adjacent guiding grooves 113 are D1, D2, and D3 respectively. When the cutting line 112 is wound around the spool 111, the head of the cutting line 112 extends directly from the first end 111A of the spool 111, while the tail of the cutting line 112 extends directly from the second end 111B of the spool 111. As discussed above, in actual cutting operations, the shape and size of the cutting line, especially the shape and size of the cutting line in the diameter direction, are not fixed. Instead, there is a difference in the degree of deformation of the cutting segment SE located in the guiding groove 113 near the first end 111A and the cutting segment SE located in the guiding groove 113 near the second end 111B. To compensate for this difference, according to the embodiments of the present invention, the spacings D1, D2, and D3 are not set to be equal to each other as in the conventional scheme, but are set according to a set rule along the arrangement direction Y of the plurality of cutting segments SE according to the deformation of the cutting line 112. Thus, the distance between adjacent cutting segments SE can be changed by changing the spacing between adjacent guiding grooves to compensate for the deformation of the cutting line, so that the plurality of cut silicon wafers have a consistent thickness. Taking a silicon rod that can be cut into 400 silicon wafers at one time as an example, using a conventional wire cutting unit, the thickness difference of the 400 silicon wafers cut from the same silicon rod at one time will be greater than , while by using the wire cutting unit provided by the embodiments of the present invention, the thickness difference of the 400 silicon wafers is .

[0041] An embodiment of the present invention provides a wire cutting unit 11; according to the technical solution provided by the embodiment of the present invention, a plurality of guiding grooves 113 for guiding a cutting wire 112 are provided on a wire spool 111 of the wire cutting unit 11. Since the distance between adjacent guiding grooves 113 is set according to a set rule along the arrangement direction Y of the plurality of cutting line segments SE according to the deformation of the cutting wire 112, the thickness difference between a plurality of silicon wafers obtained by cutting due to the deformation of the cutting wire can be compensated, thereby improving the thickness consistency of different silicon wafers.

[0042] Regarding the determination of the distance between adjacent guiding grooves among a plurality of guiding grooves, specifically, refer to Figure 5 , assuming that n guiding grooves are provided to cut out N silicon wafers and the cutting wire is successively wound around the n guiding grooves to form n cutting line segments SE. Among them, the target silicon wafer thickness is T, and the diameters of the respective cutting line segments SE are d1, d2, d3, d4... in the arrangement order. Then, the distances D1, D2, D3... between adjacent guiding grooves are: , , ..., from which it can be determined that when n silicon wafers need to be cut, the distance between adjacent guiding grooves .

[0043] If the diameter change amount of the cutting line segment SE located in the nth guiding groove compared to the cutting line segment SE located in the 1st guiding groove during the cutting process is , then the distances D1, D2, D3... between adjacent guiding grooves can be further expressed as: , , ....

[0044] Through the above formulas, it can be further determined that when n guiding grooves need to be set to cut out N silicon wafers, the distance between the adjacent guiding grooves is obtained by Formula 1:

[0045] (1),

[0046] wherein, represents the distance between the nth guiding groove and the (n - 1)th guiding groove, T represents the target silicon wafer thickness, represents the initial diameter of the cutting wire, represents the diameter change amount of the cutting wire located in the nth guiding groove compared to the cutting wire located in the 1st guiding groove during the cutting process.

[0047] As can be seen from Equation (1), according to the embodiments of the present invention, the setting of the distance between the guiding grooves takes into account the diameter variation of the cutting wire, so as to compensate for this diameter variation by adjusting the distance between the guiding grooves. Only in this way can the actual distance between adjacent cutting line segments be made consistent with the target silicon wafer thickness during actual operation, and thus the multiple silicon wafers cut out have consistent thicknesses.

[0048] Regarding the diameter variation of the cutting wire in the nth guiding groove compared to the cutting wire in the 1st guiding groove during the cutting process can be obtained through Equation (2):

[0049] (2),

[0050] where K is the measured cutting wire wear coefficient.

[0051] As an example, through experiments, it is measured that after cutting out approximately 350 silicon wafers under the same conditions, for the steel wire, the deformation coefficient is approximately 0.9879, and for the structural wire, the deformation coefficient is approximately 0.9847. Then the corresponding cutting wire wear coefficients K are respectively for the steel wire: , for the structural wire: , from which the distance between adjacent guiding grooves can be calculated .

[0052] As analyzed above, if during the cutting operation, other cutting conditions do not change, such as the state of the cutting fluid, cutting temperature, etc., then the overall trend of the deformation of the cutting wire is to gradually become thinner. In view of this situation, preferably, the distance between adjacent guiding grooves among the multiple guiding grooves is set to gradually decrease along the arrangement direction of the multiple cutting line segments. Thus, the distance between each cutting line segment also gradually decreases, thereby compensating for the deformation of the cutting wire and enabling the multiple silicon wafers cut out to have consistent thicknesses.

[0053] In a conventional embodiment, the guiding grooves can be directly opened on the spool. However, in actual production, since the guiding grooves need to be in direct contact with the cutting wire and bear the wear caused by the cutting wire and the cutting fluid, in this case, the guiding grooves are also easily worn out. In order to facilitate the replacement of the worn guiding grooves and to be able to conveniently use guiding grooves spaced at different distances according to different production requirements, preferably, refer to Figure 6, taking the guiding groove with a triangular cross-section as an example, the wire cutting unit 11 includes a body 114 and a guiding portion 115 detachably mounted on the outer circumference of the body 114. The guiding groove 113 is provided on the guiding portion 115. According to this embodiment of the present invention, if the guiding groove 113 cannot be used continuously due to wear, or the distance between the guiding grooves 113 needs to be adjusted for different application requirements, it is only necessary to remove the current guiding portion 115 from the body 114 and install the target guiding portion 115 on the body 114, thereby significantly reducing the material cost and improving the production efficiency.

[0054] To achieve the flexibility of the arrangement of the guiding grooves 113, preferably, referring to Figure 7 , the guiding portion 115 includes a plurality of guiding units 1151 mounted side by side on the body 114. Each guiding unit 1151 includes one or more of the guiding grooves 113 and each guiding unit 1151 can be independently mounted and disassembled on the body 114. Thus, according to the actual production status or requirements, the guiding units 1151 can be combined to obtain a guiding portion 115 with a required arrangement scheme of the guiding groove spacing.

[0055] In a second aspect, referring to Figure 8 , an embodiment of the present invention further provides a wire cutting device CD, which includes:

[0056] The wire cutting unit 11 according to the first aspect;

[0057] A carrying unit 12 for loading and fixing the silicon rod to be processed;

[0058] A movement control unit 13 for controlling the movement of the wire cutting unit 11 and / or the carrying unit 12 so that the wire cutting unit 11 and the carrying unit 12 move towards each other to cut the silicon rod.

[0059] In a third aspect, referring to Figure 9 , an embodiment of the present invention further provides a method for manufacturing silicon wafers, which includes:

[0060] Manufacturing silicon wafers using the wire cutting device CD according to the second aspect, including the following steps:

[0061] S01: Loading and fixing the silicon rod through the carrying unit;

[0062] S02: Controlling the wire cutting unit and the carrying unit loaded with and fixed the silicon rod to move towards each other through the movement control unit to cut the silicon rod;

[0063] S03: Cleaning and detecting the silicon wafers obtained after cutting the silicon rod.

[0064] Fourthly, an embodiment of the present invention also provides a silicon wafer (not shown in the figure), and the silicon wafer is obtained by using the method according to the third aspect.

[0065] The silicon wafer obtained by using the method according to the third aspect has better thickness consistency compared with the silicon wafers produced by conventional techniques. Taking a single crystal bar that can be cut into 400 silicon wafers at one time as an example, when using a conventional wire cutting unit, the thickness difference of 400 silicon wafers cut from the same silicon bar at one time will be greater than , while by using the wire cutting unit provided in the embodiment of the present invention, the thickness difference of 400 silicon wafers is or so. Multiple silicon wafers with improved thickness uniformity can also be better processed in subsequent processing steps such as grinding and polishing steps. Especially in the steps where multiple silicon wafers are processed simultaneously, the finally obtained silicon wafers also have better flatness. For example, the flatness of the silicon wafers cut by the wire cutting equipment provided in the embodiment of the present invention can reach 500 - 1000 nm after experiencing subsequent conventional processing steps.

[0066] It should be noted that: among the technical solutions described in the embodiments of the present invention, they can be arbitrarily combined without conflict.

[0067] The above is only the specific implementation manner of the present invention, but the protection scope of the present invention is not limited thereto. Any person skilled in the art within the technical scope disclosed by the present invention can easily think of changes or substitutions, which should all be covered within the protection scope of the present invention. Therefore, the protection scope of the present invention should be subject to the protection scope of the claims.

Claims

1. A wire cutting unit, characterized in that, The wire cutting unit includes: A cutting wire; At least two spools arranged parallel to each other with a space therebetween, and a plurality of guiding grooves parallel to and spaced from each other are provided on each spool. The cutting wire is wound around each guiding groove of each spool in sequence to form an array composed of a plurality of cutting segments that span across the at least two spools and are parallel to each other. The array is used to cut a silicon rod into a plurality of silicon wafers at one time by moving along the extending direction of the cutting wire; Wherein, the spacing between adjacent guiding grooves among the plurality of guiding grooves is set according to the deformation of the cutting wire in accordance with a set rule along the arrangement direction of the plurality of cutting segments, so that the plurality of cut silicon wafers have a consistent thickness; When n guiding grooves need to be set to cut N silicon wafers, the spacing between adjacent guiding grooves is obtained by Equation 1: （1）， Wherein, represents the distance between the nth guiding groove and the (n - 1)th guiding groove, T represents the thickness of the target silicon wafer, represents the initial diameter of the cutting wire, represents the diameter change of the cutting wire in the nth guiding groove compared to the cutting wire in the 1st guiding groove during the cutting process; Represents the change in diameter of the cutting line located in the nth guiding groove compared to the cutting line located in the first guiding groove during the cutting process Obtained by Equation 2: （2）， Wherein, K is the measured wear coefficient of the cutting wire.

2. The wire cutting unit according to claim 1, wherein The spacing between adjacent guiding grooves among the plurality of guiding grooves is set to gradually decrease along the arrangement direction of the plurality of cutting segments.

3. The wire cutting unit according to claim 1, wherein The spool includes a body and a guiding part detachably mounted on the outer circumference of the body, and the guiding groove is provided on the guiding part.

4. The wire cutting unit according to claim 3, characterized in that, The guiding part includes a plurality of guiding units mounted side by side on the body. Each guiding unit includes one or more of the guiding grooves, and the spacing between each guiding unit is adjustable.

5. The wire cutting unit according to claim 4, characterized in that, Each guiding unit can be independently mounted and disassembled on the body relative to each other.

6. A wire cutting device, characterized in that, The wire cutting device includes: The wire cutting unit according to any one of claims 1 to 5; A carrying unit for loading and fixing a silicon rod to be processed; A movement control unit for controlling the movement of the wire cutting unit and / or the carrying unit, so that the wire cutting unit and the carrying unit move towards each other to cut the silicon rod.

7. A method for manufacturing a silicon wafer, characterized in that, The method includes: Manufacturing a silicon wafer using the wire cutting device according to claim 6, including the following steps: Loading and fixing the silicon rod through the carrying unit; Controlling the wire cutting unit and the carrying unit loaded with and fixed the silicon rod to move towards each other through the movement control unit to cut the silicon rod; Cleaning and detecting the silicon wafers obtained after cutting the silicon rod.

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