JP2008142842A - Wafer and method of manufacturing same - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a wafer having a main surface reduced in waviness and hard to be damaged and a method of manufacturing the wafer. <P>SOLUTION: In this method of manufacturing a wafer, at least one of a fixed abrasive grain wire tool and a member W to be machined is moved while moving at least one of the fixed abrasive grain wire tool and the member W to be machined in the moving direction Z intersecting with a predetermined axis X. The member W to be machined is cut while forming streaks drawing a curve C curved in one direction on the cutting surface Wx of the member to be machined along the moving direction Z. The angles of the streaks γa, γb on the straight lines Ma, Mb connecting one ends Va, Vb of the curve to the apex U of the curve C relative to a reference line Y connecting both ends of the curve C to each other are 1° or larger. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a wafer and a manufacturing method thereof.

  A wire tool is a tool that cuts a workpiece by pressing a wire traveled at a high speed against the workpiece (also referred to as a workpiece). Specifically, it is used for slicing that cuts out a thin plate (wafer) with high dimensional accuracy from a workpiece made of hard and brittle materials such as silicon, sapphire, quartz, and magnetic material stone.

  Such wire tools include a loose abrasive type and a fixed abrasive type. A free abrasive grain wire tool (free abrasive wire tool) is a wire tool that performs processing while rubbing a processing liquid (slurry), in which micron-size abrasive grains are mixed in a grinding liquid, against a workpiece by a wire. . A wire tool based on a fixed abrasive method (fixed abrasive wire tool) is a wire tool that performs processing using a wire in which abrasive grains are directly fixed to a surface. This fixed-abrasive wire tool has the advantage that the machining efficiency is high, although the machining accuracy is inferior to that of the loose-abrasive wire tool.

On the other hand, there is also a device having a rocking mechanism for rocking the wire side or the workpiece side during cutting. This rocking mechanism has the advantage of improving the machining accuracy by improving the discharge of chips during cutting. For example, Patent Document 1 describes a fixed abrasive wire tool that can maintain the sharpness of a wire tool for a long time by cutting an ingot while applying minute vibrations to the wire row.
Japanese Patent Laid-Open No. 11-77510

  However, in the above-mentioned fixed abrasive wire tool, a detailed examination on the swing angle (swing angle) has not been made. Further, even if the swing angle (2θ = 0 to 4 °) often set for the loose abrasive wire tool is applied to the fixed abrasive wire tool, a wafer with a large waviness of the main surface is formed. End up. In addition, linear streaks formed on the main surface of the wafer during swinging may easily damage the wafer.

  The present invention has been made in view of the above circumstances, and an object of the present invention is to provide a wafer in which the undulation of the main surface is reduced and is not easily damaged, and a method for manufacturing the same.

  The method for manufacturing a wafer according to the present invention includes cutting a member to be processed extending along a predetermined axis with a fixed abrasive wire tool in which a wire having abrasive grains fixed on a surface thereof is wound around a plurality of spindle rollers. The at least one of the fixed abrasive wire tool and the workpiece is moved while moving at least one of the fixed abrasive wire tool and the workpiece in a moving direction intersecting a predetermined axis. By swinging, the workpiece is cut while forming a plurality of traces that draw a curved curve in one direction on the cutting surface of the workpiece along the moving direction. The angle of the streak formed by the straight line connecting the vertices with respect to the reference line connecting both ends of the curve is set to 1 ° or more.

  According to the wafer manufacturing method of the present invention, the angle of the streak (streak angle) formed by the straight line connecting one end of the curve drawn by the streak and the vertex of the curve with respect to the reference line is 1 ° or more. In this way, the waviness of the main surface of the wafer is reduced as compared with the case of forming a streak having a streak angle of less than 1 °. Further, the curvature of the curve drawn by the streak is increased as compared with the case where the streak angle is less than 1 °. This increase in curvature makes it difficult for stress generated in the streak to concentrate in one direction, so that a wafer that is not easily damaged can be formed.

  Here, the streak angle is preferably 3 to 6 °. In this way, the waviness of the main surface is further reduced as compared with the case where the streak of less than 3 ° or more than 6 ° is formed. Further, it is possible to form a wafer that is less likely to be damaged as compared with the case where the streak angle is less than 3 °.

  In addition, the wafer according to the present invention has a plurality of streaks that draw a curve curved in one direction on the main surface of the wafer, and a straight line connecting one end of the curve and the vertex of the curve connects the both ends of the curve The angle of the streak is 1 ° or more.

  According to the wafer of the present invention, the angle of the streak (streak angle) formed by the straight line connecting one end of the curve drawn by the streak and the vertex of the curve with respect to the reference line is 1 ° or more. According to this, the waviness of the wafer main surface is reduced as compared with a wafer having a streak angle of less than 1 °. In addition, the curvature of the curve drawn by the streak is increased as compared with the case where the streak angle is less than 1 °. When the curvature is increased, the stress generated in the streak becomes difficult to concentrate in one direction, and thus damage to the wafer is prevented.

  Here, the streak angle is preferably 3 to 6 °. According to this, the waviness of the main surface is further reduced as compared with a wafer having a streak angle of less than 3 ° or more than 6 °. Further, the wafer is prevented from being damaged as compared with a wafer having a streak angle of less than 3 °.

  According to the wafer and the manufacturing method thereof of the present invention, it is possible to provide a wafer and a method of manufacturing the same in which the undulation of the main surface is reduced and is not easily damaged.

  Hereinafter, embodiments of the present invention will be described with reference to the accompanying drawings. In the description of the drawings, the same elements are denoted by the same reference numerals, and redundant description is omitted. For the convenience of illustration, the dimensional ratios in the drawings do not necessarily match those described.

  First, a schematic configuration of a fixed abrasive wire tool to which the wafer manufacturing method according to the first embodiment is applied will be described with reference to FIG. Here, FIG. 1 is a diagram schematically showing a fixed abrasive wire tool for performing the manufacturing method according to the present embodiment.

  As shown in FIG. 1, the fixed abrasive wire tool 100 includes three spindle rollers 10, 11, 12, a plurality of guide pulleys 20, a pair of wire reels 30 </ b> A, 30 </ b> B, a wire 50, and a swing plate. 60. The fixed abrasive wire tool 100 may not include the main shaft roller 10 or may include a further main shaft roller.

  The wire 50 is obtained by fixing abrasive grains such as diamond to the outer peripheral surface of a wire made of steel or the like by a known method.

  Both ends of the wire 50 are wound around a wire reel 30A and a wire reel 30B. The wire reels 30A and 30B are installed so as to be drivable by a driving means (not shown) such as a motor, and can feed and wind the wire 50 from the wire reel 30A to the wire reel 30B. During the operation of the fixed abrasive wire tool 100, the wire reels 30A and 30B alternately perform the feeding and winding operations of the wire 50, and slide the wire row 50C (described later) on the workpiece W. I do.

  An intermediate portion of the wire 50 is wound around three main shaft rollers 10, 11, and 12 that are rotatably provided via a guide pulley 20. A plurality of rows of parallel wire guide grooves are formed in the main shaft rollers 10, 11, and 12 at a constant pitch. The wires 50 guided by the wire guide grooves form a wire row 50C. During operation of the fixed abrasive wire tool 100, the wire row 50C directly contacts the workpiece W to cut the workpiece W.

  The main shaft rollers 10, 11, 12 are pivotally supported on the same swing plate 60. The swinging plate 60 is swingably installed by swinging means (not shown), and performs a swinging operation (described later) that swings the wire row 50C when the fixed abrasive wire tool 100 is operated. For example, when the spindle rollers 10, 11, and 12 form an equilateral triangle, the swing plate 60 swings the wire row 50C while fixing the center of gravity of the triangle.

  A work table 40 is provided below the wire row 50C. A workpiece W extending in the direction of the axis X is placed on the work table 40. The workpiece W is, for example, a columnar member. The work table 40 is installed so as to be movable up and down by a known vertical movement means (not shown), and when the fixed abrasive wire tool 100 is operated, the work table 40 is machined in the movement direction Z intersecting the axis X, for example, the vertical direction. The member W is moved. Regarding the movement of the workpiece W in the movement direction Z, the fixed abrasive wire tool 100 may be moved, or both the fixed abrasive wire tool 100 and the workpiece W may be moved.

  Further, the workpiece W may be placed on the work table 40 via a base (not shown) made of carbon, resin, glass, or the like. In this way, the workpiece W can be processed without damaging the work table 40 even when the fixed abrasive wire tool 100 is swung.

  Next, with reference to FIGS. 1-3, operation | movement of the fixed abrasive wire tool 100 is demonstrated, and the wafer manufacturing method which concerns on this embodiment is demonstrated collectively. Here, FIG. 2 is a diagram showing the operation of the fixed abrasive wire tool of FIG. FIG. 3 is a diagram illustrating a state of a cut surface of a workpiece to be processed at the time of processing.

  When the operation of the fixed-abrasive wire tool 100 is started, the wire reels 30A and 30B alternately perform the wire 50 feeding and winding operations. At the same time, as shown in FIG. 1, while the workpiece W is moved in the movement direction Z, the wire row 50C rocked by the rocking plate 60 directly contacts the workpiece W and cuts the workpiece W. Processing.

  At this time, the wire row 50 </ b> C is swung around a reference plane orthogonal to the movement direction Z. Specifically, as shown in FIG. 2, the fixed abrasive wire tool 100 alternates between two states, an inclined state 100a and an inclined state 100b. Here, 10a, 11a, and 12a are spindle rollers in the inclined state 100a, P1a and P2a are contact points between the wire row 50C and the spindle rollers 10a, 11a, and 12a, and La is a straight line that connects the contact points P1a and P2a. Similarly, for the reference numerals related to the inclined state 100b, 10b, 11b, and 12b are the main shaft rollers in the inclined state 100b, P1b and P2b are the contacts between the wire row 50C and the main shaft rollers 10b, 11b, and 12b, and Lb is the contacts P1b and P2b. A straight line connecting the two is shown. Q indicates the intersection of the straight lines La and Lb, and the reference plane S is set as a plane that includes the intersection Q and is orthogonal to the movement direction Z. The reference plane S is, for example, a horizontal plane.

  The straight lines La and Lb correspond to the wire rows 50C in the inclined states 100a and 100b, respectively. The angles −θ and + θ formed by the straight lines La and Lb and the reference surface S indicate the maximum inclination angles at which the wire row 50C can be inclined with respect to the reference surface S. When the angle between the tilted state 100a and the tilted state 100b of the fixed abrasive wire tool 100 is defined as the swing angle, the swing angle is represented by 2θ. In addition, all the codes | symbols which show the angle described in a specification show an absolute value.

  When the wire row 50C swings, the inclination angle of the wire row 50C with respect to the reference plane S continuously changes from −θ to 0 through + θ or vice versa. Therefore, as shown in FIG. 3, the workpiece W is cut while a streak that draws a curved line C curved in one direction on the cutting surface Wx of the workpiece W along the movement direction Z is formed. .

  Here, U is the vertex of curve C, Va and Vb are end points of curve C, Ma is a straight line connecting vertex U and end point Va, Mb is a straight line connecting vertex U and end point Vb, and Y is connecting end point Va and end point Vb. Reference line, γa indicates a streak angle formed by the reference line Y and the straight line Ma, γb indicates a streak angle formed by the reference line Y and the straight line Lb, and a hatched part indicates a cut processed part. The streak angles γa and γb satisfy 1 ° ≦ γa or 1 ° ≦ γb because of the advantages described later. In addition, since cutting is performed while the workpiece W is moved in the movement direction Z, streaks that draw a plurality of curves having the same streak angles γa and γb as the curve C are formed on the cut surface Wx. Is done.

  Next, the wafer according to the present embodiment will be described with reference to FIG. Here, FIG. 4 is a view showing the main surface of the wafer according to the embodiment.

  When the workpiece W is moved in the movement direction Z and the above-described cutting process is performed while a plurality of streaks are formed on the cutting surface Wx of the workpiece W, finally, the workpiece W A thin wafer is cut. On the main surface of the cut wafer, as shown in FIG. 4, streaks are formed that draw a plurality of curves C1, C2, and C3 curved in the same direction as the movement direction Z of the workpiece W.

  Here, U1 is the vertex of the curve C1, Va1 and Vb1 are the end points of the curve C1, Ma1 is a straight line connecting the vertex U1 and the end point Va1, Mb1 is a straight line connecting the vertex U1 and the end point Vb1, and Y1 is connecting the end point Va1 and the end point Vb1. The reference line, γa is the streak angle formed by the reference line Y1 and the straight line Ma1, γb is the streak angle formed by the reference line Y1 and the straight line Mb1, Z1 is the bending width of the curve C1 with respect to the reference line Y1, and X is The axis of wafer main surface Wfx is shown, respectively. The same applies to the element codes related to C2 and C3.

  The main surface Wfx of the wafer Wf corresponds to the above-described cutting surface Wx. In FIG. 4, only three stripes are shown for the sake of space, but for example, in the case of a 2-inch wafer, the stripes are formed at intervals of about 200 [μm].

The bending width Z2 with reference to the reference line Y2 passing through the axis X is Z2 = Rtanγa (1) where R is the work radius.
Sought by. When the streak angle γa, which is an acute angle, increases, the curvature width Z2 increases, so the curvature of the curve C2 increases. Also for the curves C1 and C3, since the value of the work radius R in the above equation is only replaced with another value, the curvature of the curves C1 and C3 increases as the streak angle γa increases. In the above formula, a streak angle γb may be used instead of the streak angle γa.

  Next, advantages of the wafer and the wafer manufacturing method according to the present embodiment will be described with reference to FIGS. Here, FIG. 5 shows the maximum waviness of filtered WCM (see JIS B 0610) and streak angle γ on the main surface of a 2-inch sapphire wafer cut out at a processing speed v = 16.9 [mm / h] (constant). It is a graph which shows the result of having measured the relationship. FIG. 6 is a graph showing the results of measuring the relationship between the rocking angle 2θ and the streak angle γ. FIG. 7 is a table showing the relationship between the measured value of the streak angle and the average value. The streak angle γ shown in FIG. 7 indicates the average value of the above-mentioned streak angles γa and γb (γ = (γa + γb) / 2). When the streak angle γ satisfies 1 ° ≦ γ, at least one of 1 ° ≦ γa and 1 ° ≦ γb holds with respect to the streak angles γa and γb.

  Referring to FIG. 5, when the streak angle γ satisfies 1 ° ≦ γ, the WCM is reduced to 30 [μm] or less. This is a value of about ½ compared to the conventional WCM (γ = 0 °). Furthermore, it is preferable that the streak angle γ satisfies 3 ° ≦ γ ≦ 6 °. In this way, the WCM is reduced to 15 [μm] or less. This is a value of about 1/3 compared with the conventional WCM (γ = 0 °).

  Referring to FIG. 6, it can be seen that when forming a streak having a streak angle γ of 1 ° ≦ γ, the swing angle 2θ may be set in a range of 6 ° ≦ 2θ. It can also be seen that when forming a streak having a streak angle γ of 3 ° ≦ γ ≦ 6 °, the swing angle 2θ may be set in a range of 12 ° ≦ 2θ ≦ 16 °.

  WCM corresponds to the amount of waviness of the wafer main surface Wfx. Therefore, when WCM is reduced, the waviness of wafer main surface Wfx is reduced, and the processing accuracy of wafer Wf is improved. Conventionally, in order to improve the wafer processing accuracy, it has been necessary to increase the wafer processing time. However, if the wafer processing accuracy is improved as described above, the increment of the wafer processing time can be reduced.

  Next, with reference to FIG. 8 to FIG. 11, consideration for the swing angle 2θ performed by the present inventor will be described. FIG. 8 is a diagram for explaining the swing angle and the amount of bending of the wire. 9 to 10 are diagrams showing calculation results of the difference between the swing width 2T and the deflection amount D in the case of a 2 to 4 inch wafer.

  It is important to perform processing so as not to bend the wire in the loose abrasive wire tool, but it is necessary to perform the processing while giving the wire proper bending in the fixed abrasive wire tool. The present inventor has found that the machining efficiency is good when the deflection amount of the fixed abrasive wire is n [mm] in the machining of the workpiece W having a workpiece diameter of n [inch].

  Here, with reference to FIG. 8, a condition (a condition for improving the machining efficiency) in which the contact width between the wire that swings with bending and the workpiece is shortened is approximately obtained. In FIG. 8, D is the amount of bending of the wire in the moving direction Z, Wx1 and Wx2 are contact portions between the wire 50 and the workpiece W, R is the work radius, 2T is the swinging width, and the hatched portion is the cut and processed portion. , Respectively.

Further, in FIG. 8, it is assumed that when the cylindrical workpiece W is processed, processing near the center where the contact width is relatively large is assumed. In order for the wire 50 to contact one of the contact portions Wx1 and Wx2 when the wire 50 swinging at the swing angle 2θ is inclined,
2T-D> 0 (2)
Should be satisfied. Here, since the oscillation width 2T is approximately represented by 2T = 2Rtanθ, the above equation is
tanθ> D / (2R) (3)
Can be described.

The workpiece radius R [mm] is expressed as R = 12.7n with respect to the workpiece diameter n [inch], and the fixed abrasive wire tool that improves the machining efficiency with respect to the workpiece having the workpiece diameter n [inch]. The deflection amount D is expressed as D = n [mm]. Therefore, when machining the vicinity of the central axis of the cylindrical workpiece W, the swing angle 2θ [°] may satisfy the following equation.
2θ> (360 / π) arctan (1 / 25.4) (4)

  Referring to the calculation results of 2T-D shown in FIGS. 9 to 11, the condition that satisfies 2T−D> 0 in the workpiece of 2 to 4 inches is θ ≧ 3 °. This condition matches the swing angle lower limit condition 2θ ≧ 6 ° described in FIGS. The work radius R and the wire deflection amount D shown in FIGS. 9 to 11 show different values for each figure. The values of the workpiece radius R and the wire deflection amount D in FIGS. 9 to 11 are R = 25.4 [mm], D = 2 [mm] in FIG. 9 (in the case of 2 inches), and FIG. In the case of inch), R = 38.1 [mm] and D = 3 [mm], and in FIG. 11 (in the case of 4 inch), R = 50.8 [mm] and D = 4 [mm]. .

  As described above, in the wafer and the manufacturing method thereof according to this embodiment, the straight lines Ma1 that connect the ends Va1 to Va3 of the plurality of curves C1 to C3 drawn by the streak and the vertices U1 to U3 of the curves C1 to C3, respectively. The streak angle γa formed by Ma3 with respect to the reference lines Y1 to Y3 is 1 ° or more. Alternatively, the streak angles that the straight lines Mb1 to Mb3 connecting the ends Vb1 to Vb3 of the curves C1 to C3 drawn by the streak and the vertices U1 to U3 of the curves C1 to C3 form with respect to the reference lines Y1 to Y3, respectively. γb is 1 ° or more.

  In this case, from the measurement result of FIG. 5, the WCM is reduced to about ½ compared to the case where the streak angle γ = 0 °. Therefore, the waviness of wafer main surface Wfx is reduced. This is considered to be due to the fact that the contact width of the wire with respect to the workpiece W is reduced to half or less compared to the case of 2θ <6 °, that is, γ <1 °, from the consideration of FIGS. Further, compared to the case where the streak angle γa is less than 1 °, the curvature widths Z1 to Z3 are increased from the equation (1), and thus the curvatures of the curves C1 to C3 drawn by the streak are increased. This increase in curvature makes it difficult for stress generated in the streak to concentrate in one direction, thereby preventing damage to the wafer.

  Here, if the streak angle γ satisfies 3 ° ≦ γ ≦ 6 °, the WCM is reduced to about 1/3 as compared with the case of γ = 0 ° from the measurement result of FIG. Wfx swell is further reduced. Further, since the curvature of the curve drawn by the streak is further increased as compared with the case where the streak angle is less than 3 °, damage to the wafer is further prevented.

  The wafer and the manufacturing method thereof according to the present invention are not limited to the above-described embodiment, and may be a modification of the above-described embodiment without changing the gist described in each claim.

  For example, in the present embodiment, the wafer manufacturing method in which the streak angle is formed by swinging the swinging plate that supports the spindle roller has been shown. However, by swinging the work table that fixes the workpiece, It may be a method of forming streak corners.

It is a figure showing roughly the fixed abrasive wire tool which enforces the manufacturing method concerning this embodiment. It is a figure which shows operation | movement of the fixed abrasive wire tool of FIG. It is a figure which shows the mode of the cut surface of the to-be-processed member at the time of a process. It is a figure which shows the main surface of the wafer which concerns on embodiment. It is a graph which shows a streak angle versus WCM characteristic. It is a graph which shows a rocking angle vs. streak angle characteristic. It is a table | surface which shows the relationship between the measured value of a streak angle, and an average value. It is a figure explaining the rocking | fluctuation angle and the bending amount of a wire. It is a calculation result which shows the difference of the rocking | fluctuation width in the case of a 2-inch wafer, and bending amount. It is a calculation result which shows the difference of the rocking | fluctuation width in the case of a 3-inch wafer, and bending amount. It is a calculation result which shows the difference of the rocking | fluctuation width in the case of a 4-inch wafer, and bending amount.

Explanation of symbols

  10, 10a, 10b, 11, 11a, 11b, 12, 12a, 12b ... main shaft roller, 20 ... guide pulley, 30A, 30B ... wire reel, 40 ... work table, 50 ... wire, 50C ... wire row, 60 ... rocking Moving plate, 100, 100a, 100b ... fixed abrasive wire tool, C, C1, C2, C3 ... streak, P1a, P1b ... contact, S ... reference plane, U, U1, U2, U3 ... vertex of curve, Va , Va1, Va2, Va3, Vb, Vb1, Vb2, Vb3 ... curve end points, W ... workpiece, Wx ... cutting surface, X ... predetermined axis, Y, Y1, Y2, Y3 ... reference line, Z ... Movement direction, La, Lb: straight line connecting the contacts, Ma1, Ma2, Ma3, Mb1, Mb2, Mb3, a straight line connecting the vertex and the end point, 2θ: swing angle, + θ, -θ: inclination angle, γ, γa, γb ... streak corners.

Claims (4)

A method of manufacturing a wafer by cutting a workpiece extending along a predetermined axis with a fixed abrasive wire tool in which a wire having abrasive grains fixed on a surface is wound around a plurality of spindle rollers,
While moving at least one of the fixed abrasive wire tool and the workpiece to be moved in a moving direction intersecting the predetermined axis,
By swinging at least one of the fixed abrasive wire tool and the workpiece, a plurality of striations that draw a curved curve in one direction on the cut surface of the workpiece along the moving direction are formed. While forming, cut the workpiece,
A method for manufacturing a wafer, wherein an angle of the stripe formed by a straight line connecting one end of the curve and a vertex of the curve with respect to a reference line connecting both ends of the curve is 1 ° or more.
The wafer manufacturing method according to claim 1, wherein the angle is 3 to 6 °.
A plurality of streaks that draw a curve curved in one direction on the main surface of the wafer, and a straight line connecting one end of the curve and a vertex of the curve is formed with respect to a reference line connecting both ends of the curve A wafer whose streak angle is 1 ° or more.
The wafer according to claim 3, wherein the angle is 3 to 6 °.

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