JPH0115363B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a single crystal cutting method for rapidly cutting a single crystal member.

BACKGROUND ART Recently, single crystal members such as silicon single crystal, lithium tantalate (LiTaO ₃ ), and sapphire (Al ₂ O ₃ ), which are mainly used as materials for semiconductors, are cut with a wire saw, a blade saw, or the like. The above-mentioned cutting method has the advantage of higher machining accuracy than other machining methods, but on the other hand, it has the drawback that the machining speed is particularly slow. In other words, single-crystal parts have a unique anisotropy, and depending on the crystal orientation in which the cut is made, chips are less likely to form and are also less likely to be ejected together with the abrasive grains, resulting in significantly lower machining efficiency compared to other crystal orientations. do. Moreover, in such cases, the cut wafers often become bent or warped, causing various accidents. Nevertheless, in the past, no effective measures have been taken for cutting single crystal members, and the current state is that they are cut at random. Therefore, there is a need for an efficient method for cutting single crystal members.

The present invention has been made in consideration of the above circumstances,
A positive rotation angle is defined as the direction in which chips of the single crystal member are discharged with respect to a normal line that is on the planned cutting plane of the single crystal member and perpendicular to the line of intersection between this planned cutting plane and the cleavage plane. The cutting efficiency is determined by the crystallographic properties of the single crystal member having The object of the present invention is to provide a method for cutting single crystals that is significantly improved.

The present invention will be explained in detail below.

First, in order to determine the optimal insertion direction for cutting a single crystal member, a preliminary test called a zone slicing test as described below is performed. That is,
As shown in Figure 1, a cylindrical single-crystal member 2 having an end face 1 having the same crystal orientation relationship as the planned cut plane of the single crystal to be actually cut is rotated at high speed in the direction of arrow 3. A constant load is applied via the blade processing tool 4, and the single crystal member 2 is rotated in the direction of arrow 5 at a constant rotation speed lower than that of the peripheral blade processing tool 4, thereby forming grooves on the outer peripheral surface of the single crystal member 2. Perform processing. Chips of the single crystal member 2 formed by this zone slicing test are discharged in the direction of arrow 6. Also, in the same way, move the single crystal member 2 to the arrow 7
The zone slicing test is performed by rotating the peripheral cutting tool 4 in the direction of arrow 8. At this time, the chips are discharged in the direction of arrow 9. The depths of the grooves 10 formed by the above zone slicing test in mutually opposite directions are not concentric, and the depths of the grooves 10 are not concentric, and the depths of the grooves 10 are not concentric. It has unique undulations mainly due to the magnitude of the pressure contact load with the tool 4.
The depth of the groove 10 is uneven, indicating the difficulty of cutting. In other words, when the rotation of the single crystal member 2 is stopped, the deeper the groove 10 is cut by the processing tool, the more the material is removed under a constant load and the constant rotational speed of the tool, that is, the cutting efficiency increases. It means high. In short, the direction of cutting from the deep groove 10 is the direction of easy cutting. By the way, the second
The figure shows the depth of the groove formed by carrying out the above-mentioned zone slicing test on a single crystal of lithium tantalate, and the measured values are blotted from the center of the polar coordinates. In this figure, the plane of the paper is the planned cutting plane of crystal planes 1, 0, 0. In this case, cleavage planes (not shown) of the single crystal member 2 appear as intersecting lines A and B on the planned cutting plane. Further, the groove depth curve 11 corresponds to the case where the chip discharge direction is counterclockwise in FIG. 2, and the groove depth curve 12 corresponds to the case where the chip discharge direction is clockwise. Groove depth curve 1 above
1 and 12 have approximately rotational symmetry with respect to the center point 13 in this figure. From this figure, the positions where the cutting efficiency is maximum are points 14, 15, 16, and 17 when the chip discharge direction is counterclockwise, and points 14, 15, 16, and 17 when the chip discharge direction is clockwise in Figure 2. In this case, the positions where the cutting efficiency is maximum are points 18, 19,
20, 21. In other words, as shown in the figure, the cutting direction in which cutting efficiency is maximized is either clockwise or counterclockwise from the normal lines P and Q perpendicular to the intersection lines A and B, respectively, toward the chip discharge direction. Z ₁ tilted by rotation angle θ ₁ , θ ₂ , θ ₃ , θ ₄ , θ ₅ , θ ₆ , θ ₇ , θ ₈
，
These are the Z ₂ , Z ₃ , Z ₄ , Z ₅ , Z ₆ , Z ₇ , and Z ₈ directions. In the case of lithium tantalate, the specific values of the rotation angles above are θ ₁ = 24°, θ ₂ = 7°, θ ₃ = 16°, θ ₄ = 8°, θ ₅
is 20°,
θ ₆ is 17°, θ ₇ is 16°, and θ ₈ is 5°, and the examples described later are also based on these values. Similar findings have been demonstrated for other single crystals such as silicon and ferrite. Thus, the proper cutting direction of the processing tool is perpendicular to the intersection lines A and B between the planned cutting plane of the single crystal member 2 and the cleavage plane of this single crystal member 2, and the normals P and Q on the above planned cutting plane. It is possible to infer an empirical rule that the direction is inclined toward the chip discharge direction. This rule of thumb is that in conventional polishing of single crystal members, if the cut is made on the planned cut plane of the single crystal member and in the normal direction perpendicular to the intersection of this planned cut plane and the cleavage plane, the polishing Despite the known fact that efficiency is greatly improved,
This is to determine the proper direction of cut in the cutting process. However, in cutting a single crystal member, unlike simple polishing, the processing efficiency is greatly affected by the chip formation mechanism and the efficiency of discharging the formed chips. Therefore, the optimal direction of cut for cutting is not the normal direction perpendicular to the intersection line on the planned cutting plane, as is the case with grinding, but is slightly inclined toward the chip ejection direction with respect to this normal. It is thought that the direction is oriented.

Next, a detailed description will be given based on a specific example. FIG. 3 shows the main parts of a multi-wire saw used in the single crystal cutting method of the present invention. This multi-wire saw is a conventionally known multi-wire saw equipped with a rotation mechanism 22 that rotates a cylindrical single crystal member 2 by a predetermined amount about its axis. This rotation mechanism 22 is placed on a processing table 23 that can be raised and lowered in the directions of arrows S ₁ and S ₂ by a processing table elevating mechanism (not shown). A wire drive mechanism 24 is provided above the processing table 23. This wire drive mechanism 24 is suspended so that a processing tool 25 made of a plurality of wires can reciprocate in the directions of arrows M and N. Although not shown, the wire drive mechanism 24 is provided with a switching detector, such as a limit switch, which detects switching from forward movement to backward movement and outputs an electrical signal. Inside the rotation mechanism 22, a pulse motor (not shown) capable of forward and reverse rotation is built-in. The rotation angle of this pulse motor can be precisely controlled, and a part of the rotation shaft protrudes from the case front surface 26 of the rotation mechanism 22, and a cylindrical holder 27 is pivotally supported by the protrusion. There is. This holding body 2
One end face of the cylindrical single crystal member 2 is attached to the end face 28 of 7 with a high performance adhesive.
Further, a control device 29 is installed separately from the multi-wire saw body. This control device 29 is electrically connected to the wire drive mechanism 24 via a line 30, to the processing table lifting mechanism via a line 31, and to the rotating mechanism 22 via a line 32.
In this control device 29, the holding body 2
7 rotation angle θ, processing tool 25 and single crystal member 2
The pressure welding load value is set. Further, two slurry supply pipes 34 are provided protruding from the case front surface 26 to supply a slurry 33 consisting of oil and free abrasive grains to the sliding contact portion between the processing tool 25 and the single crystal member 2.

Next, the single crystal cutting method of the present invention will be explained along with the operation of the apparatus.

As the single-crystal member to be cut, lithium tantalate is used, which has the cutting efficiency characteristics of the planned cutting surface shown in FIG. 2, which were determined in advance by the above-mentioned zone slicing test. In FIG. 2, assuming that the contour 35 is the planned cutting surface of the single crystal member 2, the appropriate cutting positions on this contour 35 are points 36, 37, 38, 39, 40, 41, 4.
2.43. Therefore, one end surface of the single-crystal member 2 is cut into high-performance parts so that the processing tool 25 contacts the points 36 among these points and the center point 13 of the single-crystal member 2 coincides with the center of rotation of the holder 27. It is fixed to the holder 27 using an adhesive. Thereafter, the rotation angle θ, which is the sum of the rotation angle θ ₁ and the rotation angle θ ₂ , is set in the control device 29 . At the same time, the pressure contact load is determined and set in the control device 29. Then, the slurry 33 is radiated from the slurry supply pipe 34 to the sliding contact area between the processing tool 25 and the single crystal member 2, and the wire drive mechanism 24 is driven to move the processing tool 25 to the arrow N in FIG.
move in the same direction. At this time, the processing table 23 controls the processing tool 25 based on the command from the control device 29.
and the single-crystal member 2 are raised in the direction of arrow _S1 so that they come into sliding contact with each other under a constant pressure load.

The processing tool 25 is a second tool for the single crystal member 2.
Cut in the direction of arrow Z ₁ tilted counterclockwise by rotation angle θ ₁ from the normal Q in the figure. The chips of the single crystal member 2 crushed and formed by the processing tool 25 are discharged together with the free abrasive grains of the slurry 33 in the direction of arrow N, that is, in the direction of arrow 44, which is tangent to point 36 on outline 35 in FIG. be done. Thus, when the forward movement in the direction of arrow N ends and the movement is switched to the backward movement in the direction of arrow M, an electric signal E is outputted from the switching detector to the control device 29 via the line 30 in FIG. 3.
Based on this electric signal E, the control device 29 outputs an electric signal R to the rotation mechanism 22 for rotating the holding body 27 by a preset rotation angle θ. This electric signal R causes the pulse motor to reverse in the direction of the arrow V in FIG.
Slide into contact with 5. Thereafter, the machining tool 25 moves back in the direction of arrow M in FIG.
Cut into the single-crystal member 2 from the direction of arrow Z ₂ , which is inclined by a rotation angle θ ₂ to the side. The chips formed at this time are discharged in the direction of arrow 45, which is tangent to point 37 on outline 35 in FIG. However, arrow M
When the backward motion in the direction is completed, the switching detector outputs the electric signal E again, the holder 27 rotates in the direction of the arrow W by the rotation angle θ, and the processing tool 25 is tilted from the normal Q by the rotation angle θ ₁ . Cut in the direction of arrow Z ₁ . In this way, the rotation mechanism 22 continues cutting until the desired wafer is separated while switching to the position where the cutting efficiency is maximized in each of the forward and backward movements. In this case, the cutting position is not limited to points 36 and 37 in Fig. 2 as described above, but also points 38 and 39.
combination, combination of point 40 and point 41, point 42
It is also possible to cut at a combination of and point 43. Further, as long as the cutting surface is of the same type and planned to be cut, the appropriate cutting direction is known, so cutting can be continued promptly using the same procedure.

Therefore, in this embodiment, the cutting efficiency is increased by 10% to 90% compared to the case where the cutting is performed from the direction where the cutting removal speed is the minimum.

As mentioned above, the single crystal cutting method of the present invention is performed on the planned cutting plane of the single crystal, and in the direction in which the chips of the single crystal member are discharged with respect to the normal line perpendicular to the intersection line between the planned cutting plane and the cleavage plane. is a positive rotation angle, and a cut is made from the direction of maximum cutting efficiency determined by the crystallographic properties of the single crystal member with this positive rotation angle and the pressure contact force between the single crystal member and the processing tool. This method cuts parts, and compared to conventional methods of cutting single-crystal parts, the cutting and removal efficiency is significantly improved, and cutting processing time, which used to be wasted over a long period of time, can be reduced to the maximum. Furthermore, since excessive strain is not applied to the single crystal member during processing, the cut wafers do not suffer from bending or warping, which is extremely beneficial in terms of quality control. Furthermore, even when performing a new cutting process, the direction of maximum cutting efficiency can be easily and easily determined by the zone slicing test, which further expands the versatility of this method. Further, when cutting a single crystal by reciprocating the processing tool, the cutting efficiency is not affected by the reciprocating movement because the cutting position is changed to an appropriate cutting position corresponding to each of the forward movement and backward movement.

In the above embodiment, the switching is made between points 36 and 37 in FIG. The combination may be changed if machining efficiency is improved. Further, in the above embodiments, a multi-wire saw was used for cutting, but a band saw or a peripheral blade processing device may be used. Furthermore, the cutting method of the present invention is not limited to lithium tantalate, but can be applied to any single crystal having crystallographic anisotropy such as silicon, sapphire, germanium, etc. Various other changes may be made without departing from the gist of the present invention.

[Brief explanation of drawings]

Figure 1 is a diagram showing the zone slicing test of a single crystal member, Figure 2 is a diagram showing the groove depth curve obtained from the zone slicing test and the appropriate cutting direction of the processing tool, and Figure 3 is a diagram showing the single crystal member. It is a front view of the cutting device which cuts. 2: Single crystal member, 25: Processing tool.

Claims (1)

[Scope of Claims] 1. The single crystal member is cut by cutting the single crystal member with the processing tool while relatively moving a single crystal member having a cleavage plane and a processing tool for cutting the single crystal member. In the cutting method of cutting along a planned cutting plane, the cutting direction of the processing tool is such that the single crystal member is is provided in a direction that is inclined toward the direction in which chips are discharged, and the inclination angle of the cutting direction from the normal direction is set at an angle that maximizes the cutting efficiency of the single crystal member by the processing tool. A single crystal cutting method characterized by: 2. The single crystal cutting method according to claim 1, wherein the cutting direction is determined by a zone slicing test.