JP3794538B2 - Double-sided simultaneous grinding apparatus and double-sided simultaneous grinding method - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a cup-type grindstone used for double-sided simultaneous grinding of a plate-like workpiece (hereinafter, also referred to as a workpiece) such as a semiconductor wafer, a quartz substrate for exposure original plate, and a double-sided simultaneous grinding apparatus provided with the same. The present invention relates to a method for simultaneous grinding on both sides.
[0002]
[Prior art]
Conventionally, surface grinding has been used in precision machining of plate-like workpieces such as semiconductor wafers and quartz substrates. In surface grinding, single-sided grinding or double-sided grinding is performed. In double-sided grinding, there are a method of grinding one surface and reversing the other surface, and a grinding method called double-sided simultaneous grinding or double-headed grinding in which both sides are ground simultaneously.
[0003]
In this case, there are several methods for double-head grinding that grinds the wafer surface simultaneously. Creep feed grinding for grinding by passing a wafer between two pairs of cylindrical grinding wheels, or a pair of cup-type grinding wheels. An in-feed grinding method is used in which the cup-type grindstone and the wafer rotate together so that the grindstone passes through the center of the wafer.
[0004]
An in-feed type double-sided simultaneous grinding apparatus 1a used for grinding a semiconductor wafer illustrated in FIG. 7 includes a pair of cup-type grindstones 2 that rotate in the same direction, two pairs of work pressing rollers 4 that support the work W from both sides, It comprises four work guide rollers 5 that support the circumference of W and a pair of work drive rollers 3 that rotationally drive the work W in the direction opposite to the grindstone. The cup-type grindstone 2 includes a cup-shaped base 2a, a grindstone portion 2b, and a grindstone rotating shaft 2c, and a grindstone is joined to the grinding surface of the grindstone portion 2b. The workpiece W and the cup-type grindstone 2 are rotated at a predetermined rotation speed. The grinding fluid is usually supplied from a central hole (not shown) of the grindstone rotating shaft 2c, or is poured over the outer periphery or inside of the grindstone. The grinding fluid is used to reduce the wear of the grindstone and improve the finishing accuracy, but it is mainly required to have cooling, penetration, lubrication and cleaning actions. Water, a water-insoluble grinding fluid, a water-soluble grinding fluid, etc. are used for a grinding fluid. These are sometimes referred to as coolants or grinding slurries.
[0005]
[Problems to be solved by the invention]
In recent years, the above-mentioned infeed type grinding method is generally used because of the advantage that high flatness is easily obtained compared to the creep feed type. However, in this method, the center of the wafer and the grindstone are always in contact with each other. The cooling effect on the center of the wafer due to liquid or the like cannot be sufficiently received. Therefore, it is considered that the wafer center is ground in a thermally expanded state, and the shape of the plate-like workpiece after grinding is a shape in which the center is recessed. Since this dent is difficult to be removed in the post-grinding process, it is a problem to be solved in the grinding process in pursuit of higher flatness.
[0006]
In order to solve such a problem, the present inventors firstly used a method of rocking a cup-type grindstone in an in-feed type double-side simultaneous grinding apparatus using a cup-type grindstone, Developed cup-shaped grindstones with a comb-teeth shape with spacing between the grindstone segments. These grindstones may or may not come into contact with the center of the plate-like workpiece to generate heat and high temperatures due to friction. In addition, to reduce cooling and improve the cooling effect at the center of the workpiece, further supply of grinding fluid (the grinding fluid aiming at positive cooling effect is expressed as coolant) and forced cooling to increase thermal expansion A double-sided simultaneous grinding apparatus, a cup-type grindstone and a grinding method were proposed (Japanese Patent Application No. 11-96263). Although these whetstones and methods succeeded in preventing the formation of a dent in the center of the workpiece, two whetstones (the two whetstones are expressed as right and left whetstones from the arrangement with reference to FIG. Depending on the device, it may be difficult to synchronize the two whetstones on the top and bottom), the left and right balance will be lost and vibration will easily occur, and the left and right grinding resistance will vary. It has been found that the flatness of the entire surface of both surfaces and the unevenness of the flatness between workpieces when a plurality of sheets are processed may not always be good. In addition, even if synchronization is achieved, in the case of a comb-shaped grindstone or the like in which the grindstone is spaced from the segment, there is a portion where the grindstone is not in contact with the workpiece. When this occurs, an impact is generated, and the wafer is easily deformed, causing vibration.
[0007]
Accordingly, the present invention has been made in view of the above problems, and the cup-type grindstone used in the in-feed type double-sided simultaneous grinding apparatus is balanced with the left and right and is generated in the center of the workpiece. Provided are a cup-type grindstone, an in-feed type double-sided simultaneous grinding apparatus and a grinding method capable of preventing formation of a dent that is easy to be processed, processing the entire surface of both surfaces of the workpiece with high flatness, and preventing variations in flatness between the workpieces. The main purpose.
[0008]
[Means for Solving the Problems]
This onset bright order to solve the above problem, recess a cup-shaped grinding wheel for use with in-feed type double-side grinding apparatus, the shape of the grinding wheel, the inner periphery and / or outer circumference of the entire circumference grinding a and stone portion A cup-type grindstone characterized by being a gear-shaped grindstone provided with a.
[0009]
Thus, if the shape of the cup-type grindstone is an all-round grindstone and a gear-shaped grindstone provided with recesses on the inner and / or outer circumference of the grindstone, there is no grindstone breakage and the entire grindstone is continuous. Since it is a circumferential grindstone, the balance between the left and right grindstones is not lost, so that the entire surface of both surfaces of the workpiece can be processed uniformly and with high flatness with less variation between the workpieces. In addition, since the gear wheel is provided with a recess on the inner periphery and / or outer periphery of the grindstone, if the grind is rotated so that the recess passes through the center of the workpiece, the grindstone does not pass through the center of the workpiece. Can be created periodically, the contact time with the center of the work is shortened, the high temperature due to frictional heat is suppressed, the thermal expansion of the center is suppressed and the formation of a recess in the center is prevented, The expansion in the workpiece surface is averaged, and a cup-type grindstone that can process the entire surface of both workpiece surfaces with high flatness is obtained. In addition, when a coolant that forcibly cools the workpiece center is used, the contact area with the coolant is increased compared to the conventional all-round grindstone, so a much higher cooling effect can be obtained and the workpiece center It is possible to suppress the formation of dents and increase the flatness of the entire work surface.
[0010]
Then, the onset bright, it a cup-shaped grinding wheel for use with in-feed type double-side grinding apparatus, the shape of the grinding stone, and has an oblique groove from the inner circumference to the outer circumference of the circumferential grinding in and grinding wheel portion Is a cup-type grindstone characterized by
[0011]
In this way, if the shape of the cup-type grindstone is a circumferential grindstone and a grindstone having a slant groove from the inner periphery to the outer periphery of the grindstone portion, even if there is a groove in the grindstone portion during grinding rotation, at the contact point with the workpiece Since the grinding wheel part is not interrupted, it looks like a continuous circumferential grinding wheel, so the balance between the left and right grinding stones will not be lost. Can be processed at a time.
[0012]
In addition, by providing the oblique grooves, even if grinding is performed with the center of the grindstone coinciding with the center of the workpiece, a state where the grindstone does not pass through the center of the workpiece can be created periodically. A cup that can shorten the contact time, suppress the high temperature caused by frictional heat, suppress the thermal expansion of the central part, prevent the formation of a recess in the central part, and process the entire surface of both surfaces of the workpiece with high flatness. It becomes a mold grindstone. Furthermore, when combined with forced cooling of the center by coolant, the coolant can flow in and out of the cup-type grindstone through the slant groove, enhancing the cooling effect and easily achieving high flatness machining. It becomes a grindstone.
[0013]
Next, the onset Ming, in the double-sided simultaneous grinding machine in-feed type with a cup-shaped grindstone, comprising means for cooling the central portion of the plate-shaped workpiece in the cup-shaped grindstone and double-sided simultaneous grinding of the The double-sided simultaneous grinding apparatus characterized by the above.
[0014]
As described above, the shape of the grindstone is an all-round grindstone, and a gear-shaped grindstone in which recesses are provided on the inner circumference and / or outer circumference of the grindstone portion, or a circumferential grindstone having a slant groove from the inner circumference to the outer circumference of the grindstone section. If a device with a cup-type grindstone and a means for cooling the center of the plate-like workpiece during double-sided simultaneous grinding is provided, the left and right grindstones can be rotated in a balanced state. Since there is no variation in grinding resistance without giving vibration to the workpiece during grinding, it becomes a double-sided simultaneous grinding machine that can process the entire surface of both surfaces of the workpiece with high flatness and reduce the variation in flatness between workpieces. . Further, forced cooling by means for cooling the center portion can be performed, and a state where the grindstone does not pass through the workpiece center portion can be periodically created. Therefore, the contact time with the center of the workpiece is shortened, and the frictional heat is reduced by the cooling effect due to the grinding fluid or the coolant that actively cools the center of the workpiece in the recess of the grindstone and the flow into and out of the slant groove. Thus, a double-sided simultaneous grinding apparatus capable of processing the entire surface of both surfaces of the workpiece with high flatness can be obtained by suppressing the temperature increase due to the above, suppressing the thermal expansion of the center portion, preventing the formation of a recess in the center portion.
[0015]
Furthermore, in this onset bright, both surfaces in double-sided simultaneous grinding infeed type using the cup-shaped grinding wheel, with a cup-shaped grinding wheel above, characterized in that grinding while cooling the center portion of the plate-shaped workpiece It is a simultaneous grinding method.
[0016]
As described above, the shape of the grindstone is an all-round grindstone, and a gear-shaped grindstone in which recesses are provided on the inner circumference and / or outer circumference of the grindstone portion, or a circumferential grindstone having a slant groove from the inner circumference to the outer circumference of the grindstone section. If you use a cup-type grindstone and simultaneously grind both sides of the workpiece while cooling the center of the plate-like workpiece, the left and right grindstones can be ground in a well-balanced state. Furthermore, since there is no variation in grinding resistance, the entire surface of both surfaces of the workpiece can be processed with high flatness, and variation between workpieces can be reduced. In addition, the state where the grindstone does not pass through the workpiece center can be created periodically, the contact time with the workpiece center is shortened, and the grinding wheel of the coolant for actively cooling the grinding fluid or the workpiece center The cooling effect by contact with the recesses and the flow into and out of the slant grooves suppresses the high temperature due to frictional heat, suppresses the thermal expansion of the center part, prevents the formation of the recess part in the center part, and increases the overall surface of both sides of the workpiece. It can be processed to flatness. Therefore, it is possible to improve yield and productivity and reduce costs in the grinding process.
[0017]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, although embodiment of this invention is described, this invention is not limited to these.
As described above, when performing both-side simultaneous grinding of a plate-shaped workpiece, the conventional in-feed type double-sided simultaneous grinding method using a cup-type all-round grindstone always brings the center of the workpiece into contact with the grindstone. The cooling effect at the center of the workpiece due to is not sufficiently received. Therefore, the workpiece center portion is ground in a thermally expanded state, and the shape after grinding is a shape in which the center portion is recessed.
[0018]
Therefore, the present inventors, in the in-feed type double-sided simultaneous grinding apparatus using a cup-type grindstone, a method of oscillating the cup-type all-round grindstone, the shape of the grindstone is polygonal or elliptical, Developed a comb-type grindstone with a comb-like segment type with spacing between the grindstone segments to prevent contact with the center of the plate-shaped workpiece to suppress heat generation and high temperature, and to force the center A cooling double-sided simultaneous grinding device, cup-type grinding wheel and grinding method were proposed. However, these grindstones and grinding methods have succeeded in preventing dents in the center of the workpiece, but the left and right grindstones are unbalanced and vibration is likely to occur. It has been found that there is a case where the degree of unevenness and the flatness between the workpieces are not always good.
[0019]
Therefore, as a result of investigating and examining the structure and shape of the cup-type grindstone and the structure of the in-feed type double-sided simultaneous grinding apparatus using the cup-type grindstone in order to solve these problems, the present inventors, To grind a workpiece with the left and right grindstones always in contact with the work piece and maintaining a balance between the left and right sides, basically use an all-round grindstone and pass through the center of the workpiece to a part of the grindstone. Recesses, grooves, etc. that periodically create a state that does not work are provided so that the left and right grindstones are balanced, shortening the contact time with the center of the workpiece, suppressing high temperatures due to frictional heat, and retaining or flowing in and out of the grinding fluid If the workpiece is ground while actively cooling the center of the workpiece to prevent local thermal expansion, there is no formation of a recess in the center of the workpiece, and the entire surface of both sides can be processed into a highly flat workpiece. To identify various conditions Invention was allowed to complete.
[0020]
First, a grinding apparatus using the cup-type grindstone of the present invention will be described with reference to the drawings.
Here, FIG. 1 is a schematic explanatory diagram for explaining an outline of the configuration of a double-sided simultaneous grinding apparatus as an example of the present invention.
[0021]
The in-feed type double-sided simultaneous grinding apparatus of the present invention is configured as an apparatus for simultaneously grinding both sides of a workpiece, for example, a semiconductor wafer. As shown in FIG. 1, the double-sided simultaneous grinding apparatus 1 has a pair of cup types that rotate in the same direction. Two pairs of work pressing rollers 4 that support the grindstone 2 and the work W from both sides, four work guide rollers 5 that support the circumference of the work W, and a pair of work driving rollers that rotationally drive the work W in the direction opposite to the grindstone It is composed of three.
[0022]
The cup-type grindstone 2 includes a cup-shaped base 2a, a grindstone portion 2b, and a grindstone rotating shaft 2c, and a grindstone is joined to the grinding surface of the grindstone portion 2b. The shape of the cup-type grindstone 2 in the present embodiment is an all-circular shape, and a recess 9 is provided on the inner circumference of the grindstone portion 2b. And the set position of the workpiece | work W is adjusted so that this recessed part 9 may pass the center of the workpiece | work W. FIG.
The workpiece W and the cup-type grindstone 2 are rotated at a predetermined rotation speed. The pair of cooling nozzles 6 are provided with their tips directed toward the center of the workpiece and the contact portions of the left and right grindstones. The grinding fluid is usually supplied from a central hole (not shown) of the grindstone rotating shaft 2c or is poured on the inside of the grindstone.
[0023]
Next, the grinding method of the workpiece | work W by the said double-sided simultaneous grinding apparatus 1 is demonstrated.
The workpiece W is set in the apparatus, both surfaces are supported by the two pairs of workpiece pressing rollers 4, the circumference of the workpiece W is supported by the four workpiece guide rollers 5, and the workpiece W is rotated by the workpiece driving roller 3. Next, while rotating the pair of cup-type grindstones 2, the workpiece W is brought close to both sides of the work W, the outer periphery of the grindstone portion 2 b is brought into contact with the work W, and the work W and the cup-type grindstone 2 are rotated in directions opposite to each other. And grind.
[0024]
During grinding, coolant such as coolant or compressed gas is sprayed from the pair of cooling nozzles 6 toward the center of the workpiece W and the contact portion of the grindstone 2 to directly cool the center of the workpiece W. The grinding liquid is supplied from a central hole (not shown) of the grindstone rotating shaft 2c or is poured on the inside of the grindstone. The coolant for cooling the center part of the workpiece and the grinding fluid may have the same composition, for example, water or water-soluble grinding fluid.
[0025]
As described above, the embodiment of the present invention is based on the fact that the cup-type grindstone is an all-circumferential shape, so that the left and right grindstones always contact the workpiece and rotate while maintaining a balance. Therefore, since the grinding resistance does not vary without giving vibration to the workpiece, the entire surface of both surfaces can be processed to a higher flatness, and the variation in flatness between the workpieces can be reduced. In addition, since a space is provided by forming recesses on the outer circumference and / or inner circumference of the all-round grindstone or by providing oblique grooves, the contact time with the center of the work is shortened, and heat generation and high temperature are suppressed. At the same time, coolant such as coolant and compressed gas is sprayed directly from the cooling nozzle to the center of the workpiece, so that the cooling effect on the center of the workpiece is sufficiently enhanced and the high temperature of the center due to frictional heat is suppressed, and the center Local thermal expansion is suppressed. Then, the expansion in the workpiece surface is averaged, and no concave portion is formed in the central portion after grinding, and the entire surface of both surfaces of the workpiece can be processed with high flatness.
[0026]
Next, the structure, shape, and action of the cup-type grindstone of the present invention will be described in detail with reference to FIGS.
First, the cause of the variation in the flatness of the left and right sides of the wafer was investigated and examined.
FIG. 4 shows a conventional segment-type circular comb-shaped cup-type grindstone. A grindstone segment 7 is joined to the grindstone portion 2b at a constant interval, and a space portion 8 is provided in a comb-tooth shape. If there is a discontinuous portion where the grindstone does not contact the wafer, the corner of the next grindstone segment 7 is likely to hit the wafer, the wafer is also susceptible to deformation, and vibration is generated. Such a phenomenon is considered to be particularly likely to occur at the periphery of the wafer. In the double-sided simultaneous grinding apparatus, the cup-type grindstone also plays a role of supporting the wafer, and surface blurring tends to occur when the non-contact portion becomes large.
[0027]
As a countermeasure against this, an all-round grindstone is basically used.
However, when an all-round grindstone is used, as shown in FIG. 5B, vibration does not occur, but the grindstone portion 2b and the wafer W are always in constant contact. The effect is hardly raised, and a dent is generated in the center of the work. p represents the contact point between the wafer and the grindstone.
[0028]
Further, in the conventional segment type circular comb-like grindstone, as shown in FIG. 5C, a state in which the grindstone 2b and the wafer W do not contact each other periodically occurs (the grindstone segments 7 and the space portions 8 appear alternately). ), There is a sufficient cooling effect at the center of the wafer, but there is a drawback that vibration is likely to occur.
[0029]
Therefore, in the present invention, in order to enhance the cooling effect while being an all-circumferential shape, as shown in FIG. 2, the concave portion 9 is provided on the inner circumference of the grindstone portion 2b as shown in FIG. The recess 9 may be provided on the outer periphery of the grindstone portion 2b or may be provided on the inner and outer periphery. However, it is necessary to set the width of the entire circumferential portion, the number of concave portions, the size of the concave portions, etc. so that the right and left grindstones can be balanced.
As another invention, as shown in FIG. 3 and FIG. 5 (a), the shape of the grindstone is a circumferential grindstone and has a slant groove 10 from the inner periphery to the outer periphery of the grindstone portion, and the grindstone has grooves. Although it has it, it was made for a part of grindstone part 2b and the wafer W to always contact.
[0030]
Next, as a second cause of vibrations in the workpiece, in the above-described conventional segment type comb-shaped cup type grindstone, the positions of the grindstone segments of the left and right grindstones are not synchronized, that is, as shown in FIG. In this way, when the parts where force is applied to the left and right sides of the wafer W are shifted or uneven, the vibrations of the left and right grindstones increase and the grinding resistance may vary. It was thought that this caused variations in the flatness between the left and right sides of the wafer and between the wafers.
[0031]
In order to increase the cooling effect at the center of the wafer, it is necessary to leave a gap between the grinding stones.To balance and synchronize the left and right grinding stones, there is no gap between the grinding stones, and it is necessary to apply force symmetrically. We have developed a grinding wheel shape that can achieve both of these characteristics.
[0032]
In the gear-type grinding wheel according to the present invention, in which the shape of the grindstone is an all-round grindstone and a recess is provided on the inner and / or outer circumference of the grindstone portion, as shown above, the entire circumference is surrounded by the grindstone. Therefore, it is easy to apply a grinding load uniformly from the left and right. In addition, since the recesses are formed in a balanced manner at a plurality of locations, if these recesses pass through the wafer center, rapid thermal expansion of the wafer can be prevented and the occurrence of recesses in the wafer center can be suppressed. .
[0033]
Furthermore, when the shape of the grindstone of the present invention is a circumferential grindstone and has a slant groove 10 from the inner periphery to the outer periphery of the grindstone portion (see FIGS. 3 and 5A), the groove is oblique to the radial direction. Since it is cut in the direction, a part of the grindstone part always matches with the left and right, and it is easy to apply a grinding load uniformly to the left and right surfaces of the wafer as in the case of the entire circumferential grindstone. In addition, since there are many oblique grooves, the grinding fluid or coolant that actively cools the center of the wafer can freely flow in and out of the cup-type grindstone, and the cooling effect at the center of the wafer is extremely high. Become.
[0034]
【Example】
EXAMPLES Hereinafter, although an Example and comparative example of this invention are given and this invention is demonstrated in detail, this invention is not limited by these.
Example 1
The double-sided simultaneous grinding apparatus shown in FIG. 1 was attached with the cup-shaped grindstone of the entire circumferential internal gear shape shown in FIG. 2 to grind the semiconductor silicon wafer.
A silicon wafer having a thickness of about 800 μm and a diameter of 200 mm (8 inches) sliced from an ingot using a wire saw was used.
A cup-type grindstone with an all-circular inner gear shape is formed by cutting 15 recesses with a radial width of 2.5 mm and a circumferential width of 20 mm at intervals of 20 mm inside the entire circumferential grindstone having an outer diameter of 200 mm and a grindstone width of 5 mm. (The whetstone is vitrified # 2000).
As a coolant for cooling the central portion, cooling water was used, and a coolant having a temperature of 25 ° C. was constantly applied to the contact portion between the wafer central portion and the grindstone at a flow rate of 10 L / min.
[0035]
Other grinding conditions, that is, the feed speed of the grindstone and the rotation speed of the wafer and grindstone were set so that the wafer surface condition, flatness, etc. would be optimal.
In this example, the feed speed of the grindstone was 50 to 200 μm / min, the grindstone rotation speed was 1000 to 3000 rpm, the work rotation speed was 10 to 30 rpm, and the spark out was 10 to 20 sec. The grinding liquid (grinding water) is applied at 10 L / min on both sides from the center position of the grindstone.
[0036]
When the center of the concave portion of this all-circular internal gear-shaped grindstone was set to be at the center of the wafer and both sides were ground simultaneously, there was almost no vibration and the recess at the center of the wafer was 0.3 μm or less on one side. In addition, a high flatness wafer having a variation in flatness (Total Thickness Variation: TTV) of 0.2 μm or less when a plurality of wafers were processed was obtained.
That is, in Example 1, 20 L / min of water is applied to both sides of the wafer in combination with the water normally supplied for grinding and the water for actively cooling the wafer center. In the case where cooling water is used as the cooling liquid (coolant), the cooling effect is sufficiently obtained when the total amount is 20 to 30 L / min together with the grinding water in this embodiment.
[0037]
(Example 2)
Next, the double-sided simultaneous grinding apparatus shown in FIG. 1 was attached to the cup-type grindstone with the circumferential slant groove shown in FIG. 3 to grind the semiconductor silicon wafer. The wafer used was the same as in Example 1.
The cup-type grindstone with a circumferential slant groove has 50 points of slant grooves with a width of 1 mm and a length of about 8 mm every 4 mm at an angle of 30 degrees with respect to the radial direction of the entire circumferential whetstone having an outer diameter of 200 mm and a width of 5 mm. It was cut (the whetstone was vitrified # 2000).
Other grinding conditions are the same as those in the first embodiment.
When setting the center of the grindstone with this circumferentially slanted groove to the center of the wafer and performing simultaneous grinding on both sides, there was almost no vibration and the dent at the center of the wafer was 0.25 μm or less on one side. In addition, a high flatness wafer having a flatness (TTV) variation of 0.2 μm or less when a plurality of wafers were processed was obtained.
[0038]
(Comparative Example 1)
The same conditions as in Example 1 except that the double-sided simultaneous grinding apparatus shown in FIG. 7 was used and a circular cup-type grindstone (whetstone width 5 mm, vitrified # 2000) having a grindstone portion on the entire circumference of the grindstone was used. It was ground with.
As a result, the left and right whetstones were well balanced and could be stably ground with almost no vibration. However, the shape of the ground wafer gradually began to dent from around R / 2 of the wafer (R is the radius of the wafer). It is deep in the part. This depth is about 0.5 μm to 1 μm on one side (1 μm to 2 μm on both sides), but if such a recess is formed, it can be restored to a flat state by subsequent processes such as etching or polishing. I can't.
[0039]
(Comparative Example 2)
Next, it grind | pulverized using the segment type circular comb-tooth shaped cup type grindstone as shown in FIG. A grindstone segment 7 having a grindstone width of 5 mm and a segment length of 30 mm was joined to a circular grindstone having a diameter of 200 mm at intervals of 30 mm (space portion 8) (ratio of the grindstone portion: 50%). The other conditions were ground under the same conditions as in Example 1.
When the outer periphery of this segment-type circular comb-like grindstone was set so that it came to the center of the wafer and both sides were ground simultaneously, the dent in the center of the wafer was reduced, but undulation was seen throughout the wafer. The variation in flatness (TTV) when processing a plurality of sheets was also about 0.6 μm, and the flatness was not improved.
[0040]
(Comparative Example 3)
As a grindstone, grinding was performed using a grindstone whose shape of a grindstone inscribed in a circle having a grindstone width of 3 mm and a diameter of 200 mm was square. Grinding was performed under the same conditions as in Example 1 except that the tops of these grindstones were set so as to be located at the center of the wafer, and that the positions of the tops of the left and right grindstones were always shifted.
In this grindstone, the force (grinding load) applied to the wafer from the grindstone fluctuates alternately left and right and becomes unbalanced, and vibration increases. The effect of cooling the central portion was sufficient, and the dent in the central portion of the wafer was 0.3 μm or less on one side, but warpage occurred on the entire surface of the wafer or the flatness deteriorated.
[0041]
In addition, this invention is not limited to the said embodiment. The above-described embodiment is an exemplification, and the present invention has substantially the same configuration as the technical idea described in the claims of the present invention, and any device that exhibits the same function and effect is the present invention. It is included in the technical scope of the invention.
[0042]
For example, the double-sided simultaneous grinding device includes a type that holds the workpiece vertically and a type that holds the workpiece horizontally. However, the present invention is not particularly limited to these types and is applicable to any type. can do.
[0043]
【The invention's effect】
As described above, according to the present invention, since the shape of the cup-type grindstone is basically an all-circular shape, it can be ground without vibration while maintaining the balance of the left and right grindstones, High flatness is possible. In addition, there was less variation in flatness between workpieces, and stable surface grinding was possible. Furthermore, by forming recesses and oblique grooves in the grindstone, it is possible to periodically create a state in which the grindstone does not contact the center of the workpiece, while suppressing high temperature due to frictional heat and centrally cooling this This eliminates local expansion of the central portion. Therefore, since the thermal expansion in the work surface is uniform, the ground work has a high flatness, and the formation of a recess in the center can be prevented. Therefore, it is possible to improve the yield and productivity in the simultaneous double-side grinding of the plate-like workpiece, and it is possible to improve the cost.
[Brief description of the drawings]
FIG. 1 is a schematic explanatory view showing an example of a double-sided simultaneous grinding apparatus of the present invention.
(A) Top view, (b) Front view, (c) Side view.
FIG. 2 is a schematic view of an all-circular gear-type grindstone of the present invention.
FIG. 3 is a schematic view of a grindstone with a circumferential oblique groove of the present invention.
(A) Top view, (b) Partial perspective view.
FIGS. 4A and 4B are operation explanatory views of a conventional segment type comb-like grindstone.
FIG. 5 is a diagram illustrating the operation of the present invention and a conventional cup-type grindstone.
(A) a grindstone with a circumferentially inclined groove of the present invention, (b) a conventional all-round grindstone,
(C) A conventional segment-type comb-like grindstone.
FIG. 6 is a view for explaining how a grinding load is applied to a wafer of a left and right cup type grindstone by a conventional segment type comb-like grindstone.
FIG. 7 is a schematic explanatory view showing an example of a conventional double-side simultaneous grinding apparatus.
(A) Top view, (b) Front view, (c) Side view.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 1, 1a ... Double-sided simultaneous grinding apparatus, 2 ... Cup type grindstone, 2a ... Cup-shaped base,
2b: Grinding wheel part, 2c: Grinding wheel rotating shaft, 3 ... Work drive roller,
4 ... Work holding roller, 5 ... Work guide roller, 6 ... Cooling nozzle,
7: Grinding stone segment, 8 ... Space, 9 ... Recess, 10 ... Oblique groove,
p: Contact point between workpiece and grinding wheel. W: Workpiece (wafer).

Claims (4)

In dual-side grinding machine in-feed type with a cup-shaped grindstone, and the cup-shaped grinding wheel is gear-shaped grinding wheel shape of the grinding wheel is provided with a recess on the inner periphery and / or outer circumference of a and stone portion entire circumference grinding wheel, And a means for cooling the center of the plate-like workpiece being simultaneously ground on both sides. In dual-side grinding machine in-feed type with a cup-shaped grindstone, and the cup-shaped grinding wheel and has a diagonal groove shape of the grinding wheel from the inner circumference to the outer circumference of the circle circumference grinding a and stone portion, in double-sided simultaneous grinding A double-side simultaneous grinding apparatus comprising: means for cooling a central portion of the plate-like workpiece. In dual-side grinding infeed type using the cup-shaped grinding wheel, with a cup-shaped grindstone shape of the grindstone is gear-shaped grinding wheel having a recess on the inner periphery and / or outer circumference of and stone portion whole circumference grindstone A double-sided simultaneous grinding method characterized by grinding while cooling the central part of a plate-like workpiece. In dual-side grinding infeed type using the cup-shaped grinding wheel, with a cup-shaped grinding wheel and it has a diagonal groove to the outer shape of the grinding wheel from the inner periphery of the circular circumferential grinding a and grinding wheel portion, the plate-shaped workpiece A double-sided simultaneous grinding method characterized by grinding while cooling the central part of an object.

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