JP3962452B2 - Semiconductor wafer lapping apparatus and lapping method using the same - Google Patents

Description

[0001]
[Field of the Invention]
The present invention relates to a semiconductor wafer lapping apparatus and a lapping method using the same, and more particularly to a semiconductor wafer lapping method for lapping a sliced wafer.
[0002]
[Prior art]
After the cut semiconductor wafer is chamfered, the cut surface is prepared by lapping or surface grinding.
Among these, lapping is batch processing for processing a plurality of semiconductor wafers, and the processing efficiency is the best. As shown in FIG. 4, this lapping is generally performed by loading a plurality of semiconductor wafers 10 into the holding holes between an upper surface plate 31 (not shown) and a lower surface plate 3 that rotate in opposite directions. The wrapping carrier 4 is disposed, and the wrapping carrier 4 is rotated by the rotational difference between the sun gear 51 and the internal gear 52, and the wrapping carrier 4 makes a planetary motion with respect to the upper surface plate 31 and the lower surface plate 3. Wrapping At this time, the semiconductor wafer 10 itself also rotates to achieve flat polishing.
[0003]
In addition, the rotation direction of the wrapping carrier 4 is a forward rotation (arrow X) in a direction opposite to the rotation of the lower surface plate 3, and a reverse rotation (arrow Y).
[0004]
Further, the surfaces of the upper and lower surface plates are not necessarily flat when they are mounted on the wrapping apparatus, and the surface shape further changes as wrapping is repeated. There are two types of this shape: a convex lower platen 3a called A-sledge as shown in FIG. 5 (a) and a concave lower platen 3a called B-sledge as shown in FIG. 5 (c). is there. Since the upper surface plate rotates by its own weight so as to follow the shape of the lower surface plate, the shape depends on the shape of the lower surface plate.
[0005]
As a method of correcting the warpage of the surface plate and making it flat as shown in FIG. 5B, the shape is measured once a day or once a week, and replaced with a wrapping carrier. There is one in which a surface plate is formed flat by arranging a correction carrier (not shown) and rotating a lapping device.
In this method, in the case of A warp (convex shape), as shown in FIG. 8A, when the correction carrier is rotated forward (arrow X) with respect to the lower surface plate 3, the hatched portion of the lower surface plate is It is easily polished and the warp becomes larger. On the other hand, as shown in FIG. 8B, by reversing the correction carrier with respect to the lower surface plate 3 (arrow Y), the portion corresponding to the protruding portion of the lower surface plate 3 is easily polished, and the lower surface plate 3 is flattened. Can be close to. On the other hand, in the case of the B warp (concave shape), the lower surface plate 3 can be made nearly flat by causing the correction carrier to rotate forward (arrow X) with respect to the lower surface plate 3.
[0006]
[Problems to be solved by the invention]
However, in the molding of the surface plate using the above-described correction carrier, the work efficiency is poor, and therefore the frequency of measurement and molding must be reduced, and the flatness of the semiconductor wafer lapped in the meantime is gradually increased as it is repeated. There was a problem of being damaged.
In view of this, a method for alternately reversing the rotation direction of the wrapping carrier in conventional wrapping has been proposed (Japanese Patent Laid-Open No. 3-251363). In this method, the deformation of the surface plate can be prevented at the initial stage of the lapping process.
However, the plurality of semiconductor wafers to be polished in such a batch type are slightly different in thickness and contact the upper and lower surface plates in a region protruding from the surface of the wrapping carrier, and rotate by the friction. When the advance thickness is equal, most of the semiconductor wafers will not rotate due to the clamping of the upper and lower surface plates. Therefore, as shown in FIG. 4, the same protruding portion 10 a of the semiconductor wafer 10 is wrapped while protruding from the surface plate 3. As a result, as shown in FIG. 12, only the portion of the upper surface plate 31 that comes into contact with the peripheral edge portion is wrapped, and the protruding portion 10a and the inner peripheral portion 10b located on the inner peripheral portion of the upper and lower surface plates 3, 31 are wrapped much. However, there is a problem in that a recess 20a is formed in the outer peripheral portion, and the shape as shown in FIG. 11 is obtained, and the total thickness variation (TTV) TTV ₂ is a large value.
SUMMARY OF THE INVENTION The present invention has been made in view of the above problems, and prevents a deformation of a surface plate caused by repeating lapping and can improve deterioration of TTV caused by stopping rotation of a semiconductor wafer. It is another object of the present invention to provide a wrapping method.
[0007]
[Means for Solving the Problems]
Therefore, in the first aspect of the present invention, the wrapping carrier loaded with the semiconductor wafer in the holding hole is disposed between the upper surface plate and the lower surface plate that rotate in opposite directions, and the wrapping carrier is rotated while rotating. In the method of lapping a semiconductor wafer for lapping a semiconductor wafer, the rotation speed of the lapping carrier is rapidly changed in order to induce rotation of the semiconductor wafer in the holding hole of the lapping carrier. To do.
According to a second aspect of the present invention, the rotation speed of the wrapping carrier is configured to change intermittently (digitally).
A third aspect of the present invention is characterized in that, in the first aspect, the rate of change of the rotation speed of the wrapping carrier is 0.1 rpm / second or more.
According to a fourth aspect of the present invention, in the first aspect, the rate of change of the rotation speed of the wrapping carrier is 1.0 rpm / second or more.
In a fifth aspect of the present invention, a wrapping carrier loaded with a semiconductor wafer in a holding hole is disposed between an upper surface plate and a lower surface plate that rotate in opposite directions, and the semiconductor wafer is rotated while the wrapping carrier rotates. In the lapping method of the semiconductor wafer for lapping, the lapping carrier is rotated so as to rotate alternately forward and reverse, and is controlled to be in the positive direction in the final step.
A sixth aspect of the present invention is characterized in that, in the fifth aspect, the rotation speed of the wrapping carrier is changed intermittently (digitally). At this time, it is desirable that the rotation speed of the wrapping carrier after inversion is kept substantially constant and the rotation speed in one direction is maintained for at least one second.
According to a seventh aspect of the present invention, in the sixth aspect of the present invention, the rotation speed of the wrapping carrier after inversion is kept substantially constant, and the rotation in one direction is maintained for at least 5 seconds.
In an eighth aspect of the present invention, a wrapping carrier loaded with a semiconductor wafer in a holding hole is disposed between an upper surface plate and a lower surface plate rotating in opposite directions, and the semiconductor wafer is rotated while the wrapping carrier rotates. In the method for wrapping a semiconductor wafer, the measuring step of measuring the shape of the lower surface plate prior to the start of lapping, and the rotation direction of the wrapping carrier so that the deformation of the lower surface plate is self-corrected from the measurement result And a calculation step for calculating the total rotation time in each rotation direction, and based on the calculation result, the rotation time of the wrapping carrier in the forward direction and the rotation time in the reverse direction are approximately the same as the rotation time calculated. And a lapping step for lapping while self-correcting the deformation of the lower surface plate.
According to a ninth aspect of the present invention, in the eighth aspect, the wrapping step is controlled such that the rotation direction of the wrapping carrier is a positive direction in the final step.
A tenth aspect of the present invention is characterized in that, in the eighth or ninth aspect, the rotational speed of the wrapping carrier is changed intermittently (digitally). At this time, it is desirable that the rotation speed of the wrapping carrier after inversion is kept substantially constant and the rotation speed in one direction is maintained for at least one second.
The eleventh aspect of the present invention is characterized in that, in the tenth aspect, the rotation speed of the wrapping carrier after inversion is kept substantially constant and the rotation in one direction is maintained for at least 5 seconds.
According to a twelfth aspect of the present invention, the upper surface plate and the lower surface plate rotating in opposite directions are mounted between the upper surface plate and the lower surface plate, and the semiconductor wafer is loaded into the holding hole. A wrapping carrier, a sun gear and an internal gear that are mounted so as to mesh with a peripheral edge of the wrapping carrier and have a rotational difference from each other so as to rotationally drive the wrapping carrier, and the sun gear. And control means for controlling the rotation of the wrapping carrier so as to induce the rotation of the wafer by controlling the rotation of the internal gear independently of each other and abruptly changing the rotation difference between the sun gear and the internal gear. It is characterized by that.
According to a thirteenth aspect of the present invention, in the twelfth aspect of the invention, there is provided surface detecting means for detecting the flatness of the surface of the lower surface plate, and the control means prior to wrapping, the wrapping carrier of the wrapping carrier according to the output of the surface detecting means. It is configured to control the rotation speed.
[0008]
DETAILED DESCRIPTION OF THE INVENTION
The present invention is to self-correct the uneven shape of the surface of the lapping apparatus, particularly the surface of the lower surface plate, by using lapping without using a correction carrier, and to prevent deterioration of TTV that has increased as lapping is repeated. .
Also, in conventional lapping, it is considered that if the rotation speed of the wrapping carrier is changed suddenly, the semiconductor wafer is likely to be cracked or chipped by an impact, and the normal idea is to gradually change the speed. It was. The present inventors discovered from various experimental results that the semiconductor wafer was efficiently rotated by giving a sudden change in the rotation speed of the wrapping carrier during lapping, and this was made with a focus on this point. It is. By rotating the semiconductor wafer efficiently, the contact position with the upper and lower surface plates can be moved. As described above, in the present invention, the semiconductor wafer is rotated by rapidly changing the rotation speed of the wrapping carrier, and the TTV value is decreased by moving the contact position between the semiconductor wafer and the upper and lower surface plates. It is what.
Furthermore, as a result of various experiments, the present inventors have found that when the direction of rotation of the wrapping carrier is normal, the amount of dents in the semiconductor wafer can be reduced, the TTV can be reduced, and flaws can be reduced. In the case where the rotation direction is reverse, the lapping speed of the semiconductor wafer is high, but the amount of dents on the surface is large, and it is easy to generate flaws. That is, as illustrated in FIGS. 8A and 8B, this is considered to be due to the fact that the portion that generates friction differs between the case where the rotation direction of the wrapping carrier is normal and the case where it is reverse. It is done. Therefore, by paying attention to this point and performing lapping while reversing forward and reverse, and controlling so that it ends with forward rotation at the end, it becomes possible to obtain a semiconductor wafer with few dents and less scratches on the surface of the semiconductor wafer. .
[0009]
【Example】
Embodiments of the present invention will be described below with reference to the drawings.
FIG. 1 is a graph showing the rotation speed of a lapping carrier in a polishing method according to a first embodiment of the present invention, FIG. 2 is a perspective view of a semiconductor wafer obtained by the polishing method of this embodiment, and FIG. -C sectional view, FIG. 4 is a plan view showing a wrapping apparatus used in an embodiment of the present invention, FIG. 5 is an explanatory view of the wrapping apparatus, and FIG. 6 is a table of the wrapping apparatus, an internal gear and a sun gear. FIG. 7 is a side sectional view showing a change in the shape of the lower surface plate, and FIG. 8 is an explanatory diagram showing the flatness in the case of normal rotation and in the case of reverse rotation.
[0010]
First, a wrapping apparatus used in the method of the present invention will be described. This apparatus includes a center drum 30 that is rotated in one direction at a predetermined rotational speed, an upper surface plate 31 and a lower surface plate 3 that are rotated in synchronization with the center drum 30 and rotate in opposite directions, and A wrapping carrier 4 mounted between the upper surface plate 31 and the lower surface plate 3 and configured to load the semiconductor wafer 10 in the holding hole 41, and mounted so as to mesh with the periphery of the wrapping carrier 4 The rotation of the sun gear 51 and the internal gear 52 and the rotation of the sun gear 51 and the internal gear 52 are controlled independently of each other while having a rotational difference to rotate the wrapping carrier 4. In order to induce the rotation of the semiconductor wafer 10 by abruptly changing the rotation difference of the internal gear and the internal gear, It is obtained and a control unit 60 for controlling the rotation of the carrier 4. Further, a detection gauge 20 for detecting the flatness of the lower surface plate surface is disposed in the vicinity of the lower surface plate 3, and the detection result is controlled so as to control the forward / reverse rotation time according to the detection result. The rotation is input to the means 60 and the rotation of the sun gear 51 and the internal gear 52 is controlled. These upper and lower surface plates rotate in conjunction with a center drum driven by a servo motor. Further, the sun gear 51 and the internal gear 52 are also driven by a servo motor so that the number of revolutions thereof changes abruptly as shown in FIG. The rotational speeds of the lower surface plate 3, the sun gear 51, and the internal gear 52 are indicated by curves a, b, and c, respectively. The rotational speed of the wrapping carrier is determined by the difference in rotational speed between the sun gear 51 and the internal gear 52.
First, the shape of the lower surface plate is measured by the surface detection gauge 20. Here, a gauge is placed on the surface of the lower surface plate, and the clearance interval at each position is measured using the clearance gauge. Based on the measurement result, the control means 60 performs the following calculation. For example, when the result is A warp (convex) as shown in FIG. 7A, the total forward rotation time T1 and the total reverse rotation time T2 are respectively calculated from the amount of the warp.
Next, as shown in FIG. 1, wrapping times t1 to t6 are input to the wrapping apparatus as a wrapping carrier rotation sequence, and forward and reverse rotation directions and rotation speeds are set. At this time, the total forward rotation time T1 = t2 + t4 + t6 and the total reverse rotation time T2 = t1 + t3 + t5 are set.
[0011]
The initial rotation direction in this wrapping is set as the reverse rotation of the wrapping time t1 until the thicknesses of the respective semiconductor wafers are almost equal in order to lengthen the reverse rotation time because the lower surface plate is A warp (convex). Thereafter, substantially the same wrapping times t2 to t6 are set so as to alternate between forward and reverse. In addition, the conversion in the rotation direction is set to be switched at a rate as rapid as possible. It should be noted that the rotation speed after inversion is set to be constant.
[0012]
In this embodiment, the wrapping time t1 is 10 minutes, the wrapping times t2 to t6 are each 1 minute, and the inversion rate is 5 rpm / second.
[0013]
By this reversal of the wrapping carrier, the semiconductor wafer is rotated to change the position where the peripheral portion of the upper and lower surface plates abuts, thereby increasing the region wrapped by the peripheral portion. As a result, for example, a semiconductor wafer 1 having a plurality of recesses 2a, 2b, and 2c as shown in FIG. 2 is obtained, and a TTV 1 that is much lower than the conventional TTV as shown in FIG. 3 is obtained. Can do.
[0014]
In addition, this lapping can reduce the machining allowance for obtaining flatness in the subsequent processes such as etching and polishing, and can shorten the process time. In the above embodiment, the semiconductor wafer obtained by several times of reversal has been described. However, by increasing the number of times of reversal, increasing the number of dents, and reducing the depth, TTV and LTV (local thickness) can be obtained. Change).
[0015]
In addition, since the shape of the lower surface plate becomes flatter than when lapping is started, deterioration of flatness due to the shape of the surface plate can be prevented even if the number of times of lapping is repeated.
Further, since the flattening by the correction carrier is not required and the work efficiency is high, and the flattening is corrected during lapping, the wear of the surface plate by the correction carrier is eliminated, and the service life of the surface plate can be improved.
[0016]
Next, a second embodiment of the present invention will be described.
In this method, wrapping is performed while reversing the wrapping carrier forward and backward, and the last is finished in the forward rotation mode.
That is, lapping was performed by switching from reverse rotation to normal rotation once, as shown in FIG. 9 showing the relationship between switching between the forward and reverse modes and the obtained surface flatness. At this time, the TTV of the semiconductor wafer after lapping is 1.316 microns as shown in FIG. Incidentally, when the reversal mode was performed only without performing the reversal, it was 3.13 microns as shown in FIG.
Further, in order to measure the relationship between the inversion frequency and the obtained flatness, when it was inverted twice, it was 1.281 microns as shown in FIG. From a comparison between FIG. 9 (a) and FIG. 9 (c), it can be seen that the TTV is improved to about 60% when it is reversed once and finished in the normal rotation mode. Further, comparing FIG. 9A and FIG. 9B, TTV is about 60% in FIG. 9A and TTV is about 58% in FIG. 9B, and switching frequency is increased. It can be seen that the flatness improved slightly, but not significantly. Here, in FIGS. 9A to 9C, it is assumed that lapping is performed using the same lapping device and only the rotation speeds of the sun gear and the internal gear are changed.
As described above, according to the method of the present invention, it is possible to obtain a semiconductor wafer having a high degree of flatness without any flaws by inverting the wrapping carrier in the forward and reverse directions and performing the wrapping so that the end ends in the forward rotation. .
In the first embodiment, an example in which the rotation control of the sun gear and the internal gear is performed in a pulse manner, that is, extremely steeply, has been described.
As a third embodiment of the present invention, rotation control may be performed as shown in FIG.
Note that the reversing speed of the wrapping carrier at this time is preferably 0.1 rpm / second or more, and if it is less than 0.1 rpm / second, an impact force sufficient to rotate the semiconductor wafer in the holding hole of the wrapping carrier. Cannot occur. More desirably, by setting the reversal speed to 1 rpm / second, the rotation of the semiconductor wafer can be caused extremely efficiently.
[0017]
【The invention's effect】
Since the present invention is configured as described above, there is an excellent effect that lapping is performed while correcting the shape of the surface plate of the lapping apparatus, and deterioration of the flatness of the semiconductor wafer due to repeated lapping can be prevented.
In addition, the rotation speed of the wrapping carrier is abruptly changed during wrapping to forcibly apply rotation to the semiconductor wafer, so that the entire semiconductor wafer can be uniformly wrapped and TTV and LTV can be improved. There is.
Furthermore, when lapping is performed while reversing the rotation of the wrapping carrier in the forward and reverse directions, the wafer is finally finished in the forward rotation, so that it is possible to obtain a polished wafer with high flatness and no scratches.
[Brief description of the drawings]
FIG. 1 is a graph showing the rotation direction and rotation speed of a lapping carrier in a polishing method according to the present invention.
FIG. 2 is a perspective view of a semiconductor wafer obtained by the polishing method of the present embodiment.
FIG. 3 is a cross-sectional view taken along the line CC of FIG.
FIG. 4 is a plan view showing a wrapping apparatus used in an embodiment of the present invention and a rotation direction in the wrapping.
FIG. 5 is an explanatory diagram of the wrapping apparatus.
FIG. 6 is a diagram showing the relationship between the rotation speed and time of the surface plate, the internal gear and the sun gear of the lapping apparatus in the first embodiment of the present invention.
FIG. 7 is a side sectional view showing a change in the shape of the lower surface plate.
FIG. 8 is an explanatory diagram showing flatness between forward rotation and reverse rotation.
FIG. 9 is a time chart showing a lapping method according to a second embodiment of the present invention.
FIG. 10 is a diagram showing the relationship between the rotation speed and time of a surface plate, an internal gear and a sun gear, illustrating a lapping method according to a third embodiment of the present invention.
FIG. 11 is a perspective view of a semiconductor wafer obtained by a conventional polishing method.
12 is a sectional view taken along the line DD of FIG.
[Explanation of symbols]
1 ... Semiconductor wafer 2a ... Recess 2b ... Recess 2c ... Recess 20 ... Surface detection gauge 3 ... Lower surface plate 31 ... Upper surface plate 3a ... Lower surface plate 3b ... Lower surface plate 3c ... Lower surface Panel 4 ... Lapping carrier 41 ... Holding hole 51 ... Sun gear 52 ... Internal gear 10 ... Semiconductor wafer 10a ... Protruding part 10b ... Inner peripheral part 20a ... Recess T1 ... Total forward rotation time T2 ... Total Reverse rotation time t1 to t6 ... Wrapping time 60 ... Control means

Claims (9)

A wrapping carrier loaded with a semiconductor wafer in a holding hole is disposed between an upper surface plate and a lower surface plate rotating in opposite directions, and the semiconductor wafer is wrapped while the wrapping carrier rotates. In the method
The wrapping carrier rotates alternately forward and reverse, and is controlled to be in the positive direction in the final process ,
A method for wrapping a semiconductor wafer, wherein the rotation speed of the wrapping carrier is abruptly changed at the time of reversal so as to induce the rotation of the semiconductor wafer in the holding hole when the wrapping carrier is reversed . 2. The method for wrapping a semiconductor wafer according to claim 1 , wherein the rate of change of the rotation speed when the wrapping carrier is reversed is 0.1 rpm / second or more. 2. The method for wrapping a semiconductor wafer according to claim 1 , wherein the rate of change of the rotation speed when the wrapping carrier is reversed is 1.0 rpm / second or more. 2. The semiconductor wafer lapping method according to claim 1, wherein the rotation speed of the lapping carrier is changed intermittently (digitally). 5. A method for wrapping a semiconductor wafer according to claim 1 , wherein the rotation speed of the wrapping carrier after inversion is kept substantially constant and the rotation in one direction is maintained for at least 5 seconds. . Furthermore, prior to the start of lapping, a measurement process for measuring the shape of the lower surface plate,
From the measurement result of the measurement step, a calculation step of calculating the rotation direction of the wrapping carrier and the total rotation time of each rotation direction so that the deformation of the lower surface plate is self-corrected,
The method for wrapping a semiconductor wafer according to claim 1 , comprising: Based on the calculation result of the calculation step, the wrapping carrier rotates while being reversed alternately forward and reverse, and is substantially the same as the rotation time calculated in the forward direction and the reverse direction. 7. The method for wrapping a semiconductor wafer according to claim 6 , wherein the wrapping is performed while self-correcting the deformation of the lower surface plate. An upper surface plate and a lower surface plate rotating in opposite directions, and a wrapping carrier mounted between the upper surface plate and the lower surface plate and configured to load a semiconductor wafer in a holding hole;
A sun gear and an internal gear that are mounted so as to mesh with the periphery of the wrapping carrier, and rotate coaxially while having a rotational difference so as to rotationally drive the wrapping carrier;
The rotation of the sun gear and the internal gear are controlled independently of each other, the wrapping carrier is rotated alternately forward and reverse, and the rotation difference of the sun gear and the internal gear is changed abruptly, thereby rotating the wafer during reversal. Control means for controlling the rotation of the wrapping carrier to induce ,
The semiconductor wafer lapping apparatus according to claim 1, wherein the control means controls the wrapping carrier so as to be in a positive direction in a final process after forward and reverse rotation of the wrapping carrier . Comprising surface detection means for detecting the flatness of the surface of the lower surface plate,
9. The semiconductor wafer wrapping apparatus according to claim 8 , wherein the control means is configured to control a rotation speed of the wrapping carrier in accordance with an output of the surface detection means prior to lapping.

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