JP3689824B2 - Method for polishing plate-like member - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a method for polishing a plate-like member such as a semiconductor wafer, for example, a method for polishing a semiconductor wafer with high flatness in lapping or mirror polishing.
[0002]
[Prior art]
It is well known to polish the wafer by rotating the holding member while revolving relative to the surface plate while holding the semiconductor wafer between the rotating upper and lower surface plates.
Increasing the flatness of a semiconductor wafer is one of the extremely important requirements in a wafer process. By the way, in the above polishing method, elements that have a particularly significant influence on the flatness of the wafer include the rotation state of the wafer holding member and the revolution state with respect to the surface plate. In order to improve the flatness, the wafer holding member Experiments have confirmed that it is more effective to increase the rotation speed than to increase the revolution speed.
[0003]
[Problems to be solved by the invention]
However, if the rotation speed is set higher than the revolution speed, (1) the life of the wafer holding member is shortened, and (2) the wafer is detached from the holding member at the initial stage of polishing when the wafer thickness is not uniform. There were problems such as becoming easier.
Therefore, in the prior art, when r is the rotation speed of the wafer holding member and R is the revolution speed of the wafer holding member, the ratio r / R between r and R is 0.5 to 1.5 during the polishing step. However, there was a limit to increasing the flatness of the wafer.
[0004]
Accordingly, an object of the present invention is to greatly increase the flatness of a plate-like member such as a semiconductor wafer, and at the same time, a plate capable of solving the above-mentioned conventional problems (1) and (2). It is providing the grinding | polishing method of a shaped member.
[0005]
[Means for Solving the Problems]
The polishing method of the present invention, when it such to rotate the holding member on a platen in a state of holding the plate-like member to the holding member is polished by Racovian rolling, the rotation number of rotations of the plate-shaped member holding member r When the revolution speed of the plate-like member holding member is R, the ratio r / R is made smaller than the ratio r / R at the end of polishing at the initial stage of polishing. is there.
[0006]
That is, in the polishing method of the present invention, the plate-like member holding member (for example, a semiconductor wafer holding metal fitting) and the plate-like member are unfamiliar with each other in the initial stage of polishing. By polishing in a state where the member is securely held by the holding member, and when the familiarity between the holding member and the plate-like member is improved, the r / R value is increased to a value suitable for high flatness polishing. The flatness of the member is greatly improved as compared with the conventional method.
[0007]
In the present invention, in the first half of the polishing step, the r / R value is an appropriate value within the range of 0.5 to 1.5, but this range has been widely adopted in the prior art, and in this range, Although high flatness polishing is impossible, polishing can be performed with the plate-like member securely held by the holding member.
In the present invention, the r / R value is set to an appropriate value within the range of 3 to 10 in the latter half of the polishing step, because the high flatness polishing cannot be expected when the r / R value is less than 3, When r / R exceeds 10, the chamfered outer peripheral portion is damaged due to friction between the wafer outer peripheral portion and the holding member, and in particular, the occurrence rate of the accident of the wafer jumping out of the holding member is increased, and the flatness of the wafer after polishing is increased. This is because the improvement will reach its peak.
[0008]
In the present invention, it is preferable that the ratio r / R is made smaller than the ratio r / R in the second half of the polishing step in the first half of the polishing step of polishing half of the polishing allowance of the plate-like member. Specifically, the ratio r / R is maintained at an appropriate value (constant value) in the range of 0.5 to 1.5 in the first half of the polishing step for polishing half of the polishing allowance, and the latter half of the polishing step. Then, a method of maintaining the ratio r / R at an appropriate value (constant value) within the range of 3 to 10 can be adopted (refer to the column of Examples described later for this).
In this method, the r / R value is lowered until the middle of the polishing, and the stable polishing is continued. Thereafter, the r / R value is increased once, and the high flatness polishing is performed in the latter half of the polishing process. Is.
[0009]
In the present invention, a method of gradually increasing the r / R value with the lapse of the polishing time can also be adopted. In this case, it may be increased stepwise a plurality of times as the polishing time elapses, or may be increased steplessly (continuously) as the polishing time elapses.
[0010]
In the present invention, it is preferable to set the r / R value to the maximum value before the remaining polishing allowance of the plate-like member reaches 1 μm. The reason is that if the r / R value is set to the maximum value after the remaining polishing allowance becomes 1 μm, the remaining polishing allowance may be lost before the high flatness polishing is completed. .
Further, in the present invention, it is desirable to automatically increase the r / R value by using a timer or a plate-like member thickness detecting means.
The polishing method of the present invention is extremely effective for lapping or mirror polishing a semiconductor wafer such as a silicon wafer.
Further, when the semiconductor wafer lapping or mirror polishing is performed by the plate member polishing method according to the present invention, wherein the ratio r / R at the initial stage of polishing is made smaller than the ratio r / R at the end of polishing. The following method, that is, the plate-like member is held by a carrier (plate-like member holding member) made of a planetary gear, the carrier is engaged with the sun gear and the internal gear, and the carrier is held by the upper surface plate and the lower surface plate. It is particularly preferable that the plate member is revolved while being rotated while being sandwiched, and the upper and lower surfaces of the plate member are simultaneously polished by the upper surface plate and the lower surface plate.
[0011]
When holding a plate-like member with a holding member, and setting this holding member in a polishing device to polish the plate-like member, the purpose is as follows:
(1) aligning the thickness of the plate-like member to the standard value;
(2) increasing the flatness of the plate-like member to a target level;
(3) equalizing the surface roughness of the plate member;
It is.
[0012]
In other words, the plate-like member before polishing is generally uneven in thickness, is not flat, and has a large surface roughness. If polishing is performed by holding a plurality of such plate-shaped members together with a holding member, the holding member vibrates at the initial stage of polishing, so that it is difficult to start polishing in a smooth state. Eventually, as the polishing progresses, each dimension of the plate-like member is adjusted, a uniform hit comes out, and the smoothness is transferred to the flatness of the plate-like member. Therefore, the polishing for improving the flatness may be performed in the latter half of the polishing process.
As described above, in the polishing method of the present invention, the dimensions of the plate-like member are adjusted in the first half of the polishing step, and the flatness of the plate-like member is raised to the target level in the second half.
[0013]
In general, since the holding member is premised on repeated use, the dimension in the direction of polishing, that is, the thickness of the holding member, is usually smaller than the thickness of the plate member after polishing. This is because the plate-like member is held relatively (relatively) by the holding metal fitting in the initial stage of polishing, and therefore, a very large load is applied to the movement of the polishing apparatus and the plate-like member in the initial stage of polishing. Means.
[0014]
In general, when wrapping a semiconductor wafer, a double-sided lapping machine shown in FIG. 1 is used.
In this lapping machine, the upper surface plate 1 is rotated in the opposite direction to the lower surface plate 2, and a holding member, that is, a carrier 3 (planetary gear) disposed between these surface plates is placed around the sun gear 4 at the center of the surface plate and its surroundings. By engaging with the internal gear 5 that is positioned, the carrier 3 is revolved in the rotational direction of the lower surface plate 2 while rotating.
In this double-sided lapping machine, movements in four directions are given to a plurality of semiconductor wafers set in the carrier 3, so that an unreasonable or biased load is not applied to the carrier 3 and the semiconductor wafer, so that reliable and stable lapping is possible. It can be performed.
[0015]
1 will be described in more detail. The power of the continuously variable transmission motor 15 is transmitted to the vertical shaft 20 via the clutch 17 and the bevel gears 18 and 19. The vertical shaft 20 is provided with a plurality of gears 21, 22, 24 and 25, and the rotation of the gear 21 is transmitted to the gear 14 provided on the drive shaft 6 of the upper lapping machine 1 through the intermediate gear 16. The The rotation of the gear 22 is transmitted to the gear 13 provided on the drive shaft 7 of the sun gear 4. The rotation of the gear 25 is transmitted to the gear 11 provided on the drive shaft 12 of the lower surface plate 2. The rotation of the gear 24 is transmitted to the gear 10 provided on the drive shaft 9 of the internal gear 5.
[0016]
Further, when the semiconductor wafer is lapped according to the present invention, the drive shafts of the upper lapping machine 1, the lower lapping machine 2, the sun gear 4 and the internal gear 5 are driven by separate motors with continuously variable transmissions in the apparatus of FIG. It is desirable to use a four-way wrapping apparatus having a structure to be used. The r / R value can be easily changed by changing the rotational speed of each drive shaft.
[0017]
【Example】
Next, examples of the present invention and comparative examples using the conventional method will be described.
Example 1
Lapping was performed on 34 silicon wafers having a diameter of 150 mm and a thickness of 0.7 mm using the lapping machine shown in FIG. In this case, the number of wafers held per holding member (carrier) was four, and five carriers were used. The polishing allowance was 0.1 mm.
The ratio (r / R) of the rotation speed and revolution speed of the holding member is set to 0.7 in the first half of the polishing process (from the start of polishing to the time when 1/2 of the polishing allowance is polished), and then The operation of the polishing apparatus was once stopped and the r / R value was increased to 3.8 all at once, and then the latter half of the polishing process was performed.
[0018]
Example 2
The same lapping was performed on the same 33 silicon wafers as in Example 1. The polishing allowance was also the same as in Example 1.
In the first half of the polishing process (from the start of polishing until the time when ½ of the polishing allowance is polished), the r / R value is set to 0.7, and then the operation of the polishing apparatus is temporarily stopped to set the r / R value to The latter half of the polishing process was carried out at a stretch to 6.1.
[0019]
Example 3
The same lapping was performed on the same 25 silicon wafers as in Example 1. The polishing allowance was also the same as in Example 1.
In the first half of the polishing process (from the start of polishing until the time when ½ of the polishing allowance is polished), the r / R value is set to 0.7, and then the operation of the polishing apparatus is temporarily stopped to set the r / R value to The latter half of the polishing process was carried out at a stretch to 9.3.
[0020]
Comparative Example 1
Lapping was performed on 35 silicon wafers identical to those in Example 1. The polishing allowance was also the same as in Example 1. The r / R value was maintained at a constant value of 0.7 throughout the polishing process.
[0021]
The results of Examples 1, 2, 3 and Comparative Example 1 are shown in FIGS. 2, 3, 4, and 5, respectively. These figures are histograms relating to the flatness of the polished wafer. In these figures, “flatness” is evaluated by TTV, and the numbers in the figures indicate the average value of each example as a relative value when the average value of Comparative Example 1 is 1.00. It is a thing. TTV is a difference between the maximum value and the minimum value of the wafer thickness when the entire area of the wafer is measured. In this case, the thickness was measured using a general-purpose thickness measuring instrument.
[0022]
As apparent from comparison of FIGS. 1 to 4, according to the polishing method of the present invention, a polishing wafer having remarkably excellent flatness can be obtained as compared with the case of the conventional polishing method. Moreover, in this invention, it turns out that the polishing wafer with higher flatness is obtained by setting r / R value in the latter half of a grinding | polishing process higher.
[0023]
【The invention's effect】
As is apparent from the above description, in the polishing method of the present invention, the rotation speed and revolution speed of the plate member holding member at the initial stage of polishing (or the first half of the polishing process) where the thickness of the plate member is not uniform. Ratio: By setting the r / R value to be low, the holding member can securely hold the plate-like member and perform stable polishing, so that the size of the plate-like member can be accurately adjusted. The holding member is not subjected to an excessive load.
Further, at the end of polishing (or the latter half of the polishing step), the flatness of the plate-like member can be improved to a high level target value by setting the r / R value to be considerably higher than that of the conventional method. . In this case, since the dimension of the plate-like member is adjusted in the initial stage of polishing, the problem that the plate-like member is detached from the holding member or the holding member is overloaded and the life is shortened is solved.
Therefore, according to the present invention, the semiconductor wafer can be stably lapped or mirror-polished to produce a wafer having a remarkably high flatness, and the life of the wafer holding member can be extended.
[Brief description of the drawings]
FIG. 1 is a cross-sectional view showing the structure of a lapping machine used in Examples 1 to 3 of the present invention.
FIG. 2 is a histogram showing the results of Example 1 of the present invention.
FIG. 3 is a histogram showing the results of Example 2 of the present invention.
FIG. 4 is a histogram showing the results of Example 3 of the present invention.
FIG. 5 is a histogram showing the results of Comparative Example 1;
[Explanation of symbols]
1 Upper surface plate 2 Lower surface plate 3 Holding member (carrier)
4 Sun Gear 5 Internal Gear

Claims (10)

Upon although while holding the plate-like member to the holding member such to rotate the retaining member with the surface plate for polishing by Racovian rolling, the rotation number of rotations of the plate-shaped member holding member is r, the plate-shaped member holding member A polishing method for a plate-like member, characterized in that, when R is the revolution number of rotation, the ratio r / R is smaller than the ratio r / R at the end of polishing at the initial stage of polishing.   The ratio r / R is set to be smaller than the ratio r / R in the second half of the polishing step in the first half of the polishing step of polishing half of the polishing allowance of the plate-like member. Polishing method for plate-like member.   In the first half of the polishing step, the ratio r / R is set to an appropriate value within the range of 0.5 to 1.5, and in the second half of the polishing step, the ratio r / R is set to an appropriate value within the range of 3 to 10. The method for polishing a plate-like member according to claim 1 or 2,   4. The plate member polishing method according to claim 1, wherein the ratio r / R is increased stepwise a plurality of times as the polishing time elapses.   4. The plate member polishing method according to claim 1, wherein the ratio r / R is increased steplessly as the polishing time elapses.   6. The method for polishing a plate member according to claim 4, wherein the ratio r / R is set to a maximum value before the remaining polishing allowance of the plate member reaches 1 [mu] m.   The method for polishing a plate member according to claim 1, wherein the operation of increasing the ratio r / R is automatically performed using a timer.   The method for polishing a plate member according to any one of claims 1 to 6, wherein the operation of increasing the ratio r / R is automatically performed using a plate member thickness detecting means. .   The plate-like member polishing method according to any one of claims 1 to 8, wherein the plate-like member is a semiconductor wafer, and the polishing step is lapping.   The method for polishing a plate member according to claim 1, wherein the plate member is a semiconductor wafer, and the polishing step is mirror polishing.

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