JP3973962B2 - Surface polishing apparatus and surface polishing method - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a surface polishing apparatus and a surface polishing method.
[0002]
[Prior art]
For example, as shown in FIG. 15, in a lapping process in the production of a semiconductor single crystal silicon wafer, a wafer (workpiece) 110 held by a carrier is sandwiched between surface plates 130 and 140 and released. Surface polishing is performed by a slurry containing abrasive grains.
[0003]
Further, a mesh is formed on the surface of the surface plates 130 and 140, and a part of the wafer 110 is configured to overhang from the surface plates 130 and 140. Therefore, excess slurry or old slurry is discharged out of the system as the surface plates 130 and 140 and the wafer 110 rotate.
[0004]
[Problems to be solved by the invention]
However, the pressure P exerted on the wafer 110 by the surface plates 130 and 140 is maximized on the end surface (singular point) S of the surface plates 130 and 140. Therefore, there is a possibility that a deeply cut shape (overhang mark) may be formed on the wafer 110 due to the pressure exerted by the end facet S.
[0005]
FIG. 16A and FIG. 16B are a perspective view and a plan view showing the shape of the polished wafer 110 based on actual measurement values. As shown in the figure, the wafer 110 has a concavo-convex shape as a whole, and has a problem in flatness.
[0006]
On the other hand, when a configuration for overhanging the wafer 110 is not provided, a problem occurs in the slurry discharge performance.
[0007]
In addition, it is also possible to obtain favorable flatness by processing the surface plate 130 in advance so that the end face has a shape displaced upward. However, since the displacement is on the order of several μm to several tens of μm, it is difficult to process, and the surface plate itself wears with time, so that it is necessary to repeat the processing. Therefore. There are problems in actual application.
[0008]
Further, the wafer after the surface polishing is subjected to a chemical corrosion treatment in order to remove distortion based on the surface polishing. At this time, the edge of the wafer tends to sag and become a loosely convex shape as a whole. However, since this is a chemical reaction, it is extremely difficult to prevent this tendency.
[0009]
Therefore, it is preferable to finish in a concave shape so that the end portion is slightly raised at the stage of surface polishing so that good flatness can be secured after etching. However, it has been difficult for the conventional surface polishing technique to stably provide the concave shape.
[0010]
The present invention has been made to solve such a conventional problem, and an object thereof is to provide a surface polishing apparatus and a surface polishing method capable of controlling the surface shape of a workpiece.
[0011]
[Means for Solving the Problems]
To achieve the above object, the present invention is configured as follows.
[0012]
(1) In a surface polishing apparatus having a surface plate for pressing a workpiece held by a carrier , wherein a part of the workpiece is configured to overhang from the surface plate ,
A surface polishing apparatus comprising pressure control means for reducing a pressure exerted on a workpiece by a singular point formed by an end surface of an end portion of a surface plate during a predetermined period immediately before the end of polishing.
[0013]
(2) In the above (1), the pressure control means reduces the pressure by deforming the end of the surface plate so that the singular point is displaced in a direction away from the workpiece. The surface polishing apparatus as described.
[0014]
(3) The pressure control means deforms the end of the surface plate by thermally contracting the surface of the end of the surface plate located on the opposite side of the polishing surface of the surface plate. The surface polishing apparatus according to (2) above.
[0015]
(4) The method further comprising: a second pressure control unit for increasing the pressure exerted on the workpiece by the singular point in a predetermined period before the start of pressure reduction by the pressure control unit. The surface polishing apparatus according to any one of 1) to (3).
[0016]
(5) In a surface polishing apparatus having a surface plate for pressing a workpiece held by a carrier , wherein a part of the workpiece is configured to overhang from the surface plate ,
A surface polishing apparatus comprising pressure control means for increasing a pressure exerted on a workpiece by a singular point formed by an end surface of an end portion of a surface plate during a predetermined period during polishing.
[0017]
(6) In the above (5), the pressure control means increases the pressure by deforming the end of the surface plate so that the singular point is displaced in a direction toward the workpiece. The surface polishing apparatus as described.
[0018]
(7) The pressure control means deforms the end of the surface plate by thermally expanding the surface of the end of the surface plate located on the opposite side of the polishing surface of the surface plate. The surface polishing apparatus according to (6) above.
[0019]
(8) In a surface polishing method in which a workpiece held on a carrier is pressed by a surface plate,
A part of the workpiece is configured to overhang from the surface plate,
A surface polishing method comprising a step of reducing a pressure exerted on a workpiece by a singular point formed by an end face of an end portion of a surface plate in a predetermined period immediately before the end of polishing.
[0020]
(9) In a surface polishing method in which a workpiece held on a carrier is pressed by a surface plate,
A part of the workpiece is configured to overhang from the surface plate,
A surface polishing method comprising: a step of increasing a pressure exerted on a workpiece by a singular point formed by an end face of an end portion of a surface plate during a predetermined period during polishing.
[0021]
DETAILED DESCRIPTION OF THE INVENTION
Next, embodiments according to the present invention will be described in detail with reference to the drawings.
[0022]
The surface polishing apparatus according to Embodiment 1 of the present invention is, for example, a lapping apparatus used in a lapping process in manufacturing a semiconductor single crystal silicon wafer.
[0023]
As shown in FIGS. 1 and 2, the surface polishing apparatus includes a carrier 20 that holds a sliced silicon wafer (workpiece) 10, and a pair of upper and lower surface plates 30 and 40 that sandwich the carrier 20 and the wafer 10. The pressure control means 50 for reducing the pressure exerted on the wafer 10 by the end face (singular point) S of the surface plate 30 and the slurry supply means (not shown) for supplying the slurry containing loose abrasive grains. And a drive mechanism (not shown) for driving the carrier 20 and the surface plates 30 and 40 to polish the surface of the wafer 10. A part of the wafer 10 is configured to overhang from the surface plates 30 and 40.
[0024]
The pressure control means 50 includes a ring-shaped tank 51 disposed along the circumferential direction of the upper surface of the end of the surface plate 30 and a refrigerant supply for supplying cold water (refrigerant) 52 made of ice water to the ring-shaped tank 51. Means (not shown).
[0025]
Therefore, the pressure control means 50 supplies the cold water 52 to the ring-shaped tank 51 and thermally shrinks the upper surface (the surface located on the opposite side of the polishing surface) of the end surface of the surface plate 30, whereby the surface plate 30. The end portion S of the surface plate 30 can be displaced upward (in a direction away from the wafer 10).
[0026]
In other words, the pressure control means 50 actively deforms the surface plate 30 to control the contact surface pressure distribution between the surface plate 30 and the wafer 10, so that the end surface S of the surface plate 30 becomes the wafer 10. The pressure exerted on can be reduced. Accordingly, by operating the pressure control means 50 in a predetermined period immediately before the end of polishing, the formation of a deeply crushed shape (overhang mark) due to the pressure exerted by the end face S of the surface plate 30 is suppressed, and the wafer The flatness of 10 can be improved.
[0027]
Symbols X and D indicate the circumferential width of the tank 51 (cooling range of the surface plate 30) and the displacement amount of the end surface S of the surface plate 30, respectively.
[0028]
FIG. 3 is a graph showing the relationship between the displacement amount D of the end surface S of the surface plate 30 and the cooling time. As understood from FIG. 3, the displacement amount D and the cooling time have a correspondence relationship.
[0029]
4A and 4B are a perspective view and a plan view showing the shape of the wafer 10 after the surface polishing is finished based on the actual measurement values, and shows a case where the wafer 10 is cooled 1 minute before the surface polishing is finished. . Although some overhang marks remain on the wafer 10, the overall flatness is improved as compared with the conventional case (see FIG. 14).
[0030]
FIGS. 5A and 5B show a case where cooling is performed 2 minutes before the end of surface polishing. The overhang mark has disappeared, and the wafer 10 has a more gradual shape as a whole compared to FIGS. 4 (A) and 4 (B).
[0031]
Therefore, the shape of the wafer 10 can be easily controlled by changing the cooling time. It should be noted that if the cooling time is too long, parts other than the target portion are displaced, and if the cooling time is too short, the overhang mark cannot be sufficiently removed. That is, the cooling time is preferably 3 minutes to 30 seconds immediately before the end of surface polishing.
[0032]
6A and 6B are a perspective view and a plan view showing the shape of the wafer 10 after the surface polishing is finished based on actual measurement values, and shows a case where the cooling range X of the surface plate 30 is 30 mm. ing. The shape of the wafer 10 is generally concave, and is different from the shape (convex shape) of the wafer 10 when the cooling range X shown in FIGS. 5A and 5B is 80 mm. Therefore, the shape of the wafer 10 can be controlled by changing the cooling range X.
[0033]
As described above, in the surface polishing apparatus according to the first embodiment, for example, the cooling time and / or the cooling range is changed according to conditions such as the physical properties and size of the work piece and the surface plate, and the polishing time. Thus, the surface shape of the workpiece can be controlled.
[0034]
Therefore, for example, since the overhang mark can be removed, the flatness of the workpiece can be improved, and a workpiece having a desired flatness can be obtained.
[0035]
In addition, the refrigerant | coolant for thermally shrinking a surface plate is not limited to cold water, For example, it is also possible to apply a low temperature gas. Further, it is possible to apply a cooling means that does not use a refrigerant, for example, a Peltier element. In particular, it is preferable not to use water in that the possibility of mixing water into the slurry is eliminated.
[0036]
Either one or both of the surface plates that cause the displacement are possible. Further, the cooling surface for displacing the singular point at the end of the surface plate is not limited to the upper surface of the end, and a combination of the upper surface and the side surface, or only the side surface can be applied.
[0037]
Furthermore, the means for deforming the end of the surface plate is not limited to that based on thermal contraction, and for example, it is possible to apply stress or use expansion and contraction of a piezoelectric element or an electrostrictive element.
[0038]
Next, a surface polishing apparatus according to Embodiment 2 of the present invention will be described.
[0039]
The surface plate 30 is flat in the initial state (see FIG. 7A), but is worn and deformed by repeated surface polishing. In the case of the surface polishing apparatus according to the first embodiment, the end surface S of the surface plate 30 is displaced, so that wear is not caused uniformly (see FIG. 7B). Accordingly, the end surface S of the surface plate 30 protrudes in the direction toward the wafer 1 over time (see FIG. 7C).
[0040]
Accordingly, as the amount of deformation of the end face of the surface plate 30 based on repeated surface polishing increases, the displacement effect of the end face of the surface plate 30 by the pressure control means becomes weaker, that is, cancels out.
[0041]
FIGS. 8A and 8B are a perspective view and a plan view showing the shape of the wafer 10 whose surface is polished using the surface plate 30 deformed with time, based on actual measurement values. As clearly shown in the figure, the overhang mark is not sufficiently removed although the end face of the surface plate 30 is displaced by the pressure control means. Therefore, regular correction of the surface plate is required.
[0042]
In order to avoid this, in the surface polishing apparatus according to the second embodiment of the present invention, the surface plate 30 is arranged so that the end surface S is displaced in the direction toward the wafer 10 (the polishing surface side (downward in the drawing)). A pressure control means 53 is provided for deforming the end portion of the (see FIG. 9B).
[0043]
Specifically, the pressure control means 53 includes a ring-shaped tank 54 arranged along the circumferential direction of the end of the surface plate 30 and a heating medium supply for supplying hot water (heating medium) 55 to the ring-shaped tank 54. Means. The pressure control means 53 heats the upper surface of the end portion of the surface plate 30 by supplying hot water 55 in the middle of the surface polishing after a predetermined time has elapsed from the start of the surface polishing (see FIG. 9A).
[0044]
As a result, the upper surface of the end portion of the surface plate 30 is thermally expanded and the surface plate 30 is deformed, whereby the end surface S of the end portion is displaced downward (see FIG. 9B). Thereby, the pressure which the edge part end surface S of the surface plate 30 exerts on the wafer 10 increases. Therefore, the contact surface pressure between the end portion of the surface plate 30 and the wafer 10 is increased, and wear of this portion is accelerated.
[0045]
Note that the wear of the end of the surface plate 40 is also accelerated. That is, the shape deformation of the other surface plate 40 can be promoted only by applying to one surface plate 30. Therefore, more effective shape control becomes possible.
[0046]
For example, after this state is continued for about 3 minutes, the heating is stopped, and the pressure exerted on the wafer 10 by the end surface S of the surface plate 30 disappears. However, since the end portion of the surface plate 30 is deformed due to wear, the end portion end surface S is displaced upward (see FIG. 9C).
[0047]
And surface polishing is further continued for about 2 minutes, for example. Therefore, as in the first embodiment, the overhang mark can be removed, and the flatness of the wafer 10 can be improved.
[0048]
Further, in the second embodiment, the wear of the end portion of the surface plate 30 is suppressed in a predetermined period immediately before the end of the surface polishing. However, the pressure control means 53 has already caused the wear to be deformed. Yes. Therefore, after the surface polishing is finished, the surface plate 30 has a surface on which wear is caused uniformly. That is, since the wear rate distribution between the surface plate 30 and the wafer 10 is controlled, periodic correction of the surface plate is not required even when surface polishing is repeated.
[0049]
FIG. 10 is a graph showing the relationship between the amount of displacement of the end face of the surface plate 30 and the heating time when hot water of 50 ° C. is used. As understood from the figure, a displacement of about 20 μm can be easily obtained as in the case of cooling.
[0050]
Therefore, the shape of the surface plate 30 can be controlled by changing the heating time. However, it is necessary to consider that if the heating time is too long, wear of portions other than the target site is accelerated, and if the heating time is too short, wear is insufficient. That is, it is necessary to set the heating time and / or heating range according to conditions such as the physical properties and size of the wafer 10 and the surface plate, and the processing time.
[0051]
As described above, in the surface polishing apparatus according to the second embodiment, for example, the heating time and / or the heating range is changed according to conditions such as the physical properties and size of the workpiece or the surface plate, the polishing time, and the like. Thus, the surface shape of the workpiece can be controlled.
[0052]
Therefore, for example, since the overhang mark can be removed, the flatness of the workpiece can be improved, and a workpiece having a desired flatness can be obtained.
[0053]
In addition, the heat medium for thermally expanding a surface plate is not limited to warm water, For example, high temperature gas can also be applied. It is also possible to apply a heating means that does not use a heat medium, for example, a solid heater. In particular, it is preferable not to use water in that the possibility of mixing water into the slurry is eliminated.
[0054]
The means for deforming the end of the surface plate is not limited to that based on thermal expansion. For example, it is possible to apply stress or use expansion and contraction of a piezoelectric element or an electrostrictive element.
[0055]
Either one or both of the surface plates that cause the displacement are possible. Further, the heating surface for thermally deforming the surface plate is not limited to the upper surface of the end portion, and a combination of the upper surface and the side surface or only the side surface can be applied.
[0056]
Next, a surface polishing apparatus according to Embodiment 3 of the present invention will be described.
[0057]
The third embodiment is different from the second embodiment in that it includes a pressure control means 56 that uses irradiation light.
[0058]
Specifically, as shown in FIG. 11, the pressure control unit 56, for example, a light irradiation unit 57 made of an incandescent lamp, and light absorption for generating heat by absorbing light irradiated from the light irradiation unit 57. It has a surface 58 and a light reflecting surface 59 that reflects the light emitted from the light irradiation means 57.
[0059]
The light absorption surface 58 is made of, for example, a black coating film formed along the circumferential direction of the end portion of the surface plate 30. The light reflecting surface 59 is made of, for example, a metal plate having a mirror finish, and is disposed so as to cover a portion other than the light absorbing surface 58.
[0060]
Therefore, since the light irradiated from the light irradiation means 57 is reflected in parts other than the light absorption surface 58, the pressure control means 56 is in the middle of the surface polishing after a predetermined time has elapsed from the start of the surface polishing. Only the upper surface of the end portion of the surface plate 30 on which 58 is disposed can be heated. As a result, the upper surface of the end portion of the surface plate 30 is thermally expanded, and the end surface S is displaced downward as the surface plate 30 is deformed.
[0061]
As a result, the pressure exerted on the wafer 10 by the end portion end surface S of the surface plate 30 increases, so that the contact surface pressure between the end portion of the surface plate 30 and the wafer 10 increases, and wear of this portion is accelerated. That is, as in the second embodiment, since the wear rate distribution between the surface plate 30 and the wafer 10 is controlled, even when surface polishing is repeated, periodic correction of the surface plate is unnecessary. Become.
[0062]
In the third embodiment, water is not used to thermally expand the surface plate, which is preferable in that the possibility of mixing water into the slurry is eliminated.
[0063]
Furthermore, it is preferable to form fins on the light absorption surface to increase the surface area because absorption and radiation of irradiation light, that is, heating and cooling become efficient.
[0064]
FIG. 12 is a graph showing the relationship between the amount of displacement of the end face of the surface plate 30 and the heating time (irradiation time) when an incandescent lamp is used as the light irradiation means 57. As understood from the figure, a displacement of about 20 μm can be easily obtained as in the case of using warm water.
[0065]
Next, a surface polishing apparatus according to Embodiment 4 of the present invention will be described.
[0066]
In the fourth embodiment, as shown in FIG. 13, a light absorbing surface 58 </ b> A formed on the upper surface and side surfaces of the end surface of the surface plate 30, and a light reflecting surface 59 </ b> A extending vertically from the upper surface of the end portion of the surface plate 30. And the third embodiment is different from the third embodiment.
[0067]
Therefore, the light irradiated from the light irradiation means 57 is blocked by the light reflecting surface 59A and does not reach any part other than the light absorbing surface 58A. Therefore, as in the third embodiment, the pressure control means 56 applies only the upper surface and side surface of the end portion of the surface plate 30 on which the light absorbing surface 58A is disposed during the surface polishing after a predetermined time has elapsed from the start of the surface polishing. Can be heated.
[0068]
That is, as in the third embodiment, since the wear rate distribution between the surface plate 30 and the wafer 10 is controlled, it is not necessary to periodically modify the surface plate even when surface polishing is repeated. Become.
[0069]
14A and 14B are a perspective view and a plan view showing the shape of the wafer 10 after the surface polishing is finished based on actual measurement values. As clearly shown in the figure, no overhang mark remained and a wafer 10 having good flatness was obtained.
[0070]
The present invention is not limited to the above-described embodiments, and various modifications can be made within the scope of the claims.
[0071]
For example, the pressure control means (second pressure control means) according to the second or third embodiment can be incorporated into the first embodiment. In this case, since the contact surface pressure distribution and the wear rate distribution between the surface plate 30 and the wafer 10 can be controlled, the flatness of the workpiece can be further improved.
[0072]
【The invention's effect】
According to the present invention described above, the surface shape of the workpiece can be controlled. Therefore, for example, the flatness of the workpiece can be improved by removing the overhang mark.
[Brief description of the drawings]
FIG. 1 is a plan view for explaining a surface polishing apparatus according to an embodiment of the present invention.
FIG. 2 is a cross-sectional view of an essential part for explaining a surface polishing apparatus according to an embodiment of the present invention.
FIG. 3 is a graph showing the relationship between the amount of displacement of the end face of the surface plate and the cooling time.
FIGS. 4A and 4B are a perspective view and a plan view showing the shape of a wafer after completion of surface polishing based on actual measurement values, showing a case of cooling from one minute before completion of surface polishing. Yes.
FIGS. 5A and 5B are a perspective view and a plan view showing the shape of a wafer after completion of surface polishing based on actual measurement values, showing a case where cooling is performed two minutes before the completion of surface polishing. Yes.
FIGS. 6A and 6B are a perspective view and a plan view showing the shape of a wafer after surface polishing is finished based on actual measurement values, showing a case where the cooling range of the surface plate is 30 mm. Yes.
FIGS. 7A to 7C are cross-sectional views for explaining temporal deformation of a platen shape based on repeated surface polishing, and the initial state, the shape during surface polishing, and the shape after completion of surface polishing, respectively. Is shown.
FIGS. 8A and 8B are a perspective view and a plan view showing the shape of a wafer whose surface is polished using a surface plate deformed with time based on actual measurement values.
FIGS. 9A to 9C are main part cross-sectional views for explaining a surface polishing apparatus according to a second embodiment of the present invention, at the time of starting surface polishing, in the middle of surface polishing, immediately before the end of surface polishing; The shape is shown.
FIG. 10 is a graph showing the relationship between the amount of displacement of the end facet of the surface plate and the heating time according to Embodiment 2 of the present invention.
FIG. 11 is a cross-sectional view of relevant parts for explaining a surface polishing apparatus according to a third embodiment of the present invention.
FIG. 12 is a graph showing the relationship between the amount of displacement of the end facet of the surface plate and the heating time according to Embodiment 3 of the present invention.
FIG. 13 is a cross-sectional view of relevant parts for explaining a surface polishing apparatus according to a fourth embodiment of the present invention.
FIGS. 14A and 14B are a perspective view and a plan view showing the shape of a wafer after completion of surface polishing based on actual measurement values, respectively.
FIG. 15 is a cross-sectional view for explaining a conventional surface polishing apparatus.
FIGS. 16A and 16B are a perspective view and a plan view showing the shape of a wafer after completion of surface polishing based on actual measurement values, respectively.
[Explanation of symbols]
10 ... silicon wafer (workpiece),
20 ... carrier,
30, 40 ... surface plate,
50 ... Pressure control means,
51 ... Ring-shaped tank,
52 ... cold water,
53 ... Pressure control means,
54 ... Ring tank,
55 ... warm water,
56 ... Pressure control means,
57 ... light irradiation means,
58, 58A ... light absorbing surface,
59, 59A ... light reflecting surface,
D: Displacement amount,
S ... End face (singular point)
X: Cooling range.

Claims (9)

In a surface polishing apparatus having a surface plate for pressing a workpiece held by a carrier, and a part of the workpiece is configured to overhang from the surface plate ,
A surface polishing apparatus comprising pressure control means for reducing a pressure exerted on a workpiece by a singular point formed by an end surface of an end portion of a surface plate during a predetermined period immediately before the end of polishing.   2. The surface polishing according to claim 1, wherein the pressure control means reduces the pressure by deforming an end of the surface plate so that the singular point is displaced in a direction away from the workpiece. apparatus.   The pressure control means deforms the end of the surface plate by thermally contracting the surface of the end of the surface plate located on the opposite side of the polishing surface of the surface plate. The surface polishing apparatus according to 1.   4. The apparatus according to claim 1, further comprising second pressure control means for increasing a pressure exerted on the workpiece by the singular point during a predetermined period before the pressure reduction by the pressure control means is started. The surface polishing apparatus according to any one of the above. In a surface polishing apparatus having a surface plate for pressing a workpiece held by a carrier, and a part of the workpiece is configured to overhang from the surface plate ,
A surface polishing apparatus comprising pressure control means for increasing a pressure exerted on a workpiece by a singular point formed by an end surface of an end portion of a surface plate during a predetermined period during polishing.   6. The surface polishing according to claim 5, wherein the pressure control means increases the pressure by deforming an end portion of the surface plate so that the singular point is displaced in a direction toward the workpiece. apparatus.   The said pressure control means deform | transforms the edge part of a surface plate by thermally expanding the surface of the edge part of a surface plate located in the opposite side with respect to the polishing surface of a surface plate. The surface polishing apparatus according to 1. In a surface polishing method of pressing a workpiece held by a carrier with a surface plate,
A part of the workpiece is configured to overhang from the surface plate,
A surface polishing method comprising a step of reducing a pressure exerted on a workpiece by a singular point formed by an end face of an end portion of a surface plate in a predetermined period immediately before the end of polishing. In a surface polishing method of pressing a workpiece held by a carrier with a surface plate,
A part of the workpiece is configured to overhang from the surface plate,
A surface polishing method comprising: a step of increasing a pressure exerted on a workpiece by a singular point formed by an end face of an end portion of a surface plate during a predetermined period during polishing.

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