JP2000198057A - Device for mirror-finishing chamfered surface of semiconductor wafer - Google Patents

Abstract

PROBLEM TO BE SOLVED: To mirror polish chamfered surfaces in both front and rear surfaces of a semiconductor wafer in a short time with a high degree of accuracy even though the holding force of a vacuum chuck is low. SOLUTION: A device for mirror-finishing chamfered surfaces 11, 12 of a semiconductor wafer 10, is composed of polishing units 1, 2 incorporating an upper surface polishing drum 5 and a lower surface polishing drum 6 for polishing the chamfered surfaces 11, 12, and polishing unit 3, 4 incorporating side surface polishing drums 7, 8 for polishing a side part 13 of the outer surface of the wafer 10. In each polishing unit, the polishing drum is wound on its side surface part with a polishing fabric and is journalled so as to be rotated by a variable speed motor incorporated in the polishing unit.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an apparatus for mirror-polishing a chamfered surface of a semiconductor wafer whose outer peripheral portion has been chamfered in advance in manufacturing a semiconductor wafer.

In manufacturing a semiconductor wafer, an apparatus as disclosed in Japanese Patent No. 26514793, for example, has been proposed as an apparatus for mirror-polishing a surface of an outer peripheral portion which has been chamfered on both front and rear surfaces in advance. .

[0003] This involves rotating a drum member on which an abrasive cloth is adhered to the outer peripheral surface, and rotating the drum member on which the abrasive cloth is adhered (a drum member on which the abrasive cloth is adhered on a cylindrical surface, or a material of the abrasive cloth). The outer peripheral portion of the semiconductor wafer held by the vacuum chuck constituting the wafer holding mechanism is brought into contact with a cylindrical drum member (hereinafter, referred to as a “polishing drum”).
By rotating the semiconductor wafer around an axis while making contact with a predetermined angle while supplying a slurry containing abrasive grains to the contact portion, the chamfered surface of the outer peripheral portion is mirror-polished.

In actuality, in order to mirror-polish the three chamfering surfaces on the front and back surfaces and the three processing surfaces on the outer peripheral side surface, three processing mechanisms set at different contact angles, and the semiconductor wafer is mounted on each processing mechanism. And a semiconductor wafer transfer mechanism for sequentially transferring the semiconductor wafer. The semiconductor wafer sequentially passes through the three processing mechanisms, and the processing surface is mirror-polished one by one by each processing mechanism, and finally, the three processing surfaces of the chamfered processing surface on the front and back surfaces and the outer peripheral side surface portion The mirror surface is polished.

[0005]

However, in the above-described system having three processing mechanisms, since a total of three processing surfaces are sequentially polished, it takes a long time to process one semiconductor wafer. For this reason, if the slurry adheres to the polished surface during the processing by the first processing mechanism, it will remain attached for a long time,
The polishing surface tends to be uneven due to the slurry etching action. This is because the slurry is obtained by dispersing fine abrasive grains such as silica in a strong alkaline aqueous solution.

Further, since the apparatus has three processing mechanisms and transport mechanisms before and after each of the processing mechanisms, the apparatus becomes expensive and large, the area occupied by the clean room is large, and the running cost is also large.

Further, in the mirror polishing of each processing surface, one side of the semiconductor wafer is held by a vacuum chuck and the processing is performed. However, when the outer peripheral portion of the semiconductor wafer comes into contact with the polishing drum and is polished, the semiconductor wafer is polished. Then, a reaction force for processing is applied to the suction surfaces of the semiconductor wafer and the vacuum chuck. The vacuum chuck must hold the wafer with a force that opposes this reaction force. Therefore, if you try to increase the processing speed by pressing the semiconductor wafer more strongly against the polishing drum, the reaction force also increases in proportion to it, and the semiconductor wafer cannot be completely retained and falls off from the vacuum chuck, or the processing shifts from the holding position. Accuracy cannot be maintained.

By the way, it is possible to increase the holding force by increasing the degree of vacuum of the chuck, but since the pressing force against the suction surface is increased, the semiconductor wafer is liable to be scratched.

Furthermore, in this method, the relative positional relationship between the chuck and the polishing drum greatly affects the mirror finishing accuracy of the chamfered surface. Deflection of the wafer due to contact with the polishing drum, warpage of the wafer, slight wear of the polishing drum, and variation in the elasticity of the polishing drum are factors that change the relative positional relationship. When these factors change, the mirror processing width varies, and the surface roughness of the processed surface varies.

SUMMARY OF THE INVENTION The present invention has been made in view of the above-mentioned problems, and has been made in consideration of the fact that when a mirror polishing process is performed on a chamfered surface on both front and back surfaces of a semiconductor wafer, the holding force of a vacuum chuck constituting a wafer holding mechanism is small even if it is small. It is an object of the present invention to provide a mirror polishing apparatus for a chamfered surface of a semiconductor wafer, which can perform processing in a long time and which can mirror-polish a chamfered surface with high precision.

The mirror polishing of the outer peripheral side surface of the semiconductor wafer can be performed in a short time in the same manner as described above, and the chamfered surface of the semiconductor wafer and the mirror polishing of the chamfered surface can be performed simultaneously. It is an object of the present invention to provide a mirror polishing device for an outer peripheral side surface portion.

[0012]

For this reason, the apparatus for mirror-polishing a chamfered surface according to the first aspect of the present invention employs an upper surface polishing drum and a lower surface polishing drum for polishing a chamfered surface on an outer peripheral portion of a semiconductor wafer. By forming a wafer holding area for holding the front and back surfaces of the outer peripheral portion of the wafer, and rotating the two polishing drums in the same direction, the reaction force applied to the front and back polishing applied to the semiconductor wafer is reduced by the wafer holding area. It was configured to cancel.

Thus, even if a large contact pressure is applied to the polishing drum, the semiconductor wafer becomes a force for clamping the semiconductor wafer from the front and back, so that the contact pressure applied to the vacuum chuck constituting the wafer holding mechanism is reduced. Is countered. In addition, since the rotation direction of the polishing drum is the same, the reaction force accompanying the polishing working in the circumferential direction of the semiconductor wafer is opposite between the front and back sides, and this is also canceled in the wafer holding area. Therefore, the force for rotating the wafer against the reaction force can be extremely small. Also, as a second invention, for example, two side polishing drums are arranged so as to sandwich the semiconductor wafer and abut against the outer peripheral side surface portion, and are brought into contact with each other. It is possible to cancel the reaction force due to working working. With this configuration, a high processing speed can be obtained as in the case of mirror polishing of the chamfered surface. As described above, the chamfered surface mirroring apparatus according to the second aspect of the present invention can simultaneously and highly precisely mirror-polish the three surfaces of the front and back chamfered surfaces and the side surfaces at a large processing speed. In addition, there is no flaw caused by being attracted by a strong force to the vacuum chuck constituting the wafer holding mechanism.

Further, since one surface is polished for each polishing drum, each polishing drum can be formed into a simple cylindrical shape, which facilitates the production and the accuracy. Although the apparatus for performing mirror polishing using a polishing drum has been described above, it is also possible to perform chamfering by grinding by using a grinding wheel in which diamond abrasive grains are embedded instead of the polishing drum. . This makes it possible to manufacture a chamfering apparatus having the same characteristics as those of the above-described mirror polishing apparatus for chamfered surfaces according to the present invention. Alternatively, each polishing drum may be replaced with a set of pulleys, and a loop of a polishing tape may be mounted thereon, driven by the pulleys to abut against the semiconductor wafer, and polished similarly. With this, a chamfering apparatus having the same characteristics as the present invention can be manufactured.

[0015]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS In the most preferred embodiment of the present invention, the chamfered surface and the side surface of the outer peripheral portions of the front and back surfaces of a semiconductor wafer can be simultaneously processed by separate polishing drums. Each of the polishing drums is rotated at a high speed by a separate motor, and is provided so that the rotation speed, the rotation direction, the contact angle to the semiconductor wafer, and the contact pressure can be adjusted.

Each of the polishing drums and a motor for rotating the polishing drums are formed into a unit including a bearing and a shaft seal, and a slurry containing abrasive grains is supplied to a contact portion between each of the polishing drums and the semiconductor wafer. Is done.

The vacuum chuck constituting the wafer holding mechanism moves while holding the semiconductor wafer, and rotates while bringing the outer peripheral portion of the wafer into contact with the polishing drum. This too
The semiconductor wafer is brought into contact with the polishing drum by a unitized automatic positioning device including a motor and a bearing, so that the semiconductor wafer is automatically set at a preset position.

The position of the vacuum chuck at the time of processing is set according to a change in processing conditions such as the diameter and thickness of the semiconductor wafer. During processing, the semiconductor wafer is rotated from 2 revolutions / minute to 10 revolutions / minute.
Rotate at the speed of a minute. The polishing drum has a peripheral speed of 100
A rotation speed corresponding to m / min to 500 m / min is given.

[0019]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described below with reference to the drawings. For convenience, the upper and lower polishing drums are omitted in FIGS. FIG. 1 is a schematic view showing a mirror polishing apparatus for a chamfered surface according to an embodiment.
As shown in FIG. 1, the apparatus of this embodiment includes a wafer holding mechanism 100 for holding a semiconductor wafer and applying a rotational force, an upper polishing drum 5 for polishing the chamfered surfaces 11, 12 of the semiconductor wafer 10, and a lower polishing drum. And polishing units 3 and 4 incorporating side polishing drums 7 and 8 for polishing the outer peripheral side portion 13 of the wafer.
And a polishing unit. The polishing units were arranged so that the respective polishing drums came into contact with the semiconductor wafer 10 at the same time. The upper surface polishing drum 5 and the lower surface polishing drum 6 rotate in the same direction, and the side surface polishing drums 7 and 8 rotate in opposite directions.
Each of the polishing units is rotatably driven by a variable speed motor incorporated in the polishing unit, with each polishing drum having a polishing cloth wound around a side portion supported by a shaft. The larger the diameter of the polishing drum, the longer the life of the polishing cloth wrapped around the side surface and the longer the uniformity of the polishing surface can be maintained for a long period of time. Becomes larger. In the present embodiment, the diameter of the upper surface polishing drum 5 and the lower surface polishing drum 6 is 100 mm, and the diameter of the side surface polishing drums 7 and 8 is 50 mm.
Polished at a rotation speed of minutes. The rotation speed of the semiconductor wafer 10 was 5 rotations / minute.

In the polishing units 1 and 2 sandwiching the front and back surfaces, the center lines 5c and 6c of the rotating shafts of the respective polishing drums intersect with each other at an angle of 10 degrees as shown in FIG. Contacts the semiconductor wafer 10 with the chamfered surface of the semiconductor wafer 10 held therebetween.
This contact angle is similar to the angle of the chamfered surface.

As shown in FIG. 3, the center lines 5c, 6c of the rotation axes of the upper polishing drum 5 and the lower polishing drum 6 are placed on a virtual plane including the wafer surface in a direction perpendicular to the plane.
Are projected, the center lines 5c and 6c of the rotation axes of the respective polishing drums cross each other at an angle of 10 degrees on the plane without passing through the rotation center of the semiconductor wafer 10.

As a result, the area of contact between the polishing cloth wound around each polishing drum and the chamfered surfaces 11 and 12 of the semiconductor wafer 10 is increased, and partial consumption of the polishing cloth is reduced. Also, the wettability of the slurry to an unnecessary portion such as the flat surface of the wafer is reduced. If the angle is less than 5 degrees, there is no effect. If the angle is more than 15 degrees, the range in contact with the polishing drum penetrates considerably deeply into the flat surface of the semiconductor wafer, and the range in which the slurry is wetted is widened.

If the slurry is left wet for a long time,
As described above, the semiconductor wafer 10 is etched, and the polished surface becomes uneven. For this reason, it is necessary to set the angle to 15 degrees or less so that the slurry does not come into contact with a flat surface particularly requiring high accuracy.

As shown in FIG. 4, the rotation center axes of the side polishing drums 7 and 8 of the polishing units 3 and 4 which sandwich the outer peripheral side surface portion 13 of the semiconductor wafer 10 from the radial direction are opened by 120 degrees from the wafer rotation center. They lie on straight lines with corners and rotate in opposite directions. Thereby, the semiconductor wafer 1
The reaction force due to the working acting in the circumferential direction of 0 can be canceled. Further, since the semiconductor wafer 10 is sandwiched with a large opening angle of 120 degrees, the side polishing drums 7 and 8
The force of pushing the semiconductor wafer 10 in the radial direction by the contact force of
Almost can be countered.

Further, as shown in FIG. 5, the side polishing drum 7 includes a tangent line of the outer periphery of the semiconductor wafer 10 in a contact area of the semiconductor wafer 10 and a rotation of a wafer holding mechanism 100 for holding the semiconductor wafer 10 by a vacuum chuck. On a virtual plane parallel to the axis center line C (a vertical plane including the line XX 'in FIG. 4), the center line 7c of the rotation axis of the side polishing drum 7 and the wafer Holding mechanism 1
When the center line C of the rotation axis of 00 is projected {as viewed in the direction of arrows in FIG. 4XX}, the two center lines are provided to intersect at an angle of 5 degrees. Similarly, the side polishing drum 8 also includes an imaginary plane (including a tangent line on the outer periphery of the semiconductor wafer 10) parallel to the center axis C of the rotation axis of the wafer holding mechanism 100 that holds the semiconductor wafer 10 with a vacuum chuck (Y in FIG. 4). −Y ′ line) on the vertical surface including the Y ′ line from the direction perpendicular thereto.
When the center line 8c of the rotation axis of FIG. 4A and the center line C of the rotation axis of the wafer holding mechanism 100 are projected {as viewed in the direction of arrows in FIG.
The two center lines are provided to intersect at an angle of 5 degrees.
As a result, the contact area between the polishing cloth and the outer peripheral side surface portion 13 of the semiconductor wafer 10 is increased as in the case of the upper surface polishing drum 5 and the lower surface polishing drum 6 for holding and polishing the chamfered surfaces 11 and 12. Can be.

Thus, the consumption of the polishing cloth can be made uniform, and the mirror surface state can be made uniform. When the angle is less than 2 degrees, there is no effect, and when the angle is more than 15 degrees, the force for bending the semiconductor wafer 10 in a direction perpendicular to the surface becomes large. The contact is not stable, and the mirror surface state becomes uneven.

The outer peripheral side portion 13 of the semiconductor wafer 10
FIG. 6 shows another embodiment in which three side polishing drums are brought into contact with the drum. By doing so, the side polishing drum 7,
Although the holding force of the vacuum chuck can be reduced by auxiliary holding of the semiconductor wafer 10 by the operations of 8 and 9, the held semiconductor wafer 10 is the same among the three side surface polishing drums. The rotational driving action of the two side polishing drums 7 and 8 rotating in the opposite directions and the polishing action of the one polishing drum 9 rotating in the opposite direction work together, and large suction from the vacuum chuck is achieved. Speedy polishing will be performed without any action.

The reason why the diameter of the side surface polishing drums 7 and 8 holding the outer peripheral side surface portion 13 is 1/2 of that of the upper surface polishing drum 5 and the lower surface polishing drum 6 holding the front and back chamfered portions is that the chamfering is performed. This is because the area of the outer peripheral side portion 13 is about か ら to ５ of the area of the processing surfaces 11 and 12, so that the processing speed can be reduced. In consideration of maintenance, commonality of parts, and the like, it is also possible to use polishing drums all having the same diameter.

Using the apparatus of the present invention, a diameter of 200 mm
The chamfered surface of the silicon semiconductor wafer and the outer peripheral side surface were mirror-polished. In the conventional apparatus, it took about 8 minutes to completely make the chamfered surface and the outer peripheral side surface of one semiconductor wafer into a mirror state, but in the case of the apparatus of the present invention, it took 2 minutes to complete the process. I was able to mirror it. For this reason, the time during which the slurry was attached was shortened, and corrosion of the already mirror-finished portion and sticking of the abrasive grains were significantly reduced. Also, the mirror surface state was stable, and the uniformity of the surface roughness was excellent as compared with the conventional case. Furthermore, the device of the present invention occupies one third of the area of the conventional device,
Since the configuration of the device is simpler than that of the conventional device, the price of the device is also about 1/2.

[0030]

According to the first aspect of the present invention, as described above, the mirror polishing of the chamfered surface of the semiconductor wafer can be completed in a shorter time than in the prior art. Therefore, the mirror surface state is made uniform, and the quality is improved. In addition, since the area formed between the upper polishing drum and the lower polishing drum is used as a wafer clamping area to hold the wafer, the wafer is held against the polishing force in the same manner as when holding the wafer by vacuum suction. You no longer need to rely solely on power. For this reason, a large vacuum suction force is not applied to the wafer surface, and it is possible to prevent the occurrence of scratches and the deterioration of polishing accuracy due to the warpage of the wafer.

In addition, in the second aspect, the chamfered surface and the outer peripheral side surface of the semiconductor wafer are simultaneously mirror-polished, so that the processing can be completed in a shorter time than in the conventional case. Because of this,
As described above, the mirror surface state is made uniform, and the quality is improved. Further, since the apparatus is configured to be small, the area occupied by the clean room is small, and the running cost can be reduced. Further, since the apparatus configuration is simple, the apparatus cost can be reduced. As described above, it is possible to produce semiconductor wafers of excellent quality while achieving both high productivity and low cost.

In the third and fourth aspects of the present invention, since the contact area between the semiconductor wafer and each of the polishing drums is increased, the polishing rate per unit time is improved, and the partial wear of the polishing cloth is reduced. . Since the set angle is set in a range where the polishing slurry does not advance on the wafer surface, there is no adverse effect on the wafer surface.

[Brief description of the drawings]

FIG. 1 is a schematic view showing a mirror polishing apparatus for a chamfered surface according to an embodiment.

FIG. 2 is a partial side view showing contact between a semiconductor wafer and an upper polishing drum and a lower polishing drum.

FIG. 3 is a partial plan view showing contact between a semiconductor wafer and an upper polishing drum and a lower polishing drum.

FIG. 4 is a plan view showing contact between a semiconductor wafer and two side polishing drums.

FIG. 5 is a side view showing contact between a semiconductor wafer and two side polishing drums.

FIG. 6 is a plan view showing contact between a semiconductor wafer and three side polishing drums in another embodiment.

[Explanation of symbols]

 1 Polishing unit 2 Polishing unit 3 Polishing unit 4 Polishing unit 5 Top polishing drum 5c・ Center line 6 ・ ・ ・ ・ ・ ・ Bottom polishing drum 6c ・ ・ ・ ・ ・ ・ Center line 7 ・ ・ ・ ・ ・ ・ Side polishing drum 7c ・ ・ ・ ・ Center line 8 ・ ・ ・ ・ ・ ・ Side polishing drum 8c ・ ・..Center line 9 ... Surface polishing drum 10 ... Semiconductor wafer 11 ... Chamfered surface 12 ... Chamfered surface 13 ... Outer side surface 100 ... Wafer holding Mechanism C: Center line

Claims (4)

[Claims] 1. A mirror polishing apparatus having a chamfered surface for polishing an outer peripheral portion of a semiconductor wafer which has been chamfered in advance, thereby polishing the outer peripheral portion of the semiconductor wafer, wherein the upper surface has a substantially cylindrical shape which rotates in the same direction. A polishing drum and a lower surface polishing drum, and a wafer holding mechanism for holding and rotating the semiconductor wafer to be polished, and having the upper surface polishing drum and the lower surface polishing drum intersect with each other at a plane perpendicular to the rotation center axis. A mirror polishing apparatus for a chamfered surface of a semiconductor wafer, wherein a region formed by a side surface of the upper polishing drum and a side surface of the lower polishing drum is arranged as a wafer holding region. 2. In addition to an upper polishing drum and a lower polishing drum, a plurality of side polishing drums for polishing an outer peripheral side portion of a semiconductor wafer to be polished are provided, and at least one side polishing drum is connected to another side polishing drum. 3. The mirror polishing apparatus according to claim 1, wherein the mirror is configured to rotate in a reverse direction. 3. A center line of a rotation axis of an upper polishing drum and a lower polishing drum is projected from a direction perpendicular to a virtual plane including a surface of a semiconductor wafer to be polished held by the wafer holding mechanism. 3. The mirror polishing apparatus according to claim 1, wherein the two center lines projected on the plane intersect at an angle of 5 degrees to 15 degrees. 4. An imaginary plane parallel to a rotation axis of the wafer holding mechanism and including a tangent line of a periphery of the semiconductor wafer to be polished in a contact area between at least one side surface polishing drum and the semiconductor wafer to be polished. When the center line of the rotation axis of the side polishing drum and the center line of the rotation axis of the wafer holding mechanism are projected from above in a direction perpendicular to this, the rotation axis of the wafer holding mechanism and the rotation axis of the side polishing drum are aligned. 3. The apparatus according to claim 2, wherein the center lines intersect at an angle of 2 to 15 degrees.