JP3781576B2 - Polishing device - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a polishing apparatus for polishing a polishing object such as a semiconductor wafer in a flat and mirror-like manner, and in particular, the polishing object by sliding it while relatively pressing the polishing object and the polishing pad or grindstone. The present invention relates to a polishing apparatus for polishing an object.
[0002]
[Prior art]
In recent years, as semiconductor devices are highly integrated, circuit wiring is becoming finer and the distance between wirings is becoming narrower. In particular, in the case of photolithography having a line width of 0.5 μm or less, the allowable depth of focus becomes shallow, so that the flatness of the imaging surface of the stepper is required. Therefore, it is necessary to flatten the surface of the semiconductor wafer, but polishing is performed by a polishing apparatus as one means of this flattening method.
[0003]
Conventionally, this type of polishing apparatus has a turntable with a polishing pad and a top ring, the top ring applies a constant pressure to the turntable, and an object to be polished is placed between the turntable and the top ring. The surface of the polishing object is polished to a flat and mirror surface while supplying an abrasive liquid.
[0004]
FIG. 10 is a diagram showing a main part of an example of a conventional polishing apparatus. The polishing apparatus supplies a polishing liquid Q to a rotating turntable 5 having a polishing pad 6 attached to the upper surface, a top ring 1 that holds a semiconductor wafer 4 that is a polishing target so as to be able to rotate and press, and a polishing pad 6. A polishing liquid supply nozzle 9 is provided. The top ring 1 is connected to a top ring drive shaft 8, and the top ring 1 has an elastic mat 2 made of polyurethane or the like on its lower surface, and holds the semiconductor wafer 4 in contact with the elastic mat. Further, the top ring 1 is provided with a cylindrical guide ring 3 at the outer peripheral edge so that the semiconductor wafer 4 does not come off from the lower surface of the top ring 1 during polishing. Here, the guide ring 3 is fixed in a circumferential direction with respect to the top ring 1, and a lower end surface thereof is formed so as to protrude from a holding surface of the top ring 1, and is held by a semiconductor wafer 4 that is a polishing object. It is held in the surface and is prevented from jumping out of the top ring by frictional force with the polishing pad 6 during polishing.
[0005]
The semiconductor wafer 4 is held below the elastic mat 2 on the lower surface of the top ring 1, the semiconductor wafer 4 is pressed against the polishing pad 6 on the turn table 5 by the top ring 1, and the turn table 5 and the top ring 1 are rotated. Then, polishing is performed by sliding the polishing pad 6 and the semiconductor wafer 4 relative to each other. At this time, the abrasive liquid Q is supplied onto the polishing pad 6 from the abrasive liquid supply nozzle 9. As the abrasive liquid, for example, an abrasive solution in which abrasive grains made of fine particles are suspended is used, and a semiconductor wafer is polished by a combined action of a chemical polishing action by alkali and a mechanical polishing action by abrasive grains.
[0006]
In addition, a method of polishing using a grindstone in which abrasive grains are bonded with a resin is known instead of a method of supplying a polishing liquid Q to a polishing pad and chemically and mechanically polishing. According to this method, since a relatively soft polishing pad and a slurry-like abrasive liquid are not used, highly accurate polishing can be performed. In addition, there is an advantage that the burden of environmental problems such as waste liquid treatment is reduced.
[0007]
A spherical seat 7 is disposed at a connecting portion between the top ring 1 and the top ring drive shaft 8. Thereby, even if there is a slight inclination on the upper surface of the turntable 5, the top ring 1 quickly tilts with respect to the top ring drive shaft 8 by the spherical seat 7. Even if the top ring 1 is tilted, the torque transmission pin 107 on the top ring drive shaft 8 side and the torque transmission pin 108 on the top ring 1 side are point contacted so that the contact point is shifted in each case. The rotational torque is reliably transmitted to the top ring 1.
[0008]
[Problems to be solved by the invention]
By the way, in the above conventional technique, when polishing the polishing object, there is a problem that a large vibration may be generated in the entire polishing apparatus due to the frictional force intervening the polishing object between the turntable and the top ring. There is. The cause of the occurrence of this vibration phenomenon is that the top ring that rotates independently according to the frictional force between the surface of the polishing object and the surface of the polishing pad or the grindstone, the force pulled by the rotational force of the turntable, and the drive shaft It is considered to be a resilience.
[0009]
When such a vibration phenomenon becomes large, there is a problem that unevenness of polishing occurs on the surface to be processed of the polishing object or a polishing flaw occurs, so that stable polishing cannot be performed. Furthermore, when the vibration phenomenon becomes severe, the semiconductor wafer may pop out and it may be impossible to continue polishing.
[0010]
The present invention has been made in view of the above-described circumstances, and provides a polishing apparatus capable of preventing a vibration phenomenon generated in a polishing apparatus and stably polishing the surface of a polishing target object in a flat and mirror-like shape. Objective.
[0011]
[Means for Solving the Problems]
The polishing apparatus of the present invention has a turntable having a polishing pad or a grindstone pasted on the upper surface and a top ring, and presses with a predetermined force with a polishing object interposed between the turntable and the top ring. In the polishing apparatus that polishes and polishes the object to be polished to a flat and mirror surface, the polishing apparatus includes a bearing that supports an outer peripheral portion of the top ring, and a support mechanism that fixes the bearing to a gantry of the polishing apparatus. The top ring is composed of a top ring body and a guide ring disposed on the outer periphery of the top ring body, and the movable side of the bearing is fixed to the outer periphery of the guide ring, and the guide ring and the top ring body Is fixed so that it can move up and down by the key and rotate together in the circumferential direction. It is characterized in.
[0012]
According to the present invention, the vibration of the holding member or the like can be suppressed by supporting the outer peripheral side surface of the holding member or the like holding the polishing target object with the bearing. The vibration derived from the frictional force generated on the surface to be polished of the polishing object, the rotational force of the holding member and polishing member that rotate independently, and the restoring force of the drive shaft is a member supported by a relatively thin drive shaft. Appear the largest in For this reason, by supporting the outer peripheral surface of the member with a bearing, the vibration of the member is suppressed, thereby suppressing the vibration of the polishing apparatus as a whole. Therefore, even if the rotational speed of the holding member and the polishing member is increased or the frictional force is increased by increasing the pressing force against the polishing object, the polishing apparatus as a whole is not vibrated under any operating condition. Stable polishing can be performed.
[0013]
In this way, by rotating and driving while supporting the outer peripheral portion of the holding member with a bearing, it is possible to suppress the vibration of the holding member that occurs during polishing. This is a polishing device that combines a top ring and a turntable. It is applicable to other devices. In other words, the present invention can be applied to a cup type in which polishing is performed by placing a polishing object with its polishing surface facing upward and pressing a polishing member holding a grindstone or a polishing pad while rotating. Further, the present invention can also be applied to a scroll type polishing apparatus that performs polishing by performing a scroll motion while pressing a polishing surface of a polishing object with a polishing surface of a grindstone or a polishing pad facing upward. Further, as the bearing, not only a mechanical bearing but also a non-contact type bearing such as a magnetic bearing may be used.
[0014]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, embodiments of a polishing apparatus according to the present invention will be described with reference to FIGS.
[0015]
FIG. 1 is a diagram showing an overall configuration of a polishing apparatus according to a first embodiment of the present invention, and FIG. 2 is a diagram showing a longitudinal section thereof. As shown in the figure, a turntable 5 having a polishing pad or grindstone 6 attached to the surface and a top ring 1 for holding a polishing object are provided. The turntable 5 is fixed to a drive shaft 11, and the drive shaft is supported by a bearing (not shown) in the gantry 10, and is similarly rotationally driven by a motor and a pulley (not shown). Similarly, the top ring 1 is fixed to the drive shaft 8, and the drive shaft 8 is rotationally driven by a motor and a pulley (not shown) housed in the top ring casing 12. Similarly, the top ring casing 12 is provided with a bearing for supporting the drive shaft 8 and pressing means for pressing the top ring such as an air cylinder toward the turntable 5, and supports the top ring 1 rotatably. Meanwhile, the top ring 1 is pressed. That is, the top ring 1 is fixed to the gantry 10 via the top ring casing 12 and the support shaft 16. The top ring 1 is a disk-shaped member, and holds a semiconductor wafer 4 as an object to be polished on its lower surface side.
[0016]
The outer peripheral surface of the top ring 1 is supported by a bearing 13, and the bearing 13 is accommodated in a bearing casing 14. The bearing casing 14 is detachably fixed to the gantry 10 of the polishing apparatus via the support 15.
[0017]
The operation of this polishing apparatus is roughly as follows. First, the semiconductor wafer 4 as a polishing object is adsorbed to the lower surface recess of the top ring 1 by means such as vacuum adsorption. Then, the top ring 1 holding the polishing object 4 is moved to a predetermined position on the turntable 5, and the polishing object 4 is brought into contact with the polishing pad or the grindstone 6. And the bearing casing 14 is latched to the support | pillar 15, and the bearing casing 14 is firmly fixed to the mount frame 10 side.
[0018]
Next, while the turntable 5 and the top ring 1 are respectively raised to a predetermined number of revolutions, the top ring 1 is pressed against the polishing pad or the grindstone 6 on the turntable 5 by a predetermined pressing force on the surface to be polished. Press to ascend. As a result, the surface to be polished of the polishing object is polished by the abrasive grains supplied onto the polishing pad or by the abrasive grains of the grindstone. At this time, it is preferable that the rotational speed of the turntable 5 and the rotational speed of the top ring 1 be made equal. Thereby, uniform polishing can be performed over the entire surface of the polishing object.
[0019]
When the rotational speeds of the turntable 5 and the top ring 1 are increased, the polishing speed of the polishing object is thereby increased. Further, by increasing the pressing force for pressing the polishing object 4 against the polishing pad or the grindstone 6 through the top ring 1, the polishing speed of the polishing object is similarly improved. However, as described above, a vibration phenomenon may occur in the entire polishing apparatus due to an increase in frictional force accompanying an increase in the rotation speed of the turntable and the top ring or an increase in the pressing force of the top ring.
[0020]
However, in the polishing apparatus of this embodiment, the outer peripheral surface of the top ring 1 is firmly fixed to the gantry 10 via the bearing 13. Such a vibration phenomenon is most remarkable because the portion of the top ring 1 is supported by the relatively thin drive shaft 8, but the top ring 1 is firmly fixed to the gantry 10 side by the bearing 13. The vibration of the top ring 1 is suppressed. Therefore, by suppressing the vibration of the top ring 1, the vibration of the upper casing 12 and the vibration of the support mechanism 16 are also suppressed. Similarly, vibrations of the turntable 5 and the drive shaft 11 are also suppressed.
[0021]
FIG. 3 is a view showing a modification of the polishing apparatus according to the first embodiment of the present invention.
In this modification, the support column 15 is rotatably supported by the gantry 10 and the support casing 15 can be retracted from the turntable by rotating the support column 15 when not polished. That is, as shown in FIG. 3, a swing groove D for swinging the support column 15 in the horizontal direction is formed in the gantry 10 so that the support column 15 can swing in the direction of the arrow d. It can swing together with the ring 1. The swing groove D is formed in an arc shape centered on the support shaft 16 with the distance from the support shaft 16 to the support column 15 being a radius. In the case where the swing groove D is formed as shown in FIG. 5, the support column 15 is firmly fixed by the stopper 25 protruding so as to cross the swing groove D during the polishing process. Thus, by making the bearing casing 14 swingable, it is possible to overhang the top ring 1 and the bearing casing 14 together until they protrude from the turntable 5 at the end of polishing, and a polishing pad or grindstone on the turntable. The wafer 6 in close contact with the polishing surface 6 can be easily lifted and moved by turning.
[0022]
FIG. 4 is a diagram illustrating an example of a detailed structure of the top ring portion. An elastic mat 2 such as urethane material is attached to the lower surface of the top ring body 1a. A guide ring 3 is disposed on the outer periphery of the top ring body 1a. Then, the semiconductor wafer 4 which is a polishing object is held in a recess surrounded by the guide ring 3 and the elastic mat 2. The surface to be polished of the polishing object 4 is brought into contact with the polishing pad or the grindstone 6 of the turntable 5 for polishing.
[0023]
The top ring 1 is connected to a drive shaft 8 via a spherical seat 7, and the top ring drive shaft 8 is driven by a rotational drive means such as a motor and a pulley housed in a top ring casing 12 and a pressing means such as an air cylinder. The top ring 1 is rotated while the top ring 1 is pressed. As a result, the polishing object 4 held on the lower end surface of the top ring 1 is slid while being pressed by the polishing pad or the grindstone 6 of the turntable 5 so that polishing proceeds.
[0024]
The guide ring 3 is connected to the top ring main body 1a via a key 18. The guide ring 3 is movable up and down with respect to the top ring 1 and rotates integrally with the top ring main body 1a. . The guide ring 3 is connected to the guide ring pressing member 20 via the guide ring bearing 19 so as to be able to rotate in the horizontal direction and to transmit the vertical movement. The guide ring pressing member 20 is connected to an air cylinder (not shown) via a shaft 21 so as to press the guide ring 3. The outer peripheral surface of the guide ring pressing member 20 is supported by a bearing 33, and the bearing 33 is accommodated in a bearing casing 32. The bearing casing 32 is firmly fixed to the gantry 10 by a support mechanism such as the support column 15. A vibration damping material 30 such as an O-ring is inserted between the top ring 1 and the guide ring 3 so as to absorb vibrations accompanying polishing of the polishing object 4.
[0025]
Therefore, even if a vibration derived from the frictional force of the surface to be polished of the polishing object and the restoring force of the top ring drive shaft occurs, this vibration is first absorbed by the elastic mat 2, and further, the top ring 1 and the guide ring 3 It is absorbed by the vibration damping material 30 interposed therebetween. Larger vibrations are transmitted from the polished surface of the polishing object to the guide ring 3 via the elastic mat 2, the top ring 1, and the key 18, but the guide ring 3 can be firmly rotated by the bearing 33 as described above. Since it is supported, this vibration is suppressed at the bearing 33 portion.
[0026]
In addition, although the ball bearing is employ | adopted as a bearing in the top ring shown in FIG. 4, the same effect is acquired even if it uses a slide bearing. In the above embodiment, the guide ring is supported by the bearing. However, the top ring main body may be directly supported by the bearing. In the above-described embodiment, the example in which the top ring 1 is connected to the drive shaft 8 via the spherical seat 7 has been described. However, the same effect can be expected when the drive shaft 8 is directly connected to the top ring body 1a. it can.
[0027]
In the above embodiment, the bearing for supporting the top ring is fixed to the frame of the polishing apparatus. However, the present invention is not limited to this, and any portion that is difficult to receive vibration of the top ring (a portion other than the top ring casing) may be used. .
[0028]
FIG. 5 shows a polishing apparatus according to a second embodiment of the present invention and shows an application example to a cup-type polishing apparatus. The grindstone holder 41 has a ring-shaped grindstone 42 fixed thereto, and performs a rotational motion in the direction of arrow C in the figure while pressing the semiconductor wafer 4 as a polishing object by the drive mechanism 43. The drive mechanism 43 is polished while reciprocating in the direction indicated by the arrow A in the figure. Here, in this embodiment, the grindstone 42 is ring-shaped, but a plurality of small disc-shaped grindstones may be arranged in a ring shape. On the other hand, the semiconductor wafer 4 is held by a wafer holder 44, and the wafer holder 44 rotates as shown by an arrow B in the figure. The wafer holder 44 is fixed to a support 45 and is rotated by a motor (not shown) to rotate the semiconductor wafer 4. The outer peripheral surface of the wafer holder 44 is supported by a bearing, and this bearing is accommodated in a bearing case 46. The bearing case 46 is firmly fixed to the casing 48 by a column 47. Therefore, the vibration generated as the semiconductor wafer 4 is polished is suppressed by the outer peripheral surface of the wafer holder 44 being supported by the bearing.
[0029]
FIG. 6 shows a polishing apparatus according to a third embodiment of the present invention, which is an application example to a scroll type polishing apparatus. In this apparatus, a holder 52 on which a grindstone or a polishing pad 51 is affixed is scrolled (circulationally translated) as its support shaft 53 is indicated by an arrow D. Here, the scrolling movement is to rotate and move the grindstone or the polishing pad 51 at a radius d while translating. On the other hand, a wafer holder 54 that holds a semiconductor wafer (not shown) is fixed to a support shaft 55 and is rotationally driven in the direction of arrow C in the figure by a rotational driving force transmitted through a drive mechanism 57. The outer peripheral surface of the wafer holder 54 is supported by a bearing (not shown). The bearing is accommodated in a bearing case 55, and supports the wafer holder 54 in a rotatable manner, while suppressing movement in the radial direction. The bearing case 55 is firmly fixed to the casing 58 by bearing columns 56. Therefore, in this apparatus, the grindstone or polishing pad 51 is held by the holder 52 with its polishing surface facing upward, and the semiconductor wafer (not shown) is held by the wafer holder 54 with its polishing surface facing downward, by the drive mechanism 57. It is rotated and pressed against the polishing surface of the grindstone or polishing pad. Then, the polishing proceeds by the scroll motion of the radius d of the grindstone 51 and the rotational motion and pressing force of the semiconductor wafer. Here, even if vibration occurs between the frictional force of the semiconductor wafer and the restoring force of the support shaft 55 due to polishing, the vibration is suppressed because the wafer holder 54 is supported by the bearing.
[0030]
7 and 8 show a polishing apparatus according to a fourth embodiment of the present invention, and show an application example to an apparatus having no top ring shaft. In this apparatus, the grindstone or polishing pad 61 is rotationally driven by the support shaft 62 as in the apparatus of the first embodiment described above. Although the semiconductor wafer which is the polishing target is held by the top ring 63, unlike the apparatus of the first embodiment, the top ring does not have a support shaft. Instead, the outer surface of the top ring 63 is rotatably supported by a bearing accommodated in the bearing case 64, and the bearing case 64 is fixed to the casing 70 via the arm 64 a and the column 66. The top ring 63 receives a rotational driving force from the motor 69 by the belt 65, and the top ring 63 rotates. Further, a pressurizing cylinder 67 is provided, and a vertical load is applied to the surface to be polished of the polishing object 4 by pressing the bearing case 64 downward. Even in this apparatus, even if vibration is generated in the polishing object, the outer peripheral surface of the top ring 63 is rotatably supported by the bearing, so that vibration is suppressed.
[0031]
FIG. 9 shows a modification of the fourth embodiment, in which a magnetic bearing is used as a bearing. The magnetic bearing is a bearing that supports the rotating shaft in a non-contact manner at a predetermined flying position by controlling the magnetic attractive force of the electromagnet. Therefore, in this case, the top ring corresponds to the rotating shaft, and this rotating shaft is held at a fixed position regardless of the presence of disturbance. As a result, vibration generated in the top ring is similarly suppressed. In this case, the top ring 63 includes the rotated portion 63a, and the vertical load force of the pressurizing cylinder 67 is transmitted by the pressing force transmitting force beam 65a. And the magnetic bearing 71 gives a rotational force to a top ring without contact. Therefore, also in this apparatus, polishing of the polishing object proceeds by the rotational movement of the grindstone or the polishing pad 61, the rotational movement of the semiconductor wafer 4 held by the top rings 63 and 63a, and the pressing force of the pressure cylinder 67. . Even if the top ring vibrates due to the progress of polishing, it can be suppressed by the magnetic bearing.
[0032]
The polishing apparatus described in the prior art has been designed so that the spline shaft, the top ring arm, the swing shaft, and the like that support the top ring have high rigidity in order to suppress vibration generated in the apparatus. For this reason, there is a problem that the weight is very large and the whole apparatus is enlarged. However, as described above, vibration of the holding member is suppressed by rotatably supporting the holding member that supports the polishing object with the bearing. For this reason, it is not necessary to increase the rigidity of the various shafts and arms described above, which can contribute to weight reduction and compactness of the entire apparatus.
[0033]
In the above embodiment, vibration suppression by holding the outer peripheral surface of a holding member that holds a polishing object such as a semiconductor wafer with a bearing has been described, but in a cup-type or scroll-type polishing apparatus, etc. The outer peripheral surface of the polishing member that holds the grindstone or the polishing pad may be held by a bearing to suppress the occurrence of vibration. Thus, various modified embodiments are possible without departing from the spirit of the present invention.
[0034]
【The invention's effect】
As described above, according to the present invention, by supporting the holding member or the like that holds the object to be polished with the bearings, vibrations generated in these members and their drive shafts can be suppressed, and thus vibrations generated in the entire polishing apparatus. Can be suppressed. Therefore, stable polishing can always be performed with respect to various operating conditions such as an increase in the relative rotational speed of the polishing object and the grindstone or polishing pad, or an increase in the pressing force.
[Brief description of the drawings]
FIG. 1 is a perspective view showing an overall configuration of a polishing apparatus according to a first embodiment of the present invention.
FIG. 2 is a longitudinal sectional view of FIG.
FIG. 3 is a perspective view showing a modification of the polishing apparatus shown in FIG.
FIG. 4 is a cross-sectional view showing an example of a detailed structure of a top ring portion.
FIG. 5 is a perspective view showing an overall configuration of a polishing apparatus according to a second embodiment of the present invention. FIG. 6 is a perspective view showing an overall configuration of a polishing apparatus according to a third embodiment of the present invention. 7 is a perspective view showing an overall configuration of a polishing apparatus according to a fourth embodiment of the present invention. FIG. 8 is a longitudinal sectional view showing a main part of FIG.
9 is a longitudinal sectional view showing a modification of the polishing apparatus shown in FIG.
FIG. 10 is a diagram showing an outline of a conventional polishing apparatus.
[Explanation of symbols]
1 Top Ring 1a Top Ring Body 2 Elastic Mat 3 Guide Ring 4 Polishing Object (Semiconductor Wafer)
5 Turntable 6 Polishing pad or grinding wheel 7 Spherical seat 8 Top ring drive shaft 10 Base (casing)
11 Turntable drive shaft 12 Top ring casing 13, 19 Bearing 14, 20 Bearing casing 15 Post

Claims (3)

It has a turntable having a polishing pad or a grindstone pasted on its upper surface and a top ring. The polishing object is polished by pressing the polishing object between the turntable and the top ring with a predetermined force. In a polishing apparatus that is flat and mirror-finished,
The polishing apparatus includes a bearing that supports an outer peripheral portion of the top ring, and a support mechanism that fixes the bearing to a frame of the polishing apparatus .
The top ring is composed of a top ring main body and a guide ring disposed on the outer periphery of the top ring main body, and the movable side of the bearing is fixed to the outer periphery of the guide ring, and the guide ring and the top ring main body are A polishing apparatus characterized by being fixed so as to be movable in the vertical direction by a key and to rotate together in the circumferential direction .   The top ring includes a holding portion for a polishing object on a lower surface thereof and a drive shaft on an upper surface thereof, and a side surface thereof is supported by a bearing. The polishing apparatus according to claim 1, wherein the polishing apparatus is fixed to a frame that rotatably supports the turntable. The polishing apparatus according to claim 1 , wherein a vibration damping material is interposed between the top ring body and the guide ring.

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