JP2000127025A - Polishing device and polishing method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a polishing device feeding no abrasive liquid to a wafer suction face when an object to be polished is held via vacuum suction for polishing and provide a polishing method. SOLUTION: A wafer 24 held by a carrier 35 via vacuum suction is pressed to an abrasive cloth fitted to the upper face of a rotary tape arranged to face its polished face for polishing in this polishing device. The polishing device is provided with a guide ring 40 surrounding the wafer 24, a packing 41 blocking the gap generated between the carrier 35 and the wafer 24, and a water flowing pipeline 43 (shunt pipeline 44) provided in the carrier 35 and feeding pure water to a gap portion 42 surrounded by the wafer 24, guide ring 40 and packing 41.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a polishing apparatus and a polishing method for polishing an object to be polished such as a semiconductor wafer.

[0002]

2. Description of the Related Art In a polishing process for flattening a surface of a semiconductor wafer used for a super LSI or the like, an element wiring tends to be miniaturized and multilayered with an increase in the integration degree of the LSI. In addition, planarization of the wiring film is essential. For this reason, the semiconductor wafer needs to be flattened with high precision, and in order to perform such flattening, polishing is performed by a CMP method.

When a semiconductor wafer is polished by the CMP method, a polishing apparatus is used. The polishing apparatus includes a carrier for holding a wafer, a drive motor for rotating and driving the carrier, an air cylinder for pressing the carrier and the drive motor against a table, which will be described later, with a predetermined pressure, and is disposed to face the carrier. Table and
A polishing cloth provided on the upper surface of the table and made of non-woven fabric or polyurethane foam, and a drive motor for rotating the table are provided.

A supply means for supplying a polishing liquid comprising abrasive grains and a chemical is provided on the polishing upper surface side of the polishing surface. The carrier is provided facing the upper surface of the table, and holds the wafer on the surface facing the table. A guide ring is provided on the outer periphery of the wafer to prevent the wafer from coming off the carrier during polishing.

There are various types of holding of the wafer on the carrier. The holding of the wafer on the carrier is performed by a method of directly vacuum-adsorbing the carrier, a method of fixing the carrier with wax, and a method of applying a soft film of water to the carrier. By providing a film and pressing the wafer onto the polishing cloth with an air cylinder, the polished surface of the wafer is removed and processed by the physical action of the abrasive grains in the polishing liquid and the chemical action of the chemical contained in the polishing liquid. While finishing to a flat surface.

[0006]

In order to polish a wafer flat, it is important to press the wafer against a polishing cloth on a polishing surface with a uniform load.
In order to realize such flattening, flatness design of a carrier holding a wafer and its manufacture are regarded as important. Here, if the wafer suction surface of the carrier is flattened with high accuracy and the wafer is vacuum-adsorbed on the flattened wafer suction surface, ideal polishing can be realized.

However, when the wafer is directly held and polished by the above-mentioned carrier by vacuum suction or the like, the polishing liquid penetrates into the contact boundary between the carrier and the wafer during polishing, and the polishing liquid dries and solidifies. There is a problem that the flatness cannot be maintained.

For this reason, when the wafer is held by the carrier, a method is employed in which the carrier and the wafer are bonded with wax to prevent the polishing liquid from entering the boundary surface.

[0009] However, when the wafer is bonded to the carrier using wax, there is a disadvantage that the wax is unevenly applied and the wafer is not flattened accurately. In addition, since an organic solvent is used for removing the wax and for cleaning, it has an environmental impact. In addition, since steps for removing wax and cleaning are separately provided, disadvantages such as an increase in processing steps are caused.

In addition, there is a method of holding a wafer on a carrier by using a water-adhered film. In this case, even if the polishing liquid solidifies, a buffering effect is exerted against the load concentration on the solidified portion. Since it works, the problem of intrusion of the polishing liquid can be ignored. However, the water-laminated film does not have a uniform thickness and has a thickness variation of 10 μm or more. This thickness variation becomes a pressure distribution acting on the polished surface, and the pressure distribution is transferred to the wafer. Will be. For this reason, this is one of the causes of the deterioration of the flatness of the wafer. Therefore, it is conceivable to make this water-coated film a uniform thickness, but it is difficult to manufacture a water-coated film made of a soft material such as a urethane material with a thickness variation of 1 μm or less. This also leads to an increase in the cost of consumables, which is not preferable.

The present invention has been made in view of the above circumstances, and an object of the present invention is to allow a polishing liquid to enter a wafer suction surface when a polishing object is to be polished while being held by a vacuum suction method. It is an object of the present invention to provide a polishing apparatus and a polishing method that do not require any polishing.

[0012]

According to a first aspect of the present invention, an object to be polished held by a holding means by vacuum suction is disposed opposite to a polishing surface of the object to be polished, and is placed on a table upper surface. In a polishing apparatus for performing polishing by pressing against an attached polishing cloth, a guide ring member surrounding the object to be polished, an elastic member provided between the holding means and the object to be polished, and the holding means And a cleaning liquid supply means for supplying a cleaning liquid to a region surrounded by the object to be polished, the guide ring member, and the sealing member.

According to a second aspect of the present invention, there is provided a polishing process for polishing an object to be polished held by a holding means by vacuum suction by sliding a polishing cloth mounted on a table upper surface disposed opposite to a polishing surface thereof. In the method, a polishing step of polishing the object to be polished by rotating the object to be polished and the table, and holding the object to be polished by the holding means after the polishing step is completed. And a cleaning step of cleaning the object to be polished.

According to a third aspect of the present invention, when the object to be polished is detached from the holding means after the completion of the cleaning step, the cleaning liquid is simultaneously directed outward from the holding portion of the object to be polished of the holding means. 3. The polishing method according to claim 2, further comprising a removing step of discharging.

According to a fourth aspect of the present invention, there is provided the polishing method according to the third aspect, further comprising a second cleaning step of cleaning the holding means again after the removal step is completed.

As a result of taking the above measures, the following operation occurs. According to the first aspect of the present invention, the cleaning liquid is supplied to the region surrounded by the object to be polished, the guide ring member, and the sealing member by the cleaning liquid supply means. When the object to be polished is removed, the cleaning liquid is discharged outward from the enclosed area.

According to the second aspect of the present invention, the polishing liquid attached to the holding means and the object to be polished in the cleaning step is washed away. According to the invention of claim 3, in the removing step, the cleaning liquid is discharged outward from the holding portion of the object to be polished of the holding means simultaneously with the removal of the object to be polished. It is prevented from adhering to the holding part, and is washed away when the cleaning liquid is discharged. According to the fourth aspect of the present invention, after the removal step is completed, the holding means is washed again.

[0018]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described below with reference to FIGS. The polishing apparatus 20 shown in FIG. The rotary table 21 has an upper surface formed as a flat surface, and a rotary shaft 22 for rotating the rotary table 21 is integrally attached to the lower surface of the center of the diameter. The rotating shaft 22 is connected to a drive source (not shown), and thereby rotates the polishing pad 23 attached to the upper surface of the rotating table 21 to rotate the polishing pad 23. , The wafer 24) can be polished.

On the upper surface of the table 21, a wafer 24
A polishing cloth 23 for polishing the wafer 24 is attached, and the upper surface of the polishing cloth 23 is flattened with high precision because it is necessary to polish the wafer 24 with high precision.

A work rotation driving device 30 having a smaller rotation diameter than the diameter of the polishing pad 23 is disposed above the polishing pad 23. The work rotation drive device 30 is provided with an air cylinder 3 as a pressing means on the upper end side in the figure.
1 so that the wafer 24 can be pressed against the polishing pad 23 with a predetermined pressing force. A support arm (not shown) is provided further above the air cylinder 31 and supports the entire work rotation drive device 30.

A drive source 32 such as a motor is provided below the air cylinder 31 directly.
The drive source 32 is configured to be connected to the rotating shaft 33 on the lower side opposite to the side connected to the air cylinder 31. The rotating shaft 33 extends downward by a predetermined length and is connected to a rotating head 34 having a substantially disk shape.

As shown in FIG. 2, the rotary head 34 has a carrier 35 as a holding means for holding the wafer 24.
Is provided on the turntable 21. This carrier 35
Since high rigidity and low thermal expansion are desirable, for example, alumina, silicon carbide, glass, or the like is used as a material. The carrier 35 is provided with fine suction holes 36 so that the other end side is exposed on the wafer suction surface 37. The suction holes 36 are formed so as to be substantially perpendicular to the wafer suction surface 37, and when the wafer 24 is located on the wafer suction surface 37, which is a holding portion, a deviation or separation with respect to the rotation torque occurs. Insufficient holding capacity is created by vacuum suction.

The suction holes 36 are provided on the wafer suction surface 3.
On the 7 side, it is formed so that its diameter is fine,
The upper side of the work rotation driving device 30 in the drawing is formed so as to have a slightly larger diameter. Further, a space portion 38 is formed further on the upper side, and all the suction holes 36 are provided so as to communicate with the space portion 38.

From the space 38 toward the rotating shaft 33,
A vacuum pipe 39 is provided. This vacuum pipe is connected to a suction means such as a pump (not shown), so that when the wafer 24 is positioned on the wafer suction surface 37,
The wafer 24 is provided to generate a vacuum suction force.

With such a path, the wafer suction surface 37 to which a vacuum suction force is applied when the wafer 24 is positioned.
Is flattened with high precision, so that the wafer 24 can be attracted to this portion and good polishing can be performed.

In order to facilitate removal of the wafer 24 after polishing, not only a suction means such as a pump (not shown) but also a pressurized air source (not shown) is provided. This makes it easy to switch between the vacuum suction state and the pressurized state by air at the time of separation.

A guide ring 40 is provided on the peripheral portion of the wafer suction surface 37. This guide ring 4
Numeral 0 is provided over the entire outer periphery of the wafer suction surface 37 to prevent the wafer 24 from deviating from the wafer suction surface 37.

In order to prevent a gap from being formed between the guide ring 40 and the wafer 24 when the wafer 24 is sucked and held on the wafer suction surface 37, a packing 41 is provided between the guide ring 40 and the wafer 24. The packing 41 is made of an elastic material such as rubber or silicon rubber coated with a fluorine resin, for example, to prevent the polishing liquid supplied during polishing on the polishing surface from entering the wafer suction surface 37,
Further, it prevents the pure water supplied by the flowing water pipe 43 described later from leaking from this portion.

In order to supply pure water to the guide ring 40, the outer peripheral edge of the wafer 24, and the gap 42 surrounded by the packing 41, a cleaning liquid supply means is provided from the rotating shaft 33 to the inside of the rotating head 34. A flowing water pipe 43 is formed.

The flowing water pipe 43 is connected to a pure water supply mechanism such as a tank (not shown) on the upper side of the work rotation driving device 30, and within the rotation shaft 33 so as to be along the rotation axis. Is formed. The rotary shaft 33 communicates with the rotary head 34. The rotary head 34 is provided with a branch pipe 44 for splitting pure water radially outward at predetermined intervals. The branch pipe 44 has an opening facing the wafer 24 disposed facing the rotary head 34 so as to communicate with the gap portion 42 from a predetermined position radially outward of the rotary head 34.

A large number of openings of the branch pipe 44 are provided along the circumferential direction.
It suffices if it is formed to about mm. Also, the wafer 24
When the wafer 24 is mounted on the wafer suction surface 37, if there is a misalignment, the exposure hole of the branch pipe 44 to the wafer suction surface 37 is closed by the wafer 24. And the alignment is ± 0.2
Mechanical adjustments have been made so that they can be performed within an error of mm.

The operation and polishing method of the polishing apparatus 20 having the above-described configuration will be described below. The wafer 24 is held on the wafer suction surface 37 by holding the wafer 24 by vacuum suction, and when holding the wafer 24, the packing 41 closes a gap formed between the wafer 24 and the guide ring 40. ,
The polishing liquid is provided so that the polishing liquid does not adhere to the wafer suction surface 37 side from the outside.

Then, pure water is supplied to the gap portion 42.
In this supply, if the supply pressure of the pure water is set too high, pure water flows on the boundary surface between the wafer 24 and the wafer suction surface 37, and the holding ability of the wafer 24 is reduced. For this reason, it is desirable that the pressure of pure water be 0.5 kgf / cm ² or less.

In this state, the work rotation driving device 30 is operated, and at the same time, the rotation table 21 is also driven to rotate, thereby performing the polishing process on the wafer 24 (polishing process). After the polishing process is completed, the polishing surface of the wafer 24 and the work rotation driving device 30 are moved from a spray nozzle or the like while the holding state of the wafer 24 to the work rotation driving device 30 is maintained. Cleaning is performed by immersion in a cleaning water tank provided separately from the above (cleaning step). As a result, the polishing liquid adhering to the polishing surface of the wafer 24 and the work rotation driving device 30 is washed away, and fine particles generated during polishing of the wafer 24 included in the polishing liquid are also flown away. Further, by flowing the polishing liquid, no abrasive aggregates are formed due to drying of the polishing liquid.

However, the polishing liquid adhering to this portion may not be completely washed away, and there may be a case where the abrasive grains slightly remain. Therefore, if the wafer 24 is removed as it is, the wafer suction surface 3
It is conceivable that this polishing liquid adheres to the substrate 7.

For this reason, when the wafer 24 is removed from the wafer suction surface 37, the flowing water pipe 43 (shunt pipe 44)
Accordingly, it is preferable to discharge the pure water existing in the gap portion 42. That is, in the present embodiment, at the same time when the wafer 24 is removed from the wafer suction surface 37,
Pure water is discharged outward (removal step). For this reason, even if the polishing liquid (fine particles) adheres to the vicinity, it can be washed away by discharging pure water.

After the pure water is discharged to remove the wafer 24, the carrier 35 (in the vicinity of the wafer suction surface 37) is further cleaned (second cleaning step), and the polishing liquid and fine particles remaining slightly are further removed. You may wash away.

According to the polishing apparatus 20 and the polishing method having the above-described structure, the carrier 35 and the wafer 24 are cleaned while the wafer 35 is held on the carrier 35 before the removing step. This makes it possible to wash away the adhering polishing liquid.
That is, by this cleaning, the carrier 35 and the wafer 2
The polishing liquid adhering to 4 can be largely washed away.

Further, since pure water is supplied to the gap portion 42 by the branch flow pipe 44 (flow water pipe 43), polishing of the wafer 24 is completed, and when the wafer 24 is taken out, the outside of the gap portion 42 is removed. The pure water is discharged toward the direction (removal process). For this reason, the packing 4 of the guide ring 40
1 and the polishing liquid adhering to the outer peripheral portion of the wafer 24 can be washed away with pure water.

For this reason, the polishing liquid adheres to the wafer suction surface 37, and fine particles generated during the polishing process and contained in the polishing liquid, and abrasive aggregates generated by drying the polishing liquid are formed on the wafer. It is not formed on the suction surface 37.

Therefore, the flatness of the wafer suction surface 37 at the time of initial design can be maintained for a long time, and the wafer 24 can be favorably held for a long time. Therefore, even if the wafer 24 is repeatedly held by the carrier 35,
4 can be made uniform.

As an example of this, when the wafer 24 having a diameter of 8 inches is polished, the flatness of the wafer 24 is 1.0 μm
V, 0.25 μm STIR, but by applying the present invention, 0.8 μm TTV, 0.18 μm STI
R could be improved.

Further, since the polishing process can be performed while holding the wafer 24 repeatedly by the vacuum suction method, the use of an indirect material such as a water-adhesive film or wax can be eliminated, and the cost can be reduced. Further, since it is not necessary to use any wax, it is possible to abolish the organic cleaning using the organic solvent used for washing off the wax, so that the burden on the environment is reduced.

The packing 41 is made of, for example, fluororesin,
Because it is made of an elastic material such as coated rubber or silicon rubber,
When the wafer 24 is sucked and held by the wafer suction surface 37, the packing 41 is elastically deformed and can hold the wafer 24. Therefore, even if the wafer 24 is slightly displaced, no gap is formed between the guide ring 40 and the wafer 24, and the airtightly closed state can be maintained.

Further, after the removal step is completed, the carrier 35 is again washed, so that the polishing solution slightly remaining in the vicinity of the wafer suction surface 37 of the carrier 35 is washed away before the polishing solution is dried and leveraged. It is possible to further prevent the polishing liquid from adhering to the wafer suction surface 37.

Although the embodiment of the present invention has been described above, the present invention can be variously modified in addition to this. This is described below. In the above-described embodiment, pure water is stored in the gap 42 by the flowing water pipe 43 (diversion pipe 44), and the gap 42 is removed when the wafer 24 is removed.
Is configured to discharge pure water existing in the carrier 35.
A configuration may be adopted in which a pure water circulation path is formed inside and the pure water existing in the gap portion 42 is circulated.

Further, another cleaning liquid may be used instead of pure water. In addition, various modifications can be made without departing from the scope of the present invention.

[0048]

As described above, according to the present invention,
Since the cleaning liquid is supplied to the region surrounded by the object to be polished, the guide ring member, and the sealing member by the cleaning liquid supply means, when the polishing process is completed and the object to be polished is removed, the region faces outward from this region. The cleaning liquid is discharged, whereby the polishing liquid adhering to the holding means and the object to be polished adheres to the holding portion of the object to be polished, and is dried to form abrasive aggregates. The problem that the flatness cannot be maintained can be prevented, and the object to be polished can be favorably held for a long period of time.

Therefore, even if the object to be polished is repeatedly held by the holding means, the pressure applied to the object to be polished can be made uniform. Further, even in the method of holding the object to be polished by vacuum suction, the object can be repeatedly held and polished, so that the use of an indirect material such as a water-adhesive film or wax can be eliminated, and the cost can be reduced. In addition, by stopping the use of the wax, it is possible to reduce the environmental load due to the elimination of the organic washing with the organic solvent performed when the wax is used.

[Brief description of the drawings]

FIG. 1 is a diagram showing a configuration of a work rotation drive device of a polishing device according to an embodiment of the present invention.

FIG. 2 is a diagram showing an overall configuration of a polishing apparatus according to the embodiment;

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 20 ... Polishing apparatus 21 ... Rotary table 23 ... Polishing cloth 24 ... Semiconductor wafer 30 ... Work rotation drive unit 34 ... Rotating head 35 ... Carrier 36 ... Suction hole 37 ... Wafer suction surface 40 ... Guide ring 41 ... Packing 42 ... Gap part 43 … Running water line 44… branching line

Claims (4)

[Claims] 1. A polishing apparatus for performing a polishing process by pressing an object to be polished held by a holding means by vacuum suction onto a polishing cloth mounted on a table upper surface which is disposed opposite to a polishing surface thereof. A guide ring member surrounding the object; an elastic member provided between the holding means and the object to be polished; and an elastic member provided on the holding means, the object to be polished, the guide ring member, and the sealing member. And a cleaning liquid supply means for supplying a cleaning liquid to the enclosed area. 2. A polishing method for polishing an object to be polished held by a holding means by vacuum suction by sliding a polishing cloth attached to an upper surface of a table disposed opposite to a polishing surface thereof. A polishing step of rotating the object and the table to polish the object to be polished, and the holding means and the object to be polished in a state where the object to be polished is held by the holding means after the completion of the polishing step A polishing step, comprising: a cleaning step of cleaning. 3. When the object to be polished is detached from the holding means after the completion of the cleaning step, a detaching step of discharging the cleaning liquid outward from the holding portion of the object to be polished of the holding means simultaneously with the detachment is provided. The polishing method according to claim 2, wherein the polishing is performed. 4. The polishing method according to claim 3, further comprising a second cleaning step of cleaning said holding means again after said removing step.