JPH11179652A - Polishing device and method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a polishing device and method whereby nonuniformity of polishing can be easily corrected, and to polish so as to adjust a stock removable in aimed partial region of a polishing surface. SOLUTION: This device has a turntable 5 sticking a polishing cloth 6 in an upper surface and a top ring 1, a polishing object 4 is interposed between the turntable 5 and the top ring 1, and by pressing with prescribed force, the polishing object 4 is polished into flatness and mirror finished. Here, in a hold surface with the top ring 1 holding the polishing object, a plurality of vacuum suction possible openings 10 , 20 are provided, a plurality of the openings 10 , 20 are divided into a plurality of regions C1 , C2 , C3 , and vacuum suction is made possible in each region.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a polishing apparatus and method, and more particularly to a polishing apparatus and method for polishing a surface of an object to be polished such as a semiconductor wafer to a flat and mirror surface.

[0002]

2. Description of the Related Art In recent years, as the degree of integration of semiconductor devices has increased, circuit wiring has become finer, and the distance between wirings has become smaller. In particular, in the case of optical lithography of 0.5 μm or less, since the depth of focus becomes shallow, flatness of the image forming surface of the stepper is required. Therefore, it is necessary to flatten the surface of the semiconductor wafer. As one means of this flattening method, polishing is performed by a polishing apparatus. Conventionally, this type of polishing apparatus has a turntable and a top ring that rotate at independent rotation speeds, the top ring applies a constant pressure to the turntable, and a polishing cloth containing an abrasive liquid on the turntable. An object to be polished is interposed between the top ring and the top ring, and the object to be polished is held and polished.

The performance of the above-mentioned polishing apparatus is as follows.
A highly accurate flatness of the object to be polished after polishing is required. Therefore, the holding surface for holding the semiconductor wafer at the time of polishing, that is, the lower end surface of the top ring, the contact surface of the polishing cloth in contact with the semiconductor wafer, and the surface to which the polishing cloth of the turntable is adhered have high flatness. Have been considered desirable and have been used.

On the other hand, factors affecting the polishing action of the polishing apparatus include not only the shape of the holding surface of the top ring and the contact surface of the polishing cloth, but also the relative speed of the polishing cloth and the semiconductor wafer, and the pressing force on the polishing surface of the semiconductor wafer. It is known that the distribution of the polishing liquid, the amount of the abrasive liquid on the polishing cloth, the use time of the polishing cloth, and the like affect. Therefore, it is considered that if these elements are made equal over the entire polished surface of the semiconductor wafer, a highly accurate flatness can be obtained.

[0005] However, of the above-mentioned factors affecting the polishing action, those that can be made uniform over the entire polished surface include:
There are extremely difficult elements. For example, the relative speed between the polishing cloth and the semiconductor wafer can be made uniform by making the rotation of the turntable and the top ring the same number of revolutions and in the same direction, but the amount of the polishing liquid is made uniform by the centrifugal force. Have difficulty. Therefore, the idea of equalizing the factors affecting the polishing action over the entire polishing surface, including flattening the upper surface of the polishing cloth on the turntable at the lower end surface of the top ring, is limited to the flatness of the polished surface after polishing. And the required flatness may not be obtained in some cases.

Therefore, as a method for obtaining a more accurate flatness, the pressing force on the polishing surface of the semiconductor wafer is given a distribution by forming the shape of the holding surface of the top ring into a concave surface or a convex surface. The non-uniformity of the polishing action due to the intrusion of the liquid and the variation in the use time of the polishing cloth has been corrected.

[0007]

However, when the shape of the holding surface of the top ring is devised, the holding surface of the top ring is always in contact with the semiconductor wafer.
Continuously affects polishing over the entire time during polishing. That is, since the shape of the holding surface of the top ring has an excessively sensitive effect on the polishing action, it is extremely difficult to correct the holding surface of the top ring to be intentionally non-flat, and the intentional shape given is If even a small amount is inappropriate, there is a problem that the flatness of the polished surface of the wafer is rather lost, or the correction is insufficient and a sufficient flatness of the polished surface of the wafer cannot be obtained.

In order to solve the above problem, a plurality of openings through which a pressurized fluid can be ejected are provided on a holding surface where a top ring holds an object to be polished, and the plurality of openings are divided into a plurality of regions. A polishing apparatus that supplies a pressurized fluid every time is known. In such a polishing apparatus, it is possible to control a pressing force on a back surface of, for example, a semiconductor wafer which is a polishing target for each region. As a result, the polishing rate for each region of the polishing target can be corrected, and the flatness of the polished surface of the polishing target can be improved.

However, the method of adjusting the pressing force of the pressurized fluid by dividing the back surface of the object to be polished into each region and supplying the pressurized fluid is divided into each region on the top ring side on the back surface of the wafer. However, the pressurized fluid supplied from the opening provided on the holding surface for holding the object to be polished is mixed with the back surface of the object to be polished since a small space is provided between the holding surface and the holding surface. This makes it difficult to finely adjust the pressure in each area of the back surface of the polishing object.

[0010] That is, FIG. 7 shows pressure adjustment for each region by the pressurized fluid. And dividing the respective areas as shown in (A) radially _{C 1, C 2, C 3} . Here, the respective regions communicate with each other in the circumferential direction, and each pressure in the circumferential direction is constant. At this time, the pressure distribution indicated by the dotted line in (B) is set as a target pressure distribution for correction, and is a pressure distribution adjusted for each valve and the like.
That is, no particular application of pressurized fluid to the region C ₃ in the region C ₁ and the outer peripheral portion of the central portion (A), the a region C ₂ by supplying a pressurized fluid in the middle region C ₂ The back pressure of the object to be polished is increased at the corresponding portion. However, as described above, since a very small common space exists between the back surface and the holding surface of the polishing object, the actual pressure distribution has a gentle mountain shape as shown by the solid line in FIG. It becomes a distribution.

SUMMARY OF THE INVENTION The present invention has been made to solve the above-mentioned problems, and has a polishing apparatus and method capable of easily correcting non-uniformity of polishing, and a polishing amount of a target area of a polishing surface. It is an object of the present invention to provide a polishing apparatus and a polishing method capable of polishing so as to increase or decrease the amount of polishing.

[0012]

In order to achieve the above object, a first aspect of the present invention has a turntable and a top ring each having an upper surface on which a polishing cloth is adhered, and the turntable, the top ring and the turntable. In a polishing apparatus in which the polishing target is polished by pressing the polishing target with a predetermined force with a polishing target interposed therebetween, and the polishing target is flattened and mirror-finished, the top ring holds the polishing target with a vacuum. A plurality of openings capable of being sucked are provided, the plurality of openings are divided into a plurality of regions, and evacuation can be performed for each of the regions.

According to a second aspect of the present invention, there is provided a turntable having an abrasive cloth adhered on an upper surface thereof and a top ring, and a predetermined force is applied by interposing an object to be polished between the turntable and the top ring. In the polishing method of polishing the polishing object by pressing with a pressure, and flattening and polishing the polishing object, a plurality of openings capable of vacuum suction are provided on a holding surface where the top ring holds the polishing object, and the plurality of openings are provided. Is divided into a plurality of regions, and vacuum suction is possible for each of the regions, and the pressing force of the pressurized fluid on the polishing cloth against the polishing object is changed between the central portion side and the outer peripheral portion side of the polishing object to polish. It is characterized by doing.

[0014]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS One embodiment of the present invention will be described below with reference to FIGS.

FIG. 1 is a view showing a structure of a top ring portion according to an embodiment of the present invention. In FIG. 1, reference numeral 1 denotes a top ring. Inside the top ring 1, a circular first chamber C ₁ located at a central portion, and an annular second chamber C ₂ located at an outer peripheral side of the first chamber C _1. and the third chamber C ₃ cyclic located in the second outer peripheral side of the chamber C ₂ is formed. The first chamber C ₁ is connected via a valve V ₁ to an evacuation unit, the second chamber C ₂ is connected via a valve V ₂ to an evacuation unit, and the third chamber C ₃ is connected via a valve V _3. It is connected to a vacuum pump. The top ring 1 has a concave portion 1 a for accommodating a semiconductor wafer 4 to be polished, and an elastic mat 2 is attached to a lower surface of the top ring 1.

The top ring 1 and the elastic mat 2 have a plurality of openings 1 _O and 2 _O aligned with each other, and each of the openings 1 _O and 2 _O is provided in the first to third chambers C ₁ to C. _Three
To any one of the chambers. That is, a plurality of openings 1 _O and 2 _O capable of vacuum suction are provided on a holding surface of the top ring 1 for holding a semiconductor wafer to be polished, and the plurality of openings 1 _O and 2 _O are respectively a first opening and a second opening.
By communicating with any of the third to third chambers C _{1 to} C ₃ , it is divided into three concentric annular regions, and vacuum suction can be performed for each of these regions.

A pressing ring 3 is arranged on the outer periphery of the top ring 1. The pressing ring 3 is vertically movable with respect to the top ring 1. Below the top ring 1, a turntable 5 having an abrasive cloth 6 adhered to the upper surface is provided.

In the above configuration, the top ring 1 presses the semiconductor wafer 4 to be polished against the polishing cloth 6 on the turntable 5 with a predetermined pressing force F ₁ (pressure gf / cm ² per unit area). Then, the semiconductor wafer 4 is polished. The pressing force F ₁ is made to the variable. Then, the first to third chambers C _{1 to} C ₃ are evacuated as appropriate during polishing.
Due to this vacuum suction, the upper surface of the semiconductor wafer 4 is attracted to the wafer holding surface of the elastic mat 2 held on the lower surface of the top ring 1.

At this time, an annular region to be evacuated is appropriately selected. For example, only the first chamber C ₁ is evacuated, the second, third when the chamber C _2, C ₃ to prevent evacuation, elastic at a pressure lower than the outer peripheral portion side central portion the semiconductor wafer 4 by vacuum suction Pressed against mat 2. That is, the semiconductor wafer 4 is in a state where the central portion is depressed with respect to the polishing cloth 6 side. Therefore, when the central portion of the semiconductor wafer 4 tends to be polished from the outer peripheral portion side, the excessive polishing at the central portion can be corrected by using the pressing action of the vacuum suction as described above.

On the other hand, when the outer peripheral portion of the semiconductor wafer 4 tends to be excessively polished more than the central portion, on the other hand, only the third chamber C ₃ is evacuated, and the first and second chambers C ₁ , C ₁ ,
C ₂ is to prevent vacuum suction. As a result, the polishing pressure on the outer peripheral portion side of the semiconductor wafer 4 can be made lower than the polishing pressure on the central portion side, excessive polishing on the outer peripheral portion side can be corrected, and the entire surface of the semiconductor wafer 4 can be uniformly polished.

Further, suction is performed while changing the vacuum suction pressure to the first chamber C ₁ , the second chamber C _2, and the third chamber C ₃ . Thus, the space interposed between the holding surface of the top ring 1 and the upper surface of the semiconductor wafer 4 is given a pressure gradient such that the pressure gradient gradually increases or decreases from the central region toward the outer peripheral region, and the semiconductor wafer 4 is moved. A force is applied to the polishing pad 6 to give a gradient. As a result, it is possible to correct an excessive or insufficient local polishing amount of the semiconductor wafer 4 to be polished.

FIG. 2A shows an example of pressure adjustment on the back surface of the polishing object by the vacuum suction method. An area C ₁ for vacuum suction near the center of the polishing object in this embodiment, an intermediate portion and a region C ₂ to vacuum suction, are divided into areas peripheral portion to the area C ₃ to vacuum suction. Therefore, as shown in FIG. 2B, for example, only the region C ₂ is vacuum-sucked, and the region C ₂ in the intermediate portion and the region C _{3 in the} outer peripheral portion are sucked.
If no vacuum suction bets, only the portion of the region C ₂ is decreased the pressure exerted on the polishing object back. According to the vacuum suction method, because it can not gap between the back and the elastic pad 2 polishing object is to reduce the back pressure of the polishing object only region C ₂ moiety being evacuated The vacuum suction part does not extend to the central part or the outer peripheral part.

Therefore, under certain polishing conditions, FIG.
Assume that there is a distribution of the polishing amount of the object to be polished as shown in FIG. This is a case where the polishing amount in the middle portion and the outer peripheral portion of the object to be polished is excessive compared with the polishing amount. In such a case, when the pressure distribution on the back surface of the polishing target is given as shown in FIG. 2B, the excessive polishing amount in the middle portion is corrected, and as shown in FIG. A uniform polishing amount distribution can be obtained over the entire surface.

In this embodiment, the elastic mat 4 has a polyurethane foam layer having a thickness of 0.5 mm.
With such a degree, are used as a diameter of approximately 1mm is as a hole 1 _0, 2 _0. Also, as the negative pressure of vacuum suction,
About -70 to -90 kpascal is used. The pressing force applied to the object to be polished by the top ring is 40
It is about 0 gf / cm ² .

Next, an example of the overall configuration of a polishing apparatus according to the present invention will be described with reference to FIGS. FIG. 4 is a cross-sectional view showing the overall configuration of the polishing apparatus. FIG. 5 is a cross-sectional view showing the main configuration of the polishing apparatus.
FIG. 7 is a sectional view taken along line VII-VII of FIG. 5.

In FIGS. 4 and 5, reference numeral 1 denotes a top ring. Inside the top ring 1, there is a circular first chamber C ₁ located at the center and an annular ring located at the outer peripheral side of the first chamber C _1. the second chamber C ₂ and the second chamber C ring positioned on the outer peripheral side of the ₂ third chamber C ₃ of are formed. The first chamber C ₁ is the valve V1, the regulator R ₁
Is connected to a vacuum pump 24 which is a vacuum source through
The second chamber C ₂ is connected to a vacuum pump 24 via a valve V ₂ and a regulator R ₂ , and the third chamber C ₃ is connected to a vacuum pump 2 via a valve V ₃ and a regulator R _3.
4 is connected. The top ring 1 has a concave portion 1a for accommodating a semiconductor wafer 4 to be polished. An elastic mat 2 is adhered to the lower surface of the top ring 1.

The top ring 1 and the elastic mat 2 have a plurality of openings 1 _O and 2 _O aligned with each other, and the openings 1 _O and 2 _O are respectively provided in the first to third chambers C ₁ to C _{1. Three}
To any one of the chambers. That is, a plurality of openings 1 _O and 2 _O capable of vacuum suction are provided on a holding surface of the top ring 1 for holding a semiconductor wafer to be polished, and the plurality of openings 1 _O and 2 _O are respectively a first opening and a second opening. ~
By communicating with any one of the third chambers C _{1 to} C ₃ , three annular areas A ₁ ,
The area is divided into A ₂ and A ₃ , and vacuum suction can be performed for each of these areas.

A pressing ring 3 is disposed on the outer periphery of the top ring 1. Below the top ring 1, a turntable 5 having an abrasive cloth 6 adhered to the upper surface is provided.

The top ring 1 is connected to a top ring shaft 8 via a ball 7, and the top ring shaft 8 is connected to a top ring air cylinder 10 fixed to a top ring head 9. The top ring shaft 8 moves up and down by the top ring air cylinder 10, and presses the semiconductor wafer 4 held on the lower end surface of the top ring 1 against the turntable 5. In the top ring shaft 8, the first
Channel for evacuating the ~ third chamber C ₁ -C ₃ are formed.

The top ring shaft 8 is connected to a rotary cylinder 11 via a key (not shown), and the rotary cylinder 11 has a timing pulley 12 on its outer periphery. The timing pulley 12 is connected via a timing belt 13 to a timing pulley 15 provided on a top ring motor 14 fixed to the top ring head 9. Therefore, when the top ring motor 14 is rotationally driven, the rotary cylinder 11 and the top ring shaft 8 rotate integrally via the timing pulley 15, the timing belt 13, and the timing pulley 12, and the top ring 1 rotates. The top ring head 9 is supported by a top ring head shaft 16 fixedly supported by a frame (not shown).

On the other hand, the pressing ring 3 is connected to the top ring 1 via a key 18, and the pressing ring 3 is vertically movable with respect to the top ring 1 and is rotatable integrally with the top ring 1. I have. The press ring 3 is connected to the press ring air cylinder 2 via a shaft 21 and a bearing retainer 20 holding a bearing 19.
2 are connected. The press ring air cylinder 22 is fixed to the top ring head 9. A plurality of air cylinders 22 for the pressing ring are provided on the circumference (in this embodiment, three air cylinders).
Pieces) are arranged.

The air cylinder 10 for the top ring and the air cylinder 22 for the pressing ring are each provided with a regulator R
_4, is connected to a compressed air source via the R _5. And
By the regulator R ₄ can adjust the pressing force the top ring 1 to press the semiconductor wafer 4 to the polishing cloth 6 by adjusting the air pressure supplied to the air cylinder 10 for the top ring air for the pressure ring by the regulator R ₅ By adjusting the air pressure supplied to the cylinder 22, the pressing force of the pressing ring 3 pressing the polishing pad 6 can be adjusted.

A polishing liquid supply nozzle 25 is provided above the turntable 5 so that the polishing liquid Q is supplied onto the polishing cloth 6 on the turntable 5 by the polishing liquid supply nozzle 25. ing.

In the polishing apparatus having the above configuration, the semiconductor wafer 4 is held on the lower surface of the top ring 1, and the top ring 1 is pressed toward the turntable 5 by operating the top ring air cylinder 10 and is rotated. The semiconductor wafer 4 is pressed against the polishing cloth 6 on the upper surface of the turntable 5. On the other hand, by flowing the polishing abrasive Q from the abrasive supply nozzle 25, the polishing abrasive Q is held on the polishing cloth 6, and the surface (lower surface) of the semiconductor wafer 4 to be polished and the polishing cloth 6
Polishing is performed in a state in which the polishing liquid Q is present.

When the first to third chambers C _{1 to} C ₃ are evacuated from the evacuation pump 24 during polishing, the opening 1
_O , 2 _O to the lower surface of the elastic mat 2, that is, the top ring 1
The upper surface of the semiconductor wafer 4 is attracted to the holding surface of the semiconductor wafer 4.

At this time, a chamber for vacuum suction is appropriately selected, and annular regions A ₁ , A ₂ , and A ₃ for vacuum suction are appropriately selected. For example, only the first chamber C ₁ and vacuum suction, second, polishing the third when the chamber C _2, C ₃ to prevent vacuum suction, the semiconductor wafer 4 is lower pressures outer periphery side central portion by vacuum suction It is pressed against the cloth 6. Therefore, when the central portion of the semiconductor wafer 4 tends to be polished from the outer peripheral portion side, excessive polishing at the central portion can be corrected by the action of vacuum suction as described above.

In the above embodiment, the top ring is provided with a plurality of openings capable of vacuum suction on the holding surface for holding the object to be polished, and the openings are divided into a plurality of regions to perform vacuum suction for each region. However, some areas may be pressurized by compressed air or the like instead of vacuum suction. Thereby, for example, the central portion and the outer peripheral portion can be vacuum-sucked, and only the intermediate portion can be pressurized, so that excessive or insufficient polishing can be more effectively corrected. Thus, various modifications can be made without departing from the spirit of the present invention.

[0038]

As described above, according to the polishing apparatus and method of the present invention, it is possible to prevent the pressing force distribution at the peripheral portion of the polishing object from becoming non-uniform at the time of polishing and to reduce the polishing pressure of the polishing object. It can be made uniform over the entire surface, and it is possible to prevent the polishing amount of the object to be polished from becoming excessive or insufficient. Therefore, the entire surface of the object to be polished can be polished flat and mirror-finished. Further, high-quality polishing can be performed in a semiconductor manufacturing process or the like, and a product can be provided to a peripheral portion of a semiconductor wafer, thereby contributing to an improvement in the yield of the semiconductor wafer.

Further, according to the present invention, there is a demand for intentionally increasing or decreasing the polishing amount of the peripheral portion of the polishing object from the inner side depending on the polishing object such as a semiconductor wafer. Therefore, the amount of polishing at the peripheral portion of the object to be polished can be intentionally increased or decreased. Furthermore, polishing can be performed so as to increase or decrease the amount of polishing not only at the peripheral portion of the polishing target, but also at a target region (for example, the central portion, the outer peripheral portion, etc.) of the polishing surface.

[Brief description of the drawings]

FIG. 1 is an explanatory diagram of a structure of a top ring portion according to an embodiment of the present invention.

FIG. 2A is a diagram showing vacuum suction of the back surface of the polishing object, and FIG. 2B is a diagram showing the resulting pressure distribution on the back surface of the polishing object.

3A and 3B are explanatory diagrams showing a polishing amount distribution of an object to be polished, wherein FIG. 3A is before correction and FIG.

FIG. 4 is a cross-sectional view showing an overall configuration of a polishing apparatus according to the present invention.

FIG. 5 is a cross-sectional view illustrating a main configuration of a polishing apparatus according to the present invention.

FIG. 6 is a sectional view taken along line VII-VII of FIG. 5;

FIG. 7A is a diagram showing that the back surface of the polishing object is pressurized with a fluid, and FIG. 7B is a diagram showing the resulting pressure distribution on the back surface of the polishing object.

[Explanation of symbols]

1 Top Ring 2 Elastic Mat 3 Press Ring 4 Semiconductor Wafer 5 Turntable 6 Polishing Cloth 7 Ball 8 Top Ring Shaft 9 Top Ring Head 10 Air Cylinder for Top Ring 18 Key 19 Bearing 20 Bearing Holder 22 Air Cylinder for Press Ring 24 Vacuum Exhaust Source 25 Abrasive liquid supply nozzle 26 Press ring holder R _{1 to} R ₅ Regulators C _{1 to} C ₃ First to third chambers

 ──────────────────────────────────────────────────の Continued on the front page (72) Inventor Naosuke Matsuo 4-2-1 Motofujisawa, Fujisawa-shi, Kanagawa Inside Ebara Research Institute Co., Ltd.

Claims (4)

[Claims] 1. A polishing apparatus comprising: a turntable having an abrasive cloth adhered to an upper surface thereof; and a top ring, wherein a polishing target is interposed between the turntable and the top ring and pressed with a predetermined force to thereby apply the polishing target. In a polishing apparatus for polishing and flattening an object, a plurality of openings capable of vacuum suction are provided on a holding surface where the top ring holds an object to be polished, and the plurality of openings are divided into a plurality of regions, A polishing apparatus wherein vacuum suction is enabled for each area. 2. The polishing apparatus according to claim 1, wherein the plurality of regions are concentric annular regions. 3. The polishing apparatus according to claim 1, wherein a pressure of vacuum suction applied to the polishing target by the top ring can be independently changed for each of the regions. 4. A polishing apparatus comprising: a turntable having a polishing cloth adhered to an upper surface thereof; and a top ring, wherein an object to be polished is interposed between the turntable and the top ring and pressed with a predetermined force to thereby apply the object to be polished. In a polishing method of polishing an object and flattening and mirror-finishing, a plurality of openings capable of vacuum suction are provided on a holding surface where the top ring holds an object to be polished, and the plurality of openings are divided into a plurality of regions, A polishing method, wherein vacuum evacuation is enabled for each of the regions, and polishing is performed by changing the pressing force of the object to be polished against the polishing cloth by the vacuum evacuation for each of the regions of the object to be polished.