JP2000233360A - Polishing device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a polishing device capable of uniformly polishing the whole polishing face of a substrate to be polished and realizing highly precise flatness. SOLUTION: In a polishing device, an outer peripheral stepped part protruding in at least outer peripheral part by a predetermined amount is formed directly or through a predetermined packing member 4 on a hold face of a substrate to be polished of a top ring 1, a space part 9b is formed between the hold face of the substrate to be polished and the substrate to be polished while the substrate to be polished (semiconductor wafer 6) is held on the hold face of the substrate to be polished, pressurizing fluid is supplied into 8 space part 9a while the top ring 1 is pressed against a face of a polishing cloth 11 of a turn table 10, a pressurizing means pressurizing the inside of the space part 9a is provided, and a groove is provided on a top face of the polishing cloth 11 affixed on a top face of the turn table 10.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a polishing apparatus for polishing and flattening a substrate to be polished of a semiconductor wafer.

[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 spacing between wirings has been narrowing. In particular, when a groove having a line width of 0.5 μm or less is formed by photolithography on the surface of a semiconductor wafer, the allowable depth of focus becomes shallow, so that the image plane of the stepper needs to be flat. Therefore, it is necessary to flatten the surface of the semiconductor wafer with high precision. As one means of this flattening, polishing by a polishing apparatus is performed.

Conventionally, this type of polishing apparatus has a turntable and a top ring, the top ring applies a constant pressure to the turntable, and an object to be polished is interposed between the turntable and the top ring.
The surface of the object to be polished is polished flat and mirror-finished while supplying a polishing liquid.

In the above-mentioned polishing apparatus, an elastic mat (backing member) made of, for example, polyurethane or the like, which is elastic, is attached to the holding surface of the polishing object, and the pressing force applied from the top ring to the polishing object is made uniform. Attempts have been made. This is intended to alleviate local polishing of the object to be polished by making the pressing force uniform, and to improve the flatness of the object to be polished.

FIG. 1 is a diagram showing a main part of a conventional polishing apparatus. The polishing apparatus has a polishing cloth 10 on the upper surface.
2 and a rotating turntable 101, and a semiconductor wafer 10 to be rotated and pressed so as to be polished.
3 is provided, and a polishing liquid supply nozzle 108 for supplying a polishing liquid Q to the polishing pad 102 is provided. The top ring 105 is connected to a top ring shaft 109. The top ring 105 has a backing member 107 having elasticity such as polyurethane on the lower surface thereof, and holds the semiconductor wafer 103 in contact with the backing member 107. .

Further, the top ring 105 is provided with a cylindrical guide ring 106 on the outer periphery thereof in order to prevent the semiconductor wafer 103 from coming off the lower surface of the top ring 105 during polishing. Here, the guide ring 106 is fixed to the top ring 105, and the lower end surface thereof is formed so as to project from the holding surface of the top ring 105. Thus, the semiconductor wafer 103 to be polished is separated from the holding surface by the frictional force with the polishing pad 102 during polishing, and is prevented from jumping out of the top ring 105.

[0007] The semiconductor wafer 103 is placed on a top ring 105.
The semiconductor wafer 103 is held under the backing member 107 on the lower surface of the
Is pressed by the top ring 105, and the turntable 101 and the top ring 105 are rotated so that the polishing pad 102 and the semiconductor wafer 103 are moved relative to each other for polishing. At this time, the polishing cloth 1
The polishing liquid Q is supplied onto the substrate 02. The polishing liquid is, for example, a suspension of abrasive grains composed of fine particles in an alkaline solution, and polishes the semiconductor wafer 103 by a combined action of a chemical polishing action by alkali and a mechanical polishing action by abrasive grains.

In the above-mentioned conventional polishing apparatus, the backing member 107 is attached to the lower surface of the top ring 105, and the semiconductor wafer 103 is held and brought into contact with the lower surface of the top ring 105 for polishing. 107 is easily affected by the elasticity of the semiconductor wafer 1.
03 appears as uneven polishing (polishing).

The polishing cloth on the turntable 101 is also made of, for example, IC1000 / SUBA manufactured by Rodel Nitta.
400 (a punched hole is formed on the polished surface of the IC 1000) is an elastic body made of polyurethane, so that when the one compressed by the edge of the semiconductor wafer 103 during polishing recovers, it comes into strong contact with the semiconductor wafer. Therefore, polishing of this portion proceeds faster than other portions, and therefore, as shown in FIG. 2, the end portion of the semiconductor wafer 103 is excessively polished and becomes non-flat (fringing occurs).

FIG. 3 shows a measured value of a film thickness with respect to a radial position when a 6-inch semiconductor wafer having an oxide film formed on the surface is polished by the above polishing apparatus, and a pressure with respect to a radial position obtained by a finite element method. It is a figure which shows the calculation value of. In FIG. 3, A indicates the measured value of the film thickness, and B indicates the calculated value of the pressure. As is clear from FIG. 3, the calculated value of the pressure at the radial position obtained by the finite element method and the measured value of the film thickness at the radial position substantially match. This tendency was the same for an 8-inch semiconductor wafer.

[0011]

SUMMARY OF THE INVENTION The present invention has been made in view of the above points, and provides a polishing apparatus which can uniformly polish a polished surface of a substrate to be polished over the entire surface and realize high-precision flatness. The purpose is to do.

[0012]

Means for Solving the Problems In order to achieve the above object, the invention according to claim 1 comprises a turntable having an upper surface to which a polishing cloth is adhered, and a top ring for holding a substrate to be polished. A polishing apparatus that applies a predetermined pressure to the top ring and presses the substrate to be polished against the polishing cloth surface of the turntable, and polishes and flattens the substrate to be polished by relative movement between the top ring and the turntable. An outer peripheral step portion is formed on the polishing target substrate holding surface of the top ring at least on the outer peripheral portion by a predetermined amount directly or via a predetermined member, and the polishing is performed while the polishing target substrate is held on the polishing target substrate holding surface. A space is formed between the target substrate holding surface and the polishing target substrate, A pressurizing means for supplying a pressurized fluid to the space portion while pressing the polishing pad against the polishing cloth surface of the turntable, providing a pressurizing means for pressurizing the space, and providing a groove on the upper surface of the polishing cloth attached to the upper surface of the turntable. It is characterized by.

As described above, in the conventional polishing apparatus, the portion of the polishing cloth that has been compressed by the end of the substrate to be polished recovers and strongly contacts the substrate to be polished is fixed by the backing member. Although the polishing amount increased, as described above, a pressurized fluid was supplied to the space between the polishing target substrate holding surface of the top ring and the polishing target substrate to apply pressure, and further adhered to the upper surface of the turntable. Since a groove is provided on the upper surface of the polishing cloth, this space becomes a buffer band, and uniform polishing can be realized by making the pressure uniform.

[0014] The invention described in claim 2 is the first invention.
Wherein the pressurizing means for pressing the top ring against the turntable and the pressurizing means for supplying the pressurized fluid to the space are independent from each other.

As described above, the pressurizing means for pressing the top ring against the turntable and the pressurizing means for supplying the pressurized fluid to the space are formed independently of each other, so that the top ring is pressed against the turntable. By balancing the force to be applied and the force to press the space, more accurate flatness of the object to be polished can be obtained.

According to a third aspect of the present invention, there is provided a turntable having an abrasive cloth adhered on an upper surface thereof, and a top ring for holding a substrate to be polished, wherein the polishing is performed by applying a predetermined pressure to the top ring. In a polishing apparatus for pressing the target substrate against the polishing cloth surface of the turntable and polishing and flattening the substrate to be polished by the relative movement of the top ring and the turntable, the polishing target substrate holding surface of the top ring is directly or directly polished. 10 to 20 mm width at least on the outer peripheral part via a predetermined member
Forming an outer peripheral step portion projecting by a predetermined amount so that a space is formed between the polishing target substrate holding surface and the polishing target substrate in a state where the polishing target substrate is held on the polishing target substrate holding surface. A pressurizing means for supplying a pressurized fluid to the space while the top ring is pressed against the polishing cloth surface of the turntable and pressurizing the space is provided.

[0017]

Embodiments of the present invention will be described below with reference to the drawings. FIG. 4 is a diagram showing a configuration example of a top ring used in the polishing apparatus according to the present invention.
4A is a sectional view, and FIG. 4B is a bottom view. The top ring 1 includes a flange 2, a ventilation plate 3, a backing member 4, and a guide ring 5.

A guide ring 5 is provided on the outer periphery of the lower surface of the flange 2.
The ventilation plate 3 is fixed to the lower surface of the flange 2 on the inner peripheral side of the guide ring 5, and the annular backing member 4 is fixed to the outer peripheral portion of the lower surface of the ventilation plate 3. A turntable 10 is located on the lower surface of the top ring 1, and a polishing cloth 11 is attached to the upper surface of the turntable 10. The semiconductor wafer 6 is interposed between the backing member 4 of the top ring 1 and the polishing pad 11 of the turntable 10, and the top ring 1 is pressed against the turntable 10,
By rotating the top ring 1 and the turntable 10 with respect to each other, the lower surface of the semiconductor wafer 6 (the contact surface with the polishing cloth 11) is polished.

The guide ring 5 holds the semiconductor wafer 6 during polishing.
Is provided to prevent the semiconductor wafer 6 from being detached from the lower surface of the top ring 1 and jumping out, and the lower surface of the guide ring 5 protrudes from the holding surface holding the semiconductor wafer 6 by a predetermined dimension. A predetermined gap is formed between the lower surface of the guide ring 5 and the polishing pad 11. With the semiconductor wafer 6 held by the top ring 1, a space surrounded by the upper surface of the semiconductor wafer 6, the lower surface of the ventilation plate 3, and the backing member 4 is provided between the upper surface of the semiconductor wafer 6 and the lower surface of the ventilation plate 3. 9a is formed.

The ventilation plate 3 is provided with a space 9b surrounded by the ventilation plate 3 and the flange 2, and a large number of ventilation holes 3a communicating the space 9a. The flange 2 is provided with a vent 2a for supplying compressed air to the space 9b and for evacuating the space 9b. By evacuating the space 9b through the vent 2a, the space 9a is also evacuated through the vent 3a, so that the semiconductor wafer 6 is vacuum-adsorbed. When compressed air is introduced from the vent 2a with the semiconductor wafer 6 interposed between the top ring 1 and the turntable 10 and the top ring 1 is pressed against the turntable 10, the space 9b is pressurized. It has become.

It is desirable that a plurality of vents 2a are arranged in a ring at a position near the backing member 4. This is the case where the semiconductor wafer 10 shown in FIG.
3 is excessively polished, so that the edge is excessively polished. When the ventilation port 2a is provided at a position close to the backing member 4, this is eliminated. Further, the vents 2a may be arranged in a plurality of rows and annularly at positions near the backing member 4.

The uniformity of polishing varies depending on polishing parameters such as the ring width of the backing member 4, the pressing force of the top ring 1, and the fluid pressure in the space 9a. As an example, the dependence of the ring width on various conditions is considered. And the results are shown in FIG. The semiconductor wafer used in this experiment was 8 inches, and the amount of polishing was measured at 69 points uniformly within the semiconductor wafer surface to illustrate the uniformity of polishing of the wafer (the degree of variation in the amount of polishing). Note that the peripheral portion of the wafer of 3 mm is excluded.

FIG. 11 shows that when the ring width of the backing member 4 is 10 to 20 mm, the dependence of the ring width is reduced, and good uniformity of in-plane polishing of the semiconductor wafer of less than 5% is obtained. Therefore, this range was set as the optimum ring width of the backing member 4. Note that the pressing force of the top ring 1 at this time is the total load when the entire upper surface of the semiconductor wafer is pressed by the top ring shaft with the backing member having the same shape as the conventional semiconductor wafer, and the area of the ring-shaped backing member 4. It is 0.8 to ² kg / cm ² when converted to.

FIG. 5 is a view showing an example of the structure of a polishing cloth stuck on the upper surface of a turntable. FIG. 5 (a) is an entire external view of the polishing cloth, and FIG. 5 (b) is a partial external view of the polishing cloth. It is. As shown in the figure, the surface of the polishing pad 11 used in the present embodiment is arranged in a lattice pattern, for example, 1 mm in width, 5 mm in pitch, and about 1 m in depth.
m grooves 11a are provided. The size of the groove is 0.3 to 2 mm in width, 3 to 15 mm in pitch, and 0.1 mm in depth.
It is desirable to set the above range. Further, the shape of the groove 11a is also a lattice shape in this embodiment, but may be another shape such as a circumferential groove.

FIG. 6 is a diagram showing an example of the structure of a polishing apparatus using a top ring having the structure shown in FIG. 4 as the top ring and a polishing cloth having the structure shown in FIG. 5 as the polishing cloth. The top ring shaft 8 is fixed to the top ring head 12 and connected to the top ring air cylinder 13.
The top ring shaft 8 moves up and down by the top ring air cylinder 13, and presses the semiconductor wafer 6 held on the lower end surface of the top ring 1 against the polishing cloth 11 of the turntable 10. A ball bearing for accommodating the ball 7 is formed on the upper surface of the top ring 1 and the lower surface of the top ring shaft 8.
It can be tilted around.

The top ring shaft 8 is connected to a rotary cylinder 14 via a key (not shown). The rotary cylinder 14 has a timing pulley 15 on its outer periphery. The timing pulley 15 is connected via a timing belt 16 to a timing pulley 15 provided on a top ring motor 17 fixed to the top ring head 12. Accordingly, when the top ring motor 17 is rotationally driven, the rotary cylinder 14 and the top ring shaft 8 rotate integrally via the timing pulley 18, the timing belt 16 and the timing pulley 18, and the top ring 1 rotates. The top ring head 12 is supported by a top ring head shaft 19 supported by a frame (not shown) so as to swing (turn).

[0027] The top ring air cylinder 13 is a pipe 20, is connected via a valve V ₁ and the regulator R1 to a compressed air source 22, vent 2a of the flange 2 of the top ring 1 is pipe 21, valve V ₂ and the regulator R
2 to a compressed air source 22 and a pipe 21
And a valve V ₀ and a vacuum exhaust source 26. By adjusting the air pressure supplied to the top ring air cylinder 13 by the regulator R1, the pressing force of the top ring 1 pressing the semiconductor wafer 6 against the polishing pad 11 can be adjusted. Further, by controlling the air pressure supplied to the space 9a between the ventilation plate 3 and the semiconductor wafer 6 by the regulator R2, the pressing force for pressing the semiconductor wafer 6 can be adjusted. I have.

The regulators R1 and R2 are independently controlled by a controller (not shown). A polishing liquid supply nozzle 23 is provided above the turntable 10, and the polishing liquid Q is supplied onto the polishing cloth 11 on the turntable 10 by the polishing liquid supply nozzle 23.

In the polishing apparatus having the above structure, the semiconductor wafer 6 is held on the lower surface of the top ring 1 and is rotated by a top ring motor 17, and the top ring 1 is rotated by operating the top ring air cylinder 13. Is pressed against the polishing cloth 11 of the turntable 10. On the other hand, the polishing liquid Q is held on the polishing cloth 11 by flowing the polishing liquid Q from the polishing liquid supply nozzle 23 to the upper surface of the polishing cloth 11, and the polishing liquid is applied between the polishing surface and the polishing cloth 11 of the semiconductor wafer 6. Polished while remaining.

At this time, the top ring 1 is pressed against the upper surface of the turntable 10 by the top ring air cylinder 13 as described above, and at the same time, the space 9a of the top ring 1 is moved from the compressed air source 22 to the regulator. R
2 through which compressed air is supplied. This space 9a
To the pressing force of the top ring 1 (that is, the applied pressure of the semiconductor wafer when mechanically pressed by the semiconductor wafer top ring shaft 8 via a disc-shaped backing material having the same shape as the semiconductor wafer). The value is determined within a range of a small value to twice. Further, the compressed air supplied to the space 9a is sealed by the backing member 4, and a substantially set value is secured by continuously supplying the compressed air.

FIGS. 7 to 10 show the results of polishing when an oxide film formed on the surface of an 8-inch semiconductor wafer is polished. FIG. 7 shows a case where the top ring of the present invention shown in FIG. 4 is used as a top ring and polished by a polishing apparatus using a polishing cloth having punch holes formed on the surface, and FIG. FIG. 9 shows a case where the polishing pad is polished by a polishing apparatus using a polishing cloth having a lattice-like groove formed on the surface as shown in FIG. 5, and FIG. 9 shows the top ring of the present invention shown in FIG. FIG. 5 shows a case where the polishing cloth used is polished by a polishing apparatus using a polishing cloth having a lattice-shaped groove formed on the surface as shown in FIG.
FIG. 10 shows a case where polishing is performed by the conventional polishing apparatus of FIG.

7 to 10, the vertical axis represents the thickness (Å) of the oxide film after polishing (polishing), and the horizontal axis represents the distance from the center (0) of the semiconductor wafer. Here, an alkaline solution containing a silica-based abrasive is used as the polishing liquid. As shown in FIG. 9, when the top ring of the present invention shown in FIG. 4 is used as the top ring and a polishing cloth having a lattice-like groove formed on the surface as shown in FIG. 7 and FIG. 8, it is apparent that the polishing is performed with high flatness from the center to the end, and that the polishing is performed with less uneven polishing. In particular, the flatness and polishing are significantly improved as compared with the conventional polishing apparatus shown in FIG.

This is because, as described above, the polishing pad 11 compressed by the end of the semiconductor wafer 6 during polishing recovers and the portion that comes into strong contact with the semiconductor wafer 6 is conventionally fixed by the backing member. The polishing amount was large. In contrast, in the present invention, since the upper surface of the semiconductor wafer 6 (opposite to the polished surface) supplies compressed air to the space 9a, the upper surface of the semiconductor wafer 6 is uniformly pressed. This space portion 9a became a buffer band, and it was possible to perform uniform polishing without polishing unevenness.

Also, a grid-like groove 11 is formed on the surface of the polishing cloth 11.
Since a is formed, the surplus abrasive liquid Q of the abrasive liquid Q flowing out from the abrasive liquid supply nozzle 23 flows into the groove 11a, and the polishing surface (lower surface) of the semiconductor wafer 6 and the upper surface of the polishing cloth 11 The polishing liquid Q spreads evenly in between, and uniform polishing can be performed in cooperation with the action of the top ring.

The material of the polishing pad 11 on the turntable 10 is not particularly limited. The material of the backing member 4 can be a soft material such as polyurethane or rubber, or a hard material such as Teflon (registered trademark) or plastic. Further, the lower surface of the top ring 1 itself may be formed in a shape like the backing member 4, that is, an outer peripheral step portion protruding by a predetermined amount like the backing member 4 may be formed in the outer peripheral portion. In short, it is sufficient that the semiconductor wafer 6 is configured so that a space is formed between the holding surface and the semiconductor wafer 6 while the semiconductor wafer 6 is held on the holding surface of the top ring 1.

In the above embodiment, a semiconductor wafer has been described as an example of a substrate to be polished. However, the present invention is not limited to this, and is applicable to polishing of a substrate that requires high precision flatness. Of course it is available.

[0037]

As described above, according to the invention described in each claim, the following excellent effects can be obtained.

According to the first and third aspects of the present invention, a pressurized fluid is supplied to the space between the polishing target substrate holding surface of the top ring and the polishing target substrate and pressurized. Since a groove is provided on the upper surface of the attached polishing cloth, this space portion serves as a buffer band, and uniform pressing can be achieved by uniform pressing.

According to the second aspect of the present invention, the pressurizing means for pressing the top ring against the turntable and the pressurizing means for supplying the pressurized fluid to the space are made independent from each other, so that By balancing the force that presses the ring against the turntable and the force that presses the space, more accurate flatness of the object to be polished can be obtained.

[Brief description of the drawings]

FIG. 1 is a diagram showing a main part of a conventional polishing apparatus.

FIG. 2 is a diagram for explaining a polishing state of an end portion when a semiconductor wafer is polished by a conventional polishing apparatus.

FIG. 3 is a diagram showing a measured value of a film thickness and a calculated value of a pressure with respect to a position in a radial direction when a semiconductor wafer is polished by a conventional polishing apparatus.

4A and 4B are diagrams showing a configuration example of a top ring used in a polishing apparatus according to the present invention. FIG.
(B) is a bottom view.

FIG. 5A is a diagram showing a configuration example of a polishing cloth stuck on the upper surface of a turntable of the polishing apparatus according to the present invention, and FIG.
FIG. 5B is an entire external view of the polishing cloth, and FIG. 5B is a partial external view of the polishing cloth.

FIG. 6 is a diagram showing a configuration example of a polishing apparatus according to the present invention.

FIG. 7 is a diagram showing an example of a polishing result when an oxide film formed on a surface of a semiconductor wafer is polished by a polishing apparatus.

FIG. 8 is a view showing an example of a polishing result when an oxide film formed on the surface of a semiconductor wafer is polished by a polishing apparatus.

FIG. 9 is a view showing an example of a polishing result when an oxide film formed on the surface of a semiconductor wafer is polished by the polishing apparatus according to the present invention.

FIG. 10 is a view showing an example of a polishing result when an oxide film formed on the surface of a semiconductor wafer is polished by a conventional polishing apparatus.

FIG. 11 is a diagram showing a ring width of a backing member and a polishing result.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 Top ring 2 Flange 3 Vent plate 4 Backing member 5 Guide ring 6 Semiconductor wafer 7 Ball 8 Top ring shaft 9a, b Space 10 Turntable 11 Polishing cloth 12 Top ring head 13 Air cylinder for top ring 14 Rotating cylinder 15 Timing pulley 16 timing belt 17 top ring motor 18 timing pulley 19 top ring head shaft 20 pipe 21 pipe 22 compressed air source 23 abrasive liquid supply nozzle 26 evacuation source R1 regulator R2 regulator V ₀ valves V ₁ valve V ₂ valve

Claims (3)

[Claims] 1. A turntable having a polishing cloth adhered on an upper surface thereof, and a top ring for holding a substrate to be polished, wherein a predetermined pressure is applied to the top ring to apply the polishing target substrate to the polishing cloth of the turntable. While pressing against the surface, in a polishing apparatus for polishing and flattening the substrate to be polished by relative movement of the top ring and the turntable, at least directly or via a predetermined member to the substrate holding surface to be polished of the top ring A space is formed between the polishing target substrate holding surface and the polishing target substrate in a state where an outer peripheral step portion protruding by a predetermined amount is formed on the outer peripheral portion, and the polishing target substrate is held on the polishing target substrate holding surface. In a state where the top ring is pressed against the polishing cloth surface of the turntable. Supplying pressurized fluid to the space portion, a pressurizing means for pressurizing the space portion provided, a polishing apparatus is characterized in that a groove on the upper surface of the polishing pad was affixed to the turntable upper surface. 2. The polishing apparatus according to claim 1, wherein a pressurizing unit that presses the top ring against a turntable and a pressurizing unit that supplies a pressurized fluid to the space are independent from each other. A polishing apparatus characterized in that: 3. A turntable having a polishing cloth adhered to an upper surface thereof, and a top ring for holding a substrate to be polished, wherein a predetermined pressure is applied to the top ring to apply the polishing target substrate to the polishing cloth of the turntable. While pressing against the surface, in a polishing apparatus for polishing and flattening the substrate to be polished by relative movement of the top ring and the turntable, at least directly or via a predetermined member to the substrate holding surface to be polished of the top ring 10-2 width on the outer circumference
An outer peripheral step is formed by projecting a predetermined amount at 0 mm, and a space is formed between the polishing target substrate holding surface and the polishing target substrate while the polishing target substrate is held on the polishing target substrate holding surface. A polishing device for supplying a pressurized fluid to the space while the top ring is pressed against the polishing cloth surface of the turntable, and pressurizing the inside of the space.