JPH08267357A - Abrasive device of substrate and abrasive method thereof - Google Patents

Abstract

PURPOSE: To have no substrate left behind on an abrasive table after abrasion is oven, and to control an abrasive in-plane distribution as well as to improve the extent of holdability in a substrate during the abrasion. CONSTITUTION: In a substrate holding part 20 holding a backside 12 of a substrate 10 in order to grinda surface side 11 of this substrate 10, a circumferential part around the backside 12 of the substrate 10 is subjected to vacuum suction and thereby it is provided with such a structure as forming the surface side 11 of the substrate 10 into a projection form, and this projection form is maintained in a range from the duration of abrasion to the midst of the separation after the abrasion is over.

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 a polishing method, and more particularly to a polishing apparatus and a polishing method for flattening a surface of a device on a semiconductor substrate in a semiconductor wafer state.

[0002]

2. Description of the Related Art Techniques for smoothing the surface of a substrate by polishing have been used in various fields including the manufacturing process of semiconductor substrates. On the other hand, in recent years, also in the device manufacturing process on a semiconductor substrate, a chemical mechanical polishing method is being adopted in which unevenness on the surface formed in the manufacturing process, for example, unevenness on the surface of an interlayer insulating film is flattened by polishing. This method has a number of differences from the method of polishing the surface of the substrate itself such as a semiconductor substrate, and has its own problems.

In the case of smoothing the surface of the substrate itself, a relatively soft polishing cloth has been used for the purpose of polishing the surface of the substrate, that is, polishing.

However, when the surface of the device on the semiconductor substrate in the state of a semiconductor wafer is to be planarized, a hard polishing cloth is used because the purpose is to reduce the absolute step. When a hard polishing cloth is used, local thickness variation on the back surface of the substrate, dust, scratches, etc. directly affect the distribution of polishing on the surface.

This is because the pressure of pressing the substrate against the polishing cloth locally changes due to dust or the like. That is, a soft polishing cloth absorbs the change in a relatively wide area, whereas a hard polishing cloth cannot disperse the pressure, and thus a local polishing rate nonuniformity occurs.

As one of the measures to solve this, an elastic film called an insert pad is provided between the back surface of the substrate and the substrate holding portion. Specifically, product name DF-200
(Made by Rodel) is used. This insert pad has, for example, a thickness of about 0.5 mm and a compression ratio (1800 g /
(measured in cm ² , the same below) 32%. Therefore, in this case, even if a pressure of 1800 g / cm ² is locally applied, the insert pad is deformed by 160 μm, and if the size of dust or scratches on the back surface of the substrate is less than this, the effect on polishing uniformity is mitigated. can do. This thickness,
Any compression rate can be selected.

Further, when a hard polishing cloth is used, the polishing agent is less likely to enter between the substrate and the polishing cloth, so that the polishing rate at the central portion of the substrate tends to be low. For this reason,
A method of improving the in-plane distribution of polishing by applying air pressure from the back surface of the central portion of the substrate during polishing to increase the relative pressure in the central portion of the substrate is currently generally used.

FIG. 7 shows a substrate holder used in the polishing for flattening the unevenness of the device surface described above. In FIG. 7, (A) is a sectional view,
(B) is a plan view of (A) as seen from below.

An insert pad 1 is provided on the main body 5 of the substrate holding portion on a substrate mounting surface having substantially the same diameter as the substrate, and a retainer ring 2 is provided around the insert pad 1 to prevent the substrate from jumping out during polishing. There is. A vacuum suction / back surface pressing opening 14 is concentrically formed in the central portion of the substrate mounting.

The central portion of the front surface (lower surface) of the substrate is made into a concave shape by vacuum suction through the vacuum suction / back surface pressing opening 14, and the back surface pressure is applied through the opening 14 during processing so that the substrate surface It is necessary to make the central part of the convex shape. Therefore, the vacuum suction / back surface pressing opening 14 must be located at the center of the substrate mounting surface. Specifically, the dimension N is 50 mm or less. FIG. 7 shows a substrate holding part for flattening the surface of a device on a semiconductor substrate in the state of a semiconductor wafer having a diameter of 150 mm and a thickness of 625 μm, and on a concentric circle with a radius of 50 mm from its center,
Eight vacuum suction / backside pressing openings 14 with a diameter of 2 mm
Are evenly arranged. Or 30m from the center
Four vacuum suction / backside pressing openings are evenly arranged and formed on a concentric circle of m. Alternatively, 6 vacuum suction / backside pressurizing openings are evenly arranged on a concentric circle of 40 mm from the center, and 3 vacuum suction / backside pressurizing openings are evenly arranged on a concentric circle of 20 mm from the center. Arrange and form,
One opening is formed in the center.

Further, the vacuum device 51 and the pressurizing device 61 are connected to the input port of the switching valve 72 through the vacuum pipe 53 and the pressurizing pipe 63, respectively, and the output port is connected through the pipe 73 for the vacuum suction / back surface pressurizing opening 1.
Connected to 4.

A conventional polishing method will be described with reference to FIGS.

First, in FIG. 8A, the substrate 10 is mounted on the substrate holding portion from the carrying portion or the like. This is because the back surface of the substrate is bonded to the insert pad while the back surface 12 of the insert pad 1 or the substrate 10 is wetted with water, and the vacuum suction / back surface pressing / opening opening 14 switching valve 72 is used.
The vacuum device 51 communicates with the vacuum device 51 by means of vacuum suction shown by an arrow 50. A suction pressure of 1 kg / cm ² is applied through eight vacuum suction / back surface pressurizing openings 14 having a diameter of 2 mm, and in the prior art, since the opening 14 is located on the center side as described above, a diameter of 150 mm
The front surface side (the lower surface side in contact with the polishing table in the figure) 11 of the substrate 10 which is a semiconductor wafer of mm has a concave shape in which the central portion is elevated by about 50 μm from the peripheral portion.

Next, in FIG. 8B, the substrate 10 is pressed against the polishing table 30 having a polishing cloth on its upper surface, and both the polishing table and the substrate holder are rotated. At this time, the opening 14 for both vacuum suction and back side pressurization is communicated with the pressurizing device 61 by the switching valve 72 so that the back side pressurization shown by the arrow 60 is performed so that the load at the center of the substrate becomes relatively high. To By doing so, it is possible to improve the polishing rate in the central portion of the substrate, where the polishing rate is low due to insufficient supply of the polishing agent, and to improve the uniformity of polishing distribution. Specifically, eight vacuum suction / backside pressurizing openings 14 with a pressure of 250 g / cm ^{2 at the time} of pressurization have a diameter of 2 mm.
Is applied through the substrate 10, which is a semiconductor wafer having a diameter of 150 mm (the lower surface side in contact with the polishing table in the figure) 11, has a convex shape in which the central portion is pushed down by about 30 μm from the peripheral portion.

Next, in FIG. 8C, after polishing is completed, the backside pressure 60 is switched to the vacuum suction 50, the substrate is brought into close contact with the insert pad again, and the substrate holding portion is polished to the polishing table 5.
Lift from. At this time, as in FIG. 8A, the diameter 1
The surface side 11 of the 50 mm semiconductor wafer 10 has a concave shape in which the central portion is elevated by about 50 μm from the peripheral portion.

[0016]

However, in the conventional polishing apparatus and polishing method, there is a problem that the substrate is left on the polishing table when the substrate holding part is separated from the polishing table after the polishing is completed.

This is because a through-hole is formed in the center of the substrate to serve as a hole for pressing the back surface and a hole for vacuum suction.
This is because back surface pressure → vacuum suction is performed, and the surface side of the substrate that contacts the polishing table is changed in shape from concave shape → convex shape → concave shape.

As a result, as shown in FIG. 8 (C), when vacuum suction for lifting the substrate is performed after polishing,
Due to the elasticity of the insert pad, the substrate becomes a suction cup with respect to the polishing table, the substrate sticks to the polishing table, and the substrate remains.

Further, in the conventional method of controlling the distribution of polishing by backside pressing, the substrate is prevented from jumping out only by the retainer ring during polishing, so that the substrate jumps out during polishing due to some factor. The danger was great.

Therefore, an object of the present invention is to provide a polishing apparatus in which the substrate does not remain on the polishing table after the polishing is completed.

Another object of the present invention is to provide a polishing apparatus and a polishing method capable of controlling the in-plane distribution of polishing without the substrate remaining on the polishing table after completion of polishing.

Another object of the present invention is to provide a polishing apparatus and a polishing method in which the holding property of a substrate during polishing is improved.

[0023]

A feature of the present invention is that in a polishing apparatus having a substrate holding portion for holding the back surface side of the substrate on a substrate mounting surface for polishing the front surface side of the substrate, the substrate holding portion is The substrate polishing apparatus has a structure in which the back side of the substrate is vacuum-sucked to make the front side of the substrate convex. Here, it is preferable that an insert pad is provided between the substrate holder and the substrate. Further, the vacuum suction opening may be formed only in the peripheral portion of the substrate mounting surface of the substrate holding unit. Alternatively, a vacuum suction opening may be formed in a peripheral portion of the substrate mounting surface of the substrate holding portion, and a back surface pressing opening may be formed in a central portion of the substrate mounting surface.

Another feature of the present invention is a substrate polishing method for holding a back surface side of a substrate on a substrate mounting surface of a substrate holding portion and polishing the front surface side of the substrate, wherein the substrate mounting surface of the substrate holding portion is A method of polishing a substrate in which the peripheral portion on the back surface side of the substrate is vacuum-sucked through a vacuum suction opening provided in the peripheral portion and the in-plane distribution of polishing is adjusted by adjusting the strength of the vacuum suction. .

Another feature of the present invention is a substrate polishing method for holding the back surface side of a substrate on the substrate mounting surface of the substrate holding portion and polishing the front surface side of the substrate, wherein the substrate mounting surface of the substrate holding portion is Vacuum suction is applied to the peripheral portion on the back surface side of the substrate through the vacuum suction opening provided in the peripheral portion, and at the same time, the rear surface pressing opening of the substrate is provided through the back surface pressing opening provided in the central portion of the substrate mounting surface of the substrate holding portion. This is a method for polishing a substrate in which the in-plane distribution of polishing is adjusted by pressing the central portion on the back surface side.

[0026]

According to the above-mentioned substrate holder of the present invention, since the surface side of the substrate is made convex by vacuum suction, the substrate becomes convex with respect to the polishing table by vacuum suction after polishing, and the substrate and polishing Air enters from the outside between the polishing cloths on the table surface, and the substrate can be easily separated from the polishing table.

Further, the amount of deformation of the substrate can be controlled by controlling the suction strength from the vacuum suction opening formed in the peripheral portion, and the relative load within the substrate can be controlled. Since this is a method of vacuum-adsorbing the substrate even during polishing, the holding property of the substrate during polishing is improved.

[0028]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described below with reference to the drawings.

FIG. 6 is a view showing the outline of a chemical mechanical polishing apparatus which is a polishing apparatus according to an embodiment of the present invention. On the polishing table 30 in which the polishing cloth 32 is attached on the support plate 31, the polishing agent 41 is provided.
A polishing agent supply port 40 is provided for flowing the substrate, and the substrate holder 20 of the present invention is provided. As the abrasive, a dispersion of silica particles in an alkaline aqueous solution, specifically, trade name I
C1 (made by Cabot) or the like is used. As the polishing cloth 32, foamed polyurethane, specifically, trade name IC1000 (made by Rodel) or the like is used. Polishing table 30 and substrate (semiconductor wafer) 10 having a polishing cloth 32 attached to the upper surface thereof
The substrate holding unit 20 holding the substrate has a rotating mechanism. Further, the substrate holding unit 20 has a pressing mechanism for pressing the polishing surface, that is, the front surface side (lower surface side in the figure) of the substrate against the polishing cloth 32 of the polishing table 30. Have

For example, metal wiring is formed on the front surface side of a semiconductor substrate in the state of a semiconductor wafer, and the interlayer insulating film formed on this metal wiring is polished by the chemical mechanical polishing apparatus. That is, the polishing cloth of the polishing table is brought into contact with only the convex portions on the upper surface of the interlayer insulating film to polish the upper surface of the interlayer insulating film.

1A and 1B are views showing a substrate holding portion of a polishing apparatus according to a first embodiment of the present invention. FIG. 1A is a sectional view and FIG. 1B is a plan view of FIG. .

A retainer ring 2 having an inner diameter slightly larger than the outer diameter of the substrate is provided on the substrate holding body 5 to prevent the substrate from jumping out during polishing. Is provided with an insert pad 1. As the insert pad 1, specifically, the above-mentioned product name DF-200 (manufactured by Rodel) is used. The vacuum suction openings 3 of the substrate are concentrically arranged around the substrate as shown in FIG.

For example, the inner diameter of the retainer ring 2 is about 153 m so that a 6-inch semiconductor wafer can be mounted inside.
m, and twelve vacuum suction openings 3 having a diameter of 2 mm are formed in a concentric circle spaced inwardly from the substrate holding part main body 5 and the insert pad 1 with a uniform distribution. There is. Insert pad 1 of this embodiment
The compression rate of is 32%.

Since it is necessary to make the central portion of the surface (lower surface) of the semiconductor wafer convex by vacuum suction from the vacuum suction opening 3, the vacuum suction opening 3 is formed in the peripheral portion of the substrate holding surface. To be done. Therefore, although it depends on the size of the semiconductor wafer or the thickness and compression rate of the insert pad, it is preferable that L is 20 mm or less in practice.
In this example, L = 15 mm.

Each vacuum suction opening 3 has a vacuum pipe 5
3 is connected to one port of the opening / closing valve 52, and the other port of the opening / closing valve 52 is connected to the vacuum device 51 including a vacuum pump or the like.

Next, FIG. 2 shows a polishing method using this polishing apparatus.
A description will be given using (A) and (B).

First, in FIG. 2A, the substrate 10 is mounted on the substrate holding unit 20 from the carrier unit or the like. The substrate of this example has a front surface side 11 and a back surface side 12 on which a wiring structure including a semiconductor element or an interlayer insulating film is formed, and a thickness of 625 μm.
6 inch (152 mm) semiconductor wafer 10. This is because the insert pad 1 or the back surface 12 of the semiconductor wafer 10 is wet with water.
The back surface 12 is adhered to the insert pad 1, the opening / closing valve 52 is opened, and the vacuum suction opening 3 is communicated with the vacuum device 51. By applying a suction pressure (negative pressure) of 1 kg / cm ² through the eight vacuum suction openings 3 having a diameter of 2 mm in the peripheral portion, the front surface side of the semiconductor wafer 10 (the lower surface contacting the polishing table in the figure). The side 11 has a convex shape in which the central portion is pushed down from the peripheral portion.

Next, referring to FIG. 2B, the semiconductor wafer 1
The surface side 11 of the central convex shape of 0 is pressed against the polishing cloth of the polishing table 30 and both the polishing table and the substrate holding part are rotated. At this time, vacuum adsorption is continuously performed. This allows
The insert pad 1 in the peripheral portion of the substrate is compressed, the surface side of the substrate (the side contacting the polishing table) is deformed into a convex shape,
The load at the center of the substrate becomes relatively high. This makes it possible to improve the polishing rate in the central portion of the substrate, where the polishing rate is lowered due to insufficient supply of the polishing agent, and to improve the uniformity of polishing distribution.

Since it changes depending on the polishing conditions, the thickness and elastic modulus of the insert pad, and the arrangement and size of the vacuum suction openings, these must be selected as optimum conditions.

In some cases, the strength of vacuum adsorption may be changed during polishing. For example, in this embodiment, by controlling the control mechanism in the vacuum device 51, the suction force 50 during polishing is reduced to 600 g / cm ^{2, which} is lower than that in the state of FIG. The amount is controlled to be the optimum 30 μm.

As described above, even if the vacuum suction force is weakened, there is no change in that the substrate is sucked during polishing, so that the risk of the substrate popping out is reduced as compared with the prior art.

After the polishing is completed, the substrate holding part is separated from the polishing table while vacuum suction is performed. At this time, since the surface (lower surface) 11 of the substrate is still deformed in a convex shape with respect to the polishing table, air can enter between the substrate and the polishing cloth on the upper surface of the polishing table, and the polishing table can be easily Can be pulled away from.

3A and 3B are views showing a substrate holding portion of a polishing apparatus according to a second embodiment of the present invention. FIG. 3A is a sectional view and FIG. 3B is a plan view of FIG. . It should be noted that in FIG. 3, the portions having the same or similar functions to those in FIG.

In this example, the back surface pressing opening 4 is provided in the center of the substrate holding portion separately from the vacuum suction opening 3 in the peripheral portion. The back surface pressing opening 4 needs to have a convex shape in the central portion of the front surface (lower surface) of the semiconductor wafer by pressing the back surface from here, and the dimension M from the center is 20.
It is preferably less than or equal to mm, and in this embodiment, eight back surface pressing openings 4 having a diameter of 2 mm are formed uniformly on a concentric circle of M = 10 mm. The backside pressurizing opening 4 is connected to one port of the open / close valve 62 through the pressurizing pipe 63, and the other port of the open / close valve 62 is connected to the pressurizing device 61 such as the compressed air pipe or the compressed nitrogen cylinder. ing.

This makes it possible to control the vacuum suction of the peripheral portion and the back surface pressure of the central portion simultaneously and independently.

Next, referring to the sectional views of FIGS. 4 and 5,
Each polishing method using the structure of FIG. 3 will be described.

In the method of FIG. 4, the opening / closing valve 62 is operated during polishing.
Is opened and 250 g /
30μ performed backside pressure 60 with compressed nitrogen gas cm ²
A convex shape of m is formed in the center to control the in-plane distribution of polishing. The method shown in FIG. 4 is applied to a vacuum system opening / closing valve 5 during polishing.
2 is in a closed state and is not vacuum-adsorbed, so the semiconductor wafer 1
It can be applied to a combination of 0 and the retainer ring 2 when there is no risk of the substrate jumping out even if vacuum suction is not performed during polishing. Further, in the case of the method of this embodiment, the compression rate of the insard pad 1 does not matter.

At the time of lifting after completion of polishing, the opening / closing valve 52 of the vacuum system is opened and vacuum suction is performed from the vacuum suction opening 3 in the peripheral portion, so that the polishing table 5 is placed on the polishing table 5 as in the first embodiment. Prevents the board from sticking.

In the method of FIG. 5, the opening / closing valve 62 is used during polishing.
Is opened and 250 g /
Simultaneously with backside pressure 60 using compressed nitrogen gas of cm ² , the opening / closing valve 52 is also opened to perform vacuum suction 50 with a suction force of 250 g / cm ² from the vacuum suction opening 3 in the peripheral portion, and further convex shape. It is possible to make the central part of the surface protrude by 40 μm from the peripheral part of the surface by strengthening the pressure, and at the same time, the holding property of the substrate during polishing is improved by performing vacuum suction while performing back surface pressure. Further, in the case of the method of this embodiment, the compression rate of the insard pad 1 is 4%.

[0050]

As described above, according to the present invention, when a substrate is vacuum-sucked after polishing, the substrate is deformed into a convex shape with respect to the polishing table, so that air is trapped between the substrate and the polishing cloth. The substrate can be easily separated from the polishing table.

Further, the amount of deformation of the substrate can be controlled by controlling the strength of sucking the substrate from the opening provided in the periphery, and the relative load in the substrate can be controlled. As a result, the in-plane distribution of polishing can be controlled as in the conventional backside pressing method.

Further, by arranging an opening for backside pressure in the central part and an opening for vacuum suction in the peripheral part and making them independent, it is possible to more control the in-plane distribution of polishing by backside pressing. It can be performed meticulously, and the problem of sticking after polishing can be solved at the same time.

Further, since the method of vacuum suctioning the substrate during polishing can be improved, the holding property of the substrate during polishing is improved and the risk of damage to the substrate due to popping out can be reduced.

[Brief description of drawings]

FIG. 1 is a view mainly showing a substrate holding part in a polishing apparatus of a first embodiment of the present invention, (A) is a sectional view, and (B) is a plan view of (A) as seen from below. .

2A to 2D are cross-sectional views showing a polishing method using the substrate holding part of FIG. 1 in order of steps.

3A and 3B are diagrams mainly showing a substrate holding portion in a polishing apparatus of a second embodiment of the present invention, FIG. 3A being a sectional view and FIG. 3B being a plan view of FIG. .

4 is a cross-sectional view showing an example of a polishing method using the substrate holding part of FIG.

5 is a cross-sectional view showing another example of the polishing method using the substrate holding part of FIG.

FIG. 6 is a diagram showing an outline of a chemical mechanical polishing apparatus.

7A and 7B are diagrams mainly showing a substrate holding part in a conventional polishing apparatus, FIG. 7A being a cross-sectional view and FIG. 7B being a plan view of FIG.

8A to 8C are cross-sectional views showing a conventional polishing method using the substrate holding unit of FIG. 7 in step order.

[Explanation of symbols]

 1 Insert Pad 2 Retainer Ring 3 Vacuum Suction Opening 4 Back Side Pressing Opening 5 Substrate Holding Main Body 10 Semiconductor Wafer (Substrate) 11 Semiconductor Wafer Front Side 12 Semiconductor Wafer Back Side 14 Vacuum Suction / Back Side Pressurizing Opening Part 20 Substrate holding part 30 Polishing table 31 Support plate 32 Polishing cloth 40 Polishing agent supply port 41 Polishing agent 50 Vacuum adsorption 51 Vacuum device 52, 62 Open / close valve 53 Vacuum pipe 60 Back pressure 61 Pressure device 63 Pressure pipe 72 Switching Valve 73 pipe

Claims (6)

[Claims] 1. A polishing apparatus having a substrate holding portion for holding a back surface side of the substrate on a substrate mounting surface for polishing the front surface side of the substrate, wherein the substrate holding portion vacuum-sucks the back surface side of the substrate. Accordingly, the substrate polishing apparatus has a structure in which the front surface side of the substrate is convex. 2. The apparatus for polishing a substrate according to claim 1, further comprising an insert pad provided between the substrate holder and the substrate. 3. The substrate polishing apparatus according to claim 1, wherein a vacuum suction opening is formed only in a peripheral portion of a substrate mounting surface of the substrate holder. 4. A vacuum suction opening is formed in a peripheral portion of a substrate mounting surface of the substrate holding portion, and a back surface pressing opening is formed in a central portion of the substrate mounting surface. Item 1. A substrate polishing apparatus according to Item 1. 5. A substrate polishing method for holding a back surface side of a substrate on a substrate mounting surface of a substrate holding portion and polishing a front surface side of the substrate, the method being provided in a peripheral portion of the substrate mounting surface of the substrate holding portion. A method for polishing a substrate, characterized in that the peripheral portion on the back surface side of the substrate is vacuum-sucked through a vacuum suction opening, and the in-plane distribution of polishing is adjusted by adjusting the strength of the vacuum suction. 6. A substrate polishing method for holding a back surface side of a substrate on a substrate mounting surface of a substrate holding portion and polishing a front surface side of the substrate, the method being provided in a peripheral portion of the substrate mounting surface of the substrate holding portion. At the same time as vacuuming the peripheral portion on the back surface side of the substrate through the vacuum suction opening portion, the central portion on the back surface side of the substrate is opened through the back surface pressing opening portion provided in the central portion of the substrate mounting surface of the substrate holding portion. A method for polishing a substrate, wherein the in-plane distribution of polishing is adjusted by applying pressure.