JPH1158221A - Device and method for polishing semiconductor substrate - Google Patents

Abstract

PROBLEM TO BE SOLVED: To uniformly flatten the front surface of a film to be polished, by preventing a situation in which the polishing speed is different according to the part of the film to be polished formed on a wafer. SOLUTION: A film to be polished of a wafer 13 is polished by being pressed in the first range 12a of a polishing pad 12 to which abrasive materials 15 are to be supplied when it is rotated. An annular dummy material to be polished 17A made of the same material as the film to be polished of the wafer 13 is held by a dummy holding tool 18 and polished by being pressed to the second range 12b positioned on the opposite side of the center of the first range 12a on the polishing pad 12 with respect to the center. Therefore, the sum of the time in which the polishing pad 12 is brought in contact with the film to be polished of the wafer 13 and the time in which the polishing pad 12 is brought in contact with the surface to be polished of the dummy material to be polished 17B is uniformized.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a semiconductor substrate polishing apparatus and method for performing chemical mechanical polishing (CMP) for flattening a surface of a semiconductor substrate made of, for example, silicon. .

[0002]

2. Description of the Related Art Since 1990, in chemical mechanical polishing of a film to be polished formed on a semiconductor substrate made of silicon or the like, the diameter of the semiconductor substrate has been increased to 15 cm or more, and the polishing has tended to be a single wafer processing. . Further, since the design rule of the pattern formed on the semiconductor substrate is reduced to 0.5 μm or less, the steps on the semiconductor substrate caused by the formation of the semiconductor element and the wiring layer on the semiconductor substrate are flattened. In the polishing method, it is required that the step on the semiconductor substrate be surely reduced and that the polishing be performed uniformly over the entire surface of the semiconductor substrate.

Hereinafter, a conventional semiconductor substrate polishing apparatus and a conventional polishing method will be described with reference to the drawings.

FIG. 8 shows a schematic configuration of a conventional semiconductor substrate polishing apparatus. As shown in FIG. 8, a surface plate 1 includes a pad mounting portion 1a made of a rigid body having a flat surface and a pad mounting portion 1a. It has a surface plate rotating shaft 1b extending vertically downward from the lower surface of the mounting portion 1a, and rotating means (not shown) for rotating the surface rotating shaft 1b, and an upper surface of the pad mounting portion 1a of the surface plate 1. A polishing pad 2 having elasticity is adhered to. Above the polishing pad 2, a wafer carrier 4 that holds and rotates a wafer 3 as a semiconductor substrate is provided.
The wafer carrier 4 includes a wafer holding unit 4a for holding the wafer 3, a carrier rotating shaft 4b extending vertically upward from the upper surface of the wafer holding unit 4a, and a carrier rotating shaft 4b.
and rotation means (not shown) for rotating b. On the polishing pad 2, a predetermined amount of abrasive 6 containing abrasive grains is dropped from an abrasive supply pipe 5.

In the polishing apparatus for a semiconductor substrate constructed as described above, the polishing pad 2 is rotated while the polishing agent 5 is dropped on the polishing pad 2 and the wafer carrier 4 is rotated.
When the wafer 3 held by the wafer holding portion 4a is pressed against the polishing pad 2, the film to be polished formed on the surface of the wafer 3 receives the pressure from the polishing pad 2 and the relative speed with the polishing pad 2, and Polishing is performed by the action of the abrasive 5 existing between the polishing pad 3 and the polishing pad 2.

At this time, if the film to be polished of the wafer 3 has an uneven portion, the polishing rate is increased at the convex portion of the film to be polished because the contact pressure with the polishing pad 2 is large. Since the contact pressure with the polishing pad 2 is small, the polishing rate is reduced. Thereby, the unevenness of the film to be polished is alleviated, and the surface of the film to be polished becomes flat. This chemical mechanical polishing is performed, for example, in "January 1994, Monthly Semiconductor World", 58
-59 pages and "Solid State Tech"
nology "July. 1992 / Japanese version 32-
It is introduced on page 37.

[0007]

However, when the film to be polished of the wafer 3 is actually polished by using the above-mentioned conventional semiconductor substrate polishing apparatus, the film to be polished is irrespective of the degree of unevenness of the film to be polished. A phenomenon in which the polishing rate varies depending on the portion of the polishing film is observed. If the polishing rate differs depending on the portion of the film to be polished, the surface of the film to be polished cannot be uniformly flattened.

In view of the above, it is an object of the present invention to prevent a situation in which a polishing rate is different depending on a portion of a film to be polished, so that the surface of the film to be polished can be uniformly flattened.

[0009]

The present inventors have studied the reason why the polishing rate varies depending on the portion of the film to be polished, and as a result, have found that it is based on the cause described below.

FIG. 9 is a plan view for explaining that the length of time during which the polishing pad 2 is pressed is different depending on the radial portion of the polishing area 2a of the polishing pad 2. FIG.
0 is a diagram showing the relationship between the distance from the center of the polishing pad 2 during polishing and the time (arbitrary unit) in which the polishing pad 2 is pressed.

When chemical mechanical polishing is performed using the conventional polishing apparatus shown in FIG. 8, the time during which the polishing pad 2 is in contact with the wafer 3 (that is, the polishing pad 2 receives pressure from the wafer 3). Time) depends on the location of the polishing pad 2 (distance from the center of rotation). That is, the first region a of the radius r ₁ in the polishing pad 2 shown in FIG. 9, a third portion c of the second region b and the radius r ₃ of radius r _2, as shown in FIG. 10, the wafer 3 Are different from each other, and accordingly, the first portion a, the second portion b, and the third portion c in the polishing pad 2 are different from each other.
Is different from the time when the wafer 3 is not pressurized. In the vicinity of the second portion “b” through which the substantially central portion of the wafer 3 passes, the time during which the polishing pad 2 is pressed by the wafer 3 is longer than the first portion “a” and the third portion “c”. The time during which the wafer 2 is not pressed by the wafer 3 is shorter than the first part a and the third part c.

As described above, the film to be polished on the wafer 3 is polished by the pressure received from the polishing pad 2 and the relative speed with respect to the polishing pad 2. At this time, frictional heat is generated in the film to be polished on the wafer 3. I do. Generally, the frictional heat can be considered to be proportional to the product of the pressure and the relative speed, and the calorific value is obtained by multiplying the frictional heat by the polishing time. When the polishing pad 2 and the wafer 3 are rotating at the same rotation speed, the average relative speed viewed from the wafer 3 is constant in the plane of the wafer 3, but the average relative speed viewed from the polishing pad 2 is The speed varies depending on the position of the polishing pad 2. That is, since the polishing pad 2 is rotating, the first pad near the center of the polishing pad 2
The rotation speed is different between the portion a and the third portion c near the peripheral portion, and the relative speed is different between the first portion a and the third portion c due to the rotation of the wafer 3. (In the first part a, the polishing pad 2 and the wafer 3 rotate in the opposite directions, but in the third part c, the polishing pad 2
And the wafer 3 rotate in the same direction. In the polishing region 2a of the polishing pad 2, the integrated value and the average value of the relative speed between the polishing pad 2 and the wafer 3 are not constant. Therefore, in the polishing area 2a of the polishing pad 2, the amount of heat generated differs depending on the distance in the radial direction of the polishing pad 2.

When chemical mechanical polishing is performed using the polishing agent 6, heat is generated due to a chemical reaction between the wafer 3 and the polishing agent 6, that is, a chemical factor. It changes according to the difference of the contact time.

Due to the above two factors, in the chemical mechanical polishing, the calorific value in the polishing area 2a of the polishing pad 2 greatly differs depending on the position of the polishing pad 2.

As can be seen from the above description, the region (the second region b) where the time in contact with the wafer 3 (the polishing pad 2 is pressed by the wafer 3) in the polishing region 2a of the polishing pad 2 is long. In the area near (), the amount of heat generation is large, and the time during which the wafer 3 is not in contact with the wafer 3 is short and the amount of heat radiation is small.
Regions in which the contact time with the wafer 3 in the polishing region 2a of the polishing pad 2 is short (first region a and third region c
In each of the vicinity areas), the temperature rise is small. Therefore, the temperature distribution in the polishing area 2a of the polishing pad 2 becomes non-uniform.

When the film to be polished of the wafer 3 is polished in a state where the temperature distribution in the polishing region 2a of the polishing pad 2 is non-uniform, the central portion of the film to be polished is a high temperature region (the second portion b) in the polishing pad 2. , While the peripheral edge of the film to be polished has a region where the temperature of the polishing pad 2 is high (the region near the second portion b) and a low region (the region near the second portion b) as the wafer 3 rotates. The first part a and the third part c) are alternately contacted.

When the film to be polished of the wafer 3 is polished by a mechanical method, the polishing rate is hardly affected by the temperature. However, when the film to be polished is polished by the chemical mechanical polishing method, the polishing rate is not increased. Significantly affected by temperature. That is, the higher the temperature, the faster the chemical reaction, and the higher the polishing rate. For this reason, in the central portion of the film to be polished, which is always in contact with the high-temperature region in the polishing pad 2, the polishing rate increases and the polishing amount increases, but the high-temperature region and the low-temperature region in the polishing pad 2 alternate. In the peripheral portion of the film to be polished in contact with the surface, the polishing rate is reduced and the polishing amount is reduced.

The present invention has been made based on the above-mentioned findings, and it has been proposed that a polishing pad be provided with a film to be polished in a region where the temperature is low in the polishing pad, that is, a region where the contact time with the film to be polished of the semiconductor substrate is relatively short. The total time of the contact time of the polishing pad with the film to be polished and the time of contact with the dummy polished material is made uniform by contacting the dummy polished material made of the same material for a longer time than other regions. It becomes something.

More specifically, a first semiconductor substrate polishing apparatus according to the present invention comprises a polishing pad mounted on a surface plate that moves in a plane, and a polishing device for supplying an abrasive onto the polishing pad. Agent supply means, a substrate holding means for holding a semiconductor substrate on which a film to be polished is formed, and pressing and polishing the held film to be polished of the semiconductor substrate against a polishing pad; and a material formed of the same material as the film to be polished. The surface to be polished has a shape such that the contact time with the film to be polished is relatively short as compared with the other regions of the polishing pad, and the contact time with the region of the polishing pad is longer as compared with other regions. And a dummy polished material whose polishing surface is polished by a polishing pad.

According to the first semiconductor substrate polishing apparatus of the present invention, a polishing target having a shape in which the contact time with the region to be polished is relatively short compared with other regions. Since a dummy polishing target having a surface is provided, when the polishing target surface of the dummy polishing target is polished by a polishing pad, a region where a contact time with a polishing target film in the polishing pad is shorter than other regions is, Since the contact time of the dummy polished material with the surface to be polished is longer than in other regions, the time for the polishing pad to contact the film to be polished of the semiconductor substrate and the time for contact with the surface to be polished of the dummy polished material Is made uniform in a region of the polishing pad in contact with the film to be polished on the semiconductor substrate.

In the first apparatus for polishing a semiconductor substrate, it is preferable that the dummy workpiece is independently pressed against the semiconductor substrate and polished by a polishing pad.

In the first semiconductor substrate polishing apparatus, the planar motion is a rotational motion, the film to be polished on the semiconductor substrate is circular, and the surface to be polished of the dummy material is annular.
The center of the film to be polished and the center of the surface to be polished of the dummy material to be polished are preferably on the same circumference.

In this case, it is more preferable that the inner diameter of the annular polished surface of the dummy polished material is slightly larger than the outer diameter of the polished film of the semiconductor substrate.

In this case, it is more preferable that the dummy polished material rotates independently of the semiconductor substrate.

In the first semiconductor substrate polishing apparatus, it is preferable that the film to be polished of the semiconductor substrate and the dummy material to be polished are formed of the same metal film.

A polishing apparatus for a semiconductor device according to a second aspect of the present invention includes: a polishing pad mounted on a surface plate that moves in a plane; a polishing agent supply means for supplying a polishing agent onto the polishing pad; A substrate holding means for holding the semiconductor substrate on which the film to be polished is formed, pressing the film to be polished of the held semiconductor substrate against a polishing pad and polishing, and being formed of the same material as the film to be polished; The polishing pad has a surface to be polished that is in contact with only a region of the polishing pad and a region in the vicinity thereof that is relatively short in contact time with the film compared with other regions of the polishing pad, and the surface to be polished is polished by the polishing pad. A dummy polished material.

According to the second semiconductor substrate polishing apparatus, there is provided a dummy material to be polished having a surface to be polished which comes into contact only with a region having a relatively short contact time with the film to be polished and a region near the region. When the surface to be polished of the dummy material to be polished is polished by the polishing pad, the total time of the time for which the polishing pad is in contact with the film to be polished of the semiconductor substrate and the time for which the polishing pad is in contact with the surface to be polished is polished. The pad is made uniform in a region where the pad comes into contact with the film to be polished on the semiconductor substrate.

The method for polishing a semiconductor substrate according to the present invention includes a polishing step of polishing a film to be polished formed on the semiconductor substrate with a polishing pad to which a polishing agent is supplied while making a plane motion. It is formed of the same material as the film to be polished, and the contact time with the film to be polished is relatively short as compared with other regions of the polishing pad, and the contact time with the region of the polishing pad is longer as compared with other regions. A polishing step of polishing a polished surface of a polished material having a polished surface with a polishing pad by a polishing pad.

According to the method for polishing a semiconductor substrate of the present invention,
The polishing pad is used to polish the surface to be polished in such a shape that the contact time with the region to be polished is relatively short compared to the other regions. The total time of the time of contact with the polishing target and the time of contact with the surface to be polished of the dummy polished material is made uniform in the region of the polishing pad in contact with the film to be polished of the semiconductor substrate.

In the method for polishing a semiconductor substrate according to the present invention,
The dummy polishing target material polishing step preferably includes a step of independently pressing the dummy polishing target material against the polishing pad against the semiconductor substrate.

In the method for polishing a semiconductor substrate according to the present invention,
The polishing target film polishing step includes a step of pressing a circular polishing target film against a rotating polishing pad, and the dummy polishing target material polishing step includes a step in which the center is on the same circumference as the center of the circular polishing target film. It is preferable to include a step of polishing the to-be-polished surface to be polished by using a polishing pad.

In this case, it is preferable that the step of polishing the dummy polished material includes a step of independently rotating the dummy polished material with respect to the semiconductor substrate.

In the method for polishing a semiconductor substrate according to the present invention,
The film to be polished of the semiconductor substrate and the dummy material to be polished are preferably formed of a metal film of the same quality.

[0034]

Embodiments of a polishing apparatus and a polishing method for a semiconductor substrate according to the present invention will be described below with reference to the drawings.

(First Embodiment) FIG. 1A shows a schematic configuration of an apparatus for polishing a semiconductor substrate according to a first embodiment of the present invention. As shown in FIG. Board 11 is
A pad mounting portion 11a made of a rigid body having a flat surface;
It has a surface plate rotating shaft 11b extending vertically downward from the lower surface of the pad mounting portion 11a, and rotating means (not shown) for rotating the surface rotating shaft 11b. A polishing pad 12 having elasticity is attached to the upper surface of the polishing pad. Above the first area 12a (see FIG. 1B) of the polishing pad 12, a wafer carrier 14 that rotates while holding a wafer 13 as a semiconductor substrate is provided. A wafer holder 14a for holding the wafer 13;
Rotating shaft 14b extending vertically upward from the upper surface of the carrier
And rotating means (not shown) for rotating the carrier rotating shaft 14b. As a result, the wafer 13 is pressed against the first region 12a of the polishing pad 12. Also,
Above the central part of the polishing pad 2, an abrasive 1 containing abrasive grains
A polishing agent supply pipe 16 is provided for dropping a predetermined amount 5 on the polishing pad 2.

As a feature of the first embodiment, the first region 12a on the polishing pad 12 and the second region 12b (see FIG. 1B) located on the opposite side to the center are located above the first region 12a. There is provided a dummy holder 18 that holds and rotates an annular dummy polished material 17A. The dummy holder 18 includes a dummy holding plate 18a that holds the dummy polished material 17A, and a dummy holding plate 18a. A dummy rotating shaft 18b extending perpendicularly from the upper surface of the dummy rotating shaft 18a and rotating means (not shown) for rotating the dummy rotating shaft 18b are provided. FIG.
In (a), in order to show the inside of the annular dummy polished material 17A, a part of each of the dummy holding plate 18a and the dummy polished material 17A is cut away.

As shown in FIG. 1B, the dummy polished material 17A is formed so that the inner diameter thereof is slightly larger than the outer diameter of the wafer 13 and the center of the polishing pad 12 at the center thereof. Is provided at a position where the distance from the center of the wafer 13 to the center of the polishing pad 12 is substantially equal. Also, the dummy polishing target 17A is the wafer 1
3 is formed of the same material as the film to be polished formed on the surface.

Hereinafter, a polishing method performed by using the polishing apparatus according to the first embodiment will be described.

First, the polishing pad 12 is rotated while the polishing agent 15 is dropped on the central portion of the polishing pad 12. By doing so, the polishing agent 15 is diffused with the rotation of the polishing pad 12 and spreads over the entire surface of the polishing pad 12. Further, the wafer 13 held on the wafer holding portion 14a of the wafer carrier 14 is pressed against the first region 12a of the polishing pad 12, and the dummy polishing target 17A held on the dummy holding plate 18a of the dummy holder is polished. The second region 12b of the pad 12 is pressed.

In this way, the heat of the chemical reaction between the film to be polished on the wafer 13 and the polishing agent 15 and the frictional heat of the mechanical grinding of the film to be polished on the wafer 13 by the polishing pad 12 cause
As the temperature of the first region 12a of the polishing pad 12 increases, the polishing is performed by the heat of the chemical reaction between the dummy polishing target 17A and the polishing agent 15 and the frictional heat of the mechanical polishing of the dummy polishing target 17A by the polishing pad 12. The temperature of the second region 12b of the pad 12 also increases.

FIG. 2 shows the relationship between the distance from the center of the polishing pad 12 and the time during which the polishing pad 12 is pressed from the dummy workpiece 17A (contacts the dummy workpiece 17A) with a solid line. The relationship between the distance from the center of the polishing pad 12 and the time during which the polishing pad 12 is pressed from the wafer 13 is indicated by a broken line. The dashed line graph is the same as the solid line graph in FIG. Also in FIG. 2, the distance from the center of the polishing pad 12 is the radius r ₁ and the radius r shown in FIG.
₂ and radius r ₃ .

As apparent from FIG. 2, the polishing pad 12
Is distributed from the wafer 13 to the first portion a having the radius r ₁ and the third portion c having the radius r ₃ , that is, both ends of the first region 12 a (the first region 12 a is a circular shape). For this reason, the polishing pad 12 is not an end, but a portion near and far from the center of the polishing pad 12 is referred to as both ends for convenience.)
The distribution of time pressed from 7A is longer at both ends of the first region 12a.

Accordingly, the first region 12 of the polishing pad 12
The amount of heat generated by contact with the wafer 13 at both ends of the first region 12a is smaller than that at the center of the first region 12a (a region whose distance from the center of the polishing pad 12 is intermediate is referred to as the center for convenience). Although small, the amount of heat generated by contact with the dummy polished plate 17A increases, so that the difference in temperature rise between both ends and the center in the first region 12a of the polishing pad 12 decreases. This difference in temperature rise can be further reduced by controlling the dimensions of the inner and outer diameters of the dummy polished plate 17A, the rotation speed, the rotation direction, and the pressing force. The polishing rate in the first region 12a can be made more uniform.

Further, since the material of the dummy polished material 17A is the same as the material of the film to be polished formed on the wafer 13, the substance generated by polishing the dummy polished material 17A is a wafer. 13 can be eliminated.

Further, since the dummy polished material 17A and the film to be polished are of the same quality, the friction coefficient of the dummy polished material 17A with respect to the polishing pad 12 and the friction coefficient of the polished film become equal, and the abrasive 15 Since a similar chemical reaction occurs between the dummy workpiece 17A and the film to be polished (that is, the reaction coefficients are equal), the temperature rise at both ends and the temperature rise at the center in the first region 12a of the polishing pad 12 are reduced. Can be made extremely small.

Further, in the first embodiment, since the inner diameter of the dummy workpiece 17A is slightly larger than the outer diameter of the wafer 13, the peak of the graph shown by the solid line in FIG. Since it is located outside of the first region 12a, there is no region in the first region 12a where the temperature distribution changes abruptly. Therefore, it is easy to control the temperature uniformity in the first region 12a of the polishing pad 12.

In the first embodiment, the dummy polishing target 17A is positioned with respect to the center of the polishing pad 12 on the wafer 1.
3, but the position of the dummy polished material 17A is not limited. However, the dummy polished material 17A
Distance from the center of the polishing pad 12 to the center of the wafer 1
Preferably, the center of 3 is equal to the distance from the center of polishing pad 12.

(Second Embodiment) FIG. 3 shows a plan shape of a dummy workpiece 17B of a polishing apparatus according to a second embodiment. As shown in FIG.
Has a shape in which a circle having the same diameter as the wafer 13 has been removed from a fan shape having two radii extending outward from the center of the polishing pad 12 on each side. In this case, the distance between the center of the circular pad to be removed from the center of the polishing pad 12 and the wafer 13
Is preferably equal to the distance from the center of the polishing pad 12.

The dummy polishing target 17B of the polishing apparatus according to the second embodiment has a shape in which a circle having the same diameter as the wafer 13 has been removed from the sector shape as described above, so that the polishing pad 12 has one polishing pad. During the rotation, the time during which the polishing pad 12 is pressed by the dummy workpiece 17B and the wafer 13 is equal in the first region 12a of the polishing pad 12. Therefore, the dummy polished material 17B is
When the pressure per unit area for pressing the polishing pad 12 and the pressure per unit area for pressing the wafer 13 against the polishing pad 12 are made equal, the first region 12a of the polishing pad 12 is formed by the dummy workpiece 17B and the wafer 13. Pressed uniformly. However, the dummy polishing material 17B of the polishing pad 12
And the relative speed with respect to the wafer 13 is higher at the peripheral portion of the polishing pad 12 than at the central portion, so that the calorific value is
2, the temperature distribution of the polishing pad 12 is inclined in one direction from the central portion to the peripheral portion. Therefore, when the wafer 13 is rotated, the surface to be polished of the wafer 13 is polished. The quantities are averaged in the plane.

Also in the second embodiment, the material of the dummy polished material 17B is preferably the same as the polished film formed on the wafer 13. By doing so, it is possible to eliminate the adverse effect of the substance generated by polishing the dummy polished material 17B on the polished film of the wafer 13.

Further, since the dummy polished material 17B and the film to be polished are of the same quality, the friction coefficient of the dummy polished material 17B with respect to the polishing pad 12 and the friction coefficient of the polished film become equal, and the abrasive 15 Since a similar chemical reaction occurs between the dummy polishing target material 17B and the film to be polished, the difference between the temperature rise at both ends and the temperature rise at the center in the first region 12a of the polishing pad 12 is extremely small. Can be.

In the second embodiment, the central angle of the sector of the dummy workpiece 17B (the angle at which the two sides of the sector intersect) is not particularly limited.

(Third Embodiment) FIG. 4 shows a planar shape of a dummy workpiece 17C of a polishing apparatus according to a third embodiment. As shown in FIG.
Has a shape from a large circle having a diameter slightly smaller than that of the polishing pad 12 to a small circle having a diameter slightly larger than that of the wafer 13 and a central opening for supplying the polishing agent 15 removed. In this case, it is preferable that the distance from the center of the polishing pad 12 to the center of the small circle to be removed is equal to the distance from the center of the polishing pad 12 to the center of the wafer 13.

The dummy polishing target 17C of the polishing apparatus according to the third embodiment has a shape obtained by removing the small circle having the same diameter as the wafer 13 from the large circle as described above. When the pressure per unit area for pressing the polishing pad 12 by the material 17C and the pressure per unit area for pressing the polishing pad 12 by the wafer 13 are equal, the polishing pad 12 has a uniform pressing force over the entire surface of the wafer 13 and the dummy. This means that the workpiece 17C is being polished. However, since the relative speed of the polishing pad 12 with respect to the dummy polishing target material 17C and the wafer 13 is larger at the peripheral portion of the polishing pad 12 than at the central portion, the calorific value is larger at the peripheral portion of the polishing pad 12. Since the temperature distribution of the polishing pad 12 is inclined in one direction from the center to the periphery, the polishing amount of the surface to be polished of the wafer 13 is averaged in the plane by rotating the wafer 13.

Also in the third embodiment, the material of the dummy polished material 17C is preferably the same as the polished film formed on the wafer 13. By doing so, it is possible to eliminate the adverse effect of the substance generated by polishing the dummy polishing target material 17 </ b> C on the polishing target film of the wafer 13.

Since the dummy material 17C and the film to be polished are of the same quality, the friction coefficient of the dummy material 17C to the polishing pad 12 and the friction coefficient of the film to be polished become equal, and the polishing agent 15 Since the same chemical reaction is caused between the dummy polishing target material 17C and the polishing target film, the difference between the temperature rise at both ends and the temperature rise at the central portion in the first region 12a of the polishing pad 12 is extremely reduced. Can be.

(Fourth Embodiment) FIG. 5 shows a dummy polishing member 17D and a dummy holding plate 18a for holding the dummy polishing member 17D in a polishing apparatus according to a fourth embodiment.
2 shows a cross-sectional shape of the hologram. As shown in FIG. 5, as in the third embodiment, the dummy polished material 17D is formed from a large circle having a diameter slightly smaller than that of the polishing pad 12 to the wafer 13.
It has a small circle with a diameter slightly larger than that and a shape in which a central opening for supplying the abrasive 15 is removed, and has a plurality of concave grooves 19 arranged concentrically on the surface to be polished. doing.

Also in the fourth embodiment, it is preferable that the material of the dummy polished material 17D is the same as the film to be polished formed on the wafer 13.

The dummy polished material 17D of the polishing apparatus according to the fourth embodiment has a plurality of concentric concave grooves 19 on the polished surface as described above. Even when the contact area with the pad 12 is large, the polishing agent 15 can be supplied to the surface of the polishing pad 12 through the concave groove 19, so that the new polishing agent 15 is always supplied to the surface of the polishing pad 12. Therefore, the polishing agent 15 always exists on the polishing pad 12. Thus, the polishing agent 15 degraded by the polishing of the film to be polished of the wafer 13 can be renewed, and stable polishing can be achieved even if the dummy polished material 17D is provided on the polishing pad 12.

(Fifth Embodiment) FIG. 6 shows a plan shape of a dummy workpiece 17E of a polishing apparatus according to a fifth embodiment. As shown in FIG.
Has a pair of small circular shapes each having a center at a position of a radius r _{1 and} a position of a radius r ₃ from the center of the polishing pad 12.

As described in the first embodiment,
The distribution of the time during which the polishing pad 12 is pressed from the wafer 13 is shorter at the portion having the radius r _{1 and at} the portion having the radius r ₃ , whereas the dummy polished plate 17 </ b> E is at the portion having the radius r ₁ and the radius r 3. _{Since the} vicinity of each of the _three portions is pressed, the difference between the temperature rises at both ends and the center in the first region 12a of the polishing pad 12 becomes small, as in the first embodiment.
This difference in temperature rise can be reduced by controlling the outer diameter dimension, rotation speed, rotation direction or pressing force of the dummy polishing target plate 17E.
The polishing rate in the first region 12a can be made uniform.

Also in the fifth embodiment, it is preferable that the material of the dummy polished material 17E is the same as the film to be polished formed on the wafer 13.

In the first to fifth embodiments, the dummy polished materials 17A, 17B, 17C, 17D, 17E are used.
The surface that contacts the polishing pad 12 is preferably formed flat. By doing so, the dummy polishing target material 1
7A, 17B, 17C, 17D, 17E are polishing pads 1
No roughening of the surface of 2.

In the second to fourth embodiments,
The polishing target material 17B, 17C, 17D is the polishing pad 1
2 and the pressure per unit area where the wafer 13 presses the polishing pad 12 is equal to the pressure per unit area where the wafer 13 presses the polishing pad 12, but the dummy polishing materials 17 B, 17 C and 17 D press the polishing pad 12 per unit area. Pressure is wafer 1
Even if 3 is smaller than the pressure per unit area pressing the polishing pad 12, the polishing rate in the first region 12a of the polishing pad 12 can be made uniform as compared with the conventional case.

The film to be polished formed on the wafer 13 and the dummy polished materials 17A, 17B, 17C, 1
The materials of 7D and 17E are not particularly limited as long as they are of the same quality.
Silicon oxide, polysilicon, amorphous silicon, tungsten, copper, aluminum, and the like which are usually formed on the wafer 13 can be used. However, the present invention is particularly effective in a chemical mechanical polishing method for a metal film having a greater effect of temperature during polishing, that is, a metal film having a higher rate of polishing due to a chemical factor than a silicon oxide film or a polysilicon film.

The reason why it is particularly desirable to make the temperature distribution uniform in the plane of the wafer 13 in the chemical mechanical polishing of the metal film will be described below.

In chemical mechanical polishing of a metal film,
Since polishing by a chemical factor acts more strongly than polishing by a mechanical factor, the temperature distribution in the plane of the wafer 13 greatly affects the polishing rate. In other words, the polishing rate increases at a portion of the wafer 13 where the temperature is high, while the polishing rate decreases at a portion where the temperature is low.
Therefore, in the chemical mechanical polishing method for the metal film, it is strongly desired to make the temperature within the surface of the wafer 13 uniform, and if the temperature is made uniform, the polishing rate becomes uniform.
In particular, according to a recently proposed polishing method in which a wafer is pressed against a polishing pad by pressurized air, the wafer can be uniformly pressurized in a plane. When the temperature distribution in the wafer surface is made uniform using each embodiment of the present invention, the variation in the polishing rate in the wafer surface can be greatly reduced.

Hereinafter, a method for manufacturing a semiconductor device by applying each embodiment of the present invention to chemical mechanical polishing of a metal film on a semiconductor substrate will be described with reference to FIGS. 7 (a) to 7 (c).

First, as shown in FIG. 7A, after a trench 21 is formed so as to surround a transistor forming region in a semiconductor substrate 20, a source region 22 and a drain region 23 are formed in the transistor forming region. Then, a gate electrode 25 is formed on the semiconductor substrate 20 between the source region 22 and the drain region 23 with a gate oxide film 24 interposed therebetween. Next, an on-gate oxide film 26 is formed on the gate electrode 25, and a sidewall 27 is formed on a side surface of the gate electrode 25. Then, a first interlayer insulating film 28 is formed on the entire surface of the semiconductor substrate 20. Is deposited. Next, after a first contact 30 connected to the source region 22 and a second contact 31 connected to the drain region 23 are formed on the first interlayer insulating film 28, the first contact 30 is formed on the first interlayer insulating film 28. After forming the second interlayer insulating film 32,
A contact hole and a recess for wiring are formed in the second interlayer insulating film 32.

Next, as shown in FIG. 7B, after a metal film 33 made of tungsten is deposited on the entire surface of the second interlayer insulating film 32, the present invention is applied to the metal film 33. The chemical mechanical polishing is performed by applying each embodiment of FIG.
As shown in (c), a third contact 34 and a buried wiring 35 made of a metal film 33 are formed. Thus, a semiconductor device having a damascene structure made of tungsten is obtained.

As the metal film deposited on the second interlayer insulating film 32, a copper film or an aluminum film can be used instead of the tungsten film.

Here, the metal film 33 made of tungsten is used.
Abrasives used for chemical mechanical polishing of the present invention will be described. As a polishing agent for the metal film 33 made of tungsten, a mixed solution of an alumina slurry and an iron nitrate solution is known. The alumina slurry performs polishing by a mechanical factor, and the iron nitrate solution performs polishing by a chemical factor. . Since iron nitrate has an effect of oxidizing tungsten, after oxidizing tungsten, the oxidized tungsten is mechanically polished. Since tungsten is a hard metal, if the polishing rate due to mechanical factors is large, the polishing rate is reduced and the polished surface is full of scratches. However,
When the rate of polishing by a chemical factor is increased by using an iron nitrate solution, polishing can be performed at an appropriate polishing rate and scratches generated on a polished surface can be reduced.

As described above, polishing by a chemical factor is temperature-sensitive. Therefore, in order to make the polishing rate for a metal film made of tungsten, copper, aluminum or the like uniform, the temperature distribution in the wafer surface must be uniform. Therefore, the semiconductor substrate polishing method according to each embodiment of the present invention is effective.

[0074]

According to the first apparatus for polishing a semiconductor substrate according to the present invention, the total time of the time during which the polishing pad is in contact with the film to be polished of the semiconductor substrate and the time during which the polishing pad is in contact with the surface to be polished of the dummy material is polished. Is uniform in the region of the polishing pad in contact with the film to be polished on the semiconductor substrate, so that frictional heat generated in the region of the polishing pad in contact with the film to be polished (between the polishing pad and the film to be polished on the semiconductor substrate) The sum of the frictional heat generated by the polishing pad and the frictional heat generated between the polishing pad and the surface to be polished of the dummy polished material) and the reaction heat (reaction heat generated between the polishing pad and the film to be polished on the semiconductor substrate) And the reaction heat generated between the polishing pad and the surface to be polished of the dummy material to be polished) are also uniformized in the region of the polishing pad in contact with the film to be polished. Contact Temperature rise of the region is made uniform,
Thereby, the polishing rate of the film to be polished on the semiconductor substrate is made uniform.

Further, since the dummy polished material is formed of the same material as the film to be polished of the semiconductor substrate, a substance generated by polishing the polished surface of the dummy polished material gives the film to be polished. In addition to eliminating adverse effects, the polishing pad has the same coefficient of friction and reaction coefficient with respect to the film to be polished and the surface to be polished of the dummy material to be polished. It is easy to control the frictional heat and reaction heat generated in the process.

In the first semiconductor substrate polishing apparatus, when the dummy polished material is independently pressed against the semiconductor substrate and polished by the polishing pad, the gap between the polishing pad and the polished surface of the dummy polished material is reduced. It is easy to control the frictional heat and reaction heat generated in the process.

In the first semiconductor substrate polishing apparatus, the plane motion is a rotational motion, and the center of the circular polished film of the semiconductor substrate is the same as the center of the annular polished surface of the dummy polished material. When on the circumference, the total time of the contact time of the polishing pad with the film to be polished and the time of contact with the surface to be polished of the dummy material to be polished is made uniform in the region of the polishing pad that contacts the film to be polished. It becomes easier.

In this case, if the inner diameter of the polished surface of the dummy polished material is slightly larger than the outer diameter of the polished film of the semiconductor substrate,
The temperature distribution in the polishing pad changes rapidly because the position of the polishing pad where the time when the polishing pad comes into contact with the surface to be polished of the dummy material to be polished is located outside the region where the polishing pad comes into contact with the film to be polished. Since there is no region to be polished, it is easy to control the temperature uniformity of the region of the polishing pad in contact with the film to be polished.

Further, when the dummy polished material is independently rotated with respect to the semiconductor substrate, control of frictional heat and reaction heat generated between the polishing pad and the polished surface of the dummy polished material becomes easy.

In the first semiconductor substrate polishing apparatus, when the film to be polished of the semiconductor substrate and the dummy material to be polished are formed of the same metal film, the polishing rate is greatly affected in the chemical mechanical polishing of the metal film. Since the temperature distribution in the polishing pad, which is the basis of the chemical factor, can be made uniform, the metal film can be reliably flattened.

According to the apparatus for polishing a second semiconductor substrate, similarly to the apparatus for polishing a first semiconductor substrate, the polishing pad is in contact with the film to be polished of the semiconductor substrate and the dummy pad is in contact with the surface to be polished. Since the total time with the time is uniformed in the region in contact with the film to be polished in the polishing pad,
Since the frictional heat and reaction heat generated in the region of the polishing pad in contact with the film to be polished are also made uniform, the polishing rate of the film to be polished is made uniform.

Since the surface to be polished of the dummy material to be polished is formed of the same material as that of the film to be polished of the semiconductor substrate, a substance generated by polishing the surface to be polished of the dummy material to be polished is coated. The polishing pad has the same coefficient of friction and reaction coefficient with the film to be polished and the surface to be polished of the dummy material to be polished, and the polishing pad and the dummy material to be polished can be eliminated. Control of frictional heat and reaction heat generated between the surfaces becomes easy.

Therefore, when the film to be polished of the semiconductor substrate is polished by using the polishing apparatus for the first or second semiconductor device according to the present invention, the film to be polished is surely planarized.

According to the method for polishing a semiconductor substrate of the present invention,
Since the total time of the contact time of the polishing pad with the film to be polished of the semiconductor substrate and the time of contact with the surface to be polished of the dummy material to be polished is made uniform in the region of the polishing pad that contacts the film to be polished, As described above, the frictional heat and reaction heat generated in the region of the polishing pad in contact with the film to be polished are also made uniform, so that the polishing rate of the film to be polished is made uniform.

In the method for polishing a semiconductor substrate according to the present invention,
When the dummy polished material is pressed against the polishing pad independently against the semiconductor substrate and polished, the frictional heat and reaction heat generated between the polishing pad and the polished surface of the dummy polished material can be easily controlled. .

In the method for polishing a semiconductor substrate according to the present invention,
When a dummy polishing target material having an annular polishing surface whose center is on the same circumference as the center of the circular polishing target film is pressed against the polishing pad and polished, the contact time between the polishing pad and the polishing target film is reduced. It is easy to make the total time including the time of contact with the surface to be polished of the dummy material to be polished uniform in the region of the polishing pad in contact with the film to be polished of the semiconductor substrate.

In this case, when the dummy polished material is independently rotated with respect to the semiconductor substrate, control of frictional heat and reaction heat generated between the polishing pad and the polished surface of the dummy polished material becomes easy. .

In the method for polishing a semiconductor substrate according to the present invention,
If the film to be polished of the semiconductor substrate and the dummy material to be polished are formed of the same metal film, the temperature distribution in the polishing pad, which is a source of a chemical factor that greatly affects the polishing rate in the chemical mechanical polishing of the metal film, is reduced. Since the metal film can be made uniform, the metal film can be reliably flattened.

[Brief description of the drawings]

FIG. 1A is a schematic perspective view of a semiconductor substrate polishing apparatus according to a first embodiment of the present invention, and FIG.
FIG. 4 is a plan view of a polishing pad in the semiconductor substrate polishing apparatus according to the embodiment.

FIG. 2 is a view for explaining uniform contact time in a polishing method performed by using the semiconductor substrate polishing apparatus according to the first embodiment.

FIG. 3 is a diagram showing a planar structure of a dummy workpiece in a semiconductor substrate polishing apparatus according to a second embodiment of the present invention.

FIG. 4 is a diagram showing a planar structure of a dummy polished material in a semiconductor substrate polishing apparatus according to a third embodiment of the present invention.

FIG. 5 is a view showing a cross-sectional structure of a dummy polished material in a semiconductor substrate polishing apparatus according to a fourth embodiment of the present invention.

FIG. 6 is a diagram showing a planar structure of a dummy workpiece in a semiconductor substrate polishing apparatus according to a fifth embodiment of the present invention.

FIGS. 7A to 7C are cross-sectional views showing steps of a method of manufacturing a semiconductor device to which the semiconductor substrate polishing method according to the first to fifth embodiments is applied;

FIG. 8 is a schematic perspective view of a conventional semiconductor substrate polishing apparatus.

FIG. 9 is a plan view illustrating a problem of a polishing method performed using a conventional semiconductor substrate polishing apparatus.

FIG. 10 is a characteristic diagram illustrating a problem of a polishing method performed using a conventional semiconductor substrate polishing apparatus.

[Explanation of symbols]

Reference Signs List 11 surface plate 11a pad mounting portion 11b surface plate rotation axis 12 polishing pad 12a first area 12b second area 13 wafer 14 wafer carrier 14a wafer holding part 14b carrier rotation axis 15 abrasive 16 abrasive supply pipe 17A, 17B , 17C, 17D, 17E Dummy polishing material 18 Dummy holder 18a Dummy holding plate 18b Dummy rotating shaft 19 Concave groove 20 Semiconductor substrate 21 Trench groove 22 Source region 23 Drain region 24 Gate lower oxide film 25 Gate electrode 26 Gate oxide film on gate 27 Side wall 28 First interlayer insulating film 30 First contact 31 Second contact 32 Second interlayer insulating film 33 Metal film 34 Third contact 35 Embedded wiring

Claims (12)

[Claims] 1. A polishing pad mounted on a surface plate which moves in a plane, a polishing agent supply means for supplying a polishing agent on the polishing pad, and a semiconductor substrate on which a film to be polished is formed is held. A substrate holding means for pressing the held film to be polished of the semiconductor substrate against the polishing pad to polish the film; and a material made of the same material as the film to be polished, and a contact time with the film to be polished is the polishing time. The polishing pad has a surface to be polished having a shape such that a contact time with a region of the polishing pad that is relatively short as compared with another region of the pad is longer than that of the other region, and the surface to be polished is the polishing pad. And a dummy workpiece to be polished by the method. 2. The semiconductor substrate polishing apparatus according to claim 1, wherein the dummy polishing target material is independently pressed against the semiconductor substrate and polished by the polishing pad. 3. The planar motion is a rotary motion, the film to be polished on the semiconductor substrate is circular, the surface to be polished of the dummy material to be polished is annular, and the center of the film to be polished is 2. The semiconductor substrate polishing apparatus according to claim 1, wherein the center of the polished surface of the dummy polished material is on the same circumference. 4. The semiconductor substrate polishing apparatus according to claim 3, wherein an inner diameter of an annular polished surface of the dummy polished material is slightly larger than an outer diameter of a polished film of the semiconductor substrate. . 5. The semiconductor substrate polishing apparatus according to claim 3, wherein the dummy workpiece is independently rotated with respect to the semiconductor substrate. 6. The apparatus according to claim 1, wherein the film to be polished of the semiconductor substrate and the dummy material to be polished are formed of a metal film of the same quality. 7. A polishing pad mounted on a surface plate which moves in a plane, a polishing agent supply means for supplying a polishing agent on the polishing pad, and a semiconductor substrate on which a film to be polished is formed. A substrate holding means for pressing the held film to be polished of the semiconductor substrate against the polishing pad to polish the film; and a material made of the same material as the film to be polished, and a contact time with the film to be polished is the polishing time. The polishing pad has a surface to be polished that is in contact only with the region of the polishing pad and a region in the vicinity thereof, which is relatively short as compared with the other region of the pad, and the surface to be polished is a dummy material to be polished by the polishing pad. An apparatus for polishing a semiconductor substrate, comprising: 8. A polishing process for polishing a film to be polished formed on a semiconductor substrate with a polishing pad to which a polishing agent is supplied while performing a planar motion, and using a material of the same quality as the film to be polished. A shape in which a contact time with the polishing target film is relatively short compared to the other region of the polishing pad, and a contact time with the polishing pad region is longer than the other region. Polishing a dummy polished material of the polished material having the polished surface with the polishing pad. 9. The semiconductor according to claim 8, wherein the step of polishing the dummy polished material includes a step of independently pressing the dummy polished material against the polishing pad against the semiconductor substrate. Substrate polishing method. 10. The polishing of the film to be polished includes the step of polishing the circular film to be polished by the polishing pad that makes a rotational movement. The method for polishing a semiconductor substrate according to claim 8, comprising a step of polishing an annular surface to be polished on the same circumference as the center with the polishing pad. 11. The method for polishing a semiconductor substrate according to claim 10, wherein the step of polishing the dummy polished material includes a step of independently rotating the dummy polished material with respect to the semiconductor substrate. 12. The method for polishing a semiconductor device according to claim 8, wherein the film to be polished of the semiconductor substrate and the dummy material to be polished are formed of a metal film of the same quality.