JP3514743B2 - Film thickness measuring device and substrate polishing device - Google Patents

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a film thickness measuring device and a substrate polishing device, and more particularly to a film thickness measuring device for measuring the film thickness of a conductive film formed on a semiconductor substrate and a substrate provided with this measuring device. It is suitable to be applied to a polishing device.

[0002]

2. Description of the Related Art Recently, a CMP (Chemical Mechanical Polishing) method has been widely used as a method for flattening a laminated film on a semiconductor substrate. Polishing by the CMP method can significantly improve the flatness as compared with the conventional flattening technique such as the etch back method.

During polishing by the CMP method, end point detection is performed in order to detect whether or not a predetermined film has been polished. The endpoints are detected by irradiating the wafer surface with light from the polishing pad side and then measuring the reflectance from the reflected light.A eddy current method that detects the current value between the conductive films formed on the wafer. A torque detection method for detecting the rotation torque of the pad is known.

[0004]

[Problems to be Solved by the Invention] However, CMP
Even with polishing by the method, it is still difficult to obtain flatness of several Å level over the entire area of the wafer. Particularly, in the case of a large-diameter wafer having a diameter of 300 mm, the polishing amount varies within the surface of the wafer. For example, when forming a copper wiring pattern by the damascene method, it is necessary to make the variation in the polishing amount within the wafer surface as close as possible to 0, but it is difficult to suppress the variation in the entire area of a wafer having a diameter of 300 mm. It was

Further, in the above-described detection of the endpoint, the endpoint is detected only when the lower layer film of the film to be polished is exposed. Therefore, before the lower layer film is exposed, the polishing amount of the film to be polished, The film thickness could not be detected. That is, in the spectroscopic method, since the endpoint is detected from the fluctuation of the reflectance of the light irradiated on the substrate, the reflectance does not change while the film to be polished remains on the entire surface of the wafer, and the lower layer of the film to be polished is not changed. The fluctuation of the polishing amount could not be detected until the film was exposed.

Also in the torque detection method, since the torque does not fluctuate while the film to be polished remains on the entire surface, the fluctuation of the torque cannot be detected until the lower layer film is exposed.

In the eddy current method, a current flowing between conductive patterns on a semiconductor substrate, which is a film to be polished, is detected. However, the amount of change in current value due to polishing is minute, and it is difficult to detect the film thickness with high accuracy. Met. Further, the nonuniformity of polishing can be detected by the eddy current method just before the lower interlayer insulating film is exposed, so that the polishing amount cannot be corrected thereafter.

FIG. 8 is a schematic cross-sectional view showing a step of forming a copper wiring by the so-called damascene method.
Trench 10 formed in the interlayer insulating film 102 on
4 is filled with the copper film 103 and is polished by the CMP method. As shown in FIG. 8, when planarization is not performed uniformly, a partial region 105 on the semiconductor substrate 101 is formed.
Only by that, the interlayer insulating film 102 under the copper film 103 is exposed.

In the above endpoint detection method,
As shown in FIG. 8, the endpoint is detected only after the interlayer insulating film 102 in the region 105 is exposed. However, as shown in FIG. 8, even if the polishing profile adjustment is performed after the lower interlayer insulating film 102 is exposed, since the polishing is performed over the entire area of the wafer, excessive polishing is performed in the vicinity of the region 105. I will end up. As a result, the uniformity of the film thickness of the wiring pattern is impaired, and the film thickness of the wiring pattern locally decreases. The reduction in the film thickness of the wiring pattern increases the wiring resistance, which hinders high-speed operation.

The present invention has been made to solve the above problems, and measures the film thickness of a film to be polished during polishing even before the film underlying the film to be polished is exposed. An object of the present invention is to provide a film thickness measuring device and a substrate polishing device capable of performing the above.

[0011]

A film thickness measuring apparatus of the present invention comprises a plurality of films which are brought into contact with a conductive film on a rotating substrate, which is an object to be measured, so as to be conductive, and which are rotated with the movement of the conductive film. A rotating part is provided, and the film thickness of a predetermined portion of the conductive film is repeatedly measured from a potential difference and a current value applied between the plurality of rotating parts while the substrate is rotated .

The plurality of rotating parts are used as electrodes, and a pair of current injection electrodes and another pair of voltage measurement electrodes arranged between the pair of current injection electrodes are provided. It is a thing.

Further, the rotating portion is made of a conductive ball.

Further, the rotating portion is composed of a conductor disk.

Further, according to the film thickness measuring apparatus of the present invention, the tip portion is filled with a plurality of thin tubes arranged below the surface of the conductive film to be measured, and the inside of the thin tubes is filled by the capillary phenomenon.
A liquid metal that projects above the tip and contacts the conductive film is provided, and the film thickness of the conductive film is measured from the potential difference and the current value applied between the liquid metals of the plurality of thin tubes. .

Further, the plurality of thin tubes are used as electrodes, and a pair of current injection electrodes and another pair of voltage measurement electrodes arranged between the pair of current injection electrodes are provided. Is.

The liquid metal is mercury.

The liquid metal is a lipophilic conductive liquid.

Further, the substrate polishing apparatus of the present invention comprises a rotary head on which a substrate to be polished is mounted, a polishing pad which adheres to the surface of the substrate to polish the substrate surface,
Having a plurality of electrodes in contact with the surface of the substrate,
Anti the thickness of a predetermined portion of said plurality of conductive films of the substrate surface from the voltage and current applied between the electrodes while rotating
And a film thickness measuring means for performing a recursive measurement.

As the plurality of electrodes, a pair of electrodes for current injection and another pair of electrodes for voltage measurement arranged between the pair of electrodes for current injection are provided. .

Further, the electrode is provided in a predetermined region of the polishing pad.

Further, the electrode is provided so as to face the surface of the substrate independently of the polishing pad.

Further, the electrode is provided with a rotating portion which comes into contact with the substrate and rotates with the movement of the substrate.

Further, the rotating portion is made of a conductive ball.

Further, the rotating portion is composed of a conductor disk.

Further, the electrode fills the inside of the thin tubes with a plurality of thin tubes whose tip portions are disposed below the surface of the substrate, and projects upward from the tip portions due to a capillary phenomenon. A liquid metal in contact with the substrate.

The liquid metal is mercury.

The liquid metal is a lipophilic conductive liquid.

[0029]

BEST MODE FOR CARRYING OUT THE INVENTION Embodiment 1. Embodiment 1 of the present invention will be described below with reference to the drawings. FIG. 1 is a sectional view showing a schematic configuration of a substrate polishing apparatus according to the first embodiment. As shown in FIG. 1, this substrate polishing apparatus has a surface plate 1 provided with a polishing pad 2 such as urethane foam, and a rotary head 3 on which a semiconductor substrate 4 is mounted. The surface of the semiconductor substrate 4 is polished by pouring the slurry between the two and rotating the surface plate 1 and the rotary head 3 together.

A film thickness measuring unit 5 is provided on the surface plate 1. The film thickness measuring unit 5 is a unit having four terminals, and an electric current is passed through a conductive film (a film to be polished) formed on the surface of the semiconductor substrate 4 to obtain a so-called four-terminal method (4
The film thickness of the conductive film is measured from the sheet resistance value of the conductive film by the probe method).

FIG. 2 is a schematic perspective view showing the upper surface of the surface plate 1. As shown in FIG. 2, the surface plate 1 and the urethane foam 2 are provided with a recess 6 into which the film thickness measuring unit 5 is inserted.

FIG. 3 is a schematic sectional view showing the structure of the film thickness measuring unit 5. As shown in FIG. 3, in the film thickness measurement unit 5 of the first embodiment, four terminals are composed of balls 7. Each ball 7 is rotatably attached to a holder 8, and the holder 8 is attached to a unit body 9. A spring 10 is provided between the holder 8 and the unit body 9.
Is provided.

Since the ball 7 is rotatable in all directions, the ball 7 is not restricted by the position of the film thickness measuring unit 5 on the surface plate 1, and the ball 7 is relatively positioned between the semiconductor substrate 4 and the surface plate 1. It rotates following the movement.

In the film thickness measurement by the four-terminal method, the two outer terminals are I ₁ terminal and I ₂ terminal as shown in FIG.
The two inner terminals are referred to as V ₁ and V ₂ terminals. And
By passing a current i between the outer I ₁ and I ₂ terminals and measuring the potential difference v between the inner V ₁ and V ₂ terminals, R
= Measure the wiring resistance between the V ₁ and V ₂ terminals from v / i.
Since the wiring resistance is inversely proportional to the film thickness of the conductive film, the film thickness can be obtained from the value of the wiring resistance.

In the film thickness measurement by the 4-terminal method, almost no current flows between the V ₁ and V ₂ terminals inside which the potential difference is measured, so that the contact resistance of the V ₁ and V ₂ terminals can be ignored. Therefore, even if the contact resistance is generated, the voltage drop generated between the V ₁ and V ₂ terminals can be accurately measured. Therefore, based on this principle, the potential difference between the V ₁ and V ₂ terminals can be accurately measured even when the rotating ball 7 constitutes four terminals as shown in FIG. The film thickness of the conductive film being polished can be measured with high accuracy.

As a result, the film thickness of the conductive film on the semiconductor substrate 4 can be monitored with high accuracy during polishing. Then, the thickness profile of the conductive film can be measured before the conductive film is removed and the lower interlayer insulating film is exposed.
It becomes possible to perform profile control so as to focus the polishing on a region having a small polishing amount. This gives a diameter of 30
Even with a large-diameter wafer such as a 0 mm wafer, the polishing amount can be kept constant over the entire area of the wafer. Profile control is performed by changing parameters such as a downward force (polishing processing pressure) applied to the rotary head 3, a processing pressure of the surface plate 1 and the rotary head 3, a rotation speed, and a slurry supply amount. This makes it possible to increase the polishing amount in the region where the conductive film has a large film thickness and reduce the polishing amount in the region where the conductive film has a small film thickness. Variations can be minimized.

As described above, according to the first embodiment, since the film thickness measuring unit 5 is composed of the unit including the four balls 7, the surface plate 1 and the rotary head 3 are in a rotating state. Also, the balls can be brought into contact with the semiconductor substrate 4. This makes it possible to measure the film thickness by the four-terminal method using the four balls 7 as terminals. Therefore, even during polishing, it is possible to obtain the profile of the film thickness of the conductive film being polished in real time, and the polishing profile can be adjusted. Then, it becomes possible to uniformly polish the entire area of the semiconductor substrate 4, it is possible to prevent the wiring pattern formed by the damascene method or the like from being excessively polished, and to form a wiring pattern having a desired film thickness. It will be possible.

Embodiment 2. Next, a second embodiment of the invention will be described with reference to FIGS. 4 and 5. In the second embodiment, the four terminals I ₁ of the film thickness measuring unit 5,
I ₂ , V ₁ and V ₂ are composed of four rotatable rollers 11, and the film thickness is measured by the 4-terminal method as in the first embodiment.

As shown in FIG. 4, the four rollers 11 are
It is rotatably inserted into the rotary shaft 12 of the book. Each roller 11 is made of a disc-shaped metal. In order to reduce the contact resistance with the semiconductor substrate 4, the outer periphery of each roller 11 has an edge-shaped acute angle shape.

A conductive film 12a is formed on the rotary shaft 12 so as to correspond to the four rollers 11. Each roller 11 and each conductive film 12a are electrically connected to each other, a current flows to each roller 11 through the conductive film 12a, and each roller 11
Is measured.

As described above, in the second embodiment, since the film thickness measuring unit 5 is composed of the four rollers 11 and the rotating shaft 12, the rotating mechanism of the four terminals can be simply constructed, and the manufacturing cost can be reduced. Can be reduced.

In the film thickness measuring unit 5 of the second embodiment,
It is desirable that the moving direction of the semiconductor substrate 4 be perpendicular to the rotation axis 12. Therefore, as shown in FIG. 5, it is suitable when the film thickness measuring unit 5 is provided independently of the polishing pad 2.

FIG. 5 shows an example in which the film thickness measuring unit 5 of the second embodiment is provided in a substrate polishing apparatus having a polishing pad 2 smaller than the semiconductor substrate 4. In this substrate polishing apparatus, the polishing pad 2 is arranged on the semiconductor substrate 4. Then, the surface of the semiconductor substrate 4 is polished by rotating the semiconductor substrate 4 and the polishing pad 2 smaller than the semiconductor substrate 4 together.

In the substrate polishing apparatus shown in FIG. 5, the rotation direction of the semiconductor substrate 4 and the longitudinal direction of the rotation shaft 12a of the film thickness measuring unit 5 are perpendicular to each other. Thereby, the rotation of the semiconductor substrate 4 is efficiently transmitted to the roller 11, and it is possible to prevent the semiconductor substrate 4 and the roller 11 from being subjected to an excessive force.

Embodiment 3. Next, a third embodiment of the invention will be described with reference to FIGS. 6 and 7. In the third embodiment, the four terminals I ₁ of the film thickness measurement unit 5,
I ₂ , V ₁ and V ₂ are composed of liquid metal (for example, mercury (Hg)).

As shown in FIG. 6, the film thickness measuring unit 5 has four conductive capillaries 13, and the mercury 14 sucked upward by the capillarity phenomenon.
Is spherically projected at the tip of the capillary tube 13. The protruding mercury 14 does not flow due to surface tension and does not flow into the capillary tube 13.
Stays at the tip of.

In the film thickness measuring unit 5 of the third embodiment, the mercury 14 projecting from the tip of the capillary tube 13 is brought into contact with the conductive film on the semiconductor substrate 4, so that the film is formed by the four-terminal method as in the first embodiment. The thickness is measured. Mercury 14
Since the contact between the conductive film and the conductive film is metal-to-metal contact and the adhesion is high, the surface plate 1 and the rotary head 3 rotate to rotate the semiconductor substrate 4
The mercury 14 and the conductive film can be surely brought into contact with each other even during polishing. Further, since the mercury 14 and the slurry are hard to fit in, it is possible to prevent the slurry from entering between the mercury 14 and the conductive film.

FIG. 7 is a schematic sectional view showing a state in which the mercury 14 at the tip of the capillary tube 13 and the surface of the semiconductor substrate 4 are in contact with each other. As shown in FIG. 7, the distance d between the tip of the capillary tube 13 and the semiconductor substrate 4 is made sufficiently small with respect to the inner diameter 2r of the capillary tube 13. This can prevent the mercury 14 in the capillary tube 13 from flowing out onto the semiconductor substrate 4. In particular, since the surface tension of mercury 14 is large, it is possible to prevent the mercury 14 from flowing out between the capillary tube 13 and the semiconductor substrate 4 by making the distance d sufficiently smaller than the inner diameter 2r.

If the inner diameter of the capillary tube 13 is less than a predetermined value,
Due to the capillary phenomenon, the mercury 14 can naturally be caused to protrude to the tip of the capillary tube 13. Preferably, the capillary phenomenon can be utilized by setting the inner diameter 2r of the capillary tube 13 to about 1 mm or less. The inner diameter 2r can be reduced to the minimum value under the condition that the mercury 14 passes. Alternatively, pressure may be applied from below to cause the mercury 14 to project to the tip of the capillary tube 13. In this case, the amount of protrusion of the mercury 14 can be controlled by adjusting the pressure,
The adhesion with the film on the semiconductor substrate 4 can be changed.

When the conductive film on the semiconductor substrate 4 is completely polished to expose the underlying interlayer insulating film, the capillary tube 13
The mercury 14 protruding at the tip of the tube is housed in the capillary tube 13.

Further, liquid metal may be made to flow from the capillary tube 13. Since the surface of the semiconductor substrate 4 is wet with the slurry, it is desirable to use a lipophilic conductive liquid such as black carbon as the liquid metal in order to surely conduct electricity to the conductive film on the semiconductor substrate 4. In this case, since the capillary phenomenon is not used, there is no particular restriction on the inner diameter of the capillary tube.

As described above, by flowing the lipophilic conductive liquid such as black carbon from the capillary tube 13 to the surface of the semiconductor substrate 4, the capillary tube 13 and the conductive film on the semiconductor substrate 4 can be electrically connected. At this time, if a certain amount or more of the lipophilic conductive liquid flows on the semiconductor substrate 4, a short circuit may occur between the terminals, so it is desirable to flow the conductive liquid in a pulsed manner. Accordingly, the measurement can be performed before the adjacent capillaries 13 are short-circuited.

[0053]

Since the present invention is constructed as described above, it has the following effects.

During the polishing of the conductive film, a plurality of rotating portions are provided which are brought into contact with the conductive film on the substrate to be measured so as to be conductive and rotate with the movement of the conductive film. In addition, the rotating part can be brought into contact with the conductive film. Then, the film thickness can be measured during polishing from the potential difference between the two points on the conductive film and the current value.

By providing a pair of current injection electrodes and another pair of voltage measurement electrodes arranged between the pair of current injection electrodes, the plurality of rotating parts are used as electrodes. The film thickness can be measured by the so-called 4-terminal method.

Since the rotating portion is composed of the conductive sphere, the rotating portion can be brought into contact with the conductive film without being restricted by the moving direction of the substrate on which the conductive film to be measured is formed.

Since the rotating portion is composed of the conductive disk, it is possible to follow the movement of the conductive film of the substrate with a simple structure.
The cost of the measuring device can be reduced.

By bringing the liquid metal filling the narrow tube into contact with the conductive film to be measured, the liquid metal can be brought into contact with the conductive film even while the conductive film is being polished. Then, the film thickness can be measured during polishing from the potential difference between the two points on the conductive film and the current value.

By using a plurality of thin tubes as electrodes, a pair of electrodes for current injection and another pair of electrodes for voltage measurement arranged between the pair of electrodes for current injection are provided. The film thickness can be measured by the 4-terminal method.

By using mercury having a high surface tension as the liquid metal, it is possible to prevent the liquid metal from flowing out from the thin tube onto the conductive film. Therefore, the liquid metal and the conductive film can be brought into contact with each other without short-circuiting the plurality of thin tubes.

By using the liquid metal as the lipophilic conductive liquid, the conductive liquid and the conductive film are surely formed even when the liquid such as the slurry supplied on the conductive film to be polished is supplied. Can be contacted.

[Brief description of drawings]

FIG. 1 is a sectional view showing a schematic configuration of a substrate polishing apparatus according to a first embodiment.

FIG. 2 is a schematic perspective view showing an upper surface of a surface plate.

FIG. 3 is a schematic cross-sectional view showing the configuration of the film thickness measurement unit according to the first embodiment.

FIG. 4 is a schematic cross-sectional view showing a configuration of a film thickness measurement unit according to a second embodiment.

FIG. 5 is a schematic perspective view showing an example in which a film thickness measuring unit according to the second embodiment is provided in a substrate polishing apparatus in which a polishing pad is provided on a semiconductor substrate.

FIG. 6 is a schematic sectional view showing a configuration of a film thickness measurement unit according to a third embodiment.

FIG. 7 is a schematic cross-sectional view showing a state where mercury at the tip of a capillary tube and the surface of a semiconductor substrate are in contact with each other.

FIG. 8 is a schematic cross-sectional view showing a step of forming a copper wiring by a damascene method.

[Explanation of symbols] 1 surface plate, 2 polishing pad, 3 rotating head, 4
Semiconductor substrate, 5 film thickness measurement unit, 6 recess,
7 balls, 8 holders, 9 unit body, 1
0 spring, 11 roller, 12 rotating shaft, 13
Capillary, 14 mercury.

Front page continuation (58) Fields surveyed (Int.Cl. ⁷ , DB name) G01B 7/06 B24B 37/04 H01L 21/304

Claims (18)

(57) [Claims] 1. The substrate is rotated , comprising a plurality of rotating portions which are brought into contact with a conductive film on a rotating substrate, which is an object to be measured, so as to be conductive, and which rotate with the movement of the conductive film . thickness measuring device according to claim <br/> repeating measuring the thickness of a predetermined portion of the conductive layer from the potential and the current value is applied between the plurality of rotating parts in between. 2. A pair of electrodes for current injection and a pair of electrodes for voltage measurement arranged between the pair of electrodes for current injection using the plurality of rotating parts as electrodes. The film thickness measuring device according to claim 1, wherein 3. The film thickness measuring device according to claim 1, wherein the rotating portion is made of a conductive sphere. 4. The film thickness measuring device according to claim 1, wherein the rotating portion is formed of a conductor disk. 5. The surface of a conductive film whose tip is an object to be measured.
A plurality of thin tubes arranged in the lower part of the
Also includes a liquid metal protruding upward and in contact with the conductive film, wherein the film thickness of the conductive film is measured from a potential difference and a current value applied between the liquid metals of the plurality of capillaries. measuring device. 6. A plurality of thin tubes are used as electrodes, and a pair of electrodes for current injection and another pair of electrodes for voltage measurement arranged between the pair of electrodes for current injection are provided. The film thickness measuring device according to claim 5. 7. The film thickness measuring device according to claim 5, wherein the liquid metal is mercury. 8. The film thickness measuring device according to claim 5, wherein the liquid metal is a lipophilic conductive liquid. 9. A rotary head on which a substrate to be polished is mounted, a polishing pad that adheres to the surface of the substrate to polish the substrate surface, and a plurality of electrodes that contact the substrate surface, The substrate
Anti the thickness of a predetermined portion of said plurality of conductive films of the substrate surface from the voltage and current applied between the electrodes while rotating
A substrate polishing apparatus comprising: a film thickness measuring means for performing a recursive measurement. 10. The plurality of electrodes comprises a pair of electrodes for current injection and another pair of electrodes for voltage measurement arranged between the pair of electrodes for current injection. The substrate polishing apparatus according to claim 9. 11. The substrate polishing apparatus according to claim 9, wherein the electrode is provided in a predetermined region of the polishing pad. 12. The substrate polishing apparatus according to claim 9, wherein the electrode is provided so as to face the surface of the substrate independently of the polishing pad. 13. The substrate polishing apparatus according to claim 9, wherein the electrode is provided with a rotating portion that comes into contact with the substrate and rotates with the movement of the substrate. . 14. The substrate polishing apparatus according to claim 13, wherein the rotating portion is a conductive ball. 15. The substrate polishing apparatus according to claim 13, wherein the rotating portion is made of a conductor disk. 16. The electrode includes a plurality of capillaries tip disposed below the surface of the substrate, fill the narrow tube, from the distal end by capillary action
The substrate polishing apparatus according to any one of claims 9 to 12, further comprising a liquid metal protruding upward and contacting the substrate. 17. The substrate polishing apparatus according to claim 16, wherein the liquid metal is mercury. 18. The substrate polishing apparatus according to claim 16, wherein the liquid metal is a lipophilic conductive liquid.