JPH11204473A - Polishing method and polishing apparatus - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an abrasive processing method, which can control position of an end point of an abrasive processing of an insulating film with high accuracy regardless of the positions of wiring layers, and an abrasive processing device of a structure, wherein the thickness of the residual film of the insulating film can be detected by the high resolving-power of the device. SOLUTION: A mark 9 for residual film thickness detection is provided on an insulating film 4 under an insulating film 10 on which an abrasive processing is performed, the distance between the surface of the film 4 and the surface of the film 10 and the distance between the surface of the film 4 and the surface of the mark 9 are respectively measured and the thickness of the residual film of the film 10 is found from a difference between both measured values of the distances. As a result, the thickness of the residual film of the film 10 can be polished while being monitored accurately and the end point of the polishing can be controlled with high accuracy, regardless of the position in laminated layer of the film 10.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a polishing method and a polishing apparatus, and more particularly, to a polishing method particularly suitable for flattening the surface of a semiconductor wafer in a wiring step which is one of manufacturing steps of a semiconductor integrated circuit. The present invention relates to a method and a polishing apparatus used for the method.

[0002]

2. Description of the Related Art The manufacture of a semiconductor device includes many steps. As a part of a wiring step, a step of polishing and flattening irregularities on the surface of a thin film formed on the surface of a semiconductor wafer is included. This flattening step will be described with reference to FIG.

FIG. 2A shows a cross section of a wafer when a first-layer wiring is formed. A first insulating film 2 is formed on a surface of a semiconductor substrate 1 on which a transistor (not shown) is formed, and a first wiring layer 3 made of aluminum or the like is provided thereon. In order to connect the wiring layer 3 to the transistor, the wiring layer 3 is in contact with the semiconductor substrate 1 via the contact hole formed in the first insulating film 2.
A dent is formed on the upper surface.

In a second wiring step, as shown in FIG. 2B, after a second insulating film 4 is formed on the first wiring layer 3, a second wiring is formed thereon. Form a layer, but the second
When the insulating film 4 is formed, the surface is not flat but uneven. Therefore, in the subsequent lithography process, if the exposure is performed while leaving the above irregularities,
Improper transfer due to defocus occurs, and it is difficult to form various patterns with high accuracy.

[0005] In order to prevent such obstacles, level 5
Polishing is performed until, as shown in FIG.
After the surface of the insulating film 4 is flattened, a contact hole 6 is formed in the second insulating film 4 as shown in FIG. 2D, and further a second hole is formed as shown in FIG. Wiring layer 7
To form

Next, as shown in FIG. 2F, after the third insulating film 10 is formed, the surface is flattened by polishing to level 8. By repeating these steps, a multilayer wiring can be formed.

The above-mentioned polishing used for flattening the surface will be described with reference to FIG. Polishing pad 11 to platen 12
And rotate it. On the other hand, the semiconductor substrate 1 to be polished is fixed to a wafer holder 14 via an elastic holding pad 13. By applying a load on the polishing pad 11 while rotating the wafer holder 14 and further supplying a polishing liquid 15 on the polishing pad 11, the convex portion of the insulating film (not shown) on the surface of the semiconductor substrate 1 is polished. It is removed and planarized. In this case, the polishing liquid 15
By using colloidal silica or the like suspended in an aqueous potassium hydroxide solution, a chemical etching action is added, and a processing speed several times higher than that obtained by performing only mechanical polishing can be obtained. This method is generally a chemical mechanical polishing method (CM
P method).

[0008]

However, in the conventional polishing described above, there is no good polishing end point detection method necessary for terminating the polishing process with high accuracy, so that the polishing can be accurately performed at an optimum position. There was a problem that can not be stopped. For example, when the surface is flattened by polishing to level 5 or level 8 shown in FIG. 2, it is necessary to detect that polishing has progressed to level 5 or level 8 and immediately end the polishing operation at that point. . However, as shown in FIG. 3, the semiconductor substrate 1 is polished by being sandwiched between the polishing pad 11 and the holding pad 13. From the change in the distance between the polishing pad 11 and the holding pad 13 each having elasticity, it is extremely difficult to know the decrease in the thickness of the insulating film 4 at the level of 0.1 μm.

Conventional methods for detecting the end point of polishing include a method in which the polishing rate is checked in advance and the thickness of the remaining film is estimated from the elapsed time, and a method in which the unevenness of the surface to be processed is reduced as the polishing progresses. Focusing on a phenomenon in which the frictional force between the polishing pad and the surface to be processed changes, a method of measuring a change in the rotational torque of the polishing platen 12 or the like was used. However, all of these methods have a drawback that the detection accuracy changes when the polishing processing conditions change, and it has been difficult to stably know the polishing end point with high accuracy.

In order to solve this drawback, Japanese Patent Application Laid-Open No. 7-285050 proposes a method of detecting the thickness of a residual film by attaching a fluid micro and an optical focus position detector coaxially. However, as shown in FIG.
Detection of the thickness of the remaining film (thickness of the insulating film obtained from the second reflection surface) when polishing the insulating film 10 of the upper wiring of the second layer and thereafter is determined by the thickness of the lower insulating film 4 ( (Thickness of the insulating film obtained from the first reflecting surface), and it is difficult to accurately detect the polishing end point. In addition, since the thickness of the remaining film is detected during the polishing process, the detected pressure value of the fluid micro fluctuates due to the fluctuation of the dynamic pressure caused by the relative movement between the polishing platen and the semiconductor substrate. It was not possible to accurately detect the thickness of the remaining film with a resolution of 1 μm.

As described above, conventionally, there has been no method for monitoring the progress of polishing with high accuracy, and it has not been possible to stop the progress of polishing with high accuracy.

SUMMARY OF THE INVENTION An object of the present invention is to solve the problems of the prior art and to provide a polishing method capable of processing while accurately monitoring the thickness of a desired remaining film even in an upper insulating film. It is to be.

Another object of the present invention is to provide a polishing apparatus capable of accurately detecting the thickness of the remaining film and controlling the polishing with a high resolution of 0.1 μm.

[0014]

In order to achieve the above object, a polishing method according to the present invention is directed to a single-layer film formed on the surface of a substrate or an uppermost film of a plurality of films formed by lamination. A polishing process using a polishing pad, wherein a residual film thickness is formed at a desired portion between the single-layer film and the substrate or between the uppermost film and a film immediately below the uppermost film. A measurement mark is provided, and the distance from the surface of the remaining film thickness measurement mark and the surface of the single-layer film or the uppermost film is measured, and the single-layer film or the uppermost film on the remaining film thickness measurement mark is measured. The film thickness of the upper layer is detected, and the end point of the polishing process is controlled by the film thickness.

That is, for example, when the flattening is performed at the flattening level 8 shown in FIG.
As shown in FIG. 6, a mark 9 for measuring the remaining film thickness is formed together with the wiring layer 7 on the insulating film 4, and then, as shown in FIG. The distance from the surface of the remaining film thickness measuring mark 9 and the uppermost insulating film 10 was measured, and the film thickness of the remaining insulating film 10 on the remaining film thickness measuring mark 9 was determined from the difference between the two measured values. The thickness is determined, and the polished amount (thickness) is determined. Therefore, the end point of the polishing process can be controlled with high accuracy by using the remaining film thickness of the insulating film 10 and the polished amount (thickness) thus obtained.

For the mark for measuring the remaining film thickness, for example, a film made of a material selected from the group consisting of aluminum, copper and tungsten can be used.

The film under the uppermost layer is an insulating film,
In many cases, a wiring layer having a predetermined shape is formed on the insulating film. Therefore, in this case, both the mark for measuring the remaining film thickness and the wiring layer are formed between the insulating film and the uppermost film. When both the residual film thickness measurement mark and the wiring layer are formed on the same insulating film, the residual film thickness measurement mark and the wiring layer are simultaneously formed from the same film by one photoetching step. If it is formed, the process is simplified and preferable.

The above polishing can be performed while supplying a polishing liquid between the polishing pad and the film to be polished.

Further, the polishing apparatus of the present invention comprises a substrate holder for holding a substrate having a film to be polished formed on a surface thereof, a polishing platen for holding a polishing pad, the above-mentioned film and the above-mentioned polishing pad. Means for polishing the film by contacting and moving relative to each other at a predetermined pressure, and an end point position detector for detecting the thickness of the film reduced by the polishing, wherein the end point position detector comprises the film Detecting the thickness of the film from the difference between the height of the surface of the surface and the height of the surface of the remaining film thickness measurement mark formed in contact with the lower surface of the film,
It is characterized in that it is arranged at or near the center of rotation of the polishing platen.

That is, the polishing apparatus of the present invention has an end point position detector for detecting the thickness of the residual film reduced by polishing, and the end point position detector is provided with the surface of the film to be polished. The thickness of the film is detected from the difference between the height of the film and the height of the surface of the mark for measuring the remaining film thickness formed in contact with the lower surface of the film. Since the end position detector is arranged at or near the rotation center position of the polishing platen on which the polishing pad is disposed, the end film position detector is capable of removing the residual film with high accuracy without being substantially affected by the rotation of the polishing platen. A thickness measurement can be made.

As the end point position detector, a fluid micrometer can be used. Further, as the end point position detector, a first distance detection for irradiating an imaged light spot on the surface of the mark for measuring the remaining film thickness and obtaining the height of the mark for measuring the remaining film thickness from the reflected light. The detector can be used in combination with a second detector for determining the height of the surface of the membrane.

An end point position detector hole for disposing the end point position detector is provided on the polishing platen, and the optical refractive index substantially equal to the insulating film formed on the substrate is provided in the end point position detector hole. It is preferable to fill the liquid having the following formula to measure the thickness of the remaining film with high accuracy.

As the end point position detector, a light wave type interference film thickness measuring device can be used.

[0024]

BEST MODE FOR CARRYING OUT THE INVENTION When a semiconductor substrate whose surface is to be flattened and fixed on a substrate holder is pressed against a polishing pad on a polishing platen to carry out polishing, the remaining film of the insulating film which is the surface to be processed. To detect the thickness, for example, an optical distance detector S1
And the second distance detector S2 can be used. The optical distance detector S1 is a so-called focus position detector, and the second position detector S2 detects the position of the processing surface of the insulating film. The irradiation beam of the detector S1 reaches the bottom surface of the uppermost insulating film and is reflected by the surface of the mark for measuring the remaining film thickness.

In this state, when a relative movement is made between the irradiation beam and the uppermost insulating film, the position of the surface of the mark for measuring the remaining film thickness can be determined from the output of the optical position detector S1, The distance of the surface of the uppermost insulating film is detected by the second distance detector S2, and the thickness of the remaining uppermost insulating film is determined from the difference between the signals from the detector S1 and the second detector S2. Is required.

In the present invention, the distance detectors S1, S
Instead of 2, the fluid micrometer or the light wave type optical interference film thickness measuring device shown in FIG. 7 as described above can be used as the detector.

The fluid micrometer has the feature of being capable of real-time measurement. A relative speed difference occurs, causing a dynamic pressure in the vicinity of the fluid micrometer, causing an error in the distance measurement.

The light wave type optical interference film thickness measuring device is a measuring device utilizing the phenomenon that the intensity of reflected light changes depending on the refractive index of the film to be measured and the wavelength of irradiation light. This measuring instrument is 1
It has the features that required measurements can be performed on a table and high resolution on the order of Angstroms can be obtained, but the measurement takes a long time and real-time measurement cannot be performed. If the density is disturbed by the dynamic pressure between the semiconductor substrate and the detector, an error occurs in the measured value.

However, if the fluid micrometer and the light wave type optical interference film thickness measuring device are arranged at the position of the rotation axis of the polishing table 12 as shown in FIG. Since the peripheral speed due to rotation is almost zero,
Errors in the measured values are prevented.

According to the present invention, not only a normal polishing method using a polishing pad, but also a CMP method using a polishing liquid having a chemical etching action, or abrasive grains fixed with a resin or the like instead of the polishing pad. Even when applied to a polishing method using a pad in which a grindstone or abrasive grains are embedded, extremely favorable results are obtained.

[0031]

<Embodiment 1> As shown in FIG. 1, a semiconductor substrate 1 whose surface is to be flattened is fixed on a substrate holder 14 via an elastic pad 13 for suction, and attached on a polishing platen 12. Polishing was performed by pressing against the polishing pad 11.

An optical distance detector S1 and a second distance detector S2 are provided to detect the remaining film thickness of the insulating film 10, which is the surface to be processed. The optical distance detector S1 is a so-called focus position detector, and the second position detector S2 detects the position of the processed surface of the insulating film 10. The end point detector hole 16 formed in the polishing platen 12 is filled with a liquid (pure water in this embodiment) having a refractive index substantially the same as the optical refractive index of the insulating film 10. The irradiation beam 22 reaches the bottom surface of the insulating film 10 and is reflected on the surface of the mark 10 for measuring the remaining film thickness.

In this state, relative movement (in this embodiment, the polishing platen 12 and the substrate holder 14 are rotated) is performed between the irradiation beam 22 and the insulating film 10, and the output of the optical position detector S1 is output. The position of the surface of the mark 10 for measuring the remaining film thickness was determined from the above. On the other hand, the position of the surface of the insulating film 10 was detected by the second distance detector S2, and the thickness of the remaining film of the insulating film 10 was determined from the difference between the signals from the detector S1 and the signal from the second detector S2. .

As a result, the remaining film thickness of the insulating film 10 as the uppermost layer can be detected with a practically sufficient accuracy of 0.1 μm, and it is confirmed that it is extremely useful for controlling the end point of the polishing process. Was done.

<Embodiment 2> After a predetermined amount of polishing is performed by the method shown in FIG. 3, the load on the substrate holder 14 is reduced, and as shown in FIG. The semiconductor substrate 1 is moved to a position where the distance detectors S1 and S2 arranged in the end point detector hole 16 can be detected, and the remaining film thickness of the predetermined film formed on the semiconductor substrate 1 is reduced. It was measured.

The remaining required time was calculated from the thickness of the remaining film thus measured, and based on the result, polishing was performed again for the remaining required time.

According to this embodiment, even if the polishing rate fluctuates halfway, flattening processing could be performed with high accuracy.

<Embodiment 3> It is desirable that the size of the mark for detecting the remaining film thickness and the area where the mark for detecting the remaining film thickness be formed be as large as possible within the limits allowed by the device layout. Yes, it is difficult to make it too wide. In this embodiment, as shown in FIG. 5, the marks 9 for detecting the remaining film thickness are formed on the outer peripheral portion of the semiconductor substrate 1. As a result, it is possible to accurately detect the thickness of the remaining film without particularly precisely positioning the relative position between the semiconductor substrate 1 and the end position detector. However, the formation position of the remaining film thickness detection mark 9 is not limited to this, and the remaining film thickness detection mark 9 may be formed in the surface of the semiconductor substrate 1. that way,
This is desirable in quality control because polishing unevenness in the surface of the semiconductor substrate 1 can be monitored at the same time.

<Embodiment 4> First, as shown in FIG. 6A, a semiconductor substrate 1 having a thickness of 50
A first insulating film 2 made of a 0 nm silicon oxide film and a first wiring layer 3 having a predetermined shape were formed.

As shown in FIG. 6B, the thickness 1500
After forming a second-layer insulating film 4 made of a silicon oxide film having a thickness of 10 nm on the entire surface, polishing is performed to a level 5 to obtain a structure shown in FIG.
As shown in FIG. 6C, the surface was flattened, and a contact hole 6 was formed using well-known photo-etching as shown in FIG. 6D.

After an aluminum film having a thickness of 500 nm is formed on the entire surface, the aluminum film is patterned into a predetermined shape by using a well-known photoetching, and as shown in FIG.
The wiring layer 7 and the pattern 9 for measuring the remaining film thickness were simultaneously formed.

As shown in FIG. 6F, the thickness 1500
After forming a third insulating film 10 made of a silicon oxide film having a thickness of 10 nm on the entire surface, the remaining film thickness of the insulating film 10 is measured by using the method described in the first embodiment. Polishing was performed up to level 8 by controlling the end point. As a result, the polishing process could be completed with high accuracy at level 8.

In the conventional method, as described above, it is difficult to accurately measure the thickness of the remaining upper layer film due to the influence of the lower layer film. However, according to the present embodiment, as shown in FIG. 6E, the mark 9 for measuring the remaining film thickness is formed between the insulating film 10 to be polished and the lower insulating film 4. The noise from the lower insulating film 4 is cut off by the remaining film thickness measuring mark 9 and the upper insulating film 10 is removed.
Can be measured with high accuracy. Therefore, the formation and planarization of the upper film can be sequentially repeated without being affected by the lower film, which is particularly advantageous for forming a multilayer wiring having a large number of wiring layers.

The steps shown in FIGS. 6A to 6D correspond to the steps shown in FIGS. 2A to 2D.
In the present embodiment, the marks 9 for measuring the remaining film thickness were not used for the flattening at the flattening level 5 shown in FIG. 6B, but the flattening level 8 shown in FIG. Needless to say, a mark 9 for measuring the remaining film thickness may be formed between the insulating film 2 and the insulating film 4 in the same manner as in the case of flattening.

Embodiment 5 FIG. 7 shows an example of a detector used in the present invention. In this embodiment, the optical distance detector S
This is an example in which the first and second distance detectors S2 are integrated. The optical disc pickup used as the optical distance detector S1 has a high detection resolution of about 0.01 μm,
Very suitable. A fluid micrometer was used as the second distance detector S2.

As shown in FIG. 7, the opening of the tip of the nozzle 31 was brought close to the insulating film 4 formed on the semiconductor substrate 1, and the polishing liquid 32 was supplied to the nozzle 31 at a constant pressure P0. On the other hand, the back pressure in the nozzle 31 was detected by the pressure sensor 33. In the detector having the structure shown in FIG. 7, the signal output of the pressure sensor 33 depends on the gap between the tip of the nozzle 31 and the polished surface of the insulating film 4. Can be known with high accuracy.

As shown in FIG. 7, when the fluid micrometer is used as the distance detector S2, if the arrangement position is inappropriate, an error occurs in the measured value as described above.
In this embodiment, as in the case of FIG. 1, a distance detector S2 composed of a fluid micrometer is provided at the position of the rotation axis of the polishing plate 12.
The measurement was performed with high accuracy without causing such an error.

[0048]

As described above in detail, according to the present invention, the end point of the polishing process can be increased while monitoring the thickness of the remaining film without being affected by noise from the lower film or rotation of the rotary platen. Since the precision can be controlled and the reliability and throughput of the flattening process are remarkably improved, it is particularly useful for the flattening step in the manufacture of a semiconductor device.

[Brief description of the drawings]

FIG. 1 is a diagram for explaining a first embodiment of the present invention.

FIG. 2 is a process chart for explaining a wafer surface flattening process.

FIG. 3 is a diagram illustrating a chemical mechanical polishing method.

FIG. 4 is a diagram for explaining a second embodiment of the present invention.

FIG. 5 is a diagram for explaining a third embodiment of the present invention.

FIG. 6 is a process chart for explaining a fourth embodiment of the present invention.

FIG. 7 is a diagram for explaining a fifth embodiment of the present invention.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 ... Semiconductor substrate, 3 ... Wiring layer, 4 ... Insulating film, 9 ... Mark for detecting remaining film thickness, 11 ... Polishing pad, 12 ... Polishing surface plate, 1
4: board holder, 16: hole for end point position detector, S1, S
2 ... End point position detector

Claims (10)

[Claims] 1. A method of polishing a surface of a single-layer film formed on a surface of a substrate or an uppermost film of a plurality of films formed by lamination using a polishing pad. A mark for measuring the remaining film thickness is provided in a desired portion between the substrate and the substrate or between the film of the uppermost layer and a film immediately below the film of the uppermost layer, and the surface of the mark for measuring the remaining film thickness and the single layer Measuring the distance from the surface of the film or the uppermost film to detect the film thickness of the single layer film or the uppermost film on the mark for measuring the remaining film thickness, and determining the end point of the polishing by the film thickness. A polishing method characterized by controlling the following. 2. The mark for measuring a remaining film thickness is made of aluminum,
The polishing method according to claim 1, wherein the polishing method is made of a material selected from the group consisting of copper and tungsten. 3. The insulating film according to claim 1, wherein the mark for measuring the remaining film thickness and a wiring layer having a predetermined shape are formed between the insulating film and the uppermost film. The polishing method according to claim 1 or 2, wherein: 4. The polishing method according to claim 3, wherein the mark for measuring the remaining film thickness and the wiring layer are formed simultaneously. 5. The polishing method according to claim 1, wherein the polishing is performed while supplying a polishing liquid between the polishing pad and a film to be polished. 6. A substrate holder for holding a substrate having a film to be polished formed on the surface thereof, a polishing platen holding a polishing pad, and a film and said polishing pad being brought into contact with each other at a predetermined pressure to make a relative contact. Means for polishing the film by moving, and an end position detector for detecting the thickness of the film reduced by the polishing, wherein the end position detector comprises the height of the surface of the film and the height of the film. The thickness of the film is detected from the difference in height of the surface of the remaining film thickness measurement mark formed in contact with the lower surface, and is disposed at or near the rotation center position of the polishing plate. A polishing apparatus characterized by the above-mentioned. 7. The polishing apparatus according to claim 6, wherein said end point position detector is a fluid micrometer. 8. The end point position detector irradiates an imaged light spot onto the surface of the mark for measuring the remaining film thickness, and obtains the height of the mark for measuring the remaining film thickness from the reflected light.
7. The polishing apparatus according to claim 6, further comprising: a distance detector for determining the height of the surface of the film. 9. The polishing platen is provided with an end point position detector hole for arranging the end point position detector, and the end point position detector hole is provided substantially with an insulating film formed on the substrate. 9. The polishing apparatus according to claim 8, wherein a liquid having an equal optical refractive index is filled. 10. The polishing apparatus according to claim 6, wherein said end point position detector is a light wave type interference film thickness measuring device.