JPH11170155A - Polishing device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To easily keep the flatness of an abrasive cloth by providing, on a conditioning equipment, a mechanism moved on the surface of the abrasive cloth on the basis of the measurement result of an unevenness measuring instrument to flatten the surface. SOLUTION: When an unevenness measuring instrument is moved on a transfer bar 15 set in parallel thereto on an abrasive surface plate 11, the radius vector directional uneven form on the surface of an abrasive cloth 12 is measured. When this measurement is repeated about 6 times while rotating the abrasive surface plate 11 by about 30 deg., the unevenness on the whole abrasive cloth can be measured. The unevenness measuring instrument 14 and a conditioner 13 are moved so that the conditioner 13 reaches the position on the abrasive cloth 12 measured by the unevenness measuring instrument 14 after a fixed time. The load added to the conditioner 13 is set by transmitting a signal 19 from a control device 17 in proportional to the output 18 of the unevenness measuring instrument 14. Thus, the conditioning can be ended in a minimum time while keeping the flatness of the surface of the abrasive cloth 12.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a polishing apparatus for manufacturing semiconductor devices and the like, and more particularly, to a polishing apparatus used for a chemical mechanical polishing method in a fine processing step.

[0002]

2. Description of the Related Art In recent years, a new fine processing technology has been developed in accordance with high integration and high performance of a semiconductor integrated circuit (hereinafter referred to as LSI). The chemical mechanical polishing method (Chemical Mechanical Polishing, hereinafter abbreviated as CMP) is one of them, and is used in the process of flattening the surface of a silicon wafer, flattening an interlayer insulating film in a multilayer wiring forming process, forming a metal plug, and forming a buried wiring. This is a frequently used technology. This method is reported, for example, in US Pat. No. 4944836.

[0003] CM generally used for such applications
The P device (hereinafter, referred to as a polishing device) includes a polishing plate and a wafer holder (also called a carrier or a processing head). A polishing cloth is used for the polishing platen, and a porous resin called a backing pad is used for the wafer holder. The structure is such that a sheet is attached to support a wafer, and CMP is performed while the two are in contact / rotation via an abrasive. CMP
The wafer holder is provided with a retainer ring so that the wafer does not come off. The polishing load under normal CMP conditions is 100 to 500 g / cm ² , and the rotation speeds of the platen and the holder are both about 10 to 50 rpm.

The mechanical factors that determine the polishing rate are mainly the pressure or load during polishing and the relative speed between the substrate to be polished and the polishing cloth. Therefore, during polishing, it is necessary to maintain a uniform pressure over the entire surface of the substrate to be polished. If projections having a long period, for example, a diameter of 1 cm and a height of about several tens of microns exist on the polishing cloth, the pressure applied to the substrate to be polished increases at the projections, and the polishing rate locally increases. As described above, when the polishing rate fluctuates from place to place depending on the unevenness of the polishing cloth, the uniformity of the polishing rate deteriorates.

[0005] However, the thickness of the polishing cloth itself is about 1 mm, and thickness variations of about ± several tens of microns exist in many cases. Also, since the polishing cloth is attached to the polishing platen through a double-sided adhesive tape or an adhesive having a thickness of several to several tens of microns, irregularities of plus or minus 100 microns or more are generated on the surface of the polishing cloth after application. Things are not uncommon. Further, if the CMP is performed continuously, the abrasive grains in the polishing agent will adhere to the polishing pad surface, causing a reduction in the polishing rate and an uneven distribution of the polishing rate. In addition, the surface of the polishing cloth is worn away in the process of polishing the surface of a large number of substrates to be polished, so that the flatness of the polishing cloth in the diameter direction of the polishing platen is deteriorated, and the polishing speed becomes non-uniform.

Conditioning is performed to remove such irregularities and fixed abrasive grains generated on the surface of the polishing pad, and to keep the roughness of the polishing pad surface constant. As the conditioner, a disk-shaped or ring-shaped substrate in which diamond particles are embedded is used, and this is pressed while rotating a polishing platen to grind the polishing cloth surface. In general, since the diameter of the conditioner is smaller than the diameter of the polishing platen,
The conditioner is moved on the polishing cloth attached to the polishing platen to remove protrusions or to bring the surface into a predetermined state. Thereby, local unevenness is removed, and the polishing platen is substantially flattened in the diameter direction.

[0007]

However, a condition (hereinafter referred to as a conditioner condition) for determining a position, a pressure, a rotation speed, a processing time, a moving speed, and the like of the conditioner to which position on the polishing platen is used. If) is not optimized, a substantially flat abrasive cloth surface in the diameter direction cannot be created. For example, by repeatedly performing the polishing, a region where the substrate to be polished mainly passes through the polishing cloth is depressed, and the central portion and the peripheral portion of the polishing platen become high. When such irregularities occur on the surface of the polishing cloth, the polishing rate at the central portion of the substrate to be polished is low and the polishing speed at the peripheral portion is high, resulting in non-uniformity.

Conventionally, after conditioning is performed under predetermined conditioner conditions, the polishing pad is peeled off from the polishing platen, the thickness of the polishing pad is measured, and the distribution of the amount removed is measured.
Optimize the conditioner conditions by, for example, finding the relationship between the conditioner conditions and the remaining thickness of the polishing cloth, and flatten the polishing cloth surface using the conditioner conditions corresponding to the uneven polishing conditions. I was planning.

However, in such a method, when the flatness of the surface is greatly deteriorated, it is sometimes difficult to find conditions for returning to the flat surface. Therefore, the conditioner is changed by trial and error to change the conditioner condition. Then, a method has been practiced in which the dummy substrate is actually polished, the uniformity of the polishing rate is measured, and readjustment of the conditioner conditions is repeated. As described above, conventionally, there is no means for directly measuring the unevenness of the surface of the polishing cloth attached to the polishing platen, and the process of measuring the conditioning and the uniformity of the polishing rate has to be repeated. I was

SUMMARY OF THE INVENTION The present invention has been made for the purpose of solving the problems of the prior art, and provides a conditioning method capable of easily maintaining the flatness of a polishing cloth and a polishing apparatus provided with the mechanism. provide.

[0011]

The object of the present invention is to provide an unevenness measuring device which can measure the unevenness of a polishing cloth on a polishing platen, and the unevenness measuring device moves on the polishing platen in a diametrical direction while the unevenness of the polishing cloth surface is increased. Using a device equipped with a mechanism for measuring the conditioner and, if necessary, transmitting the output of the measurement result from the unevenness measuring device to the control mechanism of the conditioner, and changing the conditioner condition.
This is achieved by measuring the unevenness of the surface without peeling the polishing cloth and substantially flattening the polishing cloth surface under the conditioner corresponding thereto. For example, set the conditioner conditions so that the shaving amount of the portion determined as a convex by the unevenness measuring device is increased, while shaving the polishing cloth surface,
Alternatively, the flatness may be measured by using an unevenness measuring device after a predetermined amount has been cut, and the measurement may be continued until the unevenness falls within a predetermined range.

In addition, since the polishing cloth surface has many local irregularities caused by bubbles having a diameter / depth of several tens of microns and variations in fiber density on the polishing cloth surface,
It is desirable that the diameter of the stylus or probe of the unevenness measuring device be at least larger than their local unevenness. For example, if the diameter of the local irregularities on the polishing cloth surface is about 30 microns, the radius of the tip of the stylus is preferably 100 microns or more. Further, a method in which a rotating object such as a ballpoint pen tip is supported and contacted with the tip may be used.

Further, there are cases where holes or grooves having a diameter or a width of several millimeters are formed in the polishing cloth in order to facilitate the supply of the abrasive. If the stylus enters such a hole or groove, it will not be possible to measure the correct unevenness. However, the depth of these holes and grooves is generally significantly larger than the range of irregularities to be considered on the polishing cloth surface, and the depth is known, and may be significantly larger than the local irregularities of the substrate to be polished. Due to the large number, it is easy to remove them from the group of measurement data, so that the correct diametrical roughness of the polishing pad can be measured.

When the surface of the polishing cloth is measured by an unevenness measuring device while the polishing platen is stopped, an ordinary needle-shaped stylus may be used.
When measuring the rotating polishing cloth surface, measurement may not be possible with a normal needle-like stylus depending on the cross-sectional shape of holes or grooves on the polishing cloth surface. In that case, a stylus having a shape like a boat, which is long in the rotation direction of the surface plate and short in the diameter direction, may be used.

As a method of moving the unevenness measuring device on the polishing platen in the diameter direction, a guide having a known linearity in the diameter direction on the polishing platen is installed, and the guide is moved along the guide. You can do it. The guide may be in the form of a metal rod, or may be one that moves while electrically measuring and correcting the position.

In the case where the structure of the polishing platen is not the disk type but a belt type, an unevenness measuring device which moves perpendicularly to the moving direction of the polishing pad is installed, and conditioning can be performed in the same manner. . It is desirable that the unevenness measuring instrument has a resolution of ± 10 microns, preferably ± 5 microns or less. If the resolution is less than ± 2.5 microns, the measurement accuracy can be further improved by performing statistical processing of the data.

The unevenness measuring device may be other than the above-mentioned mechanical measuring device. For example, the distance may be optically measured using a semiconductor laser.

[0018]

(Embodiment 1) An unevenness measuring device 14 for a polishing cloth surface used in this embodiment is mounted on a polishing cloth 12 in a polishing apparatus as shown in FIG. There is a projection perpendicular to the surface of the polishing cloth from the unevenness measuring device, and the projection comes into contact with the surface of the polishing cloth and expands and contracts according to the unevenness of the polishing cloth. Then, a voltage signal 18 proportional to the amount of expansion / contraction is output. The tip of the projection has a structure in which a ball having a diameter of 10 mm is supported (similar to the tip of a ballpoint pen), and has an effect of reducing friction and unevenness noise.

When this unevenness measuring device is moved on a transfer rod 15 installed in parallel on the polishing table 11, the unevenness of the polishing cloth surface in the radial direction is measured. When this measurement is repeated six times while rotating the polishing platen by 30 degrees, the unevenness of the entire polishing cloth is measured as shown in FIG. When the polishing platen is rotated once by fixing the unevenness measuring device, the unevenness in the concentric direction is measured.

FIG. 2 shows the results of measurement of the unevenness on the surface of the polishing pad subjected to conditioning by the conventional method. The polishing cloth is IC-1000 manufactured by Rodel Nitta. The portion between the center and the outer periphery of the polishing cloth tends to be cut deepest because the conditioner frequently reciprocates that portion to scrape off the surface layer. As described above, the unevenness of the polishing cloth surface is uniaxially symmetric, and it is possible to indicate almost the entire structure by the measured value of only the radius portion. Therefore, hereinafter, only the measurement of this portion is performed.

Next, the method of the present invention for performing conditioning based on the measurement results of the unevenness measuring device will be described.

The polishing platen is rotated to operate the unevenness measuring device. The conditioner uses a 5-inch diamond disk 13 and moves on a polishing cloth following an unevenness measuring device. That is, as shown in FIG. 3, the two are moved so that the conditioner 13 comes to a position on the polishing cloth measured by the unevenness measuring device 14 after a predetermined time. When both move in the radial direction as shown in FIG. 3, the position on the polishing cloth always passes between them with a constant time difference.
In the polishing apparatus of this embodiment, since the position of the unevenness measuring device and the conditioner are shifted by 60 degrees, when the rotation speed of the platen is 30 rpm, the two pass through both at a time difference of 1/3 second.

In this embodiment, the load applied to the conditioner is set by sending a signal 19 from the control device 17 in proportion to the output 18 of the unevenness measuring device. The proportionality factor can be changed by the operator. If the proportional coefficient is too small, the condition becomes the same as that of the conventional conditioning. If the proportional coefficient is too large, the unevenness of the polishing pad may become large. It is necessary to set an optimum proportional coefficient according to the hardness of the polishing pad and the cutting speed of the conditioner. The signal of the unevenness measuring instrument is 1/3
After a second, the load is transmitted to the conditioner and the load increases and decreases. In the present embodiment, an average load of 200 g / cm ² was applied to the polishing cloth IC-1000, and a load of 50 g / cm ² was added to the surface protrusion of 10 μm.

By this method, conditioning can be performed for 20 times.
FIG. 4 shows the results of the measurement performed for one minute. It can be seen that the irregularities of 10 μm or less are flattened, and the irregularities of 50 μm or more of the conventional conditioning are flattened. Moreover, in the conventional method, the flatness of the polishing cloth surface has been reduced every time conditioning is performed.
With the method of the present invention, conditioning could be completed in a minimum time while always maintaining flatness. In addition, in this embodiment, the polishing cloth which has already deteriorated in flatness is already conditioned, but when the conditioning of the present invention is repeated each time CMP is performed, the clogging of the polishing abrasive grains should be prevented by the conditioning for 5 minutes or less. Was possible.

(Embodiment 2) In this embodiment, a method for performing conditioning and flattening until the unevenness value of the polishing cloth surface measured by an unevenness measuring instrument becomes a predetermined value or less will be described. Further, the unevenness detector in this embodiment is a combination of a semiconductor laser and a detector, and has a mechanism for detecting the unevenness by measuring the distance to the polishing bat. Example 1
1 in the same manner as described above. The accuracy is higher than that of the mechanical unevenness detector of the first embodiment.

First, the polishing platen is rotated to operate the unevenness measuring device. The polishing cloth IC-1000 conditions the state shown in FIG. When the unevenness measuring device moves in the radial direction, the position where the polishing cloth surface is most concave is used as a reference. Next, conditioning of the convex portion was started by applying a load of 200 g / cm ² , and 10% from the reference value.
The conditioner moves in the radial direction when the concavo-convex value of only micrometers is reached. Therefore, the conditioning time of the reference point is the shortest, and the convex portion performs conditioning over time. Finally, when the surface height of the polishing cloth indicated by the unevenness measuring device becomes equal to the reference value, the planarization of the entire polishing cloth is completed.

FIG. 5 shows the result of conditioning for 20 minutes by this method.

It can be seen that the irregularities of 10 μm or less are flattened, and the irregularities of 100 μm or more of the conventional conditioning shown in FIG. 3 are flattened. Moreover, in the conventional method, the flatness of the surface of the polishing pad deteriorates every time conditioning is performed, but in the method of the present invention, the conditioning can be completed in a minimum time while always maintaining the flatness. Also,
In this example, the polishing cloth having already flatness is already conditioned, but if the conditioning of the present invention is repeated every time the CMP is performed, it is possible to prevent clogging of the abrasive grains by conditioning for 5 minutes or less. Met.

(Embodiment 3) In this embodiment, a data processing method in a case where a polishing pad has grooves or holes will be described. The polishing cloth is an IC 1000 having grooves of about 15 mm pitch and 3 mm width and 0.5 mm depth formed over the entire polishing cloth. If the stylus enters such a groove, it is impossible to measure the correct unevenness. Therefore, a process of removing those data from the group of the measurement data is performed. Thereby, the unevenness of the polishing cloth in the correct diameter direction can be measured.

FIG. 6 shows the result. The measured value is shown on the lower side, and the data overflows due to the stylus falling into the groove. Since the depth of the groove is about 0.5 mm, the step setting value is set to 0.3 mm, and any value exceeding this value is excluded. The line obtained by removing and re-processing this data is the upper data. By performing the data processing in this manner, it is possible to adjust the polishing load according to the unevenness value as described in the first embodiment, and to perform conditioning until the unevenness value becomes a certain value or less as described in the second embodiment. Can be used.

(Embodiment 4) In this embodiment, the effect of wafer polishing uniformity when CMP was performed with a conventional conditioned polishing cloth and the conditioned polishing cloth of the present invention was evaluated. The polishing cloth subjected to the conventional conditioning has the surface unevenness “before the conditioning of the present invention” in FIG. 4, and the polishing cloth “after the conditioning of the present invention” has a surface roughness of 1% as shown in FIG.
The surface irregularities are flattened to 0 μm or less.

For the sample for which the polishing uniformity was measured, a silicon oxide film was formed to a thickness of 500 nm on a silicon substrate, a 50 nm-thick TiN layer was formed thereon as an adhesive layer, and then a copper thin film was formed to a thickness of 800 nm. It is a film continuously formed in a vacuum by the method.

FIG. 7 shows the structure of the polishing apparatus. In FIG. 7, 16 is a pure water supply port, 71 is a wafer holder, 72 is a wafer, 73 is a backing pad, 74 is a retainer ring, and 75 is an abrasive supply port. The abrasive is supplied from a first supply port 75 provided on a surface plate to a polishing pad at about 30 cc / cm.
CMP is performed by dropping at a speed of min. The polishing load during CMP was 150 g / cm ² , and the rotation speeds of the platen and the holder were both 30 rpm. The abrasive used was a mixture of 30% hydrogen peroxide solution (a commercially available 30% aqueous solution) in an alumina abrasive manufactured by Rodel Nitta. The CMP time is 3 minutes. At the end of the CMP, the first supply port 75 is closed to stop the supply of the polishing liquid, and pure water is supplied from the second supply port 16 at a speed of about 3000 cc / min to flush 15 times.
Perform for ~ 30 seconds. Thereafter, the wafer is washed and dried.

As shown in FIG. 8, the polishing uniformity of the wafer which was subjected to the CMP using the conventional conditioned polishing cloth was about 30%, and the polishing amount at the outer peripheral portion of the wafer was larger than that at the central portion. This is considered to be because the polishing rate was increased because the polishing cloth was convex at the wafer peripheral portion, and the substantial over-polishing amount became larger than that at the wafer central portion. On the other hand, the wafers subjected to CMP with the conditioned polishing cloth of the present invention have polishing uniformity of 1%.
It could be reduced to 0% or less.

Therefore, by performing CMP using the conditioned polishing cloth of the present invention, the uniformity of polishing was improved.

[0036]

According to the polishing apparatus provided with the unevenness detector and the conditioning device of the present invention, the CMP can be performed while confirming the flatness of the polishing pad, so that the uniformity of the CMP is improved. In addition, since the polishing pad is conditioned and flattened in an optimum time, the life of the polishing pad is prolonged.

[Brief description of the drawings]

FIG. 1 is a front view showing a schematic configuration of a polishing apparatus according to the present invention.

FIG. 2 is a schematic diagram showing the surface irregularities of the entire polishing cloth subjected to conventional conditioning.

FIG. 3 is a plan view showing a positional relationship between an unevenness measuring instrument and a conditioner in the polishing apparatus of the present invention.

FIG. 4 is a measurement diagram of surface irregularities of the conditioned polishing cloth of Example 1 of the present invention.

FIG. 5 is a measurement diagram of surface irregularities of a conditioned polishing cloth according to Example 2 of the present invention.

FIG. 6 is an explanatory diagram of a method for illustrating surface irregularities excluding grooves of a polishing cloth.

FIG. 7 is a front view of the CMP apparatus.

FIG. 8 is a measurement diagram showing polishing uniformity.

[Explanation of symbols]

11: polishing platen, 12: polishing cloth, 13: conditioner, 14: unevenness measuring instrument, 15: transfer rod, 16: pure water supply port, 17: control device, 18: voltage signal converted from unevenness value, 19 ... Conditioner pressurization / movement signal, 61 ... C
u, 62 ... TiN, 63 ... SiO 2, 64 ... Si 3 N 4,
65: Si substrate, 71: Wafer holder, 72: Wafer,
73: backing pad, 74: retainer ring, 7
5 ... Abrasive supply port.

 ──────────────────────────────────────────────────続 き Continued on the front page (72) Inventor Masayuki Nagasawa 1-280 Higashi Koigakubo, Kokubunji-shi, Tokyo Inside Central Research Laboratory, Hitachi, Ltd.

Claims (6)

[Claims] An apparatus for measuring irregularities on the surface of a polishing cloth (hereinafter referred to as an apparatus).
And a device for applying a load to the polishing cloth to scrape the surface layer of the polishing cloth (hereinafter referred to as conditioning). The conditioning device performs polishing based on the measurement result of the roughness measuring device. A polishing apparatus comprising a mechanism for moving and flattening a cloth surface. 2. A mechanism for flattening a polishing cloth by increasing or decreasing a load applied to a conditioning device as a function of the size of the roughness of the polishing cloth surface measured by the roughness measuring device. The polishing apparatus according to claim 1. 3. A means for measuring the unevenness of the polishing cloth surface by using an unevenness measuring device after the conditioning, and repeating this process until the unevenness value of the polishing cloth surface reaches a certain value or less. Item 3. The polishing apparatus according to Item 1 or 2. 4. An instrument for measuring the unevenness is a stylus type,
4. The tip according to any one of claims 1 to 3, wherein the tip of the stylus has a spherical surface or a disk with a radius of 100 microns or more, or a gently and thicker shape, or a rotating object. The polishing apparatus according to the above. 5. An apparatus for measuring unevenness, comprising: a guide whose linearity is maintained within a predetermined range; and a guide for measuring the unevenness while moving in a predetermined direction on a polishing cloth based on the guide. The polishing apparatus according to any one of claims 1 to 4, further comprising a stylus probe and a mechanism for detecting a movement position with respect to a predetermined reference point. 6. A mechanism according to claim 1, further comprising a mechanism for removing data when the measured data of the unevenness exceeds a predetermined set value (hereinafter referred to as a step set value). Polishing equipment.