JP2002103202A - Polishing method and polishing device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To effectively use an abrasive cloth and prolong a life of a dresser by dispensing with or restraining to be minimal an initial dress, and to perform precise working. SOLUTION: When the abrasive cloth 13 is replaced with a new cloth, a conversion factor for converting an integral value of a rotation torque of a surface plate 12 at working into a working amount is initially set by a trial working of a first workpiece, the integral value is found at working, and working of following workpieces are performed such that a target working amount found using the integral value and the conversion factor is achieved. The working amount by such a working is measured, and when the measured working amount is deviated from an allowable value of the target working amount, the conversion factor is corrected while taking a difference between both working amounts into consideration.

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 an apparatus for performing an MP (Chemical Mechanical Polishing) process or the like, and more particularly, to an effective use of a polishing cloth and an extension of a dresser life.

[0002]

2. Description of the Related Art FIG. 4 is a view showing an outline of a processing portion of a conventional polishing apparatus main body (mechanical portion) 10, and a surface plate 12 is attached to an upper end of a rotating shaft 11. Surface plate 1
A polishing cloth 13 composed of a soft layer 13a and a hard layer 13b is affixed to the surface of 2 as shown in FIG. In addition, on the surface of the hard layer 13b, a grid-shaped groove 14 is provided.

A polishing head 15 is disposed above the surface plate 12 so as to face the surface plate 12. The polishing head 15 has a top plate 17 attached to a lower end of a rotating shaft 16, and holds a plate-like workpiece W such as a wafer on a lower surface of the top plate 17 via a backing pad 18. A guide ring 19 is attached to a lower surface of the top plate 17 via a backing pad 18 so as to prevent the workpiece W from jumping out.

A dresser 20 is arranged above the surface plate 12 in parallel with the polishing head 15. The dresser 20 includes a rotating shaft 21 and a dressing tool 22 attached to a tip of the rotating shaft 21.
The dressing tool 22 includes a base 23 and the base 2
3 has a chip 24 attached to the vicinity of the outer periphery of the lower surface thereof, and abrasive particles such as finely ground diamond abrasive particles are attached to the surface of the chip 24.

A polishing cloth 1 is provided above the center of the surface plate 12.
A nozzle 26 for supplying the abrasive 25 is disposed on the surface of the nozzle 3.

In the CMP processing by this polishing apparatus, the polishing plate 15 is rotated toward the platen 12 by rotating the platen 12 and the polishing head 15 while supplying the abrasive 25 from the nozzle 26, as shown in FIG. The workpiece W is pressed with the pressing force of
Pressing against the surface of.

In the meantime, in the CMP processing, it is necessary to measure the processing amount during the processing because the processing amount is minute and the surface to be processed is pressed against the surface of the polishing pad 13 and does not appear outside. Conventionally, since the rotation torque of the surface plate 12 during the processing shown in FIG. 6 has been detected, the integral value of the surface plate rotation torque (the area of the hatched portion in FIG. 6) has become a predetermined value. By the way, a method has been proposed in which the processing end point is reached, that is, a predetermined processing amount is reached.

In the method of estimating the machining amount based on the integral value of the surface plate rotation torque, the integral value has a correlation with the machining amount because the surface plate rotation torque is related to the work amount, that is, the machining amount. In fact, it has been confirmed that the integrated value of the platen rotational torque and the machining amount have a high correlation as shown in FIG.

However, the correlation between the integrated value of the rotation torque of the platen and the machining amount may be slightly different depending on the surface condition of the polishing pad 13 and the like. In the CMP processing, a method of managing the processing amount based on the processing time is generally adopted, in which the relationship between the processing time and the processing amount is obtained in advance, irrespective of the method using the correlation.

[0010]

By the way, the method of managing the processing amount by the processing time is more affected by the surface condition of the polishing pad 13 than the above-mentioned method utilizing the correlation between the integrated value of the rotating torque of the platen and the processing amount. Therefore, when the polishing cloth 13 is replaced with a new one, the new polishing cloth 13 is not used as it is, but is dressed with the dresser 20 shown in FIG. It is used after the surface of the polishing cloth 13 is smoothed (hereinafter referred to as an initial dress).

FIG. 8 shows a change in the processing amount with respect to a predetermined processing time when dressing is performed in parallel with the processing. In FIG. And the amount of processing becomes stable as the initial dress advances.

However, the extent to which the initial dress is performed to obtain a sufficient effect depends on the initial surface properties of the polishing pad 13. Therefore, it is actually determined empirically. In addition, the polishing cloth 13 has a problem that the initial dressing time cannot be constant because the individual difference of the surface property is large due to the difference of the production lot.
At the processing site, the actual situation is that the processing is started after performing an initial dress that is too sufficient based on experience without measuring the initial surface properties of all the polishing cloths 13 to be used.

Since the dresser 20 is a tool for scraping the surface of the polishing pad 13, the initial dress wastes the polishing pad 13, and the initial dress is not inexpensive. In addition, the actual operation rate is reduced, the production amount per unit time is reduced, and the processing cost is increased.

The present invention has been made in order to solve the aforementioned problems.
It is an object of the present invention to provide a polishing method and a polishing apparatus capable of minimizing or reducing the number of initial dresses, effectively using a polishing pad and extending the life of a dresser, and at the same time, enabling more accurate processing.

[0015]

In order to achieve the above object, a polishing method according to the present invention comprises a polishing head for holding a workpiece, a polishing head arranged opposite to the polishing head, and a relative movement with respect to the polishing head. And a polishing machine comprising: a surface plate having a polishing cloth on a surface thereof; and a dresser arranged in parallel to the polishing head to face the surface plate and dressing the polishing cloth. A method of polishing the surface of the above, wherein after replacing the polishing cloth with a new one, a first workpiece is trial-processed, and an integrated value and a processing amount of a platen rotational torque at the time of the trial processing are obtained. A trial processing step of calculating and initially setting a conversion coefficient for converting the integrated value into a processing amount, and similarly obtaining an integrated value of the platen rotational torque and calculating the product. An actual machining step of machining the second and subsequent workpieces to achieve the target machining amount calculated using the value and the conversion coefficient, a step of measuring the actual machining amount after the actual machining step, A step of determining whether the amount is within an allowable value of the target machining amount; and, when the actual machining amount is out of the allowable value of the target machining amount, an integrated value of a platen rotation torque in the actual machining step. And a step of calculating a new conversion coefficient from the value obtained by adding the difference between the two processing amounts to the actual processing amount, and sequentially correcting the conversion coefficient set in advance.

In this polishing method, the machining amount is estimated from the integral value by utilizing the fact that the integral value of the surface plate rotating torque at the time of machining and the machining amount have a substantially predetermined correlation, and the actual machining amount is equal to the predetermined value. It is processing to become
Detecting the integral value and the actual machining amount during the actual machining process,
When the actual machining amount is out of the target machining amount tolerance, the conversion coefficient is calculated taking into account the difference between the two machining amounts, and the previously set conversion coefficient is sequentially modified, so that the initial dress Even if the polishing cloth or initial dress is not enough, and the processing efficiency is reduced or the processing instability phenomenon occurs, the actual processing amount closer to the target processing amount can be obtained. In addition, effective use of the polishing cloth and prolongation of the life of the dresser can be achieved, and more accurate processing can be performed.

It is preferable to dress the polishing cloth surface with the dresser in parallel with or before or after the trial processing step and the actual processing step. Further, instead of calculating and initially setting the conversion coefficient in the trial processing step, a conversion coefficient may be obtained in advance, and this may be initially set. In this case, the conversion coefficient may be set in parallel with the actual processing step. It is preferable to dress the polishing cloth surface with a dresser before or after. Furthermore, if the rate of change of the conversion coefficient with the progress of the actual processing step and / or dressing is determined in advance and added to the correction of the conversion coefficient, a more accurate processing amount can be obtained.

According to another aspect of the present invention, there is provided a polishing apparatus, comprising: a polishing head for holding a workpiece; a polishing head disposed to face the polishing head, and performing a relative motion with the polishing head; A polishing apparatus comprising: a surface plate having a polishing cloth on its surface; and a dresser arranged parallel to the polishing head so as to face the surface plate and dressing the polishing cloth. Means for calculating an integrated value, means for measuring the actual processing amount of the workpiece from the start of processing to the end of processing, and the integrated value from the start of processing to the end of processing obtained by the means for obtaining the integrated value, and A calculation unit for calculating a conversion coefficient for converting the integral value into a processing amount from the actual processing amount, and a processing opening for the processing of each workpiece. A command unit for issuing a machining end signal for the workpiece when the integrated value from the above reaches a target integrated value calculated from the preset target machining amount using the conversion coefficient, and the actual machining amount Means for judging whether or not the target machining amount is within the allowable value, and when the actual machining amount is outside the target machining amount allowable value, the conversion coefficient is corrected in consideration of a difference between the two machining amounts. And means for performing the operation.

According to this polishing apparatus, the above polishing method can be automatically performed. In addition,
The arithmetic unit, after replacing the polishing cloth with a new one, calculates a conversion coefficient from the actual machining amount at an arbitrary machining time and the integrated value of the platen rotation torque at that time, and sets it as an initial setting value. It may be configured, or may be configured to set a conversion coefficient obtained in advance as an initial setting value.

[0020]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described below with reference to FIGS. FIG. 1 is a control block diagram of a polishing apparatus according to the present invention.
Polishing device body (mechanical part) whose main parts are shown in FIG.
It is. The surface plate 12 of the polishing apparatus main body 10 includes:
It is rotationally driven by a DD (direct drive) motor 31 controlled by a motor driver 30.

Numeral 32 denotes a polishing machine computer, which is operated by an operator 33 to process conditions, that is, the surface plate 12.
And the number of rotations of the polishing head 15 and the dresser 20 shown in FIG.
The polishing apparatus main body 10 is automatically operated via the sequencer 34 by inputting and setting a pressing force of 0 or the like.

A process monitor 35 is connected to the motor driver 30 to receive the rotational torque of the surface plate 12. Surface plate 12 taken into process monitor 35
Is taken into the data processing operation unit 41 of the processing end point detection computer 40, and the data processing unit 4
In step 1a, integration is started by a data processing start signal transmitted from the sequencer 34, and a torque integrated value during machining is obtained.

The integrated torque value during machining obtained by the data processing operation unit 41 is taken into the coefficient condition operation unit 42.
The coefficient condition calculating section 42 is provided in the polishing apparatus main body 10.
The work W actually processed is preferably automatically taken out, and the work amount is taken in from the machined film thickness measuring device 36 for automatically measuring the work amount, and the work amount and the data processing calculation unit 41 are taken in. From the integrated torque during machining, a conversion coefficient for converting the integrated torque into the machining amount is calculated and stored.

The coefficient condition calculating section 42 fetches a target processing amount for detecting a processing end point set by the operator 33 in the initial condition setting section 43, and uses the conversion coefficient to set a target processing amount corresponding to the target processing amount. The torque integrated value is calculated, and the target torque integrated value is given to the data processing calculation unit 41 as a processing stop condition.

The data processing operation unit 41 compares the target torque integrated value fetched from the coefficient condition operation unit 42 with the in-process torque integrated value obtained as described above by the data judgment unit 41b.
When the torque integrated value during processing reaches the target torque integrated value, a processing end signal is transmitted from the command unit 41c to the sequencer 34, and the CMP processing for one workpiece W is completed.

The coefficient condition calculating section 42 is configured to calculate a conversion coefficient for each workpiece W. In addition, in the processing performed after the calculation and storage of the preceding conversion coefficient, the processing film is processed. The processing amount fetched from the thickness measuring device 36 is compared with the target processing amount, and if the target processing amount is within an allowable value (for example, within ± 2%) set in advance as a data processing condition in the initial condition setting unit 43. For example, it is configured to leave the preceding conversion coefficient as it is and to calculate a new conversion coefficient by taking into account the difference between the taken-in processing amount and the target processing amount when the conversion coefficient is out of the predetermined range, and to correct the conversion coefficient. ing.

Next, the operation of the polishing apparatus will be described with reference to the flowchart of FIG. The operator 33 inputs and sets processing conditions such as the number of revolutions of the platen 12, the polishing head 15 and the dresser 20, and the pressing force of the polishing head 15 and the dresser 20, into the polishing apparatus computer 32.

After these initial settings, initial dressing is preferably performed for about 5 minutes. As shown in FIG. 2, first, in order to obtain a conversion coefficient for converting the torque integrated value into a processing amount, the actual processing is performed. The first workpiece W is trial-processed under the same processing conditions. At this time, the rotation torque of the surface plate 12 is taken into the data processing calculation unit 41 from the motor driver 30 by the process monitor device 35. The data processing calculation unit 41 starts the sequencer 34
, The data processing unit 41a starts integration of the rotational torque of the surface plate 12. This trial processing is performed for an arbitrary predetermined time, and a torque integrated value A0 during that time is obtained.

Incidentally, during the trial processing, in parallel with the processing,
Alternatively, dressing of the polishing pad 13 by the dresser 20 shown in FIG. 4 is performed for a predetermined time after the trial processing, as is generally performed in the CMP processing. This dressing is performed in the same manner in the actual processing described below.

When the trial processing is completed, the processed amount B0 is measured by the processed film thickness measuring device 36. Coefficient condition calculator 4
2 fetches the machining amount B0 and the torque integral value A0, and calculates a conversion coefficient C0 for converting the torque integral value A0 into the machining amount B0. This conversion coefficient C0 is stored and set in the coefficient condition calculation unit 42 as an initial conversion coefficient.

After the trial machining, the operator 33 sets the target machining amount in the initial condition setting section 43 and starts the actual machining of the second and subsequent workpieces W. Prior to the actual machining of the second workpiece W, the coefficient condition computing unit 42 captures the target machining amount set in the initial condition setting unit 43, and uses the conversion coefficient C0 obtained in the trial machining to set the target machining amount. A target torque integral value corresponding to the machining amount is calculated.

In the actual machining of the second workpiece W, the target torque integral value and the in-machining torque integral value An obtained by the data processing operation unit 41 in association with the actual machining are determined by the data judgment unit 4.
The comparison is made at 1b until the integrated torque value during machining An reaches the target integrated torque value. Integral torque during machining A
When n reaches the target torque integrated value, the command section 41c sends a processing end signal to the sequencer 34 to end the actual processing of the second workpiece W.

When the actual machining of the second workpiece W is completed, the machining amount Bn is measured by the machined film thickness measuring device 36, and the conversion coefficient Cn is calculated based on the machining amount Bn and the target torque integrated value. , Conversion coefficient C0 obtained by trial processing
Is replaced with the new conversion coefficient Cn.

Next, the coefficient condition calculating section 42 determines whether or not the difference between the processed amount Bn measured by the processed film thickness measuring device 36 and the target processed amount is, for example, within ± 2%, and if it is within ± 2%. For example, the process shifts to actual machining of the third workpiece W, and
The actual processing is performed in the same manner as the actual processing of the sheet W to be processed.

On the other hand, when the difference between the processed amount Bn measured by the processed film thickness measuring device 36 and the target processed amount is out of, for example, ± 2%, the conversion coefficient Cn is corrected by the coefficient condition calculating section 42. . The correction of the conversion coefficient Cn is performed by multiplying the new conversion coefficient Cn by the deviation ratio of the measured processing amount Bn with respect to the target processing amount, and the corrected conversion coefficient Cn + 1 is newly obtained. Is set.

The correction of the conversion coefficient is performed as needed for each workpiece W. Therefore, even if the surface properties of the polishing pad 13 change with the progress of the processing, the change can be dealt with. Since the conversion coefficient is set, the deviation of the actual machining amount from the target machining amount can be further reduced. The operation is terminated when the processing of the target number of workpieces W is completed.

FIG. 3 shows that after performing an initial dress for 5 minutes, processing is performed by the above-described method of the present invention.
The processing amount and the time required for continuously processing the oxide film of 250 wafers while performing dressing in parallel with this processing are shown for every ten wafers. As is apparent from this figure, according to the present invention, it is possible to shorten the initial dress time and obtain a processing amount with less variation.

In the above-described embodiment, an example in which the initial conversion coefficient is obtained by trial processing has been described. However, the present invention is not limited to this, and conversion is performed in accordance with the surface properties of a specific polishing pad 13. The trial processing may be omitted by obtaining the coefficients in advance and storing them in a database, and quoting the initial set values from the coefficients.
In addition, the change ratio of the conversion coefficient accompanying the progress of processing and dressing is obtained in advance, and this is also stored in a database,
By taking into account the correction of the conversion coefficient Cn described above, a more accurate actual machining amount can be obtained.

[0039]

As described above, according to the present invention, it is possible to obtain a processing amount close to a target processing amount without performing an initial dress or only by performing a smaller initial dress. The effect that effective utilization and extension of the dresser life can be achieved is obtained.

[Brief description of the drawings]

FIG. 1 is a control block diagram showing an embodiment of a polishing apparatus according to the present invention.

FIG. 2 is a flowchart showing an embodiment of a polishing method according to the present invention.

FIG. 3 is a diagram showing an example of a processing amount and a processing time when processing is performed by a polishing method according to the present invention.

FIG. 4 is a schematic sectional view showing an example of a processing section of a polishing apparatus to which the present invention is applied.

FIG. 5 is a plan view and a partially enlarged perspective view of a polishing cloth in the polishing apparatus shown in FIG. 4;

FIG. 6 is a diagram showing an example of a platen rotation torque during processing.

FIG. 7 is a diagram showing a correlation between a machining amount and a platen rotation torque integrated value.

FIG. 8 is a diagram showing changes in the number of processed wafers and the amount of processing.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 10 Polishing apparatus main body 12 Surface plate 13 Polishing cloth 15 Polishing head 17 Top plate 18 Backing pad 19 Guide ring 20 Dresser 22 Dressing tool 23 Base 24 Chip 25 Abrasive 26 Nozzle 30 Motor driver 31 DD motor 32 Polishing apparatus computer 34 Sequencer 35 Process Monitor device 36 Processing film thickness measuring device 40 Computer for processing end point detection 41 Data processing calculation unit 41a Data processing unit 41b Data determination unit 41c Command unit 42 Coefficient condition calculation unit 43 Initial condition setting unit W Workpiece.

Claims (8)

[Claims] 1. A polishing head for holding a workpiece, a platen disposed opposite to the polishing head, performing a relative movement with the polishing head, and having a polishing cloth on a surface thereof; A method of polishing the surface of the workpiece by a polishing apparatus including a dresser that is disposed in parallel to the surface plate and dresses the polishing cloth, wherein the polishing cloth is a new one. After the replacement, the first workpiece is trial-processed, an integrated value of the platen rotation torque and the processing amount at the time of the trial processing are obtained, and a conversion coefficient for converting the integrated value into the processing amount is calculated. A trial machining step for initial setting; and similarly calculating an integrated value of the platen rotation torque, and applying the second and subsequent applied machining amounts to the target machining amount calculated using the integrated value and the conversion coefficient. An actual machining step of machining an object; a step of measuring an actual machining amount after the actual machining step; a step of determining whether the actual machining amount is within an allowable value of the target machining amount; Is outside the allowable value of the target machining amount, a new conversion coefficient from the integrated value of the platen rotation torque during the actual machining process and the value obtained by adding the difference between the two machining amounts to the actual machining amount. And a step of sequentially correcting the conversion coefficient that has been calculated and set in advance. 2. The polishing method according to claim 1, wherein the dresser dresses the surface of the polishing cloth in parallel with or before or after the trial processing step and the actual processing step. 3. A polishing head for holding a workpiece, a platen disposed opposite to the polishing head, performing a relative movement with the polishing head, and having a polishing cloth on a surface thereof; A method of polishing the surface of the workpiece by a polishing apparatus including a dresser that is disposed in parallel to the surface plate and dresses the polishing cloth, wherein the polishing cloth is a new one. When replacing, a process of initial setting a conversion coefficient for converting the integrated value of the platen rotational torque at the time of processing previously obtained into the machining amount, and obtaining the integrated value of the platen rotational torque and An actual machining step of machining the workpiece to be a target machining amount calculated using the conversion coefficient, and a step of measuring an actual machining amount after the actual machining step; A step of determining whether or not the actual machining amount is within an allowable value of the target machining amount; and, when the actual machining amount is out of the allowable value of the target machining amount, a platen rotation torque during the actual machining process. Calculating a new conversion coefficient from the integrated value of the above and the value obtained by adding the difference between the two processing amounts to the actual processing amount, and sequentially correcting the previously set conversion coefficient. Polishing method. 4. The polishing method according to claim 3, wherein the dressing is performed on the surface of the polishing pad with the dresser in parallel with or before or after the actual processing step. 5. The method according to claim 1, wherein a rate of change of the conversion coefficient with the progress of the actual machining step and / or dressing is obtained in advance, and is added to the correction of the conversion coefficient. The polishing method according to one of the above. 6. A polishing head for holding a workpiece, a platen disposed opposite to the polishing head and performing a relative movement with the polishing head, and having a polishing cloth on a surface thereof; A polishing device comprising a dresser arranged in parallel to the surface plate and dressing the polishing cloth, wherein a means for obtaining an integrated value of a rotation torque of the surface plate; and Means for measuring the actual machining amount of the workpiece, and converting the integral value into a machining amount from the integral value from the machining start to the machining end obtained by the means for calculating the integral value and the actual machining amount. A calculating unit for calculating a conversion coefficient for the processing of each of the workpieces, wherein the integrated value from the start of the processing is obtained by converting the integrated value from a preset target processing amount. A command unit that issues a machining end signal for the workpiece when the target integral value calculated using the number is reached, and a unit that determines whether the actual machining amount is within an allowable value of the target machining amount. And a means for correcting the conversion coefficient in consideration of a difference between the two machining amounts when the actual machining amount is out of the allowable value of the target machining amount. 7. The arithmetic unit calculates a conversion coefficient from an actual machining amount for an arbitrary time after the replacement of the polishing pad with a new one and an integral value of the platen rotation torque at that time, and sets the conversion coefficient as an initial setting value. 7. The polishing apparatus according to claim 6, wherein the polishing apparatus is configured to set. 8. The polishing apparatus according to claim 6, wherein said arithmetic unit is configured to set a previously obtained conversion coefficient as an initial setting value.