US20200061774A1 - Method for determining polishing pad height and polishing system - Google Patents
Method for determining polishing pad height and polishing system Download PDFInfo
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- US20200061774A1 US20200061774A1 US16/542,312 US201916542312A US2020061774A1 US 20200061774 A1 US20200061774 A1 US 20200061774A1 US 201916542312 A US201916542312 A US 201916542312A US 2020061774 A1 US2020061774 A1 US 2020061774A1
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- dresser
- height
- polishing
- polishing pad
- dressing
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- 238000005498 polishing Methods 0.000 title claims abstract description 381
- 238000000034 method Methods 0.000 title claims abstract description 27
- 238000012937 correction Methods 0.000 claims abstract description 78
- 239000000758 substrate Substances 0.000 claims abstract description 69
- 230000008859 change Effects 0.000 claims abstract description 53
- 238000005299 abrasion Methods 0.000 claims description 31
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- 238000004364 calculation method Methods 0.000 claims description 22
- 238000012544 monitoring process Methods 0.000 claims description 20
- 230000010355 oscillation Effects 0.000 description 14
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- 239000006061 abrasive grain Substances 0.000 description 5
- 239000004065 semiconductor Substances 0.000 description 5
- 239000002002 slurry Substances 0.000 description 5
- 238000009825 accumulation Methods 0.000 description 4
- 239000000126 substance Substances 0.000 description 4
- 238000005516 engineering process Methods 0.000 description 3
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- 230000009471 action Effects 0.000 description 2
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- 239000010432 diamond Substances 0.000 description 2
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- VYPSYNLAJGMNEJ-UHFFFAOYSA-N Silicium dioxide Chemical compound O=[Si]=O VYPSYNLAJGMNEJ-UHFFFAOYSA-N 0.000 description 1
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- 239000010408 film Substances 0.000 description 1
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- 238000000206 photolithography Methods 0.000 description 1
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Images
Classifications
-
- B—PERFORMING OPERATIONS; TRANSPORTING
- B24—GRINDING; POLISHING
- B24B—MACHINES, DEVICES, OR PROCESSES FOR GRINDING OR POLISHING; DRESSING OR CONDITIONING OF ABRADING SURFACES; FEEDING OF GRINDING, POLISHING, OR LAPPING AGENTS
- B24B53/00—Devices or means for dressing or conditioning abrasive surfaces
- B24B53/005—Positioning devices for conditioning tools
-
- B—PERFORMING OPERATIONS; TRANSPORTING
- B24—GRINDING; POLISHING
- B24B—MACHINES, DEVICES, OR PROCESSES FOR GRINDING OR POLISHING; DRESSING OR CONDITIONING OF ABRADING SURFACES; FEEDING OF GRINDING, POLISHING, OR LAPPING AGENTS
- B24B53/00—Devices or means for dressing or conditioning abrasive surfaces
- B24B53/017—Devices or means for dressing, cleaning or otherwise conditioning lapping tools
Definitions
- the disclosure relates to a method for determining a height of a polishing pad used for polishing a substrate such as a wafer.
- the disclosure relates to a polishing system for polishing a substrate such as a wafer using such a method.
- this step coverage has to be ameliorated and flattening processing has to be performed through an appropriate process.
- the depth of focus becomes shallow in accordance with micronization of optical lithography, there is a need to flatten surfaces of semiconductor devices such that uneven steps on the surfaces of the semiconductor devices are confined within the depth of focus.
- CMP chemical mechanical polishing
- a polishing apparatus for performing CMP includes a polishing table that supports a polishing pad having a polishing surface, and a polishing head that holds a substrate.
- the substrate is held by the polishing head, and this substrate is pressurized to the polishing surface of the polishing pad at a predetermined pressure.
- the substrate comes into sliding contact with the polishing surface by causing relative movement between the polishing table and the polishing head, and therefore the surface of the substrate is polished into a flat mirror surface.
- the polishing pad is dressed with a dresser.
- a dresser has hard abrasive grains such as diamond particles which are fixed to its lower surface, and the polishing surface of the polishing pad is regenerated by grinding off the polishing surface of the polishing pad using this dresser. The polishing pad is dressed every time one substrate is polished.
- Polishing pads become gradually abraded as dressing is repetitively performed. When a polishing pad is abraded, intended polishing performance can no longer be exhibited. Therefore, there is a need to regularly replace the polishing pad. Generally, polishing pads are used until their abrasion loss reaches a threshold value set in advance. In the polishing apparatus described above, the height of the polishing surface of the polishing pad is determined by measuring the height of the dresser when the polishing pad is being pressurized. In addition, the amount of change in height of the dresser is monitored as the abrasion loss of the polishing pad.
- Patent Document 1 Japanese Laid-Open Patent No. 5390807
- Patent Document 2 Japanese Laid-Open Patent No. 5511600
- the dresser When a dressing load applied to a polishing pad from a dresser is changed, the dresser may change in height depending on the characteristics of the polishing pad. Therefore, in order to stably determine the height of a polishing pad, there is a need to measure the height of the dresser with every dressing by pressurizing the polishing pad with the same dressing load.
- the dressing load is arbitrarily set through a recipe depending on the type of a substrate to be polished, the same dressing load is not always applied to a polishing pad every time. Therefore, an error may be caused in the determined height of a polishing pad due to the difference between the dressing loads.
- the disclosure provides a method for determining an accurate height of a polishing pad even when a dressing load applied to the polishing pad is changed. Moreover, the disclosure provides a polishing system for polishing a substrate such as a wafer using such a method.
- a method for determining a polishing pad height in a polishing apparatus including a polishing table which supports a polishing pad, a polishing head which pressurizes a substrate onto a polishing surface of the polishing pad, and a dresser which dresses the polishing surface of the polishing pad.
- the method for determining a polishing pad height includes a step of measuring a reference dresser height that is a height of a dressing surface of the dresser when the polishing surface of the polishing pad in an unused state is being pressed with a reference dressing load for polishing the substrate, a step of calculating a correction amount for a dresser height corresponding to an amount of change in dressing load from the reference dressing load, a step of measuring a current dresser height that is a current height of the dressing surface of the dresser when the polishing surface of the polishing pad is being pressed, and a step of correcting the current dresser height using the correction amount.
- a polishing system including at least one polishing apparatus that polishes a substrate, and a polishing pad height monitoring part that is connected to the polishing apparatus.
- the polishing apparatus includes a polishing table which supports a polishing pad, a polishing head which pressurizes the substrate onto a polishing surface of the polishing pad, a dresser which dresses the polishing surface of the polishing pad, and a displacement sensor which measures a dresser height.
- the polishing pad height monitoring part includes a correction amount calculation part which calculates a correction amount for the dresser height corresponding to an amount of change in dressing load, and a dresser height correction part which corrects the dresser height measured by the displacement sensor using the correction amount.
- FIG. 1 is a schematic view illustrating an embodiment of a polishing system.
- FIG. 2 is a flowchart showing an embodiment of a method for determining a polishing pad height.
- FIG. 3 is a flowchart showing the embodiment of the method for determining a polishing pad height.
- FIG. 4 is a schematic view illustrating another embodiment of the polishing system.
- FIG. 5 is a schematic view illustrating still another embodiment of the polishing system.
- the step of calculating a correction amount for the dresser height may include steps of measuring an Nth dresser height when the dresser is pressurizing the polishing pad with a first dressing load differing from the reference dressing load, and calculating the correction amount that is a difference between the Nth dresser height and an N ⁇ 1th dresser height.
- the N ⁇ 1th dresser height may be the height of the dressing surface of the dresser when the polishing surface of the polishing pad is being pressed with the reference dressing load, and may be measured prior to the Nth dresser height.
- a change in abrasion loss of the polishing pad from a time of measuring the N ⁇ 1th dresser height to a time of measuring the Nth dresser height may be substantially zero.
- the N ⁇ 1th dresser height may be the reference dresser height.
- the step of calculating a correction amount for the dresser height may further include steps of measuring an N+1th dresser height when the dresser is pressurizing the polishing pad with the first dressing load, measuring an N+2th dresser height when the dresser is pressurizing the polishing pad with a second dressing load differing from the first dressing load, and updating the correction amount based on a difference between the N+2th dresser height and the N+1th dresser height.
- a change in abrasion loss of the polishing pad from a time of measuring the N+1th dresser height to a time of measuring the N+2th dresser height may be substantially zero.
- the step of calculating a correction amount for the dresser height may be a step of calculating a correction amount for the dresser height using a relational expression expressing a relationship between the amount of change in dressing load and an amount of change in dresser height.
- the embodiment may further include a step of calculating an abrasion loss of the polishing pad by subtracting the current dresser height being corrected from the reference dresser height.
- the correction amount calculation part may be configured to calculate the correction amount that is a difference between an Nth dresser height and an N ⁇ 1th dresser height.
- the N ⁇ 1th dresser height may be a height of a dressing surface of the dresser when the polishing surface of the polishing pad is being pressed with a reference dressing load.
- the Nth dresser height may be a height of the dressing surface of the dresser when the polishing surface of the polishing pad is being pressurized with a first dressing load differing from the reference dressing load.
- the correction amount calculation part may store a relational expression expressing a relationship between the amount of change in dressing load and an amount of change in dresser height.
- a dresser height is corrected in a direction in which a change in dressing load is canceled. Therefore, a corrected dresser height can express an accurate current polishing pad height. Accordingly, the accuracy of monitoring an abrasion loss of a polishing pad is improved, and therefore the accuracy of controlling a position for lowering a polishing head and the accuracy of controlling a polishing profile of a substrate can be improved.
- FIG. 1 is a schematic view illustrating an embodiment of a polishing system.
- the polishing system includes a polishing apparatus 1 for polishing a substrate such as a wafer.
- This polishing apparatus 1 includes a polishing table 12 supporting a polishing pad 22 , a polishing head oscillation arm 16 connected to the upper end of the swivel shaft 14 , a polishing head shaft 18 attached to a free end of the polishing head oscillation arm 16 , a polishing head 20 connected to the lower end of the polishing head shaft 18 , and an operation control part 47 .
- the operation control part 47 has a storage part 47 a storing data and a program, and a computation processing part 47 b executing computation in accordance with the program.
- the operation control part 47 operates in accordance with the program stored in the storage part 47 a.
- a dedicated computer or a general-purpose computer can be used as the operation control part 47 .
- the polishing head shaft 18 is connected to a polishing head rotating motor (not illustrated) disposed inside the polishing head oscillation arm 16 , and the polishing head shaft 18 is rotated by the polishing head rotating motor. Due to rotation of this polishing head shaft 18 , the polishing head 20 rotates about the polishing head shaft 18 in a direction indicated by an arrow.
- the polishing table 12 is connected to a table rotating motor 70 disposed therebelow via a table shaft 12 a.
- the polishing table 12 is rotated by this table rotating motor 70 about the table shaft 12 a in a direction indicated by an arrow.
- the polishing pad 22 is pasted to the upper surface of this polishing table 12 .
- the upper surface of the polishing pad 22 constitutes a polishing surface 22 a for polishing a substrate W such as a wafer.
- the polishing head shaft 18 can move upward and downward relative to the polishing head oscillation arm 16 by a lifting/lowering mechanism 24 , and the polishing head 20 can move upward and downward relative to the polishing head oscillation arm 16 when this polishing head shaft 18 moves upward and downward.
- a rotary joint 25 is attached to the upper end of the polishing head shaft 18 .
- the polishing head 20 is configured to be able to hold the substrate W such as a wafer on its lower surface.
- the polishing head oscillation arm 16 is configured to be able to swivel about the swivel shaft 14 , and the polishing head 20 holding the substrate W on the lower surface moves between a position (not illustrated) for receiving the substrate W and a position above the polishing table 12 when the polishing head oscillation arm 16 swivels.
- the lifting/lowering mechanism 24 lifting and lowering the polishing head shaft 18 and the polishing head 20 includes a bearing 26 rotatably supporting the polishing head shaft 18 , a bridge 28 having the bearing 26 fixed thereto, a ball screw mechanism 32 attached to the bridge 28 , a support base 29 supported by struts 30 , and a servo motor 38 fixed to the support base 29 .
- the support base 29 supporting the servo motor 38 is connected to the polishing head oscillation arm 16 via the struts 30 .
- the ball screw mechanism 32 includes a screw shaft 32 a connected to the servo motor 38 , and a nut 32 b into which this screw shaft 32 a is screwed.
- the nut 32 b is fixed to the bridge 28 .
- the polishing head shaft 18 is lifted and lowered (moved upward and downward) integrally with the bridge 28 . Therefore, when the servo motor 38 is driven, the bridge 28 moves upward and downward via the ball screw mechanism 32 , and therefore the polishing head shaft 18 and the polishing head 20 move upward and downward.
- the substrate W is polished as follows. While the polishing head 20 and the polishing table 12 are respectively rotated, a slurry is supplied onto the polishing pad 22 from a slurry supply nozzle (not illustrated) provided above the polishing table 12 .
- the polishing head 20 is lowered to a predetermined polishing position by the lifting/lowering mechanism 24 .
- the polishing head 20 pressurizes the substrate W onto the polishing surface 22 a of the polishing pad 22 at the polishing position.
- the substrate W is brought into sliding contact with the polishing surface 22 a of the polishing pad 22 .
- the front surface of the substrate W is polished by means of a combination of chemical action by chemical components of the slurry and mechanical action by abrasive grains contained in the slurry.
- the polished substrate is detached from the polishing head 20 .
- the polishing head 20 holds a new substrate, and the new substrate is polished in a similar manner. In this manner, polishing of a substrate is repetitively performed, and a plurality of substrates are polished using one polishing pad 22 .
- the polishing pad 22 is used until its abrasion loss reaches a threshold value set in advance. When the abrasion loss of the polishing pad 22 reaches the threshold value, the polishing pad 22 is replaced with a new polishing pad.
- the servo motor 38 is connected to a motor driver 48 .
- the motor driver 48 controls a rotation angle and a rotation frequency of the servo motor 38 .
- the servo motor 38 is connected to the ball screw mechanism 32 , and the ball screw mechanism 32 is connected to the polishing head 20 via the bridge 28 and the polishing head shaft 18 . Therefore, the height (that is, the position in a vertical direction) of the polishing head 20 is determined based on the rotation angle and the rotation frequency of the servo motor 38 .
- the motor driver 48 is configured to be connected to the operation control part 47 and to send the rotation angle and the rotation frequency of the servo motor 38 to the operation control part 47 .
- the operation control part 47 is configured to calculate the height (that is, the position in the vertical direction) of the polishing head 20 from the rotation angle and the rotation frequency of the servo motor 38 .
- the polishing apparatus 1 includes a dressing part 40 which dresses the polishing surface 22 a of the polishing pad 22 .
- This dressing part 40 includes a dresser 50 brought into sliding contact with the polishing surface 22 a of the polishing pad 22 , a dresser shaft 51 having the dresser 50 connected thereto, an air cylinder 53 provided at the upper end of the dresser shaft 51 , and a dresser oscillation arm 55 rotatably supporting the dresser shaft 51 .
- the lower surface of the dresser 50 constitutes a dressing surface 50 a, and this dressing surface 50 a is configured to include abrasive grains (for example, diamond particles).
- the air cylinder 53 is disposed on a support base 57 supported by struts 56 , and these struts 56 are fixed to the dresser oscillation arm 55 .
- the dresser oscillation arm 55 swivels about the swivel shaft 58 .
- the dresser shaft 51 rotates in accordance with driving of a dresser motor (not illustrated) disposed inside the dresser oscillation arm 55 , and the dresser 50 rotates about the dresser shaft 51 in a direction indicated by an arrow in accordance with rotation of this dresser shaft 51 .
- the air cylinder 53 is connected to the dresser 50 via the dresser shaft 51 .
- the air cylinder 53 causes the dresser shaft 51 and the dresser 50 to integrally move upward and downward and pressurizes the dressing surface 50 a of the dresser 50 onto the polishing surface 22 a of the polishing pad 22 with a predetermined pressurizing force.
- a load applied to the polishing surface 22 a of the polishing pad 22 from the dresser 50 when the dresser 50 is pressurizing the polishing pad 22 is defined as a dressing load.
- the polishing surface 22 a of the polishing pad 22 is dressed as follows. While the polishing pad 22 is rotated by the table rotating motor 70 together with the polishing table 12 , pure water is supplied to the polishing surface 22 a from a pure water supply nozzle (not illustrated). While the dresser 50 rotates about the dresser shaft 51 , the dressing surface 50 a of the dresser 50 is pressurized onto the polishing surface 22 a by the air cylinder 53 . In a state where pure water is present on the polishing surface 22 a, the dresser 50 is brought into sliding contact with the polishing surface 22 a.
- the dresser 50 While the dresser 50 rotates, the dresser 50 is moved in a radial direction of the polishing surface 22 a by causing the dresser oscillation arm 55 to swivel about the swivel shaft 58 . In this manner, the polishing pad 22 is ground off by the dresser 50 , and the polishing surface 22 a is dressed (regenerated). The polishing surface 22 a of the polishing pad 22 is dressed every time one substrate is polished.
- the dressing part 40 further includes a displacement sensor 60 measuring the height (that is, the position of the dresser 50 in the vertical direction) of the dresser 50 , a target plate 61 , and a sensor holder 63 .
- the sensor holder 63 is fixed to the dresser shaft 51 , and the sensor holder 63 moves upward and downward integrally with the dresser shaft 51 and the dresser 50 .
- the displacement sensor 60 is fixed to the sensor holder 63 .
- the target plate 61 is fixed to the dresser oscillation arm 55 , and the height of the target plate 61 is unchangeable.
- the displacement sensor 60 moves upward and downward integrally with the dresser shaft 51 , the dresser 50 , and the sensor holder 63 .
- a displacement of the displacement sensor 60 with respect to the target plate 61 is measured by the displacement sensor 60 .
- the displacement sensor 60 can indirectly measure the height of the dresser 50 by measuring a displacement of the displacement sensor 60 with respect to the target plate 61 .
- the height of the dressing surface 50 a of the dresser 50 from a certain original position when the dresser 50 is pressurizing the polishing surface 22 a of the polishing pad 22 is defined as a dresser height.
- a contact-type displacement sensor which comes into contact with the target plate 61 is used as the displacement sensor 60 .
- a non-contact-type displacement sensor which does not come into contact with the target plate 61 may be used.
- a linear scale, a laser sensor, an ultrasound sensor, an eddy current-type sensor, or the like can be used as the displacement sensor 60 .
- the polishing system further includes a polishing pad height monitoring part 80 monitoring the height of the polishing surface 22 a of the polishing pad 22 (which will hereinafter be referred to as a polishing pad height).
- This polishing pad height is measured by the displacement sensor 60 when the dressing surface 50 a of the dresser 50 is pressurizing the polishing surface 22 a of the polishing pad 22 .
- the height of the dressing surface 50 a of the dresser 50 when the dresser 50 is pressurizing the polishing surface 22 a of the polishing pad 22 is defined as a dresser height.
- the polishing pad height corresponds to the dresser height.
- the polishing pad height monitoring part 80 is connected to the polishing apparatus 1 . More specifically, the displacement sensor 60 and the operation control part 47 are electrically connected to the polishing pad height monitoring part 80 .
- the displacement sensor 60 may be connected to the polishing pad height monitoring part 80 via the operation control part 47 .
- the polishing pad height monitoring part 80 may be an edge server connected to the polishing apparatus 1 through a communication line, may be a cloud server connected to the polishing apparatus 1 through a network such as the internet, or a fog computing device (a gateway, a fog server, a router, or the like) installed in a network connected to the polishing apparatus 1 .
- the polishing pad height monitoring part 80 may be a plurality of servers connected through a network such as the internet.
- the polishing pad height monitoring part 80 may be a combination of an edge server and a cloud server.
- the polishing pad height monitoring part 80 includes a correction amount calculation part 83 calculating a correction amount for the dresser height corresponding to an amount of change in dressing load, a dresser height correction part 85 correcting the dresser height using the correction amount, and a pad abrasion loss calculation part 86 calculating an abrasion loss of a polishing pad based on a reference dresser height (which will be described below) and a corrected dresser height.
- a load applied to the polishing surface 22 a of the polishing pad 22 from the dresser 50 when the dresser 50 is pressurizing an unused polishing pad 22 is defined as a reference dressing load
- the height of the dressing surface 50 a of the dresser 50 from a certain original position when the dresser 50 is pressurizing the polishing surface 22 a of an unused polishing pad 22 is defined as a reference dresser height.
- the abrasion loss of the polishing pad 22 corresponds to an amount of change in dresser height from the reference dresser height under a condition of the same dressing load.
- FIGS. 2 and 3 are a flowchart showing the embodiment of the method for determining a polishing pad height.
- Step 1 while the polishing surface 22 a of an unused polishing pad 22 which has not been used for polishing a substrate is dressed by the dresser 50 with the reference dressing load, the dresser height is measured by the displacement sensor 60 .
- the dresser height obtained in Step 1 will be referred to as a reference dresser height.
- Step 2 the substrate is polished on the polishing pad 22 dressed in Step 1 .
- Step 3 while the polishing surface 22 a of the polishing pad 22 is dressed by the dresser 50 with the reference dressing load after the substrate is polished, the dresser height is measured by the displacement sensor 60 .
- Steps 2 and 3 are performed at least k ⁇ 1 times (k is a natural number equal to or larger than 1). When k is 1, Steps 2 and 3 are not performed.
- Step 4 the dressing load applied to the polishing pad 22 is changed to a first dressing load from the reference dressing load. After a kth substrate is polished, the polishing surface 22 a of the polishing pad 22 is dressed by the dresser 50 with the first dressing load, and a current dresser height is measured by the displacement sensor 60 .
- Step 5 in order to cancel the change in dresser height caused by the change in dressing load, the correction amount for the dresser height corresponding to the amount of change in dressing load is calculated.
- the correction amount calculation part 83 calculates the correction amount for the dresser height as the difference between the Nth dresser height and the reference dresser height. More specifically, the correction amount calculation part 83 calculates the correction amount for the dresser height by subtracting the reference dresser height from the Nth dresser height. In the embodiment, the correction amount calculation part 83 may calculate the correction amount for the dresser height by subtracting the Nth dresser height from the reference dresser height.
- the reference dresser height is an N ⁇ 1th dresser height.
- the N ⁇ 1th dresser height is a dresser height when the dresser 50 is pressurizing the polishing pad 22 with the reference dressing load and is measured prior to the Nth dresser height.
- the characters N ⁇ 1, N, N+1, N+2, and so on are characters irrelevant to the number of substrates.
- the polishing surface 22 a of the polishing pad 22 is dressed every time one substrate is polished.
- the polishing pad 22 gradually wears.
- the abrasion loss of the polishing pad 22 in one dressing is insignificant to the extent that the change in abrasion loss of the polishing pad 22 can be disregarded.
- the change in abrasion loss of the polishing pad 22 is less than an upper limit value (for example, less than 1 ⁇ m) set in advance, the change in abrasion loss of the polishing pad 22 is substantially regarded as zero.
- the Nth dresser height is a dresser height when the polishing pad 22 is dressed after the first substrate is polished.
- the change in abrasion loss of the polishing pad 22 during a period from measurement of the reference dresser height to measurement of the Nth dresser height is substantially zero.
- the dresser height when the polishing pad 22 is dressed after a 1+ ⁇ th substrate ( ⁇ is a natural number equal to or larger than 1) is polished may be adopted as the Nth dresser height.
- the polishing pad 22 is dressed with the reference dressing load. After the kth substrate is polished, the polishing pad 22 is dressed with the first dressing load differing from the reference dressing load. More specifically, after a k ⁇ 1th substrate is polished, the polishing surface 22 a of the polishing pad 22 is dressed by the dresser 50 with the reference dressing load, and the N ⁇ 1th dresser height is measured by the displacement sensor 60 . After the kth substrate is polished, the polishing surface 22 a of the polishing pad 22 is dressed by the dresser 50 with the first dressing load, and the Nth dresser height is measured by the displacement sensor 60 .
- the correction amount calculation part 83 calculates the correction amount for the dresser height as the difference between the Nth dresser height and the N ⁇ 1th dresser height. More specifically, the correction amount calculation part 83 calculates the correction amount for the dresser height by subtracting the N ⁇ 1th dresser height from the Nth dresser height. In the embodiment, the correction amount calculation part 83 may calculate the correction amount for the dresser height by subtracting the Nth dresser height from the N ⁇ 1th dresser height.
- the change in abrasion loss of the polishing pad 22 during a period from measurement of the N ⁇ 1th dresser height to measurement of the Nth dresser height is substantially zero.
- the dresser height when the polishing pad 22 is dressed after a k+ ⁇ th substrate ( ⁇ is a natural number equal to or larger than 1) is polished may be adopted as the Nth dresser height.
- Step 6 after the substrate is polished, the polishing surface 22 a of the polishing pad 22 is dressed by the dresser 50 with the first dressing load, and the current dresser height is measured by the displacement sensor 60 .
- Step 7 the current dresser height measured in Step 6 is corrected based on the correction amount calculated in Step 5 .
- the dresser height correction part 85 corrects the current dresser height by subtracting the correction amount from the current dresser height.
- the dresser height correction part 85 corrects the current dresser height by adding the correction amount to the current dresser height.
- the corrected current dresser height obtained in this manner corresponds to a current polishing pad height.
- the current dresser height is corrected in a direction in which the change in dressing load is canceled. Therefore, a corrected current dresser height can express an accurate current polishing pad height. Accordingly, the accuracy of monitoring an abrasion loss of a polishing pad is improved, and therefore the accuracy of controlling a position for lowering the polishing head 20 and the accuracy of controlling a polishing profile of a substrate can be improved.
- Step 8 the pad abrasion loss calculation part 86 calculates the abrasion loss of the polishing pad 22 by subtracting the corrected current dresser height obtained in Step 7 from the reference dresser height.
- polishing of a new substrate and dressing of the polishing pad 22 are repetitively performed.
- the following is steps when the dressing load is further changed to a second dressing load from the first dressing load after a plurality of new substrates are polished.
- the polishing pad 22 is dressed with the first dressing load, and after the mth substrate is polished, the polishing pad 22 is dressed with the second dressing load differing from the first dressing load.
- Step 9 after an m ⁇ 1th substrate is polished, the polishing surface 22 a of the polishing pad 22 is dressed by the dresser 50 with the first dressing load, and an N+1th dresser height is measured by the displacement sensor 60 .
- Step 10 after the mth substrate is polished, the polishing surface 22 a of the polishing pad 22 is dressed by the dresser 50 with the second dressing load differing from the first dressing load, and an N+2th dresser height is measured by the displacement sensor 60 .
- the change in abrasion loss of the polishing pad 22 from a time of measuring the N+1th dresser height to a time of measuring the N+2th dresser height is substantially zero.
- the second dressing load differs from the first dressing load, the amount of pushing the polishing pad 22 by the dresser 50 when the N+2th dresser height is being measured changes. Therefore, the N+2th dresser height differs from the N+1th dresser height.
- the correction amount calculation part 83 updates the correction amount based on the difference between the N+2th dresser height and the N+1th dresser height. More specifically, the correction amount calculation part 83 updates the correction amount by adding the value obtained by subtracting the N+1th dresser height from the N+2th dresser height to the correction amount calculated in Step 5 . In the embodiment, the correction amount calculation part 83 may update the correction amount by subtracting the value, which is obtained by subtracting the N+2th dresser height from the N+1th dresser height, from the correction amount calculated in Step 5 , or by adding the value to the correction amount calculated in Step 5 .
- the difference between the N+2th dresser height and the N+1th dresser height is equivalent to the difference between the amounts of pushing the polishing pad 22 .
- the dresser height at the time of dressing after a m+ ⁇ th substrate ( ⁇ is a natural number equal to or larger than 1) is polished may be adopted as the N+2th dresser height.
- Step 12 after the substrate is polished, the polishing surface 22 a of the polishing pad 22 is dressed by the dresser 50 with the second dressing load, and the current dresser height is measured by the displacement sensor 60 .
- Step 13 the current dresser height measured in Step 12 is corrected based on the updated correction amount obtained in Step 10 .
- the dresser height correction part 85 corrects the current dresser height by subtracting the updated correction amount from the current dresser height.
- the dresser height correction part 85 corrects the current dresser height by adding the correction amount to the current dresser height.
- the corrected current dresser height obtained in this manner corresponds to the current polishing pad height.
- Step 14 the pad abrasion loss calculation part 86 calculates the abrasion loss of the polishing pad 22 by subtracting the corrected current dresser height obtained in Step 13 from the reference dresser height.
- polishing of a new substrate and dressing of the polishing pad 22 are repetitively performed. Even when the dressing load is further changed, the current dresser height corrected through steps similar to Steps 9 to 13 , that is, the current polishing pad height can be determined.
- FIG. 4 is a schematic view illustrating another embodiment of the polishing system. Since configurations and operations which are not particularly described in the present embodiment are the same as those in the embodiment which has been described with reference to FIGS. 1 to 3 , duplicate description thereof will be omitted.
- the polishing pad height monitoring part 80 of the present embodiment further includes a data accumulation part 87 and a relational expression determination part 91 .
- the data accumulation part 87 accumulates data such as measurement values of dresser heights measured by the displacement sensor 60 , and the dressing loads set in advance.
- the relational expression determination part 91 receives the accumulated data from the data accumulation part 87 and obtains a relational expression expressing the relationship between the amount of change in dressing load and the amount of change in dresser height based on the amount of change in plurality of dressing loads and the amount of change in plurality of dresser heights corresponding to the amount of change in plurality of dressing loads.
- a regression equation is determined by plotting a plurality of data points determined from the amounts of change in plurality of dressing loads and corresponding amounts of change in plurality of dresser heights on a coordinate system having the vertical axis indicating the amount of change in dressing load and the horizontal axis indicating the amount of change in dresser height, and performing regression analysis with respect to the plurality of data points.
- This regression equation is a relational expression expressing the relationship between the amount of change in dressing load and the amount of change in dresser height.
- the relational expression determined by the relational expression determination part 91 is sent to the correction amount calculation part 83 and is stored in the correction amount calculation part 83 .
- the correction amount calculation part 83 can calculate the correction amount for the dresser height corresponding to the amount of change in dressing load from the relational expression described above.
- the dresser height correction part 85 corrects the dresser height based on the correction amount calculated by the relational expression described above.
- FIG. 5 is a schematic view illustrating still another embodiment of the polishing system.
- the polishing system of the present embodiment includes a plurality of polishing apparatuses 1 and the polishing pad height monitoring part 80 which has been described with reference to FIG. 1 or 4 . Since configurations of the polishing system which are not particularly described in the present embodiment are the same as those in the embodiment which has been described with reference to FIG. 1 or 4 , duplicate description thereof will be omitted.
- the polishing pad height monitoring part 80 is connected to the plurality of polishing apparatuses 1 via a network such as the internet.
- the polishing system may include one polishing apparatus 1 .
- the polishing system of the present embodiment can correct the dresser heights of the plurality of polishing apparatuses 1 using one polishing pad height monitoring part 80 .
- the dresser height can be corrected by a method similar to the method in the embodiment which has been described with reference to FIGS. 2 and 3 , or the method in the embodiment which has been described with reference to FIG. 4 .
- the polishing system of the present embodiment can improve the accuracy of calculating the correction amount for the dresser height corresponding to the amount of change in dressing load.
- the correction amount for the dresser height corresponding to the amount of change in dressing load is calculated, and the dresser height is corrected based on the correction amount. Therefore, a corrected dresser height can express an accurate current polishing pad height. Accordingly, the accuracy of monitoring an abrasion loss of a polishing pad is improved, and therefore the accuracy of controlling a position for lowering a polishing head and the accuracy of controlling a polishing profile of a substrate can be improved.
Abstract
Description
- This application claims the priority benefits of Japan Patent Application No. 2018-156497, filed on Aug. 23, 2018. The entirety of the above-mentioned patent application is hereby incorporated by reference herein and made a part of this specification.
- The disclosure relates to a method for determining a height of a polishing pad used for polishing a substrate such as a wafer. In addition, the disclosure relates to a polishing system for polishing a substrate such as a wafer using such a method.
- Recently, in accordance with semiconductor devices which have become highly integrated and highly dense, wiring for circuits has been further micronized, and the number of layers in multi-layer wiring has also increased. When it is intended to realize multi-layer wiring while achieving micronization of circuits, a step becomes larger with unevenness on a surface of a layer on a lower side. Therefore, when the number of layers of wiring increases, film coverage (step coverage) with respect to the shape of a step in thin film formation deteriorates.
- Therefore, in order to achieve multi-layer wiring, this step coverage has to be ameliorated and flattening processing has to be performed through an appropriate process. In addition, since the depth of focus becomes shallow in accordance with micronization of optical lithography, there is a need to flatten surfaces of semiconductor devices such that uneven steps on the surfaces of the semiconductor devices are confined within the depth of focus.
- Therefore, in a step of manufacturing a semiconductor device, technologies of flattening a surface of a semiconductor device have become increasingly important. The most important technology of these flattening technologies is chemical mechanical polishing. This chemical mechanical polishing (which will hereinafter be referred to as CMP) is polishing performed by supplying a polishing liquid containing abrasive grains such as silica (SiO2) onto a polishing pad and bringing a substrate such as a wafer into sliding contact with a polishing surface.
- A polishing apparatus for performing CMP includes a polishing table that supports a polishing pad having a polishing surface, and a polishing head that holds a substrate. When a substrate is polished using such a polishing apparatus, the substrate is held by the polishing head, and this substrate is pressurized to the polishing surface of the polishing pad at a predetermined pressure. Moreover, the substrate comes into sliding contact with the polishing surface by causing relative movement between the polishing table and the polishing head, and therefore the surface of the substrate is polished into a flat mirror surface.
- When a substrate is polished, abrasive grains or a polishing residue adheres to the polishing surface of the polishing pad, and polishing performance is degraded. Therefore, in order to regenerate the polishing surface of the polishing pad, the polishing pad is dressed with a dresser. A dresser has hard abrasive grains such as diamond particles which are fixed to its lower surface, and the polishing surface of the polishing pad is regenerated by grinding off the polishing surface of the polishing pad using this dresser. The polishing pad is dressed every time one substrate is polished.
- Polishing pads become gradually abraded as dressing is repetitively performed. When a polishing pad is abraded, intended polishing performance can no longer be exhibited. Therefore, there is a need to regularly replace the polishing pad. Generally, polishing pads are used until their abrasion loss reaches a threshold value set in advance. In the polishing apparatus described above, the height of the polishing surface of the polishing pad is determined by measuring the height of the dresser when the polishing pad is being pressurized. In addition, the amount of change in height of the dresser is monitored as the abrasion loss of the polishing pad.
- [Patent Document 1] Japanese Laid-Open Patent No. 5390807
- [Patent Document 2] Japanese Laid-Open Patent No. 5511600
- When a dressing load applied to a polishing pad from a dresser is changed, the dresser may change in height depending on the characteristics of the polishing pad. Therefore, in order to stably determine the height of a polishing pad, there is a need to measure the height of the dresser with every dressing by pressurizing the polishing pad with the same dressing load.
- However, since the dressing load is arbitrarily set through a recipe depending on the type of a substrate to be polished, the same dressing load is not always applied to a polishing pad every time. Therefore, an error may be caused in the determined height of a polishing pad due to the difference between the dressing loads.
- The disclosure provides a method for determining an accurate height of a polishing pad even when a dressing load applied to the polishing pad is changed. Moreover, the disclosure provides a polishing system for polishing a substrate such as a wafer using such a method.
- According to an embodiment, there is provided a method for determining a polishing pad height in a polishing apparatus including a polishing table which supports a polishing pad, a polishing head which pressurizes a substrate onto a polishing surface of the polishing pad, and a dresser which dresses the polishing surface of the polishing pad. The method for determining a polishing pad height includes a step of measuring a reference dresser height that is a height of a dressing surface of the dresser when the polishing surface of the polishing pad in an unused state is being pressed with a reference dressing load for polishing the substrate, a step of calculating a correction amount for a dresser height corresponding to an amount of change in dressing load from the reference dressing load, a step of measuring a current dresser height that is a current height of the dressing surface of the dresser when the polishing surface of the polishing pad is being pressed, and a step of correcting the current dresser height using the correction amount.
- According to another embodiment, there is provided a polishing system including at least one polishing apparatus that polishes a substrate, and a polishing pad height monitoring part that is connected to the polishing apparatus. The polishing apparatus includes a polishing table which supports a polishing pad, a polishing head which pressurizes the substrate onto a polishing surface of the polishing pad, a dresser which dresses the polishing surface of the polishing pad, and a displacement sensor which measures a dresser height. The polishing pad height monitoring part includes a correction amount calculation part which calculates a correction amount for the dresser height corresponding to an amount of change in dressing load, and a dresser height correction part which corrects the dresser height measured by the displacement sensor using the correction amount.
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FIG. 1 is a schematic view illustrating an embodiment of a polishing system. -
FIG. 2 is a flowchart showing an embodiment of a method for determining a polishing pad height. -
FIG. 3 is a flowchart showing the embodiment of the method for determining a polishing pad height. -
FIG. 4 is a schematic view illustrating another embodiment of the polishing system. -
FIG. 5 is a schematic view illustrating still another embodiment of the polishing system. - According to the embodiment, the step of calculating a correction amount for the dresser height may include steps of measuring an Nth dresser height when the dresser is pressurizing the polishing pad with a first dressing load differing from the reference dressing load, and calculating the correction amount that is a difference between the Nth dresser height and an N−1th dresser height. The N−1th dresser height may be the height of the dressing surface of the dresser when the polishing surface of the polishing pad is being pressed with the reference dressing load, and may be measured prior to the Nth dresser height.
- According to the embodiment, a change in abrasion loss of the polishing pad from a time of measuring the N−1th dresser height to a time of measuring the Nth dresser height may be substantially zero.
- According to the embodiment, the N−1th dresser height may be the reference dresser height.
- According to the embodiment, the step of calculating a correction amount for the dresser height may further include steps of measuring an N+1th dresser height when the dresser is pressurizing the polishing pad with the first dressing load, measuring an N+2th dresser height when the dresser is pressurizing the polishing pad with a second dressing load differing from the first dressing load, and updating the correction amount based on a difference between the N+2th dresser height and the N+1th dresser height.
- According to the embodiment, a change in abrasion loss of the polishing pad from a time of measuring the N+1th dresser height to a time of measuring the N+2th dresser height may be substantially zero.
- According to the embodiment, the step of calculating a correction amount for the dresser height may be a step of calculating a correction amount for the dresser height using a relational expression expressing a relationship between the amount of change in dressing load and an amount of change in dresser height.
- The embodiment may further include a step of calculating an abrasion loss of the polishing pad by subtracting the current dresser height being corrected from the reference dresser height.
- According to the embodiment, the correction amount calculation part may be configured to calculate the correction amount that is a difference between an Nth dresser height and an N−1th dresser height. The N−1th dresser height may be a height of a dressing surface of the dresser when the polishing surface of the polishing pad is being pressed with a reference dressing load. The Nth dresser height may be a height of the dressing surface of the dresser when the polishing surface of the polishing pad is being pressurized with a first dressing load differing from the reference dressing load. According to the embodiment, the correction amount calculation part may store a relational expression expressing a relationship between the amount of change in dressing load and an amount of change in dresser height.
- According to the disclosure, a dresser height is corrected in a direction in which a change in dressing load is canceled. Therefore, a corrected dresser height can express an accurate current polishing pad height. Accordingly, the accuracy of monitoring an abrasion loss of a polishing pad is improved, and therefore the accuracy of controlling a position for lowering a polishing head and the accuracy of controlling a polishing profile of a substrate can be improved.
- Hereinafter, embodiments of the disclosure will be described with reference to the drawings.
FIG. 1 is a schematic view illustrating an embodiment of a polishing system. As illustrated inFIG. 1 , the polishing system includes apolishing apparatus 1 for polishing a substrate such as a wafer. This polishingapparatus 1 includes a polishing table 12 supporting apolishing pad 22, a polishinghead oscillation arm 16 connected to the upper end of theswivel shaft 14, a polishinghead shaft 18 attached to a free end of the polishinghead oscillation arm 16, a polishinghead 20 connected to the lower end of the polishinghead shaft 18, and anoperation control part 47. Theoperation control part 47 has astorage part 47 a storing data and a program, and acomputation processing part 47 b executing computation in accordance with the program. Theoperation control part 47 operates in accordance with the program stored in thestorage part 47 a. A dedicated computer or a general-purpose computer can be used as theoperation control part 47. - The polishing
head shaft 18 is connected to a polishing head rotating motor (not illustrated) disposed inside the polishinghead oscillation arm 16, and the polishinghead shaft 18 is rotated by the polishing head rotating motor. Due to rotation of this polishinghead shaft 18, the polishinghead 20 rotates about the polishinghead shaft 18 in a direction indicated by an arrow. - The polishing table 12 is connected to a
table rotating motor 70 disposed therebelow via atable shaft 12 a. The polishing table 12 is rotated by thistable rotating motor 70 about thetable shaft 12 a in a direction indicated by an arrow. Thepolishing pad 22 is pasted to the upper surface of this polishing table 12. The upper surface of thepolishing pad 22 constitutes a polishingsurface 22 a for polishing a substrate W such as a wafer. - The polishing
head shaft 18 can move upward and downward relative to the polishinghead oscillation arm 16 by a lifting/loweringmechanism 24, and the polishinghead 20 can move upward and downward relative to the polishinghead oscillation arm 16 when this polishinghead shaft 18 moves upward and downward. A rotary joint 25 is attached to the upper end of the polishinghead shaft 18. - The polishing
head 20 is configured to be able to hold the substrate W such as a wafer on its lower surface. The polishinghead oscillation arm 16 is configured to be able to swivel about theswivel shaft 14, and the polishinghead 20 holding the substrate W on the lower surface moves between a position (not illustrated) for receiving the substrate W and a position above the polishing table 12 when the polishinghead oscillation arm 16 swivels. - The lifting/lowering
mechanism 24 lifting and lowering the polishinghead shaft 18 and the polishinghead 20 includes abearing 26 rotatably supporting the polishinghead shaft 18, abridge 28 having the bearing 26 fixed thereto, aball screw mechanism 32 attached to thebridge 28, asupport base 29 supported bystruts 30, and aservo motor 38 fixed to thesupport base 29. Thesupport base 29 supporting theservo motor 38 is connected to the polishinghead oscillation arm 16 via thestruts 30. - The
ball screw mechanism 32 includes ascrew shaft 32 a connected to theservo motor 38, and anut 32 b into which thisscrew shaft 32 a is screwed. Thenut 32 b is fixed to thebridge 28. The polishinghead shaft 18 is lifted and lowered (moved upward and downward) integrally with thebridge 28. Therefore, when theservo motor 38 is driven, thebridge 28 moves upward and downward via theball screw mechanism 32, and therefore the polishinghead shaft 18 and the polishinghead 20 move upward and downward. - The substrate W is polished as follows. While the polishing
head 20 and the polishing table 12 are respectively rotated, a slurry is supplied onto thepolishing pad 22 from a slurry supply nozzle (not illustrated) provided above the polishing table 12. The polishinghead 20 is lowered to a predetermined polishing position by the lifting/loweringmechanism 24. Moreover, the polishinghead 20 pressurizes the substrate W onto the polishingsurface 22 a of thepolishing pad 22 at the polishing position. In a state where the slurry is present on the polishingsurface 22 a of thepolishing pad 22, the substrate W is brought into sliding contact with the polishingsurface 22 a of thepolishing pad 22. The front surface of the substrate W is polished by means of a combination of chemical action by chemical components of the slurry and mechanical action by abrasive grains contained in the slurry. - When polishing of a substrate ends, the polished substrate is detached from the polishing
head 20. The polishinghead 20 holds a new substrate, and the new substrate is polished in a similar manner. In this manner, polishing of a substrate is repetitively performed, and a plurality of substrates are polished using onepolishing pad 22. Thepolishing pad 22 is used until its abrasion loss reaches a threshold value set in advance. When the abrasion loss of thepolishing pad 22 reaches the threshold value, thepolishing pad 22 is replaced with a new polishing pad. - The
servo motor 38 is connected to amotor driver 48. Themotor driver 48 controls a rotation angle and a rotation frequency of theservo motor 38. Theservo motor 38 is connected to theball screw mechanism 32, and theball screw mechanism 32 is connected to the polishinghead 20 via thebridge 28 and the polishinghead shaft 18. Therefore, the height (that is, the position in a vertical direction) of the polishinghead 20 is determined based on the rotation angle and the rotation frequency of theservo motor 38. Themotor driver 48 is configured to be connected to theoperation control part 47 and to send the rotation angle and the rotation frequency of theservo motor 38 to theoperation control part 47. Theoperation control part 47 is configured to calculate the height (that is, the position in the vertical direction) of the polishinghead 20 from the rotation angle and the rotation frequency of theservo motor 38. - The polishing
apparatus 1 includes a dressingpart 40 which dresses the polishingsurface 22 a of thepolishing pad 22. This dressingpart 40 includes adresser 50 brought into sliding contact with the polishingsurface 22 a of thepolishing pad 22, adresser shaft 51 having thedresser 50 connected thereto, anair cylinder 53 provided at the upper end of thedresser shaft 51, and adresser oscillation arm 55 rotatably supporting thedresser shaft 51. The lower surface of thedresser 50 constitutes a dressingsurface 50 a, and this dressing surface 50 a is configured to include abrasive grains (for example, diamond particles). Theair cylinder 53 is disposed on asupport base 57 supported bystruts 56, and thesestruts 56 are fixed to thedresser oscillation arm 55. - When a motor (not illustrated) connected to a
swivel shaft 58 is driven, thedresser oscillation arm 55 swivels about theswivel shaft 58. Thedresser shaft 51 rotates in accordance with driving of a dresser motor (not illustrated) disposed inside thedresser oscillation arm 55, and thedresser 50 rotates about thedresser shaft 51 in a direction indicated by an arrow in accordance with rotation of thisdresser shaft 51. Theair cylinder 53 is connected to thedresser 50 via thedresser shaft 51. Theair cylinder 53 causes thedresser shaft 51 and thedresser 50 to integrally move upward and downward and pressurizes the dressingsurface 50 a of thedresser 50 onto the polishingsurface 22 a of thepolishing pad 22 with a predetermined pressurizing force. In this specification, a load applied to the polishingsurface 22 a of thepolishing pad 22 from thedresser 50 when thedresser 50 is pressurizing thepolishing pad 22 is defined as a dressing load. - The polishing
surface 22 a of thepolishing pad 22 is dressed as follows. While thepolishing pad 22 is rotated by thetable rotating motor 70 together with the polishing table 12, pure water is supplied to the polishingsurface 22 a from a pure water supply nozzle (not illustrated). While thedresser 50 rotates about thedresser shaft 51, the dressingsurface 50 a of thedresser 50 is pressurized onto the polishingsurface 22 a by theair cylinder 53. In a state where pure water is present on the polishingsurface 22 a, thedresser 50 is brought into sliding contact with the polishingsurface 22 a. While thedresser 50 rotates, thedresser 50 is moved in a radial direction of the polishingsurface 22 a by causing thedresser oscillation arm 55 to swivel about theswivel shaft 58. In this manner, thepolishing pad 22 is ground off by thedresser 50, and the polishingsurface 22 a is dressed (regenerated). The polishingsurface 22 a of thepolishing pad 22 is dressed every time one substrate is polished. - The dressing
part 40 further includes adisplacement sensor 60 measuring the height (that is, the position of thedresser 50 in the vertical direction) of thedresser 50, atarget plate 61, and asensor holder 63. Thesensor holder 63 is fixed to thedresser shaft 51, and thesensor holder 63 moves upward and downward integrally with thedresser shaft 51 and thedresser 50. Thedisplacement sensor 60 is fixed to thesensor holder 63. Thetarget plate 61 is fixed to thedresser oscillation arm 55, and the height of thetarget plate 61 is unchangeable. Thedisplacement sensor 60 moves upward and downward integrally with thedresser shaft 51, thedresser 50, and thesensor holder 63. - A displacement of the
displacement sensor 60 with respect to thetarget plate 61 is measured by thedisplacement sensor 60. Thedisplacement sensor 60 can indirectly measure the height of thedresser 50 by measuring a displacement of thedisplacement sensor 60 with respect to thetarget plate 61. In this specification, the height of the dressingsurface 50 a of thedresser 50 from a certain original position when thedresser 50 is pressurizing the polishingsurface 22 a of thepolishing pad 22 is defined as a dresser height. - In the present embodiment, a contact-type displacement sensor which comes into contact with the
target plate 61 is used as thedisplacement sensor 60. However, a non-contact-type displacement sensor which does not come into contact with thetarget plate 61 may be used. Specifically, a linear scale, a laser sensor, an ultrasound sensor, an eddy current-type sensor, or the like can be used as thedisplacement sensor 60. - As polishing of a substrate and dressing of the
polishing pad 22 are repetitively performed, thepolishing pad 22 gradually wears. In the present embodiment, the polishing system further includes a polishing padheight monitoring part 80 monitoring the height of the polishingsurface 22 a of the polishing pad 22 (which will hereinafter be referred to as a polishing pad height). This polishing pad height is measured by thedisplacement sensor 60 when the dressingsurface 50 a of thedresser 50 is pressurizing the polishingsurface 22 a of thepolishing pad 22. As described above, the height of the dressingsurface 50 a of thedresser 50 when thedresser 50 is pressurizing the polishingsurface 22 a of thepolishing pad 22 is defined as a dresser height. Thus, the polishing pad height corresponds to the dresser height. - The polishing pad
height monitoring part 80 is connected to thepolishing apparatus 1. More specifically, thedisplacement sensor 60 and theoperation control part 47 are electrically connected to the polishing padheight monitoring part 80. Thedisplacement sensor 60 may be connected to the polishing padheight monitoring part 80 via theoperation control part 47. The polishing padheight monitoring part 80 may be an edge server connected to thepolishing apparatus 1 through a communication line, may be a cloud server connected to thepolishing apparatus 1 through a network such as the internet, or a fog computing device (a gateway, a fog server, a router, or the like) installed in a network connected to thepolishing apparatus 1. The polishing padheight monitoring part 80 may be a plurality of servers connected through a network such as the internet. For example, the polishing padheight monitoring part 80 may be a combination of an edge server and a cloud server. - The polishing pad
height monitoring part 80 includes a correctionamount calculation part 83 calculating a correction amount for the dresser height corresponding to an amount of change in dressing load, a dresserheight correction part 85 correcting the dresser height using the correction amount, and a pad abrasionloss calculation part 86 calculating an abrasion loss of a polishing pad based on a reference dresser height (which will be described below) and a corrected dresser height. - Hereinafter, a method for determining a polishing pad height will be described. In this specification, a load applied to the polishing
surface 22 a of thepolishing pad 22 from thedresser 50 when thedresser 50 is pressurizing anunused polishing pad 22 is defined as a reference dressing load, and the height of the dressingsurface 50 a of thedresser 50 from a certain original position when thedresser 50 is pressurizing the polishingsurface 22 a of anunused polishing pad 22 is defined as a reference dresser height. The abrasion loss of thepolishing pad 22 corresponds to an amount of change in dresser height from the reference dresser height under a condition of the same dressing load. -
FIGS. 2 and 3 are a flowchart showing the embodiment of the method for determining a polishing pad height. InStep 1, while the polishingsurface 22 a of anunused polishing pad 22 which has not been used for polishing a substrate is dressed by thedresser 50 with the reference dressing load, the dresser height is measured by thedisplacement sensor 60. In the following description, the dresser height obtained inStep 1 will be referred to as a reference dresser height. - In
Step 2, the substrate is polished on thepolishing pad 22 dressed inStep 1. InStep 3, while the polishingsurface 22 a of thepolishing pad 22 is dressed by thedresser 50 with the reference dressing load after the substrate is polished, the dresser height is measured by thedisplacement sensor 60.Steps Steps - In
Step 4, the dressing load applied to thepolishing pad 22 is changed to a first dressing load from the reference dressing load. After a kth substrate is polished, the polishingsurface 22 a of thepolishing pad 22 is dressed by thedresser 50 with the first dressing load, and a current dresser height is measured by thedisplacement sensor 60. - When the dressing load is changed from the reference dressing load, an amount of pushing the
polishing pad 22 by thedresser 50 is changed. As a result, a correct abrasion loss of thepolishing pad 22 cannot be calculated. Therefore, in Step 5, in order to cancel the change in dresser height caused by the change in dressing load, the correction amount for the dresser height corresponding to the amount of change in dressing load is calculated. - Hereinafter, details of Step 5 will be described.
-
- (i) When k is 1
- When k is 1, after a first substrate is polished, the polishing
surface 22 a of thepolishing pad 22 is dressed by thedresser 50 with the first dressing load differing from the reference dressing load, and an Nth dresser height is measured by thedisplacement sensor 60. The correctionamount calculation part 83 calculates the correction amount for the dresser height as the difference between the Nth dresser height and the reference dresser height. More specifically, the correctionamount calculation part 83 calculates the correction amount for the dresser height by subtracting the reference dresser height from the Nth dresser height. In the embodiment, the correctionamount calculation part 83 may calculate the correction amount for the dresser height by subtracting the Nth dresser height from the reference dresser height. - In this case (i), the reference dresser height is an N−1th dresser height. The N−1th dresser height is a dresser height when the
dresser 50 is pressurizing thepolishing pad 22 with the reference dressing load and is measured prior to the Nth dresser height. The characters N−1, N, N+1, N+2, and so on are characters irrelevant to the number of substrates. - In the present embodiment, the polishing
surface 22 a of thepolishing pad 22 is dressed every time one substrate is polished. As polishing of a substrate and dressing of thepolishing pad 22 are repetitively performed, thepolishing pad 22 gradually wears. However, the abrasion loss of thepolishing pad 22 in one dressing is insignificant to the extent that the change in abrasion loss of thepolishing pad 22 can be disregarded. In this specification, when the change in abrasion loss of thepolishing pad 22 is less than an upper limit value (for example, less than 1 μm) set in advance, the change in abrasion loss of thepolishing pad 22 is substantially regarded as zero. - In the case (i) described above, the Nth dresser height is a dresser height when the
polishing pad 22 is dressed after the first substrate is polished. The change in abrasion loss of thepolishing pad 22 during a period from measurement of the reference dresser height to measurement of the Nth dresser height is substantially zero. In the embodiment, as along as the change in abrasion loss of thepolishing pad 22 during a period from measurement of the reference dresser height to measurement of the Nth dresser height is substantially zero, the dresser height when thepolishing pad 22 is dressed after a 1+αth substrate (α is a natural number equal to or larger than 1) is polished may be adopted as the Nth dresser height. -
- (ii) When k is a natural number other than 1
- When k is a natural number other than 1, before the kth substrate is polished, the
polishing pad 22 is dressed with the reference dressing load. After the kth substrate is polished, thepolishing pad 22 is dressed with the first dressing load differing from the reference dressing load. More specifically, after a k−1th substrate is polished, the polishingsurface 22 a of thepolishing pad 22 is dressed by thedresser 50 with the reference dressing load, and the N−1th dresser height is measured by thedisplacement sensor 60. After the kth substrate is polished, the polishingsurface 22 a of thepolishing pad 22 is dressed by thedresser 50 with the first dressing load, and the Nth dresser height is measured by thedisplacement sensor 60. - The correction
amount calculation part 83 calculates the correction amount for the dresser height as the difference between the Nth dresser height and the N−1th dresser height. More specifically, the correctionamount calculation part 83 calculates the correction amount for the dresser height by subtracting the N−1th dresser height from the Nth dresser height. In the embodiment, the correctionamount calculation part 83 may calculate the correction amount for the dresser height by subtracting the Nth dresser height from the N−1th dresser height. - The change in abrasion loss of the
polishing pad 22 during a period from measurement of the N−1th dresser height to measurement of the Nth dresser height is substantially zero. In the embodiment, as along as the change in abrasion loss of thepolishing pad 22 during a period from measurement of the N−1th dresser height to measurement of the Nth dresser height is substantially zero, the dresser height when thepolishing pad 22 is dressed after a k+αth substrate (α is a natural number equal to or larger than 1) is polished may be adopted as the Nth dresser height. - After the correction amount for the dresser height is calculated, polishing of a new substrate and dressing of the
polishing pad 22 are repetitively performed. InStep 6, after the substrate is polished, the polishingsurface 22 a of thepolishing pad 22 is dressed by thedresser 50 with the first dressing load, and the current dresser height is measured by thedisplacement sensor 60. - In
Step 7, the current dresser height measured inStep 6 is corrected based on the correction amount calculated in Step 5. Specifically, the dresserheight correction part 85 corrects the current dresser height by subtracting the correction amount from the current dresser height. In the embodiment, the dresserheight correction part 85 corrects the current dresser height by adding the correction amount to the current dresser height. - The corrected current dresser height obtained in this manner corresponds to a current polishing pad height. According to the present embodiment, the current dresser height is corrected in a direction in which the change in dressing load is canceled. Therefore, a corrected current dresser height can express an accurate current polishing pad height. Accordingly, the accuracy of monitoring an abrasion loss of a polishing pad is improved, and therefore the accuracy of controlling a position for lowering the polishing
head 20 and the accuracy of controlling a polishing profile of a substrate can be improved. - In
Step 8, the pad abrasionloss calculation part 86 calculates the abrasion loss of thepolishing pad 22 by subtracting the corrected current dresser height obtained inStep 7 from the reference dresser height. - Thereafter, polishing of a new substrate and dressing of the
polishing pad 22 are repetitively performed. The following is steps when the dressing load is further changed to a second dressing load from the first dressing load after a plurality of new substrates are polished. In the embodiment described below, before an mth substrate is polished, thepolishing pad 22 is dressed with the first dressing load, and after the mth substrate is polished, thepolishing pad 22 is dressed with the second dressing load differing from the first dressing load. - In
Step 9, after an m−1th substrate is polished, the polishingsurface 22 a of thepolishing pad 22 is dressed by thedresser 50 with the first dressing load, and an N+1th dresser height is measured by thedisplacement sensor 60. - In
Step 10, after the mth substrate is polished, the polishingsurface 22 a of thepolishing pad 22 is dressed by thedresser 50 with the second dressing load differing from the first dressing load, and an N+2th dresser height is measured by thedisplacement sensor 60. - The change in abrasion loss of the
polishing pad 22 from a time of measuring the N+1th dresser height to a time of measuring the N+2th dresser height is substantially zero. On the other hand, since the second dressing load differs from the first dressing load, the amount of pushing thepolishing pad 22 by thedresser 50 when the N+2th dresser height is being measured changes. Therefore, the N+2th dresser height differs from the N+1th dresser height. - In
Step 11, the correctionamount calculation part 83 updates the correction amount based on the difference between the N+2th dresser height and the N+1th dresser height. More specifically, the correctionamount calculation part 83 updates the correction amount by adding the value obtained by subtracting the N+1th dresser height from the N+2th dresser height to the correction amount calculated in Step 5. In the embodiment, the correctionamount calculation part 83 may update the correction amount by subtracting the value, which is obtained by subtracting the N+2th dresser height from the N+1th dresser height, from the correction amount calculated in Step 5, or by adding the value to the correction amount calculated in Step 5. The difference between the N+2th dresser height and the N+1th dresser height is equivalent to the difference between the amounts of pushing thepolishing pad 22. - In the embodiment, as along as the change in abrasion loss of the
polishing pad 22 from a time of measuring the N+1th dresser height to a time of measuring the N+2th dresser height is substantially zero, the dresser height at the time of dressing after a m+αth substrate (α is a natural number equal to or larger than 1) is polished may be adopted as the N+2th dresser height. - Thereafter, polishing of a new substrate and dressing of the
polishing pad 22 are repetitively performed. InStep 12, after the substrate is polished, the polishingsurface 22 a of thepolishing pad 22 is dressed by thedresser 50 with the second dressing load, and the current dresser height is measured by thedisplacement sensor 60. - In
Step 13, the current dresser height measured inStep 12 is corrected based on the updated correction amount obtained inStep 10. Specifically, the dresserheight correction part 85 corrects the current dresser height by subtracting the updated correction amount from the current dresser height. In the embodiment, the dresserheight correction part 85 corrects the current dresser height by adding the correction amount to the current dresser height. The corrected current dresser height obtained in this manner corresponds to the current polishing pad height. - In
Step 14, the pad abrasionloss calculation part 86 calculates the abrasion loss of thepolishing pad 22 by subtracting the corrected current dresser height obtained inStep 13 from the reference dresser height. - Thereafter, polishing of a new substrate and dressing of the
polishing pad 22 are repetitively performed. Even when the dressing load is further changed, the current dresser height corrected through steps similar toSteps 9 to 13, that is, the current polishing pad height can be determined. -
FIG. 4 is a schematic view illustrating another embodiment of the polishing system. Since configurations and operations which are not particularly described in the present embodiment are the same as those in the embodiment which has been described with reference toFIGS. 1 to 3 , duplicate description thereof will be omitted. The polishing padheight monitoring part 80 of the present embodiment further includes adata accumulation part 87 and a relationalexpression determination part 91. - The
data accumulation part 87 accumulates data such as measurement values of dresser heights measured by thedisplacement sensor 60, and the dressing loads set in advance. The relationalexpression determination part 91 receives the accumulated data from thedata accumulation part 87 and obtains a relational expression expressing the relationship between the amount of change in dressing load and the amount of change in dresser height based on the amount of change in plurality of dressing loads and the amount of change in plurality of dresser heights corresponding to the amount of change in plurality of dressing loads. For example, a regression equation is determined by plotting a plurality of data points determined from the amounts of change in plurality of dressing loads and corresponding amounts of change in plurality of dresser heights on a coordinate system having the vertical axis indicating the amount of change in dressing load and the horizontal axis indicating the amount of change in dresser height, and performing regression analysis with respect to the plurality of data points. This regression equation is a relational expression expressing the relationship between the amount of change in dressing load and the amount of change in dresser height. - The relational expression determined by the relational
expression determination part 91 is sent to the correctionamount calculation part 83 and is stored in the correctionamount calculation part 83. The correctionamount calculation part 83 can calculate the correction amount for the dresser height corresponding to the amount of change in dressing load from the relational expression described above. The dresserheight correction part 85 corrects the dresser height based on the correction amount calculated by the relational expression described above. -
FIG. 5 is a schematic view illustrating still another embodiment of the polishing system. The polishing system of the present embodiment includes a plurality of polishingapparatuses 1 and the polishing padheight monitoring part 80 which has been described with reference toFIG. 1 or 4 . Since configurations of the polishing system which are not particularly described in the present embodiment are the same as those in the embodiment which has been described with reference toFIG. 1 or 4 , duplicate description thereof will be omitted. The polishing padheight monitoring part 80 is connected to the plurality of polishingapparatuses 1 via a network such as the internet. In the embodiment, the polishing system may include onepolishing apparatus 1. - The polishing system of the present embodiment can correct the dresser heights of the plurality of polishing
apparatuses 1 using one polishing padheight monitoring part 80. The dresser height can be corrected by a method similar to the method in the embodiment which has been described with reference toFIGS. 2 and 3 , or the method in the embodiment which has been described with reference toFIG. 4 . Thedata accumulation part 87 illustrated inFIG. 4 can accumulate pieces of data including the dresser heights of the plurality of polishingapparatuses 1 and the dressing loads of the plurality of polishingapparatuses 1, and the relationalexpression determination part 91 can obtain the relational expression between the amount of change in dressing load and the amount of change in dresser height based on the amount of change in plurality of dresser heights corresponding to the amount of change in plurality of dressing loads. Since the relationalexpression determination part 91 can obtain the foregoing relational expression based on more pieces of data, the polishing system of the present embodiment can improve the accuracy of calculating the correction amount for the dresser height corresponding to the amount of change in dressing load. - According to the embodiments described above, the correction amount for the dresser height corresponding to the amount of change in dressing load is calculated, and the dresser height is corrected based on the correction amount. Therefore, a corrected dresser height can express an accurate current polishing pad height. Accordingly, the accuracy of monitoring an abrasion loss of a polishing pad is improved, and therefore the accuracy of controlling a position for lowering a polishing head and the accuracy of controlling a polishing profile of a substrate can be improved.
- The embodiments described above are disclosed to allow persons having general knowledge in the technical field where the disclosure belongs to perform the disclosure. Various modification examples of the foregoing embodiments can be naturally performed by those skilled in the art, and the technical idea of the disclosure can also apply to another embodiment. Therefore, the disclosure is not limited to the disclosed embodiments and is to be interpreted within a widest scope in accordance with the technical idea defined by the claims.
Claims (11)
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JP2018156497A JP7265848B2 (en) | 2018-08-23 | 2018-08-23 | Method for determining polishing pad height, and polishing system |
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Cited By (2)
Publication number | Priority date | Publication date | Assignee | Title |
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US20200130136A1 (en) * | 2018-10-29 | 2020-04-30 | Taiwan Semiconductor Manufacturing Co., Ltd. | Chemical mechanical polishing apparatus and method |
US20220048160A1 (en) * | 2020-08-11 | 2022-02-17 | Ebara Corporation | Substrate processing apparatus and method for controlling dressing of polishing member |
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JP7421460B2 (en) | 2020-09-29 | 2024-01-24 | 株式会社荏原製作所 | Polishing equipment and how to determine when to replace polishing pads |
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JP5390807B2 (en) * | 2008-08-21 | 2014-01-15 | 株式会社荏原製作所 | Polishing method and apparatus |
JP5511600B2 (en) * | 2010-09-09 | 2014-06-04 | 株式会社荏原製作所 | Polishing equipment |
JP6121795B2 (en) * | 2013-05-15 | 2017-04-26 | 株式会社荏原製作所 | Dressing apparatus, polishing apparatus equipped with the dressing apparatus, and polishing method |
JP6313611B2 (en) * | 2014-02-28 | 2018-04-18 | 株式会社荏原製作所 | Polishing equipment |
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- 2018-08-23 JP JP2018156497A patent/JP7265848B2/en active Active
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US20200130136A1 (en) * | 2018-10-29 | 2020-04-30 | Taiwan Semiconductor Manufacturing Co., Ltd. | Chemical mechanical polishing apparatus and method |
US20220048160A1 (en) * | 2020-08-11 | 2022-02-17 | Ebara Corporation | Substrate processing apparatus and method for controlling dressing of polishing member |
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