WO2001032360A1 - Closed-loop ultrasonic conditioning control for polishing pads - Google Patents

Closed-loop ultrasonic conditioning control for polishing pads Download PDF

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Publication number
WO2001032360A1
WO2001032360A1 PCT/US2000/029831 US0029831W WO0132360A1 WO 2001032360 A1 WO2001032360 A1 WO 2001032360A1 US 0029831 W US0029831 W US 0029831W WO 0132360 A1 WO0132360 A1 WO 0132360A1
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WIPO (PCT)
Prior art keywords
pad
polishing
conditioning
monitoring
conditioner
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Application number
PCT/US2000/029831
Other languages
French (fr)
Inventor
Timothy S. Dyer
Original Assignee
Speedfam-Ipec Corporation
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Publication date
Priority to US43151399A priority Critical
Priority to US09/431,513 priority
Application filed by Speedfam-Ipec Corporation filed Critical Speedfam-Ipec Corporation
Publication of WO2001032360A1 publication Critical patent/WO2001032360A1/en

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Classifications

    • BPERFORMING OPERATIONS; TRANSPORTING
    • B24GRINDING; POLISHING
    • B24BMACHINES, DEVICES, OR PROCESSES FOR GRINDING OR POLISHING; DRESSING OR CONDITIONING OF ABRADING SURFACES; FEEDING OF GRINDING, POLISHING, OR LAPPING AGENTS
    • B24B53/00Devices or means for dressing or conditioning abrasive surfaces
    • B24B53/017Devices or means for dressing, cleaning or otherwise conditioning lapping tools
    • BPERFORMING OPERATIONS; TRANSPORTING
    • B24GRINDING; POLISHING
    • B24BMACHINES, DEVICES, OR PROCESSES FOR GRINDING OR POLISHING; DRESSING OR CONDITIONING OF ABRADING SURFACES; FEEDING OF GRINDING, POLISHING, OR LAPPING AGENTS
    • B24B1/00Processes of grinding or polishing; Use of auxiliary equipment in connection with such processes
    • B24B1/04Processes of grinding or polishing; Use of auxiliary equipment in connection with such processes subjecting the grinding or polishing tools, the abrading or polishing medium or work to vibration, e.g. grinding with ultrasonic frequency
    • BPERFORMING OPERATIONS; TRANSPORTING
    • B24GRINDING; POLISHING
    • B24BMACHINES, DEVICES, OR PROCESSES FOR GRINDING OR POLISHING; DRESSING OR CONDITIONING OF ABRADING SURFACES; FEEDING OF GRINDING, POLISHING, OR LAPPING AGENTS
    • B24B49/00Measuring or gauging equipment for controlling the feed movement of the grinding tool or work; Arrangements of indicating or measuring equipment, e.g. for indicating the start of the grinding operation

Abstract

A method and apparatus for controlling the conditioning of a polishing pad using noncontact ultrasonic techniques. Ultrasonic transducers (310) are employed to measure the thickness of an individual layer or layers of the polishing pad (100). These transducers may be located about the workpiece carrier, the pad conditioner (300) or in other appropriate positions to monitor pad parameters and provide metrology feedback to the carrier and/or conditioning assembly. The metrology data may include any one or more of the useful pad parameters such as pad layer thickness, pad compression, pad density, and pad fluid saturation. All these parameters may be used to control a variety of process variables, including pad conditioning, removal rate and other variables to extend pad useful life and improve planarization.

Description

CLOSED-LOOP ULTRASONIC CONDITIONING CONTROL FOR POLISHING PADS
BACKGROUND OF THE INVENTION
Field of the Invention
The present invention relates generally to the polishing of semiconductor wafers utilizing chemical mechanical polishing technology and, more particulariy, the present invention relates to conditioning the surfaces of polishing pads used therein,
Background of the Related Art
The advances in integrated circuit device technology have necessitated the advancement of chemical mechanical polishing (CMP) technology to provide better and more consistent surface planarization processes. The manufacture of these devices (i.e., CMOS, VLSI, ULSI, microprocessors, semiconductor memory, and related technologies) on prepared substrates and the preparation of the substrates themselves (prime wafer polishing) require very highly planar and uniform surfaces. To achieve these high levels of planarity and uniformity on substrate surfaces, the processes that produce them must be performed reliably and consistently. Surfaces that are underpolished, overpolished, nonun'tform, and/or nonplanar will not produce quality microelectronic devices.
In CMP fabrication techniques, a free abrasive chemical slurry is often used along with a rotating polishing pad, linear polishing belt, or rotating drum to contact the workpiece surface and to polish and planarize that surface. Typical examples of these types of apparatus are described in U.S. Patent No. 5,329,732, assigned to SpeedFam, disclosing a rotating polishing pad polisher; PCT Publication WO 97/20660, assigned to Applied Materials, disclosing a linear belt polisher; and U.S. Patent No. 5,643,056, assigned to Ebara Corporation and Kabushiki Kaisha Toshiba, disclosing a rotating drum polisher. The disclosures of the foregoing patents, in relevant part, are incorporated herein by reference.
In such prior art polishing methods, one side of the wafer is attached to a wafer carrier and the other side of the wafer is pressed against a polishing surface. In general, the polishing surface comprises a polishing pad or belt that can be formed of various commercially available materials such as blown polyurethane from Rodel Corporation of Scottsdale, Arizona. Typically, a water-based colloidal abrasive slurry such as cerium oxide, aluminum oxide, fumed/precipitated silica or other particulate abrasives is deposited upon the polishing surface. In other embodiments, a polishing pad with fixed abrasives may be used and such pads are available from 3M Corporation. During the polishing or planarization process, the workpiece (e.g., silicon wafer) is typically pressed against the moving (e.g., rotating or linearly translating) polishing surface. In addition, to improve the polishing effectiveness, the wafer may also be rotated about its vertical axis and/or oscillated over the inner and outer peripheries of the polishing surface. When pressure is applied between the polishing surface and the workpiece being polished, the combined abrasive particles and chemicals within the slurry produce mechanical abrasion and chemical corrosion of the surface being polished, thereby removing material from the workpiece.
However, a severe disadvantage to these methods is that any imperfections in the polishing surface will be transferred to the workpiece surface leading to a lessening of polishing planarity and uniformity of that workpiece. For these reasons, it is paramount not only to correct for degradation of the polishing surface due to wear, but also to correctly prepare the surface prior to use. The recent and continuing advances in semiconductor technology, including the use of novel materials and decreasing size geometries, forces the need to more osely control the regularity of the polishing processes. In particular, the use of soft metals such as copperas a replacement for the harder aluminum and tungsten in metal interconnects often produces irregular, nonplanar, and nonuniform polishing results when using polishing surfaces conditioned by currently known processes. A second type of device structure, namely shallow trench isolation (STl), also has the same difficulties. it has been generally understood that nonuniform surface wear and bulk deformation of the pad are the most significant causes of nonplanar and nonuniform polishing results. To alleviate this problem, methods have been developed to recondition the surface of the pad. These methods primarily abrade the pad, as described in U.S. Patent No. 5,486,131 , assigned to SpeedFam, that discloses an oscillating and rotating abrasive coated ring assembly and control system used in pad conditioning.
Other typical types of polishing pad conditioners and control systems therefor are described in the following patents and published applications: U.S. Patent No. 5,456,627, assigned to Westech Systems, discloses a rotating abrasive pad conditioner with variable position, velocity, and applied pressure. U.S. Patent No. 5,787,595, assigned to MEMC Electric Materials, discloses a fixed reference based polishing pad flatness measurement system using a laser sensor. U.S. Patent No. 5,801,066, assigned to Micron Technology, discloses a laser based differential thickness measurement system. U.S. Patent No. 5,618,447, assigned to Micron Technology, discloses a contour indicator using mechanical or laser measurement U.S. Patent No. 5,833,519, assigned to Micron Technology, discloses a force feedback and compare system. U.S. Patent No. 5,708,506, assigned to Applied Materials, discloses a light scattering technique and apparatus for measuring polishing pad roughness. PCT Application No. WO 97/22442, assigned to Applied Materials, discloses a friction sensing technique for determination of pad roughness. European Patent Application No. EP0829327A1, assigned to SpeedFam Co.. Ltd., discloses a laser based or mechanical contact sensor for pad thickness and contour measurement. European Patent Application No. EP0816017A1, assigned to Ebara Corporation, discloses a mechanical contact sensor for pad height measurement and feedback to control the pad conditioner. U.S. Patent No. 5,875,559, assigned to Applied Materials, discloses a gantry mounted contact sensor for pad thickness measurement. U.S. Patent No, 5,823.854, assigned to Industrial Technology Research Institute, discloses a through-the-pad current flow, Sherwood number calculation, method to control pad conditioning. The disclosures of the foregoing patents, in relevant part, are incorporated herein by reference.
Laser systems require the use of a fixed reference surface and all measurements are made relative to this surface. Therefore, a true direct absolute thickness measurement is not always possible because the laser only measures the distance to the exposed top surface of the polishing pad. Further limitations include instability in measurement due to scattering of the laser light by an uneven and constantly changing particle-entrained fluid layer on the surface of the pad. Other significant scattering is caused by the inherent roughness of the polishing pad surface itself, Furthermore, chemicals or polishing residuals in the fluid layer on the top of the pad may severely adsorb any incident light and effectively void any measurement. Mechanical assemblies may be added to the system to aid in controlling the fluid layer or providing a stabilized fixed reference during the laser measurement, but this adds complications witlrpotential fσrdowntime due to equipment failure.
Mechanical contact probe methods for measurement of the polishing pad thickness parameters and topology likewise pose difficulties. Unlike lasers, these systems are not limited by the fluid layer, but also only measure the location of the exposed surface of the polishing pad relative to some fixed reference surface. The mechanical interaction of the probe with the caustic, acidic, and/or abrasive slurries used during the polishing process often results in rapid deterioration of the probe. The wear of the probe produces free particulates that result in contamination of the polishing pad and the workpieces with debris and other chemical agents derived from the mechanical parts. The necessity of a fixed reference point also promotes complications in measurement due to the inherent vibration of the polishing tool so attached.
Electrochemical monitoring systems are inherently troublesome in the chemical mechanical polishing environment due to the instability and multiple influences of numerous electrical and electrochemical factors. These factors include such sources as static potentials, friction-induced current flows, leakage currents from motors and other sources, and, most significantly, the electrochemical activity of the chemical polishing slurries and deionized water mixtures.
In light of these restrictions, process engineers commonly cut pieces out of the polishing pad in order to use a dial indicator to measure the pad stack thickness. This technique requires a stationary platen, is very sensitive to pressures applied during measurement (the polishing pad is constructed of elastically compressible materials), and provides reference data only. The tool must be stopped to make the measurement, leading to increased downtime and decreased productivity of the equipment. Therefore, the measurement is (1 ) completely separate from the polishing or pad conditioning process requiring stoppage of that process, and (2) is a destructive method requiring physical removal of a section for measurement of the pad. In addition, these selective single point measurements are not truly representative of the global properties of the pad. Local variations in pad density make these single point measurements questionable. Also, technician interaction creates some degree of subjectivity in the testing that may result in biased measurements.
The only common in-situ practice of pad monitoring is by surrogate and involves monitoring of the rate of removal of material from polished workpieces. Any changes in this removal rate may directly relate to the surface condition of the pad. This procedure does not have universal application. The removal rate also depends on characteristics on slurries, rotation speeds, and other typical CMP process variables. Further, if the polishing pad surface has degraded, the polished workpiece may be damaged and this method would only detect pad damage after workpiece damage has occurred.
Presently known pad monitoring techniques are unable to provide sufficient flexibility, precision, simplicity, ease of use, and/or automation. There is a need for apparatus and methods that will eliminate or reduce these limitations, thereby permitting a higher degree of polishing pad metrology, appropriate conditioning, extended pad life and move uniformly polished workpieces.
SUMMARY OF THE INVENTION
This summary of invention section is intended to introduce the reader to aspects of the invention and is not a complete description of the invention. Particular aspects of the invention are pointed out in other sections hereinbelow, and the invention is set forth in the appended claims which alone demarcate its scope.
A principal object of the present invention is to provide methods and apparatus for in-situ metrology and control of conditioning for polishing pads. Another object of the present invention is to provide improved control of the surface texture and topology of a polishing pad surface through improved pad conditioning control. Another object of the present invention is to provide a polishing tool with a noncontact thickness measurement probe that is compatible with the chemical mechanical polishing environment. Another object of the present invention is to provide methods and apparatus for determining the degree of polishing pad fluid saturation.
Another object of the invention is to provide an automated system for pad monitoring, determination of when and how much conditioning is needed, and appropriate conditioning of the pad. Briefly, the present Invention provides methods and apparatus for conditioning a polishing surface comprising the steps of monitoring a polishing pad with an ultrasonic sensor, and removing material from the surface of the polishing pad depending upon monitor-provided information and predetermined pad parameters.
The present invention may include one or more ultrasonic sensors that communicate with a controller that directs the material removing process based on information derived from the sensors. The operational parameters of the material removing device, for example, include conditioner rotation velocity, conditioner rotation acceleration, conditioner position, applied conditioning force, conditioner and polishing pad relative velocity, fluid flow, slurry flow, and temperature.
BRIEF DESCRIPTION OF THE DRAWINGS
The following drawings are illustrative of embodiments of the invention and therefore do not limit the scope of the invention, but are presented to assist in providing a proper understanding of the invention. The drawings are not to scale, and are intended for use in conjunction with the explanations in the following detailed description section.
Fig. 1 is a perspective view of a platen assembly including a conditioning gantry and conditioning end-effector incorporating an embodiment of the present invention;
Fig. 2 is a schematic view of an ultrasonic sensor in accordance with the present invention;
Fig.3 is a process flow diagram in accordance with an embodiment of the present invention;
Fig. 4 is a plot of actual measurements of pad thickness comparing use of the present invention to the prior art; and
Fig.5 is another plot of actual measurements of pad thickness comparing use of the present invention with the prior art.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS
This section describes aspects of the invention, and points out certain preferred embodiments of these aspects. This section is not intended to be exhaustive, but rather to inform and teach the person of skill in the art who will come to appreciate more fully other aspects, equivalents, and possibilities presented by the invention, and hence the scope of the invention as set forth in the claims which alone limit its scope. The present invention relates to a method and apparatus for improving a polishing surface for use in processing workpiece surfaces. Although the workpiece may comprise virtually any device requiring a controlled surface finish, the present invention is conveniently described with reference to semiconductor wafers that require a controlled, planar, and uniform surface finish. It will be understood by those skilled in the art, however, that the invention is not limited to any particular type of workpiece, polishing surface (e.g., pad, belt, lapping plate, etc.) or any particular type of workpiece surface finish. As the methods of operation and apparatus for performing these polishing and lapping functions are well known in the art, they will not be described in detail here.
Fig. 1 depicts platen assembly 200 and conditioning assembly 300 in accordance with an embodiment of the present invention. Platen assembly 200 includes a platen 210 with platen surface 220. The platen assembly 200 is mounted for rotation in direction A, shown as counter-clockwise, on platen support 260. A polishing pad 100 with a polishing surface 120 is mounted to the platen surface 220 using well-known methods. The surface 120 of pad 100 may be shaped to enhance the polishing process; however, it is preferably a substantially planar surface, often with surface features such as pinholes, but otherwise insignificant surface irregularities to avoid interference with the planarizing process. Polishing pad 100 may be comprised of a variety of materials such as polyurethane, felt, fabric-land the like.
The shape and size of pad 100 is not of significance, but in the semiconductor polishing art, as currently preferred, polishing pad 100 has a diameter D1 of 25 to 40 inches (most preferably 32 inches) and a thickness T1 of 0.04 to 0.15 inches (most preferably 0.10 inches). Pad 100 may also be comprised of multiple layers that are often formed of different materials (e.g., the top layer is a material of type IO1000 and the bottom layer is a material of type Suba IV, both as manufactured by Rodel Corporation of Scottsdale, Arizona). A conditioning gantry assembly 300, positioned to overhang the platen assembly 200, includes a z-axis (normal to the polishing surface) actuator 320 that raises and lowers, a radially oscillating arm 340, and a conditioning tool 360 attached by a spindle 365 to the end of arm 340. Motors, linear actuators, ball screws, hydraulic mechanisms, or other similar mechanisms that are known in the art may be used to control the motion of conditioning tool 360, arm 340, and z-axis actuator 320.
Polishing pad thickness sensor 310 is preferably mounted to the arm 340 proximate the conditioning tool 360. This permits local reading of the polishing pad thickness immediately following or prior to (depending upon rotation direction A) the conditioning and material removal from that specific locality on the surface 120.
In another embodiment, a plurality of sensors is placed in both following 310 and leading positions (not shown) relative to the conditioning tool 360. Alternatively, an array of sensors 310 may be used to allow for measurement of a larger area of the polishing pad 100. The sensors could be contact or non-contact probes and may be stationary (hovering above the pad), attached to the pad conditioning arm, or mobile (for instance moving along a track). Transducers could also be in an array to record an instantaneous pad profile or produce a pad thickness contour map in real-time.
In another embodiment, a single sensor or multiple sensors may be mounted proximate to a wafer carrier assembly (not shown) to provide in-s"rtu information during the polishing of a workpiece.
The polishing pad thickness measuring sensor is preferably a type of ultrasonic transducer that is available from such suppliers as Panametrics located in Waltham, Massachusetts, Unicom Automation NDT Ltd. in the United Kingdom. Digital Wave of Englewood, Colorado, and NDT International of West Chester, Pennsylvania. These sensors commonly operate in a frequency range of about 1 to about 10 MHz. and this frequency may be optimized to achieve the best possible signal for a specific set of measuring conditions.
During operation of the conditioning process, there is commonly a (discontinuous) fluid layer 140 comprising slurry, deionized water, and other chemicals and polishing residual solids in random locations on~fhe surface 120όfthe~polishiπg pad 100. This fluid layer 140 does not interfere or degrade the sensor signal, but provides a coupling medium for permitting increased transmission of the ultrasonic signal relative to air.
When a new polishing pad 100 is placed onto the platen assembly 200, a break-in cycle is commonly performed. This process involves the conditioning and preparation of the polishing pad surface 120 with the appropriate contour and topology. This process also requires that the pad be "stable". Pad stability relates to the performance of the polishing pad 100 in terms of the substantial invartance of the removal rate of material (over a period of time) from processed workpieces during a polishing process. Aside from the requirement that the pad have the proper contour for a selected polishing process and workpiece, it is also, for example, necessary for the pad to be at the appropriate temperature and to be saturated with process fluids. Establishing a set temperature and saturation criteria that are met prior to processing reduces the risk of initial transient characteristics during the workpiece processing. During any downtime or inactive periods of use, polishing pad stability characteristics will change and, prior to restarting use, the polishing process including the polishing pad must be requalified to the criteria preset to begin wafer processing. This process is time-consuming and adds to wafer production cost. The present invention with its incorporation of an ultrasonic thickness measurement device determines the polishing pad saturation, pad "break-in", and polishing pad thickness within a short time period, thereby reducing costs related to requalification.
The present invention in its multiple embodiments provides various forms and arrangements of sensors for detecting topology and thickness by determining the distance between interfaces within the polishing pad and platen assembly.
As shown in Fig.2, the ultrasonic transducer transmits a signal toward the surface of material to be measured and this signal is reflected or echoed by the material or materials that are sampled by the signal. The echoed signal has well-known properties that allow the determination of positions of interfaces existent in the sample being probed . These interfaces include, for example, the top surface of the polishing pad 120, the interfaces of any intermediate layers in the polishing pad layered structure 130, and the pad-platen interface 140. Since the sensor is able to determine the positions of both the top and bottom interfaces of the polishing pad layers being probed, a mechanically fixed reference point is not necessary. By using multiple sensors mounted both leading and lagging the wafer carrier or conditioning head, it is possible to resolve compression hysteresis response methods of the elastic polishing pad. This condition effectively results in direct thickness measurement of single or multiple layers at specific points or locations of the pad without the added complications of corrections that would otherwise be required with a fixed reference point and without measurement error due to vibrations, platen "runout", or other mechanical motions that would occur with the use of a contact probe.
Since the speed of sound is directly proportional to the material through which it travels, the sensor and related electronics are able to determine the level of pad saturation. Simply stated, in a dry polishing pad the speed of sound is significantly greater than the speed of sound in a fully liquid saturated pad. Therefore, as the degree of polishing pad saturation changes, the time for an echo of the probe pulse to return to the sensor will change in a measurable way. A variable spot size can easily allow signal averaging of the polishing pad area to present a detailed
Figure imgf000012_0001
of the "degree of saturation versus position" across the entire pad. Additionally, the use of a variable spot size allows for signal averaging to either enhance or eliminate the effects of the polishing pad surface roughness on thickness measurement. This adjustability allows the user to selectively measure or eliminate either the pad thickness or pad surface roughness during data reduction. Furthermore, certain types of polishing pads are formed with combinations of grooves and holes that alter process performance. These features may be selectively measured or ignored by averaging over the smaller or larger spot sizes, respectively.
Fig. 3 shows a flow chart of a preferred series of process steps for controlling the conditioning of a polishing pad using the present invention. The conditioning control process begins with step 3000, that determines the thickness and other properties of the pad using the ultrasound sensor. Next, the measurements are compared to a conditioning recipe that either references and compares static predetermined parameters or performs a dynamic evaluation of the data from step 3000. After evaluation of the data, a selection is made between three options of how to proceed. The selection between these options is based on a feedback system that inteφrets the data and provides an interface between the measurement device and the conditioning assembly or other polishing tool systems that in turn modify the polishing pad. A digital pad thickness sensor could feed information back to a control circuit to measure both the pad cut rate (removal rate of material from the polishing pad surface) and profile. It is important to control these parameters because the pad cut rate correlates directly with material removal rates during polishing of wafers, and pad contour affects polish uniformity. In terms of components, the feedback and control system includes a sensing unit, a transducer and a feedback loop to an imbedded control system in a CMP tool. The control system may include a personal computer or other instrumentation controllers. Using historical data, the feedback and control system predicts pad lifetime continuously through a series of sequential polishing processes. This assists in improving pad-to-pad control of material removal rates by permitting adjustment of conditioning time or downforce (closed loop cut rate control). With improved control of pad performance, parameters, process and equipment cost-of-ownership (COO) is reduced. —Pad performance and COO related factors that can be optimized by this system include reduced pad-related downtime, improved polishing process performance, higher equipment utilization, and a reduction of unnecessary maintenance. The first of the three possible options referenced above is an "under" condition response. The "under" condition is selected when the pad is either thinner or less saturated than expected by the recipe. Upon this determination, the process flow advances to step 3200: no polishing pad material is removed and/or fluid may be added to aid in saturation. The second possible option for selection is a "correct'' condition response which means that measured parameters are as required by the recipe. No action is taken and the process flow advances to step 3400.
The third option for action is selected when there is an "over" condition. An "over" condition means that material must be removed from the polishing pad surface. During step 3300, the conditioning assembly parameters are controlled to remove the required amount of material to bring the thickness to within the criteria set by the recipe. These parameters include, but are not limited to, the conditioner rotation velocity, conditioner rotation acceleration, conditioner position, applied conditioning force, conditioner and polishing pad relative velocity, fluid flow, slurry flow, and temperature. Once the necessary amount of material has been removed, the process returns to step 3000. Due to the constant motion of the platen and conditioning assembly, the material removal may have to be performed as a series of removal steps instead of removal of all material in one step.
Detailed below is an example of the control of the "velocity operational parameter." During conditioning, the "feed rate" or relative velocity of the pad conditioning with respect to the pad surface, as the tool traverses the polishing pad, is preferably in the range of about 0.05 to about 1.0 m/s. Slower velocities will remove less pad material, whereas higher velocities will remove more material. This rate of motion is provided by the combined actions of the relative movement of the polishing surface for example any one or combination of (rotation, translation, etc. motion) and the oscillating arm and conditioning tool. Either the pad or the conditioning tool rate of motion may be changed. or both, to achieve a desired removal rate. Other operational parameters may likewise be controlled. To achieve a desired pad material removal rate.
Figs. 4 and 5 show actual data comparing practice of the invention with the prior art based on two different types of polishing pads. In Fig. 4, the pad thickness measurements using the invention are from a single layer pad of a type known as IC1000 from Rodel Corporation, and these are compared with measurements using a prior art dial indicator on the same pad. This graph shows that the in-situ noncontact ultrasonic method of the invention produces measurements that correlate well with the ex-situ contact probe method and that the measurements are equivalent and reproducible to within about 0.005 inches. Deioπized water was used as the preferred coupling medium for the sound transducer; however, slurry may also be used.
The measurements in Fig. 5 are from a dual layer pad of a type known as IC1000/Suba IV, also from Rodel Corporation. From these measurements, it is apparent that the ultrasonic sensor used in accordance with the invention is able to differentiate the thickness of the top layer discretely from the overall polishing pad thickness, which cannot be accomplished with the contact or laser probe prior art methods.
Although the present invention is set forth herein in the context of the appended drawing figures, it should be appreciated by those skilled in the art that the invention is not limited to the specific forms shown. Various other modifications, variations, and enhancements in the design and arrangement of the apparatus as set forth herein may be made without departing from the spirit and scope of the present invention as set forth in the appended claims. For example, while one embodiment of the invention includes a device for polishing semiconductor wafers, it should be understood that the invention is not limited to any particular type of workpiece such as device wafers, hard disks, or glass. Moreover, other embodiments and methods of use of the ultrasonic measurement devices, as well as other types of feedback and control systems, are possible.

Claims

What is claimed is:
1. A method for automatically conditioning a polishing surface of a polishing pad comprising the steps of: (a) monitoring a polishing pad with an ultrasonic sensor; (b) comparing information from monitoring with predetermined pad criteria; and (c) removing material from the surface of said polishing pad based on the step of comparing.
2. The method of claim 1 wherein said monitoring step comprises monitoring the polishing pad with a plurality of ultrasonic sensors.
3. The method of claim 1 wherein said monitoring comprises monitoring with an ultrasonic sensor not in contactwfth the pad.
4. The method of claim 1 wherein the removing comprises adjusting operational parameters of a pad conditioner performing the removing of material.
5. The method of claim 4 wherein said operational parameters are selected from the group comprising conditioner rotation velocity, conditioner rotation acceleration, conditioner position, applied conditioning force, relative velocity between conditioner and polishing pad, fluid flow, slurry flow, and temperature.
6. An apparatus for conditioning a polishing surface comprising: (a) a polishing pad with a surface for polishing workpieces; (b) a conditioning device for conditioning the polishing pad; (c) an ultrasonic sensor monitoring the surface of the pad; and
(d) an information feedback system receiving signals from the sensor and transmitting signals to control the conditioning device.
7. The apparatus of claim 6 wherein said conditioning device comprises an abrasive coated ring.
8. The apparatus of claim 6 comprising ultrasonic sensors mounted proximate
> said conditioning device.
9. The apparatus of claim 6 further comprising controls to control speed and location in three dimensional space of the conditioning device.
10. The apparatus of claim 9 wherein said controls for controlling the three- dimensional position and speed of said conditioning device comprises an oscillating arm and a z-axis motion control device.
1 11. The apparatus of claim 9 wherein said controls for controlling the three- dimensional position and speed of said conditioning device comprises a three-axis gantry.
1 12. A chemical mechanical polishing tool for polishing workpieces, the tool
2 comprising:
3 (a) at least one carrier for holding a workpiece for polishing; (b) a polishing pad mounted to a platen for polishing workpieces in the
5 carrier against the pad;
6 (c) a controlled pad conditioning device proximate the pad, the pad
7 conditioning device adapted for removing material from the pad to condition a polishing
8 surface of the pad; (d) at least one ultrasonic sensor mounted for monitoring the polishing surface of the pad; and
(e) a pad conditioning control system receiving input from the at least one sensor, comparing the input with pad criteria, and selecting action based on the comparison, the control system controlling the conditioning device.
13. The tool of claim 1 wherein the conditioning device is an abrasive ring.
14. The tool of claim 12, wherein the carrier is adapted for holding semiconductor wafers.
15. The tool of claim 14, wherein the pad is adapted for polishing semiconductor wafers with an abrasive chemical slurry.
16. The tool of claim 15, wherein the conditioning device conditions the pad by removing material from the polishing surface of the pad.
AMENDED CLAIMS
[received by the International Bureau on 27 February 2001 (27.02.01); original claims 1 - 16 amended; new claims 17 - 21 added; remaining claims unchanged (3 pages)] What is claimed is:
1. A method for automatically conditioning a polishing surface of a polishing pad comprising the steps of:
(a) monitoring a polishing pad with an ultrasonic sensor;
(b) comparing information from monitoring with predetermined pad criteria; and
(c) removing material from the surface of said polishing pad based on the step of comparing.
2. The method of Claim 1, wherein said monitoring step comprises monitoring the polishing pad with a plurality of ultrasonic sensors.
3. The method of Claim 1 , wherein said monitoring comprises monitoring with an ultrasonic sensor not in contact with the pad.
4. The method of Claim 1 , wherein the removing comprises adjusting operational parameters of a pad conditioner performing the removing of material.
5. The method of Claim 4, wherein said operational parameters are selected from the group consisting of conditioner rotation velocity, conditioner rotation velocity, conditioner rotation acceleration, conditioner position, applied conditioning force, relative velocity between conditioner and polishing pad, fluid flow, slurry flow, and temperature.
6. An apparatus for conditioning a polishing surface comprising:
(a) a polishing pad with a surface for polishing workpieces;
(b) a conditioning device for conditioning the polishing pad;
(c) an ultrasonic sensor monitoring the surface of the pad; and
- 18 - AMENDED SHEET (RULE 19) (d) an information feedback system receiving signals from the sensor and transmitting signals to control the conditioning device.
7. The apparatus of Claim 6, wherein said conditioning device comprises an abrasive coated ring.
8. The apparatus of Claim 6, comprising ultrasonic sensors mounted proximate said conditioning device.
9. The apparatus of Claim 6, wherein said controls for controlling the three-dimensional position and speed of said conditioning device comprises an oscillating arm and a z-axis motion control device.
11. The apparatus of Claim 9, wherein said controls for controlling the three-dimensional position and speed of said conditioning device comprises a three-axis gantry.
12. A chemical mechanical polishing tool for polishing workpieces, the tool comprising:
(a) at least one carrier for holding a workpiece for polishing;
(b) a polishing pad mounted to a platen for polishing workpieces in the carrier against the pad;
(c) a controlled pad conditioning device proximate the pad, the pad conditioning device adapted for removing material from the pad to conditioning device adapted for removing material from the pad to condition a polishing surface of the pad;
(d) at least one ultrasonic sensor mounted for monitoring the polishing surface of the pad; and
(e) a pad conditioning control system receiving input from the at least one sensor, comparing the input with pad criteria, and selecting action based on the comparison, the control system controlling the conditioning device.
13. The tool of Claim 12, wherein the conditioning device is an abrasive ring.
- 19 - AMENDED SHEET (RULE 19)
14. The tool of Claim 12, wherein the carrier is adapted for holding semiconductor wafers.
15. The tool of Claim 14, wherein the pad is adapted for polishing semiconductor wafers with an abrasive chemical slurry.
16. The tool of Claim 15, wherein the conditioning device conditions the pad by removing material from the polishing surface of the pad.
17. A method for automatically conditioning a polishing surface of a polishing pad comprising the steps of:
(a) monitoring a polishing pad with at least one ultrasonic sensor;
(b) comparing information from monitoring with predetermined pad criteria; and
(c) conditioning the pad when the comparing of information indicates a divergence of monitored polishing pad condition from predetermined pad criteria by greater than a predetermined margin.
18. The method of Claim 17, wherein the step of conditioning comprises removing material from a polishing surface of the polishing pad.
19. The method of Claim 17, wherein the monitoring comprises monitoring operational parameters selected from the group consisting of conditioner rotation velocity, conditioner rotation acceleration, conditioner position, applied conditioning force, relative velocity between conditioner and polishing pad, fluid flow, slurry flow, and temperature.
20. The method of Claim 17 further comprising signal averaging of information about the polishing pad area being monitored to determine degree of pad saturation versus position across at least a portion of the pad.
21. The method of Claim 17, wherein the monitoring comprises monitoring the polishing pad with a plurality of ultrasonic sensors.
- 20 -
AMENDED SHEET ( RULE 19)
PCT/US2000/029831 1999-11-01 2000-10-30 Closed-loop ultrasonic conditioning control for polishing pads WO2001032360A1 (en)

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KR102113067B1 (en) * 2018-11-29 2020-05-21 한국생산기술연구원 Apparatus for determining pad replacement time of cmp apparatus for wafer and control method therefor
KR102154583B1 (en) 2020-07-28 2020-09-10 (주)티씨에스 Method for measuring a cmp pad and bute of fabricating device

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