Polishing apparatus

A polishing apparatus is used for polishing a workpiece such as a semiconductor wafer to a flat mirror finish, and allows a polishing pad to be automatically replaced without stopping rotary or circulatory motion of a polishing table. The polishing apparatus comprises a polishing table for making rotary or circulatory motion, a top ring vertically movably disposed above the polishing table for removably holding a workpiece to be polished, a pair of rolls rotatable about their own axes and movable in unison with the polishing table, and a polishing pad which is wound on one of the rolls and supplied over an upper surface of the polishing table toward the other of the rolls.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to a polishing apparatus for polishing a workpiece such as a semiconductor wafer to a flat mirror finish, and more particularly to a rotary-type polishing apparatus which allows a polishing pad to be automatically replaced without stopping rotary or circulatory motion of a polishing table.

2. Description of the Related Art

Recent rapid progress in semiconductor device integration demands smaller and smaller wiring patterns or interconnections and also narrower spaces between interconnections which connect active areas. One of processes available for forming such interconnections is photolithography. Though a photolithographic process can form interconnections that are at most 0.5 μm wide, it requires that surfaces on which pattern images are to be focused by a stepper be as flat as possible because depth of focus of an optical system is relatively small.

It is therefore necessary to make surfaces of semiconductor wafers flat for photolithography. One customary way of flattening surfaces of semiconductor wafers is to polish them with a polishing apparatus, and such a process is called Chemical Mechanical Polishing (CMP) in which semiconductor wafers are chemically and mechanically polished while supplying a polishing liquid comprising abrasive grains and chemical solution such as alkaline solution.

In a manufacturing process of a semiconductor device, a thin film is formed on a semiconductor device, and then micromachining processes, such as patterning or forming holes, are performed thereon. Thereafter, the abov processes are repeated to form thin films on the semiconductor device. Recently, semiconductor devices have become more integrat d, and structure of semiconductor elements has become more complicated. In addition, the number of layers in multilayer interconnections used for a logical system has been increased. Therefore, irregularities on a surface of a semiconductor device are increased, so that step height on the surface of the semiconductor device becomes larger.

When irregularities of a surface of a semiconductor device are increased, the following problems arise. Thickness of a film formed in a portion having a step is relatively small. An open circuit is caused by disconnection of interconnections, or a short circuit is caused by insufficient insulation between layers. As a result, good products cannot be obtained, and yield is lowered. Further, even if a semiconductor device initially works normally, reliability of the semiconductor device is lowered after a long-term use.

Thus, during a manufacturing process of a semiconductor device, it is increasingly important to planarize a surface of the semiconductor device. The most important one of planarizing technologies is chemical mechanical polishing (CMP). During chemical mechanical polishing, a polishing apparatus is employed. While a polishing liquid containing abrasive particles such as silica (SiO2) therein is supplied onto a polishing surface such as a polishing pad, a substrate such a semiconductor wafer is brought into sliding contact with the polishing surface, so that the substrate is polished.

FIGS. 16 and 17of the accompanying drawings show a conventional polishing apparatus for carrying out a CMP process. As shown inFIGS. 16 and 17, the conventional polishing apparatus comprises a polishing table102having a polishing pad (polishing cloth)100attached to its upper surface, a motor104for rotating the polishing table102, and a vertically movable top ring106for holding a substrate W such as a semiconductor wafer with its surface, to be polished, facing the polishing pad100. While the polishing table102and the top ring106ar being rotated independently about their own axes, the substrate W is pressed against the polishing pad100under a constant pressure by the top ring106, and a polishing liquid is supplied from a nozzle (not shown) to the polishing pad100, thereby polishing the surface of the substrate W to a flat mirror finish. The polishing liquid comprises fine abrasive particles of silica or the like suspended in an alkaline solution or the like. The substrate W is polished by a chemical mechanical polishing action which is a combination of a chemical polishing action performed by the alkaline solution and a mechanical polishing action performed by the abrasive particles of silica or the like.

The polishing pad100is usually regenerated by a dresser which comprises a nylon brush, diamond particles, or the like. When the polishing pad100is worn to an extent that its polishing capability can no longer be restored by the dresser, the polishing pad100is replaced with a new one.

The polishing pad100is generally attached to an upper surface of the polishing table102by an adhesive tape. For replacing the polishing pad100with a new one, it is necessary to temporarily stop a CMP process, and a skilled operator is required to peel off the polishing pad100and attach a new polishing pad100to the polishing table102.

FIG. 18of the accompanying drawings shows another conventional polishing apparatus for eliminating the above drawbacks. The polishing apparatus shown inFIG. 18has a polishing pad100attached to a polishing table102under vacuum developed by a vacuum attraction section108provided in the polishing table102. Since the polishing pad100is removed from the polishing table102by releasing the vacuum, the polishing pad100can easily and quickly be replaced with a new one. However, replacing the polishing pad100requires temporarily stopping a CMP process because the polishing pad cannot b replac d while the polishing pad table102is rotating.

Still another conventional polishing apparatus is shown inFIG. 19of th accompanying drawings. InFIG. 19, a polishing table110is fixed in position, and a pair of rolls112,114are rotatably disposed one on each side of the polishing table110. An elongate polishing pad116wound onto the roll112is continuously fed at a constant speed along an upper surface of the polishing table110, and beneath a substrate W, toward the other roll114onto which the polishing pad116is wound. The substrate W is polished by the elongate polishing pad116as the polishing pad travels over the polishing table110in one direction. Principles of the polishing apparatus shown inFIG. 19are not applicable to a rotary-type polishing apparatus in which a polishing table makes rotary or circulatory motion.

SUMMARY OF THE INVENTION

It is therefore an object of the present invention to provide a rotary-type polishing apparatus which has a polishing table that makes rotary or circulatory motion, and which allows a polishing pad to be automatically replaced without stopping a CMP process.

Another object of the present invention is to provide a polishing apparatus which has a polishing table that makes predetermined motion, and which allows a polishing pad to be automatically replaced without stopping a CMP process.

According to a first aspect of the present invention, there is provded a polishing apparatus comprising: a polishing table for making rotary or circulatory motion; a top ring vertically movably disposed above the polishing table for removably holding a workpiece to be polished; a pair of rolls rotatable about their own axes and movable in unison with the polishing table; and a polishing pad which is wound on one of the rolls and supplied over an upper surface of the polishing table toward the other of the rolls.

Even when the polishing table is in rotary or circulatory motion, the polishing pad can be transported from one of the rolls over the upper surface of the polishing table toward the other roll by a distance corresponding to a region of the polishing pad that has been used to polish workpieces. A used region of the polishing pad can thus automatically be replaced with a new region thereof.

In a preferred aspect of the present invention, the polishing table has an attraction section for attracting and holding the polishing pad to the polishing table.

In a preferred aspect of the present invention, the polishing apparatus further comprises a roll motor connected to at least the other of the rolls, wherein the roll motor is controllable in a wireless or wired fashion. When a signal is transmitted to the roll motor to energize the roll motor to rotate the rolls, a used region of the polishing pad can automatically be replaced with a new region thereof.

In a preferred aspect of the present invention, the polishing pad comprises one of a polyurethane foam pad, a suede type pad, and a fixed abrasive pad comprising abrasive particles embedded therein.

In a preferred aspect of the present invention, the polishing apparatus further comprises a sensor for detecting surface roughness of the polishing pad.

In a preferred aspect of the present invention, the polishing apparatus further comprises a sensor for detecting surface for detecting surface roughness of the polishing pad, and the roll motor is energized on the basis of a detection signal of the sensor.

In a preferred aspect of the present invention, the polishing pad comprises a plurality of sub-pads which are divided along a take-up direction of the polishing pad.

According to a s cond aspect of the pres nt invention, there is provided a polishing apparatus comprising: a polishing table for making predetermined motion; a top ring vertically movably disposed above the polishing table for removably holding a workpiece to be polished; a polishing pad supply device for holding an elongate polishing pad and supplying the polishing pad therefrom; and a polishing pad holding device for holding the polishing pad supplied from the polishing pad supply device and placing the polishing pad such that the polishing pad makes predetermined motion integrally with the polishing table.

According to the second aspect of the present invention, the polishing pad is supplied from the polishing pad supply device, and the supplied polishing pad is held by the polishing pad holding device and placed in an elongate state on the polishing table. Thus, even if the polishing table is in motion, a used region of the polishing pad can thus automatically be replaced with a new region of the polishing pad.

In a preferred aspect of the present invention, the polishing pad supply device comprises a supply roll onto which the elongate polishing pad is wound.

In a preferred aspect of the present invention, the polishing pad holding device comprises a take-up roll onto which the elongate polishing pad is to be wound.

In a preferred aspect of the present invention, the polishing table has an attraction section for attracting and holding the polishing pad to the polishing table.

In a preferred aspect of the present invention, the polishing apparatus further comprises a roll motor connected to the take-up roll, wherein the roll motor is controllable in a wireless or wired fashion.

In a preferred aspect of the present invention, the predetermined motion of the polishing table is one of rotary motion, circulatory motion, and lin ar reciprocating motion.

According to a third aspect of the present invention, there is provided a polishing apparatus comprising: a polishing table for making predetermined motion; a top ring vertically movably disposed above the polishing table for removably holding a workpiece to be polished; a polishing pad supply device for holding an elongate polishing pad and supplying the polishing pad therefrom; a polishing pad holding device for holding the polishing pad supplied from th polishing pad supply device and placing the polishing pad such that the polishing pad makes predetermined motion integrally with the polishing table; and a sensor for detecting surface roughness of the polishing pad.

According to a fourth aspect of the present invention, there is provided a polishing apparatus comprising: a polishing table for making predetermined motion; a top ring vertically movably disposed above the polishing table for removably holding a workpiece to be polished; a polishing pad supply device for holding an elongate polishing pad and supplying the polishing pad therefrom; a polishing pad holding device for holding the polishing pad supplied from the polishing pad supply device and placing the polishing pad such that the polishing pad makes predetermined motion integrally with the polishing table; and a brush for removing from the polishing pad ground-off material produced during a polishing process.

According to a fifth aspect of the present invention, there is provided a polishing apparatus comprising: a polishing table for making predetermined motion; a top ring vertically movably disposed above the polishing table for removably holding a workpiece to be polished; a polishing pad supply device for holding an elongate polishing pad and supplying the polishing pad therefrom; a polishing pad holding d vice for holding the polishing pad supplied from the polishing pad supply device and placing the polishing pad such that the polishing pad makes predetermined motion integrally with the polishing table; and an atomizer for spraying a gas-liquid mixture onto the polishing pad.

According to a sixth aspect of the present invention, there is provided a polishing apparatus comprising: a polishing table for making predetermined motion; a top ring vertically movably disposed above the polishing table for removably holding a workpiece to be polished; a polishing pad supply device for holding an elongate polishing pad and supplying the polishing pad therefrom; a polishing pad holding device for holding the polishing pad supplied from the polishing pad supply device and placing the polishing pad such that the polishing pad makes predetermined motion integrally with the polishing table; and an eddy-current sensor for monitoring thickness of a film of the workpiece.

According to a seventh aspect of the present invention, there is provided a polishing apparatus comprising:a first polishing table which mounts a polishing pad on a surface of the first polishing table, wherein the polishing pad being is held by at least two rolls disposed around the first polishing table; anda second polishing table which mounts a polishing pad on a surface of the second polishing table, wherein the polishing pad is held by at least two rolls disposed around the second polishing table.

According to an eighth aspect of the present invention, there is provided a polishing apparatus comprising:a first polishing table which mounts a polishing pad on a surface of the first polishing table, wherein the polishing pad is held by at least two rolls disposed around the first polishing table; anda second polishing table which mounts a polishing pad on a surface of the second polishing table, wherein the polishing pad is held by at least two rolls disposed around the second polishing table, wherein respective shafts of the rolls are substantially parallel to a polishing surface of the polishing pad.

The above and other objects, features and advantages of the present invention will become apparent from the following description when taken in conjunction with the accompanying drawings which illustrate a preferred embodiment of the present invention.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

A polishing apparatus according to embodiments of the present invention will be described with reference to drawings.

FIGS. 1 and 2show a polishing apparatus according to a first mbodiment of the present invention. As shown inFIGS. 1 and 2, a polishing apparatus according to the present invention comprises a rectangular planar polishing table10, a motor12for rotating the polishing table10, and a top ring14vertically movably disposed above the polishing table10for removably holding a substrate W such as a semiconductor wafer with its surface, to be polished, facing the polishing table10.

Support plates16,18are attached to lower surfaces of opposite sides of the polishing table10and extend horizontally away from each other from the opposite sides of the polishing table10. The support plate16supports a bearing20on its upper surface. An elongate supply roll22has an end rotatably supported by the bearing20, and an opposite end connected by a coupling24to a supply roll motor26that is supported on an upper surface of the support plate16. When the supply roll motor26is energized, the supply roll22is rotated about its own axis. The other support plate18supports a bearing28on its upper surface. An elongate take-up roll30has an end rotatably supported by the bearing28and an opposite end connected by a coupling32to a take-up roll motor34that is supported on an upper surface of the support plate18. When the take-up roll motor34is energized, the take-up roll30is rotated about its own axis.

An elongate polishing pad36is wound onto the supply roll22, extends along an upper surface of the polishing table10, and has a free end removably gripped by the take-up roll30. When the supply roll motor26and the take-up roll motor34are energized, the supply roll22and the take-up roll30are synchronously rotated about their own axes in one direction to cause the polishing pad36to travel from the supply roll22along the upper surface of the polishing table10toward the take-up roll30onto which the polishing pad36is wound. Tension of the polishing pad36between the supply roll22and the take-up roll30can be adjusted by regulating rotational speeds of the supply roll22and the take-up roll30. The polishing pad36can be returned from the take-up roll30toward the supply roll22when the supply roll22and the take-up roll30are reversed.

The polishing table10has an attraction section40for attracting the polishing pad36under vacuum to the upper surface of the polishing table10. The attraction section40comprises a plurality of vacuum holes which are formed in the polishing table10, and are open at the upper surface of the polishing table10and connected to a vacuum source such as a vacuum pump. A rotary joint46which connects a cable44extending from a controller42, and cables extending respectively from the supply roll motor26and the take-up roll motor34, is attached to the motor12. The controller42controls the supply roll motor26and the take-up roll motor34, respectively, through the cable44and the cables extending from the motors. However, the controller42may be arranged to control the supply roll motor26and the take-up roll motor34in a wireless fashion.

The polishing apparatus shown inFIGS. 1 and 2operates as follows: While the polishing table10and the top ring14are being rotated independently about their own axes, the substrate W is pressed against the polishing pad36under a constant pressure by the top ring14, and a polishing liquid is supplied from a nozzle (not shown) to the polishing pad36, thereby polishing the surface of the substrate W to a flat mirror finish. At this time, the supply roll22and the take-up roll30also rotate about the axis of the polishing table10in unison with the polishing table10. The polishing pad36is attracted to and held by the upper surface of th polishing table36under vacuum developed in the vacuum holes of the attraction section40. Therefore, the polishing pad36is prevented from being displaced with respect to the polishing table while the substrate W is being polished thereby.

For polishing an oxide film on the substrate W, for example, the polishing liquid comprises a silica slurry such as SS-25 (manufactured by Cabbot), a CeO2slurry, or the like. For polishing a tungsten film on the substrate W, for example, the polishing liquid comprises a silica slurry such as W2000 (manufactured by Cabbot) containing H2O2as an oxidizing agent, an alumina-base slurry of iron nitrate, or the like. For polishing a copper film on the substrate W, for example, the polishing liquid comprises a slurry containing an oxidizing agent, such as H2O2for turning the copper film into a copper oxide film, a slurry for polishing a barrier layer, or the like. In order to remove particles or defects from the substrate being polished, surfactant or alkali solution as a polishing liquid may be supplied halfway through a polishing operation for conducting a finish polishing.

The polishing pad36is made of polyurethane foam such as IC1000 or a suede-like material such as Polytex. In order to increase resiliency of the polishing pad36, the polishing pad36may be lined with a layer of nonwoven cloth or sponge, or a layer of nonwoven cloth or sponge may be attached to the upper surface of the polishing table10.

The polishing pad36may comprise a fixed abrasive pad comprising particles of CeO2, silica, alumina, SiC, or diamond embedded in a binder, so that the polishing pad36can polish the substrate W while not a polishing liquid containing abrasive particles, but rather a polishing liquid containing no abrasive particles, is being supplied thereto. An ammeter, a vibrometer, or an optical sensor may be incorporated into the polishing table and/or the top ring14for measuring a state of the substrate W while the substrate W is being polished.

When a region of the polishing pad36which has been used is worn to such an extent that its polishing capability can no longer be restored by a dresser, the controller42sends a signal to energize the supply roll motor26and the take-up roll motor34to rotate the supply roll22and the take-up roll30, respectively, in synchronism with each other in one direction. Thus, the polishing pad36travels from the supply roll22toward the take-up roll30along the upper surface of the polishing table10. After the polishing pad36has traveled a predetermined distance, which is long enough to displace the worn region of the polishing pad36off the upper surface of the polishing table10, the controller42de-energizes the supply roll motor26and the take-up roll motor34to stop the supply roll22and the take-up roll30, thus positioning a new region of the polishing pad36over the upper surface of the polishing table10.

Even when the polishing table10is in rotation, the worn region of the polishing pad36can be automatically replaced with a new region thereof by transporting the polishing pad36from the supply roll22toward the take-up roll30over the upper surface of the polishing table10by the predetermined distance corresponding to a length of the polishing table10, i.e. one pad and then stopping the polishing pad36. Alternatively, the polishing pad36may be wound onto the take-up roll30by a distance “a”, shown inFIGS. 1 and 2, corresponding to a distance from an end of the polishing table10to a center of the substrate W located at a polishing position. Thus, a new polishing pad and a used polishing pad are simultaneously presented, with the new polishing pad and the used polishing pad having different regions in a radial direction of the substrate W for thereby imparting a polishing action equally to an entire surface of the substrate W.

The polishing pad36and the supply roll22may be25integrally combined into a cartridge, so that they can be quickly installed and removed between the bearing20and the coupling24. The supply roll motor26may be eliminated, and the polishing pad36may be supplied from the supply roll22toward the take-up roll30only by the take-up roll motor34. The polishing pad table10may be of a circular shape.

FIGS. 3 and 4show the polishing apparatus shown inFIGS. 1 and 2to which a dressing apparatus and the like are added. Specifically, the polishing apparatus is provided with a diamond dresser60and a water jet nozzle65. The polishing liquid supply nozzle70denotes a polishing liquid supply nozzl for supplying a polishing liquid onto a central area of the polishing table10. The diamond dresser60is angularly movable in a horizontal plane between a dressing position over the polishing table10and a standby position off the polishing table10. The diamond dresser60has an electrodeposited diamond ring61which comprises fine grains of diamond electrodeposited on a lower surface of the ring. Specifically, the electrodeposoted diamond ring61is produced by attaching fine grains of diamond to its lower surface and then plating its lower surface with nickel for thereby fixing the fine grains of diamond with a plated nickel layer. The dresser60may be replaced with an SiC dresser having a ring of sectors made of silicon carbide. The SiC dresser has on surfaces of its sectors a number of pyramidal projections each having a height of about several tens of μm.

On the other hand, the water jet nozzle65extends to a central area of the polishing pad36in a width direction of the polishing pad36, and has a plurality of openings disposed on its lower surface at certain intervals for ejecting pure water jets therefrom. The water jet nozzle65is connected to a pump66, and pressure of the waterjets ejected from the openings can be maintained in a range of 490 to 2940 kPa (5 to 30 kg/cm2) by controlling rotational speed of the pump66.

With the above arrangement, the substrate W is polished by supplying the polishing liquid containing abrasive particles from the polishing liquid supply nozzle70onto the polishing pad36, and then finish-polished by stopping supply of the polishing liquid from the polishing liquid supply nozzle70and supplying ultrapure water from the waterjet nozzle65onto the polishing pad36. When the polishing pad36starts to be used, it is first dressed by the diamond dresser60for initial conditioning. Thereafter, the substrate W is polished using the dressed polishing pad36. Between polishing processes, the polishing pad36is dressed by the water jet nozzle65with water jets ejected therefrom.

Alternatively, when the polishing pad36starts to be used, it is first dressed by the diamond dresser60for initial conditioning. Thereafter, the substrate W is polished using the dressed polishing pad36. Between polishing processes, the polishing pad36is dressed in two steps, i.e., first by the diamond dresser60and then by the water jet nozzle65with water jets ejected therefrom.

According to the polishing apparatus of the present invention, finish-polishing can be conducted by supplying ultrapure water as a polishing liquid to the polishing pad36from the water jet nozzle65. Further, after initial conditioning of the polishing pad36by the diamond dresser60, a polishing process of the substrate W is carried out, and after completing the polishing process, dressing of the polishing pad36with water jets is carried out by the water jet nozzle65. Thereafter, a polishing process is carried out again. Further, between polishing processes, dressing of the polishing pad36by the diamond and water jets may be combined.

In the illustrated embodiment, the diamond dresser60is a contact-type dresser. However, the diamond dresser may be replaced with a brush dresser.

Next, sensors provided in the polishing table for monitoring a state of the substrate being polished will be described with reference toFIGS. 5 through 7.FIG. 5shows the polishing table and top ring in cross-section. InFIG. 5, the polishing pad36is attached to the polishing table10under vacuum.

As shown inFIG. 5, an eddy-current sensor67is mounted in the polishing table10, and is electrically connected to a controller86by a wire84extending through the polishing table10, a table support shaft10a, and a rotary connector or slip ring85mounted on a lower end of the table support shaft10a. The controller86is connected to a display unit87.

An optical sensor75is mounted in the polishing table10adjacent to the eddy-current sensor67. The optical sensor75comprises a light-emitting element and a light-detecting element. The light-emitting element applies light to the surface, being polished, of the substrate W, and the light-detecting element det cts reflected light from the surface, being polished, of the substrate W. The polishing pad36has an opening36cat a position corresponding to the optical sensor75. The optical sensor75is electrically connected to a controller89by a wire88extending through the polishing table10, the table support shaft10a, and the rotary connector85mounted on the lower end of the table support shaft10a. The controller89is connected to the display unit87.

The top ring14is coupled to a motor (not shown) and connected to a lifting/lowering cylinder (not shown). Therefore, the top ring14is vertically movable and rotatable about its own axis, as indicated by arrows, and can press the substrate W against the polishing pad36under a desired pressure. The top ring14is connected to the lower end of a vertical top ring drive shaft73, and supports on its lower surface an elastic pad74of polyurethane or the like. A cylindrical retainer ring69is provided around an outer circumferential edge of the top ring14for preventing the substrate W from being dislodged from the top ring14while the substrate W is being polished.

FIG. 6is a plan view showing the polishing pad36and the polishing table10in which the sensors are mounted. As shown inFIG. 6, the eddy-current sensor67and the optical sensor75are positioned so as to pass through a center CWof the substrate W held by the top ring14while the substrate W is being polished, when the polishing table10rotates about its own axis CT. While the eddy-current sensor67and the optical sensor75pass along an arcuate path beneath the substrate W, the eddy-current sensor67and the optical sensor75continuously detect a thickness of a film such as a copper layer on the substrate W. In order to shorten an interval between detecting intervals, one or more eddy-current sensors67and one or more optical sensors75may be added as indicated by imaginary lines inFIG. 6, so that at least two sets of sensors are provided in the polishing table10.

The polishing apparatus shown inFIG. 6operates as follows: The substrate W is held on a lower surface of the top ring14, and pressed by th lifting/lowering cylinder against the polishing pad36on the polishing table10which is rotating. The polishing liquid supply nozzle70supplies polishing liquid Q to the polishing pad36on the polishing table10, and the supplied polishing liquid Q is retained on the polishing pad36. The substrate W is polished in the presence of th polishing liquid Q between a lower surface of the substrate W and the polishing pad36. While the substrate W is being thus polished, the eddy-current sensor67passes directly beneath the surface, being polished, of the substrate W each time the polishing table10makes one revolution. Since the eddy-current sensor67is positioned on an arcuate path extending through the center CWof the substrate W, the eddy-current sensor67is capable of continuously detecting a thickness of a film on the substrate W as the eddy-current sensor67moves along the arcuate path beneath the substrate W.

Principles of detecting a thickness of a film of copper, aluminum or the like on the substrate W with the eddy-current sensor67will be described below.

The eddy-current sensor has a coil which is supplied with a high-frequency current. When the high-frequency current is supplied to the coil of the eddy-current sensor, an eddy current is generated in film on the substrate W. Since the generated eddy current varies depending on a thickness of the film, combined impedance of the eddy-current sensor and the film, such as a copper layer, is monitored to detect the thickness of the film. Specifically, combined impedance Z of the eddy-current sensor and the copper layer is represented by inductive and capacitive elements L, C of the eddy-current sensor, and resistive element R of the copper layer which is connected in parallel to the inductive and capacitive elements L, C. When the resistive element R in the equation shown below varies, the combined impedance Z also varies. At this time, resonance frequency also varies, and a rate of change of the resonance frequency is monitored to determine an end point of a CMP process.Z=jwL(1-ω2⁢LC)+jwLR
where Z is combined impedance, j is square root of −1 (imaginary number), L is inductance, f is resonance frequency, C is electrostatic capacitance, R is resistance of the copper layer, and ω=2 πf.

FIGS. 7A and 7Bare graphs showing changes in resonance frequency of a detected signal that is produced by the eddy-current sensor67and processed by the controller86while the substrate W is being polished. InFIGS. 7A and 7B, the horizontal axis represents polishing time, and the vertical axis represents the resonance frequency (Hz).FIG. 7Ashows changes in the resonance frequency when the eddy-current sensor67passes a plurality of times directly below the substrate W, andFIG. 7Bshows, at an enlarged scale, an encircled portion A in FIG.7A. Results shown inFIGS. 7A and 7Bare obtained when the film on the substrate W is a copper layer.

As shown inFIG. 7A, as polishing of the substrate W progresses, a value produced by processing a detected signal from the eddy-current sensor67is progressively reduced. This processing of the detected signal is performed by the controller86. Specifically, as thickness of the copper layer decreases, resonance frequency obtained by processing the detected signal from the eddy-current sensor67is progressively reduced. InFIG. 7A, the resonance frequency decreases from an initial value of 6800 Hz. Therefore, if a value of the resonance frequency, at a time when the copper layer is removed, except for copper in interconnection grooves, has been examined, then an end point of a CMP process can be detected by monitoring the value of the resonance frequency. InFIG. 7A, the value of the resonance frequency at the tim when the copper layer is removed, except for copper in the interconnection grooves, is 6620 Hz. If a certain frequency before reaching the end point of the CMP process is established as a threshold, then it is possible to polish the substrate W under a first polishing condition, then polish the substrate W under a second polishing condition after the threshold is reached, and finish the CMP process when the end point thereof is reached by removing the copper layer and a barrier layer completely.

Next, the principles of detecting the thickness of the copper layer on the substrate W by the optical sensor75will be briefly described.

During polishing, every time the polishing table10makes one revolution, the optical sensor75passes along an arcuate path beneath the substrate W. Thus, light emitted from the light-emitting element in the optical sensor75passes through the hole of the polishing table10and the opening36cof the polishing pad36and is incident on a surface, being polished, of the substrate W, and light reflected from the surface of the substrate W is received by the light-detecting element in the optical sensor75. The light received by the light-detecting element is processed by the controller89to measure a thickness of a top layer on the substrate W.

Principles of detecting a thickness of a film by the optical sensor utilizes interference of light caused by the top layer and a medium adjacent to the top layer. When light is applied to a thin film on a substrate, a part of the light is reflected from a surface of the thin film while a remaining part of the light is transmitted through the thin film. A part of the transmitted light is then reflected from a surface of an underlayer or the substrate, while a remaining part of the transmitted light is transmitted through the underlayer or the substrate. In this case, when the underlayer is made of a metal, light is absorbed in the underlayer. A phase difference between light reflected from the surface of the thin film and light reflected from the surface of the underlayer or the substrate creates the interference. When phases of these two lights are identical to each other, light intensity is increased, while when the phases of the two lights are opposite to each other, the light intensity is decreased. That is, reflection intensity varies with a wavelength of incident light, film thickness, and a refractive index of the film. Light reflected from the substrate is separated by a diffraction grating or the like, and a profile depicted by plotting intensity of reflected light for each wavelength is analyzed to measure the thickness of the film on the substrate.

By the polishing apparatus incorporating two kinds of sensors for measuring film thickness, until a thickness of the film, such as a copper layer, is reduced to a certain smaller value, thickness of the film is monitored by the controller86which processes a signal from the eddy-current sensor67. When thickness of the film reaches the certain smaller value and begins to be detected by the optional sensor75, thickness of the thin film is monitored by the controller89which processes a signal from the optical sensor75. Therefore, by using the optical sensor75which is of a higher sensitivity with regard to thickness of a copper layer (film), it is possible to accurately detect when a copper layer is removed, except for copper in the interconnection grooves, thereby determining an end point of a CMP process.

Alternatively, both the eddy-current sensor67and the optical sensor75can be used until an end point of a CMP process is reached. Specifically, the controllers86and89process respective signals from the eddy-current sensor67and the optical sensor75to detect when a copper layer is removed, except for copper in interconnection grooves, thereby determining an end of the CMP process. In the above embodiments, the film on the substrate W is made of copper. However, the film to be measured may comprise an insulating layer such as SiO2.

In the illustrated embodiments, the polishing table10is rotated about its own axis. However, principles of the present invention are also applicable to a polishing apparatus in which a polishing table makes circulatory motion, i.e. scroll motion.

Next, a polishing table which makes scroll motion will be described with reference toFIGS. 8,9A and9B.FIG. 8is a cross-sectional view showing a polishing table and a motor section,FIG. 9Ais a plan view showing a section for supporting the polishing table, andFIG. 9Bis a cross-sectional view taken along line A—A of FIG.9A. InFIG. 8, polishing pad36is held by a polishing table130under vacuum.

As shown inFIG. 8, circular polishing table130is supported by a cylindrical casing134which houses a drive motor133therein. Specifically, an annular support plate135extending radially inwardly is provided at an upper part of the cylindrical casing134, three or more support sections136are formed in a circumferential direction on the annular support plate135, and the circular polishing table130is supported by these support sections136. The support sections136and the circular polishing table130have a plurality of recesses138,139, respectively, in upper and lower surfaces thereof at positions facing each other. The recesses are arranged at circumferentially equal intervals, and bearings140,141are fitted into the recesses138,139, respectively (see FIG.9B). Connecting members144which have upper and lower shafts142,143of each connecting member144are fitted into the bearings140,141, respectively.

An axis of the upper shaft142of a connecting member144is displaced from an axis of the lower shaft143of the connecting member by an eccentric distance “e” as shown inFIG. 9B, thereby allowing the polishing table130to mak circulative translation motion (scroll motion) along a circle having a radius “e”.

As shown inFIG. 8, a recess148is formed in a central area of a bottom surface of the polishing table130for accommodating a drive shaft146of a main shaft145through a bearing147fitted in the recess148. An axis of the drive shaft146is displaced from an axis of the main shaft145by an eccentric distance “e” as well. The drive motor133is housed in a motor chamber149formed in the casing134, and the main shaft145of the drive motor133is supported by upper and lower bearings150,151.

The polishing table130has a diameter slightly larger than the sum of twice offset length “e” and a diameter of a substrate to be polished, and is constructed by joining two plate-like members153,154. A space155is defined between the two plate-like members153,154, and communicates with a vacuum source such as a vacuum pump and a plurality of vacuum holes157which are open at an upper surface of the polishing table130. Thus, when the space155communicates with the vacuum source, the polishing pad36is attracted to the polishing table130under vacuum through the vacuum holes157. A top ring (not shown) as a pressing device has the same structure as those shown inFIGS. 1 and 5, except that this top ring rotates at a slower rotational speed.

With the above structure, while the polishing table130makes scroll motion and top ring14(seeFIGS. 1 and 5) is rotated about its own axis, substrate W is pressed against the polishing pad36under a constant pressure by the top ring14while a polishing liquid is supplied from a nozzle (not shown) onto the polishing pad36, thereby polishing a surface of the substrate W to a flat mirror finish. At this time, the polishing pad36is attracted to and held by the upper surface of the polishing table130under vacuum, and hence the polishing pad36is prevented from being displaced with respect to the polishing table130during polishing. Action of minute circulative translation motion (scroll motion) of radius “e” between the substrate W and a polishing surface of the polishing pad36produces a uniform polishing over an entire surface of the substrate W. If a positional relationship between a surface, to be polished, of the substrate W and the polishing surface of the polishing pad36is the same, then a polished surface of the substrate is adversely influenced by local differences in surface conditions of the polishing pad36. In order to avoid such adverse influence, the top ring14is slowly rotated about its own axis to prevent the surface of the substrate W from being polished at the same position on the polishing pad36.

Because the polishing table130shown inFIGS. 8,9A and9B is a scroll motion type, a size of the polishing table130needs only to be larger than a size of a substrate, to be polished, by the eccentric distance “e”. Therefore, installation space required for installing the polishing table is reduced significantly in comparison to a rotating-type polishing table. Further, since the polishing table130makes a scrolling motion, the polishing table130can be supported at a plurality of positions near a peripheral portion thereof as shown inFIG. 8, and hence a substrate can be polished to a higher degree of flatness in comparison with a rotation-type polishing table which rotates at a high speed.

The polishing table shown inFIGS. 8,9A and9B may supply a polishing liquid onto the polishing surface of the polishing pad36through the polishing table. In this case, the space155is connected to a polishing liquid supply source, and through-holes are formed in the polishing pad36at positions corresponding to the holes157of the polishing table130. With this arrangement, polishing liquid may be supplied onto an upper surface of the polishing pad36through the space155, th holes157and the through-holes of the polishing pad36.

FIGS. 10 and 11show an essential part of a polishing apparatus according to a second embodiment of the present invention, whereinFIG. 10is a schematic cross-sectional view of the polishing apparatus andFIG. 11is a plan view of the polishing apparatus. As shown inFIG. 10, the polishing apparatus comprises a circular planar polishing table10, a motor12for rotating the polishing table10, and a top ring14vertically movably disposed abov the polishing table10for removably holding a substrate W such as a semiconductor wafer with its surface, to be polished, facing the polishing table10. A support plate16is attached to a lower surface of the polishing table10, and supports a supply roll22and a take-up roll30thereon through bearings20,28, respectively. The polishing table10is rotated about its own axis by the motor12. While the substrate W is being polished, the take-up roll30is rotated by energizing a take-up roll motor34to cause the polishing pad36to travel along an upper surface of the polishing table10in a direction shown by an arrow. The polishing table10has a fluid passage10cformed therein, and the fluid passage10cis connected to a fluid source such as a compressed air source through a rotary connector85. The fluid passage10cis open at the upper surface of the polishing table10, and when fluid is supplied to the fluid passage10c, fluid such as compressed air is ejected from the upper surface of the polishing table10.

With the above structure, during movement of the polishing pad36, fluid such as compressed air is supplied to the fluid passage10cfrom the fluid source, and then supplied fluid is ejected from the upper surface of the polishing table10toward the polishing pad36. Thus, a frictional force between the polishing table10and the polishing pad36is reduced, and movement of the polishing pad36along the polishing table10, i.e. automatic replacement of the polishing pad36can b smoothly conducted. When pressure of fluid ejected from the fluid passage10ctoward the polishing pad36is varied in accordance with a radial position of the substrate W, a pressing force applied between the substrate W and the polishing pad36can be changed at a central area and an outer circumferential area of the substrate W. Specifically, polishing pressure applied to the substrate W can be varied in accordance with positions in a radial direction of the substrate W to thus control a polishing profile.

InFIG. 10, an air cylinder51for moving the top ring14vertically, a swing arm52for angularly movably supporting the top ring14, and a motor53for angularly moving the swing arm52are shown. Further, a motor54for rotating the top ring14about its own axis is also shown.

In the embodiment shown inFIG. 10, a sensor55for detecting a surface roughness of the polishing pad is provided downstream of a polishing surface of the polishing pad36(i.e. a side of the take-up roll30). In the sensor55, light is applied to the polishing surface of the polishing pad36by a light-emitting element, reflected light from the polishing surface of the polishing pad36is received by a light-detecting element, and surface roughness of the polishing pad36is detected on the basis of intensity of the reflected light received by the light-detecting element. The sensor55is connected to a controller56, and when the sensor55detects wear of the polishing pad36and sends a signal to the controller56, the take-up roll motor34is energized to rotate the take-up roll30, and thus the polishing pad36is wound by a predetermined length. Further, a UV irradiating source57is provided below the polishing pad36. In a case where a fixed abrasive pad is used as polishing pad36, an ultraviolet ray is applied onto the polishing pad36from the UV irradiating source57to cause binder, for fixing abrasive particles of the abrasive pad, to deteriorate and to cause the abrasive particles of the polishing pad36to be liberated.

According to this embodiment, the polishing pad36comprises a plurality of sub-pads which are divided in a longitudinal direction thereof. Specifically, as shown inFIG. 11, two sub-pads36adisposed at both sides, and a sub-pad36bdisposed at a central portion, are held by a common supply roll22and a common take-up roll30, thus providing a plurality of polishing surfaces on the polishing table10. By moving the top ring14between the two kinds of the sub-pads36a,36b, when substrate W held by the top ring14is positioned at a central portion of the polishing table10, the substrate W is polished only by the sub-pad36b, and when substrate W held by the top ring14is positioned at an outer peripheral portion of the polishing table10, the substrate W is mainly polished by one of the sub-pads36a. According to these divided-type polishing pads of the present invention, multi-stage polishing of substrate W can be conducted under different conditions on a single polishing table. At this time, a rotational speed of the polishing table10may be changed during a mid-portion of a polishing process, and a take-up speed of the sub-pads36a,36bmay be varied during a mid-portion of a polishing process. Further, substrate W may be disposed on the sub-pads36a,36bsimultaneously, and the substrate W may be polished in such a manner that the substrate W is brought into contact with different sub-pads at a central portion of an outer peripheral portion of the substrate W.

Polishing liquid supply nozzle70extends over the sub-pads36aand36b, and has a plurality of openings at positions corresponding to the sub-pads36aand36bso that a polishing liquid is supplied onto the sub-pads36aand36bsimultaneously. A high-pressure pure water spray or atomizer71is disposed above the polishing table10and adjacent to the polishing liquid supply nozzle70so that high-pressure pure water, or a gas-liquid mixture (foggy mixture of pure water and nitrogen), can be sprayed therefrom. Thus, high-pressure pure water, or a gas-liquid mixture is sprayed over polishing surfaces of the sub-pads36aand36bby the high-pressure pure water spray or atomizer71, for thereby conducting cleaning and dressing of the polishing surfaces. Further, a brush72having nylon bristles may be provided to remove ground-off material, produced during a polishing process, from the polishing surfaces as a kind of a dressing process.

According to this embodiment, as shown inFIG. 11, a gap g is provided between each sub-pad36aand the sub-pad36b. Thus, light emitted from optical sensor75(see FIG.5), comprising a light-emitting element and a light-detecting element mounted in the polishing table10, passes through one of the gaps g between one of the sub-pads36aand the sub-pad36band is incident on a surface of the substrate W, and hence thickness of film on the substrate W can be measured when the substrate W passes above this gap g between the sub-pad36aand the sub-pad36b. After thickness of the film on the substrate W measured by the optical sensor75reaches a predetermined value, rotational speed of the top ring, rotational speed of the polishing table, and a pressing applied to the substrate W may be varied.

In a case where a thin polishing pad is used, a medium such as light, sound waves (acoustic emission), electromagnetic waves, or X-rays passes through the polishing pad, and hence by applying such medium to substrate W from a side of the polishing table, thickness of a film on the substrate W can be measured.

Next, structure of components associated with the polishing surface of polishing pad36will be described below.

If ground-off material or fine particles produced by polishing are attached to rolls or other rotating parts, a drive of such rolls or parts is adversely affected. Thus, in the polishing apparatus of the present invention, the following measures are taken: portions which are brought in sliding contact with each other are constructed from synthetic resin; portions which are brought in sliding contact with each other are coated with synthetic resin; portions from which dust is generated are exhausted; and portions from which dust is generated have a labyrinth structure. With this arrangement, fine particles are prevented from being scattered, or from adhering to driving portions.

Further, pressure in a polishing space in which a polishing table, a polishing pad and a top ring are disposed is set such that pressure decreases from high to low in the order of: a position where a substrate to be polished is located, a polishing position of the substrate; and a position where a polished substrate is located.

FIGS. 12 and 13show an essential part of a polishing apparatus according to a third embodiment of the present invention, whereinFIG. 12is a schematic cross-sectional view andFIG. 13is a plan view. In the polishing apparatus of this embodiment, polishing table10makes a linear reciprocating motion in a horizontal direction.

The polishing table10comprises a rectangular planar table, and the polishing table10reciprocates linearly along a guide rail80. A linear motor81is provided at a portion which supports the polishing table10, and the polishing table10reciprocates along the guide rail80by energizing the linear motor81. A ball screw may be used instead of the linear motor. Other construction of the polishing apparatus shown inFIGS. 12 and 13is identical to the polishing apparatus shown inFIGS. 10 and 11. In the polishing apparatuses shown inFIGS. 10 through 13, the polishing pad may be attracted under vacuum to the polishing table.

FIG. 14shows an entire structure of a polishing apparatus, and specifically a layout of various components of the polishing apparatus according to the present invention.FIG. 15shows a relationship between top ring14and polishing tables10and130. In this polishing apparatus, a fixed abrasive pad and/or a polishing pad made of polyurethane foam or the like shown inFIGS. 1 through 13, which can be automatically replaced, are used.

As shown inFIG. 14, a polishing apparatus according to the present invention comprises four load-unload stages222each for receiving a wafer cassette221which accommodates a plurality of substrates W such as semiconductor wafers. Each load-unload stage222may have a mechanism for raising and lowering a respective wafer cassette221. A transfer robot224having two hands is provided on rails223so that the transfer robot224can move along the rails223and access respective wafer cassettes221on respective load-unload stages222.

The transfer robot224has two hands which are located in a vertically spaced relationship, wherein a lower hand is used only for removing a substrate W from a wafer cass tte221and an upper hand is used only for returning the substrate W to the wafer cassette221. This arrangement allows that a clean semiconductor wafer which has been cleaned is placed at an upper side and is not contaminated. The lower hand is a vacuum attraction-type hand for holding a semiconductor wafer under vacuum, and the upper hand is a recess support-type hand for supporting a peripheral edge of a semiconductor wafer by a recess formed in the hand. The vacuum attraction-type hand can hold a semiconductor wafer and transport th semiconductor wafer even if the semiconductor wafer is not located at a normal position in a wafer cassette221due to a slight displacement, and the recess support-type hand can transport a semiconductor wafer while keeping the semiconductor wafer clean because dust is not collected, unlike the vacuum attraction-type hand. Two cleaning apparatuses225and226are disposed at an opposite side of the wafer cassettes221with respect to the rails223of the transfer robot224. The cleaning apparatuses225and226are disposed at positions that can be accessed by the hands of the transfer robot224. Between the two cleaning apparatuses225and226and at a position that can be accessed by the transfer robot224, there is provided a wafer station270having four wafer supports227,228,229and230. The cleaning apparatuses225and226have a spin-dry mechanism for drying a substrate by spinning the substrate at a high speed, and hence two-stage cleaning or three-stage cleaning of the substrate can be conducted without replacing any cleaning module.

An area B in which the cleaning apparatuses225and226and the wafer supports227,228,229and230are disposed, and an area A in which the wafer cassettes221and the transfer robot224are disposed, are partitioned by a partition wall284so that cleanliness of area B and area A can be separated. The partition wall284has an opening for allowing substrates W to pass25therethrough, and a shutter231is provided at the opening of the partition wall284. A transfer robot280having two hands is disposed at a position where the hands of the transf r robot280can access the cleaning apparatus225and three wafer supports227,229and230, and a transfer robot281having two hands is disposed at a position where the hands of the transfer robot281can access the cleaning apparatus226and three wafer supports228,229and230.

The wafer support227is used to transfer a substrate W between the transfer robot224and the transfer robot280and has a sensor291for detecting whether or not a substrate W is present. The wafer support228is used to transfer a substrate W between the transfer robot224and the transfer robot281and has a sensor292for detecting whether or not a substrate W is present. The wafer support229is used to transfer a substrate W from the transfer robot281to the transfer robot280and has a sensor293for detecting whether or not a substrate is present, and rinsing nozzles295are provided for supplying a rinsing liquid to prevent a substrate W from drying or to conduct rinsing of a substrate W. The wafer support230is used to transfer a substrate W from the substrate robot280to the transfer robot281and has a sensor294for detecting whether or not a substrate W is present, and rinsing nozzles296are provided for supplying a rinsing liquid to prevent a substrate W from drying or to conduct rinsing of a substrate W. The wafer supports229and230are disposed in a common water-scatter-prevention cover which as an opening defined therein for transferring substrates therethrough, wherein the opening is combined with a shutter297. The wafer support229is disposed above the wafer support230, and the wafer support229serves to support a substrate which has been cleaned while the wafer support230serves to support a substrate to be cleaned, so that the cleaned substrate is prevented from being contaminated by rinsing water which would otherwise fall thereon. The sensors291,292,293and294, the rinsing nozzles295and296, and the shutter297are schematically shown inFIG. 14, and their positions and shapes are not illustrated exactly.

The transfer robot280and the transfer robot281each have two hands which are located in a vertically spaced relationship. Respective upper hands of the transfer robot280and the transfer robot281are used for transporting a substrate W, which has been cleaned, to the cleaning apparatuses or the wafer supports of the wafer station270, and respective lower hands of the transfer robot280and the transfer robot281are used for transporting a substrate W which has not been cleaned or a substrate W to be polished. Since each lower hand is used to transfer a substrate to or from a reversing device, each upper hand is not contaminated by drops of a rinsing water which fall from an upper wall of a reversing device.

A cleaning apparatus282is disposed at a position adjacent to the cleaning apparatus225and is accessible by the hands of the transfer robot280, and another cleaning apparatus283is disposed at a position adjacent to the cleaning apparatus226and is accessible by the hands of the transfer robot281.

All the cleaning apparatuses225,226,282and283, the wafer supports227,228,229and230of the wafer station270, and the transfer robots280and281are placed in area B. Pressure in area B is adjusted so as to be lower than pressure in area A. Each of the cleaning apparatuses282and283is capable of cleaning both surfaces of a substrate.

The polishing apparatus has a housing266for enclosing various components therein. An interior of the housing266is partitioned into a plurality of compartments or chambers (including areas A and B) by partition walls284,285,286and287.

A polishing chamber separated from area B by the partition wall287is formed, and is further divided into two areas C and D by a partition wall267. In each of areas C and D, there are provided two polishing tables, and a top ring for holding a substrate W and pressing the substrate W against the polishing tables. That is, one polishing table10(seeFIG. 1) and one polishing table130(seeFIG. 8) are provided in area C, and another polishing table10(seeFIG. 1) and another polishing table130(seeFIG. 8) are provided in area D. Further, one top ring14is provided in area C and another top ring14is provided in area D. One polishing liquid supply nozzle70for supplying a polishing liquid to polishing table10in area C and one dresser60(seeFIG. 3) for dressing this polishing table10are disposed in area C. Another polishing liquid supply nozzle70for supplying a polishing liquid to the polishing table10in area D and another dresser60(seeFIG. 3) for dressing this polishing table10are disposed in area D. A dresser268for dressing polishing table130in area C is disposed in area C, and a dresser269for dressing polishing table130in area D is disposed in area D. The polishing tables130and130may be replaced with wet-type thickness measuring devices for measuring a thickness of a layer on a substrate. If such wet-type thickness measuring devices are provided, then they can measure a thickness of a layer on a substrate immediately after the substrate is polished, and hence it is possible to further polish the polished substrate or control a polishing process for polishing a subsequent substrate based on a measured value.

As shown inFIG. 14, in area C separated from area B by partition wall287and at a position that can be accessed by the hands of the transfer robot280, there is provided a reversing device278for reversing a semiconductor wafer, and at a position that can be accessed by the hands of the transfer robot281, there is provided a reversing device278′ for reversing a substrate W. The partition wall287between area B and areas C, D has two openings each for allowing substrates to pass therethrough, one of which openings is used for transferring a substrate W to or from the reversing device278and the other of which openings is used for transferring a substrate W to or from the reversing device278′. Shutters245and246are provided at respective openings of the partition wall287.

The reversing devices278and278′ each have a chuck mechanism for chucking a substrate W, a reversing mechanism for reversing a substrate W, and a wafer detecting sensor for detecting whether or not the chuck mechanism chucks a substrate W. The transfer robot280transfers a substrate W to the reversing device278, and the transfer robot281transfers a substrate W to the reversing device278′.

As shown inFIGS. 14 and 15, a rotary transporter277is disposed below the reversing devices278and278′ and top ring14(in area C) and top ring14(in area D), for transferring substrates W between a cleaning chamber (area B) and a polishing chamber (areas C and D). The rotary transporter277has four stages for placing substrates W at equal angular intervals, and can hold a plurality of substrates thereon at the same time.

A substrate W which has been transported to the reversing device278or278′ is transferred to a lifter279or279′ disposed below the rotary transporter277by actuating the lifter279or279′ when a center of a stage of the rotary transporter277is aligned with a center of the substrate W held by the reversing device278or278′. The substrate W which has been transported to the lifter279or279′ is transferred to the rotary transporter277by lowering the lifter279or279′. The substrate W placed on a stage of the rotary transporter27is transported to a position below top ring14(in area C) or top ring14(in area D) by rotating the rotary transporter277by an angle of 90°. At this time, the top ring14(in area C) or the top ring14(in area D) is positioned above the rotary transporter277beforehand by a swinging motion thereof.

The substrate W is transferred from the rotary transporter277to a pusher290or290′ disposed below the rotary transporter277, and finally the substrate W is transferred to the top ring14(in area C) or the top ring14(in area D) by actuating the pusher290or290′ when a center of the top ring14(in area C) or the top ring14(in area D) is aligned with a center of the substrate placed on the rotary transporter277.

The substrate transferred to the top ring14(in area C) or the top ring14(in area D) is held under vacuum by vacuum attraction mechanism of this top ring, and transported to the polishing table (in area C) or the polishing table10(in area D). Thereafter, the substrate is polished by a polishing surface comprising a polishing pad made of polyurethane foam or the like, or a fixed abrasive pad held by this polishing table10. In a case where a polishing pad made of polyurethane foam or the like and/or a fixed abrasive pad according to the present invention are used, a polished surface of the substrate having very few scratches can be obtained during a first-stage polishing. Polishing tables130and130are disposed at positions that can be accessed by the top rings14and14, respectively. With this arrangement, a primary polishing of the substrate W can be conducted by one of the polishing tables10, and then a finish polishing of the substrate W is conducted by a finish polishing pad held by a corresponding one of the polishing tables130. With this polishing table130, finish polishing of the substrate is conducted by a polishing pad comprising SUBA400 or POLITEX (manufactured by Rodel Nitta) while supplying pure water onto the polishing pad or supplying slurry onto the polishing pad. Alternatively, primary polishing of a substrate can be conducted by the polishing table130or130, and then secondary polishing of the substrate can be conducted by a corresponding one of polishing table10or10. In this case, since the polishing table130has a smaller-diameter polishing surface than does the polishing table10, a fixed abrasive pad which is more expensive than a polishing pad made of polyurethane foam or the like is attached to the polishing table130to thereby conduct a primary polishing of the substrate. On the other hand, a polishing pad made of polyurethane foam or the like having a shorter life, but being cheaper than a fixed abrasive pad, is held by the polishing table10to thereby conduct a finish polishing of the substrate. This arrangement or utilization may reduce a running cost of the polishing apparatus. If a polishing pad made of polyurethane foam or the like is held by the polishing table10and a fixed abrasive pad is held by the polishing table130, then this polishing table system may be provided at a lower cost. This is because the fixed abrasive pad is more expensive than the polishing pad made of polyurethane foam or the like, and price of the fixed abrasive pad is substantially proportional to a diameter of the fixed abrasive pad. Further, since a polishing pad made of polyurethane foam or the like has a shorter life than that of a fixed abrasive pad, if the polishing pad is used under a relatively light load such as a finish polishing, then life of the polishing pad is prolonged. Further, if a diameter of a polishing pad is large, chance or frequency of contact with a substrate is distributed to thus provide a longer life, a longer maintenance period, and an improved productivity of semiconductor devices.

As described above, according to one aspect of the present invention, even when a polishing table is in motion such as rotary motion or circulatory motion, a polishing pad can be transported from one roll over an upper surface of a polishing table toward another roll by a distance corresponding to a region of the polishing pad that has been used to polish workpieces. The used region of the polishing pad can thus automatically be replaced with a new region of the polishing pad.

Furthermore, according to another aspect of the present invention, a polishing pad is supplied from a polishing pad supply device, and the supplied polishing pad is held by a polishing pad holding device and placed in an elongat state on a polishing table. Thus, even if the polishing table is in motion, a used region of the polishing pad can thus automatically be replaced with a new region of the polished pad.