JPH09260317A - Substrate polishing equipment - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a substrate polishing equipment which can accuretely detect the termination of polishing by realizing a very precise in-process measurement of a film thickness. SOLUTION: This polishing equipment is so located as to face a processed face of a substrate 24 during a polishing process. As cleaning units for removing measurement inhibitors such as a polishing material from the processed face of the substrate, a turbine air supply system including a turbine nozzle 41 and a pure water supply system including an exhaust nozzle 46 for pure water are used. The equipment is also provided with a head 27 for measuring a film thickness which has its optical path for measuring the film thickness on the substrate 24 being formed on a head shaft which is extended from an optical flat 33 to a shaft hole 45 and a film thickness measuring device 28 for optically measuring the film thickness on the substrate 24 through the optical path of the head 27 for measuring a film thickness.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a substrate polishing apparatus that performs polishing while pressing a pad surface on a polishing plate against a substrate held by a polishing holder, and particularly to an insulating film formed on a semiconductor substrate. It is suitable for use in flattening the like with high precision.

[0002]

2. Description of the Related Art Semiconductor process technology has entered the era of sub-half micron to quarter micron, and flattening technology in VLSI process has been taken up as one of the independent elemental technologies like other miniaturization processing technologies. Has become. The reason is that the planarization technique is extremely important for increasing the density and miniaturization of the semiconductor element, and is considered to be a technical decisive factor for downscaling the device. In particular, as the device structure becomes three-dimensional and the electrode wiring has a multilayer structure, its importance is increasing. By the way, in recent years, as a global flattening technique of an interlayer insulating film in a semiconductor process, a CMP (Chemical Mechanical Polishing) method has attracted attention.
In the substrate polishing apparatus used for this CMP method, a substrate (working substrate) mounted on a substrate holding table and a polishing pad on a polishing plate are brought into pressure contact with each other, and chemicals of a polishing agent (slurry) supplied during processing are chemically applied. The substrate surface is globally polished by the polishing action and the mechanical polishing action.

However, this type of substrate polishing apparatus is
These are all extensions of the existing polishing apparatus, and at present, they do not sufficiently satisfy the demand for advanced processing accuracy. In particular, the variation in the film thickness within a lot or between lots is controlled by setting the processing time, but the polishing amount per unit time (polishing rate) varies, for example, clogging of the polishing pad, Various factors that change from time to time, such as the polishing pressure, the supply amount of the abrasive, and the temperature environment around the substrate, cannot be dealt with. In addition, the film thickness after processing is measured by a special measuring device (such as an ellipsometer), and this is fed back to a substrate polishing device to control the film thickness. However, a film obtained from a polished substrate is also used. Since the measurement data of the thickness cannot cope with the above-mentioned fluctuation factor, the variation of the film thickness within a lot or between lots also occurs.

Therefore, in the past, in addition to detecting the polishing end point by time management, as an end point detection method in the in-process (during polishing process), a detection method utilizing torque fluctuation of a motor for driving the polishing plate, , A detection method using a detection head that combines a fluid macromometer and an optical pickup has been proposed. The former utilizes the fluctuation of the polishing resistance due to the change of the material of the surface to be processed at the polishing end point, and the fluctuation of the polishing resistance is monitored from the motor torque to detect the polishing end point. The latter, on the other hand, detects the distance to the work surface of the insulating film with a fluid micrometer, and the position of the reflection surface, which is the reference surface for film thickness measurement, is optically detected with an optical pickup, and the difference between them is detected. The polishing end point is detected by detecting the remaining film of the insulating film.

[0005]

However, the former case is effective in the case where the material changes at the polishing end point (for example, when the underlying silicon is exposed in the process of polishing the oxide film), In the case where the unevenness of the surface of the same film is desired to be flattened with high accuracy (± 1 μm), the accuracy is insufficient, and the motor torque does not change significantly at the polishing end point. I can not do it. Also, in the latter case, the position of the reflection surface (measurement reference surface) by the optical pickup is due to the presence of an abrasive between the substrate and the detection head and the presence of foreign matter such as polishing dust and dust during the polishing process. Very difficult to detect.
For this reason, the end point can be detected only during the rinsing at the end of the processing or at the time of the interruption of the processing, and it cannot be said that the complete in-process film thickness measurement has been realized.

The present invention has been made to solve the above problems, and its purpose is to realize highly accurate film thickness measurement in-process, thereby making it possible to detect the polishing end point more accurately. It is to provide a substrate polishing apparatus.

[0007]

The present invention has been made in order to achieve the above-mentioned object, and by pressing the pad surface on the polishing plate against the substrate held by the substrate holding table, the polishing action of the polishing agent is performed. A substrate polishing apparatus for polishing a substrate, which is arranged so as to be able to face a surface to be processed of a substrate being polished, has a cleaning unit for removing a measurement inhibitor containing an abrasive from the surface to be processed, and the substrate A film thickness measuring head having an optical path for measuring the film thickness above, and a film thickness measuring means for optically measuring the film thickness on the substrate through the optical path of the film thickness measuring head. It is equipped with it.

In the substrate polishing apparatus having the above structure, the film thickness measuring head is used to process the substrate while the pad surface on the polishing plate is pressed against the substrate held by the substrate holder to perform the polishing process. The measurement block containing the polishing agent is arranged facing the surface, and in this state, the cleaning unit of the film thickness measuring head removes the measurement block from the surface to be processed. As a result, the film thickness measuring means can optically measure the film thickness on the substrate through the optical path of the film thickness measuring head without being hindered by a measurement inhibitor such as an abrasive even during polishing. Is possible.

[0009]

Embodiments of the present invention will be described below in detail with reference to the drawings. FIG. 1 is a cross-sectional view of essential parts showing an embodiment of a substrate polishing apparatus according to the present invention.
FIG. 1 is a perspective view showing an overall structure of a substrate polishing apparatus in one embodiment.

First, the overall structure of the substrate polishing apparatus will be described with reference to FIG. In the illustrated substrate polishing apparatus 1, a main body column 3 is provided on a main body base 2. A Z-axis slider 4 is attached to the front surface side of the main body column 3 so as to be movable in the Z-axis direction (vertical direction). Z
The shaft slider 4 is moved in the Z-axis direction by a Z-axis drive motor 5 incorporated in the main body column 3 and positioned in the same direction. A spindle air bearing 6 and a spindle motor 7 built in the spindle air bearing 6 are coaxially attached to the Z-axis slider 4. Of these, a polishing plate (polishing platen) 8 is attached to the rotary shaft of the main shaft air bearing 6. As a result, when the main spindle motor 7 is driven, its driving force is transmitted to the polishing plate 8 via the main spindle air bearing 6, and thereby the polishing plate 8 is rotationally driven.

Further, on the lower surface of the polishing plate 8, a polishing pad 9 made of foamed polyurethane or the like is stretched. Further, in the center of the polishing plate 8, there is provided a hole (not shown) for spraying an abrasive, which is in communication with the pad surface.
On the other hand, a joint 10 for supplying an abrasive is provided at the upper end of the spindle motor 7. As a result, the abrasive (slurry) sent out from the abrasive supply system (not shown) is introduced from the joint 10 into the main spindle system and is radially ejected and supplied from the hole at the center of the polishing plate 8.

On the other hand, a guide groove (not shown) is formed on the upper surface of the main body base 2 in the X-axis direction (left-right direction) orthogonal to the Z-axis direction.
Is formed, and the X-axis slider 11 is movably engaged with the guide groove. A nut (not shown) side of a ball screw mechanism is fixed to the lower surface of the X-axis slider 11, and a screw shaft 12 of the ball screw mechanism is screwed into this nut. An X-axis drive motor 13 is attached to the side surface of the main body base 2, and one end of the screw shaft 12 is connected to the output shaft of the X-axis drive motor 13 via a coupling or the like. With this configuration, when the X-axis drive motor 13 is driven, the driving force is converted into the linear movement of the X-axis slider 11 by the ball screw mechanism, so that the X-axis drive motor 13 is driven (rotation speed, rotation direction, etc.). Accordingly, the X-axis slider 11 moves in the X-axis direction.

Further, on the upper surface of the X-axis slider 11, an X
A shaft rotary table 14 is mounted, and a chuck plate 15 serving as a substrate holding table is mounted on the table. A substrate adsorption film (backing film) made of urethane rubber or the like on the chuck plate 15.
16 is stretched, and a substrate such as a wafer (substrate to be processed) is sucked and held by the chuck plate 15 via the substrate suction film 16. A drive motor (not shown) is built in the X-axis rotary table 14, and the chuck plate 15 is driven by the drive motor.
Is driven to rotate.

The mounting structure of the chuck plate 15 to the X-axis rotary table 14 will be described in detail with reference to FIG. First, the X-axis rotary table 1
A rotary plate 17 which is rotatably driven by the drive motor (not shown) is provided on the drive plate 4. A vacuum hole 18 for vacuuming is formed at the center of the rotary plate 17. A guide ring groove 19 having a concave cross section is formed on the upper surface of the rotary plate 17,
Further, a seal ring 20 having rubber-like elasticity is doubly attached to the peripheral portion thereof. On the other hand, the lower surface of the chuck plate 15 is similarly formed with a guide ring groove 21 having a concave cross section, and further, a double sealing groove 22 is formed on the peripheral portion thereof. Both these plates 15,
A positioning ring member 23 is interposed between the members 17. The ring member 23 is fitted in the guide ring grooves 19 and 21 formed on both plate surfaces, and the inner peripheral surface side thereof serves as a reference surface for plate positioning.

When the chuck plate 15 is mounted on the rotary plate 17, the positioning ring member 23 is attached to the guide ring groove 19 on the rotary plate 17 side.
Fit in. At this time, the upper portion of the ring member 23 is in a state of protruding by a predetermined amount from the upper surface of the rotary plate 17. In this state, the guide ring groove 2 on the bottom surface of the plate
The chuck plate 17 is placed on the rotary plate 17 while fitting 1 into the protruding portion of the ring member 23. At this time, the seal ring 20 on the rotary plate 17 side is also fitted into the seal groove 22 of the chuck plate 15.

In this state, a vacuum is drawn from the vacuum hole 18, whereby the chuck plate 15 is positioned and fixed to the rotary plate 17 with a vacuum suction force. Further, the fitting of the seal ring 20 and the seal groove 22 prevents foreign matter (such as an abrasive) from entering between the plates. On the other hand, when the chuck plate 15 is removed from the rotary plate 17, the vacuum drawing from the vacuum hole 18 is stopped and the chuck plate 15 is pulled straight up. As a result, the guide ring groove 21 on the lower surface of the plate is disengaged from the ring member 23, the seal groove 22 is disengaged from the seal ring 20, and only the chuck plate 15 is lifted.

On the other hand, when the substrate (wafer, etc.) 24 is adsorbed and held on the chuck plate 15 via the substrate adsorbing film 16, the retainer ring 25 is fitted to the outer peripheral portion of the plate. The retainer ring 25 has an upper part of its inner peripheral surface facing the outer peripheral surface of the substrate 24 to prevent the substrate 24 from protruding during polishing.

As described above, the chuck plate 15 which is attachable to and detachable from the rotary table 14 moves in the X-axis direction together with the X-axis slider 11 by the drive of the X-axis drive motor 13 shown in FIG. Moreover, in the X-axis direction,
The rotation axis of the polishing plate 8 and the rotation axis of the chuck plate 15 are set on substantially the same line. Furthermore, when the chuck plate 15 is advanced below the polishing plate 8 by the movement of the X-axis slider 11 and the polishing pad 9 is arranged so as to be in contact with the entire surface of the substrate 24 on the chuck plate 15 by the rotation of both, at least the substrate 24. The outer diameter of the polishing plate 8 is set so that a part of the surface to be processed (the upper surface in the illustrated example) protrudes from the polishing plate 8 to the outside. Incidentally, in the present embodiment, the polishing plate 8
By setting the outer diameter of the substrate to be substantially the same as the outer diameter of the substrate 24, a part of the surface to be processed of the substrate 24 during polishing is
The polishing plate 8 is configured to protrude outside.

Further, in the present embodiment, a film thickness measuring unit 26 is attached to the main body column 3 in order to realize film thickness measurement during polishing. The film thickness measuring unit 26 mainly comprises a film thickness measuring head 27 and a film thickness measuring device (film thickness measuring means) 28, and a drive system for the polishing plate 8 (main shaft air bearing 6, main shaft spindle motor 7). Is disposed above the moving path of the X-axis slider 11. In addition, the film thickness measuring head 27
Is attached to the lower part of the unit body so that it can be raised and lowered. Further, the position of the film thickness measuring head 27 in the X-axis direction is set so as to be able to face the surface to be processed of the substrate 24 protruding from the polishing plate 8 during polishing.

The structure of the film thickness measuring head 27 will be described with reference to FIG. The film thickness measuring head 27 shown in FIG.
And a pair of guide pins 30 at the bottom of the head body 29.
And a flushing head 32 installed in the center of the trace member 31.
It is composed of Of these, the central portion of the head main body 29 serving as a base is formed in a concave shape, and an optical flat 33 made of, for example, a polishing glass or the like is fixed to the bottom surface of the concave portion by a pressing plate 34. A pure water chamber 35 is formed directly below the optical flat 33 through a small hole. The pure water chamber 35 is defined by the optical flat 33 and the flange portion of the flushing head 32. Also,
The pure water chamber 35 has two water supply paths 36 (in the figure,
(Only the system is displayed) is connected, and each water supply channel 36
A pure water supply system (not shown) is connected to the inlet part of the via a joint 37.

Further, a pair of left and right pressure cylinders 38 are slidably incorporated inside the head body 29. The pressurizing cylinder 38 urges the trace member 31 downward during film thickness measurement, and the lower end surface thereof is abutted against the upper surface of the trace member 31. In addition, an air supply path 39 is provided in the built-in space of the pressurizing cylinder 38.
Are connected to each other, and a pressurized air supply system (not shown) is connected to an inlet portion of the air supply path 39 via a joint 40. With this configuration, when pressurized air is supplied through the joint 40, the air pressure is applied to the pressure cylinder 38 via the air supply path 39, and accordingly, the pressure cylinder 38 attaches the trace member 31 downward. Energize.

On the other hand, in the trace member 31, two turbine nozzles 41 and two static pressure bearing air supply holes 42 are formed with their phases shifted by 90 ° in the circumferential direction. Of these, the outlet portion of the turbine nozzle 41 is opened toward the outer peripheral surface of the lower end of the flushing head 32, and a turbine air supply system (not shown) is connected to the inlet portion opposite to the outlet portion via a joint 43. On the other hand, the outlet portion of the static pressure bearing air supply hole 42 opens to the tapered surface of the flushing head 31 via the small diameter portion of the guide pin 30, and further bends upward from there to also open to the flange portion of the flushing head 31. ing. An air supply system (not shown) for a hydrostatic bearing is connected to the inlet on the opposite side via a joint 44.

The flushing head 32 is a head half body having a substantially T-shaped cross section and a head half body having a substantially conical shape, which are integrated by a coupling means such as press fitting, for the reason of assembly. A shaft hole 45 communicating with the pure water chamber 35 is formed. A jet nozzle 46 is formed in the flushing head 32 in a bifurcated manner from the middle of the shaft hole 45, and the nozzle outlet portion is open to the lower surface of the head. As a result, the pure water supplied from the unillustrated pure water supply system through the joint 37 flows through the water supply passage 36 to fill the pure water chamber 35, and the shaft of the flushing head 32 communicating with the pure water chamber 35. It flows down through the hole 45 and is discharged from the lower surface of the head. At this time, pure water is also discharged from the ejection nozzle 46 that is bifurcated from the shaft hole 45. As a result, an optical path for film thickness measurement is formed on the central axis of the film thickness measuring head 27 by the optical flat 30 and the pure water filled in the pure water chamber 35 and the shaft hole 45.

Further, as shown in FIG. 4, a plurality of turbine fins 47 are formed on the outer peripheral surface of the lower end of the flushing head 32 at a predetermined circumferential pitch. In addition, among (a) to (c) in FIG. 4, (a) is a side view of the flushing head 32, (b) is a development view of a lower end outer peripheral surface of the flushing head 32, and (c) is a developed center. A cross-sectional view of line L is shown. On the outer peripheral surface of the lower end of the flushing head 32 having such a shape, the jet direction of the turbine air from the turbine nozzle 41 is as shown in FIG.
It is set along the taper shape of the turbine fin 47 as indicated by the dashed arrow. As a result, when the turbine air is ejected from the turbine nozzle 41, the turbine air is continuously ejected to the turbine fins 47, so that a rotational force is applied to the flushing head 32.

When pure water is supplied to the water supply passage 36 and the flushing head 32 is rotated by the supply of turbine air, pure water is jetted radially from the shaft hole 45 and the jet nozzle 46. The turbine air sprayed on the turbine fin 47 is sprayed downward from the outer peripheral surface of the lower end of the flushing head 32. The injection of pure water and the injection of turbine air serve to remove measurement obstacles from the surface to be processed of the substrate 24 during polishing. That is, the pure water supply unit and the turbine air supply unit described above have the functions of forming an optical path for film thickness measurement and imparting a rotational force to the flushing head 32, as well as of the film thickness measurement head 27. Among them, it also has a function as a cleaning unit for removing the measurement inhibitor from the surface to be processed of the substrate 24 during the polishing process.

Here, the "measurement inhibitor" is a substance which, when optically measuring the film thickness on the substrate 24, absorbs and scatters the light emitted from the optical system to inhibit the film thickness measurement. Say. Therefore, the measurement inhibitors include not only the polishing agent supplied during the polishing process, but also polishing scraps generated by polishing and foreign substances mixed in during polishing.

In addition, in this embodiment, as an additional function of the film thickness measuring device 28, an objective lens 48 is provided immediately above the film thickness measuring head 27. The objective lens 48 converges the light emitted from the film thickness measuring device 28 and reduces the spot diameter on the measurement reflection surface.

The film thickness measuring device 28 optically measures the film thickness on the substrate 24 by utilizing the principle of multiple reflection interferometry. A light source (such as a laser) that emits light, a polarization beam splitter (PBS) arranged on the optical path of incident light, a first photodiode that photoelectrically converts the amount of light incident on the substrate, and a first photodiode that photoelectrically converts the amount of light reflected from the substrate. The second photodiode has an aperture and the like arranged on the optical path of the reflected light.

In the film thickness measurement using the principle of this repeated reflection interference, if the reflectance of the light incident on the thin film on the substrate is known, and the refractive index of the film and the substrate are known, from the calculation formula of repeated multiple reflection, Since the reflectance for a certain film thickness is accurately calculated, the film thickness is estimated based on this. This type of measuring method is a standard method that is widely used as a method for measuring the thickness of a thin film, and the structure of the measuring system is simple, and since it is possible to perform point measurement simply by photoelectrically converting the amount of reflected light,
It is possible to measure all over the substrate. The calculation formula and the like showing the principle of repetitive reflection interference have already been described in many documents, and therefore the description thereof is omitted here.

Subsequently, the substrate polishing apparatus 1 having the above structure
The operation procedure of will be described with reference to FIG. First,
In the polishing process, as shown in FIG. 5A, the chuck plate 15 is removed from the rotary table 14, and the substrate suction film 16 is attached to the chuck plate 15.
The substrate 24 is attached via. After mounting the substrate 24, the chuck plate 15 is mounted on the rotary table 1 again.
Put on top of 4. The attachment / detachment work of the chuck plate 15 is performed in a state in which the X-axis slider 11 is arranged closest to the X-axis drive motor 13. Next, when the chuck plate 15 is completely attached, the rotary table 14 and the chuck plate 15 are moved in the X-axis direction together with the X-axis slider 11 by the drive of the X-axis drive motor 23. The board 24 is advanced.

Then, the polishing plate 8 is rotated by driving the spindle motor 7 and the polishing agent is supplied from a polishing agent supply system (not shown) through the joint 10. As a result, the abrasive is spouted radially from the center of the rotating polishing plate 8. On the other hand, also on the rotary table 14 side, the chuck plate 15 is rotated by driving the built-in motor, and in this state, the Z-axis motor 5 is driven.
Drive the Z-axis slider 4 downward. As a result, as shown in FIG. 5B, with the polishing plate 8 and the chuck plate 15 being rotated relative to each other, the polishing pad 9 is pressed against the surface to be processed of the substrate 24, and substantial polishing is started. It By the way, during the polishing process, the X-axis slider 11 traverses (reciprocates) by the drive of the X-axis drive motor 13. Even during this traverse motion, a part of the surface to be processed (upper surface) of the substrate 24 is always the polishing plate 8
It protrudes and is exposed to the outside.

Subsequently, as shown in FIG. 5C, the film thickness measuring head 27 of the film thickness measuring unit 26 descends, and the lower end of the head 27, that is, the flushing head 3 shown in FIG.
The lower end surface 2 of the substrate 24 protrudes from the polishing plate 8.
Are arranged so as to be close to and opposite to the surface to be processed. At this time, pure water is supplied from a pure water supply system (not shown) via the joint 37, and pressurized air is supplied from a pressurized air supply system (not shown) via the joint 40. Also,
Joint 43 from turbine air supply system (not shown)
Turbine air is supplied via an air supply system, and static pressure bearing air is supplied via a joint 44 from an air supply system (not shown) for a hydrostatic bearing.

Of these, the pure water supplied through the joint 37 is filled in the pure water chamber 35 through the water supply passage 36 and the shaft hole 45 of the flushing head 32.
And is jetted onto the surface to be processed of the substrate 24 through the jet nozzle 46. At that time, an optical path for film thickness measurement is formed on the central axis of the film thickness measuring head 27 by the optical flat 33, the pure water chamber 35, and the shaft hole 45. On the other hand, the pressurized air supplied through the joint 40 acts on the pressure cylinder 38 through the air supply passage 39. As a result, the pressurizing cylinder 38 urges the flushing head 32 together with the trace member 31 toward the substrate 24 against the reaction caused by the jetting of pure water from the lower end of the head.

Further, the turbine air supplied through the joint 43 is jetted to the outer peripheral surface of the lower end of the flushing head 32 through the turbine nozzle 41, thereby imparting a rotational force to the flushing head 32.
On the other hand, the hydrostatic bearing air supplied through the joint 44 is sprayed on the taper surface and the flange surface of the flushing head 32 as indicated by the broken line arrow in FIG. A minute air gap is formed in the fitting portion with the flushing head 32. That is, the flushing head 32 is in a rotation free state. In this state, when the turbine air is sprayed on the outer peripheral surface of the lower end of the flushing head 32 as described above, the plurality of turbine fins 47 formed therein receive the turbine air, so that the flushing head 32 is driven at a high speed (for example, 100000 rpm). ) Will rotate.

As a result, pure water is jetted radially at high speed from the flushing head 32, which is rotating at high speed, toward the surface to be processed of the substrate 24, and at the same time, the outer peripheral portion of the flushing head 32 is processed to process the substrate 24. High-speed injection of turbine air toward the surface. Therefore, as shown in FIG. 6, the measurement inhibitors 49 such as the polishing agent supplied during the polishing process, the polishing dust generated during the polishing process, and the foreign substances mixed in during the polishing process are generated by the injection of pure water and the turbine air. It is removed from the processed surface of the substrate 24 by the jetting. As a result, even during the polishing process, the processed surface of the substrate 24 located directly below the film thickness measurement head 27 is always held on a clean surface free from the interfering measurement obstruction, so that the measurement area is kept there. The film thickness measuring device 28 optically measures the film thickness on the substrate 24 through the optical path of the film thickness measuring head 27.

As shown in FIG. 5C, the film thickness measurement data obtained during the polishing process is converted from the film thickness measuring device 28 into an electric signal and output to the main control section of the entire apparatus. In response to this output signal, the main control unit controls the film thickness measuring device 2
The film thickness information obtained from the output signal of No. 8 is compared with the specified film thickness information, and a control signal is output to each drive system based on the comparison result. That is, while the actually measured film thickness has not reached the specified film thickness, a control signal for continuing the polishing process is output, and then the polishing end point is reached when the measured film thickness reaches the specified film thickness. Then, a control signal indicating that the polishing process is to be finished is output.

When the polishing control signal is output from the main controller in this manner, the Z-axis drive motor 15 drives the Z-axis slider 4 and the polishing plate 8 to rise, as shown in FIG. 5D. . As a result, the polishing pad 9 is separated from the surface of the substrate 24 to be processed, and the substantial polishing process is completed. Subsequently, the chuck plate 15 is moved toward the film thickness measuring head 27 by the drive of the X-axis drive motor 13, and the traverse motion is restarted there. During that time, pure water and turbine air are continuously jetted from the lower end of the film thickness measuring head 27 toward the surface to be processed of the substrate 24, whereby the surface to be processed of the substrate 24 is spread over its entire area. It is cleaned by the film thickness measuring head 27. As a result, the in-process film thickness measurement and the in-process substrate cleaning can be realized, and thus the conventional scrub cleaning after completion of polishing can be omitted.

After that, when the cleaning of the substrate 24 by the film thickness measuring head 27 is completed, the film thickness measuring head 27 is retracted upward, and the X axis drive motor 13 drives the X axis slider 11 to move the chuck plate 15 together. The process returns to the initial position (the position where the plate is attached / detached), thereby completing the series of polishing processes.

As described above, in the substrate polishing apparatus 1 of the present embodiment, when the in-process film thickness measurement is performed, the film thickness measuring head 27 is opposed to the surface to be processed of the substrate 24 during the polishing process. At this time, the measurement inhibitor 49 such as an abrasive is removed from the surface to be processed by the injection of pure water from the lower end of the head or the injection of turbine air. As a result, the film thickness measuring device 28 can optically measure the film thickness on the substrate 24 through the optical path of the film thickness measuring head 27 without being hindered by the measurement inhibitor 49 such as an abrasive. Become. As a result, since in-process highly accurate film thickness measurement is realized, the film measured during the polishing process is not confused by factors such as clogging of the polishing pad 9, polishing process pressure, and ambient temperature environment. It is possible to accurately detect the polishing end point based on the thickness data. For reference, in order to confirm the reliability of the film thickness measurement data by the substrate polishing apparatus 1, the same substrate 24 is used as a measurement sample and the film thickness data measured by the substrate polishing apparatus 1 and the film thickness measured by the off-line ellipsometer are used. When compared with the data, there was almost no error in both data.

By the way, as a film structure on the substrate 24 to be measured in the in-process, as shown in FIG. 7A, a SiO ₂ film (interlayer insulating film) 51 is formed on a Si-Substrate 50. S as a so-called solid film
The film thickness T ₁ of the io ₂ film 51 and S as shown in FIG.
The Al wiring 52 is formed on the i-Substrate50, SiO ₂ in the case of forming the SiO ₂ film 51 is formed thereon
The film thickness T _{2 of the} film 51, and further the Si-Substrate
As an example, a film thickness T ₃ of the SiO ₂ film 51 having a so-called multi-layer structure in which the Al wiring 52 and the SiO ₂ film 51 are doubly formed on the 50 is considered.

In the film structure shown in FIG. 7, for example, A
When the light emitted from the light source is incident on the substrate 24 as parallel light as the parallel wiring 52 has a narrow interval, if the surfaces having different reflectances are mixed in the spot, accurate film thickness measurement cannot be performed. . In that case, as shown in Figure 1,
The objective lens 48 is provided on the optical axis of the film thickness measuring device 28, and the light emitted from the light source is converged by the objective lens 48 so that the substrate 24
Incident on top. As a result, the spot diameter on the reflecting surface becomes smaller than that of parallel light, so that accurate film thickness measurement is possible even if the wiring interval is narrow.

Next, another embodiment of the substrate polishing apparatus according to the present invention will be described. FIG. 8 shows the structure of a film thickness measuring head, which is the main part of the film thickness measuring unit, as another embodiment of the present invention. In the figure, (a) is its plan view and (b) is its side. Sectional drawing, (c) has shown the bottom view.

The film thickness measuring head 60 shown in FIG. 8 is mainly composed of a head main body 61 serving as a base, and a flushing head 62 incorporated in the head main body 61. Of these, the central portion of the upper surface of the head body 61 is formed in a concave shape, and a laser irradiation window 63 made of, for example, a transparent parallel plate is fixed to the bottom surface of the concave portion by a pressing plate 64. Further, a water supply nozzle 66 is formed right below the laser irradiation window 63 together with the pure water chamber 65, and a shaft hole 66 a is formed along the axis of the water supply nozzle 66. Then, the flushing head 6 described above
Reference numeral 2 is slidably engaged with a water supply nozzle 66 of the head body 61.

9A and 9B are external views of the flushing head 62 in this embodiment. FIG. 9A is a plan view thereof, and FIG. 9B is a view thereof.
Shows a side view thereof, and (c) shows a bottom view thereof. FIG.
The flushing head 62 shown in (1) has a substantially conical integral structure, and an engaging hole 67 that engages with the water supply nozzle 66 on the head body 61 side is formed in the center thereof. The conical surface 62a of the flushing head 62 is provided with dynamic pressure generating pockets 68 at four locations. Each pocket 68 is based on the head conical surface 62a,
For example, pocket depth: t ₁ = 0.1 mm, t ₂ = 0.3
mm, t ₃ = 0.5 mm, etc.

On the other hand, a plurality of turbine fins 69 are formed on the lower end outer peripheral surface 62b of the flushing head 62 at a predetermined circumferential pitch, as in the previous embodiment. Further, on the bottom surface 62c of the flushing head 62, pockets 70 for generating dynamic pressure are provided at four places, and these pockets 70 are also formed in a step shape like the pocket 68.

Incidentally, with respect to the pocket 68 on the head conical surface 62a and the pocket 70 on the head bottom surface 62c, the flushing head 6 is determined by the shape of the turbine fin 69.
The depth of each pocket is set to gradually increase in accordance with the rotation direction θ of 2.

The flushing head 62 having the above structure
In the state in which the above is incorporated in the head main body 61, the vacuum chamber 71 is secured at the base end portion of the water supply nozzle 66 that engages with the flushing head 62. A vacuum line 72 is formed in the head main body 61 so as to communicate with the vacuum chamber 71, and a suction port 73 is provided at a leading portion of the vacuum line 72, that is, an upper end surface of the head main body 61. The set screw 74 incorporated in the end surface of the head main body 61 serves as a stopper for unifying the vacuum line 72.

Further, inside the head body 61, a first water supply passage 75 communicating with the pure water chamber 65, a second water supply passage 76 facing the conical surface (pocket forming surface) 62a of the flushing head 62, and further, An air supply passage 77 is formed to face the lower end outer peripheral surface 62b (turbine fin forming surface) of the flushing head 62. The water supply port 78 for filling the laser light path is provided in the leading portion of the first water supply passage 75, and the water supply port 7 for the conical bearing is provided in the leading portion of the second water supply passage 76.
9. A turbine air supply port 80 is provided at each leading portion of the air supply passage 77.

Incidentally, also in the present embodiment, a laser focus lens 81 such as an objective lens is arranged immediately above the film thickness measuring head 60, and the laser focused by this laser focus lens 81 is also provided, as in the above-described embodiment. Although a configuration is adopted in which the beam is applied to the processing surface 82a of the substrate (wafer or the like) 82, other than this, for example, the above-described optical flat 33 (FIG. 1) and the laser irradiation window 63 are used.
By replacing (FIG. 8) with a convex lens convex upward, the laser beam is focused (focusing) on the film thickness measuring heads 27 and 60 without using an objective lens or the like.
It becomes possible.

Next, the operation procedure of the substrate polishing apparatus provided with the film thickness measuring head 60 having the above structure will be described. First, in the polishing process, as shown in FIG. 10A, a substrate (semiconductor wafer or the like) 82 to be processed is set on a rotary table (substrate holding table) 83, and then connected to a lower end of a processing main shaft portion 84. The slider 86 is moved to the bottom of the polished plate 85. At this time, the film thickness measuring head 60 stands by in the state of FIG. 11A near the polishing plate 85.

That is, in the state of FIG. 11A, the vacuum chamber 71 becomes a negative pressure through the vacuum line 72 due to the forced exhaust from the suction port 73 (see FIG. 8), which causes the flushing head 62 to move to the head body 61. It is supported in a sucked state. At this time, the clearance C ₁ between the flushing head 62 and the substrate 82 that moves under the flushing head 62 is secured at, for example, about 140 μm so that the substrate 82 can freely move in the left-right direction.
Incidentally, in the case of a semiconductor wafer or the like, since the flatness of the substrate 82 is about 0.3 μm and the variation in the height direction is 20 μm or less, if the clearance C ₁ between the two is set as described above, The flushing head 62 is the substrate 82.
Does not hinder the movement of.

Then, as shown in FIG. 10B, the polishing plate 85 is lowered together with the processing spindle portion 84, and the pad surface on the polishing plate 85 is pressed against the surface (work surface) of the substrate 82 to form the processing spindle. Rotation of part 84 (300 rp
m), the rotation of the rotary table 82 (60 rpm), and the traverse movement of the slider 86 start polishing.

During this polishing process, in the film thickness measuring head 60, as shown in FIG. 11 (b), the forced exhaust by the vacuum line 72 is continued and the turbine air (compressed air) is supplied from the turbine air supply port 80. )
Is supplied. At the same time, pure water is supplied with a predetermined water supply pressure from the water supply port 78 for filling the laser optical path and the water supply port 79 for the conical bearing.

Of these, the turbine air supplied from the turbine air supply port 80 is jetted to the lower end outer peripheral surface 62c of the flushing head 62 through the air supply passage 77, and the jetted turbine air is sequentially supplied to the four turbine fins 69. By being sprayed, a rotational force is applied to the flushing head 62. Further, the turbine air thus supplied is exhausted and jetted from the outer peripheral portion of the flushing head 62 toward the processed surface 82a of the substrate 82. By the way, the turbine air pressure is 0.4M.
When the pressure was set to Pa, the rotation speed of the flushing head 62 was about 20,000 rpm, and when the turbine air pressure was further increased, a high speed rotation of 30,000 rpm could be achieved.

On the other hand, the pure water supplied from the water supply port 78 is
The pure water chamber 65 is filled with the water through the first water supply passage 75, and is sprayed onto the processed surface 82a of the substrate 82 through the shaft hole 66a of the water supply nozzle 66. As a result, a stable cleaning water film of pure water is formed between the flushing head 62 and the substrate 82. Further, on the central axis of the film thickness measuring head 60, an optical path for film thickness measurement is formed by the laser irradiation window 63, the pure water chamber 65, and the shaft hole 66a.

On the other hand, the pure water supplied from the other water supply port 79 is the conical surface 62a of the flushing head 62.
To the flushing head 62 by receiving the water pressure.
Slides down on the water supply nozzle 66, and a water film is formed outside the conical surface 62a of the flushing head 62. As a result, on the conical surface 62a of the flushing head 62,
A centering force in the radial direction of rotation is generated together with the pressure applied to the substrate 82, and at the same time, the flushing head 62
A thrust force that opposes the pressing force from the conical surface 62a is generated on the bottom surface 62c.

At this time, the thickness of the water film formed on the outer side of the conical surface 62a is from the shaft hole 66a of the water supply nozzle 66 to the substrate 8a.
It is determined by the balance between the water pressure of pure water jetted toward 2 and the water pressure of pure water jetted toward the conical surface 62a of the flushing head 62. By the way, in this embodiment, the flushing head 62 moves over the water supply nozzle 66.
The water pressure balance is adjusted so as to slide down by .mu.m, whereby the flushing head 62 and the substrate 82 are adjusted.
A clearance C ₂ of about 100 μm is ensured between

In the present embodiment, the conical surface 62a of the flushing head 62 is formed with the dynamic pressure generating pocket 68, and the lower end outer peripheral surface 62b is also formed with the dynamic pressure generating pocket 70. With the rotation of the flushing head 62, the pressure level at the conical surface 62a and the pressure level at the head bottom surface 62c are amplified by the pressure increasing effect of the pockets 68 and 70. As a result, a high-speed and high-pressure cleaning water film is formed between the flushing head 62 and the substrate 82, so that a strong cleaning effect can be obtained. As a result, compared to the previous embodiment, by supplying a smaller amount of pure water with a water pressure of 0.5 MPa or less, the measurement inhibitor is strongly removed from the surface 82a to be processed of the substrate 82, and it is extremely clean. It becomes possible to hold it on the surface.

By the way, when the pure water supply pressure is set to 0.3 MPa, the conical surface 62a and the head bottom surface 62 are
In c, a pressure of about 2 MPa corresponding to 7 times that was obtained. Since this pressure value increases in proportion to the square of the rotation speed of the flushing head 62, the stability does not decrease even when the flushing head 62 is rotated at a high speed, and a stronger cleaning effect can be obtained. Become.

Due to the operation function of the film thickness measuring head 60, the measurement region of the substrate 82, that is, the region facing the flushing head 62, is held on the clean surface free from the interfering measurement object during polishing. Thickness measurement head 6
A laser beam (for film thickness measurement) is irradiated onto the substrate 82 through an optical path formed on the center axis of 0, and the film thickness on the substrate 82 is optically measured according to the same principle as the previous embodiment. Then, when the measured film thickness thus obtained reaches the specified film thickness, as shown in FIG.
4 rises. As a result, the processed surface 82a of the substrate 82 is
The polishing plate 85 is separated from, and the substantial polishing process is completed.

After that, the substrate 82 moves together with the slider 86 toward the original initial position. During the movement, the substrate 82 is washed by the film thickness measuring head 60, and the surface 82a to be processed of the substrate 82 is entirely covered. Is cleaned over.
Then, when the cleaning of the substrate 82 is completed, the supply of pure water and turbine air to the film thickness measuring head 60 is stopped, and only forced exhaust from the vacuum line 72 is continued. As a result, the flushing head 62 is again attracted to the film thickness measuring head 60, that is, in FIG.
The standby state of (a) is entered. After that, as shown in FIG. 11D, when the slider 86 returns to the initial position, machining / processing is performed.
The cleaned substrate 82 is removed, which completes the series of polishing processes.

As described above, in the film thickness measuring head 60 employed in the present embodiment, a very stable high-speed cleaning water film is obtained between the flushing head 62 and the substrate 82, whereby the substrate 82 to be measured is covered. Since the measurement inhibitor can be completely removed from the processed surface 82a, more stable and highly accurate film thickness measurement can be realized. Also the head body 6
By adopting a structure in which the flushing head 62 incorporated in No. 1 is suction-held by vacuum, a mechanism for raising and lowering the film thickness measurement head 60 is unnecessary,
It is possible to reduce the size of the entire device and simplify the configuration.

In the above embodiment, the film thickness on the substrate is measured by utilizing the principle of the repeated reflection interferometry, but as the film thickness measuring means, another principle such as the absorbance measuring method, Interferometric multi-wavelength spectroscopy, infrared interferometry, ultraviolet interferometry, etc., as long as it is possible to optically measure the film thickness on the substrate using the optical path formed in the film thickness measurement head, any method can be used. You can use it.

Further, as a cleaning unit for the film thickness measuring head, in addition to removing the measurement inhibitor by jetting pure water and air, for example, a head surface facing the surface to be processed of the substrate is used for film thickness measuring. Alternatively, a cleaning pad or a brush may be attached so as to surround the optical path, and the measurement inhibitor may be removed by synergistic action with pure water.

Further, as an application other than film thickness measurement during polishing, for example, by setting a large diameter of the optical path by water supply, the purpose of observing and photographing the processed surface during processing and the mirror surface in a poor environment. It can also be used for cleaning in water because the power source is only air and water.

[0066]

As described above, according to the substrate polishing apparatus of the present invention, the measurement inhibitor containing the polishing agent forms a film in the state where the film thickness measuring head faces the surface to be processed of the substrate during polishing. Since it is removed from the surface to be processed by the cleaning unit of the thickness measuring head, the film thickness measuring means can prevent the film thickness measuring head from being interfered with by the measurement inhibitor such as an abrasive even during the polishing process. The film thickness on the substrate can be optically measured through the optical path. As a result, in-process high-precision film thickness measurement is realized, so that the polishing end point can be accurately detected based on the film thickness data measured during the polishing process. As a result, it is possible to always finish the polishing process with the specified remaining film thickness without depending on the polishing time and the like as in the conventional method, so that there is variation in film thickness within the lot or between lots in the substrate polishing process. It can be minimized. Furthermore, since the polishing end point can be accurately detected without being affected by pad clogging, polishing processing pressure, polishing agent supply amount, temperature environment, etc. that cause polishing rate fluctuations, the management of various fluctuation parameters is simplified. It is also possible to do.

[Brief description of drawings]

FIG. 1 is a cross-sectional view of an essential part showing an embodiment of a substrate polishing apparatus according to the present invention.

FIG. 2 is a perspective view showing an overall structure of a substrate polishing apparatus according to an embodiment.

FIG. 3 is an exploded sectional view showing a mounting structure of a chuck plate.

FIG. 4 is a diagram illustrating a partial structure of a film thickness measuring head.

FIG. 5 is a diagram illustrating an operation procedure of the substrate polishing apparatus.

FIG. 6 is a diagram for explaining the operation of the film thickness measuring head during polishing.

FIG. 7 is a diagram showing an example of a film structure to be measured.

FIG. 8 is a diagram illustrating another embodiment of the substrate polishing apparatus according to the present invention.

FIG. 9 is an external view of a flushing head according to another embodiment.

FIG. 10 is a diagram illustrating an operation procedure of a substrate polishing apparatus according to another embodiment.

FIG. 11 is an operation explanatory diagram of a film thickness measuring head according to another embodiment.

[Explanation of symbols]

1 Substrate Polishing Device 8 Polishing Plate 9 Polishing Pad 15 Chuck Plate (Substrate Holding Table) 24, 82
Substrate 26 Film thickness measuring unit 27,60 Film thickness measuring head 28 Film thickness measuring device (film thickness measuring means) 29,61 Head body 31 Trace member 32,62 Flushing head 33 Optical flat 35,65 Pure water chamber 41 Turbine nozzle 45, 66a shaft hole 46
Jet nozzle 49 Measurement obstacle 66 Water supply nozzle 68, 70
pocket

Claims (1)

[Claims] 1. A substrate polishing apparatus for polishing the substrate by a polishing action of an abrasive while pressing a pad surface on a polishing plate against a substrate held by a substrate holder, wherein a surface to be processed of the substrate during polishing processing. And a cleaning unit for removing the measurement inhibitor containing the polishing agent from the surface to be processed, and forming an optical path for measuring the film thickness on the substrate. A substrate polishing apparatus comprising: a film thickness measuring head; and a film thickness measuring unit that optically measures a film thickness on the substrate through an optical path of the film thickness measuring head.