Polishing endpoint detection device and CMP device

Abstract

To provide a polishing end-point detector capable of accurately detecting the film thickness of work during polishing in a short time, and a CMP device.SOLUTION: A polishing end-point detector is equipped with a fixed side lens barrel 25 that is provided outside a platen 2, and is connected to a light source 21 and a spectral device 23 through a first fiber 24, a rotation side lens barrel 26 that is provided on the platen 2 and transfers light between the fixed side lens barrel 25 and the rotation side lens barrel 26, and a sensor head 22 that is stored in an observation hole 8 formed on the platen 2 and a polishing pad 5, is connected to the rotation side lens barrel 26 through a second fiber 27, emits measurement light toward work W when the work W passes through the observation hole 8, and receives reflection light from the work W.SELECTED DRAWING: Figure 2

Description

[Technical Field]

[0001] The present invention relates to a polishing endpoint detection device and a CMP device. [Background technology]

[0002] 2. Description of the Related Art In the field of semiconductor manufacturing, CMP devices are known that polish and flatten semiconductor silicon wafers and the like (hereinafter referred to as "workpieces").

[0003] The polishing apparatus described in Patent Document 1 is a polishing apparatus that applies chemical mechanical polishing (CMP) technology. This CMP apparatus polishes a workpiece mounted on a polishing head by pressing the workpiece against a polishing pad. In addition, a sensor head located below the platen irradiates light onto the workpiece through an observation hole every time the platen rotates once, and detects the polishing endpoint of the workpiece based on the light intensity spectrum of the reflected light. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Japanese Patent Application Publication No. 2017-52027 Summary of the Invention [Problem to be solved by the invention]

[0005] However, in the polishing apparatus described in Patent Document 1, the film thickness is measured at only one point on the workpiece each time the platen makes one rotation. As shown in FIG. 4, the polishing head is moved in the horizontal direction d1, and the measurement position mp of the sensor head 101 is scanned within the workpiece 100 rotating in the rotation direction d2, and the film thickness is measured at the number of measurement points required to accurately detect the polishing end point (eight points in FIG. 4), which results in a problem that film thickness measurement takes a long time.

[0006] Therefore, there arises a technical problem that must be solved in order to accurately detect the film thickness of a workpiece being polished in a short time, and an object of the present invention is to solve this problem. [Means for solving the problem]

[0007] In order to achieve the above-mentioned object, the polishing apparatus of the present invention is a polishing end point detection device that measures the film thickness of a workpiece being pressed against a polishing pad on a platen and polished, and detects the polishing end point based on the film thickness of the workpiece, and is equipped with a fixed side barrel that is provided outside the platen and connected to a light source and a spectrometer via a first fiber, a rotating side barrel that is provided on the platen and transmits light wirelessly between the fixed side barrel, and a sensor head that is housed in an observation hole formed in the platen and the polishing pad and connected to the rotating side barrel via a second fiber, that irradiates measurement light toward the workpiece as it passes over the observation hole and receives reflected light from the workpiece.

[0008] The CMP apparatus according to the present invention is equipped with the polishing endpoint detection device described above. [Effects of the Invention]

[0009] The present invention can detect the film thickness of a workpiece being polished with high accuracy in a short time. [Brief explanation of the drawings]

[0010] [Figure 1] 1 is a perspective view schematically showing a CMP apparatus according to a first embodiment of the present invention. [Figure 2] FIG. 2 is a longitudinal sectional view schematically showing a main part of a CMP apparatus. [Figure 3] A schematic diagram showing how the film thickness measurement position on the workpiece is scanned during one rotation of the platen. [Figure 4] FIG. 1 is a schematic diagram showing how a polishing head moves horizontally to scan a film thickness measurement position within a workpiece in a conventional CMP apparatus. DETAILED DESCRIPTION OF THE INVENTION

[0011] An embodiment of the present invention will be described with reference to the drawings. Note that, hereinafter, when referring to the number, numerical value, amount, range, etc. of components, unless otherwise specified or when it is clearly limited to a specific number in principle, the number is not limited to the specific number, and may be more or less than the specific number.

[0012] Furthermore, when referring to the shape or positional relationship of components, etc., it includes things that are substantially similar or approximate to those shapes, etc., unless otherwise specified or when it is clearly considered otherwise in principle.

[0013] In addition, the drawings may exaggerate characteristic parts to make the features easier to understand, and the dimensional proportions of the components may not be the same as in reality. In addition, in cross-sectional views, hatching of some components may be omitted to make the cross-sectional structure of the components easier to understand.

[0014] 1 is a perspective view schematically showing a CMP apparatus 1 according to one embodiment of the present invention. The CMP apparatus 1 polishes one surface of a workpiece W to a flat surface. The CMP apparatus 1 includes a platen 2 and a polishing head 3. The workpiece W is, for example, a silicon wafer, but is not limited to this.

[0015] The platen 2 is formed in a disk shape and is connected to a rotating shaft 2a disposed below the platen 2. The rotating shaft 2a is rotated by the drive of a motor 4, causing the platen 2 to rotate in the direction of arrow D1 in Fig. 1. A polishing pad 5 is attached to the upper surface of the platen 2, and CMP slurry, which is a mixture of abrasives and chemicals, is supplied onto the polishing pad 5 from a nozzle (not shown).

[0016] The polishing head 3 is formed with a smaller diameter than the platen 2 and is connected to a rotating shaft 3a disposed above the polishing head 3. The rotating shaft 3a is rotated by a motor (not shown), causing the polishing head 3 to rotate in the direction of arrow D2 in FIG. 1. The polishing head 3 is configured to be movable vertically and horizontally by a head movement mechanism (not shown). When polishing the workpiece W, the polishing head 3 descends and presses the workpiece W against the polishing pad 5.

[0017] The operation of the CMP apparatus 1 is controlled by a controller 6. The controller 6 controls each of the components that make up the CMP apparatus 1. The controller 6 is, for example, a computer, and is composed of a CPU, memory, etc. The functions of the controller 6 may be realized by control using software, or may be realized by something that operates using hardware.

[0018] Next, the main parts of the CMP apparatus 1 will be described with reference to Fig. 2. The polishing head 3 is provided with a chuck 7 that is connected to a rotary shaft portion 3a and rotates together with the rotary shaft portion 3a.

[0019] A chuck 7 is provided at the bottom of the polishing head 3. The chuck 7 has a chuck table 7a made of alumina. The chuck 7 is connected to a vacuum source and a compressed air source (not shown). By activating the vacuum source, the workpiece W is sucked and held on the holding surface 7b of the chuck 7. By activating the compressed air source, compressed air is supplied between the holding surface 7b and the workpiece W, and the suction holding of the workpiece W is released.

[0020] With this configuration, the CMP apparatus 1 polishes the workpiece W in the following procedure. First, the workpiece W is adsorbed and held by the polishing head 3 with the layer to be polished of the workpiece W facing downward. Next, the polishing head 3 moves above the platen 2, and the platen 2 and polishing head 3 rotate in the same direction. Then, while slurry is being supplied onto the polishing pad 5, the polishing head 3 presses the workpiece W against the polishing pad 5 to polish the workpiece W. Furthermore, when the polishing endpoint detection device 10, which will be described later, detects the polishing endpoint of the workpiece W, the controller 6 stops the platen 2 and polishing head 3, and polishing of the workpiece W ends.

[0021] The CMP apparatus 1 is equipped with a polishing endpoint detection device 10 that detects the polishing endpoint of the workpiece W during polishing. The polishing endpoint detection device 10 is equipped with a measurement unit 20 that measures the film thickness of the workpiece W, and a detection unit 30 that detects the polishing endpoint of the workpiece W.

[0022] The measuring unit 20 is a so-called optical interference type film thickness sensor, and includes a light source 21, a sensor head 22, and a spectrometer 23.

[0023] The light source 21 is, for example, but not limited to, a halogen light source that emits white light with a wavelength of 400 to 800 nm. The measurement light emitted from the light source 21 is transmitted to the sensor head 22 via the first optical fiber 24, the fixed-side lens barrel 25, the rotating-side lens barrel 26, and the second optical fiber 27.

[0024] The first optical fiber 24 is a Y-shaped optical fiber that is a bundle of multiple optical fibers and that branches midway, with one end connected to the light source 21 and the spectrometer 23, respectively, and the other end connected to the fixed-side lens barrel 25. The bundle diameter of the first optical fiber 24 is set to, for example, 1000 μm. However, the configuration of the first optical fiber 24 is not limited to this.

[0025] The fixed-side barrel 25 and the rotating-side barrel 26 are disposed opposite each other at a predetermined distance, and can emit and receive light from each other. That is, light is transmitted wirelessly between the fixed-side barrel 25 and the rotating-side barrel 26. Hereinafter, the optical path through which light is transmitted wirelessly will be referred to as the "hollow optical path OP."

[0026] The optical axis of the fixed-side barrel 25 and the optical axis of the first optical fiber 24 are configured to approximately coincide. The fixed-side barrel 25 is supported by a support arm 28. The support arm 28 is placed on a moving stage 29, and the fixed-side barrel 25 can move relative to the rotating-side barrel 26 by moving the moving stage 29 in the horizontal direction or the vertical direction.

[0027] The rotation-side lens barrel 26 is attached to the bottom of the rotation shaft portion 2a of the platen 2 via an attachment 26a. The outer periphery of the rotation-side lens barrel 26 is supported by the attachment 26a. The attachment 26a is configured to be detachable from the rotation shaft portion 2a by fastening bolts to elongated holes (not shown), for example. Furthermore, the attachment 26a's assembly position relative to the rotation shaft portion 2a can be finely adjusted in the horizontal direction.

[0028] The second optical fiber 27 is an I-shaped optical fiber formed by bundling a plurality of optical fibers, and one end is connected to the rotation-side barrel 26 and the other end is connected to the sensor head 22. The bundle diameter of the second optical fiber 27 is set to, for example, 1000 μm. However, the configuration of the second optical fiber 27 is not limited to this. The optical axis of the rotation-side barrel 26 and the optical axis of the second optical fiber 27 are configured to approximately coincide with each other.

[0029] The sensor head 22 is housed in the observation hole 8 and is arranged opposite the observation window 9. The observation hole 8 is formed to penetrate the platen 2 and the polishing pad 5 in the vertical direction. The observation hole 8 is offset a predetermined distance in the radial direction from the rotation axis A of the platen 2. The shape of the observation hole 8 is formed, for example, as an elongated ellipse when viewed from above.

[0030] The observation window 9 is arranged to close the upper end of the observation hole 8. The observation window 9 is integrated with the polishing pad 5 by, for example, gluing the periphery of the observation window 9 to the polishing pad 5 so that slurry and the like on the polishing pad 5 does not leak during polishing. The material of the observation window 9 may be any material that is optically transparent to the wavelength of the measurement light described below, and is, for example, made of urethane.

[0031] The measurement light emitted from the light source 21 is transmitted to the sensor head 22 via the first optical fiber 24, the fixed-side lens barrel 25, the rotating-side lens barrel 26, and the second optical fiber 27. That is, the measurement light passes through a hollow optical path OP.

[0032] The measurement light irradiated from the sensor head 22 toward the workpiece W passes through the observation window 9 and reaches the workpiece W. At this time, the sensor head 22 rotates integrally with the platen 2, so as the workpiece W passes over the observation window 9, as shown in Fig. 3, the film thickness measurement position MP at which the sensor head 22 irradiates the measurement light onto the workpiece W is scanned within the workpiece W in the direction of rotation D1 of the platen 2, passing through the center of rotation of the workpiece W and traversing the workpiece W. In other words, multiple points can be measured in an extremely short time while the platen 2 makes one rotation.

[0033] The sensor head 22 also receives reflected light that is reflected by the front and back surfaces of the layer to be polished of the workpiece W and passes through the observation window 9. The reflected light received by the sensor head 22 is transmitted to the spectrometer 23 via the second optical fiber 27, the rotating-side lens barrel 26, the fixed-side lens barrel 25, and the first optical fiber 24. In other words, the reflected light passes through the hollow optical path OP. Note that the sensor head 22 is not limited to one that irradiates or receives light perpendicular to the observation window 9, and the optical path may be refracted by a reflecting member or the like.

[0034] The spectrometer 23 is connected to the fixed-side lens barrel 25 via a first optical fiber 24. The spectrometer 23 resolves the reflected light from the workpiece W according to wavelength, and generates a spectral waveform that indicates the relationship between the wavelength and the intensity of the reflected light. The spectrometer 23 also calculates the film thickness of the workpiece W being polished from the spectral waveform using Fourier analysis or the like.

[0035] The detection unit 30 compares the film thickness of the workpiece W being processed, measured by the spectroscopic device 23, with a pre-stored set value of film thickness corresponding to the polishing end point, and when the measured value of the film thickness of the workpiece W reaches the set value, the detection unit 30 detects the polishing end point of the workpiece W. In addition, the detection unit 30 outputs a stop signal for the CMP device 1 to the controller 6 to terminate polishing of the workpiece W.

[0036] Next, a description will be given of a suitable configuration of the fixed-side lens barrel 25 and the rotating-side lens barrel 26 so that the polishing end-point detection device 10 can detect the polishing end point with high accuracy.

[0037] If the amount of reflected light acquired by the measurement unit 20 is unstable and fluctuates, the measurement accuracy will decrease. Therefore, it is preferable that fluctuations in the amount of measurement light and reflected light be stable to the extent that they do not affect the measurement accuracy. The main causes that may cause significant fluctuations in the amount of light in the measurement unit 20 are, for example, as follows. (1) Circumferential runout between the rotation axis A of the platen 2 and the optical axis of the rotating lens barrel 26 (2) Distance of hollow optical path OP (3) Coaxiality between the optical axis of the fixed-side lens barrel 25 and the optical axis of the rotating-side lens barrel 26

[0038] (1) Circumferential runout between the rotation axis A of the platen 2 and the optical axis of the rotating lens barrel 26 The smaller the circumferential runout between the rotation axis A of the platen 2 and the optical axis of the rotation-side barrel 26 during rotation, the smaller the fluctuation in the amount of acquired light. Table 1 shows the variation in the amount of acquired light and the variation in measurement values ​​for the ratio (circumferential runout ratio) of the circumferential runout of the rotation-side barrel 26 to the diameter of the second optical fiber 27. Note that the "circumferential runout ratio" in Table 1 is the percentage obtained by dividing the circumferential runout of the rotation-side barrel 26 (15 μm, 30 μm, and 50 μm) by the bundle diameter of the second optical fiber 27 (1000 μm).

[0039] [Table 1]

[0040] According to Table 1, it can be seen that as the circumferential runout ratio of the rotation-side lens barrel 26 increases, the variations in the amount of acquired light and film thickness measurement also increase, and the measurement accuracy deteriorates.

[0041] Therefore, in this embodiment, to obtain a stable amount of acquired light, the runout of the optical axis of the rotation-side barrel 26 relative to the rotation axis A of the platen 2 during rotation is set to 1.5 μm (circumferential runout ratio: 1.5%). Note that the assembly of the rotation-side barrel 26 to the rotation shaft portion 2a is performed, for example, by checking the circumferential runout of the rotation-side barrel 26 with an electric micrometer while rotating the platen 2, and adjusting the mounting condition of the attachment 26a to the rotation shaft portion 2a so that the rotation-side barrel 26 is positioned at a position where the circumferential runout is equal to or less than a predetermined value.

[0042] (2) Distance of hollow optical path OP If the distance of the hollow optical path OP (the gap between the fixed-side barrel 25 and the rotating-side barrel 26) is excessively wide, the light will diverge, reducing the light transmission rate and deteriorating the measurement accuracy, and the diverged light reflected at the end face of the fixed-side barrel 25 or the end face of the rotating-side barrel 26 will become noise.

[0043] On the other hand, if the distance of the hollow optical path OP is too close, there is a risk that the rotating-side lens barrel 26 will come into contact with the fixed-side lens barrel 25 and be damaged when the platen 2 rotates. Table 2 shows the relationship between the distance (gap width) of the hollow optical path OP and the variation in the measured film thickness.

[0044] [Table 2]

[0045] According to Table 2, when the distance of the hollow optical path OP is 1.5 mm or more, the variation in the measured film thickness worsens as the distance of the hollow optical path OP increases. On the other hand, when the distance of the hollow optical path OP is 1 mm or less, the variation in the measured film thickness is approximately constant.

[0046] Therefore, in this embodiment, in order to reduce the variation in the measured film thickness and to suppress the divergence of light, the distance of the hollow optical path OP is set to 0.5 mm. The distance of the hollow optical path OP is adjusted, for example, by driving the movable stage 29 from a state in which the fixed-side lens barrel 25 and the rotating-side lens barrel 26 are in contact with each other to move the fixed-side lens barrel 25 away from the rotating-side lens barrel 26, and stopping the movable stage 29 when the movement amount of the movable stage 29 reaches 0.5 mm.

[0047] (3) Coaxiality between the optical axis of the fixed-side lens barrel 25 and the optical axis of the rotating-side lens barrel 26 The smaller the deviation of the optical axis of the fixed-side lens barrel 25 relative to the optical axis of the rotating-side lens barrel 26, the smaller the fluctuation in the amount of acquired light.

[0048] Therefore, in this embodiment, the relative position of the fixed-side barrel 25 with respect to the rotating-side barrel 26 is set so that the amount of variation in the amount of acquired light falls within ±5%. The horizontal positioning of the fixed-side barrel 25 is performed, for example, by rotating the platen 2 while driving the moving stage 29 to move the fixed-side barrel 25 in the horizontal direction, and checking the amount of variation in the amount of acquired light of the spectrometer 23 according to the position of the fixed-side barrel 25.

[0049] In this way, the polishing endpoint detection device 10 of the above-described embodiment is a polishing endpoint detection device 10 that measures the film thickness of the workpiece W being pressed against the polishing pad 5 on the platen 2 and polished, and detects the polishing endpoint based on the film thickness of the workpiece W, and is configured to include a fixed side barrel 25 that is provided outside the platen 2 and connected to the light source 21 and the spectrometer 23 via a first optical fiber 24, a rotating side barrel 26 that is provided on the platen 2 and transmits light wirelessly between the fixed side barrel 25, and a sensor head 22 that is housed in an observation hole 8 formed in the platen 2 and the polishing pad 5 and connected to the rotating side barrel 26 via a second optical fiber 27, and that irradiates measurement light toward the workpiece W as the workpiece W passes over the observation hole 8 and receives reflected light from the workpiece W.

[0050] With this configuration, the sensor head 22 and the fixed side barrel 25 can rotate together with the platen 2, and the film thickness measurement position MP is scanned across the workpiece W every time the platen 2 rotates once, so that film thickness measurements can be performed accurately over a wide area within the workpiece W in a short time.

[0051] Furthermore, if the light source 21 and the spectrometer 23 are mounted on the platen 2, there is a risk that the light source 21 and the spectrometer 23 may be damaged by the centrifugal force generated when the platen 2 rotates, or that the power supply to the light source 21 and the spectrometer 23 may become unstable or noise may be introduced. However, by providing the light source 21 and the spectrometer 23 outside the platen 2, the film thickness measurement of the workpiece W can be performed stably.

[0052] Furthermore, the polishing endpoint detection device 10 according to this embodiment is configured such that the fixed-side lens barrel 25 and the rotating-side lens barrel 26 are arranged opposite each other with a gap therebetween.

[0053] This configuration prevents the fixed-side lens barrel 25 and the rotating-side lens barrel 26 from coming into contact and breaking when the platen 2 rotates at high speed, so that film thickness measurement of the workpiece W can be performed stably.

[0054] Furthermore, in the polishing endpoint detection device 10 according to this embodiment, the rotation-side lens barrel 26 is provided on the rotation shaft 2a of the platen 2 via an attachment 26a that is detachable from the platen 2.

[0055] This configuration allows the rotation-side lens barrel 26 to be easily assembled to the rotation shaft portion 2a.

[0056] Moreover, the polishing endpoint detection device 10 according to this embodiment is configured to further include a moving stage 29 that moves the fixed-side lens barrel 25 relative to the rotating-side lens barrel 26.

[0057] With this configuration, by changing the relative position of the fixed-side barrel 25 with respect to the rotating-side barrel 26, the gap between the fixed-side barrel 25 and the rotating-side barrel 26 and the coaxiality between the optical axis of the fixed-side barrel 25 and the optical axis of the rotating-side barrel 26 can be easily adjusted, thereby enabling stable film thickness measurement of the workpiece W.

[0058] The CMP apparatus 1 according to this embodiment is also configured to include a polishing endpoint detection device 10.

[0059] With this configuration, the sensor head 22 and the fixed side barrel 25 can rotate together with the platen 2, and the film thickness measurement position MP is scanned across the workpiece W every time the platen 2 rotates once, so that film thickness measurements can be performed accurately over a wide area within the workpiece W in a short time.

[0060] Furthermore, the present invention can be modified in various ways other than those described above without departing from the spirit of the present invention, and it goes without saying that the present invention also covers such modifications. [Explanation of symbols]

[0061] 1:CMP equipment 2: Platen 2a: Rotating shaft (of platen) 3: Polishing head 3a: Rotating shaft (of polishing head) 4: Motor 5: Polishing pad 6: Controller 7: Zipper 7a: Chuck table 7b: Holding surface 8: Observation hole 9: Observation window 10: Polishing end point detection device 20: Measuring part 21:Light source 22: Sensor head 23: Spectroscopic device 24: First optical fiber 25: Fixed side lens barrel 26: Rotating tube 26a: Attachment 27: Second optical fiber 28: Support arm 29: Moving stage 30: Detection unit A: Rotation axis OP: Hollow optical path W: Workpiece

Claims

1. A polishing end point detection device that measures a film thickness of a workpiece being pressed against a polishing pad on a platen and polished, and detects a polishing end point based on the film thickness of the workpiece, a fixed-side lens barrel provided outside the platen and connected to a light source and a spectrometer via first fibers; a rotating-side lens barrel provided on the platen and configured to wirelessly transmit light between the rotating-side lens barrel and the fixed-side lens barrel; a sensor head that is housed in an observation hole formed in the platen and the polishing pad and is connected to the rotating barrel via a second fiber, and that irradiates measurement light onto the workpiece when the workpiece passes over the observation hole and receives reflected light from a film thickness measurement point where the measurement light is irradiated onto the workpiece; Equipped with The polishing endpoint detection device is characterized in that the rotating barrel is attached to the rotation shaft of the platen via an attachment that can adjust its horizontal position relative to the rotation shaft of the platen.

2. 2. The polishing endpoint detection device according to claim 1, wherein the fixed-side lens barrel and the rotating-side lens barrel are arranged opposite each other with a gap therebetween.

3. 3. The polishing endpoint detection device according to claim 1, further comprising a moving stage for moving the fixed-side lens barrel relative to the rotating-side lens barrel.

4. 4. A CMP apparatus comprising the polishing endpoint detection device according to claim 1.

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