TWI823762B - Grinding end point detection device and CMP device - Google Patents

Abstract

Provide a polishing end point detection device and a CMP device that can detect the film thickness of a workpiece being polished in a short time and with high accuracy.

The polishing end point detection device 10 is provided with: a fixed-side lens barrel 25, which is located outside the platform 2 and is connected to the light source 21 and the spectroscopic device 23 through the first optical fiber 24; a rotating-side lens barrel 26, which is located on the platform 2 and on the fixed side. Light is transmitted wirelessly between the lens barrel 25; and the sensing head 22 is accommodated in the observation hole formed on the platform 2 and the polishing pad 5, and is connected to the rotating side lens barrel 26 through the second optical fiber 27, and in When the workpiece W passes through the observation hole 8, the measurement light is irradiated toward the workpiece W and the reflected light from the workpiece W is received.

Description

Grinding end point detection device and CMP device

The present invention relates to a grinding end point detection device and a CMP device.

In the field of semiconductor manufacturing, a CMP apparatus that polishes and flattens a semiconductor silicon wafer or the like (hereinafter referred to as a “workpiece”) is known.

The polishing device described in Patent Document 1 is a polishing device that applies chemical mechanical polishing, so-called CMP (Chemical Mechanical Polishing) technology. This CMP device pushes the workpiece mounted on the grinding head toward the polishing pad to grind the workpiece. In addition, the sensor head arranged below the platen irradiates light to the workpiece through the observation hole every time the platen rotates one unit, and detects the polishing end point of the workpiece based on the light intensity spectrum of the reflected light.

[Prior technical literature]

[Patent Document]

[Patent Document 1] Japanese Patent Application Publication No. 2017-52027

However, in the polishing device described in Patent Document 1, the film thickness is measured at only one point in the workpiece every time the stage rotates one unit, as shown in Figure 4 As shown, the grinding head is moved in the horizontal direction d1, and the measurement position mp of the sensing head 101 in the workpiece 100 rotating in the rotation direction d2 is scanned, because it is necessary to measure the number of measurement points required to accurately detect the grinding end point. (eight points in Figure 4), there is a problem that it takes a long time to measure the film thickness.

Therefore, in order to detect the film thickness of the workpiece being polished in a short time and with high precision, a technical problem that should be solved is derived, and the present invention aims to solve the problem.

In order to achieve the above object, the polishing device of the present invention measures the film thickness of a workpiece being polished by a polishing pad pressed on a platform, and detects the polishing end point based on the film thickness of the workpiece. The polishing end point detection device includes: a fixed side The lens barrel is located outside the aforementioned platform and is connected to the light source and the spectroscopic device respectively through the first optical fiber; the rotating side lens barrel is located on the aforementioned platform and wirelessly transmits light between the aforementioned fixed side lens barrel; and sensing The head is housed in an observation hole formed in the platform and the polishing pad, and is connected to the rotating side lens barrel through a second optical fiber, and irradiates the measurement light toward the workpiece when the workpiece passes through the observation hole, and receives the measurement light from the Reflected light from the aforementioned workpiece.

Moreover, the CMP apparatus of this invention is equipped with the above-mentioned polishing end point detection device.

The present invention can detect the film thickness of a workpiece being polished in a short time and with good accuracy.

1:CMP device

2:Platform

2a: Rotation axis (of the platform)

3: Grinding head

3a: Rotating shaft (of grinding head)

4: Motor

5: Polishing pad

6:Controller

7:Chuck

7a:Chuck table

7b: Keep surface

8: Observation hole

9: Observation window

10: Grinding end point detection device

20: Measurement Department

21:Light source

22: Sensing head

23: Spectroscopic device

24: 1st optical fiber

25: Fixed side lens barrel

26: Rotating side lens barrel

26a: Accessories

27: 2nd optical fiber

28:Support arm

29:Mobile station

30:Detection Department

A:Rotation axis

D1: Rotation direction

D2: Rotation direction

MP: film thickness measurement position

OP: Hollow optical path

W: workpiece

100:Artifact

101: Sensing head

d1: horizontal direction

d2: rotation direction

mp: determined position

[Fig. 1] is a perspective view schematically showing the CMP device according to the first embodiment of the present invention.

[Fig. 2] is a longitudinal sectional view schematically showing the main parts of the CMP device.

[Fig. 3] is a schematic diagram showing how the film thickness measurement position in the workpiece is scanned while the stage rotates one unit.

[Fig. 4] is a schematic diagram showing a state in which the film thickness measurement position in the workpiece is scanned by moving the polishing head horizontally in a conventional CMP apparatus.

An embodiment of the present invention will be described based on the drawings. In addition, when the number, numerical value, amount, range, etc. of the constituent elements are mentioned below, they are not limited to the specific number unless otherwise expressly stated and the case is clearly limited to a specific number in principle, even if it is a specific number. It does not matter if it is above or below a specific number.

In addition, when referring to the shape and positional relationship of components, etc., unless otherwise expressly stated or otherwise considered to be obviously different in principle, the term essentially includes those that are similar or similar to the shape, etc.

In addition, in order to make the features easier to understand, the drawings may enlarge and exaggerate the features, and the dimensional proportions of the constituent elements may not be the same as the actual ones. In addition, in order to make the cross-sectional structure of the constituent elements easy to understand, the cross-sectional lines of some constituent elements may be omitted in the cross-sectional drawings.

FIG. 1 is a perspective view schematically showing a CMP device 1 according to an embodiment of the present invention. The CMP device 1 grinds one surface of the workpiece W flat. The CMP apparatus 1 includes a stage 2 and a polishing head 3 . The workpiece W is, for example, a silicon wafer, but is not affected by This is limited.

The platform 2 is formed into a disk shape and is connected to the rotation shaft portion 2 a arranged below the platform 2 . The platform 2 rotates in the direction of the arrow mark D1 in FIG. 1 due to the rotation of the rotating shaft portion 2a driven by the motor 4. A polishing pad 5 is attached to the upper surface of the platform 2, and a mixture of abrasives and chemicals, that is, CMP slurry, is supplied to the polishing pad 5 from a nozzle (not shown).

The polishing head 3 has a smaller diameter than the table 2 and is connected to the rotation shaft portion 3 a arranged above the polishing head 3 . When the rotating shaft part 3a is rotated by driving a motor (not shown), the polishing head 3 rotates in the direction of the arrow mark D2 in FIG. 1 . The polishing head 3 is configured to be movable in the vertical direction and the horizontal direction by a head moving mechanism (not shown). When polishing the workpiece W, the polishing head 3 is lowered to push the workpiece W toward the polishing pad 5 .

The operation of the CMP device 1 is controlled by the controller 6 . The controller 6 controls the components constituting the CMP device 1 respectively. The controller 6 is, for example, a computer, and is composed of a CPU, a memory, and the like. In addition, the functions of the controller 6 can be realized by using software for control, and can be realized by using hardware for operation.

Next, the main parts of the CMP device 1 will be described based on FIG. 2 . The grinding head 3 is equipped with the chuck 7 connected to the rotation shaft part 3a and rotating together with the rotation shaft part 3a.

The lower part of the grinding head 3 is provided with a chuck 7 . The chuck 7 is provided with an alumina chuck table 7a. The chuck 7 is connected to a vacuum source and a compressed air source not shown in the figure. By activating the vacuum source, the workpiece W is adsorbed and held on the holding surface 7b of the chuck 7 . Furthermore, by activating the compressed air source, the space between the holding surface 7b and the workpiece W is Compressed air is supplied to release the adsorption and holding of the workpiece W.

With this configuration, the CMP device 1 grinds the workpiece W in the following sequence. That is, first, the workpiece W is adsorbed and held by the polishing head 3 with the polished layer of the workpiece W facing downward. Then, the grinding head 3 moves on the platform 2, and the platform 2 and the grinding head 3 rotate in the same direction. Then, while the polishing fluid is supplied to the polishing pad 5 , the polishing head 3 polishes the workpiece W by pressing the workpiece W toward the polishing pad 5 . In addition, when the polishing end point detection device 10 to be described later detects the polishing end point of the workpiece W, the controller 6 stops the table 2 and the polishing head 3 to complete polishing of the workpiece W.

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

The measuring unit 20 is a so-called optical interference type film thickness sensor. The measurement unit 20 includes a light source 21, a sensor head 22, and a spectroscopic device 23.

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

The first optical fiber 24 is a Y-shaped optical fiber that bundles a plurality of optical fibers and branches in the middle. One end is connected to the light source 21 and the light splitting device 23 respectively, and the other end is connected to the fixed side barrel 25. The bundle diameter of the first optical fiber 24 is set to 1000 μm, for example. In addition, the structure of the first optical fiber 24 is not limited to this.

The fixed side lens barrel 25 and the rotating side lens barrel 26 are only separately scheduled. They are arranged facing each other at a distance so that they can illuminate and receive light from each other. That is, the light system is transmitted wirelessly between the fixed side lens barrel 25 and the rotating side lens barrel 26 . Hereinafter, the optical path through which light is transmitted wirelessly is called "hollow optical path OP".

The optical axis of the fixed side lens barrel 25 and the optical axis system of the first optical fiber 24 are configured to substantially coincide with each other. The fixed side lens barrel 25 is supported by a support arm 28 . The support arm 28 is placed on the moving platform 29. By moving the moving platform 29 in the horizontal direction or the up and down direction, the fixed side lens barrel 25 can move relatively to the rotating side lens barrel 26.

The rotating side lens barrel 26 is mounted on the bottom of the rotating shaft portion 2a of the platform 2 through an attachment 26a. The outer periphery of the rotating side barrel 26 is supported by an attachment 26a. The attachment 26a is configured to be detachable from the rotating shaft 2a by fastening a bolt to a long hole (not shown) or the like. In addition, the attachment device 26a can finely adjust the installation position of the rotating shaft portion 2a in the horizontal direction.

The second optical fiber 27 is an I-type optical fiber in which a plurality of optical fibers are bundled. One end is connected to the rotating side barrel 26 and the other end is connected to the sensing head 22 . The bundle diameter of the second optical fiber 27 is set to 1000 μm, for example. In addition, the structure of the second optical fiber 27 is not limited to this. The optical axis of the rotating side barrel 26 and the optical axis system of the second optical fiber 27 are configured to substantially coincide with each other.

The sensing head 22 is accommodated in the observation hole 8 and is arranged facing the observation window 9 . The observation hole 8 is formed through the platform 2 and the polishing pad 5 in the up and down direction. The observation hole 8 is offset from the rotation axis A of the platform 2 by a predetermined distance in the radial direction. The shape of the observation hole 8 is, for example, an oblong shape when viewed from a plan view.

The observation window 9 is arranged to block the upper end of the observation hole 8 . view The observation window 9 is integrated with the polishing pad 5 by bonding the peripheral surface of the observation window 9 to the polishing pad 5 and the like so that the polishing fluid etc. on the polishing pad 5 does not leak during polishing. The observation window 9 may be made of any material as long as it is optically transparent with respect to the wavelength of the measurement light described below, and may be made of urethane, for example.

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

Then, the measurement light irradiated toward the workpiece W from the sensor head 22 passes through the observation window 9 and reaches the workpiece W. At this time, since the sensor head 22 rotates integrally with the platform 2, as shown in FIG. 3, when the workpiece W passes through the observation window 9, the sensor head 22 irradiates the workpiece W with the film thickness measurement position MP of the measurement light. It is scanned within the workpiece W in a manner that it passes through the rotation center of the workpiece W and traverses the workpiece W along the rotational direction D1 of the platform 2 . That is, while the stage 2 rotates one unit, multi-point measurement can be performed in an extremely short time.

In addition, the sensor head 22 receives the reflected light reflected on the surface and back surface of the polished layer of the workpiece W and transmitted through the observation window 9 . The reflected light received by the sensing head 22 is transmitted to the spectroscopic device 23 via the second optical fiber 27 , the rotating lens barrel 26 , the fixed lens barrel 25 and the first optical fiber 24 . That is, the reflected light will pass through the hollow optical path OP. In addition, the sensor head 22 is not limited to emitting or receiving light perpendicularly to the observation window 9, and it does not matter if the optical path is refracted by a reflective member or the like.

The spectroscopic device 23 is connected to the fixed side barrel 25 through the first optical fiber 24 . The spectroscopic device 23 decomposes the reflected light from the workpiece W according to the wavelength, and generates a spectroscopic waveform representing the relationship between the wavelength and the intensity of the reflected light. In addition, the spectroscopic device 23 calculates the spectral waveform from the spectral waveform using Fourier analysis or the like. The film thickness of the workpiece W being ground.

The detection part 30 compares the film thickness of the workpiece W being processed measured by the spectroscopic device 23 with the set value of the film thickness corresponding to the polishing end point stored in advance. 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. Furthermore, the detection unit 30 outputs a signal to stop the CMP device 1 to the controller 6, thereby completing the grinding of the workpiece W.

Next, since the polishing end point detection device 10 can accurately detect the polishing end point, the preferred structure of the fixed side lens barrel 25 and the rotating side lens barrel 26 will be described.

When the acquired light amount of reflected light is unstable and fluctuates, the measurement accuracy of the measurement unit 20 decreases. Therefore, it is preferable that the light quantity fluctuations of the measurement light and the reflected light are stable to the extent that they do not affect the measurement accuracy. The following may be considered as a main reason why significant light quantity variation may occur in the measurement unit 20 .

(1) Circular deflection between the rotation axis A of the platform 2 and the optical axis of the rotating side 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

(1) Circular deflection between the rotation axis A of the platform 2 and the optical axis of the rotating side lens barrel 26

The smaller the circumferential deflection of the rotation axis A of the stage 2 and the optical axis of the rotation side lens barrel 26 during rotation, the smaller the variation in the amount of acquired light. Table 1 shows the non-uniformity of the acquired light amount and the non-uniformity of the measured value in the circumferential deflection ratio (circular deflection ratio) of the rotating side barrel 26 to the diameter of the second optical fiber 27 . In addition, the so-called "circular deflection ratio" in Table 1 refers to the rotating side lens barrel The percentage obtained by dividing the circular deflection of 26 (15 μm, 30 μm, and 50 μm) by the bundle diameter of the second optical fiber 27 (1000 μm).

[Table 1]

From Table 1, it can be seen that as the yaw ratio of the rotating side lens barrel 26 increases, the unevenness of the acquired light amount and film thickness measurement also increases, and the measurement accuracy deteriorates.

Therefore, in this embodiment, the deflection when the optical axis of the rotating side lens barrel 26 rotates with respect to the rotation axis A of the stage 2 is set to 1.5 μm (circumferential deflection ratio: 1.5%), so that the acquired light amount can be stably obtained. In addition, the mounting of the rotating side lens barrel 26 to the rotating shaft part 2 a is performed by, for example, confirming the circumferential deflection of the rotating side lens barrel 26 with an electric micrometer while rotating the stage 2 to rotate the rotating side lens barrel 26 The attachment of the accessory device 26a to the rotation shaft portion 2a can be adjusted so that the circumferential deflection becomes less than a predetermined value.

(2) Distance of hollow optical path OP

When the distance of the hollow optical path OP (the gap between the fixed side lens barrel 25 and the rotating side lens barrel 26) is too wide, light divergence reduces the transmission rate of the light amount. In addition to deteriorating the measurement accuracy, the light diverges and forms on the end face of the fixed side lens barrel 25. Or the light reflected from the end surface of the rotating side lens barrel 26 becomes noise.

On the other hand, when the distance of the hollow optical path OP is too close, the rotating side lens barrel 26 may contact the fixed side lens barrel 25 and be damaged when the platform 2 rotates. Table 2 shows the relationship between the distance (gap width) of the hollow optical path OP and the non-uniformity of the measured film thickness.

[Table 2]

According to Table 2, when the distance of the hollow optical path OP is 1.5 mm or more, it can be seen that as the distance of the hollow optical path OP becomes longer, the non-uniformity of the measured film thickness worsens. On the other hand, when the distance of the hollow optical path OP is 1 mm or less, it is found that the non-uniformity in the measured film thickness is approximately constant.

Therefore, in this embodiment, in order to reduce the unevenness of the measured film thickness and suppress the divergence of light, the distance of the hollow optical path OP is set to 0.5 mm. In addition, the distance of the hollow optical path OP is adjusted by, for example, driving the moving stage 29 to cause the fixed side lens barrel 25 to rotate away from the rotating side lens barrel 26 from the state where the fixed side lens barrel 25 and the rotating side lens barrel 26 are in contact. Move in a separated manner, and stop the moving stage 29 after the movement amount of the moving stage 29 reaches 0.5 mm.

(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 deflection of the optical axis of the fixed-side lens barrel 25 relative to the optical axis of the rotating rotating-side lens barrel 26 is, the smaller the variation in the amount of acquired light is.

Therefore, in this embodiment, the relative position of the fixed-side lens barrel 25 with respect to the rotating-side lens barrel 26 is set so that the variation in light intensity is within ±5%. In addition, the fixed-side lens barrel 25 is positioned in the horizontal direction as follows. For example, while rotating the platform 2, the moving stage 29 is driven to move the fixed-side lens barrel 25 in the horizontal direction, and it is confirmed that the fixed-side lens barrel 25 is aligned with the position of the fixed-side lens barrel 25. The amount of variation in the amount of light acquired by the spectroscopic device 23 at the position.

In this way, the above-mentioned polishing end point detection device 10 of this embodiment measures the film thickness of the workpiece W being polished by the polishing pad 5 pressed on the platform 2, and detects the polishing end point based on the film thickness of the workpiece W. The polishing end point detection device 10 is configured to include: a fixed side lens barrel 25, which is installed outside the platform 2, and is connected to the light source 21 and the spectroscopic device 23 through the first optical fiber 24; a rotating side lens barrel 26, which is installed on the platform 2 and between Light is transmitted wirelessly between the fixed side lens barrel 25; and the sensing head 22, which is housed in the observation hole formed on the platform 2 and the polishing pad 5, and is connected to the rotating side lens barrel 26 through the second optical fiber 27. When the workpiece W passes through the observation hole 8, the measurement light is irradiated toward the workpiece W, and the reflected light from the workpiece W is received.

With this configuration, the sensing head 22 and the fixed-side lens barrel 25 can rotate together with the stage 2. Since the film thickness measurement position MP is scanned across the workpiece W every time the stage 2 rotates 1 unit, The film thickness can be measured in a short time and with high accuracy over a wide range covering the workpiece W.

Furthermore, when the light source 21 and the spectroscopic device 23 are mounted on the platform 2, the centrifugal force generated when the platform 2 rotates will cause the light source 21 and the spectroscopic device to move. 23 is damaged, or the power supply to the light source 21 and the spectroscopic device 23 becomes unstable, or there is a risk of noise being mixed in. However, by installing the light source 21 and the spectroscopic device 23 outside the platform 2, the film thickness of the workpiece W can be measured stably.

In addition, in the polishing end point detection device 10 of this embodiment, the fixed-side lens barrel 25 and the rotating-side lens barrel 26 are configured to face each other with a gap.

With this configuration, when the stage 2 rotates at high speed, the fixed-side lens barrel 25 and the rotating-side lens barrel 26 are prevented from being damaged due to contact with each other, so that the film thickness of the workpiece W can be measured stably.

Furthermore, the polishing end point detection device 10 of this embodiment is configured such that the rotation side lens barrel 26 is installed on the rotation shaft portion 2a of the platform 2 through an attachment 26a that is detachably attached to the platform 2.

With this configuration, the rotating side lens barrel 26 can be easily attached to the rotating shaft portion 2a.

Furthermore, the polishing end point detection device 10 of this embodiment is further equipped with a moving stage 29 for relatively moving the fixed side lens barrel 25 to the rotating side lens barrel 26 .

With this configuration, by changing the relative position of the fixed side lens barrel 25 to the rotating side lens barrel 26, the gap between the fixed side lens barrel 25 and the rotating side lens barrel 26, and the optical axis of the fixed side lens barrel 25 can be easily adjusted. The coaxiality of the optical axis of the rotating side lens barrel 26 enables stable measurement of the film thickness of the workpiece W.

Furthermore, the CMP apparatus 1 of this embodiment is configured to include a polishing end point detection device 10 .

With this structure, the sensing head 22 and the fixed side lens barrel 25 can rotate together with the platform 2 because the film thickness measurement position MP is located every time the platform 2 rotates The film thickness is scanned across the workpiece W during one unit rotation, so the film thickness can be measured in a short time and with high accuracy over a wide range covering the workpiece W.

In addition, the present invention can be modified in various ways other than those described above without departing from the spirit of the present invention, and the present invention is naturally applicable to such modifications.

2:Platform

2a: Rotation axis (of the platform)

3: Grinding head

3a: Rotating shaft (of grinding head)

5: Polishing pad

7:Chuck

7a:Chuck table

7b: Keep surface

8: Observation hole

9: Observation window

21:Light source

22: Sensing head

23: Spectroscopic device

24: 1st optical fiber

25: Fixed side lens barrel

26: Rotating side lens barrel

26a: Accessories

27: 2nd optical fiber

28:Support arm

29:Mobile station

30:Detection Department

A:Rotation axis

D2: Rotation direction

OP: Hollow optical path

W: workpiece

Claims (5)

A grinding end point detection device is used to measure the film thickness of a workpiece being ground by a polishing pad pressed on a platform, and detects the grinding end point based on the film thickness of the workpiece. The characteristics of the grinding end point detection device are: The fixed side lens tube is located outside the aforementioned platform and is connected to the light source and the light splitting device through the first optical fiber; A rotating side lens tube is provided on the aforementioned platform and transmits light wirelessly between the aforementioned fixed side lens tube; and The sensing head is accommodated in an observation hole formed in the platform and the polishing pad, and is connected to the rotating side lens barrel through a second optical fiber, and irradiates the measurement light toward the workpiece when the workpiece passes through the observation hole, Receive the reflected light from the aforementioned workpiece. For example, the grinding end point detection device of claim 1, wherein The fixed side lens barrel and the rotating side lens barrel are disposed facing each other with a gap therebetween. For example, the grinding end point detection device of claim 1, wherein The rotating side lens barrel is installed on the rotation axis of the platform through an accessory device, and the accessory device can adjust the horizontal position relative to the rotation axis of the platform. The grinding end point detection device of claim 1 is further provided with a moving stage to move the fixed side lens barrel relative to the rotating side lens barrel. A CMP device, characterized by having any of the requirements 1 to 4 A grinding end point detection device.

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