JP7333709B2 - CMP equipment - Google Patents

Description

The present invention relates to a CMP apparatus, and more particularly to a CMP apparatus that polishes a wafer using chemical mechanical polishing (CMP).

As a wafer polishing apparatus, a CMP polishing apparatus for polishing an oxide film or the like formed on the surface of a wafer is known. Polishing by CMP involves pressing the wafer against the polishing pad with a predetermined pressure while rotating the polishing pad attached to the polishing surface plate and the wafer, and supplying an abrasive (slurry) between the polishing pad and the wafer. done by

As such a CMP polishing apparatus, a CMP apparatus described in Patent Document 1 is known. In this CMP apparatus 100, a light source and a camera C for photographing the wafer 1 illuminated by the light source are arranged in a housing B, and the state of the wafer 1 is observed. In addition, the code|symbol is described in patent document 1. FIG.

Further, in the wafer polishing apparatus 10 described in Patent Document 2, a radiation thermometer 90 is provided for detecting temperature change at a detection point 92 set on the polishing pad 20 near the holding head 14 to detect slip-out of the wafer. . In addition, the code|symbol is described in the patent document 2. FIG.

JP 2006-114714 A Japanese Patent Application Laid-Open No. 2007-134478

However, in the CMP apparatus 100 described in Patent Document 1, the camera C must be arranged in the housing B, and the state of the wafer 1 must be observed from the photographed image, which tends to complicate the configuration and slow response. There was a problem that

Further, in the wafer polishing apparatus described in Patent Document 2, it is necessary to provide the radiation thermometer 90 for constantly observing the vicinity of the polishing head 14, which complicates the configuration.

Therefore, there arises a technical problem to be solved in order to quickly and simply detect the polishing abnormality of the wafer being polished, and an object of the present invention is to solve this problem.

In order to achieve the above object, a CMP apparatus according to the present invention is a CMP apparatus that polishes a wafer accommodated in a housing portion of a polishing head by pressing it against a polishing pad, wherein the wafer is polished in the housing portion during polishing of the wafer. an optical measuring unit that projects light toward the wafer or the polishing head, receives the reflected light from the wafer or the polishing head, and obtains a waveform pattern corresponding to the wavelength of the reflected light; and the wafer or the polishing head during polishing of the wafer. A waveform pattern for comparison, which is a waveform pattern for a predetermined wavelength range of the reflected light from the normal polishing, is compared with a previously stored waveform pattern for normal polishing, which is a waveform pattern for a predetermined wavelength range of the reflected light during normal polishing . When the waveform pattern for comparison in the wavelength range does not include a characteristic tendency that appears in the waveform pattern during normal polishing in a predetermined wavelength range, at least one of a plurality of polishing abnormalities corresponding to the characteristic tendency and an abnormality detection unit that detects a polishing abnormality.

According to this configuration, the waveform pattern of the reflected light during polishing is compared with the waveform pattern during normal polishing, and the characteristic tendency that appears in the waveform pattern during normal polishing is included in the waveform pattern of the reflected light during polishing. Abnormal polishing can be detected early and easily by determining whether or not there is.

Further, in the CMP apparatus according to the present invention, when the abnormality detection unit detects that the signal value within the predetermined wavelength range in the waveform pattern to be compared is less than a preset threshold value, the wafer slips out of the polishing head. It is preferable to detect the occurrence of an out.

According to this configuration, the slip-out of the wafer is prevented by detecting that the signal value of the reflected light during polishing has decreased below the threshold, which is a characteristic tendency set based on the waveform pattern during normal polishing. It can be detected early and easily.

Further, in the CMP apparatus according to the present invention, the abnormality detection unit detects the occurrence of wafer cracks that damage the wafer when the peak of reflectance within the predetermined wavelength range decreases in the waveform pattern to be compared. Detection is preferred.

According to this configuration, the waveform pattern indicating the reflectance of the reflected light during polishing has a characteristic tendency set based on the waveform pattern during normal polishing, that is, the peak of reflectance (fluctuation range of reflectance) is remarkable. By detecting the decrease, wafer cracks can be detected early and easily.

Further, in the CMP apparatus according to the present invention, the abnormality detection unit detects the occurrence of wafer cracks that damage the wafer when the peak value of FFT analysis within a predetermined film thickness decreases in the waveform pattern to be compared . Detection is preferred.

According to this configuration, it is detected that the peak value of FFT analysis of the reflected light during polishing is significantly reduced compared to the peak value of FFT analysis, which is a characteristic tendency set based on the waveform pattern during normal polishing. By doing so, wafer cracks can be detected early and easily.

Further, in the CMP apparatus according to the present invention, when the abnormality detection unit detects that the reflected light intensity within the predetermined wavelength range in the waveform pattern to be compared is less than a preset threshold value, the metal layer on the wafer surface is It is preferable to detect the occurrence of peeling of the film.

According to this configuration, by detecting that the waveform pattern indicating the light intensity of the reflected light during polishing has decreased below the threshold, which is a characteristic tendency set based on the waveform pattern during normal polishing, the film is Peeling can be detected early and simply.

The present invention compares the waveform pattern of reflected light during polishing with the waveform pattern during normal polishing to determine whether the characteristic tendency that appears in the waveform pattern during normal polishing is included in the waveform pattern of reflected light during polishing. Abnormal polishing can be detected early and easily by determining whether the

1 is a perspective view schematically showing a CMP apparatus according to one embodiment of the present invention; FIG. FIG. 2 is a vertical cross-sectional view schematically showing main parts of the polishing head; FIG. 4 is a schematic diagram showing how the state of a wafer is observed during processing; It is a graph which shows the signal value for every wavelength, (a) shows the case where processing was normally performed, and (b) shows the case where slip-out occurred. It is a graph which shows various data at the time of normal processing, (a) shows the reflectance for every wavelength, (b) shows the power spectrum for every film thickness value. It is a graph which shows various data when a wafer crack generate|occur|produces, (a) shows the reflectance for every wavelength, (b) shows the power spectrum for every film thickness value. It is a graph which shows the reflected light intensity for every wavelength, (a) shows the case where it processed normally, (b) shows the case where film peeling generate|occur|produced.

An embodiment of the present invention will be described based on the drawings. In addition, hereinafter, when referring to the number, numerical value, amount, range, etc. of the constituent elements, unless otherwise specified or clearly limited to a specific number in principle, it is limited to the specific number It does not matter if it is more than or less than a certain number.

In addition, when referring to the shape and positional relationship of components, etc., unless otherwise specified or in principle clearly considered otherwise, etc. include.

In addition, the drawings may exaggerate characteristic parts by enlarging them in order to make the characteristics easier to understand. In addition, in cross-sectional views, hatching of some components may be omitted in order to facilitate understanding of the cross-sectional structure of the components.

FIG. 1 is a perspective view schematically showing a CMP apparatus 1 according to one embodiment of the invention. The CMP apparatus 1 polishes one surface of the wafer W flat. A CMP apparatus 1 includes a platen 2 and a polishing head 10 .

The platen 2 is disc-shaped and connected to a rotating shaft 3 arranged below the platen 2 . As the rotating shaft 3 is driven by the motor 4 to rotate, the platen 2 rotates in the direction of arrow D1 in FIG. 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 from a nozzle (not shown) onto the polishing pad 5 .

The polishing head 10 is shaped like a disk having a diameter smaller than that of the platen 2 and is connected to a rotating shaft 10 a arranged above the polishing head 10 . The polishing head 10 rotates in the direction of arrow D2 in FIG. 1 by rotating the rotary shaft 10a driven by a motor (not shown). The polishing head 10 can be raised and lowered in the vertical direction V by a lifting device (not shown). The polishing head 10 descends to press the wafer W against the polishing pad 5 when the wafer W is polished. The wafer W to be polished by the polishing head 10 is transferred by a wafer transfer mechanism (not shown).

The operation of the CMP apparatus 1 is controlled by control means (not shown). The control means controls each component constituting the CMP apparatus 1 . The control means is, for example, a computer, and is composed of a CPU, a memory, and the like. Note that the function of the control means may be realized by controlling using software, or may be realized by operating using hardware.

Next, the polishing head 10 will be explained. FIG. 2 is a vertical cross-sectional view schematically showing the essential parts of the polishing head 10. As shown in FIG. 3A and 3B are a longitudinal sectional view and a bottom view schematically showing the lower portion of the polishing head 10. FIG.

The polishing head 10 includes a head body 20, a carrier 30, a retainer ring 40, a membrane film 50, and a backing film 60.

The head body 20 is connected to the rotating shaft 10a and rotates together with the rotating shaft 10a. The head body 20 is connected to a carrier 30 arranged below the head body 20 via a rotating portion 21, and the head body 20 and the carrier 30 rotate together.

The carrier 30 is provided with airlines 31 spaced at regular intervals along the periphery of the carrier 30 . A lower end of the airline 31 opens into an air chamber A formed between the lower surface 30 a of the carrier 30 and the membrane film 50 . The air line 31 is connected to an air supply source as air supply means (not shown), and air is introduced into the air chamber A via the air line 31 . The pressure of air supplied to the air line 31 is adjusted by a regulator (not shown). The air supplied into the air chamber A forms an air layer above the membrane film 50 by the rim formed on the outer periphery of the carrier 30, and presses the entire surface of the membrane film 50 downward.

A carrier pressing means 32 is provided between the head body 20 and the carrier 30 . The carrier pressing means 32 is an airbag or the like that is inflated by air supplied from an air supply source (not shown). The pressure of air supplied from the air supply source is adjusted by a regulator (not shown). The carrier pressing means 32 presses the wafer W against the polishing pad 5 via the carrier 30 according to the pressure of the supplied air.

The retainer ring 40 is arranged to surround the carrier 30 . The retainer ring 40 includes a retainer ring holder 41 having a membrane film 50 adhered to its upper surface.

The retainer ring holder 41 is made of resin such as glass epoxy, polyetheretherketone (PEEK), or polyphenylene sulfide (PPS), for example. The retainer ring holder 41 is formed in an annular shape and has a housing pocket 41a for housing the wafer W in the center. The retainer ring holder 41 is attached to the retainer pressing member 43 via the snap ring 42 . A retainer pressing means 44 is provided between the head body 20 and the retainer pressing member 43 . Reference numeral 45 denotes a cover that covers the snap ring 42 from above.

The retainer pressing means 44 is an air bag or the like that is inflated by air supplied from an air supply source (not shown). The pressure of air supplied from the air supply source is adjusted by a regulator (not shown). The retainer pressing means 44 presses the retainer ring 40 against the polishing pad 5 via the retainer pressing means 44 according to the pressure of the supplied air.

The membrane film 50 is adhered to the retainer ring holder 41 so as to cover the storage pocket 41a, and when compressed air is introduced into the air chamber A, the membrane film 50 is elastically deformed into the storage pocket 41a by the air pressure.

The backing film 60 is, for example, a suede film. The backing film 60 is adhered to the membrane film 50 with its center positioned on the rotating shaft 10 a of the polishing head 10 . When compressed air is introduced into the air chamber A, the backing film 60 elastically deforms with the elastic deformation of the membrane film 50 to press the wafer W. As shown in FIG.

An elastic pressing member (not shown) arranged coaxially with the rotating shaft 10a of the polishing head 10 is provided on the lower surface 30a of the carrier 30. As shown in FIG. The elastic pressing member is made of, for example, polyethylene terephthalate resin (PET), fluorine resin (PFA), or polyphenylene sulfide (PPS). PFA has a low water absorption rate, is moderately flexible, and is resistant to elongation and deformation. PPS has a low water absorption rate, is resistant to elongation and deformation, and is less expensive than PFA.

The elastic pressing member is divided into multiple zones. Each zone is independently inflatable with air supplied from an air supply. Thereby, the elastic pressing member is configured such that each zone can be expanded independently.

In the CMP apparatus 1 having such a configuration, the pressing force applied to the carrier 30 by the compressed air supplied into the air chamber A is transmitted to the wafer W via the membrane film 50, so that the wafer W is uniformly pressed with a uniform pressure distribution. can be pressed against the polishing pad 5 to polish the wafer W.

In addition, by independently expanding each zone of the elastic pressing member according to the pressure of the compressed air, each zone can be selectively pressurized to polish the wafer W locally.

That is, in the CMP apparatus 1, the polishing pressure acting on the wafer W is divided into the pressure with which the elastic pressing member presses the membrane film 50 according to the air pressure in each zone, and the pressure of the membrane film 50 according to the air pressure in the air chamber A. 50 is the sum of the pressure with which the wafer W is pressed.

The CMP apparatus 1 also includes a detection mechanism 70 for detecting polishing abnormality of the wafer W being processed. As shown in FIG. 3 , the detection mechanism 70 includes an optical measurement section 71 and an abnormality detection section 72 . 3, the configuration of the CMP apparatus 1 is partially omitted.

The optical measuring unit 71 is a well-known film thickness measuring device, and can measure the film thickness of the wafer W in real time during the polishing process by receiving reflected light reflected by the surface of the wafer W to be polished. The optical measurement unit 71 is configured by, for example, connecting a plurality of optical fibers 74 and 75 to a lens 73 in a bundle. The optical fiber 74 is connected to the light source unit 76 . The light source unit 76 is, for example, a halogen light source that emits white light with a wavelength of 380 to 800 nm, but is not limited to this. The optical fiber 75 is connected to a spectroscope 77 .

The lens 73 is arranged to face a transparent observation window 80 provided in the platen 2 and polishing pad 5 . The lens 73 is not limited to irradiating light perpendicularly to the observation window 80, and the optical path may be refracted by a reflecting member or the like. Note that the observation window 80 is made of acrylic, for example.

The irradiation light emitted from the light source unit 76 passes through the observation window 80 via the optical fiber 74 and the lens 73, and is irradiated toward the polished surface of the wafer W or the accommodation pocket 41a. Reflected light received by the lens 73 after being reflected by the surface to be polished of the wafer W or the storage pocket 41 a is guided to the spectroscope 77 via the optical fiber 75 .

The abnormality detection unit 72 is preliminarily provided with a waveform pattern (normal polishing waveform pattern) of the reflected wave reflected by the surface to be polished of the wafer W when polishing is normally performed, and a characteristic tendency that appears in the normal polishing waveform pattern. remembered. In addition, the "characteristic tendency" means a remarkable feature that can be easily compared in the waveform pattern during normal polishing. can be considered. The abnormality detection unit 72 also compares the normal polishing waveform pattern with the waveform pattern of the reflected wave reflected by the polished surface of the wafer W being processed (comparison target waveform pattern) to determine whether there is an abnormality.

Specifically, the abnormality detection unit 72 detects abnormalities such as slip-out, wafer cracking, and film peeling. The procedure for detecting an abnormality for each content of the abnormality will be described below with reference to the drawings. The types of polishing abnormality are not limited to these. Also, the method of detecting polishing abnormality is not limited to the one described below.

[Slip out]
Figure 4 is a graph in which the horizontal axis is the wavelength [nm] of the reflected wave and the vertical axis is the signal value. This is when it occurs. Note that the horizontal axes of FIGS. 4A and 4B are obtained by substituting data numbers (0 to 1000) for wavelengths of 360 to 1100 nm.

Slip-out means that the wafer W jumps out of the polishing head 10 . When the slip-out occurs, the reflected light that should be reflected by the surface of the wafer W to be processed is reflected by the storage pocket 41a. As a result, the waveform pattern of the reflected light reflected by the surface to be processed of the wafer W (normal polishing pattern) does not match the waveform pattern of the reflected light reflected by the storage pocket 41a.

When slip-out is to be detected, a waveform pattern relating to the wavelength and signal value of the reflected wave is prepared as the waveform pattern for normal polishing. Then, the abnormality detection unit 72 reads a characteristic tendency of signal values within a predetermined wavelength range in the normal polishing waveform pattern, and sets a predetermined threshold value. For example, the threshold may be set slightly below the average value of signal values within a predetermined wavelength range, or may be set according to the maximum value of signal values within a predetermined wavelength range.

In the normal polishing waveform pattern shown in FIG. 4(a), the average value of the signal values within the wavelength range of 400 to 650 nm of the reflected light reflected by the polished surface of the wafer W shows a characteristic tendency of 0.82. , the abnormality detection unit 72 sets the threshold for detecting the occurrence of slip-out to 0.5.

Next, the abnormality detection unit 72 determines that a slip-out has occurred when the waveform pattern to be compared is below the above threshold. For example, in the case of the waveform pattern as shown in FIG. , to detect the occurrence of slip-out.

[Wafer crack]
FIG. 5A is a graph in the case of normal polishing, in which the horizontal axis is the wavelength [nm] and the vertical axis is the reflectance. FIG. 5B is a graph of FFT analysis in the case of normal polishing, in which the horizontal axis is the film thickness value [μm] and the vertical axis is the power spectrum. FIG. 6(a) is a graph in which the horizontal axis is the wavelength [nm] and the vertical axis is the reflectance when cracking occurs in the wafer. FIG. 6(b) is a graph of FFT analysis when wafer cracking occurs, with the film thickness value [μm] on the horizontal axis and the power spectrum on the vertical axis.

Wafer cracking means that the wafer W is damaged. When wafer cracking occurs, the amount of reflected light becomes insufficient or the reflected light is disturbed. In this way, the waveform pattern of the reflected light when it is reflected by the surface to be processed of the normal wafer W (normal polishing pattern) and the waveform pattern of the reflected light when it is reflected by the surface to be processed of the wafer W with cracks. does not match the

When wafer cracking is to be detected, a pattern relating to the wavelength and reflectance of the reflected wave as shown in FIG. 5A is prepared as a waveform pattern for normal polishing. Then, the abnormality detection unit 72 reads characteristic tendencies in the waveform pattern during normal polishing. For example, in the waveform pattern shown in FIG. 5(a), there is a so-called peak at which the reflectance fluctuates significantly around 0.2.

Next, the abnormality detection unit 72 determines that wafer cracking has occurred when the above-described tendency of the normal polishing waveform pattern does not appear in the comparison target waveform pattern of the reflected wave obtained during polishing. For example, in the case of the waveform pattern to be compared as shown in FIG. 6(a), the fluctuation width of the reflectance is remarkably reduced. That is, the waveform pattern of FIG. 6A does not include the tendency of the normal polishing waveform pattern described above, and the abnormality detection unit 72 detects damage to the wafer W. FIG.

Further, when detecting wafer cracks, wafer cracks may be detected based on the film thickness values and the power spectrum as shown in FIG. 5(b) as the waveform pattern during normal polishing. The abnormality detection unit 72 reads a characteristic tendency that a large peak exists near the film thickness of 16 μm in the waveform pattern of the FFT analysis shown in FIG. 5(b).

If the above-described tendency of the normal polishing waveform pattern does not appear in the comparison target waveform pattern of the reflected wave obtained during polishing, the abnormality detection unit 72 determines that wafer cracking has occurred. For example, in the case of the comparative waveform pattern as shown in FIG. 6B, the peak near the film thickness of 16 μm is greatly reduced. That is, the waveform pattern of the FFT analysis in FIG. 6B does not include the tendency of the normal polishing waveform pattern described above, and the abnormality detection unit 72 detects the breakage of the wafer W. FIG.

[Film peeling]
FIG. 7 is a graph showing the wavelength [nm] on the horizontal axis and the reflected light intensity R [%] for each wavelength on the vertical axis. Indicates when it occurs. In addition, the reflected light intensity is calculated by considering the reference spectrum and the dark spectrum obtained in advance for the reflected light.

Film peeling means that the metal layer on the surface of the wafer W is peeled off. When film peeling occurs, the light intensity of the reflected light becomes insufficient. In this way, the waveform pattern of the reflected light when it is reflected by the surface to be processed of the normal wafer W (pattern during normal polishing) and the waveform of the reflected light when it is reflected by the surface to be processed of the wafer W where film peeling occurs. Does not match pattern.

When film peeling is to be detected, a waveform pattern relating to the wavelength of the reflected wave and the intensity of the reflected light is prepared as the normal polishing waveform pattern. Then, the abnormality detection unit 72 sets a threshold value of the reflected light intensity within a predetermined wavelength range. The threshold may be set, for example, slightly below the average reflected light intensity within a predetermined wavelength range. The wavelength range can be arbitrarily set according to the type of film. For example, when detecting peeling of a copper film, it is preferable to set the wavelength range to 600 to 800 nm.

In the normal polishing waveform pattern shown in FIG. 7A, the reflected light intensity within the wavelength range of 400 to 780 nm of the reflected light reflected by the polished surface of the wafer W shows a characteristic tendency of exceeding 100%. Therefore, the threshold value of the reflected light intensity R for detecting the occurrence of film peeling was set to 100.

Next, the abnormality detection unit 72 determines that film peeling has occurred when the waveform pattern to be compared is below the above-described threshold value. For example, in the case of the waveform pattern as shown in FIG. 7B, the reflected light intensity R within the wavelength range of 400 to 780 nm is significantly below the threshold, so the abnormality detection unit 72 detects the occurrence of film peeling. .

In this manner, the CMP apparatus 1 according to the present embodiment described above compares the waveform pattern during normal polishing with the waveform pattern to be compared, and the characteristic tendency that appears in the waveform pattern during normal polishing is found in the waveform pattern to be compared. Abnormal polishing can be detected early and simply by determining whether or not it is included.

Furthermore, by acquiring the waveform pattern of the reflected wave during polishing using the optical measurement unit 71 used for film thickness measurement, it can be introduced at low cost.

It should be noted that the present invention can be modified in various ways without departing from the spirit of the present invention, and it is a matter of course that the present invention extends to the modified ones.

Reference Signs List 1 CMP apparatus 2 Platen 3 Rotary shaft 4 Motor 5 Polishing pad 10 Polishing head 10a Rotary shaft 20 Head body 21 Rotating portion 30 Carrier 30a Lower surface 31 Air line 32 Carrier pressing means 40 Retainer ring 41 Retainer ring holder 41a Accommodating pocket (accommodating portion)
42 ... Snap ring 43 ... Retainer pressing member 44 ... Retainer pressing means 50 ... Membrane film 60 ... Backing film 70 ... Detection mechanism 71 ... Optical measuring section 72 ... Abnormality detector 73 Lenses 74, 75 Optical fiber 76 Light source unit 77 Spectroscope 80 Observation window A Air chamber W Wafer

Claims (5)

A CMP apparatus for polishing by pressing a wafer housed in a housing portion of a polishing head against a polishing pad,
an optical measurement unit that projects light toward the housing unit during polishing of the wafer, receives reflected light from the wafer or the polishing head, and acquires a waveform pattern corresponding to the wavelength of the reflected light;
A waveform pattern for comparison , which is a waveform pattern for a predetermined wavelength range of the reflected light from the wafer or the polishing head during polishing of the wafer, and a previously stored waveform pattern for a predetermined wavelength range of the reflected light during normal polishing. When the comparison target waveform pattern in the predetermined wavelength range does not include the characteristic tendency that appears in the waveform pattern in the predetermined wavelength range when compared with the waveform pattern during normal polishing , the characteristic tendency is found. an abnormality detection unit that detects at least one polishing abnormality among a plurality of polishing abnormalities according to
A CMP apparatus comprising: The abnormality detection unit detects occurrence of slip-out in which the wafer jumps out of the polishing head when a signal value within the predetermined wavelength range in the waveform pattern to be compared is less than a preset threshold value. 2. The CMP apparatus according to claim 1. 2. The abnormality detection unit detects occurrence of a wafer crack that breaks the wafer when a peak of reflectance within the predetermined wavelength range decreases in the waveform pattern to be compared . CMP apparatus as described. 2. The abnormality detection unit detects occurrence of a wafer crack that breaks the wafer when a peak value of FFT analysis within a predetermined film thickness decreases in the waveform pattern to be compared . CMP apparatus as described. The abnormality detection unit detects occurrence of film peeling, that is, peeling of a metal layer on the surface of the wafer, when the intensity of reflected light within the predetermined wavelength range in the waveform pattern to be compared is less than a preset threshold value. The CMP apparatus according to claim 1, characterized by: