JP2005340679A - Polishing equipment, polishing end detecting method, and manufacturing method of semiconductor device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide polishing equipment and a polishing end detecting method capable of detecting the end even when the polishing amount of a film formed on a substrate is small or when a target film thickness is small, as to end detection utilizing the interference of light in a CMP polishing process. <P>SOLUTION: Positions and angles of a collimeter 13 and a detector 14 constituting a laser interferometer 12 are changed according to the target thickness of a film formed on a wafer 3, and the incident angle of a laser beam 16 to the wafer 3 and the detection angle at which the detector 14 detects the reflected light are set so that a peak of an interference optical signal is obtained. Thus, the polishing end detection is enabled, and even when the polishing amount of a film is small, the end detection can be performed at a desired film thickness upon a polishing process. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a polishing apparatus, a polishing end point detection method, and a semiconductor device manufacturing method using chemical mechanical polishing (hereinafter referred to as CMP) in manufacturing a semiconductor device.

  In recent years, semiconductor elements incorporated in a semiconductor integrated circuit device have been rapidly miniaturized, and accordingly, a CMP technique for flattening the surface has been increasingly used. When CMP is used, it is possible to flatten local steps on the wafer surface, but wear of the polishing pad of the CMP apparatus, deterioration of the dresser that regenerates by removing clogging due to polishing pad abrasive grains and polishing debris, There are disadvantages in that the polishing rate and polishing time fluctuate due to fluctuations in the polishing pressure and the rotation speed of the polishing platen and polishing head in the case of a rotary CMP apparatus, and fluctuations in film thickness immediately after deposition of the film to be polished.

Thus, an end point detection technique using light interference has been proposed in the CMP apparatus.
Hereinafter, a conventional polishing apparatus and a polishing end point detection method for detecting an end point using light interference will be described with reference to FIG.

FIG. 6 is a configuration diagram of a conventional CMP apparatus.
As shown in FIG. 6, a conventional CMP apparatus 29 has a polishing head 32 for holding a wafer 31 against a polishing platen 30. The polishing platen 30 is covered with a polishing pad 33. The polishing pad 33 typically has a backing layer 34 that provides an interface between the cover layer 35 and the polishing platen 30 used with the polishing slurry to polish the wafer 31. The polishing platen 30 normally rotates about its central axis 36. Further, normally, the polishing head 32 rotates around its own central axis 37 and is further supported by the parallel movement arm 38 and moves in parallel from end to end of the surface of the polishing platen 30 while rotating.

  Holes 39 are formed in the polishing platen 30 and the polishing pad 33, and polishing is performed during a certain time zone in which the polishing platen 30 is rotating regardless of the translational movement of the polishing head 32 on the polishing pad 33. The position of the hole 39 is given so that the surface of the wafer 31 held by the head 32 can be seen. When the laser interferometer 40 is under the polishing platen 30 and the hole 39 is close to the wafer 31, the laser beam 41 projected by the laser interferometer 40 passes through the hole 39 of the polishing platen 30 and the polishing pad 33. It is fixed at a position where it enters the surface of the wafer 31 on the top.

During operation, the CMP apparatus 29 uses the laser beam 41 from the laser interferometer 40 to determine the amount of deposited film material that has been removed from the surface of the wafer.
This process will be described with reference to FIG.

FIG. 7 is a diagram for explaining the configuration of a laser interferometer mounted on a conventional CMP apparatus.
In FIG. 7, the laser and collimator 42, the beam splitter 43, and the detector 45 are depicted as elements of the laser interferometer 40. The laser and collimator 42 generates a collimated laser beam 41 that is incident on the lower side of the beam splitter 43. A part of the laser beam 41 travels through the beam splitter 43 and the quartz insert 19. When this portion of the laser beam 41 reaches the lower end of the quartz insert 19, it propagates through the polishing slurry 20 and is incident on the surface of the wafer 3. Here, 2 is a polishing platen, 5 is a polishing pad, 6 is a backing layer, and 7 is a cover layer.

FIG. 8 is a diagram for explaining laser beam interference caused by a film deposited on a substrate.
As shown in detail in FIG. 8, the wafer 3 (see FIG. 7) has a substrate 23 having silicon and an insulating film layer (for example, a silicon nitride film 22) thereon. A part of the laser beam 41 incident on the wafer 3 is partially reflected by the surface of the silicon nitride film 22 to form a first reflected beam 46. However, a part of the light passes through the silicon nitride film 22 to form a transmission beam 47 that is incident on the underlying substrate 23. At least a part of the light reflected from the transmission beam 47 reaching the substrate 23 is reflected to the silicon nitride film 22 to form a second reflected beam 48. The first reflected beam 46 and the second reflected beam 48 interfere with each other due to their phase relationship to form a combined beam 44. The combined beam 44, which is a combination of the first reflected beam 46 and the second reflected beam 48, propagates back through the polishing slurry 20 and the insert 19 and reaches the upper portion of the beam splitter 43 as shown in FIG. . The beam splitter 43 redirects a part of the combined beam 44 toward the detector 45.

  The first reflected beam 46 and the second reflected beam 48 described above form a combined beam 44 as shown in FIGS. 7 and 8 and cause interference detected by the detector 45. If the first reflected beam 46 and the second reflected beam 48 are in phase with each other, they will have a maximum value at the detector 45. When the phases of these beams are shifted by 180 °, the detector 45 has a minimum value. Due to the other phase relationship between these reflected beams, the interference signal will be either the maximum value or the minimum value detected by the detector. As a result, the signal output from the detector 45 periodically changes as the thickness of the silicon nitride film 22 is reduced during CMP polishing.

  FIG. 9 is a graph showing the relationship between the polishing time and the interference light intensity change in the conventional polishing apparatus. The amplitude (Y-axis) represents the intensity of the detection signal over the interference signal sampling time with respect to the polishing time (X-axis). ) Integration. This data was obtained by monitoring the laser interferometer output of the apparatus of FIG. 6 while performing the CMP procedure on a wafer having an insulating film layer formed on a silicon substrate.

During each period of the output signal of FIG. 9, the oxide layer is removed by a certain thickness. The removed thickness is proportional to the wavelength λ of the laser beam and the refractive index n of the oxide layer. Specifically, the detection signal takes the maximum value when the film thickness of the film to be polished is an integral multiple of λ / 2n, and the detection signal takes the minimum value when it is (N + ½) times. Here, λ is the free space wavelength of the laser beam, n is the refractive index of the oxide layer, and N is an integer. Since the maximum value and the minimum value can be easily detected by a known signal processing method, the film thickness of the film to be polished at the time of taking the maximum value or the minimum value is reduced from the target film thickness after polishing, By dividing by the polishing rate, the polishing time from that point to the target film thickness is obtained, and the end point of polishing is detected. (For example, see Patent Document 1)
Japanese Patent Laid-Open No. 9-7985

  However, as the semiconductor element pattern of the semiconductor integrated circuit device becomes finer, the deposited film thickness becomes thinner, and if the amount of polishing to be polished for planarization by CMP decreases, the initial film thickness before polishing is reduced after polishing. During polishing to a target film thickness, the maximum or minimum value due to light interference does not appear in the conventional method, and there is a problem that control for ending polishing at a desired film thickness cannot be performed.

Specifically, it appears in a polishing step of a semiconductor device having a structure as shown in a cross-sectional view illustrating a semiconductor substrate having conventional groove type element isolation of FIG.
In FIG. 10, a silicon nitride film 22 is formed on a substrate 23, a groove is formed in the substrate using the silicon nitride film 22 as a mask, and a portion of the element isolation insulating film 21 protruding on the substrate 23 is removed by CMP polishing to be planarized. However, since most of the protrusions are removed in advance in order to ensure the uniformity of polishing, protrusions are generated only around the separation grooves.

  In order to planarize the element isolation insulating film 21 in this state, when the silicon nitride film 22 (for example, a film thickness of about 150 nm) serving as a stopper film during the CMP process is polished to a thickness of, for example, 100 nm, the conventional technique is used. When the polishing apparatus and the end point detection method are used, if a laser of λ = 670 nm is used and the refractive index of the silicon nitride film is 2.01, the detection signal takes a maximum value at a silicon nitride film thickness of 167 nm and is 83 nm. Therefore, the maximum and minimum values of the detection signal do not appear between 100 and 150 nm, and polishing cannot be completed when the silicon nitride film thickness is 100 nm.

  In view of the above problems, an object of the present invention is to detect an end point with a desired film thickness during a polishing process even when the polishing amount of the film is small.

  In order to achieve the above object, a polishing apparatus according to claim 1 of the present invention is a polishing apparatus for polishing a film on a semiconductor substrate to a desired film thickness when manufacturing the semiconductor device, and polishing the semiconductor substrate. Polishing means, a collimator capable of irradiating the substrate with a laser beam having a single wavelength at an arbitrary angle, and a detector for detecting the reflected interference light intensity of the laser beam at a detection angle corresponding to the incident angle. And adjusting the irradiation angle of the collimator so that the reflected interference light intensity reaches a peak when the desired film thickness is obtained, and detecting the peak of the reflected interference light intensity at that time to detect the desired It is characterized in that it is confirmed that the film has been polished to the film thickness.

  The polishing apparatus according to claim 2 is a polishing apparatus that polishes a film on a semiconductor substrate to a desired film thickness when manufacturing a semiconductor device, and a polishing unit that polishes the semiconductor substrate and a single wavelength on each of the substrates. And a plurality of laser interferometers for detecting the reflected interference light intensity of the laser beam, and a wavelength at which the reflected interference light intensity reaches a peak when the desired film thickness is reached. A laser interferometer capable of irradiating the laser beam is selected, and the peak of the reflected interference light intensity is detected by the selected laser interferometer to confirm that the film has been polished to the desired film thickness. .

  A polishing apparatus according to claim 3 is the polishing apparatus according to claim 2, wherein a film thickness measuring device for measuring a film thickness before polishing, and a memory for storing a refractive index of the film and a set film thickness after polishing of the film. A laser interferometer having a peak reflected reflection light intensity at the set thickness after polishing based on the film thickness before polishing, the refractive index of the film, and the set thickness after polishing. The peak of the reflected interference light intensity is detected by a selected laser interferometer to confirm that the film has been polished to the desired film thickness.

  5. The polishing end point detection method according to claim 4, wherein the film on the semiconductor substrate in the manufacture of the semiconductor device is detected by observing the reflected interference light of the laser beam irradiated on the film. A method for detecting a polishing end point, the step of setting an irradiation angle of the laser beam at which the reflected interference light intensity reaches a peak when the polished film thickness reaches the desired film thickness; A step of irradiating a laser beam of one wavelength and a step of observing the intensity of the reflected interference light, the peak of the reflected interference light intensity being detected, and the film being polished to a desired thickness It is characterized by confirming that.

  6. The polishing end point detection method according to claim 5, wherein a reflection of a laser beam irradiated to the film using a laser interferometer including a plurality of films on a semiconductor substrate polished to a desired film thickness in the manufacture of a semiconductor device. A polishing end point detection method for detecting interference by observing interference light, wherein a laser beam irradiates a laser beam having a wavelength at which the reflected interference light intensity reaches a peak when the polished film thickness reaches the desired film thickness. A step of selecting an interferometer, a step of irradiating a laser beam from the laser interferometer, and a step of measuring the intensity of the reflected interference light. It is characterized by confirming that the film has been polished to a desired film thickness.

A method for manufacturing a semiconductor device according to a sixth aspect uses the polishing end point detection method according to the fourth or fifth aspect.
As described above, even when the polishing amount of the film is small, the end point can be detected with a desired film thickness during the polishing process.

  According to the polishing apparatus, the polishing end point detection method, and the semiconductor device manufacturing method according to the present invention, the reflected interference light from the film on the substrate in the laser beam irradiated to the semiconductor substrate being polished has a peak when the film thickness is a desired thickness. Thus, by setting the irradiation angle of the laser beam to irradiate, when polishing a film formed on the substrate using a polishing method such as CMP, the film to be polished always has a desired film thickness Since the maximum or minimum peak of reflected interference light intensity from is obtained, the end point can be detected with a desired film thickness even when the polishing amount of the film is small.

  Also, it has a plurality of laser interferometers that irradiate laser beams of different wavelengths, and the peak wavelength when the reflected interference light by the film on the substrate in the laser beam irradiated on the semiconductor substrate being polished has a desired film thickness When a film formed on a substrate was polished by using a polishing method such as CMP, a desired film thickness was always obtained by selecting a laser interferometer that irradiates the laser beam and irradiating the laser beam. Since the maximum or minimum peak of reflected interference light intensity from the film to be polished is obtained, the end point can be detected with a desired film thickness even when the film polishing amount is small.

(Embodiment 1)
Hereinafter, a polishing apparatus and a polishing end point detection method according to Embodiment 1 of the present invention will be described with reference to the drawings.

  FIG. 1 is a diagram showing a configuration of a CMP apparatus according to the first embodiment, and has a polishing head 4 for holding a wafer 3 with respect to a polishing platen 2. The polishing platen 2 is covered with a polishing pad 5. The polishing pad 5 typically has a backing layer 6, which provides an interface between the cover layer 7 and the polishing platen 2 that is used with the polishing slurry to polish the wafer 3. The polishing platen 2 is usually rotated about its own central axis 8 while pressing the wafer 3 against the polishing pad 5 with the pressure applied to the polishing platen 2. Further, the polishing head 4 normally rotates around its central axis 9, which is fixed to the translation arm 10 and moves in parallel from end to end of the surface of the polishing platen 2 while rotating.

  A hole 11 is formed in the polishing platen 2 and the polishing pad 5, and the polishing platen 2 is rotating for a certain period regardless of the translational movement of the polishing head 4 on the polishing pad 5. The position of the hole 11 is given so that the surface of the wafer 3 held by the polishing head 4 can be seen.

  The laser interferometer 12 includes a collimator 13, a detector 14, and a linear guide 15. When the hole 11 is close to the wafer 3, the laser beam 16 projected by the collimator 13 is applied to the polishing platen 2 and the polishing pad 5. It passes through the hole 11 and is incident on the surface of the wafer 3 above it, and is placed at a position where the reflected beam from the wafer enters the detector 14. The collimator 13 can be moved in parallel by a linear guide 15 and can be arbitrarily set with respect to the incident angle of the laser beam 16 with respect to the wafer 3 by moving around the rotation shaft 17. Similarly, the detector 14 can arbitrarily set an angle with respect to the wafer 3 by the linear guide 15 and the rotating shaft 18.

The CMP apparatus 1 determines the amount of deposited film material removed from the surface of the wafer 3 using the laser beam 16 from the laser interferometer 12 during polishing.
This process will be described with reference to FIGS.

  FIG. 2 is a diagram for explaining a configuration of a laser interferometer mounted on the CMP apparatus in the first embodiment, and FIG. 3 is a diagram for explaining laser beam interference due to a film deposited on the substrate in the first embodiment.

  In FIG. 2, the collimator 13 and the detector 14 are depicted as elements of the laser interferometer 12. The collimator 13 generates a collimated laser beam 16. A portion of the laser beam 16 travels through the quartz insert 19. When this portion of the laser beam 16 reaches the lower end of the quartz insert 19, it propagates through the polishing slurry 20 and impinges on the surface of the wafer 3. As shown in detail in FIG. 3, the wafer 3 has a substrate 23 having silicon and an insulating film layer (hereinafter, silicon nitride film 22 will be described as an example) thereon.

  A part of the laser beam 16 incident on the wafer 3 is partially reflected by the surface of the silicon nitride film 22 to form a first reflected beam 24. However, a part of the light passes through the silicon nitride film 22 and forms a transmission beam 25 incident on the underlying substrate 23. At least a part of light from the transmission beam 25 reaching the substrate 23 is reflected to the silicon nitride film 22 to form a second reflected beam 26. The first reflected beam 24 and the second reflected beam 26 interfere with each other due to their phase relationship to form a combined beam 27. The first reflected beam 24 and the second reflected beam 26 form a combined beam 27 as shown in FIGS. 2 and 3, propagate through the polishing slurry 20 and the insert 19, and are detected by the detector 14. Cause interference.

The intensity I of the combined beam 27 is expressed by the following equation.
I = I1 + I2 + 2√ (I1 · I2) · cos (Φ) (1)
Here, I1 and I2 are the intensities of the first reflected beam 24 and the second reflected beam 26, respectively, and Φ is a phase difference between the first reflected beam 24 and the second reflected beam 26. This difference in phase is due to the difference in optical path length between the first reflected beam 24 and the second reflected beam 26, and is expressed by the following equation.

Φ = 2π · D / λ = 2π {n · (AB + BC) −AD} / λ (2)
Here, D is the optical path difference between the first reflected beam 24 and the second reflected beam 26, λ is the free space wavelength of the laser beam, n is the refractive index of the silicon nitride film 22, and AB, BC, and AD are figures. 3 represents the geometric distance at positions A, B, C, and D in FIG. Expression (2) is expressed as follows by the film thickness d of the silicon nitride film 22 and the refraction angle α.

Φ = 2π · 2 · n · d · cos α / λ (3)
When the silicon nitride film 22 is polished, the film thickness d decreases, resulting in a change in Φ. For example, when D = Nλ and N is an integer, I is the maximum value, and N = 1/2, 3/2,. . . At this time, the intensity I is minimized. That is, d = N · λ / (2 · n · cos α) (N is an integer) (4)
Then I is at maximum,
d = (2L + 1) λ / (4 · n · cos α) (L is an integer) (5)
Then I is minimized.

  Therefore, when a single wavelength laser of λ = 670 nm is used for the laser beam 16 and the film is the silicon nitride film 22 and the target film thickness after polishing is 100 nm, α = 16 °, that is, the collimation is obtained from the equation (5). The meter 13 is installed at a position where the laser beam 16 is incident on the wafer in a state inclined by 16 ° with respect to the wafer 3, and the detector 14 is inclined with respect to the wafer 2 by an angle corresponding to α = 16 ° and the combined beam 27 Install at a position to detect and polish. By doing so, it can be seen that the film thickness d is 100 nm when the combined beam intensity I is minimum, so that the end point of CMP polishing can be detected accurately. The minimum value of the light intensity I can be easily detected by a known signal processing method. By stopping polishing at this time, it is possible to polish to a target film thickness.

  In the first embodiment, the linear guide 15 and the rotating shafts 17 and 18 are used as a method of changing the positions and angles of the collimator 13 and the detector 14 of the laser interferometer 12, but the embodiment shown in FIG. You may have the moving mechanism 28 as shown to the figure explaining the starting mechanism in the form 1. FIG. In this apparatus, the CMP polishing mechanism is the same as the apparatus shown in FIG. 1, but the laser interferometer is different. That is, the collimator 13 and the detector 14 are installed on a moving mechanism having a circular curved surface centered on the surface of the wafer 3 substantially at the position of the hole 11, and the collimator 13 and the detector 14 can freely move on the curved surface. By moving, the incident angle on the wafer 3 can be changed on the laser beam 16. Various mechanisms such as changing the incident angle or traveling direction of the wafer by changing the incident angle of the laser beam 16 on the wafer or changing the traveling direction of the combined beam 27 by changing the position or angle of the mirror are used. The mechanism can be used.

  In Embodiment 1, a quartz insert 19 made of quartz is used as a material through which the laser beam 16 is transmitted. However, this material has a refractive index of 1 for fluorite (CaF2, λ = 656.3 nm). .4325) or a material such as optical glass (for example, LaK3 (refractive index 1.6896 for λ = 656.3 nm) can also change the film thickness at which the detection signal peaks. The end point can be detected.

In the present embodiment, the case where the silicon nitride film thickness is deposited to about 150 nm and the post-polishing film thickness is 100 nm has been described. By setting the angle α to an appropriate value, it is possible to detect the end point as in the present embodiment. Further, the case of planarizing the element isolation oxide film at the time of forming the STI has been described. However, it is also possible to detect the end point similarly in other film structures and film types such as planarization of the wiring interlayer film. Not too long.
(Embodiment 2)
Hereinafter, a CMP apparatus and a polishing method using the same according to the second embodiment of the present invention will be described with reference to the drawings.

FIG. 5 is a diagram showing the configuration of the CMP apparatus according to the second embodiment.
As shown in FIG. 5, the CMP apparatus 49 of the present invention is the same as the conventional CMP apparatus 29 shown in FIG. 6 except for the polishing platen 50, the polishing pad 53, the first laser interferometer 60, and the second laser interferometer 63. It has a similar structure. The first laser interferometer 60 and the second laser interferometer 63 are installed in the polishing platen 50. A first hole 59 and a second hole 62 are formed in the polishing platen 50 and the polishing pad 53. The polishing head 52 rotates around the central axis 57 and translates on the polishing pad 53 by the translation arm 58, but a part of the time during which the polishing platen 50 is rotated regardless of the translational movement. During the period, the positions of the first hole 59 and the second hole 62 are given so that the surface of the wafer 51 held by the polishing head 52 can be seen.

  During the polishing, the first laser interferometer 60 and the second laser interferometer 63 are built and fixed inside the polishing platen 50, and thus rotate around the central axis 56 of the polishing platen together with the polishing platen 50, When the first hole 59 and the second hole 62 pass through the wafer 51, the laser beam 61 is irradiated onto the polishing film formed on the surface of the wafer 51. At this time, the first laser interferometer 60 generates a laser having a wavelength λ1 (for example, 670 nm), and the second laser interferometer 63 generates a laser having a wavelength λ2 (for example, 1150 nm). The detection signal detected by the first laser interferometer 60 takes a maximum value when the film thickness of the film to be polished is an integral multiple of λ1 / 2n, and takes a minimum value when it is (N + 1/2) times. On the other hand, the second laser interferometer 63 takes a maximum value when the film thickness of the film to be polished is an integral multiple of λ2 / 2n, and takes a minimum value when the film thickness is (N + 1/2) times. That is, the first laser interferometer 60 and the second laser interferometer 63 have different polishing amounts because the film thickness of the film to be polished at which the detection signal has the maximum or minimum peak is different. Even when the desired amount of polishing is finished before the detection signal reaches a peak, the remaining laser interferometer can detect a peak that means the end of polishing. In this example, when the initial film thickness of the film to be polished (for example, silicon nitride film) is 140 nm and the target film thickness after polishing is 80 nm, the first laser interferometer 60 can detect the peak. However, when it is desired to set the film thickness after polishing to 100 nm for the film to be polished having an initial film thickness of 150 nm, the first laser interferometer 60 cannot detect the peak of the detection signal. Even in such a case, the peak can be detected by using the second laser interferometer 63. In this manner, the polishing end point can be detected even when the polishing amount of the film to be polished is small. Needless to say, when only the second laser interferometer 63 is provided, the peak of the detection signal cannot be detected when it is desired to polish the film to be polished having an initial film thickness of 140 nm with a target film thickness of 80 nm after polishing. It is clear.

  In this polishing apparatus, the in-line film thickness measuring device, the refractive index n of the film to be polished and the target film thickness after polishing are stored in the storage unit as a database, and the initial film thickness and refractive index n of the film to be polished are measured in line. Measured by the instrument, calculated the difference in the target film thickness after polishing on the database, calculated the polishing amount, and configured so that the peak of the interference light detection signal detected by the end point detector appears during polishing The end point is detected. For example, the end point detection system is constructed by selecting one of the laser interferometers 60 and 63 having different wavelengths as the interferometer for detecting the end point.

  As described above, the laser interferometer selected by selecting the laser interferometer that has a peak in the interference waveform according to the polishing amount among the plurality of laser interferometers that generate lasers having different wavelengths is provided. Can be detected as the end point of polishing. In the second embodiment, the case where two laser interferometers are mounted on the same polishing platen has been described. However, two or more laser interferometers having different wavelengths may be used. When there are three or more, it becomes possible to detect the end point of a smaller polishing amount more accurately. Further, the laser interferometer in which the incident angle of the laser with respect to the wafer and the detection angle of the reflected light is fixed has been described, but an end point detector in which the incident angle and the reflection angle of the laser beam are variable may be used in combination. .

  In the above-described invention, a laser with a standard wavelength of 670 nm is used. However, the maximum and minimum intensity change of interference light can also be monitored by monitoring the film thickness of the polishing film during CMP polishing using a laser beam with a shorter wavelength. Since the period becomes shorter with respect to the film thickness change, the end point can be detected when the polishing amount is small. Further, it is possible to measure the film thickness by changing the wavelength by a method such as spectroscopic ellipsometry, and to finish polishing by detecting the end point of the target film thickness. However, since it takes time to calculate the film thickness (for example, in the case of spectroscopic ellipsometry, fitting of the measured value of the reflectance intensity ratio Ψ and the phase difference Δ and the calculated value), the time between the film thickness measurement and the polishing is stopped. The delay time is considered to be longer than when the wavelength is fixed. Therefore, it is considered necessary to construct an algorithm that stops polishing in consideration of this delay time.

  In the present invention, a polishing apparatus in which the polishing platen rotates about its own central axis is described. However, the end point can also be detected in a polishing apparatus having a belt-type polishing platen.

  In the above description, the case where polishing is performed using CMP is described. However, the polishing may be performed using other methods.

  The polishing apparatus, the polishing end point detection method and the semiconductor device manufacturing method of the present invention can detect the end point with a desired film thickness during the polishing process even when the polishing amount of the film is small. It is useful for a polishing apparatus using a mechanical mechanical polishing, a polishing end point detection method, a semiconductor device manufacturing method, and the like.

The figure which shows the structure of the CMP apparatus in Embodiment 1. FIG. 6 illustrates a configuration of a laser interferometer mounted on a CMP apparatus according to Embodiment 1. FIG. 5 illustrates laser beam interference caused by a film deposited on a substrate in Embodiment 1. The figure explaining the starting mechanism in Embodiment 1 The figure which shows the structure of the CMP apparatus in Embodiment 2. Configuration diagram of a conventional CMP apparatus The figure explaining the structure of the laser interferometer mounted in the conventional CMP apparatus Diagram explaining laser beam interference by a film deposited on a substrate A graph of the relationship between polishing time and interference light intensity change in a conventional polishing machine Sectional view illustrating a semiconductor substrate having conventional trench element isolation

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 CMP apparatus 2 Polishing platen 3 Wafer 4 Polishing head 5 Polishing pad 6 Backing layer 7 Cover layer 8 Center axis 9 Center axis 10 Translation arm 11 Hall 12 Laser interferometer 13 Collimator 14 Detector 15 Linear guide 16 Laser beam 17 Rotating shaft 18 Rotating shaft 19 Quartz insert 20 Polishing slurry 21 Device isolation insulating film 22 Silicon nitride film 23 Substrate 24 First reflected beam 25 Transmission beam 26 Second reflected beam 27 Combined beam 28 Moving mechanism 29 CMP apparatus 30 Polishing platen 31 Wafer 32 Polishing Head 33 Polishing Pad 34 Backing Layer 35 Cover Layer 36 Rotation Center Axis 37 Rotation Center Axis 38 Translation Arm 39 Hole 40 Laser Interferometer 41 Laser Beam 42 Collimator 43 Beam Splitter 44 Connection Beam 45 Detector 46 First reflected beam 47 Transmitted beam 48 Second reflected beam 49 CMP apparatus 50 Polishing platen 51 Wafer 52 Polishing head 53 Polishing pad 56 Central axis 57 Rotation central axis 58 Translation arm 59 First hole 60 First laser interferometer 61 Laser beam 62 Second hole 63 Second laser interferometer

Claims (6)

A polishing apparatus for polishing a film on a semiconductor substrate to a desired film thickness when manufacturing a semiconductor device,
Polishing means for polishing the semiconductor substrate;
A collimator capable of irradiating the substrate with a single wavelength laser beam at an arbitrary angle;
A detector for detecting the reflected interference light intensity of the laser beam at a detection angle corresponding to an incident angle, and the collimator so that the reflected interference light intensity reaches a peak when the desired film thickness is reached. The polishing apparatus is characterized in that the irradiation angle is adjusted, the peak of the reflected interference light intensity at that time is detected, and the polishing to the desired film thickness is confirmed. A polishing apparatus for polishing a film on a semiconductor substrate to a desired film thickness when manufacturing a semiconductor device,
Polishing means for polishing the semiconductor substrate;
A plurality of laser interferometers for irradiating the substrate with a single wavelength laser beam and detecting the reflected interference light intensity of the laser beam, and the reflected interference light intensity when the desired film thickness is reached Select a laser interferometer that can irradiate a laser beam with a wavelength such that the peak of the reflected interference light intensity is detected by the selected laser interferometer, and the film is polished to the desired film thickness. A polishing apparatus characterized by checking. A film thickness measuring instrument for measuring the film thickness before polishing;
A storage unit that stores a refractive index of the film and a set film thickness after polishing of the film, and the post-polishing setting based on the film thickness before polishing, the refractive index of the film, and the set film thickness after polishing Select a laser interferometer whose reflected interference light intensity peaks at the film thickness, and detect the peak of the reflected interference light intensity with the selected laser interferometer to confirm that it has been polished to the desired film thickness. The polishing apparatus according to claim 2. A polishing end point detection method for detecting that a film on a semiconductor substrate in the manufacture of a semiconductor device is polished to a desired film thickness by observing reflected interference light of a laser beam applied to the film,
Setting the irradiation angle of the laser beam at which the reflected interference light intensity reaches a peak when the polished film thickness reaches the desired film thickness;
Irradiating a single wavelength laser beam at the irradiation angle;
A step of observing the reflected interference light intensity, and detecting that the reflected interference light intensity is at a peak and confirming that the film has been polished to a desired film thickness. Detection method. Polishing end point detected by observing reflected interference light of a laser beam irradiated on the film using a laser interferometer having a plurality of films on a semiconductor substrate polished to a desired film thickness in the manufacture of a semiconductor device A detection method,
Selecting a laser interferometer that emits a laser beam having a wavelength at which the reflected interference light intensity peaks when the polished film thickness reaches the desired film thickness;
Irradiating a laser beam from the laser interferometer;
Measuring the reflected interference light intensity, and detecting that the reflected interference light intensity is at a peak and confirming that the film has been polished to a desired film thickness. Detection method.   A method for manufacturing a semiconductor device, comprising using the polishing end point detection method according to claim 4.

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