JPH06252113A - Method for flattening semiconductor substrate - Google Patents

Method for flattening semiconductor substrate

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Publication number
JPH06252113A
JPH06252113A JP3762793A JP3762793A JPH06252113A JP H06252113 A JPH06252113 A JP H06252113A JP 3762793 A JP3762793 A JP 3762793A JP 3762793 A JP3762793 A JP 3762793A JP H06252113 A JPH06252113 A JP H06252113A
Authority
JP
Japan
Prior art keywords
substrate
polishing
film thickness
film
planarizing
Prior art date
Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
Granted
Application number
JP3762793A
Other languages
Japanese (ja)
Inventor
Minoru Fujii
Mikio Nishio
Noboru Nomura
稔 藤井
幹夫 西尾
登 野村
Original Assignee
Matsushita Electric Ind Co Ltd
松下電器産業株式会社
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
Filing date
Publication date
Application filed by Matsushita Electric Ind Co Ltd, 松下電器産業株式会社 filed Critical Matsushita Electric Ind Co Ltd
Priority to JP3762793A priority Critical patent/JPH06252113A/en
Publication of JPH06252113A publication Critical patent/JPH06252113A/en
Granted legal-status Critical Current

Links

Abstract

(57) [Summary] (Modified) [Purpose] While constantly monitoring the film thickness of the film deposited on the substrate on which the concavo-convex pattern is formed, by using a polishing device equipped with one or more polishing heads sufficiently smaller than the substrate. The film is polished to flatten the substrate surface. A silicon substrate 11 on which a concavo-convex pattern has been formed and a film has been deposited is bonded to a rotating substrate holding turntable 13 with its main surface facing upward, and then a rotating polishing head 12 is brought into pressure contact with the silicon substrate 11 in a radial direction thereof. And the main surface is polished. During polishing, the detection head unit 14 of the film thickness detection device
Is controlled so that it is always located on the same circumference as the polishing head on the substrate, so the average film thickness on the circumference is always monitored by the film thickness measuring device. The film thickness data is sent to a computer, and the position of the polishing head and the amount of polishing by the polishing head are controlled based on the data, and polishing is performed from the outer peripheral portion of the substrate to the central portion or from the central portion of the substrate to the outer peripheral portion. Proceed.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a planarization process in manufacturing a semiconductor device.

[0002]

2. Description of the Related Art As the degree of integration of LSI is improved and the miniaturization of devices is advanced, the device manufacturing process is becoming more and more three-dimensional.
A step having a height equal to or higher than the processing dimension required for the semiconductor substrate is formed. If such a step having a steep and complicated shape is left on the substrate as it is, various problems as described below occur.

(1) In the photolithography process, the optimum focus position is different above and below the step portion, so that the pattern accuracy is deteriorated. (2) Since anisotropic etching is used in the etching step, if the film thickness at the step portion becomes thick, etching residue is likely to occur.

(3) When the metal of the wiring material is deposited by the sputtering method or the like, the coverage of the film at the step portion is lowered and the reliability of the wiring is lowered. In order to solve such a problem, in an LSI manufacturing process, a technique of eliminating a step on a substrate and flattening the surface of the substrate is becoming more and more important.

The conventional flattening method is mainly the coating method (S
OG (Spin no Glass)), fluidization method (B
PSG flow), etch-back method, etc. have been used (for example, Seijiro Furukawa, et al.
1989). However, although these methods can locally obtain a relatively flat surface, satisfactory flatness has not been obtained in a relatively wide range over several mm. Further, with the recent high integration of LSI, local flatness is becoming unsatisfactory.

As a method for obtaining a flat surface over a wide area, a method using chemical mechanical polishing has attracted attention (for example, S. Sivaram et al. Sol.
idState Tech. May 1992 p.
87). This method is very simple in principle, in that after the film is deposited on the surface of the semiconductor substrate on which the pattern is formed, the convex portions are removed by polishing to flatten the surface. Presently, this method has been shown to polish various metals (Al, W, Cu), oxides, etc. deposited on the semiconductor surface flat over a very wide range on the substrate surface.

An example of the planarization method by chemical mechanical polishing will be described below with reference to the drawings. FIG. 6 shows a main part of a polishing apparatus used for the above chemical mechanical polishing.

In FIG. 6, reference numeral 1 denotes a substrate pressing jig. On the lower surface of the substrate pressing jig 1, a fine uneven pattern is formed by repeating film deposition, photolithography and dry etching, and then the entire surface is covered. Substrate 2 on which film is deposited
However, they are detachably bonded by, for example, vacuum suction. On the other hand, a polishing cloth 4 is provided on the upper surface of the turntable 3 located below the substrate pressing jig 1. The main surface of the substrate 2 adhered to the lower surface of the substrate holding jig 1 by pressing the polishing cloth 4 of the substrate 2 by the substrate holding jig 1 and rotating the turntable 3 and the substrate holding jig 1 To polish. At that time, an aqueous solution containing a polishing agent such as weakly alkaline colloidal silica is supplied to the polishing cloth 4 as a slurry, for example, when polishing a silicon oxide film. A polyurethane pad or the like is used as the polishing pad on the turntable 3.

[0009]

However, with the above-described polishing method, it is very difficult to polish a large number of substrates 2 which have undergone various steps and with high precision. Usually, in the polishing using the polishing apparatus as described above, there is a problem that the polishing rate decreases as the polishing progresses due to a change with time of the polishing cloth 4 itself. Therefore, every time one substrate 2 is processed, it is necessary to regenerate the polishing cloth 4 or to empirically increase the polishing time in consideration of the decrease in the polishing rate. It is hard to say that the sex is good. In order to improve controllability, it is necessary to detect the film thickness of the film on the substrate 2 in situ during polishing. However, in the above-described configuration, the entire main surface of the substrate 2 is in contact with the polishing cloth 4, so that the film thickness of the film deposited on the main surface of the substrate 2 cannot be measured during polishing.

Further, although the substrate 2 which has undergone various steps is generally convex or concave, the polishing apparatus as described above cannot uniformly polish the film deposited on the curved substrate 2. For example, in the case where it is convexly warped, only the central portion of the substrate 2 is selectively polished.

The present invention has been made in view of the above points, and is characterized in that it polishes a film deposited on the surface of a semiconductor substrate, and performs polishing with excellent controllability that is not affected by the change with time of the polishing cloth. It is an object of the present invention to provide a method for planarizing a substrate that can be used. It is another object of the present invention to provide a method for planarizing a substrate that can uniformly polish a film deposited on a warped substrate even when the substrate is convex or concave.

Other objects and novel features of the present invention will be apparent from the description of this specification and the accompanying drawings.

[0013]

In order to achieve the above object, the present invention polishes a substrate by a polishing apparatus having a polishing head smaller than a semiconductor substrate. There is a region where the polishing head does not exist on the substrate, and that portion is used to measure the film thickness in-situ during polishing to accurately detect the end point of polishing.

Further, according to the present invention, the detection head part of the film thickness detection device is moved over the substrate, or a film thickness detection device having a plurality of detection head parts is used to polish the film thickness distribution in the substrate surface. And polishing while monitoring on the spot. Based on the film thickness distribution data, the film is polished while controlling the position of the polishing head, the pressure applied to the polishing head, and the like. Further, in the present invention, a plurality of polishing heads smaller than the substrate are used simultaneously. Further, in the present invention, a plurality of polishing heads that are sufficiently smaller than the substrate that rotates only are spread over the substrate and polished.

[0015]

According to the present invention, since the film thickness of the film deposited on the substrate can be detected at all times during polishing, the desired polishing amount can always be obtained without being affected by the change with time of the polishing head. It is possible to polish. Further, since the polishing head is sufficiently smaller than the substrate and most of the space on the surface of the substrate is exposed, either the detection head unit of the film thickness detection device is moved over the substrate or a plurality of film thickness detection head units are provided. It is possible to calculate the film thickness distribution in the surface of the substrate in-situ during polishing by using the film thickness detector. It is possible to control the position of the polishing head and the amount of polishing by the polishing head based on the film thickness distribution in the surface of the substrate to uniformly polish a film deposited on a warped substrate. Become. That is, it is possible to prevent preferential polishing of only the peripheral portion when the substrate is warped concavely, and preferentially polishing only the central portion when the substrate is warped convexly. Further, a plurality of polishing heads are used, a reduction in the polishing rate due to the use of a small head is prevented, and a polishing rate comparable to the conventional method is obtained while having the above-mentioned excellent characteristics.

[0016]

(Embodiment 1) An embodiment of the present invention will be described below with reference to the drawings.

FIG. 1 shows a main part of a polishing apparatus used in the present invention. In FIG. 1, reference numeral 13 indicates a substrate holding turntable. On the substrate holding turntable 13, a silicon substrate 11 having a diameter of 150 mm or 200 mm, which has been subjected to film deposition after forming an uneven pattern by repeating film deposition, photolithography and etching, is bonded by, for example, vacuum suction. In this embodiment, the substrate holding turntable 13 is designed to rotate only on its own axis. On the other hand, the silicon substrate 11
A polishing head 12 having a diameter of 50 mm, which is sufficiently smaller than the silicon substrate 11, is arranged on the upper surface of the. The polishing head 12 has a structure capable of moving in the radial direction of the silicon substrate 11 while rotating. On the other hand, the detection head unit 14 of the film thickness measuring device is installed at a position symmetrical to the polishing head 12 on the silicon substrate 11. The detection head unit 14 of the film thickness measuring device is configured to move in the radial direction of the silicon substrate in synchronization with the movement of the polishing head 12 in the radial direction of the silicon substrate.

Next, the procedure of flattening by polishing using this apparatus will be described. The polishing head 12 is brought into pressure contact with the main surface of the silicon substrate 11 adhered to the substrate holding table 13, and the polishing head 12 is rotated to rotate the silicon substrate 1
The main surface of the silicon substrate 11 is polished by moving the silicon substrate 1 in the radial direction of the silicon substrate 11. At this time,
The rotation of the substrate holding table 13 is also performed at the same time. When polishing the silicon oxide film deposited on the silicon substrate 11, as the polishing agent, for example, colloidal silica dispersed in an aqueous solution and pH adjusted to be weakly alkaline with KOH is used. The polishing agent is supplied onto the silicon substrate 11 from the center of the polishing head 12. Further, for example, a polyurethane pad is attached to the polishing surface of the polishing head 12 and used as a polishing cloth. During the polishing, the detection head portion 14 of the film thickness detection device is controlled so as to be always located on the same circle as the polishing head 12 on the silicon substrate 11, so that the polishing head 12 on the silicon substrate 11 exists. The average film thickness on the circumference is constantly monitored by a film thickness measuring device. The film thickness data obtained by the film thickness detection device is sent to a computer, and the computer uses the film thickness data to position the polishing head 12, the pressure applied to the polishing head 12, the number of revolutions of the polishing head 12, and the polishing head 12. While controlling the amount of the polishing agent supplied from the device, the temperature of the polishing head 12, and the like, the polishing proceeds from the outer peripheral portion of the silicon substrate 11 to the central portion or from the central portion of the silicon substrate 11 to the outer peripheral portion.

According to the present embodiment, since the polishing is performed while always obtaining the average film thickness of the circumferential portion on the silicon substrate 11 which is actually being polished, the desired remaining film thickness is accurately polished. Can be finished. Another major feature of this embodiment is that the polishing head 12 that is sufficiently smaller than the silicon substrate 11 is used to perform polishing while always obtaining the film thickness of the polished portion, so that the flat silicon substrate 11 is used.
Not only the film deposited on the upper surface, but also the film deposited on the silicon substrate 11 that is convex or concave can be polished flatly in a shape that is warped to the shape of the silicon substrate 11. That is,
It is possible to prevent preferential polishing of only the peripheral portion when the silicon substrate 11 is warped concavely, or preferentially polishing only the central portion when the silicon substrate 11 is curved convexly.

In this embodiment, the polishing head 12 is not moved only once from the outer peripheral portion of the silicon substrate 11 toward the central portion or from the central portion of the silicon substrate 11 toward the outer peripheral portion to perform the target polishing for each reciprocation. 1 / thickness
By repeatedly moving the polishing head 12 in the radial direction of the silicon substrate 11 while polishing about 100,
It can be polished more flatly.

In the present embodiment, the detection head unit 14 of the film thickness measuring apparatus is moved in synchronization with the position of the polishing head 12, and the detection head unit 14 is always in the same circumference on the polishing head 12 and the silicon substrate 11. Controlled to be on top. As another method of monitoring the average film thickness on the same circumference as the polishing point, the position of the film thickness detection head unit 14 is not synchronized with the position of the polishing head 12, and, for example, the moving speed of the polishing head 12 is changed. There is a method of reciprocating on the silicon substrate 11 in the radial direction at a speed of about 10 times while constantly monitoring the film thickness. According to this method, not only the film thickness on the circumference currently being polished but also the film thickness distribution on the silicon substrate 11 can be obtained.
Since it is possible to proceed with the polishing while grasping the overall polishing status, it is possible to further improve the flatness of the silicon substrate 11 after the polishing.

Further, instead of the film thickness detecting head portion 14 which moves at a high speed, a detecting head portion 14 of a film thickness measuring apparatus having a plurality of film thickness detecting head portions 14 in the radial direction of the silicon substrate 11 is provided. By arranging them in a line, the substrate 1
1, the film thickness distribution on 1 can be obtained in real time, and it is possible to proceed with polishing while grasping the polishing state over the entire silicon substrate 11, so that the flatness of the silicon substrate after polishing can be further improved. . (Embodiment 2) The substrate polishing method of Embodiment 1 is a very simple method and is a very excellent method capable of accurately determining the polishing end point. However, since the polishing head is small, the polishing rate is lower than that of the conventional example. The present embodiment relates to a polishing method that improves the polishing rate while having all the features of the first embodiment.

FIG. 2 shows the essential parts of the polishing apparatus used in the present invention. The structure of the apparatus is almost the same as that of the polishing apparatus of Embodiment 1 (FIG. 1). The difference from the first embodiment is that there are three polishing heads 22 and they are independently controlled. The polishing heads 22 are designed so that they can move freely in the radial direction of the silicon substrate 21, and they can be on the same circumference on the silicon substrate 21 or can be located at arbitrary positions. is there. Also,
As the film thickness detection device, the film thickness measurement device having a plurality of polishing heads described in Embodiment 1 is used, and the film thickness detection head row 24 is arranged in the radial direction of the silicon substrate 21.

The procedure of flattening by polishing using this apparatus is basically the same as that of the first embodiment except that there are three polishing heads 22. The film thickness distribution of the film on the silicon substrate 21 is monitored in real time by a film thickness measuring device equipped with a plurality of detection head rows 24. Based on the film thickness distribution data, the position of each polishing head 22, the pressure applied to each polishing head 22, the number of rotations of each polishing head 22, the temperature, the amount of the polishing agent supplied from each polishing head 22, etc. are independently determined. The silicon substrate 21 is controlled and polished to be flat.

According to this embodiment, as in the first embodiment, the film thickness data is fed back to the control unit of the polishing head 22 while always obtaining the film thickness of the circumferential portion of the silicon substrate 11 which is actually being polished. Therefore, the polishing can be accurately finished with a desired remaining film thickness. Further, since the polishing head 22 which is sufficiently smaller than the silicon substrate 21 is used for polishing while constantly obtaining the film thickness of the polished portion, not only the film deposited on the flat silicon substrate 21 but also the convex or concave surface The film deposited on the silicon substrate 21
The silicon substrate 21 can be flatly polished in a warped shape. Furthermore, since a plurality of polishing heads 22 are provided, the above performance can be maintained while significantly increasing the polishing rate as compared with the polishing method of the first embodiment.

In the present embodiment, the case where the number of the polishing heads 22 is three is shown, but the number of the polishing heads 22 can be set to the head row 24 of the film thickness measuring apparatus, and the movement of each polishing head 22 can be changed. As long as the number of polishing heads 22 does not interfere with each other, the polishing speed increases as the number of polishing heads 22 increases. (Embodiment 3) In the polishing methods of Embodiments 1 and 2, the end point of polishing can be accurately detected, and a film deposited on a silicon substrate which is convex or concave is also warped to the shape of the silicon substrate. It has an excellent feature that it can be polished flat. This example is based on Examples 1 and 2.
The polishing method of (1) has been further advanced, and not only the film deposited on a convex or concave silicon substrate but also a silicon substrate with a more complicated surface (for example, a silicon substrate with convex or concave curvature, A silicon substrate whose center is offset from the center of the silicon substrate) is planarized at a higher speed. This embodiment will be described below with reference to the drawings.

FIG. 3 shows the main part of the polishing apparatus used in this embodiment. In FIG. 3, reference numeral 33 indicates a substrate holding turntable. On the substrate holding turntable 33, a silicon substrate 31 having a diameter of 200 mm, which has been subjected to film deposition after forming an uneven pattern by repeating film deposition, photolithography and etching, is bonded by, for example, vacuum suction. Meanwhile, the silicon substrate 31
A plurality of polishing heads 32 are densely spread on the upper surface of the so as to cover the entire surface of the silicon substrate 31. The diameter of each polishing head 32 is, eg, about 40 mm. Unlike the first and second embodiments, each polishing head 32 only rotates, and the polishing head central axis 36 is fixed. The polishing agent is supplied to the surface of the silicon substrate 31 from the center of each polishing head 32. In the clearance between each polishing process 32 and the polishing head 32, the detection unit 34 of the film thickness detector is provided.
Is installed, and the film thickness at each point is measured in real time.

Next, the procedure of flattening by polishing using this apparatus will be described. A plurality of polishing heads 32 spread on the silicon substrate 31 are brought into pressure contact with the main surface of the silicon substrate 31 adhered onto the substrate holding turntable 33, and the individual polishing heads 32 are rotated to rotate the main surface of the silicon substrate 31. To polish. At the time of polishing, one of the features of this embodiment is that the main surface of the silicon substrate 31 is polished more uniformly by rotating the substrate holding table 33 as well as revolving it. As a polishing agent for polishing, for example, when polishing a silicon oxide film, colloidal silica is dispersed in an aqueous solution, and since it is KOH, it has a weak alkaline pH.
The adjusted one is used. Further, for example, a polyurethane pad is bonded to the polishing surface of the polishing head 32 and used as a polishing cloth. During polishing, the film thickness at each point on the silicon substrate 31 is monitored by a film thickness detection device having a plurality of detection head portions 34. The film thickness data obtained by the film thickness detection device is sent to a computer, and the computer calculates the position of each measurement point on the silicon substrate 31 from the rotation and revolution data of the silicon substrate 31, and calculates the position on the silicon substrate 31. Calculate the film thickness distribution data in real time. The computer polishes the silicon substrate 31 flat while changing the load applied to each polishing head 32 based on the film thickness distribution data.

According to the present embodiment, similar to the first and second embodiments, while always obtaining the film thickness of the film on the silicon substrate 31,
Since the film thickness data is fed back to the control unit of the polishing head 32, polishing can be accurately completed with a desired remaining film thickness. Further, the polishing head 32, which is sufficiently smaller than each silicon substrate 31, is not moved but fixed at a certain position on the silicon substrate 31, so that the film thickness detection device is provided between the polishing head 32 and the polishing head 32 on the silicon substrate 31. It is possible to install the head portion 34 of the. To accurately identify the film thickness measurement point on the silicon substrate 31 by processing the acquisition timing of the signal from each detection head unit 34, the rotation speed of the silicon substrate 31, and the revolution radius and speed of the silicon substrate 31 by a computer. Therefore, not only the average film thickness on each circumference on the silicon substrate 31 but also the film thickness at each point on the silicon substrate 31 can be measured. By controlling the pressure applied to each polishing head 32 based on the obtained film thickness distribution on the silicon substrate 31, not only the film on the flat silicon substrate 31 but also the convex or concave is warped. Not only the film deposited on the silicon substrate 31 but also the silicon substrate 31 having a more complicated surface shape
A film deposited on (for example, a silicon substrate 31 in which the center of the convex or concave is displaced from the center of the silicon substrate 31 even if the convex or concave is warped) is also warped to the shape of the surface of the silicon substrate 31. It can be ground flat. Further, since the polishing heads 32 are densely spread, the polishing rate can be significantly increased.

In this embodiment, the pressure applied to each polishing head 32 was changed as a method of controlling the polishing rate for each polishing head 32, but the number of revolutions of each polishing head 32 is changed. The polishing rate by each polishing head 32 can also be controlled by. Further, the polishing rate by each polishing head 32 can also be controlled by controlling the amount of slurry supplied to the wafer from each polishing head. Further, the polishing speed of each polishing head 32 can be controlled also by providing each polishing head 32 with a heater and controlling the temperature of the heater. Furthermore, the pressure applied to each polishing head 32, the number of revolutions of each polishing head 32, the amount of slurry supplied from each polishing head 32 to the silicon substrate 31, and the control of the temperature of each polishing head 32 are combined. As a result, the polishing rate of each polishing head 32 can be controlled.

In each of Examples 1, 2 and 3 described above, polishing is performed while monitoring the film thickness of the film on the silicon substrate during polishing. It is relatively difficult to detect the film thickness when the uneven pattern is formed on the silicon substrate and the film is deposited thereon. Next, the film thickness detection method used in this example will be described. As shown in FIG. 4, the silicon substrate 10
1, a polysilicon pattern 102 having a height of 1 μm is formed, and a silicon oxide film 103 having a thickness of 2.5 μm is formed thereon.
The substrate on which is formed is polished. The target remaining film thickness is 0.5 μm on the polysilicon pattern.

A white light source such as a tungsten lamp is used as a light source, and the reflectance spectrum of the substrate is measured by a well-known ordinary method. Figure 5 (A)
(B) is a reflectance spectrum obtained from the pattern of FIG. In this embodiment, as the energy of incident light,
A range of 1.5 eV to 4 eV was used. The fact that the reflectance increases while oscillating as the energy increases is that the refractive index of the silicon oxide film 103 shows almost no dispersion in this energy range, but the underlying silicon substrate 101 and the polysilicon pattern 102 are Due to exhibiting relatively large variance. Fourier transform of the spectra of FIGS. 5A and 5B is shown in FIG.
(C) However, in FIGS. 5A and 5C, the absolute value of the complex spectrum obtained by the Fourier transform is 2
After taking the power, interpolation is performed using a three-dimensional spline curve. The horizontal axis of FIGS. 5A and 5C is the dimension of the reciprocal of energy. In FIGS. 5A and 5C, the film thickness is the same on the step and below the step, and since the refractive index of the silicon oxide film 103 has almost no dispersion in this energy range, a single peak appears. ing.
The very large value in the part where the horizontal axis is 1 or less is due to the DC component in FIGS. 5A and 5B and the signal with a very long period due to the dispersion of the refractive index of silicon. is there. Assuming that the refractive index of the silicon oxide film 103 does not have dispersion, the film thickness can be calculated from the peak position of FIGS.

[0033]

[Equation 1]

The reflectance spectrum and its Fourier transform in the case where polishing is started from FIG. 5 (A) (a) to reach the state of FIG. 5 (B) (a) are shown in FIG. 5 (B) (b), FIG. 5 (B)
It shows in (c). At this stage, only the film deposited on the step is polished and the film deposited under the step is not polished, so that the peak is divided into two corresponding to each film thickness. The peak from the film deposited under the step is located at the same position as in FIGS. 5A and 5C, and the peak from the film on the step shifts to the smaller value corresponding to the thinning due to polishing. .

As the polishing progresses further, as shown in FIGS. 5C and 5A, the reflectance spectrum and the Fourier transform thereof when the height above the step and the height below the step match are shown in FIGS. ,
It shows in FIG.5 (C) (c). The signal from the film deposited under the step is still located at the same position, but the signal from the film deposited on the step is shifted to a lower value.

As shown in FIGS. 5D and 5A, as shown in FIGS. 5D and 5A, the reflectance spectrum and its Fourier transform when the film above and below the step are polished are shown in FIGS. Figure 5
(D) Shown in (c). Since the film deposited under the step is also polished, the signal from the film deposited under the step also shifts to a lower value, and at the same time the signal from the film deposited on the step shifts to a lower value. To do. That is, by constantly monitoring the Fourier transform spectrum, it is possible to accurately grasp the moment when the film on the lower portion of the step starts to be polished.

5 (E) (b) and 5 ((E) (b) and FIG. 5 (F), the reflectance spectrum and its Fourier transform when the target remaining film thickness is reached as shown in FIGS. E)
It shows in (c).

As described above, the peak position after the Fourier transform of the reflectance spectrum is constantly monitored, and the polishing is performed while converting it to the successive film thickness according to the equation (1) to deposit it on the substrate on which uneven steps are formed. Even when polishing the formed film, the absolute value of the film thickness can be monitored, and the polishing end point can be accurately detected. By the way, the sampling interval of the spectrum after the Fourier transform depends on the measured energy range of the reflectance spectrum, and when the measured energy range is narrow, it is difficult to accurately identify the peak position. In this embodiment, after taking the square of the absolute value of the complex spectrum obtained by the Fourier transform, interpolation is performed by a three-dimensional spline curve to accurately read the peak position, and the film is measured within the measurement range. If the refractive index of No. does not change, the absolute value of the film thickness can be obtained with an accuracy of about 0.05 μm.

In this embodiment, the case where there is only one step is shown, but the film thickness detection method of the present invention is applied not only when there is one step but also when there are two steps and three steps. be able to.

In this embodiment, since it is necessary to measure the film thickness in real time, it is necessary to combine the spectroscope and the multi-channel photodetector to measure the reflectance spectrum. Further, in a CCD camera, it is preferable to use a two-dimensional detector such as a CCD camera rather than using a one-dimensional photodetector such as a Thai array as a multi-channel photodetector. Therefore, when the pixels arranged in one direction are used for detecting the intensity of the light wavelength-separated by the spectroscope, the arrangement in the other direction can be used for other purposes. In Examples 2 and 3, polishing is performed while monitoring the film thickness at a plurality of points on the surface of the substrate. Therefore, a plurality of one-dimensional photodetectors are required. By using a CCD camera, a single element can perform the same function as that in which a plurality of one-dimensional photodetectors are arranged, and at the same time, cost reduction and device size reduction can be achieved at the same time. Further, since a single element is used, the accuracy of the detected film thickness between the film thickness detection heads can be greatly improved.

[0041]

The effects obtained by the typical ones of the inventions disclosed in the present invention will be briefly described as follows.

According to the present invention, since the film thickness of the film deposited on the substrate can be detected at all times during polishing, a desired polishing amount can always be obtained without being influenced by the change with time of the polishing head. It is possible to polish. Further, since a polishing head that is sufficiently smaller than the substrate is used, most of the space on the surface of the substrate is exposed. Therefore, the detection head unit of the film thickness detection device is moved over the substrate, or a plurality of film thickness detection heads are used. By using the film thickness detection device provided with the section, it is possible to calculate the film thickness distribution in the surface of the substrate on the spot during polishing. By controlling the polishing head based on the film thickness distribution in the surface of the substrate, it becomes possible to uniformly polish the film deposited on the warped substrate. That is, it is possible to prevent preferential polishing of only the peripheral portion when the substrate is warped concavely, and preferentially polishing only the central portion when the substrate is warped convexly. Further, by using a plurality of polishing heads, it is possible to prevent a reduction in polishing rate due to the use of a small head, and it is possible to obtain a polishing rate comparable to the conventional method while having the above-mentioned excellent characteristics.

[Brief description of drawings]

1A is a plan view showing a part of a polishing apparatus used for carrying out a polishing method according to a first embodiment of the present invention, and FIG. 1B is a sectional view of the same.

FIG. 2A is a plan view showing a part of a polishing apparatus used for carrying out a polishing method according to a second embodiment of the present invention, and FIG. 2B is a sectional view of the same.

FIG. 3A is a plan view showing a part of a polishing apparatus used for carrying out a polishing method according to a third embodiment of the present invention, and FIG.

FIG. 4 is a cross-sectional view of a substrate on which a silicon oxide film is deposited after forming a step of polysilicon on the silicon substrate.

5A is a state before polishing, FIG. 5B is a state after polishing 0.5 μm, FIG. 5C is a state where the substrate surface is flat, and FIG. 5D is a state after polishing 0.5 μm. (E) shows the state when the target remaining film thickness is reached after polishing by 2.0 μm, (a)
Is a cross-sectional view of the substrate as polishing progresses, (b) is a spectrum diagram of the reflectance of the substrate, (c) is the Fourier transform of the spectrum of the reflectance of the substrate, and then the square of the absolute value is obtained, after which the three-dimensional spline is obtained. Spectral diagram interpolated by curve

FIG. 6 is a sectional view showing a part of a conventional polishing apparatus.

[Explanation of symbols]

 11 Silicon Substrate 12 Polishing Head 13 Substrate Holding Turntable 14 Head of Film Thickness Measuring Device

Claims (15)

[Claims]
1. After depositing a film on the surface of a substrate on which an uneven pattern is formed, while constantly detecting the film thickness of the film, a polishing apparatus having a polishing head smaller than the substrate is used to rotate the substrate on the rotating substrate. A method of planarizing a semiconductor substrate, comprising: polishing a film to planarize the surface of the substrate.
2. The position of the polishing head, which is smaller than the substrate for polishing the substrate by moving in the radial direction of the substrate while rotating on its own axis, and the position of the detection head portion of the film thickness measuring device are always on the substrate. 2. The method of planarizing a semiconductor substrate according to claim 1, wherein the position of the detection head portion of the film thickness measuring device is controlled so that it is on the same circumference.
3. The substrate surface is measured by reciprocating the detection head portion of the film thickness measuring device in the radial direction of the substrate faster than the moving speed of the substrate regardless of the position of the polishing head on the substrate. The method for planarizing a semiconductor substrate according to claim 2, wherein the film thickness distribution in the inside is constantly monitored.
4. A film thickness measuring device equipped with a plurality of film thickness detecting heads arranged in a line in the radial direction of the substrate to constantly monitor the film thickness distribution in the substrate surface.
A method for planarizing a semiconductor substrate according to claim 1.
5. The method of planarizing a semiconductor substrate according to claim 1, further comprising a plurality of polishing heads.
6. The method of planarizing a semiconductor substrate according to claim 5, wherein a plurality of polishing heads are not moved and only rotation is performed.
7. The center axes of the plurality of polishing heads do not overlap with the center axes of the substrates.
A method for planarizing a semiconductor substrate according to claim 1.
8. The method of planarizing a semiconductor substrate according to claim 6, wherein a plurality of polishing heads are densely spread on the substrate.
9. The method of planarizing a semiconductor substrate according to claim 6, wherein the substrate is not only rotated but also revolved.
10. A film thickness measuring apparatus comprising a plurality of detection head units, wherein each detection head unit is installed on a substrate at an arbitrary position where a polishing head does not exist, and polishing is performed while always detecting the film thickness distribution of the film. 7. The method for planarizing a semiconductor substrate according to claim 6, wherein:
11. Based on the film thickness distribution data of the film on the substrate,
7. The method for planarizing a semiconductor substrate according to claim 6, wherein the number of rotations of the plurality of polishing heads is controlled for each individual head.
12. Based on the film thickness distribution data of the film on the substrate,
7. The method for planarizing a semiconductor substrate according to claim 6, wherein the pressure applied to the plurality of polishing heads is controlled for each individual head.
13. Based on the film thickness distribution data of the film on the substrate,
7. The method of planarizing a semiconductor substrate according to claim 6, wherein the supply amount of the aqueous solution containing the polishing agent supplied onto the substrate surface from a plurality of polishing heads is controlled for each individual head.
14. Based on the film thickness distribution data of the film on the substrate,
7. The method of planarizing a semiconductor substrate according to claim 6, wherein the temperatures of the plurality of polishing heads are controlled for each individual head.
15. Irradiating a substrate having a concavo-convex pattern with white light, determining the wavelength dependence of the reflectance of the substrate, and then Fourier transforming the spectrum of the reflectance to obtain the unevenness of the reflection spectrum. The reflectance spectrum from the film deposited on the convex portion of the pattern and the reflectance spectrum from the film deposited on the concave portion of the concave-convex pattern are separated and deposited on the film thickness and the convex portion of the film deposited on the concave portion of the concave-convex pattern. The method for planarizing a semiconductor substrate according to claim 1, wherein the film thickness of the formed film is measured at the same time.
JP3762793A 1993-02-26 1993-02-26 Method for flattening semiconductor substrate Granted JPH06252113A (en)

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JP3762793A JPH06252113A (en) 1993-02-26 1993-02-26 Method for flattening semiconductor substrate

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JP3762793A JPH06252113A (en) 1993-02-26 1993-02-26 Method for flattening semiconductor substrate

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JPH06252113A true JPH06252113A (en) 1994-09-09

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