JP2008307609A - Polishing method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a polishing method which determines polishing conditions through simple work procedures, uniformly levels a polished surface of a polishing object, and efficiently finishes the polished surface to a desired face shape. <P>SOLUTION: The polishing method is composed of the following steps. In the first step, the polished surface of a semiconductor wafer 2b on which an SiO<SB>2</SB>film is formed, is abutted on a polishing pad 15, and the former and the latter in an abutting state are relatively moved, followed by acquiring a polishing rate (a change of a polished and removed amount) during polishing of the polished surface of the semiconductor wafer 2b. In the following step, the polishing conditions on which a glass sheet 2a made of SiO<SB>2</SB>is polished are obtained from the acquired polishing rate (the change of the polished and removed amount). In the last step, the glass sheet 2a is polished based on the obtained polishing conditions. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to a polishing method for polishing a surface of an object to be polished such as a semiconductor wafer or a glass plate.

  Chemical mechanical polishing is attracting attention as an efficient flattening technique for large areas as a polishing technique for polishing objects such as semiconductor wafers and glass plates. This is a polishing process called CMP (Chemical Mechanical Polishing). This CMP is an important technique for global planarization in a process of polishing the surface of an object to be polished by using a chemical action in combination with physical polishing. Specifically, an abrasive called slurry in which abrasive grains (silica, alumina, cerium oxide, etc. are commonly used) are dispersed in a soluble solvent of an abrasive such as acid, alkali, or oxidizer, and further polished. Polishing is advanced by pressurizing the surface of the object to be polished with a pad and rubbing with relative motion.

  Conventionally, in a polishing apparatus that performs CMP, in a large-diameter pad method that uses a polishing pad having a considerably larger diameter than the polishing object, the polishing object is smaller than the polishing pad, and the entire surface of the polishing object always contacts the polishing pad. Therefore, it is extremely difficult to preferentially polish some areas of the object to be polished with respect to other areas, and it is very difficult to uniformly flatten the surface of the object to be polished. . Therefore, recently, a small-diameter pad type polishing apparatus using a polishing pad having a diameter substantially equal to or smaller than that of an object to be polished has been developed and used. In the small-diameter pad method, it is possible to freely change the polishing profile by changing the existence probability of the polishing pad in each part on the surface of the object to be polished. Therefore, the surface of the polishing object can be uniformly flattened (see Patent Document 1).

International Publication No. 04/075276 Pamphlet

  However, the fact that the polishing profile can be freely changed in polishing using a small-diameter pad means that the polishing conditions must be determined more finely. In other words, in order to change the existence probability of the polishing pad on the surface of the object to be polished, control is performed to change the reciprocating motion of the polishing pad and the contact pressure. As the number of times increases, more time is required to determine one polishing condition.

  The present invention has been made in view of such problems, and it is possible to determine polishing conditions with a simple work procedure, to uniformly flatten a surface to be polished of an object to be polished, and to efficiently polish the object to be polished. An object is to provide a polishing method capable of finishing a surface into a desired surface shape.

  In order to solve the above problems and achieve the object, a polishing method according to the present invention is configured to move the polishing object relative to each other while the polishing object made of a predetermined material and the polishing pad are in contact with each other. A polishing method for polishing, wherein a surface to be polished of a polishing removal amount measuring member on which a film made of the material is formed and the polishing pad are brought into contact with each other to move the surface to be polished. Based on the determined polishing conditions, a step of determining a change in polishing removal amount when polishing, a step of determining a polishing condition when polishing the object to be polished from the change in the determined polishing removal amount, and And polishing a polishing object.

  In the polishing method, the step of determining a change in the amount of polishing removal includes polishing the surface to be polished using the polishing pad and measuring the thickness of the film, and measuring the thickness of the film from the measured film thickness. It is preferable to obtain a change in the removal amount.

In the polishing method, it is preferable that the object to be polished is a rectangular glass plate made of SiO ₂ , and the polishing removal amount measuring member is a semiconductor wafer in which a SiO ₂ film is formed on the surface to be polished. .

  According to the polishing method of the present invention, a change in the amount of polishing removal when the surface to be polished of the polishing amount measuring member on which a film made of a predetermined material is polished is obtained, and the predetermined amount is determined from the change in the polishing removal amount. Since polishing conditions for polishing a polishing object made of a material are required, the surface to be polished of the polishing object can be polished based on the polishing conditions, and the surface to be polished can be uniformly flattened, The surface to be polished can be efficiently finished into a desired surface shape.

  Hereinafter, preferred embodiments of the present invention will be described with reference to the drawings. FIG. 1 shows a schematic configuration of a CMP apparatus 1 which is a typical example of a polishing apparatus according to the present invention. The CMP apparatus 1 includes a polishing apparatus 10 that performs surface polishing of a polishing object 2, and an object holding apparatus 20 that holds the polishing object 2 so that a surface to be polished of the polishing object 2 faces the polishing apparatus 10. It is configured with.

  The polishing apparatus 10 and the object holding apparatus 20 are supported by a support frame 30. The support frame 30 includes a horizontal base 31 and a rail (not shown) provided on the base 31 so as to extend in the Y direction (the direction perpendicular to the paper surface is the front-rear direction). A first stage 32 that is movably provided, a vertical frame 33 that extends vertically from the first stage 32 (Z direction; vertical direction in the drawing), and a vertical frame 33 that extends in the Z direction. A second stage 34 provided movably, a horizontal frame 35 provided horizontally extending from the second stage 34 (X direction; left and right direction in the drawing), and moved on the horizontal frame 35 in the X direction. The third stage 36 is freely provided.

  A first drive mechanism D1 using an electric motor or the like as a drive source is provided in the first stage 32, and the first stage 32 can be moved in the Y direction along the rail by the first drive mechanism D1. it can. A second drive mechanism D2 is provided in the second stage 34, and the second stage 34 can be moved in the Z direction along the vertical frame 33 by the second drive mechanism D2. Further, a third drive mechanism D3 is provided in the third stage 36, and the third stage 36 can be moved in the X direction along the horizontal frame 35 by the third drive mechanism. For this reason, it is possible to move the third stage 36 to an arbitrary XY position (horizontal position) above the object holding device 20 by performing drive control of the drive mechanisms D1 and D3 and combining the respective operations. . In addition, the third stage 36 can be moved to an arbitrary Z position (a height position above the object holding device 20) by performing drive control of the second drive mechanism D2. The drive mechanisms D2 and D3 are configured using an electric motor or the like as a drive source, similarly to the first drive mechanism D1.

  The polishing apparatus 10 includes a polishing head rotating shaft 11 provided so as to extend downward from the third stage 36, and a polishing head 12 attached to a lower end portion of the polishing head rotating shaft 11. On the lower surface of the polishing head 12, a disk-like support plate 13 having a polishing pad 15 attached to the lower surface using a double-sided adhesive tape or the like is attached by vacuum suction. For this reason, the vacuum suction is released, and the polishing pad 15 can be removed from the polishing head 12 together with the support plate 13 and replaced.

  The polishing pad 15 is formed in a disk shape having substantially the same outer diameter as the support plate 13 using a foam resin material such as foaming polyurethane, or a thin donut shape having a hole in the center. In this embodiment, the polishing pad 15 is a thin donut shape. On the polishing surface of the polishing pad 15, lattice-like grooves are formed at substantially equal intervals in the vertical and horizontal directions, and the diffusion of the abrasive (slurry) is promoted during the polishing process.

  The polishing head rotating shaft 11 is rotated by a fourth drive mechanism D4 using an electric motor or the like provided in the third stage 36 as a drive source, and thereby the polishing head 12 is rotated so that the polishing surface of the polishing pad 15 is XY. It can be rotated in a plane (horizontal plane). Further, the third stage 36 includes an air cylinder (not shown), and the polishing head 12 is moved up and down via the polishing head rotating shaft 11 by this air cylinder to polish the polishing surface of the polishing pad 15. The surface to be polished of the object 2 can be pressed with a predetermined contact pressure.

  The object holding device 20 includes a turntable support portion 21 provided on a base 31, a chuck rotation shaft 22 provided vertically extending from the turntable support portion 21, and an upper end portion of the chuck rotation shaft 22. The chuck turntable 23 is mounted horizontally, and the vacuum chuck 24 is provided on the chuck turntable 23 and holds the glass plate 2 on the upper surface side.

  A vacuum suction chuck mechanism (not shown) is provided in the vacuum chuck 24, and the polishing object 2 is detachably sucked and held by this vacuum suction chuck mechanism. A fifth drive mechanism D5 using an electric motor or the like as a drive source is provided in the turntable support portion 21, and a chuck rotation shaft 22 provided extending from the turntable support portion 21 is provided with the fifth drive mechanism D5. Thus, the chuck turntable 23 can be rotated.

Next, a polishing method for polishing the surface of the rectangular glass plate 2a made of SiO ₂ to be polished in the CMP apparatus 1 (polishing apparatus 10) configured as described above will be described with reference to a flowchart.

A polishing method for polishing the surface of the glass plate 2a using the polishing apparatus 10 is shown in the flow chart of FIG. 2. Here, first, in step S1, a semiconductor wafer which is a member for measuring polishing removal amount using the polishing apparatus 10 is shown. Polish the 2b SiO ₂ film. The semiconductor wafer 2b has a SiO ₂ oxide film formed on the surface to be polished. This SiO ₂ film has the same physical composition as the glass plate 2a, and has the same polishing characteristics for CMP. Show.

  Specifically, the semiconductor wafer 2b is sucked and attached to the upper surface of the vacuum chuck 24 in the object holding device 20. Then, the chuck rotating base 23 is rotated via the chuck rotating shaft 22 by the fifth drive mechanism D5. That is, the chuck rotating base 23 is rotated by the fifth drive mechanism D5, and the vacuum chuck 24 provided on the chuck rotating base 23 and the semiconductor wafer 2b sucked and held by the vacuum chuck 24 are rotated.

Next, the third stage 36 is moved by the driving mechanisms D1 and D3 so that the polishing head 12 is positioned above the semiconductor wafer 2b, and the polishing head 12 is rotated via the polishing head rotating shaft 11 by the fourth driving mechanism D4. . Then, the second stage 34 is moved in the Z direction by the second drive mechanism D2 so that the polishing surface of the polishing pad 15 is positioned close to the SiO ₂ film (surface to be polished) of the semiconductor wafer 2b, and the third stage 36 is placed. The polishing head 12 is lowered using an air cylinder (not shown) built into the semiconductor wafer ₂ to press the polishing surface of the polishing pad 15 against the SiO ₂ film of the semiconductor wafer 2b with a predetermined contact pressure. Thereafter, the third stage 36 is reciprocated along the horizontal frame 35 by the third drive mechanism D3. That is, the polishing head 12 (the polishing surface of the polishing pad 15) is reciprocated in the X direction. At this time, the polishing agent is pumped from a polishing agent supply device (not shown) to supply the polishing agent to the lower surface side of the polishing surface of the polishing pad 15. Thereby, the SiO ₂ film of the semiconductor wafer 2b is polished by the rotational movement of the semiconductor wafer 2b itself and the rotation and reciprocation of the polishing head 12 (polishing pad 15) while being supplied with the abrasive.

In step S1, the polishing of the SiO ₂ film on the semiconductor wafer 2b is stopped every predetermined time, and the thickness of the SiO ₂ film on the polished surface of the semiconductor wafer 2b is measured (step S2). Specifically, while scanning an optical measuring device (interference type film thickness measuring instrument) at a surface to be polished of the semiconductor wafer 2b, irradiating light to the SiO ₂ film, the upper and lower surfaces of the SiO ₂ film (SiO ₂ film The amount of reflected light reflected on the surface and the substrate surface) is measured. The intensity of the reflected light changes depending on the thickness of the SiO ₂ film due to the interference effect of the SiO ₂ film. For this reason, the film thickness of the SiO ₂ film of the semiconductor wafer 2b can be measured by measuring the intensity of the reflected light. For example, as described in Patent Document 1, a cavity is formed in the center of a polishing head rotating shaft 11, a polishing head 12, a support plate 13, and a polishing pad 15 constituting the polishing apparatus 10, and the cavity is optically formed. Provide an optical fiber connected to the measuring instrument. By moving in the XY plane of the polishing apparatus 10 above the semiconductor wafer 2b by a drive mechanism D1, D3, scanning the SiO ₂ Makujo semiconductor wafer 2b with an optical measuring instrument, the SiO ₂ film of a semiconductor wafer 2b The film thickness can be measured. The optical measuring device may be provided separately from the polishing apparatus 10.

When the measurement of the film thickness of the SiO ₂ film of the semiconductor wafer 2b at every predetermined time is completed in step S2, the process proceeds to step S3, and the polishing rate (change in polishing removal amount) of the SiO ₂ film of the semiconductor wafer 2b is obtained from the obtained measurement data. ) Is calculated. The polishing rate of the SiO ₂ film of the semiconductor wafer 2b can be calculated from the film thickness of the SiO ₂ film of the semiconductor wafer 2b measured over time. The polishing removal amount is obtained by integrating the polishing rate over time. Is calculated. Further, the flatness of the surface to be polished can be known by comparing the film thickness measured at each point on the surface to be polished of the semiconductor wafer 2b.

When the polishing rate of the SiO ₂ film of the semiconductor wafer 2b in step S3 is calculated, the process proceeds to step S4, and the surface to be polished of the glass plate 2a is polished from the calculated polishing rate of the SiO ₂ film of the semiconductor wafer 2b. The polishing conditions are obtained. As described above, since the SiO ₂ film has the same composition as the glass plate 2a and exhibits similar polishing characteristics to CMP, the same polishing conditions (contact pressure, polishing pad 15) as those of the semiconductor wafer 2b are described. It can be considered that the polishing rate on the surface to be polished of the glass plate 2a and the polishing rate on the SiO ₂ film of the semiconductor wafer 2b in the relative speed between the surface and the surface to be polished are substantially equal.

Next, in step S5, similarly to the semiconductor wafer 2b, the glass plate 2a is sucked and attached to the upper surface of the vacuum chuck 24 in the object holding device 20, and based on the polishing conditions (polishing rate) obtained in step S4. Surface polishing of the glass plate 2a is performed. Thus, it is possible to obtain the polishing conditions for polishing the surface to be polished of the glass plate 2a from the polishing rate at the SiO ₂ film of the semiconductor wafer 2b, that is, the polishing rate at the surface to be polished of the glass plate 2a, Since the surface to be polished of the glass plate 2a is polished based on this polishing condition, the surface to be polished can be uniformly flattened and the surface to be polished can be efficiently finished into a desired surface shape.

In step S1, the polishing of the SiO ₂ film of the semiconductor wafer 2b is stopped every predetermined time and the thickness of the SiO ₂ film on the surface to be polished of the semiconductor wafer 2b is measured. it may be measured the thickness of the SiO ₂ film at the same time as the polishing of the SiO ₂ film. However, in this case, it is necessary to provide an optical measuring device so that a time lag does not occur at the measurement time, that is, the film thickness of the surface to be polished can be measured at the same time.

FIG. 3 is experimental data showing the polishing rate in the radial direction of the semiconductor wafer 2b when the polishing apparatus 10 is used to polish the SiO ₂ film of the semiconductor wafer 2b. The horizontal axis indicates 0 as the center of the semiconductor wafer 2b. 5 is a graph in which the polishing rate is plotted for each position on the semiconductor wafer 2b in the radial direction, with the position on the semiconductor wafer 2b (SiO ₂ film) in the radial direction and the vertical axis representing the polishing rate.

Incidentally, was carried out in FIG. 3, a diameter of 200 mm, the polishing of the semiconductor wafer 2b of SiO ₂ film having a thickness of 1um is formed on the Si surface of the substrate having a thickness of 0.725 mm. As the polishing pad 15, a donut-shaped pad having a diameter of 170 mm and a hole having a diameter of 54 mm was used, and the polishing surface of the polishing pad 15 was pressed against the SiO ₂ film of the semiconductor wafer 2b with a contact pressure of 0.25 psi. . 3A, the rotation speed of the semiconductor wafer 2b is 251 rpm, the rotation speed of the polishing pad 15 is 51 rpm, the semiconductor wafer 2b and the polishing pad 15 rotate in the same direction, and the reciprocating speed of the polishing pad 15 is 60 mm. / sec, the reciprocation range was 25 to 40 mm from the center of the semiconductor wafer 2b. In FIG. 3B, the rotational speed of the semiconductor wafer 2b is 100 rpm, the rotational speed of the polishing pad 15 is 101 rpm, the semiconductor wafer 2b and the polishing pad 15 rotate in the opposite direction, and the reciprocating speed of the polishing pad 15 is 60 mm / sec. The reciprocating range was 28 to 50 mm from the center of the semiconductor wafer 2b.

  According to this experimental data, in FIG. 3A, it can be seen that the polishing rate near the center of the semiconductor wafer 2b is large, and the polishing rate gradually decreases toward the end (edge) of the semiconductor wafer 2b. This is because the semiconductor wafer 2b and the polishing pad 15 are rotated in the same direction for polishing. Further, in FIG. 3B, it can be seen that the polishing rate near the center of the semiconductor wafer 2b is small, and the polishing rate gradually increases toward the end (edge) of the semiconductor wafer 2b. This is because the semiconductor wafer 2b and the polishing pad 15 are rotated in the opposite directions to perform polishing. That is, when polishing is performed by rotating the semiconductor wafer 2b and the polishing pad 15 in the same direction, positive polishing (center fast polishing) near the center is performed rather than the end of the semiconductor wafer 2b. Conversely, when polishing is performed by rotating the semiconductor wafer 2b and the polishing pad 15 in the opposite directions, the edge of the semiconductor wafer 2b is more actively polished (edge fast polishing) than the vicinity of the center.

  FIG. 4 shows a polished surface of a glass plate 2a formed in a 152 mm × 152 mm square shape (excluding the outer peripheral portion of 5 mm) for 5 minutes under the same conditions as above. Is the experimental data showing the relative change of the shape of the glass plate 2a in the diagonal direction, the horizontal axis is the position in the diagonal direction on the glass plate 2a where one vertex of the glass plate 2a is 0, and the vertical axis is the shape before and after polishing. It is the graph which took the relative change amount and plotted the shape relative change amount for every position of the diagonal direction on the glass plate 2a. The relative shape change amount is obtained by measuring the distance to the surface to be polished of the glass plate 2a before and after polishing, and obtaining the deviation from the obtained distance data with respect to the reference plane (the position where the relative shape change amount is 0). It is.

  According to this experimental data, in FIG. 4A, the relative shape change amount near the center of the glass plate 2a is large, and the relative shape change amount gradually decreases toward the end (edge) of the glass plate 2a. I understand that. In FIG. 4B, it can be seen that the relative shape change amount near the center of the glass plate 2a is small, and the relative shape change gradually increases toward the end (edge) of the glass plate 2a. That is, when polishing is performed by rotating the glass plate 2a and the polishing pad 15 in the same direction, aggressive polishing near the center (center fast polishing) is performed rather than the end of the glass plate 2a. Conversely, when polishing is performed by rotating the glass plate 2a and the polishing pad 15 in the opposite directions, the edge of the semiconductor wafer 2b is more actively polished (edge-fast polishing) than the vicinity of the center. Therefore, comparing FIG. 3 and FIG. 4, it can be seen that when the glass plate 2a is polished, the relative change in shape before and after polishing is close to the tendency of the polishing rate (change in polishing removal amount) of the semiconductor wafer 2b.

As described above, the SiO ₂ film of the semiconductor wafer 2b is polished using the polishing apparatus 10 and the thickness of the SiO ₂ film is measured every predetermined time. From this measurement data, the SiO ₂ film of the semiconductor wafer 2b is measured. A polishing rate (change in polishing removal amount) is calculated. Then, since the SiO ₂ film of the semiconductor wafer 2b and the glass plate 2a show similar polishing characteristics, the polishing conditions for polishing the glass plate 2a from the calculated polishing rate of the SiO ₂ film can be obtained. Since the surface to be polished of the glass plate 2a is polished based on this polishing condition, the surface to be polished can be uniformly flattened and the surface to be polished can be efficiently finished into a desired surface shape.

In addition, this invention is not limited to said embodiment, A various deformation | transformation is possible within the range of the summary. For example, the film formed on the object to be polished and the member for measuring the polishing amount is not necessarily formed of SiO ₂ , and it is only necessary that both are formed of materials exhibiting similar polishing characteristics.

It is a front view which shows the CMP apparatus which is an example of the grinding | polishing apparatus which concerns on this invention. It is a flowchart explaining the grinding | polishing method which grind | polishes a glass plate using the said CMP apparatus. It is a diagram showing experimental data obtained by plotting the polishing rate of the radial for each position on the semiconductor wafer when polishing the SiO ₂ film of a semiconductor wafer using the CMP apparatus. It is a figure which shows the experimental data which plotted the shape relative variation | change_quantity for every position of the diagonal direction on a glass plate when the to-be-polished surface of a glass plate is grind | polished using the said CMP apparatus.

Explanation of symbols

1 CMP apparatus 2a glass plate (object to be polished)
2b Semiconductor wafer (member for polishing removal measurement)
10 Polishing device 15 Polishing pad (polishing pad)

Claims (3)

A polishing method for polishing the polishing object by relatively moving both of the polishing object and a polishing pad made of a predetermined material in contact with each other,
The amount of polishing removal when the surface to be polished is polished while the surface to be polished and the polishing pad are in contact with each other, with the film made of the material being formed in contact with the polishing pad. A step for change,
Obtaining polishing conditions for polishing the object to be polished from a change in the determined polishing removal amount;
Polishing the object to be polished based on the determined polishing conditions.   The step of obtaining a change in the polishing removal amount comprises polishing the surface to be polished using the polishing pad and measuring the thickness of the film, and determining the change in the polishing removal amount from the measured film thickness. The polishing method according to claim 1, wherein the polishing method is obtained. 2. The polishing object is a rectangular glass plate made of SiO ₂ , and the polishing removal amount measuring member is a semiconductor wafer having a SiO ₂ film formed on the surface to be polished. Alternatively, the polishing method according to claim 2.

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