JP2009172711A - Polishing device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a polishing device capable of correcting fluctuation of a polishing amount profile according to concentration of a polishing pad. <P>SOLUTION: This polishing device 1 is constituted to perform polishing of a substrate W by relatively moving a polishing surface of the polishing pad 23 held by a polishing head 21 by making the polishing surface abut on a surface to be polished of the substrate W held by a holding mechanism 10. The polishing device 1 has a data input part 60 inputted with the concentration of the polishing pad 23 and a control device 50 for correcting a polishing condition in the polishing so that the surface to be polished after the polishing may be flattened according to the concentration of the polishing pad 23 inputted in the data input part 60. The polishing is performed by the polishing condition corrected by the control device 50. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to a polishing apparatus for polishing a substrate such as a semiconductor wafer.

A CMP apparatus is exemplified as a polishing apparatus for polishing the substrate surface. A CMP apparatus is widely used for polishing a substrate such as a semiconductor wafer or a glass substrate as a technique for polishing a substrate surface with high precision by chemical mechanical polishing (CMP). In such a polishing apparatus, the substrate held by the chuck and the polishing pad mounted on the polishing head are relatively rotated and pressed, and a slurry (Slurry) corresponding to the polishing content is brought into contact with the substrate and the polishing pad. Is supplied to cause a chemical and mechanical polishing action, and the substrate surface is polished flatly (see, for example, Patent Document 1). The polishing pad is made of an independent foam such as foamed polyurethane.
JP 2006-319249 A

  However, the polishing apparatus as described above has a problem that the polishing amount profile (polishing amount distribution) varies depending on the density of the polishing pad even when the same polishing recipe (processing conditions) is used.

  The present invention has been made in view of such problems, and an object of the present invention is to provide a polishing apparatus capable of correcting fluctuations in the polishing amount profile according to the density of the polishing pad.

  In order to achieve such an object, a polishing apparatus according to the present invention includes a holding mechanism that holds a substrate, a polishing pad that is made of an independent foam and can polish the substrate, and the substrate that is held by the holding mechanism. A polishing head that holds the polishing pad so as to face the substrate, and a polishing surface of the polishing pad held by the polishing head is in contact with a surface to be polished of the substrate held by the holding mechanism. In a polishing apparatus configured to move and polish the substrate, an input unit to which the density of the polishing pad is input, and the polishing according to the density of the polishing pad input from the input unit A correction unit that corrects a processing condition in the polishing process so that the polished surface after processing is flattened, and the polishing process is performed under the processing condition corrected by the correction unit. To have.

  In the above-described invention, the polishing head holds the polishing pad so as to be rotatable within the polishing surface, and the correction unit performs the polishing according to the density of the polishing pad input by the input unit. It is preferable to correct the rotational speed of the polishing pad, which is the processing condition, so that the polished surface after processing is flattened.

  Furthermore, in the above-described invention, it is preferable that the corrected rotational speed of the polishing pad is obtained using a linear equation having the polishing pad density as a variable.

  According to the present invention, it is possible to correct the fluctuation of the polishing amount profile according to the density of the polishing pad.

  Hereinafter, preferred embodiments of the present invention will be described with reference to the drawings. A schematic configuration of a polishing apparatus 1 to which the present invention is applied is shown in FIG. The polishing apparatus 1 includes a holding mechanism 10 that rotatably holds a substrate W such as a semiconductor wafer, a pad rotating mechanism 20 that rotates a polishing head 21 on which the polishing pad 23 is mounted, and a polishing pad 23 that is attached to the substrate W. A head moving mechanism 30 that moves up and down and relatively swings, a slurry supply mechanism 40 that supplies slurry to the center of the polishing pad 23, rotation of the substrate W and the polishing pad 23, lifting and swinging of the polishing pad 23 relative to the substrate W, The controller 50 is mainly configured to control the operation of the polishing apparatus 1 such as supply of slurry to the polishing unit.

  The holding mechanism 10 includes a disc-shaped chuck 11, a spindle 14 extending vertically downward from the lower portion of the chuck 11, a chuck driving motor 15 that transmits a rotational driving force to the spindle 14 and rotates the chuck 11 in a horizontal plane, and the like. It is configured. The chuck 11 includes a chuck plate 12 formed in a disk shape with high flatness using a highly rigid material such as ceramic, and a suction pad 13 attached to the upper surface of the chuck plate 12. The chuck plate 12 is provided with a vacuum chuck structure for vacuum-sucking the lower surface of the substrate W so that the substrate W can be attached and detached, and the chuck upper portion is exposed from the processing table T. The surface to be polished (that is, the surface to be polished) of the substrate W held by suction is held in an upward horizontal posture.

  The operation of the chuck drive motor 15 is controlled by the control device 50, and the control device 50 controls the rotation / stop, rotation direction, rotation speed, and the like of the substrate W attracted and held by the chuck 11 based on the machining program. Further, a head moving mechanism 30 is provided adjacent to the holding mechanism 10, and the pad rotating mechanism 20 is provided at the tip of the polishing arm 32 constituting the head moving mechanism 30.

  The pad rotating mechanism 20 includes a disk-shaped polishing head 21, a spindle 24 extending vertically upward from the upper portion of the polishing head 21, and a pad driving motor that transmits the rotational driving force to the spindle 24 to rotate the polishing head 21 in a horizontal plane. 25 or the like.

  The polishing head 21 includes a polishing plate 22 formed in a disk shape with high flatness using a high-rigidity material similar to that of the chuck 11, and a polishing pad 23 attached to the lower surface of the polishing plate 22. Is done. The polishing pad 23 is formed in an annular shape whose outer diameter is somewhat smaller (about 80 to 95%) than the diameter of the substrate W to be polished. For example, a hard polyurethane sheet having an independent foam structure is used. The polishing surface is attached to the lower surface of the polishing plate 22 and the polishing surface is held in a downward horizontal posture.

  A slurry supply structure for supplying the slurry supplied by the slurry supply mechanism 40 to the center of the polishing pad 23 is provided in the center of the polishing head 21 so as to penetrate the center of the polishing plate 22 vertically. In addition, a so-called airbag-type pad pressurizing mechanism is provided in which air is supplied to a pressurization chamber formed inside the polishing head 21 to pressurize the polishing plate 22 downward. By controlling the pressure in the pressurizing chamber with the surface in contact with the surface to be polished of the substrate W, the contact pressure between the substrate W and the polishing pad 23, that is, the polishing pressure can be controlled.

  The operation of the pad drive motor 25 and the pressure in the pressurizing chamber are controlled by the control device 50, and the rotation / stop, rotation direction, rotation speed, polishing pressure, and the like of the polishing pad 23 mounted on the polishing head 21 are included in the machining program. Based on this, it is controlled by the control device 50.

  The head moving mechanism 30 horizontally swings the polishing arm 32 around a base 31 protruding upward from the processing table T, a polishing arm 32 extending horizontally from the base 31, and a swinging shaft extending vertically through the base 31. An arm swinging mechanism 35 to be moved and an arm lifting / lowering mechanism (not shown) for vertically moving the entire polishing arm 32 are configured. The pad rotation mechanism 20 described above is provided at the tip of the polishing arm 32. Yes. The head moving mechanism 30 is configured such that the holding mechanism 10 is positioned on the swing locus of the polishing head 21 when the polishing arm 32 is horizontally swinged by the arm swing mechanism 35. The entire polishing arm 32 is moved up and down while facing the substrate 11, and the polishing pad 23 can be horizontally swung with respect to the substrate W while the polishing surface of the polishing pad 23 is in contact with the surface to be polished of the substrate W. Is done.

  The operations of the arm swing mechanism 35 and the arm lifting mechanism are controlled by the control device 50, and the swing start point of the polishing pad 23 (the swing start angle position of the polishing arm 32) with respect to the substrate W held by the chuck 11 is swung. The movement stroke (the rocking angle range of the polishing arm 32), the rocking speed, and the like are controlled by the control device 50 based on the machining program.

  The control device 50 reads a polishing recipe (a polishing processing condition) from the processing program input from the data input unit 60. In the processing program, as a polishing recipe, the rotation speed of the polishing pad 23, the rotation speed of the substrate W, the swing start point of the polishing pad 23 relative to the substrate W, the swing stroke, the swing speed of the polishing pad 23, the polishing pressure, the slurry And the condition values such as the slurry supply flow rate are included.

  Further, the data input unit 60 is configured to be able to input the density of the polishing pad 23 (by key operation or data transfer from the outside), and the control device 50 receives the polishing pad input by the data input unit 51. The rotational speed of the polishing pad 23 in the processing program is corrected so that the polishing profile is flattened according to the density of 23 (that is, the polished surface after polishing is flattened), and the corrected processing program Based on the above, the operation of the polishing apparatus 1 is controlled.

  FIG. 2 shows an example of the polishing amount profile. In FIG. 2, the vertical axis of the graph is the polishing amount (Removal), and the horizontal axis of the graph is the diameter direction position (Wafer Diameter) on the wafer as the substrate W. In FIG. 2, the polishing shape factor is expressed by the following equation (1) based on the polishing amount at the center (Center Removal), the polishing amount at the left end (Left Edge Removal), and the polishing amount at the right end (Right Edge Removal). Defined in

Polishing shape factor =
Center Removal / {(Left Edge Removal + Right Edge Removal) / 2} (1)

  Further, in FIG. 2, the polishing uniformity (Range) is defined by the following equation (2) from the average polishing amount (Average Removal), the maximum polishing amount (Max Removal), and the minimum polishing amount (Min Removal).

  Range = (Max Removal-Min Removal) / Average Removal (2)

  Here, the correlation between the polishing uniformity (Range) and the polishing shape factor is shown in FIG. From FIG. 3, it can be seen that when the polishing shape factor is 1, the polishing uniformity (Range) is minimized. According to the equation (1), when the polishing shape factor is larger than 1, it is in a center-first state (a state where the center portion has a larger polishing amount than the end portion), and when the polishing shape factor is smaller than 1. The center throw state (the center portion is less polished than the end portion).

FIG. 4 shows the correlation between the density of the polishing pad 23 and the polishing shape factor. As can be seen from this figure, a high correlation is recognized between the density of the polishing pad 23 and the polishing shape factor, and the correlation equation between the density ρ (g / cm ³ ) of the polishing pad 23 and the polishing shape factor Y1 is the minimum. It is expressed by the following equation (3) using a square method or the like. Note that the rotation speed of the polishing pad 23 in the case of FIG. 4 is 110 rpm.

  Y1 = 1.9798 × ρ−0.5803 (3)

Furthermore, the correlation between the rotational speed of the polishing pad 23 and the polishing shape factor is shown in FIG. As can be seen from this figure, a high correlation is recognized between the rotational speed of the polishing pad 23 and the polishing shape factor, and the correlation equation between the rotational speed N (rpm) of the polishing pad 23 and the polishing shape factor Y2 is at least two. It is expressed by the following equation (4) using multiplication or the like. Note that the density of the polishing pad 23 in the case of FIG. 5 is 0.776 g / cm ³ .

  Y2 = 0.0116 x N-0.3172 (4)

In this embodiment, since the target of the polishing shape factor is 1, the rotation speed N (rpm) of the polishing pad 23 such that the polishing shape factor is always 1 is obtained by using the following equation (5). A correlation equation with the density ρ (g / cm ³ ) of the polishing pad 23 can be obtained.

  Y1-1 =-(Y2-1) (5)

  Substituting the equations (3) and (4) into this equation (5) yields the following equation (6).

  N = −171 × ρ + 250 (6)

In the present embodiment, when the density ρ of the polishing pad 23 is input from the data input unit 51, the control device 50 uses the equation (6) (that is, a linear equation with the density ρ of the polishing pad 23 as a variable). Thus, the rotational speed N of the polishing pad 23 to be corrected is obtained. For example, when ρ = 0.75 g / cm ³ is input, N = 122 rpm. Then, the control device 50 controls the operation of the polishing device 1 based on the processing program in which the rotational speed of the polishing pad 23 is corrected in this way, and the polishing processing of the substrate W by the polishing device 1 is performed. In order to polish the substrate W, the polishing arm 32 is swung by the head moving mechanism 30 so that the polishing head 21 is positioned above the chuck 11 and both the chuck 11 and the polishing head 21 are rotated. While the polishing head 21 is lowered to the polishing position, the polishing pad 23 is brought into contact with the substrate W, and the polishing pad 23 is pressed against the substrate W with a predetermined polishing pressure by a pressurizing mechanism provided in the polishing head 21. At this time, the slurry is supplied from the center of the polishing pad 23 to the contact portion between the substrate W and the polishing pad 23 using the slurry supply mechanism 40.

  As described above, according to the polishing apparatus 1 of the present embodiment, the control device 50 flattens the polishing profile according to the density of the polishing pad 23 input by the data input unit 51 (that is, after polishing processing). By correcting the rotation speed (processing conditions) of the polishing pad 23 so that the surface to be polished is flattened), the fluctuation of the polishing amount profile according to the density of the polishing pad 23 can be corrected. In addition, since the fluctuation | variation of the grinding | polishing amount profile according to the density of the polishing pad 23 can be correct | amended, it becomes possible to use the polishing pad 23 of the comparatively wide density range which was not used conventionally.

  At this time, if the rotational speed of the polishing pad 23 to be corrected is obtained using a linear equation (equation (6)) with the density of the polishing pad 23 as a variable, the rotational speed of the polishing pad 23 is simply corrected. can do.

  In the above-described embodiment, the linear equation for obtaining the rotation speed of the polishing pad 23 is not limited to the equation (6), and the coefficients a and b of the linear equation represented by N = a × ρ + b are It depends on the type of substrate W and other processing conditions.

1 is a schematic view of a polishing apparatus according to the present invention. It is a figure which shows an example of a grinding | polishing amount profile. It is a figure which shows the correlation with polishing uniformity and polishing shape factor. It is a figure which shows the correlation with the density of a polishing pad, and a polishing shape factor. It is a figure which shows the correlation with the rotational speed of a polishing pad, and a polishing shape factor.

Explanation of symbols

W substrate 1 Polishing device 10 Holding mechanism 21 Polishing head 23 Polishing pad 50 Control device (correction unit) 60 Data input unit

Claims (3)

A holding mechanism that holds the substrate; a polishing pad that is made of an independent foam and can polish the substrate; and a polishing head that holds the polishing pad so as to face the substrate held by the holding mechanism. Polishing configured to polish the substrate by moving the polishing surface of the polishing pad held by the polishing head relative to the polishing surface of the substrate held by the holding mechanism while abutting the polishing surface. In the device
An input unit for inputting the density of the polishing pad;
A correction unit that corrects a processing condition in the polishing process so that the polished surface after the polishing process is flattened according to the density of the polishing pad input in the input unit;
A polishing apparatus that performs the polishing process under the processing conditions corrected by the correction unit. The polishing head holds the polishing pad rotatably in the polishing surface;
The correction unit corrects the rotation speed of the polishing pad, which is the processing condition, so that the surface to be polished after the polishing process is flattened according to the density of the polishing pad input by the input unit. The polishing apparatus according to claim 1, wherein:   The polishing apparatus according to claim 2, wherein the corrected rotational speed of the polishing pad is obtained using a linear equation having a density of the polishing pad as a variable.

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