JP6594124B2 - Wafer polishing equipment - Google Patents

Description

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

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

  As such a CMP polishing apparatus, a wafer polishing apparatus described in Patent Document 1 is known. In this wafer polishing apparatus, an observation hole is provided at a position eccentric from the rotation center of the polishing surface plate, and measurement means such as an irradiation / light reception optical system for measuring the film thickness of the wafer is installed in the observation hole. Yes. The measuring means irradiates the wafer with white light emitted from the light source, and receives the reflected light reflected by the polished surface of the wafer. With such a configuration, the polishing amount of the wafer is controlled, and the polishing end point that reaches the desired polishing amount is measured.

Japanese Patent No. 3804064

  However, in the wafer polishing apparatus as described above, the measuring means irradiates the wafer with white light and receives the reflected light every time the polishing pad makes one rotation, and measures the film thickness of the wafer. The measurement data acquisition interval for calculating the end point becomes long, and there is a possibility that the wafer being polished and the calculation result based on the measurement data are not synchronized.

  In addition, since the slurry interposed between the polishing pad and the wafer flows from the center toward the outer periphery on the polishing pad due to the centrifugal force generated by the rotation of the polishing pad, the optical path of light reciprocating between the measuring means and the wafer is There was a problem that it was not stable.

  Therefore, a technical problem to be solved in order to accurately measure the film thickness of the wafer being polished in real time arises, and the present invention aims to solve this problem.

The present invention has been proposed to achieve the above object, and the invention according to claim 1 is a wafer polishing apparatus for pressing a wafer against a polishing pad mounted on a polishing surface plate to polish the wafer. An observation hole formed in the center of the polishing surface plate and the polishing pad, and accommodated in the observation hole, and measures the film thickness of the wafer so as to always face the wafer during the wafer polishing. Optical measuring means, polishing end point detecting means for calculating the polishing end point of the wafer based on the film thickness of the wafer, a traverse mechanism for moving the polishing surface plate in the horizontal direction, and reflected light of the optical measuring means Is compared with the normal signal intensity of the reflected light stored in advance, whether the rotation axis of the polishing surface plate and the rotation axis of the chuck table holding the wafer are parallel or not. Providing a wafer polishing apparatus comprises a control device for constant for, a.

According to this configuration, since the optical measuring means is disposed at the center of the polishing surface plate and the polishing pad, the film thickness of the wafer can be measured in real time. In addition, a centrifugal force due to the rotation of the polishing platen does not act on a liquid such as slurry or pure water immediately above the optical measuring means, and a stable optical path is formed between the optical measuring means and the wafer. Therefore, the film thickness of the wafer can be accurately measured. Further, when the rotation axis of the polishing platen and the rotation axis of the wafer are not parallel, the signal intensity of the reflected light deviates from the normal range, so that the normal signal intensity stored in advance is compared with the signal intensity of the reflected light. Thus, it can be determined whether or not the rotation axis of the polishing surface plate is parallel to the rotation axis of the wafer.

  According to a second aspect of the present invention, in addition to the configuration of the wafer polishing and grinding apparatus according to the first aspect, a wafer polishing apparatus is provided in which the observation hole is filled with a liquid.

  According to this configuration, since a stable optical path is ensured between the optical measuring means and the wafer, the film thickness of the wafer can be accurately measured.

  According to a third aspect of the present invention, in addition to the configuration of the wafer polishing apparatus according to the first or second aspect, a wafer polishing apparatus is provided in which a drain groove communicating with the outer periphery is formed on the surface of the polishing pad.

  According to this configuration, surplus slurry on the polishing pad is drained to the outside through the drain groove, so that light refraction caused by the surplus slurry is suppressed between the optical measuring means and the wafer. Therefore, the film thickness of the wafer can be measured with high accuracy.

  In the present invention, since the optical measuring means is disposed at the center of the polishing surface plate and the polishing pad, the film thickness of the wafer can be measured in real time. In addition, a centrifugal force due to the rotation of the polishing platen does not act on a liquid such as slurry or pure water immediately above the optical measuring means, and a stable optical path is formed between the optical measuring means and the wafer. Therefore, the film thickness of the wafer can be accurately measured.

1 is a partial cross-sectional schematic view showing a wafer polishing apparatus according to an embodiment of the present invention. The longitudinal cross-sectional view which shows the grinding | polishing stage of the wafer grinding | polishing apparatus shown in FIG. The A section enlarged view of FIG. The principal part enlarged view of the grinding | polishing stage used for the wafer grinding | polishing apparatus which concerns on a modification. The schematic diagram which shows a mode that an optical measurement means is horizontally moved to the radial direction of a wafer chuck.

In order to achieve the purpose of accurately measuring the film thickness of a wafer being polished in real time, the wafer polishing apparatus according to the present invention presses the wafer against a polishing pad mounted on a polishing surface plate, A wafer polishing apparatus that polishes an observation hole formed in the center of a polishing surface plate and a polishing pad, and is accommodated in the observation hole, and measures the film thickness of the wafer constantly facing the wafer during wafer polishing. Optical measuring means, polishing end point detecting means for calculating the polishing end point of the wafer based on the film thickness of the wafer, a traverse mechanism for moving the polishing surface plate in the horizontal direction, and a signal of the reflected light of the optical measuring means The rotation axis of the polishing surface plate and the rotation axis of the chuck table holding the wafer are parallel by comparing the intensity and the normal signal intensity of the reflected light stored in advance. Realized by that and a control unit determining whether.

  Hereinafter, a wafer polishing apparatus 1 according to an embodiment of the present invention will be described with reference to the drawings. In the following examples, when referring to the number, numerical value, quantity, range, etc. of the constituent elements, the specific number is used unless otherwise specified and clearly limited to a specific number in principle. It is not limited, and it may be a specific number or more.

  In addition, when referring to the shapes and positional relationships of components, etc., those that are substantially similar to or similar to the shapes, etc., unless otherwise specified or otherwise considered in principle to be apparent. Including.

  In addition, the drawings may be exaggerated by enlarging characteristic portions in order to make the features easy to understand, and the dimensional ratios and the like of the constituent elements are not always the same. In the cross-sectional view, hatching of some components may be omitted in order to facilitate understanding of the cross-sectional structure of the components.

  FIG. 1 is a partial cross-sectional schematic diagram showing a wafer polishing apparatus 1. The wafer polishing apparatus 1 is a chemical mechanical polishing (CMP) apparatus.

  The wafer polishing apparatus 1 includes a wafer chuck 2 and a frame 3 that supports the wafer chuck 2.

  The wafer chuck 2 is connected to a vacuum source (not shown), and vacuum-sucks the wafer placed on the surface with the surface to be polished facing downward. The wafer chuck 2 can be rotated around the rotation shaft 2a. The wafer chuck 2 can be moved up and down in the vertical direction H by the lifting mechanism 2b.

  A polishing surface plate 10 for polishing the surface to be polished of the wafer is disposed below the wafer chuck 2.

  A polishing pad 20 is attached to the surface of the polishing surface plate 10. The polishing surface plate 10 and the polishing pad 20 are formed in a disk shape, and their outer diameters are set larger than the outer diameter of the wafer. Further, the radii of the polishing surface plate 10 and the polishing pad 20 are set smaller than the outer diameter of the wafer. Accordingly, at least a part of the wafer is always present on the center of the polishing platen 10 and the polishing pad 20. The polishing surface plate 10 can be rotated around a rotation shaft 10a by a rotation motor (not shown).

  The polishing surface plate 10 is integrally attached to a traverse mechanism 30 that moves the polishing surface plate 10 in the horizontal direction H. The traverse mechanism 30 includes a surface plate traveling shaft 31 that is a ball screw, a surface plate mounting base 32 that is attached to the front end side of the surface plate traveling shaft 31 and on which the polishing surface plate 10 is placed, and a base for the surface plate traveling shaft 31. And a platen travel motor 33 disposed on the end side. In the traverse mechanism 30, the surface plate mounting base 32 and the polishing surface plate 10 move horizontally along the surface plate traveling shaft 31 by driving the surface plate traveling motor 33.

  An index fixing mechanism 4 is disposed above the polishing surface plate 10. The index fixing mechanism 4 positions the chuck table 2 above the polishing surface plate 10 by moving the index fixing pins 4 a fitted into the pin receiving portions 2 c of the wafer chuck 2. Reference numeral 5 denotes a dresser head that stands out from the surface of the polishing pad 20.

  The control of the wafer polishing apparatus 1 is performed by the controller 6. The control device 6 includes, for example, a device control unit having a CPU, a memory, and the like, an input / output unit that controls input / output of data, and a storage unit that stores data. The function of the control device 6 may be realized by controlling using software or may be realized by operating using hardware. The control device 6 functions as a polishing end point measuring unit.

  Next, specific forms of the polishing surface plate 10 and the polishing pad 20 will be described. FIG. 2 is a longitudinal sectional view of the polishing surface plate 10. FIG. 3 is an enlarged view of a portion A in FIG.

  An observation hole 40 is formed in the center of the polishing surface plate 10 and the polishing pad 20. The observation hole 40 is provided with a transparent bracket 50 and a transparent observation window 60. The bracket 50 is made of, for example, stainless steel. The bracket 50 is not limited to a transparent one and may be opaque. The observation window 60 is made of acrylic, for example. In addition, a water passage hole 21 that opens to the surface 20 a of the polishing pad 20 is disposed around the observation window 60. A liquid supply source (not shown) is connected to the water passage hole 21, and pure water, slurry, or the like is supplied to the surface 20a. The observation window 60 is arranged in the observation hole 40 via the O-ring 61 and seals the observation hole 40, and the liquid supplied from the water passage hole 21 onto the surface 20 a is dropped into the observation hole 40. Is suppressed.

  On the surface 20 a of the polishing pad 20, a drain groove (not shown) is engraved. The drainage groove communicates with the outer periphery of the polishing pad 20, and excess slurry on the polishing pad 20 is drained to the outside through the drainage groove. The polishing pad 20 is not limited to the one provided with the drainage groove. For example, the urethane pad having a continuous foam formed therein, the suede pad having irregularities formed on the surface, or the nonwoven fabric pad. Etc.

  An optical measuring means 70 is disposed immediately below the observation window 60. The optical measuring means 70 is, for example, a bundle of a large number of optical fibers, and the lower end is bifurcated. One of the branches is connected to the light source unit 71 and the other is connected to the spectroscope 72. The upper end of the optical measuring means 70 receives the irradiation light emitted from the light source unit 71 and the reflected light reflected by the polished surface of the wafer. The reflected light received by the optical measuring means 70 is guided to the spectroscope 72.

  Next, wafer polishing using the wafer polishing apparatus 1 will be described.

  In the wafer polishing apparatus 1, the polishing surface plate 10 and the chuck table 2 rotate in opposite directions to polish the surface to be polished of the wafer. At this time, the slurry is supplied from the water passage hole 21 to the surface 20 a of the polishing pad 20.

  At the time of polishing, the optical measuring means 70 measures the film thickness of the wafer. Specifically, the upper end of the optical measuring means 70 disposed at the center of the polishing surface plate 10 and the polishing pad 20 always emits irradiation light to the surface to be polished of the wafer and receives reflected light in real time. The film thickness can be measured. Further, since the upper end of the optical measuring means 70 is arranged on the rotating shaft 10a of the polishing surface plate 10, no centrifugal force acts on the slurry immediately above the optical measuring means 70, so a stable optical path is ensured. And light scattering can be suppressed. The control device 6 compares the measured value of the film thickness of the wafer sent in real time with the preset value of the film thickness corresponding to the polishing end point stored in advance. When the measured value of the film thickness of the wafer reaches the set value, the control device 6 stops the polishing surface plate 10 and the chuck table 2 and the polishing is finished.

  Note that, as in the modification shown in FIG. 4, the polishing surface plate 10 may not include an observation window. In such a polishing platen 10, slurry is stored in the recess 51 in the bracket 50 during the primary polishing. By omitting the observation window 60 described above, an adhesive that adheres the bracket 50 and the observation window 60 and disturbance of light when passing through the observation window 60 are avoided, so that a more stable optical path is ensured. Can do.

  Next, the operation of the traverse mechanism 30 will be described. FIGS. 5A to 5C are views showing how the optical measuring means 70 horizontally moves the wafer W in the radial direction. The traverse mechanism 30 moves the polishing platen 10 in the horizontal direction H, and the optical measuring means 70 is scanned in the radial direction of the wafer W, whereby the profile of the wafer W can be measured and the polishing platen 10 rotates. It can be measured whether or not the shaft 10a and the rotating shaft 2a of the chuck table 2 are parallel to each other. Specifically, when the rotating shaft 10a of the polishing surface plate 10 and the rotating shaft 2a of the chuck table 2 are not parallel, the signal intensity of the reflected light of the optical measuring means 70 deviates from the normal range. Therefore, the control device 9 compares the normal signal intensity stored in advance with the signal intensity of the reflected light when the polishing platen 10 is moved horizontally, and the rotation axis 10a of the polishing platen 10 It can be determined whether or not the rotation axis 2a of the chuck table 2 is parallel.

  As described above, the wafer polishing apparatus 1 according to this embodiment described above measures the film thickness of the wafer in real time because the optical measuring means 70 is arranged at the center of the polishing surface plate 10 and the polishing pad 20. can do. Further, a centrifugal force due to the rotation of the polishing platen 10 does not act on a liquid such as slurry or pure water immediately above the optical measuring means 70, and a stable optical path between the optical measuring means 70 and the wafer. Therefore, the film thickness of the wafer can be accurately measured.

  The present invention can be variously modified without departing from the spirit of the present invention, and the present invention naturally extends to the modified ones.

DESCRIPTION OF SYMBOLS 1 ... Wafer polisher 2 ... Chuck table 2a ... (Rotation axis | shaft of the chuck table) 2b ... Elevating mechanism 2c ... Pin receiving part 3 ... Frame 4 ... Index fixing mechanism 4a・ ・ ・ Index fixing pin 5 ・ ・ ・ Dresser head 6 ・ ・ ・ Control device 10 ・ ・ ・ Polishing surface plate 20 ・ ・ ・ Polishing pad 20 a ・ ・ ・ Surface 21 (of the polishing pad) ・ ・ ・ Water flow hole 30 ・.. Traverse mechanism 40 ... Observation hole 50 ... Bracket 60 ... Observation window 61 ... O-ring 70 ... Optical measuring means 71 ... Light source unit 72 ... Spectroscope

Claims (3)

A wafer polishing apparatus for polishing a wafer by pressing the wafer against a polishing pad mounted on a polishing surface plate,
An observation hole formed in the center of the polishing surface plate and the polishing pad;
An optical measuring means that is accommodated in the observation hole and constantly measures the film thickness of the wafer while facing the wafer during the wafer polishing;
Polishing end point detection means for calculating the polishing end point of the wafer based on the film thickness of the wafer,
A traverse mechanism for moving the polishing surface plate in a horizontal direction;
Comparing the signal intensity of the reflected light of the optical measuring means with the normal signal intensity of the reflected light stored in advance, the rotation axis of the polishing table and the rotation axis of the chuck table holding the wafer are parallel. A control device for determining whether or not
A wafer polishing apparatus comprising:   The wafer polishing apparatus according to claim 1, wherein the observation hole is filled with a liquid.   3. A wafer polishing apparatus according to claim 1, wherein a drainage groove communicating with the outer periphery is formed on the surface of the polishing pad.

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