JP2019162705A - Polishing device - Google Patents

Abstract

To provide a polishing device that can be smoothly set.SOLUTION: A polishing device 1 comprises: a polishing head 10 comprising a polishing pad 30 for polishing an upper surface of a wafer W and a housing part 12 that opens to a polishing surface 31 of the polishing pad 30; thickness measuring means 60 that comprises a sensor head 61 provided in the housing part 12 and measures a thickness of the wafer W through the opening in a non-contact manner; a feeding mechanism 40 mounted with the polishing head 10 and connected integrally to the sensor head 61, which moves up and down the polishing head 10 and the sensor head 61; and a control device 70 that controls feeding amounts of the feeding mechanism 40. The feeding mechanism 40 separates the polishing head 10 when the polishing head 10 is moved down to sit on the wafer W, and then moves down the sensor head 61 to a measurement position separated by a predetermined distance from the upper surface of the wafer W.SELECTED DRAWING: Figure 1

Description

  The present invention relates to a polishing apparatus for polishing a wafer.

  In the semiconductor manufacturing field, a polishing apparatus for polishing a wafer to remove a clutch remaining on a semiconductor wafer such as a silicon wafer (hereinafter referred to as “wafer”) is known.

  The polishing apparatus described in Patent Document 1 is a polishing apparatus that polishes the upper surface of a wafer by seating the polishing pad on the wafer during polishing and pressing the polishing pad against the wafer while rotating the wafer and the polishing pad. In such a polishing apparatus, a thickness measuring means for measuring the thickness of the wafer is arranged on the rotating shaft of the polishing head outside the polishing apparatus, and while supplying slurry to the upper surface of the wafer through the cavity in the center of the polishing head, A thickness measuring means measures the thickness of the wafer through the cavity in a non-contact manner.

Japanese Patent Laid-Open No. 2015-134383

  However, the polishing apparatus described in Patent Document 1 is suitable for measuring the distance from the thickness measuring means to the upper surface of the wafer when the wafer height changes for each wafer and the optical thickness measuring means is used. Therefore, it is necessary to manually perform a complicated operation for adjusting the distance to match the distance and seating the polishing pad on the wafer.

  Therefore, a technical problem to be solved in order to smoothly set the polishing apparatus arises, and the present invention aims to solve this problem.

  In order to achieve the above object, a polishing apparatus according to the present invention is a wafer polishing apparatus, comprising: a polishing pad for polishing an upper surface of the wafer; and a housing portion opened to the polishing surface of the polishing pad. An optical thickness measuring means for measuring the thickness of the wafer in a non-contact manner through the opening, and a polishing head mounted on the polishing head. A feed mechanism that is integrally connected to the thickness measuring means and moves the polishing head and the thickness measuring means up and down; and a control device that controls the feed amount of the feed mechanism; When the head is lowered until it is seated, the polishing head is separated, and the sensor head is lowered to a measurement position at a predetermined distance from the upper surface of the wafer.

  According to this configuration, when the polishing head is seated on the wafer while the feeding mechanism descends the sensor head to the measurement position, the polishing head is separated from the feeding mechanism, so that the operation of seating the polishing head on the wafer is omitted. Since the head is smoothly lowered to a measurement position suitable for measurement, the polishing apparatus can be set smoothly.

  In the polishing apparatus according to the present invention, the control device corrects a reference feed amount for lowering the sensor head from the initial position to the measurement position in accordance with a pre-measured height of the wafer before polishing. It is preferable.

  According to this configuration, since the measurement position of the sensor head can be adjusted according to the height of the wafer, a predetermined distance from the sensor head to the upper surface of the wafer can be maintained regardless of the height of the wafer. The thickness of the wafer can be measured with high accuracy.

  In the present invention, when the polishing head is seated on the wafer while the feeding mechanism is lowered to the measurement position, the polishing head is separated from the feeding mechanism, so that the operation of seating the polishing head on the wafer is omitted and the sensor head is Since it is smoothly lowered to a measurement position suitable for measurement, the polishing apparatus can be set smoothly.

1 is a longitudinal sectional view schematically showing a polishing apparatus according to an embodiment of the present invention. The longitudinal cross-sectional view which shows the principal part of a grinding | polishing head typically. The schematic diagram which shows the positional relationship of a polishing pad and a wafer. The schematic diagram which shows the setting procedure of the grinding | polishing apparatus before a process.

  Embodiments of the present invention will be described with reference to the drawings. In the following, when referring to the number, numerical value, quantity, range, etc. of the constituent elements, it is limited to the specific number unless otherwise specified and clearly limited to the specific number in principle. It may be more than a specific number or less.

  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 longitudinal sectional view schematically showing a polishing apparatus 1 according to an embodiment of the present invention. FIG. 2 is a longitudinal sectional view schematically showing the main part of the polishing head 10. The polishing apparatus 1 polishes the upper surface of the wafer W attracted and held by the wafer chuck 2 and removes a damaged layer including microcracks generated during grinding.

  The wafer chuck 2 is provided so as to be rotatable around a rotation axis a <b> 1 passing through the center of the wafer chuck 2. The wafer chuck 2 has an adsorbent (not shown) made of a porous material such as alumina embedded in the upper surface. The wafer chuck 2 includes a pipe line (not shown) that extends to the surface through the inside. The pipe line is connected to a vacuum source, a compressed air source, or a water supply source via a rotary joint (not shown). When the vacuum source is activated, the wafer W placed on the wafer chuck 2 is sucked and held by the wafer chuck 2. Further, when the compressed air source or the water supply source is activated, the adsorption between the wafer W and the wafer chuck 2 is released.

  A plurality of wafer chucks 2 are arranged on an index table (not shown). The wafer chucks 2 are arranged at a predetermined interval on a concentric circumference around the rotation axis of the index table. Accordingly, when the polishing apparatus 1 and a grinding apparatus for grinding the upper surface of the wafer W are used in combination, the wafer W is continuously moved by rotating the index table and transporting the ground wafer W to the polishing apparatus 1. Can be processed.

  The wafer W is sucked and held by the wafer chuck 2 while mounted on a support substrate such as a bag grind tape, a glass substrate, or a silicon substrate. In particular, a support substrate is often used as the wafer W becomes thinner and has a larger diameter.

  The polishing apparatus 1 includes a polishing head 10 provided above the wafer chuck 2. A polishing pad 30 is horizontally attached to the lower end of the spindle 20 of the polishing head 10.

  The spindle 20 includes a motor 21, a hollow cylindrical rotating part 22 connected to the motor 21, a fixing part 23 that accommodates the rotating part 22, and a bearing interposed between the rotating part 22 and the fixing part 23. 24. The rotating unit 22 is rotated about the rotation axis a2 by the motor 21.

  The polishing pad 30 is integrated with the rotating unit 22 and rotates as the rotating unit 22 rotates. The polishing surface 30 of the polishing pad 30 is pressed downward by a pressure cylinder (not shown). In this way, the polishing pad 30 is pressed downward by the pressure cylinder while rotating, whereby the upper surface of the wafer W is polished. The amount of polishing by the polishing pad 30 is set to 2 μm from the upper surface of the wafer W, for example.

  A supply hole 32 that opens to the polishing surface 31 is formed in the polishing pad 30. The supply holes 32 are provided in three rows from the inner side to the outer side in the radial direction of the polishing head 10. Eight supply holes 32 are provided in each row. The supply holes 32 of each row are arranged concentrically around the rotation axis a2 of the polishing head 10 and spaced apart from each other by a predetermined distance.

  The polishing apparatus 1 includes a feed mechanism 40. The feed mechanism 40 is a known ball screw slider mechanism including a motor 41, a ball screw 42, and a slider 43. The ball screw 42 is rotated by the motor 41, and the slider 43 moves up and down in the vertical direction according to the rotation direction of the ball screw 42. The slider 43 supports the supported portion 25 protruding from the outer periphery of the fixed portion 23 so as to be placed thereon.

  In the cavity 26 in the rotating part 22, a spiral pipe 50 is provided for flowing slurry therein. The upper end of the pipe 50 is connected to an external slurry supply source 52 via a rotary joint 51. The lower end of the pipe 50 is connected to the supply hole 32 as shown by the broken line in FIG. The slurry supplied to the upper surface of the wafer W is diffused over the entire surface of the wafer W by centrifugal force accompanying the rotation of the wafer W.

  In the center of the polishing head 10, an accommodating portion 12 that opens to the center of the polishing surface 31 is formed. Specifically, the accommodating portion 12 is formed from the lower portion of the cavity 26 to the lower end of the polishing pad 30.

  A translucent window 14 is attached to the opening 13 of the housing portion 12. The translucent window 14 is bonded so as to close the housing portion 12. As a result, the slurry supplied to the upper surface of the wafer W is prevented from entering the accommodating portion 12.

  The polishing apparatus 1 includes a thickness measuring unit 60 that measures the thickness of the wafer W in a non-contact manner during polishing. The thickness measuring means 60 is preferably, for example, a spectral interference type film thickness measuring device. The spectral interference type film thickness measuring instrument is resistant to disturbances such as vibration and can measure the thickness of the wafer W with high accuracy. Hereinafter, a case where a spectral interference type film thickness measuring device is employed as the thickness measuring means 60 will be described as an example.

  The thickness measuring unit 60 includes a sensor head 61 disposed in the housing portion 12. The sensor head 61 is connected to the slider 43 via a bracket 62. The sensor head 61 irradiates light toward the wafer W through the opening 13, and receives reflected light that interferes with light reflected from the upper surface and the lower surface of the wafer W. The reflected light received by the sensor head 61 is dispersed by a spectroscope (not shown), and a control device 70 described later calculates the optical path difference between the light reflected from the upper surface of the wafer W and the light reflected from the lower surface of the wafer W, Based on this optical path difference, the thickness of the wafer W is calculated.

  The measurement point on the wafer W where the sensor head 61 measures the thickness is set so as to substantially coincide with the rotation axis a2 of the polishing head 10 (including a range that can be regarded as optically coincident) when viewed from above. That is, the optical path of the light irradiated by the sensor head 61 and the optical path of the light reflected from the wafer W are set to a path connecting the sensor head 61 and the measurement point on the wafer W. Needless to say, the measurement point of the sensor head 61 is not limited to the case where the measurement point substantially coincides with the rotational axis a2 of the polishing head 10 when viewed from the plane.

  In addition, it is preferable to provide the dry air supply means 3 which supplies dry air between the translucent window 14 and the sensor head 61. As a result, the humidity in the accommodating portion 12 is kept constant by dry air, so that the thickness of the wafer W is accurately measured even when the slurry is heated by frictional heat generated during the polishing process. be able to.

  Further, it is preferable to provide moving means 4 for moving the polishing apparatus 1 in the horizontal direction. Thereby, the thickness profile of the entire wafer W can be measured using the polishing apparatus 1 without preparing an independent apparatus for measuring the thickness of the wafer, so that the throughput can be improved.

  The operation of the polishing apparatus 1 is controlled by the control device 70. The control device 70 controls each component constituting the polishing device 1. The control device 70 is constituted by, for example, a CPU, a memory, and the like. The function of the control device 70 may be realized by controlling using software or may be realized by operating using hardware.

  Next, the positional relationship between the polishing pad 30 and the wafer W will be described with reference to FIG. FIG. 3 is a schematic view of the polishing pad 30 and the wafer W viewed from below. The polishing pad 30 has a larger diameter than the wafer W. The diameters of the polishing pad 30 and the wafer W are set to 450 mm and 300 mm, for example.

  Further, the rotation directions of the polishing pad 30 and the wafer W coincide with each other, and the outer periphery of the polishing pad 30 and the outer periphery of the wafer W overlap at one point. Thereby, the velocity vectors in the wafer W plane coincide. Further, the polishing pad 30 can uniformly polish the entire surface of the wafer W by always covering the entire surface of the wafer W during processing.

  As shown in FIG. 3, when the polishing pad 30 is arranged so as to cover the wafer W, slurry is supplied to the upper surface of the wafer W from the outside of the polishing apparatus 1 and the thickness of the wafer W is measured during polishing processing. However, in the polishing apparatus 1, while the slurry is supplied to the upper surface of the wafer W through the supply hole 32, the thickness measuring unit 60 accommodated in the polishing head 10 is connected to the wafer W through the opening 13. The thickness can be measured in a non-contact manner.

  Next, the setting procedure of the polishing apparatus 1 before processing will be described with reference to FIG. FIG. 4A is a view showing a state before the polishing head 10 is seated on the wafer W. FIG. FIG. 4B is a diagram illustrating a state in which the polishing head 10 is seated on the wafer W. FIG. 4C is a diagram illustrating a state where the sensor head 61 is lowered.

  First, the height of the wafer W before being polished and held by the wafer chuck 2 is measured. This is because when the polishing apparatus 1 continuously processes the wafer W, the thickness between the different support substrates is not constant, and the height of the wafer W mounted on the support substrate tends to vary. This is because the optical thickness measuring means 70 may not be able to measure due to deviation from the measurement range due to such a variation in the height of the wafer W. For measuring the height of the wafer W, a known contact-type or non-contact-type measurement device is used. In addition, when the height of the wafer W is known, the value may be used.

  Next, the control device 70 corrects the reference feed amount stored in advance based on the height measurement value of the wafer W before polishing. The reference feed amount is a descending amount from the initial position of the sensor head 61 to the measurement position of the sensor head 61 that is a predetermined distance (for example, 80 mm) away from the upper surface of the wafer W at the reference height. The reference height is the height of the wafer W that is a virtually determined reference. Further, the distance between the sensor head 61 and the upper surface of the wafer W at the measurement position is set within a range suitable for measurement. For example, when the height measurement value of the wafer W before polishing is larger than the reference height of the wafer W by a deviation Δt, the control device 70 calculates a corrected feed amount obtained by subtracting the deviation Δt from the reference feed amount.

  Next, as shown in FIG. 4A, when the control device 70 starts to rotate the motor 41 according to the correction feed amount, the ball screw 42 rotates and the slider 43 starts to descend. As shown in FIG. 4B, when the slider 43 is lowered until the polishing head 10 is seated on the wafer W, the supported portion 25 is separated from the slider 43. On the other hand, the sensor head 61 is integrated with the slider 43 via the bracket 62 and further descends together with the slider 43.

  As shown in FIG. 4C, when the control device 70 rotates the motor 41 by the number of rotations corresponding to the corrected feed amount, the sensor head 61 is positioned at the measured value. Therefore, the sensor head 61 can measure the thickness of the wafer W at the measurement position during the polishing process.

  As described above, in the polishing apparatus 1 according to the present embodiment, when the polishing pad 30 is seated on the wafer W while the feed mechanism 40 descends the sensor head 61 to the measurement position, the polishing head 10 is separated from the slider 43. Since the operation of seating the polishing head 10 on the wafer W is omitted and the sensor head 61 is smoothly lowered to the measurement position suitable for measurement, the setting of the polishing apparatus 1 can be performed smoothly.

  Further, the present invention can be variously modified in addition to the above without departing from the spirit of the present invention, and the present invention naturally extends to the modified ones.

DESCRIPTION OF SYMBOLS 1 ... Polishing apparatus 2 ... Wafer chuck 3 ... Dry air supply means 4 ... Moving means 10 ... Polishing head 12 ... Storage part 13 ... Opening 14 ... Translucent window DESCRIPTION OF SYMBOLS 20 ... Spindle 21 ... Motor 22 ... Rotating part 23 ... Fixed part 24 ... Bearing 25 ... Supported part 26 ... Cavity 30 ... Polishing pad 31 ... Polishing Surface 32 ... Supply hole 40 ... Feed mechanism 41 ... Motor 42 ... Ball screw 43 ... Slider 50 ... Pipe 51 ... Rotary joint 52 ... Slurry supply source 60 ... Thickness measuring means 61 ... sensor head 62 ... bracket 70 ... control device W ... wafer a1 ... rotation axis a2 (of wafer chuck) ... rotation axis (of polishing head)

Claims (2)

A wafer polishing apparatus,
A polishing head comprising: a polishing pad for polishing the upper surface of the wafer; and a housing portion opened to the polishing surface of the polishing pad;
An optical thickness measuring means comprising a sensor head provided in the housing portion, and measuring the thickness of the wafer in a non-contact manner through the opening;
A feed mechanism that mounts the polishing head and is integrally connected to the thickness measuring means, and moves the polishing head and the thickness measuring means up and down;
A control device for controlling the feed amount of the feed mechanism;
With
When the polishing head is lowered until the polishing head is seated on the wafer, the feeding mechanism separates the polishing head and lowers the sensor head to a measurement position separated from the upper surface of the wafer by a predetermined distance. The said control apparatus correct | amends the reference | standard feed amount which lowers | hangs the said sensor head from the initial position to the said measurement position according to the height of the said wafer before grinding | polishing measured beforehand. Polishing equipment.