JP2009095910A - Wafer pop-out detecting mechanism for polishing device, and method of detecting pop-out of wafer - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To form a wafer pop-out detecting mechanism, using a simple structure that uses low-cost parts and prematurely detect the abnormal state of polishing by enhancing the detection accuracy. <P>SOLUTION: In a polishing device 10, a wafer W held on a polishing head 30 is pressed against a polishing pad 22 on a rotating platen 20, and the wafer W is polished while slurry is fed to the polishing pad 22. The polishing head 30 comprises a head body 32, placed opposite to the polishing pad 22 and rotatively driven, a carrier 33 so supported on the head body 32 as to be moved vertically; and a retainer ring 34 so supported on the head body 32 as to be vertically moved and brought into contact with the polishing pad 22, while surrounding the periphery of the wafer W during the polishing; an accelerator sensor 60 is incorporated in the retainer ring 34; and the polishing device also comprises an inclination detection control part 61 for monitoring the change of the inclination of the retainer ring 34, by using a detection signal from the accelerator sensor 60. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to a wafer pop-up detection mechanism and a detection method of a polishing apparatus, and in particular, in a mechanical mechanical polishing (CMP), an inclination of a wafer support portion such as a retainer ring provided in a polishing head is provided. The present invention relates to a detection mechanism and a detection method for monitoring and determining the protrusion of a wafer from the change in inclination.

  In recent years, fine processing of semiconductors has progressed, and a pattern is formed over multiple layers. It is inevitable that a certain degree of unevenness is generated on the surface of the layer on which the pattern is formed. Conventionally, the pattern of the next layer is formed as it is. However, as the number of layers increases and the width of a line or hole decreases, it becomes difficult to form a good pattern, and defects and the like easily occur.

  For this reason, the pattern of the next layer is formed after the surface of the layer on which the pattern is formed is polished and flattened. Thus, in order to polish the surface of a wafer such as a semiconductor, a polishing apparatus using a CMP process is used. This type of polishing apparatus generally has a configuration in which a wafer held by a polishing head is pressed against a polishing pad on a rotating platen and a slurry is supplied to the polishing pad to polish the wafer.

  By the way, the wafer is pressed against the polishing pad while being surrounded by a wafer support such as a retainer ring. However, the wafer may jump out of the retainer ring at some point during processing. In such a case, it is necessary to detect the protrusion of the wafer at an early stage and immediately stop the processing.

  For detection of wafer pop-up, the head body is provided with detection means such as a position sensor and pressure sensor, and the output signal of the position sensor that detects the relative position of the retainer ring in the vertical direction with respect to the polishing pad, or the radial direction that acts on the retainer ring 2. Description of the Related Art There is known a wafer polishing apparatus provided with a slip judging means for judging whether or not a wafer has slipped from a carrier based on an output signal of a pressure sensor for detecting the pressure. For example, a capacitive sensor is used as the position sensor, and a semiconductor element that measures a piezoresistance effect is used as the pressure sensor (see, for example, Patent Document 1).

  In addition, in the polishing method by the CMP process, the applicant of the present application detects the amount of carrier displacement from a preset reference position, and when the amount of displacement reaches the thickness of the wafer, the wafer is held on the carrier. A wafer polishing method for determining that there is no such material has been proposed (see, for example, Patent Document 2).

The polishing apparatus disclosed in Patent Document 2 mainly includes a head body, a carrier, a retainer ring, a carrier coupling drive mechanism, a carrier pressing mechanism, a retainer ring pressing mechanism, and a carrier displacement detector. The carrier displacement detector includes a differential transformer and a control device, detects the displacement of the carrier with respect to the head body, and determines the presence or absence of a wafer from the amount of carrier displacement. That is, when the wafer jumps out of the retainer ring and disappears from the lower portion of the carrier, the carrier is displaced downward by the thickness of the wafer. Therefore, the amount of displacement is detected to determine the presence or absence of the wafer.
JP-A-11-000860 JP 2002-307299 A

  The invention described in Patent Document 1 detects a change in the retainer ring by a capacitance type position sensor or a pressure sensor of a semiconductor element that measures a piezoresistance effect. In addition, a configuration is also known in which the upper surface of the polishing pad is monitored using a photoelectric sensor, and all of them attempt to detect the slipping out of the wafer using relatively inexpensive parts, but malfunctions due to disturbance The detection accuracy is not so good.

  The invention described in Patent Document 2 detects the amount of carrier displacement by a differential transformer, and this can also detect the protrusion of a wafer at a low cost by using relatively inexpensive parts. However, noise from the differential transformer may be picked up, and the detection accuracy decreases when the S / N ratio of the detection signal is deteriorated.

  On the other hand, there is a system that detects the crack of a wafer by computer processing an image taken with a CCD or the like, and the detection accuracy is extremely high. However, since the image processing unit is expensive at present, there is a large cost problem. .

  Therefore, a technical problem to be solved has arisen in order to form a wafer pop-up detection mechanism with a simple configuration using inexpensive parts and to detect an abnormal polishing state early by increasing the detection accuracy. Therefore, an object of the present invention is to solve this problem.

  The present invention has been proposed to achieve the above object, and the invention according to claim 1 presses the wafer held by the polishing head against the polishing pad on the rotating platen and also applies the slurry to the polishing pad. A polishing apparatus for polishing the wafer, wherein the polishing head is disposed to face the polishing pad and is driven to rotate, and a carrier supported by the head body so as to be movable in the vertical direction. And a wafer support unit that is supported by the head main body so as to be movable in the vertical direction and surrounds the periphery of the wafer during polishing and contacts the polishing pad. An acceleration sensor is incorporated in the wafer support unit. And a control means for monitoring a change in the inclination of the wafer support from the detection signal of the acceleration sensor. Eha jumped out to provide a detection mechanism.

  According to this configuration, the control means reads the detection signal of the acceleration sensor incorporated in the wafer support portion, and monitors the change in the inclination of the wafer support portion from this detection signal. When the change in the detection signal of the acceleration sensor exceeds a predetermined value set in advance, the control means determines that the change in the inclination of the wafer support portion becomes large and the wafer jumps out of the wafer support portion.

  The invention according to claim 2 provides the wafer jump-out detection mechanism of the polishing apparatus according to claim 1, wherein a plurality of the acceleration sensors are arranged at equal intervals on the same circumference of the wafer support portion. To do.

  According to this configuration, a plurality of acceleration sensors are arranged at equal intervals on the same circumference of the wafer support portion, the rotation state of the wafer support portion can be accurately detected, and the wafer is detected from the change in the inclination of the wafer support portion. Can be detected early.

  According to a third aspect of the present invention, the wafer held by the carrier of the polishing head is pressed against the polishing pad on the rotating platen, and the periphery of the wafer is surrounded by the wafer support portion of the polishing head to form the polishing pad. In a polishing method for polishing the wafer while supplying slurry, when a detection signal of an acceleration sensor incorporated in the wafer support portion is read, and a change in the detection signal of the acceleration sensor exceeds a preset predetermined value A method for detecting a pop-out of a wafer in a polishing apparatus is provided, wherein it is determined that a change in the inclination of the wafer support increases and the wafer pops out from the wafer support.

  According to this configuration, the control means reads the detection signal of the acceleration sensor incorporated in the wafer support portion, and monitors the change in the inclination of the wafer support portion from this detection signal. When the change in the detection signal of the acceleration sensor exceeds a predetermined value set in advance, the control means determines that the change in the inclination of the wafer support portion becomes large and the wafer jumps out of the wafer support portion.

  According to the first aspect of the present invention, an acceleration sensor is incorporated in the wafer support portion, and the control means reads the detection signal to monitor the change in the inclination of the wafer support portion. Whether or not an abnormality has occurred can be detected at an early stage to prevent secondary disasters due to wafer cracking after the wafer has popped out, or processing can be stopped before it pops out to prevent popping out. Is possible. Further, since the acceleration sensor is relatively inexpensive, a highly accurate detection device can be formed at low cost.

  In the invention described in claim 2, since a plurality of acceleration sensors are arranged at equal intervals on the same circumference of the wafer support portion, in addition to the effect of the invention of claim 1, the rotation state of the wafer support portion Can be detected accurately, and the protrusion of the wafer can be detected from the change in the inclination of the wafer support.

  In the third aspect of the invention, since the control means reads the detection signal of the acceleration sensor incorporated in the wafer support portion and monitors the change in the tilt of the wafer support portion from the detection signal, the change in the tilt of the wafer support portion is detected. It is possible to detect an abnormal polishing state at an early stage, to prevent wafer breakage after the wafer jumps out, or to prevent the wafer jumping out in advance.

  Hereinafter, the wafer jumping detection mechanism and the detection method of the polishing apparatus according to the present invention will be described with reference to preferred embodiments. In order to achieve the object of forming a wafer pop-up detection mechanism with a simple configuration using inexpensive parts and increasing the detection accuracy so that an abnormal polishing state can be detected at an early stage, the present invention provides a polishing head. A polishing apparatus for pressing a wafer held on a polishing pad on a rotating platen and supplying a slurry to the polishing pad to polish the wafer, wherein the polishing head is disposed opposite to the polishing pad. A head body that is rotationally driven, a carrier that is supported by the head body so as to be movable in the vertical direction, and that is supported by the head body so as to be movable in the vertical direction, and surrounds the periphery of the wafer during polishing. And a wafer support unit in contact with the wafer support unit, an acceleration sensor is incorporated in the wafer support unit, and the acceleration sensor From the output signal it was achieved by providing the control means for monitoring the change in the tilt of the wafer support.

  FIG. 1 is an overall perspective view of a CMP type polishing apparatus according to the present invention, and FIG. 2 is a longitudinal sectional view of a polishing head. The polishing apparatus 10 is mainly composed of a platen 20 and a polishing head 30. The platen 20 is formed in a disk shape, and a rotary shaft 21 is connected to the center of the lower surface thereof. The platen 20 is rotated in the direction of arrow A by driving a motor 22. A polishing pad 22 is adhered to the upper surface of the platen 20, and a slurry containing an abrasive is supplied onto the polishing pad 22 from a nozzle (not shown).

The polishing head 30 mainly includes a head main body 32, a carrier 33, a retainer ring 34, a carrier coupling drive mechanism 35, a carrier pressing mechanism 36, a retainer ring pressing mechanism 37, a carrier displacement detector 38, and the like. The head main body 32 is formed in a disk shape, and a rotary shaft 31 is connected to the center of the upper surface thereof. The head main body 32 rotates in the arrow B direction by driving a motor (not shown).

  The carrier 33 is formed in a disk shape, and is arranged coaxially with a rotary drive shaft 39 that is suspended from the lower central portion of the head body 32. A plurality of air suction ports 40 are provided on the lower surface of the carrier 33, and air is sucked from the air suction port 40 by a vacuum pump (not shown), whereby the wafer W to be polished is attracted and held on the lower surface of the carrier 33. Is done.

  The retainer ring 34 is formed in an annular shape and is disposed on the outer periphery of the carrier 33. The retainer ring 34 surrounds the outer periphery of the wafer W held by the carrier 33 and contacts the polishing pad 22 during polishing to prevent the wafer W from jumping out.

  The carrier coupling drive mechanism 35 transmits the rotation of the head main body 32 to the carrier 33 to rotate the carrier 33. A disc-shaped drive plate 41 is horizontally attached to the tip of a rotary drive shaft 39 that is suspended from the lower portion of the head body 32. The drive plate 41 is accommodated in a circular recess 42 formed on the upper surface of the carrier 33, and a pair of pins 43 erected vertically in the recess 42 are formed on the outer periphery of the drive plate 41. It is fitted in the notch 44. Therefore, the carrier 33 is supported by the pin 43 and the notch 44 so as to be movable in the vertical direction, and the rotation of the drive plate 41 is transmitted to the carrier 33.

  The carrier pressing mechanism 36 presses the carrier 33 toward the polishing pad 22. A carrier airbag 45 is provided below the head body 32. The carrier airbag 45 is formed in an annular shape, and a carrier pressing member 46 is connected to the lower portion thereof. The carrier pressing member 46 is formed in a cylindrical shape, and the carrier 33 is connected to the lower part thereof. The carrier airbag 45 is inflated when compressed air is supplied from an air supply port 47 formed on the lower surface of the head main body 32, whereby the carrier 33 is pressed downward via the carrier pressing member 46. .

  The retainer ring pressing mechanism 37 presses the retainer ring 34 toward the polishing pad 22. A retainer ring airbag 48 is provided outside the carrier airbag 45 at the lower portion of the head body 32. The retainer ring airbag 48 is formed in an annular shape, and a retainer ring pressing member 49 is connected to the lower portion thereof. The retainer ring pressing member 49 is formed in a cylindrical shape, and the retainer ring 34 is connected to the lower part thereof. The retainer ring airbag 48 is inflated when compressed air is supplied from an air supply port 50 formed in the lower surface of the head body 32, whereby the retainer ring 34 is moved downward via the retainer ring pressing member 49. Pressed.

  An outer peripheral end portion of the retainer ring airbag 48 is fixed by an annular guide ring 51, and an upper end portion of the retainer ring pressing member 49 is engaged with a lower end portion of the guide ring 51, so that the retainer ring 34 and the retainer A ring pressing member 49 is supported so as to be movable in the vertical direction.

  The carrier displacement detector 38 detects the displacement of the carrier 33 with respect to the head main body 32 and receives a differential transformer 53 installed in the hollow portion 52 of the rotary drive shaft 39 and an electric signal output from the differential transformer 53. It is comprised with the displacement detection control part 54. FIG.

  Here, an acceleration sensor 60 is incorporated in the retainer ring 34. As will be described later, the detection signal of the acceleration sensor 60 is read into the inclination detection control unit 61 which is a control means, and the change in the inclination of the retainer ring 34 is monitored to detect the jumping out of the wafer W from the retainer ring 34.

  Next, the installation position and the number of installation of the acceleration sensor 60 will be described. As for the installation height, as shown in FIG. 3, the acceleration sensor 60 is incorporated into the lower position (P1) of the retainer ring 34, and the lower position (P2), the middle position (P3), and the upper position of the retainer ring pressing member 49. Any member that moves integrally with the retainer ring 34, such as the position (P4), can be incorporated into any position, but the lowest possible position, that is, the (P1) or (P2) position is preferable in consideration of detection accuracy.

  The installation position of the acceleration sensor 60 is not limited to the retainer ring 34 and the retainer ring pressing member 49, but can be attached to any location of the wafer support portion which is a head member for supporting the wafer W. . For example, in addition to the retainer ring 34, a change in inclination from the detection signal of the acceleration sensor 60 can be attached to any part such as a carrier (back plate), a wafer protection sheet, etc., as long as the part is inclined when the wafer jumps out. It is possible to detect popping out of the wafer. Although illustration is omitted, if another ring is provided on the outer periphery of the retainer ring 34, the acceleration sensor 60 may be attached to the ring.

  As for the planar position, as shown in FIG. 4, one or a plurality of planar positions are arranged at arbitrary positions on the retainer ring 34 or the retainer ring pressing member 49 or at equal intervals on the same circumference. For example, the acceleration sensors 60 are arranged at two locations, an arbitrary position (P11) and a position (P12) on the same circumference facing the rotation center point P0. Preferably, the acceleration sensors 60 may be disposed at three positions of 120 degrees (P13) and (P14) on the same circumference as the arbitrary position (P11) across the rotation center point P0.

  Next, a method for detecting wafer jumping according to the present invention will be described. As described with reference to FIGS. 2 to 4, the acceleration sensor 60 is incorporated in the retainer ring 34, and a detection signal of the acceleration sensor 60 is input to the tilt detection control unit 61, and the tilt detection control unit 61 determines from this detection signal. The change in the inclination of the retainer ring 34 is monitored. In a normal polishing state, as shown in FIG. 5, the detection signal of the acceleration sensor 60 changes within a substantially constant range. Therefore, in this case, it can be determined that the retainer ring 34 is in a normal state without being inclined.

  On the other hand, as shown in FIG. 6, when the detection signal of the acceleration sensor 60 suddenly changes greatly and exceeds a predetermined threshold value set in advance, as shown in FIG. It can be determined that the change in the slope of is large and the state is abnormal. In this state, since the wafer W held on the carrier 33 of the polishing head 30 jumps out of the retainer ring 34, when the inclination detection control unit 61 determines that the state is abnormal, the machine is immediately stopped and polishing is performed. Stop processing.

  In this way, since the inclination detection control unit 61 reads the detection signal of the acceleration sensor 60 incorporated in the retainer ring 34 and monitors the change in the inclination of the retainer ring 34 from the detection signal, the change in the inclination of the retainer ring 34 is detected. It is possible to detect an abnormal polishing state at an early stage, to prevent wafer breakage after the wafer W jumps out, or to prevent the wafer W from jumping out.

  It should be noted that 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.

1 is an overall perspective view of a CMP type polishing apparatus according to the present invention. 1 is a longitudinal sectional view of a polishing head according to the present invention. Explanatory drawing of the installation height of the acceleration sensor which concerns on this invention. Explanatory drawing of the arrangement position of the acceleration sensor which concerns on this invention. The measurement graph of the normal state of the acceleration sensor which concerns on this invention. The measurement graph of the abnormal state of the acceleration sensor concerning the present invention. Explanatory drawing of the inclination state of the retainer ring which concerns on this invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 10 Polishing apparatus 20 Platen 22 Polishing pad 30 Polishing head 32 Head main body 33 Carrier 34 Retainer ring 49 Pressing member for retainer ring 60 Acceleration sensor 61 Inclination detection control part (control means)
W wafer

Claims (3)

A polishing apparatus for pressing a wafer held by a polishing head against a polishing pad on a rotating platen and polishing the wafer by supplying slurry to the polishing pad,
The polishing head is disposed opposite to the polishing pad and is driven to rotate;
A carrier supported by the head body so as to be movable in the vertical direction;
In a polishing apparatus comprising: a wafer support that is supported by the head body so as to be movable in the vertical direction, and surrounds the periphery of the wafer at the time of polishing, and contacts the polishing pad.
A wafer pop-up detection mechanism for a polishing apparatus, wherein an acceleration sensor is incorporated in the wafer support portion, and control means for monitoring a change in the inclination of the wafer support portion from a detection signal of the acceleration sensor is provided.   2. The wafer pop-up detection mechanism of a polishing apparatus according to claim 1, wherein a plurality of the acceleration sensors are arranged at equal intervals on the same circumference of the wafer support portion. The wafer held by the carrier of the polishing head is pressed against the polishing pad on the rotating platen, and the periphery of the wafer is surrounded by the wafer support portion of the polishing head, and the slurry is supplied to the polishing pad while supplying the slurry. In a polishing method for polishing,
When the detection signal of the acceleration sensor incorporated in the wafer support part is read and the change of the detection signal of the acceleration sensor exceeds a predetermined value, the change in the inclination of the wafer support part becomes large. A method for detecting wafer jump-out in a polishing apparatus, wherein it is determined that a wafer jumps out from a support portion.

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