JP2006315137A - Polishing pad - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To monitor the temperature closer to the actual temperature of a material to be polished in the process of polishing. <P>SOLUTION: This polishing pad 1 is provided with a temperature sensor 9 such as a thermocouple in its thickness. The back of the polishing pad 1 is provided with a groove-like storing part 12 extending in the radial direction from the central part to the outer peripheral edge, and the temperature sensor 9 and its lead wire 9a are stored and fixed in the interior thereof. A sensor signal of the temperature sensor 9 is taken out to the outside through a rotary connector 11 or the like. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a polishing pad used for polishing a semiconductor wafer such as a silicon wafer.

Generally, the surface of a semiconductor wafer is polished by a CMP (Chemical Mechanical Polishing) type polishing apparatus. In this polishing apparatus, an upper surface plate on which a wafer is held is placed on a lower surface plate equipped with a polishing pad, and while the wafer and the polishing pad are pressurized, a slurry is supplied between the wafer and the polishing pad. Is relatively slid (see, for example, Patent Document 1).
JP 2003-37089 A

  In the polishing of the wafer as described above, the temperature of the wafer rises due to friction between the polishing pad or abrasive grains in the slurry and the wafer that is the object to be polished, and heat generated by the chemical reaction of the slurry. If the temperature of the entire wafer becomes high or the temperature distribution becomes non-uniform, it becomes difficult to perform polishing stably.

  Therefore, it is necessary to detect the temperature of the wafer, but the wafer is in contact with the polishing pad during polishing, and it is very difficult to directly measure the temperature.

  Therefore, conventionally, a radiation thermometer is arranged above the polishing pad, and the temperature of the polishing surface (surface) of the polishing pad is measured by this radiation thermometer, and the temperature of the wafer is calculated from the temperature of the polishing surface of the polishing pad. I try to estimate.

  However, what is measured by the above method is not the temperature of each part of the polishing surface of the polishing pad that is actually in contact with the wafer before polishing, but before polishing or polishing at a position off the wafer. It is the temperature of the latter part. In particular, the pre-polishing part of the polishing pad is cooled by the newly supplied slurry, and its temperature should be much lower than the temperature of the part being polished.

  Moreover, the radiation thermometer can only measure a wide range of average temperatures, and cannot measure a local temperature change and temperature distribution of the polishing pad.

  Therefore, conventionally, the temperature of the wafer being polished cannot be accurately monitored, and it has been difficult to properly adjust the polishing conditions in order to stably perform the polishing.

  In view of the above problems, an object of the present invention is to enable a temperature closer to the actual temperature of an object to be polished such as a wafer being polished to be monitored via a polishing pad.

  The present invention is characterized in that, in a polishing pad for polishing an object to be polished, a temperature sensor housing portion is formed so as to be close to the polishing surface, and the temperature sensor is disposed in the housing portion.

  Here, the proximity means that it is close, means that the accommodating portion is formed near the polishing surface (surface) of the polishing pad, and is as close as possible within a range that does not affect the polishing performance. Is preferably formed. This housing part is preferably formed inside or on the back side of the polishing pad using the thickness of the polishing pad.

  According to the above configuration, the temperature of the polishing pad of the polishing pad being polished is measured with the temperature sensor disposed in the vicinity of the polishing surface in the region where the object to be polished such as a wafer is pressed. Can do.

  In this case, the temperature of the portion where the temperature sensor is provided can be locally detected, and the temperature distribution of the polishing pad can be measured by performing this local temperature detection at a plurality of locations.

  Moreover, since the temperature sensor indirectly contacts the surface of the object to be polished through a very thin portion of the surface layer of the polishing pad, it is possible to monitor a temperature very close to the actual temperature of the object to be polished. .

  In the above configuration, as the temperature sensor, a contact type temperature sensor such as a thermocouple or a thermistor is suitable. In addition to the contact type temperature sensor, there are a platinum resistance thermometer, a copper resistance thermometer, an IC temperature sensor, a crystal thermometer, and the like.

  In the polishing pad having the above configuration, it is preferable that the housing portion is formed in a groove shape extending from the center side to the outer diameter side on the back surface side of the polishing pad, and the temperature sensor is housed and fixed in the housing portion.

  According to this configuration, not only the temperature sensor can be easily provided, but also the signal line of the temperature sensor is guided to the center side of the polishing pad, and other electronic members, for example, the polishing surface side of the polishing pad or the surface plate By connecting to the rotary connector arranged at the position, the sensor signal of the temperature sensor can be continuously taken out constantly.

  Although the groove-shaped housing portion may be singular or plural, it is preferable that a plurality of temperature sensors are housed and fixed in the single groove-shaped housing portion at intervals in the radial direction. As described above, when a plurality of temperature sensors are arranged in a single housing portion, the temperatures at a plurality of locations in the same radial direction can be measured at a time, which is useful for accurate temperature distribution measurement.

  According to the present invention, the temperature of the portion of the polishing pad that is in contact with the object to be polished can be detected, and the temperature very close to the actual temperature of the object being polished can be measured.

  The best mode for carrying out the present invention will be described below with reference to the drawings. FIG. 1 is a schematic configuration diagram of a polishing apparatus equipped with a polishing pad according to the best embodiment.

  In FIG. 1, the polishing apparatus includes a lower surface plate 2 on which the polishing pad 1 of the present invention is mounted on the upper surface, and an upper surface plate 3 on which the wafer W as an object to be polished is held on the lower surface.

  The lower surface plate 2 rotates around the vertical axis, and its shaft portion 2a is linked to a motor 5 for the lower surface plate 2 via a transmission means such as a belt 4. A nozzle 6 for supplying a polishing slurry is disposed on the lower surface plate 2. The upper surface plate 3 is provided on the upper side of the lower surface plate 2, and the shaft portion 3 a is interlocked and connected to the motor 8 for the upper surface plate 3 through transmission means such as a belt 7.

  In the polishing pad 1, a contact-type temperature sensor 9 such as a thermocouple is embedded on the back surface (the lower surface in the figure) opposite to the polishing surface (front surface) side so as to be within the thickness of the polishing pad 1. Has been. On the other hand, a rotary connector 11 is disposed at the center of the polishing pad 1 on the polishing surface side for taking out a sensor signal of the temperature sensor 9. A connection structure between the temperature sensor 9 and the rotary connector 11 will be described later.

  Next, the structure of the polishing pad 1 is demonstrated based on FIG. 2 and FIG. FIG. 2 is a back view of the main part of the polishing pad 1, and FIG. 3 is a perspective view of the main part as viewed from below.

  As shown in FIGS. 2 and 3, a groove-shaped accommodation portion 12 extending in the radial direction from the central portion to the outer peripheral edge is formed on the back surface of the polishing pad 1, and the lead of the temperature sensor 9 is formed in the central portion. A through hole 13 is formed for drawing the wire 9a toward the polishing surface. The temperature sensor 9 and its lead wire (signal line) 9a are accommodated in the accommodating portion 12, and are fixed in the accommodating portion 12 by an adhesive or a filling resin (not shown).

  One or a plurality of temperature sensors 9 housed and fixed in the single housing portion 12 may be used. However, in the illustrated embodiment, three temperature sensors 9, 9, 9 are connected to each other in the single housing portion 12. They are arranged at intervals in the radial direction.

  The radial positions of these temperature sensors 9 are set according to the pressure contact position of the wafer W with respect to the polishing pad 1, and the radial distance D1 from the center of the polishing pad 1 to the temperature sensor 9 near the center is the wafer W. It corresponds to the innermost pressure contact position. A radial distance D2 to the temperature sensor 9 provided at the intermediate position in the radial direction of the polishing pad 1 corresponds to the pressure contact position at the center of the wafer W. A radial distance D3 to the temperature sensor 9 provided on the outer diameter side of the polishing pad 1 corresponds to the outermost pressure contact position of the wafer W. The lead wires 9 a of these temperature sensors 9 are led out from the housing portion 12 to the concave portion 13 on the center side.

  In the figure of the said embodiment, although the surface side which is the grinding | polishing side of the polishing pad 1 is made into the flat surface, the groove | channel or recessed part for hold | maintaining a slurry may be formed.

  Although not particularly illustrated, the polishing pad 1 has a layer structure in this embodiment, and generally includes a polishing layer on the front surface side and a base layer attached to the back surface side thereof.

  The polishing layer on the front side is a resin layer obtained by foaming and curing a foamable resin such as polyurethane. As the urethane polymer constituting the resin layer, any of a polyether urethane resin, a polyester urethane resin, a polyester ether urethane resin, and a polycarbonate urethane resin can be used. Examples of the polyol component used in the production of each urethane resin include polyoxyethylene glycol, polyoxypropylene glycol, polyoxytetramethylene glycol, polyethylene adipate, polypropylene adipate, polyoxytetramethylene adipate, and the like. Examples of the isocyanate component include 4,4'-diphenylmethane diisocyanate and 2,4-tolylene diisocyanate.

  The undercoat layer of the polishing pad is a non-woven fabric type soft layer impregnated with urethane or a foam type soft layer. As this soft layer, for example, a composition containing a urethane polymer and dimethylformamide and made into a foam by a wet coagulation method can be used. Alternatively, a composition containing a urethane polymer, a vinyl polymer such as a vinyl chloride polymer, a vinyl chloride-acetic acid copolymer, a vinyl chloride-vinyl acetate-vinyl alcohol terpolymer, and dimethylformamide is used. A foamed product obtained by a wet coagulation method can be used. The skin layer formed on the outer surface of the foam, particularly the surface on the polishing layer side, is preferably buffed so that a foamed structure appears on the surface.

  Next, the structure of the rotary connector 11 will be described with reference to FIG. FIG. 4 is a longitudinal side view of a portion where the rotary connector 11 is mounted.

  As described above, the through hole 13 is formed in the center on the polishing surface side of the polishing pad 1, and the lead wire 9 a of the temperature sensor 9 or the lead wire 9 a is connected to the inside of the through hole 13. The connection cable 14 is drawn.

  The rotary connector 11 is attached to the polishing surface side of the polishing pad 1 concentrically with the through hole 13. The rotary connector 11 uses a slip ring, and includes a mounting cylinder 22 having a wiring space 10 opened on the lower side, a rotating cylinder 16 made of an insulator fixed to the outer periphery of the mounting cylinder 22, and this rotation. The fixed case 18 is attached to the mounting cylinder 22 via the bearing 17 on the outer peripheral side of the cylinder 16. The mounting cylinder 22 is fixed to the polishing surface of the polishing pad 1 with an adhesive or the like. The wiring space 10 in the mounting cylinder 22 has an opening 15 in a part in the circumferential direction. The rotating cylinder 16 is integrally provided with a plurality of (three in the illustrated example) rings 19 made of metal having excellent conductivity, and a part of the ring 19 in the circumferential direction faces the opening 15 of the wiring space 10. It is exposed on the inner peripheral side. The connection cable 14 (or the lead wire 9a of the temperature sensor 9) is connected to the exposed portion of the ring 19 on the inner peripheral side. The fixed case 18 is provided with a plurality of terminals 20 corresponding to the rings 19, and brushes 21 that are in sliding contact with the rings 19 are connected to the terminals 20. Thereby, the lead wire 9a of each temperature sensor 9 is always connected to the corresponding terminal 20 of the rotary connector 11, and the sensor signal of the temperature sensor 9 can be taken out from the terminal 20 of the rotary connector 11. .

  In the above configuration, when polishing, the polishing pad 1 to which the temperature sensor 9 and the rotary connector 11 are attached is attached to the upper surface of the lower surface plate 2 by adhesion.

  A wafer W is held on the lower surface of the upper surface plate 3, and the wafer W is pressed against the polishing pad 1 on the lower surface plate 2 side. In this state, the lower surface plate 2 and the upper surface plate 3 are driven to rotate, and slurry is supplied from the nozzle 6 onto the polishing pad 1 to perform polishing.

  During the above polishing operation, the sensor signal of the temperature sensor 9 is input via the rotary connector 11 to a monitor device that is an external connection device, a control unit of the polishing device, or the like. In this case, the temperature sensor 9 detects the temperature of the surface portion in the accommodating portion 12 of the polishing pad 1, and the wafer W is positioned on the portion where the temperature sensor 9 is provided as shown in FIG. If it is, the temperature of the surface portion of the polishing pad 1 in contact with the wafer W is measured. Further, since the temperature sensor 9 is disposed in the vicinity of the surface (polishing surface) and only a very thin portion of the surface of the polishing pad 1 is interposed between the temperature sensor 9 and the wafer W, the actual temperature of the wafer W can be reduced. A temperature approximating the temperature will be measured.

  Further, when the plurality of temperature sensors 9 are provided at different positions as in the embodiment, the polishing pad 1 is processed by processing the sensor signal of each temperature sensor 9 in association with the position of the temperature sensor 9. The temperature distribution of the surface portion is obtained.

  The results shown in FIG. 5 were obtained by measuring the temperature with each temperature sensor 9 while actually polishing using the polishing pad 1 of the present invention. FIG. 5 is a temperature change diagram during polishing.

  The diameter of the lower surface plate 2 of the polishing apparatus is 200 mm, and therefore the polishing pad 1 is also 200 mm in diameter. As described above, the polishing pad 1 is provided with thermocouples as temperature sensors 9 at the radial distance D1, the radial distance D2, and the radial distance D3 from the center. Polishing continued for about 2 minutes.

  In the measurement result shown in FIG. 5, the detected temperature of each temperature sensor 9 shows the same rising tendency every time polishing progresses, but the detected temperature of the temperature sensor 9 of D2 is the highest, and the detected temperature of the temperature sensor 9 of D1. Is the lowest. This is because the temperature sensor 9 of D1 is closer to the center of the polishing pad 1 and the sliding speed relative to the wafer W is low, so the temperature does not rise. This is probably because the temperature rises due to contact with the wafer W in a wide range in the direction.

  From the measurement results shown in FIG. 5, it can be seen that each temperature sensor 9 accurately and locally detects the temperature of the portion where each is provided. Therefore, the temperature distribution of the surface portion of the polishing pad 1 can be obtained by processing the data of the temperature detected by each temperature sensor 9 in association with the position of each temperature sensor 9.

FIG. 6 is a temperature change diagram for showing the end point of polishing. In this experiment, polishing was performed for a longer time than in the case of FIG. In the measurement results, a state where the temperature rises gradually appears from 30 seconds to 50 seconds after the polishing is started, but an inflection point appears in the temperature change at the time T ₀ of about 90 seconds, from which the temperature changes. The ascending slope becomes steep. This is because the oxide film (SiO ₂ ) on the surface of the wafer W is polished at the beginning of polishing, but the temperature does not rise so much, but after 90 seconds, the oxide film disappears by polishing and the silicon substrate is exposed, and polishing is performed. This is probably because the surface state changes and the frictional resistance increases, causing the temperature to rise suddenly.

  In this way, it can be determined that the oxide film has disappeared when the detected temperature shifts from a gentle rising gradient to a steep rising gradient, and the polishing end point can be detected from the change in the detected temperature.

  Conventionally, in order to detect such an end point of polishing, a window hole is formed in the polishing pad in advance, and the surface state of the wafer is inspected using the reflection through the window hole, or a lower surface plate is used. The torque change of the motor that drives was inspected. In the present invention, since the inflection point of the temperature gradient appears clearly by accurate temperature measurement of the surface portion of the polishing pad 1, it is possible to detect the polishing end point.

  FIG. 7 is a temperature change diagram during polishing corresponding to a load. In this temperature measurement, polishing is performed by variously changing the load (pressure) applied to the wafer with respect to the polishing pad 1, and the temperature sensor 9 at a predetermined position in this case (provided at a position in contact with the central portion of the wafer W). The temperature detected by the D2 temperature sensor) was measured. From this experimental result, it can be seen that the higher the load, the higher the temperature. In addition, from the relationship between the temperature change mode and the load, how much load is applied, whether or not the polishing proceeds smoothly. I understand.

  In the above embodiment, a plurality of temperature sensors 9 are housed and fixed in a single groove-shaped housing portion 12, but a plurality of groove-shaped housing portions extending in different directions from the center are formed on the back surface side of the polishing pad 1. In addition, one or a plurality of temperature sensors may be housed and fixed in each housing portion. In this way, if a large number of temperature sensors are provided at various locations on the back surface of the polishing pad, a more detailed temperature distribution can be obtained.

  In the above-described embodiment, the rotation connector 11 is arranged on the polishing surface side of the polishing pad 1 and the sensor signal of the temperature sensor 9 is taken out. However, as another embodiment of the present invention, FIG. 8 and FIG. As described above, the rotation connector 11 may be provided on the shaft portion 2 a of the lower surface plate 2 on the back surface side of the polishing pad 1 to extract the sensor signal of the temperature sensor 9.

  That is, a wiring space 10 is formed in the lower surface plate 2 from the center portion of the upper surface to the inside of the shaft portion 2a. In this space 10, the lead wire 9a of the temperature sensor 9 or these lead wires 9a are connected. The connecting cable 14 is drawn. The wiring space 10 is provided with an opening 15 at a part in the circumferential direction, and the wiring space 10 communicates with the outside of the shaft portion 2 a through the opening 15. The rotary connector 11 is attached to a position corresponding to the opening 15 of the wiring space 10 in the radial direction, and the other configuration is the same as that of the above-described embodiment. Therefore, the description is omitted.

(Other embodiments)
As means for taking out the sensor signal of the temperature sensor 9, in addition to the illustrated rotary connector 11, a transmitter that wirelessly transmits the sensor signal or a memory device that temporarily stores the sensor signal may be used. The memory device may be downsized and provided on the polishing pad together with the temperature sensor.

  In the above-described embodiment, the groove-shaped housing portion is formed on the back surface of the polishing pad 1 and the temperature sensor 9 is housed. However, as another embodiment, the hole-shaped housing portion is formed to form the polishing pad. A temperature sensor may be provided inside.

  Of the sensor signals from the temperature sensor 9, only the sensor signal when the temperature sensor 9 is located in the region where the wafer W is pressed may be taken out.

  The present invention is useful as a polishing pad used for chemical mechanical polishing.

1 is a schematic configuration diagram of a polishing apparatus equipped with a polishing pad according to a best embodiment of the present invention. The back view of the principal part of the said polishing pad. The perspective view which looked at the principal part of the said polishing pad from the lower side. The vertical side view of a rotation connector mounting part. The temperature change figure at the time of grinding | polishing. Temperature change over time. The temperature change figure at the time of polish corresponding to load. The schematic block diagram of the grinding | polishing apparatus equipped with the polishing pad which concerns on other embodiment of this invention. FIG. 9 is a longitudinal side view of the rotary connector mounting portion of the embodiment of FIG. 8.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Polishing pad 2 Lower surface plate 3 Upper surface plate 9 Temperature sensor 9a Lead wire 11 Rotating connector 12 Housing part

Claims (5)

In a polishing pad for polishing an object to be polished,
A polishing pad, wherein a temperature sensor housing portion is formed so as to be close to a polishing surface, and the temperature sensor is disposed in the housing portion.   2. The polishing pad according to claim 1, wherein the housing portion is formed in a groove shape extending from the center side to the outer diameter side on the back surface side of the polishing pad, and the temperature sensor is housed and fixed in the housing portion.   The polishing pad according to claim 2, wherein a plurality of temperature sensors are housed and fixed in the single groove-shaped housing portion at intervals in the radial direction.   The polishing pad according to any one of claims 1 to 3, wherein the signal line of the temperature sensor is connected to a rotary connector disposed on the polishing surface side of the polishing pad.   The polishing pad according to claim 1, wherein the signal line of the temperature sensor is connected to a rotary connector provided on a surface plate on which the polishing pad is mounted.

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