JP2006216895A - Semiconductor wafer polishing device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To improve yields by accurately grasping the temperature of the surface of a semiconductor wafer to be dry-polished to thereby enable the operational management of dry polish for preventing the temperature from reaching the level that causes defects. <P>SOLUTION: A hollow part 28 is formed at a rotation axis 22 of a polish unit 20 and the rotation center of a polish wheel 24 across both of them. A non-contact temperature sensor 40 is inserted into the hollow part 28 while a sensor 42 is near the opening on the polish wheel 24 side, and adjoins the surface of the semiconductor wafer W to be polished. A control unit 50 determines whether the temperature detected by the temperature senser 40 exceeds a detected allowable temperature, and proceeds with polishing or performs feedback control for retracting the polish unit 20 based on the content of determination. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a semiconductor wafer polishing apparatus, and more particularly to a dry polishing apparatus that polishes a polishing material in which abrasive grains are dispersed in felt while pressing the polishing material against a surface to be polished of the semiconductor wafer.

  A semiconductor chip having an electronic circuit such as an IC or LSI formed on its surface is now indispensable for downsizing various electric / electronic devices. A semiconductor chip is a process in which a rectangular region of a lattice shape is defined by cutting lines called streets on the surface of a disk-shaped semiconductor wafer, an electronic circuit is formed in these rectangular regions, and then the semiconductor wafer is divided along the streets. Manufactured by.

  In such a manufacturing process, before the semiconductor wafer is divided into semiconductor chips, the back surface opposite to the device surface on which the electronic circuit is formed is ground by a grinding apparatus such as a grinder. The purpose of grinding the back surface is to further reduce the size and weight of the electronic device and to improve the heat dissipation and maintain the performance. For example, the initial thickness is 600 μm to 200 to 100 μm or less, or It is performed to the extent that the thickness is 50 μm or less.

  However, when the back surface of the semiconductor wafer is ground, processing strain often remains on the back surface, which causes a problem that the bending strength of the semiconductor chip is lowered and the semiconductor wafer is easily broken. Therefore, in order to solve this problem, it has been practiced that the back surface after grinding is further slightly polished (for example, about 1 to 5 μm) to remove the processing distortion to obtain a final product.

  Conventionally, chemical etching using a predetermined chemical has been mainly employed as a polishing method for removing such processing strain. However, this method has a problem in that it is inferior in productivity and waste liquid treatment in consideration of environmental pollution, which requires labor and cost. In view of this, the present applicant has proposed a dry polishing apparatus that polishes a polishing material in which abrasive grains are dispersed in a felt while pressing it against the back surface of a semiconductor wafer (Patent Documents 1 and 2).

JP 2003-188118 A Japanese Patent Laid-Open No. 2003-236752

  According to the polishing tool described in Patent Document 1, since it is dry polishing that does not use water such as water or slurry, the process is simplified and productivity is maintained, and it is freed from problems such as waste liquid treatment. There are advantages such as. However, because it is a dry type, frictional heat is generated by polishing. For example, when the temperature rises to around 100 ° C., the back surface, which is the polished surface of the semiconductor wafer, is overheated and burnt, so-called surface burning occurs. In some cases, the wafer itself was damaged. In addition, such overheating may cause problems such as melting the protective tape made of vinyl chloride or the like that is usually affixed to the surface of the semiconductor wafer, contaminating the surface, or preventing wire bonding to the electronic circuit from conducting. Met.

  Therefore, it has been studied to suppress an increase in frictional heat by blowing air on the back surface of the semiconductor wafer and cooling it, and the above-mentioned patent document 2 discloses a concrete example of this. However, even if the friction surface of the semiconductor wafer is air-cooled by using the means described in the document 2, there is a case where the temperature at which the above problem occurs, that is, the overheating temperature may be reached. For example, the abrasive is worn and thinned, the elasticity of the abrasive is lowered, and the force for pressing the semiconductor wafer becomes too strong, or the support member attached with the abrasive hits the back surface of the semiconductor wafer. Then, it was supposed to reach an overheating temperature.

  Therefore, the present invention accurately grasps the temperature of the surface to be polished that generates heat due to friction when dry polishing a semiconductor wafer, and thereby can perform operation management so that the surface to be polished does not always reach the overheating temperature, Accordingly, an object of the present invention is to provide a semiconductor wafer polishing apparatus capable of improving the yield.

  The present invention is a polishing apparatus for polishing a surface to be polished of a semiconductor wafer held on a chuck table by dry polishing means, the polishing means comprising a rotating shaft, a driving source for rotating the rotating shaft, and a rotating shaft. And a polishing wheel having a polishing surface that is brought into contact with the surface to be polished of the semiconductor wafer, and a hollow portion is formed at the rotation shaft and the rotation center of the polishing wheel. In addition, a non-contact temperature sensor is inserted in a state where the sensor portion is arranged near the opening on the polishing wheel side.

  According to the polishing apparatus of the present invention, the surface to be polished is polished by bringing the polishing surface of the rotating polishing wheel into contact with the surface to be polished of the semiconductor wafer held on the chuck table. Here, it is assumed that the hollow portion formed at the rotation shaft and the rotation center of the polishing wheel is operated on the surface to be polished of the semiconductor wafer. In this operating state, the sensor portion of the temperature sensor inserted in the hollow portion is close to the surface to be polished of the semiconductor wafer, and the temperature of the surface to be polished is detected by the temperature sensor. Since the sensor part of the temperature sensor is close to the surface to be polished, the temperature of the surface to be polished can be accurately detected, and by constantly managing the detected temperature, it becomes an overheating temperature that causes problems such as surface burning. The semiconductor wafer can be dry-polished at a temperature that does not reach it.

  Providing a control means for feedback-controlling the polishing means based on the temperature detected by the temperature sensor is a preferred form for automating the operation management of the present invention. As a specific operation of the feedback control performed by the control means, the polishing means presses the polishing wheel against the surface to be polished of the semiconductor wafer held by the chuck table or reversely separates the polishing wheel. In this configuration, it is determined whether or not the temperature detected by the temperature sensor exceeds a predetermined allowable temperature. If the temperature exceeds the allowable temperature, the feed mechanism is Is operated to move away from the semiconductor wafer to the retracted position, and polishing is stopped.

  The allowable temperature in this case is a temperature slightly lower than the above-described overheating temperature, that is, a temperature at which the surface to be polished of the semiconductor wafer is burnt or the protective tape affixed to the surface is melted. The temperature at which polishing is performed to the maximum extent within a range where the malfunction does not occur reliably. According to the above control, the surface to be polished of the semiconductor wafer can be prevented from reaching the overheating temperature, and problems such as surface burn can be reliably prevented.

  As another control mode, in the configuration including the feeding mechanism, the control unit determines whether or not the temperature detected by the temperature sensor is within a predetermined allowable temperature range, and the temperature detected by the temperature sensor is When the upper limit of the allowable temperature range is exceeded, the feed mechanism is operated so that the polishing wheel presses against the semiconductor wafer held on the chuck table, while the upper limit of the allowable temperature range is exceeded. The feed mechanism is operated so as to loosen the pressing force of the polishing wheel against the semiconductor wafer held on the chuck table, thereby maintaining the temperature detected by the temperature sensor within the allowable temperature range. The allowable temperature range in this case is a temperature range in which polishing is reliably performed, and the upper limit is equivalent to the allowable temperature set by the former control, and polishing is sufficiently performed even at the lower limit.

  In this form, when the temperature detected by the temperature sensor is below the upper limit of the allowable temperature range, the polishing wheel presses the semiconductor wafer and polishing proceeds. As a result, the polishing wheel slightly moves in a direction away from the semiconductor wafer, and the pressing force of the polishing wheel against the semiconductor wafer is relaxed. Then, the temperature of the semiconductor wafer decreases, and when the temperature falls below the upper limit of the temperature range detected by the temperature sensor, the polishing wheel is operated so as to press the semiconductor wafer. That is, this control is such that the detected temperature of the temperature sensor is polished within the allowable temperature range, and if it exceeds, the pressing force of the polishing wheel is loosened, and these two states may be repeated, and therefore always within the allowable temperature range. With dry polishing.

  According to the present invention, when a semiconductor wafer is dry-polished, the temperature of the surface to be polished can be accurately detected, and thus operation management can be performed so that the surface to be polished does not always reach the overheating temperature. Therefore, the yield can be improved.

Hereinafter, an embodiment of the present invention will be described with reference to the drawings.
[1] Configuration of Apparatus FIG. 1 shows an entire dry polishing apparatus according to an embodiment, and reference numeral 10 in the figure denotes a base on which various mechanisms are mounted. The base 10 is installed in a horizontally long state and has a rectangular parallelepiped table 11 which is the main body of the base 10 and extends vertically upward from one end in the longitudinal direction of the table 11 (end on the back side in FIG. 1). And wall portion 12.

  This polishing apparatus is an apparatus that removes processing distortion by further polishing the back surface of a disk-shaped semiconductor wafer W having an electronic circuit formed on the front surface and the back surface ground to a thickness close to that of a product by a grinder or the like. is there. On the surface of the semiconductor wafer W, a protective tape T made of vinyl chloride or the like for protecting the electronic circuit is attached.

On the table 11 of the base 10, the wall 12 side from the substantially middle part in the longitudinal direction is a polishing area 11A, and the opposite side supplies the semiconductor wafer W before polishing to the polishing area 11A, and the semiconductor after polishing A supply / recovery area 11B for collecting the wafer W is used.
Hereinafter, various mechanisms provided in this apparatus will be described separately for those provided in the polishing area 11A and those provided in the supply / recovery area 11B.

(A) Mechanism of Polishing Area 11A A rectangular recess 13 is formed in the polishing area 11A, and a rectangular stage 14 is disposed on the bottom surface of the recess 13 in the longitudinal direction of the table 11 (hereinafter referred to as Y). (Referred to as a direction). The table 11 is slidably attached to a guide rail disposed in the stage 14 and extending in the Y direction, and is reciprocated in the same direction by an appropriate drive mechanism (none of which is shown).

  One end of bellows 15 and 16 is attached to both ends of the stage 14 in the moving direction, and the other end of these bellows 15 and 16 is the inner surface of the wall portion 12 and the recess 13 facing the wall portion 12. Are attached to the inner wall surface of each. These bellows 15 and 16 cover a slit (not shown) formed on the bottom surface of the recess 13 in order to connect the stage 14 to the guide rail, and prevent polishing debris from falling into the stage 14. Thus, the stage 14 expands and contracts with the movement of the stage 14 and does not hinder the movement.

  On the stage 14, a disk-shaped chuck table 17 having a vertical direction (hereinafter referred to as “Z direction”) as a rotation center and a horizontal upper surface is rotatably provided. The semiconductor wafer W is placed horizontally on the chuck table 17 with the back surface (surface to be polished) facing upward. The chuck table 17 is rotated in one direction or both directions by a rotation drive mechanism (not shown) provided in the stage 14.

  In this case, the chuck system of the chuck table 17 is a known vacuum chuck. That is, the chuck table 17 is formed of a porous material such as porous ceramics, and an air suction port of a vacuum device (not shown) provided in the table 11 is connected to the back surface of the chuck table 17 so that the vacuum device is When operated, the semiconductor wafer W is attracted and held on the chuck table 17.

  A polishing unit (polishing means) 20 is disposed above the movement line of the chuck table 17. The polishing unit 20 is supported on the wall 12 of the base 10 via a feed mechanism 30 so as to be movable up and down in the Z direction. The feed mechanism 30 includes a pair of guide rails 31 that are fixed to the inner surface of the wall portion 12 that is a vertical surface and that extend in the Z direction, and a slider 32 that is slidably attached to the guide rails 31. And a slider drive mechanism 33 that reciprocates the slider 32 along the guide rail 31.

  The slider drive mechanism 33 is arranged in the space between the slider 32 and the wall portion 12 with the axial direction being parallel to the Z direction, and the upper end portion and the lower end portion are bearings 34 and 35 provided on the wall portion 12, respectively. And a pulse motor 37 that rotationally drives the screw rod 36. The screw rod 36 is threadedly engaged with a bracket (not shown) formed on the back surface of the slider 32 so as to pass therethrough. Thus, the slider 32 moves downward (feed direction) when the pulse motor 37 rotates forward and the screw rod 36 rotates in one direction, and the pulse motor 37 reverses and the screw rod 36 moves in the reverse direction. When rotated, it moves upward (withdrawal direction).

  The polishing unit 20 is fixed to the front surface of the slider 32 facing the table 11 via a block 32a. As shown in FIGS. 3 and 4, the polishing unit 20 is passed through a block 32a with the axial direction along the Z direction, and a cylindrical housing 21 fixed to the block 32a. A rotary shaft 22 rotatably inserted therein, a servo motor (drive source) 23 that rotationally drives the rotary shaft 22, and a polishing wheel 24 attached to the lower end of the rotary shaft 22 that protrudes downward from the housing 21 It has.

  The rotary shaft 22 is rotatably supported in the housing 21 by a known air bearing mechanism that supports a radial / thrust direction with a uniform minute gap between the rotary shaft 22 and the inner surface of the housing 21. A thrust bearing 22 a is formed on the outer peripheral surface of the lower end portion of the rotary shaft 22 in the housing 21, and the thrust bearing 22 a is rotated by being fitted into an annular groove 21 a formed on the inner peripheral surface of the housing 21. The thrust direction of the shaft 22 is supported.

  The servo motor 23 in this case is a known permanent magnet type, and is a cylindrical rotor 23a made of a permanent magnet integrally fixed to the outer peripheral surface of the upper end of the rotating shaft 22, and a housing in a state surrounding the rotor 23a. The rotor 23a rotates when a coil voltage of the stator 23b is applied, thereby rotating the rotating shaft 22 around the axis. .

  The rotating shaft 22 has a disk-shaped wheel mount 22b at the lower end thereof. The wheel mount 22b is concentric with the center of rotation of the rotating shaft 22, and, as shown in FIG. 3, bolt insertion holes 22c are formed through it at a plurality of equally spaced locations in the circumferential direction. A through hole 22 d extending along the axial direction is formed at the rotation center of the rotation shaft 22. The upper end of the rotating shaft 22 protrudes from the housing 21, and the protruding portion and the gap between the rotating shaft 22 and the housing 21 are detachably attached to the upper end surface of the housing 21 by means such as screwing. It is covered with 21a.

  The grinding wheel 24 has the same diameter as the wheel mount 22b, and is detachably attached to a mount surface that is the lower surface of the wheel mount 22b. As shown in FIG. 3, the polishing wheel 24 is formed by fixing a felt grindstone 26 that is also disk-shaped and actually polishes the back surface of the semiconductor wafer W on one surface of a disk-shaped support plate 25.

  On one surface of the support plate 25 (the surface on which the felt grindstone 26 is not fixed), there are formed a plurality of screw holes 25a that do not pass through and match the plurality of bolt insertion holes 22c of the wheel mount. At the center of the grinding wheel 24, a through hole 24a having the same diameter as the through hole 22d of the rotary shaft 22 is formed. In this case, the outer diameter of the polishing wheel 24 is approximately the same as or about 1.5 times the diameter of the semiconductor wafer W, but the dimensions are not limited thereto.

  The support plate 25 and the felt grindstone 26 have the same diameter, are stacked concentrically with each other, and are bonded to each other by, for example, an epoxy resin adhesive. The felt grindstone 26 is formed by impregnating abrasive grains in a dispersed state in a felt and hardening the whole with an appropriate adhesive.

  As the felt material, synthetic fibers such as polyester and nylon and natural fibers such as wool, cotton and hemp are used, and are molded to have an appropriate hardness and density. Moreover, as an abrasive grain, what consists of a silica, an alumina, a diamond, etc. is used, The particle diameter shall be about 0.01-100 micrometers, for example. The felt grindstone 26 is described in detail in Japanese Patent Application Laid-Open Nos. 2002-283243 and 2003-188118 in which the invention of the present applicant is described.

  In the grinding wheel 24, the support plate 25 is aligned with the mounting surface of the wheel mount 22b of the rotary shaft 22, the screw hole 25a is aligned with the bolt insertion hole 22c, and the bolt 27 passed through the bolt insertion hole 22c is screwed into the screw hole 25a. By fastening with, it is attached to the wheel mount 22b.

  In this attached state, the polishing wheel 24 is concentric with the rotating shaft 22, and the through hole 24 a of the polishing wheel 24 communicates with the through hole 22 d of the rotating shaft 22. Here, the two continuous through holes 22 d and 24 a are collectively referred to as a hollow portion 28. The grinding wheel 24 rotates integrally with the rotary shaft 22, but the axis of the rotation center extends in the Z direction and is orthogonal to the movement locus of the rotation center of the chuck table 17 that moves in the Y direction together with the stage 14. Further, the polishing unit 20 is fixed to the slider 32.

  As will be described later, on the chuck table 17, the semiconductor wafer W with the back surface facing upward is placed on the chuck table 17 in a concentric state. Therefore, the positional relationship between the semiconductor wafer W held on the chuck table 17 and the polishing wheel 24 is such that both rotation centers extending in the Z direction are parallel in the plane in the Y direction.

  Here, the operation of polishing the back surface of the semiconductor wafer W by the polishing unit 20 will be briefly described. By the stage 14, the chuck table 17 is arranged at the polishing position below the polishing wheel 24, and as shown in FIG. While the polishing wheel 24 is positioned so as to cover the semiconductor wafer W, the chuck table 17 is rotated, and while the polishing wheel 24 is rotated, the feed mechanism to the semiconductor wafer W held and rotated on the chuck table 17 is rotated. 30, the polishing unit 20 is slowly lowered at a predetermined speed.

  Thereby, the lower surface of the felt grindstone 26 of the rotating polishing wheel 24 presses the back surface of the semiconductor wafer W with a predetermined load, and the back surface is polished. During this polishing, frictional heat is generated on the back surface of the semiconductor wafer W because it is dry polishing by the felt grindstone 26.

  As shown in FIGS. 2 to 4, a temperature sensor 40 that detects frictional heat generated on the back surface of the semiconductor wafer W is inserted into the hollow portion 28 of the polishing unit 20. The temperature sensor 40 is a non-contact type such as an infrared sensor, and is a thin tube 41, a sensor unit 42 fixed to the tip of the thin tube 41, and passed through the thin tube 41 to be protected and detected by the sensor unit 42. And a lead wire 43 for outputting a temperature signal to be output to the outside.

  The temperature sensor 40 is inserted into the hollow portion 28 in a state where the sensor portion 42 is disposed in the vicinity of the opening of the hollow portion 28 on the polishing wheel 24 side, and the end of the narrow tube 41 opposite to the sensor portion 42 is attached to the cap 21a. It is supported. In order to set the temperature sensor 40 in the polishing unit 20, as shown in FIGS. 2 and 4, the end of the thin tube 41 is fixed to the cap 21a in advance, and the lead wire 43 is pulled out to the outside. After inserting 42 and the thin tube 41 into the hollow portion 28, the cap 21 a is attached to the housing 21.

  In FIG. 4, the sensor unit 42 is positioned near the lower end of the through hole 22 d of the rotating shaft 22, but the sensor unit 42 may be disposed in the through hole 24 a of the polishing wheel 24 below this. Further, the thin tube 41 and the sensor unit 42 are inserted so as not to contact the rotating shaft 22.

  As shown in FIG. 1, the polishing apparatus has a control means 50. The control means 50 is supplied with a determination unit 51 for determining whether or not the temperature detected by the temperature sensor 40 exceeds a predetermined allowable temperature, and a determination signal of the determination unit 51 is sent according to the determination contents. And a control unit 52 that rotates the pulse motor 37 of the mechanism 30 forward or backward. By this control means 50, the polishing unit 20 is feedback-controlled based on the temperature detected by the temperature sensor 40.

  The allowable temperature is that when the back surface of the semiconductor wafer W polished by the polishing wheel 24 generates heat due to friction, the back surface of the semiconductor wafer W is burnt, or the protective tape T affixed to the surface is melted. This is a temperature that is slightly lower than the temperature at which defects occur, and is the temperature at which polishing is performed to the maximum extent within a range that does not cause product defects after polishing. Specifically, the temperature is about 80 to 100 ° C.

The specific operation of the feedback control performed by the control means 50 is as follows.
That is, when the determination unit 51 determines that the temperature detected by the temperature sensor 40 is below the allowable temperature, the control unit 52 maintains the normal rotation state of the pulse motor 37 of the feed mechanism 30. As a result, the polishing unit 20 continues to descend and polishing of the back surface of the semiconductor wafer W is continued.

  Next, when the determination unit 51 determines that the temperature detected by the temperature sensor 40 has exceeded the allowable temperature, the control unit 52 reverses the pulse motor 37 of the feed mechanism 30 by a predetermined step. As a result, the polishing unit 20 rises to a retracted position where the polishing wheel 24 is separated from the semiconductor wafer W by a predetermined distance and stops there. When the detection signal (detection temperature) of the temperature sensor 40 is continuously supplied to the determination unit 51 and it is determined that the temperature is lower than the allowable temperature, the control unit 52 receives the determination signal and rotates the pulse motor 37 in the normal direction again. As a result, the polishing unit 20 is lowered, and the felt grindstone 26 of the polishing wheel 24 presses the back surface of the semiconductor wafer W to resume polishing.

(B) Mechanism of Supply / Recovery Area 11B As shown in FIG. 1, the supply / recovery area 11B set on the table 11 of the base 10 has a rectangular shape that is narrower and deeper than the recess 13. A recess 18 is formed, and a transfer mechanism 60 in which a fork 60b is attached to the tip of a two-joint link-type horizontal swivel arm 60a that can be moved up and down is installed at the bottom of the recess 18.

  Then, on the table 11 around the recess 18, the suction plate 63 b is attached to the tip of the cassette 61, the alignment table 62, and the horizontal turning arm 63 a of the first node in a counterclockwise direction as viewed from above. The recovery arm 64 having the same structure as the supply arm 63 and the supply arm 63, the horizontal turning arm 64a and the suction plate 64b, the spinner type cleaning device 65, and the cassette 66 are arranged.

  The cassette 61, the alignment table 62, and the supply arm 63 are means for supplying the semiconductor wafer W whose back surface is to be polished to the chuck table 17, and the recovery arm 64, the cleaning device 65, and the cassette 66 are the semiconductor wafer W after polishing. Is a means for recovering from the chuck table 17. Although the two cassettes 61 and 66 have the same structure, they will be referred to as a supply cassette 61 and a recovery cassette 66 according to applications. These cassettes 61 and 66 are for accommodating and carrying a plurality of semiconductor wafers W, and are set at predetermined positions on the table 11.

  In the supply cassette 61, a plurality of semiconductor wafers W whose back surfaces are to be polished by the polishing apparatus are accommodated in a stacked state. The transfer mechanism 60 takes out one semiconductor wafer W from the supply cassette 61 by raising / lowering and turning the arm 60a and gripping the fork 60b, and further, with the back surface of the semiconductor wafer W facing up, It has a function of placing on the alignment table 62.

  The semiconductor wafer W placed on the alignment table 62 is placed in a state determined at a certain position. The supply arm 63 sucks the semiconductor wafer W placed on the alignment table 62 onto the suction plate 63b, rotates the arm 63a, and places the semiconductor wafer W on the chuck table 17, and then performs a suction operation. By stopping the semiconductor wafer W, the semiconductor wafer W is placed on the chuck table 17. By placing the semiconductor wafer W positioned by the alignment table 62 on the chuck table 17 at the supply / recovery position, the semiconductor wafer W and the chuck table 17 are concentric.

  The recovery arm 64 has a function of adsorbing the semiconductor wafer W on the chuck table 17 whose back surface has been polished by the polishing unit 20 to the suction plate 64b, and rotating the arm 64a to transfer the semiconductor wafer W into the cleaning device 65. Have The cleaning device 65 has a function of rotating the semiconductor wafer W to shake off and remove moisture after the semiconductor wafer W is washed with water. The semiconductor wafer W cleaned by the cleaning device 65 is transferred and accommodated in the collection cassette 66 by the transfer mechanism 60.

  A chuck table cleaning nozzle 67 for cleaning the chuck table 17 by spraying cleaning water onto the chuck table 17 is disposed between the supply arm 63 and the recovery arm 64. As described above, when the semiconductor wafer W is placed on the chuck table 17 by the supply arm 63 and the semiconductor wafer W on the chuck table 17 is recovered by the recovery arm 64, the stage 14 is supplied to the supply / recovery area. Move to the 11B side and stop at the supply / recovery position. The supply / recovery position is a position where the line connecting the center of the semiconductor wafer W sucked by the suction plates 63a and 64a of the arms 63 and 64 and the rotation center of the chuck table 17 is along the Z direction.

  The polishing position of the semiconductor wafer W by the polishing unit 20 is a position moved by a predetermined distance from the supply / recovery position toward the wall 12, and the semiconductor wafer W on the chuck table 17 is moved to the polishing position by the movement of the stage 14. And the supply / recovery position. The chuck table 17 is cleaned by the chuck table cleaning nozzle 67 at the supply / recovery position.

[2] Operation of Apparatus Next, a method for using the polishing apparatus according to an embodiment having the above-described configuration and an operation thereof will be described below.
First, the operator sets a supply cassette 61 containing a plurality of semiconductor wafers W whose back surface is to be polished and an empty collection cassette 66 at predetermined positions in the supply / collection area 11B.

When the above preparation is completed, the semiconductor wafer W is polished in the following order.
One semiconductor wafer W is taken out from the supply cassette 61 by the transfer mechanism 60, and the semiconductor wafer W is further placed on the alignment table 62 with the back surface facing upward by the transfer mechanism 60.

  Next, the semiconductor wafer W placed on the alignment table 62 is placed concentrically by the supply arm 63 on the chuck table 17 previously stopped at the supply / recovery position with the back surface facing up. The The semiconductor wafer W is sucked and held on the chuck table 17 by a vacuum device.

  Next, the stage 14 moves to the wall 12 side, and the chuck table 17 stops at the polishing position. Here, the chuck table 17 is rotated to rotate the semiconductor wafer W. At the same time, the polishing wheel 24 of the polishing unit 20 that has been waiting in advance is rotated by the servo motor 23 and the pulse motor 37 is rotated forward so that the polishing unit 20 is slowly lowered by the feed mechanism 30 at a predetermined speed. Let The rotation direction of the chuck table 17 may be the same direction as the polishing wheel 24 or may be the opposite direction.

  When the polishing unit 20 is lowered, the felt grindstone 26 of the rotating polishing wheel 24 presses the back surface of the rotating semiconductor wafer W with a predetermined load, and the back surface is gradually polished. The positional relationship between the semiconductor wafer W and the polishing wheel 24 during polishing is such that the entire back surface of the semiconductor wafer W is uniformly polished. For example, as shown in FIG. 4, with respect to the rotation center O1 of the semiconductor wafer W, the rotation center O2 of the polishing wheel 24 is on the wall 12 side (right side in FIG. 4) along the Y direction. A state in which the distance is slightly shorter than that of the semiconductor wafer W and the lower opening of the hollow portion 28 of the polishing unit 20 faces the back surface of the semiconductor wafer W is employed.

  When the polishing state in which the felt grindstone 26 of the polishing wheel 24 presses the back surface of the semiconductor wafer W has elapsed for a predetermined time (substantially polishing time), the pulse motor 37 is reversed and the polishing unit 20 is waited by the feed mechanism 30. Raise to position. Next, the servo motor 23 is stopped to stop the rotation of the polishing wheel 24, and the rotation of the chuck table 17 is also stopped to finish the polishing. Incidentally, the polishing amount of the back surface of the semiconductor wafer W is, for example, 1 to 5 μm.

As an example of suitable conditions for the above polishing operation, the rotation speed of the polishing wheel 24 by the servo motor 23 is 4000 to 7000 RPM, the rotation speed of the chuck table 17 is 100 to 300 RPM, and the polishing unit 20 is lowered by the feed mechanism 30. The speed is 1 to 2 μm / min, and the load at which the felt grindstone 26 of the polishing wheel 24 presses the back surface of the semiconductor wafer W is 100 to 300 g / cm ² . In addition, an operation of moving the semiconductor wafer W in the radial direction by reciprocating the stage 14 in the Y direction during polishing may be combined.

  Next, the operation of recovering the polished semiconductor wafer W will be described. First, the stage 14 is moved to the supply / recovery position, the operation of the vacuum device is stopped, and the semiconductor wafer W is held on the chuck table 17. Release the state. Next, the semiconductor wafer W is transferred into the cleaning device 65 by the recovery arm 64. Here, the semiconductor wafer W is washed with water and then rotated to remove moisture.

  Next, the semiconductor wafer W is transferred and accommodated in the collection cassette 66 by the transfer mechanism 60. In addition, after the semiconductor wafer W is removed from the chuck table 17 by the recovery arm 64, cleaning water flows from the chuck table cleaning nozzle 67 toward the chuck table 17 on the stage 14 stopped at the supply / recovery position. The chuck table 17 is cleaned by spraying.

  The above is a cycle for polishing, cleaning, and collecting one semiconductor wafer W. When this cycle is repeated, all the semiconductor wafers W in the supply cassette 61 are polished and accommodated in the collection cassette 66. The operator collects the collection cassette 66 and transports the plurality of polished semiconductor wafers W to the next production process. Then, a supply cassette 61 that accommodates a plurality of new semiconductor wafers W whose surfaces are to be polished and an empty recovery cassette 66 are set at predetermined positions in the supply / recovery area 11B, and the polishing operation is subsequently performed in the above cycle. . Note that the empty supply cassette 61 may be used as the recovery cassette 66.

Next, the operation of the temperature sensor 40 and the control means 50 will be described.
During the polishing, the temperature detected by the temperature sensor 40 is supplied to the determination unit 51 of the control means 50. However, since the sensor unit 42 is close to the back surface of the semiconductor wafer W, the detected temperature is It can be regarded as temperature. That is, the temperature sensor 40 accurately detects the temperature of the back surface of the semiconductor wafer W.

  The determination unit 51 of the control unit 50 determines whether or not the temperature detected by the temperature sensor 40 exceeds the allowable temperature. If it is determined that the temperature is lower than the allowable temperature, the control unit 52 determines that the feed mechanism 30 The forward rotation state of the pulse motor 37 is maintained. As a result, the polishing unit 20 continues to descend, and the back surface of the semiconductor wafer W is continuously polished.

  When the determination unit 51 determines that the temperature detected by the temperature sensor 40 has exceeded the allowable temperature, the control unit 52 that has received the signal reverses the pulse motor 37 of the feed mechanism 30 by a predetermined step. As a result, the polishing unit 20 moves up to the retracted position, issues a signal to the operator so that the operator knows it, and stops there. The retreat position may be the same position as the standby position.

  When the detection signal (detection temperature) of the temperature sensor 40 is continuously supplied to the determination unit 51 and it is determined that the temperature falls below the allowable temperature, the control unit 52 receives the signal and rotates the pulse motor 37 forward again. As a result, the polishing unit 20 is lowered, and the felt grindstone 26 of the polishing wheel 24 presses the back surface of the semiconductor wafer W to resume polishing. The polishing is finished by raising the polishing unit 20 when the above-described substantial polishing time has elapsed.

[3] Effect of the apparatus According to the polishing apparatus of the present embodiment, when the temperature detected by the temperature sensor 40, that is, the temperature of the back surface of the semiconductor wafer W exceeds the allowable temperature by the action of the control means 50, the feeding mechanism 30 The polishing wheel 24 is separated from the semiconductor wafer W to the retracted position. For this reason, polishing in a state exceeding the allowable temperature is not performed, and an excessive increase in frictional heat generated on the back surface of the semiconductor wafer W can be avoided in advance. When the temperature detected by the temperature sensor 40 is lower than the allowable temperature, the polishing wheel 24 is pressed against the semiconductor wafer W by the feed mechanism 30 and the polishing state is maintained.

  By such a combination of controls, dry polishing can be performed while always preventing the temperature of the back surface of the semiconductor wafer W from reaching the overheating temperature at which defects such as surface burning occur. As a result, it is possible to prevent a problem that the back surface of the semiconductor wafer W is burnt or the protective tape T attached to the front surface is melted, thereby improving the yield.

[4] Another form of control According to the control means 50 in the above embodiment, the determination unit 51 determines whether or not the temperature detected by the temperature sensor 40 exceeds a predetermined allowable temperature (for example, 90 ° C.), and the allowable temperature. Is exceeded, the polishing unit 20 is raised by the feed mechanism 30 to separate the polishing wheel 24 from the semiconductor wafer W to the retracted position, but the following control different from this may be performed.

  That is, the determination unit 50 of the control unit 50 determines whether or not the detected temperature of the temperature sensor 40 is within a predetermined allowable temperature range, and the detected temperature is always maintained within the allowable temperature range. The feeding mechanism 30 is controlled to adjust the pressing force of the polishing wheel 24 against the semiconductor wafer W. The allowable temperature range in this case is a temperature range in which polishing is reliably performed, and the upper limit is equivalent to the allowable temperature set by the control of the above embodiment, and the polishing is sufficiently performed even at the lower limit. . For example, 70 to 80 ° C. is the allowable temperature range.

  According to this control, when the temperature detected by the temperature sensor 40 is below the upper limit of the allowable temperature range, the polishing unit 20 is lowered by the feed mechanism 30 and the back surface of the semiconductor wafer W is pressed by the polishing wheel 24. Polishing is performed. During polishing, if the determination unit 51 determines that the upper limit of the allowable temperature range has been exceeded, the pulse motor 37 is slightly reversed to raise the polishing unit 20 slightly. As a result, the pressing force of the polishing wheel 24 against the semiconductor wafer W is loosened.

  Then, the temperature of the semiconductor wafer W decreases, and when the temperature detected by the temperature sensor 40 falls below the upper limit of the allowable temperature range by the determination unit 51, the pulse motor 37 is rotated forward, and the polishing unit 20 is slightly moved by the feed mechanism 30. Lower. Thereby, the pressing force of the polishing wheel 24 against the back surface of the semiconductor wafer W is increased. In this way, the operation of increasing or loosening the pressing force of the polishing wheel 24 against the semiconductor wafer W is repeated. According to such control, the semiconductor wafer W can always be polished within the allowable temperature range. In the unlikely event that the allowable temperature (for example, 90 ° C.) is exceeded, the polishing wheel 24 is retracted from the semiconductor wafer W as in the above embodiment.

1 is an overall perspective view of a polishing apparatus according to an embodiment of the present invention. It is a part of polish device of one embodiment, and is a perspective view in the state where a temperature sensor was taken out from a polish unit. (A) is the perspective view of the state which decomposed | disassembled the rotating shaft and polishing wheel which comprise a grinding | polishing unit, and a temperature sensor, (b) is a perspective view which shows the lower surface of a grinding | polishing wheel. It is a longitudinal cross-sectional view of the grinding | polishing unit of the state which grind | polishes a semiconductor wafer.

Explanation of symbols

17 ... chuck table 20 ... polishing unit (polishing means)
22 ... Rotating shaft 23 ... Servo motor (drive source)
DESCRIPTION OF SYMBOLS 24 ... Polishing wheel 28 ... Hollow part 30 ... Feed mechanism 40 ... Temperature sensor 42 ... Sensor part 50 ... Control means

Claims (4)

A polishing apparatus for polishing a surface to be polished of a semiconductor wafer held on a chuck table by a dry polishing means,
The polishing means includes a rotating shaft, a drive source for rotating the rotating shaft, and a polishing wheel having a polishing surface attached to the tip of the rotating shaft and brought into contact with the surface to be polished of the semiconductor wafer. And
A hollow portion is formed at the rotation shaft and the rotation center of the grinding wheel, and a non-contact temperature sensor is inserted into the hollow portion with the sensor portion arranged near the opening on the grinding wheel side. An apparatus for polishing a semiconductor wafer, wherein:   2. The semiconductor wafer polishing apparatus according to claim 1, further comprising a control unit that feedback-controls the polishing unit based on a temperature detected by the temperature sensor. The polishing means includes a feed mechanism for processing and feeding the polishing wheel in a direction to press or reversely separate the polishing wheel against the surface to be polished of the semiconductor wafer held by the chuck table.
The control means determines whether or not the temperature detected by the temperature sensor exceeds a predetermined allowable temperature. If the temperature exceeds the predetermined allowable temperature, the feed mechanism is held by the grinding wheel on the chuck table. 3. The semiconductor wafer polishing apparatus according to claim 2, wherein the semiconductor wafer polishing apparatus is operated so as to be separated from the semiconductor wafer to a retracted position. The polishing means includes a feed mechanism for processing and feeding the polishing wheel in a direction to press or reversely separate the polishing wheel against the surface to be polished of the semiconductor wafer held by the chuck table.
The control means determines whether or not the temperature detected by the temperature sensor is within a predetermined allowable temperature range,
When the detected temperature of the temperature sensor is below the upper limit of the allowable temperature range, the feed mechanism is operated so that the polishing wheel presses against the semiconductor wafer held on the chuck table. ,
On the other hand, when the upper limit of the allowable temperature range is exceeded, the feed mechanism is operated so as to loosen the pressing force of the polishing wheel against the semiconductor wafer held by the chuck table,
3. The semiconductor wafer polishing apparatus according to claim 2, wherein the temperature detected by the temperature sensor is maintained within the allowable temperature range.

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