JP2009010227A - Wafer deformation suppressing device and method for preventing deformation of wafer - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To suppress the deformation of the peripheral edge of a wafer and to prevent a failure such as the over polishing of the wafer caused by the deformation. <P>SOLUTION: In a polishing head 13 polishing the wafer W pressed against a polishing pad 16 thereof, the reinforcement member 22A of circular shape in a plan view whose inner diameter is substantially equal to the diameter of the wafer W is applied to the top surface of the wafer W with the adhesive 21. The reinforcement member 22A is formed in a substantially inverted dish shape (or in a flat plate shape), and the wafer W is engaged to the inside of the reinforcement member 22A. Polishing the wafer W attached to the reinforcement member 22A helps suppress the buckling distortion and the like of the peripheral edge of the wafer W caused when the wafer W comes into contact or collision with the retainer ring 19 while it is being polished. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to a wafer deformation suppression device and a wafer deformation suppression method, and more particularly to a wafer deformation suppression device and a wafer deformation suppression method in a CMP apparatus that polishes a wafer by pressing the wafer against a polishing pad.

  Conventionally, this type of CMP apparatus includes a polishing head for polishing a wafer by pressing it against a polishing pad on a platen. As shown in FIG. 8, the polishing head 1 is provided on a carrier 2 that holds the wafer W by air pressure, an elastic sheet 3 provided on the lower side of the carrier 2, and a lower outer peripheral portion of the carrier 2. An annular retainer ring 4 or the like is used. Thus, during the CMP process, the wafer W held by the polishing head 1 is pressed against the polishing pad 6 on the rotating platen 5, and the polishing agent is supplied to the upper surface of the polishing pad 6 for polishing.

As described above, during the CMP process, the wafer W is surrounded by the annular retainer ring 4 and is pressed against the upper surface of the rotating polishing pad 6 together with the retainer ring 4 to be polished. At the time of this polishing, a slight gap C is formed between the outer peripheral surface of the wafer W and the inner peripheral surface of the retainer ring 4, so that the wafer W is moved inside the retainer ring 4 by the rotational force of the polishing pad 6. It is held so that it can move in the rotational direction (see, for example, Patent Document 1).
JP 2003-124169 A

  In the above prior art, the wafer W moves in the rotation direction of the polishing pad 6 in the retainer ring 4 during the CMP process. As a result, the outer peripheral side surface of the wafer W contacts and collides with the inner peripheral side surface of the retainer ring 4, and the wafer W is deformed by the impact force (deformation force) at that time. In this case, in particular, the deforming force is remarkably applied to the outer peripheral edge portion of the wafer W to generate buckling deformation or warping deformation (including distortion deformation). FIG. 9 illustrates the shape of the deformed wafer W. For example, the entire shape of the wafer W is deformed into an upwardly convex arcuate shape or a bent shape.

  Furthermore, with the deformation of the wafer W, the pressure distribution on the polished surface of the wafer W becomes uneven. Thereby, in particular, the polishing rate (polishing rate) of the outer peripheral portion of the wafer W is increased, and defects such as excessive polishing occur in the polished wafer. For this reason, as illustrated by the hatched portion in FIG. 10, a ring-shaped poor polishing region (overpolishing region) E occurs at the outer peripheral edge of the wafer W, and the effective area of the wafer W is reduced accordingly. .

  In addition, if it explains supplementarily about the deformation | transformation phenomenon of the wafer W, the outer periphery part of the wafer W which contact | connects the retainer ring 4 will generate | occur | produce the deformation | transformation phenomenon most easily in arbitrary places of the wafer W, and the wafer W center part is external force at the time of a collision. It is considered that the amount of deformation of the wafer W due to the external force is small because it is sufficiently away from the part that receives (an external force having a magnitude substantially equal to the stress generated on the wafer W when it is deformed). Further, the stress generated in the wafer W at the time of collision corresponds to the magnitude of the reaction force per unit area of the retainer ring 4. Accordingly, the larger the area or region in contact with the retainer ring 4, the smaller the stress of the wafer W, that is, the deformation force acting on the wafer W.

  Thus, there is a technical problem to be solved in order to suppress the deformation of the outer peripheral edge of the wafer during polishing and to prevent defects such as excessive polishing of the wafer due to the deformation. It aims at solving.

The present invention has been proposed to achieve the above object, and the invention according to claim 1 is a wafer deformation suppressing device in a CMP apparatus for polishing a wafer surrounded by a retainer ring by pressing it against a polishing pad. A wafer having a configuration in which a circular reinforcing member having a diameter substantially equal to the diameter of the wafer is attached to the upper surface of the wafer, and the wafer is polished while the reinforcing member is attached to the wafer. A deformation suppressing device is provided.

  According to this configuration, the reinforcing member has a diameter substantially equal to the wafer diameter, and is integrally attached to the upper surface of the wafer via the adhesive material. Therefore, even when the wafer moves during polishing and collides with the retainer ring, the deformation force acting on the wafer from the retainer ring is relaxed and absorbed by the reinforcing member. As a result, the resistance strength against the impact force acting on the wafer is substantially increased.

  According to a second aspect of the present invention, there is provided the wafer deformation suppressing device according to the first aspect, wherein the reinforcing member is formed in a substantially inverted dish shape that can be attached to the wafer.

  According to this configuration, the reinforcing member is formed in a substantially inverted dish shape, that is, a substantially inverted dish shape having a concave cross section having an upper surface portion, and is attached to the wafer and fixed. Therefore, the outer peripheral portion of the wafer is surrounded by the outer peripheral side surface of the reinforcing member. For this reason, when the wafer moves in the radial direction during polishing, the outer peripheral side surface of the reinforcing member contacts the inner peripheral surface of the retainer ring, and the outer peripheral side surface of the wafer does not contact the inner peripheral surface of the retainer ring. Further, the contact area (contact area) of the reinforcing member with respect to the retainer ring is larger than the area when the wafer is in direct contact with the retainer ring.

  According to a third aspect of the present invention, the reinforcing member is formed in a circular flat plate shape having a diameter larger than the wafer diameter, and the outer peripheral edge of the reinforcing member protrudes outside the wafer. Providing equipment.

  According to this configuration, the diameter of the reinforcing member is formed to be slightly larger than the wafer diameter, and the outer peripheral edge of the reinforcing member protrudes to the outer peripheral side of the wafer by a predetermined dimension. Therefore, when the wafer moves during polishing, the outer peripheral edge of the reinforcing member directly contacts the inner peripheral surface of the retainer ring, and the outer peripheral edge of the wafer does not contact.

  According to a fourth aspect of the present invention, there is provided the wafer deformation suppressing device according to the first aspect, wherein the adhesive material is an adhesive material having elasticity such as an adhesive tape and wax.

  According to this configuration, the adhesive material is made of a soft member having elasticity such as an adhesive tape and wax, and the reinforcing member is attached to the upper surface of the wafer through the adhesive material. Therefore, the adhesive material exhibits a high buffer absorption function between the reinforcing member and the wafer, and the deformation force acting on the wafer is absorbed and removed. As a result, the pressure distribution over the entire wafer polishing surface is made uniform, and the flatness of the wafer upper surface (back surface) is always maintained.

  The invention according to claim 5 is a wafer deformation suppressing method in a CMP apparatus for polishing by pressing a wafer surrounded by a retainer ring against a polishing pad, the upper surface of the wafer having a diameter substantially equal to the diameter of the wafer. A step of affixing a reinforcing member having a circular shape in plan view through an adhesive material, and a step of polishing the wafer while the reinforcing member is affixed to the wafer, and a deforming force acting on the wafer from the retainer ring during polishing. A method for suppressing wafer deformation absorbed by the reinforcing member is provided.

  According to this method, the reinforcing member has a diameter substantially equal to the diameter of the wafer, and is integrally attached to the upper surface of the wafer via the adhesive material. Therefore, even if the wafer moves during the polishing and collides with the retainer ring, the deformation force acting on the wafer from the retainer ring is effectively relaxed and absorbed by the reinforcing member. As a result, the resistance strength against the impact force acting on the wafer is substantially increased.

  According to the first aspect of the present invention, even when the wafer moves and collides with the retainer ring during polishing, the deformation force acting on the wafer from the retainer ring is absorbed and removed by the reinforcing member. The deformation of the polished shape of the wafer, in particular, the buckling deformation of the outer peripheral edge of the wafer can be suppressed, and poor polishing of the outer peripheral edge of the wafer due to the deformation can be prevented.

  According to the second aspect of the present invention, the impact force acting on the wafer from the retainer ring is reduced by attaching the substantially inverted dish-shaped reinforcing member to the wafer. Therefore, in addition to the effect of the first aspect of the invention, The deformation of the outer peripheral edge of the wafer due to the contact with the retainer ring can be more reliably suppressed.

  According to the third aspect of the present invention, when the wafer moves during polishing, the outer peripheral edge portion of the reinforcing member is in direct contact with the inner peripheral surface of the retainer ring. In addition to the effect of the first aspect, the retainer ring The impact force received from the outer peripheral edge of the reinforcing member can be efficiently absorbed, and there is a merit that the deformation suppressing effect on the outer peripheral edge of the wafer is increased.

  According to the invention described in claim 4, since the impact-absorbing function by the soft adhesive material having elasticity is used, the polishing pressure distribution of the wafer is made uniform, and the flatness of the back surface of the wafer can always be kept good. In addition to the effects of the present invention, deformation such as warpage of the wafer can be more reliably suppressed.

  According to the fifth aspect of the present invention, even when the wafer moves during polishing and collides with the retainer ring, the deformation force acting on the wafer from the retainer ring is absorbed by the reinforcing member. In particular, buckling deformation of the outer peripheral edge portion of the wafer can be suppressed, and poor polishing of the outer peripheral edge portion of the wafer due to the deformation can be prevented.

  The present invention suppresses deformation of the outer peripheral edge of a wafer and achieves the object of preventing overpolishing due to the deformation. In order to achieve the object, wafer deformation in a CMP apparatus that polishes a wafer surrounded by a retainer ring against a polishing pad. In the suppressing device, a circular reinforcing member having a diameter substantially equal to the wafer diameter is attached to the upper surface of the wafer, and the wafer is polished while the reinforcing member is attached to the wafer. This was realized by absorbing the deformation force acting on the wafer from the retainer ring by the reinforcing member.

  Hereinafter, a preferred embodiment of the present invention will be described with reference to FIGS. In this example, in particular, in order to cancel the adverse effects such as over-polishing due to the shape deformation of the outer peripheral edge of the wafer with a simple configuration, the reinforcing member is adhered to the upper surface of the wafer with an adhesive tape or the like and polished. In addition, deformation of the outer peripheral edge of the wafer due to contact / impact with the retainer ring is efficiently suppressed or prevented.

  As the reinforcing member, for example, a member formed in a substantially inverted dish shape (hereinafter referred to as a “petri dish shape”) having an upper surface portion on which a wafer can be fitted, or a circular flat plate corresponding to the wafer shape is formed. Although a thing etc. can be employ | adopted, if it affixes on a wafer and the deformation | transformation of this wafer outer periphery part can be suppressed, the shape etc. of a reinforcement member are arbitrary.

  FIG. 1 is a perspective view showing an outline of the CMP apparatus 11. In the figure, a CMP apparatus 11 is mainly composed of a disk-shaped platen 12 and a polishing head 13. A rotating shaft 14 is connected to the center of the lower surface of the platen 12, and the rotating shaft 14 rotates in the direction of arrow A by driving a motor 15. A polishing pad 16 is attached to the upper surface of the platen 12, and a polishing agent is supplied onto the polishing pad 16 from a nozzle (not shown).

  As shown in FIG. 2, the lower surface of the polishing head 13 includes a carrier 17 for mainly holding the wafer W, a circular elastic sheet 18 provided below the carrier 17, and a lower portion of the carrier 17. An annular retainer ring 19 or the like provided on the outer peripheral portion is formed, and a plurality of grooves (not shown) for abrasives are formed on the lower surface of the retainer ring 19.

  As shown in FIG. 1, a rotating shaft 20 is connected to the center of the upper surface of the polishing head 13, and the rotating shaft 20 rotates in the direction of arrow B in FIG.

  As shown in FIG. 2, the lower surface of the carrier 17 has an air outlet (not shown) for pressure-injecting air onto the upper side of the elastic sheet 18, a vacuum and, if necessary, pure water (DIW) or A hole (not shown) for blowing out air is formed.

  Further, the elastic sheet 18 disposed below the carrier 17 is made of a soft material such as a bendable rubber and is stretched inside the retainer ring 19. A plurality of holes (not shown) are opened at appropriate positions of the elastic sheet 18, and the holes function as wafer suction holes when the wafer is transferred, and for supplying air pressure for pressing the wafer W during polishing. Functions as a hole.

  Next, the reinforcing member having a wafer deformation suppressing function according to the present invention will be described in detail. In FIG. 2, reference numeral 22 </ b> A is a circular reinforcing member having an appropriate rigidity and thickness in a plan view. The reinforcing member 22 </ b> A is made of a synthetic resin or the like, and an adhesive material 21 such as an adhesive tape on the upper surface of the wafer W. It is pasted together through. The wafer W is polished by being pressed against the polishing pad 16 while the reinforcing member 22A is adhered.

  The reinforcing member 22A is formed in a petri dish having an upper surface portion, and a ring-shaped rib portion 24A is provided on the lower surface side of the outer peripheral edge portion 23A of the reinforcing member 22A. The lower surface of the ring-shaped rib portion 24A is formed to be flush with the lower surface of the wafer W. Further, the inner diameter of the ring-shaped rib portion 24A is set substantially equal to the wafer diameter, and the wafer W is fitted and mounted inside the ring-shaped rib portion 24A.

  The upper surface portion of the reinforcing member 22A is adhered and fixed to the upper surface of the wafer W via a soft adhesive material 21 having elasticity. As the adhesive material 21, for example, wax, an adhesive sheet (adhesive sheet), a double-sided tape, a UV tape, or the like can be used as long as it has a required adhesive force or adhesive force. The adhesive material 21 exhibits an impact absorbing function and a deformation correcting function with respect to the wafer W.

  Another embodiment of the reinforcing member according to the present invention is shown in FIG. In the figure, the reinforcing member 22 </ b> B is formed in a circular flat plate shape, and is superposed on the upper surface of the wafer W via a sticking material 21. The diameter of the reinforcing member 22B may be set substantially equal to the wafer diameter, but in the illustrated example, it is formed to be slightly larger than the wafer diameter.

  The wafer W is polished by being pressed against the polishing pad 16 while the reinforcing member 22B is adhered. In this case, the reinforcing member 22 </ b> B suppresses the deformation of the wafer W during polishing by exerting a rigidity maintaining function and a shock absorbing / removing function with respect to the wafer W.

  Next, a procedure for polishing the wafer W by the CMP apparatus 11 will be described. It is assumed that a reinforcing member 22A is attached in advance to an unpolished wafer W waiting in a predetermined location. First, the polishing head 13 is moved onto the standby unpolished wafer W. Next, by driving a vacuum line (not shown), the air chamber 25 between the carrier 17 and the elastic sheet 18 is set in a vacuum state to hold the wafer W by suction. Thereafter, the polishing head 13 is moved directly above the polishing pad 16, and the wafer W is placed on the upper surface of the polishing pad 16.

  Thereafter, by supplying air at a set pressure to the air chamber 25 or the like, the wafer W and the retainer ring 19 are pressed against the upper surface of the polishing pad 16, the platen 12 is rotated, and the polishing head 13 is rotated. A polishing agent is supplied onto the polishing pad 16 to polish the lower surface of the wafer W.

  At the time of polishing, as shown in FIG. 4, since the wafer W moves in the rotation direction R of the polishing pad 16 in the retainer ring 19, the outer peripheral side surface of the wafer W collides with the inner peripheral side surface of the retainer ring 19. At the time of this collision, in the prior art, buckling deformation or warping deformation is generated in the outer peripheral edge portion of the wafer W by the impact force. However, in this embodiment, the deformation of the outer peripheral edge portion of the wafer W due to the impact force is suppressed. The

  That is, in the present embodiment, since the petri dish-shaped reinforcing member 22A is attached to the wafer W, the outer peripheral side surface of the wafer W is surrounded by the ring-shaped rib portion 24A of the reinforcing member 22A. Therefore, even if the wafer W moves to the retainer ring side during polishing, the reinforcing member 22A comes into contact with the inner peripheral surface of the retainer ring 19, so that no impact force acts directly on the outer peripheral side surface of the wafer W.

  Further, when the petri dish-shaped reinforcing member 22A is attached to the wafer W, the rigidity strength of the wafer W is proportional to the diameter and height of the reinforcing member 22A compared to the case where the reinforcing member 22A is not attached. And the contact area of the reinforcing member 22A with the retainer ring 19 increases. As a result, the substantial impact force that the wafer W receives from the retainer ring 19 is also greatly reduced.

  As described above, since the impact force acting on the wafer W is reduced, deformation of the outer peripheral edge portion of the wafer W due to the collision with the retainer ring 19 is suppressed. In addition, poor polishing of the outer peripheral edge of the wafer W due to the deformation is prevented. Moreover, since the polishing unevenness is eliminated and high polishing accuracy and polishing shape are obtained, the device performance of the wafer W is remarkably improved.

  As shown in FIG. 6, unlike the prior art, the present invention does not generate a ring-shaped poor polishing region E in the outer peripheral edge portion of the wafer W, so that the effective area of the wafer W is widened accordingly.

  FIG. 7 shows the experimental result of the polishing rate comparing the method of the present invention with the conventional method. As can be seen from the experimental results, in the conventional method, the polishing rate of the outer peripheral edge of the wafer W was remarkably increased as indicated by the symbol G in the solid line graph. In contrast, since the deformation suppressing effect is exhibited, the polishing shape is effectively prevented from being deformed without increasing the polishing rate, and a good polishing process can be obtained.

  In the present invention, since the reinforcing member 22 </ b> A is attached to the wafer W via the adhesive material 21, the adhesive material 21 exhibits a high absorption and removal function with respect to the deformation force acting on the wafer W. Thus, the pressure distribution over the entire polishing surface of the wafer W is made uniform by absorbing and removing the deformation force with respect to the flatness of the back surface (upper surface) of the wafer W by the adhesive material 21. Therefore, buckling deformation and warpage deformation of the wafer W due to impact are automatically suppressed or corrected. The reinforcing member 22A is removed from the wafer W after polishing.

  As shown in FIG. 3, even when a flat plate-like reinforcing member 22B is attached to the wafer W by polymerization, the same effects as the petri-shaped reinforcing member 22A shown in FIG. That is, the rigidity strength of the wafer W is increased and the effect of removing the deformation force when the wafer W collides becomes remarkable.

  As a result, as shown in FIG. 5, when the outer peripheral side surface of the reinforcing member 22A collides with the inner peripheral surface of the retainer ring 19 due to the movement of the wafer W in the radial outer direction R during polishing, the retainer is compared with the conventional case. The impact force acting on the wafer W from the ring 19 is greatly reduced. Therefore, the deformation of the outer peripheral edge portion of the wafer W is suppressed, and at the same time, poor polishing of the outer peripheral edge portion of the wafer W based on the deformation is prevented.

  In particular, in the configuration example of FIG. 5, the outer peripheral edge of the reinforcing member 22 </ b> B protrudes outside the wafer W because the diameter of the circular flat reinforcing member 22 </ b> B is slightly larger than the wafer diameter. For this reason, when the wafer W moves radially outward during polishing, the outer peripheral side protruding portion of the reinforcing member 22 </ b> B contacts and collides with the inner peripheral surface of the retainer ring 19. Therefore, buckling deformation and warping deformation of the wafer W due to impact can be reliably prevented.

  Further, the reinforcing members 22A and 22B according to the present invention can be adjusted on the outer peripheral side of the wafer W in contact with the retainer ring 19 by changing and adjusting the heights and diameters of the reinforcing members 22A and 22B to optimum values according to polishing conditions and the like. The area can be changed and controlled, and the magnitude of the impact force received from the retainer ring 19 of the wafer W is also changed and controlled. Therefore, by using the reinforcing members 22A and 22B having the shape and dimensions corresponding to the polishing conditions, the deformation of the outer peripheral edge of the wafer W due to the impact force can be more easily and reliably suppressed.

  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 one.

1 is a perspective view of a CMP apparatus according to an embodiment of the present invention. The principal part sectional drawing which shows the wafer deformation | transformation suppression apparatus which uses the substantially inverted dish-shaped reinforcement member which concerns on one Example. The principal part sectional drawing which shows the wafer deformation | transformation suppression apparatus which uses the flat reinforcement member which concerns on one Example. The principal part sectional drawing of the wafer deformation | transformation suppression apparatus explaining a state when the wafer of FIG. 2 moves during grinding | polishing. The principal part sectional drawing of the wafer deformation | transformation suppression apparatus explaining a state when the wafer of FIG. 3 moves during grinding | polishing. The top view which shows the grinding | polishing surface of the wafer which concerns on one Example. The graph which shows the experimental result of the polishing rate which compared the deformation | transformation suppression system of this invention system with the conventional system. Sectional drawing which shows the principal part which shows the conventional polishing head lower surface part. Front sectional drawing which shows the modification of the wafer by a prior art. The top view which shows the grinding | polishing surface of the wafer by a prior art.

Explanation of symbols

11 CMP equipment (wafer polishing equipment)
13 Polishing head (wafer holding head)
16 Polishing pad 19 Retainer ring 21 Adhesive (adhesive, adhesive)
22A reinforcing member 22B reinforcing member

Claims (5)

A wafer deformation suppression device in a CMP apparatus that polishes a wafer surrounded by a retainer ring by pressing the wafer against a polishing pad,
A circular reinforcing member in plan view having a diameter substantially equal to the diameter of the wafer is attached to the upper surface of the wafer,
A wafer deformation suppressing device configured to polish the wafer while the reinforcing member is attached to the wafer.   2. The wafer deformation suppressing device according to claim 1, wherein the reinforcing member is formed in a substantially inverted dish shape that can be attached to the wafer.   2. The wafer deformation suppressing device according to claim 1, wherein the reinforcing member is formed in a circular flat plate shape having a diameter larger than the wafer diameter, and an outer peripheral edge portion of the reinforcing member protrudes to the outside of the wafer.   2. The wafer deformation suppressing device according to claim 1, wherein the adhesive material is an adhesive material having elasticity such as an adhesive tape and wax. A wafer deformation suppression method in a CMP apparatus for polishing by pressing a wafer surrounded by a retainer ring against a polishing pad,
A step in which a circular reinforcing member having a diameter substantially the same as the diameter of the wafer is bonded to the upper surface of the wafer via a bonding material;
Polishing while attaching the reinforcing member to the wafer,
A method for suppressing wafer deformation, wherein a deformation force acting on the wafer from the retainer ring during polishing is absorbed by the reinforcing member.

Images