JP5408883B2 - Wafer polishing equipment - Google Patents

Description

The present invention relates to a wafer polishing equipment, particularly, a chemical mechanical polishing: it relates to a wafer polishing equipment for polishing a semiconductor wafer according to (CMP Chemical Mechanical Polishing).

  In recent years, IC microfabrication has progressed, and IC patterns are formed over multiple layers. In such an IC structure, it is inevitable that a certain degree of unevenness is generated on the surface of the layer on which the pattern is formed. Conventionally, the pattern of the next layer is formed as it is even if a certain degree of unevenness is generated on the surface of the layer. However, when the number of layers increases and the width of lines and holes decreases, there is a defect that it is difficult to form a good pattern.

  Therefore, after polishing the surface of the layer on which the pattern is formed and flattening the surface, a pattern of the next layer is formed. In order to polish a wafer in the middle of forming such an IC pattern, a wafer polishing apparatus (CMP apparatus) using a CMP method is used.

  Further, as such a wafer polishing apparatus, a disk-shaped polishing surface plate having a polishing cloth affixed to the surface, and a plurality of wafers that hold one surface of the wafer to be polished and abut the other surface of the wafer against the polishing cloth A wafer polishing head and a head drive mechanism for rotating the wafer polishing head relative to a polishing surface plate, and polishing the wafer by supplying slurry as an abrasive between the polishing cloth and the wafer. Is widely known (see, for example, Patent Document 1).

  Furthermore, in recent years, the initial film thickness of each wafer is not necessarily uniform, and it is also required to correct and polish a wafer having a certain distribution. In this case, it is required to form a state in which the pressure distribution is changed with respect to the wafer surface for correction.

 Furthermore, polishing may become non-uniform due to variations in consumables. For example, even if the polishing pressure is made uniform, such as variations in slurry supply and pad surfaces, there may be a distribution with a certain polishing shape due to various non-uniform factors. In such a case, it is required to make the non-uniform elements uniform, but on the other hand, such non-uniformity of the material variation is accepted, and a request to correct the polishing shape by changing the pressure distribution is required. There is also.

With respect to such a problem, for example, in the conventional method disclosed in Patent Document 1, a plurality of air chambers are formed on the surface of the top ring that presses the wafer, and the air pressure to be placed in each air chamber is changed, thereby changing the wafer back surface. For example, it is shown that the pressure is changed for each region where the pressure is pressed to control the polishing shape.
JP 2001-179605 A.

  However, as known from Patent Document 1, in the structure in which the entire surface of the wafer is pressed using a soft member, a sudden change occurs between a plurality of pressure chambers having different pressure distributions, and each pressure is changed. If the pressure in the chamber is transmitted to the wafer side almost as it is, a stepped polished shape is formed on the wafer, which is a problem. This is because local pressure is not properly distributed in the wafer surface. Therefore, in order to obtain a smooth polished shape, it is necessary to relax the gradient of the portion that presses the wafer to some extent so that the wafer pressure is appropriately distributed.

  On the other hand, when a hard material is used for a flexible sheet (also referred to as a membrane sheet) that applies pressure from the back surface of the wafer to press the entire area of the wafer back surface, In many cases, the stepwise pressure distribution formed by a plurality of pressure chambers has a relatively smooth polished shape due to the effect of bending resistance caused by a hard material. However, as a reaction, when a flexible sheet is manufactured as a single piece of a hard material and used, the pressure changes sharply at the edge portion of the wafer. There are cases where excessive pressure is applied to the edge portion of the wafer and where pressure is hardly applied to the edge portion. In such a case, the delicate edge shape of the wafer edge portion cannot be adjusted, and it has been difficult to stably form a uniform polished shape along the outer periphery of the wafer.

  In addition, when a flexible sheet is formed of a hard material and the flexible sheet is fixed to a retainer ring or the like at the outer peripheral portion, the flexible sheet is hardly deformed at the outer peripheral portion. In order to maintain the position, the edge portion of the wafer is not pressed. However, since the central portion of the wafer is far from the outer peripheral portion to which the flexible sheet is fixed, the vertical displacement margin due to the bending deformation can be increased.

  This can be seen from the following equation (1). Equation (1) assumes that a uniform distributed load p is applied in a circular hard sheet having a radius a, where the hard sheet Poisson's ratio is ν and the flexural rigidity of the plate is D. The amount of bending δ which is bent at is expressed as follows.

As can be seen from the above equation (1), the amount of deflection δ at the center is proportional to the fourth power of the radius a.
This is because when the outer peripheral part of the wafer is fixed and the central part is viewed, the closer to the central part, the greater the amount that can be displaced, and if the amount of displacement is constant, the distributed load required for the displacement itself Also shows that a very small load is sufficient.

  In other words, when the outer periphery of the wafer is fixed, in order to displace the outer periphery of the wafer by a predetermined amount, there is a margin to be displaced and a very large pressure is required, but the center of the wafer is sufficiently displaced with a relatively small pressure. It becomes possible to make it. As a result, almost no stress is required to deform the flexible sheet at the center of the wafer, so that the pressure opposite to the wafer is applied to the wafer through the flexible sheet. It becomes possible to communicate faithfully. However, since the stress for deforming the flexible sheet itself becomes very large at the periphery of the wafer, the pressure on the side opposite to the wafer on the flexible sheet is applied via the flexible sheet. Therefore, it is impossible to transmit the wafer faithfully.

  To solve this problem, when the flexible sheet itself is formed of a sheet made of a hard material on the wafer and is fixed at the outer periphery, the wafer edge portion is affected by the bending rigidity of the flexible sheet itself. The neighborhood is very sensitive and makes it difficult to evenly apply pressure to the wafer.

Moreover, when the sheet | seat which presses a wafer with a hard flexible sheet | seat is formed, a problem will be produced when a wafer is conveyed to the following process. That is, when the wafer polishing apparatus transports the wafer to the next process, the wafer polishing apparatus holds the wafer under reduced pressure through holes provided in the hard flexible sheet. When the wafer is held under reduced pressure, the wafer cannot be efficiently sucked and sucked unless the wafer and the flexible sheet are in close contact with each other. In particular, when the flexible sheet is hard, the effect of sealing the white meat to the wafer is very small. For this reason, within the wafer surface, the flexible sheet is kept in close contact with the wafer while reducing the pressure distribution on the wafer back side and correcting the wafer surface continuously to a monotonous shape. The wafer must have a surface that can be adsorbed under reduced pressure after sufficient sealing. Moreover, when it forms with a hard sheet | seat, there exists a possibility of damaging a wafer back surface by rubbing with the wafer back surface during grinding | polishing. Even in such a meaning, it is required to have a surface that is in close contact with and grips the back surface of the wafer.

  Furthermore, in order to uniformly press the wafer, when the air pressure inside the flexible sheet is sealed and the wafer is pressed with an airbag, the posture of the wafer itself changes due to the shear stress of polishing during polishing. The stress that restores the changed posture does not work. This is because, due to Pascal's principle, the sealed air constantly presses the inside evenly regardless of the sealed state, and as a result, the wafer is stabilized in a tilted state if it is tilted. .

  Therefore, the present invention causes a technical problem to be solved in order to prevent the generation of a discontinuous polishing shape of the wafer and to achieve a smooth polishing shape up to the wafer edge. It aims at solving this subject.

The present invention has been proposed in order to achieve the above object, and the invention according to claim 1 is a wafer polishing apparatus that performs polishing while sliding a wafer against a pad and relatively moving the pad.
Applying a pressure to press the wafer against the pad from the back side of the wafer through a flexible sheet ,
In the wafer surface, with a polishing head having a pressure applying means consisting of a plurality of independent pressure chambers ,
The flexible sheet covers the plurality of independent pressure chambers in the wafer surface, and has a large deflection in-wafer region that gives a smooth pressure distribution to the wafer; and
A wafer outer region portion that has a bending rigidity that is weaker than the bending rigidity of the wafer inner region portion, and is provided on the outer periphery of the wafer inner region portion ;
A wafer polishing apparatus having two regions is provided.

According to this configuration, in the wafer surface provided with a polishing head having a pressure applying means comprising a plurality of independent pressure chambers, the flexible sheet is in a said wafer surface, said plurality of independent A wafer inner region that has a large bending rigidity that covers the pressure chamber and gives a smooth pressure distribution to the wafer, and a bending rigidity that is weaker than the bending rigidity of the inner region of the wafer, and outside the outer periphery of the inner region of the wafer And a wafer outer region provided on the substrate.

  Therefore, the stepwise pressure distribution formed in the plurality of regions can be relaxed by the large deflection rigidity of the region in the wafer. That is, since the stepwise pressure distribution can be made into a smooth pressure distribution shape, it is possible to effectively correct the pressure distribution in the inner peripheral portion of the wafer.

  On the other hand, the outer area of the wafer is made weaker than the inner flexible part and can be displaced along the wafer surface, so that the pressure gradient in the area between the retainer part and the wafer part is moderated. The shape of the wafer edge can be made continuous from the center of the wafer to be a uniform shape.

  If a hard plate placed on the inner periphery of the wafer is extended to the outer periphery of the wafer, as described above, if the plate is supported by the retainer, no pressure is applied to the outer periphery of the wafer. Sometimes it will disappear. By using a flexible sheet on the outer periphery of the wafer as an elastic material or a thin flexible material, a smooth pressure distribution is formed from the wafer center to the edge, and the polished shape is continuous from the wafer center. And uniform shape.

In addition, instead of using all of the flexible sheet with a strong bending rigidity, by using a sheet having a bending rigidity that is weaker than that in the wafer inner area in the wafer outer area, the entire area in the wafer is A displacement margin can be obtained over the entire wafer.

  According to a second aspect of the present invention, the flexible sheet includes a first flexible sheet disposed from the inner area of the wafer to the outer area of the wafer, and the first flexible sheet having substantially the same diameter as the wafer. Provided is a wafer polishing apparatus comprising a second flexible sheet disposed on a flexible sheet.

  According to this configuration, the two sheet members are overlapped without performing the troublesome task of joining different materials having different flexural rigidity in the wafer inner region portion and the wafer outer region portion at their ends. As a result, it is possible to obtain a flexible sheet having different bending rigidity in the wafer inner region and the wafer outer region.

  According to a third aspect of the present invention, there is provided a wafer polishing apparatus in which the flexible sheet is provided with a soft material at a portion in contact with the wafer.

  According to this configuration, since the wafer moves horizontally during polishing, even if the back surface of the wafer hits the flexible sheet, the wafer does not directly hit the hard flexible sheet, and there is no risk of damaging the back surface of the wafer. Hit the material. In addition, when the wafer is transported after polishing or before polishing, the wafer is closely sealed and adsorbed under reduced pressure, but since the soft member is provided on the flexible sheet in contact with the wafer, the soft material Thus, adhesion between the wafer and the flexible sheet can be obtained.

  According to a fourth aspect of the present invention, there is provided a wafer polishing apparatus wherein the soft material has water retention and is configured to be in close contact with the wafer.

  According to this configuration, the wafer and the flexible sheet are in good contact with each other with water retention of the soft material.

  The invention according to claim 5 provides the wafer polishing apparatus in which the flexible sheet has an outer peripheral portion sandwiched between retainer portions.

  According to this configuration, by attaching the flexible sheet to the retainer and sandwiching it with the retainer, the flexible sheet can be held with an appropriate tension, and the flexible sheet can be held almost in a horizontal state. For this reason, excessive stress due to bending of the flexible sheet is not applied to the wafer edge, and the wafer is also subjected to substantially continuous and uniform pressure until it reaches the wafer edge while following the wafer to the wafer edge. Can be added.

  According to a sixth aspect of the present invention, the pressure applying means includes a back plate provided on the back surface side of the flexible sheet, and air that continuously supplies air between the back plate and the flexible sheet. A supply unit configured to transmit a pressing force to the wafer through the air layer and the flexible sheet formed between the back plate and the flexible sheet by the air supply unit; A wafer polishing apparatus is provided.

  According to this configuration, air is continuously supplied between the back plate that presses the wafer and the flexible sheet to form an air layer, thereby further reducing the pressure distribution in the wafer surface.

In addition, when the outer periphery of the flexible sheet is sandwiched between the retainers, the air supplied from the gap between the back plate and the retainer that presses the wafer can be released, and clean air is constantly supplied from the back plate. In addition, an air layer is always formed uniformly between the back plate and the flexible sheet.

  Furthermore, in the air-sealed state, even when the wafer is tilted when the wafer is pressed, the wafer posture is tilted because the Pascal principle constantly applies a uniform pressure regardless of the wafer posture. Will remain. However, by forming an air layer and keeping the back plate and the flexible sheet in a non-contact state, for example, when the wafer is in an inclined posture, when the back plate and the flexible sheet are close to each other, In order to avoid the proximity state, excessive stress is locally generated, and the stress that restores the posture automatically acts. As a result, a symmetric pressure is constantly applied in the wafer surface, and as a result, a uniform polished shape is obtained under a uniform pressure distribution throughout the wafer surface.

  According to the first aspect of the present invention, it is possible to obtain a continuous polishing shape in the wafer surface by transmitting a continuous pressure distribution to the wafer, and to prevent the generation of a discontinuous polishing shape of the wafer, and smooth polishing. A shape is obtained.

Further, in the wafer surface, comprising a polishing head having a pressure applying means comprising a plurality of independent pressure chambers, the flexible sheet covers the plurality of independent pressure chambers in the wafer surface, Wafer having a large deflection rigidity that gives a smooth pressure distribution to the wafer, a deflection rigidity that is weaker than the deflection rigidity of the wafer inner area, and provided on the outer periphery of the wafer inner area. Since it comprises the outer region portion, the internal pressures of the plurality of pressure chambers can be individually adjusted. And since the difference between the pressure transmission state near the wafer central portion and the pressure transmission state near the wafer outer peripheral portion can be transmitted to the wafer in a relaxed state, a continuous smooth polishing form can be obtained within the wafer surface. Also, a smooth and uniform polished shape can be obtained at the edge portion of the outer periphery of the wafer.

  Conventionally, in the case of a rigid flexible sheet, when the flexible sheet is fixed at the outer peripheral portion, the pressure formed on the opposite side of the wafer due to a margin of deflection displacement near the outer peripheral portion. The distribution state may not be faithfully transmitted to the wafer, but when the outer region of the wafer is formed of a flexible sheet of a material having a lower bending rigidity than the inner region of the wafer as in the present invention, The displacement margin of the flexible sheet can be secured over the entire wafer surface, and the pressure can be transmitted faithfully within the wafer surface.

  In addition to the effect of the invention described in claim 1, the invention described in claim 2 gives different flexural rigidity to the inner region and the outer region of the wafer only by stacking and bonding the two sheet members. A flexible sheet can be formed, and a flexible sheet can be efficiently manufactured.

  In addition to the effects of the invention described in claim 1, the invention described in claim 3 does not damage the wafer back surface even if the wafer back surface rubs against the flexible sheet during polishing of the wafer. In addition, the soft material on the flexible sheet provided on the side that is in close contact with the wafer improves the adhesion between the wafer and the flexible sheet, so the polishing pad securely holds the wafer during wafer transfer. As a result, an effect such as elimination of a conveyance error can be obtained.

  In addition to the effect of the invention of the third aspect, the invention according to the fourth aspect can hold the wafer in close contact via a soft material, so that the wafer can be prevented from being burned out and the back surface of the wafer can be prevented. Cross contamination can be avoided. In addition, the surface tension of water improves the adhesion between the wafer and the soft material, and it is possible to obtain effects such as further eliminating a transport mistake when transporting the wafer by vacuum suction.

  In addition to the effects of the first, second, third, and fourth aspects, the invention according to the fifth aspect attaches the flexible sheet to the retainer by sandwiching the outer periphery of the flexible sheet. Can be held with tension. In addition, the flexible sheet can be held almost horizontally without being extremely bent, and the pressure distribution is efficiently transmitted in a form that affects the inherent bending rigidity of the flexible sheet. Is obtained.

  For example, if there is a back plate that presses the wafer and a retainer that covers the outer periphery of the wafer, and the flexible sheet that presses the wafer has two types of flexural rigidity, it is acceptable. When the flexible sheet is attached to the back plate, there is a place restriction, and the flexible sheet needs to be extremely bent and attached. Further, when the flexible sheet is not attached by being bent, another ring for attaching the flexible sheet is required, and there is a mechanism for fixing the ring, which complicates the structure. Further, when the flexible sheet is extremely bent and attached to the back plate that presses the flexible sheet against the wafer, the flexible sheet can be used before considering the difference in flexural rigidity between the area inside the wafer and the area outside the wafer. There is a problem that bending caused by extremely bending the flexible sheet is affected, and extreme pressure is applied to the edge portion of the wafer.

  However, in the present invention, the flexible sheet can be held at an appropriate tension by attaching the flexible sheet to the retainer and sandwiched by the retainer, and the flexible sheet can be held in an almost horizontal state without being bent extremely. Thus, the flexible sheet can be held, and the pressure distribution is efficiently transmitted in a manner that affects the inherent bending rigidity of the flexible sheet. Thereby, it is possible to achieve both the continuity of the polished shape in the wafer surface and the uniform polished shape at the edge portion of the wafer.

  According to the sixth aspect of the invention, in addition to the effect of the first, second, third, fourth, or fifth aspect, air is continuously supplied between the back plate that presses the wafer and the flexible sheet. By forming the air layer, the pressure distribution in the wafer surface can be further relaxed.

  In addition, when the outer periphery of the flexible sheet is sandwiched between the retainers, the air supplied from the gap between the back plate and the retainer that presses the wafer can be released, and clean air is constantly supplied from the back plate. In addition, since the air layer is always formed uniformly between the back plate and the flexible sheet, even when the wafer is inclined due to the shear stress of polishing, the air layer is formed by the formation of the air layer. It becomes possible to return to the original posture by the principle.

  In order to prevent the occurrence of discontinuous polishing shape of the wafer and achieve the purpose of making it a smooth polishing shape, in the wafer polishing apparatus that performs polishing while sliding the wafer against the pad and making relative movement, A polishing head having pressure applying means for applying pressure for pressing the wafer against the pad from the back surface of the wafer through the flexible sheet; and the flexible sheet is applied to the wafer within the back surface of the wafer. A region in the wafer to which pressure is applied, and a region outside the wafer that has a bending rigidity that is weaker than that in the region in the wafer and that is provided outside the outer periphery of the region in the wafer. Realized by configuring.

  Hereinafter, the wafer polishing apparatus of the present invention will be described with reference to preferred embodiments.

  FIG. 1 is a perspective view showing the overall configuration of a wafer polishing apparatus 10 to which the present invention is applied. As shown in the figure, the wafer polishing apparatus 10 is mainly composed of a polishing surface plate 12 and a wafer holding head 14.

  The polishing surface plate 12 is formed in a disk shape, and a rotating shaft 16 is connected to the center of the lower surface thereof. The polishing surface plate 12 rotates by driving a motor 18 connected to the rotating shaft 16. A polishing pad 20 is attached to the upper surface of the polishing surface plate 12, and a mechanochemical abrasive (slurry) is supplied onto the polishing pad 20 from a nozzle (not shown).

  As shown in FIG. 2, the wafer holding head 14 mainly comprises a head main body 22, a back plate (carrier) 24, a back plate pressing means 26, a retainer ring 28, a retainer ring pressing means 30 and the like.

  The head body 22 is formed in a disc shape, and a rotary shaft 32 is connected to the center of the upper surface thereof. The head body 22 is driven to rotate by a motor (not shown) connected to the rotary shaft 32.

  The back plate 24 is formed in a disc shape having an outer diameter larger than the outer diameter of the wafer W, and is arranged at the lower center of the head body 22. A cylindrical recess 34 is formed at the center of the upper surface of the back plate 24. A shaft portion 36 of the head body 22 is fitted into the recess 34 via a pin 38. The rotation of the back plate 24 is transmitted from the head main body 22 via the pins 38.

  A back plate pressing member 40 is provided on the peripheral edge of the upper surface of the back plate 24. The back plate 24 receives a pressing force from a back plate pressing means 26 via the back plate pressing member 40.

  Further, on the lower surface of the back plate 24, three annular air suction / blowout grooves 42a, 42b and 42c are formed concentrically. As shown in FIG. 3, each of the air suction / blowout grooves 42a, 42b, 42c has diaphragms 43a, 43b, 43c provided with a plurality of air suction / blowout ports (not shown) on the front surface, The diaphragms 43a, 43b, and 43c separate the air suction / blowout grooves 42a, 42b, and 42c from each other, and have independent pressure chambers. Further, a flexible sheet 50 is provided on the lower surface of the back plate 24 so as to cover the lower surface of the back plate 24 and to fix the outer peripheral edge thereof to the outer peripheral surface of the lower end of the back plate 24. .

  Air flow paths 44a, 44b, 44c formed inside the back plate 24 are communicated with the air suction / blowout grooves 42a, 42b, 42c, respectively. An air supply means 46 having an intake pump and an exhaust pump is connected to these air flow paths 44a, 44b, 44c via an air pipe (not shown). The suction and blowout of air from the air suction / blowing grooves 42a, 42b, and 42c are performed by the operation of the intake pump and the exhaust pump by the operation of the air supply means 46, and the air passages 44a, 44b, and 44c have different sizes. It is possible to individually adjust the internal pressures of the three pressure chambers.

  Further, the pressure chamber formed by the air supply means 46, the back plate 24, and the diaphragms 43a, 43b, 43c applies a pressure for pressing the wafer W against the polishing pad 20 from the back surface of the wafer W through the flexible sheet 50. The pressure application means 45 to apply is comprised.

  The back plate pressing means 26 is disposed on the outer periphery of the lower surface of the head main body 22 and applies a pressing force to the back plate pressing member 40 to transmit the pressing force to the back plate 24 coupled thereto. As shown in FIG. 2, the back plate pressing means 26 is preferably composed of a rubber sheet airbag 47 that expands and contracts by air intake and exhaust. An air supply mechanism 48 for supplying air is connected to the airbag 47, and the air supply mechanism 48 includes a regulator (not shown) that adjusts the pressure of air pumped from a pump (not shown). .

  The retainer ring 28 is formed in a ring shape, and is attached to a retainer pressing member 31 that transmits a pressing force from the retainer ring pressing means 30 to the retainer ring 28. In this example, the retainer pressing member 31 and the back plate pressing member 40 are provided so as to intersect with each other. However, the retainer ring pressing means 30 may be provided so as not to intersect with each other.

The flexible sheet 50 includes a first flexible sheet 51 and a second flexible sheet 52 each having flexibility. The first flexible sheet 51 is formed in a circular shape that is sufficiently larger than the outer diameter of the back plate 24. As shown in FIGS. 2 and 3, the first flexible sheet 51 has an outer peripheral portion 51a disposed in the wafer outer region portion 53A. In a state of being slackened in the horizontal direction, the outer peripheral edge 51b is closely fixed to the outer peripheral surface of the back plate 24, and the wafer inner region portion 53A facing the rear surface of the wafer W is disposed from the wafer outer region portion 53B. It is provided as such.

  On the other hand, as shown in FIGS. 2 and 3, the second flexible sheet 52 is formed in a disk shape having substantially the same diameter as the outer diameter of the wafer W, that is, substantially the same outer diameter as that of the in-wafer region portion 53 </ b> A. It is formed and attached to the lower surface of the first flexible sheet 51 by being attached with an adhesive or the like.

  The first flexible sheet 51 is, for example, a 0.5 mm thick polyethylene sheet, a 0.25 mm thick PET sheet, a 0.3 mm thick polypropylene sheet, a 0.3 mm thick PFA sheet, or the like. A thin film sheet is used. On the other hand, the second flexible sheet 52 is a 2 mm thick vinyl chloride plate, a 1.5 mm thick acrylic plate, a 1 mm thick SUS plate, or the like.

  In addition, as a material that is affixed to the surface of the second flexible sheet and does not cause harmful scratches on the back of the wafer even if it comes into contact with the wafer, a suede type Supreme pad sold by Nita Haas, etc. A Fujipa Atago Polypas pad is preferably used. Suede type pads contain enough water on the front surface, so even if the wafer back surface comes in direct contact with the water containing surface, the wafer back surface will not be damaged and the wafer back surface will be held firmly. can do.

  The flexible sheet 50 is formed by overlapping the bending rigidity of the in-wafer region portion 53A where the first flexible sheet 51 and the second flexible sheet 52 are overlapped with the second flexible sheet 52. The bending rigidity of the wafer outer area 53B is different from that of the non-wafer outer area 53B. The bending rigidity of the wafer outer area 53B is weaker than that of the wafer inner area 53A. The flexible sheet 50 disposed in the in-wafer region portion 53A is provided with a plurality of air suction / blowout holes 54 communicating with the air suction / blowout grooves 42a, 42b, and 42c of the back plate 24. Air is sucked and blown out from the suction / blowout grooves 42a, 42b, and 42c.

  That is, the air suction / blowout holes 54 formed in the in-wafer region portion 53A of the flexible sheet 50 act as suction holes when holding and transporting the wafer W, and at the end of polishing, the wafer W Acts as an air ejection hole for peeling.

  The retainer ring pressing means 30 is disposed at the center of the lower surface of the head main body 22 and applies a pressing force to the retainer ring pressing member 56 to press the retainer ring 28 coupled thereto against the polishing pad 20. The retainer ring pressing means 30 is also preferably constituted by a rubber sheet airbag 58 in the same manner as the back plate pressing means 26. An air supply mechanism 59 for supplying air is connected to the airbag 58, and the air supply mechanism 59 is provided with a regulator (not shown) that adjusts the pressure of air pumped from a pump (not shown). Yes.

  Next, the polishing operation of the wafer polishing apparatus 10 configured as described above will be described.

  First, the wafer W is held by the wafer holding head 14 and placed on the polishing pad 20. At this time, the wafer W is held by air suction performed through suction / blowing grooves 42 a, 42 b, 42 c formed on the lower surface of the back plate 24 and the air suction / blowing hole 54 of the flexible sheet 50.

Next, when air is blown out from the suction / blowing grooves 42a, 42b, 42c of the back plate 24 under the control of the pressure applying means 46, and simultaneously the back plate 24 is pressed, the air suction / blowing grooves 42a, 42b, 42c and the diaphragm 43a, The pressures of the three pressure chambers formed by 43b and 43c are increased, and the force by which the back plate pressing means 26 presses the back plate 24 and the force by which the back plate 24 is pushed up by the pressure of the diaphragms 43a, 43b, and 43c are the same. Then, a certain pressure is maintained.

  In this state, the polishing surface plate 12 is rotated in the direction of arrow A shown in FIG. 1, and the wafer holding head 14 is rotated in the direction of arrow B shown in FIG. Then, slurry is supplied from a nozzle (not shown) onto the rotating polishing pad 20. Thereby, the lower surface of the wafer W is polished by the polishing pad 20.

  Since the flexible sheet 50 is formed with a plurality of air suction / blowout holes 54, the air supplied from the air suction / blowout grooves 42a, 42b, 42c of the backplate 24 is supplied to the backplate 24 and the wafer. An air layer is formed between the W back surface and the flexible sheet 50, and the wafer W is pressed against the polishing pad 20.

  Further, the force for pressing the wafer W against the polishing pad 20 is performed by the air layer through the flexible sheet 50, but the flexible sheet 50 is the same as the pressure pressing the wafer W, so the flexible sheet There is almost no air flow between the wafer 50 and the wafer W, and even if there is an air flow, the amount of air is very small, so that aggregation of the slurry does not occur. Further, even if the thickness of the flexible sheet 50 is uneven, the processing accuracy of the wafer W is not affected.

  When the processing of the wafer W is completed, the wafer W is again held by the wafer holding head 14 and discharged from the polishing pad 20. At this time, the wafer W is held by air suction performed through the suction / blowout grooves 42a, 42b, 42c formed on the lower surface of the back plate 24 and the air suction / blowout holes 54 of the flexible sheet 50, and is discharged and conveyed. .

  Therefore, in the wafer polishing apparatus 10 of this embodiment, the flexible sheet 50 is subjected to pressure on the wafer W from the wafer inner region 53A that applies pressure to the wafer W within the back surface of the wafer W, and from the outer periphery of the wafer W. Since it is composed of a wafer outer region portion 53B having a bending rigidity that is weaker than the bending rigidity of the inner region portion 53A, the pressure transmission state in the vicinity of the wafer central portion and the vicinity of the wafer outer periphery portion when pressing the wafer It is possible to transmit with the difference in pressure transmission state in the wafer, that is, the pressure gradient can be relaxed, and the continuous pressure distribution is transmitted to the wafer, and the continuous smooth polishing shape is maintained in the wafer surface. In this case, a smooth and uniform polished shape can be secured.

  Further, air is continuously supplied between the back plate 24 that presses the wafer W and the flexible sheet 50 to form an air layer, so that the pressure distribution in the wafer W plane is further relaxed. .

  Next, a wafer polishing apparatus according to a second embodiment of the present invention will be described with reference to FIGS. The configuration of the polishing pad 20 in the second embodiment is such that the outer peripheral portion 51 a of the first flexible sheet 51 in the flexible sheet 50 shown in FIGS. 2 and 3 is stretched around the inner periphery of the retainer ring 28. Since other configurations are the same as those in FIGS. 2 and 3, the same components are denoted by the same reference numerals, and redundant description is omitted.

  5 and 6, the retainer ring 28 is attached to the retainer ring pressing member 31 via a retainer ring holder 57, a snap ring 58, an attachment member 59, and a clamping member 60 each formed in a ring shape.

When the flexible sheet 50 is attached to the retainer ring 28 in such a manner that the first flexible sheet 51 is stretched around the inner periphery of the retainer ring 28, the retainer ring 28 and the sandwiching member 60 are first separated. The outer peripheral end 51b of the first flexible sheet 51 is disposed between the separated retainer ring 28 and the clamping member 60 so as to be evenly pulled outward, and then the outer peripheral end 51b is clamped with the retainer ring 28. The retainer ring 28 and the sandwiching member 60 are fixed with screws 61 between the member 60 and the retainer ring 28. Next, by attaching a snap ring 58 between the retainer ring 28 and the retainer ring holder 57, integrating the retainer ring 28 and the retainer ring holder 57, and then fixing the attachment member 59 to the retainer ring pressing member 56. Assembled.

  In the polishing pad 20 configured as described above, the outer peripheral end 51 b of the first flexible sheet 51 in the flexible sheet 50 is attached to the retainer ring 28 with appropriate tension, and the outer peripheral end 51 b is attached together with the holding member 60. By sandwiching and holding, the flexible sheet 50 can be held with an appropriate tension, and the flexible sheet 50 can be held almost horizontally without being bent extremely. As a result, the pressure distribution is efficiently transmitted in a form that affects the inherent bending rigidity of the flexible sheet.

  Further, since the outer peripheral end 51b of the first flexible sheet 51 is sandwiched between the retainer ring 28 and the retainer ring 28, the supplied air is released from the gap between the back plate 24 and the retainer ring 28 that presses the wafer W. be able to. Accordingly, clean air is continuously supplied from the back plate 24, and an air layer is always formed uniformly between the back plate 24 and the first flexible sheet 51.

  In each of the above embodiments, the flexible sheet 50 has the bending rigidity in the wafer region 53A by overlapping the second flexible sheet 52 on the lower surface of the first flexible sheet 51 and bonding it. Although it is stronger than the flexural rigidity of the wafer outer region 53B, the flexural rigidity obtained by processing one flexible sheet is not necessarily required to bond the two flexible sheets 51 and 52 together. A flexible sheet having a wafer region portion 53A and a wafer outer region portion 53B may be used.

  In addition, the flexible sheet 50 is pasted with a soft material on a portion of the first flexible sheet 51 located in the wafer outer peripheral region 53B that contacts the wafer W and a portion of the second flexible sheet 52 that contacts the wafer W. Or a coated structure. If a structure in which a soft material is provided in a portion in contact with the wafer W is used, even if the wafer W moves horizontally during the polishing and the flexible sheet 50 hits the back surface of the wafer W, the soft material is brought into contact with the wafer W. As a result, the back surface of the wafer is not damaged. Furthermore, when a soft material is provided on the side that is in close contact with the wafer W, when the wafer W is transported after polishing or before polishing, the soft material is in close contact with the wafer and can be stably transported.

  Alternatively, the structure may be such that water is contained in a soft material to hold the wafer, and the wafer W and the flexible sheet 50 are in good contact with each other through the water.

  It should be noted that the present invention can be variously modified without departing from the spirit of the present invention, and the present invention naturally extends to the modified ones.

The side view which shows the whole structure of the wafer grinding | polishing apparatus of this invention. The longitudinal cross-sectional view which shows the structure of a wafer holding head. Sectional drawing which shows the structure of a flexible sheet | seat attachment part. The bottom view which shows the structure of a backplate. The longitudinal cross-sectional view which shows the other structure of a wafer holding head. Sectional drawing which shows the other structure of a flexible sheet | seat attachment part.

Explanation of symbols

DESCRIPTION OF SYMBOLS 10 Wafer polisher 12 Polishing surface plate 14 Wafer holding head 20 Polishing pad 22 Head main body 24 Back plate (carrier)
26 Back plate pressing means 28 Retainer ring 30 Retainer ring pressing means 31 Retainer ring pressing member 32 Rotating shaft 36 Shaft 40 Back plate pressing member 42a Air suction / blowing groove 42b Air suction / blowing groove 42c Air suction / blowing groove 45 Pressure application Means 46 Air supply means 48 Air supply mechanism 50 Flexible sheet 51 First flexible sheet 51a Outer peripheral portion 51b Outer end 52 Second flexible sheet 53A Wafer inner region portion 53B Wafer outer region portion 54 Air suction / blowout hole 57 Retaining ring holder 60 Clamping member

Claims (6)

In a wafer polishing apparatus that performs polishing while sliding the wafer against the pad and performing relative movement,
Applying a pressure to press the wafer against the pad from the back side of the wafer through a flexible sheet,
In the wafer surface, with a polishing head having a pressure applying means consisting of a plurality of independent pressure chambers,
The flexible sheet covers the plurality of independent pressure chambers in the wafer surface, and has a large deflection in-wafer region that gives a smooth pressure distribution to the wafer; and
A wafer outer region portion that has a bending rigidity that is weaker than the bending rigidity of the wafer inner region portion, and is provided on the outer periphery of the wafer inner region portion;
A wafer polishing apparatus characterized by having two regions.   The flexible sheet is disposed to overlap the first flexible sheet having the same diameter as the first flexible sheet disposed from the inner region of the wafer to the outer region of the wafer. The wafer polishing apparatus according to claim 1, wherein the wafer polishing apparatus comprises the second flexible sheet.   The wafer polishing apparatus according to claim 1, wherein the flexible sheet is provided with a soft material on a part surface in contact with the wafer.   4. The wafer polishing apparatus according to claim 3, wherein the soft material has water retention and is in close contact with the wafer.   The wafer polishing apparatus according to claim 1, 2, 3, or 4, wherein the flexible sheet has an outer peripheral portion sandwiched between retainer portions. The pressure applying means includes a back plate provided on the back side of the flexible sheet, and an air supply means for continuously supplying air between the back plate and the flexible sheet. 2. A pressing force is transmitted to the wafer via an air layer formed between the back plate and the flexible sheet by the supply means and the flexible sheet. , 2, 3, 4 or 5 Symbol mounting of the wafer polishing apparatus.

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