JP2009224702A - Wafer polishing device and wafer polishing method using the polishing device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To eliminate the discontinuity of polishing pressure applied to a wafer from the divided air chambers of a wafer holding member in a wafer polishing device. <P>SOLUTION: On the bottom of a wafer carrier 11 of a polishing head 6, an inner air chamber 12, an intermediate air chamber 13, and an outer air chamber 14 are ring-shaped and are concentrically provided. The air pressures of the chambers are separately controlled. On the bottom of the wafer carrier 11, a pressure disk 18 is attached which has higher bending rigidity than a wafer W, and the wafer W is placed on the underside of the pressure disk 18. By pressure air supplied to the air chambers, a pressure is applied to the pressure disk 18 having high rigidity, and the wafer W is pressed to a polishing pad 5 through the pressure disk 18, and a pressure is applied through the pressure disk 18 to partitions between the plurality of air chambers where an air pressure is not applied under normal conditions, so that the discontinuity of pressure is eliminated. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to a wafer polishing apparatus, and more particularly to a wafer polishing apparatus having an improved polishing shape correction mechanism and a wafer polishing method using the polishing apparatus.

  The manufacture of high-density semiconductor devices consists of a platen that is a circular turntable with a polishing pad affixed to the upper surface and a polishing head that presses a silicon wafer against the surface of the polishing pad. 2. Description of the Related Art CMP-type wafer polishing apparatuses that polish a surface of a wafer itself or a thin film formed on the surface of a wafer are used.

  In this type of wafer polishing apparatus, in order to ensure the flatness of the polishing, the wafer holding mechanism and the support structure of the polishing head have been devised, but the polishing unevenness in the radial direction from the center of the wafer. May occur.

  There are various forms of polishing unevenness, such as when the outer peripheral edge is excessively polished, or when the location near the outer peripheral edge or the center is insufficiently polished, and the cause is specified as one of the causes. The wafer is bent by holding the outer peripheral surface of a very thin wafer, the elastic reaction force of the polishing pad against which the wafer is pressed, and the amount of slurry entering between the polishing pad and the wafer is the center of the wafer. It is considered that various factors such as a difference in the polishing rate due to the difference in the peripheral edge and the influence of the flatness on the opposite side of the surface to be polished of the wafer are intertwined.

  Since the wafer is polished by rotating, uneven polishing appears as a circular or annular convex portion or concave portion in the radial direction from the center of rotation, and the photolithographic process interferes with the exposure of a fine pattern. In a thin film removing process such as that, excessive polishing may cause disconnection of the conductive pattern, and insufficient polishing may cause short-circuiting of the conductive pattern.

  As a technique for eliminating the above-described polishing unevenness, techniques described in the following patent documents are known.

  Patent Document 1 includes a turntable having a polished surface and a top ring. The polishing object is interposed between the turntable and the top ring and pressed with a predetermined force. In a polishing apparatus that polishes and flattenes a polishing surface, the holding surface on which the top ring holds the object to be polished can be deformed by a variable fluid pressure, and the polishing is performed with a variable pressing force disposed around the top ring. A retainer ring that presses the surface and holds the polishing object within the holding surface of the top ring is provided.

  In Patent Document 2, a fluid chamber provided in a top ring and covered with an elastic film and supplied with a fluid, an elastic film forming the fluid chamber, and a substrate W are interposed between the elastic film and the substrate. A plurality of pressurizing members for applying a pressing force to W.

  Thereby, a pressing force is applied to the plurality of pressurizing members from the fluid in the fluid chamber, and the substrate is pressed against the polishing surface on the turntable by these pressurizing members. Therefore, a uniform pressing force can be applied over the entire surface of the substrate, and the entire surface to be polished of the substrate can be uniformly polished.

Patent Document 3 includes a top ring body that holds a substrate, an elastic pad that abuts against the base,
There is a support member that supports the elastic pad, and has a contact member that includes an elastic film that contacts the elastic pad on the lower surface of the support member, and inside the space formed between the elastic pad and the support member, The first pressure chamber is formed inside the contact member and the second pressure chamber is formed outside the contact member.

  In other words, the first pressure chamber and the second pressure chamber are adjacent to each other, and an independent pressure can be applied to each pressure chamber.

In Patent Literature 4, an annular convex portion is provided on the bottom surface of the wafer holder, and the polishing pressure is locally enhanced by the convex portion. A plurality of air chambers are formed by dividing the inside in the radial direction, air pressure is applied to the upper surface of the wafer through holes formed in the bottom surface of each air chamber, the wafer is pressed against the polishing pad, and the air pressure of each air chamber is adjusted. An apparatus is described that controls and controls the polishing amount of each part of the wafer by making the pressing pressure different between the inner peripheral part and the outer peripheral part of the wafer.
JP 2001-179605 A JP 2001-138224 A (see FIG. 4) JP 2002-187060 A JP-T-2001-513451 (see FIG. 9)

  The configuration described in Patent Document 1 performs pressurization control within the wafer surface using, for example, an in-plane pressurization distribution control system of a diaphragm type top ring. The inside of the diaphragm is composed of one air chamber. When the air is made negative pressure, the diaphragm is recessed and presses the outer periphery, and when the air applied to the diaphragm is made positive pressure, the diaphragm swells and presses the wafer center relatively strongly To do.

  However, when the polishing apparatus described in Patent Document 1 having such a configuration is used, there is a case where the flexural rigidity of the diaphragm varies in a plane. Since the inside of the diaphragm is only pressed evenly by the Pascal principle, no stress that corrects the deflection of the deflection rigidity of the diaphragm is applied, so that the dispersion of the deflection rigidity of the diaphragm is a pressure fluctuation that presses the wafer from beginning to end.

  Moreover, the diaphragm which changes into a convex shape or a concave shape by the internal pressure is manufactured to have substantially the same diameter as the wafer. For this reason, the fulcrum of the diaphragm is located at substantially the same position as the outer peripheral edge of the wafer. Thus, the fulcrum of the bending deformation brings about a specific behavior as pressure. In particular, in the case of bending deformation, the vicinity changes depending on the support form of the bending member.

Usually, when forming a pressurized container like a diaphragm, the support part of a diaphragm will be in a both-ends fixed state. When the diaphragm is fixed by fixing both ends, the displacement near the fulcrum becomes zero even if the vicinity of the wafer center is bent. Moreover, the inclination of the deflection is also 0, so that substantially no pressure is applied. As the wafer moves to the inner peripheral portion of the wafer, the gradient of the diaphragm gradually increases, but the gradient has an inflection point. For this reason, the pressure distribution is theoretically expected not to change smoothly and to be a unique pressure distribution. (Refer to Patent Document 1)
Further, when the diaphragm is composed of a stretchable elastic member, such a singular point of the pressure distribution exists, but the influence of the singular point may not be remarkable. This is because the diaphragm itself has a large margin of expansion and contraction and elastic deformation, so that it is absorbed in the diaphragm and becomes an apparently smooth shape. However, when forming a diaphragm with such an elastic member, the ability to relieve local pressure distribution by the flexural rigidity of the diaphragm is greatly reduced. In other words, even when a local load is applied to the diaphragm, only the local portion is deformed, so that the function as a stress distribution plate that disperses the local load and transmits the distributed pressure is almost lost.

  For this reason, the diaphragm needs to have a certain degree of rigidity to disperse the stress, but when the diameter is approximately the same as the wafer, a specific pressure is applied near the wafer edge, and the wafer edge portion The uniformity of the image quality is greatly impaired.

  Further, an elastic membrane (membrane) is wound around the diaphragm by being bent at about 90 ° at the outer periphery. In this way, when it is bent about 90 ° near the edge and fixed to the cylindrical body, even if it is an elastic sheet, the elastic sheet is locally bent and deformed even in the vicinity of the edge. Are stored there, and the elastic modulus of the elastic sheet increases rapidly only at the wafer edge portion. As a result, the wafer edge portion was subjected to excessive stress due to deformation resistance due to the bent elastic sheet.

  From the above situation, it may be possible to correct the polished shape in the wafer surface or to form a certain distribution in the polished shape, but on the other hand, as a side effect, it is stable and uniform up to the wafer edge. It is very difficult to form a uniform pressure distribution.

  In the polishing apparatus described in Patent Document 2, the load is applied by dividing the semiconductor wafer W by a large number of pressure pins to which a pressing force is applied from the fluid in the fluid chamber 8, so that the semiconductor wafer is independent of the thickness of the wafer W. It is said that a uniform polishing pressure can be applied over the entire surface from the central part to the peripheral part of W. However, on the other hand, it is impossible in principle to form a smooth pressure change because each of the plurality of pressure members cannot be completely controlled and the plurality of pressure members are independent.

  Furthermore, the configuration in which the interior of the wafer holder is divided in the radial direction to form a plurality of air chambers is formed by dividing a portion from the radial division point to the center portion and a portion from the radial division point to the outer edge portion. Although the polishing pressure can be individually controlled and the compatibility is wide, pressure is not applied to the wafer at the air chamber division point (partition or air gap), and in extreme cases, at the location corresponding to the air chamber division point. The result is a discontinuous finished shape with convex annular steps due to insufficient polishing.

  The polishing apparatus described in Patent Document 3 is intended to provide a polishing apparatus for changing the polishing shape to make the film thickness distribution after polishing uniform in order to correct the film thickness distribution during film formation. .

  A top ring body that holds the substrate, a seal ring that abuts on the upper surface of the outer peripheral edge of the substrate, and a support member that supports the outer seal ring, and is provided in a space formed between the seal ring and the support member. Has a first pressure chamber formed inside the abutting member and a second pressure chamber formed outside the abutting member, and supplies an independent fluid or vacuum to each pressure chamber. .

  In such a configuration, the first pressure chamber and the second pressure chamber are applied with independent pressure, but the wafer region pressed by the first pressure chamber and the wafer pressed by the second pressure chamber. Since the pressure clearly changes between the regions, a stepwise pressure distribution is formed as a result. As a result, the polished shape is not smooth, and a stepped polished shape is formed.

  In particular, when an elastic film covering the first pressure chamber and the second pressure chamber is made of a material that is very soft, a step-like pressure distribution appears particularly, so that the step-like polished shape becomes more noticeable.

  Normally, the film thickness distribution at the time of film formation is a smooth distribution, and therefore the film thickness distribution cannot always be completely corrected in a system that provides such a step-like pressure distribution.

  On the other hand, when an elastic film covering the first pressure chamber and the second pressure chamber uses a member having some rigidity, the pressure of the fluid sealed in the first pressure chamber deflects the elastic film. The pressure that is used as the pressure for pressurization and is pressed into the pressure chamber cannot be effectively applied as the pressure for pressing the wafer. Therefore, when the pressure chambers are adjacent to each other, it is very difficult to give a smooth pressure distribution as a result of giving independent pressures.

  The problem to be solved by the present invention is to form a smooth pressure distribution as a pressure distribution corresponding to the initial smooth film thickness distribution, thereby obtaining a smooth polished shape.

  An apparatus in which an annular protrusion is provided on the bottom surface of the wafer holder in Patent Document 4 and the polishing pressure is locally enhanced by this protrusion can enhance the polishing pressure only at a specific location. In order to match the wafer surface condition, it is difficult to adjust the position of the protrusion for each wafer or to replace the wafer holder with a different protrusion position.

  Also, in this document, the air chamber of the wafer holder is divided into an inner chamber and an outer chamber by a chamber seal, and the thin film (a sheet member that applies pressure to the wafer) is directed downwardly on the inner portion and the outer annular portion. Although a configuration is described in which the load can be adjusted independently (see the same document 4, FIG. 9, paragraphs 0060 and 0061), in this case as well, the polishing pressure is discontinuous at the division point of the chamber by the chamber seal. Sex issues exist.

  Therefore, in a wafer polishing device that can control the polishing pressure of the inner and outer peripheral parts of the wafer, the discontinuity of the polishing pressure applied to the wafer from the air chamber divided into a plurality of wafer holders is eliminated as much as possible. Technical problems to be solved in order to improve the polishing accuracy arise, and the present invention aims to solve the following problems.

  Provided is a polishing apparatus that obtains a uniform film thickness distribution after polishing by controlling the polishing shape in accordance with the initial smooth film thickness distribution.

  When the pressure is applied to the back side of the wafer, each area (area) where the pressure is applied has an independent pressure mechanism that faithfully reflects the introduction pressure, but the pressure is stepped by separating the areas. The present invention provides an apparatus that obtains a smooth polished shape under the formation of a smooth pressure distribution by mitigating discontinuous changes that vary.

  Near the wafer edge, there is a fulcrum (fixed end) of the flexible plate near the outer periphery of the wafer, thereby eliminating excessive pressure at the edge due to inflection points of member deflection, or unusual pressure distribution, from inside the wafer. An apparatus for obtaining a smooth polished shape under a smooth pressure distribution until reaching the outer periphery of a wafer is provided.

  Edge overpolishing caused by deformation distortion caused by abrupt bending of the member at the wafer edge portion is prevented.

  Provided is a polishing apparatus that gives a smooth pressure distribution to a wafer while not scratching or contaminating the back surface of the wafer.

  A polishing apparatus having a head capable of automatically removing and attaching a wafer is provided.

This invention is proposed to achieve the above object, and the invention according to claim 1
A wafer polishing apparatus comprising a polishing head for holding a wafer, pressing the wafer held by the polishing head against the surface of the polishing pad on the platen, and polishing the wafer by moving the platen and the polishing head relative to each other, A plurality of wafer pressing portions are arranged on the wafer mounting surface which is the bottom surface of the polishing head, air is supplied to the plurality of pressing portions, and the plurality of pressing portions are independently displaced by the air pressure, A wafer polishing apparatus is provided, which is provided with a flexible plate having flexibility so as to enclose the plurality of pressing portions.

  According to this configuration, in the conventional mechanism in which the pressure is transmitted to the back surface of the wafer by a plurality of independent air pressures, the flexural rigidity of the wafer alone cannot relax the step-like pressure distribution. The corresponding polished shape was formed under the formation of the pressure distribution.

  However, according to this configuration, even if the area where the wafer in each head is pressed is changed individually, even if the flexible plate has a pressure dispersion effect, as a result, an independent pressure is applied. Appears as a smooth polished shape. This avoids the formation of a stepped polished shape by the conventional stepwise pressure distribution formation.

  In the diaphragm shown in the above-mentioned Patent Document 1, it is possible to deform the surface of the diaphragm into a convex shape or a concave shape by controlling the pressure in the diaphragm. However, when the diaphragm is deformed, the member that supports the diaphragm is hollow (air) in the diaphragm, so that the force forcibly pushing back the diaphragm does not work. This is because even if the diaphragm is deformed, only a uniform pressure is constantly applied to the inside of the diaphragm by Pascal's principle, and a force to locally recover the deformed portion does not work. For this reason, when stress in the shear direction acts on the wafer that deforms the diaphragm, if the expansion of the diaphragm deforms in the plane, the force to correct it does not act, resulting in one-sided polishing. It is assumed that a shape is formed.

  However, in the case of having a mechanism for applying an independent pressure under the flexible plate as in the present application, even if the flexible plate is deformed, the pressure set value in the mechanism for providing an independent pressure existing thereunder does not change. Even if the flexible plate is locally deformed, a force to push it back from below acts. As a result, constantly stable pressure is applied to the wafer through the flexible plate under the independent pressurizing mechanism in which the polishing pressure is also supported.

  The invention described in claim 2 includes a polishing head for holding the wafer, the wafer held by the polishing head is pressed against the surface of the polishing pad on the platen, and the platen and the polishing head are moved relative to each other to move the wafer. A wafer polishing apparatus for polishing, wherein a plurality of wafer pressing portions are arranged on a wafer mounting surface which is a bottom surface of a polishing head, air is supplied to the plurality of pressing portions, and the plurality of pressing portions are independent by the air pressure. The plurality of wafer pressing portions have an elastic film that covers each region in the wafer surface, and a plurality of air chambers that can be independently pressed by sealing air in the elastic film. And a wafer polishing apparatus comprising a flexible plate that envelops and deforms the plurality of pressing portions.

  According to this configuration, due to the elastic film covering each region in the wafer surface, the pressure of the air confined in the elastic film is repelled by the elastic film itself when pushing out the elastic film. It is possible to faithfully transmit the pressure of air sealed in the elastic film. For example, if it is not an elastic film but a hard member, it goes without saying that the pressure sealed inside cannot be transmitted faithfully. Different air pressures are contained in each elastic film, so that each air pressure is transmitted faithfully, while the pressure that presses the backside of the wafer is stepwise corresponding to the air pressure region. . Since this air pressure is uniform in each area by the Pascal principle, it is theoretically impossible to smoothly change the stationary air pressure.

  Therefore, since the pressure applied to the wafer needs to be smooth, by placing the flexible plate on the top so as to envelop the elastic film, the stepwise air pressure is relaxed by the effect of the bending of the member, and the pressure is moderated. It is possible to form a gently polished shape in the wafer surface by forming a pressure distribution that changes to, and applying the pressure distribution to the wafer.

  The invention described in claim 3 includes a polishing head for holding the wafer, the wafer held by the polishing head is pressed against the surface of the polishing pad on the platen, and the platen and the polishing head are moved relative to each other to polish the wafer. A wafer polishing apparatus, wherein a plurality of wafer pressing portions are arranged on a wafer mounting surface which is a bottom surface of a polishing head, air is supplied to the plurality of pressing portions, and the plurality of pressing portions are independent by the air pressure. The plurality of wafer pressing portions each have an elastic film covering each region in the wafer surface, and a plurality of air chambers that can be independently pressed by sealing air in the elastic film. In addition, the present invention provides a wafer polishing apparatus having a flexible plate that envelops the plurality of pressing portions, and the flexible plate has a larger bending rigidity than the elastic film.

  This configuration is a more detailed description of the invention described in claim 2, and the elastic film covering each region in the wafer surface transmits the internal pressure faithfully to the wafer side when the rigidity is smaller. The pressure chamber partitioned by the elastic membrane covering each wafer area by increasing the rigidity of the flexible plate that envelops the pressure chamber partitioned by these elastic membranes. The step-like different pressures can be relaxed in the wafer surface by the effect of the bending of the member, and a gentle polishing shape can be formed under the formation of a gentle pressure distribution.

  According to a fourth aspect of the present invention, there is provided the wafer polishing apparatus according to the first, second or third aspect, wherein a soft protective film is mounted on the surface of the flexible plate.

  Each of the flexible plates described above is made of a material that is hard enough to relieve the different pressures in the elastic film. Therefore, when this flexible plate comes into contact with the wafer, it rubs against the back surface of the wafer and scratches the back surface of the wafer. Will enter. Therefore, in order to avoid scratches on the back surface of the wafer, a soft protective film is attached to the surface of the flexible plate that contacts the wafer.

  Thereby, even if the wafer and the soft protective film are rubbed, there is no fatal scratch on the back surface of the wafer. Further, if a packing film having a water retention capability is used as the soft protective film, the wafer is softly held through water, so that the back surface of the wafer is not further damaged.

  According to a fifth aspect of the present invention, there is provided the wafer polishing apparatus according to the first, second, third or fourth aspect, wherein one or a plurality of holes penetrating the flexible plate vertically are provided.

  In this configuration, if the pressure in the air chamber between the flexible plate and the elastic membrane is set to a negative pressure by a separate decompression means, the wafer can be adsorbed in the hole provided on the surface of the flexible plate. In this state, the wafer can be transferred from the transfer mechanism to the polishing unit. Subsequently, during polishing, if air is blown with a positive pressure through the hole, the wafer can be pressed against the polishing pad and polished, and a constant air layer is formed by supplying air continuously. Polishing can be performed.

Further, when the wafer is moved from the polishing unit to the transfer mechanism, the wafer is attracted and moved to the transfer mechanism part by using the air pressure in the air chamber as a negative pressure, and then the wafer is transferred to the transfer mechanism. When removing the wafer, the wafer can be removed by ejecting air through a hole provided in the surface of the flexible plate. Therefore, the wafer can be reliably held by reduced-pressure adsorption except during the polishing operation.

  The invention according to claim 6 is characterized in that the flexible plate is attached to and integrated with a flexible film having a lower rigidity, and the low flexible film is fixed to the polishing head. A wafer polishing apparatus according to 2, 3, 4 or 5 is provided.

  Since the flexible plate is attached to a flexible film having a lower rigidity, and is integrally fixed to the polishing head, the flexible plate is displaced flexibly by the flexible film having a lower rigidity near the edge of the flexible plate. Can be relaxed and changed. As a result, a unique pressure distribution is unlikely to occur in the edge portion.

  According to a seventh aspect of the present invention, in the wafer polishing apparatus, the flexible plate that envelops the plurality of pressing portions is attached to a flexible film having lower rigidity, and the flexible film is fixed to a retainer that protects the outer periphery of the wafer. The present invention provides a method for polishing a wafer, which is performed using the polishing apparatus.

  According to this method, as the flexible film is fixed to the retainer that protects the outer periphery of the wafer, the flexible film having low rigidity can be smoothly attached to the retainer without being bent rapidly.

  Conventionally, since the fulcrum portion supporting the flexible membrane itself has a diameter substantially equal to the wafer diameter, a specific pressure portion existing near the fulcrum of the flexible membrane is applied to the wafer edge. However, by fixing the flexible film itself to the retainer, the fulcrum part supporting the flexible film having low rigidity can be made a part farther from the wafer diameter than the outer peripheral part. An extremely smooth pressure distribution can be applied to the wafer edge without being influenced by the vicinity of the inflection point due to deformation of the flexure film. As a result, it is possible to obtain an almost uniform and smooth polishing shape up to the outermost peripheral portion with respect to the polishing shape near the wafer edge.

  According to an eighth aspect of the present invention, in the wafer polishing apparatus, the flexible plate enclosing the plurality of pressing portions is attached to a flexible film having a lower rigidity, and the flexible film is fixed to a retainer that protects the outer periphery of the wafer. The retainer has a pressurizing mechanism independent of the head for pressing the wafer, and is performed using a polishing apparatus having a mechanism for applying pressure to the outer peripheral portion of the flexible film by pressurizing the retainer. A wafer polishing method is provided.

  According to this method, a pressure separate from the wafer can be applied to the retainer. Further, when the pressure applied to the retainer is different from that of the wafer, when the retainer is made of a member separated from the flexible film as in the prior art, the retainer and the flexible film that presses the wafer are different. In particular, the pressure shape may change sharply due to the retainer pressure, particularly at the wafer edge.

  However, when the flexible film that presses the wafer is sandwiched between the retainers and the retainer is pressed thereon, the pressure applied to the retainer is also distributed to some wafers via the flexible film. Conversely, the pressure that presses the wafer is also distributed to the retainer partially through the flexible membrane. Therefore, even if the retainer and the wafer are not at the same pressure, both influences to form a smooth pressure change state.

Therefore, it is possible to form a smooth polished shape up to the wafer edge. Furthermore, when the pressure of the retainer on the wafer is changed, it becomes possible to smoothly connect the shape between the polished shape at the center of the wafer and the polished shape at the wafer edge without the edge portion changing rapidly. A very smooth polished shape can be obtained as a whole.

  According to a ninth aspect of the present invention, in the wafer polishing apparatus, the flexible plate enclosing the plurality of pressing portions is attached to a flexible film having a lower rigidity, and the flexible film is against the retainer that protects the outer periphery of the wafer. The retainer has a pressure mechanism that is independent of the head that presses the wafer and is fixed by setting a tension, and a polishing mechanism that has a mechanism that applies pressure to the outer peripheral portion of the flexible film by the pressure of the retainer. Provided is a wafer polishing method which is performed using an apparatus.

  According to this method, the flexible film having low rigidity performs the valve action. That is, a seal structure is formed between the outer periphery of the carrier head and the flexible film having low rigidity, and at the time of adsorption, a sealed space is formed between the flexible film and the carrier head. Polishing is performed.

  According to a tenth aspect of the present invention, in the wafer polishing apparatus, the flexible plate that envelops the plurality of pressing portions is attached to a flexible film having lower rigidity, and the flexible film is against the retainer that protects the outer periphery of the wafer. The retainer has a pressure mechanism that is independent of the head that presses the wafer, and has a mechanism that applies pressure to the outer peripheral portion of the flexible membrane by pressurization of the retainer. The flexible film and the flexible plate have one or a plurality of holes, and the outer periphery of the carrier head and the flexible film having low rigidity are in close contact with each other when sucked under reduced pressure. The wafer surface is sucked under reduced pressure through the hole, the outer periphery of the flexible film and the carrier head is sealed to form a closed space, and the wafer is sucked and conveyed. Continuously ejecting and pressing the wafer through the flexible film having low rigidity, the pressure air escapes from between the outer periphery of the carrier head and the flexible film, and the wafer and the flexible film having low rigidity And a polishing apparatus configured to polish a wafer with a constant air layer formed between the two.

  According to this method, the flexible membrane having low rigidity serves as a valve. That is, a seal structure is formed between the outer periphery of the carrier head and a flexible film having low rigidity, and at the time of adsorption, a sealed space is formed between the flexible film and the carrier head to adsorb the wafer and polish the wafer. Sometimes, pressure air is ejected from the carrier head, and the air presses the wafer through the flexible film having low rigidity, while the pressure air escapes between the outer periphery of the carrier head and the flexible film, An air layer is formed between them, and the surface can be polished with a pressure relaxed by the air layer.

  The invention according to claim 11 includes a polishing head for holding the wafer, the wafer held by the polishing head is pressed against the surface of the polishing pad on the platen, and the platen and the polishing head are moved relative to each other to polish the wafer. A wafer polishing apparatus, wherein a plurality of wafer pressing portions are arranged on a wafer mounting surface which is a bottom surface of a polishing head, air is supplied to the plurality of pressing portions, and the plurality of pressing portions are independent by the air pressure. A flexible plate having flexibility is attached so as to envelop the plurality of pressing parts, and different pressing forces are applied to the plurality of pressing parts, and the plurality of pressing parts are enveloped. There is provided a wafer polishing method characterized in that a smooth pressure distribution is given to a wafer by relaxing a stepwise pressing force by a flexible plate.

  According to this method, it is possible to relieve the stepped pressure of the plurality of pressing portions by the flexible plate having the flexibility to envelop the plurality of pressing portions, and under a smooth pressure distribution in the wafer surface, A smooth polished shape can be obtained.

  In this configuration, it is possible to remove and replace the pressure disk from the lower surface of the polishing head, or to clean the wafer mounting site.

  Unlike the conventional configuration in which the air pressure is directly applied to the wafer or the wafer is pressed through a flexible resin sheet when the pressing pressure is applied to the wafer, the present invention is applied via a pressure disk having a rigidity higher than that of the wafer. Since pressure is applied to the wafer, polishing unevenness due to insufficient pressure at the partition between the air chambers can be eliminated and polishing accuracy can be improved in a configuration in which the air pressure to the plurality of pressurized air chambers is controlled.

  Further, by using a pressure disk having a bending rigidity higher than that of the wafer, the overall pressure continuity is further improved as compared with the case of using a disk having a low bending rigidity.

  Further, the wafer can be securely held by adsorbing the wafer to the lower surface of the pressure disk with the air pressure in the air chamber being a negative pressure, and the possibility of the wafer falling off when the polishing head is moved is eliminated.

  Furthermore, maintenance such as replacement of pressure disks having different flexural rigidity and cleaning of the polishing head can be easily performed.

  The present invention eliminates the discontinuity of the polishing pressure applied to the wafer from the air chamber divided into a plurality of wafer holders in a wafer polishing apparatus capable of controlling the polishing pressure of the inner and outer peripheral portions of the wafer. In order to achieve the purpose of improving the polishing accuracy, a polishing head for holding the wafer is provided, the wafer held by the polishing head is pressed against the surface of the polishing pad on the platen, and the platen and the polishing head are moved relative to each other. A wafer polishing apparatus for polishing a wafer, wherein a plurality of wafer pressing portions are arranged on a wafer mounting surface which is a bottom surface of a polishing head, air is supplied to the plurality of pressing portions, and the plurality of air pressures are supplied by the air pressure. It has a mechanism for independently displacing the pressing parts, and is equipped with a flexible plate having flexibility so as to envelop the plurality of pressing parts. It was achieved by providing a Eha polishing apparatus.

  A preferred embodiment of the present invention will be described below with reference to FIGS. FIG. 1 shows a wafer polishing apparatus 1, in which a disk-shaped platen 2 is mounted on a rotary drive mechanism 4 using a platen drive motor 3, and a polishing pad 5 is stuck on the upper surface of the platen 2. The polishing head 6 disposed above the platen 2 and at a position displaced from the rotation center of the platen 2 has a disk shape smaller in diameter than the platen 2, and a wafer W to be polished is attached to the lower surface thereof.

  Although not shown, the shaft 7 of the polishing head 6 is attached to a rotational drive mechanism by a motor disposed at the tip of the head carrier arm, and is retracted from the polishing position and the platen 2 in FIG. 1 by the head carrier arm. Move to and from the position and move up and down. A plurality of air pipes from the air pressure control device including the air pump, the air pressure control valve and the air pressure regulator communicate with the inside of the top cover 8 of the polishing head 6 through the rotary joint and the hollow shaft 7.

  In the polishing step, a polishing chemical solution or a polishing slurry is dropped from the chemical solution supply device (not shown) on the upper surface of the polishing pad 5, and the polishing head 6 is lowered to a height at which the wafer W comes into contact with the upper surface of the pad 5. The platen 2 and the polishing head 6 are driven to rotate in the same direction, and the surface to be polished (the lower surface) of the wafer W is polished.

  FIG. 2 is an explanatory diagram for explaining a polishing shape correction structure of the polishing head 6. A retainer ring 10 is disposed under an outer peripheral ring portion 9 that extends downward from the outer periphery of the top cover 8, and a disc-shaped carrier 11 is mounted inside the retainer ring 10. The retainer ring 10 and the carrier 11 are rotationally driven integrally with the shaft 7.

  An inner air chamber 12, an intermediate air chamber 13, and an outer air chamber 14 that are concentric circular grooves are formed on the bottom surface of the carrier 11. Although the air chamber of the carrier 11 is divided into three here, it may be divided into two or more than four. The three air chambers of the inner air chamber 12, the intermediate air chamber 13, and the outer air chamber 14 are each formed with a hole penetrating to the upper surface of the carrier 11, and each hole is empty through the air pipes 15, 16, and 17. It is connected to a pressure control device (not shown) and the air pressure is individually controlled. Note that the retainer ring 10 may be supported so that it can be lifted and lowered, and the pressing pressure of the retainer ring 10 may be controlled by air pressure, as in the known art.

  Here, the surface of each air chamber is covered with a soft rubber material. For example, chloroprene rubber or styrene rubber is desirable as the rubber material. Moreover, even if it is a soft material, it is desirable that the rubber material has a small compression set that is almost completely restored to its original state when the air chamber expands and then the air disappears after the expansion. If a material such as a material that covers the air chamber is a rigid flexible member, the pressure introduced into the air chamber is not faithfully reflected, and a pressure state that serves as a basis for pressing the wafer cannot be formed. Therefore, in order to faithfully transmit the pressure in the air chamber, a material that covers the air chamber is preferably a rubber material having as small an elastic coefficient as possible.

  On the bottom surface of the carrier 11, a pressure disk 18 that directly receives the air pressure of the three air chambers 12, 13, and 14 and a wafer W that is a material to be polished are mounted. The diameters of the pressure disk 18 and the wafer W are substantially equal to the diameter of the carrier 11, and the outer peripheral surface is in contact with the inner peripheral surface of the retainer ring 10, thereby forming a space formed by the inner peripheral surface of the retainer ring 10 and the bottom surface of the carrier 11. Retained.

  The pressure disk 18 is a resin or metal plate-like member having a higher bending rigidity than the wafer W made of silicon, and is mounted so as to contact the bottom surface of the carrier 11. The wafer W is superimposed on the bottom surface of the pressure disk 18. Is done.

  The pressure disk 18 is greatly different from the rubber material covering the air chamber, and a flexible member having high rigidity is used. This is because the basic pressure introduced into the air chamber is relaxed and applied to the wafer W.

  In the air chamber, only an independent pressure is given by partitioning, but the pressure distribution applied to the actual wafer W needs to form a smooth pressure distribution. For this reason, a flexible member having such a high rigidity as to have a function of enveloping a pressure distribution state as a basis formed by the respective air chambers is preferably used.

  As a material to be used, for example, a vinyl chloride plate (thickness of about 3 mm), an acrylic plate (thickness of about 3 mm), a SUS plate (thickness of 1 mm), or the like may be used. The surface is hard and does not compressively deform even when subjected to pressure, but a base material that deforms and deforms is used.

  As shown in FIG. 2A, when the air pressures applied to the outer air chamber 14, the intermediate air chamber 13, and the inner air chamber 12 are a, b, and c, respectively, the outer air chamber 14 and the intermediate air chamber of the pressure disk 18 are used. 13. Three portions corresponding to the inner air chamber 12 receive air pressures a, b, and c, respectively, and press the wafer W directly thereunder against the polishing pad 5 according to the pressure distribution of a, b, and c (however, The pressure is attenuated more than the air pressure a, b, c by the rigidity of the pressure disk 18).

  As a result, no pressure is applied to the wall portion of the air chamber, that is, the partitioned boundary portion. Therefore, the pressure distribution applied to the wafer W is not a continuous and smooth distribution, and FIG. ) It becomes a slightly constricted shape as shown in.

  At this time, at the position immediately below the partition walls that define the air chambers 12, 13, 14 of the wafer carrier 11, due to the rigidity of the pressure disk 18, pressure is applied to change from the air pressure on one side of the partition wall to the air pressure on the other side, The entire wafer has a smooth pressure distribution. For example, FIG. 2B shows a pressure distribution graph when air pressure is supplied in a relationship of a <b <c.

  In the case where the pressure disk 18 is inserted, the pressure distribution is relaxed so as to envelop the pressure distribution form in each air chamber.

  The pressure distribution of the air chambers creates individual pressures, so that each introduces an independent pressure, resulting in only a discontinuous pressure distribution, but by inserting a pressure disk (flexible plate), The pressure is relaxed by the action of the bending rigidity of the member, and the pressure between a and b and b and c transitions smoothly. Note that the air pressures a, b, and c are arbitrarily set according to the surface state of the wafer W, and the example of FIG. 2B is an example.

  FIG. 3A shows a state in which the pressure disk 18 is removed from the embodiment of FIG. This is the same state as the configuration in which the conventional air chamber is divided in the radial direction. In this state, when air pressures a, b, and c are supplied to the outer air chamber 14, the intermediate air chamber 13, and the inner air chamber 12, respectively, as in FIG. 2, portions corresponding to the air chambers 12, 13, and 14 of the wafer W. Receives air pressures a, b, and c, respectively, and is pressed against the polishing pad 5 according to the pressure distribution of a, b, and c, but the wafer W has pressures a, b, and c in the air chambers 12, 13, and 14, respectively. Accordingly, the pressure below the lowering pressure of the polishing head 6 is not applied at a position immediately below the partition wall that partitions the air chambers 12, 13, and 14 of the carrier 11.

  Therefore, when the pressure distribution form is constricted immediately below the partition wall, or even if the partition wall width is almost zero, a step-like pressure distribution is obtained and a smooth pressure distribution pattern can be obtained. It is not a thing.

  For example, as shown in FIG. 2 (a), when air pressure is supplied in the relationship of a <b <c, as shown in FIG. 3 (b), almost no pressure is applied at a position immediately below the partition wall. Then, polishing does not proceed as in the positions directly below the outer air chamber 14, the intermediate air chamber 13, and the inner air chamber 12, so that the polishing is insufficient and this portion remains in a ring shape to form a step.

  The above is the description of the embodiment of the invention described in claims 1 to 3, but when applying the pressing pressure to the wafer W, the conventional configuration of pressing the wafer W directly or via a flexible resin sheet Unlike the wafer W, the pressure is applied to the wafer W via the pressure disk 18 which is higher in rigidity than the wafer W. Therefore, in the mechanical configuration in which the air pressure to the plurality of concentric pressure air chambers is controlled and polished, the pressure between the air chambers Discontinuity can be eliminated, and insufficient polishing at the partition between the air chambers can be eliminated.

  In a fourth embodiment of the present invention, a soft protective film (not shown) is attached to the lower surface of the pressure disk 18 (flexible plate). This is because, since the pressure disk 18 uses a hard member as described above, when the base material comes into contact with the wafer W, the back surface of the wafer W is damaged. Therefore, it is desirable to use a member that does not damage the wafer W even if it contacts the wafer W on the surface of the pressure disk 18.

  For example, a commercially available wafer mount material or a suede type packing film material is preferably used. Moreover, porous materials, such as PVA sponge with good moisture retention, etc. may be sufficient.

Furthermore, the invention described in claim 5 is provided with suction holes 19, 19... Penetrating the front and back of the pressure disk 18 and the protective film as shown in FIG. 4, and the suction holes 19, 19. The wafer W is attracted to the pressure disk 18. When the unpolished wafer W is transferred, the wafer W is sucked into the surface of the soft member on the pressure disk 18 by sucking the wafer W together with air from the suction holes 19, 19. As a result, the wafer W can be transferred from the transfer system to the polishing portion while being attracted to the polishing head 6.

  Further, the pressure disk 18 mounted in the retainer ring 10 can be attached and detached so that replacement and maintenance of the device can be easily performed.

  Further, according to the sixth and seventh aspects of the present invention, as shown in FIG. 5, the pressure disk 18 (flexible plate) is attached to a flexible film 20 provided separately. The material used for the flexible membrane 20 is preferably a PFA sheet (0.3 mm thick), a PE sheet (0.5 mm), or the like. As compared with the pressure disk 18, the flexible film 20 is made of a relatively soft or thin material.

  This is because the pressure disk 18 functions to enclose individual set pressures in the wafer W surface, whereas the flexible film 20 relaxes the pressure change at the edge of the wafer, and the polished shape near the edge. This is because the purpose is to make the continuous and uniform.

  If only the pressure disk 18 is used to form the edge, stress tends to concentrate on the edge portion. In particular, local stress acts on the edge portion at the boundary portion between the region where the wafer W exists and the region where the wafer W does not exist. As a result, the wafer W causes excessive polishing at the edge portion. In order to alleviate this even a little, it is possible to obtain a smooth edge shape by relaxing the pressure change by utilizing the flexibility of the thin flexible film 20 for the edge portion.

  Further, as shown in FIG. 2, in the invention described in claim 8, the flexible membrane 20 to which the pressure disk 18 is attached is further sandwiched between the retainer rings 10. Thereby, the following effects can be obtained.

  When the flexible film 20 is attached to the carrier 11 as in the prior art, since the retainer ring 10 that protects the periphery of the wafer W exists around the carrier 11, the flexible film 20 has to be bent and attached abruptly. . When the flexible film 20 is abruptly bent and attached to the carrier 11, stress is accumulated at the bent portion, and as a result, the wafer edge portion corresponding to the bent portion is excessively subjected to excessive stress locally. There was a problem of being polished.

  On the other hand, by attaching the flexible film 20 to which the pressure disk 18 is attached to the retainer ring 10 portion, the flexible film 20 can be stretched to the outer periphery of the wafer W in a substantially horizontal state. Further, since the fulcrum for holding the flexible film 20 can be set at a part slightly away from the wafer edge, the flexible film 20 part corresponding to the wafer W region has no shape change due to sudden bending or the like. The wafer is smoothly deformed to form a pressure distribution at the wafer edge.

  According to the ninth aspect of the present invention, in the wafer polishing apparatus shown in FIG. 1, the pressure disk 18 enveloping a plurality of pressing portions is attached to a flexible film 20 having a lower rigidity, and the flexible film 20 is an outer periphery of the wafer W. The retainer ring 10 is fixed to the retainer ring 10 that protects the wafer W. The retainer ring 10 has a pressurizing mechanism that is independent of the carrier 11 that presses the wafer W. Pressure is applied to the outer peripheral portion of the flexible film 20 by pressurization of the retainer ring 10, and the pressure at the wafer edge portion can be changed.

In the invention according to claim 10, as shown in FIG. 6A, when the wafer W is attracted, the flexible film 20 having low rigidity is placed between the outer peripheral portions of the carrier 11 and the flexible film 20 is placed on the outer periphery of the carrier 11. The wafer W is sealed in a wound form, and the wafer W can be sucked and transferred.

  On the other hand, as shown in FIG. 5B, while the wafer W is polished, the wafer W is pressed by the pressure film supplied from the carrier 11 through the flexible film 20 having low rigidity, and the carrier 11 and the flexible film 20 are pressed. Therefore, a stable and uniform pressure distribution can be given to the wafer W.

  Further, the supplied surplus air escapes from the portion between the outer peripheral portion of the carrier 11 and the flexible film 20 to the outside. As a result, the back surface of the wafer W can be pressed through the air layer under continuously supplied air.

  From the above, the outer periphery of the flexible membrane and the carrier head has a valve structure here.

  Next, the invention described in claim 11 is provided with a polishing head 6 for holding the wafer W, the wafer W held by the polishing head 6 is pressed against the surface of the polishing pad 5 on the platen 2, and the platen 2 and the polishing head 6 are respectively connected. A wafer polishing apparatus that polishes a wafer W by relatively moving the wafer, wherein a plurality of wafer pressing portions are arranged on a wafer mounting surface that is a bottom surface of the polishing head 6, and air is supplied to the plurality of pressing portions, The plurality of pressing portions have a mechanism for independently displacing them by air pressure, and a flexible pressure disk 18 is attached so as to envelop the plurality of pressing portions, and different stepped pressing forces are applied to the plurality of pressing portions. In addition, the pressure disk 18 enveloping a plurality of pressing portions is used to relieve the stepwise pressing force, thereby giving a smooth pressure distribution to the wafer W.

  The present invention is not limited to the above-described embodiment, and various modifications are possible within the technical scope of the present invention, and it is natural that the present invention extends to those modifications.

The perspective view of a wafer polisher. (A) Longitudinal sectional view of polishing head of wafer polishing apparatus of the present invention, (b) Radial pressure distribution graph applied to wafer. (A) Longitudinal sectional view of the polishing head of FIG. 2 with the pressure disk removed, (b) A radial pressure distribution graph applied to the wafer. FIG. 3 is a plan view of a pressure disk attached to the polishing head of FIG. 2. FIG. 3 is a reference diagram showing a state in which a flexible film is attached to the upper surface of a pressure disk attached to the polishing head of FIG. (A) A cross-sectional view showing a state in which a flexible film is attached to the upper surface of the pressure disk attached to the polishing head of FIG. 2 and the wafer is adsorbed, and (b) a state in which the pressure air is pressed against the wafer from (a) above. Sectional drawing.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Wafer polisher 2 Platen 3 Platen drive motor 4 Rotation drive mechanism 5 Polishing pad 6 Polishing head 7 Axis 8 Top cover 9 Outer ring part 10 Retainer ring 11 Carrier 12 Inner air chamber 13 Intermediate air chamber 14 Outer air chamber 15, 16, 17 Air duct 18 Pressure disk 19 Suction hole 20 Flexible membrane W Wafer

Claims (11)

A wafer polishing apparatus comprising a polishing head for holding a wafer, pressing the wafer held by the polishing head against the surface of the polishing pad on the platen, and polishing the wafer by moving the platen and the polishing head relative to each other,
A plurality of wafer pressing portions are arranged on the wafer mounting surface which is the bottom surface of the polishing head,
Air is supplied to the plurality of pressing portions, and the plurality of pressing portions are independently displaced by the air pressure;
A wafer polishing apparatus comprising a flexible plate having flexibility so as to envelop the plurality of pressing portions. A wafer polishing apparatus comprising a polishing head for holding a wafer, pressing the wafer held by the polishing head against the surface of the polishing pad on the platen, and polishing the wafer by moving the platen and the polishing head relative to each other,
A plurality of wafer pressing portions are arranged on the wafer mounting surface which is the bottom surface of the polishing head,
Air is supplied to the plurality of pressing portions, and the plurality of pressing portions are independently displaced by the air pressure;
The plurality of wafer pressing parts have an elastic film covering each region in the wafer surface, and are composed of a plurality of air chambers that can be pressed independently by sealing air in the elastic film,
A wafer polishing apparatus comprising a flexible plate that envelopes and deforms the plurality of pressing portions. A wafer polishing apparatus comprising a polishing head for holding a wafer, pressing the wafer held by the polishing head against the surface of the polishing pad on the platen, and polishing the wafer by moving the platen and the polishing head relative to each other,
A plurality of wafer pressing portions are arranged on the wafer mounting surface which is the bottom surface of the polishing head,
Air is supplied to the plurality of pressing portions, and the plurality of pressing portions are independently displaced by the air pressure;
The plurality of wafer pressing portions have an elastic film covering each region in the wafer surface, and have a plurality of air chambers that can be pressed independently by sealing air in the elastic film,
A wafer polishing apparatus having a flexible plate that envelops the plurality of pressing portions, and the flexible plate has a larger bending rigidity than the elastic film.   4. A wafer polishing apparatus according to claim 1, wherein a soft protective film is mounted on the surface of the flexible plate.   5. The wafer polishing apparatus according to claim 1, wherein one or a plurality of holes penetrating vertically through the flexible plate are provided.   6. The flexible plate according to claim 1, wherein the flexible plate is attached to and integrated with a flexible film having low rigidity, and the low flexible film is fixed to a polishing head. Wafer polishing equipment.   In the above-described wafer polishing apparatus, a flexible plate enclosing a plurality of pressing portions is attached to a flexible film having a lower rigidity, and the flexible film is fixed to a retainer that protects the outer periphery of the wafer. A wafer polishing method comprising: executing the wafer polishing method. In a wafer polishing apparatus, a flexible plate that envelops a plurality of pressing portions is attached to a flexible film having lower rigidity, and the flexible film is fixed to a retainer that protects the outer periphery of the wafer, and the retainer presses the wafer. A wafer polishing method, comprising: a polishing apparatus having a pressurizing mechanism independent of a head and having a mechanism that applies pressure to the outer peripheral portion of the flexible film by pressurizing a retainer.   In the wafer polishing apparatus, a flexible plate that envelops a plurality of pressing parts is attached to a flexible film having lower rigidity, and the flexible film is fixed with a tension set to a retainer that protects the outer periphery of the wafer. The retainer has a pressurizing mechanism independent of the head for pressing the wafer, and is performed using a polishing apparatus having a mechanism that applies pressure to the outer peripheral portion of the flexible film by pressurization of the retainer. A wafer polishing method. In the wafer polishing apparatus, a flexible plate that envelops a plurality of pressing parts is attached to a flexible film having lower rigidity, and the flexible film is fixed with a tension set to a retainer that protects the outer periphery of the wafer. The retainer has a pressurizing mechanism that is independent of a head that presses the wafer, and has a mechanism that applies pressure to the outer peripheral portion of the flexible membrane by pressurization of the retainer. The flexible membrane and the flexible plate Has one or a plurality of holes, and has a structure in which the outer periphery of the carrier head and the flexible film having low rigidity are tightly sealed at the time of vacuum adsorption,
At the time of wafer adsorption, the wafer surface is adsorbed under reduced pressure through the hole, the outer periphery of the flexible film and the carrier head is sealed to form a closed space, and the wafer is adsorbed and conveyed.
During wafer polishing, pressure air is continuously ejected from the carrier head, pressing the wafer through a flexible film having low rigidity, and the pressure air is drawn from between the outer periphery of the carrier head and the flexible film. A wafer polishing method that is performed using a polishing apparatus configured to polish the wafer in a state in which the wafer exits and a constant air layer is formed between the wafer and a flexible film having low rigidity. . A wafer polishing apparatus comprising a polishing head for holding a wafer, pressing the wafer held by the polishing head against the surface of the polishing pad on the platen, and polishing the wafer by moving the platen and the polishing head relative to each other,
A plurality of wafer pressing portions are arranged on the wafer mounting surface which is the bottom surface of the polishing head,
Air is supplied to the plurality of pressing portions, and the plurality of pressing portions are independently displaced by the air pressure;
A flexible plate having flexibility is attached so as to envelop the plurality of pressing portions, and different step-like pressing forces are applied to the plurality of pressing portions, and stepped by the flexible plate enveloping the plurality of pressing portions. A wafer polishing method, characterized in that a smooth pressure distribution is given to a wafer by relaxing a pressing force.

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