Spin etching device, spin etching method, and wafer holding method

Abstract

To provide an edge chuck-type spin etching device that suppresses local etching of a back surface (lower surface) oxide film as much as possible, and does not affect the SFQR value of the upper surface of a wafer after etching.SOLUTION: There is provided a spin etching device 1 which includes a stage 5 that holds a wafer W and spins to rotate the wafer W, a removal liquid being supplied onto an upper surface of the rotating wafer W to remove a film on the upper surface of the wafer W. The spin etching device 1 includes: a plurality of edge chuck pins 13 provided on the stage 5 so as to sandwich the wafer W in point contact with an edge part 21 of the wafer W; and a plurality of wafer support pins 15 that are provided on the stage 5 and that contact a lower surface of the wafer W to support the wafer W from below in a state where a gap is formed between the stage 5 and the wafer W.SELECTED DRAWING: Figure 4

Description

[Technical field]

[0001] The present invention relates to a spin etching apparatus, a spin etching method, and a wafer holding method. [Background technology]

[0002] When semiconductor wafers undergo surface processing such as grinding, polishing, and peeling, a damaged layer is introduced to the wafer surface due to the processing. The damaged layer contains defects, dislocations, distortions, etc. that adversely affect device characteristics, so it is necessary to remove the damaged layer.

[0003] One method for removing the surface damage layer of a semiconductor silicon wafer is to thermally oxidize the damaged layer to form a silicon oxide film, and then remove the silicon oxide film including the damaged layer with a hydrofluoric acid (HF) solution. This silicon oxide film is also called a sacrificial oxide film.

[0004] One method of removing the sacrificial oxide film using an HF solution is to immerse the semiconductor silicon wafer in the HF solution stored in a chemical tank. In this case, not only the oxide film on the front side of the wafer but also the oxide film on the back side of the wafer is removed.

[0005] Depending on the process, structure, and processing conditions of a semiconductor wafer, there are cases where only the surface oxide film is removed while leaving the backside oxide film. For example, in a wafer having a buried oxide layer (BOX layer: Buried Oxide Layer) such as an SOI (Silicon On Insulator) wafer, it is necessary to balance the thickness of the BOX layer and the backside oxide film in order to suppress the warpage of the wafer. In this case, only the surface oxide film is removed using a spin etching device (spin processing device) (Patent Documents 1 to 3).

[0006] The spin processing equipment is a single-wafer rotary etching equipment. By supplying HF solution to the center of the wafer surface (top surface) while the wafer is rotating, the HF solution spreads over the entire wafer surface, removing the oxide film on the wafer surface.

[0007] In addition, by using centrifugal force to blow the HF solution from the edge of the wafer surface, it is possible to prevent the HF from reaching the back surface of the wafer, preventing the back surface oxide film from being etched, and leaving the back surface oxide film intact. Note that a spin etching device that uses HF to remove oxide films is sometimes called an HF spin device.

[0008] The HF solution that is blown off from the wafer edge by centrifugal force can be collected in a collection cup installed around the wafer and reused for the next oxide film removal process. This reduces the amount of HF used, the amount of HF waste, and the environmental impact due to the reduced amount of HF waste.

[0009] In order to efficiently remove oxide films with a thickness of 100 nm or more, it is necessary to increase the etching rate of the oxide film and keep the etching time per wafer short. For this reason, the HF concentration of the HF solution used for oxide film removal is often 10 mass % or more, unlike the HF solution used for cleaning, which has a few mass % or less. [Prior art documents] [Patent documents]

[0010] [Patent Document 1] JP 2009-206486 A [Patent Document 2] JP 2010-238782 A [Patent Document 3] JP 2012-094836 A Summary of the Invention [Problem to be solved by the invention]

[0011] The wafer is held in the spin processing apparatus either by holding the edge of the wafer with an edge chuck or by holding the back surface (lower surface) of the wafer by vacuum suction or the like.

[0012] 6(a)-(c) and 7, the method of holding the wafer edge with an edge chuck is, for example, to grip edge 21 of wafer W with edge chuck 41 on rotating stage 5, supporting the wafer W from below, and when the wafer W spins, the edge chuck has a holder that holds the wafer W so that the wafer W does not fly out of stage 5 due to centrifugal force, and only edge 21 of wafer W comes into contact with edge chuck 41, and other parts do not come into contact with it. This makes it difficult for particles to adhere to the wafer W or for it to be scratched.

[0013] By applying HF solution near the center of the surface of the wafer while rotating, the HF solution spreads over the entire surface of the wafer, and the oxide film on the surface of the wafer can be removed. In addition, by spraying the HF solution from the edge of the wafer surface using centrifugal force, the HF is prevented from reaching the back surface of the wafer, preventing etching of the back surface oxide film and leaving the back surface oxide film intact.

[0014] However, when the HF solution is ejected from the wafer edge by centrifugal force at the edge chuck, part of the HF solution hits the edge chuck and cannot be discharged outside. As a result, part of the HF solution that hits the edge chuck passes through the edge chuck and flows around to the back side of the wafer, locally etching part of the back side oxide film.

[0015] When measuring wafer flatness, the capacitance type flatness measuring instrument analyzes the wafer flatness based on the assumption that the backside of the wafer is flat. Therefore, if the backside oxide film on the backside of the wafer is locally etched at the edge chuck and the backside oxide film is locally thin, it is analyzed that there is a dent on the front side of that position, and the values ​​such as SFQR (Site Frontside ref. least square range) deteriorate.

[0016] Furthermore, if a portion of the backside oxide film is locally etched, the thickness of the oxide film becomes uneven, and the appearance of the backside of the wafer is deteriorated.

[0017] On the other hand, when the back surface of the wafer is held by vacuum suction, there is no obstacle such as an edge chuck when the HF solution is blown off from the wafer by centrifugal force, so local etching does not occur at the edge.

[0018] However, contact between the backside of the wafer and the suction pad can contaminate or scratch the backside of the wafer, which is why this method is not preferred for wafers for cutting-edge devices or 12-inch semiconductor silicon wafers.

[0019] For these reasons, there is a demand for an edge chuck type spin etching device that minimizes local etching of the backside (lower surface) oxide film and does not affect the SFQR value.

[0020] The present invention has been made to solve the above problems, and has an object to provide an edge chuck type spin etching apparatus which suppresses local etching of the back surface (lower surface) oxide film as much as possible and does not affect the SFQR value of the upper surface of the wafer after etching.

[0021] Another object of the present invention is to provide an edge chuck type spin etching method which suppresses local etching of the back surface (lower surface) oxide film as much as possible and does not affect the SFQR value of the upper surface of the wafer after etching.

[0022] It is yet another object of the present invention to provide an edge chuck type wafer holding method which suppresses local etching of the back surface (lower surface) oxide film as much as possible and does not affect the SFQR value of the upper surface of the wafer after etching. [Means for solving the problem]

[0023] The present invention has been made to achieve the above-mentioned object, and provides a spin etching apparatus having a stage that holds a wafer and spins, and removes a film on the upper surface of the wafer by supplying a removing liquid to the upper surface of the rotating wafer, characterized in that the spin etching apparatus has a plurality of edge chuck pins provided on the stage so as to make point contact with the edge portion of the wafer to clamp the wafer, and a plurality of wafer support pins provided on the stage and support the wafer from below while contacting the underside of the wafer to form a gap between the stage and the wafer.

[0024] In this type of spin etching apparatus, the edge chuck pin that holds the wafer makes point contact with the edge of the wafer to minimize the contact area with the wafer, and the wafer support pins support the wafer from below, forming a gap between the stage and the wafer and preventing the removal solution from seeping through the edge chuck pin to the underside of the wafer.

[0025] Therefore, even if the edge chuck method is used, local etching of the lower oxide film can be suppressed as much as possible, and the SFQR value of the upper surface of the wafer after etching is not affected.

[0026] In this case, at least one of the edge chuck pins and the wafer support pins can be made of resin.

[0027] This makes it difficult for the materials constituting the edge chuck pins and the wafer support pins to contaminate the wafer during etching.

[0028] In this case, at least one of the edge chuck pins and the wafer support pins can be made of PEEK, PFA, or PVDF.

[0029] As a result, at least one of the edge chuck pin and the wafer support pin has excellent chemical resistance, so that the edge chuck pin and the wafer support pin are less likely to be etched by the remover during etching.

[0030] In this case, the edge chuck pin may be cylindrical or frustoconical in shape with its horizontal cross-sectional area increasing toward its tip.

[0031] This minimizes the contact area between the wafer edge and the edge chuck pin in the vertical direction. Also, by making the edge chuck pin into a truncated cone shape whose cross-sectional area in the horizontal direction increases toward the tip, the risk of the wafer popping up during etching can be further reduced.

[0032] In this case, the edge chuck pin may be cylindrical, and the diameter of the cylinder may be 5 mm or less.

[0033] This can further prevent the remover from getting around to the underside of the wafer.

[0034] In this case, the edge chuck pin may have a cylindrical wafer contact portion that comes into point contact with the wafer, and a tip portion that is provided at the tip of the wafer contact portion and has a diameter larger than that of the wafer contact portion.

[0035] This can further reduce the risk of the wafer popping up during etching.

[0036] The present invention also provides a spin etching method in which a stage holding a wafer is spin-rotated, a removing liquid is supplied to the upper surface of the rotating wafer, and a film on the upper surface of the wafer is removed, characterized in that the wafer is held so as to be sandwiched between a plurality of edge chuck pins that make point contact with the edge of the wafer, and the wafer is further etched while being held by a plurality of wafer support pins that support the underside of the wafer from below so that the wafer does not come into contact with the stage.

[0037] According to this spin etching method, the edge chuck pin that holds the wafer makes point contact with the edge of the wafer to minimize the contact area with the wafer, and the wafer support pins support the wafer from below, thereby forming a gap between the stage and the wafer and preventing the removal solution from flowing through the edge chuck pin to the back surface (lower surface) of the wafer.

[0038] Therefore, even when the edge chuck method is used, local etching of the back surface (lower surface) oxide film can be suppressed as much as possible, and the SFQR value of the upper surface of the wafer after etching is not affected.

[0039] In this case, the wafer may be a silicon wafer with an oxide film, and the remover may be a HF solution.

[0040] This allows the oxide film formed on the upper surface of the silicon wafer to be removed by etching with an HF solution.

[0041] At this time, the concentration of the HF solution can be set to 10 to 40% by mass.

[0042] This increases the etching rate of the film and reduces the etching time per wafer.

[0043] The present invention further provides a wafer holding method for holding a wafer during spin etching, in which a stage holding a wafer is spin-rotated and a remover liquid is supplied to the rotating wafer to remove a film on the upper surface of the wafer, characterized in that the wafer is held by clamping it with edge chuck pins that make point contact with multiple points on the edge of the wafer to prevent the wafer from flying out due to centrifugal force during spin rotation, and the wafer is held by multiple wafer support pins that support the underside of the wafer from below, preventing the wafer from coming into contact with the stage.

[0044] According to this wafer holding method, the edge chuck pin that holds the wafer makes point contact with the edge of the wafer to minimize the contact area with the wafer, and the wafer support pins support the wafer from below, thereby forming a gap between the stage and the wafer and holding the wafer while preventing the removal solution from flowing through the edge chuck pin to the underside of the wafer.

[0045] Therefore, even when the edge chuck method is used, local etching of the back surface (lower surface) oxide film can be suppressed as much as possible, and the SFQR value of the upper surface of the wafer after etching is not affected. Effect of the Invention

[0046] As described above, the spin etching apparatus of the present invention can provide an edge chuck type spin etching apparatus that suppresses local etching of the back surface (lower surface) oxide film as much as possible and does not affect the SFQR value of the upper surface of the wafer after etching.

[0047] Furthermore, according to the spin etching method of the present invention, it is possible to provide an edge chuck type spin etching method which suppresses local etching of the back surface (lower surface) oxide film as much as possible and does not affect the SFQR value of the upper surface of the wafer after etching.

[0048] Furthermore, according to the present invention, it is possible to provide an edge chuck type wafer holding method which suppresses local etching of the back surface (lower surface) oxide film as much as possible and does not affect the SFQR value of the upper surface of the wafer after etching. [Brief description of the drawings]

[0049] [Figure 1] 1 shows a schematic diagram of a spin etching apparatus according to an embodiment of the present invention. [Diagram 2] 2 shows a top view of the stage, edge chuck pins, and wafer support pins of FIG. 1. [Diagram 3] (a) shows a side view of one of the edge chuck pins and the vicinity of the edge of the wafer, and (b) and (c) show modifications of (a). [Figure 4] 1 shows modified examples of the edge chuck pins and the wafer support pins. [Diagram 5] 13 shows a modified example of the arrangement of the edge chuck pins and the wafer support pins. [Figure 6] (a) shows an edge chuck of the prior art (Comparative Examples 1 and 2), and (b) and (c) show modified examples of (a). [Figure 7] FIG. 6(a) shows a top view of the stage and edge chuck pin of a spin etching apparatus using the edge chuck pin. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0050] The present invention will be described in detail below, but the present invention is not limited thereto.

[0051] As described above, there was a need for an edge chuck type spin etching apparatus that would minimize local etching of the backside oxide film and would not affect the SFQR value of the top surface of the wafer after etching.

[0052] As a result of extensive investigations into the above-mentioned problems, the inventors have found that a spin etching apparatus having a stage which holds a wafer and spins, and which removes a film on the upper surface of the wafer by supplying a removing liquid to the upper surface of the rotating wafer, the spin etching apparatus comprising a plurality of edge chuck pins which are provided on the stage so as to make point contact with an edge portion of the wafer to sandwich the wafer, and a plurality of wafer support pins which are provided on the stage and contact the lower surface of the wafer to support the wafer from below while forming a gap between the stage and the wafer, can suppress local etching of a back surface (lower surface) oxide film as much as possible and have no effect on the SFQR value of the upper surface of the wafer after etching, and have completed the present invention.

[0053] As described above, there was a need for an edge chuck type spin etching method that would minimize local etching of the backside (lower surface) oxide film and not affect the SFQR value of the upper surface of the wafer after etching.

[0054] As a result of extensive investigations into the above-mentioned problems, the inventors have found that a spin etching method in which a stage holding a wafer is spun into rotation, a removing liquid is supplied to the upper surface of the rotating wafer, and a film on the upper surface of the wafer is removed, in which the wafer is held so as to be sandwiched between a plurality of edge chuck pins that make point contact with the edge of the wafer, and the wafer is etched while being held by a plurality of wafer support pins that support the lower surface of the wafer from below so that the wafer does not come into contact with the stage, can be achieved as an edge chuck type spin etching method that suppresses local etching of the back surface (lower surface) oxide film as much as possible and does not affect the SFQR value of the upper surface of the wafer after etching, and have completed the present invention.

[0055] As described above, there was a need for an edge chuck type wafer holding method that would minimize local etching of the backside (lower surface) oxide film and not affect the SFQR value of the upper surface of the wafer after etching.

[0056] As a result of extensive investigations into the above-mentioned problems, the inventors have found that a wafer holding method for holding a wafer during spin etching, in which a stage holding a wafer is spun and a remover liquid is supplied to the rotating wafer to remove a film on the top surface of the wafer, is characterized in that the wafer is held so as to be sandwiched between edge chuck pins that make point contact with multiple points on the edge of the wafer to prevent the wafer from flying out due to centrifugal force during spin rotation, and the wafer is held by multiple wafer support pins that support the bottom surface of the wafer from below, thereby preventing the wafer from coming into contact with the stage, thereby making it possible to achieve an edge chuck type wafer holding method that suppresses local etching of a back surface (bottom surface) oxide film as much as possible and does not affect the SFQR value of the top surface of the wafer after etching, and have completed the present invention.

[0057] The present invention will be described below with reference to the drawings. First, the configuration of a spin etching apparatus according to an embodiment of the present invention will be described with reference to Fig. 1 to Fig. 5. Here, an edge chuck type apparatus that chucks the edge of a wafer and etches a film formed on the upper surface of the wafer with a remover is exemplified as the spin etching apparatus.

[0058] As shown in FIG. 1, the spin etching apparatus 1 includes a support table 3 , a stage 5 , a removal liquid supply unit 8 , a rinsing liquid supply unit 9 , a collection cup 11 , edge chuck pins 13 , and wafer support pins 15 .

[0059] The support stand 3 is a structure that supports the components constituting the spin etching apparatus 1, and is placed on the floor surface on which the spin etching apparatus 1 is provided.

[0060] The stage 5 is a disk-shaped platform that holds the wafer W and spins, i.e. rotates on its own axis, and is installed above the support platform 3 so that the axis of the disk faces vertically. A rotating shaft 7 extending vertically downward is connected to the center of the underside of the disk of the stage 5, and the power of an electric motor (not shown) is transmitted to the rotating shaft 7. Therefore, the rotating shaft 7 is rotated by the power of the electric motor, and the power of the rotation is transmitted to the stage 5, so that the stage 5 rotates around the axis of the disk.

[0061] The removal liquid supply unit 8 is a piping mechanism equipped with a pipe that supplies the removal liquid for removing the film on the top surface of the wafer W and a valve for opening and closing the pipe, one end of the pipe is connected to a tank in which the removal liquid is stored or a pipe for supplying the removal liquid, and the other end is positioned above the center of rotation of the stage 5 to supply the removal liquid to the top surface of the wafer.

[0062] For example, when the stage 5 holds the wafer W and spins while the removal liquid supply unit 8 supplies the removal liquid to the center of rotation of the stage 5, the removal liquid is pushed radially of the wafer W by the centrifugal force caused by the rotation as it rotates, spreads over the entire top surface of the wafer W, etching and removing the film on the top surface, and is finally splashed radially outward from the outer periphery of the wafer W.

[0063] The rinsing liquid supply unit 9 is a piping mechanism that supplies a rinsing liquid such as pure water to wash away the removing liquid from the upper surface of the wafer W after removal of the film on the upper surface of the wafer W by the removing liquid is completed, and can have the same structure as the removing liquid supply unit 8, except that the liquid supplied is different.

[0064] The collection cup 11 is a cylindrical member that collects the removing liquid splashed off the outer periphery of the wafer W, and is provided so as to surround the stage 5 .

[0065] The edge chuck pins 13 are pins that hold the side (edge) of the wafer W and restrict the wafer W from moving in the horizontal direction due to centrifugal force during spin rotation. As shown in Figures 2 and 3(a), a plurality of edge chuck pins 13 are erected on the stage 5 so as to come into point contact with the edge 21 of the wafer and clamp the wafer W.

[0066] The wafer support pins 15 are pins that support the wafer W from below while forming a gap between the stage 5 and the wafer W by coming into contact with the lower surface of the wafer W. A plurality of the wafer support pins 15 are provided upright on the stage 5 .

[0067] The reason why the wafer W is supported by the edge chuck pins 13 and the wafer support pins 15 in this manner will be explained below.

[0068] When holding a wafer using the edge chuck method, if one holder is used to provide both vertical support for supporting the wafer W and horizontal support for preventing the wafer from flying out due to centrifugal force, the shape of the wafer holding portion 41a that comes into contact with the edge portion 21 of the wafer W, such as in the conventional edge chuck 41 shown in Figure 6(a), will necessarily be a concave shape that follows the shape of the edge portion 21 of the wafer W from the side surface to the bottom surface of the wafer.

[0069] Therefore, when a film removal liquid (for example, an HF solution when the film is an oxide film) hits the edge chuck 41, the removal liquid on the side of the wafer W flows around to the back surface (lower surface) of the wafer along the recessed shape, etching the lower surface.

[0070] In order to prevent the remover from flowing through the edge chuck 41 to the underside of the wafer, it is necessary to make the contact area between the edge chuck 41 and the wafer W as small as possible.

[0071] Therefore, in the spin etching apparatus 1 of the present invention, in order to minimize the contact area between the member that supports the wafer W horizontally and the edge portion 21 of the wafer W, the wafer W is held by being clamped horizontally by edge chuck pins 13 that make point contact with the edge portion 21, and the wafer W is further supported from below by wafer support pins 15.

[0072] In this way, by dividing the holder (edge ​​chuck) for the wafer W into edge chuck pins 13 that prevent the wafer W from flying out due to centrifugal force, and wafer support pins 15 that support the wafer W from below to prevent the wafer W from falling and coming into contact with the upper surface of the stage 5, even with the edge chuck method, it is possible to prevent the remover from getting around to the underside of the wafer, thereby minimizing local etching of the underside as much as possible.

[0073] The above is an explanation of why the edge chuck pins 13 and the wafer support pins 15 support the wafer W.

[0074] The material and dimensions (particularly the thickness) of the edge chuck pin 13 may be appropriately selected so as to have a strength sufficient to prevent deformation during spin etching. Examples of such materials include ceramics such as alumina (Al2O3).

[0075] On the other hand, it is preferable that the edge chuck pin 13 does not scratch the wafer W and does not contain metal impurities that may contaminate the wafer W. Therefore, it is preferable to use a resin that does not contain metal impurities from the viewpoint of maintaining the cleanliness of the wafer.

[0076] As the resin material, for example, chemically resistant resins such as PVDF (polyvinylidene fluoride), PFA (perfluoroalkoxy fluororesin), and PEEK (aromatic polyether ketone) are preferable because the edge chuck pins 13 are less likely to be etched by the remover.

[0077] For the same reason, the wafer support pins 15 are preferably made of resin, and more preferably made of chemically resistant resin materials such as PVDF, PFA, and PEEK.

[0078] However, it is not necessary that both the edge chuck pins 13 and the wafer support pins 15 are made of these materials, and at least one of them may be made of resin, or PVDF, PFA, PEEK, or the like.

[0079] The outer shape of the edge chuck pin 13 is preferably linear with respect to the roundness of the edge portion 21 of the wafer W in order to minimize the contact area in the vertical direction with the edge portion 21 of the wafer W. More specifically, the edge chuck pin 13 is preferably a cylindrical rod.

[0080] However, the outer shape of the edge chuck pin 13 is not limited to a cylindrical shape, and may be a truncated cone shape whose horizontal cross-sectional area increases from the bottom end to the tip end, like an edge chuck pin 13a shown in FIG. 3(b).

[0081] If the edge chuck pin 13 has a truncated cone shape, the risk of the wafer W popping up during etching can be further reduced. When the edge chuck pin 13 has a truncated cone shape, it is preferable to form the truncated cone shape with a gentle slope so as not to interfere with (come close to) the edge portion 21, etc.

[0082] When the edge chuck pin 13 is cylindrical, the diameter of the cylinder is not particularly limited, but since the smaller the diameter is, the more the removal liquid can be prevented from being trapped around the cylinder, a diameter of 5 mm or less is preferable.

[0083] However, in order to reduce the diameter of the edge chuck pin 13, it is necessary to increase the strength of the pin itself. For example, if a ceramic pin is used, the diameter of the pin can be reduced to about 1 mm, but since ceramics is hard, the diameter should be set appropriately depending on the material and strength of the edge chuck pin 13 so as not to scratch the edge portion 21 of the wafer W.

[0084] Furthermore, when the edge chuck pin 13 is made of resin, since resin is softer than ceramics, it is preferable to determine the vertical length and the diameter of the cylinder in consideration of the vertical strength of the edge chuck pin 13. The appropriate size is also determined by the type of resin material used. Although the resin exemplified in this invention can be used with a diameter of 2 mm or 3 mm without any problems, a diameter of 5 mm or less is preferable in order to further suppress the intrusion of the removing liquid.

[0085] The edge chuck pins 13 are mounted on the stage 5, but a gap is required between the stage 5 and the wafer W to allow a robot hand to be inserted when the wafer W is transported by a robot or the like.

[0086] Therefore, it is necessary to take these factors into consideration when determining the vertical length, i.e., the height, of the edge chuck pin 13. Specifically, this is set appropriately depending on the robot hand and the thickness of the wafer W, but for example, if a gap of 10 mm is required between the stage 5 and the wafer W, the length of the edge pin is preferably about 15 mm.

[0087] If the edge chuck pin 13 is a single cylinder with a length of 15 mm standing upright from the stage 5, it may be considered that the strength is insufficient depending on the material. For that reason, as shown in Fig. 4, a pedestal 23 may be provided on the stage 5 (a gap of several mm is provided between the pedestal 23 and the wafer W so that the pedestal 23 does not come into contact with the wafer W), and the edge chuck pin 13 may be installed on the pedestal 23. In this case, the length of the edge chuck pin 13 can be set to about 3 mm.

[0088] The edge chuck pin 13 may be movable. For example, as shown in Fig. 4, the pedestal 23 and the stage 5 may be connected by a movable part 25 that is horizontally movable, so that the edge chuck pin 13 can be moved together with the pedestal 23. Of course, the edge chuck pin 13 itself may be movable.

[0089] By making the edge chuck pins 13 movable in this manner, the wafer W can be set on the stage 5 by moving some of the edge chuck pins 13 when transporting the wafer W, and the wafer W can be accurately fixed to the edge chuck pins 13.

[0090] The tip of the edge chuck pin 13 is preferably larger than the diameter of the cylinder (about 0.5 mm), which reduces the risk of the rotating wafer W jumping out during etching.

[0091] Specifically, an example of a structure is an edge chuck pin 13b shown in FIG. 3(c), which has a cylindrical wafer contact portion 31 that is erected on the stage 5 and makes point contact with the wafer W, and a tip portion 33 that is provided at the tip of the wafer contact portion 31, in this case the upper end, and has a diameter larger than the diameter of the cylinder of the wafer contact portion 31.

[0092] 1 is used to support the wafer W from below and determine the height of the wafer W in the spin etching apparatus 1, that is, the size of the gap between the stage 5 and the wafer W. Therefore, the height of the wafer support pins 15 is set appropriately depending on the robot hand that transports the wafer W, the thickness of the wafer W, etc.

[0093] In order to reduce the contact area between the bottom surface of the wafer W and the wafer support pins 15, it is desirable for the tips of the wafer support pins 15 to be thin. Specifically, a conical shape that tapers toward the upper end is preferable, as shown in Fig. 4. However, if the tips of the wafer support pins 15 are too thin, they will wear out quickly due to friction, so the tips may be rounded to support the bottom surface of the wafer W in a circle.

[0094] Furthermore, as shown in FIG. 4, by providing a pedestal 27 on the stage 5 and providing the wafer support pins 15 on the pedestal 27, the wafer support pins 15 can be made shorter.

[0095] The planar arrangement of the edge chuck pins 13 and the wafer support pins 15 is not particularly limited, but the following arrangements can be exemplified.

[0096] First, regarding the arrangement of the edge chuck pins 13, even if there is no effect on SFQR at the positions where the edge chuck pins 13 come into contact with the edge portion 21 of the wafer W, local etching of the film proceeds to some extent. Therefore, although multiple edge chuck pins 13 are installed, it is preferable to hold a small number of them. On the other hand, for stable holding, it is preferable to hold the stage 5 at three positions equidistant from the center of the stage 5 at intervals of 120°, as shown in FIG. 2.

[0097] Alternatively, as shown in FIG. 5, four points equidistant from the center of the stage 5 may be held at 90° intervals.

[0098] Next, the arrangement of the wafer support pins 15 should be such that the attitude of the wafer W can be kept horizontal and may be set appropriately according to the diameter of the wafer W, but in order to stably hold the wafer W, it is preferable to hold the wafer W at three positions equidistant from the center of the stage 5 at intervals of 120° as shown in Fig. 2. Alternatively, the wafer support pins 15 may be held at four positions equidistant from the center of the stage 5 at intervals of 90° as shown in Fig. 5.

[0099] In addition, the wafer support pins 15 are preferably disposed inside (towards the center) 10 mm from the edge portion 21 of the wafer W. This is because, since a part of the removing liquid splashed out from the edge portion 21 of the wafer W is scattered near the edge portion 21 of the wafer W, even if this scattered removing liquid flows around the underside of the wafer W, it hits the wafer support pins 15, and this more effectively prevents the film around the wafer support pins 15 from being etched.

[0100] The above is a description of the configuration of the spin etching apparatus 1 according to the embodiment of the present invention.

[0101] Next, a spin etching method according to an embodiment of the present invention and a wafer holding method during spin etching will be described using the spin etching apparatus 1 as an example.

[0102] First, a wafer W to be subjected to spin etching is prepared. The wafer W to be processed by the spin etching method and holding method of the present invention is not particularly limited, and semiconductor wafers such as silicon and other semiconductor materials can be used. It is preferable that a film to be removed is formed on both sides (front and back) of the wafer, and that a film remover is used to remove the film only on one side. The film to be removed is also not particularly limited, and various types such as oxide film, nitride film, carbide film, metal film, etc. can be used.

[0103] For example, a wafer having an oxide film on one side, such as a silicon on insulator (SOI) wafer having a buried oxide layer (BOX layer: Buried Oxide Layer), can be used.

[0104] 1, the wafer W is held on the stage 5. Specifically, the wafer W is placed on the wafer support pins 15, and is held so as to be sandwiched between the edge chuck pins 13.

[0105] Next, while rotating the stage 5, a removing liquid is supplied from the removing liquid supply unit 8 to the center of rotation of the stage 5. The supplied removing liquid rotates on the upper surface of the wafer W, is pushed in the radial direction of the wafer W, etches the film on the upper surface of the wafer W, and is splashed off from the outer periphery of the wafer W.

[0106] At this time, the wafer W is held by being sandwiched between a plurality of edge chuck pins 13 that make point contact with the edge portion 21 of the wafer W, and further, etching is performed while the wafer W is held by a plurality of wafer support pins 15 that support the underside of the wafer W from below so that the wafer W does not come into contact with the stage 5.

[0107] This forms a gap between the stage 5 and the wafer W, while preventing the remover from flowing through the edge chuck pins 13 to the underside of the wafer W.

[0108] The removal liquid to be supplied may be selected depending on the film on the top surface of the wafer W. When removing the oxide film on one side of a silicon wafer with an oxide film, it is preferable to perform spin etching using an HF solution as the removal liquid, and it is preferable to apply the wafer spin etching method and holding method of the present invention to an apparatus for spin etching using such an HF solution (HF spin apparatus) or the like.

[0109] In the case of removing an oxide film in the HF spin device, the HF concentration or HF temperature may be increased in order to increase the etching rate of the oxide film.

[0110] However, in order to prevent the progression of local etching of the back surface (lower surface) oxide film due to an increase in the HF concentration, the HF concentration is preferably 10 to 40 mass %, and more preferably 20 to 40 mass %.

[0111] Regarding the rotation speed of the wafer W during the spin process, that is, the rotation speed of the stage 5, the faster the rotation speed, the higher the centrifugal force of the film removal liquid (HF solution, etc.) and the more likely it is that the removal liquid will not wrap around the underside of the wafer W. On the other hand, the slower the rotation speed, the slower the flow rate of the removal liquid splashing out of the wafer W and the smaller the scattering of droplets when hitting the collection cup 11, making it possible to prevent the droplets from returning to the wafer W.

[0112] Furthermore, since the resin edge chuck pin 13 is weaker than the ceramic edge chuck pin 13, in order to prevent damage caused by the wafer W popping out due to deformation of the edge chuck pin 13 and shortening of the life of the edge chuck pin 13 due to deformation of the edge chuck pin 13, it is preferable to set the rotation speed of the wafer W during spin etching lower than when the ceramic edge chuck pin 13 is used.

[0113] In this way, the rotation speed of the wafer W during spin etching is preferably set to the maximum rotation speed at which there is no effect of splashes from the collection cup 11 and no deformation or the like of the edge chuck pins 13 occurs.

[0114] During spin etching, the underside of the wafer W is supported from below by the wafer support pins 15, so there is a gap between the underside of the wafer W and the stage 5. Therefore, when an HF solution is used as the removal liquid, HF vapor will flow from the recovery cup 11 to the underside of the wafer W. As a countermeasure, it is preferable to eject N2 gas from below the center of the underside of the wafer W on the stage 5 to prevent HF vapor from flowing to the underside of the wafer W.

[0115] In order to prevent the HF vapor from reaching the lower surface of the wafer W in this manner, it is preferable to increase the flow rate of the N2 gas or to narrow the gap between the lower surface of the wafer W and the stage 5.

[0116] The distance between the lower surface of the wafer W and the stage 5 is not particularly limited, but is preferably set to 10 mm or less. Basically, it is preferable to flow N2 gas between the lower surface of the wafer W and the stage 5 to prevent HF vapor from entering from the edge portion 21 of the wafer W and suppress the reduction of the oxide film on the rear surface (lower surface).

[0117] Therefore, the narrower the gap between the underside of the wafer W and the stage 5, the more the HF vapor is prevented from getting around, which is preferable. However, since the wafer W is transported to the stage 5 (holding unit) using a transport device (robot hand), it is preferable that the gap between the underside of the wafer W and the stage 5 is large enough to allow the robot hand to enter.

[0118] Therefore, it is preferable to set the gap so that the robot hand of the transfer device can enter while preventing the HF vapor from getting around. Even with such a gap, it is preferable to set the amount of N2 gas to an optimal amount that minimizes the HF from getting around.

[0119] The time for which spin etching is performed may be long enough to reach the target removal amount of the film. When the target removal amount of the film is reached, the supply of the removing liquid is stopped, and, as necessary, pure water or the like is supplied from the rinsing liquid supply unit 9 to the upper surface of the wafer W to wash away the removing liquid, film residue, and the like. This completes the spin etching. EXAMPLES

[0120] The present invention will be specifically described below with reference to examples, but the present invention is not limited thereto.

[0121] Example 1 1 and 2 was prepared as the spin etching apparatus used in Example 1, and edge chuck pins 13b (having wafer contact portion 31 as a cylinder (point contact) with a diameter of 2 mm and tip portion 33 made of alumina (ceramic) with a diameter of 2.5 mm) shown in Fig. 3(c) were provided in three locations on a rotating stage 5, and wafer support pins 15 were positioned 10 mm inward from edge chuck pin 13 to support the underside of wafer W. Wafer support pins 15 were 10 mm high and conical (with rounded tips) and were provided in three locations to hold wafer W.

[0122] Example 2 1 and 2 was prepared as the spin etching apparatus used in Example 2, and edge chuck pins 13b (made of PVFD with wafer contact portion 31 being a cylinder (point contact) with a diameter of 2.4 mm and tip portion 33 having a diameter of 2.5 mm) shown in Fig. 3(c) were provided at three locations on stage 5, and wafer support pins 15 were positioned 10 mm inward from edge chuck pin 13 to support the underside of wafer W. Wafer support pins 15 were 10 mm high and conical (with rounded tips) and were provided at three locations to hold wafer W.

[0123] (Comparative Examples 1 and 2) As the spin etching apparatus used in Comparative Examples 1 and 2, a spin etching apparatus 100 was prepared, which has a structure in which an edge chuck 41, which holds the edge portion 21 with a V-shaped wafer holding portion 41a, is held at six points around the periphery as shown in Fig. 6(a) and Fig. 7. Since the edge chuck 41 is held in a V-shape, this pin alone withstands the centrifugal force and also supports the wafer W, which is a conventional holding method. The other structures were the same as those of the spin etching apparatus 1 in Examples 1 and 2.

[0124] The oxide film on the surface (upper surface) was removed using an HF spin device (spin etching device) held in the holding method as in Examples 1 and 2 and Comparative Examples 1 and 2, and an HF solution was used as a remover. The HF concentration of the HF solution at this time is shown in Table 1.

[0125] The processed wafers W were PW wafers with oxide films formed on the front and back surfaces. Note that PW wafers are mirror-polished (polished) wafers.

[0126] For both the example and comparative example, this PW wafer with oxide film was spin-etched on the top surface at the same stage rotation speed using an HF solution with an HF temperature of 30°C as the removal solution, and the SFQR (3 mm EE) of the top surface and the maximum removal amount of the backside oxide film (3 mm EE) were confirmed.

[0127] SFQR (3mmEE) is the value of SFQR excluding the outer periphery of 3mm (denoted as 3mmEE), and was measured using a capacitance type flatness measuring device. The maximum removal amount of the rear surface oxide film was evaluated by measuring the distribution of the oxide film thickness over the entire rear surface oxide film using the light reflection method, and by the PV value of the part with the greatest degree of local etching.

[0128] The results are shown in Table 1. Table 1 summarizes the material of the edge chuck pin 13, the HF concentration during the etching process, the removal amount of the oxide film on the upper surface (target removal amount of the oxide film), SFQR (3 mm EE), and the maximum removal amount of the oxide film on the back surface (3 mm EE).

[0129] [Table 1]

[0130] In Comparative Example 1, the HF solution was allowed to flow for a time sufficient to remove 2700 nm of the oxide film on the front surface (upper surface), and the amount of the oxide film on the back surface (lower surface) of the wafer W near the edge chuck pin 13 was examined, which shows that the back surface (lower surface) was also etched by 250 nm. The SFQR at this time was 0.27 μm.

[0131] In Comparative Example 2, the HF concentration was reduced to 20 mass % compared to Comparative Example 1. When 1400 nm of the oxide film on the front surface (upper surface) was removed, etching of 52 nm was observed on the back surface (lower surface).

[0132] In Example 1, alumina (ceramics) was used as the material for the edge chuck pin 13. The HF concentration was higher than in Comparative Example 2, and the treatment was performed for a time required to remove 2700 nm of the surface oxide film, but the etching of the lower oxide film was very small, about 20 nm. The SFQR was also good, at 0.03 μm.

[0133] In Example 2, PVDF was used as the material for the edge chuck pin 13. The processing was performed for a time required to remove 2400 nm of the oxide film on the surface, but the etching of the oxide film on the lower surface was very small, about 15 nm. The SFQR was also good, at 0.03 μm.

[0134] As described above, by using the spin etching apparatus 1 of the present invention, holding the wafer W by the wafer holding method of the present invention, and processing the wafer W by the spin etching method of the present invention, the front surface (upper surface) was reliably processed, local etching of the back surface oxide film was suppressed, and processing that did not affect the SFQR value was possible. In particular, since the back surface was not adsorbed, processing was possible without scratches due to adsorption.

[0135] The present specification includes the following aspects. [1]: A spin etching apparatus having a stage that holds a wafer and spins, and that removes a film on the upper surface of the wafer by supplying a removing liquid to the upper surface of the rotating wafer, a plurality of edge chuck pins provided on the stage so as to sandwich the wafer by making point contact with an edge portion of the wafer; a plurality of wafer support pins provided on the stage and supporting the wafer from below while forming a gap between the stage and the wafer by contacting the underside of the wafer. [2]: The spin etching apparatus according to [1] above, wherein at least one of the edge chuck pins and the wafer support pins is made of resin. [3]: The spin etching apparatus according to [1] or [2] above, wherein at least one of the edge chuck pins and the wafer support pins is made of PEEK, PFA, or PVDF. [4]: The spin etching apparatus according to any one of [1] to [3] above, wherein the edge chuck pin is cylindrical or frustoconical in shape with a horizontal cross-sectional area increasing toward the tip. [5]: The spin etching apparatus according to any one of the above [1] to [4], wherein the edge chuck pin is cylindrical, and the diameter of the cylinder is 5 mm or less. [6]: The edge chuck pin is The spin etching apparatus according to any one of [1] to [3] above, characterized in having a cylindrical wafer contact portion that makes point contact with the wafer, and a tip portion provided at the tip of the wafer contact portion, the diameter of which is larger than the diameter of the wafer contact portion. [7]: A spin etching method for removing a film on the upper surface of the wafer by spinning a stage holding the wafer and supplying a removing liquid to the upper surface of the wafer, A spin etching method comprising: holding the wafer by clamping it with a plurality of edge chuck pins that make point contact with the edge of the wafer; and further holding the wafer by a plurality of wafer support pins that support the underside of the wafer from below so that the wafer does not come into contact with the stage, wherein the etching is performed while the wafer is held by these pins. [8]: The spin etching method according to [7] above, wherein the wafer is a silicon wafer having an oxide film, and the removing liquid is an HF solution. [9]: The spin etching method according to [8] above, wherein the concentration of the HF solution is 10 to 40 mass %.

[10] : A wafer holding method for holding a wafer during spin etching to remove a film on an upper surface of the wafer, comprising: spin-rotating a stage holding a wafer; supplying a removing liquid to the rotating wafer; and holding the wafer during spin etching, This wafer holding method is characterized in that the wafer is held by being clamped by edge chuck pins that make point contact with multiple points on the edge of the wafer, thereby preventing the wafer from flying out due to centrifugal force during spin rotation, and further, the wafer is held by multiple wafer support pins that support the underside of the wafer from below, preventing the wafer from coming into contact with the stage.

[0136] The present invention is not limited to the above-described embodiment. The above-described embodiment is merely an example, and anything that has substantially the same configuration as the technical idea described in the claims of the present invention and exhibits similar effects is included in the technical scope of the present invention. [Explanation of symbols]

[0137] 1...spin etching apparatus, 3...support base, 5...stage, 7...rotating shaft, 8...removal liquid supply section, 9...rinsing liquid supply section, 11...recovery cup, 13...edge chuck pin, 13a...edge chuck pin, 13b...edge chuck pin, 15...wafer support pin, 21...edge portion, 23...base, 25...movable portion, 27...base, 31...wafer contact portion, 33...tip portion, 41...edge chuck, 41a...wafer holding portion, 100...spin etching apparatus, W...wafer.

Claims

1. A spin etching apparatus having a stage that holds a wafer and spins, and that removes a film on an upper surface of the wafer by supplying a removing liquid to an upper surface of the rotating wafer, a plurality of edge chuck pins provided on the stage so as to sandwich the wafer by making point contact with an edge portion of the wafer; a plurality of wafer support pins provided on the stage and supporting the wafer from below while forming a gap between the stage and the wafer by contacting the underside of the wafer.

2. 2. The spin etching apparatus according to claim 1, wherein at least one of said edge chuck pins and said wafer support pins is made of resin.

3. 3. The spin etching apparatus according to claim 2, wherein at least one of said edge chuck pins and said wafer support pins is made of PEEK, PFA or PVDF.

4. 4. The spin etching apparatus according to claim 1, wherein the edge chuck pin has a cylindrical shape or a truncated cone shape whose horizontal cross-sectional area increases toward the tip.

5. 5. The spin etching apparatus according to claim 4, wherein the edge chuck pin is cylindrical, and the diameter of the cylinder is 5 mm or less.

6. The edge chuck pin is A spin etching apparatus as described in any one of claims 1 to 3, characterized in that it has a cylindrical wafer contact portion that makes point contact with the wafer, and a tip portion provided at the tip of the wafer contact portion, the diameter of which is larger than the diameter of the wafer contact portion.

7. 1. A spin etching method for removing a film on an upper surface of a wafer by spinning a stage holding the wafer and supplying a removing liquid to an upper surface of the wafer, comprising: A spin etching method comprising: holding the wafer by clamping it with a plurality of edge chuck pins that make point contact with the edge of the wafer; and further holding the wafer by a plurality of wafer support pins that support the underside of the wafer from below so that the wafer does not come into contact with the stage, wherein the etching is performed while the wafer is held by these pins.

8. 8. The spin etching method according to claim 7, wherein the wafer is a silicon wafer having an oxide film, and the removing solution is an HF solution.

9. 9. The spin etching method according to claim 8, wherein the concentration of the HF solution is 10 to 40 mass %.

10. 1. A wafer holding method for holding a wafer during spin etching for removing a film on an upper surface of the wafer by spin-rotating a stage holding the wafer and supplying a removing liquid to the rotating wafer, comprising: This wafer holding method is characterized in that the wafer is held by being clamped by edge chuck pins that make point contact with multiple points on the edge of the wafer, thereby preventing the wafer from flying out due to centrifugal force during spin rotation, and further, the wafer is held by multiple wafer support pins that support the underside of the wafer from below, preventing the wafer from coming into contact with the stage.

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