Polishing apparatus and polishing method

Abstract

To provide a polishing device and a polishing method which can hold even substrate pieces that are divided wafers, especially substrate pieces with sharp edge portions, prevent excessive wear of a polishing cloth and stably perform polishing processing.SOLUTION: A polishing device capable of polishing substrate pieces divided from a circular substrate, comprises: a stage on which the substrate piece is placed; a polishing mechanism which has a polishing cloth smaller in area than the substrate piece and brings the polishing cloth into sliding contact with the surface of the substrate piece to perform polishing; and a holding tool which has a cutout portion having the same planar shape as the substrate piece, and holds the substrate piece by fitting the substrate piece to the cutout portion.SELECTED DRAWING: Figure 1

Description

Technical Field

[0001] The present invention relates to a polishing apparatus and a polishing method, and more particularly to a polishing apparatus and a polishing method for a substrate piece divided from a circular substrate.

Background Art

[0002] Generally, polishing refers to a process of sliding a polishing cloth while supplying a polishing composition containing abrasive grains to a target substrate to achieve effects such as removing a damaged layer on the substrate surface and smoothing it. Polishing is usually performed using a polishing cloth with an area larger than that of the substrate (wafer). This is because the larger the polishing cloth, the more the accumulation of processing residues can be suppressed, preventing a decrease in polishing ability.

[0003] Also, polishing is often performed on circular wafers with high symmetry, and thus polishing apparatuses are designed to polish circular wafers. In a general polishing apparatus, for example, in the case of single-sided polishing, a holder called a polishing head adsorbs the non-polishing surface of the wafer, and a holder having a guide ring or the like on the outside of the wafer is used to prevent the wafer from shifting horizontally. In the case of double-sided polishing, a holder called a carrier, which is a thin plate-shaped member punched into a circular shape, is used.

[0004] By the way, as an example of processing with a polishing cloth smaller than the wafer, for example, a polishing apparatus for locally polishing a substrate is provided as in Patent Document 1. Such a polishing apparatus includes a polishing member whose processing surface contacting the substrate is smaller than the substrate, a conditioning member for conditioning the polishing member, a first pressing mechanism for pressing the conditioning member against the polishing member during polishing of the substrate, and a control device for controlling the operation of the polishing apparatus. It is disclosed that the control device is configured to control the first pressing mechanism when locally polishing the substrate with the polishing member.

[0005] Furthermore, the chemical mechanical polishing apparatus described in Patent Document 2 includes a wafer carrier for holding a wafer, a polishing platen positioned opposite the wafer-holding surface of the wafer carrier and rotatable, and a circular polishing cloth attached to the polishing platen. The polishing cloth has a diameter smaller than the diameter of the wafer W, and the polishing platen is capable of horizontal movement along the polishing surface of the wafer W. It is also disclosed that the apparatus has a control unit that controls the horizontal movement speed of the polishing platen so that the horizontal movement speed is slower in the center of the wafer than in the periphery.

[0006] Patent Document 3 discloses a polishing apparatus comprising a polishing head, a base plate to which a polishing cloth is attached, a loading stage for mounting a wafer onto the polishing head, and an unloading stage for removing the wafer from the polishing head, for polishing a wafer held by the polishing head. This polishing apparatus further comprises a local polishing pad smaller than the wafer that can move up and down, and by raising the local polishing pad relative to the polishing head, the wafer held by the polishing head and the local polishing pad come into contact, and the polishing head holding the wafer is rotated, thereby enabling local polishing of the outer circumference of the wafer in a concentric manner. [Prior art documents] [Patent Documents]

[0007] [Patent Document 1] Japanese Patent Publication No. 2018-158399 [Patent Document 2] Japanese Patent Application Publication No. 09-254024 [Patent Document 3] Japanese Patent Publication No. 2019-193968 [Overview of the project] [Problems that the invention aims to solve]

[0008] These patent documents 1-3 describe examples of devices for localized polishing, but all of them are techniques for polishing circular wafers and are not devices for polishing divided wafers. However, there are cases where it is necessary to polish wafers that have been divided into fan shapes or other shapes from a circular wafer (hereinafter also referred to as substrate pieces), rather than keeping them circular.

[0009] For example, a sample wafer may be taken from a circular product wafer for quality evaluation (verification), and that wafer may be divided. Quality verification may involve heat treatment or chemical treatment, which constitutes destructive testing. Therefore, to reduce wafer loss during inspection, a circular wafer may be divided into a fan shape for inspection. Also, quality inspection requires rapid evaluation using compact equipment, and dividing the wafer in this way has the advantage of allowing heat treatment and other processes to be performed with smaller equipment than when using a circular sample.

[0010] Furthermore, the quality of polished segmented wafers is evaluated using methods such as resistivity measurement, photoluminescence, cathodoluminescence, and other optical techniques to measure bulk quality. However, it is known that these measurements cannot be performed accurately if a damaged layer remains on the surface or if the surface is rough, as this can cause abnormal scattering.

[0011] Furthermore, wafers are often divided into shapes such as a fan shape with a central angle of 90° (4 divisions), 120° (3 divisions), or 180° (2 divisions). While wafers can be mechanically divided using a dicer, semiconductor wafers often utilize the principle that the wafer is divided (cleaved) because certain crystal orientations have weaker bonding forces between atoms, and the resulting surfaces are relatively smooth. Hereafter, wafers divided in this manner are sometimes referred to as cleaved wafers.

[0012] There are cases where, after dividing a wafer into non-circular shapes, it is necessary to polish the divided wafers. For example, polishing may be required to remove a thermal oxide film after heat treatment, to remove a damaged layer in order to measure quality using optical methods, or to achieve a surface roughness level that matches the polishing level of the final product (e.g., the level after DSP).

[0013] These segmented wafers cannot be polished using polishing equipment or wafer holding methods designed for processing normal circular wafers. This is because the same holding devices used for circular wafers cannot properly hold them, causing the wafers to move during polishing.

[0014] Furthermore, polishing wafers in this divided state is likely to shorten the lifespan of the polishing cloth. This is because, while polishing a normal circular wafer is done with the edges beveled, a cleaved wafer has a perpendicular cleavage plane, and the boundary between this cleavage plane and the wafer surface (the edge) is often not beveled. In other words, the edge is sharp, so when polishing, the polishing cloth is excessively worn down, which can lead to extremely rapid deterioration of the polishing cloth. This can result in disadvantages such as a decrease in polishing quality and a reduced lifespan of the polishing cloth.

[0015] The present invention was made to solve the above problems, and aims to provide a polishing apparatus and polishing method that can hold substrate pieces, which are divided wafers, especially substrate pieces with sharp edges, and that can prevent excessive wear of the polishing cloth and perform stable polishing. [Means for solving the problem]

[0016] To achieve the above objective, the present invention provides a polishing apparatus, The polishing device is capable of polishing substrate pieces separated from a circular substrate, A stage on which the aforementioned substrate piece is placed, A polishing mechanism comprising a polishing cloth smaller than the area of ​​the substrate piece, which polishes the surface of the substrate piece by sliding the polishing cloth in contact with it, The present invention provides a polishing apparatus characterized by having a cutout portion formed in the same shape as the planar shape of the substrate piece, and a holder for fitting and holding the substrate piece into the cutout portion.

[0017] With such a polishing apparatus of the present invention, the substrate piece can be stably held by the cutout portion having the same shape as the substrate piece in the holding tool. Moreover, since it has the above polishing mechanism, polishing can be performed so as to scan with a polishing cloth smaller than the substrate piece. In particular, even if the edge portion of the substrate piece is in a sharp state, only an arbitrary portion can be polished while avoiding the edge portion, and the polishing cloth is not damaged by the sharp edge portion. Therefore, it becomes a polishing apparatus capable of stable polishing of the substrate piece. It is possible to effectively prevent a decrease in polishing quality and a decrease in the life of the polishing cloth.

[0018] In this case, the polishing mechanism has a polishing head to which the polishing cloth is attached, The polishing head can be provided with a pressing mechanism for pressing the polishing cloth against the substrate piece held by the holding tool on the stage, a rotating mechanism for rotating the shaft, and a horizontal driving mechanism for operating in the horizontal direction.

[0019] If it is provided with these various mechanisms, while avoiding the edge portion of the substrate piece, the polishing head to which the polishing cloth is attached can be easily horizontally driven (horizontally moved) to an arbitrary place to polish an arbitrary portion other than the edge portion of the substrate piece, and it is possible to effectively prevent the polishing cloth from being damaged by the edge portion of the substrate piece.

[0020] Also, the stage is rotatable about an axis, The horizontal driving mechanism can be one that reciprocates the polishing head from the outer periphery of the stage toward the center direction.

[0021] If it is such a thing, the horizontal driving mechanism can be made into a simpler mechanism.

[0022] Also, the holding tool can be one in which the cutout portion is formed in a cylinder having the same radius as the substrate.

[0023] With this type of design, it is easier to control the rotation of the stage on which the holder is placed.

[0024] Furthermore, the holder may be a cylinder in which a sector-shaped cutout portion with a central angle of 360° / n (where n is a natural number of 2 or more) is formed.

[0025] For quality evaluation (confirmation), sector-shaped specimens with the central angle described above are commonly used, and the holder in the present invention is suitable for stably holding such specimens.

[0026] Furthermore, the present invention relates to a polishing method, When polishing a substrate piece that has been separated from a circular substrate, A cutout portion is formed in the same shape as the planar shape of the substrate piece, and a holder is provided for fitting and holding the substrate piece into the cutout portion. The substrate piece is placed on the stage and held in place by the holder, The present invention provides a polishing method characterized by using a polishing mechanism equipped with an abrasive cloth smaller than the area of ​​the substrate piece, and polishing the entire surface or a part of the substrate piece by sliding the abrasive cloth into contact with the surface of the substrate piece.

[0027] With this polishing method of the present invention, the substrate piece can be stably held by the holder described above, while the small polishing cloth described above can be used to polish only the desired area of ​​the substrate piece, avoiding the edges. Therefore, stable polishing can be achieved, and a decrease in polishing quality and a reduction in the lifespan of the polishing cloth can be effectively prevented.

[0028] Furthermore, the polishing mechanism includes a polishing head to which the polishing cloth is attached, When polishing the aforementioned substrate piece, The substrate piece held by the holder on the stage can be polished by pressing and rotating the polishing head through the polishing cloth while moving it horizontally.

[0029] In this way, the polishing head can be easily moved horizontally to any desired location while avoiding the edges of the substrate piece, allowing for polishing of any part of the substrate piece other than the edges, effectively preventing damage to the polishing cloth from the edges of the substrate piece.

[0030] At this time, the stage can be rotated axially to rotate the substrate piece on the stage, and the polishing head can be moved back and forth from the outer circumference of the stage towards the center to perform polishing.

[0031] This method allows you to polish any part with simpler actions.

[0032] Furthermore, the holder can be a cylinder having the same radius as the substrate, with the cutout portion formed within it.

[0033] Having something like this makes it easier to control the rotation of the stage on which the prepared holder is placed.

[0034] Furthermore, as the holder, one can be prepared in which a sector-shaped cutout portion with a central angle of 360° / n (where n is a natural number of 2 or more) is formed in the cylinder.

[0035] For quality evaluation (confirmation), a sector-shaped sample piece with the central angle described above is often used, and the above-mentioned holder is preferable because it can stably hold such a sample piece.

[0036] Furthermore, sample pieces for quality evaluation can be prepared as the substrate pieces to be polished.

[0037] As mentioned above, there are cases where polishing is necessary when evaluating sample pieces for quality assessment, and the polishing method of the present invention is suitable for polishing such sample pieces. [Effects of the Invention]

[0038] With the polishing apparatus and polishing method of the present invention, it becomes possible to stably hold the substrate piece in the cut-out portion of the holder, and to polish only arbitrary parts of the substrate piece with a small polishing cloth, thereby enabling stable polishing, improved polishing quality, and extended lifespan of the polishing cloth. [Brief explanation of the drawing]

[0039] [Figure 1] This is a schematic side view showing an example of the polishing apparatus of the present invention. [Figure 2] This is an explanatory diagram showing an example of an object to be polished by the polishing apparatus of the present invention. [Figure 3] This is an explanatory diagram showing the positional relationship between the substrate piece and the holder in their holding state. [Figure 4] This is an explanatory diagram showing an example of the operation of the polishing head (two-axis direction). [Figure 5] This is an explanatory diagram showing an example of the operation of the polishing head (single-axis direction). It also shows an example of how the substrate piece and holder are fixed to the stage. [Figure 6] This is an explanatory diagram showing another example of how to fix a circuit board piece to the stage. [Best Mode for Carrying Out the Invention]

[0040] As mentioned earlier, polishing equipment has mostly been used to process circular wafers, and has used holders to hold the circular wafers (carriers for double-sided polishing, templates or guide rings for single-sided polishing) and polishing with a polishing cloth larger than the wafer. However, the inventors of this invention considered that conventional polishing machines would have problems when it is necessary to polish wafers (substrate pieces) that have been divided (cleaved, etc.) for inspection or other purposes. Specifically, they considered that in addition to not being able to hold the wafer properly, the polishing cloth would wear down significantly if the edges (cleavage surfaces) of the substrate pieces were sharp. Therefore, a polishing device was needed that could stably hold cleaved wafers or other substrate pieces and also polish only the desired areas without polishing the edges.

[0041] Therefore, the inventors conducted intensive research and found that, in particular, a polishing apparatus and method that uses a polishing mechanism equipped with an abrasive cloth smaller than the area of ​​the substrate piece, or a holder that fits and holds the substrate piece in a cutout in the planar shape of the substrate piece, would enable stable holding of the substrate piece and polishing while avoiding the edges of the substrate piece, thereby improving the polishing quality and the lifespan of the abrasive cloth, and thus completed the present invention.

[0042] Embodiments of the present invention will be described below with reference to the drawings, but the present invention is not limited thereto. Figure 1 is a schematic side view showing an example of the polishing apparatus of the present invention. Figure 2 shows an example of a polishing object (substrate piece) that can be polished with the polishing apparatus of the present invention. The polishing apparatus 1 of the present invention is capable of polishing substrate pieces D (divided wafers) that have been separated from a circular substrate (wafer) W. First, let's explain the object to be polished. This substrate piece D is not particularly limited, but for example, it can be a sample piece separated from a circular substrate W by dicing or cleaving, for quality evaluation (inspection) or other reasons.

[0043] The material and structure of substrate piece D are not particularly limited, but include silicon, silicon carbide, diamond, group III-V crystals, group II-VI crystals, etc. Polishing can also be performed on single crystals, polycrystalline materials, heterostructures of the above materials, and bonded structures.

[0044] Furthermore, while the substrate piece D is obtained by dividing the circular wafer W as described above, the diameter of the original circular wafer W is not particularly limited. For example, it can be obtained by dividing a wafer with a diameter of 450 mm, 300 mm, 200 mm, 150 mm, or smaller. When cleaving a circular wafer W, the resulting shape is often a fan, square, or rectangular, but the fan shape is frequently used because it requires fewer cleavage steps. The central angle of the resulting fan is often 90°, 120°, or 180°, with 90° being particularly common. However, the shape is not limited to these and can be determined as appropriate. In the following explanation, we will use a substrate piece D that has been cleaved into a sector with a central angle of 90° (the shaded area in Figure 2) as an example.

[0045] As shown in Figure 1, the polishing apparatus 1 of the present invention comprises a stage 2 on which a substrate piece D is placed, a polishing mechanism 4 equipped with a polishing cloth 3 which polishes the surface of the substrate piece D by sliding the polishing cloth 3 against it, and a holder 5 that fits and holds the substrate piece D. Furthermore, the device may be further equipped with a nozzle N for supplying the polishing composition to the area adjacent to the polishing cloth 3. By enabling the supply of the polishing composition to the area adjacent to the polishing cloth 3 for localized polishing, the polishing speed can be improved, and polishing can be performed stably. The stage 2 on which the substrate piece D and the holder 5 are placed is preferably made of resin, and POM resin is particularly preferred, so as not to damage the substrate piece D from the back side. However, it is not limited to this material and can be determined as appropriate. Stage 2 can also be made axially rotatable by a stage rotation mechanism 12 such as a motor. Furthermore, it can also have a chuck function, allowing the substrate piece D, etc., to be fixed by a vacuum chuck. A porous chuck is one example. There are other means of fixing the substrate piece D, etc., onto the stage 2, but these fixing means will be described later.

[0046] Next, the holder 5 will be described. Figure 3 shows the positional relationship between the substrate piece D and the holder 5 in the holding state. As shown in Figure 3, this holder 5 has a cutout 6 that has the same shape as the planar shape of the substrate piece D. More specifically, here, a cutout 6 that has the same shape as the planar shape of the substrate piece D is formed in a cylinder having the same radius as the substrate W before division. The substrate piece D is then fitted into this cutout 6, which has the same shape as the substrate piece D in a plan view, and held in place. In this way, the substrate piece D can be held in contact with the holder from the side, and the substrate piece D can be held stably. The shape of the holder 5 is not limited to any shape that has a cutout portion 6 and can be held on the stage 2, and is not particularly limited to a circular, square, or other shape in plan view. However, if the shape is machined from a cylinder having the same radius as the substrate W as described above, it is preferable because it makes it easier to control the rotation of the stage 2 if the stage 2 is circular and rotatable. In particular, the holder 5 can be shaped like a cylinder with the same radius as the substrate W, with a sector having a central angle of 360° / n cut out from it. A sector-shaped substrate piece D with a central angle of 360° / n can then be positioned and held within the cutout 6. Note that n is a natural number of 2 or more, preferably around n=2, 3, or 4. This is preferable because wafers (substrate pieces D) divided at such angles are easy to handle and easy to process as inspection samples. Of course, the holder 5 can also have square or rectangular cutouts 6, as in the alternative shapes of the substrate piece D mentioned above. Figure 3 shows an example of a holder 5 for polishing substrate pieces D (cleaved wafers) obtained by dividing a circular wafer into four sections (sectors with a central angle of 90°). The holder is shaped like a cylinder with the same radius as the substrate W, from which sectors with a central angle of 90° have been cut out.

[0047] Furthermore, when held, the cleaved portion of the substrate piece D comes into contact with the side surface of the cutout portion 6 of the holder 5, making it possible to minimize contact between the cleaved surface (edge) and the polishing cloth 3 during polishing. As a result, even when polishing a cleaved substrate piece D, processing can be performed more reliably without damaging the polishing cloth 3. Since the substrate piece D and the cutout portion 6 have the same shape in plan view, for example, if the sample is fan-shaped, its two cleavage surfaces can be brought into contact with the side surface of the cutout portion 6, and if the sample is rectangular (all four sides are cleavage surfaces), its four cleavage surfaces can be brought into contact with the side surface of the cutout portion 6, making it possible to polish while avoiding sharp cleavage surfaces (edges). Considering this point, it is preferable to set the thickness (height) of the holder 5 to be thicker (higher) than the thickness (height) of the substrate piece D. By doing so, the entire cleaved portion can be brought into contact with the side surface of the holder 5, and the cleaved surface can be completely hidden (in other words, the cleaved surface does not come into contact with the polishing cloth 3 during polishing). The material of the holder 5 is not particularly limited, but it can be made of resin, for example.

[0048] Next, the polishing cloth 3 and the polishing mechanism 4 will be described. As shown in Figure 1, the polishing mechanism 4 is equipped with a polishing cloth 3 smaller than the area of ​​the substrate piece D, and any mechanism that polishes the surface of the substrate piece D with this polishing cloth is acceptable. This mechanism is capable of polishing by scanning with such a small polishing cloth. More specifically, it has a polishing head 7 to which the polishing cloth 3 is attached. The polishing head 7 is equipped with a pressing mechanism 8 (such as an air cylinder) that presses the polishing cloth 3 onto the substrate piece D via a vertically extending shaft, a rotating mechanism 9 (such as a motor) that rotates the shaft, and a horizontal drive mechanism 10 (such as a linear guide that can move in one axis direction or in two axes, X and Y) that moves horizontally. Furthermore, it has a control unit 11 for controlling these mechanisms, which controls the movement, rotation, and load (polishing conditions) of the polishing head 7 (polishing cloth 3).

[0049] This polishing mechanism 4 allows the polishing head 7 to rotate around the vertical axis of the substrate piece D placed on the stage 2, to press against the substrate piece D, and to move horizontally in any direction (any coordinate) while the polishing head 7 (polishing cloth 3) is rotating.

[0050] Because this mechanism uses a small abrasive cloth 3 for polishing, it can polish substrate pieces D of various shapes that have been separated from a non-circular wafer. In particular, it can polish only the area that needs polishing. Therefore, it is possible to polish while avoiding the sharp edges of the substrate piece D. Consequently, it is possible to prevent the abrasive cloth 3 from being damaged and severely worn down by these edges, thus preventing a decrease in the lifespan of the abrasive cloth 3 and maintaining polishing quality. Combined with the holding mechanism 5 described above, the substrate piece D can be polished stably.

[0051] Here, we will explain the operation of the polishing head 7 by the horizontal drive mechanism 10 with a specific example. Figure 4 shows an example of the operation of the polishing head 7 (two-axis direction). As shown in Figure 4, the polishing head 7 (polishing cloth 3) can move horizontally on the surface of the substrate piece D on the stage 2 while rotating on its axis, and here we show an example of operation in two axes (XY direction).

[0052] Furthermore, another form (uniaxial direction) of the operation of the polishing head 7 (polishing cloth 3) on the substrate piece D fixed on the stage 2 will be described with reference to Figures 1 and 5. As shown in Figures 1 and 5, the stage 2 is a stage that can rotate on an axis using a stage rotation mechanism 12 such as a motor, and by rotating the stage 2 on an axis, the substrate piece D on it is rotated on an axis. Meanwhile, the operation of the polishing head 7 is to reciprocate from the outer circumference of the stage towards the center while rotating on an axis. When polishing the substrate piece D by rotating the polishing head 7 (polishing cloth 3) on an axis in the direction normal to the surface of the substrate piece D and pressing it, in order to improve the uniformity of the polishing in the plane, the rotation mechanism of the stage 2 can be used to move it in the circumferential direction within the angular range of the central angle of the substrate piece D, so that the entire surface of the substrate piece D can be polished.

[0053] If the Stage 2 is also equipped with a rotation mechanism, the movement direction (polishing direction) of the polishing head 7 (polishing cloth 3) can be controlled to polish the entire surface of the substrate piece D, even with a simple mechanism that only moves back and forth from the outer circumference to the center. With this type of movement of the polishing head 7, only linear movement is required, which simplifies the structure and control of the device. Furthermore, depending on the evaluation criteria for the substrate piece D (sample piece), there may be cases where it is sufficient if only a portion of the substrate piece D is polished. In such cases, the stage 2 may not be equipped with the stage rotation mechanism 12, and instead only a mechanism capable of reciprocating in one axial direction from the outer circumference towards the center may be used.

[0054] Here, we will explain the relationship between the substrate piece D, the holder 5, and the stage 2. In this invention, it is sufficient for the substrate piece D to be held on the stage 2 by the holder 5, but it is also possible to fix the substrate piece D more firmly on the stage 2 to ensure that it does not shift position or otherwise move off the stage 2 during polishing. Figure 5 shows an example where the substrate piece D is fixed from the side and top using fasteners 13 (and screws). It also shows an example where the holder 5 is fixed to the stage 2 from the top using screws 14.

[0055] The fastener 13 may be fixed by contacting the surface near the cleavage plane of the substrate piece D, but as shown in the other fixing method in Figure 6, the fastener 13 may also be used to fix the part of the holder 5 near the cleavage plane so that the holder 5 does not shift.

[0056] By fixing the substrate piece D on the stage 2 in this manner using the fasteners 13 and screws 14, the substrate piece D can be easily secured and held on the stage 2. However, the method of securing the substrate piece D is not limited to this; instead of the fasteners 13 and screws 14, a porous chuck or the like can be used to hold it in place under vacuum from the back of the substrate piece D, as described above. In this case, equipment for vacuum adsorption is required, but the advantage is that by maintaining a vacuum, it becomes possible to polish the substrate piece D up to the part of the fastener 13. Furthermore, with this vacuum-holding fixing method, the holder 5 can be easily attached and detached. Therefore, for example, even a circular wafer can be placed on the stage 2 and polished. Although the polishing apparatus 1 of the present invention is capable of polishing substrate pieces D, with the relationship between the stage 2 and the holder 5 as described above, the same stage 2 can be used for polishing, for example, an undivided circular wafer. In other words, when polishing a circular wafer, polishing can be performed without the holder 5, allowing for flexible use depending on the situation.

[0057] Next, a preferred form of the abrasive cloth 3 will be described. The abrasive cloth 3 should be smaller than the area of ​​the substrate piece D. For example, depending on the size of the substrate piece D, it is best to make it 1 / 3 or less, or even 1 / 6 or less, of the diameter of the substrate W. Smaller cloths allow for more localized polishing, but this can also affect the lifespan due to clogging, etc. Therefore, the appropriate size should be set considering the object to be polished (material, etc.), the shape of the substrate piece D (2-part, 3-part, 4-part, etc.), and the area to be polished. For example, in the case of four divided pieces cut from a 300mm diameter wafer in a fan shape with a central angle of 90°, a circular polishing cloth with a diameter of 100mm or less is preferred, and a circular polishing cloth with a diameter of 50mm or less is even more preferred.

[0058] The abrasive cloth 3 can be appropriately selected depending on the material to be polished and the required surface accuracy, but examples of abrasive cloths that can be used include foamed urethane type abrasive cloth, a type of abrasive cloth made by impregnating nonwoven fabric with resin, and suede type abrasive cloth. The thickness of the abrasive cloth 3 is preferably 5 mm or less from the viewpoint of maintaining flatness, and more preferably 3 mm or less, but on the other hand, from the viewpoint of surface defects, it is preferably 1 mm or more. The abrasive cloth 3 may have a groove structure to facilitate the abrasive composition from the nozzle N reaching the inner circumference of the abrasive cloth 3.

[0059] Next, the polishing composition for nozzle N will be described. This polishing composition can also be appropriately selected depending on the object to be polished, but it is preferable that the polishing composition contains abrasive grains. Examples of abrasive grains include silicon dioxide, silicon carbide, diamond, aluminum oxide, zirconium oxide, manganese oxide, and cerium dioxide. Furthermore, the polishing composition may also contain basic compounds in addition to abrasive grains. Examples of basic compounds include lithium hydroxide, sodium hydroxide, potassium hydroxide, aluminum hydroxide, potassium hydroxide, calcium hydroxide, sodium carbonate, potassium carbonate, calcium carbonate, ammonia, and tetramethylammonium hydroxide. This basic compound increases the pH of the polishing composition, but from the viewpoint of promoting the polishing rate, a pH of 8.0 or higher is preferable, more preferably 9.0 or higher, and even more preferably 10.0 or higher. Furthermore, from the viewpoint of abrasive grain stability, a pH of 14.0 or lower is preferable, more preferably 13.0 or lower, and even more preferably 12.0 or lower. Furthermore, in addition to abrasive particles and basic compounds, the polishing composition may also contain water-soluble polymers such as cellulose derivatives and polyvinyl alcohol, and surfactants such as ethylene oxide adducts.

[0060] The nozzle N is preferably configured to supply the polishing composition near the point where the polishing cloth 3 and the substrate piece D are in contact, and may be supplied continuously or intermittently. In either case, the supply flow rate is not particularly limited, but for example, an average of 0.01 ml / min or more is good, and an average of 0.1 ml / sec or more is more preferable.

[0061] Furthermore, the polishing apparatus 1 of the present invention may be equipped with a dressing mechanism for the polishing cloth 3 as needed. As mentioned above, since the polishing cloth 3 is smaller than the substrate piece D to be polished, clogging of the polishing cloth is likely to occur. Therefore, it is advisable to install a dressing mechanism in the polishing apparatus 1 so that the polishing surface of the polishing cloth 3 can be easily dressed. In this way, it is preferable to have a dressing mechanism in order to prevent the surface of the polishing cloth from deteriorating as polishing continues. This dressing mechanism can be, for example, a structure that allows the polishing cloth to be pressed against a dresser on which diamond has been electroplated and rotated. Dressing by this dressing mechanism may be performed at appropriate intervals during polishing, or between the end of polishing and the start of the next polishing.

[0062] Next, the polishing method of the present invention will be described. Here, we will describe the case in which polishing is performed using the polishing apparatus 1 of the present invention as described above. First, a substrate piece D is prepared as the object to be polished, which is a piece of substrate separated from a circular substrate W. For quality evaluation of the substrate W, a sample piece can be obtained by dividing the substrate W using a dicer or cleavage. Here, a sector-shaped substrate piece D with a central angle of 360° / n (where n is a natural number greater than or equal to 2) can be obtained by cleavage, and in this case, a piece with a central angle of 90° is prepared. Next, a holder 5 is prepared in which the aforementioned cutout portion 6 is formed. For example, a cylinder having the same radius as the substrate W can be prepared, with a sector-shaped cutout portion 6 having a central angle of 360° / n (where n is a natural number greater than or equal to 2). Here, to match the substrate piece D, a holder 5 is prepared in which the central angle of the cutout portion 6 is 90°.

[0063] Next, the substrate piece D is placed on the stage 2 and fitted into the cutout 6 of the holder 5 to hold it in place. By setting the substrate piece D into the cutout 6 of the holder 5 in this way, the substrate piece D can be held in a state where the divided surface (cleavage surface) and the holder 5 are in contact. Then, while being held by the holder 5, the polishing mechanism 4 (which includes a polishing cloth 3 smaller than the area of ​​the substrate piece D, as well as a polishing head 7 equipped with a pressing mechanism 8, a rotating mechanism 9, a horizontal drive mechanism 10, and a control unit 11) is used to supply the polishing composition from the nozzle N and slide the polishing cloth 3 into contact with the surface of the substrate piece D to polish the entire surface or a part of it. Because the material is held by the holder 5 as described above, and polished with a small abrasive cloth 3, the edges of the divided surface (cleavage surface) do not come into contact with the abrasive cloth 3 during polishing, thereby reducing damage to the abrasive cloth 3.

[0064] During polishing, the polishing cloth 3 (polishing head 7) is rotated axially by a motor or other rotation mechanism 9 with respect to the direction perpendicular to the surface of the substrate piece D, while a load is applied by the pressing mechanism 8 to bring it into contact with the surface of the substrate piece D. Polishing conditions can be appropriately selected depending on the object to be polished, but for example, from the viewpoint of polishing speed, the rotation speed of the polishing cloth 3 is preferably 10 rpm or more, and more preferably 100 rpm or more. On the other hand, from the viewpoint of reducing the polishing load, 1000 rpm or less is preferred. Furthermore, the polishing load of the abrasive cloth 3 is set to 10 gf / cm² from the perspective of polishing speed. 2 The above is preferable, 100 gf / cm³ 2 The above is preferable, but from the viewpoint of surface quality, 10000 gf / cm² is preferable. 2 The following is preferable: 1000 gf / cm³ 2 The following are preferable.

[0065] The abrasive cloth 3 can be moved to scan the entire surface or a portion of the substrate piece D. It can be moved by the horizontal drive mechanism 10 to reciprocate between two points, for example, or it can be moved vertically and horizontally in two axes. At the same time, the substrate piece D may be rotated by rotating the axis of the stage 2. Alternatively, the abrasive cloth 3 may not be scanned at all. The settings should be adjusted as appropriate depending on the application, such as whether it is sufficient to polish only a portion of the surface to a mirror finish or whether the entire surface needs to be polished to a mirror finish.

[0066] This invention allows for polishing of wafers obtained through various processes and substrate pieces separated from wafers of various thicknesses. It is particularly suitable for processing such as mirror-finishing sample pieces for quality evaluation or removing excess oxide films. [Examples]

[0067] The present invention will be described more specifically below with reference to examples, but the present invention is not limited to these examples. (Example 1) As the object to be polished, a fan-shaped (semicircular) substrate piece was prepared by cleaving a silicon wafer with a diameter of 300 mm and a thickness of approximately 800 μm into two parts (with a central angle of 180°). The original wafer from which this substrate piece was made was etched and had a rough surface. In order to make this substrate piece mirror-finish, the polishing method of the present invention was carried out using the polishing apparatus of the present invention as shown in Figure 1.

[0068] The abrasive cloth used was a circular cloth with a diameter of 100 mm, made of foamed urethane, and 5 mm thick. The abrasive composition was an alkaline abrasive containing colloidal silica with a pH of 11, which was intermittently supplied near the surface where the abrasive cloth and the substrate piece were in contact, and adjusted to an average flow rate of approximately 0.1 ml / sec. The holder had a fan-shaped cutout with a central angle of 180°, and was made of POM resin with a thickness of 2 mm. The substrate piece was fitted and held in this cutout and then polished. For the abrasive cloth, the rotation speed was set to 10 rpm and the abrasive load to 1000 gf / cm². 2 Then, the device was moved in the XY direction to scan the entire surface of the substrate piece and polish it.

[0069] As a result of the polishing, the surface roughness reached the level achieved after DSP, and we were able to obtain substrate pieces with the desired surface quality. In particular, there was no damage to the polishing cloth, and its lifespan and quality remained stable, allowing us to perform various bulk quality evaluations without any problems.

[0070] (Example 2) As the object to be polished, a fan-shaped substrate piece was prepared by cleaving a silicon wafer with a diameter of 300 mm and a thickness of 750 μm into four sections (with a central angle of 90°). The original wafer from which this substrate piece was made was post-plywood (PW), and after being divided into four sections, heat treatment was performed for inspection, resulting in the formation of a thermal oxide film. The polishing method of the present invention was performed using the polishing apparatus of the present invention to remove the thermal oxide film from this substrate piece.

[0071] The abrasive cloth used was a circular cloth with a diameter of 50 mm, made of foamed polyurethane, and 3 mm thick. The abrasive composition was an alkaline abrasive containing ceria as abrasive grains, and was continuously supplied near the surface where the abrasive cloth and the substrate piece were in contact, adjusted to an average flow rate of approximately 0.05 ml / sec. The holder had a fan-shaped cutout with a central angle of 90°, and was made of POM resin with a thickness of 1 mm. The substrate piece was fitted and held in this cutout and then polished. For the abrasive cloth, the rotation speed was set to 100 rpm and the abrasive load to 100 gf / cm². 2 Then, the device was moved in the XY direction to scan the entire surface of the substrate piece and polish it.

[0072] As a result of polishing, we were able to obtain a substrate piece from which the thermal oxide film had been removed. Furthermore, even after repeated polishing as described above, there was no significant damage to the polishing cloth, and its lifespan and quality remained stable, allowing for various bulk quality evaluations to be performed without any problems.

[0073] (Example 3) As the object to be polished, a fan-shaped substrate piece was prepared by dividing a 300 mm diameter silicon wafer into four sections (with a central angle of 90°) by cleavage. The original wafer from which this substrate piece was made was a 2 mm thick sample cut from an ingot and then surface-ground. To improve the surface roughness and damage of this substrate piece, the polishing method of the present invention was performed using the polishing apparatus of the present invention.

[0074] The abrasive cloth used was a circular, non-woven fabric with a diameter of 50 mm and a thickness of 3 mm. The abrasive composition was an alkaline abrasive containing silica as abrasive particles, which was supplied continuously near the surface where the abrasive cloth and the substrate piece were in contact, and adjusted to an average flow rate of approximately 0.05 ml / sec. The holder had a fan-shaped cutout with a central angle of 90°, and was made of POM resin with a thickness of 3 mm. The substrate piece was fitted and held in this cutout and then polished. For the abrasive cloth, the rotation speed was set to 100 rpm and the abrasive load to 100 gf / cm². 2 The stage was then moved from the outer edge towards the center, and the stage was rotated to scan and polish the entire surface of the substrate piece.

[0075] As a result of the polishing, the roughness was improved and damage was removed, allowing us to produce mirror-polished samples with a thickness of 2 mm, and various bulk quality evaluations could be performed without any problems.

[0076] This specification includes the following embodiments: [1]: A polishing device, The polishing device is capable of polishing substrate pieces separated from a circular substrate, A stage on which the aforementioned substrate piece is placed, A polishing mechanism comprising a polishing cloth smaller than the area of ​​the substrate piece, which polishes the surface of the substrate piece by sliding the polishing cloth in contact with it, A polishing apparatus having a cutout portion formed in the same shape as the planar shape of the substrate piece, and a holder for fitting and holding the substrate piece into the cutout portion. [2]: The polishing mechanism has a polishing head to which the polishing cloth is attached, The polishing apparatus [1] described above, wherein the polishing head comprises a pressing mechanism that presses the polishing cloth against the substrate piece held by the holder on the stage, a rotating mechanism that rotates it on an axis, and a horizontal drive mechanism that operates it in a horizontal direction. [3]: The stage is rotatable on an axis, The polishing apparatus [2] described above, wherein the horizontal drive mechanism causes the polishing head to reciprocate from the outer circumference of the stage toward the center. [4]: The polishing apparatus according to any of [1] to [3] above, wherein the holder is a cylinder having the same radius as the substrate and the cutout portion is formed therein. [5]: The polishing apparatus according to [4], wherein the holder is a cylinder in which a sector-shaped cutout portion with a central angle of 360° / n (where n is a natural number of 2 or more) is formed. [6]: A polishing method, When polishing a substrate piece that has been separated from a circular substrate, A cutout portion is formed in the same shape as the planar shape of the substrate piece, and a holder is provided for fitting and holding the substrate piece into the cutout portion. The substrate piece is placed on the stage and held in place by the holder, A polishing method comprising using a polishing mechanism equipped with an abrasive cloth smaller than the area of ​​the substrate piece, and polishing the entire surface or a part of the substrate piece by sliding the abrasive cloth against its surface. [7]: The polishing mechanism is provided with a polishing head to which the polishing cloth is attached, When polishing the aforementioned substrate piece, The polishing method of [6] above, wherein the polishing head is pressed and rotated horizontally on the substrate piece held by the holder on the stage via the polishing cloth while being moved horizontally to polish it. [8]: The polishing method of [7], wherein the stage is rotated on an axis to rotate the substrate piece on the stage on an axis, and the polishing head is moved back and forth from the outer circumference of the stage toward the center to polish. [9]: The polishing method of any of [6] to [8] above, wherein the holder is a cylinder having the same radius as the substrate with the cutout formed therein.

[10] : The polishing method of [9] above, wherein the holder is a cylinder in which a sector-shaped cutout portion with a central angle of 360° / n (where n is a natural number of 2 or more) is formed.

[11] : A polishing method of any of the above [6] to

[10] , wherein a sample piece for quality evaluation is prepared as the substrate piece to be polished.

[0077] It should be noted that the present invention is not limited to the embodiments described above. The embodiments described above are illustrative, and any configuration that is substantially identical to the technical idea described in the claims of the present invention and achieves similar effects is included within the technical scope of the present invention. [Explanation of Symbols]

[0078] 1... Polishing apparatus of the present invention, 2... Stage, 3... Polishing cloth, 4... Polishing mechanism 5...Holder, 6...Cutout section, 7...Polishing head, 8...Pressing mechanism 9... Rotation mechanism, 10... Horizontal drive mechanism, 11... Control unit, 12…Stage rotation mechanism, 13…Clasp, 14…Screw W...Circular substrate (wafer), D...Substrate piece, N...Nozzle.

Claims

1. A polishing device, The polishing device is capable of polishing substrate pieces separated from a circular substrate, A stage on which the aforementioned substrate piece is placed, A polishing mechanism comprising a polishing cloth smaller than the area of ​​the substrate piece, which polishes the surface of the substrate piece by sliding the polishing cloth in contact with it, A polishing apparatus characterized by having a cutout portion that is the same shape as the planar shape of the substrate piece and has a depth greater than or equal to the thickness of the substrate piece, and a holder for fitting and holding the substrate piece into the cutout portion.

2. The polishing mechanism has a polishing head to which the polishing cloth is attached, The polishing apparatus according to claim 1, characterized in that the polishing head comprises a pressing mechanism that presses the polishing cloth against the substrate piece held by the holder on the stage, a rotating mechanism that rotates it on an axis, and a horizontal drive mechanism that operates it in a horizontal direction.

3. The aforementioned stage is rotatable on an axis, The polishing apparatus according to claim 2, characterized in that the horizontal drive mechanism causes the polishing head to reciprocate from the outer circumference of the stage toward the center.

4. The polishing apparatus according to any one of claims 1 to 3, characterized in that the holder is a cylinder having the same radius as the substrate and the cutout portion is formed therein.

5. The polishing apparatus according to claim 4, characterized in that the holder has a sector-shaped cutout formed in the cylinder with a central angle of 360° / n (where n is a natural number of 2 or more).

6. A polishing method, When polishing a substrate piece that has been separated from a circular substrate, A retaining device is provided which has a cutout portion that is the same shape as the planar shape of the substrate piece and has a depth greater than or equal to the thickness of the substrate piece, and which holds the substrate piece by fitting it into the cutout portion. The substrate piece is placed on the stage and held in place by the holder, A polishing method characterized by using a polishing mechanism equipped with an abrasive cloth smaller than the area of ​​the substrate piece, and polishing the entire surface or a part of the substrate piece by sliding the abrasive cloth into contact with the surface of the substrate piece.

7. As the polishing mechanism, a polishing head with the polishing cloth attached is prepared, When polishing the aforementioned substrate piece, The polishing method according to claim 6, characterized in that the polishing head is pressed and rotated horizontally on the substrate piece held by the holder on the stage, via the polishing cloth, while being moved horizontally to polish it.

8. The polishing method according to claim 7, characterized in that the stage is rotated on an axis to rotate the substrate piece on the stage on an axis, and the polishing head is moved back and forth from the outer circumference of the stage toward the center to polish.

9. The polishing method according to any one of claims 6 to 8, characterized in that the holder is a cylinder having the same radius as the substrate with the cutout portion formed therein.

10. The polishing method according to claim 9, characterized in that the holder is a cylinder in which a sector-shaped cutout portion with a central angle of 360° / n (where n is a natural number of 2 or more) is formed.

11. The polishing method according to any one of claims 6 to 8, characterized in that a sample piece for quality evaluation is prepared as the substrate piece to be polished.

12. The polishing method according to claim 9, characterized in that a sample piece for quality evaluation is prepared as the substrate piece to be polished.

13. The polishing method according to claim 10, characterized in that a sample piece for quality evaluation is prepared as the substrate piece to be polished.

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