Processing method and polishing apparatus

Abstract

To polish and clean a substrate with a simpler configuration at a lower cost.SOLUTION: A processing method for polishing a silicon oxide film of a substrate having the silicon oxide film on a surface thereof, comprises: a holding step of holding the substrate with a holding unit so that the silicon oxide film is exposed; a polishing step of polishing the silicon oxide film with a polishing pad while supplying slurry containing oxide particles to the silicon oxide film of the substrate held by the holding unit; a cleaning step of removing the slurry remaining on the silicon oxide film from the silicon oxide film by bringing a contact cleaning member into contact with the silicon oxide film and rubbing the silicon oxide film by the contact cleaning member while supplying a cleaning liquid to the silicon oxide film polished in the polishing step. A pH of the slurry supplied to the silicon oxide film in the polishing step is 6 or less, and a pH of the cleaning liquid supplied to the silicon oxide film in the cleaning step is 6 or less.SELECTED DRAWING: Figure 5

Description

[Technical Field]

[0001] The present invention relates to a processing method and a polishing apparatus for polishing a substrate, typically a silicon substrate having a silicon oxide film formed on its surface. [Background technology]

[0002] In the manufacturing process of device chips used in electronic devices such as mobile phones and computers, first, multiple devices such as ICs (Integrated Circuits) and LSIs (Large Scale Integration) are formed on the surface of a silicon substrate (silicon wafer). Next, the silicon substrate or other substrate is ground from the back side to thin it to a predetermined thickness, and the substrate is divided into individual devices to form individual device chips.

[0003] In recent years, electronic devices have become smaller, thinner, and lighter, as exemplified by mobile devices such as smartphones and tablet terminals. Accordingly, there is a demand for smaller, thinner, and more dense device chips to be mounted on electronic devices.

[0004] To meet this demand, a method for manufacturing a stacked multi-chip package (MCP) has been proposed (see, for example, Patent Document 1). In this method, first, a first silicon substrate and a second silicon substrate, each having a plurality of devices formed thereon, are prepared, and then these are bonded together via a bonding layer to form a stacked device wafer with a wafer-on-wafer (WOW) structure. Then, this stacked device wafer is divided to form the stacked multi-chip package.

[0005] To form a stacked device wafer with this WOW structure, direct bonding using a silicon oxide film formed on the surface of a silicon substrate is sometimes performed. In this bonding method, in order to bond flat, clean surfaces together, the silicon oxide film is first flattened by chemical mechanical polishing (CMP).

[0006] In CMP, a slurry is supplied as a polishing liquid to the surface of the silicon substrate to be polished. The slurry is, for example, a chemical solution in which abrasive grains are dispersed. The slurry contributes to the polishing process by acting chemically and mechanically. The slurry used in CMP is generally an alkaline solution.

[0007] After the silicon oxide film is planarized by CMP, the silicon substrate is cleaned. In the cleaning process, first, an acidic cleaner such as hydrofluoric acid (aqueous solution of hydrogen fluoride) is used to remove metal impurities adhering to the silicon oxide film. Then, an alkaline cleaner such as ammonia water is used to remove particles such as slurry remaining on the silicon oxide film. [Prior art documents] [Patent documents]

[0008] [Patent Document 1] Japanese Patent Application Laid-Open No. 2008-153499 Summary of the Invention [Problem to be solved by the invention]

[0009] However, cleaning using an acidic cleaning agent and cleaning using an alkaline cleaning agent generally cannot be performed in the same cleaning chamber due to factors such as neutralization reactions occurring between the acidic and alkaline cleaning agents, different specifications for the exhaust system and waste liquid recovery system required for the cleaning chamber, and the chemical resistance of various tools.

[0010] If only one of cleaning with an acidic cleaner or cleaning with an alkaline cleaner is performed, metal impurities or particles remain on the silicon oxide film planarized by CMP, causing air bubbles to be mixed in when the two substrates are bonded. Therefore, a polishing apparatus that performs a series of polishing and cleaning of substrates requires two processing chambers: one for cleaning with an acidic cleaner and one for cleaning with an alkaline cleaner.

[0011] A polishing apparatus equipped with two processing chambers and their associated equipment tends to be expensive to manufacture and operate, and also has the problem of being large in size. Therefore, it is desired to realize a processing method for polishing and cleaning the silicon oxide film on a substrate having a silicon oxide film on its surface, and a polishing apparatus with a low-cost and simple configuration.

[0012] The present invention has been made in view of the above problems, and its object is to provide a processing method and a polishing apparatus that can polish and clean substrates such as silicon substrates at lower cost and with a simpler configuration. [Means for solving the problem]

[0013] According to one aspect of the present invention, there is provided a processing method for polishing a silicon oxide film of a substrate having a silicon oxide film on its surface, comprising: a holding step of holding the substrate with a holding unit so that the silicon oxide film is exposed; a polishing step of polishing the silicon oxide film with a polishing pad while supplying a slurry containing oxide particles to the silicon oxide film of the substrate held by the holding unit; and a cleaning step of removing the slurry remaining on the silicon oxide film from the silicon oxide film by contacting a contact cleaning member with the silicon oxide film and rubbing it with the contact cleaning member while supplying a cleaning liquid to the silicon oxide film polished in the polishing step, wherein the slurry supplied to the silicon oxide film in the polishing step has a pH of 6 or less, and the cleaning liquid supplied to the silicon oxide film in the cleaning step has a pH of 6 or less.

[0014] Preferably, the contact cleaning member is a brush made of polyvinyl alcohol, polyurethane, or nylon, the cleaning liquid is an aqueous solution of hydrogen fluoride or citric acid, and the oxide particles include cerium oxide or aluminum oxide.

[0015] Also, preferably, the pH of the cleaning liquid supplied to the silicon oxide film in the cleaning step is lower than the pH of the slurry supplied to the silicon oxide film in the polishing step.

[0016] Preferably, the pH of the slurry supplied to the silicon oxide film in the polishing step is 4 or more and 6 or less, and the pH of the cleaning liquid supplied to the silicon oxide film in the cleaning step is 3.5 or less.

[0017] More preferably, the pH of the cleaning solution supplied to the silicon oxide film in the cleaning step is 2.5 or less.

[0018] According to another aspect of the present invention, there is provided a polishing apparatus for polishing a silicon oxide film on a substrate having a silicon oxide film on its surface, comprising: a holding unit that holds the substrate so that the silicon oxide film is exposed; a polishing unit equipped with a polishing pad, which polishes the silicon oxide film with the polishing pad while supplying a slurry containing oxide particles to the silicon oxide film of the substrate held by the holding unit; and a cleaning unit equipped with a contact cleaning member, which removes the slurry remaining on the silicon oxide film from the silicon oxide film by contacting the contact cleaning member with the silicon oxide film and rubbing it with the contact cleaning member while supplying a cleaning liquid to the silicon oxide film polished by the polishing unit, wherein the pH of the slurry supplied to the silicon oxide film in the polishing unit is 6 or less, and the pH of the cleaning liquid supplied to the silicon oxide film in the cleaning unit is 6 or less.

[0019] Preferably, the contact cleaning member is a brush made of polyvinyl alcohol, polyurethane, or nylon, the cleaning liquid is an aqueous solution of hydrogen fluoride or citric acid, and the oxide particles include cerium oxide or aluminum oxide.

[0020] Preferably, the pH of the cleaning liquid supplied to the silicon oxide film in the cleaning unit is lower than the pH of the slurry supplied to the silicon oxide film in the polishing unit.

[0021] Preferably, the pH of the slurry supplied to the silicon oxide film in the polishing unit is 4 or more and 6 or less, and the pH of the cleaning liquid supplied to the silicon oxide film in the cleaning unit is 3.5 or less.

[0022] More preferably, the pH of the cleaning liquid supplied to the silicon oxide membrane in the cleaning unit is 2.5 or less. [Effects of the Invention]

[0023] According to a processing method and polishing apparatus of one embodiment of the present invention, a silicon oxide film on a substrate is polished with a polishing pad while a slurry is supplied to the silicon oxide film, and then the silicon oxide film is scrubbed with a contact cleaning member while a cleaning liquid is supplied to the silicon oxide film, thereby removing any slurry remaining on the silicon oxide film from the silicon oxide film. In the processing method of one embodiment of the present invention, the substrate is polished with a slurry having a pH of 6 or less, and the silicon oxide film is cleaned with a cleaning liquid having a pH of 6 or less. This makes it possible to remove particles adhering to the silicon oxide film while preventing metal impurities from adhering to the silicon oxide film.

[0024] In this case, cleaning of the silicon oxide film using an alkaline cleaning solution is not necessary, simplifying the cleaning process and allowing the substrate to be polished easily and quickly. Furthermore, since the entire process from polishing to cleaning is carried out in an acidic environment, there is no need for jigs, exhaust systems, or waste liquid recovery systems that are compatible with alkaline environments. There is also no need for the polishing apparatus to have two processing chambers. In other words, the configuration of the polishing apparatus, which performs polishing and cleaning in a series, can be simplified.

[0025] Therefore, according to one aspect of the present invention, a processing method and a polishing apparatus are provided that can polish and clean a substrate at lower cost and with a simpler configuration. [Brief explanation of the drawings]

[0026] [Figure 1] FIG. 1 is a perspective view schematically showing a polishing apparatus. [Figure 2] FIG. 10 is a perspective view schematically showing how a substrate is placed on a holding unit. [Figure 3] FIG. 2 is a cross-sectional view schematically showing a state in which a substrate is polished. [Figure 4] FIG. 10 is a perspective view schematically showing how a polished substrate is carried into a cleaning unit. [Figure 5] FIG. 2 is a perspective view schematically illustrating a state in which a substrate is cleaned in a cleaning unit. [Figure 6] 1 is a flowchart showing the flow of each step of a substrate processing method. DETAILED DESCRIPTION OF THE INVENTION

[0027] An embodiment of the present invention will be described with reference to the accompanying drawings. A processing method according to this embodiment and a substrate to be processed (polished) by a polishing apparatus will be described. Fig. 2 includes a perspective view schematically showing a substrate 1. Fig. 3 includes a cross-sectional view schematically showing the substrate 1 being polished.

[0028] The substrate 1 is, for example, a substantially circular substrate (wafer, silicon substrate) made of silicon. There are no limitations on the material, shape, structure, size, etc. of the substrate 1. For example, the substrate 1 may be made of other semiconductor materials (GaAs, InP, GaN, etc.), sapphire, glass, ceramics, resin, composite oxides (LiNbO3, LiTaO3), etc. The surface 1a of the substrate 1 is partitioned into a plurality of regions by a plurality of planned division lines (streets) arranged in a grid pattern, and devices such as ICs and LSIs are formed in each of the partitioned regions.

[0029] A stacked device wafer with a WOW structure is formed by bonding multiple substrates 1 together via a bonding layer, and then this stacked device wafer is divided to form a stacked multi-chip package. To form this stacked device wafer with a WOW structure, direct bonding is performed using a silicon oxide film 5 (oxide film) formed on the front surface 1a or back surface 1b of the substrate 1 (see Figure 3). In this bonding method, the silicon oxide film 5 is polished and planarized in advance to bond flat, clean surfaces together.

[0030] The silicon oxide film 5 is formed on the substrate 1 by, for example, a chemical vapor deposition (CVD) method. Alternatively, the silicon oxide film 5 may be a natural oxide film formed by oxidizing in the atmosphere a constituent material of the substrate 1 or a constituent material of the surface layer of the substrate 1. Note that, as long as the silicon oxide film 5 is formed on the entire surface or a part of the surface layer of the substrate 1, other layers may be formed on the substrate 1. Furthermore, the silicon oxide film 5 does not need to be used as a bonding layer for multiple device wafers, and various functional layers such as semiconductor layers, metal layers (electrodes, wiring), and interlayer insulating films may be formed on the silicon oxide film 5 after the silicon oxide film 5 is polished.

[0031] When polishing the substrate 1, a protective tape 3 may be attached in advance to protect the surface of the substrate 1 that is not to be polished. The protective tape 3 protects the surface of the substrate 1 that is not to be polished from impacts that may be applied when the surface to be polished of the substrate 1 is polished or when the substrate 1 is transported, and prevents damage to the substrate 1.

[0032] The protective tape 3 has a flexible film-like substrate and a glue layer (adhesive layer) formed on one side of the substrate. For example, the substrate may be made of polyolefin, polyethylene terephthalate, polyvinyl chloride, polystyrene, or the like. The glue layer (adhesive layer) may be made of, for example, silicone rubber, an acrylic material, or an epoxy material.

[0033] Next, a polishing apparatus according to this embodiment for polishing a silicon oxide film 5 formed on a substrate 1 as a workpiece will be described. FIG. 1 is a perspective view showing a polishing apparatus 2. The polishing apparatus 2 has a base 4 that supports each component. Cassette mounting stages 6a and 6b are provided on the upper surface of the front portion of the base 4. A workpiece transport robot 10 for transporting the substrate 1 is installed on the base 4 adjacent to the cassette mounting stages 6a and 6b.

[0034] A cassette 8a containing substrates 1 before polishing is placed on the cassette placing table 6a, and a cassette 8b for containing substrates 1 after polishing is placed on the cassette placing table 6b. Alternatively, in the polishing apparatus 2, the substrates 1 contained in the cassette 8a placed on the cassette placing table 6a are polished one after another and returned to the cassette 8a. Thereafter, the substrates 1 contained in the cassette 8b placed on the cassette placing table 6b are polished one after another and returned to the cassette 8b. During this time, the cassette 8a on the cassette placing table 6a is replaced.

[0035] Further provided on the upper surface of the front portion of the base 4 are a positioning table 12 that adjusts the position of the substrate 1 by clamping the substrate 1 with a plurality of positioning pins, and a workpiece carry-in mechanism (loading arm) 14 that places the substrate 1 on a holding unit (holding table) 20. Further provided are a workpiece carry-out mechanism (unloading arm) 16 that carries the substrate 1 out of the holding unit 20, and a cleaning unit 52 that cleans and spin-dries the polished substrate 1.

[0036] An opening 4a is provided on the upper surface of the rear portion of the base 4. An X-axis moving table 18 is provided inside the opening 4a, and a holding unit (holding table) 20 that holds the substrate 1 by suction is placed on its upper surface. The X-axis moving table 18 can be moved in the X-axis direction by an X-axis moving mechanism (not shown). The X-axis moving mechanism functions to position the X-axis moving table 18 between a loading / unloading area 22 where the substrate 1 is loaded / unloaded onto / from the holding unit 20, and a processing area 24 where the substrate 1 held by the holding unit 20 is polished.

[0037] A disk-shaped porous member 20b having the same diameter as the substrate 1 is exposed on the upper surface of the holding unit (holding table) 20. The upper surface of the holding unit 20 serves as a holding surface 20a that holds the substrate 1. The holding unit 20 has an internal suction path (not shown) that has one end connected to the porous member 20b and the other end connected to a suction source (not shown). When the suction source is activated, negative pressure acts on the substrate 1 placed on the holding surface 20a, and the substrate 1 is sucked and held by the holding unit 20.

[0038] A polishing unit 26 for polishing the substrate 1 is disposed above the processing area 24. A support part 28 is erected at the rear end of the base 4 of the polishing apparatus 2, and this support part 28 supports the polishing unit 26. A pair of Z-axis guide rails 30 extending in the Z-axis direction are provided on the front surface of the support part 28, and a Z-axis moving plate 32 is slidably attached to each Z-axis guide rail 30.

[0039] A nut portion (not shown) is provided on the back side (rear side) of the Z-axis moving plate 32, and a Z-axis ball screw 34 parallel to the Z-axis guide rail 30 is threadedly engaged with this nut portion. A Z-axis pulse motor 36 is connected to one end of the Z-axis ball screw 34. When the Z-axis pulse motor 36 rotates the Z-axis ball screw 34, the Z-axis moving plate 32 moves in the Z-axis direction along the Z-axis guide rail 30. The polishing unit 26 is fixed to the lower front side of the Z-axis moving plate 32. When the Z-axis moving plate 32 is moved in the Z-axis direction, the polishing unit 26 can be moved in the Z-axis direction.

[0040] The polishing unit 26 includes a spindle 40 that is rotated by a motor connected to the base end, and a polishing wheel 44 that is fixed by a fixture 46 to a mount 42 disposed on the tip end of the spindle 40. The motor is provided inside a spindle housing 38, and when the motor is operated, the polishing wheel 44 rotates in accordance with the rotation of the spindle 40. The holding unit 20 is also connected to a rotation drive source such as a motor, and can rotate around a rotation axis 20c that is perpendicular to the holding surface 20a.

[0041] 3 is a cross-sectional view showing a schematic diagram of the polishing wheel 44. The polishing wheel 44 includes a polishing pad 44b made of, for example, urethane felt or the like, which has a diameter larger than the surface to be polished of the substrate 1, and a wheel base 44a to which the polishing pad 44b is fixed. More specifically, a pad made of polyurethane foam or nonwoven fabric impregnated with urethane or the like is preferably used as the polishing pad 44b.

[0042] The wheel base 44a is provided with a plurality of fixing holes (not shown) on the surface opposite to the surface on which the polishing pad 44b is fixed, into which a fixing tool 46 (see FIG. 1) enters. The wheel base 44a of the polishing wheel 44 is formed with a through-hole 44c penetrating through the center in the thickness direction, and the end of the through-hole 44c on the polishing pad 44b side serves as a slurry supply port 44d.

[0043] 1, a slurry supply path 50 is formed inside the polishing unit 26, penetrating the polishing unit 26 in the Z-axis direction. The upper end of the slurry supply path 50 is connected to a slurry supply source 48. The slurry supply source 48 is, for example, a tank provided in the polishing apparatus 2. When the substrate 1 is polished, slurry is supplied from the slurry supply source 48 through the slurry supply path 50 to a slurry supply port 44d (see FIG. 2) formed in the center of the polishing pad 44b.

[0044] The slurry is a chemical solution in which abrasive grains are dispersed, and functions as a polishing liquid. The material of the abrasive grains contained in the slurry, the particle size of the abrasive grains, the type of dispersion medium, and the like are selected appropriately depending on the material of the substrate 1. In particular, in the polishing apparatus 2 according to this embodiment, which polishes the silicon oxide film 5 of the substrate 1 having the silicon oxide film 5 on its surface, an acidic slurry containing oxide particles as abrasive grains and having a pH of 6 or less is used as the polishing liquid. The slurry will be described in detail below.

[0045] When polishing the substrate 1 held by the holding unit (holding table) 20 positioned in the processing region 24, a polishing pad 44b is disposed above the substrate 1. Then, the polishing wheel 44 and the holding unit 20 are rotated about their respective axes along the Z-axis direction, and the polishing wheel 44 is lowered to bring the polishing pad 44b into contact with the silicon oxide film 5 of the substrate 1. At this time, in order to supply a slurry between the substrate 1 and the polishing pad 44b, a slurry supply source 48 is operated to send the slurry to a slurry supply path 50.

[0046] 3 is a cross-sectional view schematically showing the state of polishing the substrate 1. When polishing the substrate 1, it is preferable to rotate the holding unit (holding table) 20 at a rotation speed of about 300 rpm to 800 rpm, and rotate the polishing wheel 44 at a rotation speed of about 300 rpm to 800 rpm. For example, the rotation speed of the holding unit 20 is set to 745 rpm, and the rotation speed of the polishing wheel 44 is set to 750 rpm.

[0047] The polishing amount (thickness of silicon oxide film 5 removed by polishing) is about 1 μm, and the polishing time is about 200 seconds. The polishing load is preferably set to 7 kPa or more and 21 kPa or less, for example, 7 kPa. The slurry is preferably supplied at a supply rate of 100 mL / min or more and 200 mL or less, for example, 100 mL / min. However, the polishing conditions are not limited to these.

[0048] The slurry supplied to the polishing pad 44b through the slurry supply path 50 penetrates between the polishing pad 44b and the surface of the substrate 1 to be polished when the polishing pad 44b and the substrate 1 are rotated around an axis along the Z-axis direction while being in contact with each other.

[0049] When the substrate 1 is polished by the polishing pad 44b, polishing debris is generated from the polished surface. The polishing debris is taken up by the slurry and discharged to the outside of the polishing pad 44b. The slurry that has taken up the polishing debris eventually reaches the outer periphery of the back surface 1b of the substrate 1 and drops onto the outer periphery of the holding surface 20a of the holding unit 20. The slurry then drops off from the holding unit 20 and is discharged from the drainage port 4b (see FIG. 1) formed in the opening 4a of the base 4 of the polishing apparatus 2.

[0050] A waste liquid recovery system (waste liquid path, waste liquid tank) having optimal characteristics for recovering slurry is connected to the drain port 4b, and the used slurry is recovered as waste liquid in this waste liquid recovery system. In particular, when an acidic slurry is used, the waste liquid recovery system uses a waste liquid path and a waste liquid tank that are resistant to acid solutions.

[0051] After the substrate 1 is polished in the polishing unit 26, the holding unit 20 is moved from the processing area 24 to the carry-in / out area 22. Then, after the holding of the substrate 1 by the holding unit 20 is released, the substrate 1 is transported by the workpiece carrying-out mechanism (unloading arm) 16 to the cleaning unit 52 where the substrate 1 is cleaned and spin-dried.

[0052] The cleaning unit 52 has an openable cover (not shown) that defines a cleaning chamber, and the space inside the openable cover becomes the cleaning chamber. Fig. 1 shows the cleaning unit 52 with the openable cover open. Fig. 4 is a perspective view that schematically shows the cleaning unit 52.

[0053] The cleaning unit 52 is provided with a spinner table 54 inside a cleaning chamber that can rotate while holding the substrate 1. The upper surface of the spinner table 54 is a holding surface 54a, and the spinner table 54 can hold by suction the substrate 1 placed on the holding surface 54a.

[0054] The cleaning unit 52 includes a cleaning liquid supply system that supplies a cleaning liquid to the upper surface of the substrate 1 held by the spinner table 54. The cleaning liquid supply system includes a cleaning liquid supply source 56 that is composed of a tank, a pump, etc., a cleaning liquid supply pipe 58 that has one end connected to the cleaning liquid supply source 56, and a cleaning liquid supply nozzle 60 that is connected to the other end of the cleaning liquid supply pipe 58.

[0055] When cleaning liquid supply source 56 is operated, cleaning liquid supplied to cleaning liquid supply nozzle 60 through cleaning liquid supply pipe 58 is sprayed from cleaning liquid supply nozzle 60 onto substrate 1 held by spinner table 54. If spinner table 54 is rotated at this time, the cleaning liquid is sprayed over the entire upper surface of substrate 1, cleaning the upper surface of substrate 1.

[0056] In the polishing apparatus 2 according to this embodiment, an acidic liquid having a pH of 6 or less is used as the cleaning liquid. On the other hand, the polishing apparatus 2 does not clean the substrate 1 using an alkaline cleaning liquid. The cleaning liquid supplied to the substrate 1 will be described in detail later.

[0057] A drain pipe (not shown) that serves as a discharge path for the cleaning liquid that has dropped from the substrate 1 is connected to the bottom of the cleaning chamber of the cleaning unit 52, and this drain pipe is connected to a waste liquid recovery system (waste liquid path, waste liquid tank) that has optimal properties for recovering the cleaning liquid. The used cleaning liquid is recovered as waste liquid in this waste liquid recovery system. In particular, when an acidic cleaning liquid is used, the waste liquid recovery system uses a waste liquid path and waste liquid tank that are resistant to acid solutions.

[0058] The cleaning unit 52 also uses a contact cleaning member 70 to clean the substrate 1. The contact cleaning member 70 is, for example, a brush-like member or a fabric-like member that comes into contact with the silicon oxide film 5 on the substrate 1 without damaging the silicon oxide film 5. The cleaning unit 52 rubs the contact cleaning member 70 against the silicon oxide film 5 in a stroking manner when cleaning the substrate 1. The contact cleaning member 70 is made of, for example, polyvinyl alcohol (PVA). The cleaning action of the contact cleaning member 70 will be described in detail below.

[0059] The cleaning unit 52 includes a contact mechanism 62 that brings a contact cleaning member 70 into contact with the substrate 1. The contact mechanism 62 includes a shaft 64 that extends along a direction (Z-axis direction) that intersects with the holding surface 54a outside the spinner table 54, an extendable shaft 66 built into the shaft 64, and an arm 68 that extends from the upper end of the shaft 64 above the spinner table 54. The contact cleaning member 70 is attached to the lower tip of the arm 68.

[0060] The telescopic shaft 66 of the contact mechanism 62 is configured, for example, by an air cylinder or the like, and can raise and lower the arm 68. In addition, a rotation mechanism (not shown) is provided at the lower end of the shaft 64 of the contact mechanism 62. The rotation mechanism is configured, for example, by a motor or the like. When the rotation mechanism is activated, the shaft 64 rotates around a rotation axis that runs along a direction (Z-axis direction) that intersects with the holding surface 54a outside the spinner table 54. At this time, the arm 68 rotates around the shaft 64 or the like, and the contact cleaning member 70 moves along an arc-shaped trajectory.

[0061] When cleaning the substrate 1 (silicon oxide film 5) in the cleaning unit 52, first, the substrate 1 is transported to the holding surface 54a and held by the spinner table 54. Thereafter, the spinner table 54 is rotated and a cleaning liquid is supplied to the substrate 1 from the cleaning liquid supply nozzle 60. Furthermore, the contact cleaning member 70 is brought into contact with the silicon oxide film 5 of the substrate 1.

[0062] Before being cleaned in the cleaning unit 52, the substrate 1 (silicon oxide film 5) has slurry used in polishing by the polishing unit 26 attached thereto, and in particular, oxide particles (abrasive grains) contained in the slurry are likely to remain on the substrate 1 (silicon oxide film 5). When the substrate 1 is cleaned using the contact cleaning member 70 while supplying a cleaning liquid with a pH of 6 or less, the slurry (oxide particles) can be efficiently removed, as described below. This cleaning effect will be described in detail later.

[0063] For example, the supply rate of the cleaning liquid during cleaning is about 700 mL / min, the rotation speed of the spinner table 54 is about 500 rpm, and the cleaning time with the cleaning liquid is about 30 seconds. During this time, the contact cleaning member 70 is oscillated on an orbit that overlaps the center and outer periphery of the substrate 1, and is moved back and forth along this orbit multiple times so that the contact cleaning member 70 comes into sufficient contact with the entire silicon oxide film 5 formed on the polished surface of the substrate 1. However, the cleaning conditions are not limited to these.

[0064] After the substrate 1 (silicon oxide film 5) is cleaned with the cleaning liquid, the substrate 1 (silicon oxide film 5) may be rinsed with a rinse liquid such as pure water in the cleaning unit 52. The rotation speed of the spinner table 54 at this time is set to about 500 rpm, and the rinsing is performed for about 30 seconds. However, the rinsing conditions are not limited to these.

[0065] Furthermore, after the substrate 1 (silicon oxide film 5) has been rinsed with the rinse liquid, the substrate 1 (silicon oxide film 5) may be dried in the cleaning unit 52. For example, after the supply of the rinse liquid is stopped, the rotation speed of the spinner table 54 is increased to about 1500 rpm. This causes the rinse liquid adhering to the substrate 1 to fly off from the substrate 1, and the substrate 1 is dried. The drying may be performed for about 30 seconds. However, the drying conditions are not limited to these.

[0066] As described above, cleaning unit 52 is equipped with contact cleaning member 70, and while supplying a cleaning liquid to silicon oxide film 5 on substrate 1 polished by polishing unit 26, contact cleaning member 70 is brought into contact with silicon oxide film 5 and rubbed with contact cleaning member 70. In this way, slurry remaining on silicon oxide film 5 is removed from silicon oxide film 5.

[0067] In the polishing apparatus 2, after the silicon oxide film 5 on the substrate 1 is cleaned by the cleaning unit 52, the substrate 1 is carried out of the cleaning unit 52 by the workpiece transport robot 10 and stored in the cassettes 8a and 8b.

[0068] The polishing apparatus 2 according to this embodiment includes a housing (not shown) that houses each component of the polishing apparatus 2 to prevent substances (solution, droplets, vapor, solidified material, etc.) derived from the slurry, cleaning solution, etc. from leaking to the outside, and the interior of this housing serves as a processing chamber. In this processing chamber, an acidic slurry is used to polish the substrate 1 (silicon oxide film 5), and an acidic cleaning solution is used to clean the substrate 1 (silicon oxide film 5). Therefore, the processing chamber is designed to be capable of handling acidic substances.

[0069] On the other hand, the polishing apparatus 2 according to this embodiment does not use alkaline slurry or cleaning liquid. Therefore, the polishing apparatus 2 does not need to be equipped with a processing chamber capable of handling alkaline substances, and can be realized with an extremely simple structure. More specifically, the installation area and occupied space of the polishing apparatus 2 can be reduced.

[0070] Here, the composition and pH of the slurry and cleaning liquid used in the polishing apparatus 2 according to this embodiment, and the cleaning effect of the contact cleaning member 70, will be described in detail. As described above, in the polishing apparatus 2 according to this embodiment for polishing the silicon oxide film 5 (oxide film) of the substrate 1, a slurry containing oxide particles as abrasive grains is used as the polishing liquid. Ceria (cerium oxide, CeO2) is preferably used as the oxide particles contained as abrasive grains in the slurry. Furthermore, a brush made of PVA (polyvinyl alcohol) is preferably used as the contact cleaning member 70 used for cleaning.

[0071] As a premise for the following explanation, we will show how the zeta potential of each of silicon oxide film, ceria, and PVA changes with pH. The zeta potential of each substance changes with pH, ​​as shown in Table 1 below. Note that Table 1 indicates the positive or negative zeta potential, which is an important factor in the following explanation, but does not indicate the absolute value of the zeta potential. The positive or negative zeta potentials shown in Table 1 are a summary of information obtained from Figure 2 of WO 2018 / 180256 and the sixth slide of the following document. O. Guildken and six others, “Metrology and Removal of Nanoscale Particles from EUV Substrates”, [online], publication date unknown, NSF Center for Micro and Nanoscale Contamination Control, [Retrieved April 16, 2024], Internet https: / / euvlsymposium.lbl.gov / pdf / 2004 / presentations / day2 / Me03_guldiken.pdf

[0072] [Table 1]

[0073] As shown in Table 1, the zeta potential of the silicon oxide film 5 is positive at pH 3.5 or less and negative at pH 4.0 or more. The zeta potential of ceria (oxide particles) is positive at pH 6.5 or less and negative at pH 7.0 or more. The zeta potential of PVA is positive at pH 2.5 or less and negative at pH 3.0 or more.

[0074] When the silicon oxide film 5 of the substrate 1 is polished in the polishing unit 26, if the pH of the ceria-containing slurry supplied to the silicon oxide film 5 is 6.5 or less, the zeta potential of the silicon oxide film 5 becomes negative, while the zeta potential of the ceria becomes positive. This tendency becomes more pronounced when the pH is 6.0 or less. In this case, the zeta potentials of the silicon oxide film 5 and the ceria (oxide particles) are opposite in polarity, so that the ceria is attracted to the vicinity of the silicon oxide film 5, and the ceria efficiently contributes to the polishing of the silicon oxide film 5. In other words, the polishing of the silicon oxide film 5 proceeds efficiently.

[0075] Conversely, when the pH of the slurry exceeds 7.0, the zeta potential of the silicon oxide film 5 and the zeta potential of the ceria become negative. In this case, the zeta potentials of the silicon oxide film 5 and the ceria become the same, so the ceria is not attracted to the silicon oxide film 5. As a result, the ceria does not efficiently penetrate between the polishing pad 44b and the silicon oxide film 5, and the ceria does not significantly contribute to polishing. In other words, polishing of the silicon oxide film 5 becomes inefficient.

[0076] When the pH of the slurry is 3.5 or less, the zeta potential of the silicon oxide film 5 and the zeta potential of the ceria become positive. In this case, the zeta potentials of the silicon oxide film 5 and the ceria become the same in polarity, so that the ceria is not easily attracted to the silicon oxide film 5, resulting in inefficient polishing of the silicon oxide film 5. Therefore, to efficiently proceed with polishing, the pH of the slurry is preferably 4.0 or more and 6.5 or less, and more preferably 4.0 or more and 6.0 or less.

[0077] The pH value of the slurry is adjusted to a predetermined value by adjusting the content of water and an acid, such as nitric acid or sulfuric acid. The pH decreases as the content of acid, such as nitric acid, increases, and the pH increases as the content of water increases. In the polishing apparatus 2 according to this embodiment, the pH of the slurry may be monitored, and an acid or the like may be added based on the measured pH value. Alternatively, in the polishing apparatus 2 according to this embodiment, a slurry that has been adjusted to a predetermined pH in advance is supplied and used.

[0078] Furthermore, when cleaning the silicon oxide film 5 of the substrate 1 in the cleaning unit 52, if the pH of the cleaning liquid supplied to the substrate 1 (silicon oxide film 5) is 3.5 or less, the zeta potential of the silicon oxide film 5 becomes positive, and the zeta potential of the ceria (oxide particles) also becomes positive. In this case, the ceria attached to the silicon oxide film 5 is easily liberated from the silicon oxide film 5 into the cleaning liquid, and the removal of the ceria from the silicon oxide film 5 proceeds efficiently.

[0079] Furthermore, if the pH of the cleaning solution supplied to the substrate 1 (silicon oxide film 5) is 2.5 or less, the zeta potential of the contact cleaning member 70 (e.g., a PVA brush) used for cleaning also becomes positive. In this case, a repulsive force is generated between the ceria liberated in the cleaning solution and the contact cleaning member 70, and the ceria is driven out of the substrate 1 by the oscillating contact cleaning member 70. Therefore, the ceria liberated in the cleaning solution is easily removed from the vicinity of the substrate 1 before it reattaches to the silicon oxide film 5, and the ceria is efficiently removed.

[0080] When the pH of the cleaning solution is 4.0 or higher, the zeta potential of the ceria also becomes positive, while the zeta potential of the silicon oxide film 5 becomes negative. In this case, the positive and negative zeta potentials of the silicon oxide film 5 and ceria become opposite to each other, making it difficult for the ceria to be liberated from the silicon oxide film 5, and cleaning cannot proceed efficiently.

[0081] Furthermore, if the pH of the cleaning solution is not 4.0 or higher but exceeds 2.5, the zeta potential of ceria is positive, while the zeta potential of the contact cleaning member 70 (e.g., a PVA brush) is negative. In this case, ceria liberated in the cleaning solution is more likely to be attracted to the contact cleaning member 70, which inhibits reattachment of ceria to the silicon oxide film 5 to some extent. Therefore, cleaning of the silicon oxide film 5 proceeds with a certain degree of efficiency.

[0082] Therefore, in order to efficiently carry out the washing, the pH of the washing liquid is preferably not more than 4.0, more preferably not more than 3.5, and particularly preferably not more than 2.5. From another perspective, the pH of the washing liquid is preferably lower than the pH of the slurry.

[0083] The pH value of the slurry is adjusted to a predetermined value by adjusting the content of water and an acid such as hydrofluoric acid (aqueous solution of hydrogen fluoride). The pH decreases as the content of acid such as hydrofluoric acid increases, and increases as the content of water increases. In the polishing apparatus 2 according to this embodiment, the pH of the cleaning liquid may be monitored, and an acid or the like may be added according to the measured pH value. Alternatively, in the polishing apparatus 2 according to this embodiment, a cleaning liquid previously adjusted to a predetermined pH is supplied and used.

[0084] Here, in cleaning to remove oxide particles derived from the slurry from the silicon oxide film 5 on the substrate 1, it is not necessary to mix a surfactant that acts on the oxide particles into the cleaning liquid. It is also not necessary to mix a reducing agent that reduces the oxide particles into the cleaning liquid. It has been confirmed that the cleaning liquid can sufficiently remove oxide particles even when it does not contain a surfactant or a reducing agent.

[0085] In the polishing apparatus 2 according to this embodiment, it is not necessary to mix a surfactant or a reducing agent into the cleaning liquid. Compared to when the cleaning liquid contains a surfactant or the like, the cost required for the cleaning liquid and the cost required for disposing of the used cleaning liquid are lower. However, a surfactant or the like may be mixed into the cleaning liquid.

[0086] Here, we will explain an experiment in which we investigated the state of particles remaining on substrate 1 when silicon oxide film 5 on substrate 1 was polished using a slurry containing ceria (oxide particles) and then substrate 1 (silicon oxide film 5) was cleaned.

[0087] In this experiment, three polished substrates 1 were prepared, and the substrates 1 (silicon oxide films 5) were cleaned under different conditions using a cleaning solution containing hydrofluoric acid and a PVA brush (contact cleaning member).The number of particles remaining on the substrates 1 (silicon oxide films 5) was then measured using a particle counter "SP1-DLS" manufactured by KLA Tencor.

[0088] First, the procedure of the first experiment in which the substrate 1 was cleaned under the first cleaning conditions will be described. First, in the first step, the substrate 1 was rotated at a rotation speed of 500 rpm while 0.5% hydrofluoric acid (pH 2.5 or less) was continuously supplied to the substrate 1, and cleaning was carried out for 2 minutes. Next, in the second step, a PVA brush (contact cleaning member 70) was brought into contact with the substrate 1 (silicon oxide film 5) while water was supplied to the substrate 1. The rotation speed of the substrate 1 at this time was also set to 500 rpm. The PVA brush was also moved back and forth between the center and outer edge of the substrate 1 three times.

[0089] Then, in the third step, the substrate 1 was rinsed with pure water. The rotation speed of the substrate 1 at this time was also set to 500 rpm. Finally, in the fourth step, the substrate 1 was rotated at a rotation speed of 1500 rpm to dry the substrate 1. The number of particles remaining on the substrate 1 that were 0.2 μm or larger in size was then measured, and found to be 6034.

[0090] Next, the procedure for the second experiment in which the substrate 1 was cleaned under the second cleaning conditions will be described. First, the first stage was carried out in the same manner as the first experiment described above. Next, the second stage was carried out in the same manner as the first experiment described above. However, in the second experiment, the PVA brush was moved back and forth between the center and outer edge of the substrate 1 30 times. Then, the third and fourth stages were carried out in the same manner as the first experiment described above. Then, the number of particles of 0.2 μm or larger remaining on the substrate 1 was measured, and it was found to be 2,679.

[0091] Finally, the procedure for the third experiment in which the substrate 1 was cleaned under the third cleaning conditions will be described. In this third experiment, the first and second stages were carried out simultaneously. Specifically, first, while the substrate 1 was being rotated at a rotational speed of 500 rpm, 0.5% hydrofluoric acid was continuously supplied to the substrate 1, and a PVA brush (contact cleaning member 70) was brought into contact with the substrate 1 (silicon oxide film 5). The PVA brush was then moved back and forth between the center and the outer edge of the substrate 1 three times. This cleaning was carried out for two minutes. Thereafter, the third and fourth stages were carried out in the same manner as in the first experiment. The number of particles of 0.2 μm or larger remaining on the substrate 1 was counted, and found to be five.

[0092] Comparing the results of the first experiment with the results of the second experiment, it can be seen that increasing the number of reciprocating movements of the PVA brush reduces the number of particles remaining on the substrate 1. However, the amount of reduction cannot be said to be large.

[0093] On the other hand, when the results of the first experiment and the third experiment are compared, it can be seen that the number of particles remaining on the substrate 1 is significantly reduced by simultaneously supplying hydrofluoric acid to the substrate 1 and contacting the substrate 1 with the PVA brush. This shows that an extremely high cleaning effect can be obtained by using a PVA brush in an environment where hydrofluoric acid is supplied as a cleaning liquid and the pH is lowered to a predetermined level.

[0094] Furthermore, the above experiments suggest that a sufficient cleaning effect cannot be obtained unless the supply of hydrofluoric acid and cleaning with a PVA brush are carried out simultaneously.Furthermore, if these are carried out simultaneously, it is suggested that a sufficiently high cleaning effect can be obtained without cleaning with an alkaline cleaning solution or without mixing a reducing agent or surfactant into the cleaning solution.

[0095] As described above, in the polishing apparatus 2 according to this embodiment, the contact cleaning member 70 is brought into contact with the silicon oxide film 5 and rubbed with the contact cleaning member 70 while supplying a cleaning liquid to the silicon oxide film 5, thereby efficiently removing the slurry (oxide particles) remaining on the silicon oxide film 5 from the silicon oxide film 5. This eliminates the need for equipment for handling alkaline solutions, allowing the installation area and occupied space of the polishing apparatus 2 to be reduced.

[0096] Next, a substrate processing method for polishing and cleaning a substrate 1 using the polishing apparatus 2 will be described as a method for using the polishing apparatus 2. For the substrate processing method described below, reference can be made as appropriate to the previous explanations regarding the polishing apparatus 2. Figure 6 is a flowchart showing the flow of each step of the substrate processing method.

[0097] The substrate processing method performed by polishing apparatus 2 includes a holding step S10 in which the substrate is held by holding unit 20 so that silicon oxide film 5 is exposed. In holding step S10, X-axis moving table 18 is positioned in carry-in / out area 22, and substrate 1 positioned at a predetermined position by positioning table 12 is loaded onto holding surface 20a by workpiece load mechanism 14. Figure 2 is a perspective view that schematically shows how substrate 1 is placed on holding unit 20 in holding step S10. Silicon oxide film 5 is omitted from Figure 2.

[0098] The surface of the substrate 1 to which the protective tape 3 is attached, on which no silicon oxide film 5 is formed (for example, the back surface 1b), is faced toward the holding surface 20a, and the surface to be polished on which the silicon oxide film 5 is formed (for example, the front surface 1a) is faced upward. Then, the suction source of the holding unit (holding table) 20 is activated, and the substrate 1 is held by suction with the holding unit 20. Then, the X-axis moving table 18 is moved to the processing region 24.

[0099] After the holding step S10, a polishing step S20 is performed in which the silicon oxide film 5 of the substrate 1 held by the holding unit 20 is polished with the polishing pad 44b while a slurry containing oxide particles is supplied to the silicon oxide film 5. Figure 3 is a cross-sectional view schematically showing the state in which the silicon oxide film 5 of the substrate 1 is polished in the polishing step S20.

[0100] In the polishing step S20, the holding unit (holding table) 20 is rotated around the rotation axis 20c, and the spindle 40 is rotated to rotate the polishing wheel 44. Then, while slurry is supplied from the slurry supply source 48 to the surface to be polished of the substrate 1 via the slurry supply path 50, the polishing unit 26 is lowered to bring the polishing pad 44b into contact with the silicon oxide film 5 of the substrate 1.

[0101] As described above, the slurry supplied to the silicon oxide film 5 contains oxide particles such as ceria and has a pH of 6 or less. In particular, the pH of the slurry is preferably 4 or more and 6 or less. The slurry penetrates between the polishing pad 44b and the substrate 1 (silicon oxide film 5). The substrate 1 (silicon oxide film 5) is then polished by the polishing pad 44b to become flat.

[0102] Polishing debris generated from the substrate 1 etc. is taken up in the slurry and carried out of the substrate 1. On the other hand, part of the slurry containing oxide particles remains on the silicon oxide film 5 of the substrate 1.

[0103] Next, a cleaning step S30 is performed in which a contact cleaning member 70 is brought into contact with the silicon oxide film 5 and rubbed with the contact cleaning member 70 while supplying a cleaning liquid to the silicon oxide film 5 polished in the polishing step S20, thereby removing any slurry remaining on the silicon oxide film 5 from the silicon oxide film 5.

[0104] First, the polished substrate 1 is transported from the holding unit 20 to the cleaning unit 52. More specifically, the X-axis moving table 18 is moved to the carry-in / out area 22, the suction holding of the substrate 1 by the holding unit 20 is released, and the substrate 1 is transported to the cleaning unit 52 by the workpiece carry-out mechanism 16. Then, the substrate 1 is held by suction on the spinner table 54 of the cleaning unit 52.

[0105] Next, cleaning of the substrate 1 (silicon oxide film 5) begins. Figure 5 is a perspective view that schematically shows a cleaning unit 52 that cleans the substrate 1 (silicon oxide film 5). However, the cleaning liquid is omitted from each figure.

[0106] When cleaning the substrate 1 in the cleaning unit 52, the spinner table 54 is rotated about a rotation axis that intersects with the holding surface 54a, while a cleaning liquid is supplied to the substrate 1 (silicon oxide film 5) from the cleaning liquid supply nozzle 60. Then, while the contact cleaning member 70 is brought into contact with the substrate 1 (silicon oxide film 5), the contact cleaning member 70 is oscillated on an orbit that passes through the center and outer edge of the substrate 1. This cleans the substrate 1 (silicon oxide film 5), and removes the slurry.

[0107] The cleaning liquid is as described above. The pH of the cleaning liquid is set to 6 or less. Furthermore, the pH of the cleaning liquid supplied to the silicon oxide film 5 in the cleaning step S30 is preferably lower than the pH of the slurry supplied to the silicon oxide film 5 in the polishing step S20. More specifically, when the pH of the slurry supplied to the silicon oxide film 5 in the polishing step S20 is set to 4 or more and 6 or less, the pH of the cleaning liquid supplied to the silicon oxide film 5 in the cleaning step S30 is preferably 3.5 or less. More preferably, the pH of the cleaning liquid is set to 2.5 or less.

[0108] After the cleaning liquid is supplied to the substrate 1 (silicon oxide film 5) for a predetermined time to perform cleaning, the supply of the cleaning liquid is stopped and a rinse liquid such as pure water is supplied to the substrate 1 to wash away the cleaning liquid. In other words, the substrate 1 is rinsed. After that, the supply of the rinse liquid is stopped and the rotation speed of the spinner table 54 is increased. Then, the rinse liquid is removed from the substrate 1, and the substrate 1 is dried.

[0109] After cleaning of the substrate 1 by the cleaning unit 52 is completed in this manner, the substrate 1 is placed in the cassettes 8a and 8b by the workpiece transport robot 10. Then, the substrate 1 placed in the cassettes 8a and 8b is carried out of the polishing apparatus 2.

[0110] When the substrate 1 is processed in this manner in the polishing apparatus 2, there is no need to further clean the substrate 1 with an alkaline cleaning solution, and the substrate 1 can be processed (polished and cleaned) efficiently in a short time with a simpler configuration. In addition, there is no need to mix additives such as surfactants or reducing agents into the cleaning solution.

[0111] The present invention is not limited to the above-described embodiment, and various modifications can be made. For example, the above-described embodiment describes a polishing apparatus 2 for polishing a substrate 1, in which the oxide particles contained in the slurry are ceria, the cleaning liquid is hydrofluoric acid, and the contact cleaning member 70 is a PVA brush. However, one aspect of the present invention is not limited to this.

[0112] For example, the oxide particles contained in the slurry used to polish the substrate 1 (silicon oxide film 5) may be alumina (aluminum oxide) instead of ceria (cerium oxide). The tendency of the change in zeta potential of alumina depending on the pH is relatively similar to that of ceria. Therefore, just as when ceria is contained in an acidic slurry, the alumina contained in the acidic slurry acts on the silicon oxide film 5 and contributes to the polishing of the silicon oxide film 5. Furthermore, if alumina remains on the silicon oxide film 5, it is efficiently removed by cleaning using the contact cleaning member 70 and an acidic cleaning solution.

[0113] Furthermore, the cleaning liquid used to clean the substrate 1 (silicon oxide film 5) in the cleaning unit 52 may be an aqueous solution of citric acid instead of hydrofluoric acid. Furthermore, the contact cleaning member 70 used when cleaning the substrate 1 (silicon oxide film 5) does not have to be a brush made of PVA (polyvinyl alcohol) and may be a brush made of polyurethane or nylon. However, polyurethane brushes tend to generate relatively large amounts of dust and may contaminate the substrate 1. Furthermore, nylon brushes are hard and may scratch the substrate 1. For this reason, it is most preferable to use a PVA brush for the contact cleaning member 70.

[0114] In addition, the structures, methods, etc. according to the above-described embodiments can be modified as appropriate without departing from the scope of the object of the present invention. [Explanation of symbols]

[0115] 1 board 1a surface 1b back side 3 Protective tape 5. Silicon oxide film 2 Polishing equipment 4 Foundation 4a aperture 4b Drainage port 6a, 6b Cassette placement table 8a,8b cassette 10 Workpiece transport robot 12 Positioning table 14 Workpiece loading mechanism 16 Workpiece delivery mechanism 18 X-axis moving table 20 holding unit 20a Holding surface 20b Porous member 20c Rotational Axis 22 Loading / unloading area 24 Processing area 26 Polishing unit 28 Support part 30 Z-axis guide rail 32 Z-axis moving plate 34 Z-axis ball screw 36 Z-axis pulse motor 38 Spindle housing 40 spindles 42 Mount 44 Abrasive Wheel 44a wheelbase 44b Polishing Pad 44c through hole 44d Slurry supply port 46 Fixtures 48 Slurry supply source 50 Slurry supply line 52 Cleaning unit 54 Spinner Table 54a Holding surface 56 Cleaning fluid supply source 58 Cleaning fluid supply pipe 60 Cleaning liquid supply nozzle 62 Contact mechanism 64 Shaft 66 Telescopic axis 68 Arm 70 Contact cleaning material

Claims

1. A processing method for polishing a silicon oxide film on a substrate having a silicon oxide film on its surface, comprising: a holding step of holding the substrate with a holding unit so that the silicon oxide film is exposed; a polishing step of polishing the silicon oxide film of the substrate held by the holding unit with a polishing pad while supplying a slurry containing oxide particles to the silicon oxide film; a cleaning step of removing the slurry remaining on the silicon oxide film from the silicon oxide film by bringing a contact cleaning member into contact with the silicon oxide film and rubbing the silicon oxide film with the contact cleaning member while supplying a cleaning liquid to the silicon oxide film polished in the polishing step; the pH of the slurry supplied to the silicon oxide film in the polishing step is 6 or less; The processing method is characterized in that the pH of the cleaning solution supplied to the silicon oxide film in the cleaning step is 6 or less.

2. The contact cleaning member is a brush made of polyvinyl alcohol, polyurethane, or nylon; The cleaning solution is an aqueous solution of hydrogen fluoride or an aqueous solution of citric acid, 2. The processing method according to claim 1, wherein the oxide particles include cerium oxide or aluminum oxide.

3. 3. The processing method according to claim 1, wherein the pH of the cleaning liquid supplied to the silicon oxide film in the cleaning step is lower than the pH of the slurry supplied to the silicon oxide film in the polishing step.

4. the pH of the slurry supplied to the silicon oxide film in the polishing step is 4 or more and 6 or less; 3. The processing method according to claim 1, wherein the pH of the cleaning solution supplied to the silicon oxide film in the cleaning step is 3.5 or less.

5. 5. The processing method according to claim 4, wherein the pH of the cleaning solution supplied to the silicon oxide film in the cleaning step is 2.5 or less.

6. A polishing apparatus for polishing a silicon oxide film on a substrate having a silicon oxide film on its surface, comprising: a holding unit that holds the substrate so that the silicon oxide film is exposed; a polishing unit equipped with a polishing pad, which polishes the silicon oxide film of the substrate held by the holding unit while supplying a slurry containing oxide particles to the silicon oxide film; a cleaning unit equipped with a contact cleaning member, which removes the slurry remaining on the silicon oxide film from the silicon oxide film by bringing the contact cleaning member into contact with the silicon oxide film and rubbing the silicon oxide film with the contact cleaning member while supplying a cleaning liquid to the silicon oxide film polished by the polishing unit; the pH of the slurry supplied to the silicon oxide film in the polishing unit is 6 or less; The polishing apparatus is characterized in that the pH of the cleaning liquid supplied to the silicon oxide film in the cleaning unit is 6 or less.

7. The contact cleaning member is a brush made of polyvinyl alcohol, polyurethane, or nylon; The cleaning solution is an aqueous solution of hydrogen fluoride or an aqueous solution of citric acid, 7. The polishing apparatus according to claim 6, wherein the oxide particles include cerium oxide or aluminum oxide.

8. 8. The polishing apparatus according to claim 6, wherein the pH of the cleaning liquid supplied to the silicon oxide film in the cleaning unit is lower than the pH of the slurry supplied to the silicon oxide film in the polishing unit.

9. the pH of the slurry supplied to the silicon oxide film in the polishing unit is 4 or more and 6 or less; 8. A polishing apparatus according to claim 6, wherein the pH of the cleaning liquid supplied to the silicon oxide film in the cleaning unit is 3.5 or less.

10. 10. The polishing apparatus according to claim 9, wherein the pH of the cleaning liquid supplied to the silicon oxide film in the cleaning unit is 2.5 or less.

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