Wet wafer cleaning method using nanofluid and cleaning device using the same

Abstract

A wafer cleaning method capable of uniformly cleaning the entire area of ​​a wafer and a wafer cleaning apparatus to which the method is applied are provided. [Solution] The wafer cleaning method includes the steps of: positioning a cleaning tool (40) facing the wafer surface that requires cleaning; adjusting the distance between the wafer surface and the cleaning tool (40); supplying a cleaning liquid (55) containing ions between the wafer surface and the cleaning tool (40); applying an electric field to at least a portion of the area where the cleaning liquid (55) is present; and rotating the wafer (10) and the cleaning tool (40) relative to each other to clean the wafer surface with the cleaning liquid (55).

Description

[Technical Field]

[0001] This work was funded by the Government of the Republic of Korea (Ministry of Science and ICT) and supported by the National Research Foundation of Korea (RS-2023-00272214).

[0002] This application claims the benefit of priority based on Korean Patent Application No. 10-2024-0118705, filed September 2, 2024, and all contents disclosed in the documents of that Korean patent application are incorporated herein by reference.

[0003] The present invention relates to a wafer cleaning method capable of uniformly wet cleaning the entire surface of a wafer with nanofluid, and a wafer cleaning apparatus to which the method is applied. [Background technology]

[0004] Semiconductor manufacturing technology is advancing day by day toward ultra-fine processes. To this end, manufacturing technologies capable of fine processes on the nanoscale are currently being developed. At the nanoscale, the movement of individual fluid particles affects the fluid flow to a degree that cannot be explained by the fluid continuity equation. This makes it difficult to design processes that were previously possible to predict or model at each stage of the semiconductor manufacturing process at the nanoscale.

[0005] For example, semiconductor manufacturing processes such as cleaning, deposition, and etching require predicting the flow of fluids, such as liquids and gases. Traditionally, such predictions and design were possible based on fluid dynamics and decades of accumulated data. However, as design approaches the nanoscale, previous prediction methods are no longer effective.

[0006] Meanwhile, in semiconductors manufactured using ultrafine processes, ultrafine structures are constructed on wafers through the processes. Cleaning processes are performed between each process to remove by-products of the previous process. The particles removed in the cleaning process are difficult to clean because they exist between the ultrafine structures. For example, excessive cleaning to remove such difficult-to-clean foreign particles can damage the semiconductor patterning structure.

[0007] Furthermore, due to the nature of cleaning processes that typically involve rotating semiconductor wafers, areas located radially outward from the center of rotation are over-cleaned, while areas closer to the center of rotation are under-cleaned, meaning that in order to adequately clean the areas closer to the center of rotation, the areas located radially outward must be over-cleaned.

[0008] For this reason, cleaning can be performed by applying high-frequency vibrations to the cleaning solution without using a brush. However, this method also cannot avoid cleaning deviations in the radial direction. Furthermore, if the high-frequency energy is not absorbed by the cleaning solution and is transmitted to the semiconductor patterning structure, the patterning structure may be damaged. Summary of the Invention [Problem to be solved by the invention]

[0009] The present invention has been devised to solve the above-mentioned problems, and aims to provide a wafer cleaning method and a wafer cleaning apparatus using the same, which can perform uniform cleaning of the entire wafer area regardless of the radial position in a wet wafer cleaning process corresponding to an ultrafine process.

[0010] SUMMARY OF THE INVENTION The present invention provides a wafer cleaning method and a wafer cleaning apparatus using the same, which can minimize the difference in cleaning power along the rotation radius when wet cleaning is performed in a rotational manner.

[0011] SUMMARY OF THE INVENTION The present invention provides a wafer cleaning method that can be applied to ultrafine processes without significant changes to typical wet wafer cleaning methods, and a wafer cleaning apparatus using the same.

[0012] The technical object of the present invention is not limited to the above-mentioned objects, and other unmentioned objects and advantages of the present invention can be understood from the following description and can be more clearly understood from the examples of the present invention. Furthermore, it can be easily understood that the objects and advantages of the present invention can be achieved by the means and combinations thereof set forth in the claims. [Means for solving the problem]

[0013] To solve the above-mentioned problems, the wet cleaning method for wafers of the present invention can be applied to cleaning by a rotation method.

[0014] The wet cleaning method applies a radially differential electric field to an ionic cleaning solution provided between the wafer surface and the cleaning tool, the electric field being based on a DC power source.

[0015] This allows the viscosity of the cleaning liquid to be artificially controlled for each region, so that cleaning can be performed uniformly even in regions that are at different radial distances from the center of rotation during rotation cleaning.

[0016] Specifically, the wafer cleaning method includes a first step of positioning a cleaning tool opposite the wafer surface that requires cleaning.

[0017] The wafer cleaning method further includes a second step of supplying a cleaning solution containing ions between the wafer surface and the cleaning tool.

[0018] The wafer cleaning method further includes a third step of adjusting the gap between the wafer surface and the cleaning tool.

[0019] The wafer cleaning method includes a fourth step of applying an electric field to the cleaning liquid in at least a portion of the region where the cleaning liquid is present, and rotating the wafer and the cleaning tool relative to each other to clean the wafer surface.

[0020] The region where the cleaning liquid exists includes a first region and a second region that is disposed farther from the center of rotation than the first region.

[0021] Preferably, an electric field can be applied to the first region such that the viscosity of the cleaning liquid in the first region is greater than the viscosity of the cleaning liquid in the second region.

[0022] In one example, the strength of the electric field applied to the first region may be greater than the strength of the electric field applied to the second region.

[0023] In another example, an electric field may be applied to the first region and no electric field may be applied to the second region.

[0024] Preferably, the intensity distribution of the electric field applied to the region may include a first distribution that continuously decreases with increasing distance from the center of rotation.

[0025] Preferably, the intensity distribution of the electric field applied to the region may include a second distribution that gradually decreases with increasing distance from the center of rotation.

[0026] Preferably, the intensity distribution of the electric field applied to the region may include a third distribution that gradually decreases with increasing distance from the center of rotation.

[0027] Preferably, the intensity distribution of the electric field applied to the region may include a fourth distribution that linearly decreases with increasing distance from the center of rotation.

[0028] Preferably, the intensity distribution of the electric field applied to the region may include a fifth distribution that decreases nonlinearly with increasing distance from the center of rotation.

[0029] Preferably, the intensity distribution of the electric field applied to the region may include a sixth distribution that parabolically decreases with increasing distance from the center of rotation.

[0030] Preferably, the intensity distribution of the electric field applied to the region may include a seventh distribution that hyperbolically decreases with increasing distance from the center of rotation.

[0031] The intensity distribution of the electric field applied to the region may include at least one of the first to seventh distributions.

[0032] The cleaning solution may include a H2O solution containing cations and anions.

[0033] The cleaning solution may be cation-anion equivalent so as to be totally neutral.

[0034] The ion is Na + , Cl - It may also include.

[0035] The equivalent concentration of the ions contained in the cleaning solution is 0.1 mEq / L or more 10 mEq / L or less.

[0036] The equivalent concentration of the ion is 0.1 mEq If the electric field strength is lower than 1 / L, the viscosity of the cleaning solution hardly changes even when the electric field strength is controlled, making it difficult to control the viscosity.

[0037] The equivalent concentration of the ions is 10 or more mEq If the electric field strength is higher than 1 / L, the effect of inducing a change in the viscosity of the cleaning solution by the electric field strength will not increase any further, and there is a risk that the ions will be more likely to remain as foreign matter.

[0038] Preferably, the equivalent concentration of said ions is 1.0 mEq / L or more 2.0 mEqMore preferably, the equivalent concentration of the ions is about 1.5 mEq It may be within or outside / L.

[0039] The gap between the wafer surface and the cleaning tool may be 1 nm or more and 20 nm or less. A region corresponding to the gap may be filled with a cleaning liquid.

[0040] If the distance is less than 1 nm, the effect of inducing a change in the viscosity of the cleaning solution by the strength of the electric field does not increase any more, and it is difficult to provide a cleaning solution that is sufficient for smooth cleaning.

[0041] When the distance exceeds 20 nm, the viscosity of the cleaning solution hardly changes even when the strength of the electric field is controlled, making it difficult to control the viscosity.

[0042] Preferably, the distance between the wafer surface and the cleaning tool is 2 nm to 4 nm, and more preferably, the distance is about 3 nm.

[0043] The present invention provides a cleaning apparatus to which the above-described wet cleaning method for wafers is applied.

[0044] The cleaning apparatus includes a wafer support for holding the wafer, a cleaning tool facing the wafer support, a cleaning liquid supply device for supplying cleaning liquid between the cleaning tool and the wafer support, a drive device for rotating the wafer support and the cleaning tool relative to each other, and an electric field application unit for applying an electric field to the cleaning liquid. The electric field is based on a DC power supply.

[0045] The cleaning apparatus may further include a gap adjustment device that adjusts the gap between the wafer surface and the cleaning tool.

[0046] The wafer support can rotate about a predetermined center of rotation.

[0047] The center of rotation may extend vertically, and the wafer support may extend horizontally.

[0048] The wafer support can support one or more wafers.

[0049] In a wafer support that supports one wafer, the center of the wafer may be aligned with the center of rotation of the wafer support.

[0050] In a wafer support that supports two or more wafers, the wafers may be arranged at equal intervals along the circumferential direction of the wafer support.

[0051] The wafer support can support the wafer so that the wafer surface requiring cleaning is oriented vertically.

[0052] The cleaning surface of the cleaning tool may be vertically facing the wafer surface.

[0053] In some cases, the cleaning surface may have a length that is less than the diameter of the wafer support and greater than the radius.

[0054] In some examples, the width of the cleaning surface measured circumferentially of the wafer support may remain constant along a radial direction of the wafer support.

[0055] In some examples, the width of the cleaning surface measured in a circumferential direction of the wafer support may be in the shape of a sector that gradually widens radially outwardly of the wafer support.

[0056] In some cases, the cleaning surface may be circular in shape, and the diameter of the cleaning surface may correspond substantially to the diameter of the wafer support or may correspond substantially to the radius of the wafer support.

[0057] The distance adjusting device may move the cleaning tool in an up-down direction, which may be a vertical direction.

[0058] In some instances, the cleaning surface of the cleaning tool may include a brush.

[0059] In some cases, the cleaning surface of the cleaning tool may be a vibrating plate that produces vibrations.

[0060] In some examples, the cleaning fluid supply device can supply cleaning fluid near a center of the wafer support.

[0061] In some examples, the cleaning liquid supply device may be a showerhead extending radially outward from a central portion of the wafer support.

[0062] The drive device may include a rotor connected to the wafer support at a rotation center of the wafer support, and a stator that rotates and drives the rotor.

[0063] The driving device can rotate the wafer support at a speed of 20 to 50 rpm.

[0064] The electric field applying unit may include conductive plates arranged in a matrix.

[0065] The electric field applying unit may apply an electric field to a space between the wafer support unit and the cleaning tool to which the cleaning liquid is supplied.

[0066] The electric field applying unit may be built into the cleaning tool.

[0067] Another aspect of the present invention provides a method for wet cleaning a wafer.

[0068] The wafer cleaning method includes a first step of positioning a cleaning tool facing the wafer surface that requires cleaning; a second step of supplying a cleaning liquid containing ions between the wafer surface and the cleaning tool; a third step of adjusting the distance between the wafer surface and the cleaning tool so that the viscosity of the cleaning liquid between the wafer surface and the cleaning tool is controlled by an electric field; and a fourth step of rotating the wafer and the cleaning tool relative to each other while applying an electric field to at least a portion of the area where the cleaning liquid is present, and cleaning the wafer surface with the cleaning liquid.

[0069] In some examples, the region where the cleaning liquid is present may include a first region and a second region that is positioned farther from the center of rotation than the first region.

[0070] In the fourth step, an electric field can be applied to the cleaning solution in the first region.

[0071] Additionally, an electric field can be applied to the cleaning solution in the second region.

[0072] Preferably, the strength of the electric field applied to the first region may be greater than the strength of the electric field applied to the second region.

[0073] Alternatively, no electric field may be applied to the second region.

[0074] The intensity distribution of the electric field applied to the region in the fourth step may decrease with increasing distance from the center of rotation.

[0075] In some examples, the intensity distribution of the electric field applied to the region in the fourth stage may gradually decrease with increasing distance from the center of rotation.

[0076] In some examples, the intensity distribution of the electric field applied to the region in the fourth stage may continuously decrease with increasing distance from the center of rotation.

[0077] In some examples, the intensity distribution of the electric field applied to the region in the fourth stage may gradually decrease with increasing distance from the center of rotation.

[0078] In some examples, the intensity distribution of the electric field applied to the region in the fourth stage may decrease linearly with increasing distance from the center of rotation.

[0079] In some cases, the intensity distribution of the electric field applied to the region in the fourth stage may decrease nonlinearly with increasing distance from the center of rotation.

[0080] The cleaning solution may include a H2O solution containing cations and anions.

[0081] In some instances, the cation and anion are Na + , Cl - It may also contain ions.

[0082] In some examples, the equivalent concentration of the ions contained in the cleaning solution is 0.1 mEq / L or more 10 mEq / L or less, preferably 1.0 mEq / L or more 2.0 mEq / L or less.

[0083] In some examples, the spacing may be 1 nm or more and 20 nm or less, and preferably 2 nm or more and 4 nm or less.

[0084] From another aspect, the present invention provides an apparatus for wet cleaning a wafer.

[0085] The wafer cleaning apparatus includes a wafer support for holding a wafer, a cleaning tool facing the wafer support, a cleaning liquid supply device for supplying a cleaning liquid containing ions between the cleaning tool and the wafer support, a gap adjustment device for adjusting the gap between the wafer support and the cleaning tool to set the height of the cleaning liquid between the wafer surface and the cleaning tool, a drive device for rotating the wafer support and the cleaning tool relatively, and an electric field application unit for applying an electric field to the cleaning liquid supplied onto the wafer.

[0086] Preferably, the electric field applying unit can apply an electric field based on a DC power supply.

[0087] The region on the wafer where the cleaning liquid is present may include a first region and a second region that is disposed farther from the center of rotation than the first region.

[0088] In some examples, the electric field applying unit may apply an electric field to the first region and not apply an electric field to the second region.

[0089] In some examples, the electric field applying unit may apply electric fields of different strengths to the first region and the second region.

[0090] In some examples, the electric field applying unit can apply an electric field to the cleaning solution such that the strength of the electric field decreases with increasing distance from the center of rotation. [Effects of the Invention]

[0091] According to the present invention, in a rotational wet wafer cleaning process for ultrafine processes, uniform cleaning can be achieved over the entire cleaning area of ​​a wafer by controlling the viscosity of the cleaning solution by differentially applying an electric field to each region of the ion-containing cleaning solution.

[0092] According to the present invention, the strength of the electric field to be applied to each region can be relatively accurately predicted and applied based on the ion concentration of the cleaning solution, the height of the cleaning solution, the rotation speed, and the distance of the electric field application region from the rotation center for cleaning.

[0093] The above-mentioned effects and specific effects of the present invention will be described in conjunction with the following description of the preferred embodiment of the invention. [Brief explanation of the drawings]

[0094] [Figure 1] 1 is a perspective view of a wafer cleaning apparatus according to an embodiment of the present invention. [Figure 2] FIG. 2 is a front cross-sectional view of the wafer cleaning apparatus of FIG. [Figure 3] 2 is a transparent perspective view showing a cleaning tool and an electric field application unit of the wafer cleaning apparatus of FIG. 1. FIG. [Figure 4] 2 is a perspective view showing a cleaning liquid supply device of the wafer cleaning apparatus of FIG. 1. FIG. [Figure 5] 2 is a perspective view showing a wafer support unit and a drive unit of the wafer cleaning apparatus of FIG. 1. FIG. [Figure 6] FIG. 6 is a perspective view showing a state in which a wafer is concentrically placed on the wafer support part of FIG. 5. [Figure 7] 6 is a perspective view showing a state in which a plurality of wafers are eccentrically placed on the wafer support part of FIG. 5. FIG. [Figure 8] 6 is a perspective view showing a state in which the cleaning tool of the first embodiment is placed on the wafer support part of FIG. 5. FIG. [Figure 9] 6 is a perspective view showing a state in which a cleaning tool of a second embodiment is placed on the wafer support part of FIG. 5. FIG. [Figure 10] 6 is a perspective view showing a state in which a cleaning tool of a third embodiment is placed on the wafer support part of FIG. 5. FIG. [Figure 11] FIG. 6 is a perspective view showing a state in which a cleaning tool of a fourth embodiment is placed on the wafer support part of FIG. 5. [Figure 12] This is an enlarged view of box .12 in Figure 2. [Figure 13]10 is a graph showing the linear velocity of the wafer surface as a function of the distance from the center of rotation to a specific position on the wafer surface. [Figure 14] 10 is a graph showing a first example of the distribution of the applied strength of an electric field depending on the distance from the center of rotation to a specific region of the cleaning liquid supplied onto the wafer surface. [Figure 15] 10 is a graph showing a second example of the distribution of the applied strength of the electric field depending on the distance from the center of rotation to a specific region of the cleaning liquid supplied onto the wafer surface. [Figure 16] 10 is a graph showing a third example of the distribution of the applied strength of an electric field depending on the distance from the center of rotation to a specific region of the cleaning liquid supplied onto the wafer surface. [Figure 17] 10 is a graph showing a fourth example of the distribution of the applied strength of an electric field depending on the distance from the center of rotation to a specific region of the cleaning liquid supplied onto the wafer surface. DETAILED DESCRIPTION OF THE INVENTION

[0095] In the following, preferred embodiments of the present invention will be described in detail with reference to the accompanying drawings.

[0096] The present invention is not limited to the embodiments disclosed below, but may be embodied in various different forms and may be modified in various ways. However, these embodiments are provided to complete the disclosure of the present invention and to fully convey the scope of the invention to those skilled in the art. Therefore, the present invention is not limited to the embodiments disclosed below, and should be understood to include any modifications, equivalents, or alternatives within the technical spirit and scope of the present invention, as well as the substitution or addition of the configuration of any embodiment with the configuration of another embodiment.

[0097] The accompanying drawings are intended to facilitate understanding of the embodiments disclosed in this specification, and should not be construed as limiting the technical ideas disclosed in this specification, but should be understood to include any modifications, equivalents, or alternatives that fall within the idea and technical scope of the present invention. The components in the drawings may be exaggerated in size and thickness for ease of understanding, but this should not be interpreted as limiting the scope of protection of the present invention.

[0098] The terms used in this specification are merely used to describe particular embodiments or examples and are not intended to limit the present invention. Furthermore, singular terms include plural terms unless the context clearly dictates otherwise. Terms such as "comprises," "consists," etc. in the specification are intended to specify the presence of features, numbers, steps, operations, components, parts, or combinations thereof described in the specification. In other words, terms such as "comprises," "consists," etc. in the specification should not be understood to preclude the presence or addition of one or more other features, numbers, steps, operations, components, parts, or combinations thereof.

[0099] Although terms including ordinal numbers, such as first, second, etc., are used to describe various components, the components are not limited by these terms. These terms are used only to distinguish one component from another. Therefore, unless otherwise specified, a first component may also be a second component.

[0100] When a component is referred to as being "coupled" or "connected" to another component, it should be understood that it may be directly coupled or connected to the other component, but that other components may be present therein. Conversely, when a component is referred to as being "directly coupled" or "directly connected" to another component, it should be understood that no other components are present therein.

[0101] When a component is referred to as being "on top of" or "under" another component, it should be understood that the other component may be present within the component, not just positioned directly above it.

[0102] Unless otherwise defined, all terms used herein, including technical and scientific terms, have the same meaning as commonly understood by one of ordinary skill in the art to which the present invention pertains. Terms similar to those defined in commonly used dictionaries should be interpreted to have a meaning consistent with the meaning they have in the context of the relevant art, and should not be interpreted in an idealized or overly formal sense unless expressly defined herein.

[0103] Hereinafter, a wafer cleaning apparatus according to an embodiment of the present invention and a wafer cleaning method implemented using the wafer cleaning apparatus will be described.

[0104] 1 to 12, the present invention provides a wafer cleaning apparatus to which the wet cleaning method for the wafer 10 is applied. The wafer cleaning apparatus includes a wafer support 30 that holds the wafer 10, a cleaning tool 40 facing the wafer support 30, a cleaning liquid supply unit 50 that supplies a cleaning liquid 55 between the cleaning tool 40 and the wafer support 30, a driving unit 60 that rotates the wafer support 30 and the cleaning tool 40 relatively, and an electric field application unit 70 that applies an electric field to the cleaning liquid 55.

[0105] Furthermore, the wafer cleaning apparatus further includes a gap adjusting device 80 for adjusting the gap between the surface of the wafer 10 and the cleaning tool 40 .

[0106] 5, the wafer support 30 is installed to be rotatable about a predetermined rotation center 30C. The rotation center 30C extends vertically, and the wafer support 30 extends horizontally. The wafer support 30 is rotationally driven by the driving device 60.

[0107] The driving device 60 includes a rotor 62 that is connected to the wafer support 30 at the rotation center 30C of the wafer support 30 and extends in the axial direction, and a stator 64 that drives the rotor 62 to rotate. The axial direction of the rotor 62 may extend parallel to the vertical direction. For example, the driving device 60 can rotate the wafer support 30 at a speed of 20 to 50 rpm. However, the rotation speed of the wafer support 30 is not limited to this.

[0108] 6 and 7, the wafer support 30 supports one or more wafers 10. The wafer support 30 supports the wafers 10 so that the surface of the wafer 10 that needs to be cleaned faces vertically.

[0109] 6, in a wafer support 30 supporting one wafer 10, a wafer center 10C of the wafer 10 may be aligned with a rotation center 30C of the wafer support 30. Next, as shown in Fig. 7, in a wafer support 30 supporting two or more wafers 10, the wafer centers 10C of the wafers 10 may be disposed eccentrically with respect to the rotation center 30C of the wafer support 30 and may be disposed at equal intervals along the circumferential direction of the wafer support 30. In the embodiment, an example is shown in which three wafers 10 are supported by the wafer support 30.

[0110] 8 to 11, the cleaning surface 42 of the cleaning tool 40 faces the upper surface of the wafer support part 30 in the vertical direction. As a result, the cleaning surface 42 faces the surface of the wafer 10 held on the wafer support part 30.

[0111] 8 and 9, in some embodiments, the cleaning surface 42 has a length (L) that is less than the diameter of the wafer support 30 and greater than the radius.

[0112] 8, in some embodiments, the width (W) of the cleaning surface 42, measured in the circumferential direction of the wafer support 30, remains constant along the radial direction of the wafer support 30. For example, the cleaning surface 42 may be track-shaped.

[0113] Referring to FIG. 9, in some embodiments, the width (W) of the cleaning surface 42 measured in the circumferential direction of the wafer support 30 may be fan-shaped, gradually widening as it moves radially outward from the wafer support 30.

[0114] 10 and 11, in some embodiments, the shape of the cleaning surface 42 may be circular. Referring to FIG. 10, in some embodiments, the diameter of the cleaning surface 42 may substantially correspond to the radius of the wafer support 30. Referring to FIG. 11, in some embodiments, the diameter of the cleaning surface 42 may substantially correspond to the diameter of the wafer support 30.

[0115] In some embodiments, the cleaning surface 42 of the cleaning tool 40 comprises a brush.

[0116] In some embodiments, the cleaning surface 42 of the cleaning tool 40 includes a vibrating plate that generates vibrations.

[0117] In some embodiments, the cleaning surface 42 of the cleaning tool 40 includes a brush mounted on a vibrating plate.

[0118] 2, the gap adjusting device 80 can move the cleaning tool 40 in an up-down direction, more specifically, in a vertical direction. The gap adjusting device 80 can raise and lower the cleaning tool 40 to adjust the gap between the cleaning surface 42 and the upper surface of the wafer 10 held on the wafer support 30.

[0119] 1 and 2, the cleaning liquid supply device 50 supplies a cleaning liquid 55 to the wafer 10 held on the wafer support 30 near the center of the wafer support 30. As shown in FIG. 4, the cleaning liquid supply device 50 may be in the form of a shower head extending radially outward from the center of the wafer support 30. However, the shape of the cleaning liquid supply device 50 is not limited thereto. For example, the cleaning liquid supply device 50 may be in the form of a nozzle that supplies the cleaning liquid to the center of the wafer support 30.

[0120] 3, the electric field applying unit 70 in this embodiment includes conductive plates 73 arranged in a matrix. The electric field applying unit 70 includes a housing 71 that houses the conductive plates. The electric field applying unit 70 can apply an electric field to the space between the wafer support unit 30 and the cleaning tool 40 to which the cleaning solution 55 is supplied. That is, the electric field applying unit 70 applies an electric field to the cleaning solution 55.

[0121] The electric field applying unit 70 can apply different voltages to each conductive plate 73. That is, the electric field applying unit 70 has a plurality of electric field applying regions that can apply an electric field to each region.

[0122] In the embodiment, the electric field applicator 70 is illustrated as a matrix of separate conductive plates, but this is merely an example, and the electric field applicator may have various configurations suitable for generating an electric field. For example, the cleaning surface 42 itself may be configured as a conductive plate divided into multiple regions, and different voltages may be applied to each region. Furthermore, the division may be performed in various ways.

[0123] In some embodiments, the electric field application unit 70 is built into the cleaning tool 40 and disposed below the wafer support 30. The electric field application unit 70 maintains its position even when the wafer support 30 rotates. The electric field application unit 70 is disposed adjacent to the cleaning surface 42 of the cleaning tool 40 and applies a strong electric field to the cleaning solution 55 present below the cleaning surface 42.

[0124] The strength of the electric field can be individually controlled for each area occupied by each of the conductive plates 73 arranged opposite each other above and below through the area corresponding to the cleaning surface 42 .

[0125] There are various methods for applying an electric field. It is clear that the present invention is not limited to the structure of the electric field applicator 70 embodied in the embodiment, as long as it is capable of applying a differential electric field along the radial direction of the region corresponding to the cleaning surface 42. For example, the electric field applicator 70 may be configured such that it has multiple application regions above the cleaning surface 42, each of which can apply an electric field of different strength, and the wafer support 30 is grounded. Various other known electric field application structures may also be used.

[0126] The wet cleaning method for the wafer 10 according to the present invention is applied to cleaning in a rotational manner, as embodied in the wafer cleaning apparatus described above.

[0127] In the wet cleaning method, an electric field of different strength is applied along the radial direction (r) from the rotation center 30C to the ion cleaning solution 55 supplied between the surface of the wafer 10 and the cleaning tool 40. This artificially controls the viscosity of the cleaning solution 55 for each region along the radial direction, so that cleaning can be performed uniformly even in regions at different radial distances from the rotation center 30C during rotation cleaning.

[0128] The cleaning efficiency is proportional to the flow velocity of the cleaning liquid 55 and to the viscosity of the cleaning liquid 55. That is, the higher the flow velocity of the cleaning liquid 55, the higher the cleaning power, and the higher the viscosity of the cleaning liquid 55, the higher the cleaning power. Therefore, as shown in FIGS. 13 and 16, when cleaning the wafer 10 in a rotational manner using cleaning liquid 55 with the same viscosity, the cleaning efficiency of the area farther from the rotation center 30C is higher than the cleaning efficiency of the area closer to the rotation center 30C. That is, as shown in FIG. 13, the linear velocity of the circumferential direction of the wafer 10 surface increases toward the radial outward direction, and therefore, as shown in FIG. 16, the cleaning efficiency increases linearly toward the radial outward direction.

[0129] The wet cleaning method according to the present invention artificially increases the viscosity of the cleaning liquid 55 present near the rotation center 30C in order to compensate for the difference in cleaning efficiency due to the difference in circumferential linear velocity that varies depending on the rotation radius.

[0130] By appropriately controlling the viscosity of the cleaning liquid 55, cleaning can be performed with substantially uniform cleaning efficiency even in areas with different rotation radii.

[0131] Meanwhile, the height (h) of the cleaning liquid 55 filling the gap between the surface of the wafer 10 and the cleaning surface 42, which is required to control the viscosity of the cleaning liquid 55 using an electric field, can be determined to a scale at which van der Waals force and Coulomb force can act at an equal level. The height may be 1 nm or more and 20 nm or less.

[0132] If the gap is less than 1 nm, it is difficult to fill the gap with cleaning solution 55, but the effect of inducing a change in viscosity of cleaning solution 55 by the strength of the electric field does not increase any more. If the gap is more than 20 nm, even if the strength of the electric field is controlled, the cleaning solution 55 with a height of 20 nm hardly changes in viscosity, making it difficult to control the viscosity.

[0133] Considering the microstructures stacked on the wafer 10, the distance between the wafer 10 surface and the cleaning tool 40 is preferably 2 nm to 4 nm. More preferably, the distance may be approximately 3 nm on average. Setting the height of the cleaning solution 55 at this scale can provide the volume of cleaning solution 55 required for ion migration. Furthermore, at these heights, the electric field can efficiently penetrate the depth of the solution and affect the movement and alignment of ions and solvent molecules. Furthermore, such a limited space restricts ion mobility, improves the reactivity of the solvent to the applied electric field, and minimizes energy consumption. This allows for precise control of the viscosity without reducing the solution's concentration.

[0134] The equivalent concentration of the ions contained in the cleaning solution 55 (N) is 0.1 mEq / L or more 10 mEq / L or less.

[0135] The equivalent concentration of the ion is 0.1 mEq If the electric field strength is lower than 1 / L, the viscosity of the cleaning solution 55 hardly changes even when the electric field strength is controlled, making it difficult to control the viscosity.

[0136] The equivalent concentration of the ions is 10 or more mEq If the electric field strength is higher than 1 / L, the effect of inducing a change in the viscosity of the cleaning solution 55 by the electric field strength will not increase any more, and there is a risk that the ions will be more likely to remain as foreign matter.

[0137] Preferably, the equivalent concentration of said ions is 1.0 mEq / L or more 2.0 mEq More preferably, the equivalent concentration of the ions is about 1.5 mEq / L. 1.5 mEq A concentration of 0.15g / L provides an optimal balance between ion density and solution volume, promoting improved response to an electric field while maintaining the chemical integrity of the solution. This concentration level also allows for precise viscosity control without excessive dilution or concentration, optimizing the efficiency of the viscosity control process.

[0138] In some embodiments, the cleaning solution 55 comprises a HO solution containing cations and anions. For example, the ions may be Na + , Cl - It may also include.

[0139] In some embodiments, the cleaning solution 55 is made to have equivalent cations and anions so that it is generally neutral.

[0140] Specifically, the wafer cleaning method includes the steps of: placing a cleaning tool 40 facing the surface of the wafer 10 that requires cleaning; adjusting the distance between the surface of the wafer 10 and the cleaning tool 40; supplying a cleaning solution 55 containing ions between the surface of the wafer 10 and the cleaning tool 40; applying an electric field to the cleaning solution 55 in at least a portion of the area where the cleaning solution 55 is present; and rotating the wafer 10 and the cleaning tool 40 relative to each other to clean the surface of the wafer 10.

[0141] Referring to FIG. 12, the area where the cleaning liquid 55 is present is the first area (1 st and a second area (2 nd area).

[0142] In some embodiments, the electric field may be applied to the first region such that the viscosity of the cleaning liquid 55 in the first region is greater than the viscosity of the cleaning liquid 55 in the second region, thereby increasing the viscosity of the cleaning liquid 55 in the first region and improving the cleaning efficiency of the first region.

[0143] In some embodiments, when applying an electric field to the cleaning solution, the strength of the electric field applied to the first region may be greater than the strength of the electric field applied to the second region, thereby making the viscosity of the cleaning solution 55 in the first region greater than the viscosity of the cleaning solution 55 in the second region, thereby further improving the cleaning efficiency of the first region.

[0144] In some embodiments, applying an electric field to the cleaning solution may, in another example, apply an electric field to the first region and not apply an electric field to the second region.

[0145] Preferably, the intensity distribution of the electric field applied to the region may include a first distribution that continuously decreases with increasing distance from the rotation center 30C, as shown in FIG.

[0146] Preferably, the intensity distribution of the electric field applied to the region may include a second distribution that gradually decreases with increasing distance from the center of rotation 30C, as shown in FIG.

[0147] Preferably, the intensity distribution of the electric field applied to the region may include a third distribution that gradually decreases with increasing distance from the rotation center 30C, as shown in FIG.

[0148] Preferably, the intensity distribution of the electric field applied to the region may include a fourth distribution that linearly decreases with increasing distance from the rotation center 30C, as shown in FIG.

[0149] Preferably, the intensity distribution of the electric field applied to the region may include a fifth distribution that decreases nonlinearly with increasing distance from the center of rotation 30C.

[0150] Preferably, the intensity distribution of the electric field applied to the region may include a sixth distribution that parabolically decreases with increasing distance from the center of rotation 30C.

[0151] Preferably, the intensity distribution of the electric field applied to the region may include a seventh distribution that hyperbolically decreases with increasing distance from the center of rotation 30C. According to the present invention, the intensity distribution of the electric field applied to the region may include at least one of the first to seventh distributions.

[0152] In this way, applying an electric field differentially depending on the radial position causes a difference in the EDL (electrical double layer) effect, which can induce a difference in viscosity. As a result, it is possible to clean the wafer 10 with uniform cleaning efficiency along the radial direction, as shown in Figure 17. For reference, this viscosity control principle is based on the electroosmosis principle, in which the EDL is formed by an electric field, and in principle, the electric field can be applied based on a DC power source.

[0153] According to the embodiment, the wafer cleaning apparatus is embodied in a form in which the wafer 10 rotates and the cleaning surface 42 is fixed. Furthermore, the wafer cleaning method is also embodied in a form in which the wafer rotates while the cleaning surface is fixed. However, this is merely a limited explanation for understanding, and any structure and method that allows relative rotation between the wafer 10 and the cleaning surface 42 is included in the technical spirit of the present disclosure.

[0154] Furthermore, the present invention applies the principle of uniforming the cleaning efficiency along the radial direction by inducing differences in the viscosity of the cleaning solution through differential application of electric fields, and does not aim to increase the overall viscosity of the cleaning solution. Therefore, it may be used in conjunction with other devices to lower the overall viscosity of the cleaning solution. In other words, it is possible to differentiate the viscosity of the cleaning solution in different regions while lowering the overall viscosity of the cleaning solution.

[0155] Although the present invention has been described above with reference to the illustrative drawings, the present invention is not limited to the embodiments and drawings disclosed in this specification, and various modifications may be made by those skilled in the art within the scope of the technical concept of the present invention. Furthermore, even if the effects of the configurations of the present invention are not explicitly described in the above-described embodiments of the present invention, it is natural that the effects that can be predicted by the configurations should also be recognized. [Explanation of symbols]

[0156] 10 wafers 10C Center of wafer 30 wafer support 30C Rotation Center 40 Cleaning Tools 42 Cleaning surface L length W width 50 Cleaning liquid supply device 55 Cleaning Solution 60 Drive Unit 62 rotor 64 Stator 70 Electric field application unit 71 Housing 73 Conductive Plate 80 Interval Adjustment Device

Claims

1. 1. A method for wet cleaning a wafer, comprising: a first step of positioning a cleaning tool opposite the wafer surface that requires cleaning; a second step of supplying a cleaning solution containing ions between the wafer surface and the cleaning tool; a third step of adjusting a gap between the wafer surface and the cleaning tool so that the viscosity of the cleaning liquid between the wafer surface and the cleaning tool is controlled by an electric field through an EDL (electrical double layer) effect; and a fourth step of rotating the wafer and the cleaning tool relative to each other while applying an electric field to at least a portion of the area where the cleaning liquid is present on the wafer surface, thereby cleaning the wafer surface with the cleaning liquid; the region on the wafer surface where the cleaning liquid is present includes a first region and a second region disposed farther from the center of rotation of the wafer than the first region; In the fourth step, an electric field is applied to the cleaning liquid in at least the first region of the region where the cleaning liquid is present on the wafer surface so that the viscosity of the cleaning liquid in the first region becomes higher than the viscosity of the cleaning liquid in the second region. Wafer cleaning method.

2. applying an electric field to the cleaning solution in the second region; The strength of the electric field applied to the first region is greater than the strength of the electric field applied to the second region. The wafer cleaning method according to claim 1 .

3. No electric field is applied to the second region. The wafer cleaning method according to claim 1 .

4. The intensity distribution of the electric field applied to the region includes a distribution that decreases as the distance from the rotation center increases. The wafer cleaning method according to any one of claims 1 to 3.

5. the intensity distribution of the electric field applied to the region includes a distribution that continuously decreases with increasing distance from the rotation center, The wafer cleaning method according to any one of claims 1 to 3.

6. the intensity distribution of the electric field applied to the region includes a distribution that gradually decreases as the distance from the rotation center increases. The wafer cleaning method according to any one of claims 1 to 3.

7. The intensity distribution of the electric field applied to the region includes a distribution that linearly decreases as the distance from the rotation center increases. The wafer cleaning method according to any one of claims 1 to 3.

8. The intensity distribution of the electric field applied to the region includes a distribution that decreases nonlinearly as the distance from the rotation center increases. The wafer cleaning method according to any one of claims 1 to 3.

9. The cleaning solution includes a HO solution containing cations and anions. The wafer cleaning method according to any one of claims 1 to 3.

10. The cations and anions include Na+ and Cl- ions; The wafer cleaning method according to claim 9.

11. The equivalent concentration of ions contained in the cleaning solution is 0.1 mEq / L or more and 10 mEq / L or less. The wafer cleaning method according to claim 9.

12. The equivalent concentration of the ions contained in the cleaning solution is 0.1 mEq / L or more and 10 mEq / L or less. The wafer cleaning method according to claim 10.

13. The interval is 1 nm or more and 20 nm or less. The wafer cleaning method according to any one of claims 1 to 3.

14. An apparatus for wet cleaning a wafer, comprising: a wafer support portion that holds the wafer; a cleaning tool facing the wafer support; a cleaning liquid supply device for supplying a cleaning liquid containing ions between the cleaning tool and the wafer support; a gap adjusting device for adjusting the gap between the wafer support and the cleaning tool so that the viscosity of the cleaning solution between the wafer surface and the cleaning tool is controlled by an electric field through an EDL (electrical double layer) effect, thereby setting the height of the cleaning solution between the wafer surface and the cleaning tool; a drive unit for rotating the wafer support and the cleaning tool relative to one another; an electric field applying unit that applies an electric field to the cleaning liquid supplied to the wafer surface; Including, the region on the wafer surface where the cleaning liquid is present includes a first region and a second region disposed farther from the center of rotation of the wafer than the first region; the electric field applying unit applies an electric field to the cleaning liquid in at least the first region among regions where the cleaning liquid is present on the wafer surface so that the viscosity of the cleaning liquid in the first region becomes higher than the viscosity of the cleaning liquid in the second region. Wafer cleaning equipment.

15. The electric field application unit applies an electric field based on a DC power supply. The wafer cleaning apparatus according to claim 14.

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