Wet wafer cleaning method using nanofluids and cleaning apparatus applying the same

Abstract

The present invention provides a wafer cleaning method that can uniformly clean the entire surface area of ​​a wafer, and a wafer cleaning apparatus to which such a method is applied. [Solution] The wafer cleaning method includes the steps of arranging a cleaning tool 40 so as to face the wafer surface to be cleaned, adjusting the distance between the wafer surface and the cleaning tool 40, supplying a cleaning solution 55 containing ions between the wafer surface and the cleaning tool 40, and rotating the wafer 10 and the cleaning tool 40 relative to each other while applying an electric field to at least a portion of the area where the cleaning solution 55 is present, thereby cleaning the wafer surface with the cleaning solution 55.

Description

Technical Field

[0001] This achievement is funded by the Korean government (Ministry of Science and ICT) and is a research (RS-2023-00272214) supported by the Korea Research Foundation.

[0002] This application claims the benefit of priority based on Korean Patent Application No. 10-2024-0118705 filed on September 2, 2024, and all the contents disclosed in the literature of the 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 area of a wafer with a nanofluid, and a wafer cleaning apparatus to which these methods are applied.

Background Art

[0004] Semiconductor manufacturing technology is evolving day by day towards ultra-fine processes. Therefore, currently, the development of manufacturing technologies capable of fine processes on the order of a few nanometers is underway. At the nanoscale, the movement of each fluid particle affects the fluid flow to a level that cannot be explained by the fluid continuity equation. As a result, at each stage of the semiconductor manufacturing process reaching the nanoscale, it has become difficult to design processes that could previously be predicted or modeled.

[0005] For example, semiconductor manufacturing processes such as cleaning, deposition, and etching must predict the flow of fluids such as liquids and gases. Conventionally, based on fluid mechanics and data accumulated over several decades, the above predictions and the resulting designs were possible. However, as the design level reaches the nanoscale, the previous prediction methods have become ineffective.

[0006] On the other hand, in semiconductors manufactured using ultrafine processes, ultrafine structures are built on the wafer as the process progresses. Between each process, a cleaning process is performed to remove by-products from the previous process. The particles removed in this cleaning process are present between the ultrafine structures, making cleaning difficult. For example, excessive cleaning to remove such difficult-to-clean foreign matter or particles may damage the semiconductor's patterning structure.

[0007] Furthermore, due to the characteristics of the cleaning process, which is typically performed by rotating the semiconductor wafer, areas located radially outward from the center of rotation are excessively cleaned, while areas closer to the center of rotation receive insufficient cleaning. In other words, in order to adequately clean the areas near the center of rotation, the areas located radially outward must be excessively cleaned.

[0008] For this reason, cleaning is sometimes performed by generating high-frequency vibrations in the cleaning solution without using brushes. However, this also cannot avoid cleaning deviations that occur in the radial direction. Furthermore, if the high-frequency energy is not fully absorbed by the cleaning solution and is transmitted to the semiconductor patterning structure, the patterning structure may be damaged. [Overview of the project] [Problems that the invention aims to solve]

[0009] The present invention was devised to solve the above-mentioned problems, and aims to provide a wafer cleaning method that enables uniform cleaning of the wafer over its entire surface area, regardless of its radial position, in a wet wafer cleaning process corresponding to ultrafine processes, and a wafer cleaning apparatus to which this method is applied.

[0010] The present invention aims to provide a wafer cleaning method that can minimize differences in cleaning force along the rotation radius when wet cleaning is performed using a rotary method, and a wafer cleaning apparatus to which this method is applied.

[0011] The present invention aims to provide 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 to which this method is applied.

[0012] The technical problems of the present invention are not limited to the purposes mentioned above. Other purposes and advantages of the present invention not mentioned can be understood from the following description and will be more clearly understood from the embodiments of the present invention. Furthermore, it will be readily understood that the purposes and advantages of the present invention can be achieved by the means and combinations thereof described 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 rotary cleaning.

[0014] The wet cleaning method involves applying a differentially applied electric field in the radial direction to an ionic cleaning solution supplied between the wafer surface and the cleaning tool. The electric field is based on a DC power supply.

[0015] This allows for the artificial control of the cleaning fluid viscosity in different regions, ensuring uniform cleaning even in areas where the radial distance from the center of rotation differs during rotary cleaning.

[0016] Specifically, the wafer cleaning method includes a first step of arranging cleaning tools so as to face the wafer surface that needs to be cleaned.

[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 distance 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 part of the region where the cleaning liquid exists, and relatively rotating the wafer and the cleaning tool to clean the wafer surface.

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

[0021] Preferably, an electric field can be applied to the first region so 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 intensity of the electric field applied to the first region may be even greater than the intensity of the electric field applied to the second region.

[0023] In another example, an electric field may be applied to the first region and not 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 as it gets farther from the rotation center.

[0025] Preferably, the intensity distribution of the electric field applied to the region may include a second distribution that gradually decreases as it gets farther from the rotation center.

[0026] Preferably, the intensity distribution of the electric field applied to the region may include a third distribution that decreases step by step as it gets farther from the rotation center.

[0027] Preferably, the intensity distribution of the electric field applied to the region may include a fourth distribution that decreases linearly as it gets farther from the rotation center.

[0028] Preferably, the intensity distribution of the electric field applied to the region may include a fifth distribution that decreases non-linearly as it gets farther from the rotation center.

[0029] Preferably, the intensity distribution of the electric field applied to the region may include a sixth distribution that decreases parabolic as it moves further away from the center of rotation.

[0030] Preferably, the intensity distribution of the electric field applied to the region may include a seventh distribution that decreases hyperbolically as it moves further away 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 an H2O solution containing cations and anions.

[0033] The aforementioned cleaning solution may contain cations and anions that are equivalent in nature, so that it is generally neutral.

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

[0035] The equivalent concentration of ions contained in the washing solution may be 0.1 Meg / L or more and 10 Meg / L or less.

[0036] If the equivalent concentration of the aforementioned ions is lower than 0.1 Meg / L, controlling the viscosity of the washing solution is difficult because there is almost no change in viscosity even when the strength of the electric field is controlled.

[0037] If the equivalent concentration of the aforementioned ions is higher than 10 Meg / L, the effect of inducing a change in the viscosity of the cleaning solution due to the strength of the electric field will not increase further, and there is a higher possibility that the aforementioned ions will remain as foreign matter.

[0038] Preferably, the equivalent concentration of the ion may be 1.0 Meg / L or more and 2.0 Meg / L or less. More preferably, the equivalent concentration of the ion may be around 1.5 Meg / L.

[0039] The distance between the wafer surface and the cleaning tool may be between 1 nm and 20 nm. The area corresponding to the distance may be filled with cleaning solution.

[0040] When the aforementioned interval 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 further, and it is difficult to provide a cleaning solution that allows for smooth cleaning.

[0041] When the aforementioned interval exceeds 20 nm, controlling the electric field intensity does not significantly alter the viscosity of the cleaning solution, making viscosity control difficult.

[0042] Preferably, the distance between the wafer surface and the cleaning tool may be 2 nm or more and 4 nm or less. More preferably, the distance may be around 3 nm.

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

[0044] The cleaning apparatus includes a wafer support for gripping 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 spacing adjustment device for adjusting the distance between the wafer surface and the cleaning tool.

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

[0047] The rotation center may extend in the vertical direction. The wafer support portion may extend in the horizontal direction.

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

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

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

[0051] The wafer support portion can support the wafer such that the wafer surface requiring cleaning faces vertically.

[0052] The cleaning surface of the cleaning tool may face the wafer surface in the vertical direction.

[0053] In some examples, the cleaning surface may have a length shorter than the diameter of the wafer support and longer than the radius.

[0054] In some examples, the width of the cleaning surface measured in the circumferential direction of the wafer support may be kept constant along the radial direction of the wafer support.

[0055] In some examples, the width of the cleaning surface measured in the circumferential direction of the wafer support portion may be a fan shape that gradually widens towards the radially outer side of the wafer support portion.

[0056] In some examples, the shape of the cleaning surface may be circular. The diameter of the cleaning surface may substantially correspond to the diameter of the wafer support portion or substantially to the radius of the wafer support portion.

[0057] The spacing adjustment device can move the cleaning tool in the vertical direction. The vertical direction may also be the vertical direction.

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

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

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

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

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

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

[0064] The electric field application section may include conductive plates arranged in a matrix.

[0065] The electric field application unit can apply an electric field to the space between the wafer support unit, to which the cleaning liquid is supplied, and the cleaning tool.

[0066] The electric field application unit can be incorporated into the cleaning tool.

[0067] From another perspective, the present invention provides a method for wet cleaning wafers.

[0068] The wafer cleaning method includes a first step of arranging a cleaning tool so as to face the wafer surface to be cleaned; a second step of supplying a cleaning solution 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 solution between the wafer surface and the cleaning tool is controlled by an electric field; and a fourth step of cleaning the wafer surface with the cleaning solution by rotating the wafer and the cleaning tool relative to each other while applying an electric field to at least a portion of the region where the cleaning solution is present.

[0069] In some examples, the region where the cleaning fluid is present may include a first region and a second region located further 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] Furthermore, an electric field can be applied to the cleaning solution in the second region.

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

[0073] Alternatively, an electric field does not need to be applied to the second region.

[0074] The intensity distribution of the electric field applied to the region in the fourth stage may decrease as it moves further away from the center of rotation.

[0075] In some cases, the intensity distribution of the electric field applied to the region in the fourth stage may gradually decrease as it moves further away 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 decrease continuously as it moves further away from the center of rotation.

[0077] In some cases, the intensity distribution of the electric field applied to the region in the fourth stage may gradually decrease as it moves further away 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 as it moves further away from the center of rotation.

[0079] In some examples, the intensity distribution of the electric field applied to the region in the fourth stage may decrease nonlinearly as it moves further away from the center of rotation.

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

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

[0082] In some examples, the equivalent concentration of ions contained in the washing solution may be 0.1 Meg / L or more and 10 Meg / L or less, and preferably 1.0 Meg / L or more and 2.0 Meg / L or less.

[0083] In some examples, the interval 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 perspective, the present invention provides an apparatus for wet cleaning wafers.

[0085] The wafer cleaning apparatus includes a wafer support for gripping a wafer, a cleaning tool facing the wafer support, a cleaning liquid supply device for supplying an ion-containing cleaning liquid between the cleaning tool and the wafer support, a spacing adjustment device for adjusting the distance 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 relative to each other, and an electric field application unit for applying an electric field to the cleaning liquid supplied onto the wafer.

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

[0087] The region on the wafer where the cleaning solution is present may include a first region and a second region located further from the center of rotation than the first region.

[0088] In some cases, the electric field application unit may apply an electric field to the first region but not to the second region.

[0089] In some examples, the electric field application unit can apply electric fields of different intensities to the first region and the second region.

[0090] In some cases, the electric field application unit can apply an electric field to the cleaning liquid such that the intensity of the electric field decreases as it moves further away from the center of rotation. [Effects of the Invention]

[0091] According to the present invention, in a rotary wet wafer cleaning process corresponding to ultrafine processes, by applying an electric field to the ion-containing cleaning solution in a differential manner to control the viscosity of the cleaning solution in different regions, uniform cleaning can be achieved throughout the entire cleaning area of ​​the wafer.

[0092] According to the present invention, the intensity of the electric field to be applied to each region can be predicted and applied with relatively accurate accuracy 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 relative to the center of rotation for cleaning.

[0093] The effects described above, as well as the specific effects of the present invention, will be explained and described below in the following descriptions of embodiments for carrying out the invention. [Brief explanation of the drawing]

[0094] [Figure 1] This is a perspective view of a wafer cleaning apparatus according to an embodiment of the present invention. [Figure 2] Figure 1 is a front cross-sectional view of the wafer cleaning apparatus. [Figure 3] Figure 1 is a perspective view showing the cleaning tools and electric field application section of the wafer cleaning apparatus. [Figure 4] Figure 1 is a perspective view showing the cleaning fluid supply device of the wafer cleaning apparatus. [Figure 5] Figure 1 is a perspective view showing the wafer support section and drive mechanism of the wafer cleaning apparatus. [Figure 6] Figure 5 is a perspective view showing a wafer concentrically placed on the wafer support. [Figure 7] Figure 5 is a perspective view showing multiple wafers eccentrically placed on the wafer support. [Figure 8] Figure 5 is a perspective view showing the cleaning tool of the first embodiment placed on the wafer support portion. [Figure 9] Figure 5 is a perspective view showing the cleaning tool of the second embodiment placed on the wafer support portion. [Figure 10] Figure 5 is a perspective view showing the cleaning tool of the third embodiment placed on the wafer support. [Figure 11] Figure 5 is a perspective view showing the cleaning tool of the fourth embodiment placed on the wafer support. [Figure 12] This is an enlarged view of box 12 in Figure 2. [Figure 13] This graph shows the linear velocity on the wafer surface as it is measured from the center of rotation to a specific point on the wafer surface. [Figure 14] This graph shows the first embodiment of the distribution of applied electric field intensity with respect to the distance from the rotation center to a specific region of the cleaning solution supplied onto the wafer surface. [Figure 15] This graph shows a second embodiment of the electric field intensity distribution with respect to the distance from the rotation center to a specific region of the cleaning solution supplied onto the wafer surface. [Figure 16] This graph shows a third embodiment of the electric field intensity distribution with respect to the distance from the rotation center to a specific region of the cleaning solution supplied onto the wafer surface. [Figure 17] This graph shows a fourth embodiment of the electric field intensity distribution with respect to the distance from the rotation center to a specific region of the cleaning solution supplied onto the wafer surface. [Modes for carrying out the invention]

[0095] Preferred embodiments of the present invention will be described in detail below with reference to the accompanying drawings.

[0096] The present invention is not limited to the embodiments disclosed below, and can be modified in various ways and embodied in various forms that differ from one another. However, these embodiments are provided to complete the disclosure of the present invention and to fully inform those in the ordinary skill of the scope of the invention. Therefore, it should be understood that the present invention is not limited to the embodiments disclosed below, and includes not only substitution or addition of the configurations of one embodiment to the configurations of another embodiment, but also any modifications, equivalents or substitutes that fall within the technical spirit and scope of the present invention.

[0097] The accompanying drawings are provided to facilitate understanding of the embodiments disclosed herein and should not be understood as limiting the technical concept disclosed herein, but rather as including any modifications, equivalents, or substitutions that fall within the concept and technical scope of the present invention. While the size and thickness of components in the drawings may be exaggerated or reduced for ease of understanding, this should not be interpreted as restricting the scope of protection of the present invention.

[0098] The terms used herein are used solely to describe specific examples or embodiments and are not intended to limit the invention. Furthermore, singular expressions include plural expressions unless otherwise clearly indicated in the context. Terms such as "includes" or "consists of" in the specification are intended to indicate the existence of features, figures, stages, operations, components, parts, or combinations thereof described herein. In other words, terms such as "includes" or "consists of" in the specification should not be understood as preemptively excluding the existence or possibility of adding one or more other features, figures, stages, operations, components, parts, or combinations thereof.

[0099] Terms including ordinal numbers, such as "First," "Second," etc., are used to describe various components, but the components themselves are not limited by these terms. These terms are used solely to distinguish one component from others. Therefore, unless otherwise stated, the first component may also be the second component.

[0100] When it is mentioned that one component is "linked" or "connected" to another component, it must be understood that it is directly linked to, or may be connected to, the other component, and that the other component may exist within it. On the other hand, when it is mentioned that one component is "directly linked" or "directly connected" to another component, it must be understood that the other component does not exist within it.

[0101] When one component is described as being "above" or "below" another component, it must be understood that this means not only is it positioned directly above the other component, but that the other component may exist within it.

[0102] Unless otherwise defined, technical and scientific terms are used herein, and all terms used herein have the same meaning as those generally understood by a person of ordinary skill in the art to which this invention pertains. Terms similar to those defined in commonly used dictionaries should be interpreted as having the meaning consistent with their meaning in the context of the relevant art, and not as ideal or overly formal unless explicitly defined herein.

[0103] The following describes a wafer cleaning apparatus according to an embodiment of the present invention and a wafer cleaning method implemented using the wafer cleaning apparatus.

[0104] Referring to Figures 1 to 12, the present invention provides a wafer cleaning apparatus to which a wet cleaning method for the wafer 10 is applied. The wafer cleaning apparatus includes a wafer support section 30 for gripping the wafer 10, a cleaning tool 40 facing the wafer support section 30, a cleaning liquid supply device 50 for supplying a cleaning liquid 55 between the cleaning tool 40 and the wafer support section 30, a drive device 60 for relatively rotating the wafer support section 30 and the cleaning tool 40, and an electric field application section 70 for applying an electric field to the cleaning liquid 55.

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

[0106] Referring to Figure 5, the wafer support portion 30 is rotatably mounted with respect to a predetermined rotation center 30C. The rotation center 30C extends in the vertical direction, and the wafer support portion 30 extends in the horizontal direction. The wafer support portion 30 is rotationally driven by the drive device 60.

[0107] The drive unit 60 includes a rotor 62 that extends axially and is connected to the wafer support unit 30 at its rotation center 30C, and a stator 64 that rotates the rotor 62. The axial direction of the rotor 62 may be aligned with the vertical direction. For example, the drive unit 60 can rotate the wafer support unit 30 at a speed of 20 to 50 rpm. However, the rotation speed of the wafer support unit 30 is not limited to this.

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

[0109] As shown in Figure 6, in a wafer support 30 supporting one wafer 10, the wafer center 10C of the wafer 10 may be aligned with the rotation center 30C of the wafer support 30. Next, as shown in Figure 7, in a wafer support 30 supporting two or more wafers 10, the wafer centers 10C of the wafers 10 may be eccentrically positioned with respect to the rotation center 30C of the wafer support 30 and arranged at equal intervals along the circumferential direction of the wafer support 30. The embodiment illustrates a case in which three wafers 10 are supported by the wafer support 30.

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

[0111] Referring to Figures 8 and 9, in some embodiments, the cleaning surface 42 has a length (L) that is shorter than the diameter of the wafer support portion 30 and longer than its radius.

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

[0113] Referring to Figure 9, in some embodiments, the width (W) of the cleaning surface 42 measured in the circumferential direction of the wafer support portion 30 may be a fan shape that gradually widens towards the radially outer side of the wafer support portion 30.

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

[0115] In some embodiments, the cleaning surface 42 of the cleaning tool 40 includes 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 installed on a vibrating plate.

[0118] Referring to Figure 2, the spacing adjustment device 80 can move the cleaning tool 40 in the vertical direction, more specifically, in the vertical direction. The spacing adjustment device 80 can raise and lower the cleaning tool 40 to adjust the distance between the cleaning surface 42 and the upper surface of the wafer 10 held on the wafer support 30.

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

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

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

[0122] The embodiment illustrates that the electric field application section 70 is composed of a matrix of separate conductive plates, but this is just one example, and various configurations suitable for generating an electric field can be applied to the electric field application section. For example, the cleaning surface 42 itself can be composed of conductive plates divided into multiple regions, and different voltages can be applied to each region. Furthermore, there can be various configurations for the division.

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

[0124] The electric field intensity can be individually controlled for each area occupied by the conductive plates 73, which are arranged facing each other vertically, via 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 application unit 70 embodied in the embodiment, as long as the structure can apply a differential electric field along the radial direction in the region corresponding to the cleaning surface 42. For example, the electric field application unit 70 can be configured on the upper part of the cleaning surface 42, having multiple application regions capable of applying electric fields of different intensities, with the wafer support unit 30 grounded. Various other known electric field application structures can also be applied.

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

[0127] The wet cleaning method involves applying an electric field of varying intensity along the radial direction (r) with respect to the rotation center 30C to the ion cleaning solution 55 supplied between the wafer surface 10 and the cleaning tool 40. This allows for the artificial control of the viscosity of the cleaning solution 55 in different regions along the radial direction, ensuring that cleaning is performed uniformly during rotational cleaning, even in regions with different radial distances from the rotation center 30C.

[0128] The cleaning efficiency is proportional to the flow velocity of the cleaning solution 55 and also proportional to the viscosity of the cleaning solution 55. That is, the higher the flow velocity of the cleaning solution 55, the higher the cleaning power, and the higher the viscosity of the cleaning solution 55, the higher the cleaning power. Therefore, as shown in Figures 13 and 16, when cleaning the wafer 10 using a rotary method with cleaning solution 55 of the same viscosity, the cleaning efficiency of the region farther from the rotation center 30C is even higher than the cleaning efficiency of the region closer to the rotation center 30C. That is, as shown in Figure 13, the linear velocity in the circumferential direction of the wafer 10 surface increases as you move outward in the radial direction, so as shown in Figure 16, the cleaning efficiency increases linearly as you move outward in the radial direction.

[0129] The wet cleaning method according to the present invention artificially increases the viscosity of the cleaning solution 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 which varies depending on the radius of rotation.

[0130] By appropriately controlling the viscosity of the cleaning solution 55, cleaning can be performed with substantially uniform cleaning efficiency even in regions where the turning radii differ from one another.

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

[0132] When the aforementioned interval is less than 1 nm, it is difficult to fill the interval with the cleaning solution 55, while the effect of inducing a change in the viscosity of the cleaning solution 55 by the strength of the electric field does not increase further. When the aforementioned interval exceeds 20 nm, even if the strength of the electric field is controlled, the cleaning solution 55 at a height of 20 nm shows almost no change in viscosity, making it difficult to control the viscosity.

[0133] Considering the microstructure stacked on the wafer 10, preferably the distance between the wafer 10 surface and the cleaning tool 40 may be 2 nm or more and 4 nm or less. More preferably, the distance may be around 3 nm on average. When the height of the cleaning solution 55 is set to this scale, it is possible to provide the amount of cleaning solution 55 required for ion transfer. Also, at these heights, the electric field can efficiently pass through the depth of the solution and influence the movement and arrangement 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 viscosity without reducing the concentration of the solution.

[0134] The equivalent concentration of ions contained in the washing solution 55 may be 0.1 Meg / L or more and 10 Meg / L or less.

[0135] If the equivalent concentration of the aforementioned ions is lower than 0.1 Meg / L, controlling the viscosity of the washing solution 55 is difficult because there is almost no change in viscosity even when the electric field strength is controlled.

[0136] If the equivalent concentration of the ions is higher than 10 Meg / L, the effect of inducing a change in the viscosity of the cleaning solution 55 by the strength of the electric field will not increase further, and there is a higher possibility that the ions will remain as foreign matter.

[0137] Preferably, the equivalent concentration of the ions may be between 1.0 Meg / L and 2.0 Meg / L. More preferably, the equivalent concentration of the ions may be around 1.5 Meg / L. A concentration of 1.5 Meg / L provides an optimal balance between ion density and solution volume, promoting improved responsiveness to electric fields while maintaining the chemical integrity of the solution. Furthermore, this concentration level allows for precise viscosity adjustment without excessive dilution or concentration, optimizing the efficiency of the viscosity control process.

[0138] In some embodiments, the washing solution 55 includes an H2O solution containing a cation and anion. For example, the ion is Na + Cl - It may also include.

[0139] In some embodiments, the cleaning solution 55 is made to be neutral overall, with cations and anions being equivalent.

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

[0141] Referring to Figure 12, the region where the cleaning solution 55 is present is the first region (1 st area) and a second region (2) located further away from the rotation center 30C than the first region. nd (area) and includes

[0142] In some embodiments, when applying an electric field to the cleaning solution, the electric field can be applied to the first region such that the viscosity of the cleaning solution 55 in the first region is greater than the viscosity of the cleaning solution 55 in the second region. This increases the viscosity of the cleaning solution 55 in the first region, thereby improving the cleaning efficiency of the first region.

[0143] In some embodiments, when applying an electric field to the cleaning solution, the intensity of the electric field applied to the first region may be even greater than the intensity of the electric field applied to the second region. This makes it possible to further increase the viscosity of the cleaning solution 55 in the first region compared to that of the cleaning solution 55 in the second region, thereby further improving the cleaning efficiency of the first region.

[0144] In some embodiments, when applying an electric field to the cleaning solution, in other embodiments, an electric field may be applied to the first region but not to the second region.

[0145] Preferably, the intensity distribution of the electric field applied to the region may include a first distribution that decreases continuously as it moves further away from the rotation center 30C, as shown in Figure 14.

[0146] Preferably, the intensity distribution of the electric field applied to the region may include a second distribution that gradually decreases as it moves further away from the rotation center 30C, as shown in Figure 14.

[0147] Preferably, the intensity distribution of the electric field applied to the region may include a third distribution that gradually decreases as it moves further away from the rotation center 30C, as shown in Figure 15.

[0148] Preferably, the intensity distribution of the electric field applied to the region may include a fourth distribution that decreases linearly as it moves further away from the rotation center 30C, as shown in Figure 14.

[0149] Preferably, the intensity distribution of the electric field applied to the region may include a fifth distribution that decreases nonlinearly as it moves further away from the rotation center 30C.

[0150] Preferably, the intensity distribution of the electric field applied to the region may include a sixth distribution that decreases parabolic as it moves further away from the rotation center 30C.

[0151] Preferably, the intensity distribution of the electric field applied to the region may include a seventh distribution that decreases hyperbolically as it moves further away from the rotation center 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] Thus, by applying an electric field unequally depending on the radial position, differences in the EDL (electrical double layer) effect can be generated, inducing differences in viscosity. As a result, as shown in Figure 17, it is possible to clean the wafer 10 with uniform cleaning efficiency along the radial direction. For reference, these viscosity control principles are based on the electroosmosis principle, which forms the EDL with an electric field, and in principle, the electric field can be applied based on a DC power supply.

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

[0154] Furthermore, this invention applies the principle of inducing differences in the viscosity of the cleaning solution by applying an equal electric field to make the cleaning efficiency uniform along the radial direction, and does not aim to increase the overall viscosity of the cleaning solution. Therefore, it may be applied in conjunction with other devices to lower the overall viscosity of the cleaning solution. In other words, it is possible to lower the overall viscosity of the cleaning solution and then create differences in the viscosity of the cleaning solution in different regions.

[0155] As described above, the present invention has been explained with reference to the illustrative drawings, but the present invention is not limited to the embodiments and drawings disclosed herein, and various modifications can be made by a person of ordinary skill within the scope of the technical concept of the present invention. Furthermore, even if the effects of the configuration of the present invention are not explicitly described in the embodiments described above, it is natural that the effects that can be predicted by the configuration should also be recognized. [Explanation of symbols]

[0156] 10 wafers 10C wafer center 30 Wafer support section 30C Rotation Center 40 Cleaning Tools 42 Cleaning surface L Length W width 50 Cleaning solution supply device 55 Cleaning solution 60 Drive unit 62 rotors 64 stata 70 Electric field application section 71 Housing 73 Conductive Plate 80 Interval Adjustment Device

Claims

1. A method for wet cleaning wafers, The first step involves positioning the cleaning tools so as to face the wafer surface that requires cleaning, A second step involves supplying a cleaning solution containing ions between the wafer surface and the cleaning tool, A third step involves adjusting the distance between the wafer surface and the cleaning tool so that the viscosity of the cleaning solution between the wafer surface and the cleaning tool is controlled by the electric field. A fourth step involves applying an electric field to at least a portion of the region where the cleaning solution is present, and rotating the wafer and the cleaning tool relative to each other to clean the wafer surface with the cleaning solution. including, Wafer cleaning method.

2. The region where the cleaning fluid is present includes a first region and a second region located further from the center of rotation than the first region. An electric field is applied to the cleaning solution in the first region. The wafer cleaning method according to claim 1.

3. By applying an electric field to the cleaning solution in the second region, The intensity of the electric field applied to the first region is even greater than the intensity of the electric field applied to the second region. The wafer cleaning method according to claim 2.

4. No electric field is applied to the second region. The wafer cleaning method according to claim 2.

5. The intensity distribution of the electric field applied to the region includes a distribution that decreases as it moves further away from the center of rotation. A wafer cleaning method according to any one of claims 1 to 4.

6. The intensity distribution of the electric field applied to the region includes a distribution that decreases continuously as it moves further away from the center of rotation. A wafer cleaning method according to any one of claims 1 to 4.

7. The intensity distribution of the electric field applied to the region includes a distribution that gradually decreases as it moves further away from the center of rotation. A wafer cleaning method according to any one of claims 1 to 4.

8. The intensity distribution of the electric field applied to the region includes a distribution that decreases linearly as it moves further away from the center of rotation. A wafer cleaning method according to any one of claims 1 to 4.

9. The intensity distribution of the electric field applied to the region includes a distribution that decreases nonlinearly as it moves further away from the center of rotation. A wafer cleaning method according to any one of claims 1 to 4.

10. The cleaning solution contains H, which contains cations and anions. ２ Including solution O, A wafer cleaning method according to any one of claims 1 to 4.

11. The aforementioned cation and anion are Na ＋ , Cl － Contains ions, The wafer cleaning method according to claim 10.

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

13. The aforementioned interval is between 1 nm and 20 nm. A wafer cleaning method according to any one of claims 1 to 4.

14. An apparatus for wet cleaning wafers, A wafer support section that grips the wafer, A cleaning tool facing the wafer support portion, A cleaning solution supply device that supplies a cleaning solution containing ions between the cleaning tool and the wafer support portion, A spacing adjustment device that adjusts the distance 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 that rotates the wafer support and the cleaning tool relative to each other, An electric field application unit that applies an electric field to the cleaning solution supplied onto the wafer, including, 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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