Method for cleaning semiconductor wafer, method for manufacturing semiconductor wafer, and semiconductor wafer

Abstract

The invention provides a method for cleaning a semiconductor wafer capable of suppressing the generation of spoon-shaped defects. A method for cleaning a semiconductor wafer according to the present invention is a method for cleaning a semiconductor wafer having a rotary cleaning step for supplying a cleaning liquid to at least the front surface of the semiconductor wafer while rotating the semiconductor wafer, the rotary cleaning step includes at least one group of combinations of an ozone water cleaning step in which the cleaning liquid is ozone water and a hydrofluoric acid cleaning step in which the cleaning liquid is hydrofluoric acid. The method includes a pretreatment step of supplying only one conductive liquid selected from the group consisting of hydrofluoric acid, carbonated water, and carbonated ozone water to the back surface of the semiconductor wafer while rotating the semiconductor wafer.

Description

Technical Field

[0001] The present invention relates to a semiconductor wafer cleaning method, a semiconductor wafer manufacturing method and a semiconductor wafer, and in particular to a semiconductor wafer cleaning method and a semiconductor wafer manufacturing method comprising a process of performing single-wafer rotation cleaning on the surface of the semiconductor wafer. Background Art

[0002] In the manufacturing process of semiconductor wafers such as silicon wafers, there is a cleaning process (hereinafter also referred to as "single wafer spin cleaning") in which a cleaning liquid is supplied to the surface (front and back) of the wafer while the wafer is rotated to remove particles attached to the surface.

[0003] A typical example of a single-wafer cleaning method for cleaning semiconductor wafers one by one is the SCROD (Single-Wafer Spin Cleaning with Repetitive Use of Ozonized Water and Dilute HF) method, which repeats spin cleaning with ozone water and spin cleaning with hydrofluoric acid, as described in Patent Document 1. In this method, an oxide film is formed on the wafer surface by spin cleaning with ozone water, and then particles on the wafer surface are removed along with the oxide film by spin cleaning with hydrofluoric acid.

[0004] Prior art literature

[0005] Patent Literature

[0006] Patent Document 1: Japanese Patent Application Laid-Open No. 2015-220284 Summary of the Invention

[0007] Technical problem to be solved by the invention

[0008] However, during single-wafer cleaning, so-called spoon-shaped defects, which are concave near the center and convex around the periphery, are frequently observed. The height of the protrusion of a spoon-shaped defect is approximately 5 to 20 nm, while the depth of the concave portion is approximately 5 to 20 nm. The number of LPDs (light point defects) is exacerbated by these spoon-shaped defects.

[0009] In view of the above problems, an object of the present invention is to provide a method for cleaning a semiconductor wafer and a method for manufacturing a semiconductor wafer that can suppress the occurrence of spoon-shaped defects during cleaning in a semiconductor wafer manufacturing stage before device formation.

[0010] Solutions for solving technical problems

[0011] The present inventors conducted extensive research to address the above-mentioned issues and have discovered that spoon-shaped defects are caused by electrostatic damage between the semiconductor wafer and the cleaning liquid. Furthermore, they have discovered that, during the semiconductor wafer cleaning process, by supplying a conductive liquid to the back side of the semiconductor wafer before the front side spin cleaning process, static electricity on the semiconductor wafer can be removed via the conductive liquid. The conductive liquid is a liquid that ensures conductivity, specifically, one selected from the group consisting of hydrofluoric acid, carbonated water, and carbonated ozone water. By removing static electricity from the semiconductor wafer as described above, the occurrence of spoon-shaped defects on the front side of the semiconductor wafer can be suppressed.

[0012] Furthermore, while electrostatic damage can also occur on semiconductor wafers after device formation, this is primarily caused by the spraying of charged cleaning water, made of pure water, onto the semiconductor wafer, a different problem from the present invention. Furthermore, as in the present invention, semiconductor wafer cleaning during semiconductor wafer manufacturing uses hydrofluoric acid, ozone water, and the like, making the cleaning process completely different from cleaning semiconductor wafers after device formation in terms of the chemicals used and their intended purpose.

[0013] That is, the gist of the present invention is as follows.

[0014] [1] A method for cleaning a semiconductor wafer, comprising a spin cleaning step of supplying a cleaning liquid to at least the front surface of the semiconductor wafer while rotating the semiconductor wafer, wherein:

[0015] The spin cleaning step includes one or more combinations of an ozone water cleaning step in which the cleaning liquid is ozone water and a subsequent hydrofluoric acid cleaning step in which the cleaning liquid is hydrofluoric acid.

[0016] Prior to the spin cleaning step, a pretreatment step is performed in which a conductive liquid selected from the group consisting of hydrofluoric acid, carbonated water, and carbonated ozone water is supplied only to the back surface of the semiconductor wafer while the semiconductor wafer is rotated.

[0017] [2] The semiconductor wafer cleaning method according to [1], wherein:

[0018] The conductive liquid is hydrofluoric acid.

[0019] [3] The semiconductor wafer cleaning method according to [1], wherein:

[0020] The conductive liquid is carbonated water.

[0021] [4] The semiconductor wafer cleaning method according to [1], wherein:

[0022] The conductive liquid is carbonated ozone water.

[0023] [5] The method for cleaning a semiconductor wafer according to any one of [1] to [4], wherein:

[0024] In the pretreatment step, the rotation speed of the semiconductor wafer is greater than or equal to 10 rpm and less than or equal to 100 rpm.

[0025] [6] The semiconductor wafer cleaning method according to [5], wherein:

[0026] The spin cleaning step includes a first period in which the rotation speed of the semiconductor wafer is the same as the rotation speed of the semiconductor wafer in the pretreatment step, and a second period thereafter in which the rotation speed of the semiconductor wafer is greater than 100 rpm and less than or equal to 1000 rpm.

[0027] [7] The method for cleaning a semiconductor wafer according to any one of [1] to [6], wherein:

[0028] In the pretreatment step, the flow rate of the conductive liquid is 0.3 L / min or more and 1.5 L / min or less.

[0029] [8] The method for cleaning a semiconductor wafer according to any one of [1] to [7], wherein:

[0030] In the pretreatment step, the conductive liquid is supplied for a time period of 1.0 second to 5.0 seconds.

[0031] [9] The method for cleaning a semiconductor wafer according to any one of [1] to [8], wherein:

[0032] The conductive liquid is discharged from a nozzle via a piping line and supplied to the back surface of the semiconductor wafer. The piping line and the nozzle are made of non-metal.

[0033]

[10] The method for cleaning a semiconductor wafer according to any one of [1] to [9], wherein:

[0034] The semiconductor wafer is a silicon wafer.

[0035]

[11] A method for manufacturing a semiconductor wafer, comprising the semiconductor wafer cleaning method described in any one of [1] to

[10] .

[0036]

[12] A semiconductor wafer before device formation, characterized in that:

[0037] The number of defects generated on the front surface of the semiconductor wafer including a convex portion having a height of 5 nm to 20 nm inclusive and a concave portion having a depth of 5 nm to 20 nm inclusive adjacent to the convex portion is zero.

[0038] Effects of the Invention

[0039] According to the present invention, a method for cleaning a semiconductor wafer and a method for manufacturing a semiconductor wafer that can suppress the occurrence of spoon-shaped defects can be provided. BRIEF DESCRIPTION OF THE DRAWINGS

[0040] Figure 1 (a) SEM image and (b) AFM observation results of a spoon-shaped defect.

[0041] Figure 2 This is a flowchart of a semiconductor wafer cleaning method according to one embodiment of the present invention.

[0042] Figure 3 These are diagrams showing (a) the mechanism of electrostatic damage in a conventional cleaning method and (b) the mechanism of static elimination in the cleaning method according to the present invention.

[0043] Figure 4 This is a cross-sectional view showing the arrangement of a semiconductor wafer and a cleaning nozzle in a semiconductor wafer cleaning method according to an embodiment of the present invention.

[0044] Figure 5 These are typical SEM images of (a) a spoon-shaped defect, (b) a particle, and (c) a SF defect in an example of the present invention.

[0045] Figure 6 (a) A graph showing statistical results of the number of LPDs and (b) A graph showing the average number of defect types of LPDs according to an embodiment of the present invention. DETAILED DESCRIPTION

[0046] Hereinafter, an embodiment of the semiconductor wafer cleaning method according to the present invention will be described. Note that the embodiment described below is an example of a specific embodiment of the present invention, and the configuration of the present invention is not limited to this specific example.

[0047] In this invention, the "front side" of a semiconductor wafer refers to the surface used for manufacturing semiconductor devices, attaching heterogeneous substrates, etc., while the "back side" of a semiconductor wafer refers to the flat surface opposite the front side. An identifier (laser mark) containing product information is engraved on the front or back side of the semiconductor wafer. Thus, the front and back sides of the semiconductor wafer are clearly distinguished.

[0048] In the present invention, a "spoon-shaped defect" refers to a defect having a protrusion with a height of about 5 to 20 nm and a recess with a depth of about 5 to 20 nm. Figure 1 (a) SEM observation results and (b) AFM observation results of a spoon-shaped defect are shown in FIG. The spoon-shaped defect has a shape with a depression near the center and a bulge around the periphery.

[0049] [Semiconductor wafer cleaning method]

[0050] The semiconductor wafer cleaning method according to the present invention includes a spin cleaning step in which a cleaning liquid is supplied to at least the front surface of the semiconductor wafer while the semiconductor wafer is rotated. Furthermore, the spin cleaning step includes at least one combination of an ozone water cleaning step in which the cleaning liquid is ozone water and a subsequent hydrofluoric acid cleaning step in which the cleaning liquid is hydrofluoric acid. Furthermore, the semiconductor wafer cleaning method according to the present invention is characterized in that, prior to the spin cleaning step, a pretreatment step is included in which a conductive liquid selected from the group consisting of hydrofluoric acid, carbonated water, and carbonated ozone water is supplied only to the back surface of the semiconductor wafer while the semiconductor wafer is rotated.

[0051] Figure 2 FIG. 1 is a flow chart of a method for cleaning a semiconductor wafer according to an embodiment of the present invention. Figure 2 In the process, an ozone water cleaning process, a hydrofluoric acid cleaning process, and a pure water cleaning process are sequentially performed multiple times as a spin cleaning process. Before the spin cleaning process, a pretreatment process of cleaning the back side of the semiconductor wafer with a conductive liquid is performed. The conductive liquid is set to be any one selected from the group consisting of hydrofluoric acid, carbonated water, and carbonated ozone water. In this way, the spin cleaning process includes not only an ozone water cleaning process and a hydrofluoric acid cleaning process, but also a pure water cleaning process in which the cleaning water is pure water. The pure water cleaning process in the spin cleaning process can be performed after any process, preferably after the hydrofluoric acid cleaning process. That is, the pure water cleaning process can be performed after the hydrofluoric acid cleaning process, and the ozone water cleaning process can be performed thereafter, or the ozone water cleaning process can be performed after the hydrofluoric acid cleaning process. And, as Figure 2 As shown, after the ozone water cleaning step, the hydrofluoric acid cleaning step, and the pure water cleaning step are performed multiple times in sequence, it is preferred to perform the ozone water cleaning step to end the spin cleaning step. In addition, when the spin cleaning step ends, it can also be performed after the pure water cleaning step.

[0052] In the spin cleaning process, an oxide film is formed on the surface of the semiconductor wafer by the ozone water cleaning process, and particles on the surface of the semiconductor wafer are removed together with the oxide film in the hydrofluoric acid cleaning process performed after the ozone water cleaning process. The combination of the ozone water cleaning process and the hydrofluoric acid cleaning process is considered as one group, and the spin cleaning process is set to be performed in one or more groups. The combination of the ozone water cleaning process and the hydrofluoric acid cleaning process in the spin cleaning process is preferably set to three or more groups, and more preferably to five or more groups. On the other hand, the above combination in the spin cleaning process is preferably set to seven or fewer groups.

[0053] In the ozone water cleaning step within the spin cleaning process, the ozone concentration is not particularly limited as long as an oxide film can be formed on the semiconductor wafer surface, but can be set to 15 to 30 mass ppm. Furthermore, the flow rate of the ozone water is not particularly limited as long as an oxide film can be formed on the semiconductor wafer surface, but can be set to 0.5 to 1.5 L / minute. Furthermore, the treatment time per ozone water cleaning step is not particularly limited as long as an oxide film can be formed on the semiconductor wafer surface, but can be set to 10 to 45 seconds.

[0054] In the hydrofluoric acid cleaning step in the spin cleaning process, the concentration of hydrofluoric acid can be appropriately set according to the degree of contamination of the wafer, without particular limitation, but can be set to 0.50 to 3.00 mass%. In addition, the flow rate of hydrofluoric acid can be appropriately set according to the degree of contamination of the wafer, without particular limitation, but can be set to 0.5 to 1.5 L / minute. In addition, the processing time of each hydrofluoric acid cleaning step can also be appropriately set according to the degree of contamination of the wafer, without particular limitation, but can be set to 3 to 20 seconds.

[0055] After the spin cleaning step is completed, it is preferred that the semiconductor wafer be continuously rotated without supplying the cleaning liquid to remove the cleaning liquid from the semiconductor wafer surface and dry the semiconductor wafer surface. The rotation speed of the semiconductor wafer during spin drying is not particularly limited, but can be set to 1000 to 1500 rpm.

[0056] In the present invention, a pretreatment step is performed before the spin cleaning step, in which a conductive liquid selected from the group consisting of hydrofluoric acid, carbonated water, and carbonated ozone water is supplied only to the backside of the semiconductor wafer while the semiconductor wafer is rotated. Performing this pretreatment step before the spin cleaning step eliminates static electricity from the semiconductor wafer and suppresses the occurrence of spoon-shaped defects.

[0057] Figure 3 The following shows (a) the mechanism of electrostatic damage in conventional cleaning methods and (b) the method of removing static electricity in the cleaning method of the present invention. During the manufacturing stage, semiconductor wafers are charged due to transportation, etc. Figure 3As shown in (a), in the conventional cleaning method, since the cleaning liquid is supplied to the front surface before the back surface of the semiconductor wafer, electrostatic damage occurs when the semiconductor wafer 100 contacts the cleaning liquid 20 supplied from the front cleaning nozzle 10, forming a spoon-shaped defect on the front surface. Figure 3 (b) Specifically, in the present invention, since a pretreatment step is performed before the spin cleaning step, the conductive liquid 40 supplied from the back cleaning nozzle 30 first contacts the back surface of the semiconductor wafer 100, thereby suppressing the occurrence of spoon-shaped defects on the front surface. The mechanism for preventing spoon-shaped defects on the front surface is believed to be that the conductive liquid 40 supplied to the back surface forms an arc, thereby eliminating static electricity from the semiconductor wafer 100, or that static electricity damage occurs when the conductive liquid 40 is supplied to the back surface, causing discharge of the semiconductor wafer 100. Furthermore, the back surface of the semiconductor wafer 100 does not require the same smoothness as the front surface, and even if there are irregularities caused by spoon-shaped defects, they do not pose a practical problem.

[0058] The conductive liquid supplied during the pretreatment step is selected from the group consisting of hydrofluoric acid, carbonated water, and carbonated ozone water. Furthermore, "carbonated ozone water" in the present invention refers to ozone water containing carbonic acid. When the conductive liquid is hydrofluoric acid, the concentration of the hydrofluoric acid is preferably 0.5 to 3.0% by mass. Similarly, when the conductive liquid is carbonated water, the concentration of the carbonic acid is preferably 5 to 20 ppm by mass. Similarly, when the conductive liquid is carbonated ozone water, the concentration of the carbonic acid is preferably 5 to 20 ppm by mass, and the concentration of the ozone is preferably 15 to 30 ppm by mass.

[0059] In the pretreatment process, if the discharge flow rate of the conductive liquid is 0.3 L / min or more, the semiconductor wafer can be properly de-electrified. Therefore, the discharge flow rate of the conductive liquid is preferably 0.3 L / min or more, and more preferably 0.8 L / min or more. On the other hand, if the discharge flow rate of the conductive liquid is 1.5 L / min or less, the risk of winding back, the risk of splashing, etc. can be properly suppressed. In addition, the piping for the conductive liquid mostly uses φ4 mm piping, and it may be difficult to set the discharge flow rate to more than 1.5 L / min due to the device structure. Therefore, the discharge flow rate of the conductive liquid is preferably 1.5 L / min or less.

[0060] During the pretreatment process, if the conductive liquid is supplied for a time of 1.0 seconds or longer, the semiconductor wafer can be properly de-electrified. Therefore, the conductive liquid supply time is preferably 1.0 seconds or longer. On the other hand, if the conductive liquid supply time is 5.0 seconds or shorter, the liquid can be prevented from completely distributing to the outer periphery of the back surface, and LPD degradation caused by wraparound to the front surface can be appropriately suppressed. Therefore, the conductive liquid supply time is preferably 5.0 seconds or shorter, and more preferably 3.0 seconds or shorter.

[0061] If the rotation speed of the semiconductor wafer during the pretreatment process is 10 rpm or higher, the conductive liquid can be appropriately supplied to the back side of the semiconductor wafer. Therefore, the rotation speed of the semiconductor wafer during the pretreatment process is preferably 10 rpm or higher, and more preferably 30 rpm or higher. On the other hand, by setting the rotation speed of the semiconductor wafer during the pretreatment process to a lower value of 100 rpm or lower, the conductive liquid can be appropriately prevented from flowing back to the front side of the semiconductor wafer. Therefore, the rotation speed of the semiconductor wafer during the pretreatment process is preferably 100 rpm or lower, and more preferably 50 rpm or lower.

[0062] Figure 4 A cross-sectional view showing the arrangement of a semiconductor wafer and a cleaning nozzle in a method for cleaning a semiconductor wafer according to an embodiment of the present invention. On the front side of the semiconductor wafer 100, a front cleaning nozzle (for hydrofluoric acid) 12 supplies hydrofluoric acid 22, and a front cleaning nozzle (for ozone water) 14 supplies ozone water 24. On the back side of the semiconductor wafer 100, a back side cleaning nozzle (for hydrofluoric acid) 32 supplies hydrofluoric acid 42, and a back side cleaning nozzle (for ozone water) 34 supplies ozone water 44. Each nozzle is configured to supply a cleaning liquid or the like to the center of the front side or the back side of the semiconductor wafer 100. In addition, although Figure 4 Although not shown in the figure, the nozzles for supplying pure water to the front and back surfaces of the semiconductor wafer 100 are also located at different positions in the circumferential direction at the same angle.

[0063] exist Figure 4 In the figure, the angle of the front cleaning nozzle (for hydrofluoric acid) 12 and the front cleaning nozzle (for ozone water) 14 is 4°, and the angle of the back cleaning nozzle (for hydrofluoric acid) 32 and the back cleaning nozzle (for ozone water) 34 is 70°. Here, the "nozzle angle" refers to the angle between the nozzle axis and the perpendicular to the surface of the semiconductor wafer.

[0064] like Figure 4As shown, generally speaking, in the cleaning of semiconductor wafers, the angle of the nozzle on the front side becomes a value lower than the angle of the nozzle on the back side. Therefore, when the cleaning liquid is supplied to the front and back sides, if the rotation speed of the semiconductor wafer is high, the cleaning liquid supplied to the back side will reach the end face of the semiconductor wafer before the cleaning liquid supplied to the front side, and there is a risk that the cleaning liquid will be circulated back to the front side. Therefore, in the general cleaning method of semiconductor wafers, the supply of cleaning liquid to the front side starts a few seconds earlier than the back side, and the supply of cleaning liquid is adjusted so that the cleaning liquid supplied to the front and back sides reaches the end face of the semiconductor wafer at the same time. In the present invention, since the conductive liquid has been supplied to the back side of the semiconductor wafer during the pretreatment process, the supply start time cannot be adjusted as described above. Therefore, in the present invention, it is preferred that the rotation cleaning process includes: a first period in which the rotation speed of the semiconductor wafer is the same as the rotation speed of the semiconductor wafer in the pretreatment process, and a second period in which the rotation speed of the semiconductor wafer is greater than 100 rpm and less than 1000 rpm. At the beginning of the spin cleaning process, there is a first period in which the rotation speed of the semiconductor wafer is the same as the rotation speed of the semiconductor wafer in the pretreatment process, that is, a period in which the rotation speed of the semiconductor wafer is low, so that the cleaning liquid supplied to the back side can be properly prevented from flowing back to the front side.

[0065] By setting the first period of the spin cleaning process to more than 1.0 second, the time for the cleaning liquid on the front to reach the end face of the semiconductor wafer can be appropriately ensured. Therefore, the first period of the spin cleaning process is preferably set to more than 1.0 second, and more preferably set to more than 3.0 seconds. On the other hand, from the viewpoint of the liquid chemical wrapping back to the front face of the wafer, the first period of the spin cleaning process is preferably set to less than 5.0 seconds. Moreover, after the cleaning liquid on the front reaches the end face of the semiconductor wafer, the rotation speed of the semiconductor wafer can be increased to perform normal spin cleaning. The rotation speed of the semiconductor wafer during the second period is preferably more than 100 rpm and less than 1000 rpm. In addition, the time of the second period can be set to more than 3.0 seconds and less than 15.0 seconds.

[0066] Furthermore, the nozzles that supply the cleaning liquid during the spin cleaning process can also supply the same conductive liquid during the pretreatment process. When supplying carbonated water or carbonated ozone water during the pretreatment process, these are supplied from the pure water nozzle or ozone water nozzle on the back side, respectively. Carbonated water is produced using a functional water device, while carbonated ozone water is produced by adding carbonic acid to ozone water in an ozone generator.

[0067] If the angle of the nozzle that supplies the cleaning liquid or conductive liquid to the back side of the semiconductor wafer is 60 degrees or more, the impact when the cleaning liquid contacts the back side can be appropriately alleviated. Therefore, the angle of the nozzle that supplies the cleaning liquid or conductive liquid to the back side is preferably 60 degrees or more. On the other hand, if the angle of the nozzle that supplies the cleaning liquid or conductive liquid to the back side is 80 degrees or less, the cleaning liquid can be appropriately supplied to the back side. Therefore, the angle of the nozzle that supplies the back cleaning liquid is preferably 80 degrees or less.

[0068] On the other hand, if the angle of the nozzle supplying the cleaning liquid to the front of the semiconductor wafer is 4° or more, the cleaning liquid can be supplied appropriately and evenly. Therefore, the angle of the nozzle supplying the cleaning liquid to the front is preferably 4° or more. On the other hand, if the angle of the nozzle supplying the cleaning liquid to the front is 15° or less, a liquid film can be obtained appropriately. Therefore, the angle of the nozzle supplying the cleaning liquid to the front is preferably 15° or less.

[0069] During the pretreatment process, if the diameter of the nozzle supplying the conductive liquid is 3.0 mm or larger, the supplied cleaning liquid will form a water column, effectively eliminating static electricity from the semiconductor wafer. Therefore, the diameter of the nozzle supplying the conductive liquid is preferably 3.0 mm or larger, and more preferably 4.0 mm or larger. On the other hand, if the diameter of the nozzle supplying the conductive liquid is 6.0 mm or smaller, the same as the diameter of the nozzle supplying the front surface, the risk of the liquid flowing back onto the front surface or splashing onto the cup can be appropriately reduced. Therefore, the diameter of the nozzle supplying the conductive liquid is preferably 6.0 mm or smaller.

[0070] In the case where the conductive liquid of the pretreatment process is discharged from the nozzle via the piping line and is supplied to the back of the semiconductor wafer, the piping line and the nozzle are preferably non-metallic. By making the piping line and the nozzle non-metallic, metal contamination can be properly prevented. In addition, the piping line and the nozzle are preferably made of resins such as PFA (perfluoroalkoxy fluororesin) and PTFE (polytetrafluoroethylene). In the past, in order to remove static electricity from the cleaning water, operations such as using metal piping lines and setting electric arcs in the piping were performed. However, since the cleaning liquid contacts the metal, there is a concern that the cleaning liquid and the semiconductor wafer will be contaminated by the metal. In the present invention, as described above, the cleaning liquid is supplied as a water column by adjusting the nozzle diameter, etc., so that the semiconductor wafer can be fully removed from static electricity even if the cleaning liquid does not contact the metal, so the piping line and the nozzle do not need to contain metal.

[0071] [Method for manufacturing semiconductor wafer]

[0072] A method for manufacturing a semiconductor wafer according to an embodiment of the present invention includes the above-mentioned method for cleaning a semiconductor wafer. Thus, a semiconductor wafer can be reliably manufactured in which the occurrence of spoon-shaped defects is suppressed. The method for manufacturing a semiconductor wafer according to this embodiment, for example, includes:

[0073] - A process for obtaining a single crystal ingot by the Czochralski method;

[0074] - Slicing the single crystal ingot to obtain multiple semiconductor wafers;

[0075] - Planarization process of lapping and grinding semiconductor wafers;

[0076] - Double-sided polishing and subsequent single-sided fine polishing of semiconductor wafers;

[0077] - Epitaxial growth process of forming an epitaxial layer on a semiconductor wafer;

[0078] - After cleaning the semiconductor wafer using a combination of an SC1 cleaning tank, an HF tank, an ozone tank, etc., the semiconductor wafer is rinsed with pure water and then dried;

[0079] - any subsequent inspection steps;

[0080] - A semiconductor wafer cleaning method according to this embodiment, comprising a pretreatment step and a spin cleaning step; and

[0081] - Includes a final inspection process for measuring the number of LPDs on the front side of the semiconductor wafer.

[0082] After manufacturing, the semiconductor wafer, that is, the semiconductor wafer that has passed the final inspection process, undergoes device formation processing on the front side. That is, in the present invention, the semiconductor wafer before device formation is the object.

[0083] [Semiconductor wafer]

[0084] The semiconductor wafer of the present invention is preferably a silicon wafer, more preferably a single crystal silicon wafer, and further preferably a polished wafer, an epitaxial wafer, or the like.

[0085] By cleaning a semiconductor wafer using the above-described cleaning method, a semiconductor wafer in which the occurrence of spoon-shaped defects is suppressed can be obtained. Regarding the semiconductor wafer before device formation according to the present invention, the number of defects occurring on the front surface of the semiconductor wafer, which include convex shapes with a height of 5 nm to 20 nm or less and concave shapes with a depth of 5 nm to 20 nm or less, is zero. Furthermore, LPD defects other than spoon-shaped defects, such as particles (foreign matter) and SF defects (stacking faults), may also be present.

[0086] Example

[0087] A single crystal silicon wafer (300 mm in diameter) after epitaxial growth treatment was prepared and placed in a single-wafer cleaning device. The single crystal silicon wafer was de-electrified for 2 seconds using a rod-shaped ion generator placed in a cleaning tank. The single crystal silicon wafer treated with the ion generator was cleaned. The cleaning conditions are shown in Table 1. In Example 1 of the invention, the conductive liquid of step 1 was set to hydrofluoric acid with a concentration of 1.00 mass %, and in Example 2 of the invention, the conductive liquid of step 1 was set to carbonated ozone water with a carbonic acid concentration of 15 mass ppm and an ozone concentration of 25 mass ppm. In the comparative example, step 1 was not performed but cleaning was performed. In Examples 1 and 2 of the invention and the comparative example, steps 6 and 7 were performed after steps 1 and 2, and steps 3 to 5 were repeated 3 times, and the above series of cleaning of steps 1 to 7 was repeated 4 times. The nozzle for supplying cleaning liquid to the front surface of the single crystal silicon wafer is set to have a diameter of 6 mm and a nozzle angle of 4°, and the nozzle for supplying cleaning liquid and conductive liquid to the back surface of the semiconductor wafer is set to have a diameter of 4 mm and a nozzle angle of 70°.

[0088] [Table 1]

[0089]

[0090] For each example, 25 cleaned single-crystal silicon wafers were prepared and LPDs (light point defects) larger than 14 nm on the front surface of the single-crystal silicon wafers were measured using a KLA Surfscan SP5. Five wafers were randomly selected from each example and the LPDs detected by the SP5 were observed using a scanning electron microscope (SEM). The defects were classified into particles, SF defects, and spoon-shaped defects based on the observation results. Figure 5 The following table shows typical SEM images of (a) a spoon-shaped defect, (b) a particle, and (c) a SF defect in an example of the present invention. A spoon-shaped defect is observed as a defect with depressions and protrusions and a tail-fin-like shape. A particle is observed as a spherical foreign object. An SF defect is observed as a defect with linear or square edges. Figure 6 The following table shows the statistical results of (a) the number of LPDs and (b) the number of LPD defect types. Figure 6 (a) Overlay plot of 25 slices of data.

[0091] like Figure 6 As shown in (a), the average value of the number of LPD detections in Example 1 is significantly lower than that in the comparative example, while in Example 2, although the difference is small, it is still lower than that in the comparative example. Figure 6As shown in (b), although a spoon-shaped defect was observed in the comparative example, no spoon-shaped defect was observed in Inventive Examples 1 and 2.

[0092] Industrial applicability

[0093] According to the present invention, a method for cleaning a semiconductor wafer and a method for manufacturing a semiconductor wafer that can suppress the occurrence of spoon-shaped defects can be provided.

[0094] Description of Reference Numerals

[0095] 100-semiconductor wafer, 10-front cleaning nozzle, 12-front cleaning nozzle (for hydrofluoric acid), 14-front cleaning nozzle (for ozone water), 20-front cleaning liquid, 22-front cleaning liquid (hydrofluoric acid), 24-front cleaning liquid (ozone water), 30-back cleaning nozzle, 32-back cleaning nozzle (for hydrofluoric acid), 34-back cleaning nozzle (for ozone water), 40-conductive liquid, 42-back cleaning liquid (hydrofluoric acid), 44-back cleaning liquid (ozone water).

Claims

1. A method for cleaning a semiconductor wafer, comprising a spin cleaning step of supplying a cleaning liquid to at least the front surface of the semiconductor wafer while rotating the semiconductor wafer, wherein: The spin cleaning step includes one or more combinations of an ozone water cleaning step in which the cleaning liquid is ozone water and a subsequent hydrofluoric acid cleaning step in which the cleaning liquid is hydrofluoric acid. Prior to the spin cleaning step, a pretreatment step is performed in which a conductive liquid selected from the group consisting of hydrofluoric acid, carbonated water, and carbonated ozone water is supplied only to the back surface of the semiconductor wafer while the semiconductor wafer is rotated.

2. The method for cleaning a semiconductor wafer according to claim 1, wherein: The conductive liquid is hydrofluoric acid.

3. The method for cleaning a semiconductor wafer according to claim 1, wherein: The conductive liquid is carbonated water.

4. The method for cleaning a semiconductor wafer according to claim 1, wherein: The conductive liquid is carbonated ozone water.

5. The method for cleaning a semiconductor wafer according to any one of claims 1 to 4, wherein: In the pretreatment step, the rotation speed of the semiconductor wafer is greater than or equal to 10 rpm and less than or equal to 100 rpm.

6. The method for cleaning a semiconductor wafer according to claim 5, wherein: The spin cleaning step includes a first period in which the rotation speed of the semiconductor wafer is the same as the rotation speed of the semiconductor wafer in the pretreatment step, and a second period thereafter in which the rotation speed of the semiconductor wafer is greater than 100 rpm and less than or equal to 1000 rpm.

7. The method for cleaning a semiconductor wafer according to any one of claims 1 to 4, wherein: In the pretreatment step, the flow rate of the conductive liquid is 0.3 L / min or more and 1.5 L / min or less.

8. The method for cleaning a semiconductor wafer according to any one of claims 1 to 4, wherein: In the pretreatment step, the conductive liquid is supplied for a time period of 1.0 second to 5.0 seconds.

9. The method for cleaning a semiconductor wafer according to any one of claims 1 to 4, wherein: The conductive liquid is discharged from a nozzle via a piping line and supplied to the back surface of the semiconductor wafer. The piping line and the nozzle are made of non-metal.

10. The method for cleaning a semiconductor wafer according to any one of claims 1 to 4, wherein: The semiconductor wafer is a silicon wafer. 11 . A method for manufacturing a semiconductor wafer, comprising the semiconductor wafer cleaning method according to claim 1 .

12. A semiconductor wafer before device formation, characterized in that: The number of defects generated on the front surface of the semiconductor wafer including a convex portion having a height of 5 nm to 20 nm inclusive and a concave portion having a depth of 5 nm to 20 nm inclusive adjacent to the convex portion is zero.

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