Cleaning method of silicon wafer

Abstract

To provide a cleaning method of a silicon wafer, capable of suppressing a circular concave defect generated when executing a sheet-fed type spin cleaning to a silicon wafer where a thermal oxide film is formed by an annealing treatment.SOLUTION: A cleaning method of a silicon wafer which can be adopted to a sheet-fed type spin cleaning of performing an oxide film peeling step that uses a cleaning liquid of which a hydrofluoric acid concentration is 10 mass% or more to a silicon wafer in which a thermal oxide film having a film thickness of 100Å or more is formed, and an oxidation step using an ozone water. A rinse step is performed between the oxide film peeling step and the oxidation step thereafter, and the hydrofluoric acid concentration of the cleaning liquid on the silicon wafer is reduced to 5 mass% or less before the oxidation step.SELECTED DRAWING: Figure 3

Description

Technical Field

[0001] The present invention relates to a method for cleaning a silicon wafer.

Background Art

[0002] With the high integration and high density of semiconductor devices, it is desired that the surface of a single crystal silicon wafer after annealing and mirror polishing has no microdefects. To meet such a demand, the cleaning process after the finish polishing of a silicon wafer has become an important process that affects the number of surface defects. In such a cleaning process, for example, a cleaning that combines a cleaning process using ozone water (also referred to as ozone water cleaning) and a cleaning process using hydrofluoric acid (also referred to as hydrofluoric acid cleaning) by single-wafer spin cleaning is performed, these treatments are repeated one or more times, and then a spin drying process is applied. By ozone water cleaning, an oxide film can be formed on the wafer surface, and by hydrofluoric acid cleaning, particles and the like on the wafer surface can be lifted off together with the oxide film.

[0003] However, in such a process, it has been pointed out that there is a problem that local oxidation and oxide film removal are simultaneously performed due to the coexistence of ozone water and hydrofluoric acid at the timing of switching the cleaning liquid, resulting in deterioration of the surface roughness.

[0004] In response to such a problem, Patent Document 1 discloses a method for cleaning a silicon wafer that performs a spin cleaning process using pure water between a cleaning process using ozone water and a cleaning process using hydrofluoric acid. And it is described in this Patent Document 1 that the flow rate of pure water in the spin cleaning process using pure water is 1.2 L / min or more and 2.0 L / min or less, and the rotation speed of the wafer is 1000 rpm or more and 1500 rpm or less.

[0005] In this cleaning method, a spin cleaning process (rinsing process) using pure water is performed between the cleaning process using ozone water and the cleaning process using hydrofluoric acid, and by avoiding the coexistence of ozone water and hydrofluoric acid, deterioration of the surface roughness of the wafer is suppressed. Further, in this cleaning method, by performing pure water spin cleaning at a specific pure water flow rate and wafer rotation speed, the pure water is spread to the outer peripheral portion of the wafer, and the residue of particles on the outer peripheral portion of the wafer after cleaning is improved.

[0006] On the other hand, in the method of repeating the above-described ozone water cleaning and hydrofluoric acid cleaning, and the method of performing pure water cleaning between ozone water cleaning and hydrofluoric acid cleaning described in Patent Document 1, there is a problem that mist of ozone water first discharged from the nozzle adheres to the surface of the bare wafer from which the oxide film has been removed, causing local oxidation and generating a circularly depressed step defect (watermark).

[0007] As a countermeasure against such a circularly depressed step defect (watermark), Patent Document 2 discloses a cleaning method for a silicon wafer in which a cleaning liquid is supplied to the wafer surface while rotating the silicon wafer. Specifically, the supply of hydrofluoric acid is started on the wafer surface, the supply of pure water is started before stopping the supply of hydrofluoric acid, after stopping the supply of hydrofluoric acid, before stopping the supply of pure water, the supply of ozone water is started, and a time for simultaneously supplying pure water and ozone water is provided on the wafer surface, and then the supply of pure water is stopped, and only ozone water is supplied on the wafer surface.

[0008] That is, by the above-described countermeasure, at the moment of starting the supply of ozone water, a sufficient amount of pure water layer covers the entire surface of the wafer, and the mist of ozone water does not adhere to the surface of the bare wafer, so that circularly depressed step defects caused by ozone water are suppressed.

[0009] On the other hand, even when single-wafer spin cleaning including an oxide film stripping step (hydrofluoric acid cleaning) with hydrofluoric acid and a subsequent oxidation step (ozone water cleaning) using ozone water is performed on a silicon wafer on which a thermal oxide film is formed by annealing in the manufacturing process of the silicon wafer, it has been confirmed that circular depression defects are formed.

[0010] An AFM image of this circular depression defect is shown in FIG. 5. The size of the circle has a diameter of 5.5 μm, and the depth of the depression (groove) from the interface is about 8 Å.

Prior Art Documents

Patent Documents

[0011]

Patent Document 1

Patent Document 2

Summary of the Invention

Problems to be Solved by the Invention

[0012] By the way, in the manufacturing process of a silicon wafer, since the film thickness of the thermal oxide film formed by annealing is 100 Å or more, it is washed using a cleaning liquid having a hydrofluoric acid concentration of 10% by mass or more. This is because when the hydrofluoric acid concentration is less than 10% by mass, the etching rate of the thermal oxide film is low and it takes time.

[0013] However, as a result of the inventors investigating the generation mechanism of the above-described circular depression defects, it has been found that these defects occur when the above-described single-wafer spin cleaning is performed on a silicon wafer on which a thermal oxide film having a film thickness of 100 Å or more is formed using a cleaning liquid having a hydrofluoric acid concentration of 10% by mass or more. Specifically, it has been found that this circular depression defect is caused by microbubbles contained in the cleaning liquid having a hydrofluoric acid concentration of 10% by mass or more.

[0014] On the other hand, on the premise of not changing the cleaning process using a cleaning solution with a hydrofluoric acid concentration of 10% by mass or more in consideration of the etching rate of the thermal oxide film, in order to suppress the occurrence of circular depression defects, it is necessary to improve the cleaning conditions in spin cleaning.

[0015] The present invention has been made in view of the above problems, and by suppressing circular depression defects that occur when single-wafer spin cleaning is performed on a silicon wafer on which a thermal oxide film is formed by annealing treatment, it is possible to improve the quality of the silicon wafer. Provided is a method for cleaning a silicon wafer.

Means for Solving the Problems

[0016] The method for cleaning a silicon wafer according to the present invention is applicable to single-wafer spin cleaning in which an oxide film stripping step using a cleaning solution with a hydrofluoric acid concentration of 10% by mass or more and an oxidation step using ozone water are performed on a silicon wafer on which a thermal oxide film with a thickness of 100 Å or more is formed. A method for cleaning a silicon wafer, characterized in that a rinsing step is performed between the oxide film stripping step and the subsequent oxidation step, and the hydrofluoric acid concentration of the cleaning solution on the silicon wafer is reduced to 5% by mass or less before the oxidation step. At this time, it is preferable to perform the rinsing step for 1 second or more. By setting the hydrofluoric acid concentration of the cleaning solution on the wafer surface to 5% by mass or less before the oxidation step using ozone water, circular depression defects can be suppressed.

[0017] Further, in the method for cleaning a silicon wafer according to the present invention, in the rinsing step, it is preferable to use a rinsing solution with a hydrofluoric acid concentration of 0.05% by mass or more and 5% by mass or less. Furthermore, the rotation speed of the silicon wafer in the oxide film stripping step and the rinsing step is preferably always the same within the range of 200 rpm or more and 1000 rpm or less.

[0018] By setting such cleaning conditions, it is possible to suppress circular depression defects that occur when single-wafer spin cleaning is performed on a silicon wafer on which a thermal oxide film is formed by annealing treatment.

Advantages of the Invention

[0019] According to the method for cleaning a silicon wafer according to the present invention, the generation of circular depression defects can be suppressed.

Brief Description of the Drawings

[0020]

Figure 1

Figure 2

Figure 3

Figure 4

Figure 5

Modes for Carrying Out the Invention

[0021] Hereinafter, embodiments of the method for cleaning a silicon wafer according to the present invention will be described in detail with reference to the drawings. Note that the present invention is not limited by this embodiment.

[0022] <Spin Cleaner> First, as a premise for explaining the method for cleaning a silicon wafer in this embodiment, an overview of a single-wafer spin cleaner capable of implementing this cleaning method will be briefly described. FIG. 1 is a schematic diagram showing an example of a spin cleaner capable of implementing the method for cleaning a silicon wafer in this embodiment, and for example, it schematically represents a known single-wafer spin cleaner.

[0023] This spin cleaner 1 includes a casing 2, a rotary table 5 provided within the casing 2 and rotatable integrally with a drive shaft 4 by the driving force of a motor (not shown) with a silicon wafer W placed thereon via a holding member 3, and a supply nozzle 6 for appropriately supplying a cleaning liquid such as hydrofluoric acid, ozone water, or pure water to the surface of the silicon wafer W. The waste liquid generated by cleaning is configured to be discharged to the lower part of the casing 2. Note that the supply nozzle 6 may be provided individually for each cleaning liquid of hydrofluoric acid, ozone water, and pure water.

[0024] In the spin cleaner 1 configured as described above, when a silicon wafer W is set within the casing 2, it is controlled to appropriately execute a cleaning method for a silicon wafer in the present embodiment (such as a cleaning process using hydrofluoric acid and a cleaning process using ozone water), which will be described later.

[0025] <Outline of the cleaning method for a silicon wafer> Next, an outline of the cleaning method for a silicon wafer in the present embodiment will be described.

[0026] The cleaning method for a silicon wafer in the present embodiment is a cleaning method applicable to single-wafer spin cleaning that performs a cleaning process using hydrofluoric acid (also referred to as an oxide film peeling process) and a cleaning process using ozone water (also referred to as an oxidation process) with the silicon wafer rotated. In this spin cleaning, an oxide film is formed on the wafer surface by the cleaning process using ozone water, and particles and the like on the wafer surface are removed together with the oxide film by the cleaning process using hydrofluoric acid.

[0027] The cleaning method of the silicon wafer according to this embodiment is applicable to single-wafer spin cleaning that performs an oxide film stripping step using a cleaning liquid with a hydrofluoric acid concentration of 10% by mass or more and an oxidation step using ozone water on a silicon wafer with a thermal oxide film having a thickness of 100 Å or more formed thereon. Since the thickness of the thermal oxide film formed by the annealing treatment is 100 Å or more, it is preferable to perform cleaning (stripping the thermal oxide film) using a cleaning liquid with a hydrofluoric acid concentration of 10% by mass or more. When the hydrofluoric acid concentration is less than 10% by mass, the etching rate of the thermal oxide film is low and it takes time, which is not preferable.

[0028] In such spin cleaning, it has been confirmed that when the oxide film stripping step using hydrofluoric acid and the oxidation step using ozone water are continuously performed without a time interval, circular depression defects are formed (see Fig. 5).

[0029] Here, the formation mechanism of the circular depression defects will be described. Fig. 2 shows the formation mechanism of the circular depression defects.

[0030] In the cleaning liquid with a hydrofluoric acid concentration of 10% by mass or more used in the oxide film stripping step, a large amount of microbubbles exist in the liquid. These microbubbles are formed by entraining air when discharging hydrofluoric acid from the nozzle (corresponding to the supply nozzle 6 above). When the oxide film stripping step is performed using a cleaning liquid with a hydrofluoric acid concentration of 10% by mass or more with such formed microbubbles remaining on the wafer surface, the remaining microbubbles grow by absorbing the gas generated in the process of stripping the thermal oxide film (with a thickness of 100 Å or more). Then, the grown microbubbles 11 adsorb to the wafer surface that has become a hydrophobic surface. This microbubble 11 is covered with hydrofluoric acid (see Fig. 2(a)).

[0031] Subsequently, when an oxidation step using ozone water is performed, coexistence of ozone water and hydrofluoric acid instantaneously occurs at the position where the hydrofluoric acid and the ozone water overlap, and circular depression defects are formed. That is, local etching occurs at the triple point of the wafer surface, hydrofluoric acid, and ozone water, and circular depressions are formed (see FIGS. 2(b) and 5). In FIG. 5, the size of the circle has a diameter of 5.5 μm (the diameter variation is approximately 2 to 10 μm), and the depth of the depression (groove) from the interface was about 8 Å.

[0032] In order to improve the circular depression defects as described above, it is necessary to remove the microbubbles 11 from the wafer surface.

[0033] Therefore, in the method for cleaning a silicon wafer according to the present embodiment, in single-wafer spin cleaning, a rinse step is performed between the oxide film stripping step and the subsequent oxidation step, and the hydrofluoric acid concentration of the cleaning liquid on the silicon wafer is reduced to 5% by mass or less before the oxidation step. By setting the hydrofluoric acid concentration of the cleaning liquid on the wafer surface to 5% by mass or less before the oxidation step using ozone water, the microbubbles 11 are removed from the wafer surface, and circular depression defects are suppressed.

[0034] Further, in the method for cleaning a silicon wafer according to the present embodiment, the rinse step is performed for 1 second or more. In the rinse step, a rinse liquid having a hydrofluoric acid concentration of 0.05% by mass or more and 5% by mass or less is used. Furthermore, the rotation speed of the silicon wafer in the oxide film stripping step and the rinse step is always set to a constant rotation speed in the range of 200 rpm or more and 1000 rpm or less.

[0035] By setting such cleaning conditions, in the present embodiment, it is possible to suppress circular depression defects that occur when single-wafer spin cleaning is performed on a silicon wafer on which a thermal oxide film is formed by annealing treatment.

[0036] In the method for cleaning a silicon wafer according to the present embodiment, the rotational speed of the wafer in the oxidation step using ozone water is the same as the rotational speed in the conventional oxidation step. Specifically, it can be arbitrarily set within the range of 500 rpm or more and 1500 rpm or less. That is, in the oxidation step, the rotational speed of the wafer may be constantly fixed within the range of 500 or more and 1500 rpm, or spin cleaning may be performed while varying the rotational speed of the wafer within the range of 500 or more and 1500 rpm.

[0037] In the method for cleaning a silicon wafer according to the present embodiment, the cleaning times in the oxide film peeling step and the oxidation step are the same as the cleaning time in the conventional spin cleaning. Specifically, the cleaning time in the oxide film peeling step is in the range of 5 seconds or more and 40 seconds or less, and the cleaning time in the oxidation step is in the range of 2 seconds or more and 40 seconds or less. Also, the ozone concentration is the concentration conventionally used. Specifically, the ozone concentration is in the range of 5 ppm or more and 50 ppm or less.

[0038] <Details of the method for cleaning a silicon wafer> Next, the method for cleaning a silicon wafer according to the present embodiment will be described in more detail. FIG. 3 is a flowchart showing an embodiment of the method for cleaning a silicon wafer according to the present invention.

[0039] In the method for cleaning a silicon wafer shown in FIG. 3, first, an oxide film peeling step using a cleaning liquid with a hydrofluoric acid concentration of 10 mass% or more is performed on a silicon wafer having a thermal oxide film with a film thickness of 100 Å or more formed by annealing treatment (step S1). Since metal impurities may be present in the thermal oxide film or at the interface between the thermal oxide film and the silicon wafer, it is necessary to completely peel the thermal oxide film in the oxide film peeling step (spin cleaning) using hydrofluoric acid. Here, while completely removing the thermal oxide film, the surface of the wafer is hydrophobized. At the time when the oxide film peeling step is completed, the surface of the wafer is a hydrophobic surface. In the oxide film peeling step, it is preferable that the flow rate of hydrofluoric acid (cleaning liquid) is 1 L / min or more, and the rotational speed of the silicon wafer is constantly fixed within the range of 200 rpm or more and 1000 rpm or less.

[0040] Next, in the method for cleaning a silicon wafer according to the present embodiment, a rinsing step is performed using a rinsing solution having a hydrofluoric acid concentration of 0.05% by mass or more and 5% by mass or less so that the hydrofluoric acid concentration of the cleaning solution on the silicon wafer becomes 5% by mass or less before the oxidation step (step S2). By performing the rinsing step shown in step S2 between the oxide film peeling step shown in step S1 and the subsequent oxidation step, microbubbles are discharged from the wafer surface. Then, by reducing the hydrofluoric acid concentration of the cleaning solution on the wafer surface to 5% by mass or less before the oxidation step using ozone water in the rinsing step, circular depression defects are suppressed. The circular depression defects can be suppressed by the effect of discharging microbubbles by the rinsing step and the effect of reducing the hydrofluoric acid concentration even when microbubbles remain after the rinsing step.

[0041] Specifically, even when supplying (discharging) a rinsing solution having a hydrofluoric acid concentration of 0.05% by mass or more and 5% by mass or less, microbubbles are formed by entraining air when discharging hydrofluoric acid from the nozzle. However, in the rinsing step after performing the oxide film peeling step, the gas generated in the process of peeling the oxide film is suppressed, and the absorption of gas by the remaining microbubbles is suppressed (because the growth of microbubbles is suppressed), so that circular depression defects can be suppressed.

[0042] In addition, in the rinsing step shown in step S2, it is preferable to use a rinsing solution having a low hydrofluoric acid concentration. As described above, it is particularly preferable to use a rinsing solution having a hydrofluoric acid concentration of 0.05% by mass or more and 5% by mass or less. If the hydrofluoric acid concentration exceeds 5% by mass, the effect of suppressing the formation of circular depression defects decreases, which is not preferable. Although the suppression effect is higher when the hydrofluoric acid concentration is lower, there is a possibility of generating watermarks in the case of less than 0.05% by mass or pure water. Therefore, usually, a rinsing solution having a hydrofluoric acid concentration of 0.05% by mass or more is used. For example, even when using a rinsing solution having a hydrofluoric acid concentration of 0.05% by mass, which has a high suppression effect, a rinsing step of at least 1 second or more is required.

[0043] Therefore, the rinsing process is preferably at least 1 second or more. If it is less than 1 second, it may not be possible to reduce the hydrofluoric acid concentration on the wafer surface to 5% by mass or less, and the suppression effect of circular depression defects will decrease, which is not preferable.

[0044] Also, the rotation speed of the silicon wafer in the rinsing process is preferably the same (constant) rotation speed as in the oxide film stripping process using hydrofluoric acid. That is, the wafer rotation speed in the oxide film stripping process and the rinsing process is preferably kept at a constant rotation speed in the range of 200 rpm or more and 1000 rpm or less. By setting the rotation speed of the silicon wafer in the range of 200 rpm or more and 1000 rpm or less, microbubbles can be efficiently discharged from the wafer surface. On the other hand, if the rotation speed of the silicon wafer is changed from the oxide film stripping process to the rinsing process, the flow of the cleaning liquid (rinsing liquid) will change, and the haze level on the wafer surface may deteriorate, which is not preferable. In the rinsing process, the flow rate of the rinsing agent is 1 L / min or more (the same flow rate as the cleaning liquid in step S1).

[0045] Next, in the cleaning method of the silicon wafer of this embodiment, an oxidation process using ozone water is performed (step S3). The oxidation process in step S3 is equivalent to the cleaning conditions in the conventional oxidation process. Specifically, the ozone concentration is in the range of 5 ppm or more and 50 ppm or less, the flow rate of the ozone water (cleaning liquid) is 1 L / min or more, and the rotation speed of the silicon wafer can be arbitrarily set in the range of 500 rpm or more and 1500 rpm or less. When shifting from the rinsing process to the oxidation process, the spin cleaner is controlled so as not to mix the rinsing liquid and the ozone water. This is because when the rinsing liquid and the ozone water are mixed, the concentration of the ozone water changes, and accordingly, if the oxidation rate decreases, the particle lift-off effect will decrease.

[0046] Thereafter, in the method for cleaning a silicon wafer according to the present embodiment, spin cleaning (pure water cleaning) and spin drying are performed using pure water (step S4). This pure water cleaning is equivalent to the cleaning conditions in conventional pure water cleaning. Specifically, the flow rate of pure water is set to 1 L / min or more, the wafer rotation speed can be arbitrarily set within the range of 150 rpm or more and 1500 rpm or less, and the cleaning time is set within the range of 10 seconds or more and 30 seconds or less. Also, spin drying can be performed by a known method.

Example

[0047] Next, the method for cleaning a silicon wafer according to the present invention will be further described based on examples. Note that the present invention is not limited by the following examples.

[0048] In each of the following examples (Examples and Comparative Examples) to be described later, in the oxide film stripping step, rinsing step, oxidation step, pure water cleaning, and spin drying, single-wafer spin cleaning was performed under the following cleaning conditions. · Oxide film stripping step: HF concentration 15% by mass Flow rate 1 L / min Wafer rotation speed 300 rpm · Rinsing step: HF concentration → 3% by mass (corresponding to Example 1 to be described later) → 1% by mass (corresponding to Example 2 to be described later) → 0.1% by mass (corresponding to Example 3 to be described later) Flow rate 1 L / min Wafer rotation speed 300 rpm · Oxidation step: Ozone concentration 20 ppm Flow rate 1 L / min Wafer rotation speed 1000 rpm · Pure water cleaning: Flow rate 1 L / min Wafer rotation speed 150 rpm · Spin drying: Wafer rotation speed 1500 rpm

[0049] Also, for Example 1 (Examples 1-1 to 1-5), Example 2 (Examples 2-1 to 2-5), Example 3 (Examples 3-1 to 3-5), and the Comparative Example, five silicon wafers each (80 wafers in total) were prepared using a 300-mm diameter silicon wafer with a thermally oxidized film having a thickness of 160 Å.

[0050] Also, the cleaning flow and processing time for each example (Examples 1 to 3 and the Comparative Example) are shown in Table 1.

Table 1

[0051] <Example 1 (Examples 1-1 to 1-5)> Using 25 prepared silicon wafers (five wafers for each example), the cleaning flow was carried out according to Table 1. Specifically, after the oxide film on the wafer surface was removed with a hydrofluoric acid solution having a concentration of 15% by mass for 8 seconds, a rinsing step was performed, and the wafer surface was oxidized with a cleaning solution having an ozone concentration of 20 ppm for 8 seconds. Thereafter, pure water washing (15 seconds) and spin drying (15 seconds) were performed.

[0052] In the rinsing step, a rinsing solution having a hydrofluoric acid concentration of 3% by mass was used. Also, the rinsing time (processing time) was 1 second for Example 1-1, 3 seconds for Example 1-2, 5 seconds for Example 1-3, 7 seconds for Example 1-4, and 10 seconds for Example 1-5.

[0053] <Example 2 (Examples 2-1 to 2-5)> Similar to Example 1, the cleaning flow was carried out according to Table 1.

[0054] In the rinsing step, a rinsing solution having a hydrofluoric acid concentration of 1% by mass was used. Also, the rinsing time (processing time) was 1 second for Example 2-1, 3 seconds for Example 2-2, 5 seconds for Example 2-3, 7 seconds for Example 2-4, and 10 seconds for Example 2-5.

[0055] <Example 3 (Examples 3-1 to 3-5)> Similar to Example 1 and Example 2, the cleaning flow was carried out according to Table 1.

[0056] In the rinsing step, a rinsing solution with a hydrofluoric acid concentration of 0.1% by mass was used. Also, the rinsing time (processing time) was 1 second for Example 3-1, 3 seconds for Example 3-2, 5 seconds for Example 3-3, 7 seconds for Example 3-4, and 10 seconds for Example 3-5, respectively.

[0057] <Comparative Example> Using 5 prepared silicon wafers, a cleaning flow was carried out according to Table 1 (Comparative Example). Specifically, after peeling the oxide film on the wafer surface with a pure water solution with a hydrofluoric acid concentration of 15% by mass for 8 seconds, without performing a rinsing step, the wafer surface was oxidized with a cleaning solution with an ozone concentration of 20 ppm for 8 seconds. Then, pure water cleaning (15 seconds) and spin drying (15 seconds) were carried out.

[0058] <Evaluation> After cleaning according to the cleaning flows of Examples 1 to 3 and the Comparative Example shown in Table 1, the LPD (≥19 nm LPD) on the wafer surface was measured with a "Surfscan SP5" manufactured by KLA-Tencor. Then, based on the defect coordinates of the detected LPD (≥19 nm LPD), defect observation was performed with a "Review-SEM G7" manufactured by AMAT. Figure 4 shows the measurement results of the LPD (≥19 nm LPD).

[0059] As a result, in the Comparative Example where the rinsing step was not performed, circular depression defects of 25 to 39 per wafer were detected for each silicon wafer.

[0060] On the other hand, in Example 1 (Examples 1-1 to 1-5) using a rinsing solution with a hydrofluoric acid concentration of 3% by mass, circular depression defects of 2 to 14 per sheet were detected. However, in all cases, the circular depression defects were suppressed compared to the comparative examples, and good results were obtained. In addition, in Example 2 using a rinsing solution with a hydrofluoric acid concentration of 1% by mass, the circular depression defects were further suppressed. In Examples 2-1 to 2-4, circular depression defects of 0 to 2 per sheet were detected. However, in Example 2-5 with a rinsing time of 10 seconds, the circular depression defects could be completely prevented. In addition, in Example 3 using a rinsing solution with a hydrofluoric acid concentration of 0.1% by mass, it was more effective than the case of a hydrofluoric acid concentration of 1% by mass, and the circular depression defects could be completely prevented only by maintaining the rinsing time for 1 second.

Explanation of Signs

[0061] 1 Spin washer 2 Casing 3 Holding member 4 Drive shaft 5 Rotating table 6 Supply nozzle 11 Microbubble

Claims

1. In a cleaning method for a silicon wafer applicable to single-wafer spin cleaning, which comprises an oxide film stripping step using a cleaning liquid with a hydrofluoric acid concentration of 10% by mass or more and an oxidation step using ozone water on a silicon wafer with a thermally oxidized film having a thickness of 100 Å or more, a rinsing step is performed between the oxide film stripping step and the subsequent oxidation step, and the hydrofluoric acid concentration of the cleaning liquid on the silicon wafer is reduced to 5% by mass or less before the oxidation step. A cleaning method for a silicon wafer, characterized by the above.

2. The rinsing step is performed for 1 second or more. A cleaning method for a silicon wafer according to Claim 1, characterized by the above.

3. In the rinsing step, a rinsing liquid with a hydrofluoric acid concentration of 0.05% by mass or more and 5% by mass or less is used. A cleaning method for a silicon wafer according to Claim 1, characterized by the above.

4. The rotation speed of the silicon wafer in the oxide film stripping step and the rinsing step is always the same within the range of 200 rpm or more and 1000 rpm or less. A cleaning method for a silicon wafer according to Claim 1, characterized by the above.

Images