Method for manufacturing an SOI wafer

Abstract

The present invention relates to a method for manufacturing an SOI wafer, which has a process for adjusting the film thickness of the SOI layer of the SOI wafer by wet etching. The method is characterized in that, in the process for adjusting the film thickness of the SOI layer, the following two steps are combined: a first etching step of etching the surface of the SOI layer using an SC1 solution; and a second etching step of forming an oxide film on the surface of the SOI layer by bringing the SOI layer into contact with ozone water, and then etching the surface of the SOI layer by bringing the formed oxide film into contact with an HF-containing aqueous solution to remove the oxide film, and performing the first etching step and the second etching step of etching in such a manner that the machining allowance of the SOI layer in the first etching step is less than the machining allowance of the SOI layer in the second etching step. Thus, a method for manufacturing an SOI wafer can be provided, which can take into account both the control of the etching machining allowance and the achievement of excellent in-plane uniformity of the SOI film thickness in the SOI film thickness adjustment.

Description

Technical Field

[0001] The present invention relates to a method for manufacturing an SOI wafer. Background Art

[0002] For an SOI wafer, especially an SOI wafer called an FDSOI (Fully Depleted Silicon-On-Insulator) wafer, extremely high uniformity of the film thickness of the SOI layer (SOI film thickness) is required.

[0003] In the prior art, as one of the methods for thinning an SOI wafer, the following method is carried out: the SOI wafer is heat-treated in a batch-type heat treatment furnace, and after the Si on the surface of the SOI layer is changed to an oxide film by oxidation, the oxide film is removed. In order to thin the SOI film thickness to a desired value with good accuracy by this method, it is necessary to accurately control so that the film thickness of the oxide film becomes the target value. However, for the thickness of the oxide film actually grown by heat treatment, since the oxidation rate changes according to the change in atmospheric pressure during the oxidation time, it is very difficult to accurately control the oxide film thickness. Therefore, in the case of thinning by oxidation, the following method is adopted: thinning is carried out based on oxidation, and the SOI film thickness after thinning is made slightly thicker than the desired value (about 3 nm), and then, by thinning separately by etching, the etching time is controlled to reach the target value. In this two-stage thinning method, as shown in Patent Document 1, the following method is adopted: after removing the oxidized oxide film, the SOI film thickness is measured, and based on this value, the machining allowance for the subsequent etching process is set.

[0004] In addition, in the above-mentioned two-stage thinning process of oxidation + etching, as a method for shortening the above process, the following method has been proposed: after oxidation, in a state where the oxide film is attached, the SOI film thickness is measured, and based on the measured value of the SOI film thickness, the oxide film removal and the etching + cleaning process are carried out in the same batch process as cleaning. In Patent Document 2, etching using an SC1 solution as the etching solution in this method has been proposed.

[0005] In addition, in Patent Document 3, the following method has been proposed: in the etching of the SOI wafer after oxidation, after adjusting the film thickness to be slightly thicker than the target film thickness by batch-type cleaning, in order to further adjust the SOI film thickness deviation within the batch, the final film thickness adjustment until the target value is adjusted according to the etching machining allowance of each wafer by single-wafer SC1 etching or the like, and the uniformity of the SOI film thickness is improved. In Figure 5 shows a simplified flowchart of the existing method corresponding to the method described in Patent Document 3. If such a method is used, for example, Figure 6The PV (Peak to Valley) value of the SOI film thickness deviation that occurs within a batch (25 wafers) as shown is used to improve the uniformity of the SOI film thickness. However, although the SOI film thickness adjustment performed by the single-wafer cleaning device can correct the SOI film thickness deviation within a batch, since the temperature of the chemical solution in the chemical solution coating section becomes relatively high, or because of the rotation of the wafer holding section, the flow rate of the chemical solution becomes faster due to centrifugal force the closer it is to the outer periphery of the wafer, etc., the in-plane deviation depending on the processing margin becomes larger, so the etching processing margin cannot be increased. Therefore, in Patent Document 3, the following method is proposed: In such a method, the within-batch average value of the SOI film thickness after batch cleaning is controlled between the target value and target + 0.5 nm to minimize the deterioration of film thickness uniformity caused by the single-wafer cleaning device.

[0006] On the other hand, in Patent Document 4, it is described that thinning of the SOI film thickness using ozone water and HF is used in the final film thickness adjustment of the SOI film thickness. Figure 5 The flowchart shown also corresponds to the method described in Patent Document 4. The etching using this method is etching that removes the surface oxide film formed by ozone water using HF, and the etching processing margin is controlled by the thickness of the surface oxide film formed by ozone water. However, the growth rate of the surface oxide film using ozone water depends on the surface oxide film thickness. In the case where the surface oxide film is thin, the oxidation rate is fast, and if, for example, Figure 7 as shown, the surface oxide film exceeds 1 nm, the oxidation rate becomes extremely slow and almost no growth occurs, so the etching of Si saturates at about 0.5 nm ( Figure 8 ).

[0007] Therefore, in the case of etching more than about 0.5 nm by treatment with ozone water and HF, although the in-plane uniformity of the etching processing margin is high, since it takes too much time, it is necessary to repeat the treatment with ozone water and HF. The film thickness that can be etched by repeating this treatment becomes the thickness of the oxide film saturated by ozone water, and the etching is performed in units of this thickness (equivalent to the Si thickness of 0.5 nm). In addition, even if etching below the saturation of the surface oxide film thickness using ozone water (about 0.5 nm or less) is performed for the final film thickness adjustment, since the variation in the immersion time dependence of the surface oxide film thickness formed by ozone water also becomes large, it is difficult to control the etching processing margin with high precision.

[0008] Prior Art Documents

[0009] Patent Documents

[0010] Patent Document 1: Japanese Patent Laid-Open No. 2007 - 266059

[0011] Patent Document 2: Japanese Patent Laid-Open No. 2010 - 92909

[0012] Patent Document 3: Japanese Patent Application Laid-Open No. 2016-4890

[0013] Patent Document 4: Japanese Patent Application Laid-Open No. 2004-349493 SUMMARY OF THE INVENTION

[0014] (1) Technical Problem to be Solved

[0015] The present invention has been completed to solve the above problems, and an object thereof is to provide a method for manufacturing an SOI wafer, which can control both the etching margin and achieve excellent in-plane uniformity of the SOI film thickness in adjusting the SOI film thickness of the SOI wafer.

[0016] (2) Technical Solution

[0017] To achieve the above object, the present invention provides a method for manufacturing an SOI wafer, which includes a step of adjusting the film thickness of the SOI layer of the SOI wafer by wet etching, and is characterized in that

[0018] in the step of adjusting the film thickness of the SOI layer, the following two steps are combined for performing:

[0019] a first etching step of etching the surface of the SOI layer using an SC1 solution; and

[0020] a second etching step of forming an oxide film on the surface of the SOI layer by bringing the SOI layer into contact with ozone water, and then removing the formed oxide film by bringing the oxide film into contact with an HF-containing aqueous solution to etch the surface of the SOI layer,

[0021] the first etching step and the second etching step are performed in such a manner that the etching margin of the SOI layer in the first etching step is smaller than the etching margin of the SOI layer in the second etching step.

[0022] Thus, in the method for manufacturing an SOI wafer of the present invention, in the step of adjusting the film thickness of the SOI layer, the first etching step and the second etching step are combined for performing. The first etching step uses an SC1 solution, and the second etching step performs formation of an oxide film using ozone water and removal of the oxide film using an HF-containing aqueous solution. In addition, the first and second etching steps are performed in such a manner that the etching margin of the SOI layer in the first etching step is less than the etching margin of the SOI layer in the second etching step. By performing in this way, deterioration of in-plane film thickness uniformity can be suppressed on the one hand, and an arbitrary etching margin can be controlled with high precision on the other hand. That is, the method for manufacturing an SOI wafer of the present invention can control both the etching margin and achieve excellent in-plane uniformity of the SOI film thickness in adjusting the SOI film thickness of the SOI wafer.

[0023] Preferably, the machining allowance of the SOI layer in the first etching step is set to 0.5 nm or less.

[0024] By doing so, more excellent in-plane uniformity of the SOI film thickness can be achieved.

[0025] The second etching step can be repeated multiple times.

[0026] By doing so, a highly accurate first etching step and a stepwise second etching step of 0.5 nm can be combined, and the target value after thinning can be selected from a wider range.

[0027] Preferably, a single-wafer spin etcher is used for the first etching step and the second etching step.

[0028] By using a single-wafer spin etcher, since the control can be performed according to the film thickness of each wafer, more accurate film thickness control can be performed. In addition, by using a single-wafer spin etcher, the repetition of the second etching step using ozone water and an HF-containing aqueous solution can be easily performed any number of times.

[0029] The film thickness of the SOI layer for which the film thickness adjustment is performed is preferably 50 nm or less.

[0030] The object of the present invention suitable for film thickness adjustment is the thinning of the SOI layer having an extremely thin film thickness of 50 nm or less, and a thinned SOI wafer close to the target value can be manufactured.

[0031] Although there is no particular limitation on the lower limit, the film thickness of the SOI layer for which the film thickness adjustment is performed can be, for example, 5 nm or more.

[0032] The second etching step is performed multiple times, and the machining allowance of the SOI layer in the first etching step is 1 nm or less.

[0033] If this is done, more excellent in-plane uniformity of the SOI film thickness can be achieved.

[0034] (III) Advantageous Effects

[0035] As described above, if it is the method for manufacturing an SOI wafer of the present invention, in the SOI film thickness adjustment of the SOI wafer, it is possible to balance the control of the etching machining allowance and achieve excellent in-plane uniformity of the SOI film thickness. As a result, if the method for manufacturing an SOI wafer of the present invention is used, it is possible to achieve excellent in-plane uniformity of the SOI film thickness in an extremely thin state on the one hand, and to accurately control the SOI film thickness to the target value on the other hand. Description of the Drawings

[0036] Figure 1 It is a graph showing the time dependence of the etching process margin of the SOI layer using the SC1 solution.

[0037] Figure 2 It is a graph showing the etching process margin dependence of the in-plane process margin Range (range) of each etching solution used in a single-wafer spin etcher.

[0038] Figure 3 It is a schematic diagram of an example of a single-wafer spin etcher.

[0039] Figure 4 It is a flowchart of a method for manufacturing an SOI wafer according to an example of the present invention.

[0040] Figure 5 It is a simplified flowchart of the conventional method.

[0041] Figure 6 It is a graph showing an example of the film thickness deviation within a batch using batch cleaning.

[0042] Figure 7 It is a graph showing the relationship between the time of contacting ozone water and the film thickness of the surface oxide film on the SOI in the conventional method.

[0043] Figure 8 It is a graph showing the relationship between the time of contacting ozone water and the etching process margin of the SOI layer in the conventional method. Detailed Description of the Invention

[0044] As described above, in the adjustment of the SOI film thickness of an SOI wafer, a method for manufacturing an SOI wafer is sought that can achieve both control of the etching process margin and excellent in-plane uniformity of the SOI film thickness.

[0045] The present inventors have conducted repeated and in-depth studies on the above technical problems, and as a result, have found that by using the following method, it is possible to suppress the deterioration of in-plane film thickness uniformity on the one hand and control an arbitrary etching process margin with high precision on the other hand, and thus have completed the present invention. In the process of adjusting the film thickness of the SOI layer, the first etching step and the second etching step are combined. The first etching step uses the SC1 solution, and the second etching step forms an oxide film using ozone water and removes the oxide film using an HF-containing aqueous solution. Moreover, the first etching step and the second etching step are etched in such a manner that the processing margin of the SOI layer in the first etching step is less than the processing margin of the SOI layer in the second etching step.

[0046] That is, the present invention is a method for manufacturing an SOI wafer, which has a process of adjusting the film thickness of the SOI layer of the SOI wafer by wet etching, and is characterized in that

[0047] In the process of adjusting the film thickness of the SOI layer, the following two steps are combined for implementation:

[0048] The first etching step of etching the surface of the SOI layer using an SC1 solution; and

[0049] The second etching step of forming an oxide film on the surface of the SOI layer by bringing the SOI layer into contact with ozone water, and then bringing the formed oxide film into contact with an HF-containing aqueous solution to remove the oxide film, thereby etching the surface of the SOI layer.

[0050] The first etching step and the second etching step are performed in such a manner that the machining allowance of the SOI layer in the first etching step is less than the machining allowance of the SOI layer in the second etching step.

[0051] Hereinafter, the present invention will be described in detail with reference to the accompanying drawings, but the present invention is not limited thereto.

[0052] As described above, in the method for manufacturing an SOI wafer of the present invention, in the process of adjusting the film thickness of the SOI layer, the first etching step and the second etching step are combined for implementation. In the first etching step, an SC1 solution is used, and in the second etching step, formation of an oxide film using ozone water and removal of the oxide film using an HF-containing aqueous solution (hereinafter, sometimes referred to as "etching using O3+HF") are performed. In addition, the first etching step and the second etching step are performed in such a manner that the machining allowance of the SOI layer in the first etching step is less than the machining allowance of the SOI layer in the second etching step.

[0053] Figure 1 Shows the etching time dependence (time dependence of the etching amount of the SOI layer using an SC1 solution) of the etching machining allowance (in-plane average value) in the case where the SOI film is etched using a single-wafer etching machine (rotary etching machine) with an SC1 solution.

[0054] As Figure 1 shown, the etching machining allowance (in-plane average value) using an SC1 solution is proportional to the etching time. Therefore, in the first etching step, the etching machining allowance (in-plane average value) can be arbitrarily set by adjusting the etching time.

[0055] On the other hand, as Figure 2 indicated by the black solid circles, as the etching machining allowance (in-plane average value) using an SC1 solution increases, the in-plane machining allowance range (the difference between the maximum value and the minimum value of the etching machining allowance in the plane) tends to deteriorate.

[0056] Therefore, the feature of the present invention is to adjust the SOI film thickness by combining the etching using O3+HF (the second etching step) with the first etching step using an SC1 solution.

[0057] In Figure 2 the example (hollow circle + hollow triangle), the relationship between the etching process margin (in-plane average value) and the in-plane process margin range is shown in the case where, after performing one cycle of etching using O3+HF (hollow circle), the first etching step using an SC1 solution (hollow triangle) is further performed.

[0058] According to Figure 2 , it can be seen that when the etching process margin as the target value is set to 1 nm, the in-plane process margin range for etching using only the SC1 solution is about 0.45 nm, and in the case of combining the etching using O3+HF (the second etching step) and the etching using the SC1 solution (the first etching step), the in-plane process margin range can be suppressed to about 0.25 nm.

[0059] In addition, according to Figure 2 , it can be seen that by making the "process margin obtained by subtracting the process margin of the second etching step from the etching process margin as the target value" during etching, that is, the "process margin of the SOI layer in the first etching step" less than the process margin of the SOI layer in the second etching step, the in-plane process margin range can be suppressed.

[0060] Therefore, if it is the manufacturing method of the SOI wafer of the present invention, in the SOI film thickness adjustment of the SOI wafer, it is possible to take into account the control of the etching process margin and achieve excellent in-plane uniformity of the SOI film thickness. As a result, if the manufacturing method of the SOI wafer of the present invention is adopted, it is possible to achieve excellent in-plane uniformity of the SOI film thickness on the one hand and control the SOI film thickness to the target value with high precision on the other hand.

[0061] Preferably, the process margin of the SOI layer in the first etching step is set to 0.5 nm or less.

[0062] By doing so, more excellent in-plane uniformity of the SOI film thickness can be achieved.

[0063] Although there is no particular limitation on the lower limit, the process margin of the SOI layer in the first etching step can be, for example, 0.05 nm or more.

[0064] The second etching step can be repeated multiple times.

[0065] By doing so, a highly precise first etching step and a stepwise second etching step of 0.5 nm can be combined, and the target value after thinning can be selected from a wider range.

[0066] For example, in the film thickness adjustment of an SOI wafer, the first etching step using an SC1 solution can be performed with a processing margin of 0.5 nm or less in etching amount, and the remaining thickness can be etched by repeating the second etching step using ozonated water and an HF-containing aqueous solution. In addition, in the second etching step using ozonated water and an HF-containing aqueous solution, by performing the treatment for the time (about 1 minute) when the surface oxide film using ozonated water is saturated, etching in units of 0.5 nm can be performed by repeating this treatment. By repeating the combination of the second etching step of 0.5 nm using ozonated water and an HF-containing aqueous solution and the first etching solution of 0.5 nm or less using an SC1 solution, any etching processing margin can be controlled with high precision, and more excellent in-plane uniformity of the film thickness can be achieved while taking both into account.

[0067] Alternatively, preferably, the second etching step is performed multiple times, and the processing margin of the SOI layer in the first etching step is set to 1 nm or less.

[0068] In the case where only one second etching step is performed, since the processing margin of the SOI layer is about 0.5 nm, the processing margin of the SOI layer in the first etching step needs to be set to 0.5 nm or less. However, in the case where the second etching step is performed multiple times, since the processing margin of the SOI layer is at least about 1 nm, by setting the processing margin of the SOI layer in the first etching step to 1 nm or less, the processing margin of the SOI layer in the first etching step can be made less than half of the total processing margin, and more excellent in-plane uniformity of the SOI film thickness can be achieved.

[0069] The order of the first etching step using an SC1 solution and the second etching step using ozonated water and an HF-containing aqueous solution is not particularly limited. The same effect can be obtained regardless of performing the second etching step on either one or both of the front and back of the first etching step using an SC1 solution.

[0070] In the case where the second etching step is performed multiple times, the second etching step can be performed multiple times after the first etching, or the second etching step can be performed multiple times before the first etching step. Alternatively, the second etching step can be performed one or more times during the first etching step, and the second etching step can be performed one or more times after the first etching step.

[0071] During the process of repeating the second etching step, a treatment with ozonated water can also be added at the final stage to perform a hydrophilic treatment on the surface.

[0072] In addition, after removing the oxide film using the HF-containing aqueous solution in the second etching step, a cleaning using ozonated water or an SC1 solution can be added to remove LPD.

[0073] If the first etching step (etching using SC1 solution) and the second etching step (etching using ozone water and HF-containing aqueous solution) are performed with a single-wafer spin etcher, more precise film thickness control can be achieved because the control can be performed according to the film thickness of each wafer. In addition, the repetition of etching using O3+HF can be easily performed any number of times.

[0074] Here, an example of a single-wafer spin etcher that can be used in the method for manufacturing an SOI wafer of the present invention will be described.

[0075] Figure 3 It is a schematic diagram of a single-wafer spin etcher as an example. Figure 3 The single-wafer spin etcher 10 shown includes a wafer holding / rotating mechanism 1 and a supply nozzle 2. The wafer holding / rotating mechanism 1 is configured to hold and rotate an SOI wafer 20 having an SOI layer that is an object of film thickness adjustment. The supply nozzle 2 is configured to supply a chemical solution 3 used in each etching step to the wafer 20.

[0076] In addition, the etcher that can be used in the method for manufacturing an SOI wafer of the present invention is not particularly limited, and any etcher can be used as long as it is configured to adjust the SOI film thickness of the SOI wafer. Therefore, for example, a single-wafer cleaning machine can also be used as a single-wafer etcher.

[0077] Regarding the method for thinning the SOI wafer described above, it can be applied to any method for manufacturing an SOI wafer, such as the ion implantation lift-off method, the SIMOX method, the rT-CCP method, etc.

[0078] As the SC1 solution used in the first etching step, a mixed aqueous solution of NH4OH and H2O2 that is usually used as an SC1 solution in the cleaning of silicon wafers in semiconductor manufacturing can be used.

[0079] As the ozone water in the second etching step, for example, ozone water with an ozone (O3) concentration of 1 to 50 ppm can be used.

[0080] The HF concentration of the HF-containing aqueous solution used in the second etching step can be set, for example, in the range of 0.1 mass% to 50 mass%.

[0081] Next, with reference to Figure 4 A specific example of the method for manufacturing an SOI wafer of the present invention will be described.

[0082] First, an SOI wafer to be processed is prepared (S1). As described above, in the present invention, the method for manufacturing the SOI wafer is not particularly limited.

[0083] Next, the prepared SOI wafer is subjected to oxidation film formation (S2). In this example, an oxide film is formed under the condition that the SOI film thickness is about 3 nm thicker than the target value (Target).

[0084] Next, in order to remove the oxide film formed on the surface of the SOI layer, oxide film removal cleaning is performed (S3). In this example, a batch type is used, and an oxide film is removed using an HF aqueous solution, and then RCA cleaning is performed.

[0085] Next, the SOI film thickness of the SOI wafer from which the oxide film has been removed is measured (S4). In the measurement, for example, an ellipsometer can be used.

[0086] Next, the film thickness adjustment process of the SOI layer of the SOI wafer is performed by wet etching (S5). In this example, the film thickness of the SOI layer is adjusted by single-wafer spin etching.

[0087] In Figure 4 Examples are shown in which, in the process of adjusting the SOI film thickness, after the first etching step using the SC1 solution, multiple second etching steps using O3 + HF are performed, and examples in which, after multiple second etching steps using O3 + HF, the first etching step using the SC1 solution is performed again, and finally the second etching step using O3 + HF is performed. In either example, the total machining allowance in the first etching step is made less than the total machining allowance in the second etching step.

[0088] Example

[0089] Hereinafter, the present invention will be specifically described using examples and comparative examples, but the present invention is not limited thereto.

[0090] (Example 1)

[0091] [Preparation of SOI Wafer]

[0092] Twenty-five SOI wafers with a diameter of 300 mm and an SOI film thickness of 150 nm produced by the ion implantation lift-off method were prepared.

[0093] [Oxidation Process]

[0094] The oxidation process was performed on the 25 prepared wafers under the conditions shown in Table 1 below.

[0095] [Oxide Film / SOI Film Thickness Measurement]

[0096] The oxide film / SOI film thickness measurement was performed on each wafer on which the oxidation process was performed. The results are shown in Table 1 below.

[0097] [Batch Cleaning]

[0098] For each wafer with the SOI film thickness measured after the oxidation process, batch cleaning was performed using an HF-containing aqueous solution to remove the oxide film. The conditions are shown in Table 2 below. Subsequently, SOI film thickness measurement was performed on each wafer. The results are shown in Table 2 below.

[0099] [Single-wafer film thickness adjustment etching (process for adjusting the film thickness of the SOI layer)]

[0100] After that, using a single-wafer etching machine (rotary etching machine), for each wafer, etching using SC1 solution (first etching step) and subsequent etching using O3 + HF (etching after contacting ozone water and then using an HF-containing aqueous solution (second etching step)) were performed. As shown in Table 2 below, etching using SC1 solution was performed in such a way as to adjust the film thickness with a processing margin of 0.5 nm or less. As shown in Table 2 below, etching using O3 + HF was repeated. The number of repetitions was changed according to the film thickness value of each wafer. During the repeated etching using O3 + HF, ozone water treatment was added at the final stage to perform surface hydrophilic treatment. Thus, SOI wafers were manufactured.

[0101] After the second etching step, the SOI film thickness of each SOI wafer was measured. The results are shown in Table 2 below.

[0102] (Comparative Example 1)

[0103] In Comparative Example 1, in batch cleaning, after oxide film removal cleaning, SC1 etching was performed under the conditions shown in Table 2 below, and in single-wafer film thickness adjustment etching, the second etching step was not performed. Otherwise, SOI wafers were manufactured in the same manner as in Example 1. That is, in Comparative Example 1, film thickness adjustment etching was performed only by SC1 cleaning (etching using SC1 solution).

[0104] (Comparative Example 2)

[0105] In Comparative Example 2, film thickness adjustment etching was performed only by etching using O3 + HF (second etching step). Otherwise, SOI wafers were manufactured in the same manner as in Example 1. The conditions of the second etching step performed in Comparative Example 2 are shown in Table 2 below.

[0106] The results of SOI film thickness measurement in Comparative Examples 1 and 2 and the results of Example 1 are shown together in Table 2 below.

[0107] [Table 1]

[0108]

[0109]

[0110] [Table 2]

[0111]

[0112] SC1 condition: NH4OH (29 wt%) : H2O2 (30 wt%) : H2O = 1:1:5, liquid temperature 76 °C

[0113] Ozone water: O3 (12 ppm)

[0114] HF (aqueous solution containing HF) in the second etching step: HF (15 wt%)

[0115] In the case of Comparative Example 1 where the film thickness was adjusted only using the SC1 solution, although the average value of the SOI film thickness within the same cassette was 12.0 nm and the range of the within-batch average value was 0.2 nm, which was good, due to the influence of the deterioration of the film thickness distribution within the wafer surface caused by SC1 cleaning, the average value of the in-plane range of each wafer was 0.9 nm, and deterioration was observed.

[0116] In the case of Comparative Example 2 where the film thickness was adjusted only using ozone water and hydrofluoric acid, although the in-plane range was 0.5 nm, which was good, the average value of the SOI film thickness within the same cassette was 11.8 nm, and deviation from the target value was observed. In addition, the range of the within-batch average value was also 0.9 nm, and no significant improvement was observed.

[0117] In contrast, in the examples, as can be seen from the results shown in Table 2, the average value of the SOI film thickness within the same cassette was 12.0 nm, which was accurately adjusted to the target (target value), the range of the average value within the cassette was also significantly improved to 0.2 nm, and the in-plane range was also 0.6 nm, which was better than Comparative Example 1.

[0118] In addition, the present invention is not limited to the above-described embodiments. The above-described embodiments are illustrative, and any solution having a structure substantially the same as the technical idea described in the claims of the present invention and achieving the same function and effect is included in the technical scope of the present invention.

Claims

1. A method for manufacturing an SOI wafer, which has a process of adjusting the film thickness of the SOI layer of the SOI wafer by wet etching, characterized in that: In the process of adjusting the film thickness of the SOI layer, the following two steps are combined for implementation: The first etching step of etching the surface of the SOI layer using an SC1 solution; And The second etching step of forming an oxide film on the surface of the SOI layer by bringing the SOI layer into contact with ozone water, and then bringing the formed oxide film into contact with an HF-containing aqueous solution to remove the oxide film, thereby etching the surface of the SOI layer, The first etching step and the second etching step are carried out in such a manner that the machining allowance of the SOI layer in the first etching step is less than the machining allowance of the SOI layer in the second etching step.

2. The method for manufacturing an SOI wafer according to claim 1, characterized in that: The machining allowance of the SOI layer in the first etching step is set to 0.5 nm or less.

3. The method for manufacturing an SOI wafer according to claim 1, characterized in that: The second etching step is carried out repeatedly for multiple times.

4. The method for manufacturing an SOI wafer according to claim 2, characterized in that: The second etching step is carried out repeatedly for multiple times.

5. The method for manufacturing an SOI wafer according to claim 1, characterized in that: The first etching step and the second etching step are carried out using a single-wafer spin etcher.

6. The method for manufacturing an SOI wafer according to claim 2, characterized in that: The first etching step and the second etching step are carried out using a single-wafer spin etcher.

7. The method for manufacturing an SOI wafer according to claim 3, characterized in that: The first etching step and the second etching step are carried out using a single-wafer spin etcher.

8. The method for manufacturing an SOI wafer according to claim 4, characterized in that: The first etching step and the second etching step are carried out using a single-wafer spin etcher.

9. The method for manufacturing an SOI wafer according to any one of claims 1 to 8, characterized in that: The film thickness of the SOI layer for which the film thickness is adjusted is 50 nm or less.

10. The method for manufacturing an SOI wafer according to claim 1, characterized in that: The second etching step is carried out multiple times, and the machining allowance of the SOI layer in the first etching step is set to 1 nm or less.

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