JP2011014800A - Method for measuring film thickness of epitaxial layer, method for manufacturing epitaxial wafer, and method for controlling manufacturing process of epitaxial wafer - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a means to measure the thickness of an epitaxial layer formed on a substrate without depending on substrate resistivity, and polished after the epitaxial layer is formed; and to provide an epitaxial wafer guaranteeing the thickness of the epitaxial layer of a product wafer by the means.SOLUTION: The method for measuring the film thickness of the epitaxial layer in the manufacturing step of the epitaxial wafer includes forming the epitaxial layer on the surface of a semiconductor wafer by subjecting the semiconductor wafer to the epitaxial growth process. The method includes measuring the thickness A of the semiconductor wafer before the epitaxial growth step, polishing the epitaxial layer formed on the surface of the semiconductor wafer after the epitaxial growth step, measuring the thickness B of the epitaxial wafer obtained after polishing, and computing the thickness of the epitaxial layer as a difference (B-A) between the thickness B and the thickness A. The thickness A and the thickness B are measured by a contactless displacement measuring meter.

Description

The present invention relates to an epitaxial layer thickness measurement method in an epitaxial wafer manufacturing process, and an epitaxial wafer manufacturing method capable of providing an epitaxial wafer having an epitaxial layer with a desired thickness.
Furthermore, the present invention relates to an epitaxial wafer manufacturing process management method capable of detecting an epitaxial growth failure during the process.

Measurement of the thickness of the epitaxial layer in the epitaxial wafer is generally performed by using an infrared interference method using a difference in refractive index between the wafer substrate and the epitaxial layer with respect to infrared light (see, for example, Patent Document 1).
JP 2003-065724 A

  In the infrared interference method, in order to measure the thickness of the epitaxial layer, it is necessary to reflect light at the interface between the substrate and the epitaxial layer. However, a substrate having a low impurity concentration (high resistance, for example, a resistivity of more than 20 mΩ · cm) has a small difference in refractive index between the epitaxial layer and the substrate, so that sufficient reflected light cannot be obtained. Can not be measured. In such a case, a wafer doped with impurities at a high concentration is used as a monitor wafer separately from the product, and epitaxial growth is performed under the same conditions as the product substrate, and the thickness of the epitaxial layer formed on the monitor wafer This guarantees the thickness of the epitaxial layer in the product.

However, in a single wafer epitaxial furnace, even if a monitor wafer is used at a certain frequency, it detects a wafer that has not been epitaxially grown due to equipment troubles, etc., or that has undergone multiple epitaxial growths due to errors in manual operation, etc. Therefore, a wafer without an epitaxial layer or a wafer on which an epitaxial layer exceeding a desired film thickness is formed may be shipped as a product wafer. In addition, in a batch type epi furnace, there is a distribution of heating temperature depending on the position in the furnace, so the thickness of the epitaxial layer formed on the monitor wafer may not always be the same as the thickness of the product wafer.
As described above, the product guarantee by the monitor wafer has a problem that it is not always possible to provide a highly reliable product. On the other hand, if the thickness of the epitaxial layer formed on the low resistance substrate can be measured, the epitaxial layer thickness of the product wafer itself can be measured, so that the above problem can be solved. .
In particular, the above problem is a problem when using a process of polishing an epitaxial layer formed on the surface of a semiconductor wafer after an epitaxial growth process (so-called post-epi-polishing) performed as a means for reducing the surface haze of the epitaxial wafer. .

  Accordingly, an object of the present invention is to provide a means by which an epitaxial layer is formed on a substrate regardless of the substrate resistivity, and the thickness of the epitaxial layer polished after the formation of the epitaxial layer can be measured. Therefore, it is intended to provide a high quality epitaxial wafer by guaranteeing the epitaxial layer thickness of the product wafer.

  As a result of intensive studies to achieve the above object, the present inventors have polished (1) the thickness A of the semiconductor wafer before the epitaxial growth step and the epitaxial layer formed on the surface of the semiconductor wafer after the epitaxial growth step, By measuring the thickness B of the epitaxial wafer obtained after polishing with a non-contact displacement meter, the thickness of the epitaxial layer can be obtained from the difference between the thickness A of the wafer and the thickness B of the wafer. 2) It has been found that this method can be applied regardless of the substrate resistivity, and the present invention has been completed.

That is, the object of the present invention has been achieved by the following means.
[1] A method for measuring the thickness of an epitaxial layer in a manufacturing process of an epitaxial wafer, comprising forming an epitaxial layer on a surface of the semiconductor wafer by subjecting the semiconductor wafer to an epitaxial growth step,
Measuring the thickness A of the semiconductor wafer before the epitaxial growth step;
Polishing the epitaxial layer formed on the surface of the semiconductor wafer after the epitaxial growth step;
Measuring the thickness B of the epitaxial wafer obtained after polishing,
Calculating the thickness of the epitaxial layer as the difference (B−A) between the thickness B and the thickness A, and
A method for measuring the thickness of an epitaxial layer, wherein the thickness A and the thickness B are measured by a non-contact displacement measuring instrument.
[2] The epitaxial layer thickness measuring method according to [1], wherein the resistivity of the semiconductor wafer is more than 20 mΩ · cm.
[3] A method for producing an epitaxial wafer, comprising forming an epitaxial layer on a surface of the semiconductor wafer by subjecting the semiconductor wafer to an epitaxial growth step,
Measuring the thickness A of the semiconductor wafer before the epitaxial growth step;
Polishing the epitaxial layer formed on the surface of the semiconductor wafer after the epitaxial growth step;
Measuring the thickness B of the epitaxial wafer obtained after polishing,
Calculating a difference (B−A) between the thickness B and the thickness A;
Determining whether the calculated (B-A) is within a preset target range; and
Shipping the epitaxial wafer determined to be within the target range by the above determination as a product wafer;
And
A method of manufacturing an epitaxial wafer, wherein the thickness A and the thickness B are measured by a non-contact displacement measuring instrument.
[4] An epitaxial wafer including preparing a semiconductor wafer lot including a plurality of semiconductor wafers and obtaining an epitaxial wafer lot including a plurality of wafers by subjecting each semiconductor wafer in the lot to an epitaxial growth step. A manufacturing method of
Measuring the thickness A of each semiconductor wafer before the epitaxial growth step;
Polishing each epitaxial layer formed on the surface of each semiconductor wafer after the epitaxial growth step;
Measuring the thickness B of each epitaxial wafer obtained after polishing,
Calculating a difference (B−A) between the thickness B and the thickness A;
Calculating an average value of (B-A) and / or a variation value of (B-A) in the epitaxial wafer lot;
Determining whether the calculated value is within a preset target range, and shipping an epitaxial wafer in a lot determined to be within the target range by the determination as a product wafer;
Including, and
A method of manufacturing an epitaxial wafer, wherein the thickness A and the thickness B are measured by a non-contact displacement measuring instrument.
[5] The method for manufacturing an epitaxial layer according to [3] or [4], wherein the resistivity of the semiconductor wafer is more than 20 mΩ · cm.
[6] preparing at least a semiconductor wafer lot including a plurality of semiconductor wafers and obtaining an epitaxial wafer lot including a plurality of wafers by subjecting each semiconductor wafer in the lot to an epitaxial growth step; A method of managing a single epitaxial wafer manufacturing process,
Measuring the thickness A of each semiconductor wafer before the epitaxial growth process in the same semiconductor wafer lot,
Polishing each epitaxial layer formed on the surface of each semiconductor wafer after the epitaxial growth step;
Measuring the thickness B of each epitaxial wafer obtained after polishing in the same semiconductor wafer lot,
Calculating a difference (B−A) between the thickness B and the thickness A;
Calculating an average value of (B-A) and / or a variation value of (B-A) within the same epitaxial wafer lot;
Determining whether the calculated value is within a preset target range;
Including
Measuring the thickness A and thickness B with a non-contact displacement meter; and
Epitaxial wafer manufacturing process management characterized in that the manufacturing process is stopped when it is determined by the above determination that it is outside the target range, and the manufacturing process is continued when it is determined by the above determination that it is within the target range. Method.
[7] The epitaxial wafer manufacturing process management method according to [6], wherein the silicon wafer has a resistivity of more than 20 mΩ · cm.

  ADVANTAGE OF THE INVENTION According to this invention, it is the epitaxial wafer which grind | polished the epitaxial layer formed on the surface of the semiconductor wafer after the epitaxial growth process, Comprising: A high quality epitaxial wafer can be provided with high reliability irrespective of a substrate resistivity.

3 is a graph showing an example of measurement results in Example 1. 6 is a graph showing another example of the measurement result in Example 1. 10 is a graph showing still another example of measurement results in Example 1. 10 is a graph showing still another example of measurement results in Example 1.

[Method for measuring film thickness of epitaxial layer]
The present invention relates to a method for measuring a film thickness of an epitaxial layer in a manufacturing process of an epitaxial wafer, which includes subjecting a semiconductor wafer to an epitaxial growth step to form an epitaxial layer on the surface of the semiconductor wafer and polishing the formed epitaxial layer. . The film thickness measuring method of the present invention includes the following steps.
(1) Measure the thickness A of the semiconductor wafer before the epitaxial growth step.
(2) Polishing the epitaxial layer formed on the surface of the semiconductor wafer after the epitaxial growth step, and measuring the thickness B of the epitaxial wafer obtained after the polishing.
(3) The thickness of the epitaxial layer is calculated as the difference (B−A) between the thickness B and the thickness A.
And in the film thickness measuring method of this invention, the said thickness A and thickness B are measured with a non-contact displacement measuring meter. “Non-contact displacement measuring instrument” refers to a measuring instrument that performs displacement measurement without contacting a wafer to be measured. According to the non-contact displacement measuring instrument, since the total thickness of the wafer can be measured without contacting the wafer surface, the total thickness of the wafer can be measured without contaminating the outermost surface. Further, according to the non-contact displacement measuring instrument, the reflection from the interface between the epitaxial layer and the substrate wafer is not used, and the thickness of the semiconductor wafer before the epitaxial growth step and the epitaxial layer formed on the surface of the semiconductor wafer after the epitaxial growth step are Since the thickness of the epitaxial layer can be determined by polishing and determining the thickness of the epitaxial wafer obtained after polishing, the resistivity between the substrate wafer and the epitaxial layer is small and sufficient at the interface between the substrate and the epitaxial layer. Even for an epitaxial wafer in which reflected light cannot be obtained, the thickness of the epitaxial layer can be determined.

  As the non-contact displacement meter, a capacitance displacement meter and an optical interference displacement meter can be used. For example, a wafer is placed between a pair of sensors, and the distance a between one sensor and one outermost surface of the wafer and the distance b between the other sensor and the other outermost surface of the wafer are electrostatically measured. Measurement is performed based on the capacitance or spectral reflectance, and the total thickness of the wafer is obtained by subtracting the distance a and the distance b from the distance between the sensors. Any of the above displacement measuring instruments is widely used for measuring the flatness of a wafer, and the measuring principle and measuring apparatus itself are well known. For example, capacitance displacement measuring instruments are described in detail in JP-A-3-27545, JP-A-51-55253, JP-A-61-209302, and the like. Specific examples of the measuring apparatus include Microsense 5000 series, Microsense 4800 series and AMS / AFS2200 series manufactured by KLA-Tencor. On the other hand, the optical interference displacement meter is a device that makes light incident on the surface of the object to be measured, divides the reflected light to determine the spectral reflectance, and measures the distance between the sensor and the object to be measured from the spectral interference waveform. Therefore, a measuring apparatus employing a Fizeau interferometer as the interferometer is suitable. Specific examples of the measuring apparatus include WAFERSIGHT manufactured by KLA-Tencor.

  Further, a laser displacement meter can be used as the non-contact displacement meter. The laser displacement measuring instrument is to fix the laser length measuring device at a distance from the front and back sides of the wafer, and directly measure the distance between the front and back surfaces of the wafer and the laser measuring device to calculate the wafer thickness. . According to the laser displacement meter, the thickness of the wafer in a narrow area corresponding to the spot diameter irradiated with the laser can be measured, so that the epitaxial layer thickness within the wafer surface can be accurately obtained.

  All of the above-mentioned measuring instruments have been widely used in recent years as wafer flatness measuring devices, but have not been employed at all to measure the epitaxial layer thickness as in the present invention. Any of the above-mentioned measuring instruments can measure the entire thickness of the wafer without contacting the wafer surface, and is therefore suitable for application to a product epitaxial wafer in which the outermost surface should be kept highly clean. Furthermore, since any method can be used regardless of the substrate resistivity, it can be used without limitation for an epitaxial wafer having an epitaxial layer on a high-resistance substrate. A normal non-contact displacement meter is a device that calculates flatness by calculating variations in thickness at a plurality of locations in the wafer surface, and is therefore programmed to measure the total thickness of the wafer. Therefore, in the present invention, the thickness of the semiconductor wafer before the epitaxial growth process at any one point (for example, the center of the wafer) and the semiconductor wafer The epitaxial layer formed on the surface is polished, the measured value with the thickness of the epitaxial wafer obtained after polishing is employed, and the thickness of the epitaxial layer can be calculated as the difference.

  As a semiconductor wafer (substrate wafer), various wafers used as a substrate wafer of a normal epitaxial wafer such as a silicon single crystal substrate can be used. Among these, as described above, the present invention is suitable for application to an epitaxial wafer having a substrate wafer having a high resistance (low impurity concentration). From this viewpoint, a semiconductor wafer having a resistivity exceeding 20 mΩ · cm, which makes it difficult to measure the epitaxial layer thickness by infrared interference, is preferable. The upper limit of the resistivity is, for example, 1000 Ω · cm, but is not particularly limited. Moreover, boron etc. can be mentioned as a dopant contained in the said semiconductor wafer, However It does not specifically limit. Furthermore, as a semiconductor wafer, a substrate wafer having an oxide film or a nitride film on the back surface can also be used.

  The epitaxial growth step may be performed in a single-wafer type vapor phase growth apparatus that processes substrate wafers one by one, or may be performed in a batch type vapor phase growth apparatus that processes a plurality of substrate wafers at a time. In the present invention, the total thickness (thickness A) of the semiconductor wafer before being introduced into the vapor phase growth apparatus is measured by the above method.

  In the vapor phase growth apparatus, the semiconductor wafer is heated to a predetermined growth temperature, and a source gas is supplied onto the main surface of the semiconductor wafer, whereby an epitaxial layer can be vapor grown on the main surface. . Conditions such as the heating temperature, gas flow rate, gas composition, and processing time in the epitaxial growth step may be set as appropriate so that a desired epitaxial layer is formed.

After the epitaxial growth step, the epitaxial layer formed on the surface of the semiconductor wafer is polished. For polishing the formed epitaxial layer, a single wafer polishing apparatus for polishing semiconductor wafers one by one can be employed. In addition, a batch type polishing apparatus that simultaneously polishes a plurality of semiconductor wafers can be employed. In either case, a polishing liquid having a chemical action is supplied to a polishing surface plate having a polishing cloth spread on the upper surface, and the semiconductor wafer is pressed against the rotating polishing surface plate to polish. What is necessary is just to set grinding | polishing conditions suitably so that desired polishing amount may be given.
And the wafer full thickness (thickness B) in which the epitaxial layer after grinding | polishing was formed is measured by the method mentioned above. If the thicknesses A and B are thus measured, the thickness of the epitaxial layer can be calculated as the difference (B−A) between the thickness B and the thickness A.
As described above, according to the film thickness measurement method of the present invention, even if an epitaxial wafer having a small difference in resistivity between the epitaxial layer and the substrate wafer is difficult to measure the epitaxial layer thickness by infrared interference, The thickness can be determined. As a result, when mass-producing epitaxial wafers with high-resistance substrates, it is possible to guarantee the quality of product wafers with high reliability by measuring the epitaxial layer thickness of the product wafer itself, rather than indirectly guaranteeing the film thickness using a monitor wafer. It becomes possible.

[Method of manufacturing epitaxial wafer]
The method for producing an epitaxial wafer according to the first aspect of the present invention (hereinafter, also referred to as “Production Method I”) comprises subjecting a semiconductor wafer to an epitaxial growth step to form an epitaxial layer on the surface of the semiconductor wafer, thereby forming the formed epitaxial wafer. A method for manufacturing an epitaxial wafer including polishing a layer, comprising the following steps.
(1) Measure the thickness A of the semiconductor wafer before the epitaxial growth step.
(2) Polishing the epitaxial layer formed on the surface of the semiconductor wafer after the epitaxial growth step, and measuring the thickness B of the epitaxial wafer obtained after the polishing.
(3) The difference (B−A) between the thickness B and the thickness A is calculated.
(4) It is determined whether or not the calculated (B−A) is within a preset target range.
(5) Ship the epitaxial wafer determined to be within the target range by the above determination as a product wafer.
And in the manufacturing method I, the said thickness A and thickness B are measured with a non-contact displacement measuring device similarly to the film thickness measuring method of this invention.

  In manufacturing method I, the thickness of the epitaxial layer of the product wafer itself, not the monitor wafer, was obtained after polishing the thickness A of the semiconductor wafer before the epitaxial growth step and the epitaxial layer formed on the surface of the semiconductor wafer after the epitaxial growth step. Epitaxial wafer thickness B is measured and calculated as the difference (BA) between the wafer thickness A and wafer thickness B, and an epitaxial wafer whose calculated value is within the target range is shipped as a product. Therefore, it is possible to provide an epitaxial wafer whose quality is highly guaranteed. Details of the thickness measurement, the substrate wafer used, the epitaxial growth process, the polishing of the epitaxial layer, etc. in the production method I are as described above for the film thickness measurement method of the present invention. The target range of (B-A) is not particularly limited, and is appropriately set according to the quality required for the product.

The method for producing an epitaxial wafer according to the second aspect of the present invention (hereinafter also referred to as “Production Method II”) comprises preparing a semiconductor wafer lot including a plurality of semiconductor wafers, and epitaxially growing each semiconductor wafer in the lot. Is an epitaxial wafer manufacturing method that includes obtaining an epitaxial wafer lot including a plurality of wafers and then polishing each epitaxial layer, and includes the following steps.
(1) Measure the thickness A of each semiconductor wafer before the epitaxial growth step.
(2) Polishing each epitaxial layer formed on the surface of each semiconductor wafer after the epitaxial growth step, and measuring the thickness B of each epitaxial wafer obtained after polishing.
(3) The difference (B−A) between the thickness B and the thickness A is calculated.
(4) The average value of (B-A) and / or the variation value of (B-A) in the epitaxial wafer lot is calculated.
(5) It is determined whether or not the calculated value is within a preset target range.
(6) Ship the epitaxial wafer in the lot determined to be within the target range by the above determination as a product wafer.
And in the manufacturing method II, the said thickness A and thickness B are measured with a non-contact displacement measuring device similarly to the film thickness measuring method of this invention.

  According to the manufacturing method II, the quality of the whole lot can be guaranteed and a product wafer can be provided. Examples of the variation value (B-A) include a difference between the maximum value and the minimum value (B-A) in the lot, a standard deviation, and the like. When the average value of (B-A) indicates an abnormal value, possible defects include, for example, an error in manual operation by an operator or an operation failure of the epitaxial manufacturing apparatus, and an epitaxial layer is formed on all wafers included in the lot. That is not. Moreover, when the variation value of (B-A) shows an abnormal value, as a possible defect, for example, when the substrate wafer is continuously transported to a single wafer vapor phase growth apparatus, the conveyor is temporarily stopped due to a malfunction, When the conveyor is operated again, the wafer after the epitaxial layer formation is mistakenly transported to the vapor phase growth apparatus, so that the wafer in which two epitaxial layers are formed is included in the lot. . Such a defect is difficult to detect by indirect film thickness measurement using a monitor wafer, but according to the present invention, it is possible to detect all the defects in a lot. Thereby, according to this invention, a high quality epitaxial wafer can be provided with high reliability.

  Details of the thickness measurement, the substrate wafer used, the epitaxial growth process, the polishing of the epitaxial layer, etc. in the production method II are as described above for the film thickness measurement method of the present invention. The target range of the average value and the variation value of (B-A) is not particularly limited, and is appropriately set according to the quality required for the product.

[Manufacturing method management method of epitaxial wafer]
Furthermore, the present invention provides a semiconductor wafer lot that includes a plurality of semiconductor wafers, and obtains an epitaxial wafer lot that includes a plurality of wafers by subjecting each semiconductor wafer in the lot to an epitaxial growth step. It is related with the management method of the epitaxial wafer manufacturing process which polishes each epitaxial layer after that at least once. The manufacturing process management method of the present invention includes the following processes.
(1) Measure the thickness A of each semiconductor wafer before the epitaxial growth step in the same semiconductor wafer lot.
(2) Polishing each epitaxial layer formed on the surface of each semiconductor wafer after the epitaxial growth step, and measuring the thickness B of each epitaxial wafer obtained after polishing in the same semiconductor wafer lot.
(3) The difference (B−A) between the thickness B and the thickness A is calculated.
(4) Calculate the average value of (B-A) and / or the variation value of (B-A) within the same epitaxial wafer lot.
(5) It is determined whether or not the calculated value is within a preset target range.
And in the manufacturing process management method of this invention, like the film thickness measuring method of this invention, the said thickness A and thickness B are measured with a non-contact displacement measuring device, and it determines with it being outside a target range by the said determination. If it is determined that the manufacturing process is within the target range, the process management is performed by continuing the manufacturing process.

  As described above, the thickness A of the semiconductor wafer before the epitaxial growth step, the epitaxial layer formed on the surface of the semiconductor wafer after the epitaxial growth step is polished, and the thickness B of the epitaxial wafer obtained after the polishing is measured, and the wafer By determining the thickness of the epitaxial layer as the difference (B−A) between the thickness A of the wafer and the thickness B of the wafer, the thickness of the epitaxial layer can be determined regardless of the resistivity of the substrate wafer. The total thickness of the epitaxial layer can be measured during mass production. This makes it possible to obtain the average epitaxial layer thickness value and the variation value in the lot. Therefore, in the manufacturing process management method of the present invention, when an abnormal value is detected in a certain lot, the manufacturing process is stopped and, for example, an operation such as taking out an abnormal lot is performed. Thus, according to the manufacturing process management method of the present invention, the manufacturing process can be managed so that a high-quality epitaxial wafer can be provided without shipping defective products as products. If an abnormal value is detected as a result of the above determination, the manufacturing process is stopped by stopping the manufacturing line, etc., and an alarm is sounded to notify the abnormality. It is also possible to construct a system for notifying an abnormality by a program. In the conventional method using a monitor wafer, the thickness and variation value of the epitaxial layer in the lot cannot be measured. Therefore, the above-described advanced manufacturing process management can be realized.

  Hereinafter, the present invention will be described with reference to examples. However, this invention is not limited to the aspect shown in the Example.

[Example 1]
An automatic production line including a single wafer type vapor phase apparatus and a polishing apparatus was produced. Specifically, a capacitive displacement meter (AMS / AFS3200 series) manufactured by KLA-Tecor was disposed upstream of the single wafer vapor phase growth apparatus and downstream of the polishing apparatus. The capacitance displacement measuring instrument sandwiches a wafer between two capacitance sensors at a predetermined interval, measures the distance between the upper and lower surfaces of the wafer and the sensor, and obtains the total thickness of the wafer from the measured distance. be able to. In this example, the total thickness of the wafer was calculated using the measured value at the center of the wafer. Further, the capacitance type displacement measuring instrument includes (1) the total thickness (thickness B) of the wafer after the epitaxial layer polishing by the polishing apparatus, and the total thickness (thickness A) of the wafer before carrying the single wafer type vapor phase apparatus. Difference (B−A), (2) average value of (B−A) for each lot, and (3) difference (variation value) between the maximum value and minimum value of (B−A) in one lot. A system capable of calculating the above (1) to (3) in real time during operation of an automatic production line was constructed by connecting to a computer equipped with a program for automatic calculation.

Twenty lots of wafers composed of 25 silicon single crystal substrates (substrate resistivity 10 Ω · cm) were prepared (total number of wafers: 500). The above-described 500 silicon single crystal substrates were continuously conveyed to the automatic production line, and the above (1) to (3) were measured in real time for each lot. In Example 1, four sets of the aforementioned 500 silicon single crystal substrates were prepared, and the same epitaxial growth process was performed on each of the four sets of prepared silicon single crystal substrates. The results are shown in FIGS.
In FIG. 1 to FIG. 4, the upper graph is the measurement result of the film thickness average value, and the lower graph shows the difference between the maximum value and the minimum value of the (BA) value in the lot. In both graphs, one plot corresponds to one lot.

  In the graph shown in FIG. 1, by setting a range surrounded by two broken lines in the upper graph of FIG. 1 as a target range, it is possible to determine that the film thickness average value of the eighth lot is bad. . On the other hand, by setting the range below the broken line as the target range in the lower graph of FIG. 1, it is possible to determine that the variation values of all lots are within the target range. In the graph shown in FIG. 1, since the film thickness average value of the eighth lot is twice as large as the average value of the other lots, it is determined to be defective. As a result of analysis, it was found that all the wafers in the eighth lot were subjected to the epitaxial growth process twice.

  In the graph shown in FIG. 2, by setting a range surrounded by two broken lines in the upper graph of FIG. 2 as a target range, it is possible to determine that the film thickness average value of the eighth lot is bad. . On the other hand, by setting the range below the broken line as the target range in the lower graph of FIG. 2, it is possible to determine that the variation values of all lots are within the target range. In the graph shown in FIG. 2, since the film thickness average value is about 1.4 times the average value of the other lots for the eighth lot, it is determined to be defective. Analysis of the measured values revealed that polishing was not performed on all wafers in the eighth lot.

  In the graph shown in FIG. 3, by setting a range surrounded by two broken lines in the upper graph of FIG. 3 as a target range, it is possible to determine that the film thickness average value of the eighth lot is bad. . On the other hand, in the lower graph of FIG. 3, by setting the range below the broken line as the target range, it is possible to determine that the variation values of all lots are within the target range. In the graph shown in FIG. 3, since the film thickness average value is 0 for the 8th lot and it is determined to be defective, the measurement value of each wafer is analyzed for the 8th lot. It was found that epitaxial growth was not performed on all the wafers.

  In the graph shown in FIG. 4, it is possible to determine that all lots are within the target range by setting the range surrounded by two broken lines in the upper graph of FIG. 4 as the target range. On the other hand, by setting the range below the broken line as the target range in the lower graph of FIG. 1, it is possible to determine that the variation value of the eleventh lot is defective. In the graph shown in FIG. 4, since the eleventh lot is determined to be defective, the measurement value of each wafer is analyzed for the eleventh lot, and an epitaxial layer exists on one wafer of the eleventh lot. It turned out not to. In this example, it has been found that the epitaxial layer does not exist on one wafer of the 11th lot, but there is also a case where one wafer of the 11th lot is subjected to the epitaxial growth process twice. The same result.

  From the above results, it can be seen that according to the present invention, defects in the epitaxial growth process that cannot be detected by indirect film thickness guarantee using a monitor wafer can be detected. By shipping an epitaxial wafer included in a lot other than the lot in which the defect has occurred as a product wafer, a high-quality silicon epitaxial wafer having no film thickness defect can be provided.

[Example 2]
20 silicon single crystal substrates were transported to an automatic production line including a single wafer vapor phase growth apparatus and a polishing apparatus similar to those in Example 1 except that a KFER-Tecor WAFERSIGHT was arranged as a non-contact displacement measuring instrument. . Only one of the 20 substrates was artificially grown twice epitaxially. As a result of calculating the thickness of the epitaxial layer for each wafer as the difference between the total thickness of the wafer after polishing the epitaxial layer by the polishing apparatus and the total thickness of the wafer before carrying in the single wafer vapor phase apparatus, Thus, it was possible to detect one wafer epitaxially grown twice in which the epitaxial layer thickness showed an abnormal value (a value about twice that of other wafers).

[Example 3]
Twenty silicon single crystal substrates were transported to an automatic production line including the single wafer vapor phase growth apparatus and polishing apparatus of Example 1 except that a laser displacement measurement instrument was disposed as a non-contact displacement measurement instrument. Only one of the 20 substrates was grown with an epitaxial layer having a thickness half that of the artificially formed twice epitaxial growth. For each wafer, the thickness of the epitaxial layer was calculated for each wafer as the difference between the wafer total thickness after the epitaxial layer polishing by the automatic polishing apparatus and the wafer total thickness before the single wafer vapor phase apparatus was loaded. The total thickness of the wafer was measured at the wafer center and at four locations 10 mm from the edge in the wafer surface. As a result, it was possible to detect one epitaxially grown wafer in which the epitaxial layer thickness showed an abnormal value (a value about 1.5 times that of other wafers) out of 20 epitaxially grown wafers. .

  The present invention is useful in the field of manufacturing epitaxial wafers, particularly in the field of manufacturing epitaxial wafers for polishing an epitaxial layer formed after epitaxial growth.

Claims (7)

An epitaxial layer thickness measurement method in an epitaxial wafer manufacturing process, comprising subjecting a semiconductor wafer to an epitaxial growth step, forming an epitaxial layer on the surface of the semiconductor wafer, and polishing the formed epitaxial layer,
Measuring the thickness A of the semiconductor wafer before the epitaxial growth step;
Polishing the epitaxial layer formed on the surface of the semiconductor wafer after the epitaxial growth step, and measuring the thickness B of the epitaxial wafer obtained after polishing;
Calculating the thickness of the epitaxial layer as the difference (B−A) between the thickness B and the thickness A, and
A method for measuring the thickness of an epitaxial layer, wherein the thickness A and the thickness B are measured by a non-contact displacement measuring instrument. The method for measuring a film thickness of an epitaxial layer according to claim 1, wherein the resistivity of the semiconductor wafer is more than 20 mΩ · cm. An epitaxial wafer manufacturing method comprising subjecting a semiconductor wafer to an epitaxial growth step, forming an epitaxial layer on the surface of the semiconductor wafer, and polishing the formed epitaxial layer,
Measuring the thickness A of the semiconductor wafer before the epitaxial growth step;
Polishing the epitaxial layer formed on the surface of the semiconductor wafer after the epitaxial growth step, and measuring the thickness B of the epitaxial wafer obtained after polishing;
Calculating a difference (B−A) between the thickness B and the thickness A;
Determining whether the calculated (B-A) is within a preset target range; and
Shipping the epitaxial wafer determined to be within the target range by the above determination as a product wafer;
And
A method of manufacturing an epitaxial wafer, wherein the thickness A and the thickness B are measured by a non-contact displacement measuring instrument. Preparing a semiconductor wafer lot including a plurality of semiconductor wafers, obtaining an epitaxial wafer lot including a plurality of wafers by subjecting each semiconductor wafer in the lot to an epitaxial growth step, and thereafter polishing each epitaxial layer An epitaxial wafer manufacturing method comprising:
Measuring the thickness A of each semiconductor wafer before the epitaxial growth step;
Polishing each epitaxial layer formed on the surface of each semiconductor wafer after the epitaxial growth step, and measuring the thickness B of each epitaxial wafer obtained after polishing;
Calculating a difference (B−A) between the thickness B and the thickness A;
Calculating an average value of (B-A) and / or a variation value of (B-A) in the epitaxial wafer lot;
Determining whether the calculated value is within a preset target range, and shipping an epitaxial wafer in a lot determined to be within the target range by the determination as a product wafer;
Including, and
A method of manufacturing an epitaxial wafer, wherein the thickness A and the thickness B are measured by a non-contact displacement measuring instrument. The method of manufacturing an epitaxial layer according to claim 3 or 4, wherein the resistivity of the semiconductor wafer is more than 20 mΩ · cm. Preparing a semiconductor wafer lot including a plurality of semiconductor wafers, and subjecting each semiconductor wafer in the lot to an epitaxial growth step to obtain an epitaxial wafer lot including a plurality of wafers; A method of managing an epitaxial wafer manufacturing process in which polishing is performed at least once,
Measuring the thickness A of each semiconductor wafer before the epitaxial growth process in the same semiconductor wafer lot,
Polishing each epitaxial layer formed on the surface of each semiconductor wafer after the epitaxial growth step, and measuring the thickness B of each epitaxial wafer obtained after polishing in the same semiconductor wafer lot;
Calculating a difference (B−A) between the thickness B and the thickness A;
Calculating an average value of (B-A) and / or a variation value of (B-A) within the same epitaxial wafer lot;
Determining whether the calculated value is within a preset target range;
Including
Measuring the thickness A and thickness B with a non-contact displacement meter; and
An epitaxial wafer manufacturing process management method characterized by stopping the manufacturing process when determined to be outside the target range by the determination and continuing the manufacturing process when determined to be within the target range by the determination. . The epitaxial wafer manufacturing process management method according to claim 6, wherein the resistivity of the silicon wafer is more than 20 mΩ · cm.

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