Method for determining electrode area and method for measuring resistivity

Abstract

To provide a method for calculating the area of an electrode that is used in measuring the resistivity of a silicon wafer by an evaporation CV method, with which it is possible to accurately measure the area of the electrode even immediately after electrode evaporation or after a progress of electrode discoloration.SOLUTION: Provided is a method for calculating the area of an electrode in measuring the resistivity of a silicon wafer by an evaporation CV method. This calculation method includes: adjusting the white balance of a camera using the image of a silicon wafer that is in the background; capturing the image of an electrode with the white balance adjusted camera and acquiring RGB data; converting the RGB data to data in a HSV format; calculating the expression S×|Cos((H-Hi) / 2)| for each pixel of the electrode data in the HSV format on the basis of the value Hi of hue immediately after electrode evaporation and converting the electrode data in the HSV format to a monochrome image; and applying binarization processing to the monochrome image to separate between the electrode and the background and calculating the area of the electrode.SELECTED DRAWING: Figure 1

Description

[Technical field]

[0001] The present invention relates to a method for determining the area of ​​an electrode in resistivity measurement by deposition CV method of a silicon wafer, and a method for measuring the resistivity of a silicon wafer by deposition CV method. [Background technology]

[0002] Silicon wafers are required to have high inter-wafer uniformity and high in-plane uniformity in order to obtain uniformity in semiconductor devices formed thereon.

[0003] In silicon wafers used as materials for analog devices, the uniformity of resistivity is particularly important.

[0004] There are two methods for measuring resistivity: the four-probe method and the CV (Cyclic Voltammetry) method. The CV method is often used as the method for inspecting silicon wafers.

[0005] In the CV method, the carrier concentration N(w) is calculated from the electrode area and CV characteristics using the following formula, and is converted to resistivity using a conversion table.

[0006] N(W)=2 / (q ε A 2 (d(1 / C 2 ) / dV)), W=ε·A / C A: electrode area, q: elementary charge, ε: permittivity.

[0007] From this formula, it can be seen that the carrier concentration is inversely proportional to the square of the electrode area A and has a significant effect on the calculation of the resistance value.

[0008] Among the CV methods, the mercury probe method or the deposition CV method is often used.

[0009] The mercury probe method is a method in which a resin "mold" is brought into contact with a wafer and mercury is injected into the gap between the two to form an electrode.

[0010] In the mercury probe method, since it is not possible to directly observe the area of ​​the formed electrode, mercury is injected in advance between the transparent glass plate and the resin "mold" to observe the area of ​​the formed electrode in advance.

[0011] However, as mercury is used, it reacts with oxygen in the air and produces impurities, which can mean that the mercury does not reach every corner of the mold, resulting in errors when calculating using an area observed in advance.

[0012] The deposition CV method is a method for forming an electrode by depositing a material for forming a Schottky junction on a wafer.

[0013] With the deposition method, there are problems such as the holes in the deposition mask 2 becoming smaller as the deposition mask 2 is used multiple times, causing the area of ​​the electrode (deposited film) 3 formed on the wafer 1 to gradually become smaller, as shown in Figure 5; the direction 4 of the deposition material changes depending on where the deposition mask 2 and wafer 1 are placed in the deposition machine, causing the area of ​​the electrode 3 to change, as shown in Figure 6; and the fact that part 5 of the electrode 3 is chipped off when the deposition mask 2 is peeled off, as shown in Figure 7.

[0014] This variation in the area of ​​the electrodes should not be a problem if the area is measured individually from camera images, etc., and substituted into the formula, but Au and Sm, both of which are used in CV measurements of silicon wafers, have the property of gradually discoloring after deposition, and it was not possible to stably measure the area using general-purpose software (Fig. 8).In particular, in the early stages of discoloration, the discolored area gradually spreads from the periphery, making it extremely difficult to detect the boundary between the electrode and the background (Fig. 9).

[0015] Patent Document 1 discloses an image region extraction method that includes a step of converting the RGB values ​​of each pixel of color image data into HSV values, and then performing threshold processing to binarize at least one of the converted S values ​​and V values ​​into HS'V' values.

[0016] Patent Document 2 describes a semiconductor wafer for resistivity calibration used in CV measurement and a method for producing the same. [Prior art documents] [Patent documents]

[0017] [Patent Document 1] JP 2018-128904 A [Patent Document 2] JP 2020-136583 A Summary of the Invention [Problem to be solved by the invention]

[0018] To improve the accuracy of silicon wafer resistivity measurements using the deposition CV method, it is necessary to accurately measure the electrode area. However, as mentioned above, the Au and Sm deposited electrodes on silicon wafers are prone to discoloration, and accurate area measurements were not possible using camera images.

[0019] The present invention has been made to solve the above problems, and has an object to provide a method for determining the area of ​​an electrode that can accurately measure the area of ​​an electrode used in resistivity measurement by deposition CV method of a silicon wafer, even immediately after deposition of the electrode or after discoloration of the electrode has progressed, and a resistivity measurement method that can measure the resistivity of a silicon wafer with high accuracy. [Means for solving the problem]

[0020] In order to solve the above problems, the present invention provides a method for determining an area of ​​an electrode in resistivity measurement by a deposition CV method of a silicon wafer, comprising the steps of: When taking a photo of the electrode with a camera to measure its area, adjusting the white balance of the camera by a gray world method using an image of a background silicon wafer; The electrode is photographed with the camera with the white balance adjusted to obtain RGB data; The acquired RGB data is converted into HSV format data including a hue value H, a saturation value S, and a brightness value V; Based on the hue value Hi immediately after deposition of the electrode, a calculation of S×|Cos((H−Hi) / 2)| is performed for each pixel of the HSV format data of the electrode to convert the HSV format data of the electrode into a monochrome image; Next, the monochrome image is subjected to a binarization process to separate the electrode from the background, thereby determining the area of ​​the electrode.

[0021] According to such a method for determining the area of ​​an electrode, in resistivity measurement of a silicon wafer by the deposition CV method, the contour of the electrode can be correctly detected and the area of ​​the electrode can be determined not only immediately after deposition of the electrode but also after discoloration of the electrode has progressed. Therefore, according to the method for determining the area of ​​an electrode of the present invention, the area of ​​the electrode used in resistivity measurement of a silicon wafer by the deposition CV method can be accurately measured immediately after deposition of the electrode and even after discoloration of the electrode has progressed, making it possible to perform highly accurate measurement of the resistivity of a silicon wafer.

[0022] The present invention also provides a method for measuring resistivity of a silicon wafer by a deposition CV method, comprising the steps of: The present invention provides a resistivity measuring method, comprising the steps of: calculating the resistivity of the silicon wafer to be measured by using the area of ​​the electrode determined by the method for determining the area of ​​the electrode of the present invention.

[0023] According to the resistivity measuring method of the present invention, the area of ​​the electrode accurately measured by the method for determining the area of ​​the electrode is used to calculate the resistivity of the silicon wafer, so that the resistivity of the silicon wafer can be measured with high accuracy. Effect of the Invention

[0024] As described above, the method for determining the area of ​​an electrode of the present invention makes it possible to accurately measure the area of ​​an electrode used in resistivity measurement of a silicon wafer by a deposition CV method, whether immediately after deposition of the electrode or after discoloration of the electrode has progressed, thereby enabling highly accurate measurement of the resistivity of a silicon wafer.

[0025] Furthermore, the resistivity measuring method of the present invention makes it possible to measure the resistivity of a silicon wafer with high accuracy. [Brief description of the drawings]

[0026] [Figure 1] 4 is a flowchart of a method for determining the area of ​​an electrode according to the present invention. [Diagram 2] 1 shows an image of an electrode that has begun to discolor, as well as a monochrome image and a binarized image obtained by converting this image, in an example of a method for determining the area of ​​an electrode of the present invention. [Diagram 3] 1 shows an image of an electrode immediately after deposition in a reference example, as well as a monochrome image and a binarized image obtained by converting this image. [Figure 4] 1 shows an image of an electrode in a reference example where discoloration has begun, as well as a monochrome image and a binarized image obtained by converting this image. [Diagram 5] FIG. 2 is a schematic diagram illustrating an example in which the area of ​​an electrode used in a deposition CV method is reduced. [Figure 6] FIG. 2 is a schematic diagram for explaining an example of variation in the area of ​​an electrode used in a deposition CV method. [Figure 7] FIG. 13 is a schematic diagram illustrating another example in which the area of ​​the electrode used in the deposition CV method is reduced. [Figure 8] These are examples of images taken with general-purpose software of Au electrodes and Sm electrodes immediately after deposition, and Au electrodes and Sm electrodes that have progressed in discoloration. [Figure 9] 13 is an example image of a Au electrode in the early stages of discoloration. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0027] As described above, there has been a need for a method for accurately determining the area of ​​an electrode used in resistivity measurement of a silicon wafer by the deposition CV method, which can accurately measure the area of ​​the electrode either immediately after deposition of the electrode or after discoloration of the electrode has progressed, and for developing a resistivity measurement method capable of measuring the resistivity of a silicon wafer with high accuracy.

[0028] As a result of extensive investigations into the above-mentioned problems, the inventors of the present invention have discovered that by photographing an electrode with a camera in which the white balance has been adjusted by the gray world method using an image of a silicon wafer as the background, converting the RGB data thus obtained into HSV format data, and converting the obtained HSV format data into a monochrome image with saturation based on the hue value Hi immediately after deposition, and then binarizing this monochrome image to clearly separate the electrode from the background and obtain the area of ​​the electrode, it is possible to correctly detect the outline of the electrode not only immediately after deposition of the electrode but also after discoloration of the electrode has progressed, and to accurately obtain the area of ​​the electrode while suppressing the effects of noise, dirt, and foreign matter, thereby completing the present invention.

[0029] That is, the present invention is a method for determining an area of ​​an electrode in resistivity measurement by a deposition CV method of a silicon wafer, comprising the steps of: When taking a photo of the electrode with a camera to measure its area, adjusting the white balance of the camera by a gray world method using an image of a background silicon wafer; The electrode is photographed with the camera with the white balance adjusted to obtain RGB data; The acquired RGB data is converted into HSV format data including a hue value H, a saturation value S, and a brightness value V; Based on the hue value Hi immediately after deposition of the electrode, a calculation of S×|Cos((H−Hi) / 2)| is performed for each pixel of the HSV format data of the electrode to convert the HSV format data of the electrode into a monochrome image; Next, the monochrome image is subjected to a binarization process to separate the electrode from the background and determine the area of ​​the electrode.

[0030] The present invention also provides a method for measuring resistivity of a silicon wafer by a deposition CV method, comprising the steps of: The resistivity measuring method of the present invention is characterized in that the resistivity of the silicon wafer being the measurement target is calculated using the area of ​​the electrode determined by the method for determining the area of ​​the electrode of the present invention.

[0031] The present invention will be described in detail below with reference to the drawings, but the present invention is not limited thereto.

[0032] Fig. 1 is a flow chart of the method for determining the area of ​​an electrode of the present invention. Hereinafter, the method for determining the area of ​​an electrode of the present invention will be described step by step with reference to Fig. 1.

[0033] (Adjusting the camera's white balance) First, to prepare the camera, adjust the white balance of the camera. For example, attach a lens that allows coaxial epi-illumination to a camera equipped with a CCD (Charge Coupled Devices) or CMOS (complementary metal oxide semiconductor) image sensor, and while illuminating the camera, take a picture of the silicon wafer in the background and adjust the white balance of the camera using the gray world method.

[0034] The gray world method is a method for determining the white balance of a camera. It involves calculating the average value of all pixels for the R, G, and B values ​​of the captured image, and then determining the white balance coefficients Rgain and Bgain using the following formula so that the average values ​​are equal.

[0035] Ra=(ΣRi) / n, Ga=(ΣGi) / n, Ba=(ΣBi) / n Rgain=Ga / Ra, Bgain=Ga / Ba (where i is the pixel number and n is the number of pixels)

[0036] Many cameras equipped with semiconductor image sensors can store white balance coefficients, and once set, can output the R, G, and B values ​​obtained by shooting by calculating the following formula:

[0037] R'=Rgain×R, G'=G, B'=Bgain×B

[0038] If your camera does not have this function, you can perform similar calculations on your PC.

[0039] By this process of photographing the silicon wafer and setting the white balance coefficient by the gray world method, the saturation value S of the silicon wafer, which forms the background of the electrodes, photographed thereafter with a camera for which the white balance has been adjusted, will be approximately zero.

[0040] (Getting RGB data) Next, the electrodes are photographed with a white-balanced camera to obtain RGB data.

[0041] The electrode to be photographed is not particularly limited, but may be an Au vapor deposition electrode or an Sm vapor deposition electrode formed on a silicon wafer. The electrode to be photographed may be an electrode immediately after vapor deposition, or an electrode in which discoloration has progressed. The method for determining the area of ​​an electrode of the present invention can accurately determine the area of ​​an electrode not only immediately after vapor deposition, but also an electrode in which discoloration has progressed.

[0042] (RGB data converted to HSV format data) Next, the obtained RGB data is converted into HSV format data including a hue value H, a saturation value S, and a brightness value V. The conversion into HSV format data will be described later.

[0043] (Converts HSV format data into a monochrome image) Next, based on the hue value Hi of the electrode immediately after deposition, the calculation S × |Cos((H-Hi) / 2)| is performed for each pixel of the HSV format data of the electrode, and the HSV format data of the electrode is converted into a monochrome image.

[0044] The hue value Hi immediately after deposition of the electrode used in this conversion can be obtained by the following procedure.

[0045] First, an Au vapor-deposited electrode and an Sm vapor-deposited electrode are formed on a silicon wafer. Immediately after deposition, the Au vapor-deposited electrode and the Sm vapor-deposited electrode are photographed with a camera with adjusted white balance to obtain image data in RGB format.

[0046] Next, the acquired RGB data is converted into image data in HSV format (a format expressed by hue, saturation, and brightness) using the following formula. H=60×(GR) / (Max-Min)+60 (When B value is the smallest of R, G and B values) H=60×(BG) / (Max-Min)+180 (When R value is the smallest of R, G and B values) H=60×(RB) / (Max-Min)+300 (When G is the smallest of R, G, and B values) S=(Max-Min) / Max V=Max Here, the maximum value of the R value, G value, and B value is set to Max, and the minimum value is set to Min.

[0047] Of the data converted to HSV format, the hue values ​​H of the parts where the electrodes are visible are averaged and designated as Hau and Hsm for Au evaporated electrodes and Sm evaporated electrodes, respectively. These are recorded as the basic data, the hue values ​​Hi immediately after deposition.

[0048] The RGB data for the electrodes to be imaged can also be converted into HSV format data using the above formula.

[0049] When converting HSV format data to a monochrome image, if the photographed electrode is an Au evaporated electrode, the basic data Hau is used as the hue value Hi immediately after deposition of the electrode, S × |Cos((H-Hau) / 2)| is calculated for all pixels, and the image is converted to a monochrome image using these values ​​as data. If the photographed electrode is an Sm evaporated electrode, the basic data Hsm is used as the hue value Hi immediately after deposition of the electrode, S × |Cos((H-Hsm) / 2)| is calculated for all pixels, and the image is converted to a monochrome image using these values ​​as data.

[0050] (Binarization processing) Next, the monochrome image is subjected to a binarization process to separate the electrodes from the background and determine the area of ​​the electrodes.

[0051] For the binarization process, for example, a binarization process known as Otsu's binarization (discriminant analysis method) can be used.

[0052] The area of ​​the electrode can be calculated from the binarized image, for example, as follows: First, in the binarized image, the number of pixels with a value of 1 is counted. This number is compared with the number of pixels of a standard sample with a known area photographed under the same conditions to obtain the electrode area.

[0053] FIG. 2 shows an example of a method for calculating the area of ​​an electrode of the present invention, in which (A) is an image of an electrode that has started to discolor, (B) a monochrome image obtained by calculating and converting S×|Cos((H-Hau) / 2)| for all pixels of image (A), and (C) an image obtained by binarizing monochrome image (B). Note that image (A) is actually a color image. The two white lines extending horizontally in FIG. 2 indicate the positions of the upper and lower ends of the outline of the electrode immediately after deposition.

[0054] As shown in Figure 2, from the image obtained by binarization processing in the method for calculating the area of ​​an electrode of the present invention, even if the electrode has started to discolor, the outline can be correctly detected and the image is not easily affected by noise, dirt, foreign matter, etc. In other words, this binarization processing makes it possible to accurately separate the electrode from the background.

[0055] For comparison, image conversion according to a reference example is shown in FIG. 3 to FIG.

[0056] In the reference example, image data obtained by photographing is converted into monochrome images based on brightness instead of saturation, and the monochrome images are then binarized.

[0057] Figure 3 shows an image (A) of an electrode immediately after deposition in a reference example, a monochrome image (B) obtained by converting image (A), and an image (C) obtained by binarizing monochrome image (B). Note that image (A) is actually a color image.

[0058] As is clear from FIG. 3, when image (B) that has been monochromeized based on brightness as in the reference example is binarized, the image (C) is significantly affected by uneven lighting.

[0059] FIG. 4 shows an image (A) of an electrode in a reference example where discoloration has begun, a monochrome image (B) obtained by converting image (A), and an image (C) obtained by binarizing monochrome image (B). Note that image (A) is actually a color image. In addition, the two white solid lines extending horizontally in FIG. 4 indicate the positions of the upper and lower ends of the outline of the electrode immediately after deposition. The two white dashed lines shown only in image (C) indicate the positions of the upper and lower ends of the outline of the electrode detected from image (C).

[0060] As shown in Figure 4, when an image (A) of an electrode that has started to discolor is converted to monochrome and then binarized using brightness as in the reference example, it becomes an image (C) in which the contour cannot be detected correctly. The area of ​​the electrode cannot be calculated correctly from such an image (C).

[0061] On the other hand, according to the method of the present invention for determining the area of ​​an electrode, the contour can be correctly detected and the area of ​​the electrode can be accurately determined not only immediately after deposition of the electrode, but also after discoloration of the electrode has progressed, as shown in Figure 2.

[0062] In measuring the resistivity of a silicon wafer by the deposition CV method, if the area of ​​each electrode used in measuring the resistivity is determined by the method for determining the area of ​​an electrode of the present invention described above, and the determined area is used to calculate the resistivity, the resistivity of the silicon wafer to be measured can be calculated without being affected by the variation in the electrode area.

[0063] Therefore, the method of determining the area of ​​an electrode of the present invention enables highly accurate measurement of the resistivity of a silicon wafer.

[0064] Furthermore, the resistivity measuring method of the present invention calculates the resistivity of the silicon wafer to be measured using the area of ​​the electrode determined by the method for determining the area of ​​the electrode of the present invention, and therefore the resistivity of the silicon wafer can be measured with high accuracy.

[0065] In the embodiment described above, for ease of explanation, a method is used in which the saturation of the silicon wafer in the background is set to zero using white balance. However, the white balance may be adjusted by performing a mathematically equivalent process. EXAMPLES

[0066] The present invention will be specifically described below using examples and comparative examples, but the present invention is not limited to these.

[0067] (Example) A camera equipped with a 3.2 megapixel color CMOS image sensor was used to photograph the electrodes. A telecentric lens with a magnification of 1 that allows coaxial epi-illumination was attached to this camera and fixed to a camera stand. An LED spotlight was attached to the illumination port of the lens to illuminate the sample.

[0068] First, a silicon wafer was set on the stage under the camera and photographed, and the white balance was adjusted by the gray world method according to the procedure described above, and the white balance coefficients were stored in the camera.

[0069] Next, with the above camera with the white balance adjusted, we photographed a 2 mm square standard sample of vapor deposition on glass. Since the vapor deposition surface of the standard sample was black and the other parts were transparent, we placed a white sheet in the background and photographed it.

[0070] The RGB data from the captured image was then converted to a monochrome image based on brightness. The monochrome image was then subjected to a binarization process known as Otsu's binarization, resulting in an image with 341,033 pixels with a value of 1.

[0071] The standard sample's certificate from the National Institute of Standards and Technology (NIST) indicates that each side is 2.00032 mm, so the area of ​​the standard sample is 4.00128 mm. 2 The area of ​​one pixel is 11.733 μm 2 This calculation of the area of ​​one pixel only needs to be done once when you purchase a new camera or lens.

[0072] Next, as a measurement sample, a P / P+ silicon wafer was prepared by evaporating Sm into a circle having a diameter of approximately 2 mm.

[0073] The sample immediately after deposition was placed on a stage under a camera whose white balance had been adjusted as described above, and the deposited electrode was photographed to obtain data in RGB format.

[0074] This RGB data was converted to HSV format image data using the procedure explained above. The average hue value of the part of the electrode in this HSV format image data was 48, which was recorded as Hsm. This task of calculating the average hue value only needs to be done once for each electrode material.

[0075] Next, the following formula was calculated for all pixels of the HSV format image data to create a monochrome image.

[0076] Gray = S × |Cos((H-Hsm) / 2)|

[0077] This monochrome image was subjected to Otsu's binarization process, resulting in an image with 267,037 pixels with a value of 1.

[0078] The area of ​​one pixel is 11.733μm based on the standard sample results. 2 Therefore, the area A of the Sm evaporated electrode is 3.1331 mm 2 was asked.

[0079] This silicon wafer was placed on the CV measurement table, and the CV characteristics were measured by contacting a probe with the Sm evaporated electrode. The results are shown in Table 1 below. Electrode area A: 3.1331 mm 2 The depth W and carrier concentration N were obtained using

[0080] [Table 1]

[0081] Furthermore, the carrier concentration N was converted to resistivity R using the Irvin curve, and the resistivity was averaged over the range of 0.6 to 0.7 μm in depth where the values ​​were stable. The resistivity at the position where the electrode was evaporated on the silicon wafer was calculated to be 18.46 ohm-cm.

[0082] Next, this sample was left in the air for about 24 hours, and the electrode with its surface discolored was photographed with a camera with the white balance adjusted as described above.

[0083] As in the case immediately after deposition, the acquired RGB data was converted to HSV format image data, and then S × |Cos((H-Hsm) / 2)| was calculated for every pixel in the HSV format data to create a monochrome image. At this time, the value acquired immediately after deposition was used for Hsm.

[0084] This monochrome image was subjected to Otsu's binarization process, resulting in an image with 267,003 pixels with a value of 1.

[0085] Area of ​​1 pixel: 11.733μm 2 From this, the area A' of the Sm evaporated electrode left in the air for approximately 24 hours was calculated to be 3.1333 mm.

[0086] The results of the CV characteristics measured earlier were used to calculate W' and carrier concentration N' using area A', and then converted into resistance value R' and averaged over a depth range of 0.6 to 0.7 μm.The resistivity at the position where the electrode was evaporated on the silicon wafer was calculated to be 18.46 ohm-cm, the same as when area A measured immediately after deposition was used.

[0087] (Comparative Example) Using the same device as in the example, the area of ​​the electrode was measured by a commonly used method of binarizing from grayscale conversion, and CV measurement was performed according to the following procedure.

[0088] First, a silicon wafer was set on the stage under the camera and photographed, and the white balance was adjusted by the gray world method according to the procedure described above, and the white balance coefficients were stored in the camera.

[0089] Next, the silicon wafer before the electrodes were evaporated was photographed with the above camera with the white balance adjusted, image data in RGB format was obtained, and the obtained image data was imported into a PC.

[0090] The captured images were converted to monochrome using the following grayscale conversion formula: Gray=R×0.3+G×0.59+B×0.11

[0091] The coefficients multiplied by the R, G, and B values ​​in this formula are widely used to adjust for the human characteristic of perceiving different brightnesses depending on the color.

[0092] Because the subject was a uniform silicon surface, all pixels should have the same value, but due to uneven lighting, they did not have the same value.

[0093] Therefore, the illumination unevenness correction data Corr was created by the following formula. Gray_a = (ΣGray_i) / n Corr_i = Gray_a / Gray_i (where i is the pixel number and n is the number of pixels)

[0094] Next, a measurement sample was prepared by depositing Sm in a circle with a diameter of about 2 mm on a P / P+ silicon wafer, separate from the measurement sample in the example. The sample immediately after deposition was set on a stage below a camera with the white balance adjusted as described above, and the evaporated electrode was photographed to obtain RGB data.

[0095] The data was then converted to monochrome using the commonly used grayscale conversion formula: Gray=R×0.3+G×0.59+B×0.11

[0096] Furthermore, a monochrome image Gray' was created by correcting the unevenness of the illumination using the following formula: Gray' = Corr×Gray

[0097] This monochrome image was subjected to Otsu's binarization process, resulting in an image with 269,292 pixels with a value of 1.

[0098] The area of ​​one pixel is 11.733μm based on the standard sample results. 2 Therefore, the electrode area A of Sm is 3.1596 mm 2 was asked.

[0099] This wafer was placed on the CV measurement table, and the CV characteristics were measured by contacting the electrodes with a probe. The results are shown in Table 2 below. Electrode area A: 3.1596 mm 2 The depth W and carrier concentration N were obtained using

[0100] [Table 2]

[0101] Furthermore, the carrier concentration N was converted to resistivity R using the Irvin curve, and the resistivity was averaged over the range of 0.6 to 0.7 μm in depth where the values ​​were stable. The resistivity at the position where the electrode was evaporated on the silicon wafer was calculated to be 18.55 ohm-cm.

[0102] Next, this sample was left in the air for about 24 hours, and the electrode with its surface discolored was photographed with a camera with the white balance adjusted as described above.

[0103] As with the case immediately after deposition, the acquired RGB data was converted to grayscale, and then a monochrome image Gray' was created by correcting for uneven lighting using Corr.

[0104] This monochrome image was subjected to Otsu's binarization process, resulting in an image with 225,831 pixels with a value of 1.

[0105] Area of ​​1 pixel: 11.733μm 2 Therefore, the area A' of the Sm electrode left in the air for about 24 hours is 2.6497 mm 2 was asked.

[0106] The results of the CV characteristics measured earlier were used to calculate W' and carrier concentration N' using area A', and then converted into resistance value R' and averaged over a depth range of 0.6 to 0.7 μm.The resistivity at the position where the electrode was evaporated on the silicon wafer was calculated to be 12.92 ohm-cm, a significant change from 18.55 ohm-cm when area A measured immediately after deposition was used.

[0107] That is, in the comparative example, the area of ​​the electrode after discoloration progressed could not be accurately measured, and as a result, the resistivity of the silicon wafer could not be measured with high accuracy.

[0108] In contrast, in the embodiment of the present invention, as described above, it was possible to accurately measure the area of ​​the electrode after discoloration had progressed, and as a result, it was possible to measure the resistivity of the silicon wafer with high accuracy.

[0109] The present invention is not limited to the above-described embodiment. The above-described embodiment is merely an example, and anything that has substantially the same configuration as the technical idea described in the claims of the present invention and exhibits similar effects is included in the technical scope of the present invention. [Explanation of symbols]

[0110] 1...wafer, 2...deposition mask, 3...electrode (deposition film), 4...direction of incidence, 5...part of electrode.

Claims

1. A method for determining an area of ​​an electrode in resistivity measurement of a silicon wafer by a deposition CV method, comprising the steps of: When taking a photo of the electrode with a camera to measure its area, adjusting the white balance of the camera by a gray world method using an image of a background silicon wafer; The electrode is photographed with the camera with the white balance adjusted to obtain RGB data; The acquired RGB data is converted into HSV format data including a hue value H, a saturation value S, and a brightness value V; Based on the hue value Hi immediately after deposition of the electrode, a calculation of S×|Cos((H−Hi) / 2)| is performed for each pixel of the HSV format data of the electrode to convert the HSV format data of the electrode into a monochrome image; Next, the monochrome image is subjected to a binarization process to separate the electrode from the background and determine the area of ​​the electrode.

2. A method for measuring resistivity of a silicon wafer by a deposition CV method, comprising the steps of:

2. A resistivity measuring method, comprising the steps of: calculating a resistivity of the silicon wafer to be measured by using an area of ​​the electrode determined by the method for determining an area of ​​the electrode according to claim 1.

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